一种基于纳米压痕技术估算残余应力的计算模型

A computational model for estimating residual stress based on nanoindentation technology

通过分析纳米压痕实验中压头的压入过程,推导了残余应力在此过程中所作的功,根据能量守恒原则,建立了压痕功和残余应力功之间的关系,并推导出了基于能量法的残余应力计算公式。使用此公式估算材料残余应力并与已有Suresh模型、Lee模型和X射线衍射法的结果进行比较,结果表明,在固定压头载荷或压痕深度的纳米压痕实验中,能量法模型计算结果大于Suresh模型、Lee模型的计算结果,随着压头载荷或压痕深度的增加,能量法的计算结果与Suresh模型、Lee模型的变化趋势基本一致。当固定压头载荷时,能量法计算结果的平均值约为实际施加应力值的1.5倍,使用能量法计算选区激光熔化Ti-6Al-4V合金铺粉面的残余应力,计算结果约为X射线衍射测量结果的1.5倍。

In nanoindentation experiments,the indentation results under the same experimental conditions will be affected by residual stress.In this paper,the work of residual stress is deduced by analyzing the indentation process of the indenter in the nanoindentation experiment.According to the principle of energy conservation,the relationship between the indentation work and the residual stress work is established,and the formula for calculating residual stress based on the energy method is deduced.The material residual stress is estimated by this formula and compared with the calculation results of the Suresh model,the Lee model and the X-ray diffraction method.The results show that,in the nanoindentation experiment with a fixed indenter load or indentation depth,the calculation result of the energy-based method is larger than those of the Suresh model and the Lee model.But,with the increase of the indenter load or the indentation depth,the calculation result of the energy-based method is basically consistent with those of the Suresh model and the Lee mode.When the indenter load is fixed,the average value calculated by the energy-based method is about 1.5 times the actual applied stress value.The energy-based method is used to calculate the residual stress of the powder surface of Ti-6Al-4V alloy by selective laser melting,and the calculation result is about 1.5 times the X-ray diffraction measurement.The validity of the model is proved by comparison,and a more convenient calculation model is provided for measuring residual stress based on nanoindentation experiments.