Simulation and Experimental Research about Temperature Fields of PDMS Cooled by Liquid Nitrogen Jet Impingement.

In order to explore the changes and distributions of the temperature of PDMS sample being impacted and cooled by the liquid nitrogen jet during the cryogenic micro-abrasive air jet machining the PDMS microchannels, this paper proposed a systematic research method of temperature that composed of temperature measurement experiments, Beck's inverse estimation method fitting and APDL temperature field simulation. The errors between the final simulation results and the temperature measurement ones are only 1.735%. The simulations find that it will take 5.747 s for the surfaces to reach the obvious embrittlement temperature -147 °C. PDMS may not reach a machinable embrittlement state at the moment of contact with liquid nitrogen, so it is necessary to pay attention to the pre-cooling time before machining. The simulation data was used to fit the cooling rate of PDMS to -147 °C, and the cooling rate was used as a reference to predict the pre-cooling time required in the actual machining. By comparing the cooling rate, it is found that the cooling rate in the depth range of 0~100 µm from the surface of the PDMS specimen is 22.054% faster than that in the depth range of 0~1500 µm, and the cooling rate of the aluminum alloy workbench is about 22.311% higher than that of the adiabatic workbench. [ABSTRACT FROM AUTHOR]