Fatigue Crack Detection Research Articles

Attempt on detection of fatigue crack by high-sensitivety magnetic non-destructive inspection

Attempt on detection of fatigue crack by high-sensitivety magnetic non-destructive inspection

Fatigue Crack Detection in Steel Plates Using Guided Waves and an Energy-Based Imaging Approach

Fatigue Crack Detection in Steel Plates Using Guided Waves and an Energy-Based Imaging Approach

Nondestructive Phase Variation-Based Chipless Sensing Methodology for Metal Crack Monitoring

This article presents a new methodology for structural health monitoring (SHM) applications using a passive microwave sensor. This sensor provides sensitivities on metallic structures for nondestructive testing (NDT) and detecting fatigue cracks or damages. In this method, two different microstrip-based designs are mounted on metal, spiral, and comb sensing structures. Both sensing structures are interrogated by a 2.45 GHz signal in CST Microwave Studio, and their sensitivities for crack detection are compared through the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{11}$ </tex-math></inline-formula> scattering parameter. We demonstrate that measuring the reflected signal’s phase parameter from a sensor on a damaged metal provides information from the surface crack by comparing it to the same metal without any crack. The vision is to provide a new chipless, low-cost sensor with increased detection reliability and durability in harsh environments. Simulation results of the comb sensing (CS) structure show that the signal phase shift caused by a crack envisions the possibility of submillimeter-width crack detection through smart structures.

Research on Dynamic Detection of Rail Rolling Contact Fatigue Crack Based on Eddy Current Thermography

Research on Dynamic Detection of Rail Rolling Contact Fatigue Crack Based on Eddy Current Thermography

An instantaneous-baseline multi-indicial nonlinear ultrasonic resonance spectral correlation technique for fatigue crack detection and quantification

This article presents an instantaneous-baseline multi-indicial nonlinear ultrasonic resonance spectral correlation technique for fatigue crack detection and quantification. A reduced-order nonlinear oscillator model is tailored to illuminate the contact acoustic nonlinearity (CAN) and the nonlinear resonance phenomena. The analytical formulation considers the rough surface condition of the fatigue cracks, with a crack open–close transitional range for the effective modeling of the variable-stiffness nonlinear mechanism. Multiple damage indices (DIs) associated with the degree of nonlinearity of the interrogated structures are then proposed by correlating the ultrasonic resonance spectra. Three perspectives of the nonlinear resonance phenomena are investigated to detect and monitor the fatigue crack growth: (1) time-history dependence, which evolves different resonance states depending on the loading history; (2) amplitude dependence, which renders significantly different nonlinear responses under various levels of excitation amplitudes; (3) breakage of superposition, which effectively distinguishes nonlinear resonant responses from the linear counterparts. These DIs are established using instantaneous baselines, facilitating the fatigue damage monitoring without the prior knowledge of a pristine structure. Fatigue tests on a thin aluminum plate with a rivet hole are conducted to induce fatigue cracks in the specimen. The experimental results demonstrate that the proposed technique shows remarkable sensitivity to the nucleation and growth of the fatigue cracks. This paper differs from the existing literature on nonlinear resonance-based techniques in that it focuses on the resonance phenomenon aroused by the contact acoustic nonlinearity from localized fatigue cracks, rather than the diffused material nonlinearity. The novelty of the paper resides in the establishment of an instantaneous baseline technique utilizing the nonlinear resonance features without the need of referring to a pristine baseline situation. The paper finishes with discussion, concluding remarks, and suggestions for future work.

Development of Fatigue Crack detection method using Active Temperature Gap Method

Development of Fatigue Crack detection method using Active Temperature Gap Method

Thermal Method in the Control of Fatigue Cracks in Welded Bridge Superstructures

The purpose of the work is the use of infrared thermography in examinations and diagnostics of bridges to detect fatigue cracks. The research methods accepted laboratory and natural tests. The configuration of samples (cantilever sheet samples reinforced with stiffeners) and loading conditions corresponded to the actual operating conditions of the bridge beams. As a result of laboratory experiments, the process of metal self-heating around the fatigue crack tips was shown, as well as the general process of temperature change across the entire field of the sample. Also, studies were conducted on the process of self-heating of metal on operated bridge designs with fatigue cracks. The results of laboratory and field studies on welded superstructures are presented, as well as the applied algorithms for the software processing of thermal images are described. Studies have shown the applicability of infrared thermography to identify and assess the degree of development of fatigue cracks in welded superstructures of railway bridges.

Crack Identification in Necked Double Shear Lugs by Means of the Electro-Mechanical Impedance Method.

This contribution investigates fatigue crack detection, localization and quantification in idealized necked double shear lugs using piezoelectric transducers attached to the lug shaft and analyzed by the electro-mechanical impedance (EMI) method. The considered idealized necked lug sample has a simplified geometry and does not includes the typical bearing. Numerical simulations with coupled-field finite element (FE) models are used to study the frequency response behavior of necked lugs. These numerical analyses include both pristine and cracked lug models. Through-cracks are located at 90 and 145 to the lug axis, which are critical spots for damage initiation. The results of FE simulations with a crack location at 90 are validated with experiments using an impedance analyzer and a scanning laser Doppler vibrometer. For both experiments, the lug specimen is excited and measured using a piezoelectric active wafer sensor in a frequency range of 1 kHz to 100 kHz. The dynamic response of both numerical calculations and experimental measurements show good agreement. To identify (i.e., detect, locate, and quantify) cracks in necked lugs a two-step analysis is performed. In the first step, a crack is detected data-based by calculating damage metrics between pristine and damaged state frequency spectra and comparing the resulting values to a pre-defined threshold. In the second step the location and size of the detected crack is identified by evaluation of specific resonance frequency shifts of the necked lug. Both the search for frequencies sensitive to through-cracks that allow a distinction between the two critical locations and the evaluation of the crack size are model-based. This two-step analysis based on the EMI method is demonstrated experimentally at the considered idealized necked lug, and thus, represents a promising way to reliably detect, locate and quantify fatigue cracks at critical locations of real necked double shear lugs.

Effect of Crack Closure on Magnitude of Modulated Wave

Fatigue cracks generated by repeated loads cause structural failures. Such cracks grow continuously and at an increasing speed owing to the concentration of stresses near the crack tips. Therefore, the early detection of fatigue cracks is imperative in the field of structural-health monitoring for the safety of structures exposed to dynamic loading. In particular, the detection of those cracks subjected to compression is known as a challenging problem in the nondestructive inspection area. The nonlinear ultrasonic modulation technique is effective for the detection of microcracks smaller than the size of a wavelength because this technique uses the deformation of waves passing through the crack surfaces. However, the technique has not been thoroughly verified for detecting cracks subjected to external forces. In this study, nonlinear ultrasonic modulation tests are performed on two types of crack specimens under compressive forces. The results show that in fatigue-cracked specimens, the cracks can be detected using modulated waves even under strong compressions. With artificial cracks, buckling occurs at a relatively low compression, and the amounts of modulated waves rapidly increase due to the bending of the specimen before buckling failure takes place. In this study, the crack detection methodology under compression is proposed and experimentally verified. The proposed method might be beneficial to find cracks under compression in various structural components.

Detection of Micro-Cracks in Metals Using Modulation of PZT-Induced Lamb Waves.

The ultrasonic modulation technique, developed by inspecting the nonlinearity from the interactions of crack surfaces, has been considered very effective in detecting fatigue cracks in the early stage of the crack development due to its high sensitivity. The wave modulation is the frequency shift of a wave passing through a crack and does not occur in intact specimens. Various parameters affect the modulation of the wave, but quantitative analysis for each variable has not been comprehensively conducted due to the complicated interaction of irregular crack surfaces. In this study, specimens with a constant crack width are manufactured, and the effects of various excitation parameters on modulated wave generation are analyzed. Based on the analysis, an effective crack detection algorithm is proposed and verified by applying the algorithm to fatigue cracks. For the quantitative analysis, tests are repeatedly conducted by varying parameters. As a result, the excitation intensity shows a strong linear relationship with the amount of modulated waves, and the increase of modulated wave is expected as crack length increases. However, the change in the dynamic characteristics of the specimen with the crack length is more dominant in the results. The excitation frequency is the most dominant variable to generate the modulated waves, but a direct correlation is not observed as it is difficult to measure the interaction of crack surfaces. A numerical analysis technique is developed to accurately simulate the movement and interaction of the crack surface. The crack detection algorithm, improved by using the observations from the quantitative analyses, can distinguish the occurrence of modulated waves from the ambient noises, and the state of the specimens is determined by using two nonlinear indexes.

Dynamic Stability Analysis of a Cracked Beam using a Lumped Parameter Model

Vibration based condition monitoring is one of the predictive maintenance strategies applied for structures and rotating machinery. Detection and identification of fatigue crack in structures has been a widely discussed problem in the literature of condition monitoring. This paper discusses the numerical results that have been obtained from the study of bending vibration of a cracked beam. The crack is primarily modelled as an opening/ closing crack resulting in a periodic variation in stiffness. The mathematical model considered for the cracked beam is a lumped single degree of freedom system. The resulting system equation of motion has the canonical form of a Mathieu equation. For obtaining the system response, the equation is written in a state-space form and then solved using fourth order Runge-Kutta numerical integration. The time and frequency domain responses are obtained for a specific harmonic excitation. Further, the stability of the cracked beam is discussed with respect to the variation in stiffness, by numerical analysis, using a Vander Pol and Strutt stability chart diagram.

Detection of the Fatigue Cracks Initiated near the Rivet Holes by Eddy Current Inspection Techniques

Abstract Eddy current (EC) method is considered as most applicable for in-service detection of fatigue subsurface cracks initiated in aircraft multilayer structures near the rivet holes. At the same time, the successful solution of this problem is obstructed by additional noise created by defect-free rivets. All EC inspection techniques for the detection of subsurface cracks around the rivets can be classified into three main groups: 1) static mode – carried out by placing the EC probe concentrically on the rivet head; 2) rotational mode – when the EC probe is rotated around the rivet axle and 2) sliding mode – performed by the movement of EC probe along the rivet line or near it. All these approaches have some advantages and limitations. In this study, known EC techniques for the detection of cracks in multilayer aircraft structures are analyzed. New advanced EC techniques for the detection of fatigue cracks in internal layers of the riveted structures based on different types (ring, sliding, and rotational) probes are presented. The static EC method with developed low-height ring-type probe creates the possibility to detect cracks in the difficult of access areas. The possibility to estimate the length of detected cracks by a ring-type probe is shown. The proposed rotational remote field EC probe can detect as small as 1.0 mm long cracks under the button-head rivet and 2 mm thick upper skin with a high signal-to-noise ratio. Therefore, in many aircraft structures, fatigue cracks will be detected before a critical threshold achieved. New EC sliding techniques based on remote field and double differential probes were proposed for the rapid detection of cracks in internal layers of riveted aircraft structures. Remote-field EC probe for reliable detection of fatigue cracks in third and fourth layers of five-layer units was proposed. Another sliding technique based on a double differential EC probe gives the possibility to detect transverse cracks in the second layer without the rivet row area access. The main advantage of developed techniques is high inspection reliability due to the possibility to discriminate the signals created by cracks and defect-free rivets. Presented inspection procedures include the selective signal analysis in the complex plane diagram. Proposed EC inspection techniques were successfully implemented into the aircraft maintenance practice.

Fatigue-Crack Detection and Monitoring through the Scattered-Wave Two-Dimensional Cross-Correlation Imaging Method Using Piezoelectric Transducers.

Piezoelectric transducers are convenient enablers for generating and receiving Lamb waves for damage detection. Fatigue cracks are one of the most common causes for the failure of metallic structures. Increasing emphasis on the integrity of critical structures creates an urgent need to monitor structures and to detect cracks at an early stage to prevent catastrophic failures. This paper presents a two-dimensional (2D) cross-correlation imaging technique that can not only detect a fatigue crack but can also precisely image the fatigue cracks in metallic structures. The imaging method was based on the cross-correlation algorithm that uses incident waves and the crack-scattered waves of all directions to generate the crack image. Fatigue testing for crack generation was then conducted in both an aluminum plate and a stainless-steel plate. Piezoelectric wafer transducer was used to actuate the interrogating Lamb wave. To obtain the scattered waves as well as the incident waves, a scanning laser Doppler vibrometer was adopted for acquiring time-space multidimensional wavefield, followed with frequency-wavenumber processing. The proof-of-concept study was conducted in an aluminum plate with a hairline fatigue crack. A frequency-wavenumber filtering method was used to obtain the incident wave and the scattered wave wavefields for the cross-correlation imaging. After this, the imaging method was applied to evaluate cracks on a stainless-steel plate generated during fatigue loading tests. The presented imaging method showed successful inspection and quantification results of the crack and its growth.

Synthetic Aperture Imaging in Cylindrical Component Using Ultrasonic Immersion Forward Vector Algorithm

Abstract—Ultrasonic nondestructive testing has been widely used in the detection and evaluation of fatigue cracks and defects of high-speed railway. In order to improve the detection speed of cylindrical components such as rims, a theoretical model of the forward vector algorithm of ultrasonic immersion curved surface is established. For improving image quality, an averaging correction factor is introduced in this paper to avoid multiple irradiation of the same pixel by the same element, and the visualization of cylindrical components with internal defects is realized by simulation and experiment. The traditional synthetic aperture focusing technique (SAFT), Newton iterative synthetic aperture (NISA) and ultrasonic forward vector algorithm (UFVA) are compared and analyzed on the aspects of imaging effect, array performance index (API) and imaging efficiency. Compared with the other two algorithms, the ultrasonic forward vector algorithm can effectively overcome the iteration of calculation of the refraction point and improve the imaging efficiency. The efficiency is improved by 2 and 1 orders of magnitude respectively while imaging quality is guaranteed. At the same time, this algorithm plays an important role on the measurement of the inner and outer diameter of the rim, the defect detection, and the quantitative analysis of the surface wear, which provides an effective means for the rapid detection of internal defects of the regular curved parts.

Fatigue crack inspection and characterisation using non-collinear shear wave mixing

In recent years, nonlinear ultrasonic techniques have been developed rapidly for defect detection and characterization at its early development stage. In this paper, non-collinear shear wave mixing is used for fatigue crack detection and characterization, exploring how orientation and size may be determined. This is achieved through measuring the amplitude of the generated longitudinal wave from a crack of interest. This amplitude is a function of the interaction angle and frequency ratio of two incident shear waves and the resulting amplitude parameter space is termed the nonlinear fingerprint of the crack. Numerical analysis of the nonlinear interaction between two incident shear waves and cracks was performed using two-dimensional finite element models to explore a broader parameter space than possible experimentally. It is shown that the interaction angle which leads to the maximum generated longitudinal wave amplitude is related to the orientation angle of the crack. To confirm these conclusions the model was validated using experimental measurements of vertical fatigue cracks grown using 3-point bending tests from initiation notches. The polarity flipping method was used to improve signal to noise ratio in such measurements. It is shown that there is a good agreement between the experimentally measured fingerprints and those simulated using finite element methods. Finally, an approximate method for sizing fatigue cracks was introduced that uses multiple non-collinear measurements along the crack length to determine its extent. As expected, the measured sizes from the proposed method indicate greater crack lengths than seen with linear ultrasonic phased array images due to the closed fatigue cracks being undetectable with linear arrays.

Modelling and analysis of a cracked rotor: a review of the literature and its implications

Timely detection of fatigue cracks is necessary to avoid catastrophic failure of rotating machines which can lead to economical losses and accidental risk. This paper presents an exhaustive literature survey on theoretical and experimental vibration analysis of the rotating shaft in the presence of crack. Various non-destructive methods adopted by several researchers for crack detection in rotating machinery have been discussed. The vibration-based crack detection methods such as vibration-based diagnostics methods and vibration-based signal processing techniques have been broadly categorized along with their advantages and disadvantages. In general, various methodologies such as breathing mechanism, finite-element method, Hilbert–Huang transform, artificial intelligence techniques, wavelet transform and wavelet finite-element transform have been applied to investigate the presence of crack in the rotating shaft. The parameters such as natural frequencies, $$1{\times }$$, $$2{\times }$$ and $$3{\times }$$ harmonic components of dynamic response, critical speeds and whirl orbits have been significantly influenced due to the presence of crack in the rotating shaft. Several studies have been carried out to study variations in these parameters. Still, there is a need of more reliable and accurate modelling approach to detect variations in these parameters. In this paper, an attempt has been made to deliver all the modelling approaches implemented by the various researchers to detect crack within the rotating shaft. The modelling approaches are categorized based on the methodologies adopted by the various researchers to detect crack. Moreover, the critical observations made from the proposed modelling approaches are summarized and presented.

Machine Learning Based Features Matching for Fatigue Crack Detection

Abstract The detection of fatigue cracks has gained widespread attention as it affects the safety of daily lives. Many crack detection methods have been developed up to now and perform well. However, there are still some problems left. It is hard to check the huge objects (such as bridge, building) by using vibration or ultrasonic sensor. Especially the inspection of bridges needs human inspectors. It is high cost, difficult access and dangerous. Vision based fatigue crack detection is considered as a good solution as the system can be carried by a drone and overcomes the above problem. In this study, FAST, ORB, SIFT and SURF features are employed to detect the fatigue cracks by feature matching and this study compares their performance. The experimental results show that ORB based feature matching gives the best result and it is an effective method to detect the fatigue crack.

Foundational investigation for detection of weld-bead non-penetrating fatigue crack by temperature gap method

Foundational investigation for detection of weld-bead non-penetrating fatigue crack by temperature gap method

Luminescence-based early detection of fatigue cracks

Classic non-destructive fatigue crack detection methods reveal the state of the fatigue damage evolution at the moment of application, generally not under operational conditions. The here introduced crack luminescence method realizes a clear visibility of the occurred and growing crack in loaded components during operation. Different established experiments show that due to the sensitive coating a crack formation can be detected even in early stage under the premise the crack reached the surface. The coating consists of two layers with different properties and functions. The bottom layer emits light as fluorescence under UV radiation. The top layer covers the fluorescing one and prevents the emitting of light in case of no damage at the surface. In case of surface crack occurrence, the luminescent light is clearly noticeable by visual observations and also by standard camera equipment which makes automated crack detection possible as well. It is expected that crack luminescence can increase structural safety as well as reduce costs and time for inspections and preventive maintenance.

Natural Crack Diagnosis System Based on Novel L-Shaped Electromagnetic Sensing Thermography

Nondestructive detection of small fatigue cracks is a critical and challenging task in evaluating the properties of material. This article proposes a novel L-shaped ferrite magnetic open sensing structure of the eddy current pulsed thermography system for fatigue crack inspection on metallic materials with anomalistic geometry. The theoretical derivation model of the proposed structure is developed to generate a guided distribution of electromagnetic field for enhancing the weak thermal signal detection. The proposed detection model provides a region of interest that has relatively uniform magnetic field. This significantly enhances the detectability and thermal contrast of omnidirectional microfatigue cracks. In addition, the detection is completely in the open view of the infrared camera, and the configuration has advantages of dramatically increasing portability and efficiency for detecting complex workpiece. Experiments on natural cracks in several samples have been conducted to validate the reliability and efficiency of the proposed system.