Failure review · Worked example
Evidence preservation after an early cycle-test stop
The sound and crack are observations. Material, machining, and fixture effects remain candidate causes until photographs, traces, and sections are reviewed.
The stop
The target is 8,000 cycles. An unusual sound is heard at cycle 3,200, and the test stops. A short crack is visible beside the hole; the fixture and load head show no obvious movement.
The immediate note says “crack beside the hole”. It does not say “insufficient material strength”, which would require microscopy, sectioning and the load history.
Preserve location as well as appearance
The specimen is photographed before removal, the load and displacement traces are saved, and 3 section locations are marked around the crack. Each photograph carries the specimen identifier, orientation and a scale.
A missing pre-removal photograph or an untraceable section location is recorded as an evidence gap.
Possible causes remain possible
Edge machining damage, a local layup shift, fixture-induced bending and a material defect can all stay on the candidate list. They are not ranked before the evidence returns.
The review closes with actions: inspect the machined edge, compare the layup position and check fixture alignment. This article does not select a root cause for the hypothetical data.