Numerical Investigation of the Permanent Longitudinal Strain and Web-warping in Chain-die Formed AHSS Variable Width Sections

摘要

Chain-die forming is a new sheet metal forming technology proposed and it emerges as a supplement to roll forming and stamping in fabricating non-uniform AHSS products.The permanent longitudinal strain on the flange edges and the web-warping are two significant issues which determine the success of the fabrication of an irregular AHSS component.In this paper,finite element analysis (FEA) is employed to investigate the longitudinal and web-warping in Chain-die forming non-uniform sections with varying widths.Two forming strategies are employed in the numerical investigation,specifically,the section is formed by three consecutive forming passes and one single forming pass respectively.The results indicate that the final permanent longitudinal strain and web-warping co-exist in the Chain-die formed irregular AHSS components while they are much gentler compared with those of flexible roll formed irregular sections.In this study,it is proved that the final permanent longitudinal strain and web-warping have a reciprocal relationship.The increase of tensile strength results in the reduction of permanent longitudinal strain and the increase of the web-warping.In addition,the final longitudinal strain is independent of the transient forming angles and other interim forming passes.That means,unlike the flexible roll forming process,it is possible to fabricate an AHSS non-uniform section through just one forming pass as the effective longitudinal strain path behaves like a linear accumulation process.