Sufficient stiffness and robustness of the brake piston lead to an effective and safe braking process. While the brake pedal is being pressed, the pressure transmitted on the piston should cause a possibly minimum compression of the latter. The lower this volume absorption, the faster the brake reacts.
Another important aspect is a lightweight design of this component - the unsprung mass of the piston should be minimised without any greater disadvantage regarding robustness. The optimum material employment has to be found for a given stiffness determined by the application.
In this study, Finite Element Method (FEM) has been applied in order to work out an improved design of the brake piston regarding its weight and performance. The forming process chain from a blank to a finished piston has been modelled within a numerical simulation. Its results (geometry, stresses, strains, etc.) could be transmitted to the structural analysis considering the history of the material properties out of deep drawing. Next, a compression test with a defined, linearly increasing pressure has been simulated for various designs. The mass of the component, driven by the applied design elements, could be controlled directly; the above-mentioned braking behaviour was measured with the so-called volume absorption (Î”V). An approach that has been developed for this purpose allows not only the calculation of the total value, but also its portions for cylindrical wall and bottom. Since absolute volume absorption values are not evaluable without any reference, the evaluation is based on the comparison of the tested design variants to a state of the art reference design which is intended to be improved.
The resulting design shall be suitable for high-volume manufacturing by use of deep drawing followed by further steps. Hence, its feasibility and manufacturability have to be proved for latest production technology.
Kamil Zawalich, Matthias G. Müller - Erdrich Umformtechnik GmbH