Evaluation of residual stress relaxation and its effect on fatigue strength of AISI 316L stainless steel ground surfaces: Experimental and numerical approaches

TLDR: In this article, the authors evaluated the residual stress relaxation and its effect on the fatigue strength of AISI 316L steel ground surfaces in comparison to electro-polished surfaces.

About: This article is published in International Journal of Fatigue.The article was published on 2013-03-01 and is currently open access. It has received 76 citations till now. The article focuses on the topics: Fatigue limit & Stress concentration.

Figures

Table 1 Grinding conditions.

Fig. 4. Texture of the AISI 316L steel ground surface.

Fig. 5. Micro-hardness profiles in-depth of the electro-polished and ground surfaces.

Fig. 3. (a) Two plane bending configurations and (b) devise of 4-point plane-bending fatigue test.

Fig. 16. Comparison between numerical and experimental profiles of stabilized residual stresses under 4-point bending test: (a) longitudinal stresses (rRxx) and (b) transversal stresses (rRyy).

Fig. 17. The stress/plastic-strain relationship at the notch root of ground specimens subjected to 4-point bending test at the fatigue limit (showing an elastic shakedown after the first loading).

Frequently asked questions

Q1. What is the effect of residual stress relaxation on the fatigue strength of metals?

The relaxation during the first cycle (quasi static loading) occurs when the superposition of the applied and residual stresses exceeds the monotonic yield strength of the material in tension and compression, while relaxation during successive cycles is related to the cyclic yield strength [13]. 

Q2. What is the main mechanical properties after an annealing treatment?

The main mechanical properties after an annealing treatment (cooling in air after heating for 1 h at 1050 C) are: E(GPa) = 196, rY0.2(MPa) = 220, rUTS(MPa) = 600, rF(MPa) = 400, T.E.(%) = 80, HV0.1 = 190. 

Q3. How was the strain amplitude of the cyclic loading determined?

The total strain amplitude of the cyclic loading were applied with four values: Det/2 (%) = 0.3, 0.5, 0.7 and 1 which are controlled by means of a longitudinal extensometer. 

Q4. What is the relationship between the residual stress relaxation and the number of cycles?

Since the relaxation is associated with dislocation movement, it is therefore correlated to the plastic strain accumulation with the number of cycles. 

Q5. What is the micro-hardness profile of the electro-polished surface?

The micro-hardness profile measured in-depth of the ground surface (Fig. 5) shows that the grinding induces a high hardening gradient over a superficial layer of 100 lm. 

Q6. What is the effect of grinding residual stresses on the fatigue limits of AISI 316L?

This degradation is accompanied by a slight relaxation of the grinding residual stresses which remain with tensile values at the surface and which play a detrimental effect on fatigue strength [10]. 

Q7. What is the criterion for predicting the fatigue strength of a ductile?

In fact, the Dang Van’s criterion allows predicting the fatigue limit with a satisfactory accuracy when only the stabilized surface residual stresses are taken into account. 

Q8. What is the effect of grinding residual stresses on the fatigue strength of AISI 316L?

This confirms that the influence of grinding residual stresses on fatigue strength of the AISI 316L steel surfaces is more important than the combined effect of superficial hardening and roughness. 

Q9. What is the role of residual stresses in the fatigue behaviour of metal parts?

It is well established that these stresses play an important role in service behaviour, particularly, in presence of cyclic loadings [3–6].