Many high performance structures are manufactured from thin wall ductile materials. The mechanical behaviour of such materials is different from thick wall materials due to size effects. Therefore, fracture mechanics (FM) theories and conclusions appropriate for thick wall structures can not be straightforward applicable when analyzing thin wall structures. Resistance of the structures to crack growth is usually characterized by the fracture toughness. Standardized approaches are based on assumption that fracture toughness may be measured indirectly using some characteristic fracture parameter. However it is difficult apriori guarantee that the assumptions of FM theory used are satisfied for given measurement especially if ductile material is used. Consequently we can receive different values of fracture toughness measured in dependence on FM theory applied. Much more appropriate determination of the fracture toughness would be evaluation of the energy responsible for fracture advancing. Related problems of energy dissipated in process and plastic zones in dependence on specimen geometry and material used are basis of the project proposed. Solution will be done experimental-numerically.