ME274 FEA Term Project F2023

The effects of a fastener loosening over time due to vibrations was examined to understand its behavior and the specific conditions under which this phenomenon occurs. Parameters used were friction, preload, external vibrational forces, resonance frequencies, and material properties. By understanding how and why a bolt loosens over time under dynamic conditions, strategies to mitigate or prevent it from occurring can be implemented.

The objective is to determine the clamping force under a specific load in various frequencies to determine when the fastener will loosen during a vibration-driven scenario. Non-linear contact analysis and harmonic simulation and analysis were performed through ANSYS Workbench.

Results from contact analysis indicated vibrational driven load must provide more than 14.65 N-m to self loosen the bolt. Running a full harmonic analysis, indicated peak reaction force occurred at 3000-Hz then decreases. Compared to 500 N and 4000 N vibration load yielding tangential (frictional) forces of 13.97 N and 111.74 N, the bolt will not loosen. A 10 kN load that was tested separately yield 279.342 N. Further future analysis is required due to a large error.

To note, errors occurred when adding pre-stress condition into harmonic analysis and issue with hardware limitations. By improving meshing, increasing data points and successfully adding the pre-stress condition using command APDL inistate method, and running more iterations in loading conditions to the harmonic analysis, results will be more accurate and the behavior of the bolts’ rotational self-loosening phenomenon can be captured.