4. Mechanical testing and FE Modelling of spot
welded Joint
4.1. Tensile test of the base material and spot welded Joint
Tensile-Shear test of spot weld joint has objectives for determining the elastic plastic behaviours of the welded joints being tested. Two specimen with different materials
stainless steel and Mild steel and thickness were used. The chemical composition of two base steel are listed in Table 4.1. Stainless steel used is stainless steel grade 304 with a
width of 25mm, and thickness of 0.8mm, the other specimen is mild steel with a width of 25mm and thickness of 1.44mm. Spot welded joint of two material combinations have
been prepared and tested. The first one is stainless steel to stainless steel; while the other one is stainless steel to mild steel. Tensile tests were performed using a Lloyd LR 30K
Universal material testing machine which can perform both tensile and compression tests. The machine has a maximum loading capacity of 30kN, with the readings being accurate
to 0.5 of the force. The Lloyd is interfaced with a microcomputer so graphical printout of the tests can be obtained and test data saved. The control console of the testing machine
has a digital display where the machine can be operated either manually or remotely. The test-piece is loaded into position and the jaws tightened with a pre-load of approximately
50 N. In the test the specimen was clamped with two gaskets to avoid the bending during test. The tensile test was performed at a loading rate 5 mmminute. Typical testing data
was shown in Figure 4.1. The initial elastic loading part is comparable between these two specimens, but the yielding point and the plastic deformation part is significantly different,
with the SS-MS specimen much stronger than the SS-SS specimen. Table 4.1. Chemical Composition material spot weld joint
Concentration C Cr Ni Mn Si P S
Stainless steel G304
0.08 17.5-20 8-11 2 1 0.045 0.03 Mild steel
0.14 0.01 0.01 0.32 0.03 0.2 0.05
4.2. Drop mass impact tests and results
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