A fracture mechanics analysis of fatigue crack growth data for various materials

Frost, Nancy; Pook, L. P.; Denton, Kristin

doi:10.1016/0013-7944(71)90003-8

Cited by 184 publications

(43 citation statements)

References 13 publications

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“…In fatigue crack growth problems, stress intensity factors can be taken as providing a reasonable description of the stress field at the crack tip provided that the net section stress does not exceed 80% of the yield stress [5]. Results are therefore discarded if the average shear stress on the weld exceeds 80% of the nominal shear yield stress, which is taken as half the 0.2% proof stress of the parent plate.…”

Section: (2)mentioning

confidence: 99%

“…A crack will not grow under fatigue loading unless AK exceeds a threshold value AK [5], and this is the reason for the existence of a fatigue limit foCr specimens containing crack-like flaws. Values of AK for steel depend on the ratio of mean to alternating stress but c are largely independent of composition and tensile str~$th.…”

Section: (4)mentioning

confidence: 99%

“…Plotted in terms of AK, the results are much less scattered, in particular the fatigue limit is more clearly defined. The inverse slope is 10/3 in both cases; in the original analysis [i] inverse slopes of about 3 were observed and it was pointed out that this was consistent with fatigue crack growth data.A crack will not grow under fatigue loading unless AK exceeds a threshold value AK [5], and this is the reason for the existence of a fatigue limit foCr specimens containing crack-like flaws. Values of AK for steel depend on the ratio of mean to alternating stress but c are largely independent of composition and tensile str~$th.…”

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Fracture mechanics analysis of the fatigue behaviour of spot welds

Pook¹

1975

Int J Fract

144

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Overbeeke and Draisma have recently published [i] results of fatigue tests on heavy-duty spot welded lap joints. The tests were carried out in air under zero to tension loading and the results were ~nalysed in terms of load. However a spot weld is equivalent to a crack-like flaw, so that virtually the whole life is occupied by fatigue crack growth, and a fracture mechanics analysis becomes appropriate [2]. Of the six test series reported, II, III, and IV were carried out on spot-welded lap joints, and the results obtained are used in the present paper for an analysis in terms of stress intensity factors, which describe the elastic stress field in the vicinity of a crack tip.Series II tests were on single spot welds ( Fig. i@) between plates of grade 37 KF steel (0.2% proof stress 260 FIN/m'). Spot diameters were in the range 7 to 23 mm, and individual spot diameters [3] are used in the calculation of stress intensity factors. Series III tests were on single spot w~ids between plates of grade 56 KF steel (0.2% proof stress 475 ~/ m ). Spot diameters were in the range 18 to 22 rm, but as individual spot diameters are not available, the average is used to calculate stress intensity factors. The possible error due to use of the average diameter is 11%. Series IV tests were on two spot welds in line (Fig. ib) between plates of grade 56 KF steel. Spot diameters were in the range 18 to 22 mm, the average again being used to calculate stress intensity factors and giving a possible error of 16%. In all tests, cracks originated at a point A (Fig. I) in the parent plate. The subsequent pattern of crack growth was complicated, but final failure was generally in the parent plate, except that nearly half the testpieces in the series II tests failed across the weld.Approximate opening mode K_ and edge sliding mode KII stress intensity factors at point A (Fi&. I) are [4] as follows. For a single spot weld, radius a, between plates thickness 2b, with a/b <_ I0 and o (2)For two spot welds in line, with centres at least three spot diameters apart, and 1.92 < a/b < i0, KII is the same andInt Journ of Fracture ii (1975) 174In (i) to (3), Q is the applied load per spot weld. The edge of a spot weld must be at least one spot diameter from a plate edge.In fatigue crack growth problems, stress intensity factors can be taken as providing a reasonable description of the stress field at the crack tip provided that the net section stress does not exceed 80% of the yield stress [5]. Results are therefore discarded if the average shear stress on the weld exceeds 80% of the nominal shear yield stress, which is taken as half the 0.2% proof stress of the parent plate. Application of this limitation eliminates one series IV result and nearly half the series II results. The results eliminated are nearly all those where weld failure took place, which suggests that shear failure of a weld is associated with yielding. This agrees with the observation that mode II fatigue crack growth can take place under general yielding conditions [6] whereas, under ...

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Section: (2)mentioning

confidence: 99%

Section: (4)mentioning

confidence: 99%

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Fracture mechanics analysis of the fatigue behaviour of spot welds

Pook¹

1975

Int J Fract

144

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“…Additionally, the DD simulations require a crack growth law as input. Fatigue experiments on metals and metallic alloys range greatly but are around 3 [32] or 4 [33] for metals and 2 for many alloys [33].…”

Section: Crack Growth Per Cyclementioning

confidence: 99%

An atomistic investigation into the nature of near threshold fatigue crack growth in aluminum alloys

Baker

Warner

2014

Engineering Fracture Mechanics

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a b s t r a c tDespite decades of study, the atomic-scale mechanisms of fatigue crack growth remain elusive. Here we use the coupled atomistic-discrete dislocation method, a multiscale simulation method, to examine the influence of dislocation glide resistance on near-threshold fatigue crack growth in an aluminum alloy. The simulations indicate that the threshold increases with an increase in dislocation glide resistance, and that a transition in the crack growth direction can occur when dislocation nucleation is inhibited by other nucleated dislocations. Three main mechanisms of fatigue crack propagation are observed: cleavage along the primary slip plane, crack extension by dislocation emission, and crack extension by opening along lattice defects.

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“…The stress intensity factor K I has been studied for various cracked geometry configurations and the master curve for various materials has been provided to relate the crack growth rate and stress intensity factor range (ΔK) that are available in the literature [13][14][15]. Besides, the models based on ΔK have been proposed for different crack tip geometries to predict fatigue crack growth [16][17][18]. The applicability of linear elastic parameter SIF concept is uncertain and unreliable for high temperature crack growth where the plastic flow surrounding the crack tip could not satisfy small yield region condition.…”

Section: Fracture Mechanicsmentioning

confidence: 99%

Life Assessment by Fracture Mechanics Analysis and Damage Monitoring Technique on Combustion Liners

Altunlu

Hoogt

Boer

2011

Volume 6: Structures and Dynamics, Parts a and B

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A methodology has been developed and tested including a multi-disciplinary framework towards integrated analysis of gas turbine combustors. The sub-elements consist of combustion dynamics, stress and modal analysis, fracture mechanics and structural health monitoring have been interlinked indicating the damage evaluation to life assessment. The interaction between the interrelated combustion driven flame dynamics, acoustic pressure fluctuations and liner wall vibration has been investigated in the laboratory combustor test system. During the operation, the combustion, acoustics and wall vibrations have been coupled together. The dynamic combustion process generates high amplitude pressure oscillations resulting in vibration of the liner structure at about constant elevated temperature in base load operation. The thermo-acoustic instabilities have a significant destructive impact on the life of the liner material due to high cyclic vibration levels at high temperature.A structural health monitoring (SHM) method has been established to identify the damage, detect the flaw existence and determine the location, severity and progress of the damage for the combustion liners. Vibration-based and acoustic emission (AE) techniques have been applied in the test system to assess the structural behavior. The applicability of the technique has been tested by examining the dynamic modal parameters of the structure. The method enables a reliable assessment on the liner specimen at elevated temperatures by means of non-destructive evaluation under continuous operation of the combustor. The combustion liner specimen material has been assessed by calculating the near-tip fields at the crack tip by finite element based stress and fracture mechanics analysis. An algorithm based on J-Integral has been utilized to analyze the crack growth behavior under various loading conditions considering both linear and non-linear elastic fracture mechanics concepts. The location and the direction of the cracking on the liner specimen have been predicted. The presented work interrelates the different mechanisms in gas turbine combustors and the applicability of the concepts has been verified and validated in the test systems.

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A fracture mechanics analysis of fatigue crack growth data for various materials

Cited by 184 publications

References 13 publications

Fracture mechanics analysis of the fatigue behaviour of spot welds

Fracture mechanics analysis of the fatigue behaviour of spot welds

An atomistic investigation into the nature of near threshold fatigue crack growth in aluminum alloys

Life Assessment by Fracture Mechanics Analysis and Damage Monitoring Technique on Combustion Liners

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