| Summary: | 碩士 === 逢甲大學 === 機械工程學所 === 94 === This thesis mainly introduces the finite element analysis software, ANSYS, to simulate the tensile-shear testing of spot-welded metal sheets, and verifies the computational results by experiment. It is aimed to investigate the effects of spot welding parameters (i.e. the type and size of spot welding head, gap and plate thickness) on the strength and fracture behavior of spot-welded metal sheets.
It is shown by the study that
1. The computed force-displacement curves for metal sheets welded by using both circle-type and annulus-type heads are in good agreement with experimental data, and fractures occur in experiments approximately at the same positions as the maximum equivalent stress from simulation.
2. The maximum tensile force for metal sheets welded by the circle-type head increases with the increase of diameter of nugget, and the computed force-diameter curve is very close to the experimental data.
3. For metal sheets welded by the annulus-type head, under a constant outer diameter of the nugget, there may exist an optimum inner diameter of the nugget. Therefore, under such a specification, a welded metal sheet with the smaller welding zone may have the same strength as the welded metal sheet made by the circle-type head of equal diameter. As a result, it is possible to save energy in spot welding using the annulus-type head by properly choosing its inner diameter.
4. The gaps occurring in spot welding have no significant effect on the distribution of the equivalent stress in base metal around the nugget. However, if the gap is too small, stress concentration may occur in the region of the nugget exposed to the gap.
5. For the diameter of nugget being set to 4 mm, it is shown by computation that the maximum tensile force for metal sheets welded by the circle-type head increases with the increase of the thickness of metal sheet, and the maximum tensile force may reach a constant value, 560 kgf, as the thickness of metal sheet becomes larger than 1.8mm.
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