An Analysis of Grain Size and Yield Stress Effects on Stress at Fatigue Limit and Threshold Stress Intensity Factor

1981 ◽  
Vol 103 (3) ◽  
pp. 229-233 ◽  
Author(s):  
Y. Mutoh ◽  
V. M. Radhakrishnan
Keyword(s):  
Stress Intensity Factor ◽  
Grain Size ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Yield Stress ◽  
Fatigue Limit ◽  
Threshold Stress ◽  
Threshold Region ◽  
Threshold Stress Intensity ◽  
Threshold Stress Intensity Factor

Fatigue limits of smooth specimens and threshold stress instensity factors of specimens with large cracks depend on the microstructure of the material. A simple model in which it is assumed that the plastic zone size near the crack tip is of the order of the grain size at the threshold region has been presented in this analysis which explains the dependence of stress at the fatigue limit and the threshold stress intensity factor on yield stress and grain size.

Effect of Grain Size and Load Ratio on the near Threshold Stress Intensity Factor during Fatigue Crack Propagation of Dual Phase Steel

2012 ◽  
Vol 510-511 ◽  
pp. 67-74 ◽  
Author(s):  
M. Sarwar ◽  
E. Ahmad ◽  
T. Manzoor
Keyword(s):  
Stress Intensity Factor ◽  
Grain Size ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Threshold Stress ◽  
Load Ratio ◽  
Threshold Stress Intensity ◽  
Threshold Stress Intensity Factor ◽  
Near Threshold

Fatigue crack growth near-threshold stress intensity factor is affected by the microstructure of the material. A large portion of microstructural influence is due to the change in grain size of the material. Grain size in the dual phase steel was varied and found that the near-threshold stress intensity factor (rKth) increased as the grain size increased. Influence of load ratio nearthreshold fatigue crack propagation was also studied. It was observed that the near-threshold stress intensity range, rKthfor fatigue growth decreased with increasing load ratio.

Engineering Relation for Dependence of Threshold Stress Intensity Factor for Delayed Hydride Cracking on Crack Orientation

2008 ◽  
Author(s):  
Douglas A. Scarth ◽  
Gordon K. Shek ◽  
Steven X. Xu
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Threshold Stress ◽  
Pressure Tube ◽  
Threshold Stress Intensity ◽  
Tube Material ◽  
Fuel Bundle ◽  
Threshold Stress Intensity Factor ◽  
Cold Worked

Delayed Hydride Cracking (DHC) in cold-worked Zr-2.5 Nb pressure tubes is of interest to the CANDU industry in the context of the potential to initiate DHC at an in-service flaw. Examples of in-service flaws are fuel bundle scratches, crevice corrosion marks, fuel bundle bearing pad fretting flaws and debris fretting flaws. To date, experience with fretting flaws has been favourable, and crack growth from an in-service fretting flaw has not been detected. However, postulated DHC growth from these flaws can result in severe restrictions on the allowable number of reactor Heatup/Cooldown cycles prior to re-inspection of the flaw, and it is important to reduce any unnecessary conservatism in the evaluation of DHC from the flaw. One method to reduce conservatism is to take credit for the increase in the isothermal threshold stress intensity factor for DHC initiation at a crack, KIH, as the flaw orientation changes from an axial flaw to a circumferential flaw in the pressure tube. This increase in KIH is due to the texture of the pressure tube material. An engineering relation that provides the value of KIH as a function of the orientation of the flaw relative to the axial direction in the pressure tube has been developed as described in this paper. The engineering relation for KIH has been validated against results from DHC initiation experiments on unirradiated cold-worked Zr-2.5 Nb pressure tube material.

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