Heat Transfer Modelling of AC Waveform Submerged Arc Welding Process

Matur, Vinayak S (2016) Heat Transfer Modelling of AC Waveform Submerged Arc Welding Process. Masters thesis, Indian Institute of Technology Hyderabad.

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Abstract

Heat transfer during Alternate Current (AC) waveform Submerged Arc Welding (SAW) is simulated in the current work to capture the representative heat source model of the welding process to obtain accurate weld bead shape and size. The polarity of electrode in AC waveform SAW flips as compared to conventional arc welding process within a cycle resulting in Electrode Negative (EN) ratio varying from 0 to 1. The positive polarity controls the penetration of the weld nugget, while the negative controls the melting rate of the electrode. Experimentally, it is observed that AC SAW process yields finger type of penetration of the weld nugget [1]. In the present work, several heat source model are proposed to simulate the SAW with various EN ratio. Focus of the present work is to capture accurate heat source model that are in agreement with the experiments by quantifying the Semi Penetration (SP) ratio. To achieve the validation of AC waveform SAW is simulated as metal deposition on a medium carbon steel JIS-G-3106. The weld deposition simulations are performed using element birth and death feature present in commercially available ANSYS APDL finite element software. Three different heat sources models i.e., model 1: Combined heat source model, model 2: Alternative Goldak profile one each for positive and negative polarity, model 3: Bead shape profile obtained by summing the Goldak’s profiles of positive and negative polarity are carried out to match the experiments. It is observed that both the model 1 and 3 predicts exact penetration profile. While in the SP validation, model 2, 3, and 1 shows the increasing match with the experiments. However accurate prediction of Semi Penetration (SP) ratio is not fully achieved. Hence, present work needs to be extended to capture more realistic heat source model. Nevertheless, from these studies model-1 heat source is recommended to get preliminary insights into simulations of AC waveform SAW process.

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