Square-Cup Deep Drawing of Relatively Thick Sheet Metals through a Conical Die without Blankholder

Square-Cup Deep Drawing of Relatively Thick Sheet Metals through a Conical Die without Blankholder

Walid Mahmoud Shewakh (Beni-Suef University, Beni-Suef, Egypt), M A. Hassan (Mechanical Engineering Department, Assiut University, Asyut, Egypt) and Ibrahim M. Hassab-Allah (Faculty of Engineering, Assiut University, Asyut, Egypt)
DOI: 10.4018/IJMFMP.2015070103
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The present study introduces a finite element analysis and experimental verification of the square cup drawing. Experimental results are presented for deep drawing using two different sheet metal; an annealed aluminum (AL99.5w) and brass alloy (CuZn37) having nominal thickness to of 2, 2.5 and 3 mm. The experiments were conducted using a conical die of 18o half cone angle with square aperture at the die exit of 44×44mm and different relative punch/die clearances 1.5, 1.0, 0.9, and 0.8to. The last three values for relative punch/die clearance give nominal simultaneous corrective ironing ratios 0, 10, and 20% respectively. Flat-bottomed square punches with nose radius of 4mm and different sizes of side wall lengths were used. The corner radii for the punch and die aperture were 8 and 10 mm respectively. The experimental and finite element results showed a very good agreement between results of the deep drawing loads, limiting drawing ratios and modes of failures.
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1. Introduction

The square cups of sheet metals are widely used in many industrial fields. Commonly, the square cups are manufactured by deep drawing using flat blanks of sheet metal. The traditional design of drawing dies are complicated and tedious procedure, in spite of all precautionary measures there are several chances of denting, cracking and wrinkling which needs to be rectified. Using these techniques leads to high rates of scrap from sheet metal drawing processes. Therefore, it is very important to replace these techniques by a computer aided method to determine the strain distributions, tool forces and potential sources of defects and failures. One of the most popular methods in simulating and optimizing the sheet metal forming today is the finite element (FE) simulation (Yoon, 2014). FE simulation allows to capture behaviour that cannot be readily measured it provides deeper insight into the sheet metal forming. Nowadays, FE simulation is highly adopted in by modern industry to reduced production cost and time prototyping, improved formability and easy modification of part design. In deep drawing processes FE simulation have been applied to understand the deformation mechanism, improve the quality of deep drawn parts, facilitate the metal flow into die cavity, maximizing the height of drawn cup, and shorten design cycle (Regueras, 2014); (Li et al, 2006).

The deep drawability and quality of deep drawn products depend upon many process parameters such as; blank thickness, blank and die geometries, holding pressure, blank materials, friction conditions at tools/blank interface surfaces, and so on. Many researchers have been carried out using diverse technologies in order to better understand square cup drawing processes. The work of (Marumo et al, 1999,1998);(Kuwabara et al, 1993); and (Kawai,1987) investigated the effects of drawing process parameters on the deep drawability of square cups made of aluminum sheets, while (Chen & Lin, 2007) investigated the effects of deep drawing parameters on the deformation characteristics for the forming square cups of stainless steel. (Kitayama et al, 2010) introduced an algorithm to determine the trajectory of the blank holder force in square cup drawing process. (Modi & Kumar, 2013) developed a method to determine the path of the variable blank holder force for successful hydroforming of the cups with the assistance of programmable logic controller and data acquisition system. The main aspect to be considered in drawing of square cup is that deformation states vary along the contour of the cup cross section which leads to metal flow concentration at the square cup corners (Saxena & Dixit, 2009).

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