The variation of resonance frequency in fatigue tests as a tool for in-situ identification of crack initiation and propagation, and for the determination of cracked areas

Lorenzino, P.; Navarro, A.

doi:10.1016/j.ijfatigue.2014.08.002

Cited by 18 publications

(14 citation statements)

References 28 publications

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“…Use of resonance vibration for in-situ monitoring of structural degradation and residual stiffness of components during fatigue testing is not new [14][15][16]. Since first studies in the 50's [17], the vibration fatigue testing method has become standard practice [18,19], exploiting the resonance conditions to perform quick tests to a high degree of accuracy, even in the Very High Cycle Fatigue (VHCF) regime, up to the gigacycle [20].…”

Section: Introductionmentioning

confidence: 99%

Damage initiation and structural degradation through resonance vibration: Application to composite laminates in fatigue

Magi

Maio

Sever

2016

Composites Science and Technology

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General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. AbstractThe definition of failure is fundamental to the characterisation of fatigue strength of components and structures and is often expressed as a percentage of stiffness degradation. This article proposes a new method to capture damage initiation and structural degradation during a fatigue test, by exploiting resonance vibrations. The method entails monitoring dynamic parameters, including the phase angle between excitation and response, which suddenly changes as soon as the overall stiffness changes as a consequence of damage. In this paper, a theoretical approach based on equations of motion is presented in order to describe the possible scenarios in which a component undergoes structural degradation. In the proposed approach, an abrupt change in the time history of the stiffness of the component is assumed and analysed in both the quasi-static case at low excitation frequencies and the dynamic case, when the excitation frequency is close to the resonance frequency.The resulting analytical solution shows that any small stiffness variation is amplified by the dynamic response of the component as a large phase change, even when it is too small to be captured by the quasi-static response. The idea is successfully applied to capture the initiation of delamination in CFRP laminates, and the relative S-N curve to initiation is drawn. The experimental evidence of a critical event in the fatigue life of a component is found both in the dynamic phase response and in the base acceleration. The critical event is captured from a sudden change in the dynamic parameters of the structure as soon as a delamination is initiated. Thermography, C-scan and micrograph confirmed that the onset of delamination occurs at the moment of the critical event,after an initial stage of microcracking.

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Section: Introductionmentioning

confidence: 99%

Damage initiation and structural degradation through resonance vibration: Application to composite laminates in fatigue

Magi

Maio

Sever

2016

Composites Science and Technology

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“…The strain mapping based on DIC was already utilized by several authors to describe the strain field around cracks. The DIC methods that do not address the crack discontinuity directly (Ref [17][18][19] can be characterized as continuous DIC methods. In these methods, the crack is detected by thresholding the deformation field.…”

Section: Introductionmentioning

confidence: 99%

Fatigue Crack Growth in Bodies with Thermally Sprayed Coating

et al. 2015

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Many applications of thermally sprayed coatings call for increased fatigue resistance of coated parts. Despite the intensive research in this area, the influence of coating on fatigue is still not completely understood. In this paper, the localization of crack initiation sites and the dynamics of crack propagation are studied. The resonance bending fatigue test was employed to test flat specimens with both sides coated. Hastelloy-X substrates coated with classical thermal barrier coating consisting of yttria stabilized zirconia and NiCoCrAlY layers. The strain distribution on the coating surface was evaluated by the Digital Image Correlation method through the whole duration of the fatigue test. Localization of crack initiation sites and the mode of crack propagation in the coated specimen are related to the observed resonance frequency. The individual phases of specimen degradation, i.e., the changes of material properties, crack initiation, and crack propagation, were identified. The tested coatings strongly influenced the first two phases, and the influence on the crack propagation was less significant. In general, the presented crack detection method can be used as a sensitive nondestructive testing method well suited for coated parts.

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“…In addition, with reference to the course of the resonant frequency, Lorenzino and Navarro [27] correlated this stabilization stage during the lifetime to the initiation of a crack with an overall length of at least 0.2 mm. Regarding the course of the nonlinearity parameter a plateau is recognized earlier after passing 2 × 10 5 cycles.…”

Section: D) In Situ Courses: Temperature Nonlinearity Parameter and mentioning

confidence: 99%

“…In addition, this method enables the in situ investigation of the influence of nonmetallic inclusions on the crack initiation by various complementary non-destructive testing methods, i.e. analysis of the resonant frequency [26,27], analysis of the nonlinearity parameter [23,28,29] and thermography measurements [30,31,32,33,34,35,36]. Both, the analysis of the resonant frequency as well as the nonlinearity parameter are limited to a temporal resolution of the in situ courses.…”

Section: Introductionmentioning

confidence: 99%

Application of full-surface view in situ thermography measurements during ultrasonic fatigue of cast steel G42CrMo4

Krewerth

Lippmann

Weidner

et al. 2015

International Journal of Fatigue

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The variation of resonance frequency in fatigue tests as a tool for in-situ identification of crack initiation and propagation, and for the determination of cracked areas

Cited by 18 publications

References 28 publications

Damage initiation and structural degradation through resonance vibration: Application to composite laminates in fatigue

Damage initiation and structural degradation through resonance vibration: Application to composite laminates in fatigue

Fatigue Crack Growth in Bodies with Thermally Sprayed Coating

Application of full-surface view in situ thermography measurements during ultrasonic fatigue of cast steel G42CrMo4

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