摘要:

Abstract—A unified fracture mechanics test method for quasi‐static testing of materials is described. It builds on the ESIS Procedures P1 and P2 and introduces additional aspects, such as the δ5crack tip opening displacement, non‐standard CT and SENB specimen configurations, centre cracked tensile specimens, testing of weldments, and guidance for statistical treatment of scattere

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1995.tb01185.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract—An analytical procedure for the prediction of opening load levels for cracks growing from notches is presented, and estimates are made using experimental crack opening load data. The procedure is based on McClung's original procedure for estimating the local elastic‐plastic stress—strain situation at the point of a hypothetical crack tip in a notched but uncracked body. A crack opening stress value for a crack in an urmotched body under the same stress—strain condition is then predicted. The corresponding opening load level for the crack stress‐strain configuration in the notched but uncracked body is then predicted with a simple backward calculation. For the evaluation of the elastic‐plastic stress distribution, simple analytical relationships, such as Neuber's rule, are used. Estimation of the crack opening stress level is performed using various crack opening stress formulae reported in the literature for cracks in unnotched specimens under a uniform stress distribution. The accuracy of all the investigated crack opening stress formulae within the scope of the presented procedure is checked, and discussed in detail using experimental data sets for opening load levels of comer cracks and through‐thickness cracks in notched specimens of FeE460 and A15086. The predicted results using Newman's crack opening stress formulae, simply modified in respect to the definition of the flow stress, have been identified to be qualitatively and quantitatively consistent with the trends observed in experimental crack

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1995.tb01186.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract—The work described in this paper characterizes short fatigue crack growth behaviour of Q2N steel having a complex microstructure and designated for pressure vessel and offshore structure applications. Short and long fatigue crack growth tests for this steel were conducted under three point bend loading conditions. It was found that, in the initial stages of growth, short cracks propagate much faster than those of long cracks when correlated with the linear elastic fracture mechanics (LEFM) parameter ΔK.A period of crack growth retardation was observed at crack lengths of approx 50 μm. The theory of the interaction between short cracks and grain boundaries fails to predict the occurrence of this deceleration minima. A new short crack deceleration mechanism is proposed based on experimental observation. Observation of the characteristic behaviour of short cracks allowed the development of a short crack growth model based on microstructural fracture mechanics analy

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1995.tb01187.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract—Usually, scatter in fracture toughness values is studied by assuming the employed steel plate to be macroscopically homogeneous in toughness, but it is probable that inhomogeneity contributes to scatter. This paper proposes a method which can discriminate scatter due to inhomogeneity from scatter measured in tests by using small size test pieces, cut out of previously fractured test specimens used for fracture toughness tests. By this method, the observed scatter of Kc(J) in a previous paper by some of the present authors was shown to be affected considerably by inhomogeneity, although the observed scatter was fairly well described by a Weibull distribution analysi

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1995.tb01188.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract—In the present investigation the ultimate capacity of cracked tubular T‐joints, loaded in tension or out‐of‐plane bending, is computed by means of non‐linear finite shell element analyses. The cracks are accounted for using inelastic line springs. The calculated results are compared to corresponding test data and other published case computations. Global load‐displacement behaviour and local behaviour by means of theJintegral are utilised for the cracked joints. The analyses demonstrate the feasibility of the FE analyses in assessing the joint capacity, but some deficiencies in the modelling are

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1995.tb01189.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract—The influence of Al2O3particle reinforcement on the fatigue crack growth properties of 6061‐T6 aluminium alloy in the near threshold regime has been investigated at a load ratio ofR=– 1 using an alloy with 15 vol.% fine particles (6061/Al2O3/15p) and one with 21 vol.% coarser particles (6061/Al2O3/21p). The Al2O3particles act as obstacles for fatigue crack growth and are especially effective at very low cyclic loads. For the reinforced alloy with fine particles the threshold of the stress intensity amplitude is higher than that for the alloy containing coarse particles, and the lowest threshold value ofKmaxwas obtained for pure 6061‐T6. Fracture of ceramic particles and interfaces between matrix and Al2O3particles, both more frequent for coarser particles, may serve as an explanation for the more effective improvement of fatigue crack growth properties by fine particles. At maximum stress intensity factors above 6.5 MPa√m, fatigue crack growth in the particle reinforced alloys is faster than in the unreinforced alloy 6061‐T6, which is attributed to more frequent particle and interface

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1995.tb01190.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract—Thermal fatigue damage may be caused when incompletely mixed hot and cold fluid streams pass over the surface of a component or structure. This kind of thermal fatigue, known as thermal striping, is of particular concern in various types of nuclear reactors and for rapid shut‐downs of hot plant. A computer code, known as TBL, is an engineering design tool which has been developed to assess thermal striping damage for fully constrained plates. This model is further developed to account for various plate‐constraint conditions. It is compared with two other methods of assessing thermal striping damage. Good agreement is found for the cases when the component is (a) a plate, constrained in various ways and exposed to a sinusoidally varying temperature time striping history and (b) a shroud tube found in the above‐core region of a fast reactor pressure vessel and striped with a random temperature time

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1995.tb01191.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract—Fatigue crack growth tests have been carried out on a medium carbon structural steel over a wide range of stress ratios, i.e. from 0 to 0.7. All tests were conducted under constant amplitude loading conditions corresponding to growth rates in the Paris regime. Crack closure behaviour was observed experimentally by a surface strain gauge technique, and numerically by a finite element analysis under plane stress condition. While the crack closure could not be detected by experimental measurements at stress ratios equal to or greater than 0.5, the numerical results showed that closure occurred even at high stress ratios up to 0.7. The differences between experimentally and numerically determined crack opening levels were found for each stress ratio. A cause for these differences is discussed. In addition, two new types of crack tip parameters which have been proposed recently are evaluated by finite element analysis and their relevance to fatigue crack growth are discussed. It is concluded that fatigue crack growth rates are substantially determined by the effective stress intensity factor range which is based on the crack closure concep

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1995.tb01192.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract—Fatigue tests were carried out to study the growth and coalescence behaviour of multi‐surface cracks which were initiated at semi‐circular surface notches, and an existing crack growth simulation program was developed to predict and compare with the experimental results. Additional comparisons with ASME and BSI conditions were also carried out to enhance the reliance and integrity of structures and machine elements. The results presented in this paper show that the simulation procedure has utility for fatigue life predi

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1995.tb01193.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1995.tb01184.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY