Z. Gronostajski

The constitutive equations for FEM analysis

Abstract The main aim of this paper is to review briefly different models, from simple to very complicated, for computing the changes in flow stress depending on the deformation conditions. The models are divided into two main groups, each of them characterised by a different set of deformation parameters. Some of the models can be applied to cold forming and some (the more complicated) to hot and warm forming. To be correct, models for hot and warm forming must take into account the history of deformation.

Quasi-static and dynamic deformation of double-hat thin-walled elements of vehicle controlled body crushing zones joined by clinching

A controlled body crushing zones are of considerable interest to automotive industry. The most popular technique of joining deformable zone components is spot welding. This paper presents a new technique of joining these elements using a metal forming process called clinching. Two methods of clinching: round press joining (RPJ) and square press joining (SPJ) are considered. Quasi – static and dynamic crushing tests of thin-walled specimens joined by clinching were carried out. The results show that clinch joining could be applied in controlled body crushing zones.

The use of thin-walled sections for energy absorbing components: a review

This paper presents the key aspects of the use of thin-walled sections for collision energy absorbing components. The process of deformation of thin-walled structures and the parameters expressing their energy absorption are described in detail. The research on improving the energy absorption of thin-walled sections, through the use of, e.g., tailored blanks, polyurethane foams and mechanical joining methods, conducted for many years in the Institute of Production Engineering and Automation at Wroclaw University of Technology is reported.

Bearing materials obtained by recycling of aluminium and aluminium bronze chips

Abstract In this paper, a new method of chips recycling is presented. The method consists in the conversion of the chips directly (without intervening metallurgical processes) into a finished product, and has been applied to the production of conventional and composite materials. The sintering criterion for chips recycling is described and discussed. The application of the recycling method for the production of bearing materials is precisely described.

Physical and mathematical modelling of extrusion processes

Abstract The main objective of the work is to study the extrusion process using physical modelling and to compare the findings of the study with finite element predictions. The possibilities and advantages of the simultaneous application of both of these methods for the analysis of metal forming processes are shown.

The deformation processing map for control of microstructure in CuAl9.2Fe3 aluminium bronze

Abstract The flow stress data obtained in torsion test of CuAl9.2Fe3 aluminium bronze at different temperatures and strain rate are analysed using dynamic materials model which considers the workpiece as a power dissipator causing microstructural changes. A processing map representing the efficiency of power dissipation as a function of temperature and strain rate has been established and optimum processing conditions for the aluminium bronze are determined.

Influence of cold and hot pressing on densification behaviour of titanium alloy powder Ti6Al4V

This paper analyzes three ways of processing Ti-6%Al-4%V titanium alloy powders: compacting specimens in 25 mm diameter under different pressures by a floating die and sintering in a vacuum furnace, producing axially symmetric PM compacts in a compacting device with a plastic die, hot compacting a powder in a die under protective argon atmosphere. The powder was produced by the following two methods: HDH (hydride-dehydride) and gas atomization (GA). A special device, allowing the simultaneous compaction and sintering of powder under protective argon atmosphere, was constructed. A solid material was obtained from Ti6Al4V titanium alloy powders produced by GA. It seems that the proposed technology of compaction under argon atmosphere could be used to manufacture products from titanium alloys on the industrial scale more economically since it combines compaction and sintering and does not require costly equipment.

Model describing the characteristic values of flow stress and strain of brass M63 and aluminium bronze BA93

Abstract The Garafalo model was applied for determination of the characteristic values of flow stress and strain of brass M63 and aluminium bronze BA93 at different deformation conditions. The relationships between flow stress and strain characteristic values on the one hand and Zener–Hollomon parameter on the other, are very good. The relationships obtained can be used for calculation of the models describing the continuous changes of flow stress with strain and for design of the metal forming processes.

The effect of crashworthiness parameters on the behaviour of car-body elements

In the paper, special emphasis was put on the structural stiffness of car elements described by crashworthiness parameters. We showed how the structure parameters described by crashworthiness indicators can be calculated for various structures. The effect of crashworthiness parameters of different constructions and profiles on the relationship between the energy absorption and the maximum collision force is given. One- and multi-layer, empty and filled with different-density plastic foam elements were described. The behaviour of different elements and the effect of plastic foam density on the crashworthiness parameters were analyzed.

Bearing materials obtained by diffusion bonding of aluminium and aluminium bronze chips

An original concept of production a bearing composite by the mixing and bonding of aluminium and aluminium bronze chips through press molding, extrusion and heat treatment has been developed. Diffusion bonding process of aluminium and aluminium bronze chips leads to creation of phases typical for Cu-Al. alloys. The phases are created in small amount during extrusion of cold compacted mixture of aluminium and aluminium bronze chips and mainly during heat treatment applied after extrusion. This way, without participation of metallurgical processes good bearing materials can be manufactured