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Service life of cyclically loaded components is often determined bystage I-crack propagation, which is highly influenced by microstructural features suchas grain boundaries. A 2D-model to simulate the growth of these short fatigue cracks ispresented discretising the crack by displacement discontinuity boundary elements. Theyallow an opening and slide displacement of the crack flanks. The direct boundary ele-ment method is used to mesh the grain boundaries which only carry out absolute dis-placement. A superposition procedure allows to employ these different types of bound-ary elements in one model. Being enclosed by elements, individual elastic properties ofthe grains can be considered. Stress intensity factors are determined to verify the elasticmodel. To simulate short crack propagation the plastic deformation in front of a cracktip is modelled as slip on individual slip planes. Displacement discontinuity boundaryelements which only allow a slide displacement mesh the activated slip band. Its lengthis limited by the distance between crack tip and grain boundary. In the neighbouringgrain, stress increases while the crack tip progresses to the grain boundary. If a criticalshear stress intensity is reached on a potential slip plane of the adjacent grain, thisplane is activated and the plastic zone overcomes the boundary. Varying elastic proper-ties influence the direction of maximum shear stress and therefore the highest loadedslip plane which is activated can differ. Furthermore a change in crack tip slide dis-placement determining stage I-crack propagation is observed.