Finite element simulation of wire arc additive manufacturing : prediction of temperature and stress evolution during processing
Fakhar ul Zaman, Fakhar (2025)
Diplomityö
2025
School of Energy Systems, Konetekniikka
Kaikki oikeudet pidätetään.
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe20251215119316
https://urn.fi/URN:NBN:fi-fe20251215119316
Tiivistelmä
This thesis is a research on the Wire Arc Additive Manufacturing (WAAM) process using finite element simulation. WAAM is a metal additive manufacturing process that is based on the deposition of layer-by-layer components, where a metal wire is melted into a stream of an electric arc. It has a high deposition rate and low cost of operation which has made WAAM gain more application in large metallic structures fabrication. Nevertheless, non-uniform heating of the deposition causes too many thermal gradients, large residual stresses, and geometrical distortion, which undermine dimensional accuracy and structural integrity (Montevecchi et al., 2016; Tatemoto et al., 2023).
The current paper is devoted to the numerical modeling of temperature change and stress buildup when the 1 bead of S235 structural steel is deposited. Heat flow was simulated using a transient heat model that used the double-ellipsoidal heat source of Goldak and coupled thermo-mechanical analysis was used to approximate the formation of stress. Using the values of the process parameters determined; the heat input of 40 W/mm, travel speed of 5 mm/s and the inter-pass cooling time of 20 s, the maximum temperature during deposition was about 1500-1600 °C, which was concentrated at the center of the molten pool. The generated thermal gradients created tensile residual stresses of the order of 200-300 Mpa, which also correlate with earlier values in the literature of WAAM research (Bauer et al., 2021; Tatemoto et al., 2023).
The simulations also affirm that process parameters have a strong effect on the quality of parts: heat input is lower or cooling times are increased, the effect on thermal gradients minimized, and consequent material in the form of residual stress and distortion is minimized. All in all, the FEM simulation proves to be highly proficient in simulating the thermo-mechanical nature of WAAM, which makes it a credible predictive instrument of optimizing the parameters and enhancing the quality of metal components made through the WAAM method.
The current paper is devoted to the numerical modeling of temperature change and stress buildup when the 1 bead of S235 structural steel is deposited. Heat flow was simulated using a transient heat model that used the double-ellipsoidal heat source of Goldak and coupled thermo-mechanical analysis was used to approximate the formation of stress. Using the values of the process parameters determined; the heat input of 40 W/mm, travel speed of 5 mm/s and the inter-pass cooling time of 20 s, the maximum temperature during deposition was about 1500-1600 °C, which was concentrated at the center of the molten pool. The generated thermal gradients created tensile residual stresses of the order of 200-300 Mpa, which also correlate with earlier values in the literature of WAAM research (Bauer et al., 2021; Tatemoto et al., 2023).
The simulations also affirm that process parameters have a strong effect on the quality of parts: heat input is lower or cooling times are increased, the effect on thermal gradients minimized, and consequent material in the form of residual stress and distortion is minimized. All in all, the FEM simulation proves to be highly proficient in simulating the thermo-mechanical nature of WAAM, which makes it a credible predictive instrument of optimizing the parameters and enhancing the quality of metal components made through the WAAM method.