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Spoke broken at elbow from fatigue
This was a DT Alpine III spoke (2.3mm diameter at the elbow), laced into a disk-braked wheel as an inbound spoke on the non-drive side. Hard disk braking cause spoke to go slack cyclically with brake vibration and screeching, leading to fatigue. The crack started at the upper left of the photo on the inside of the elbow, then propagated normal to the banding seen in the crack surface. The spoke failed when only about 1/6 of the original material remained attached, leaving a 45-degree shear failure that can be seen at the lower right.

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