RESEARCH PAPER Prediction of welding-induced distortions in large weld structure through improved equivalent load method based on average plastic strains Saurav Suman 1,2 & P. V. S. S. Sridhar 2 & Pankaj Biswas 2 & Deepjyoti Das 3 Received: 16 October 2018 /Accepted: 7 October 2019 # International Institute of Welding 2019 Abstract Prediction and minimisation of weld-induced distortion at the design stage incites pre and in-process mitigation techniques to improve the weld structure. As a result, it inhibits the need for post welding processes like line heating, straightening etc. In this work, to get more accurate results for distortion prediction, an effort has been made to improve the existing equivalent load method. In this method, the transient behaviour of plastic strain distribution was considered to analyse the large welded structure. Here, the actual transient phenomenon of a weld was considered, i.e. the effect of start, end and middle quasi-steady-state was considered. The separate average loads were applied at the start, middle and end regions of the welding line instead of the same average load throughout the weld length. This proposed method was validated with experimentally obtained results, which showed a perfect agreement and hence, confirmed its efficacy. This method was also validated for published results for different welding joints to assure its effectiveness. At last, a large weld structure was analysed for distortion prediction by using the proposed equivalent load-based technique. Keywords Equivalent load technique . Distortion . Large structure . Thermal-mechanical elastic-plastic analysis 1 Introduction In general, welding structures are exposed to non-uniform rapid heating and cooling. It leads to generate welding-induced resid- ual stresses and distortions. Consequently, the final assembled structures undergo defects like misalignment, directional mis- match etc. So, it stands in need for post-processes like mechan- ical straightening, line heating etc. and brings over expenses in terms of energy, material losses and labour cost. As a result, prediction and analysis of welding deformations before the ac- tual practice plays an important role to control it at the design stage. Welding distortions can easily be determined experimen- tally. However, it is almost impractical for large weld structures. Researchers have conducted various experiments from time to time to analyse welding distortions for different welding pro- cesses. Pattee studied the buckling deformation pattern to in- vestigate the effect of varying boundary conditions [1]. Terassaki et al. conducted experiments and examined the criti- cal requirements of buckling deformations to study the effect of welding parameters [2]. On the other hand, it is entirely infea- sible to conduct experiments for prediction of distortion in large and complicated weld structures. Researchers developed vari- ous analytical and numerical methods to model and simulated the actual welding process for parametric study and prediction of residual deformation and stresses. Analysis results depend on the properties of the base and weld metal and various welding conditions (types of process, welding parameters, fixtures, etc.) [3–5]. Different moving heat source models have been pro- posed to simulate the actual welding process successfully [6]. Though, the nonlinearity and complexities of this method make it comparatively, insignificant and incompetent in analysing the large complex structure in terms of computational time and Recommended for publication by Commission XV - Design, Analysis, and Fabrication of Welded Structures * Pankaj Biswas panu012@yahoo.co.in 1 Department of Mechanical Engineering, National Institute of Technology Mizoram, Aizawl, Mizoram, India 2 Department of Mechanical Engineering, Indian Institute of Technology Guwahati, Guwahati, Assam, India 3 Department of Mechanical Engineering, Royal School of Engineering and Technology, Guwahati, Assam, India Welding in the World https://doi.org/10.1007/s40194-019-00805-1