Fatigue crack propagation rates and threshold stress intensity factors for welded joints of HT80 steel at several stress ratios

1982 ◽  
Vol 4 (4) ◽  
pp. 233-237 ◽  
Author(s):  
A OHTA ◽  
E SASAKI ◽  
M NIHEI ◽  
M KOSUGE ◽  
M KANAO ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Stress Intensity ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Stress Intensity Factors ◽  
Welded Joints ◽  
Threshold Stress ◽  
Threshold Stress Intensity ◽  
Intensity Factors ◽  
Stress Ratios

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.

Experimental Study and Numerical Simulation on Fatigue Crack Growth Behavior of GH4133B Superalloy

2012 ◽  
Vol 512-515 ◽  
pp. 980-988
Author(s):  
Rong Guo Zhao ◽  
Xiu Juan Li ◽  
Yong Zhou Jiang ◽  
Xi Yan Luo ◽  
Jun Fei Li ◽  
...  
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
Stress Intensity Factors ◽  
Threshold Stress ◽  
Threshold Stress Intensity ◽  
Intensity Factors

The fatigue crack growth tests for nickel-based GH4133B superalloy used in turbine disk of a type of aero-engine are carried out at room temperature. The stress intensity factor ranges and the fatigue crack growth rates at various stress ratios are measured, and the corresponding threshold stress intensity factor ranges are determined. Using the Paris formula, the experiment data of fatigue crack growth are analyzed. It is shown that the fatigue crack growth rate increasing with increasing stress intensity factor range and stress ratio, and a modified Paris formula considering threshold stress intensity factor range can describe the fatigue crack growth behavior precisely. The fracture surface morphologies are investigated using a scanning electron microscope. It is shown that in the crack initiation region, steady growth region and rapid growth region, the fracture surface exhibits a cleavage fracture mode, fatigue striations and an intergranular fracture mode, respectively. Finally, the von Mises stresses and stress intensity factors at the crack tip of specimen of GH4133B superalloy at various external loads and crack lengths are simulated using the finite element method, and the threshold stress intensity factors under different maximal external loads at a certain crack length are calculated. The comparison between test and simulation indicates that the stress intensity factors at the crack tip calculated by the finite element method agree well with experimental data.

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