On Material Removal Mechanism in High Speed Single Grit Scratch-Grinding of Cryo-Treated Al2024-T351 Aluminium Alloy

Feasibility of utilizing cryogenic technology to improve the shearability of Al2024-T351 alloy is experimentally investigated by carrying out a single grit scratch-grinding test. A single grit brazed diamond grinding tool is developed for the study. Al2024-T351 work specimens are treated with liquid nitrogen for 6 hours before the scratch test. Although there was no significant change in the tensile strength of the material, the surface experiences change in the microhardness. It helps in arresting the side flow and ploughing of the material during high speed scratch grinding. The scratched grooves on cryo-treated samples, compare to those of untreated specimens, shows signs of cleaner shear-cuts, superior finish and produces less grinding force during grinding

Numerical and Experimental Analysis of Material Removal and Surface Defect Mechanism in Scratch Tests of High Volume Fraction SiCp/Al Composites

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.

Research on the Size Effect of Specific Cutting Energy Based on Numerical Simulation of Single Grit Scratching

A method of research on the size effect of the specific cutting energy based on the numerical simulation has been proposed. The theoretical model of the research on size effect of specific cutting energy using single grit scratching simulation has been presented. A series of single grit scratch simulations with different scratching depths have been carried out to acquire different material removal rates. Then, the specific cutting energy has been calculated based on the power consumed and the material removal rate. The relationship between the specific cutting energy and the material removal rate has been given which agrees well with that presented by Malkin. The simulation results have been analyzed further to explain the size effect of specific cutting energy.