Fatigue Design of Spot‐welded Austenitic and Duplex Stainless Sheet Steels

Abstract

The fatigue strength of spot‐welded stainless sheet steels has been investigated. The main part of the fatigue tests was performed on a cold rolled austenitic stainless sheet steel (AISI304) in air at ambient temperature. For comparison, a duplex stainless steel (SAF2304) of similar yield strength as AISI304 was also incorporated into the test programme. Since the fatigue strength of spot‐welded joints depends on the mode of loading, both shear‐loaded and peel‐loaded joints were tested. The fatigue strength of the spot‐welded stainless steels was found to decrease with decreasing sheet thickness. Furthermore, the fatigue strength for peel‐loaded joints is lower than that of shear‐loaded joint for sheets of equal thickness. The local loading conditions at the weld edge have been analysed in terms of finite element calculations and fracture mechanics. A design parameter derived from a fracture mechanics analysis was defined for spot‐welded stainless sheet steels. It was shown to predict the fatigue life of the present steels and joint configurations in a satisfactory way.

On the resistance spot weldability of galvanized interstitial free steel sheets with austenitic stainless steel sheets

“…The specimen stiffness decreases as fatigue cracks propagate. Specimen failure was defined as 25% stiffness drop [2]. Therefore, the specimen stiffness was evaluated during each fatigue test.…”

“…More cracks and failures tend to occur around these welds, in the heat affected zone (HAZ), because those joints are exposed to dynamic and static loads in the automobile structures [1,2].…”

Effect of welding nugget diameter on the fatigue strength of the resistance spot welded joints of different steel sheets

“…They applied the tensile-shear and cross-tension loading modes to the specimens and reported that the fatigue performance of the welded sheets is determined by geometric factors rather than material strength and microstructure. Linder and Malender have used austenitic and duplex stainless steel sheets to determine the fatigue behaviour of the spot welded joints [8]. Anastassiou and co-workers [9] have studied the stress distribution and fatigue behaviour of the spot welded thin steel sheets.…”

Corrosion fatigue of spot‐welded austenitic stainless steels in 3.5% NaCl solution

“…This explanation is supported by an investigation where the spot-welded specimens consisted of two sheets of different thickness. In fatigue testing in air, the fatigue crack propagation took place in the thicker sheet at long lives, but in both sheets at short lives [14]. Since the thicker sheet is stiffer the phenomenon was probably related to the stress concentration at the notch.…”

“…The influence of the sheet thickness is linked to the resistance against bending of the sheets and the subsequent rotation of the joint during loading. Bending will result in a tensile load in combination with the shear load and induce locally very high stresses just outside the spot weld [14].…”