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The guarantee of long-term reliability of cars is becoming increasingly important in society. It is extremely important to confirm whether the condition of the accelerated deterioration test (for evaluating long-term reliability) is reasonable with respect to recent use environment conditions. In this paper, we propose how to promote degradation test conditions to guarantee the function of parts (resin materials of interior parts) exposed over a long period of time to a severe temperature environment inside the car. Heat-resisting grade nylon 66 fiber (hereinafter referred to as H-PA 66), which is a constituent material of parts requiring long-term reliability, was used as a specific resin material. High-temperature accelerated deterioration test of H-PA 66 fiber was carried out to obtain the time (hereinafter referred to as 90% strength time,) during which the tensile strength retention rate decreased to 90%.

Demands are increasing for the reduction of vehicle weight to enhance automobile fuel efficiency and driving performance, with the use of aluminum alloys expected to help. High-strength aluminum alloys (6xxx series, 7xxx series) are called for to enhance crash safety performance, and the prediction of material fracture is a key factor in the application of these alloys. This research presents a FEM model that can predict both tensile fracture and bending fracture when large deformations occur in the extrusion direction of high-strength aluminum alloy extrusion. The fracture characteristics of high-strength aluminum alloy extrusion were obtained by tensile and bending tests, and the factors governing ductile performance were clarified. Fracture was defined in the FEM model using the Cockcroft-Latham ductile fracture model.