Fatigue life of automotive structures depends on static strength, the range of stress, mode of cycling, load histories, and environmental conditions. i.e., temperature, humidity, moisture, etc. This paper presents results on the flexural fatigue life and damage accumulation of SAE 1040 steel and Glass/Epoxy composite automotive material tubes at room temperature in the dry condition. The correlation between their structure, geometry and fatigue behavior is a subject area that needs to be understood and investigated in the automotive applications like anti-roll bars and tubes. For comparative durability studies, the flexural static and fatigue tests were carried out on test specimens under constant amplitude with a sinusoidal waveform for a frequency of 3 Hz. Flexural fatigue loading conditions were analyzed at different load levels from 30% to 87% of the material ultimate flexural strength. Fatigue tests were stopped after 1 million cycles even if fracture or damage were not observed. Experimental S-N curves of SAE 1040 steel and Glass/Epoxy composite tube specimens were obtained under constant amplitude loading conditions. Fatigue properties obtained from specimen testing are then used in life predictions using the S-N approach. The predicted lives and damage evaluated from experimental and Finite Element codes using ANSYS software are found to be in good agreement. The fracture features of the steel and composite tubes observed with a Scanning Electron Microscope (SEM) were observed to agree with the obtained test data and predicted mechanism. © 2019 SAE International. All Rights Reserved.
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