Effect of parameters on properties of sheet metal welded by rocker arm spot welding machine

Mohd Amir, Nadia Syahida (2017) Effect of parameters on properties of sheet metal welded by rocker arm spot welding machine. Project Report. Universiti Teknikal Malaysia Melaka, Melaka, Malaysia. (Submitted)

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Abstract

The aim of this study is to investigate the effect of parameters on tensile properties, hardness, and weld nugget diameter and to suggest optimum parameter to weld steel sheets by using rocker arm spot welding machine. Nowadays, industries can only use 30% of the total amount of spot weld due to difficulty in determine the welding parameter. There are many factors that can affect the quality of spot welds as it is a very fast process. Failure also could happen on spot welds cause the spot welds to have less strength and can lead into destruction of joining parts of car bodies. The specimens were welded by setting range of parameters on spot welding machine. The weld parameters were generated by using Taguchi method from Minitab 17. There were two dimensions used in the study. The mechanical properties of the spot weld were tested by using tensile shear test and micro hardness test. The nugget diameter of spot weld was observed by using stereo microscope to determine the quality and strength of a spot weld. Tensile test was used to determine the tensile shear strength of a spot weld against weld current and weld time. Then, it was proved that tensile shear strength and hardness value increase parallel with the increase of weld current and weld time. Weld nugget diameter also extended when high heat input was applied. Based on ANOVA analysis, weld time highly influenced tensile shear strength as it came out in first rank. Confirmation test had been conducted to prove that weld time is the optimum parameter in this research. Therefore, it can be concluded that when weld current and weld time increase, tensile shear strength, hardness value and nugget diameter also increase. The optimum parameter to weld mild steel was weld time.

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