Influence of near-surface stress gradients and strength effect on the very high cycle fatigue behavior of 42CrMo4 Steel

Korn, M.; Rohm, Thomas; Lang, Karl‐Heinz

doi:10.1007/978-3-658-24531-3_11

Cited by 1 publication

(2 citation statements)

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“…On the one hand, the inhibited transition from short crack propagation to long crack propagation results in a higher fatigue life. On the other hand, compressive residual stresses lead to a shift of the crack initiation site into the interior of the material, as also observed in many other studies [33,[42][43][44][45][46][47][48]. This is presumably promoted by tensional residual stresses, which occur in sample interior due to the equilibrium of forces [2].…”

Section: Discussionmentioning

confidence: 52%

“…Compressive residual stresses seem to shift the initiation site of the fatal crack from the sample surface to the interior of the sample [33,[42][43][44][45][46][47][48]. Despite existing compressive residual stresses, crack initiation of the fatal crack also happens at the sample surface, particularly at surfaces of unpolished samples with an increased surface roughness due to shot peening [39,[49][50][51].…”

Section: Introductionmentioning

confidence: 99%

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Influence of Residual Stresses on the Crack Initiation and Short Crack Propagation in a Martensitic Spring Steel

Wildeis

Christ

Brandt

2022

Metals

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The crack initiation and short crack propagation in a martensitic spring steel were investigated by means of in-situ fatigue testing. Shot peened samples as well as untreated samples were exposed to uniaxial alternating stress to analyze the impact of compressive residual stresses. The early fatigue damage started in both sample conditions with the formation of slip bands, which subsequently served as crack initiation sites. Most of the slip bands and, correspondingly, most of the short fatigue cracks initiated at or close to prior austenite grain boundaries. The observed crack density of the emerging network of short cracks increased with the number of cycles and with increasing applied stress amplitudes. Furthermore, the prior austenite grain boundaries acted as obstacles to short crack propagation in both sample conditions. Compressive residual stresses enhanced the fatigue strength, and it is assumed that this beneficial effect was due to a delayed transition from short crack propagation to long crack propagation and a shift of the crack initiation site from the sample surface to the sample interior.

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