有限元分析结果理解（Finite...

有限元分析结果理解（Finite element analysis results are
understood）
Structure Analysis in many aspects, such as: physical, molecules, structure, etc. (the SA method is Structured Analysis, Structured Analysis), it is a typical data flow oriented Analysis method. Because of its simple, which can be achieved through the method of manual, can also be applied to automatic and semi-automatic analytical tools, so it is widely used in the development of medium and small system. In SA phase, there are two: the basic means for decomposition and abstraction. Its task is to input data into output data in the system of the processing procedure. The SA USES "top-down, decompose step by step", the method to analyze problems.)
Load: is that an object or molecules can bear the weight of the largest, (usually refers to in the design of machinery applied to mechanical or structural force; usually refers to the power needed to complete the work in the machinery; it refers to the electrical devices or components in electrical engineering from the power source of power. In addition, sometimes also can put some mechanical structure internal force caused by factors other than mechanical called load.)
Displacement: in the coordinate system (0, 0) as the reference point, any orientation of the movement. It could be a line, a distance
Stress: additional internal force on unit area, with positive stress and shear stress.
Strain: when the force of the object is deformed, the deformation degree of the body is generally different. The amount of mechanics used to describe a degree of deformation is the strain at that point. For this purpose, a cell can be found at that point, and the size and shape of the cells are changed before and after the deformation. The strain is the relative deformation of the object caused by the load, temperature and humidity. Main cable strain and shear strain two kinds.
Ask: after question on cosmosworks analysis results of the analysis, the safety factor of the display, such as: 15.153 the book explain safety coefficient, is the theory of the material yield limit and the ratio of the actual stress, so I understand: the safety coefficient, the greater the structure more security! But the results show that the structure has been deformed and sometimes deformed. What is the safety factor? If it is explained as the safety of the analysis results, but the structure has been deformed, the deformation structure should be unsafe and a little contradictory, I hope you will be able to give me a point and I will pay attention online
In fact, the generation of deformation is not necessarily unsafe, the simplest case, the spring force is stretched or compressed, as long as the bearing range is safe! In the field of material mechanics, all materials are elastic (elastic modulus E), which is in accordance with hooke's law, that is, force is proportional to the variation of deformation (displacement). In general, elastic deformation (force disappears, deformation recovery) is a safe plastic deformation occurred (force disappears, irreversible
deformation) is not safety note: the above refers to the general situation, sometimes deliberately in the structural design of a parts or components to produce plastic deformation and meet certain use purpose!
The second floor is good
The safety factor is less than 1 and can be destroyed by the failure of the strength failure
For example, if you can lift a 100 kg person up the waist may be bent but the bone is constantly
In mechanical design, materials have yield strength and tensile strength, often used in plastic materials and brittle materials.
Divide the yield strength or tensile strength by the safety factor and then the allowable stress of the material. , for example, usually use the bolt is 8.8, the yield strength = 640 mpa, inherit the shear force, if safety factor S is 5, the allowable shearing stress is 640/5 = 128 mpa, namely the bolt the actual maximum shear stress must be within 128 mpa; Why take the safety factor? This is because there are many factors to consider, such as material defects, ambient temperature, fatigue damage, etc. Different components usually take different safety coefficients, but the purpose is to ensure the safety and reliability of the parts in actual use. Personal learning experience, for reference only!
Those deformations may be the result of amplification just to
make intuitive sense
The view on the sixth floor is exquisite
The safety factor cannot be less than 1, but it is not better than the greater the safety coefficient, and the economy should be considered at the same time in meeting its design requirements
Generally large welding safety factor, such as crane frame
When we calculate the large welding frame, the safety factor is theoretically placed at 1.6-1.8, which is not too much cost and can guarantee the strength of the use.
The safety coefficient of the welder is larger than that of cast steel, more than 1.5
To illustrate the understand the upstairs On many occasions is judged according to the tensile strength of watching your product use in what occasion If allowed to trace the occasion of deformation is safe But if it comes to the seal if there is no trace of deformation occasions such as the actual stress intensity is greater than the elastic limit that will definitely happen leakage and other problems There are some other materials in the relatively poor working conditions of brittle failure
Quote: the fifth floor ulww reference published in the
2007-12-07 struck: in terms of mechanical design, material yield strength and tensile strength, they can be used for
plastic material and brittle material, the yield strength or tensile strength divided by the safety factor is the allowable stress of material. , for example, usually use the bolt is 8.8, the yield strength = 640 mpa, inherit the shear force, if safety factor S is 5, the allowable shearing stress is 640/5 = 128 mpa, namely the bolt the actual maximum shear stress must be within 128 mpa; Why take the safety factor? This is because there are many factors to consider, such as material defects, ambient temperature, fatigue damage, etc. Different components usually take different safety coefficients, but the purpose is to ensure the safety and reliability of the parts in actual use. Personal learning experience, for reference only! The top... I've seen it.
I would like to ask. How is the safety factor taken
People this is connector design, for the life of the terminal and deformation should be considered. So himself in self-study COSMOS, analysis of the COSMOS is not very good. So ask safety factor is how to take, I am a technical secondary school culture... I'm sorry...
All of this is true, but I have improved the structure. How can the safety factor be improved
When we calculated the large welding frame, the safety factor was put in 1.6-1.8.
This is not too much of a cost increase, but it can also be used to ensure the intensity of use. According to my experience strength enough stiffness is not enough to consider this
situation
Quote: 15th floor zcforange reference published in the
2007-12-29 strip: this is people make connector design, for the life of the terminal and deformation should be considered. So I am in the COSMOS, the analysis of the COSMOS is not very good. So ask safety factor is how to take, I am a technical secondary school culture... I'm sorry... The basic element of the finite element is to understand the discrete grid partition of the stiffness matrix and so on
The analysis of COSMOS is sometimes incorrect, especially unstable, and it's best to check it with ANSYS.
Safety should be subject to professional requirements
Quote: the 19th floor chliang reference published in the 2008-04-04 time, the analysis results of COSMOS, sometimes is not correct, particularly unstable, best can verify together with ANSYS. ANSYS is truth? Finite element is just a tool for COSMOS analysis not to come out from my experience as ANSYS not line! ` ANYS as out of things inside the COSMOS is the same way and same [this post was back in the 2008-04-05 struck by the magic ii editor]
COSMOS2008 according to my experience with the much better, I don't mean to compare to them. Don't get me wrong upstairs. But does appear to be a plausible. ANSYS COSMOS2006 to something, you do 10 times, there may be several different, have time more. The fact that even?
Quote: 22nd floor chliang reference published in the 2008-04-05 20:51: according to the experience of himself and COSMOS2008 is much better, I don't mean to compare to them. Don't get me wrong upstairs. But does appear to be a plausible. ANSYS COSMOS2006 done something, you do 10 times, there may be several different, have time more. The fact that even? The assembly is accidentally or intentionally changed some conditions as long as no penetration to the surface to surface it is possible to produce different effect of translational meshing density Or a connection form of beam grid has a different Could be different in COSMOS too intuitive Settings is a fool Some of these changes, intentionally or not, change the question for you I were identified for the first 2 months this year more than 1000 groups of similar analysis Have a little experience, of course, I use a lot about the '07 ansys to manually input is not easy to change when not exactly the same results To see if everything is the same as I completely unfamiliar road pavement in order to follow the traditional ANSYS analysis the battle is civil professionals obtain correct results, analyzing the various constantly check the boundary conditions constantly check the grid division,
Added a lot of roads for this professional knowledge will finally completely brought all the people of the civil engineering laboratory When I was a mechanical personnel to dry before how much these ridiculous is all some car suspension bracket type of analysis is the friend lifts as civil experts All there is to use ANSYS before my first brought into the COSMOS, I use the surface ability to solve the problem of their former processing A fly is known as the big gun Civil people to build a slightly more complex geometric model analysis in the UG, but
seldom learn Isn't the necessary SW will be enough and I'm a civil engineering doctoral student Its master's and undergraduate course is mechanical professional his doctoral thesis is according to the result of dynamics analysis of the vehicle on the road as the equivalent of the nonlinear load make out the results of the analysis is his mentor program of national natural fund with a master's thesis as a foreshadowing his doctoral thesis But he has been proved that is without any innovation entity unit doesn't come out The road use plate unit was not reasonable Even entity unit model I still have not seen a reasonable finite element model of the road is so many papers on the Internet Including some professors based on ANSYS analysis results of books have been I overturned In addition there is a problem is mechanical problems Some professors also cannot solve Is eight meters in length of the road surface tensile stress is one of the biggest had long been short of small some specific reasons I haven't understood
/read.php? welcome to comment out the subject Tid = 531651, my advice to him: to unify with MSC series of ADAMS software for the dynamic simulation of finite element software ANSYS connection with another company is good to be a problem It is better to COSMOS Connection to prepare Another thing to improve even more Boundary conditions including And the equivalent equation of nonlinear Especially the viscosity equation of nonlinear dynamic with linear static often 2 yards matter must avoid stress concentration caused by sharp corners Some even said grid too close cause stress concentration I can't agree at the same time I had a light rail vehicles, by the way /read.php? frame optimization design and out of the subject Tid = 513832 I am 26 years old and I welcome more criticism. [this post is reedited by devil ii in
2008-04-06 02:55]
另外提示一下模态分析不是万能工具机械出现了非常的振动的问题有可能机械本身结构不合理造成的未必就是因为共振振动理论本身就是一个大学问一般来说钢丝抖动最好先怀疑结构的问题钢丝抖动是个是普遍的问题本人致力能总结出一个通用的解决方案以替代笼统的经验公式不必太迷信专家书本任何人的知识都是有限的例如机器人来说特型机器人的设计能否成功要理论与经验并重才能设计成功目前有些硕士论文是分析某种车架的特性在下看来意思不大并且很少能提出多少通用的方案的其实分析过多种总结出通用改进的方法才是方法但是起码是博士到博士后的研究任务了如果想搞出一些实际的东西的话我目前还没有时间专门攻那个但是对车架我还是有一定的经验的我认识一个博士兼教授他的博士论文作的石油井喷还是有一定意义的我以前搞过一个概念的太阳能电冰箱用的是SW 曲面巨无霸CATIA我的水平相当肤浅只会建立一些基本的模型汽车A级曲面至今不会建立惭愧有限元只是我使用的多种工具之一用的并不太好加之年纪所限并且还要兼顾CAD任务还要兼顾工程机械的改进致力对土木的分析致力于对高级曲面的钻研因为车辆特别是电动车的建模要用 PROE我会一些要是想跟我讨论PROE或者CAXA也可以一定有不当之出欢迎能手批评指导[ 此贴被魔二世在2008-04-06 03:36重新编辑 ]
I also learn mechanical, but did not have car, can't disorderly speak. Very admire of knowledge in this field for upstairs. I to the SW and upstairs opinion, a good thing, although there are a lot of people say it is inferior to PRO/E, I don't think so. The finite element is a good tool, learning more difficult to master.
Quote: 25th floor chliang reference published in the 2008-04-06 20:08: I also am learning mechanical, but did not have car,
can't disorderly speak. Very admire of knowledge in this field for upstairs. I to the SW and upstairs opinion, a good thing, although there are a lot of people say it is inferior to PRO/E, I don't think so. The finite element is a good tool, learning more difficult to master. General machinery I also make some civil will mainly use the SW + COSMOS So if the original poster out some mechanical it's convenient for example I could read, please upload to discuss finite element to the accumulation of experience A solid basis of knowledge of and to [in the space of 2008-04-06 to edit this post is the magic ii]
The deformation does not necessarily exceed the yield limit, and may be in the elastic range for reference.
According to the design of the reasonable choice of safety factor, is the deformation large in software or in practice? Should pay attention to the size of the absolute value. The above mentioned problem of bolt, the bolt is divided into two kinds, a kind of call friction model, a direct tensile. The allowable stress of two kinds of different. Remind everyone. See < steel structure design code >
Taught
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