Near-Threshold Fatigue Crack Growth Behavior of ECAPed Ultrafine-Grained Copper

2021 ◽  
Vol 1016 ◽  
pp. 1193-1198
Author(s):  
Shou Dao Qu ◽  
Ze Sheng You
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Threshold ◽  
Coarse Grained ◽  
Crack Growth Behavior ◽  
Fatigue Crack Growth Resistance ◽  
Ultrafine Grained ◽  
Stress Ratios ◽  
Near Threshold

Fatigue crack growth resistance of ultrafine grained Cu processed by equal channel angular pressing (ECAP) was investigated. Particular emphasis was devoted to the effects of microstructure evolution on fatigue crack growth in the near-threshold regime. The ultrafine grained Cu exhibits a lower fatigue threshold than coarse-grained Cu at stress ratios of 0.1 and 0.7. Fatigue induced coarsening of the UFG structure near the fatigue crack and intergranular fatigue crack growth are observed.

Fatigue-Crack-Growth Behavior of Ultrafine-Grained Al-Mg-Sc Alloy Produced by ECAP

2008 ◽  
Vol 584-586 ◽  
pp. 821-826 ◽  
Author(s):  
Elena Avtokratova ◽  
Oleg Sitdikov ◽  
Rustam Kaibyshev ◽  
Yoshimi Watanabe
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Behavior ◽  
Coarse Grained ◽  
Polycrystalline Materials ◽  
Gradual Transition ◽  
Crack Growth Behavior ◽  
Threshold Region ◽  
Ultrafine Grained

Fatigue-crack-growth in an ultrafine-grained (UFG) Al-6%Mg-0.3%Sc alloy is investigated in conjunction with a precise analysis of the fracture surface. The comparison of the crack growth behavior of the UFG and ordinary polycrystalline materials has shown that the fatigue crack growth rate in the UFG alloy is higher than that in the coarse-grained material only in the near-threshold region. In the intermediate fatigue stage, propagation of the fatigue-crack in the UFG structure becomes insensitive to the grain size. At larger stress-intensity-factor-increments, K, the crack resistance of the UFG material is better than that of un-ECAPed specimen. Analysis of the surface features indicates that such inhibition of the crack growth in the UFG structure upon increasing K may be related to the gradual transition from intergranular- to transgranular mode of fatigue fracture.

Threshold and Near Threshold Fatigue Crack Growth of Five Cast Steels at Room Temperature and −45°C

1985 ◽  
Vol 107 (2) ◽  
pp. 166-171
Author(s):  
R. I. Stephens ◽  
S. G. Lee ◽  
H. W. Lee
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Room Temperature ◽  
Load Ratio ◽  
Crack Growth Behavior ◽  
Fatigue Crack Growth Resistance ◽  
Cast Steels ◽  
C 50 ◽  
Near Threshold

Threshold and near threshold fatigue crack growth behavior was obtained for five carbon or low alloy cast steels at room temperature and −45°C (−50°F) with the load ratio R=0.05 and 0.5. Mean stress effects at both temperatures appear to be substantially dependent upon crack closure. ΔKth did not correlate well with other mechanical properties such as Su, Sy, Sy′ or Sf. Threshold and near threshold fatigue crack growth resistance was generally improved at −45°C despite the fact that this temperature was below the NDT temperature for three of the five cast steels. SEM fractography also established that the NDT temperature is not associated with a possible ductile-brittle constant amplitude fatigue crack growth transition in cast steels. ΔKth values for these five cast steels appear to be quite favorable relative to values found in the literature for wrought steels.

scholarly journals Near-threshold fatigue crack growth in bulk metallic glass composites

2009 ◽  
Vol 24 (12) ◽  
pp. 3611-3619 ◽  
Author(s):  
Kombaiah Boopathy ◽  
Douglas C. Hofmann ◽  
William L. Johnson ◽  
Upadrasta Ramamurty
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Volume Fraction ◽  
Fatigue Crack Initiation ◽  
Stress Intensity Factor Range ◽  
Crack Growth Behavior ◽  
Major Drawback ◽  
Fatigue Crack Growth Resistance ◽  
Near Threshold

A major drawback in using bulk metallic glasses (BMGs) as structural materials is their extremely poor fatigue performance. One way to alleviate this problem is through the composite route, in which second phases are introduced into the glass to arrest crack growth. In this paper, the fatigue crack growth behavior of in situ reinforced BMGs with crystalline dendrites, which are tailored to impart significant ductility and toughness to the BMG, was investigated. Three composites, all with equal volume fraction of dendrite phases, were examined to assess the influence of chemical composition on the near-threshold fatigue crack growth characteristics. While the ductility is enhanced at the cost of yield strength vis-à-vis that of the fully amorphous BMG, the threshold stress intensity factor range for fatigue crack initiation in composites was found to be enhanced by more than 100%. Crack blunting and trapping by the dendritic phases and constraining of the shear bands within the interdendritic regions are the micromechanisms responsible for this enhanced fatigue crack growth resistance.

Evaluation of Fatigue Crack Growth Curves in Existing Codes and a Proposed Modification Based on Experimental Data of Cr-Ni-Mo-V Steel Welded Joints

2016 ◽  
Author(s):  
Yan-Nan Du ◽  
Ming-Liang Zhu ◽  
Fu-Zhen Xuan ◽  
Shan-Tung Tu
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Welded Joints ◽  
Growth Curves ◽  
Crack Growth Behavior ◽  
Fatigue Assessment ◽  
Crack Growth Model ◽  
Threshold Regime ◽  
Near Threshold

A comparison of currently available codes for assessment of fatigue crack growth, including ASME (America Society of Mechanical Engineers) SEC. XI, FKM (Forchungskuratorium Maschinenbau) guideline, WES (Japan Welding Engineering Society) 2805, BS7910 and JSME (The Japan Society of Mechanical Engineers), was carried out by paying attention to the suitability of application and the easiness to obtain the parameters, based on fatigue crack growth data of Cr-Ni-Mo-V steel welded joints. Results showed that fatigue crack growth curves provided by the FKM or WES were good choice when few inputs were at hand while the curves in the BS7910, JSME and ASME were recommended for precise estimation. It was indicated that the assessment of welded joints solely by fatigue crack growth behavior at base metal part and the assessment of fatigue crack growth for the aged condition by as-received one both resulted in non-conservativeness, albeit dependent on the range of stress ratios, R. A new bilinear form of fatigue crack growth model independent of R was developed based on transition point occurred in the near-threshold regime. This constituted the bilinear approach to fatigue assessment, and thus contributed to the optimization of fatigue assessment in the near-threshold regime.

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