预应变对工业纯钛TA2疲劳裂纹尖端应变场的影响

Effect of Pre-strain on Strain Field at Fatigue Crack Tip of Commercial Pure Titanium TA2

摘要:

钛制承压设备在制造和服役过程中会产生塑性变形,影响其抗疲劳性能。为了研究预应变对工业纯钛TA2疲劳裂纹扩展行为的影响,本文对原始材料、预应变量为10%、20%和30%的材料进行疲劳裂纹扩展试验,结合数字图像相关(Digital image correlation, DIC)技术获取裂纹尖端应变场,研究预应变对裂纹尖端应变场的影响。结果表明：随着预应变量的增加,稳态疲劳裂纹扩展阶段的扩展速率减小,裂纹张开位移减小,裂纹张开载荷增大,裂纹尖端塑性区、塑性变形量以及循环塑性应变累积量均减小。因此预应变抑制了裂纹尖端的塑性变形及循环塑性累积,致使裂纹闭合效应愈加明显,从而抑制了裂纹的扩展。研究结果对钛制承压设备的安全评定具有参考意义。

Abstract:

Plastic deformation will be produced in the process of manufacture and service for the titanium bearing equipment, which will affect its fatigue resistance. In order to study the effect of pre-strain on the fatigue crack propagation behavior of commercial pure titanium TA2, fatigue crack propagation tests were carried out on the original material and the materials with 10%, 20% and 30% pre-strained value. Combined with the digital image correlation (DIC) technology, the strain fields at the crack tip were obtained, and the effect of pre-strain on the strain field at the crack tip was researched. The results show that, with the increase in pre-strained value, the propagation rate decreased during the steady-state fatigue crack propagation stage, meanwhile the crack opening displacement decreased and the crack opening load increased, and the plastic zone at the crack tip, the plastic deformation and the cyclic plastic strain accumulation decreased. Therefore, the pre-strain inhibits the plastic deformation and cyclic plastic accumulation at the crack tip, which leads to the more obvious crack closure effect, thus inhibiting the crack propagation. The research results have reference significance for the safety evaluation of titanium bearing equipment.