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Forming Limit Diagrams (FLD) are extensively used in North American press shops during tooling trials and in production for problem identification/resolution. The Keeler-Goodwin FLC shape and the correlation developed by Keeler and Brazier (based on n-value and thickness) have been widely accepted as the Standard FLC Method to predict forming limit curves for commercial steels. In this paper, the Standard FLC Method is reviewed, and an alternative approach used at the authors' laboratory (Bethlehem FLC Method) is described. The two methods are discussed in the context of more recent experimental determinations of FLC's for a variety of “modern” sheet steels including DQSK, Interstitial Free and Bake-Hardening steels, as well as coated sheet products. Some specific press-shop examples are also presented, which further highlight the value to industry of re-examining the Standard FLC Methodology used in circle-grid analysis.

Surface friction is an important characteristic which influences the formability of sheet steel products. Numerous friction tests have been developed, and many previous investigations have reported effects of surface characteristics, coatings, lubrication, etc., on formability. Recently, increased attention has been focussed on reducing friction via the application of solid film lubricants or special surface post-treatments such as phosphates, metallics/intermetallics, etc. This paper presents the results of selected laboratory evaluations conducted using a variety of steels and surface treatments. Formability was measured using Limiting Dome Height and Drawbead Simulator friction testing, along with Limiting Draw Ratio testing in one instance. The examples highlight some potential opportunities which may be considered for improving formability in industrial stamping operations.

Galvanneal powdering was examined on a stabilized ultra low carbon steel substrate as a function of strain state using cup drawing and in-plane stretching experiments to simulate deformations encountered in production stampings. Significant powdering was encountered in drawing while minimal powdering occurred in in-plane stretching. Powdering was measured at specific locations and correlated with strains in those locations. A powdering map was generated in strain space using the experimental data. A few measurements of powdering on selected regions of an automotive stamped part are reported.