Dynamic Separation of Resistance Spot Welded Joints: Part I—Experiments

Abstract

An analysis for an impact system is presented. The results are then used to interpret the test data from dynamic separation of resistance spot welded joints. In this Part I of the investigation emphasis is placed on the design consideration, development of a test system and verification of the design from actual test data obtained from the test system. In addition, the inertia effect of a generic dynamic system is analyzed using the principle of rigid body dynamics. It is shown that the load recorded by a load cell could include both the load experienced by the test specimen and the inertia force generated from the mass and acceleration between the specimen and the load cell, when the load cell is placed on the fixed side of the test specimen. Impact fixtures designed for spot weld strength testing are then studied for the inertia effect.

Dynamic Separation of Resistance Spot Welded Joints: Part II—Analysis of Test Results and a Model

“…Using a drop weight system as described in Part I [1], over 500 impact tests on resistance spot welded joints were performed. Cross-tension (CT) and lap-shear (LS) specimens were tested.…”

“…They are spot welded together following SAE ANSI/AWS/SAE/D8.9-97 [12] as shown in Figs. 5 and 6 of Part I [1]. The weld in CT specimen is under opening load while under shear load in LS specimen.…”

“…Fig. 7 of Part I [1] show representative load history curves from four spot welded specimens, i.e. slow and fast impact of LS and CT, using a drop weight system.…”

“…In Part I [1] of this investigation, analysis and design of a generic impact testing system were presented. A drop weight impact testing system and associated fixtures were built for testing lap-shear (LS) and cross-tension (CT) specimens.…”

Failure mechanism of resistance-spot-welded specimens impacted on base material by bullets

“…For the safety design of spotwelded body shell components, knowledge of the mechanical behavior and especially the failure mechanisms under the static, impact and fatigue loading is of particular interest. [1][2][3][4][5][6][7][8] For vehicles in a crash scenario, the strain rate effect on the ultimate or fracture strength of the spot welds is of paramount importance as these welds may separate under the dynamic loading. In response to the demand for the development of practically applicable modes, some authors [9][10][11][12] developed models that can describe the physical properties of spot weld failure in the impact tests including the "cross-tension testing" and "lap-shear testing".…”