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

将有限元方法应用于多孔材料的分析。数值计算采用了Gurson准则、Tvergaard修正的Gurson准则、Goya-Ngaki-Soerby准则和基于体视学的修正Goya-Ngaki-Soerby准则四种不同的塑性本构关系。为了验证规则的有效性，对放电等离子烧结法制备的多孔材料进行了数值模拟，并与实验数据进行了比较。结果表明，用Tvergaard对Gurson规则的修正或基于体视学的修正所得到的数值结果可以预测实验结果。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存在较大偏差。其次，在大气条件下采用固态焊接方法，将金属粉末介质插入试件的两根实心棒(即母材)之间，纵向压缩，同时传导电流产生焦耳热热。利用电阻焊获得了接头力学性能和冶金性能的一些基础数据。在实验中，母材为纯铝棒，粉末介质为镍粉。为了优化固体试件之间的粉末介质制备方法，获得了实验数据，并用显微镜、扫描电子显微镜、X射线能谱、X射线衍射仪、拉伸强度、维氏硬度和弯曲U形弯曲试验进行了观察、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.