In-Plane Compression: A New Laboratory Forming Technique to Study the Effect of Large Drawing Deformations in Sheets on Their Subsequent Mechanical Behavior

The deformation mode or strain path imposed during sheet forming can have a strong influence on the mechanical behavior of materials, both during and after forming. To study strain path effects, laboratory forming techniques capable of producing deformed samples that are flat, of sufficient size, and relatively free from strain gradients are desirable. A new laboratory forming technique, called in-plane compression, has been developed in this study to produce samples in which the strain state approximates that observed in the flange of a partially drawn cylindrical deep-drawn cup, that is, ϵ₂ < 0, ϵ₁ and ϵ₃ > 0, where ϵ₁, ϵ₂, and ϵ₃ are the principal logarithmic strains. These samples exhibit good strain uniformity and are of adequate size (31.8 by 76.2 mm by sheet thickness) to permit subsequent measurement of the postformed mechanical properties. For a 552-MPa (80-ksi) yield-strength high-strength low-alloy (HSLA) steel, it is shown that the postformed tensile properties after in-plane compression agree well with those observed after cup drawing, thus validating the use of in-plane compression to simulate drawing deformations.