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The lifetime of power train components can be improved dramatically by finding crack initiation points with suitable software tools and optimization of the critical areas. With increasing capacities of computers the prediction of the lifetime for components by numerical methods gets more and more important. This paper discusses some applications of the outstanding fatigue simulation program FEMFAT supporting the assessment of uniaxially and multiaxially loaded components (as well as welding seams and spot joints). The theory applied in FEMFAT differs in some aspects from classical approaches like the nominal stress concept or the local one and can be characterized by the term “influence parameter method”. The specimen S/N-curve is locally modified by different influence parameters as stress-gradient to take into account notch effects, mean-stress influence which is quantified by means of a Haigh-diagram, surface roughness and treatments, temperature, technological size, etc.

The lifetime of dynamically loaded components can be improved dramatically by finding the crack initiation point with suitable software tools and optimization of the critical areas. With increasing capacities of computers the prediction of the lifetime for components by numerical methods gets more and more important. Using the program FEMFAT the assessment of uniaxially and multiaxially loaded components as well as welding seams and spot joints is possible. The theory applied in FEMFAT differs in some aspects from classical approaches like the nominal stress concept or the local one and can be characterized by the term „influence parameter method”. The specimen S/N-curve is locally modified by different influence parameters as e.g. stress-gradient to take into account notch effects, mean-stress influence which is quantified by means of a Haigh-diagram, surface roughness and treatments, temperature, technological size, etc.

A software package is described which permits the assessment of welded structures under dynamic loadings. Based on the stresses calculated using the Finite Element Method and a database with notch factors of welded seams and S/N-curves the process of this assessment can be automated. Safety factors and damage values can be quickly displayed on the Finite Element structure.

A postprocessor program for the calculation of the fatigue life of components calculated with the finite element method (FEM) is described. Based on the stresses calculated by FEM and the material data of unnotched test specimens, s/n curves in relation to FE nodes are calculated for components taking into account the most varied influencing factors, such as amplitude stress tensor, mean stress tensor, relative stress gradient, surface roughness, technological influences, local plastic deformations etc. The results of the calculations, such as damage distribution and insusceptibility to permanent rupture, are graphically represented in the form of FE colour plots. Besides the possibility of the calculation of the fatigue life of components also costs and time can be reduced during the development phase of vehicles.