Some factors exerting an influence on the coaxing effect of austenitic stainless steels

Abstract

The present paper describes some factors exerting an influence on the coaxing effect of austenitic stainless steels. Particularly, the influence of prestrain was investigated in detail. The materials used were austenitic stainless steels, type 304 and 316. Type 304N2 was also used to examine the properties of the stabilized austenitic phase in type 304. Two types of rotating bending fatigue tests, i.e. the conventional constant amplitude tests and stress‐incremental tests, were performed using the specimens subjected to the several tensile‐prestrain levels. Under the constant amplitude tests, the fatigue strengths of type 304 and 316 increased with increasing prestrain. Under the stress‐incremental tests, type 304 showed a remarkable coaxing effect, where the fatigue failure stress significantly increased regardless of the prestrain level. The coaxing effect in the unprestrained specimens was larger than those of the prestrained ones. Type 304N2 showed lower coaxing effect than type 304. In addition, the strain‐induced martensitic transformation did not occur because of the higher stability of austenitic phase in type 304N2. In type 316, the coaxing effect was dependent on the prestrain level, i.e. below 15% prestrain the coaxing effect became smaller with increasing prestrain, whereas above 25% prestrain the coaxing effect reappeared. Based on the tests results, it was considered that the coaxing effect in austenitic stainless steel was due to the mechanisms such as work hardening, strain ageing and strain‐induced martensitic transformation. The contribution of these mechanisms to the coaxing effect was different among type 304, 304N2 and 316.

Residual fatigue life prediction based on a novel damage accumulation model considering loading history

“…In the strengthening region, the residual fatigue strength firstly increased and then decreased with the increasing of consumed life fraction under the previous loading. Generally, the coaxing effect was attributed to the work hardening due to the increase of dislocation density regardless of the preloading level . As can be seen in Figure B, the residual fatigue strength would be weakened when the previously consumed life fraction exceeded a specific value in the strengthening region.…”

Intrinsic Factors that Trigger the Coaxing Effect in Binary Fe–C Ferritic Alloys with a Focus on Strain Aging

“…However, the underlying mechanism of the coaxing effect has not been elucidated yet. It has been reported that the coaxing effect appears when work hardening 11) or strain-age hardening of carbon 12,13) are significant during fatigue. The latter factor likely plays an important role in the appearance of the coaxing effect in ferritic steels.…”

Intergranular Fatigue Crack Initiation and Its Associated Small Fatigue Crack Propagation in Water-quenched Fe–C Fully Ferritic Steel

“…21) Note that the coaxing effect in most cases has been found in metallic materials where strain age hardening occurs significantly, 22) except for austenitic stainless steels. 23,24) More specifically, the coaxing effect in carbon steels is considered to stem from non-propagating fatigue crack phenomenon associated with strain age hardening. Hence, many researches [24][25][26][27][28] have studied the small fatigue cracking behavior to understand the coaxing effect in the crack propagation portion of fatigue lives.…”