Some selected examples of fem modelling of structure-affecting material and manufacturing faults

In design practice, in most of cases, stresses and deformations of structures with nominal dimensions and average material properties were analyzed. It have been concluded that such procedure is most often sufficient. However, there are design solutions, especially in high-effort structures for example aircraft and turbine engines, where scatter of geometrical dimensions consistent with assumed tolerances cause significant scatter of stresses and strains, differ from values coming from nominal dimensions. Scatter of these values have essential influence on service life of presented structures. Example of such effect is described in the paper. There were used FEM analyses to determination of scatter of stresses and stres s concentration coefficient in herringbone lock joint of K-15 engine's turbine. Another example of fault impact on stresses in structure is analysis of undercarriage element with material fault. Both these examples indicate on great sensitivity of stress distribution on manufacturing imperfections. The impact of these faults and imperfections reaches hundreds of per cent, and in some cases could be serious menace of operating safety. In structures with the multiple 3D stress state, non-linear geometric and material phenomena, with contact between friction-affected elements, any geometric imperfections can cause considerable local changes in the stress and strain.