划痕损伤对含铆钉孔2198-T8铝锂合金疲劳性能的影响

Effect of scratch damage on fatigue performance of 2198-T8 aluminum-lithium alloy with rivet holes

针对飞机蒙皮搭接处的划痕损伤问题,研究了含划痕缺陷的含铆钉孔2198-T8铝锂合金板材的疲劳性能。首先,利用Abaqus有限元仿真软件,通过正交试验法确定了划痕关键影响参数,优化了疲劳试验方案。其次,预制了9类划痕损伤试样,分析了划痕参数对其疲劳性能的影响,并结合数字图像相关技术对裂纹扩展路径进行了讨论。最后,利用体视显微镜及扫描电子显微镜对断口进行了表征并分析了疲劳断裂机理。结果表明,划痕尖端角度θ对力学性能影响最小;划痕深度D是影响疲劳性能的主要因素。在D=0.8 mm、c=72 mm、θ=45°的损伤条件下,疲劳寿命下降至1795次,较无损试样下降97.66%。当D>D_(s)=0.15 mm时,断裂位置由铆钉孔截面转移至划痕截面,且断裂模式由单一疲劳源扩展的韧性断裂转变为多疲劳源放射状扩展的准解理断裂。

Aiming at the scratch damage problem of the aircraft skin lap joints,the fatigue performance of 2198-T8 aluminum-lithium al-loy with rivet holes plate with scratch defects was studied.Firstly,the Abaqus finite element simulation software was used to determine the key influencing parameters of scratches by orthogonal test method,and the fatigue test plan was optimized.Secondly,9 types of scratch damage specimens were prefabricated,the effect of scratch parameters on the fatigue performance of the specimens was analyzed,and the crack propagation path was discussed in combination with digital image correlation(DIC)technology.Finally,the stereo microscope and the scanning electron microscope(SEM)were used to characterize the fracture and the fatigue fracture mechanism was analyzed.The re-sults show that the effect of scratch tip angleθon the mechanical performance is the least;the scratch depth D is the main factor affecting the fatigue performance.Under the damage condition of D=0.8 mm,c=72 mm,θ=45°,the fatigue life is reduced to 1795 times,which is 97.66%lower than that of the non-destructive sample.When D>D_(s)=0.15 mm,the fracture position is transferred from the rivet hole section to the scratch section,and the fracture mode changes from ductile fracture extended by single fatigue source to quasi-cleavage fracture extended radially by multiple fatigue sources.