高温仪器化压入测试中热接触对位移测量漂移的影响

基于对室温压头和热试样接触后传热过程的分析, 重点研究热接触引起的压头基托热膨胀对高温仪器化压入测试中位移测量漂移的影响. 首先, 通过热传导理论分析, 获得热接触后基托内温度场分布的解析解, 进而研究基托热膨胀引起的位移测量漂移量; 然后, 建立有限元分析模型, 数值模拟高温仪器化压入过程, 验证理论模型的准确性. 研究发现, 压头与热试样接触面间的热传导性质显著影响基托内的温度场分布; 对于不同材料的试样, 接触面间传热性能不同, 基托的热膨胀量差异可以达到几个数量级. 研究结果有助于优化高温压入测试程序, 提高测试的可靠性.

THERMAL CONTACT-INDUCED DISPLACEMENT DRIFT IN HIGH-TEMPERATURE NANOINDENTATION

Based on the analysis of heat transfer between indenter at room temperature and hot sample during their contact, this paper mainly studies the influence of thermal contact-induced expansion of the indenter holder on the displacement measurement in high-temperature instrumented nanoindentation. First of all, we derive an analytical solution of temperature distribution of the holder from the basic theory of heat conduction by appropriately simplifying the analysis model of hot nanoindentation, and use it to study the additional displacement caused by thermal expansion. Secondly, a finite element model (FEM) is established to investigate the thermal expansion-induced drift in hot nanoindentation to verify the analytical solution. It is found that the contact thermal properties between indenter and hot sample may significantly affect the distribution of temperature in holder. The thermal contact conductance between indenter and test sample varies from material to material, which can lead to the difference of several orders of magnitude of holder's thermal expansion. The research results may help to optimize the test program and improve the reliability of high-temperature instrumented nanoindentation.