A novel macroscopic computational methodology to predict the locations and orientation of solidification-cracks: Application to pulsed laser welding

The prevention of solidification cracks in critical engineering applications demands generalised predic-tive approaches. The first part of the manuscript reports the computation of transient temperature and flow fields using high-fidelity CFD simulations of the mixed-mode pulsed laser welding process, us-ing iterative calculations of the volumetric heat source. The temperature field is verified by comparing the experimental and numerical weld profiles with different power-deposited-per-unit-length phi, which varied from 76 J/mm to 177 J/mm . The second part of this manuscript presents a novel and generalised macro-scale computational methodology which allows in situ numerical estimation of the Crack Vulnera-ble Index (CVI). Unlike the previous attempts, here, only the thermal characteristics, i.e., the temperature, melt flow velocity, and fluid fraction, are used to predict the locations and orientation of the cracks dynamically. The predictions agree well with the experimentally obtained findings of pulsed laser weld-ing. The study shows that the heat-flow direction correlates closely with the crack-orientations obtained from experiments. It is experimentally observed that the cracking tendency is substantially reduced as the power-deposited-per-unit-length is increased. The bulk weld-pool solidification velocity is inversely proportional to the number-of-cracks (a measure of cracking tendency) observed in the post-solidified weldments. Further, for the case with the lower cracking tendency, the peak values of the temperature gradient and the normalized bulk weld-pool solidification velocity are similar to 33% and 11% higher than the respective values for the case with the higher cracking tendency.(c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

This study presents generalised predictive approaches for the prevention of solidification cracks in critical engineering applications. It first uses high-fidelity CFD simulations to compute transient temperature and flow fields in pulsed laser welding, and verifies the temperature field by comparing experimental and numerical weld profiles. Then, it proposes a novel macro-scale computational methodology for in situ numerical estimation of the Crack Vulnerable Index (CVI) based on thermal characteristics. The predictions agree well with experimental findings, indicating that the heat-flow direction is closely related to crack orientations.