连铸机外论文中英文对照资料外文翻译文献

中英文对照资料外文翻译文献
Effect of Porosity on Deformation, Damage,
and Fracture of Cast Steel
R.A. HARDIN and C. BECKERMANN
A combined experimental and computational study is performed to investigate the effect of
centerline shrinkage porosity on deformation, damage, and fracture of cast steel under tensile
testing. Steel plates containing shrinkage porosity are cast in sand molds, machined into test coupons, and tensile tested to fracture. The average volumetric porosity in the gage section of
the specimens with porosity ranges from 0.10 to 0.27 pct. Ductility in the test castings with porosity is markedly reduced with the percent elongation data ranging from 12.8 to 19.6 pct; vs
22 pct elongation for the sound material. Radiographic imaging is used to measure and reconstruct the porosity field in the test specimens. The reconstructed porosity field is then used
in a finite-element stress analysis simulating the tensile testing. Local elastic properties are reduced according to the porosity fraction present. Porous metal plasticity theory is used to model the damage due to porosity and the fracture. Good agreement is obtained between the
measured and predicted stress–strain curves and fracture behaviors. The reduction in ductility is
predicted well by comparing the measured and the simulated elongations. The computational
modeling approach used in this study allows for a detailed evaluation of the effect of porosity,
including its size, shape, and location, on the fracture behavior of steel castings.
DOI: 10.1007/s11661-013-1669-z
The Minerals, Metals & Materials Society and ASM International 2013
I.INTRODUCTION
STEEL castings are under-utilized because of uncertainties in their performance and lack of expertise in casting design. Discontinuities in castings, like porosity,play an important role in casting underutilization.Porosity creates uncertainty in a design’s robustness,since there are no methodologies for including its presence in the design. As a result, designers employ overly large safety factors to ensure reliability leading to heavier components than necessary. Contributing to the issue, the processes of designing and producing castings are usually uncoupled except for the specification of nondestructive evaluation (NDE) requirements. Unless mdesign
engineers have test data or experience for a part,they call for NDE requirements without knowing how this relates to part performance. By predicting porosity accurately from casting simulation and realistically modeling its effects on the part performance, engineers can develop robust designs that are tolerant of the porosity and reliable. In the current study, engineering approaches have been applied to simulate the effect of porosity on deformation, damage, and fracture for a cast steel during tensile testing, and the simulation
results are compared with measurements.The material used in this study is ASTM A216 Grade WCB steel. It is a cast carbon steel having a combination of good ductility and strength. It has the following chemical composition (maximum wt pct): C 0.3; Mn 1.0;P 0.035; S 0.035; Si 0.6; Cu 0.3; Ni 0.5; Cr 0.5; Mo 0.2;and V 0.03; and the total of Cu, Ni, Cr, Mo, and V cannot exceed 1.0 wt pct. At room temperature, Grade WCB steel has a yield strength and a tensile strength of 248 and 485 MPa, respectively, and 22 pct elongation as minimum tensile requirements in ASTM A216. Failure of such ductile metals occurs on the microscopic scale by mechanisms of void nucleation, growth, and coalescence.[1]Voids can pre-exist as microporosity and can also nucleate from imperfections like second-phase particles. After nucleation, voids grow with increasing hydrostatic stress and local plastic straining. As voids nucleate and grow, the void (or porosity) volume fraction increases. The voids begin to interact, and the porosity fraction at which interactions between voids begins is the critical porosity volume fraction fc. As plastic strain continues to increase, local necking and coalescence occur in the material between voids until a connected chain of voids forms and failure occurs. The porosity fraction at which fracture occurs is the failure porosity volume fraction fF. The effects of porosity on the structural performance of carbon and low alloy steel castings on the macroscopic scale are not as clearly defined as the y are on the microscopic scale. In previous studies, the effects of large amounts of porosity on stiffness and fatigue life were investigated.[2,3] Porosity less than a few percent does not result in a measurable loss of stiffness, or large stress concentrations, or stress redistribution, but itgreatly affects fatigue resistance.[4,5]Also, the presence of low-level porosity will reduce the ductility of metals since microvoids pre-exist before any stress is applied and the nucleation stage is bypassed. Porosity larger than a few percent in metals causes gross section loss,and locally reduces their effective stiffness.[6–8]This higher-level porosity is not uniformly distributed throughout the entire cast part, and the material properties in the casting are heterogeneous. As a result,stress redistribution occurs in parts because of macropores, and stress concentrations occur near them, which lead to localized plastic deformation and the development of microcracks causing failure. Generally speaking, the performance of a casting with macroporosity depends on the amount, size, and location of porosity relative to the cast component’s geometry and loading. All these factors must be considered together. Determining the effects of large levels of porosity on part ,performance is typically more case-by-case dependent than for lower levels It has been proposed that the stiffness and strength behaviors of porous materials can be categorized into three groups based on porosity amounts[9]: less than 10,10 through 70 pct, and materials
with greater than 70pct. This division is promoted because the materials at the extremes (<10, and>70 pct) behave quite differently.The highest porosity group is not applicable to cast steels; these are foams and cellular structures. The elastic–plastic behavior of porous materials in the 10,through 70 pct porosity range exhibit a nonlinear dependence on the amount of porosity[2,6–9]The behavior of materials in the lowest range demonstrate a more linear dependence on porosity amount, assuming that voids do not interact [10]and by considering isolatedpores,[11]or a uniform distribution of pores.[12]Applying the ductile failure micromechanical mechanisms described previously, one such micromechanics-based model is the porous metal plasticity model. It is av ailable in the finite element analysis (FEA) softwareABAQUS.[11–15]In the model, the volume fraction of porosity is a primary state variable, and the inelastic flow of the material is modeled as voids grow and coalesce at higher strains until failure occurs. Porous metal plasticity was developed assuming voids are spherical and grow as spheres. It also assumes the material’s plastic behavior is dependent on hydrostatic pressure because of the porosity, and therefore neglects effects of shear stresses on porous material behavior. Considering this and the limitations of porous metal plasticity, there have been numerous developments in modeling of ductile fracture[16] ]addressing other void geometries and stress states. While not state-of-the-art, porous metal plasticity is a constitutive model readily available to designers of cast components, and can be a useful tool to investigate the effect of porosity on a casting’s fracture behavior. It is a common constitutive model found in many commercial finite element pack ages. This article uses the porous metal plasticity model in FEA to predict the ductile fracture of cast steel with centerline porosity. The primary goal of the current study tests whether or not this commonly available model can predict the fracture of steel with relativelylarge amounts of porosity detectable through typical industrial radiography.
Here, castings with porosity were produced, made into plate specimens, and radiographed. The porosity was quantitatively determined from the radiographs. The castings underwent tensile testing. Using porosity data from the radiographs, finite element stress models of the test specimens with porosity were created, and the tensile testing simulated using an elastic–plastic material model. Results of the simulated fracture are compared here with the measured fracture to test the model’s capabilities in predicting the fracture behavior of steelwith centerline shrinkage porosity
II. MATERIAL PREPARATION,
MEASUREMENT, AND ANALYSIS
A.Cast Specimens and Mechanical Testing
For the tensile fracture study presented in this article,WCB steel specimens were produced from 2.5 cm thick 9 12.7 cm wide vertically cast plates of two lengths (38.1 cm and 45.7 cm) as shown in Figure 1(a). The plates were designed through casting simulation with MAGMAsoft
[17]to contain centerline shrinkage as shown in Figures 1(b) and (c). Five cast plates were produced and tested from the longer length castings, and four were produced and tested for the shorter-length castings. The letters ‘‘D’’ and ‘‘E’’ were used to identify the shorter
and longer plates, respectively; followed by numbers 1 through 5. The cast plates were normalized and tempered, and machined into 19-mm-thick tensile test coupons with a gage section width of 86 mm as shown in the front and side views for the specimen in Figure 2(a). The tensile specimen dimensions for the plates with centerline porosity were determined from the ASTM E8 tensile test standard.[18] The positioning of the extensometer on the narrow/thickness face of the specimen is indicated in Figure 2(a). In Figure 2(b), a smaller tensile test specimen is shown, which was machined from the porosity-free (or‘‘sound’’) section of a cast plate. The specimen shown in Figure 2(b) was tested to characterize the steel’s fr acture behavior in the absence of porosity. The sound steel specimen was taken from the top end of the plate, and its dimensions shown in front and end views in Figure 2(b) were taken from ASTMM E8. Parameters in the porous metal plasticity model were determined by achieving good agreement between the measured and predicted sound steel tensile curves. Tensile testing of the sound material was performed at the University of Iowa, and the steel plates with porosity were tested at the SSAB Americas Montpelier, Iowa Steelworks. Examining the fracture surfaces of the plates with porosity, the porosity was found to lie about the mid-thickness of the plates as expected from centerline porosity
B. Radiographic Porosity Measurement, Testing,
and Fracture Analysis of the Specimens
Film radiography was performed on the as-cast plates at the foundry where they were produced. All plateswere found to contain shrinkage porosity of levels 4 or 5 according to the radiographic testing standard ASTM E446.[19]In the standard, le vel 5 signifies the worst levelof porosity defect, and level 1 signifies the least defective. Since the cast plates had porosity of levels 4 or 5, they would typically be scrapped at the foundry. Aftermachining and before testing, digital radiographs of the plate tensile test coupons with centerline shrinkage and the sound specimen were taken at 16-bit gray scale and 10 pixels per mm at Alloyweld Inspection Co. in Bensenville, Illinois. The radiograph of the sound specimen was free of any indications of shrinkage or other defects. Stepped gage blocks were placed in the radiographs of the plate specimens with centerline shrinkage as shown in Figure 3(a). Using the gage blocks and image analysis, a calibration curve of radiographic gray level vs plate thickness was determined for each radiograph. All curves were found to be within the same margin of error, but the individual radiograph calibration curves were used in analyzing the porosity level in the plates. Filtering and background corrections were performed, and only indications identified by image analysis were analyzed for porosity level as seen Figure 3(b). The thickness of the steel, as shown in Figure 3(c), was determined from the gray level vs thickness calibration curve. Finally, the measured porosity fraction through the plate thickness at each pixel of the radiograph was calculated by dividing the thickness of steel measured from the radiograph by the nominal machined plate thickness tplate (19.1 mm) which is shown in Figure 3(d). Given the radiography equipment used, and the image analysis, the detectable threshold porosity fraction for the current study was estimated to be 1.5 pct. A radiograph for the specimen D3 is shown in Figure 4(a), where the fracture region is indicated by the area in the box. The fracture region on the radiograph was determined from the fractured specimen by measuring from the gripped plate ends and using punch marks made before testing on the
narrow/edge faces of the specimens. A box is used to identify the fracture region due to the irregularity of thefracture surface and the uncertainty in the measurements. Since the tensile testing force was applied along in the length direction of the specimen, the cross section porosity normal to the force was determined as plotted in Figure 4(b) along the specimen length. Note here that positive distances are above the plate mid-length and negative values below. The overall average porosity in the gage section of each test plate was determined by averaging all the pixel measurements within the gage section, and as indicated in Figure 4(b) it is about 0.19 pct for specimen D3. The maximum cross section porosity for specimen D3 in Figure 4(b) is seen to be about 0.8 pct, and it falls within the observed fracture region along the length. For specimen D3, the fracture region is seen to correspond with a region of relatively high cross sectional porosity along the gage length, and this correspondence was observed in the other specimens as well. As shown in Figure 5, the average gage section porosity for all specimens was determined, ranging from 0.07 to 0.23 pct. The tensile testing results for the sound WCB steel and the steel containing centerline porosity are shown in Figure 6. Note the sound material has the greatest elongation at fracture. The ‘‘D’’ centerline shrinkage porosity specimens (the shorter-length plates) generally have greater elongations than the ‘‘E’’ family of plates, but the most ductile of the plates with porosity was plate E1. In addition, the tensile curve for plate E1 appears quite different from the other curves and has much lower yield and ultimate strengths. Unfortunately, X-ray tomography was not performed on the steel specimens because of their relatively large size. Because of this, an assumption about how the porosity measured from the radiographs was distributed through the plate thickness had to be made. Regionswith porosity on the fracture surfaces of the specimens were examined and measured to establish a reasonable assumption for the distribution of porosity in the plates. An example of a fracture surface having a region of porosity is shown in Figure 7(a), where the porosity appears to be centerline type located near the midthickness of the plate. Measurements of the thickness ofthe porosity regions were performed on the fracture surfaces to determine a reasonable thickness of porosity to use in simulating fracture of the plates. Since these regions lie on the fracture surface, they are representative of the porosity that determines the fracture behavior of the specimen. For a given region with porosity on the fracture surface, the maximum thickness dimensiontregion of a given region of porosity was measured as shown for example in Figure 7(a). A frequency histogram of the fraction of plate thickness data corresponding to the tregion measurements is shown in Figure 7(b). Note that eight regions of porosity were found to fall into both the 20 to 25 pct, and the 40 to 45 pct, ranges of fraction of plate thickness. These measurements do not appear the follow a normal distribution. In Figure 7(b), the average tregion for all the fracture surface regions with porosity is indicated at 33 pct of the plate thickness. However, note that the bin range for the average contains relatively few observations, and might not be the best choice as a representative thickness dimension for the centerline porosity. A constant thickness of centerline porosity was assumed when reconstructing the porosity in the simulated plates. For this constant thickness, the average fraction of plate thickness with porosity from Figure 7(b) was used as a starting point in comparing predicted and measured tensile curves to establish a simulated centerline porosity thickness that would produce the best agreement. Iterative
trial and error simulations were performed, varying the thickness of the simulated porosity region until the best combined agreement between measured and predicted tensile curves was found. Specimens D4 and E4 (representing the smallest measured elongation), and specimens D3 and D5 (representing the largest measured elongation) were used in these comparisons. The fracture behavior of specimen E1, which has the greatest elongation of the plates with porosity, appeared anomalous and was not used to establish the thickness of the porosity region. After these trial and error comparisons, a centerline region with porosity having 25 pct of the plate thicknesswas found to give the best overall agreement between the measured and predicted fracture behavior for the plates.
C. Mapping of Measured Porosity onto Stress Analysis
Mesh
Finite element meshes of the tensile test plates were developed with mesh refinement at the plate midthickness to better resolve the centerline porosity as shown in Figure 8(a). The extensometer position during testing is shown in Figure 8(a). The edge of the plate where the extensometer was positioned during testing, relative to the porosity distribution in the plate, was carefully followed because of the nonuniform straining of the plate. FEA of the test plate specimens with porosity required development of a method to transfer the through-section porosity measurements determined from the radiographs onto the nodes of the FEA mesh. The porosity from the radiograph (Figure 3(d)) was mapped to the mesh assuming that it lies symmetrically about the mid-thickness of the plate in a region 25 pct of the plate thickness. A computer code was written to transfer the measurements from the radiographs to the FEA nodes where the average porosity about a nodal position in the plane of the radiograph is determined, conserving porosity. The averaging volume used about each node had dimensions of half the nodal spacing. Since this averaged porosity mapped to the FEA nodes is assumed to lie in a region 25 pct of the plate thickness, it must be scaled up by a factor (0.25) 11 from the averaged values determined from the radiograph, where it is distributed through the entire plate thickness. Once ,the averaged/scaled-up porosity was determined at a nodal position, it was mapped to all nodes within the region centered at the plate mid-thickness. An example of the porosity mapping is shown for a simulated test plate on the mid-thickness plane and for a slice through the plate thickness in Figure 8(b). Comparing the porosity determined from the radiograph in Figure 3(d) to the centerline region of Figure 8(b), the porosity at the FEA nodes are diffused (caused by the averaging process about the nodes) and then amplified (due to the scaling-up at the centerline region).
CONCLUSIONS
The current study demonstrates that the tensile fracture of cast steel with porosity can be predicted from industrial radiographs using a porous metal
plasticity material model commonly implemented in FEA software. Nine model
material parameters were determined for sound WCB steel from its tensile
curve. ,Using these model parameters and porosity fields mapped from the
radiographs of the test specimens to nodes of FEA models, the tensile test
curves for the castings with centerline porosity were simulated. Predicted and
measured tensile curves compared well, andthe measured and predicted
elongation comparisons were also good. The most noticeable effect of porosity
in cast steel is reduction in ductility, and the model predicted it well. It is difficult to make general statements about the effect of porosity on fracture behavior, since it has been demonstrated here that its effects are dependent on the porosity distribution relative to the load. For the seemingly small amounts of porosity shown here, where the average volumetric porosities in the gage sections of the specimens ranged from 0.10 to 0.27 pct, the ductility in the test castings with porosity is markedly reduced with the percent elongation dataranging from 12.8 to 19.6 pct vs 22 pct elongation for the sound material. This range of ductility behavior is due to the differing porosity distributions in the specimens. The current study demonstrates that the effect of porosity on ductility and fracture behaviors can be predicted provided that a reasonably accurate porosity field is used in the simulations. Some disagreement still remains between prediction and measurement. The clearest factors contributing to the disagreement are ascribed to assumptions and limitations in the porous metal plasticity model, and the assumptions and deficiencies in determining how the porosity was distributed through the thickness of the plate specimens. The current study can be improved by more realistically reconstructing the porosity distribution through the plate thickness via tomography, for example. In addition to improving the fidelity of the measured porosity distributions, the authors plan to investigate whether porosity distributions predicted from casting simulation can be used in place of measured porosity distributions to accurately model
the mechanical performance of castings.
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孔隙率对变形的影响,伤害,和断裂的铸钢
哈丁
中心线收缩孔隙度在变形、损伤、断裂的铸钢在拉伸测试。

钢板含有收缩孔隙度是在砂铸模具、机加工到测试优惠券、拉伸测试,以断裂。

平均体积孔隙度在计部分标本与孔隙度范围从0.10到0.27。

在测试铸件的延性孔隙度明显下降的百分比伸长数据从12.8到19.6;vs22 pct对声音材料伸长。

射线成像是用来测量和重构孔隙度场在测试标本。

重建的孔隙度场然后使用在有限元应力分析模拟拉伸试验。

局部弹性属性减少根据孔隙度分数呈现。

多孔金属塑性理论用于模型造成的损失,孔隙和裂缝。

良好的协议之间的获得测量和预测的应力-应变曲线和断裂行为。

延性下降预测井通过比较测量和模拟elongations。

计算本研究中使用的建模方法允许一个详细的效应评价孔隙度,包括其大小、形状和位置,在断裂行为钢铸件。

DOI:10.1007 / s11661 - 013 - 1669 - z矿物、金属与材料协会和ASM国际2013即介绍钢铸件未因为不确定性在他们的性能和缺乏专业的铸造设计。

不连续的铸件,如孔隙度、发挥重要作用在铸造未充分利用。

孔隙度产生了不确定性在设计的鲁棒性,因为没有方法,包括它的存在在设计。

因此,设计师采用过大的安全因素,确保可靠性导致重比必要组件。

导致这个问题,流程的设计和生产铸件通常分开除了规范的无损评价(NDE)需求。

除非mdesign工程师有测试数据或经验的一部分,他们呼吁NDE需求不知道如何与部分性能。

通过预测孔隙度准确地从铸造模拟和实际建模其影响部分性能,工程师可以开发健壮的设计,是宽容的孔隙度和可靠的。

在目前的研究中,工程方法应用于模拟孔隙度的影响在变形、损伤、断裂为铸钢在拉伸测试和仿真结果与测量。

本研究中使用的材料是ASTM A216年级WCB钢。

这是一个铸造碳钢有良好的延性和强度相结合。

它具有以下的化学成分(最大重量pct):C 0.3;锰1.0;P 0.035;0.035;0.6;S硅铜0.3;0.5;0.5;镍铬钼0.2;和V 0.03,总铜、镍、铬、钼、V不能超过1.0 wt pct。

在室温下,钢有年级WCB屈服强度和抗拉强度的248和485 MPa,分别和22 pct伸长最小拉力要求A216美国ASTM标准。

失败这样的韧性金属发生在微观尺度的机制空隙的成核、生长、聚结。

[1]作为显微疏松和孔洞可以出现也可以从像第二相颗粒成核缺陷。

在成核、生长和增加流体静应力空隙和局部塑性应变。

作为空洞成核和生长,空白(或孔隙度)体积分数增加。

这些空洞开始互动,和孔隙度分数在孔隙之间的交互开始是关键的孔隙体积分数fc。

作为塑性应变不断增加,局部颈缩及合并发生在材料的空隙之间,直到连接链的空洞形式和发生故障。

的孔隙度分数,骨折是失败孔隙度体积分数fF。

孔隙度的影响在结构性能的碳和低合金钢铸件的宏观尺度并不清楚地定义为它们在微观尺度。

在以前的研究的影响,大量的孔隙率对刚度和疲劳寿命进行了调查。

[2、3]孔隙度小于百分之几不会导致一个可衡量的损失,或者大的刚度应力集中或应力重分布,但itgreatly抗疲劳的影响。

[4,5]同时,存在低级孔隙度将降低延性金属微孔以来出现在任何压力是应用和成核阶段是绕过。

孔隙度大于几个百分点在金属引起总截面损失,降低了他们在本地有效刚度。

(6 - 8]这种高层次的孔隙度不是均匀分布在整个铸造部件,材料性能的铸件是异构的。

因此,应力再分配发生在部分因为macropores,应力集中发生在他们附近,导致局部塑性变形和微裂隙的发展导致失败。

一般来说,性能的铸件和大孔隙度取决于数量、大小和位置的孔隙度相对于铸造组件的几何和载荷。

所有这些因素必须被考虑在一起。

确定影响大级别的孔隙度部分,性能通常是更多比低水平的依赖个案已建议刚度和强度的多孔材料的行为可以分为三组基于孔隙数量[9]:不到10、10到70年pct、材料与大于70。

这个部门是提升,原因是材料在极端的情况下(< 10,> 70)表现得完全不同。

最高的孔隙度集团并不适用于铸造钢;这些都是泡沫和细胞结构。

多孔材料的弹塑性行为在10到70年pct孔隙度范围表现出非线性依赖数量的孔隙度[2,6 - 9]材料的行为在最低范围展示一个更线性依赖孔隙数量,假设孔隙不互动[10],通过考虑isolatedpores,[11]或一个均匀分布的孔。

[12]应用塑性细观机制失败,这样前面描述的基于微观力学模型是多孔金属塑性模型。

它可以在有限元分析(FEA)softwareABAQUS。

(11 - 15)在模型中,体积分数的孔隙度是一个初级状态变量和非弹性流的材料被建模为空洞生长和合并在更高的压力,直到故障出现。

多孔金属塑性是发达假设孔隙是球形,并成长为球体。

它还假定材料的塑性行为是依赖于静水压力由于孔隙度,因此忽略剪切应力的影响在多孔材料的行为。

考虑到这和多孔金属塑性的局限性,有大量的发展在建模中韧性断裂[16]]解决其他空白的几何形状和应力状态。

虽然不是最先进的,多孔金属塑性本构模型是一个容易为设计者的铸造组件,可以是一个有用的工具来研究孔隙度的影响在一个铸造的断裂行为。

它是一种常见的本构模型,发现在许多商业有限元软件包。

本文使用多孔金属塑性模型在有限元分析来预测韧性断裂的铸钢与中心线孔隙度。

的主要目标当前的研究测试是否这种常用的模型可以预测钢的断裂与relativelylarge大量的孔隙度检测通过典型工业射线照相。

在这里,铸件与孔隙度被生产出来,制成板标本,和射线透照。

的孔隙度进行了定量确定射线照片。

铸件进行了拉伸试验。

利用孔隙度数据从片、有限元应力模型的测试标本与孔隙度出现,和拉伸试验模拟使用弹塑性材料模型。

结果模拟裂缝比较来测量裂缝测试模型的功能在预测断裂行为steelwith中心线收缩孔隙度
材料制备,测量和分析
a .铸标本和机械测试
对拉伸断口进行研究本文中给出,WCB钢试样的生产从2.5厘米宽12.7厘米厚9投板的垂直两个长度(38.1厘米和45.7厘米)如图1所示(一个)。

盘子被设计通过铸造模拟MAGMAsoft[17]包含中心线收缩如图1(b)和(c)。

五投板制造和测试从长的长度,和四个生产铸件,铸件的测试长度缩短。

字母“D”和“E”被用来识别短和长板,分别地;其次是数字1到5。

演员盘子是正火加回火,加工成19毫米厚的拉伸试验与计部分优惠券宽度86毫米见前面和侧面视图的标本在图2(一个)。

拉伸试样尺寸的板中心线孔隙度确定从ASTM E8拉伸试验标准。

[18]的定位伸长计在狭窄的/厚度面对标本显示在图2(一个)。

在图2(b),一个较小的拉伸试样显示,这是加工从孔隙度自由(或“声音”)段铸板。

样品如图2(b)进行了测试表征钢的断裂行为缺乏孔隙度。

声音是从钢试样的顶端板,其尺寸显示在前和结束的观点在图2(b)来自ASTMM E8。

参数的多孔金属塑性模型,确定了实现良好之间的协议测量和预测声音钢拉伸曲线。

拉伸测试声音的材料进行了爱荷华大学的,钢板与孔隙度进行了测试在美洲,爱荷华州SSAB蒙彼利埃炼钢厂。

检查裂缝表面板块的孔隙度,孔隙度被发现说谎的板块的中部厚度如预期从中心线孔隙度
b .影像学孔隙度测量、测试、和断裂分析的标本
电影摄影进行了铸态板铸造他们生产。

所有plateswere发现含有收缩孔隙度的水平4或5根据射线检测E446 ASTM标准。

[19]5级标准,意味着最糟糕的levelof孔隙缺陷,1级表示最小的缺陷。

自铸板有孔隙度的水平4或5,他们通常被废弃在铸造。

Aftermachining和在测试之前,数字片板的拉伸测试优惠券与中心线收缩和声音的标本被在16位灰度和10像素每毫米在Alloyweld检验公司在Bensenville,伊利诺斯州。

声音的x光照片的样品是完全免费的,没有任何迹象表明,收缩或其他缺陷。

加强规块被放置在板片标本与中心线收缩如图3(一个)。

使用计模块和图像分析,校准曲线的射线照相灰度vs板厚度确定每个x光照片。

所有的曲线被发现是在相同的误差幅度,但个人x光照片校正曲线被用于分析孔隙度水平的盘子。

过滤和背景进行了修正,只有迹象识别图像分析来分析孔隙度水平见图3(b)。

钢板厚度的,如图3(c),决心从灰度vs厚度校正曲线。

最后,实测孔隙度分数通过板厚度在每个像素的x光照片是除以测量厚度的钢从x光照片的名义加工板厚度tplate(19.1毫米)如图3所示(d)。

考虑到摄影设备使用,和图像分析,可检测阈值为当前研究孔隙度分数大约在1.5。

一个x光照片的标本D3如图4(A),骨折区域的面积来表示在盒子里。

骨折区域的x光照片决心从断裂的试样,测量从抓住板结束和使用穿孔标志在测试之前在狭窄的/边缘的面孔标本。

一个盒子是用来识别断裂区域由于不规则的thefracture表面和不确定性测量。

因为拉伸试验力沿长度方向的应用的标本,截面孔隙度正常的力被确定为绘制在图4(b)沿试样长度。

这里需要注意的是,积极的距离是高于板中长和负价值低于。

总体平均孔隙度在计部分的每个测试板是由平均所有的像素测量在计部分,显示在图4(b)它是关于0.19的标本D3。

最大截面孔隙度为标本D3在图4(b)被认为是大约0.8,它属于观察骨折区沿长度。

对标本D3,断裂区被认为与一个地区的相对高截面孔隙度在标距长度,这对应出现在其他标本一样。

如图5,平均计部分孔隙度确定所有标本,从0.07到0.23,拉伸试验结果的钢铁和钢铁声音WCB包含中心线孔隙度是图6所示。

注意声音的材料最大的断裂延伸率。

“D”中心线收缩孔隙度标本(短长度板块)通常有更大的elongations比“E”。