Recently the residual stress fields near the weld toe of welded joints have been investigated according either to the theoretical linear elastic solution obtained by Williams in 1952 or to the elasto-plastic solution obtained by Hutchinson, Rice and Rosengren in 1968, depending on the process parameters and boundary conditions. These approaches are appropriate if the weld toe region is modelled as a pointed V-notch having a zero notch root radius, according to a “worst case” geometrical hypothesis. Accordingly, the intensity of the residual singular stress distribution can be quantified by the residual notch stress intensity factor (R-NSIF), which might be a useful stress parameter to include in local approaches for fatigue strength assessments of welded joints, though its use has not yet been validated. In order to calculate the residual stress fields by means of welding process simulations, the mesh adopted in numerical models has necessarily to be very fine, the smallest element size being of the order of 10-5 mm. Unfortunately, the non-linear and transient behaviour of the welding simulation makes numerical analyses extremely demanding in terms of computational time, particularly if large welded structures and/or multi-pass welds have to be simulated. In this scenario, the use of methods aimed at reducing the computational effort to estimate local stresses and strains in welded structures can be effective. Among these, the peak stress method has been proposed to estimate the NSIFs at sharp V-notches, using coarse finite element patterns, characterized by a uniform average element size and by a mesh density within a proper range of applicability. In this work, the PSM has been used to calculate the R-NSIF of a full penetration welded T-joint. It has been shown that the PSM can successfully be used to estimate R-NSIFs values, provided that the stress redistribution induced by plasticity in the zone very close to the notch tip is negligible.
Rapid calculation of Residual Notch Stress Intensity Factors (R-NSIFs) by means of the Peak Stress Method
M. Colussi;P. Ferro;G. Meneghetti
2018
Abstract
Recently the residual stress fields near the weld toe of welded joints have been investigated according either to the theoretical linear elastic solution obtained by Williams in 1952 or to the elasto-plastic solution obtained by Hutchinson, Rice and Rosengren in 1968, depending on the process parameters and boundary conditions. These approaches are appropriate if the weld toe region is modelled as a pointed V-notch having a zero notch root radius, according to a “worst case” geometrical hypothesis. Accordingly, the intensity of the residual singular stress distribution can be quantified by the residual notch stress intensity factor (R-NSIF), which might be a useful stress parameter to include in local approaches for fatigue strength assessments of welded joints, though its use has not yet been validated. In order to calculate the residual stress fields by means of welding process simulations, the mesh adopted in numerical models has necessarily to be very fine, the smallest element size being of the order of 10-5 mm. Unfortunately, the non-linear and transient behaviour of the welding simulation makes numerical analyses extremely demanding in terms of computational time, particularly if large welded structures and/or multi-pass welds have to be simulated. In this scenario, the use of methods aimed at reducing the computational effort to estimate local stresses and strains in welded structures can be effective. Among these, the peak stress method has been proposed to estimate the NSIFs at sharp V-notches, using coarse finite element patterns, characterized by a uniform average element size and by a mesh density within a proper range of applicability. In this work, the PSM has been used to calculate the R-NSIF of a full penetration welded T-joint. It has been shown that the PSM can successfully be used to estimate R-NSIFs values, provided that the stress redistribution induced by plasticity in the zone very close to the notch tip is negligible.Pubblicazioni consigliate
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