Equivalent stress approach to predicting the effect of stress ratio on fatigue threshold stress intensity range

2004 ◽  
Vol 26 (3) ◽  
pp. 299-303 ◽  
Author(s):  
S Kwofie
Keyword(s):  
Stress Intensity ◽  
Threshold Stress ◽  
Stress Ratio ◽  
Equivalent Stress ◽  
Fatigue Threshold ◽  
Threshold Stress Intensity ◽  
Stress Intensity Range ◽  
Intensity Range

scholarly journals Effect of TiB Orientation on Near-Threshold Fatigue Crack Propagation in TiB-Reinforced Ti-3Al-2.5V Matrix Composites Treated with Heat Extrusion

Materials ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 3685 ◽  
Author(s):  
Shoichi Kikuchi ◽  
Shunsuke Tamai ◽  
Takao Kawai ◽  
Yoshikazu Nakai ◽  
Hiroki Kurita ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Stress Intensity ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Threshold Stress ◽  
Matrix Composites ◽  
Threshold Stress Intensity ◽  
Stress Intensity Range ◽  
Intensity Range

TiB-reinforced Ti-3Al-2.5V matrix composites, in which TiB whiskers are oriented parallel to the direction of heat extrusion, were fabricated via mechanical alloying and hot isostatic pressing (HIP). To investigate the near-threshold fatigue crack propagation in TiB-reinforced Ti-3Al-2.5V matrix composites, stress intensity factor K-decreasing tests were conducted for disk-shaped compact specimens having two different orientations of TiB whiskers at force ratios from 0.1 to 0.8 under ambient conditions. The crack growth rates, da/dN, for the composites incorporating TiB whiskers oriented perpendicular to the direction of crack growth were constantly lower than those obtained in the case where the orientation was parallel at the same stress intensity range ΔK, while the threshold stress intensity range, ΔKth, was higher. This effect can be explained by the increase in the degree of roughness-induced crack closure resulting from the perpendicular TiB, because fatigue cracks preferentially propagated across the boundaries between the matrix and the TiB in certain regions. In contrast, the effective threshold stress intensity range, ΔKeff,th, for composites was unaffected by the TiB orientation at low force ratios.

Effect of Yield Stress and Grain Size on Threshold and Fatigue Limit

1986 ◽  
Vol 108 (2) ◽  
pp. 174-178 ◽  
Author(s):  
Y. Mutoh ◽  
V. M. Radhakrishnan
Keyword(s):  
Grain Size ◽  
Stress Intensity ◽  
Yield Stress ◽  
Fatigue Limit ◽  
Threshold Stress ◽  
Experimental Investigations ◽  
Threshold Stress Intensity ◽  
Stress Intensity Range ◽  
Intensity Range ◽  
Analytical Relations

Experimental investigations have been carried out to study the effects of grain size and yield stress on fatigue limit and threshold stress intensity range. The relations between fatigue limit and grain size and yield stress and those between threshold stress intensity range and grain size and yield stress which were predicted according to the model proposed in the previous paper agreed quite well with the experimental data. The difference in the dependence of fatigue limit and threshold stress intensity range on yield stress was discussed based on the analytical relations between them.

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