Weld Angle Research Articles

Weld performance under creep using finite element modelling

The service life of a high temperature plant is frequently limited by creep damage in welded joints. The factors affecting weld performance under creep conditions are poorly understood. This paper presents the results of modelling of creep in some 240 different girth welds. The effects of weld angle, weld metal and heat affected zone material properties, heat affected zone width, and added axial loading were noted on the stress response of the models. A significant increase in stresses was seen with added axial loadings. The results include a number of results which allow us to specify construction and operation parameters, to assess which welds are at risk in service, and to define inspection or replacement strategies.

Stress-intensity factors for semi-elliptical surface cracks in welded joints

A method for calculating stress intensity factors for edge and surface cracks in weldments has been presented. The weight function method was applied and appropriate weight functions have been derived using the Petroski-Achenbach crack opening displacement expression. The derived weight functions account for both the global weldment geometry and the weld profile characterised by the weld angle. Finally analysis of several parameters such as the type of loading, crack aspect ratio, weld angle and weld toe radius have been carried out assessing their effect on the stress intensity factor. The calculated stress intensity factors were verified against available finite element data. Very close agreement was achieved between the finite element data and the weight function based calculations.

The weld profile effect on stress intensity factors in weldments

A method for the determination of weight functions relevant to welded joints and subsequent calculation of stress intensity factors is presented. The weight function for edge cracks emanating from the weld toe in a T-butt welded joint has been derived by using the Petroski-Achenbach crack opening displacement function. The weight function makes it possible to study efficiently the effect of weld profile parameters, such as the weld toe radius and weld angle, on stress intensity factors corresponding to different stress systems.

Fatigue of fillet welded joints

The Albrecht method was used to compute stress intensity factors in non-load carrying fillet welds subjected to tension and cantilever bending for cracks growing from the tip of the weld toe through the plate thickness. The stresses were obtained using a two dimensional finite element programme with eight node isoparametric elements with two degrees of freedom in each node. A detailed study of the influence of weld and plate geometry on both the stress concentration and stress intensity factor values was carried out. The results in bending showed stress intensity values 20 to 30% lower than in tension. The weld affected the stress intensity and stress concentration results only for small crack length values less than 0.1 to 0.12 of the thickness of the main plate. The results also indicated that neither the lack of penetration nor the plate length affected the stress intensity values significantly. Weld angle and plate thickness were the main parameters influencing the stress intensity values. The results in tension were compared with similar results published in the literature and good agreement was found.