Effect of Trimming Process Parameters on Sheared Edge Geometry and Stretch Limit: An Experimental Investigation
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JMEPEG https://doi.org/10.1007/s11665-020-05062-8
Effect of Trimming Process Parameters on Sheared Edge Geometry and Stretch Limit: An Experimental Investigation K. Wang, G. Ayoub, A. Ilinich, and G. Kridli (Submitted March 30, 2020; in revised form July 1, 2020) The stretchability and flangeability of sheared sheet metal in stamping are directly influenced by the trimmed edge quality. In this work, the effect of the trimming parameters on the edge quality was investigated using experimental and statistical approaches. The material of study was a 6xxx-series aluminum sheet. A digital 3D optical microscope was used to assess the quality of the sheared edge geometry by measuring several distinct trimmed edge geometrical features, namely rollover, burnish, fracture, and burr. The evolution of the sheared edge geometry was studied by changing four trimming parameters, namely clearance, offal support, lower tool sharpness, and upper tool sharpness. The sheared edgeÕs ability to stretch was assessed by measuring both the total elongation and the local strain of trimmed half dog-bone specimens tested under uniaxial tensile loading conditions. A generalized linear model regression was used to investigate the relationship between the edge stretch, edge geometry, and trimming process parameters. The burr size was found to be the most significant factor for predicting elongation, while clearance between the upper tool and the lower tool was found to be the most significant controllable regression variable. Furthermore, the use of high support was reported to decrease the sensitivity of the trimmed edge quality to the upper and lower tool sharpness. Keywords
generalized linear model regression, trimming, trimmed edge geometry, trimmed edge stretchability, trimming process parameters
1. Introduction The need to produce fuel-efficient vehicles has resulted in a significant increase in the use of lightweight materials, such as aluminum alloys and advanced ultra-high-strength steels (AHSS and UHSS) by the automotive industry. New challenges have emerged with the application of the existing manufacturing processes for these lightweight metals. Shih et al. (Ref 1) stated that the trimming process is extensively used by the automotive industry, driven by speed and cost advantages relative to other cutting methods, such as laser cutting and water jet. The stretchability and flangeability of the sheared metallic sheet in stamping are directly influenced by the trimmed edge quality. In order to effectively resolve the problem of early fracture that some trimmed metallic sheets exhibit under stamping operations, it is of high importance to understand the mechanisms of fracture controlling the shearing operation. Indeed, when the tools are in contact with the blank, a region of intense shear stress develops, referred to as the plastic zone, and is accompanied with bending caused by the offset loading that
K. Wang, G. Ayoub, and G. Kridli, Department of Industrial and Manufacturing Systems Engineering, University of MichiganDearborn, Dearborn,
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