Papers by Author: Jan Szweda

Abstract: The presented paper deals with the influence of manufacturing process on the stress state of mechanical parts. The problem is presented in the assembly of the belt drum. The connections of individual parts are realized by press fitting and welding technology. The practical use of the belt drum shows the initiation of cracks in the weld body. The presence of press fitting connection in the structure is marked as the origin of high stresses in the weld body. The paper proposes the new assembly method in order to reduce the stress level in the weld structure and points the assembly method as one of important factors influencing the stress state of mechanical parts.

Abstract: The contribution and presented work deals with the CFD simulation of heating and air conditioning process of a special vehicle. The aim of the work is then the capacity validation of the heat exchanger which provides the heating or cooling of the air supplying the vehicle. Because of the high dimensionality and complexity of the whole task, the number of simplifications in the form of proper boundary conditions and constraint equations was proposed by authors. The presented paper contains the presentation and discussion of the used simplifications, the saved computational capacities are accented and results in the form of distribution of thermomechanical quantities are presented. Finally, the capacity of heat exchanger used is validated.

Abstract: The numerical analysis of large mechanical systems brings specific problems. As an example the contact of two surfaces can serve. The contact situation occurs when two surfaces touch each other. The pressure forces can be then transferred whilst the tension forces can not. The solution of mentioned large systems by FEM leads usually to the large number of degrees of freedom (DOF). Even the nowadays used HW equipment makes possible solving the large scale systems, in certain cases (especially when the number of DOFs exceeds approximately 1e7) it is convenient to use an alternative approach leading to shorter solution times and HW demands. One of these approaches is the substructure technique. The paper deals with the description of this technique used for the contact problem arising in the body of roller bearing.

Abstract: This article deals with a way of interpretation the results of numerical simulations solved for the mechanism of lifting platform. Subject of analysis is the atypical design solution of lifting mechanism with one degree of freedom, which members are connected by revolute joints and linear sliding guidance. The mechanism movement is provided by linear hydromotors. Computational simulations are carried out by FEM, where linear coupling equations are used for modeling of revolute joints and linear sliding guidance is modeled by structural contact of rail and slider. The way of modeling and parameters setting of structural contact significantly affects the stability of numerical solutions and the obtained results. The authors assume that the interpretation of the observed behavior and results of the numerical simulations allow to deduce the mechanism operability and gives a clue for setting the gap of real bounds.

Abstract: The paper describes modal analysis of lifting platform usually used in theatre technologies. The platform itself consists of several components mutually connected by joints. The behavior of particular joints can be linear or nonlinear. The connection of two main parts - tables and pillars of lifting platform-must be considered as nonlinear because the force transfer between these parts can occur only in one direction. Since standard modal analysis is in principle linear, the method of linear description of nonlinear behavior has to be proposed. The contribution presents such method using application of three different boundary conditions which allow describing the nonlinear behavior of system by tools of linear analysis. Consequently, the modal analysis of the entire system is performed for all three types of boundary conditions. On the base of mode shapes visualization the proper mode shapes are extracted which satisfy the real behavior of the lifting platform.

Abstract: In this paper is discussed the way of suitable numerical solution of contact shape optimization problem. The first part of the paper is focused on method of global optimization field among which the genetic algorithm is chosen for computer processing and for application on contact problem optimization. The brief description of this method is done with emphasis of its characteristic features. The experiment performed on plane structural problem validates the ability of genetic algorithm in search the area of the global optimum. On the base of the research described in this work, it is possible to recommend optimization technique of genetic algorithm to use for shape optimization of engineering contact problems in which it is possible for any shape to achieve successful convergence of contact task solution.