4. Bolt fatigue strength

This characteristic, which is fundamental to the dimensioning of most bolted mechanical engineering assemblies, is obtained from tests carried out on whole screws fitted with their nuts.

The test conditions are perfectly defined by standard NF ISO 3800 on fatigue testing under axial load. However, no specification of permissible alternating stress is imposed and, for verification calculations, reference should be made to published test results .

For a number of stresses greater than 2 × 10 ⁶ cycles, these data seem sufficient; for a lower number of cycles, you need to carry...