This paper presents experimental and numerical analysis of the change of temperature and force in the vertical direction during the friction stir welding of high-strength aluminium alloy 2024 T3. This procedure confirmed the correctness of the numerical model, which is subsequently used for analysis of the temperature field in the welding zone, where it is different to determine the temperature experimentally. 3D finite element model is developed using the software package Abaqus; arbitrary Lagrangian-Eulerian formulation is applied. Johnson-Cook material law and Coulomb's Law of friction are used for modelling the material behaviour. Temperature fields are symmetrical with respect to the welding line. The temperature values below the tool shoulder, i. e. in the welding zone, which are reached during the plunge stage, are approximately constant during the entire welding process and lie within the interval 430-502 °C. The temperature of the material in the vicinity of the tool is about 500 °C, while the values on the top surface of the welding plates (outside the welding zone, but close to the tool shoulder) are about 400 °C. The temperature difference between the top and bottom surface of the plates is small, 10-15 °C.

This study focuses on the estimation of residual life of damaged thermal power plant components. The high-pressure turbine housing was chosen as an example of thermal power plant component where, during the years of exploitation, damage appeared in the form of dominant crack. Residual life estimation procedure, based upon experimental and numerical methods has been introduced and applied. Material properties were determined experimentally both at room and operating temperature, while all necessary calculations were performed by the special finite element method, so-called X-FEM. The residual life estimation of the damaged high-pressure turbine housing was performed by applying the Paris's law for crack growth analysis.

Dual phase ADI material microstructure consists of different amounts and morphologies of ausferrite and free ferrite, obtained by subjecting ductile iron to specific heat treatment. As such, its strength is lower compared to comparable ADI materials, but exhibiting a higher ductility, the major disadvantage of ADI. In the current study, an unalloyed ductile iron was intercritical austenitised in two-phase regions (?+?) at four temperatures from 840 to 780?C for 2 hours and austempered at 400?C for 1 hour to obtain dual phase ADI with different percentages of free ferrite and ausferrite. Metallographic and fracture studies were performed by light and scanning electron microscopy, respectively. Microscopy results were correlated to tensile testing results. The results indicated that, as the amount of ausferrite present in the matrix increases, higher values of strength and lower ductility are obtained. The fracture surfaces of dual phase ADI microstructures with 22.8% of ausferrite in their matrix have regions of quasi-cleavage fracture around last-to-freeze zones, related to the presence of ausferrite in those areas. The specimens with the highest values of ausferrite of 86.8% among the dual phase microstructure have a dominant quasi-cleavage type of fracture.