Zhao Xiaohui, Wang Mingyi, Zhang Zhiqiang, Liu Yu
Key Laboratory of Automobile Materials, School of Materials Science and Engineering, Jilin University, Changchun 130025, China.
School of Mechanical Science and Engineering, Jilin University, Changchun 130025, China.
Materials (Basel). 2016 Jun 14;9(6):471. doi: 10.3390/ma9060471.
Ultrasonic peening treatment (UPT) as a method of severe plastic deformation was used to treat cruciform welded joints of Q345 steel. The application of UPT achieves material surface nanocrystallization of the peening zone, reduces stress concentration, and produces residual compressive stresses at the welded toe. Micro-structure, hardness, stress relief, - curve, and the fatigue fracture mechanism of cruciform welded joint of Q345 steel, both before and after UPT, were analyzed in detail. The main results show that: stress concentration and residual tensile stress are the main reasons to reduce fatigue strength of cruciform welded joints. The fatigue life of cruciform welded joints is improved for surface hardening, compressive stress, and grain refinement by UPT. Residual compressive stress caused by UPT is released with the increase of fatigue life. A very significant fatigue strength improvement happens when UPT is replenished repeatedly after a certain number of cycles.
超声冲击处理（UPT）作为一种严重塑性变形方法，被用于处理Q345钢的十字形焊接接头。UPT的应用实现了喷丸区材料表面纳米晶化，降低了应力集中，并在焊趾处产生残余压应力。详细分析了Q345钢十字形焊接接头在UPT前后的微观结构、硬度、应力释放、S-N曲线和疲劳断裂机制。主要结果表明：应力集中和残余拉应力是降低十字形焊接接头疲劳强度的主要原因。通过UPT进行表面硬化、施加压应力和细化晶粒，提高了十字形焊接接头的疲劳寿命。由UPT引起的残余压应力随着疲劳寿命的增加而释放。在一定循环次数后重复进行UPT时，疲劳强度有非常显著的提高。
