importance-of-surface-hardening-for-life-span0 10Press. Tens.RemovedChippingmachinedAbrasiveblastedShot peenedNormalized residual stress in circumferential directionNormalized depth1.91 10 1001.2Normalized cycle numberNormalized stressamplitude (tension-compression stress) Shot peenedAbrasive blastedSurface createdby machiningResidual stress pattern over the depth Residual stress pattern over the depth Cyclical life span, depending on thedynamic loadsThe influence of the scratch depth on thetolerable stress amplitude at an equal life spanDisk made from a nickel alloy:Disk made from a titanium alloy:0 Press. Tens.Normalized residual stress in circumferential directionNormalized depth0 1 2Shot peeningHigh-intensityshot peeningCold rolling1Normalized vibration-resistantstress amplitude (tension-compression stress) Normalized scratch depth0 0.05 0.1 0.15 0.2 0.25 0.3 0.35ChippingmachinedShot peenedCold rolledEvidently acceptable scratch depths insurfaces with different treatments1.2 1.10.90.80.71Dynamic strength of atitanium alloy disk withscratches over a spec-ified life span Surface hardening is very important for the cyclicallife span of parts.