**Abstract:** (4258 Views)

In this research, the effect of RSW parameters including current intensity, welding time and welding force (coded by A, B and C) on the radius, thickness and area of the nugget and the radius of the HAZ of TRIP steel joints was investigated by DOE and RSM. A 3D coupled thermal-electrical-structural FEM was used to model RSW. To validate the FE model, two TRIP steel sheets were welded experimentally. During welding, the temperature was measured and the results were compared with the FE results and a good agreement was obtained. The boundaries of the welding zones were determined according to the critical temperatures and the responses in all samples were calculated. Using analysis of variance, direct, quadratic and interaction effects of parameters on the responses were studied and a mathematical model was obtained for each response. The direct linear effects of all parameters on all responses were significant. But among the interaction effects, the effect of B×C on the nugget radius, the effect of A×B on the nugget thickness, the effect of A×B on the nugget area and the effects of A×B and B×C on the HAZ radius were significant. Also, current intensity had the greatest effect on all responses.

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Highlights
- The effect of RSW parameters on the size of welding zones in TRIP steel joints, was investigated by DOE using the RSM and applying FE simulation. The input parameters were current intensity (A), welding time (B) and welding force (C). To validate the finite element model, two TRIP steel sheets were experimentally welded and the temperature measured during the process was compared with the finite element results and a very good agreement was obtained.
- Examination of the microstructure of the weld zone in the experimental sample showed that two subdivided zone formed during welding: NZ and HAZ. Based on the critical temperatures, the NZ and HAZ were determined in all finite element models, and the Nugget radius, Nugget thickness, Nugget area, and HAZ radius were calculated. Using ANOVA, the direct, quadratic and interaction effect of parameters on the responses were evaluated and a mathematical model was extracted for each response.
- The direct linear effects of all parameters on all responses were significant. But among the interaction effects, the effect of B×C on the nugget radius, the effect of A×B on the nugget thickness, the effect of A×B on the nugget area and the effects of A×B and B×C on the HAZ radius were significant.
- Increasing the current intensity increases the all responses, but when the its value approaches 10 kA, the responses decrease, which in most cases is due to the occurrence of expulsion and to prevent the spread of heat.
- Increasing the welding time continuously increases the nugget thickness, but in other responses it first increases and then decreases the size of the response.
- The effect of increasing the welding force is completely different from the effect of the other two parameters. Increasing the force, although initially increases the responses slightly (except for the nugget radius, which remains constant at first), but very soon due to increasing the contact surface of the sheets and reducing the electrical resistance reduces the heat generation and thus reduces the size of the zones.

Type of Study:

Research Paper |
Subject:

Biomaterials