液氮射流冲击冷却聚二甲基硅氧烷的温度场仿真和实验研究

为探究低温微磨料气射流加工聚二甲基硅氧烷(PDMS)微流道过程中PDMS试样受液氮射流冲击冷却的温度变化和分布，提出了测温实验Beck反求算法拟合APDL温度场仿真的系统研究方法，仿真结果与测温结果的误差仅1.735%。仿真发现，表面到达明显脆化温度-147℃需要5.747 s,说明PDMS无法在接触液氮的瞬间就达到可加工的脆化状态，有必要重视加工前的预冷却时间；又通过仿真数据拟合了PDMS冷却至-147℃的冷却速度，以冷却速度为参考预测了实际加工中所需的预冷却时间。对比冷却速度发现，距PDMS试样表面0～100μm深度范围内的冷却速度比0～1500μm深度范围内冷却速度快22.054%,PDMS试样放置在铝合金工作台上的冷却速度比绝热工作台上快22.311%。

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 ℃. 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 ℃, 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.