A Novel Approach for Process and Tool Design During Manufacturing of Industrial Sheet Metal Components

Abstract

Manufacturing of sheet metal components feeds into several domains such as automotive, aerospace and strategic applications. The optimum process and tool design are crucial in ensuring successful manufacturing of components without developing any defects. The current trend is to do it right the first time during the industrial stamping practice, so that the costly shop floor trials are eliminated or at least minimized. One of the common failures that are observed during manufacturing of industrial sheet metal components is the splitting/cracking. The present work focuses on addressing the design considerations for preventing development of such defects. Traditionally, the strain-based forming limit diagram (FLD) is used to assess if a proposed process and tool design will lead to splitting failures. The approach is to measure or predict the strains that will develop during the stamping process and to infer that splitting failures will occur if these strains are above the FLD. The optimum process and tool design should ensure that the strains developed in the component must be below the FLD. The approach of using the strain-based FLD has serious limitation, as it does not account for the influence of complex strain paths on the forming limit strains. As an alternative, stress-based FLDs have been proposed, which does address the effect of complex strain paths. But, the stress-based FLDs are not intuitive and therefore are not very suitable to use for analysis of industrial sheet metal components. In this work, a novel approach, based on monitoring development of local thickness gradients during manufacturing of sheet metal components, is proposed to assess a given process and tool design for developing splitting/cracking failures. The novel approach is validated for sheets of different metals and thicknesses. The effect of bilinear strains paths on the forming limits is captured and validated using this proposed novel approach. A new approach, based on the novel thickness gradient criteria, is proposed for quantifying the forming severity of industrial sheet metal components.