仪器化压入技术在高铁轮辋原位性能表征中的应用

Application of instrumented indentation technique in in situ performance characterization of high-speed rail rim

本文建立了工业化实施仪器化压入技术的集成方法.以实测各卸载段最大载荷、刚度与压入深度为输入量,提出了多变量解耦最优Hollomon本构关系的显式算法,并引入Meyer幂律模型对屈服强度进行修正,确保压入法评测拉伸性能的可靠性.基于“临界压入能量”相关原理,提出了以拉伸断裂应变为临界断裂损伤因子,并以此估测等效断裂韧度的技术路径.同时,选择典型的高铁轮辋实施无取样压入法拉伸性能与等效断裂韧度的评测,获得了与常规标准化试验一致的性能结果.基于原位实测的压入性能结果,定量研究了包括强度、屈强比、硬度及韧性在内的轮辋性能从踏面由表及里的分布特征.综上,仪器化压入技术可作为标准化力学取样试验的重要补充,成为短流程无取样及原位高通量力学性能评估的重要技术手段.

A purely experimental integrated algorithm for the industrial implementation of instrumented indentation technology has been established in the present study. This study proposes a multivariable iterative decoupling optimization algorithm to solve the best Hollomon constitutive model to estimate the indentation tensile properties by performing incremental cyclic indentation to take the measured maximum force, stiffness, and indentation depth of each unloading segment as the input. The Meyer power-law model is employed to improve the accuracy of the as-estimated yield strength. In addition, the critical indentation energy model is used to estimate the equivalent fracture toughness KJC. Tensile fracture strain or elongation is used as a damage factor to calculate the critical effective indentation depth relative to the threshold of indentation cracking, which is required to obtain the necessary indentation energy for KJC. Thereafter, the indentation tensile and toughness properties of typical high-speed rail rims were evaluated without sampling, consistent with relative results from regular standardized testing. Moreover, the distribution features of strength, hardness, yield strength ratio,and toughness, along with the depth from the surface to the inner substrate of rail rims, were studied quantitively based on the estimated indentation results. This gave a practical way for short-process nonsampling and in situ mechanical property evaluation with high-throughput results for such metallic materials or components as rail rims.