I have a question about shot peening.
Is there a way to calculate or confirm how effective shot peening is to the stress (fatigue strength) when it is performed?
I have a small problem here as my torsion springs with a wire diameter of 7mm (material SWP-B) have high stress.
Unfortunately, there is no calculation method for the effectiveness of shot peening, but I think it is possible to measure the residual stress (Please contact us directly for this).
For hard materials used for springs, the degree of hardening by shot peening is slight, and the most effective way is to increase the fatigue strength is by generating compressive residual stress. Therefore, shot peening seems to have little effect on increasing the allowable stress of springs that receive static loads.
Thank you for your answer.
Is setting more suitable for increasing the allowable stress? I’ve never heard of performing setting on a torsion spring, but is it possible in general? I’m sorry for asking you many questions.
The allowable stress is determined by the tensile strength of the material used. In the case of torsion coil springs, it is the bending stress determined by the tensile strength, so it is common to set the bending stress to 0.75 to 0.8 of the tensile strength.
Although setting is possible, the purpose of setting is to increase the fatigue strength and decrease the fatigue deformation (sagging), and the main effect of this is that the residual stress in the opposite direction is generated by yielding only the surface layer.
Therefore, I do not think that the allowable stress will increase due to the setting.
