Modeling Fracture and Failure with Abaqus

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ABAQUS初学者入门导读之一

ABAQUS初学者入门导读之一作者：cafe0519摘要：全文分8篇，分别就ABAQUS的基础背景，ABAQUS的文件组织和数据准备，ABAQUS的CAE回顾，ABAQUS的子程序调试，ABAQUS的批处理和程序自动化，ABAQUS的后处理以及ABAQUS与第三方Pre/Post处理器EDS FEMAP，Altair HyperMesh，MSC Patran和TNO FEMGV的亲密接触等几个最常遇到的话题。

第一篇主要讲述ABAQUS的基础资料的构成以及如何使用较快地入手了解你最关心的功能。

关键词：ABAQUS 有限元SIMWE 模块ABAQUS是一套功能强大的工程有限元软件，其解决问题的范围覆盖了从相对简单的线性分析到非常复杂的非线性问题。

ABAQUS拥有丰富可模拟任意形状的单元库和与之对应的各种类型的材料模型库，可以模拟大多数典型工程材料的性能，其中包括金属、橡胶、高分子材料、复合材料、钢筋混凝土、可压缩高弹性的泡沫材料以及类似于土和岩石等地质材料。

ABAQUS的最新版本是6.4-2，产品包括下面8个主要模块关于ABAQUS的进一步的介绍和ABAQUS的安装本文不做赘述。

ABAQUS Core ProductsABAQUS/Standard - 通用分析模块ABAQUS/Explicit - 显式分析模块ABAQUS/CAE - 前后处理模块ABAQUS Add-on ProductsABAQUS/AquaABAQUS/DesignABAQUS/FoundationABAQUS/Safe or FE/SAFEABAQUS Interface ProductsABAQUS Interface ABAQUS/C-MOLDABAQUS Interface for MoldflowABAQUS Interface for MSC.ADAMSABAQUS for CATIA V5正是由于ABAQUS的强大功能也带来了学习入门的复杂性，本文将通过简单介绍学习ABAQUS的体会，希望能对刚刚接触ABAQUS的学生一族给予一定的启示。

Abaqus Documentation学习方法

Lecture Notes
Additional reading and comments
Also read chapter 24 on Elements in the Abaqus Analysis User's Manual. Element Selection in Abaqus/Standard Benchmark Problem:
Benchmark Problems:
3.2.2 Test of ORNL plasticity theory under biaxial loading 3.2.8 Simple proportional and nonproportional cyclic tests 3.2.15 Creep of a thick cylinder under internal pressure 3.2.17 Stretching of a plate with a hole
Also read Section 6.10 of the Abaqus Analysis User's Manual.
Tire Modeling using Abaqus
Also read Section 6.4 of the Abaqus Analysis User's Manual.
Automotive Powertrain Assembly Analysis with Abaqus
Also read sections 10.6 and 11.4 of the Abaqus Analysis User's Manual.
Analysis of Geotechnical Problems with Abaqus
Also read Sections 6.8, 19.3, 19.4 of the Abaqus Analysis User's Manual.

岩土材料固有各向异性的模拟

第23卷第10期岩石力学与工程学报 23(10)：1604～16072004年5月 Chinese Journal of Rock Mechanics and Engineering May ，20042003年10月26日收到初稿，2003年12月25日收到修改稿。

作者余天堂简介：男，32岁，2000年于河海大学工程力学系水工结构专业获博士学位，现任副教授，主要从事计算力学方面的研究工作。

E-mail ：tiantangyu@ 。

岩土材料固有各向异性的模拟余天堂(河海大学土木工程学院南京 210098)摘要给出了岩土材料的一种各向异性模型，并用一个各向异性参数来描述岩土材料的固有各向异性。

各向异性参数、单轴抗压强度和单轴抗拉强度是分布函数，其分布可以用微结构张量和加载方向表示。

建立了一个既能描述岩土材料的固有各向异性又能反映开裂和屈服2种破坏模式的破坏准则。

数值模拟结果表明，该模型能有效地描述岩土材料的固有各向异性。

关键词岩土力学，破坏准则，各向异性，微结构张量分类号 TU 411.3 文献标识码 A 文章编号 1000-6915(2004)10-1604-04MODELING OF INHERENT ANISOTROPY FOR GEOTECHNICALMATERIALYu Tiantang(College of Civil Engineering ，Hohai University ， Nanjing 210098 China )Abstract A model of anisotropy for geotechnical material is presented. The inherent anisotropy of this kind of material is described with an anisotropy parameter. A microstructure tensor and loading direction are incorporated in the distribution functions of anisotropy parameter ，uniaxial compressive strength and uniaxial tensile strength. A failure criterion describing the fracture and yielding for geotechnical material is set up. Numerical simulation results show that the inherent anisotropy of geotechnical material can be efficiently described with the model. Key words rock and soil mechanics ，failure criterion ，anisotropy ，microstructure tensor1 引言由于在岩土体内部存在层理、片理等，或者，在某一方向有非常发育的节理系统，从而形成某种程度的成层现象，并沿着层面方向和垂直层面方向具有不同的弹性常数，因此，岩土体具有很强的固有各向异性。

接收时间最快的SCI杂志

nternational Journal for Numerical Methods in Engineering此刊最猛，一个月5期，一年4卷，以卷2100页面同样：THE International Journal ADVANCED Manufacturing Technology也很猛，一个月4期，一年5卷，一卷1800页面2、Journal of Materials Science 一个月2期，一年4卷，一卷1800页面3、Computer Methods in Applied Mechanics and Engineering 一个月2期，一年2卷，一卷4000页面4、Engineering Fracture Mechanics 18期5500页面5、International Journal of Solids and Structures 一月2期，4800页面6、Journal of Materials Processing Technology 一月3期，6300页面7、Journal of Sound and Vibration 一月3期，一年8卷，10300页面8、Materials Science and Engineering: A 一月4期，一年29卷，7500journal of materials processing technology一月2期，一年1卷，6200页面0、ACTA MECHNICS 1200页面0、Applied Physics A: Materials Science & Processing 4000页面0、Applied Mathematics and Optimization 1200页面01、Archive of Applied Mechanics 1200页面02、Communications in Numerical Methods in Engineering 2300页面04、Computational Mechanics1500页面05、Fatigue & Fracture of Engineering Materials & Structures1200页面1、International Journal of Applied Mechanics (IJAM) New创刊，可关注，在新加坡的WORLDSCI2\International Journal of Modeling, Simulation, and Scientific Computing (ijmssc)3、International Journal of Fracture 月刊，一期110页面4、Journal of Engineering Mathematics 月刊，一期110页面5、Journal of Engineering Mechanics 月刊，一期110页面6、Computer-Aided Design 月刊，一期110页面7、Engineering Failure Analysis 共2700页面8、Engineering Structures 2800页面9、Finite Elements in Analysis and Design 800页面6、Journal of Mechanical Science and Technology7、 Journal of Structural Engineering8、Materials and Structures 10期1750页面9、Automatica 12期2400页面10、International Journal of Engineering Science 1200页面11、International Journal of Fatigue 2100页面（11月就安排1月）12、International Journal of Impact Engineering 1300页面（11月安排1月）13、International Journal of Mechanical Sciences（1000页面14、 International Journal of Non-Linear Mechanics 1300页面15、International Journal of Plasticity 2500页面16、International Journal of Pressure Vessels and Piping 900页面17、 Journal of the Mechanics and Physics of Solids 2000页面18、Mechanics of Materials 13400页面19、Mechanics Research Communications 900页面20、 Mechanism and Machine Theory 2300页面21、Mechatronics 1500页面22、Simulation Modelling Practice and Theory 1800页面23、 Wear 2500页面23、Tribology International 1500页面全名影响因子* 投稿难易一审周期materials science and engineering a-structural materials properties microstructure and processing 容易超快，一般1-3周materials letters 容易超快，一般1-3周journal of materials science 容易超快，一般1-3周journal of materials processing technology 容易超快，一般1-3周nuclear instruments & methods in physics research section b-beam interactions with materials and atoms 容易超快，一般1-3周journal of magnetism and magnetic materials 容易超快，一般1-3周rare metal materials and engineering 容易很快，2-3周journal of optoelectronics and advanced materials 容易很快，2-3周materials chemistry and physics 容易很快，2-3周applied physics a-materials science & processing 容易很快，2-3周journal of nuclear materials 容易很快，2-3周materials transactions 容易较快，3-4周materials research bulletin 容易较快，3-4周journal of materials science-materials inmedicine 容易较快，3-4周journal of materials research 容易较快，3-4周computational materials science 容易较快，3-4周metallurgical and materials transactions a-physical metallurgy and materials science 容易较快，3-4周optical materials 容易较快，3-4周journal of materials science-materials in electronics 容易一般，4-6周inorganic materials 容易一般，4-6周construction and building materials 容易一般，4-6周materials characterization 容易一般，4-6周journal of electronic materials 容易一般，4-6周journal of inorganic materials 容易一般，4-6周materials & design 容易一般，4-6周materials science & engineering c-biomimetic and supramolecular systems 容易一般，4-6周smart materials & structures 容易一般，4-6周journal of wuhan university of technology-materials scienceedition 容易一般，4-6周materials science and technology 容易一般，4-6周international journal of materials research 容易偏慢，6-8周journal of materials science & technology 容易偏慢，6-8周advanced engineering materials 容易偏慢，6-8周journal of composite materials 容易偏慢，6-8周reviews on advanced materials science 容易偏慢，6-8周materialwissenschaft und werkstofftechnik 容易偏慢，6-8周bulletin of materials science 容易偏慢，6-8周archives of metallurgy and materials 容易偏慢，6-8周materials and structures 容易偏慢，6-8周materials and manufacturing processes 容易偏慢，6-8周journal of intelligent material systems and structures 容易偏慢，6-8周materials science-poland 容易偏慢，6-8周journal of materials engineering and performance 容易偏慢，6-8周materials science and engineering b-solid state materials for advanced technology 较易偏慢，6-8周jom-journal of the minerals metals & materials society 容易偏慢，6-8周jom-journal of the minerals metals & materials society 容易偏慢，6-8周materials and corrosion-werkstoffe und korrosion 容易偏慢，6-8周international journal of materials & product technology 容易较慢，8周-12周journal of porous materials 容易较慢，8周-12周macromolecular materials and engineering 较易较慢，8周-12周fatigue & fracture of engineering materials & structures 容易较慢，8周-12周science and technology of advanced materials 容易较慢，8周-12周metallurgical and materials transactions b-process metallurgy and materials processing science 容易较慢，8周-12周materials world 容易较慢，8周-12周journal of materials in civil engineering 容易较慢，8周-12周international journal of refractory metals & hard materials 容易较慢，8周-12周materials science 容易较慢，8周-12周advanced materials & processes 容易较慢，8周-12周ieee transactions on device and materials reliability 容易较慢，8周-12周materiale plastice 容易较慢，8周-12周materials performance 容易较慢，8周-12周indian journal of engineering and materials sciences 容易较慢，8周-12周modelling and simulation in materials science and engineering 容易较慢，8周-12周aci materials journal 容易较慢，8周-12周materials evaluation 容易较慢，8周-12周mechanics of composite materials 容易较慢，8周-12周journal of engineering materials and technology-transactions of the asme 容易较慢，8周-12周bio-medical materials and engineering 容易较慢，8周-12周mechanics of advanced materials and structures 容易较慢，8周-12周materials research innovations 容易 12周以上或约稿magnetic resonance materials in physics biology and medicine 较易 12周以上或约稿road materials and pavement design 容易 12周以上或约稿anti-corrosion methods and materials 容易 12周以上或约稿materiales de construccion 容易 12周以上或约稿sensors and materials 容易 12周以上或约稿materials technology 容易 12周以上或约稿journal of new materials for electrochemicalsystems 容易 12周以上或约稿journal of biomaterials applications 较易 12周以上或约稿journal of thermoplastic composite materials 容易 12周以上或约稿journal of advanced materials 容易 12周以上或约稿materials at high temperatures 容易 12周以上或约稿journal of advanced materials 容易 12周以上或约稿fire and materials 容易 12周以上或约稿易 12周以上或约稿science and engineering of composite materials 容易 12周以上或约稿cmc-computers materials & continua 较易 12周以上或约稿high temperature materials and processes 容易 12周以上或约稿materialprufung 容易 12周以上或约稿mechanics of time-dependent materials 容易 12周以上或约稿informacije midem-journal of microelectronics electronic components and materials 容易 12周以上或约稿易 12周以上或约稿journal of sandwich structures & materials 容易 12周以上或约稿high temperature material processes 容易 12周以上或约稿journal of energetic materials 容易 12周以上或约稿materials science in semiconductor processing 容易 12周以上或约稿progress in structural engineering and materials 容易 12周以上或约稿jsme international journal series a-solid mechanics and material engineering 容易 12周以上或约稿journal of computer-aided materials design 容易 12周以上或约稿journal of hazardous materials 容易超快，一般1-2周chemistry of materials 较易超快，一般1-2周advanced materials 较难很快，2-3周journal of materials chemistry 较易很快，2-3周microporous and mesoporous materials 容易很快，2-3周acta materialia 较易很快，2-3周scripta materialia 容易很快，2-3周biomaterials 较难很快，2-3周journal of biomedical materials research part a 容易较快，3-4周advanced functional materials 较难较快，3-4周diamond and related materials 容易较快，3-4周journal of biomedical materials research part b-applied biomaterials 容易一般，4-6周solar energy materials and solar cells 容易一般，4-6周dental materials 容易一般，4-6周NATURE MATERIALS 极难偏慢，6-8周journal of biomaterials science-polymer edition 较易偏慢，6-8周mechanics of materials 较易较慢，8周-12周annual review of materials research 约稿形式可能是约稿，周期不定materials science & engineering r-reports 很难可能是约稿，周期不定international materials reviews 一般 12周以上或约稿progress in materialsscience 很难可能是约稿，周期不定soft materials 较易 12周以上或约稿critical reviews in solid state and materials sciences 较难可能是约稿，周期不定progress in crystal growth and characterization of materials 较易 12周以上或约稿current opinion in solid state & materials science 较易 12周以上或约稿。

国际著名岩土工程SCI期刊中英文简介

1. Canadian Geotechnical Journal 加拿大岩土工程学报1963年开始出版，世界上发行量最大的三家岩土工程学术期刊之一，以刊登有关基础、隧道、水坝、边坡问题精彩文章及相关学科的新技术、新发展而闻名月刊SCI期刊ISSN : 1208-6010主编：Dr. Ian Moore, Queen's Universityhttp://pubs.nrc-cnrc.gc.ca/rp-ps ... de=cgj&lang=eng/ehost/d ... #db=aph&jid=35HPublished since 1963, this monthly journal features articles, notes, and discussions related to new developments in geotechnical and geoenvironmental engineering, and applied sciences. The topics of papers written by researchers, theoreticians, and engineers/scientists active in industry include soil and rock mechanics, material properties and fundamental behaviour, site characterization, foundations, excavations, tunnels, dams and embankments, slopes, landslides, geological and rock engineering, ground improvement, hydrogeology and contaminant hydrogeology, geochemistry, waste management, geosynthetics, offshore engineering, ice, frozen ground and northern engineering, risk and reliability applications, and physical and numerical modelling. Papers on actual case records from practice are encouraged and frequently featured.2. Geotechnical Engineering, Proceedings of ICE 岩土工程/journals/英国土木工程师协会（ICE）主办，集中了岩土工程实践中的所有方面内容，包括工程实例、工程设计讨论、计算机辅助设计等SCI期刊双月刊影响因子(2006): 0.286 ISSN 1353-2618 (Print) ISSN 1751-8563 (Online)Geotechnical Engineering covers all aspects of geotechnical engineering including tunnelling, foundations, retaining walls, embankments, diaphragm walls, piling, subsidence, soil mechanics and geoenvironmental engineering. Presented in the form of reports, design discussions, methodologies and case records it forms an invaluable reference work, highlighting projects which are interesting and innovative.Geotechnical Engineering publishes six issues per year.3. Géotechnique, Proceedings of ICE 土工国际著名的有关土力学、岩石力学、工程地质、环境岩土工程的岩土技术期刊，每期只刊登几篇文章，都是鸿篇巨著。

国际著名岩土类SCI期刊中英文简介

之前tangzhichengok 虫子发过一个【分享】岩土领域内几个SCI期刊，连接如下：/bbs/viewthread.php?tid=1754221我稍微做点补充吧！国际著名岩土类SCI期刊中英文简介转载请注明原出处：临峰山庄详细介绍1. Canadian Geotechnical Journal加拿大岩土工程杂志，1963年开始出版，世界上发行量最大的三家岩土工程学术期刊之一，以刊登有关基础、隧道、水坝、边坡问题精彩文章及相关学科的新技术、新发展而闻名月刊SCI期刊主编：Dr. Ian Moore, Queen's Universityhttp://pubs.nrc-cnrc.gc.ca/rp-ps ... de=cgj&lang=eng/ehost/d ... #db=aph&jid=35Hmonthly ISSN : 1208-6010 影响因子Impact factor: 0.542NATL RESEARCH COUNCIL CANADA, RESEARCH JOURNALS,MONTREAL RD, OTTAWA, CANADA, K1A 0R6Published since 1963, this monthly journal features articles, notes, and discussions related to new developments in geotechnical and geoenvironmental engineering, and applied sciences. The topics of papers written by researchers, theoreticians, and engineers/scientists active in industry include soil and rock mechanics, material properties and fundamental behaviour, site characterization, foundations, excavations, tunnels, dams and embankments, slopes, landslides, geological and rock engineering, ground improvement, hydrogeology and contaminant hydrogeology, geochemistry, waste management, geosynthetics, offshore engineering, ice, frozen ground and northern engineering, risk and reliability applications, and physical and numerical modelling. Papers on actual case records from practice are encouraged and frequently featured.更多资讯请上浏览2. Geotechnical Engineering, Proceedings of ICE/journals/英国土木工程师协会（ICE）主办，集中了岩土工程实践中的所有方面内容，包括工程实例、工程设计讨论、计算机辅助设计等SCI期刊双月刊影响因子(2006): 0.286 Geotechnical Engineering covers all aspects of geotechnical engineering including tunnelling, foundations, retaining walls, embankments, diaphragm walls, piling, subsidence, soil mechanics and geoenvironmental engineering.Presented in the form of reports, design discussions, methodologies and case records it forms an invaluable reference work, highlighting projects which are interesting and innovative.Geotechnical Engineering publishes six issues per year.ISSN 1353-2618 (Print)ISSN 1751-8563 (Online)Impact Factor (2006): 0.2863. Géotechnique, Proceedings of ICE国际著名的有关土力学、岩石力学、工程地质、环境岩土工程的岩土技术期刊，每期只刊登几篇文章，都是鸿篇巨著。

czm内聚力模型

Barenblatt (1959) was
first to propose the concept of Cohesive zone model to brittle fracture
➢ Molecular force of cohesion acting near the edge of the crack at its surface (region II ). ➢ The intensity of molecular force of cohesion ‘f ’ is found to vary as shown in Fig.a. ➢ The interatomic force is initially zero when the atomic planes are separated by normal
Phase transformation
Inter/trans granular fracture
FCC
Corner atoms
Face centered atoms
BCC
Corner atoms
Body centered atoms
Active dissipation mechanisims participating at the cohesive process zone
C
y B
NO MATERIAL SEPARATION
A
l1
d max
FORWARD
D
LOCATION OF COHESIVE CRACK TIP
d D
l2
WAKE
COMPLETE MATERIAL SEPARATION
E d, X
d sep
MATERIAL CRACK TIP

FRAC-W03-ThreePointCohesive

Select vertices inside drag shape.
© Dassault Systè mes, 2009
Modeling Fracture and Failure with Abaqus
W3.4
Deleting obsolete attributes The cut made in the previous step effectively deleted the mesh seam and sharp crack that existed in the original model. Thus, any model attributes associated with these must also be deleted. 1. In the Model Tree, expand the Engineering Features container underneath the Assembly. Expand the Cracks container and click MB3 on Crack-1. In the menu that appears, select Delete. 2. In the Model Tree, expand the History Output Requests container. Delete the output requests associated with the sharp crack ( H-Output-2 and H-Output-3). Step definition and output The step definition will be edited to include geometrically nonlinear effects. Because the cohesive behavior introduces additional highly nonlinear effects into the model, the time incrementation parameters will be adjusted. The rotation and applied moment at one of the reference points will be written as history data to the output database file to evaluate the moment-rotation response and detect the onset of crack growth. 1. In the Model Tree, expand the Steps container and double-click Step-1. 2. In the Basic tabbed page of the step editor, toggle on Nlgeom. 3. To aid convergence once the specimen breaks in half, use automatic stabilization with a constant damping factor equal to 0.01 (toggle off adaptive stabilization). 4. Set the maximum number of increments to 250, the initial time increment size to 0.01, the minimum time increment size to 1.e-8, and the maximum time increment size to 0.01. 5. Write history output of the variables UR3 and CM3 for set right-refPt to the output database file. 6. Edit the default field output request to include the element status, as shown in Figure W3–4. This will allow you to easily evaluate when the cohesive elements fail when postprocessing the results.

Fracture Mechanics and Fatigue

Fracture Mechanics and Fatigue
Fracture mechanics and fatigue are crucial concepts in the field of materials science and engineering. Fracture mechanics deals with the study of how materials behave when subjected to stress, particularly focusing on the initiation and propagation of cracks. On the other hand, fatigue is the phenomenon where materials fail due to repeated loading and unloading cycles, leading to the gradual growth of cracks until catastrophic failure occurs. Understanding these phenomena is essential for designing safe and reliable structures in various industries, such as aerospace, automotive, and civil engineering. One of the key aspects of fracture mechanics is the concept of stress intensity factor, which quantifies the stress field near the tip of a crack and predicts the likelihood of crack propagation. By analyzing the stress distribution around a crack, engineers can assess the critical conditions under which a crack will grow and ultimately lead to failure. This knowledge is crucial for determining the safety margins of structures and components, ensuring that they can withstand the expected loading conditions throughout their service life. Fatigue, on the other hand, poses a different challenge for materials engineers. Unlike static loading, fatigue loading involves cyclic stress variations that can lead to crack initiation and propagation even at stress levels below the material's ultimate strength. This phenomenon is particularly critical in applications where components are subjected to repeated loading, such as aircraft wings, automotive suspension systems, and offshore structures. By studying the fatigue behavior of materials, engineers can predict the fatigue life of a component and implement strategies to mitigate fatigue failure, such as improving material quality, introducing surface treatments, or redesigning the component geometry. In practice, fracture mechanics and fatigue analysis are often combined to assess the structural integrity of complex systems. Engineers use advanced modeling techniques, such as finite element analysis and computational simulations, to predict the behavior of materials under different loading conditions. By incorporating experimental data and theoretical models, engineers can optimize the design of structures and components to minimize the risk of failure due to fracture or fatigue. This integrated approach allows engineers to balance performance, cost, and safetyconsiderations in the design process, ensuring that structures meet the required standards and regulations. Despite the advancements in materials science and engineering, challenges still exist in predicting and preventing fracture and fatigue failures. The complex nature of material behavior, combined with the variability of loading conditions and environmental factors, makes it difficult to accurately predict the lifetime of structures and components. Moreover, unexpected failure events can have catastrophic consequences, leading to injuries, financial losses, and damage to the environment. As such, ongoing research and development efforts are focused on improving the understanding of fracture mechanics and fatigue behavior, developing new materials with enhanced durability and reliability, and implementing advanced testing and monitoring techniques to detect early signs of damage. In conclusion, fracture mechanics and fatigue are fundamental concepts in materials science and engineering that play a crucial role in ensuring the safety and reliability of structures and components. By studying the behavior of materials under different loading condition likelihood of crack initiation and propagation, assess the fatigue life of components, and optimize the design of structures to minimize the risk of failure. While challenges exist in predicting and preventing fracture and fatigue failures, ongoing research and development efforts are aimed at improving our understanding of material behavior and developing innovative solutions to enhance the durability and performance of engineering systems. By addressing these challenges, engineers can continue to push the boundaries of materials science and engineering, creating safer and more sustainable structures for the future.

abaqus粘聚力屈服应力英语

abaqus粘聚力屈服应力英语Cohesive Zone Modeling in Abaqus: Tutorial and Best Practices.Introduction.Cohesive zone modeling (CZM) is a powerful tool in Abaqus for simulating the behavior of interfaces between dissimilar materials. It is commonly used to model delamination, debonding, and fracture. In CZM, theinterface is represented by a cohesive zone, which is athin layer of material with a constitutive law that defines its behavior under traction-separation loading.Material Properties for Cohesive Zone Modeling.The constitutive law for a cohesive zone is defined by the following material properties:Cohesive strength: The maximum traction that thecohesive zone can sustain before failure.Fracture energy: The energy required to completely separate the cohesive zone.Shape of the traction-separation law: The shape of the curve that defines the relationship between traction and separation.In Abaqus, the traction-separation law is defined using a bilinear or exponential function. The bilinear functionis simpler to use, but the exponential function provides a more accurate representation of the material behavior.Creating a Cohesive Zone Model in Abaqus.To create a cohesive zone model in Abaqus, you mustfirst create a cohesive element set. This is done by selecting the surfaces that will be bonded together and then using the Cohesive Zone option in the Element Type dialog box.Once the cohesive element set has been created, you must specify the material properties for the cohesive zone. This is done by creating a new material definition and then selecting the Cohesive option in the Material dialog box.In the Cohesive Material dialog box, you must specify the following material properties:Cohesive strength: The maximum traction that the cohesive zone can sustain before failure.Fracture energy: The energy required to completely separate the cohesive zone.Shape of the traction-separation law: The shape of the curve that defines the relationship between traction and separation.Best Practices for Cohesive Zone Modeling.The following are some best practices for cohesive zone modeling in Abaqus:Use a fine mesh in the cohesive zone. This will help to ensure that the model is accurate.Use a convergence study to determine the optimal mesh size. This will help to ensure that the model is not mesh-dependent.Use a material model that is appropriate for the problem being solved. The bilinear function is simpler to use, but the exponential function provides a more accurate representation of the material behavior.Validate the model by comparing the results to experimental data. This will help to ensure that the model is accurate and reliable.Conclusion.Cohesive zone modeling is a powerful tool for simulating the behavior of interfaces between dissimilar materials. By following the best practices outlined in thistutorial, you can create accurate and reliable cohesive zone models.。

lecture 9-material damage and failure

DMICRT
DMICRT ≥ 1 indicates damage has initiated
Ductile
Shear
Different damage initiation criteria on an aluminum double-chamber profile
Copyright 2005 ABAQUS, Inc.
Ductile criterion for Aluminum Alloy AA7108.50-T6 (Courtesy of BMW)
Copyright 2005 ABAQUS, Inc.
ABAQUS/Explicit: Advanced Topics
L9.10
Damage Initiation Criteria for Ductile Metals
Copyright 2005 ABAQUS, Inc.
ABAQUS/Explicit: Advanced Topics
L9.5
Progressive Damage and Failure
• Two distinct types of bulk material failure can be modeled with ABAQUS/Explicit – Ductile fracture of metals • Void nucleation, coalescence, and growth • Shear band localization – Necking instability in sheet-metal forming • Forming Limit Diagrams • Marciniak-Kuczynski (M-K) criterion
• Components of material definition

基于天然裂缝破坏行为的页岩储层压裂微地震事件预测

基于天然裂缝破坏行为的页岩储层压裂微地震事件预测李强;尹成;王俊力;罗浩然【摘要】微地震事件的分布范围和密度与页岩气井的产量有较好的正相关关系,经济、高效地进行微地震事件的压前预测和压后评估,对压裂增产优化设计具有重要的指导意义.针对微地震监测技术成本高和施工受限的问题,基于渗流力学和岩石力学理论,结合天然裂缝张性和剪切破坏准则,建立了水力裂缝动态扩展过程中微地震事件模拟预测的流固耦合数学模型,给出了数值求解方法.采用涪陵页岩气示范区HF-X水平井的储层地质参数和施工参数,对页岩储层压裂过程中剪切和张性微地震事件的动态演化和展布进行数值模拟,模拟结果与实时监测的微地震数据吻合度高于80％.结果表明,该理论方法能够经济、高效和可靠地预测微地震事件的展布.【期刊名称】《石油物探》【年(卷),期】2018(057)006【总页数】7页(P878-883,891)【关键词】页岩;压裂;微地震;破坏准则;动态演化;数值模拟;压前预测;压后评估【作者】李强;尹成;王俊力;罗浩然【作者单位】西南石油大学地球科学与技术学院 ,四川成都 610500;西南石油大学地球科学与技术学院 ,四川成都 610500;中国石油天然气股份有限公司西南油气田分公司蜀南气矿 ,四川泸州 646000;西南石油大学地球科学与技术学院 ,四川成都610500【正文语种】中文【中图分类】P631页岩储层渗透率极低,但通常发育有大量天然裂缝,水平井多段分级压裂使储层产生复杂裂缝网络,为气体流动提供“高速通道”,是实现页岩气工业开采的有效技术[1-2]。

伴随着大量低粘液体在大排量的条件下注入,多条水力裂缝同时延伸,压裂液向地层滤失,扰动增产区域地层压力场和应力场[3-4],以剪切或张性破坏的形式激活周围处于闭合状态的天然裂缝[5-10],形成具有较高表观渗透率的复杂裂缝网络,极大地提高了页岩气井的产量。

天然裂缝或岩石在破坏的瞬间发生应力松弛,部分应变能以弹性波的形式释放,即产生微地震事件[11-13]。

Fracture Mechanics with ABAQUS_中文翻译版.

第 4 讲弹塑性估计方法.......................................................................................................... - 28 第 5 讲线弹性单元 ................................................................................................................. - 32 -
6.1.1 二维情况裂尖奇异性建模............................................................................ - 42 6.1.2 三维情况裂尖奇异性建模............................................................................ - 44 6.2 裂尖有限应变分析.................................................................................................... - 45 6.3 围线积分的计算 ....................................................................................................... - 47 6.4 不同裂尖网格的对比................................................................................................ - 50 6.5 撕开型模型的计算.................................................................................................... - 55 6.6 围线积分计算时应用*NORMAL 选项......................................................................... - 56 6.7 多裂纹尖端的 J 积分................................................................................................ - 57 6.8 壳中穿透裂纹 ........................................................................................................... - 57 6.9 混合型断裂 ............................................................................................................... - 60 6.10 裂纹扩展 ................................................................................................................. - 62 6.11 弹-塑性材料的数值计算........................................................................................ - 70 6.12 关于断裂其它的 ABAQUS 应用................................................................................ - 70 -

ABAQUS中的损伤模型

本周主要是研究了ABAQUS中自带的损伤模型。

关于弹塑性力学的内容，感觉再看下去会跑偏，故先回归损伤力学。

主要阅读ABAQUS用户帮助手册及一些用ABAQUS建立损伤模型的相关文献。

[1]Abaqus Analysis User’s Manual[2]婴幼儿摇椅金属底座的破裂分析.2010 Abaqus Taiwan Users’ Conference.[3]曹明,ABAQUS损伤塑性模型损伤因子计算方法研究.[4]Failure Modeling of Titanium 6Al-4V and Aluminum 2024-T3 With the Johnson-Cook Material Model另外，在Abaqus Example Problems Manual中有考虑损伤的模拟薄板铝材在准静态荷载和动力荷载下的累进失效分析的操作范例，还没来得及看。

ABAQUS中包括延性金属损伤、服从Traction-Separation法则的损伤、纤维增强复合物的损伤、弹性体损伤。

实际上对于混凝土还有塑性损伤模型，东南大学的曹明[3]对该模型有详尽描述。

在此仅讨论金属损伤模型。

对于损伤的主菜单，定义的是损伤的萌发模型，子选项为损伤的演化。

先来谈谈损伤的萌发模型。

1、损伤萌发模型延性金属损伤包括柔性损伤、Johnson-Cook损伤、剪切损伤、FLD损伤、FLSD 损伤、M-K损伤、MSFLD损伤。

服从Traction-Separation法则的损伤是针对Cohesive Element（黏着单元），应该不适合厚钢板结构，不予考虑。

纤维增强复合物损伤不考虑。

弹性体损伤针对于类似橡胶类物质，不考虑。

对于延性金属损伤，剪切损伤模型用于预测剪切带局部化引起的损伤，FLD、FLSD、MSFLD、M-K损伤都是用于预测金属薄片成型引起的损伤，故现在只剩柔性损伤和Johnson-Cook损伤符合厚钢板结构的损伤研究。

柔性损伤和Johnson-Cook损伤都是一类模型，预测由于延性金属内部空隙成核、成长、集结引起的损伤萌生。

Hydraulic_Fracturing_Simulation

Development and Validation of Fully-CoupledHydraulic Fracturing Simulation CapabilitiesMatias G. Zielonka, Kevin H. Searles, Jing Ning and Scott R. BuechlerExxonMobil Upstream Research Company3120 Buffalo Speedway, Houston, TX 77098Abstract: The problem of the propagation of a hydraulically driven fracture in a fully saturated, permeable, and porous medium is investigated. Fluid driven fracture propagation in porous media is a coupled problem with four unknown fields: the flow of the fracturing fluid within the fracture, the flow of the pore fluid within the pores, the porous medium deformation, and the fracture configuration. The corresponding governing equations are the mass balance of the fracturing fluid, mass balance of the pore fluid, equilibrium of the porous medium, and fracture initiation and propagation criteria. In this work, the recently co-developed Abaqus fully-coupled hydraulic fracturing modeling capabilities are evaluated by assessing their consistency, convergence, and accuracy qualities. The Abaqus “coupled pressure/deformation cohesive elements” and “coupled pressure/deformation extended finite elements (XFEM)” are used to model the propagation of the fracture and the flow of the fracturing fluid, while the porous medium deformation and pore-fluid flow are modeled with coupled “pore-pressure/deformation” continuum finite elements. The propagation of a vertical planar fluid-driven fracture with constant height and vertically uniform width within a prismatic-shaped reservoir (KGD model), and the propagation of a horizontal, circle-shaped, planar, fluid-driven fracture within a cylindrical reservoir (“Penny-Shaped” model) are simulated in both two and three dimensions. The Abaqus numerical solution obtained with each modeling technique (cohesive and XFEM) is compared with asymptotic analytical solutions for both the KGD and Penny-shaped models in the toughness/storage dominated and viscosity/storage dominated propagation regimes. Both methods are found to accurately reproduce the analytical solutions, and converge monotonically as the mesh is refined. This validation of the newly developed hydraulic fracturing capabilities within Abaqus provides confidence in its ability and readiness to simulate fluid driven fracturing applications for the oil and gas industry including injection, stimulation, and drilling operations.Keywords: geomechanics, soil mechanics, fracture mechanics, hydraulic fracturing, fluid-driven fracturing, geostatic, soils, pore pressure, cohesive elements, extended finite elements, XFEM, reservoir, drilling, injection.1. IntroductionHydraulic fracturing is a fundamental problem in Petroleum Engineering and plays a critical role in many applications within the oil and natural gas industry. The process can be generally defined as the intentional (or unintentional) initiation and propagation of a fracture due to the2014 SIMULIA Community Conference 1 /simuliapressurization of fluid that flows within the fracture. Examples of applications include (a) the stimulation of rock formations with poor or damaged permeability to increase conductivity between the reservoir and the producing wells, (b) improvement of produced water re-injection (PWRI) where water is injected to replace produced fluids and maintain reservoir pressure or provide enhanced oil recovery, (c) cuttings reinjection (CRI) where a slurry of drill cuttings is injected into a formation to mitigate the cost and risk of surface disposal, (d) in-situ stress measurement by balancing the fracturing fluid pressure in a hydraulically opened fracture with the geostatic stresses, and (e) wellbore integrity analysis of drilling operations to avoid propagating near-wellbore fractures that could result in drilling fluid losses to the formation and an inability to effectively clean the wellbore.Knowledge of the fracture dimensions (length/width/height), fracture geometry, and wellbore pressure is crucial for both the design and integrity of hydraulic fracturing field operations. For stimulation, PWRI and CRI, one of the fundamental questions is whether or not fracture containment is achieved. This means that the injection fluid and fracture are confined to a target interval or “pay” zone for PWRI and stimulation, or a dedicated disposal domain for CRI. Other important considerations include predictions of the injection rate, pressure, or injected volume required to initiate fractures, inject under matrix conditions, or minimize the potential for inducing fractures while drilling.Currently, there are no reliable techniques to measure fracture geometries during or after the hydraulic fracturing process. Furthermore, direct solutions of the underlying differential equations representing the different physical processes occurring during fracturing are difficult to construct, even in their most simplified forms. Therefore, the development of a numerical simulator with accurate predictive capability is of paramount importance.The computational modelling of hydraulic fracturing of porous media is a challenging endeavor. The difficulty originates primarily from the strong non-linear coupling between the governing equations, as the process involves at least the interaction between four different phenomena: (i) the flow of the fracturing fluid within the fracture, (ii) the flow of the pore fluid and seepage of fracturing fluid within the pores, (iii) the deformation of a porous medium induced by both the hydraulic pressurization of the fracture and the compression/expansion and transport of pore fluid within the pores, and (iv) the fracture propagation which is an inherently an irreversible and singular process. Additionally, fracture propagation typically occurs in heterogeneous formations consisting of multiple layers of different rock types, subjected to in-situ confining stresses with non-uniform magnitudes and orientations. Furthermore, fracturing fluids typically exhibit nonlinear rheologies and the leakoff of these fluids from the fracture into the surrounding rock is often history dependent.There are a number of commercial hydraulic fracture simulators used in the oil and natural gas industry for rapid design, analysis and prediction of fracture size, treating pressures, and flows (Clearly 1980, Meyer 1989, Warpinski 1994). These simulators rely in strong simplifying assumptions to render the problem solvable in realistic times:∙Fractures are assumed to be planar and symmetric with respect to the wellbore∙Fracture geometries are represented with few geometric parameters2 2014 SIMULIA Community Conference/simulia∙The formation is assumed to be unbounded and modeled using linear elasticity theory resulting in an integral equation relating fracture opening and fluid pressure ∙The fracture propagation is modeled within the framework of linear elastic fracture mechanics without any consideration of pore fluid pressure effects∙Leakage of fracturing fluid from the fracture into the rock is modeled as one dimensional and decoupled from the porous medium deformation.Although these simulators are useful in predicting broad trends and upper/lower bounds in operational parameters, their reliability and accuracy are restricted to unrealistic scenarios intrinsic simplistic assumptions apply, i.e., situations where some of the coupling between the many different processes involved can be neglected, and with strong symmetry in confinement stresses and geology.The accurate modelling of the hydraulic fracturing process under realistic geologies, wellbore configurations, confining stress states, and operational conditions calls for a more advanced, multi-physics numerical simulator that incorporates the complex coupling between the injected fluid, the pore fluid, the rock deformation, and the fracture configuration, thus overcoming the limitations of currently available commercial simulation tools.To this end, fully-coupled hydraulic fracturing simulation capabilities that leverage (i) the existing Abaqus non-linear soil consolidation analysis solver, (ii) Abaqus cohesive elements for modelling interface decohesion, and (iii) Abaqus extended finite element method (XFEM) for modelling propagating discontinuities, are being co-developed between ExxonMobil Upstream Research Company and Dassault Systemes Simulia Corporation.Specifically, two new element classes have been integrated into the existing Abaqus/Standard coupled pore fluid diffusion and solid stress porous media analysis solver:i. A coupled pressure/deformation cohesive element that models the progressive damage ofnormal mechanical strength and normal hydraulic conductivity as well as the flow offracturing fluid within the opening fracture.ii.An enriched version of the continuum coupled pore fluid diffusion/stress elements capable of activating arbitrarily oriented discontinuities in both displacements and porepressures while simultaneously modelling the fracturing fluid flow along the fracture. This work describes and validates these two new formulations for hydraulic fracturing modeling by assessing consistency, accuracy and convergence qualities. The propagation of a fluid-driven vertical planar fracture of uniform width and constant height within a prismatic-shaped rock formation (Khristianovich-Geertsma-de Klerk, or KGD model) and the propagation of a horizontal, circle-shaped, planar, fluid-driven fracture within a cylindrical reservoir (radial or “Penny-Shaped” model) are simulated for both two and three dimensions (Clearly 1980, Geertsma 1969, Yew 1997). The numerical solution obtained with each new modeling technique (cohesive and XFEM) are then compared with available asymptotic analytical solutions for both the KGD and Penny-shaped models in the toughness/storage dominated and viscosity/storage dominated propagation regimes. Finally, the consistency, accuracy and convergence attributes are assessed for both methods.2014 SIMULIA Community Conference 3 /simulia42014 SIMULIA Community Conference /simuliaSection 2 describes the governing equations for each of the coupled processes as well as theconstitutive and kinetic relations assumed for the porous medium, pore fluid and fracturing fluid, including:i.Equilibrium equation for the porous medium ii.Constitutive equation for the porous medium (Biot’s theory of poroelasticity) iii.Continuity equation for the pore fluid iv.Continuity equation for the fracturing fluid v.Momentum equation for the pore fluid (Darcy’s Law) vi. Momentum equation for the fracturing (Lubrication Equation)Section 3 details the procedures employed by both formulations (cohesive and extended finite element methods) and the fracture initiation and propagation criteria. Section 4 defines the test models (KGD plane-strain and the Penny-Shaped models) and the model set-up and assumptions used within Abaqus, while Section 5 presents numerical results and assesses accuracy and convergence by comparing the main solution variables obtained with meshes of differentresolutions with available asymptotic analytical solutions. Finally, some concluding remarks are summarized in Section 6.2. Governing EquationsAs stated in the introduction, hydraulic fracturing involves the interaction between four different phenomena:i.Porous medium deformation ii.Pore fluid flow iii.Fracturing fluid flow iv. Fracture propagationThe equations and constitutive relation governing these coupled processes, i.e., Biot’s theory of poroelasticity for porous media, Darcy’s Law for pore fluid flow, Reynold’s lubrication theory for fracturing fluid flow and the cohesive zone model to characterize fracturing (Abaqus 2013, Charlez 1997)) are summarized in what follows.2.1 Porous Media DeformationPorous media can be modelled as an isotropic, poroelastic material undergoing quasistaticdeformation. The equilibrium equation enforced by Abaqus, when body forces are neglected is,, 0(1) while the poroelastic constitutive relation, assuming small strains, is given by, 2 (2) 2 13in which is Biot’s coefficient, and are the dry elastic shear and bulk moduli, is the dry Young’s modulus, and is the dry Poisson’s ratio. Abaqus is formulated in terms of Terzaghi effective stresses ′, defined for fully saturated media as (Abaqus 2013, Charlez 1997)In terms of the latter, the constitutive relation takes the form2 1Defining effective strains as1the constitutive relation simplifies to2This identity is identical to the constitutive relation for linear elastic materials, but expressed in terms of Terzaghi effective stresses ′ and effective strains ′. Abaqus internally translates total stresses and strains into Terzaghi effective stresses and strains to leverage this equivalence (Abaqus 2013).2.2 Pore Fluid FlowThe continuity equation for the pore fluid is, assuming small volumetric strains, given by1, 0where is the pore fluid seepage velocity, and and are Biot’s modulus and Biot’s coefficient, respectively. These two poroelastic constants are defined by the identities111where is the pore fluid bulk modulus, is the porous medium solid grain bulk modulus, and is the initial porosity. In Abaqus, the two compressibilities and are specified using the *POROUS BULK MODULI keyword. Pore fluid is assumed to flow through an interconnected pore network according to Darcy’s law,,in which is the permeability, is the pore fluid viscosity, is the hydraulic conductivity and is the pore fluid specific weight. Combining with the continuity equation, the pore fluid diffusion equation is obtained2014 SIMULIA Community Conference 5 /simulia62014 SIMULIA Community Conference /simulia1 , (3) Within Abaqus, the hydraulic conductivity and specific weight are specified through the *PERMEABILITY keyword.2.3 Fracturing Fluid FlowLongitudinal fluid flow within the fracture is governed by Reynold’s lubrication theory defined by the continuity equation0 and the momentum equation for incompressible flow and Newtonian fluids through narrow parallel plates (i.e., Poiseuille flow)where is the fracture gap (Figure 1), ∙ is the fracturing fluid flow (per unit width) across the fracture, and are the normal flow velocities of fracturing fluid leaking through the top and bottom faces of the fracture into the porous medium, is the fracturing fluid viscosity, and is the fracturing fluid pressure along the fracture surface parameterized with the curvilinear coordinate, .Figure 1: Fracture aperture, width and fracturing fluid flowAbaqus computes the normal fracturing fluid velocities as(4where and are the pore fluid pressures on the top and bottom surface of the fracture and and are the so-called “leakoff coefficients”. This simple leakoff model simulates a layer of filtrate that might accumulate and reduce the effective normal permeability of the fracture surfaces.Inserting the Poiseuille flow equation and the simplified leakoff model into the continuity equation for the fracturing fluid yields the final form: ∙2014 SIMULIA Community Conference 7 /simulia(5) Abaqus specifies the fracturing flow viscosity and leakoff coefficients with the *GAPFLOW and the *LEAKOFF keywords, respectively.2.4 Fracture Initiation and PropagationFracturing can be conceptualized as the transition between two limiting states: the undamaged state with continuous displacements and non-zero tractions in all directions and the fully damaged state characterized by the presence of a displacement discontinuity along a material interface with zero tractions in the direction normal to the interface. In Abaqus, this transition process is modeled as a progressive degradation of cohesive strength along a zero-thickness interface whoseorientation and extent is either predefined (cohesive element method) or calculated during the simulation (extended finite element method). The gradual loss of strength in the interface with increasing separation is defined with an interface traction/interface separation relation or cohesive law (Abaqus 2013, Ortiz 1999).For the purpose of this study, a traction-separation cohesive law with linear softening (Figure 2) is assumed, defined by the cohesive energy (area under the softening part of the traction separation curve) and the cohesive strength . For the cohesive element procedure, it is also required to define the traction-separation behavior prior to damage initiation, which is assumed to be linear with initial stiffness . The cohesive traction of the interface thus evolves from a maximum tensile strength at damage initiation, down to zero when the interface is fully damaged and free to open beyond the total separation . If the interface is unloaded prior to complete damage, the traction is assumed to ramp down linearly with a damaged stiffness . The interface effective tractions are therefore given byFigure 2: Cohesive law for Cohesive and XFEM proceduresUpon damage initiation, the fracture is pressurized by instantaneously applying the fracturing fluid pressure, , calculated from the fracturing fluid equations in Equation 5. The total tractions resisted by (and acting on) the interface elements are therefore given by T r a c t i o nSeparationCOHESIVEXFEM82014 SIMULIA Community Conference /simuliaAs stated in Section 2.1, the Abaqus porous media analysis solver is formulated in terms of Terzaghi effective stresses. Therefore, the cohesive strength defining the onset of interface decohesion must be understood in terms of an effective strength (and not total strength).3. Cohesive Element and Extended Finite Element MethodsThe evolution of a fracture is modelled in Abaqus through zero-thickness interface elements with separation resisted by gradually decreasing tensile tractions. For the cohesive element procedure, these interface elements are defined a priori and placed between continuum element faces, whereas in the extended finite element method (XFEM), they are inserted and oriented automatically during the course of the simulation within existing continuum elements.3.1 Cohesive Element MethodThe coupled pressure/deformation cohesive elements implemented in Abaqus (COHPE4P , COHAX4P , COH3D8P ) are standard linear isoparametric elements with displacement and pore pressure degrees of freedom associated with their corner nodes, as depicted in Figure 3 (nodes 1,2,3,4). Theseelements must be inserted a priori between the faces of adjacent pressure diffusion/stress elements (CPE4P , CAX4P , C3D8P ) in order to model the yet to open fracture. To accommodate the coupling of the fracturing fluid flow equations, the elements are equipped with additional pressure degrees of freedom (attached to the center of the element edges perpendicular to the fracture) to interpolate the fracturing fluid pressure after damage initiation (nodes 5 and 6, Figure 3).Figure 3: Coupled pressure/deformation cohesive elements for hydraulic fracturing The cohesive elements can have arbitrary undeformed geometric thickness as the instantaneous gap coupled in the fracturing fluid flow equation (Equation 5) is defined in Abaqus as thedifference between the deformed and underfed thickness, i.e., . Prior to damage, the top and bottom faces of the unopened fracture are subjected to the pore fluid pressure acting towards increasing separation and the cohesive effective tractions resisting separation,where is the stiffness of the cohesive element prior to failure (Figure 2). After damageinitiation, the pore fluid is displaced by the fracturing fluid pressurizing the interface. The total tractions acting on the top and bottom faces of the opening fracture are then substituted by5 64UndeformedConfiguration Deformed Configuration 243 12 56312014 SIMULIA Community Conference 9 /simuliawhere is the damaging stiffness (Figure 2). A coupled cohesive element method for hydraulic fracturing similar to the formulation just outlined is described by Boone, 1990 and Carrier, 2012.3.2 Extended Finite element method (XFEM)The Extended Finite Element Method (XFEM) is implemented within Abaqus using the so called “phantom node” approach (Abaqus 2013, Remmers 2008, Song 2006, Sukumar 2003). In this implementation, each enriched pressure diffusion/stress element (CPE4P , CAX4P , C3D8P ) isinternally duplicated with the addition of corner phantom nodes, as depicted in Figure 4, in which original nodes are represented with full circles and corner phantom nodes with hollow circles. Prior to damage initiation only one copy of the element is active. Upon damage initiation the displacement and pore pressure degrees of freedom associated with the corner phantom nodes are activated and both copies of the element are allowed to deform independently, pore pressures are allowed to diffuse independently, and the created interface behavior is enforced with a traction-separation cohesive law.Figure 4: Implementation of the XFEM with “corner” and “edge” phantom nodes In order to enable the solution of the fracturing fluid flow equations, the enriched elements also incorporate new “edge-phantom nodes” (depicted as red triangles in Figure 4) that interpolate the fracturing fluid pressure within the fracture. The pore fluid pressure and at the top and bottom faces of the fracture are interpolated from the pore pressure degrees of freedom at the corner real nodes and phantom nodes. The difference with the fracturing fluid pressure(interpolated at the edge-phantom node) is the driving force that controls the leakage of fracturing fluid into the porous medium (Equation 4).The fracture is extended to a new element ahead of the fracture tip when the maximum effective principal stress at this element (interpolated to the tip) in a given iteration is equal to the cohesive strength . The orientation of the fracture segment to be extended into the tip element is set to the Undeformedconfigurationafter damage Deformed configuration after damage 2,2 4,4 3,3 1,1342 13 4 1 22 43 1 Undeformed configuration before damagedirection perpendicular to the minimum principal stress of the current iteration. This fracture initiation/orientation criterion is defined in Abaqus through the keyword*DAGAMAGE INITATION, CRITERION=MAXPS, POSITION=CRACKTIPAs in the cohesive element formulation, the fracturing fluid pressure is applied to the top and bottom faces of the fracture and superposed to the cohesive tractions.4. Benchmark ModelsIn this section, the two formulations previously outlined (coupled pressure/displacement cohesive and extended finite elements) are applied to model the propagation of a hydraulically driven fracture in two different configurations:i.Horizontal, circle-shaped, planar, fracture within a cylindrical domain, (radial or “Penny-Shaped” model (Clearly 1980, Charlez 1997, Yew 1997))ii.Vertical, rectangle-shaped, planar fracture within a prismatic-shaped domain (Khristianovich-Geertsma-de Klerk, or KGD model (Charlez 1997, Geertsma 1969, Yew 1997)).These models serve as benchmark examples to assess the consistency, convergence and accuracy of the numerical solution obtained with Abaqus.4.1 Fracture Propagation RegimesDespite the simplicity of the fracture geometry and strong symmetry in the chosen benchmark problems, there are no available closed-form analytical solutions for these problems when all coupled processes are considered in the analysis, i.e., when the formation is assumed to be porous and permeable with pore fluid flow and fracturing fluid is leaking into the pore space displacing the pore fluid. However, using the more restrictive theoretical framework resulting from assuming (i) an infinite domain, (ii) material fully impermeable, (iii), material linear elastic, (iv) linear-elastic fracture mechanics, and (v) Carter’s leakoff model (Howard 1957, Charlez 1997), approximate analytical solutions exist in the form of regular asymptotic expansions (Bunger 2005, Detournay 2006, Garagash 2006, Hu 2010, Garagash 2011, Peirce 2008, Savitski 2002). The governing equations then simplify to (i) the equilibrium equation for the linear elastic material, that for an infinite domain can be represented as an singular integral equation relating fracture opening and fluid pressure, (ii) the local and global mass balance equations for the fracturing fluid, and (iii) the fracture propagation criterion, also expressible as a singular integral equation relating fracturing pressure and fracture toughness. A non-dimensional analysis of this reduced system of equations uncovers the presence of two pairs of competing physical processes. The first pair consists of competing dissipative mechanisms: (a) energy dissipated due to fluid viscosity and (b) energy dissipated due to fracture propagation; the second pair consists of competing components of fluid balance: (a) fluid storage within the fracture and (b) fluid leakage from the fracture into the surrounding material. Depending on which of the two dissipative mechanisms and which of the two storage mechanisms dominate, four primary limiting regimes of propagation emerge: ∙Viscosity dominated and storage dominated propagation regime ( ).∙Toughness dominated and storage dominated propagation regime ( ).10 2014 SIMULIA Community Conference/simulia2014 SIMULIA Community Conference 11 /simulia∙Viscosity dominated and leak-off dominated ( ). ∙ Toughness dominated and leak-off dominated regime (). These four fracture propagation regimes can be conceptualized in a rectangular parametric space where each limiting regime corresponds to each of the vertices of the rectangle with one dissipation mechanism dominating and the other being neglected, and one component of fluid global balance dominating with the other also neglected (Figure 5).Figure 5: Parametric diagram representing the four limiting propagation regimes ofhydraulically driven fracturesThis work analyzes each benchmark problem in both the toughness/storage-dominated (near- ) and the viscosity/storage-dominated (near- ) propagation regimes. The near- and the near- asymptotic solutions (small time solutions in the toughness and viscosity regimes) are used to compare to Abaqus numerical solutions for each formulation (cohesive element method and XFEM) with material parameters, loads, and boundary conditions that reproduce each of these propagation regimes.In order to render the Abaqus solution comparable with the asymptotic solutions, the modeldimensions and material properties are selected such that the more restrictive conditions for which these solutions apply are adequately recreated. Specifically, the dimensions of the domain of analysis are much bigger than the fracture aperture and length, the permeability is defined tominimize the influence of poroelastic effects ahead of the fracture tip, and cohesive properties are selected to ensure a small cohesive zone relative to the size of the fracture.4.2 Radial (Penny-Shaped) ModelThe first benchmark problem consists of an axisymmetric, penny-shaped, hydraulically-driven fracture propagating in a cylindrically shaped poroelastic formation as illustrated in Figure 6.∞∞0 ∞∞12 2014 SIMULIA Community Conference/simuliaFigure 6: Cylindrical domain with a horizontal, circular-shaped, hydraulically drivenfractureThe domain of analysis is characterized by the inner radius , outer radius , and height . The porous medium is characterized by Young’s modulus , Poisson ratio , fracture toughness , porosity , Biot’s coefficient , Biot’s modulus , and hydraulic conductivity. An incompressible Newtonian fluid with viscosity is injected at a constant rate at the center of the fracture from a vertical wellbore. The fracture aperture , , the net pressure , (defined as the difference between the fracturing fluid pressure , and the confining stress ), and the fracture radius are the sought quantities.4.3 Plane Strain (KGD) ModelThe second benchmark problem considers a hydraulically-driven vertical fracture propagating in a poroelastic prismatic-shaped formation of length L, depth R and height H as illustrated in Figure 7. 01,,。

abaqus损伤参数与断裂拉紧

abaqus损伤参数与断裂拉紧1.在abaqus中，我们可以通过定义损伤参数来模拟材料的断裂行为。

In Abaqus, we can simulate the fracture behavior of materials by defining damage parameters.2.损伤参数可以设置为材料的力学行为、应力状态和断裂准则等因素进行调整。

Damage parameters can be adjusted according to the mechanical behavior, stress state, and fracture criteria of the material.3.通过调整损伤参数，我们可以模拟出不同条件下材料的变形和破坏过程。

By adjusting the damage parameters, we can simulate the deformation and failure process of materials under different conditions.4.损伤参数的选择对于模拟材料的断裂拉紧行为具有重要影响。

The selection of damage parameters has a significant influence on simulating the fracture behavior of materials under tension.5.在abaqus中，我们可以使用各种损伤模型来定义不同类型的材料断裂行为。

In Abaqus, we can use various damage models to define different types of material fracture behavior.6.通过实验数据的分析，我们可以确定合适的损伤参数来描述材料的拉伸性能。

By analyzing experimental data, we can determine appropriate damage parameters to describe the tensile performance of materials.7.损伤参数的精确设置可以有效预测材料的疲劳寿命和断裂准确。

Workshop 7 Abaqus XFEM Pressure Vessel

Workshop 1Crack in a Three-point Bend SpecimenWorkshop 7Modeling Crack Propagation in a Pressure Vessel IntroductionIn this workshop, we will model crack propagation in a steel pressure vessel using XFEM. The procedure is similar to that used earlier, but the ease of modeling as compared to conventional methods will become more evident here in three dimensions. In the postprocessing section of this workshop, we will get acquainted with tools and features available in the Visualization module that allow one to effectively probe the cracked geometry in a three-dimensional solid.Figure W7–1 The pressure vesselThe structure being modeled here is a 10m thick cylindrical pressure vessel with an inner diameter of 40m at the base with a hemispherical cap. The entire structure is ~94m high and is modeled using reduced-integration solid continuum elements (C3D8R). Themeshed model is shown in Figure W7–1. The pressure vessel is constrained at the bottom against movement in all directions, and a uniform pressure of 210 MPa is applied on all the interior surfaces. We will assume the material to be linear elastic; failure initiates when the maximum principal stress reaches a critical value (the MAXPS damage initiation criterion is used). We will use an energy-based damage evolution criterion that accounts for mode mixing.An initial crack is located in one of the nozzles near the bottom of the pressure vessel, as shown in Figure W7–2. As done previously, the initial crack is defined using a part constructed in the shape of the crack and instanced in the assembly at the desired location. The crack geometry, i.e., the crack surface and the crack front are defined by means of two level set functions φ and ψ which Abaqus/CAE calculates using the geometric feature —in this case the part instance — used to define the crack. Note that this part need not be meshed or assigned material properties; it is a dummy part present only for the purpose of defining the initial crack.Figure W7–2 Initial crack in the nozzle shown in (a) the unmeshed part (b) themeshed partPreliminaries1.Enter the working directory for this workshop: ../fracture/vessel.2.Run the script named ws_press_vessel_xfem.py.The model created by this script contains the part geometry, model assembly, mesh and the sets and surfaces necessary for defining the crack, boundary conditions and loads. We will make the following additions to configure the model.Material and section propertiesHere we will define a linear elastic material named steel with a Young’s modulus of 210 GPa and Poisson’s ratio of 0.3, and specify damage initiation, evolution and stabilization. We will then create a solid section referencing this material and assign it to the part.1.In the Model Tree, double-click Materials; in the material editor that appears,enter s teel as the name.2.Select Mechanical → Elasticity → Elastic. Enter 210.0E9 and 0.3 as theYoung’s modulus and the Poisson’s ratio, respectively.3.Select Mechanical → Damage for Traction Separation Laws → MaxpsDamage. As shown in Figure W7–3, change the tolerance to 0.1 and enter 8.44E7 as the maximum principal stress.Figure W7–3 The material editor4.Select Suboptions → Damage Evolution. In the suboption editor that appears,select Energy as the type and Power Law as the mixed mode behavior. Toggle on Power and enter 1 in the data field. Enter 4220 in the three data fieldscorresponding to fracture energy. The editor should resemble Figure W7–4. Click OK.5.Select Suboptions→ Damage Stabilization Cohesive. In the suboption editorthat appears, enter 1.0E-4 as the viscosity coefficient and click OK.6.Click OK in the material editor.7.In the Model Tree, double-click Sections and create a homogeneous solid sectionnamed Solid with steel as the material.8.Assign the section Solid to the predefined set named vessel. This set encompassesthe entire model.Figure W7–4 Specifying damage evolution using the suboption editorStep, time incrementation, and analysis controlsWe will now create a general static step. The default choices for time incrementation are usually not sufficient for crack propagation analyses that employ XFEM. We will reduce the sizes of the minimum time increment as well as the initial increment. In general, the discontinuous nature of crack propagation causes convergence difficulties, which can be alleviated by specifying certain analysis controls. These analysis controls may not always be necessary; but more often than not, they prove useful in bringing an analysis to completion.Three-dimensional XFEM analyses are usually time intensive and may require a large number of increments. Here we will run the analysis just long enough to produce some crack propagation for illustration purposes.1.In the Model Tree, double-click Steps. In the Create Step dialog box that appears,select Static, General as the procedure type and click Continue.2.In the step editor that appears, toggle on Nlgeom and set the time period to 1.3.Switch to the Incrementation tabbed page of the editor. Enter 0.05 as the initialand the maximum time increment sizes. Reduce the minimum increment size to1.0e-12. Enter 10 as the maximum number of increments and click OK.4.From the main menu bar in the Step module, select Other → General SolutionControls → Edit → Step-1. Abaqus/CAE displays a warning message. Review it and click Continue.5.In the General Solutions Controls Editor that appears, go to the TimeIncrementation tabbed page and toggle on Specify. Then, toggle onDiscontinuous Analysis.Note: This increases I0and I R to 8 and 10, respectively. While solving theequations in any given increment, the automatic time integration algorithm willcheck the behavior of residuals from iteration to iteration to gauge the likelihood of convergence and decide whether or not to abandon iterations and begin againwith a smaller time increment. A check is made for quadratic convergence after I0 iterations and if quadratic convergence is not achieved, then a check is made tomaintain logarithmic convergence after I R iterations. In discontinuous analyses convergence is generally slow and we are simply postponing these checks toaccount for this by increasing I0 and I R.6.Click the first More tab on the left to display the default values of timeincrementation parameters. Increase the value of I A, the maximum number ofattempts before abandoning an increment, from the default value of5to 20.This data field is highlighted in Figure W7–5. Click OK.Figure W7–5 The general solution controls editorOutput requestsThe output variables required to visualize and probe an XFEM crack are not included in the default output. Edit the default field output request to include the output variables PHILSM, PSILSM and STATUSXFEM. The first two are found under the category Failure/Fracture, and the latter is found under State/Field/User/Time, as shown in Figure W7–6.Figure W7–6 Output requestsXFEM crack definitionCreate a frictionless interaction property for the crack surfaces and define a propagating XFEM crack in the Interaction module using the part instance crack-1.crack as the initial crack location.1.In the Model Tree, double-click Interaction Properties. In the CreateInteraction Property dialog box that appears, enter noFric as the name andContact as the type. Click Continue.2.In the interaction editor that appears, select Mechanical → Tangential Behavior.Accept the default friction formulation Frictionless.3.Select Mechanical → Normal Behavior. Accept the default selection for thepressure-overclosure relationship and click OK.4.From the main menu bar in the Interaction module, select Special → Crack →Create. In the Create Crack dialog box that appears, choose XFEM as the typeas shown in Figure W7–7 and click Continue.5.Choose Single instance as the crack domain in the prompt area and select theinstance of the pressure vessel in the viewport. If the Region Selection dialog box appears, click Select in viewport in the prompt area to select the instance directly from the viewport.6.In the crack editor that appears, toggle on Allow crack growth.7.Toggle on Crack location and click ; then click Sets in the prompt area. Inthe Region Selection dialog box that appears, select crack-1.crack and clickContinue.8.Toggle on Specify contact property in the crack editor. If it is not alreadyselected, select the contact property noFric. The crack editor should appear asshown in Figure W7–8. Click OK.Figure W7–7 Creating an XFEM crackFigure W7–8 The crack editorBoundary conditions and loadsCreate an encastre boundary condition and apply it to the bottom of the pressure vessel in the initial step. Use the predefined set named pressure_vessel-1.bottom for this purpose.1.In the Model Tree double-click BCs. In the Create Boundary Condition dialogbox that appears, enter fixed as the name. Select Initial as the step andSymmetry/Antisymmetry/Encastre as the type, and click Continue.2.Click Sets in the prompt area and select the set pressure_vessel-1.bottom in theRegion Selection dialog box that appears. Click Continue.3.In the boundary condition editor, select ENCASTRE and click OK.Apply a pressure of 210 MPa on the interior surface of the pressure vessel. Use the predefined surface named pressure_vessel-1.interior.1.In the Model Tree double-click Loads. In the Create Load dialog box thatappears, enter Pressure as the name. Select Step-1 as the step and Pressure as the type, and click Continue.2.Select the predefined surface pressure_vessel-1.interior in the Region Selectiondialog box and click Continue.3.In the load editor, enter 2.1E8 as the magnitude and click OK.Job1.In the Model Tree, double-click Jobs to create a job for this model. Name the jobvessel.2.Save your model database.3.Click mouse button 3 on the job name and select Submit from the menu thatappears. From the same menu, you may also select Monitor to monitor theprogress of the job and Results to automatically open the output database file for this job (vessel) in the Visualization module.ResultsAs we limited the maximum number of increments to 10, the job will exit with the error message, Error in job vessel: Too many increments needed to complete the step. Ignore the message and open vessel.odb in the Visualization module.4.Plot the deformed shape and contour the stress distribution in the specimen.Animate the response. Figure W7–9 shows the Mises stress at the end of the 10thincrement.When enriched elements are used and PHILSM is requested as an output variable, Abaqus/CAE automatically creates an isosurface named Crack_PHILSM where the value of the signed distance function is zero corresponding to the surface ofthe crack. This isosurface cut is turned on by default so that the crack is visibleupon opening the output database.5.Contour and animate the variable STATUSXFEM to visualize crack propagation.The last frame is shown in Figure W7–10. STATUSXFEM varies between 0 and 1, with 0 for elements where a crack has not initiated and 1 for elements that have cracked completely. This allows us to pin-point the crack location at any giventime and to assess the extent of failure in a particular region.Figure W7–9 Mises stress distribution in the pressure vesselFigure W7–10 STATUSXFEM showing progressive damage and failure6.Change the common plot options to display only the feature edges and contour theoutput variable PHILSM. This allows us to view the crack in the pressure vessel more clearly.a.From the toolbar click to open the Common Plot Options dialog box.b.Select Feature edges as shown in Figure W7–11 and click OK.c.In the field output toolbar choose PHILSM. The resulting contour plot nearthe cracked region is displayed in Figure W7–12.7.Make the assembly translucent to visualize internal crack surfaces.a.Click the Toggle Global Translucency icon to turn this feature on.b.Click the Translucency value icon next to . Abaqus/CAE displays aslider which can be used to set the translucency level. Adjust the slider untilthe crack surfaces can be seen clearly. Rotate the model for better clarity ifnecessary.c.Animate PHILSM to view crack propagation on the exterior as well as in theinterior. The last frame is shown in Figure W7–13.Figure W7–11 Changing common plot optionsW7–12 Contour plot of PHILSM near the nozzleW7–13 Contour plot of PHILSM with global translucency turned oning the View Cut Manager, it is possible to display the model on the cut,which in the case of an XFEM crack will show only the crack surface without the surrounding material.a.From the main menu bar, select Tools → View Cut → Manager.b.In the View Cut Manager that appears, toggle off for the cut namedCrack_PHILSM as shown in Figure W7–14. The resulting crack surface isdisplayed in the viewport. Figure W7–15 shows the crack surface without the surrounding material.Figure W7–14 The view cut managerFigure W7–15 The crack surfaceNote: A script that creates the complete model described in these instructions is available for your convenience. Run this script if you encounter difficulties following the instructions outlined here or if you wish to check your work.The script is namedws_press_vessel_xfem_answer.pyand is available using the Abaqus fetch utility.。

ABAQUS帮助

ABAQUS帮助初始损伤对应于材料开始退化，当应⼒或应变满⾜于定义的初始临界损伤准则，则此时退化开始。

Abaqus 的Damage for traction separation laws 中包括：Quade Damage、Maxe Damage、Quads Damage、Maxs Damage、Maxpe Damage、Maxps Damage 六种初始损伤准则，其中前四种⽤于⼀般复合材料分层模拟，后两种主要是在扩展有限元法模拟不连续体（⽐如crack 问题）问题时使⽤。

前四种对应于界⾯单元的含义如下：Maxe Damage 最⼤名义应变准则：Maxs Damage 最⼤名义应⼒准则：Quads Damage ⼆次名义应变准则：Quade Damage ⼆次名义应⼒准则最⼤主应⼒和最⼤主应变没有特定的联系，不同材料适⽤不同准则就像强度理论有最⼤应⼒理论和最⼤应变理论⼀样～ABAQUS帮助⽂档10.7.1 Modeling discontinuities as an enriched feature using the extended finite element method 看看⾥⾯有没有你想要的Defining damage evolution based on energy dissipated during the damage process根据损伤过程中消耗的能量定义损伤演变You can specify the fracture energy per unit area, , to be dissipated during the damage process directly.您可以指定每单位⾯积的断裂能量，在损坏过程中直接消散。

Instantaneous failure will occur if is specified as 0.瞬间失效将发⽣However, this choice is not recommended and should be used with care because it causes a sudden drop in the stress at the material point that can lead to dynamic instabilities.但是，不推荐这种选择，应谨慎使⽤，因为它会导致材料点的应⼒突然下降，从⽽导致动态不稳定。