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焊接接头超高周疲劳实验研究

ISSN号：1001-4888
期刊名称：实验力学
时间：2011
页码：617-624
分类：TG040[金属学及工艺]
作者机构：[1]四川大学力学与工程科学系,成都610065, [2]四川大学锦城学院土建系,成都610065
相关基金：基金项目：本课题得到国家杰出青年基金（项目编号：10925211）和自然科学基金（项且编号：50978174）支持.
相关项目：实验力学

关键词：超高周疲劳, 焊接接头, 超声振动疲劳技术, S—N曲线, 裂纹萌生, very high cycle fatigue, welded joint , ultrasonic fatigue test , S-- N curve, crack initiation

中文摘要：

本文基于超声疲劳振动技术，设计了三种焊接接头试样（圆形对接焊接试样及其喷丸处理试样和板状十字焊接试样），并利用超声疲劳试验系统测定了其超高周疲劳性能，实验应力比为-1，频率20kHz，实验在室温条件下进行。实验结果表明，圆形对接焊接接头的疲劳性能高于板状十字焊接接头，喷丸处理能提高焊接接头的疲劳强度。将焊接接头的疲劳性能与对应形状的母材进行对比分析，发现焊接接头的疲劳性能远低于母材。在相同疲劳寿命的条件下，圆形焊接接头试件的疲劳强度仅为母材的45％，十字焊接接头试件仅为母材的29％；圆形对接接头在5×10^6周次以后，试件仍然发生疲劳断裂，而板状十字焊接接头在超高周区域（10^7～10^9周次）存在疲劳极限。超声疲劳断口的扫描电子显微镜分析结果显示，圆形焊接接头试件断口位置主要位于熔合区的焊趾处或焊接接头表面几何非连续处，十字接头试件断口位于焊趾处；焊接接头试件裂纹萌生于焊接缺陷、试样表面夹杂或熔合区的不连续处；喷丸处理对焊接接头的裂纹萌生机制没有显著影响。

英文摘要：

Three groups of welded joints, including circular butt welded joint without and with shot peening treatment and cross-plate welded joint, were adopted and their very high cycle fatigue behavior study was carried out by using ultrasonic fatigue testing technique in ambient air and at room temperature with a stress ratio R=-1. Experimental results show that fatigue strength of circular butt welded joint is much higher than that of cross-plate welded joint, and the fatigue strength of welded joint is improved by shot peening treatment. The comparison of fatigue strength between welded joint and its base material with corresponding joint shape shows that the fatigue property of welded joint is much lower than that of base metal. Under the condition of same fatigue life, the fatigue strength of circular butt welded joint is only 45% of base metal while that is only 29% of base metal for cross joint. Fracture can still occur at circular ioint beyond 5 ×10^6cycles, while cross joint has a fatigue limit at very high cycle region （10^7- 10^9 cycles）. The fracture surface analysis by scanning electron microscope shows that cracks mainly initiate from the welded toes at fusion area or geometric discontinuity at the surface of circular butt welded joint and initiate from welded toes in cross-plate welded joint. Furthermore, cracks may initiate from weld defects, including the surface of specimen or discontinuity site at fusion area. The influence of shot peening on the site of crack initiation is not significant.

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