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.

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.

A Model for Fatigue Crack Initiation From Notches

2001 ◽  
Author(s):  
A. S. Zaki ◽  
H. Ghonem
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Initiation ◽  
Threshold Stress ◽  
Fatigue Crack Initiation ◽  
Threshold Stress Intensity ◽  
Threshold Stress Intensity Factor ◽  
Number Of Cycles

Abstract A model is developed to predict the number of cycles for fatigue crack initiation from a notch. It is based on the concept that the initiation of a fatigue crack occurs when the accumulated plastic shear deformation in the notch root reaches a critical limit which is defined in terms of the threshold stress intensity factor of the material under consideration. A viscoplastic analysis using unified constitutive equations is employed in order to describe the evolution of the notch plastic zone size as well as the stress and plastic strain distributions within this zone on cycle by cycle basis. This analysis takes into consideration the material s time- and cyclic-dependent characteristics. Experimental verification of the model was carried out using specimens made of AM350, an austenitic steel alloy: A series of crack growth measurements were performed in order to calculate the threshold stress intensity factor which is then used to determine the plastic deformation limit of this alloy. The model is used to calculate the number of cycles to crack initiation which is compared to that obtained experimentally under various loading parameters. The correlation between the model prediction and the experimental results are reported and discussed.

Sign in / Sign up

Export Citation Format

Share Document