Zhao Xu, Gong Yadong, Cai Ming, Han Bing
School of Mechanical Engineering and Automation, Northeastern University, Shenyang 110819, China.
School of Mechanical Engineering and Automation, University of Science and Technology Liaoning, Anshan 114051, China.
Materials (Basel). 2020 Feb 10;13(3):796. doi: 10.3390/ma13030796.
This paper addresses a comprehensive and further insight into the sensitivity of material removal and the surface defect formation mechanism to scratch depth during single-grit scratch tests of 50 vol% SiCp/Al composites. The three-dimensional (3D) finite element model with more realistic 3D micro-structure, particle-matrix interfacial behaviors, particle-particle contact behaviors, particle-matrix contact behaviors and a Johnson-Holmquist-Beissel (JHB) model of SiC was developed. The scratch simulation conducted at scratch velocity 10 mm/min and loading rate 40 N/min revealed that the scratch depth plays a crucial role in material removal and the surface forming process. Brittle fracturing of SiC particles and surface defects become more deteriorative under a large scratch depth ranging from 0.0385 to 0.0764 μm. The above phenomenon can be attributed to the influence of scratch depth on SiC particles' transport; the increase in the amount of SiC particle transport resulting from an increase of scratch depth raises the occurrence of particle-particle collision which provides hard support and shock for the scratched particles; therefore, brittle fracturing gradually becomes the major removal mode of SiC particles as the scratch depth increases. On the deteriorative surface, various defects are observed; i.e., lateral cracks, interfacial debonding, cavies filled with residually broken particles, etc. The von Mises stress distribution shows that SiC particles bear vast majority of load, and thus present greater stress than the surrounding Al matrix. For example: their ratio of 3 to 30 under the scratch depth of 0.011 mm. Namely, SiC particles impede stress diffusion within the Al matrix. Finally, the SEM images of the scratched surface obtained from the single-grit scratch experiments verify the numerical analysis's results.
本文对50 vol% SiCp/Al复合材料单颗粒划痕试验中材料去除敏感性和表面缺陷形成机制随划痕深度的变化进行了全面且深入的研究。建立了具有更真实三维微观结构、颗粒-基体界面行为、颗粒-颗粒接触行为、颗粒-基体接触行为以及SiC的Johnson-Holmquist-Beissel（JHB）模型的三维（3D）有限元模型。在划痕速度为10 mm/min和加载速率为40 N/min下进行的划痕模拟表明，划痕深度在材料去除和表面形成过程中起着关键作用。在0.0385至0.0764μm的大划痕深度下，SiC颗粒的脆性断裂和表面缺陷变得更加严重。上述现象可归因于划痕深度对SiC颗粒迁移的影响；划痕深度增加导致SiC颗粒迁移量增加，从而增加了颗粒-颗粒碰撞的发生率，为被划伤颗粒提供了硬支撑和冲击；因此，随着划痕深度的增加，脆性断裂逐渐成为SiC颗粒的主要去除方式。在恶化的表面上，观察到各种缺陷，即横向裂纹、界面脱粘、填充有残余破碎颗粒的空洞等。冯·米塞斯应力分布表明，SiC颗粒承受了绝大部分载荷，因此其应力比周围的Al基体更大。例如：在划痕深度为0.011 mm时，它们的比值为3至30。即SiC颗粒阻碍了应力在Al基体内的扩散。最后，单颗粒划痕试验获得的划痕表面的SEM图像验证了数值分析结果。
