Hydroforming Process for Uniform Wall Thickness Products

Abstract

A fundamental new approach of deep drawing processes for uniform wall thickness is suggested and proved experimentally. It is based on imposition of a back-up fluid pressure which is prescheduled to vary with respect to the punch position during the drawing stroke in the hydroforming process. The formula for scheduling this fluid pressure path is generated via the plastic limit analysis and presented in terms of the geometry of the product, the work-hardening of the material, and the friction coefficient. It leads systematically to better results than empirical procedures reported in the current literature and industrial technical reports. Experiments in hydroforming sheets to cups and hemispheres performed on different materials (Al, Cu, and stainless steel) substantiate the improvement suggested. The associated overall punch load is overestimated (at most by 15 percent) with the unique feature of including Coulomb friction into the rigorous upper bound analysis.

Experimental and numerical study of stamp hydroforming of sheet metals

“…The second challenge is the relationship between the uid pressure and the punch stroke during the process. As shown by Yossifon and Tirosh [6][7][8][9][10] uid pressures within the upper uid chamber that are too high will cause the material to bend to the radius of curvature of the punch much faster than the ductility of the material may allow. This will lead to premature rupturing of the sheet metal.…”

A simple method to determine pressure curve for sheet hydro-forming and experimental verification

“…In the study, they used pressure curve predicted by Tirosh et al [1]. Hsu and Chu [7] also analyzed a hydro-forming process with the finite element method and showed that hydro-forming improves strain distribution and hence better formability results.…”

“…Tirosh et al [1] found an appropriate relationship for pressure versus punch stroke so as to maintain the thickness unchanged for the hydro-forming of axisymmetric shapes by using the upper bound method. Yossifon et al [2] derived a theoretical relationship for wrinkling for axisymmetric hydro-forming.…”

Influence of Punch on Blank Holder Pressure in Hydroforming Deep Drawing Process

“…The fluid pressure effects on radial, hoop and drawing stresses of blanks in during the process. The various types of fluid forming are Hydroforming process [1][2][3][4][5], hydro mechanical deep drawing process [6][7][8], Aquadraw process [9], hydraulic counter pressure process [10][11][12].These processes have some differences and some features are common. These principles are utilized for imp rovement in production of drawing cups with help of hydraulic pressure through conventional methods.…”