摘要:

Abstract—The threshold value for fatigue crack growth of a medium carbon steel was increased when the test‐environment was changed from air to an aggressive H2S‐containing brine. This increase in fatique threshold was shown to be caused by corrosion product‐induced crack closure. Further, the fatigue threshold and crack closure level were shown to be dependent on the growth rate history in approaching threshold. The differences in fatigue crack growth rate and fatigue threshold resulting from test procedure and growth rate history were significantly reduced by employing the effective stress intensity

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1983.tb00346.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—Sharply notched specimens of a structural low‐carbon steel were fatigued under several ratios of the maximum to minimum loads. The growth behavior of a short fatigue crack near the notch tip was analyzed based on crack closure measurements. A fatigue crack first decelerates with increasing crack length, and then accelerates or becomes non‐propagating depending on the applied stress. A similar deceleration is seen when the rate is correlated to the stress intensity range. The effective stress intensity range is a unique parameter in correlating the growth rate of a short crack for all the stress levels examined, and the relation is identical to that obtained for a long crack. By considering the increase in crack closure with crack length, a quantitative method is proposed for predicting the non‐propagating crack length and the fatigue limit of notched specimens as a function of the applied stress and the notch g

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1983.tb00347.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—The influence of age‐hardening on the middle and low crack growth rates of a 7075 Al alloy is studied in vacuum. A transition in fracture surfaces morphology and crack growth curves is observed with the T 651 and T 7351 treatments in the near‐threshold regime. Measurements of crack closure show its dependance on surfaces roughness and explain the lack of dependance of ΔKthwith load ratio, except for the T 7351 alloy. An equation of crack growth rate to the fourth power of ΔKeffis in good agreement only with the crack propagation curves obtained for microstructure with an homogeneous deformati

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1983.tb00348.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—Four particularly pronounced beachmarks have been identified on the fracture surface of a cracked rotor. A correlation has been made between these beachmarks and events in the operational record. Fatigue crack growth calculations have been performed for a chordally cracked shaft subject to alternating self‐weight bend stresses. The shaft dimensions and loading used correspond to the position of the crack in the rotor and growth rates were calculated over a range of crack depths spanning the positions of the major beachmarks. The results of the calculations agree with the beachmark correlation if allowance is made for the effect of the torsional loading of the sh

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1983.tb00349.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—Fatigue crack growth measurements are usually made on standard specimens containing long cracks (∼10 mm) although in most practical situations, a large part of the fatigue life is spent with much shorter dimensions. The purpose of the present study is a comparison of crack growth behaviour for long cracks (∼13–16 mm) in CT specimens and smaller ones (∼0.3–0.5 mm) in four point bend specimens. Large effects are noticed indicating that, at a given stress intensity factor amplitude, the crack growth rate is significantly higher in specimens with short cracks. Mouth displacement measurements for both specimen configurations show that the crack closure phenomenon accounts for the observed effect. Crack closure is likely to be associated with fracture surface roughness as shown by partly machining the material left behind the crack tip in C

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1983.tb00350.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—Crack closure in the near‐crack‐tip region has been considered to be an important contribution to the development of a crack‐growth threshold for macroscopic cracks. Recent analytical work, however, has suggested that closure well back of the tip may be the controlling factor. In order to check on this possibility, material has been machined away far behind the crack tip in order to eliminate long‐range closure. Removal of this material did not eliminate the threshold, but did lower the threshold level by approx. 10% for tests conducted on 6.3 mm‐thick X7090‐T6 powder metallurgy a

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1983.tb00351.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—Segmented fitting of fatigue crack growth rate data is shown to give a more accurate prediction of fatigue life with less statistical scatter than by a single fitting using the straight line of a Paris‐type plot. Changes in the slope of the log (da/dN) vs log ΔKdata are seen to correlate well with changes in the mode and mechanism of frac

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1983.tb00352.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1983.tb00353.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1983.tb00345.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY