Cycle counting for fatigue crack growth analysis

Sunder, R.; Seetharam, SA; Bhaskaran, TA

doi:10.1016/0142-1123(84)90032-x

Cited by 29 publications

(15 citation statements)

References 7 publications

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“…ASTM E 1049-85 describes the rainflow cycle-counting technique. The validity of the technique for crack growth analysis under an arbitrary load sequence was demonstrated in [13]. The linear hysteresis model described by the above equations was used to approximate the crack opening stress for the different cycles in the root test load sequences # 1 and # 2 used in this study.…”

Section: Minor Cycle I On the Falling Half Of A Major Cyclementioning

confidence: 99%

Notch Root Crack Closure Under Cyclic Inelasticity

Sunder

1993

Fatigue Fract Eng Mat Struct

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Aluminium alloy sheet coupons with a central hole were tested in fatigue under specially designed programmed load sequences. Electron microscopy of the fatigue fracture surfaces showed striation mode fatigue crack extension up to more than a millimeter before onset of rapid failure. Crack opening stress was determined from striation patterns. Under variable amplitude loading and conditions of notch root cyclic inelasticity, crack opening stress exhibits noticeable hysteresis. The hysteresis is attributed to a difference between crack closure and opening stresses. A linear model of this phenomenon appears to describe observed behaviour.

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Section: Minor Cycle I On the Falling Half Of A Major Cyclementioning

confidence: 99%

Notch Root Crack Closure Under Cyclic Inelasticity

Sunder

1993

Fatigue Fract Eng Mat Struct

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“…As noted in Part I of this review [l] this is a reasonable, though not always rigorously correct, approach (see also [4]). However, any values of A q which produce values of A K below AKth are omitted from the summation.…”

Section: Determination Of Cyclic Values Of Kmentioning

confidence: 95%

“…with the proviso that if AK is below the threshold value (AKth), da/dN = 0. However, it is suggested that the following may be more accurate if AK is close to AKth: da dN -= B(AK -AKth)n (4) The values of A and B selected should correspond to the mean plus two standard deviations level of log(da/dN). No crack growth data as such are included, the recommendation being either to test relevant specimens or to use values from the literature, PD 6493 being referenced [2].…”

Section: Crack Growth Lawsmentioning

confidence: 99%

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A Review of Fatigue Crack Growth Characterisation by Linear Elastic Fracture Mechanics (Lefm). Part Ii—advisory Documents and Applications Within National Standards

Allen

Booth

Jutla

1988

Fatigue Fract Eng Mat Struct

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This paper presents a review of the application of LEFM to the characterisation of fatigue crack growth. This part covers national standards and other documents of comparable status that (a) offer explicit advice on the use of fatigue crack growth data, and (b) in which crack growth considerations are implicit. Documents falling into the first category were noted to have many features in common, differences occurring only in areas where the current understanding of the subject is far from complete (e.g. variable amplitude loading, long life, etc.). Documents implicitly addressing fatigue crack growth comprise three distinct groups: (i) those which aim to simplify fracture mechanics analyses for the user, (ii) those in which fracture mechanics has influenced design criteria, and (iii) those which aim to provide inspection and/or acceptance criteria. As with the "explicit documents", a degree of commonality was observed within each group of "implicit documents", the exception being the military aircraft specifications of the U.K. and the U.S.A.

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“…ds As Figure 2. Effect of minor stress range and stress ratio on envelop of notch root mean stress variation (Sunder et al 1984).…”

Section: Rainflow Cycle Counting In Cumulative Fatigue Damange Analysismentioning

confidence: 99%

Studies on fatigue crack growth for airframe structural integrity applications

Sunder

1995

Sadhana

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A review is made of efforts at the National Aerospace Laboratories in the development of fatigue crack growth prediction technology for airframe applications. The research was focused on extension of rainflow techniques for crack growth analysis and development of accelerated crack growth calculation methods for spectrum loading. Fatigue crack closure forms a crucial element of modelling and fractographic techniques were developed for its study. These, combined with binary coded event registration enabled crack growth and closure mapping for part-through cracks in metallic materials. Experimental research on short cracks at notches led to discovery of the hysteretic nature of crack closure, which explains wellknown history-sensitive local mean stress effects in notch root fatigue. Optical fractography of failures obtained under simulated service conditions revealed that short cracks do not exhibit any more scatter than long cracks at comparable growth rates. The nature of multi-site crack initiation and growth of small cracks at notches was investigated and the effort extended to lug joints that are widely used in airframe applications. Results from this work suggest the possibility of modelling crack growth from a size smaller than 50 microns through to failure, thereby accounting for a major fraction of total life.

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Cycle counting for fatigue crack growth analysis

Cited by 29 publications

References 7 publications

Notch Root Crack Closure Under Cyclic Inelasticity

Notch Root Crack Closure Under Cyclic Inelasticity

A Review of Fatigue Crack Growth Characterisation by Linear Elastic Fracture Mechanics (Lefm). Part Ii—advisory Documents and Applications Within National Standards

Studies on fatigue crack growth for airframe structural integrity applications

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