Prediction of the Evolution of the Surface Roughness in Dependence of the Lubrication System for Cold Forming Processes

Lubricants for cold forging operations do not only enable a reliable forging process, but also affect the results of forging processes. A sound lubrication decreases the occurring forces and may result in a smooth specimen surface. However, some lubricants are known to increase the initial surface roughness of the specimen as a consequence of the forming. Therefore, the decision which lubricant should be used is of special interest for near-net shape operations. The paper at hand presents the results of a finite element investigation of the first stage of an industrial rod extrusion process which was investigated with two different lubrication systems. The numerical investigations focus on a reliable prediction of the development of the surface roughness in due consideration of the lubricant

OPTIMAL PROCESS DESIGN IN STEADY-STATE METAL-FORMING BY FINITE-ELEMENT METHOD .2. APPLICATION TO DIE PROFILE DESIGN IN EXTRUSION

A new approach to optimal process design in steady-state metal forming is applied to the problem of die profile design in extrusion. The die profiles for minimizing the forming energy are predicted for various process conditions and materials. The results are compared to theoretical solutions found in the literature. It is demonstrated that the die profiles thus obtained are also effective in controlling the formation of defects and the die wear.X1141sciescopu

AN APPROXIMATE ANALYSIS OF HOT-STRIP ROLLING - A NEW APPROACH

A new method of predicting the effect of rolling parameters on the roll pressure, roll force and power and energy consumption in hot-strip rolling is presented. This method is based on approximate solutions to the velocity, strain-rate and stress distributions in the roll gap. The degree of approximation was examined by comparison with finite element solutions. The theoretical predictions were compared with experimental data from hot rolling of steel strips and plates.X114sciescopu

PASS SCHEDULE OPTIMAL-DESIGN IN MULTIPASS EXTRUSION AND DRAWING BY FINITE-ELEMENT METHOD

A finite element-based approach is presented for pass schedule optimal design in multi-pass extrusion and drawing. A basic formulation of the design problem is described, with emphasis on employing the criterion of minimum forming energy as a basis for optimization. The procedure for calculating the design sensitivities is given, and a numerical test is conducted to evaluate the accuracy of the predicted design sensitivities. The approach is applied to the problem of optimizing the pass schedule in extrusion and wire-drawing under various design constraints. Comparison is made between the optimal and initial design to examine the effect of optimization on the process and product.X1113sciescopu

ANALYSIS OF HOT-STRIP ROLLING BY A PENALTY RIGID-VISCOPLASTIC FINITE-ELEMENT METHOD

A new approach to the analysis of hot-strip rolling is presented. This approach is based on the rigid-viscoplastic finite element method and employs a penalty algorithm to relax the contact boundary condition for the determination of the stress distributions at the roll-strip interface. The approach is applied to the investigation of the various aspects of deformation mechanics in hot-strip rolling, with particular emphasis given to examining the effect of the coefficient of friction. An investigation is also carried out for a multi-pass rolling problem in which the strip is subject to simultaneous rolling at the two different roll gaps.X1120sciescopu

OPTIMAL PROCESS DESIGN IN STEADY-STATE METAL-FORMING BY FINITE-ELEMENT METHOD .1. THEORETICAL CONSIDERATIONS

A new approach to optimal process design in steady-state metal forming is presented. In the approach, optimal process design problems are mathematically formulated and solved using a penalty rigid-viscoplastic finite element method as a tool for carrying out necessary calculations for optimization. The basic formulation is presented and the solution procedure is described with the emphasis on the method of calculating the design sensitivities. The accuracy of the design sensitivities thus obtained is assessed by a series of numerical tests. An iterative scheme for optimizing the design variables based on the predicted design sensitivities is also given.X1132sciescopu

FINITE-ELEMENT ANALYSIS OF TEMPERATURES, METAL FLOW, AND ROLL PRESSURE IN HOT STRIP ROLLING

This paper presents a new approach for the analysis of hot strip rolling processes. The approach is based on the finite element method and capable of predicting velocity field in the strip, temperature field in the strip, temperature field in the roll, and roll pressure. Basic finite element formulations are described with emphasis on modeling roll pressure, and friction at the roll-strip interface and on treating the numerical instability resulting from a standard Galerkin formulation. Comparison with the theoretical solutions found in the literature is made to evaluate the accuracy of the temperature solutions. An iterative scheme is developed for dealing with strong correlations between the metal flow characteristics and thermal behavior of the roll-strip system. A series of process simulations are carried out to investigate the effect of various process parameters including interface friction, interface heat transfer coefficient, roll speed, reduction in thickness, and spray zone. The results are shown and discussed.X1131sciescopu

Optimum blank design by the predictor-corrector scheme of SLM and FSQP in the deep drawing process of square cup with flange

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