About Calculation of Imperfections for Welding Simulations

Ladislav Novotný, Adan Vega Saenz

Abstract


Many metal structures are assembled from thin plate with welded supports. However welded joints, which require large heat input, may incur significant distortion in the finished plate. Distortion of the welded assembly is largely affected by residual stress generated in the weld and is dependent on the constraints imposed by the geometry of the welded structure. Welded components are typically subjected to several types of deformation. Most of these types of deformation result from the shrinkage of the weld metal during cooling. The ideal straight geometry may be changed by imperfections to enable buckling behavior. Real component shapes contain various imperfections. Finite element mesh may contain imperfections too. When the simple weld model shapes are used, the shape of the result distortion is predictable. The imperfections are created in the same shape as predicted. The sufficient magnitude of an imperfection is about 1/100 of result distortion, or it respects model dimension. When the complex weld model shapes are used, it is not easy to predict the correct imperfection shape. For general purpose as well, the common procedure for calculation of correct imperfections shapes is required. Thermal source is time-dependent, moves along the weld line. For welding distortions and residual stress simulations, nonlinear mechanical analysis is required. Nonlinearities are caused by both nonlinear behaviour of the material and geometrical nonlinearity. Usually, the element birth technique is used to simulate weld material additions. This article present possibility of calculations of geometrical imperfection. Algorithm to consider imperfections has been developed and implemented in a thermo-elastic-plastic analysis within a finite element analysis framework.

Keywords


finite element method, imperfection, welding distortions, welding simulation

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ISSN 1801-1217 (Print)
ISSN 1805-9422 (Online)
Published by the Czech Technical University in Prague, Faculty of Mechanical Engineering