International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

This study investigates the influence of distance and relative orientation of semi-elliptical twin surface cracks in cylindrical bars under tensile loading on the stress intensity factors (SIF). Finite element analysis was used to analyze the interactions between two identical cracks with different spacing (5-20 mm) and rotation angles (0°-180°). The results show that the crack orientation has a significant effect on the stress distribution patterns and stress intensity factor values, with a 45° rotation producing the highest SIF values, while a parallel orientation has a favorable shielding effect with significantly lower values. All configurations gradually converge to the reference value for a single crack at larger distances (20 mm), indicating decreasing interaction effects. These results can provide insights for the assessment of structural integrity, especially for components with multiple closely spaced defects, and provide a basis for the development of more accurate predictive models for fracture behavior in engineering applications.

The present work deals with the analysis of the influence of internal forces and moments on the nozzle of the main boiler of a steam boiler used in the waste incineration industry. The analysis is carried out analytically by performing calculations using standards, and later numerically using finite element method software. As results of the analyses, equivalent von Mises stresses, displacements and buckling eigenvalues are obtained and compared with analytical solutions.