Dual phase versus TRIP strip steels: Comparison of dynamic properties for automotive crash performance

Abstract

The need to simultaneously reduce vehicle emissions and increase the safety of passengers is encouraging the automotive industry to incorporate new technologies and materials into today's vehicles. To remain competitive, the steel industry has developed steel grades with increased energy absorbing properties allowing down gauging of body in white components to address the competition from alternative materials such as aluminium alloys and composites. Two of the more important developments are the introduction of dual phase (DP) and transformation induced plasticity (TRIP) grades for the automotive industry. These grades offer superior strength/ formability and work hardening properties compared to conventional high strength grades of similar tensile strength. Utilising thinner gauge components with increased energy absorbing properties would permit addressing the mass/safety issues by the automotive industry. This paper relates the crash performance of a range of both commercial and experimental DP and TRIP grades. Dynamic tensile testing was performed at low and very high strain rates within the range of 0 . 001-200 s 21 , to allow an extensive analysis of the effect of strain rate on the material properties. Crash testing was also performed on closed top hat sections at low, medium and high strain rates and the results compared to the dynamically tested tensile specimens. This study helped clarify the enhanced performance offered by high strength DP and TRIP strip steel grades during dynamic tensile testing and impact loading conditions. This advantageous behaviour is attributed to the favourable microconstituents present in these novel grades and their deformation characteristics. This paper concentrates only on the crash properties measured from dynamic tensile tests. The microstructural analysis is presented in a separate publication. 1

Strain Rate Effect on Tensile Behavior for a High Specific Strength Steel: From Quasi-Static to Intermediate Strain Rates

“…It is well known that excellent candidates for energy absorbers require materials that are (i) capable of keeping a high value of the yield strength upon deformation, and (ii) able to absorb more energy up to fracture [30,32]. In addition to the high specific yield strength and the large uniform elongation under quasi-static conditions for this HSSS when compared to the other dual phase steels [11,14,[16][17][18][19], the simultaneously improved strength and the improved tensile toughness at the intermediate strain rates are very appropriate for the application of this HSSS in the automotive industry to enhance safety during a vehicle crash since the applied strain rate range for vehicle crushing is generally between 1 and 100/s (intermediate strain rates) [51][52][53][54][55] or even higher.…”

“…It is also well known that the observed resistance to plastic deformation is a rate-controlling process and can be affected by the strain rate [23][24][25]27,28]. The quasi-static tensile behaviors and the dynamic behaviors at high strain rates (~10 3 /s) for TRIP steels, TWIP steels, DP steels and HSSS have been well characterized in previous research [1,2,20,[41][42][43][44][45][46][47][48][49][50], while there is very limited experimental data on various steels at the intermediate strain rates (from 1 to 100/s) [51][52][53][54][55], which is an extremely important transition region in application of automobile industry, since vehicle crushing often happens in this strain rate range or within an even higher strain rate range. Thus, the potential applications for the HSSS in the automobile industry require a comprehensive understanding of deformation physics subjected to dynamic loading at intermediate strain rates.…”

Phase-transformation behavior and micromechanical properties of a dual-phase steel after chemical modifications

“…1 However, with the development of the technology and deterioration of the environment, an even better performance of advanced steel was required, especially for the automotive industry. 2 As a result, DP steels were developed. The matrix of DP steels consists of two different phases: ferrite and martensite; the former shows great plasticity and toughness, while the later shows high strength.…”

Influence of Filler Alloy Composition and Process Parameters on the Intermetallic Layer Thickness in Single-Sided Cold Metal Transfer Welding of Aluminum-Steel Blanks

“…Particularly high-strength steels, e.g., dual phase (DP), transformation-induced plasticity (TRIP), and twinning-induced plasticity (TWIP) steel grades [1,2] as well as aluminum (Al) alloys, e.g., series AW 5xxx and AW 6xxx, [3][4][5] play important roles in innovative multimaterial car body design. In order to benefit from the specific advantages of each of these material groups and to obtain car bodies offering both high safety and low weight, joining of aluminum alloys with steels is mandatory.…”