Monitoring short fatigue cracks with miniature strain gages

Verreman, Yves

doi:10.1007/bf02319757

Cited by 10 publications

(4 citation statements)

References 7 publications

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“…The main features of the strain gauge technique for monitoring the crack depths and the opening levels were presented in a previous paper [ 101 and a complete description was recently published [7]. It is based on the progressive decrease of the surface strain as the fatigue crack propagates, when it is open.…”

Section: Experimental Conditions and General Resultsmentioning

confidence: 99%

“…These welds present a severe V-notched geometry that is very regular along the toe, with the result that one straight-fronted crack develops at the very beginning of fatigue life. An experimental technique using miniature strain gauges installed close to the weld toe has been developed to have a continuous and accurate monitoring of this crack from 10pm in depth [7]. The technique, which also gives a measurement of the crack opening level, allowed us to rationalize, in terms of the effective AK-parameter, the influences of notch plasticity and of residual stresses on the short crack behavior; these influences being particularly pronounced under fully reversed loading.…”

Section: Introductionmentioning

confidence: 99%

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Early Development of Fatigue Cracking at Manual Fillet Welds

Verreman

Nie

1996

Fatigue Fract Eng Mat Struct

126

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An experimental study within the Canadian Offshore Corrosion Fatigue Research Programme was performed on the early development of fatigue cracking along the wavy toe of manual fillet welds between structural steel plates. Stress relieved and as-welded cruciform joints were tested under R = -1 and R = 0 loading at different stress amplitudes. The depth and the opening level of cracks as small as 10-20 pm were monitored using miniature strain gauges installed along the toe apex, in combination with beach marking. Most of the "initiation life" (25% to 50% of total life), conventionally defined by a crack depth of 0.5 mm, is consumed in short crack propagation. Three types of short crack development for different combinations of local mean stress and stress range are identified and analyzed. Growth rates in as-welded specimens are faster than in stress relieved specimens, which results in shorter "initiation lives". This is associated with a higher effective stress range, particularly under R = -1 loading where cracks are open over nearly the full stress range. The V-notch stress intensity factor is a promising parameter to rationalize the crack "initiation life". It takes into account the thickness effect experimentally observed. Under R = -1 loading of as-welded joints, using R = 0 data and taking the whole stress range gives a reasonably conservative approximation of the crack "initiation life".

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Section: Experimental Conditions and General Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Early Development of Fatigue Cracking at Manual Fillet Welds

Verreman

Nie

1996

Fatigue Fract Eng Mat Struct

126

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“…Placing the sensors close to the defect may allow for the detection of very small changes in depth [1]. Previous work on a similar methodology has been reported by Verreman [2] and Otegui et al [3], who employed electric resistance strain gauges to monitor fatigue cracks in welded joints, being able to successfully detect variations of up to 20 µm in crack size. The advantage of using piezoelectric materials as dynamic strain sensors is their high sensitivity [4], which allows the lowlevel strains generated by the piezoelectric actuator to be properly sensed.…”

Section: Introductionmentioning

confidence: 93%

Application of Piezoelectric Materials for Monitoring the Growth of Defects in Structures

Morikawa

Lannes²,

Gama³

2010

MSF

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This paper presents the results of an experimental investigation on the use of piezoelectric materials as a technique for monitoring the growth of defects in structures. The method consists of exciting the structure with piezoelectric actuators while recording the electromechanical responses from sensors placed close to the defect. The piezoelectric sensors detect the damage growth or an incipient defect by monitoring changes in the dynamic strain field, induced by the piezoelectric actuator, near the defect. This technique was evaluated through experiments using an aluminum frame structure. Results show that the piezoelectric active method is capable of detecting small changes in defect depth.

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“…Verreman [24] displayed the ability to measure propagation of fatigue cracks with miniature strain gages in cruciform welded joints. Strain gages in this research were installed above a crack in a cruciform joint with varying distances between the sensors and the crack.…”

Section: Crack Detection With Conventional Technologymentioning

confidence: 99%

Monitoring the structural condition of fracture-critical bridges using fiber optic technology

Doornink

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Monitoring short fatigue cracks with miniature strain gages

Cited by 10 publications

References 7 publications

Early Development of Fatigue Cracking at Manual Fillet Welds

Early Development of Fatigue Cracking at Manual Fillet Welds

Application of Piezoelectric Materials for Monitoring the Growth of Defects in Structures

Monitoring the structural condition of fracture-critical bridges using fiber optic technology

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