Influence of HAZ cracks on fatigue resistance of resistance spot welded joints made of advanced high strength steels

Abstract

A method is reported with which heat affected zone (HAZ) cracks in a specific region of spot welded joints, made of advanced high strength steels, could be realised. The influence of HAZ cracks on the fatigue behaviour, which is the focus of the contribution, was studied by evaluating the stiffness characteristics as a function of the number of cycles N in comparison with crack-free specimens, i.e. by analysing HAZ and fatigue cracks on the specimen surface and the surface of fatigue fractures containing beach marks. It was found that the fatigue cracks are not initiated at the HAZ cracks. The number of cycles to failure N f is not significantly reduced for specimens with HAZ cracks. Overall, the examinations did not reveal any influence of HAZ cracks on the fatigue strength of resistance spot welded joints.

Fatigue Behavior of Resistance Spot Welded Steel Sheets Fabricated Using Electrodes with Different Tip Diameters

“…KEY WORDS: fatigue; resistance spot weld; high strength steel; electrode; corona bond. many studies on the fatigue strength of RSW joints have been conducted [7][8][9][10][11][12][13][14][15][16][17] including ultra-high-strength steels. In those studies, it has been reported that the static tensile shear strength of RSW joint increased with increasing yield strength of steel, while fatigue strength was insensitive to the yield strength of steel.…”

3D characterization of the propagation of liquid metal embrittlement inner cracks during tensile shear testing of resistance spot welds

“…In the case of LME outer cracks, Gaul et al [5], Brauser et al [6], Kim et al [7] showed that the fatigue life of spot welds was not signicantly aected by the presence of the cracks. Choi et al [8] showed that small LME outer cracks (< 500 microns) in TRIP spot welds would not induce signicant loss of cross tension strength, absorbed energy and fatigue life, while longer crack could.…”

Study of Fatigue Behavior for Spot Welded Tensile Shear Specimens of Advanced High Strength Steels

“…It should be noted that for the production of surface cracks in the weld area, a welding current near the splash limit has to be used. For more details regarding the production of cracked samples see 11…”

“…For investigating the influence of gaps on the fatigue behavior different upper loads F U were used, while for the cracked samples a constant upper load F U of 2.75 kN was selected. Recently, Gaul et al11, 12 have shown that the specimen stiffness change during the fatigue test correlates with the fatigue crack propagation. Therefore, the stiffness characteristics of specimens with and without a crack were used to show the influence of cracks on the fatigue strength.…”