Optimalizált lépésközű Newton-Raphson algoritmus EHD feladat megoldásához

Rolling-sliding machines such as gears, cams and followers, and bearings, which are often subjected to high loads, high speeds and high slip conditions when not only the pressure distribution in the lubricant is a question but the surface deformation, and variation of the viscosity due to pressure. To analyse the tribological conditions of the contact surfaces, the generalized Reynolds equation was developed by Dowson [2]. Although several methods have been already developed for solving EHD problems, the solution of the highly nonlinear problem is still quite challenging. Handling the numerical problems during the solution quadratic step optimized Newton-Raphson method has been implemented for solving the nonlinear equation system. The proposed technique reduces the step number during the iteration and the solution is stabilized

Study of the Stress State of a Dissimilar Metal Weld Due to Manufacturing and Operational Conditions

Welding is accompanied by the presence of weld residual stresses, which in case of dissimilar metal welds even with post weld heat treatment cannot be removed completely therefore they should be considered when assessing possible welding defects. The measurement of residual stress in metal weld is a very complex procedure and also in the investigated case could not be carried out as it is the part of a working plant. However, by modelling these processes, the residual stresses and deformation of the components caused by this manufacturing method can be determined. It is important to calculate these values as accurately as possible to determine the maximum load capacity of the structure. The structure under examination was the dissimilar metal weld of a VVER-440 steam generator. 2D simulations were performed, where temperature and phase-dependent material properties were implemented. Different loading scenarios were considered in the numerical analysis. The results can be useful to determine the real loading conditions of a given component and can be used to predict stress corrosion crack initiation locations, as well as to evaluate the lifetime and failure mode prediction of welded joints

Coupled Numerical Method for Rolling Contact Fatigue Analysis

In this paper, our aim was to create a coupled numerical simulation method for rolling contact fatigue (RCF) analysis which takes into account the effects of results of the heat treatment process of the manufacturing of specimen/machine parts, such as hardness, mechanical properties, residual stresses in the carburized layers of the body. Thus, the finite element method (FEM) simulation process calculates the material properties and stress close to the realistic state and using them as an input data, the RCF analysis is carried out by this coupled method. The Dang Van, Matake and Findley multiaxial fatigue criteria were used for failure analysis. In parallel with the development of the method, validation experiments were carried out to decide which criterion is the most appropriate for our purpose and to determine the coupled method efficiency