Detection and measurement of crack closure and opening by an ultrasonic method

Bouami, Driss; Vadder, D. De

doi:10.1016/0013-7944(86)90101-3

Cited by 16 publications

(3 citation statements)

References 3 publications

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“…Moreover, when the stress is removed, the residual plastic region may force the crack close fully at the crack tip [2]. However, many experiments show the difficulties in measuring the crack-opening load, depending on the measuring location [5] and the techniques employed, such as by electrical potential method [6], by ultrasonic method [7] [8], and numerical method [9]. Further, it is found that commonly employed notch-mouth clip-gauge method is not sensitive enough to detect the closure of short cracks in regions of notch plasticity [10] and changes in the stresses ahead of the crack tip are more important than closure behind the crack tip [11].…”

Section: Introductionmentioning

confidence: 98%

Subcycle Fatigue Crack Growth Mechanism Investigation for Aluminum Alloys and Steel

Yang

Zhang

Liu

2013

54th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference

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An experimental investigation of the subcycle fatigue crack growth mechanisms at different scales is proposed in this paper for aluminum alloy and steel using in-situ mechanical testing and imaging analysis. At lower resolution, digital images are taken with optical microscopy at the micrometer scale. Digital image correlation is used to get the strain distribution in front of the crack tip to analyze the plastic deformation behavior. At higher resolution, images are taken with scanning electron microscopy at the nanometer scale. Automatic image tracking is used to obtain detailed crack tip deformation and crack growth. The epxrimental study is performed for two types of metallic materials, i.e., aluminum 7075-T6 and ANSI 4340 steel. Crack closure is observed in allumnium materials, but not in steels. Their plastic zone variation shows very different behavior under constant amplitude loadings. The underlying mechanism is discussed. Finally, the potential application of the proposed investigation method to other materials and to other types of mechanical damage is discussed. Nomenclature a = crack length K = stress intensitive factor = stress intensitive factor at crack opening moment = stress intensitive factor at crack closing moment = stress at crack closing moment = yielding strength = plastic zone size from the crack tip = plastic zone size from the crack tip at the end of forward loading = plastic zone size from the crack tip at the end of reverse loading

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Section: Introductionmentioning

confidence: 98%

Subcycle Fatigue Crack Growth Mechanism Investigation for Aluminum Alloys and Steel

Yang

Zhang

Liu

2013

54th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference

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show abstract

“…Moreover, when the stress is removed, the residual plastic region may force the crack close fully at the crack tip (Wolf, 1970). However, many experiments show the difficulties in measuring the crack-opening load, depending on the measuring location (Macha, Corbly, & Jones, 1979) and the techniques employed, such as by electrical potential method (Shih and Wei 1974), by ultrasonic method (Bouami & De Vadder, 1986;Singh, Srivastav, Gupta, Keller, & Ray, 2009), and numerical method (Riddell, Piascik, Sutton, Zhao, McNeill & Helm, 1999). Further, it is found that commonly employed notchmouth clip-gauge method is not sensitive enough to detect the closure of short cracks in regions of notch plasticity (Fleck & Shin, 1985) and changes in the stresses ahead of the crack tip are more important than closure behind the crack tip (Sadananda, 1999).…”

Section: Introductionmentioning

confidence: 99%

A Multi-resolution Experimental Methodology for Fatigue Mechanism Verification of Physics-based Prognostics

2012

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An experimental methodology is proposed in this paper for mechanism verification of physics-based prognosis of mechanical damage, such as fatigue. The proposed experimental methodology includes multi-resolution in-situ mechanical testing, advanced imaging analysis, and mechanism analysis based on digital measurements. A case study is presented for fatigue crack growth mechanism investigation. In-situ fatigue testing at lower resolutions, i.e., optical microscopy, and digital image correlation is used to analyze the plastic deformation behavior and strain distribution near crack tips. In-situ fatigue testing under higher resolutions, i.e., scanning electron microscopy, and automatic image tracking is used to obtain detailed crack tip deformation and crack growth kinetics at the nanometer scales. Following this, the proposed experimental methodology is applied to two different metallic materials, aluminum alloys and steels. Very different experimental observations are observed and the underlying mechanisms are discussed in detail. The impact on the prognosis algorithm development is also discussed. Finally, the potential application of the proposed experimental methodology to other materials systems and to other types of mechanical damage is discussed.

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“…Preventive measures are necessary if the flaw is a fatigue crack, but immediate measures are not needed if it proves to be a flaw remaining after manufacturing. One common NDT method used to characterize flaws and identify fatigue cracks is detecting the fluctuations of ultrasonic echoes due to crack tip closure under stress fluctuations 1) .…”

Section: Introductionmentioning

confidence: 99%

Radiation Characteristics of Ultrasonic Tip Echo and Its Application to Detect Fatigue Crack Closure in Welding Residual Stress Fields

Miki

Onishi

Kubota

et al. 2010

Structural Eng./Earthquake Eng.

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Detection and measurement of crack closure and opening by an ultrasonic method

Cited by 16 publications

References 3 publications

Subcycle Fatigue Crack Growth Mechanism Investigation for Aluminum Alloys and Steel

Subcycle Fatigue Crack Growth Mechanism Investigation for Aluminum Alloys and Steel

A Multi-resolution Experimental Methodology for Fatigue Mechanism Verification of Physics-based Prognostics

Radiation Characteristics of Ultrasonic Tip Echo and Its Application to Detect Fatigue Crack Closure in Welding Residual Stress Fields

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