This article will look at an extension spring, manufactured from stainless steel wire, which failed during fatigue testing. The spring was part of a safety-critical system used in the control panel of a plane. The end user sent several springs for fatigue testing, half of which were failing the fatigue requirements. The failures were all located in the same position, within the hook of the spring. Multiple failed samples were supplied for evidence, along with an unfractured sample for comparison.
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