Influence of the edge rounding process on the behaviour of blanked parts: numerical predictions with experimental correlation

Abstract

Blanking of sheet metal is an important forming process in the automotive industry for the manufacture of mechanical components. The final component shape, obtained at the end of bending or deep-drawing processes, often has sharp edges due to the blanking operation. Concerning passenger safety components, like seat belt anchors, rounding of the edges by punching is necessary to avoid cutting the belt material. In addition to removing the sharp edges, the punching results in work hardening of the material in the rounded zones which results in an increase in the local resistance of the material. In this study, a high-strength low-alloy steel (HSLA S500MC) has been tested with the aim of quantifying the blanking and edge rounding operations. The mechanical behaviour of test specimens is investigated by means of tensile tests and the material is characterised in terms of Vickers micro-hardness. Numerical simulations of the edge rounding process are developed using previously identified material behaviour laws. The residual stress fields are characterised and compared to experimental results. This is done so that numerical simulation can be done in the future to prediction the in-service behaviour of the component. Specimens with rounded edges are compared to specimens that were not submitted to the rounding operation. It is shown that Edge Rounding by Punching improves the component resistance, therefore justifying the use of this process in the manufacture of automotive safety components.

Influence of metal inserts with microformed edges on subsequent injection assembly moulding for media tight electronic systems

“…Hence, an edge rounding process has potential to shape a more regular cross section and can also improve the mechanical properties. This was shown for blanked steel parts with a thickness of 4 mm and formed edge radii between 1.25 mm and 2.25 mm [5]. In contrast, the scope of this paper is to form radii of the edges in the submillimetre range and therefore this process can be assigned to microforming [6].…”

Application of a SPH Coupled FEM Method for Simulation of Trimming of Aluminum Autobody Sheet

“…The measured results indicate that the maximum strain has reached a value of 1.5 at the middle of cut surface, and it exponentially decays away from the edge. Analysis of residual stress state in cut surface is presented on Fig 9. In the following, the von Misses equivalent stress is used to define and compare the residual stress state (Achouri et al, 2014) which is by definition is a complex three-dimensional stress state with interaction between the components of the stress tensor. In each analyzed cut surface area a high increase of stresses at a small tool penetration can be seen.…”

Experimental study of the impact of punching operations on the high cycle fatigue strength of Fe–Si thin sheets

“…punching only or punching and polishing). For punching operations, surface tensile residual stresses are generated as a result of the important deformation gradients imposed by the shearing process [8]. For polishing operations, the introduction of superficial plastic strains is usually responsible for the development of surface compressive residual stresses [19].…”

“…dislocations), are generally responsible for a deterioration of both magnetic [3][4][5] and mechanical properties [6,7] including fatigue strength. Finally, important residual stresses, which significantly affect fatigue resistance, may exist because of punching [8][9][10].…”