超载试验中TC18钛合金低周疲劳特性研究与断口分析

Analysis on the Low Cycle Fatigue Properties and Fractography of TC18 Titanium Alloy in Overload Testing

为了研究超载试验对TC18钛合金低周疲劳特性的影响,常温下,在恒幅低周疲劳和间隔超载载荷两种工况下,对两种厚度的β锻TC18钛合金中心开孔试样进行了研究;对其低周疲劳性能及断口形貌开展了深入探索。同时,在应力比和恒幅载荷相同的情况下,与无超载情况下的裂纹扩展速率进行了对比分析。疲劳试验结果表明:β锻TC18钛合金存在明显的超载迟滞效应;每100次恒幅载荷间隔2次1.3倍超载载荷时,低周疲劳寿命约为恒幅低周疲劳寿命的2倍。

Aiming to research the effect of overload testing on low cycle fatigue properties of TC18 titanium alloy,two kinds of β phase TC18 titanium alloy samples with a center-hole was studied deeply,and low cycle fatigue( LCF) behavior and fractography were analyzed under constant amplitude and interval overload condition at room temperature. At the same time,the crack growth rate was compared between non-overloading and overloading with same stress ratio and constant amplitude load. The fatigue testing results showed that β phase TC18 titanium alloy kept obvious retardation effect. Moreover,1. 3 times overloads applied twice between every 100 constant amplitude loads,LCF life was almost twice as long as constant amplitude.