Effect of expulsion on peak load and energy absorption of low carbon steel resistance spot welds

Abstract

The effects of weld nugget size and expulsion on the performance of low carbon steel resistance spot weld have been investigated in the present paper. Failure mode, peak load and failure energy obtained in tensile-shear test have been used to describe the performance of spot weld. The influence of voids and porosity as well as electrode indentation associated with expulsion on peak load and failure energy is discussed. The results showed that although expulsion does not reduce the load carrying capacity of spot welds, it decreases their energy absorption capability which was attributed to the change of failure location due to excessive electrode indentation associated with expulsion.

Failures in Spot Welding

“…Final fracture occurs as the crack propagates through the sheet thickness. The observed mechanism is in agreement with mechanism suggested by Zuniga and Sheppard [5]. They divided the failure sequence of the spot welds in the coach-peel specimens into four stages: I) Propagation of the notch tip toward the fusion zone, II) Large tensile strains at the faying surface blunt the notch tip.…”

Properties of Resistance Spot-Welded TWIP Steels

“…Generally, there are three measures for the quality evaluation of resistance spot welds, including physical weld attributes, mechanical properties, and failure mode [1,7,8]. Due to high alloying content of AHSS, which influences the heat generation during resistance spot welding, high alloying content increase the bulk resistivity of the metal, which leads to excessive heat at the interface and, therefore, suitable current range shifts to the lower current side.…”

Effect of Electrode Force on Fracture Type of DQSK Steel Resistance Spot Welds

“…(3) Increasing electrode force beyond a critical limit increases the risk of the interfacial failure mode due to the small weld nugget size. (4) Increasing electrode force leads to failure of spot welds at lower load.…”

“…Spot welds that fail in the nugget pullout mode provide higher peak loads and energy absorption levels than spot welds that fail in the interfacial fracture one. To ensure reliability of spot welds during vehicle lifetime, process parameters should be adjusted so that the pullout failure mode is guaranteed [2][3][4][5][6][7][8][9][10]. It is well established that the geometrical attributes of spot welds, particularly weld nugget size, are the most important controlling factors determining the mechanical strength of RSWs [8][9][10][11][12][13][14][15].…”