A problem that I recently come across is confusing.

As far as I know, for a certain type of material, say 1040 steel, the slope of the wohler curve is constant (3 for normal stress & 5 for shear stress), for any type of weldment. But a document that we recently obtain tells that weld type ( fillet, butt...) and quality (weld finishing, grinding...) affects not only the endurance limits, but also the slope of S-N curve.

Does anyone have an idea about this slope issue?

Thx