STATIC AND DYNAMIC CHARACTERISTICS OF SPOT WELDED SHEET-METAL BEAMS

Although widely employed as structural components in the auto industry , spot welded sheet metal beams manifest static and dynamic behavior t hat is not well characterized. For the present study, sample beams of three representative cross-sections-hat, box and box with partition-we re fabricated of sheet steel. The spacing between the spot welds that hold these sections together was varied from 25.4 mm (1 in.) to 203.2 mm (8 in.) using a 25.4 mm (1 in.) increment. The beams were subjected to static bending and static torsion tests, and bending and torsional stiffnesses were determined as functions of spot weld spacing. The be ams were then vibrated and significant lower natural frequencies were determined as functions of spot weld spacing. Mode shapes were also ob served for these frequencies. Pains were taken throughout the testing to ensure that the results obtained were of good statistical quality. Work was also done to distinguish the effect on results of beam length and end conditions from that of spot weld spacing. As part of the stu dy finite element models of the beams were constructed. The results of finite element analysis (FEA) and experiment are compared and insight s are offered concerning the appropriate modeling of such structures.