LEFM Analysis and Service Simulation Testing of a Welded Frame Structure

In this paper the results from fatigue analysis and testing of a welded frame are discussed. The structure contains some typical welds, which can be found on a frame to a wheel loader. The test was carried out with a service load spectrum with an overall stress ratio, R, of about ‐1. The fatigue cracks started from the root side of the welds in all cases. The test results were correlated with linear elastic fracture mechanics (LEFM) including different assumptions of residual stress distributions.     

FEM Study of Fatigue Response of 3‐Sheet Spot Welded Joints

The commercial software used for predicting fatigue strength for load‐carrying spot welds in sheet structures, like car bodies, is mainly developed for two‐sheet joints. The purpose of this work was to study the fatigue properties of three‐sheet spot welded joints with a dimensioning method used in the automotive industry and to compare such computational results to those obtained from a more accurate method and to experimental data. Eleven three‐sheet, single spot welded specimens were studied using a structural stress approach, followed by shell element simulations, similar to those used in commercial software. These results were compared to calculations based on fine meshed solid element models. Fracture mechanics was used to evaluate the loading conditions at the spot welds. Comparison between the results from the different methods and experimental results for three shear loaded specimens, consisting of triple sheets, found in literature showed good correlation. The shell element method in shear loaded cases gives stress intensities within +35% to ‐5% of the solid element method results. In peel loaded cases the results differ up to ‐60%, an under‐estimation that leads to an increase of estimated fatigue life up to 65 times.     

Assessment of the Primary Structure of Slabs and the Influence on Hot‐ and Cold‐Rolled Strip Structure

The quality of the delivered strips depends ‐ among other things ‐ on the internal structure of the slabs. Solidification phenomena as micro‐ and macro‐segregation are of particular importance. This paper deals with the micro‐ and macro‐segregations in slabs of the steel grades DP and S355. The method for the investigation of segregations based on electron probe microanalysis is described in brief. Characteristic values of segregations are derived from quantitative element distribution images. These results serve as a basis for decisions on further processing steps in the hot and cold rolling mill.