Papers by Author: Kanwar Bir Sidhu

Abstract: High strength aluminium wrought alloys as well as powder metallurgical aluminium alloys are limited regarding massive formability. The formability at room temperature can be significantly affected by superimposing hydrostatic pressure. Depending on the process control, cold forming enables locally induced strain hardening effects, whereby increased hardness or hardness gradients can be regulated. Simultaneously, the necessity of mechanical post processing is reduced by a metal forming fabrication of joint and connection elements at room temperature. By splitting the component in strengthened and not strengthened regions, specially adapted property profiles can be adjusted to the application. Thus, specially load adapted components with locally optimised property profiles e.g. ductile or high strength, brittle areas can be manufactured. A defined buckling or folding of a component in case of a crash can thereby be achieved. In this project innovative tool principles for superimposed cold solid forming will be developed. They will be used to manufacture high strength and complex aluminium structure components with specific adjustment of local strain hardening. A tool technique is to be created in order to generate locally hardened areas within massive structures by metal forming. Furthermore, the task is to determine the procedures limits for superimposed cold massive forming with specifically adjusted strain hardening of aluminium alloys. For the realisation of these aims fundamental research has to be made, by which the coherences between specific process parameters and the increased formability are determined. Furthermore, the cold hardening effects are to be adjusted by cold massive forming with superimposed hydrostatic pressure and displayed with the help of FEA. In the long term, the analysis aims at the development of pressure superimposed forming that is technically utilisable as a near net shape manufacturing process for high complex aluminium structure components with selective adjustment of local properties.

Abstract: Ductile fracture processes for discrete crack propagation using nodal release approach is well established for modelling crack in metal sheet. In this method, the crack is assumed to initiate or propagate along the element edges; hence, a new crack is implemented in the FE mesh. In Blanking process, the crack trajectory is unknown; therefore a very fine mesh is required to simulate a realistic crack propagation using the nodal release method. Consequently, the nodal release method has to be modified in which first the direction of crack extension is calculated and then, accordingly, the local element topology near the crack-tip is modified such that the nodes of elements are moved to predicted crack-tip in order to accommodate the crack extension. The advantage of this method is that it is possible to model the predicted crack with only slight modification in the local mesh near to the crack tip. However, it is necessary to transfer history variables from old local elements of previous increment to the new local elements of the current increment at the vicinity of crack-tip. But this method can lead to slight loss of accuracy to predict the subsequent crack extension due to interpolations. However, the advantage of this method is that remeshing can be either completely eliminated or reduced to a greater extend during the simulation. Therefore, in this paper, modified nodal release method for modelling ductile crack propagation in blanking process with the uncoupled damage approach is presented, and is further implemented in commercial FE software - MSC.Marc® together with predefined user-subroutines