加载方式对异种铝/钢无匙孔搅拌摩擦焊接接头疲劳性能的影响

Effect of Loading Methods on the Fatigue Properties of Dissimilar Al/Steel Keyhole-Free FSSW Joints.

作者信息

Zhang Zhongke, Yu Yang, Zhao Huaxia, Tong Hui

机构信息

School of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050, China.

School of Materials Science and Engineering, Tongji University, Shanghai 201804, China.

出版信息

Materials (Basel). 2020 Sep 23;13(19):4247. doi: 10.3390/ma13194247.

DOI:10.3390/ma13194247

PMID:32977709

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC7579601/

Abstract

The energy evolution, fatigue life and failure behaviour of dissimilar Al/steel keyhole-free Friction stir spot welding (FSSW) joints were studied under different fatigue loads. The absorption energy of fatigue fracture, the fracture mechanism and the sensitivity of the fatigue limits to the fatigue load parameters were analysed. It was found that the stress ratio R determines the fatigue limit Ff, while the fatigue limit F is not sensitive to the loading frequency. The high-frequency fatigue load will increase the displacement deformation μ and fatigue fracture absorption energy E of the spot-welded joint, which are larger under asymmetric fatigue loading than those under symmetrical fatigue loading. At the same time, the symmetrical fatigue load can form the steady-state hysteresis loop, while asymmetric fatigue loading cannot, but asymmetric fatigue loading exhibits the displacement increment of fatigue softening. The fracture failure of spot-welded joints is a multiple crack source and the mixed-mode of ductile and brittle fracture mechanism, which exhibits typical fatigue striations in the fatigue fractures.

摘要

研究了不同疲劳载荷下异种铝/钢无匙孔搅拌摩擦点焊（FSSW）接头的能量演化、疲劳寿命和失效行为。分析了疲劳断裂的吸收能量、断裂机制以及疲劳极限对疲劳载荷参数的敏感性。结果发现，应力比R决定疲劳极限Ff，而疲劳极限F对加载频率不敏感。高频疲劳载荷会增加点焊接头的位移变形μ和疲劳断裂吸收能量E，不对称疲劳载荷下的位移变形μ和疲劳断裂吸收能量E大于对称疲劳载荷下的。同时，对称疲劳载荷可形成稳态滞后环，而非对称疲劳载荷则不能，但非对称疲劳载荷表现出疲劳软化的位移增量。点焊接头的断裂失效是多裂纹源以及韧性和脆性断裂机制的混合模式，在疲劳断口中呈现出典型的疲劳条纹。