TC4钛合金的超高周疲劳行为及其竞争失效模型构建

Very high cycle fatigue behavior of TC4 titanium alloy and construction of its competitive failure model

针对现有模型对TC4竞争失效预测的不准确性,建立了基于最大应力强度因子的竞争失效模型。在室温以及两种应力比下,针对TC4钛合金进行超高周疲劳试验,通过试验与最弱键竞争失效理论相结合的方法进行评估,研究其超高周疲劳性能。通过对试样断口形貌的观察,可将其失效模式分为如下两类:表面失效以及内部失效。对试样表面缺陷以及内部解理刻面尺寸进行测量,并评估其最大应力强度因子值。进一步通过正态分布得到最大应力强度因子的累计分布函数,基于两参数泊松分布建立了与最大应力强度因子有关的竞争失效模型。通过模型计算结果,可以得出在任一最大应力强度因子下试样发生各种失效模式的概率,且经分析对比,本文中TC4两种疲劳失效模式的失效概率评估结果与试验数据吻合较好,为分析TC4钛合金超高周疲劳状态下的疲劳失效模式提出了新的评估方法。

In view of the inaccuracy of existing models in TC4 competitive failure prediction,a competitive failure model based on maximum stress intensity factor was established.The very high cycle fatigue test of TC4 titanium alloy was carried out at room temperature under two stress ratios,and the performance of TC4 titanium alloy was studied by combining the test with the weakest bond competition failure theory.By observing the fracture morphology of the specimen,the failure modes were divided into two categories:surface failure and internal failure.The dimensions of the surface defects and internal cleavage facet of the specimen were measured,and the value of the maximum stress intensity factor was evaluated.In addition,the cumulative distribution function of the maximum stress intensity factor was obtained through normal distribution,and a competitive failure model related to the maximum stress intensity factor was established based on the two-parameter Poisson distribution.With model calculation results,the probability of different failure modes of the specimen under any maximum stress intensity factor could be obtained.Analysis shows that the failure probability evaluation results of the two fatigue failure modes of TC4 in this study were in good agreement with the test data.A new evaluation method was proposed for analyzing the fatigue failure modes of TC4 titanium alloy under very high cycle fatigue.