A Study on Strength Evaluation using Plastic Constitutive Rule of Porous Material

将有限元法应用于多孔材料的分析。数值计算采用四种不同的塑性本构规则，如Gurson规则，Tvergaard的Gurson规则的修改，Goya-Ngaki-Soerby规则和基于体视学的规则，是一个修改的Goya-Ngaki-Soerby规则。为了验证规则的有效性，将数值计算结果与放电等离子烧结法制备的多孔材料的实验数据进行了比较，结果表明放电等离子烧结法制备的多孔材料具有较高的孔隙率。从比较得出的结论是，使用Tvergaard的Gurson规则的修改或基于体视学的修改得到的数值结果可以预测的实验结果。然而，对于孔隙率较高的多孔材料，数值计算结果与实验数据有偏差。接下来，固态焊接方法在大气条件下通过使用金属粉末介质来应用，所述金属粉末介质插入在两个固体棒的试样（即，基底金属）之间的空间中，并且纵向压缩，同时传导电流以产生焦耳热。通过电阻焊试验，获得了接头力学性能和冶金性能的一些基础数据。试验中，基体金属采用纯铝合金棒，粉末介质采用镍粉。通过金相显微镜、扫描电镜、X射线能谱仪、X射线衍射仪、抗拉强度、维氏硬度和弯曲U型弯曲试验等手段对试样进行观察、分析和评价。

The Finite Element Method was applied to the analysis of porous materials. The numerical calculation was performed using four different plastic constitutive rules such as Gurson's rule, Tvergaard's modification of Gurson's rule, Goya-Ngaki-Soerby's rule and a stereology-based rule that was a modification of Goya-Ngaki-Soerby's rule. For the investigation of the validity of the rules, the numerical results were compared with experimental data for the porous materials produced by Spark Plasma Sintering method that could product porous materials of higher porosity. From the comparison it was concluded that the numerical results obtained using Tvergaard's modification of Gurson's rule or the stereology-based modification could predict the experimental results. However, the numerical results deviate from the experimental data for the porous material of higher porosity. Next, the solid-state welding method was applied under atmospheric conditions by using metal powder medium that was interposed in the space between the two solid bars of specimen (i.e. base metal), and was compressed longitudinally and simultaneously current was conducted to generate Joule thermal heat. Some fundamental data on the mechanical and metallurgical properties of the joint were obtained by using resistance welding. In the experimental, the base metal was used pure aluminum bar and the powder media was nickel powder. The experimental data were obtained with the intent of optimizing the method using powder medium between a pair solid sample specimen and observation, analysis and assessment were made with microscope, Scanning Electron Microscope, Energy Dispersive X-ray spectroscopy, X-ray Diffraction, tensile strength, Vickers hardness and bending U-shape flexure tests.