Factor Affecting The Determination Of Wrinkling Limit Diagram For Metal Sheets

Abstract

Wrinkling is one of defects in sheet metal forming operations, it is produced by a compressive stress field. The prediction of wrinkling is important for the design of stamping and deep-drawing processes . Wrinkling is unacceptable in the outer skin panels where the final part appearance is crucial. Wrinkling on the mating surfaces can adversely affect the part assembly and part functions, such as sealing and welding. In addition, severe wrinkles may damage or even destroy dies. Therefore, the prediction and prevention of wrinkling are extremely important in sheet metal forming.In this paper the wrinkling limit diagrams for steel , aluminum and aluminum alloy (AA3103 , AA5182) sheets have been determined theoretically using Marciniak-Kuczynski analysis with Hosford anisotropic yield function . The effect of strain hardening exponent, normal anisotropic ratio, Strain rate sensitivity exponent and imperfection factors could be determined theoretically, it is shown that the highest wrinkling limit curve appeared in steel sheet and the lowest curve in aluminum alloy (AA 3103)sheet (low resistance of wrinkling). The increase in each of the value of factors (strain hardening exponent, normal anisotropic ratio, Strain rate sensitivity exponent and imperfection factor) improve the resistance sheet against wrinkling.Keywords :Wrinkling is one of defects in sheet metal forming operations, it is produced by a compressive stress field. The prediction of wrinkling is important for the design of stamping and deep-drawing processes . Wrinkling is unacceptable in the outer skin panels where the final part appearance is crucial. Wrinkling on the mating surfaces can adversely affect the part assembly and part functions, such as sealing and welding. In addition, severe wrinkles may damage or even destroy dies. Therefore, the prediction and prevention of wrinkling are extremely important in sheet metal forming.In this paper the wrinkling limit diagrams for steel , aluminum and aluminum alloy (AA3103 , AA5182) sheets have been determined theoretically using Marciniak-Kuczynski analysis with Hosford anisotropic yield function . The effect of strain hardening exponent, normal anisotropic ratio, Strain rate sensitivity exponent and imperfection factors could be determined theoretically, it is shown that the highest wrinkling limit curve appeared in steel sheet and the lowest curve in aluminum alloy (AA 3103)sheet (low resistance of wrinkling). The increase in each of the value of factors (strain hardening exponent, normal anisotropic ratio, Strain rate sensitivity exponent and imperfection factor) improve the resistance sheet against wrinkling.