The deep-drawability of a sheet metal blank is strongly influenced by the tribological conditions prevailing in a deep-drawing process. Therefore, new methods to influence the tribology represent an important research topic. In this work, the application of a process-integrated lubrication in a deep-drawing process is investigated. Most promising geometries of the lubrication channels and outlet openings are first identified by means of numerical simulation at the example of a demonstrator process. Cylindrical test specimens with the specified channel geometries are additively manufactured and installed in a strip drawing test stand. Additive manufacturing enables the possibility of manufacturing complex channel geometries which cannot be manufactured by conventional methods. A hydraulic metering device for conveying lubricant is connected to the cylindrical test specimens. Thus, hydraulically lubricated strip drawing tests are performed. The tests are evaluated according to the force curves and the fluid mechanical buildup of pressure cushion. The performance of process-integrated lubrication is thus analyzed and evaluated. By means of a coupled forming and SPH simulation, the lubrication channels could be optimally designed. From the practical tests, it could be achieved that the drawing force decreases up to 27% with pressure cushion build up. In this research, a hydraulic lubrication in the area of highest contact normal stresses is the most optimal process parameter regarding friction reduction.
Medium manganese steels offer a wide range of advantages in hot forming compared to conventional boron steels such as lower heating temperatures and critical quenching rates. Furthermore, the combination of increased strength and ductility makes them a promising material for lightweight components in the mobility sector. For an efficient process design of such components, the finite element simulation is an effective tool to identify a suitable process window and minimise experimental trial-and-error tests. However, a realistic modelling of the material behaviour is essential for reliable simulation results. Therefore, this research focuses on the characterisation and modelling of the flow behaviour of a novel medium manganese steel for the simulation of hot forming processes. Isothermal tensile tests are carried out in a forming and quenching dilatometer under varying forming temperatures and strain rates. To reproduce the heat treatment at the steel producer and the hot forming at the parts manufacturer, the specimens are heat-treated before forming in a process route consisting of annealing, cooling and reheating. After the tests, flow curves are evaluated and modelled using different hardening laws, which are verified by means of numerical simulations.
The use of hybrid components in the automotive industry is steadily increasing due to their lightweight potential. By combining fibre-reinforced plastics with metallic materials, high-strength components with lower weight than monolithic metal parts can be realised. The overall aim of the project “HyFiVe” is to exploit this potential for electric vehicles by developing a scaled battery housing structure made of a glass mat reinforced thermoplastic (GMT) paired with unidirectional reinforced (UD) tapes and a metallic reinforcement frame. The GMT is formed by compression moulding and serves as the base of the battery housing structure. Numerical simulation is an efficient tool for process design that can determine a suitable process window and reduce experimental trial-and-error tests. Particularly, realistic modelling of the GMT flow behaviour is essential for reliable simulation results. In this contribution, the rheological properties of a GMT consisting of a polyamide 6 (PA6) matrix with 30% glass fibre reinforcement were determined. Isothermal compression tests were carried out with a parallel plate rheometer at different temperatures and varying squeeze rates. The squeeze force and punch displacement were evaluated to determine the rheological data of the GMT. Two methods for the modeling of the flow behaviour were considered. At first, pure shear flow was assumed and the viscosity was modelled as a function of the shear rate by means of a power-law. Secondly, a pure biaxial extension was assumed and the true stress was modelled in dependence of true strain and strain rate. Subsequently, for a verification of the material models, the compression tests were simulated in ABAQUS using the Coupled Eulerian-Lagrange (CEL) approach and the results were compared to the experiments.