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Technical Paper

Applications and Properties of a Specially Processed Nitrogenized AISI 1010 Steel with Consideration of Strength in a Completed Vehicle

The static and dynamic strength properties and the fabricability of a specially processed, nitrogenized AISI 1010 steel are discussed. Typical applications are presented, and it is indicated that one important area of application for this steel is in parts that preserve the integrity of the passenger compartment to enhance safety. In addition, a method is described by which an estimate can be made of the static strength of the steel after it has been fabricated and installed in a vehicle.
Technical Paper

Advances in Designing Ultra High Strength Steel Bumper Reinforcement Beams

The use of M-190 MartINsite for bumper reinforcement beams was first described in a 1979 SAE paper. Since that time, considerable progress has been made in proving its worth for such applications. The purpose of this paper is to document the additional information that has been obtained in the intervening years.
Technical Paper

Predicting Structural Performance of Automotive Bodies from As-Shipped Properties of Steel

The purpose of this paper is to provide a simple analytic procedure for determining the potential for thickness reduction of structural body parts using mild and high strength steels where it is assumed that the effect of buckling or crippling is considered separately. Static, collision and fatigue loading cases are evaluated for both the bulk steel and for spot welds. In addition, the effect of forming and paint-bake aging on the as-received properties of the steel is considered.
Technical Paper

Predicting Yield Strength and Tensile Strength After Forming for Automotive Integral Body Structural Rail Type Parts

Samples of cold rolled and hot dip galvanized mild steel, microalloyed high strength steel, and dual phase steel were prestrained by bending and straightening, bending and straightening with superimposed tensile strain in a die, and cold rolling (dual phase steels only). In all three cases, the strain state was approximately plane strain. Stress-strain behavior was evaluated by conventional tensile testing of as-received and prestrained samples. For the mild and the high strength microalloyed steels, it is shown that the use of effective prestrain calculated assuming isotropy coupled with simple parabolic work hardening provides reasonable engineering estimates of the yield and tensile strength after prestraining if κ and n are taken from as-received tensile tests oriented coaxially to the restrain direction. It was also found that in bending and straightening, only the absolute average value of the bending strain should be used in calculating the effective prestrain.
Technical Paper

A System for Comparing High Strength Steels for Automotive Integral Body Structural Rail Type Parts

The paper describes a system for comparing different steels for use in automotive integral body structural rail type parts. Methodology is described for estimating yield strength, tensile strength, and thickness after forming and paint bake aging. Methods are also referenced for using these data to estimate maximum load capacity of structural members at collision loading rates and to estimate the ability to absorb collision energy. With these (or other) design methods, the material strength properties can be directly related to part performance. Indices are also developed that may be quantitatively relatable to the practical difficulties in controlling curl and springback in high strength steel. For splitting tendency during forming, important steel characteristics are identified, but no methodology is provided to quantitatively relate these parameters to part performance.
Technical Paper

A Practical Failure Limit for Sheared Edge Stretching of Automotive Body Panels

Edge cracking is one of the major formability concerns in advanced high strength steel (AHSS) stamping. Although finite element analysis (FEA) together with the Forming Limit Diagram has been widely used, it has not effectively predicted edge cracking. Primary problems in developing a methodology to insure that parts are safe from edge cracking are the lack of an effective failure criterion and a simple and accurate measurement method that is not only usable in both die tryout and production but also can be verified by finite element analysis. The intent of this study is to develop a methodology to ensure that parts with internal cutouts, such as a body side panel can be produced without edge cracking. During tryout and production, edge cracking has traditionally been detected by visual examination, but this approach is not adequate for ensuring freedom from edge cracking.