The final quality of sheet and tube metal–formed components strongly depends on the tribology and friction conditions between the tools and the material to be formed. Furthermore, it has been recently demonstrated that friction is the numerical input parameter that has the biggest effect in the numerical models used for feasibility studies and process design. For these reasons, industrial dedicated software packages have introduced friction laws which are dependent on sliding velocity, contact pressure and sometimes strain suffered by the sheet, and currently, temperature dependency is being implemented as it has also a major effect on friction. In this work, three lubricants having different viscosity have been characterized using the tube-sliding test. The final aim of the study is to fit friction laws that are contact pressure and sliding velocity dependent for their use in tube hydroforming modeling. The tests performed at various contact pressures and velocities have demonstrated that viscosity has a major effect on friction. Experimental hydroforming tests using the three different lubricants have corroborated the importance of the lubricant in the final forming of a triangular shape. The measurement of the axial forces and the final principal strains of the formed tubes have shown the importance of using advanced friction laws to properly model the hydroforming process using the finite element modeling.

Today’s stamping simulations are realized by ignoring the elastic deformation of the press and tooling system through the assumption of a rigid behavior and a perfect press stroke. However, in reality, the press and tool components deform elastically and are one of the major error sources for the final adjustment and blue-spotting of the dies. In order to tackle this issue, a new approach is proposed in this study that substitutes the press stiffness by means of a substitutive model composed of cost-effective shell and beam elements. The substitute model was calibrated using full-scale measurements, in which a 20,000 kN trial press was experimentally characterized by measuring its deformation under static loads. To examine the robustness of the substitute model, a medium-size tool and a large-size tool were simulated together with the substitutive model. To this end, a B-pillar tool was re-machined based on the substitute-model results and a new cambering procedure was proposed and validated throughout the blue-painting procedure. The newly developed substitute model was able to replicate the global stiffness of the press with a high accuracy and affordable calculation time. The implementation of the findings can aid toolmakers in eliminating most of the reworking and home-line trials.

Roll levelling is commonly used in cut to length and blanking lines to flatten initial coils and produce residual stress free precuts. Roll straightener is also used to remove coil-set when progressive dies are used and the starting raw material is a coil. Industrial evidences have proved that roll leveler or straightener tuning is crucial to get a robust process and to obtain repetitive springback values after stamping. This is more relevant when using Advanced High Strength Steels and aluminum coils. However, the mechanisms affecting this material behavior are unknown and how the levelling technology affects the material properties has not been yet reported. In this paper, the influence the roll levelling process has on the final properties of a 6xxx aluminum alloy is studied. For that, as received coils have been relevelled using two different leveler set-ups and tensile tests have been performed using both initial and final material states. Aiming to quantify the effect of the material hardening on a real forming process, a new tangential bending prototype has been developed. As received and levelled precuts have been bent and the forming torques and the postforming angles have been compared.

Ti-6Al-4V is a widely employed material in the aerospace, power generation and bioengineering industries due to its low density, excellent corrosion resistance and outstanding mechanical properties. Hammer forging is one of the most utilized manufacturing processes to produce high-performance titanium components and it is known that the process parameters highly affect the microstructure, and thus, the mechanical properties of the manufactured parts. Ti-6Al-4V alloy has a temperature dependent dual structure and forging below or above the β-transus transition temperature (≈980ºC) highly influences the resultant microstructure. Due to the significant adiabatic heating in high-speed hammer forging processes the β-transus temperature can be exceeded during the process. Therefore, it is of vital importance to study the phase transformation limits and the resultant effects on the mechanical properties to establish the optimum processing window for the hammer forging of Ti-6Al-4V. In this work, the Direct-Impact Drop Hammer (DIDH), a purpose-built laboratory hammer with a maximum blow speed of 5 m/s is employed to perform intermediate strain rate (≈200 s-1) uniaxial compression tests of Ti-6Al-4V at 900ºC, 940ºC, 980ºC, 1000ºC and 1020ºC. The flow behaviour of this titanium alloy is experimentally characterized under a wide range of hammer forging conditions, and the microstructure of the tested samples is analysed to study the influence of the adiabatic heating on the phase transformation of Ti-6Al-4V.