Civil Engineering Study 89-2
INTRODUCTION During recent years, automotive manufacturers have produced lighter vehicles for the purpose of achieving fuel economy. To accomplish the construction of such automobiles, high strength sheet steels with various yield strengths up to 190 ksi have been used for auto parts and structural components 1-9. In order to provide some technical assistance for the design of such high strength steels, the first edition of the "Guide for Preliminary Design of Sheet Steel Automotive Structural Components" was issued by American Iron and Steel Institute (AISI) in February 1981. 10 The use of the Guide was discussed by Errera at the SAE International Congress and Exposition held in Detroit, Michigan in February 1982 5. In view of the fact that the design information contained in this document can be used only for sheet steels with yield strengths of up to 80 ksi, a research project has been conducted at the University of Missouri-Rolla (UMR) since 1982 to study the structural strength of automotive components using high strength sheet steels. In the first phase of the UMR program, typical mechanical properties and representative stress-strain curves were established by a series of static tests for different grades of sheet steels with yield strengths ranging from 49 to 164 ksi. The second phase of the UMR project was directed toward the web crippling strength of beam webs and the strength of members consisting of flat and curved elements. The research findings were presented in ten progress reports 11-20. In addition, the effective design widths of high strength cold-formed steel members were also investigated 21. Some of the research results were used in the first edition of the AISI Automotive Steel Design Manual published in 1986 59. This Manual brings together material properties, product design, and manufacturing information to make the most effective use of sheet steels with yield strengths of up to 140 ksi. The contents and use of the Design Manual were discussed by Cowie and Lutz at the 1987 SAE International Congress and Exposition 22 - 23. Because the previous UMR studies were limited only to the tests subject to static loads and it is well known that the yield strength, tensile strength, and the stress-strain relationship of sheet steels are affected by the rate of strain used for the tests, additional research work was conducted at the University of Missouri-Rolla in 1988. This study primarily involved the experimental determination of the dynamic material properties of three selected sheet steels with nominal yield strengths ranging from 35 to 100 ksi under different strain rates. The strain rates ranged from 10-4 to 1.0 in./in./sec. All tests were performed at UMR Engineering Research Laboratory by using the new MTS 880 Test System. The test data developed from this work will be used for the evaluation of future member tests on the design of automotive components. This study began with a review of the available literature on stress-strain curves of sheet steels and the effects of the strain rate and strain rate history on the mechanical properties of sheet steels. The literature survey is presented in Section II. Section III presents the detailed information obtained from 124 tension tests. This Section also discusses the strain rate effects on the mechanical properties of the sheet steels tested. Finally, the research findings are summarized in Section IV.
Civil, Architectural and Environmental Engineering
American Iron and Steel Institute
Wei-Wen Yu Center for Cold-Formed Steel Structures
Missouri University of Science and Technology
01 Jan 1989
© 1989 Missouri University of Science and Technology, All rights reserved.
Kassar, Maher and Yu, Wei-wen, "Design of automotive structural components using high strength sheet steels the effect of strain rate on mechanical properties of sheet steels" (1989). CCFSS Library (1939 - present). 144.