The demand to preserve weight and costs is a crucial claim for new technical designs. For example, this implies lower fuel consumption in a short - term period but environmental and economical advantages in a long - term period referring to energy consumption and pollutant emission. Components which are engineered according to light weight rules, must be designed close to mechanical strength limitations. To do so, accurate knowledge of loads and material behaviour is crucial for successful application. If the lifetime period is known assemblies can be optimized by respecting the low cycle fatigue limit. Today components are engineered very conservative, local, high resolution methods to analyse the true weld seam load are missing. Therefore lifetime analysis can be developed to higher level in accuracy by considering the local load and stress behaviour of components. In this work, a local method which considers residual welding stresses, stresses induced by mechanical loads and geometrical effects on the stress distribution, is suggested for assessment of the lifetime for certain zones of laser weld seams. Therefore tubular specimens are joined in an innovative weld seam design. Based on filler free welded similar and dissimilar material combinations two different approaches are suggested for accurate, local fatigue analysis in dependency of the level of detail. By assessing the real weld seam load evaluated by local methods the control volume - model enables rapid lifetime calculation amongst standard weld seam designs. Furthermore the phase - model allows to calculate the fatigue behaviour of any arbitrary weld seam design. Different seam topologies can be compared and optimized. Experimental prototype effort and development time can be reduced by covering all design steps in an integrated virtual environment.