Field note — fatigue life
The axle flange passed visual. Peening time matched the recipe. Field failures at 40% of design cycles traced to Almen strips that had not been run in three shifts—while production strips kept getting hung back on the same fixture.
Shot peening owns documented intensity, not grit in the air. Saturation coverage and Almen arc height are the process. Nozzle pressure and media flow are inputs that must be proven on strips before they touch production.
Before you run production
- Fresh Almen strip per shift start (or per OEM interval), same holder and exposure geometry as qualification.
- Arc height within band; if not, stop and requalify—do not nudge pressure.
- Coverage check on a witness coupon when geometry changes.
Rule
No production peening without a signed strip log tied to machine ID and media lot. A strip in the drawer is not a strip in the holder.