【摘要】 对TC4钛合金薄板母材及其激光焊缝进行了低周疲劳损伤规律的理论分析和试验研究。在对应力疲劳不同周次后试样的拉伸性能进行测定及分析表明,残余伸长率对该材料的疲劳损伤较为敏感,可以作为表征其低周疲劳损伤的有效物理参量。结果表明,对TC4钛合金薄板母材,以残余伸长率定义的损伤变量初始值D0为0.037,损伤变量D随着循环周次的增加缓慢增加,当循环周次达寿命的90%后才进入快速增加阶段。连续损伤力学理论分析结果可以很好的解释TC4薄板的低周疲劳损伤规律,理论模型与实验结果吻合很好。而激光焊接接头试样中由于存在组织不均匀性及焊接缺陷,使得焊缝的低周疲劳损伤规律偏离了理论模型,由于焊缝中有气孔等缺陷的存在使得焊缝试样循环到寿命的1%时,初始损伤变量值即达到0.4,而且由于焊缝中心晶粒粗大使得循环周次达寿命的50%时损伤变量即开始快速增加。更多还原

【Abstract】 Theoretical analysis and experimental research on the low cycle fatigue damage of TC4 titanium alloy sheet and its laser welding joint were conducted.The tensile tests of specimens after different fatigue cycles show that elongation is sensitive to fatigue damage,which is used as an effective physical parameter to characterize the low cycle fatigue damage behavior of TC4 titanium alloy sheet and its laser welding joint.The initial value of the damage variable for base metal is 0.037,which increases slowly with fatigue cycles and increases rapidly when the cycles up to 90% of the fatigue life.Continuum damage mechanics theory analysis results can be a good explanation for the low cycle fatigue damage law of TC4 base metal sheet,the theoretical model fits well with the experiment results.The microstructure of laser welding joint of TC4 alloy is not uniform.There are welding defects,which make the low cycle fatigue damage curve of the welding joint deviates from the theoretical model.The pores in the welding joint make the initial damage variable value change to 0.4.As the coarse grains in the welding joint center,the damage variable starts to increase rapidly,when the fatigue cycles reaches 50% of the fatigue life.更多还原