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Technical Paper

Implications of Hot-Stamped Boron Steel Components in Automotive Structures

The demand for fuel economy and the stringent requirements on automobile safety have required automakers to emphasize strength over stiffness in designing light-weight body structures. The change in emphasis has necessitated the exploitation of ultra high-strength steels to achieve improved crashworthiness and durability in automotive vehicles. In this paper, the viability of hot-stamped boron steels in high-performance automotive structures will be discussed. A brief discussion of hot-stamping process will be followed by recent mechanical property data that underscore the superiority of boron steels in enabling the development of safe and fuel-efficient vehicles. The relatively low-carbon and low-alloy content of boron steels enable better weldability compared with high-carbon and high-alloy steels.
Technical Paper

Boron Steels for Superior Durability in Automotive Structures

The potential of hot-stamped boron steel in aiding improved durability coupled with mass reduction is explored through two case studies involving a lightweight truck frame and a shock tower assembly. Through a computational approach, analyses are performed using service loading conditions. The stress fields calculated through the analyses are used to predict fatigue life cycles. It is shown that the advanced steel grades such as Boron can offer superior resistance to fatigue loading conditions while offering an opportunity to reduce the weight of the component.
Technical Paper

A Comprehensive Study of Door Slam

As part of an ongoing technical collaboration between Ford and Rouge Steel Company, a comprehensive study of door slam event was undertaken. The experimental phase of the project involved measurements of accelerations at eight locations on the outer panel and strains on six locations of the inner panel. Although slam tests were conducted with window up and window down, results of only one test is presented in this paper. The CAE phase of the project involved the development of suitable “math” model of the door assembly and analysis methodology to capture the dynamics of the event. The predictability of the CAE method is examined through detailed comparison of accelerations and strains. While excellent agreement between CAE and test results of accelerations on the outer panel is obtained, the analysis predicts higher strains on the inner panel than the test. In addition, the tendency of outer panel to elastically buckle is examined.
Technical Paper

Grade and Gage Sensitivities to Oil-Canning Loads of a Door Assembly Considering Forming Effects

A finite element methodology, based on implicit numerical integration procedure, for simulating oil-canning tests on Door assemblies is presented. The method takes into account nonlinearities due to geometry, material and contact between parts during deformation. The simulation results are compared with experimental observations. Excellent correlation between experimental observations and analytical predictions are obtained in these tests. Armed with the confidence in the methodology, simulations on a door assembly are conducted to study the gage and grade sensitivities of the outer panel. The sensitivity studies are conducted on three different grades of steel for the outer panel. Further studies are conducted to understand the effects of manufacturing (forming operation) on the oil canning behavior of door assembly. Results demonstrate the utility of the method in material selection during pre-program design of automotive structures.
Technical Paper

Application of Advanced High Strength Steels for Enhanced Durability of a Shock Tower Assembly

The potential of advanced high strength steels such as TRIP versus conventional HSLA350 steel in achieving improved durability with weight savings is explored in the case of a shock tower assembly. Through a computational approach a linear analysis and a nonlinear analysis are performed. The nonlinear analysis takes into account the effect of geometry, material and contact nonlinearities. The results from both the linear and nonlinear analysis are used to predict fatigue lives. It is shown that the advanced steel grades, in particular, TRIP steels, can offer superior resistance to fatigue loading conditions while offering an opportunity to reduce the weight of the component.
Journal Article

Influence of Geometric Parameters and Their Variability on Fatigue Resistance of Spot-Weld Joints

Spot welding is the primary method of joining sheet metal for body and structural applications in the ground vehicle industry. A typical automobile may contain over 5000 spot welds. The fatigue failure of spot welded joints results in the degradation of both structural and Noise, Vibration, and Harshness (NVH) performance. Therefore, designers need reliable information about the total fatigue life of spot welded joints early on in the design phase. Currently, automotive structures are employing ever increasing amounts of Advanced High Strength Steels (AHSS) including dual-phase steels. As a result, automotive designers require fatigue strength information on AHSS spot welds. The Auto/Steel Partnership (A/SP) has conducted fatigue tests with lap shear and coach peel specimens made of AHSS, HSLA and low carbon steels. Overall, the test data showed good correlation with the applied load range for all of the materials, regardless of base material strength.