不同冲击角度外物损伤对TC4钛合金高循环疲劳强度的影响

Effect of foreign object damage at different impact angles on high cycle fatigue strength of TC4 titanium alloys

基于空气炮冲击试验装置在不同冲击角度下进行了TC4钛合金平板试件的外物损伤模拟试验,采用逐级加载试验方法测试获得了光滑和冲击损伤试件的高循环疲劳(high cycle fatigue,HCF)强度,研究了冲击角度、冲击位置以及冲击损伤宏观几何尺寸与HCF强度的关系.结果表明:不同冲击角度下的损伤对HCF强度的影响程度不同.冲击损伤在试件边缘时,30°冲击使试件HCF强度的下降幅度最大;冲击损伤在试件表面时,60°冲击使试件HCF强度的下降幅度最大.试件边缘产生的缺口使HCF强度的下降幅度一般大于试件表面产生弹坑的影响.但在60°冲击时,冲击缺口损伤的影响要小于冲击弹坑损伤的影响.冲击损伤宏观几何尺寸一定程度上可以表征损伤试件HCF强度下降的严重程度.

Based on the air-gun impact test device,the foreign object damage（FOD）simulation test of TC4 titanium alloy plate specimens was conducted at different impact angles.The high cycle fatigue（HCF）strength of smooth and impact damage samples was obtained with the step-test method.The relationship among the impact angles,impact positions,macroscopic geometry of impact damage and HCF strength of the damaged samples was studied.Results show that,the effect of impact damages on the HCF strength at different impact angles is not the same.When the impact damage appears at the edge of sample,the maximum decrease of HCF strength occurs in the impaction of 30°;while the impact damages appear at the middle of sample,the maximum decrease of HCF strength occurs in the impaction of 60°.In most cases,impact notches at the samples’ edge compared to impact pits at the sample’s intermediate surface have a more seriously effect on the HCF strength.However,at the impaction of 60°,the impact pit damage has a more serious effect.The geometry of the impact damage to a certain extent can characterize the changes of the HCF strength severity of damaged sample.