This work is a contribution to the study of the rigidity of rotational friction welding of cylindrical specimens made on a parallel lathe. We performed welding of three combinations of parts: steel / steel, aluminium / aluminium and steel / aluminium according to three numbers of rotations of the spindle (900, 1250 and 1800 rpm). To control the rigidity and quality of these assemblies, tensile tests are used followed by ultrasonic testing to ensure that the tips are welded and that there are no internal defects. Hardness profile of the welded zone according to the welding parameters was obtained. Metallographic observations have detected the profile of the various zones welded and affected thermally. The results of the mechanical tests showed that a rotation speed of 1250 rpm can produce a very good weld, with other parameters kept constant.

In order to study the behaviour of a notch specimen under plane mixed mode I +II, a Brazilian disc specimen weakened by U-notch located at the edge of disc is considered. A high-strength steel material was used for the disc specimen subjected to diametral compressive loading. A local approach represented by strain energy density approach based on determination of mean value of the strain energy density (that is over a given finite-size volume surrounding the highly stressed regions near the notch tip) was utilized. A finite element analysis by cast3m code have been undertaken in order to determine the evolution of the stress intensity factors and averaged strain energy density for different location of notch from the axis of force application. Variations of radius and angle of notch will cause disturbance in the stress field and local energy in the vicinity of the notch tip. The results of finite element computations were expressed as mathematical relations showing the influence of notch position and its radius on stress intensity factors and averaged strain energy density. The reduction of the angle increases the local energy unlike the increase of the radius tends to reduce it.

Simulation and visualization of the mechanical components have become a predominant phase during the design and the production stages. Several means are used to improve the design and to reduce study time. Today, the powerful hardware and the software available on the market have contributed greatly on the improvement of design, visualization and manufacturing process of complex parts (turbine blade). In this context, our study is a contribution to the establishment of a methodology to a CAD modelling and finite element analysis, which allows us to identify the mechanical behavior of a gas turbine blade. The profile of the blade turbine model is obtained after regeneration using the CATIA V5R20 software from the retro-design technique using a FARO-type scanner. The turbine blade is analyzed under a static mechanical behavior. It has been observed that the maximum stresses and deformations are located in the vicinity of the root and the upper surface along the turbine blade. On the other hand, the elastic energy is located at a distance from the root of the turbine blade.