Prediction of the Shear Tension Strength of Resistance Spot Welded Thin Steel Sheets from High- to Ultrahigh Strength Range

Abstract

The tensile strength of newly developed ultra-high strength steel grades is now above 1800 MPa, and even new steel grades are currently in development. One typical welding process to join thin steels sheets is resistance spot welding (RSW). Some standardized and not standardized formulas predict the minimal shear tension strength (STS) of RSWed joints, but those formulas are less and less accurate with the higher base materials strength. Therefore, in our current research, we investigated a significant amount of STS data of the professional literature and our own experiments and recommended a new formula to predict the STS of RSWed high strength steel joints. The proposed correlation gives a better prediction than the other formulas, not only in the ultra-high strength steel range but also in the lower steel strength domain.

Global Approach on the Shear and Cross Tension Strength of Resistance Spot Welded Thin Steel Sheets

“…Because as discussed also in [29,30], the scatter is high ~1-4, and due to the nature of Eq. ( 17), the normalized STS values decrease till R m = 1340 MPa, and then they start to increase again.…”

“…After extended literature and experimental research, data of approx. 160 papers were analyzed [30] and a prediction for the STS values was given in a wide tensile strength range (R m = 400-2000 MPa), for thin steel sheets (t = 0.3-4 mm) (Eq. ( 19)).…”

“…( 1) according to Radakovic and Tumuluru [14] and Tumuluru [25], according to the ISO standard [26] and the Eq. ( 18) according to the AWS standard [28] was also presented here [30]. Xu et al [31,32] conducted many experiments in a wide tensile strength range of R m = 250-1600 MPa steel, t = 0.6-1.6 mm thickness in similar and dissimilar combinations.…”

“…Previously [30] a plane was fitted on the optimized STS values (similar joints) depending on the base materials' tensile strength and sheet thickness (Eq. ( 19)).…”

“…The measured CTS values are shown for similar and dissimilar RSWed joints. For the dissimilar joints, the weaker side is depictured according to Eq (30)…”