Predicting fatigue failure of power conductors

Natural frequency and fatigue failure lifetime of finger projections were investigated for the purpose of design of a reliable and inexpensive vibration indicator to be mounted on power transmission lines. The effect of notches on the natural frequency of the fingers was investigated. A computer script based on the Finite Element Method was developed to find the natural frequency of the notched rods. Aluminum alloy 6061-T6 material was chosen as the material of the fingers. Several fingers with different lengths and notch radii were designed and machined. An experimental setup was designed to measure the lifetime and natural frequency of the designed fingers. The optimum length and notch radius for a given frequency of 20Hz were obtained. It was found that inclusion of notch adds a random factor and large scattering to the fatigue lifetime due to the creation of random surface defects. It was also found that grinding the surface of the rod decreases the scatter of the lifetime results. The most appropriate finger that has a natural frequency of 20 Hz has a length of 670mm with no notch.