超声冲击强化铝合金小孔构件的试验研究

目的提升铝合金小孔构件的疲劳寿命,改善表面性能。方法采用超声冲击强化工艺对铝合金小孔构件进行试验研究,利用MHV2000显微硬度测量仪、XRD射线应力测定仪、疲劳试验机分别测量试件的显微硬度、残余应力、疲劳寿命。利用扫描电镜拍摄试件强化加工前后的显微照片。针对不同阻抗阈值条件,考察主要工艺参数对小孔构件强化效果的影响。结果研究表明,采用基于等效阻抗控制的超声冲击强化工艺,阻抗阈值设定为75Ω时,孔边的平均残余应力值出现极大值,距离孔壁的残余应力分布呈现先增大后减小的规律。孔壁的显微硬度趋势保持一致,阻抗阈值越大时,其平均值也越大。微观组织反映孔被强化后的痕迹,被强化试件疲劳断口齐整,组织均匀,有明显被压实的现象。结论超声冲击强化工艺适合小孔构件强化,疲劳寿命最大提高3.1倍,孔口表面形成了有效的残余压应力场,孔内表面显微硬度提高了1倍。

Experimental Study of Aluminium Alloy Hole Test Specimen Reinforced by Ultrasonic Impact

The work aims to improve the fatigue life and the surface performance of aluminium alloy hole test specimen. Ultrasonic impact strengthening technology was adopted to study the aluminium alloy hole test specimen through experiment and MHV2000 microhardness tester, X ray stress tester and fatigue testing machine were used to measure the microhardness, residual stress and fatigue life of the specimen. Then, SEM was applied to take the microphotos of specimen before and after the reinforcement. According to different impemdance thresholds, the strengthened effects on the hole specimens by main parameters were studied. Through the experiment, the ultrasonic shock processing based on the equivalent impedance control was adopted. If the impedance threshold was 75 ?, the average residual stress of the hole was maximum and the distribution of residual stress from the distance of hole increased first and then decreased. The trend of microhardness of hole wall was consistent and the average increased as the impemdance threshold grew. The reinforced trace was obvious through microstructure and the fatigue fracture of strenthened specimen was neat and uniform with obvious trace of compression. Ultrasonic impact strengthening technology is suitable for small hole component and can improve the fatigue life by 3.1 times. The effective residual compressive stress field can be obtained on the hole surface and the surface microhardness inside the hole doubles.