Clarification of the effect of cooling rate on abrasive embedding behavior of PDMS in cryogenic abrasive air-jet machining

Cryogenic abrasive air-jet machining (CAJM) technology is widely used to create microchannels in polydimethylsiloxane (PDMS) material, where the cooling temperature distribution directly affects the abrasive embedding degree and surface quality of the eroded surface. At present, the researchers assumed that the convective heat transfer coefficient of PDMS material remains unchanged during the heat transfer process of LN2 jet impact, and carried out the finite element analysis of the cooling temperature distribution of PDMS. However, the definition of effective embrittlement domain of PDMS material, that avoids the abrasive embedding, is still an unsolved problem. In this work, Beck's method and thermocouple temperature data are used to obtain the convective heat transfer coefficient during LN2 jet cooling of the PDMS substrate. Based on the analysis of the PDMS material cooling temperature field, the evolution law of abrasive embedding degree in different embrittlement domains are predicted and analyzed. The research results show that the proposed systematic research method of LN2 jet cooling temperature distribution of the PDMS material, based on Beck's method, has obtained the critical process conditions for effective embrittlement domain definition in PDMS material erosion processing by adjusting the LN2 jet nozzle traverse speed for the first time. This study provides a theoretical basis for the non-abrasive embedded eroded surface of PDMS materials in the range of large impact angles.