Modeling Of Deformation Processes Research Articles

Modeling of Deformation Processes in Vacuum Thermoforming of a Pre-stretched Sheet

Modeling of deformation processes in vacuum thermoforming for a preliminary stretched thermoplastic sheet (plug-assist vacuum thermoforming) is investigated in this paper. The model can be used for production of polymeric articles with minor wall-thickness variation. A nonlinear rheological model is implemented for developing the process model. It describes deformation process of a prestretched sheet at any phase of vacuum thermoforming process. This process is described by a set of deformation processes, each specified by appropriate boundary conditions. For model validation, a comparative analysis of the theoretical and experimental data is presented. The wall-thickness distributions obtained from modeling results corresponded well with experiments. A method for prediction and enhancement of the quality of the final products on the basis of wall-thickness distribution criterion has been established.

Development of a CAD/CAM system for the closed-die forging process

The application of computer-aided engineering (CAE), computer-aided design (CAD), and computer-aided manufacturing (CAM), is essential in modern metal forming technology. Thus, the process of modelling for the investigation and understanding of deformation mechanics has become a major concern in recent and advanced research, and the finite element method (FEM) has assumed increased importance, particularly in the modelling of deformation processes. This work is devoted to the development of a CAD/CAM system for the closed-die forging process. The system development consists of three stages: namely, metal flow simulation, die failure analysis and design optimisation, and the development and implementation of a machining code. In the first stage, the FEM was used to simulate the axisymmetric closed-die forging process of copper material. The method is used to study the metal flow; die filling, retaining the non-linearity involved in the large change in the geometry; the continuous change in the contact surface condition; and the isotropic material work-hardening characteristics. In the second stage, a finite element analysis and optimisation algorithm is developed to examine the die fatigue life and to optimise the die design. The finite element analysis in the first and second stage was carried out using commercially available finite element software called LUSAS. In the third stage, a machining code for the optimised die is developed and implemented using CAD/CAM software called UniGraphics and CNC machine.

The permeable element method for modelling of deformation processes in porous and powder materials: theoretical basis and checking by experiments

Abstract The permeable element method (PEM), as the development of an arbitrary Eulerian–Lagrangian finite element approximation, intended for the description of densification of porous bodies, is elaborated. The Eulerian frame of reference, for which the material movement is independent of the movement of a discretizing network, is the basis for the consideration of the deformation process. The shape of the elements and network movement are deliberately determined from the point of view of convenience for the analysis of the calculation results. Using the PEM, the pressing of hollow cylinders in a rigid die is considered. The computed spatial density distributions are compared with the experimental data obtained, using quantitative metallography analysis. The problem of pressing an article of a stepped shape is solved. The peculiarities of material flow and density distributions are discussed.

Equilibrium failure processes of granular composites

The macroscopic failure of inhomogeneous media results from damage accumulation on different structural levels. During rigid loading, when given displacements of boundary points are ensured, irrespective of the body's resistance, structural-failure processes of composite materials take place in an equilibrium regime and result in the manifestation of such nonlinear-behavior effects as a descending branch on the strain diagram. the structural elements of a granular composite are homogeneous and firmly connected along the interface. Their geometry and mutual arrangement are given and do not change during deformation and failure of the medium, and the medium itself is macrohomogenous. The strength of isotropic structural elementsis estimated by comparing the second invariant of the stress tensor with its critical value. Nonfulfillment of the indicated strength criterion is associated with loss of ability to resist changes in form; at this point, the positive value of the first invariant corresponds to loss of such ability to resist and increase in volume. The deformation and structural failure of the medium are investigated as a single process that can be described under quasi-static loading by a boundary problem consisting of a closed system of Eqs. (1) and (2) and boundary conditions providing for a macrohomogeneous strain state. A principal feature of the boundary problem under consideration is the possibility of considering in constitutive relationships the states of the inhomogeneous medium, which correspond to partial or complete loss of bearing capacity of the structural elements. The random structural strength constants correspond to three-parameter Weibull distribution (6). The representative volume of a granular composite, which fills a domain in the form of a cube, is modeled by a set of istropic elastobrittle strain diagrams containing a descending branch are obtained as a result of the mathematical modeling of deformation processes and structural failure to realized a representative volume containing 384 structural elements with different strength and similar elastic constants.

A model of deformation processes of compressible materials with pore formation taken into account. I. Determining equations and loading surface

A model of deformation processes of compressible materials with pore formation taken into account. I. Determining equations and loading surface