Abstract: The tensile tests and metallurgical microscopy of the hot-forming material and part are investigated. The yield limitation of the part by hot forming is more than 1 000 MPa, and the strength limitation is 1 600 MPa. Three-point bending test and impacting numerical simulation are implemented. The experimental and simulation results show the parts by hot forming have excellent loading capability and impact resistance, and are good alternative materials in application of impact resistance. The new design method, i.e. functional design, is provided, which applies the parts by hot forming to vehicle body design. Three models are design by using hot-forming parts to compare the numerical simulation results in the vehicle side impacts. Based on the comparison, the mechanism of the improved impact resistance of the whole vehicle by using hot-forming parts is analyzed. The parts by hot-forming should be the overall skeleton layout and form the ultra high strength car-protecting cab and passenger living space. The single part by hot-forming should not be simply employed to the vehicle body design in order that it thrusts into the vehicle body when vehicle crashes. Finally the functional design methods of hot-forming parts used in the vehicle body design are summarized.

Key words: Functional design, Hot forming, Impact, Numerical simulation, Three-point bending