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Abstract.In an automotive industry, hot stamped, die quenched structural components have been widely used to provide extra protection against crash intrusion. Boron alloyed steel exhibit limited ductility, but it also promotes improvement in impact performance. This study analyzed the effect of cooling rate on the hardness and energy absorption. Selfquenched specimens were heated to 850qC and cooled in air of room temperature, water at room temperature and cold water. Vickers hardness test and tensile test was then carried out to analyze the effect of different quenching rate. Self-quenched specimens were compared to the properties of the die-quenched specimens obtained from commercial automobile body. Result shows that boron steel with the highest cooling rate has the highest value of hardness but low in strength.

This paper describes a newly-developed damage-based fatigue life model for the longterm reliability assessment of drawn steel wires and wire ropes. The methodology is based on the computed local stress field in the critical trellis contact zone of a stranded wire rope by FE simulations and the estimated fretting damage of the drawn wire material. A case study using a single strand (1x7) steel wire rope with 5.43 mm-dia. drawn wires is employed to demonstrate the damage-based fatigue life prediction procedures. Under applied tensile loading with peak stress corresponding to 50%MBL (P = 145 kN, R = 0.1), the von Mises stress cycles in-phase and with an identical stress ratio to the applied axial load. The damage initiation life at the trellis contact along the core wire is No = 673 cycles with an additional 589 load cycles to reach the first separation of the material point. The threshold load cycle for the fretting fatigue damage is predicted to be 12.3%MBL. An improved data set of the damage model parameters of the drawn steel wires is indispensable in achieving an accurate and validated life prediction model.

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