Development of a Practical Straightening Simulation for Welded Structures Using Inherent Strain Method


Welding is the most widely used assembly method available to industries in the construction of metal structures, ships, and offshore platforms. However, this method always produces a certain amount of distortion that will not only degrade the performance but also increase the building cost of the structure, and it should be straightened. Murakawa [1] developed a thermal elastic plastic based and inherent strain based welding simulation FE code JWRIAN. Coarse shell FE models are usually used in the inherent strain based JWRIAN elastic analyses. This drastically reduces the manpower needed for modeling and computer resources needed for the calculation. However, it is not easy to perform straightening analysis using JWRIAN because gas heating’s inherent strain distributes over a range much smaller than element sizes of the shell model.

RUIZ [2] modified JWRIAN’s code so that the inherent strain equivalent nodal forces along the heating line are calculated and applied in the elastic shell analysis. However, a discrepancy between 3-dimensional thermal-elastic-plastic analysis and elastic analysis was observed. This is mainly because of the nature of solid and shell elements. RUIZ [3] proposed a linearized inherent strain and applied it to both 3-d and 2d analysis, getting matching results between solid and shell element models. In this study, as a working example, a thin plate panel with an opening is considered utilizing the developed system at the same time a friendly user interface for staffs and workers on a production site is developed.  

Keywords: Inherent strain, straightening, finite element method, Gauss-Legendre quadrature

[1] Murakawa H, “Concept of inherent strain, inherent stress, inherent deformation and inherent force for prediction of welding distortion and residual stress” et al. Trans. JWRI, 39, 2, pp. 103-105 (2010).

[2] Ruiz H, Osawa N, Murakawa H, Rashed S, “Prediction of Distortion produced in welded structures During Straightening Process using the Inherent Strain Method” Proceedings of the ASME 2016 35th International Conference on Ocean, Offshore and Arctic Engineering, OMAE2016, June 19-24, 2016, Busan, South Korea.

[3] Ruiz H, Osawa N, Murakawa H, Rashed S, “Prediction of Welded Structures due to Straightening using Linear Inherent Strain Method” Annual Assemble & International Conference, IIW2017, June 25th – 30