Abstract

In order to determine the response of aluminum karabiners to cyclic loading, a single type of karabiner (cold forged, D shape, weight 50 g, 7075 aluminum) was cycled to failure under a range of conditions. Deformations were recorded continuously by the testing machine and verified by manual measurement of the karabiner and an uncalibrated strain gauge affixed to the karabiner spine. Internal crack growth was monitored by taking long-exposure X-ray photos of the karabiners near the end of their lifetimes; after failure, the crack surface area was recorded. The load/life (L/N) curve isL C =85.4 (N C)−0.25 for the closed-gate condition andL O = 39.3 (N O)−0.25for the open-gate condition. Deformation occurs only at loads above 12 kN and all measurable deformation occurs in the first three cycles of loading. Crack growth was never observed before failure; crack size is consistent with expectations but the asymmetrical karabiner geometry makes it difficult to compare this data to standards. These results suggest anL/N curve can be used to characterise karabiner lifetime. Verf.-Referat