Fatigue Crack Growth Under the Conjoint Action of Major and Minor Stress Cycles

Hawkyard, M.; Powell, B. E.; Hussey, I.W.; Grabowski, L.

doi:10.1111/j.1460-2695.1996.tb00961.x

Cited by 24 publications

(10 citation statements)

References 13 publications

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“…For this case, however, the data are taken to represent a circular specimen with a circumferential notch having a stress concentration factor Kt = 2 as in the investigation of Guedou and Rongvaux [10]. The threshold stress intensity factor as a function of R is taken from [9] as above using the case where AKth is constant for R > 0.7.…”

Section: Numerical Resultsmentioning

confidence: 99%

“…Similarly, in fracture mechanics, the threshold stress intensity which is the value below which cracks will not propagate above a very low chosen value of growth rate (10-J0 m/cycle in some standards) is a decreasing function of stress ratio or mean stress. Under combined LCF/HCF loading, for example, it has been shown that the threshold at which HCF influences the growth rate under LCF, denoted by AKonset, is not a material constant, but rather it is a function of R [9].…”

Section: Damage Tolerant Design For Hcfmentioning

confidence: 99%

“…Using data from either compact tension (CT) or comer notch (CN) specimens, the value of AKonset is found to decrease by over a factor of two in Ti-6A1-4V when R increases from 0.1 to 0.7 whereas it remains nearly constant for R > 0.7 [9]. From the above, it appears that a margin of safety which is either a fixed fraction of the allowable alternating or vibratory stress or a fixed value of vibratory stress, independent of mean stress, becomes smaller as mean stresses become higher.…”

Section: Damage Tolerant Design For Hcfmentioning

confidence: 99%

“…The Goodman line for initiation is, by definition, a straight line and is assumed to decrease linearly from cra= 240 MPa at Crm = 0 to aa = 0 at o m ----1200 MPa. For essentially the same alloy and heat treatment, threshold data are taken from Hawkyard et al [9] which show that AKth decreases linearly from 5 MPav/-m at R = 0 to 2.25 MPav/-m at R = 0.7, and remains constant at that value for R > 0.7. As a second assumption, the straight line decrease of AKth is continued beyond R = 0.7.…”

Section: Failure Under Combined Lcf/hcfmentioning

confidence: 99%

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On the use of the Goodman diagram for high cycle fatigue design

1996

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Materials in rotating machinery are typically subjected to vibratory loading from a number of sources which, in turn, is superimposed on mean stresses which result primarily from steady-state centrifugal loads. In addition, components subjected to vibratory stresses can sustain damage during manufacturing, break-in cycles, or during service such as from foreign objects, fretting, or other types of wear. The combination of vibratory and 'steady' stress levels can, for certain load levels, produce low cycle fatigue damage in addition to the damage produced from the high frequency (HCF) vibratory loading since the 'steady' stresses are actually low cycle fatigue (LCF) which results in one cycle for every startup and shutdown operation. Design for HCF is generally based on a Goodman diagram which takes into account the vibratory as well as the steady stress amplitudes for fatigue runout or fatigue under a given number of cycles. It does not, however, take into account the combined effects of LCF and HCE In this investigation, the combined effects are demonstrated analytically by numerical examples which consider both the initiation and propagation phases of fatigue. In addition to the analysis of LCF/HCF interactions, considerations which must be accounted for in design are reviewed in light of a number of failures of components in service in U.S. Air Force fighter engines. A critical assessment of the concepts embedded in the use of the Goodman diagram is presented. Comments on the limitations on the use of a Goodman diagram for design are provided. Some suggestions are offered for the improvement of the design methodology for HCF which involve both damage tolerance considerations and methods for assessing and improving the margin of safety.

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Section: Numerical Resultsmentioning

confidence: 99%

Section: Damage Tolerant Design For Hcfmentioning

confidence: 99%

Section: Damage Tolerant Design For Hcfmentioning

confidence: 99%

Section: Failure Under Combined Lcf/hcfmentioning

confidence: 99%

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On the use of the Goodman diagram for high cycle fatigue design

1996

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“…The test material, U720LI, is a nickel‐based superalloy, possessing a low concentration of interstitial elements. Corner‐notched (CN) specimens 13 of 10 × 10 mm cross‐section were used. The stress intensity solution for the CN specimen developed by Pickard 14 is:…”

Section: Methodsmentioning

confidence: 99%

The characterization of fatigue crack growth behaviour by constant ΔK control testing

Zhong

Powell

Byrne

et al. 1999

Fatigue Fract Eng Mat Struct

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Essential to the assessment of the fatigue integrity of critical components is the prediction of their crack propagation lives. This requires the effective and efficient characterization of the fatigue crack growth behaviour of the material when using a small number of specimens. A test facility, able to control the range of applied load (ΔP ) and range of stress intensity factor (ΔK ), has been used to determine the fatigue crack growth rates in corner notched specimens of Udimet 720 for stress ratios of 0.5, 0.1 and −1.0. Initially, the results were analysed in terms of the three‐point secant data reduction method. Subsequently, the benefits to be gained by the use of alternative methods involving regression analysis have been examined. The effectiveness of the procedures has been assessed in terms of the extent to which they reduce the width of the scatter band representing the fatigue crack growth behaviour and the accuracy with which the experimental observed fatigue lives are predicted. On this basis, the results from the ΔK controlled tests were superior to those obtained under ΔP control, when analysed by similar data reduction methods. In addition, the results from ΔK tests were improved when the secant method was replaced by a linear regression method, which allowed the sample interval to be reduced and more levels of constant ΔK to be examined in a single specimen.

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Combined cycle fatigue testing with ultrasonic frequency component of S350 steel welded joint

Liu

Wang

Deng

et al. 2014

Trans. Tianjin Univ.

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Abstract：A combined cycle fatigue (CCF) testing system with ultrasonic frequency component was developed to evaluate the CCF properties of S350 steel welded joints in this study. The fatigue testing results indicated that the S-N curves of CCF did not have fatigue limit, which agreed with those of pure high frequency fatigue of welded joints. The S-N curves showed that the CCF strength of welded joints dropped greatly with the increasing interaction between high and low frequency fatigue loading. An approximation design method of CCF was presented using amplitude envelope as the stress range.Fatigue fracture is a main form of welded structure failures. Most of fatigue design specifications of welded joint and evaluations of welded structure are based upon the fatigue testing data of single cycle load [1] . The general fatigue testing is single cycle loading, i.e., just pure low cycle fatigue (LCF) or pure high cycle fatigue (HCF). However, many important welded structures also bear different degrees of high frequency vibration when they bear low frequency high amplitude fatigue loading, namely, combined cycle fatigue (CCF). Several CCF failures have occurred in the gas turbine etc [2] .For the CCF of base material, Refs. [3 -5] have shown a two-phase crack growth process. Namjoshi and Mall [6] conducted the fretting-fatigue tests under variable loading involving a two-level block of low frequency (1 Hz) high amplitude cycles and high frequency (200 Hz) low amplitude cycles, which represented the low cycle and high cycle components of the turbine engine mission loading. Testing results showed that damaged fraction was induced by the LCF and HCF components of combined cycle loading. Dungey and Bowen [7] found that the effect of combined loading was variable and dependent upon the testing conditions. Byrne et al [8] , Mendia et al [9] and Schweizer et al [10] have proved that for metal material, the LCF/HCF interaction led to accelerated fatigue crack growth of micro-crack in comparison to pure LCF loading. However, welded joint is very different from metal material because of its inhomogeneity. Few scholars have researched the CCF of welded joint. In this study, the CCF tests with ultrasonic frequency component were performed on the welded joints of S350 steel, and then the fatigue behaviors were discussed. ExperimentThe CCF tests were conducted on a fatigue testing system, which was a combination of an electromagnetic resonant fatigue testing machine and an ultrasonic fatigue testing machine, as shown in Fig. 1(a). The electromagnetic resonant fatigue testing machine provided low frequency loading, meanwhile, the ultrasonic fatigue testing machine provided high frequency loading. Testing frequencies of low cycle fatigue and high cycle fatigue were 75 Hz and 20 kHz, respectively. The static load error of the electromagnetic resonant fatigue testing machine for full measuring range was ±0.2%. Besides, the dynamic load error was ±2%. The wave shape of loading was a sinusoidal wave. The specimens were prepared ...

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Fatigue Crack Growth Under the Conjoint Action of Major and Minor Stress Cycles

Cited by 24 publications

References 13 publications

On the use of the Goodman diagram for high cycle fatigue design

On the use of the Goodman diagram for high cycle fatigue design

The characterization of fatigue crack growth behaviour by constant ΔK control testing

Combined cycle fatigue testing with ultrasonic frequency component of S350 steel welded joint

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