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The need of lightweight construction for the body in white of modern cars increases due to legal restrictions of CO2 emissions and the passengers wishes of safety and low fuel consumption. One approach of lightweight construction is the use of high and ultra high strength steel, to reduce the weight of the single parts, another approach is the use of modern forming technologies, e.g. hydroforming with the possibility to create undercuts, to produce complex parts and thus to reduce the number of parts, the number of joining operations and the weight. The mentioned ultra high strength steels show a poor formability at room temperature and the necessary process forces are high compared to standard deep drawing steels. Warmforming operations can help to reduce the process forces and to increase form ability [1]. To combine the benefits of warmforming and hydroforming new forming media are necessary to overcome the problem of temperature stability of fluids, which is limited to about 350 °C [2]. Beside gases, which tend to leakage and which are highly compressible, granular material like small ceramic beads can be used as a forming medium. First results of forming operations using this medium were presented in [3]. The experimental tool used for those tests pressurizes the medium by a punch. To divide the effects caused by temperature and steel grade from the other effects experiments were carried out at room temperature using the well known deep drawing steel DC04. Influences of the ceramic beads diameter, the number of repetitions, the punch geometry as the punch position, determining the volume of media, on the forming are presented.

The influence of silica nanoparticles on the elasticity of a polymethylmethacrylate (PMMA) melt was investigated. The extrudate swell obtained from the extrusion of the melt through a die and the recoverable deformation after a creep test were measured. As well known from other materials, the extrudate swell becomes smaller by adding fillers, i.e. the elasticity decreases. This is usually explained by the effect of substituting viscoelastic polymer molecules by rigid particles. The linear steady‐state recoverable compliance Je0, however, attains values which are significantly higher than those of the matrix indicating an increase of the elasticity. This effect is postulated to be due to interactions of the matrix molecules with the particle surface giving rise to longer retardation times and higher retardation strengths which lead to larger Je0 according to the theory of linear viscoelasticity. The apparent discrepancy between these two contrary effects is solved by the finding that the recoverable compliance becomes smaller with stress above a critical value and approaches the elasticity of the matrix. This decrease is found in a stress range which is much lower than that applied in the extrudate‐swell experiment. The results of an elastic compliance becoming smaller with stress are interpreted by a detachment of the matrix molecules from the particles.

Due to strain hardening of the material, the hardness of cold forged parts is considerably improved. It is well known that the hardness of cold forged parts is closely related to its deformation, and that this relation is not dependent on the deformation process. The effective strain defines the local deformation, and can be determined in simulation of the cold forming process. In order to reach the required or to set specific hardness distribution with cold forging without any heat treatment processes, it is necessary to find out which manufacturing parameters influence the effective strain, and determine the effects of these parameters. The research work covered in this paper investigates the influence of the die geometry (as manufacturing parameter) on the effective strain. For that, a full forward extrusion process was modeled using the FE‐software Simufact. Forming and three parameters of the die geometry, namely the deformation ratio, the shoulder radius and the opening angle were varied. The maximum effective strain from each combination is determined, and the effects of each considered parameter as well as the effects of interactions between these factors are checked.

Sheet and bulk metal forming are widely used manufacturing methods. The industrial trend towards function integration leads to a demand for workpieces having features of both methods. The new forming technology sheet‐bulk metal forming is a promising approach to manufacture workpieces with functional elements. Tribological aspects generally play an important role in metal forming processes. Especially for the formability of functional elements friction is very important. The coexistence of low and high contact pressures is characteristic of sheet‐bulk metal forming and presents a challenge for the friction modelling. The surfaces of tool and workpiece are always rough, so that initial contact only occurs at the asperities of surface roughness. Consequently for small and moderate loads the real contact area is smaller than the apparent contact area. Surface traction can only occur in the real contact area, so that it is necessary to determine the real contact area in order to study the tribological behaviour of contact pairs. In order to get an accurate determination of the real contact area it is necessary to calculate the surface deformation in a three‐dimensional model and to validate the simulation model by measurements. The halfspace approach has the significant advantage that only the surface has to be discretised, while in a Finite Element Analysis the whole bulk has to be discretised. Consequently the numerical effort, and thus the calculation time, in the halfspace model are much lower than in FE‐modelling. The numerical solution scheme based on the halfspace theory is presented in this paper. Results of the calculation of the real contact area of rough surfaces are compared to experimental data from ultrasonic inspection. Friction coefficients calculated with the halfspace model are compared to results of strip drawing tests.