Crack Detection Technique Research Articles

Fast and Non-invasive Surface Crack Detection of Press Panels Using Image Processing

The crack detection during the manufacturing process is an important step for quality management of panel products. Traditional crack detection methods are subjective and expensive because they are performed by experienced human inspectors. Therefore, crack detection techniques for automated and accurate inspection are required. In this paper, a crack detection technique based on image processing is proposed, which utilizes the images of panel products captured by a regular CCTV camera system. First, the binary panel object image is extracted from various backgrounds after considering RGB color factors. Edge lines are then generated from a binary image using a percolation process. Finally, crack detection and localization are performed with a unique edge line evaluation. In order to demonstrate the capability of the proposed technique, lab-scale experiments were carried out with a thin aluminum plate and a real sample panel. In addition, the test was performed with the images acquired at an actual press line. Experimental results show that the proposed technique could effectively detect panel cracks with an improved rate and speed.

Detection of back-surface crack based on temperature gap measurement

For large-scale steel structures such as orthotropic steel decks in highway bridges, nondestructive inspection of deteriorations and fatigue damages are indispensable for securing their safety and for estimating their remaining strength. As conventional NDT techniques for steel bridges, visual testing, magnetic-particle testing and ultrasonic testing have been commonly employed. However, these techniques are time- and labor- consuming inspections, because special equipment is required for inspection, such as scaffolding or a truck mount aerial work platform. The present authors developed a new thermography NDT technique for crack detection, which is based on temperature gap appeared on the surface of structural members due to thermal insulation effect of the crack. The practicability of the developed technique to through crack was demonstrated by the field experiments for highway steel bridges in service. In this paper, the applicability of the inspection technique based on temperature gap measurement to back-surface crack detection is investigated by the laboratory testing. The testing was conducted for several specimens. A fatigue crack was introduced in a back surface of each specimen by 4 point bending fatigue test. This investigation has revealed that back surface fatigue crack can be detected by the proposed technique.

Research on fatigue crack detection technique by residual stress measurement

Research on fatigue crack detection technique by residual stress measurement

Image Based Techniques for Crack Detection, Classification and Quantification in Asphalt Pavement: A Review

Pavement condition information is a significant component in Pavement Management Systems. The labeling and quantification of the type, severity, and extent of surface cracking is a challenging area for weighing the asphalt pavements. This paper presents a widespread review on various platform and image processing approaches for asphalt surface interpretation. The main part of this study presents a comprehensive combination of the state of the art in image processing based on crack interpretation related to asphalt pavements. An attempt is made to study the existing methodologies from different points of views accompanied by extensive comparisons on three stages of methods—distress detection, classification, and quantification to facilitate further research studies. This paper presents a survey of the developed pavement inspection systems up to date. Additionally, emerging and evolution technologies considered to automate the processes are discussed.

Development and field application of a nonlinear ultrasonic modulation technique for fatigue crack detection without reference data from an intact condition

In this study, a fatigue crack detection technique, which detects a fatigue crack without relying on any reference data obtained from the intact condition of a target structure, is developed using nonlinear ultrasonic modulation and applied to a real bridge structure. Using two wafer-type lead zirconate titanate (PZT) transducers, ultrasonic excitations at two distinctive frequencies are applied to a target inspection spot and the corresponding ultrasonic response is measured by another PZT transducer. Then, the nonlinear modulation components produced by a breathing-crack are extracted from the measured ultrasonic response, and a statistical classifier, which can determine if the nonlinear modulation components are statistically significant in comparison with the background noise level, is proposed. The effectiveness of the proposed fatigue crack detection technique is experimentally validated using the data obtained from aluminum plates and aircraft fitting-lug specimens under varying temperature and loading conditions, and through a field testing of Yeongjong Grand Bridge in South Korea. The uniqueness of this study lies in that (1) detection of a micro fatigue crack with less than 1 μm width and fatigue cracks in the range of 10–20 μm in width using nonlinear ultrasonic modulation, (2) automated detection of fatigue crack formation without using reference data obtained from an intact condition, (3) reliable and robust diagnosis under varying temperature and loading conditions, (4) application of a local fatigue crack detection technique to online monitoring of a real bridge.

Review of Electromagnetic-Based Crack Sensors for Metallic Materials (Recent Research and Future Perspectives)

Evaluation and non-destructive identification of stress-induced cracks or failures in metals is a vital problem in many sensitive environments, including transportation (steel railway tracks, bridges, car wheels, etc.), power plants (steam generator tubing, etc.) and aerospace transportation (landing gear, aircraft fuselages, etc.). There are many traditional non-destructive detection and evaluation techniques; recently, near-field millimeter waves and microwave methods have shown incredible promise for augmenting currently available non-destructive techniques. This article serves as a review of developments made until now on this topic; it provides an overview of microwave scanning techniques for crack detection. This article summarizes the abilities of these methods to identify and evaluate cracks (including describing their different physical properties). These methods include applying filters based on dual-behavior resonators (DBRs), using complementary split-ring resonators (CSRRs) for the perturbation of electric fields, using waveguide probe-loaded CSRRs and using a substrate-integrated-waveguide (SIW) cavity for the detection of sub-millimeter surface and subsurface cracks.

Quantitative Index and Abnormal Alarm Strategy Using Sensor-Dependent Vibration Data for Blade Crack Identification in Centrifugal Booster Fans

Centrifugal booster fans are important equipment used to recover blast furnace gas (BFG) for generating electricity, but blade crack faults (BCFs) in centrifugal booster fans can lead to unscheduled breakdowns and potentially serious accidents, so in this work quantitative fault identification and an abnormal alarm strategy based on acquired historical sensor-dependent vibration data is proposed for implementing condition-based maintenance for this type of equipment. Firstly, three group dependent sensors are installed to acquire running condition data. Then a discrete spectrum interpolation method and short time Fourier transform (STFT) are applied to preliminarily identify the running data in the sensor-dependent vibration data. As a result a quantitative identification and abnormal alarm strategy based on compound indexes including the largest Lyapunov exponent and relative energy ratio at the second harmonic frequency component is proposed. Then for validation the proposed blade crack quantitative identification and abnormality alarm strategy is applied to analyze acquired experimental data for centrifugal booster fans and it has successfully identified incipient blade crack faults. In addition, the related mathematical modelling work is also introduced to investigate the effects of mistuning and cracks on the vibration features of centrifugal impellers and to explore effective techniques for crack detection.

Comparison of Supervised Classification Techniques for Vision-Based Pavement Crack Detection

In this study, the application of four classification techniques for computer vision–based pavement crack detection systems was investigated. The classification methods—artificial neural network (ANN), decision tree, k–nearest neighbor, and adaptive neuro-fuzzy inference system (ANFIS)—were selected on the basis of the complexity and clarity of their procedures. These methods were evaluated for ( a) prediction performance, ( b) computation time, ( c) stability of results for highly imbalanced data sets, ( d) stability of the classifiers’ performance for pavements in different deterioration stages, and ( e) interpretability of results and clarity of the procedure. According to the results, the ANN and ANFIS methods not only provide superior performance but also are more flexible and compatible for the crack detection application. The ANFIS method is called a “white-box classifier,” and the inferred knowledge from its membership functions can be used to characterize the imagery properties of detected image components.

Identification of Beam Cracks by Solution of an Inverse Problem

Detection of cracks in mechanical components as earlier as possible enables structural health monitoring and scheduling more effectively the maintenance tasks, such as replacing the critical parts just in time. Vibration analysis based techniques for crack detection have been largely considered in the literature. This methodology relies essentially on the observed changes of beam frequencies and mode shapes that are induced by the presence of damage. In the present work, using an explicit analytical model assessing the effect of a crack on beam strain energy, the beam first resonance frequencies were evaluated as function of a single crack defect characteristics. The crack equations were obtained by means of fracture mechanics approach. Variations of the first beam frequencies and modes shapes were then related explicitly to the location and depth of the crack. Measuring the beam frequency changes and monitoring their variations is shown to enable identification of the crack defect parameters by solution of an inverse problem.

104 温度ギャップ法による疲労き裂検出技術の実用化(FM2 実務に使えそうな最新の計測技術(2),研究討論セッション)

104 温度ギャップ法による疲労き裂検出技術の実用化(FM2 実務に使えそうな最新の計測技術(2),研究討論セッション)

Fatigue crack detection using structural nonlinearity reflected on linear ultrasonic features

This paper theoretically and experimentally demonstrates that (1) a localized nonlinear mechanism such as a fatigue crack not only generates nonlinear modulations or harmonics, but also reduces the amplitudes of the linear responses at the excitation frequencies, (2) the energy in the linear responses is partially transmitted to the nonlinear components in the presence of structural nonlinearity, and (3) the amplitude reduction of the linear responses is larger than the amplitude increase of the nonlinear components. In addition, a baseline-free fatigue crack detection technique is proposed considering the additional amplitude reduction of the linear components due to nonlinear ultrasonic modulation.

Soil crack morphology analysis using image processing techniques

The present paper demonstrated an image processing technique of surface soil crack analysis. The geometric features of cracks, such as width, length, and surface area are estimated. These parameters are important, because they influence both the soil hydraulics and mechanics. The crack intensity factor was introduced as a descriptor of the extent of surficial cracking. The correlation analysis indicates that area-weighted mean ratio of soil-crack area to perimeter and index r has a much closed positive relationship with cracks intensity and the area weighted mean of crack fractal dimension declines continuously as the degree of development of soil cracks increases, indicating that the degree of complexity of the soil cracks also gradually decreases. However, traditional visual assessment, which is the primary method in use, is slow and expensive. The present works involve image processing technique for the automatic detection and analysis of cracks in the digital image of a concrete surface.

Crack modelling and detection in Timoshenko FGM beam under transverse vibration using frequency contour and response surface model with GA

In the present work, dynamic response of cracked Timoshenko beam with functionally graded material properties are obtained by a numerical technique using Ritz approximation. In order to verify the applicability and performance of the formulation, comparisons of the present numerical method with three-dimensional FEM models are made. Crack is assumed to be transverse and open throughout the vibration cycle. Two different crack detection techniques have been proposed. Results obtained by the numerical technique are used in both of the crack detection techniques. In the first technique, the frequency contours with respect to crack location and size are plotted and the intersection of contours of different modes helps in the prediction of crack location and size. In the second technique, crack is modelled using response surface methodology (RSM). The sum of the squared errors between the numerical and RSM regression model natural frequencies is used as the objective function. This objective function is minimised using genetic algorithm optimisation technique. Both the crack detection techniques and the numerical analysis have shown good agreement with each other.

Round-robin tests on damage evaluation of concrete based on the concept of acoustic emission rates

Making out a draft of a recommendation practice on damage evaluation of concrete by acoustic emission (AE) technique was postponed in RILEM TC 212-ACD (AE and related NDE techniques for crack detection and damage evaluation in concrete). A follow-up RILEM committee TC 239-MCM (On-Site Measurement of Concrete and Masonry Structures by Visualized NDT) was approved in March, 2010. In this committee, therefore, round-robin tests have been conducted and results are under examination for preparing the recommendation. Damage estimation of concrete by the compression test of core samples is developed, by applying AE measurement and the scalar damage parameter in damage mechanics. The procedure is named damage estimation of concrete by acoustic emission technique (DeCAT), which is based on estimating the intact modulus of elasticity in concrete from AE database. In addition to available data already published, results of the round-robin tests conducted by three groups are discussed.

Application of laser ultrasonic technique for non-contact detection of structural surface-breaking cracks

Abstract Based on the finite element method (FEM), the surface-breaking cracks have been investigated by using the laser-generated Rayleigh wave. The features of laser-generated Rayleigh wave interaction with cracks are analyzed in time and frequency domain. The simulation results show that the surface acoustic wave induced by the pulsed laser is sensitive to the surface-breaking cracks. As the crack depth increases, the transmission coefficients almost linearly decrease and the reflection coefficients show a dip. The corresponding experimental results have verified the feasibility of numerical calculation and reached a good agreement with simulation results. The research findings would provide a potential application for testing surface-breaking cracks of aircraft parts.

A Modified Particle Swarm Optimization Technique for Crack Detection in Cantilever Beams

An inverse analysis of the crack identification problem is investigated by the modified particle swarm optimization (MPSO) technique. The objective of the present analysis is to predict the unknown crack location and its depth from the knowledge of frequency data obtained from theoretical and experimental investigation. In this paper, the proposed modified PSO (MPSO) mechanism employs the strategy of squeezing the physical domain of the search space in each iteration to accelerate the search process while maintaining the inherent structure of PSO algorithm. Analytical and experimental results of the cracked beam structure are compared with those obtained by modified PSO (MPSO) to ensure the integrity of the algorithm. To show its effectiveness, the results of the MPSO are compared with the results obtained by differential evolution. Simulation results reveal the better performance of the proposed algorithm in terms of predicting the location and depth of the crack.

Pulsed Eddy Current Detection of Cracks in Multilayer Aluminum Lap Joints

Aging aircraft is susceptible to cyclic fatigue cracks around ferrous fasteners in multilayer aluminum wing lap joints, as found on Canadian Military aircraft CP-140 Aurora and CC-130 Hercules. Current methods of crack detection utilize bolt hole eddy current, requiring fastener removal, a time consuming process that also has the potential to result in collateral damage. In this paper, pulsed eddy currents (PECs) are induced in the aluminum wing structure by a probe centered over a ferrous fastener. The response signals are analyzed using a modified principal components analysis (PCA) and cluster analysis to show separation of groups of PCA scores from fasteners with and without notches in the bore hole. The Mahalanobis distance (MD), a cluster analysis method, is used to obtain a relative distance measurement between scores associated with cracks from those without cracks. The MD evaluation provides confidence intervals for detection of cracks, which range in extent from fastener holes from 0.9 to 5.5 mm, and a means of potentially sizing larger (>3 mm) second layer cracks. In this paper, 100% of the cracks in the sample were detectable. The results demonstrate PEC as a viable technique for second layer crack detection with ferrous fasteners present.

Health Monitoring of Civil Structures with Integrated UAV and Image Processing System

Abstract This paper describes an innovative protocol for full field mapping of a large civil structures involving effective use of Unmanned Aerial Vehicles (UAVs) to enable real time structural health monitoring. The proposed frameworks integrates UAVs, image processing and data acquisition procedures for crack detection and assessment of surface degradation. A novel approach is proposed combining hat transform and HSV thresholding technique for crack detection. In addition, grey scale thresholding is employed for the measurement of surface degradations. A Demonstration multi-rotor UAV model is developed to carry out full field inspection of civil structures and real time testing is performed in our large university campus. In order to provide sophisticated monitoring platform for users, a MATLAB Graphical User Interface (GUI) is developed to analyse real time as well as acquired images and the results are validated successfully. The obtained results confirms that, the envisaged approach is the foundation for cost effective and time compressing solution for monitoring of large civil structures.

Identification of crack characteristics in beams by using modal frequencies and inverse problem

Detection of cracks in mechanical components as early as possible enables monitoring structural health and scheduling efficiently the maintenance tasks such as replacing the critical parts just in time. Vibration analysis based techniques for crack detection have been largely considered in the framework of beam-like structures. This methodology relies essentially on the observed changes of beam frequencies and mode shapes induced by the presence of damage. In the present work, using an explicit analytical model assessing the effect of a crack on beam strain energy, the beam first resonance frequencies as they depend on a single crack defect characteristics were evaluated. The crack equations were obtained by means of fracture mechanics approach. Variations of the first beam frequencies and modes shapes were then related explicitly to the location and depth of the crack. Measuring the beam frequency changes and monitoring their variations can be used to perform identification of the crack defect parameters by solution of an inverse problem.

Crack detection technique for operating wind turbine blades using Vibro-Acoustic Modulation

This article presents a new technique for identifying cracks in wind turbine blades undergoing operational loads using the Vibro-Acoustic Modulation technique. Vibro-Acoustic Modulation utilizes a low-frequency pumping excitation signal in conjunction with a high-frequency probing excitation signal to create the modulation that is used to identify cracks. Wind turbines provide the ideal conditions in which Vibro-Acoustic Modulation can be utilized because wind turbines experience large low-frequency structural vibrations during operation which can serve as the low-frequency pumping excitation signal. In this article, the theory for the vibro-acoustic technique is described, and the proposed crack detection technique is demonstrated with Vibro-Acoustic Modulation experiments performed on a small Whisper 100 wind turbine in operation. The experimental results are also compared with two other conventional vibro-acoustic techniques in order to validate the new technique. Finally, a computational study is demonstrated for choosing a proper probing signal with a finite element model of the cracked blade to maximize the sensitivity of the technique for detecting cracks.