PDMS material embrittlement and its effect on machinability characteristics by cryogenic abrasive air-jet machining

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Abstract The use of cryogenic abrasive jet machining (CAJM) technology for polydimethylsiloxane (PDMS) materials is increasing rapidly due to its high material removal rate and high surface quality. However, how the material properties of PDMS affect the machining properties under cryogenic conditions is still an unsolved problem. Firstly, the thermodynamic and mechanical properties of PDMS materials are studied by dynamic thermo-mechanical analysis and universal material testing. The results show that the PDMS material’s embrittlement temperature is 126 K. Secondly, evaluation of cooling temperature of PDMS during CAJM shows that the machined area has reached embrittled state. Thirdly, the effect of PDMS material’s embrittlement on the machining behaviour is studied. The experimental results show that the PDMS material exhibit increased abrasive erosion at medium-angle under cryogenic conditions and shows a semi-brittle wear mechanism. Furthermore, the erode surface’s roughness is evaluated. The result shows that the roughness decreases with decreasing air pressure at the same impact angle; with increasing impact angle, the roughness shows a trend of increase initially and then decreases. This work shows that the PDMS material’s embrittlement and the erosion response behaviour during CAJM are due to the combined effects of thermo-mechanical properties and material removal mechanisms, providing a better understanding of CAJM technology.