Journal articles: 'Dynamic crack detection with photogrammetry'

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Merkle, D., A. Schmitt, and A. Reiterer. "SENSOR EVALUATION FOR CRACK DETECTION IN CONCRETE BRIDGES." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLIII-B2-2020 (August 14, 2020): 1107–14. http://dx.doi.org/10.5194/isprs-archives-xliii-b2-2020-1107-2020.

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Abstract. Bridges are one of the most critical traffic infrastructure objects, therefore it is necessary to monitor them at regular intervals. Nowadays, this monitoring is made manually by visual inspection. In recent projects, the authors are developing automated crack detection systems to support the inspector. In this pre-study, different sensors, like different camera systems for photogrammetry, a laser scanner, and a laser triangulation system are evaluated for crack detection based on a defined required minimum crack width of 0.2 mm. The used test object is a blasted concrete plate, sized 70 cm × 70 cm × 5 cm and placed in an outdoor environment. The results of the data acquisition with the different sensors are point clouds, which make the results comparable. The point cloud from the chosen laser scanner is not sufficient for the required crack width even at a low speed of 1 m/s. The RGB or intensity information of the photogrammetric point clouds, even based on a low-cost smartphone camera, contain the targeted cracks. The authors advise against using only the 3D information of the photogrammetric point clouds for crack detection due to noise. The laser triangulation system delivers the best results in both intensity and 3D information. The low weight of camera systems makes photogrammetry to the preferred method for an unmanned aerial vehicle (UAV). In the future, the authors aim for crack detection based on the 2D images, automated by using machine learning, and crack localisation by using structure from motion (SfM) or a positioning system.

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Wang, Jun, and Ruishe Jiang. "Eggshell crack detection by dynamic frequency analysis." European Food Research and Technology 221, no. 1-2 (April 21, 2005): 214–20. http://dx.doi.org/10.1007/s00217-005-1149-9.

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Mohammed, O. D., and M. Rantatalo. "Gear tooth crack detection using dynamic response analysis." Insight - Non-Destructive Testing and Condition Monitoring 55, no. 8 (August 1, 2013): 417–21. http://dx.doi.org/10.1784/insi.2012.55.8.417.

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Qian, G. L., S. N. Gu, and J. S. Jiang. "The dynamic behaviour and crack detection of a beam with a crack." Journal of Sound and Vibration 138, no. 2 (April 1990): 233–43. http://dx.doi.org/10.1016/0022-460x(90)90540-g.

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Belloni, V., A. Sjölander, R. Ravanelli, M. Crespi, and A. Nascetti. "TACK PROJECT: TUNNEL AND BRIDGE AUTOMATIC CRACK MONITORING USING DEEP LEARNING AND PHOTOGRAMMETRY." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLIII-B4-2020 (August 25, 2020): 741–45. http://dx.doi.org/10.5194/isprs-archives-xliii-b4-2020-741-2020.

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Abstract. Civil infrastructures, such as tunnels and bridges, are directly related to the overall economic and demographic growth of countries. The aging of these infrastructures increases the probability of catastrophic failures that results in loss of lives and high repair costs; all over the world, these factors drive the need for advanced infrastructure monitoring systems. For these reasons, in the last years, different types of devices and innovative infrastructure monitoring techniques have been investigated to automate the process and overcome the main limitation of standard visual inspections that are used nowadays. This paper presents some preliminary findings of an ongoing research project, named TACK, that combines advanced deep learning techniques and innovative photogrammetric algorithms to develop a monitoring system. Specifically, the project focuses on the development of an automatic procedure for crack detection and measurement using images of tunnels and bridges acquired with a mobile mapping system. In this paper, some preliminary results are shown to investigate the potential of a deep learning algorithm in detecting cracks occurred in concrete material. The model is a CNN (Convolutional Neural Network) based on the U-Net architecture; in this study, we tested the transferability of the model that has been trained on a small available labeled dataset and tested on a large set of images acquired using a customized mobile mapping system. The results have shown that it is possible to effectively detect cracks in unseen imagery and that the primary source of errors is the false positive detection of crack-like objects (i.e., contact wires, cables and tile borders).

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Miya, K., H. Yanagi, and K. Someya. "A new technique for detection of dynamic crack initiation." Nuclear Engineering and Design 94, no. 3 (July 1986): 281–89. http://dx.doi.org/10.1016/0029-5493(86)90010-5.

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Meng, G., and E. J. Hahn. "Dynamic Response of a Cracked Rotor With Some Comments on Crack Detection." Journal of Engineering for Gas Turbines and Power 119, no. 2 (April 1, 1997): 447–55. http://dx.doi.org/10.1115/1.2815595.

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By considering time-dependent terms as external excitation forces, the approximate dynamic response of a cracked horizontal rotor is analyzed theoretically and numerically. The solution is good for small cracks and small vibrations in the stable operating range. For each steady-state harmonic component, the forward and backward whirl amplitudes, the shape and orientation of the elliptic orbit, and the amplitude and phase of the response signals are analyzed, taking into account the effect of crack size, crack location, rotor speed, and unbalance. It is found that the crack causes backward whirl, the amplitude of which increases with the crack. For a cracked rotor, the response orbit for each harmonic component is an ellipse, the shape and orientation of which depend on the crack size. The influence of the crack on the synchronous response of the system can be regarded as an additional unbalance whereupon, depending on the speed and the crack location, the response amplitude differs from that of the uncracked rotor. The nonsynchronous response provides evidence of crack in the subcritical range, but is too small to be detected in the supercritical range. Possibilities for crack detection over the full-speed range include the additional average (the constant) response component, the backward whirl of the response, the ellipticity of the orbit, the angle between the major axis and the vertical axis, and the phase angle difference between vertical and horizontal vibration signals.

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Haldar, A., R. Martinez-Flores, and H. Katkhuda. "Crack detection in existing structures using noise-contaminated dynamic responses." Theoretical and Applied Fracture Mechanics 50, no. 1 (August 2008): 74–80. http://dx.doi.org/10.1016/j.tafmec.2008.04.007.

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Hampel, U., and H. G. Maas. "Cascaded image analysis for dynamic crack detection in material testing." ISPRS Journal of Photogrammetry and Remote Sensing 64, no. 4 (July 2009): 345–50. http://dx.doi.org/10.1016/j.isprsjprs.2008.12.006.

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Plachy, Tomáš, Jakub Okénka, Pavel Tesárek, and Michal Polák. "Damage Detection and Localization on Cement Specimens." Applied Mechanics and Materials 617 (August 2014): 229–32. http://dx.doi.org/10.4028/www.scientific.net/amm.617.229.

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This paper is focused on cement specimen testing by impact excitation non-destructive technique. The impulse excitation method was used for measuring of the natural frequencies and modes of longitudinal, transversal and torsional vibration of the specimens. The objective was to find dynamic properties of the specimens without a crack, with a crack and with a healed crack by cement paste and based on their comparison detect and localize the crack.

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Xue, Dan, and Weiqi Yuan. "Dynamic Partition Gaussian Crack Detection Algorithm Based on Projection Curve Distribution." Sensors 20, no. 14 (July 17, 2020): 3973. http://dx.doi.org/10.3390/s20143973.

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When detecting the cracks in the tunnel lining image, due to uneven illumination, there are generally differences in brightness and contrast between the cracked pixels and the surrounding background pixels as well as differences in the widths of the cracked pixels, which bring difficulty in detecting and extracting cracks. Therefore, this paper proposes a dynamic partitioned Gaussian crack detection algorithm based on the projection curve distribution. First, according to the distribution of the image projection curve, the background pixels are dynamically partitioned. Second, a new dynamic partitioned Gaussian (DPG) model was established, and the set rules of partition boundary conditions, partition number, and partition corresponding threshold were defined. Then, the threshold and multi-scale Gaussian factors corresponding to different crack widths were substituted into the Gaussian model to detect cracks. Finally, crack morphology and the breakpoint connection algorithm were combined to complete the crack extraction. The algorithm was tested on the lining gallery captured on the site of the Tang-Ling-Shan Tunnel in Liaoning Province, China. The optimal parameters in the algorithm were estimated through the Recall, Precision, and Time curves. From two aspects of qualitative and quantitative analysis, the experimental results demonstrate that this algorithm could effectively eliminate the effect of uneven illumination on crack detection. After detection, Recall could reach more than 96%, and after extraction, Precision was increased by more than 70%.

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Weinmann, M., J. Leitloff, L. Hoegner, B. Jutzi, U. Stilla, and S. Hinz. "Thermal 3D mapping for object detection in dynamic scenes." ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences II-1 (November 7, 2014): 53–60. http://dx.doi.org/10.5194/isprsannals-ii-1-53-2014.

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The automatic analysis of 3D point clouds has become a crucial task in photogrammetry, remote sensing and computer vision. Whereas modern range cameras simultaneously provide both range and intensity images with high frame rates, other devices can be used to obtain further information which could be quite valuable for tasks such as object detection or scene interpretation. In particular thermal information offers many advantages, since people can easily be detected as heat sources in typical indoor or outdoor environments and, furthermore, a variety of concealed objects such as heating pipes as well as structural properties such as defects in isolation may be observed. In this paper, we focus on thermal 3D mapping which allows to observe the evolution of a dynamic 3D scene over time. We present a fully automatic methodology consisting of four successive steps: (i) a radiometric correction, (ii) a geometric calibration, (iii) a robust approach for detecting reliable feature correspondences and (iv) a co-registration of 3D point cloud data and thermal information via a RANSAC-based EPnP scheme. For an indoor scene, we demonstrate that our methodology outperforms other recent approaches in terms of both accuracy and applicability. We additionally show that efficient straightforward techniques allow a categorization according to background, people, passive scene manipulation and active scene manipulation.

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Kim, Jung Ho, Jung Woo Lee, and Jung Youn Lee. "Multi-crack Detection of Beam Using the Change of Dynamic Characteristics." Transactions of the Korean Society for Noise and Vibration Engineering 25, no. 11 (November 20, 2015): 731–38. http://dx.doi.org/10.5050/ksnve.2015.25.11.731.

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Mohammed, Omar D., and Matti Rantatalo. "Dynamic response and time-frequency analysis for gear tooth crack detection." Mechanical Systems and Signal Processing 66-67 (January 2016): 612–24. http://dx.doi.org/10.1016/j.ymssp.2015.05.015.

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Wang, ShanShan, and QingWen Ren. "Dynamic response of gravity dam model with crack and damage detection." Science China Technological Sciences 54, no. 3 (February 1, 2011): 541–46. http://dx.doi.org/10.1007/s11431-010-4226-7.

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Wang, Zuo-cai, and Wei-xin Ren. "Crack detection using integrated signals from dynamic responses of girder bridges." Journal of Central South University 20, no. 6 (June 2013): 1759–66. http://dx.doi.org/10.1007/s11771-013-1669-6.

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Sawicki, Jerzy T. "Rotor Crack Detection Using Active Magnetic Bearings." Solid State Phenomena 144 (September 2008): 9–15. http://dx.doi.org/10.4028/www.scientific.net/ssp.144.9.

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Well-established procedures exist to monitor and diagnose fairly severe problems with rotating machinery but little progress has been made in developing techniques to detect subtle changes in machine condition for both improved diagnostics, and to develop prognostic procedures for determining remaining service life. Of all machine faults, crack initiated problems present probably the most significant safety and loss hazard in modern turbomachinery, including aircraft engines and power generation units. Different approaches are used to model, detect, and localize crack-induced damage in rotating structures. This paper presents novel application of active magnetic bearings (AMBs) for on-line rotor crack detection. AMB-actuators provide convenient means to apply a broad spectrum of known dynamic forces and monitor responses in a rotor-bearing system, which facilitates more sensitive and precise diagnostics. The paper presents theoretical modeling and description of the experimental facility for proof-of-concept testing.

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Mott, P. H., and C. M. Roland. "Ozone Detection by Crack-Induced Opacity in Rubber." Rubber Chemistry and Technology 72, no. 4 (September 1, 1999): 769–78. http://dx.doi.org/10.5254/1.3538833.

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Abstract Initially transparent polybutadiene develops micron-sized surface cracks when stretched and exposed to ozone. The consequent reduction in the transparency of the rubber provides a facile method for quantifying the ambient ozone concentration. The rate at which opacity develops is linearly dependent on the amount of ozone, and increases with increasing strain. This method of detecting atmospheric ozone has high sensitivity (1 ppb), a broad dynamic range, and is unaffected by the presence of other chemicals. The surface morphology of exposed material can be interpreted in terms of crack nucleation and growth.

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Guidi, G., S. Gonizzi, and L. L. Micoli. "Image pre-processing for optimizing automated photogrammetry performances." ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences II-5 (May 28, 2014): 145–52. http://dx.doi.org/10.5194/isprsannals-ii-5-145-2014.

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The purpose of this paper is to analyze how optical pre-processing with polarizing filters and digital pre-processing with HDR imaging, may improve the automated 3D modeling pipeline based on SFM and Image Matching, with special emphasis on optically non-cooperative surfaces of shiny or dark materials. Because of the automatic detection of homologous points, the presence of highlights due to shiny materials, or nearly uniform dark patches produced by low reflectance materials, may produce erroneous matching involving wrong 3D point estimations, and consequently holes and topological errors on the mesh originated by the associated dense 3D cloud. This is due to the limited dynamic range of the 8 bit digital images that are matched each other for generating 3D data. The same 256 levels can be more usefully employed if the actual dynamic range is compressed, avoiding luminance clipping on the darker and lighter image areas. Such approach is here considered both using optical filtering and HDR processing with tone mapping, with experimental evaluation on different Cultural Heritage objects characterized by non-cooperative optical behavior. Three test images of each object have been captured from different positions, changing the shooting conditions (filter/no-filter) and the image processing (no processing/HDR processing), in order to have the same 3 camera orientations with different optical and digital pre-processing, and applying the same automated process to each photo set.

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Green, Itzhak, and Cody Casey. "Crack Detection in a Rotor Dynamic System by Vibration Monitoring—Part I: Analysis." Journal of Engineering for Gas Turbines and Power 127, no. 2 (April 1, 2005): 425–36. http://dx.doi.org/10.1115/1.1789514.

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Many practical rotor dynamic systems contain shaft/rotor elements that are highly susceptible to transverse cross-sectional cracks due to fatigue. The early detection of mechanical malfunction that can be provided by an effective vibration monitoring system is essential. Two theoretical analyses, global and local asymmetry crack models, are utilized to identify characteristics of the system response that may be directly attributed to the presence of a transverse crack in a rotating shaft. A model consisting of an overhung whirling rotor is utilized to match an experimental test rig. A 2X harmonic component of the system response is shown to be the primary response characteristic resulting from the introduction of a crack. Once the unique characteristics of the system response are identified, they serve then as target observations for the monitoring system.

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Ma, Jun, and Wen Ying Su. "Performance Dynamic Tracking and Analysis System of Road Traffic Signs." Applied Mechanics and Materials 130-134 (October 2011): 2404–8. http://dx.doi.org/10.4028/www.scientific.net/amm.130-134.2404.

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In view of the heavy workload and possible intervention to the normal traffic flow during the performance testing of road traffic signs, this paper is designed to present a system that can be installed in an automobile and automatically track and analyze the performance of traffic signs. The system consists of a carrying vehicle, GPS, IMU, area-array cameras, frame grabbers, data acquisition software and data analysis software. Based on close-range photogrammetry technology, the system is designed with a set of effective road traffic signs automatic detection algorithms, which can automatically measure and analyze the properties of road traffic signs, such as dimensions, headroom and verticality of the column, etc.

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Wang, Wenyun, Xuejun Li, and Anhua Chen. "A Method of Modal Parameter Identification for Wind Turbine Blade Based on Binocular Dynamic Photogrammetry." Shock and Vibration 2019 (April 15, 2019): 1–10. http://dx.doi.org/10.1155/2019/7610930.

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The identification of operational modal parameters of a wind turbine blade is fundamental for online damage detection. In this paper, we use binocular photogrammetry technology instead of traditional contact sensors to measure the vibration of blade and apply the advanced stochastic system identification technique to identify the blade modal frequencies automatically when only output data are available. Image feature extraction and target point tracking (PT) are carried out to acquire the displacement of labeled targets on the wind turbine blade. The vibration responses of the target points are obtained. The data-driven stochastic subspace identification (SSI-Data) method based on the Kalman filter prediction sequence is explored to extract modal parameters from vibration response under unknown excitation. Hankel matrixes are reconstructed with different dimensions, so different modal parameters are produced. Similarity of these modal parameters is compared and used to cluster modes into groups. Under appropriate tolerance thresholds, spurious modes can be eliminated. Experiment results show that good effects and stable accuracy can also be achieved with the presented photogrammetry vibration measurement and automatic modal identification algorithm.

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He, Min, Jianyu Li, Yuanwei Zhang, and Weijun Li. "Research on crack visualization method for dynamic detection of eddy current thermography." NDT & E International 116 (December 2020): 102361. http://dx.doi.org/10.1016/j.ndteint.2020.102361.

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Lukasiewicz, S., and K. Palka. "ON DETECTION OF DEFECTS IN BEAMS AND TRUSSES FROM DYNAMIC RESPONSES." Transactions of the Canadian Society for Mechanical Engineering 24, no. 1A (March 2000): 1–31. http://dx.doi.org/10.1139/tcsme-2000-0001.

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This paper presents an identification method to detect cracks and corroded members in vibrating structures. The mathematical identification procedure based on the least square technique uses the measured dynamic response of a structure as the source of information. The application of the Finite Element Method (FEM) for the representation of all constraints and model equations allows presentation of the identification process in a simple and very efficient mathematical form. Propagation of cracks and other failures of the members cause changes in the bending and axial stiffness of the members. One can detect the crack by observing the change in the bending stiffness caused by the closing and opening of the crack in two different configurations. The proposed identification method provides highly precise calculated results which allows detection of small changes in the bending stiffness of the members resulting from cracks and corrosion. The method was tested on simulated experimental data.

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Yang, Dong, Dan Li, and K. S. C. Kuang. "A Novel Fatigue Crack Monitoring Method Based on Nonlinear Dynamic Characteristics of Strain." International Journal of Structural Stability and Dynamics 20, no. 01 (December 4, 2019): 2050016. http://dx.doi.org/10.1142/s0219455420500169.

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This paper presents a novel fatigue crack monitoring method for steel specimens based on the smoothness priors method (SPM) and Tsallis entropy (TE) of strain measurements. The aim of the study is to detect initiation of a crack in steel specimens and subsequently to monitor its propagation under the fatigue load, based on real-time strain measurements. The nonlinear dynamic response of the structure was exploited since it degrades due to the initiation and subsequent propagation of the crack under the external dynamic excitation. The proposed method was experimentally validated. Here, the SPM is applied to decomposing the structural strain response into a nearly-stationary (NS) component and a low frequency aperiodic trend (LFAT) component. Features associated with crack initiation can be extracted from the NS component. The LFAT component, on the other hand, can be used to identify crack propagation. To tackle the singularity of the structural responses associated with a crack, the TE of the NS component was used in detection and monitoring of the crack in the steel specimen. Two other techniques, namely, acoustic emission (AE) sensor and crack opening displacement (COD) gauge were used for the purpose of calibration and comparison. The results show remarkable resemblance in terms of crack initiation and propagation identification exhibited by all three types of sensors, highlighting the potential of the proposed method for real-time detection and subsequent monitoring of crack propagation in steel structures.

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Yang, B., C. S. Suh, and A. K. Chan. "Characterization and Detection of Crack-induced Rotary Instability." Journal of Vibration and Acoustics 124, no. 1 (July 1, 2001): 40–48. http://dx.doi.org/10.1115/1.1421053.

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System instability and chaotic response are the failure modes that could significantly impact the reliability and operating safety of high-speed rotor-dynamical machines. Initiation and propagation of surface cracks in rotary shafts are common causes for such failure modes. To be able to detect the onset and progression of these faults will considerably extend the lifetime and improve the reliability of the mechanical system. A wavelet-based algorithm effective in identifying mechanical chaotic response has been applied to determine the nonlinear dynamical characteristics of a model-based, cracked rotor. This investigation confirms reported correlation of surface crack breathing with rotor chaotic motions. The effectiveness of the algorithm in detecting rotor-dynamic instability induced by mechanical faults as contrast to algorithms that are based on nonlinear dynamics is discussed. The results show not just the feasibility of the algorithm in mechanical fault diagnosis but also suggest its applicability to in-line, real-time condition monitoring at both the system and component levels.

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Wu, Ming-Chuan, and Shyh-Chin Huang. "In-Plane Vibration and Crack Detection of a Rotating Shaft-Disk Containing a Transverse Crack." Journal of Vibration and Acoustics 120, no. 2 (April 1, 1998): 551–56. http://dx.doi.org/10.1115/1.2893864.

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Dynamic response and stability of a rotating shaft-disk containing a transverse crack is investigated. FFT analysis of response amplitudes showed that the 2Ω component (Ω: rotation speed) was excited by crack breathing and could serve as a good index for crack identification. Intensive numerical studies of crack location, crack depth, rotation speed, and sensing position on response amplitudes displayed a feasible technique for the identification of crack depth and crack location. It is achieved by intersecting the two equi-amplitude response curves of two separated sensing probes. Finally, the instability of the system caused by a crack is examined via Floquet theory and the multiple scale method. The stability diagrams, illustrated as functions of crack depth, rotation speed, and damping, are shown and discussed.

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Zhou,, Tong, Jianxue Xu, and, and Zhengce Sun. "Dynamic Analysis and Diagnosis of a Cracked Rotor." Journal of Vibration and Acoustics 123, no. 4 (April 1, 2001): 539–43. http://dx.doi.org/10.1115/1.1401075.

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In this paper, the nonlinear dynamical behavior of a horizontal Jeffcott rotor system with a transverse crack is analyzed numerically. A new acceleration scheme is suggested to reduce shocks to the rotor and diagnose the existence of cracks. Particular stress is laid on the analysis of the spectrum of transient and stable response by using a new approach of signal processing, which could erase both the gravitational effect and the free vibration with inherent frequency for the purpose of accurate crack detection.

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Sekhar, A. S. "Detection and monitoring of cracks in rotors through Q factors." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 214, no. 7 (July 1, 2000): 949–54. http://dx.doi.org/10.1243/0954406001523173.

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Dynamic analysis of a cracked Jeffcott rotor has been carried out, considering the effects of fluid film bearings. Q factors and dissipation coefficients have been evaluated in addition to the harmonic responses of the rotor. The coast down phenomenon was analysed for the effects of crack depth. Sensitivity studies were carried out, considering dissipation, response and the Q factor. Measurement of Q factors of second harmonics, Qx1 and Qy2, has been suggested for crack detection, while measurement of Q factors of first harmonics is recommended for crack monitoring as these proved to be more sensitive to cracks compared with other methods.

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Feng, Z. C., and Yi Shang. "Breathing Crack Detection Using Dynamic Equations and Measurement Data Regression and Filtering Techniques." Journal of Vibration Testing and System Dynamics 5, no. 4 (December 2021): 359–72. http://dx.doi.org/10.5890/jvtsd.2021.12.004.

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Thatoi, D. N., J. Nanda, H. C. Das, and D. R. Parhi. "Analysis of the Dynamic Response of a Cracked Beam Structure." Applied Mechanics and Materials 187 (June 2012): 58–62. http://dx.doi.org/10.4028/www.scientific.net/amm.187.58.

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In this research, dynamic behaviour of a cracked cantilever beam has been analysed using finite element and experimental analysis. Deviations in mode shapes and natural frequencies have been noticed due to the presence of crack in the beam. The variation in the dynamic response is due to change in local flexibility because of the presence of crack in the beam. Finite element and experimental analyses have been carried out to find out the vibration indices of the cracked cantilever beam for validating the robustness of the theoretical model used for crack detection. The numerical results obtained through FEA are in good agreement with experimental results.

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Nwosu, D. I., A. S. J. Swamidas, and J. Y. Guigne´. "Dynamic Response of Tubular T-Joints Under the Influence of Propagating Cracks." Journal of Offshore Mechanics and Arctic Engineering 118, no. 1 (February 1, 1996): 71–78. http://dx.doi.org/10.1115/1.2828804.

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This paper presents an analytical study on the vibration response of tubular T-joints for detecting the existence of cracks along their intersections. The ABAQUS finite element program was utilized for carrying out the analysis. Frequency response functions were obtained for a joint with and without cracks. The joint was modeled with 8-node degenerate shell elements having 5 degrees of freedom per node. Line spring elements were used to model the crack. The exact crack configuration (semielliptical shape, Fig. 5(b)), as observed from numerous experimental fatigue crack investigations at the critical location, has been achieved through a mapping function, that allows a crack in a planar element to be mapped on to the tube surface. The natural frequency changes with respect to crack depth show little changes, being 4.82 percent for a 83-percent crack depth for the first mode. On the other hand, significant changes have been observed for bending moment and curvature as a function of crack depth. For an 83-percent chord thickness crack, a 97-percent change in bending moment at points around the crack vicinity, and 34.15 to 78 percent change in bending moments, for those locations far away from the crack location, have been observed. Natural frequency change should be combined with other modal parameters such as “bending moment (or bending strain)” and “curvature” changes for crack detection. The presence of the crack can be detected at locations far away from the crack location using such sensors as strain gages.

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Kulesza, Zbigniew. "An Induced Shaft Deflection for Rotating Shaft Crack Detection." Solid State Phenomena 199 (March 2013): 3–8. http://dx.doi.org/10.4028/www.scientific.net/ssp.199.3.

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Over the years various techniques have been developed to extract information on the dynamic state of the rotating machinery. This paper introduces a new method based on the phase data of the shaft rotation angle. Usually the phase data is omitted and only the frequency components of the vibration spectrum are taken into consideration. However, the transverse shaft crack has a specific angular location about the shaft axis. Therefore, it is supposed that by measuring the vibration response of the rotor deflected by an additional constant force applied perpendicularly to the shaft axis at different angular locations, different vibration signatures can be obtained. Such signatures can then be used to detect the crack. The method utilizes also the coupling phenomenon between the lateral/torsional vibrations of the cracked rotor, since the shaft is additionally excited by an external harmonic torque. The computer simulation study is based on the uncracked and cracked rotor models obtained by using the finite element (FE) approach. The results of the numerical analysis demonstrate the potential of the suggested method for the effective shaft crack detection.

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Gama, Antonio Lopes, and Sergio Ricardo Kokay Morikawa. "Monitoring Fatigue Crack Growth in Fracture Mechanics Specimens with Piezoelectric Sensors." Materials Science Forum 758 (June 2013): 83–88. http://dx.doi.org/10.4028/www.scientific.net/msf.758.83.

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This paper presents the results of an experimental study on the application of piezoelectric dynamic strain sensors for monitoring the crack growth in fracture mechanics specimens. The performance of the piezoelectric sensors was assessed through fatigue crack propagation tests in three point bend (TPB) specimens and compact tension (CT) specimens. Piezoelectric sensors of lead zirconate titanate (PZT) were placed close to the crack edge of TPB specimens and piezoelectric polyvinilidene fluoride polymer (PVDF) was bonded to the back face of CT specimens. The piezoelectric sensors detect the crack growth by monitoring changes in the dynamic strain field of the specimen. In its simplest mode, the piezoelectric sensors behave like dynamic strain gages, with the main advantage of having a high sensitivity which allows detection of lower strain levels and lower increase in crack length.

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Liu, XinChang, Qi Sun, and ChunJun Chen. "Damage Degree Detection of Cracks in a Locomotive Gear Transmission System." Shock and Vibration 2018 (November 18, 2018): 1–14. http://dx.doi.org/10.1155/2018/5761064.

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The gear transmission system is a vital component of the locomotive bogie. During locomotive operation, the damage to the gear transmission system spreads rapidly and affects the locomotive’s operational safety. In this paper, a method is proposed to detect the degree of tooth root crack damage. First, a dynamic locomotive model with a gear transmission is built, and the vertical acceleration of the locomotive subsystem (car body, bogie frame, wheelset, and motor) vibrations is obtained under various degrees of tooth root crack damage on the gear transmission system. By comparing the characteristics of those signals, the subsystem that is more sensitive to the effect of the tooth root crack is found. The characteristic parameters of the sensitive subsystem are calculated, and a multidimensional characteristic parameter matrix is established. The multidimensional characteristic parameter matrix is optimized and reduced by principal component analysis (PCA). Using the Grey relational analysis method, the degree of tooth root crack damage is detected. The proposed method demonstrates the ability to recognize the degree of tooth root crack damage.

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Li, Xiao Li, Zong Guang Sun, and Ying Fang Fan. "Static and Dynamic Test Detection of Steel Tube Truss Arch Bridge." Applied Mechanics and Materials 178-181 (May 2012): 2513–20. http://dx.doi.org/10.4028/www.scientific.net/amm.178-181.2513.

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Static and dynamic test of 85m span half-through steel tube concrete truss arch were in. Follow contents were determined in the static test:control section deflection of steel tube concrete arch rib under test load;deck control section deflection and strain measuring in test load;deflection and strain measuring of suspender beam;strain test of suspender;crack observation of beam in loading. The deflection and strain measuring point of deck control section were on the beam. The content of dynamic load test :the measuring of impact coefficient、natural frequency and cable tension by frequency methods. Finally, operational situation of bridge was estimated.

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Deng, Yue Cheng, Hong Chun Sun, and Jia Li. "Overview: Methods of Crack Damage Detection Based on Modal Analysis." Advanced Materials Research 424-425 (January 2012): 723–27. http://dx.doi.org/10.4028/www.scientific.net/amr.424-425.723.

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Introduced the history of development of crack damage detection technology and summarized the current state of damage detection technique based on modal analysis. Finite element method is the main method for mechanical structure modal analysis at present. Many researchers studied a single crack or multiple cracks impact on different structure’s dynamic characteristics, however, these studies only limited to the current state of structures with damage. Considering damage extending when mechanical structure being on work, a new method combines modal analysis and theory of damage extend is proposed to analysis the extending trend of damage, which make it easy to assess remaining life of mechanical structures and make structures that meeting design life can still being on work before they lose their effectiveness, this can save lots of costs

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Doğan, Oğuz, and Fatih Karpat. "Crack detection for spur gears with asymmetric teeth based on the dynamic transmission error." Mechanism and Machine Theory 133 (March 2019): 417–31. http://dx.doi.org/10.1016/j.mechmachtheory.2018.11.026.

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Shen, Gang, Xin Qiu, Jue Qiang Tao, Ning Da Du, and Yong Ju Hu. "Diagnostic Testing on Crack Propagation of Asphalt Pavement Materials." Key Engineering Materials 667 (October 2015): 396–401. http://dx.doi.org/10.4028/www.scientific.net/kem.667.396.

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Asphalt concrete is a typical road building material of advanced asphalt pavements. Under the reciprocating vehicle loading, fatigue cracks are reduced inevitably, which seriously affect road performance. Therefore, effective detection and diagnosis of fatigue crack propagation has become a hot research issue. Acoustic emission detection test is a new dynamic nondestructive testing technology which has some features of real-time, online and overall detection. The main purpose of this paper systematically analyses the development process of acoustic emission technology applied in health monitoring field of asphalt concrete pavement structure, and to state the acoustic emission source localization principle, the parameters of acoustic emission signal analysis method, the acoustic emission signal waveform analysis method, etc. Furthermore, from the aspects of the asphalt concrete fatigue performance, crack evolution process and positioning technology, this paper fundamentally discuss the future technological development prospect of acoustic emission technology which is applied in the field of monitoring and diagnosis of asphalt concrete pavement structure, and provide a new perspective for the whole dynamic maintenance of road , and the information implementation of pavement maintenance strategies at later stage.

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Pugno, N., and A. Carpinteri. "Tubular Adhesive Joints Under Axial Load." Journal of Applied Mechanics 70, no. 6 (November 1, 2003): 832–39. http://dx.doi.org/10.1115/1.1604835.

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In this paper a general study on tubular adhesive joint under axial load is presented. We focus our attention on both static and dynamic behavior of the joint, including shear and normal stresses and strains in the adhesive layer, joint optimization, failure load for brittle crack propagation, and crack detection based on free vibrations. First, we have considered the shear and normal stresses and strains in the adhesive layer to propose an optimization to uniform axial strength (UAS) and to reduce the stress peaks in the bond. The stress analysis confirms that the maximum shear stresses are attained at the ends of the adhesive and that the peak of maximum shear stress is reached at the end of the stiffer tube and does not tend to zero as the adhesive length approaches infinity. A fracture energy criterion to predict brittle crack propagation for conventional and optimized joint is presented. The stability of brittle crack propagation and the strength of the joint, as well as the ductile-brittle failure transition, are analyzed. A detection method to predict crack severity, based on joint dynamic behavior, is also proposed. The crack detection is achieved through the determination of the axial natural frequencies of the joint as a function of the crack length, by determining the roots of a determinantal equation.

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Lee, Sang Eon, and Jung-Wuk Hong. "Detection of Micro-Cracks in Metals Using Modulation of PZT-Induced Lamb Waves." Materials 13, no. 17 (August 29, 2020): 3823. http://dx.doi.org/10.3390/ma13173823.

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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.

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Henschel, Sebastian, and Lutz KrÜger. "Temperature dependent crack initiation of 42CrMo4 steel at high loading rates." EPJ Web of Conferences 183 (2018): 02001. http://dx.doi.org/10.1051/epjconf/201818302001.

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Dynamic crack initiation with crack tip loading rates K˙ of approximately 2 ‧ 106 MPa√ms− in high-strength 42CrMo4 steel was investigated. To this end, a recently developed split Hopkinson pressure bar with four-point bending was utilized. V-notched and precracked Charpy specimens were tested. The tests were performed at temperatures of –40 °C and 20 °C. The loading of the specimen was determined by analyzing the strain in the incident and transmission bars. Furthermore, strain gauges at the specimen’s surface were applied to measure the crack tip loading. High-speed photography complemented the analysis of the specimens loading and the detection of the crack initiation. Fracture surface analysis by means of scanning electron microscopy enabled the measurement of the fracture surface topography and, consequently, stretch zone height and width. Hence, the macroscopically measured dynamic crack initiation toughness was correlated with the toughness at microscopic scale. It was observed that the resistance against dynamic crack initiation decreased with decreasing temperature. Microscopically, a decrease in toughness was analogously observed. Non-metallic inclusions resulted in crack path deflection with localized shear zones. After a small stable crack extension, cleavage fracture was observed.

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Karim, M. R., T. Kundu, and C. S. Desai. "Detection of Delamination Cracks in Layered Fiber-Reinforced Composite Plates." Journal of Pressure Vessel Technology 111, no. 2 (May 1, 1989): 165–71. http://dx.doi.org/10.1115/1.3265653.

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In this paper, the dynamic response of delamination cracks in a layered fiber-reinforced composite plate is analytically studied. The plate is subjected to an antiplane loading and its surface response is computed in absence as well as in presence of delaminatioin cracks. To what extent the surface response is influenced by the presence of internal delamination cracks is investigated here. This study is important for nondestructive evaluation of internal damage in composites due to delamination. The problem is formulated in terms of integral equations in frequency domain. These equations are then solved by expanding the unknown crack opening displacement in a complete set of Chebychev’s polynomials, whose coefficients are solved by satisfying the traction-free condition at the crack surface. The time histories are obtained numerically by inverting the spectra via Fast Fourier Transform (FFT) routine. The results show significant influence of delamination crack geometries on the surface response of the plate.

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Cui, Li, Hao Xu, Jing Ge, Maosen Cao, Yangmin Xu, Wei Xu, and Dragoslav Sumarac. "Use of Bispectrum Analysis to Inspect the Non-Linear Dynamic Characteristics of Beam-Type Structures Containing a Breathing Crack." Sensors 21, no. 4 (February 7, 2021): 1177. http://dx.doi.org/10.3390/s21041177.

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A breathing crack is a typical form of structural damage attributed to long-term dynamic loads acting on engineering structures. Traditional linear damage identification methods suffer from the loss of valuable information when structural responses are essentially non-linear. To deal with this issue, bispectrum analysis is employed to study the non-linear dynamic characteristics of a beam structure containing a breathing crack, from the perspective of numerical simulation and experimental validation. A finite element model of a cantilever beam is built with contact elements to simulate a breathing crack. The effects of crack depth and location, excitation frequency and magnitude, and measurement noise on the non-linear behavior of the beam are studied systematically. The result demonstrates that bispectral analysis can effectively identify non-linear damage in different states with strong noise immunity. Compared with existing methods, the bispectral non-linear analysis can efficiently extract non-linear features of a breathing crack, and it can overcome the limitations of existing linear damage detection methods used for non-linear damage detection. This study’s outcome provides a theoretical basis and a paradigm for damage identification in cracked structures.

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Imam, I., S. H. Azzaro, R. J. Bankert, and J. Scheibel. "Development of an On-Line Rotor Crack Detection and Monitoring System." Journal of Vibration and Acoustics 111, no. 3 (July 1, 1989): 241–50. http://dx.doi.org/10.1115/1.3269848.

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A very comprehensive technology of on-line rotor crack detection and monitoring has been developed. The technique, based on the vibration signature analysis (VSA) approach, can detect incipient transverse rotor cracks in an “on-line mode.” The technique is generic and is applicable to all machines whose rotors are subjected to some kind of bending load. These machines include turbines, generators, pumps and motors, etc. The technique is based on the analytical modeling of the dynamics of the system. The basic idea is that through the modeling approach, the crack symptoms can be determined in terms of characteristic vibration signatures. These signatures are then used to diagnose the flaw in real life situations. A 3-D finite element crack model and a nonlinear rotor dynamic code have also been developed to accurately model a cracked rotor system. This program has been used to develop a variety of unique vibration signatures indicating a rotor crack. Both the analytical crack model and the crack signature analysis techniques have been experimentally validated. A microprocessor-based on-line rotor crack detection and monitoring system has been developed. The system has successfully detected cracks of the order of 1 to 2 percent of shaft diameter deep in an “on-line” mode in a series of large-scale laboratory tests. The system has been installed on a turbine-generator set at a utility in the field in October 1986 and has since been operating continuously, both in on-line as well as in coast-down modes, essentially, flawlessly. The system has also been applied in a crack detection program for nuclear reactor vertical coolant pumps. This paper describes all aspects of the development, starting from the technical concept to the commercial field applications.

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Chouiyakh, H., L. Azrar, K. Alnefaie, and O. Akourri. "Crack identification based on the nonlinear response of plates with variably oriented surface crack." MATEC Web of Conferences 149 (2018): 02061. http://dx.doi.org/10.1051/matecconf/201814902061.

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In order to secure structural and operational safety of structures, it is important to implement a structural health monitoring (SHM) strategy to issue early warnings on damage or deterioration prior to costly repair or even catastrophic collapse. Developing a SHM strategy for structures enables evaluating structural integrity, durability and reliability of the monitored structure. Hence, the main objective of this work is to develop a damage detection procedure based on a plate’s dynamic response and the Hilbert transform. Rectangular plates are considered and assumed to contain a surface crack which is centrally located, with a depth of h0, a length of 2C and inclined with an angle β. Von Karman plate theory is adopted herein, and the crack is modeled through the line spring model given by fracture mechanics. The plate is assumed to behave nonlinearly due to large deformation. The differential quadrature method is used to investigate the linear and nonlinear dynamic behaviors of cracked plates. The influence of crack’s parameters on modal properties is discussed. The eigenfrequencies of cracked plates with respect to crack half length C and orientation β are performed. For crack characterization, Hilbert transform is applied to the obtained linear and nonlinear time responses. It is shown throughout this paper that identified backbones describe changes in crack orientation.

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Sayyad, FB, B. Kumar, and SA Khan. "Approximate analytical method for damage detection in free–free beam by measurement of axial vibrations." International Journal of Damage Mechanics 22, no. 1 (March 27, 2012): 133–42. http://dx.doi.org/10.1177/1056789512440897.

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Nowadays, sophisticated structures and machinery parts are constructed by using metallic beams. Beams are widely used as structural element in civil, mechanical, naval, and aeronautical engineering. In structures and machinery, one undesirable phenomenon is crack initiation in which the impact cannot be seen overnight. Cracks develop gradually through time that lead finally to catastrophic failure. Therefore, crack should be monitored regularly with more care. This will lead to more effective preventive measure and ensure continuous operation of the structure and machine. Damage in structure alters its dynamic characteristics. The change is characterized by change in modal parameters, that is, modal frequencies. Thus, vibration technique can be suitably used as a nondestructive test for crack detection of component to be tested. Mostly modal frequencies are used for monitoring the crack because modal frequencies are properties of the whole structure component. In this paper, efforts are made to develop suitable methods that can serve as the basis to detection of crack location and crack size from measured axial vibration data. This method is used to address the inverse problem of assessing the crack location and crack size in various beam structure. The method is based on measurement of axial natural frequencies, which are global parameter and can be easily measured from any point on the structure and also indeed, the advantage in modeling complexity. In theoretical analysis, the relationship between the natural frequencies, crack location, and crack size has been developed. For identification of crack location and crack size, it was shown that data on the variation of the first two natural frequencies is sufficient. The experimental analysis is done to verify the practical applicability of the theoretical method developed.

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Chakraborty, Joyraj, Andrzej Katunin, Piotr Klikowicz, and Marek Salamak. "Early Crack Detection of Reinforced Concrete Structure Using Embedded Sensors." Sensors 19, no. 18 (September 9, 2019): 3879. http://dx.doi.org/10.3390/s19183879.

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The damage in reinforced concrete (RC) structures can be induced either by the dynamic or static load. The inspection technologies available today have difficulty in detecting slowly progressive, locally limited damage, especially in hard-to-reach areas in the superstructure. The four-point bending test on the benchmark RC structure was used as a test of the quality and sensitivity of the embedded sensors. It allowed assessment of whether any cracking and propagation that occurs with the embedded sensors can be detected. Various methods are used for the analysis of the ultrasonic signals. By determining the feature from the ultrasonic signals, the changes in the whole structure are evaluated. The structural degradation of the RC benchmark structure was tested using various non-destructive testing methods to obtain a comprehensive decision about structural condition. It is shown that the ultrasonic sensors can detect a crack with a probability of detection of 100%, also before it is visible by the naked eye and other techniques, even if the damage is not in the direct path of the ultrasonic wave. The obtained results confirmed that early crack detection is possible using the developed methodology based on embedded and external sensors and advanced signal processing.

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Lin, Chern-Sheng, Shih-Hua Chen, Che-Ming Chang, and Tsu-Wang Shen. "Crack Detection on a Retaining Wall with an Innovative, Ensemble Learning Method in a Dynamic Imaging System." Sensors 19, no. 21 (November 3, 2019): 4784. http://dx.doi.org/10.3390/s19214784.

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In this study, an innovative, ensemble learning method in a dynamic imaging system of an unmanned vehicle is presented. The feasibility of the system was tested in the crack detection of a retaining wall in a climbing area or a mountain road. The unmanned vehicle can provide a lightweight and remote cruise routine with a Geographic Information System sensor, a Gyro sensor, and a charge-coupled device camera. The crack was the target to be tested, and the retaining wall was patrolled through the drone flight path setting, and then the horizontal image was instantly returned by using the wireless transmission of the system. That is based on the cascade classifier, and the feature comparison classifier was designed further, and then the machine vision correlation algorithm was used to analyze the target type information. First, the system collects the target image and background to establish the samples database, and then uses the Local Binary Patterns feature extraction algorithm to extract the feature values for classification. When the first stage classification is completed, the classification results are target features, and edge feature comparisons. The innovative ensemble learning classifier was used to analyze the image and determine the location of the crack for risk assessment.

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Shah, Bhumi Ankit, and Dipak P. Vakharia. "Online condition monitoring for detection of crack in the shaft using vibration analysis method." Industrial Lubrication and Tribology 70, no. 7 (September 10, 2018): 1193–200. http://dx.doi.org/10.1108/ilt-11-2017-0348.

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Purpose The purpose of this study is to identify the crack in the shaft at incipient stage. Transverse crack is the most common type of crack found on the periphery of the shaft. The changes in dynamic behaviour of the rotor at high speed are enormous. The reliable operation of the machinery is paramount for the safety of individual and plant. Condition-based maintenance monitors the mechanical and operational condition of the machine. During such inspection, if any unhealthy symptoms are detected, then affected part is identified and taken out for the maintenance at most appropriate time. Design/methodology/approach Simulating the transverse crack of different depth and location is the most challenging part of the experimental analysis. To optimize the total experimental cost for simulation of crack in the shaft, inverted crack is proposed to be produced in shaft and investigation shall be carried out for of early crack detection in shaft using vibration analysis. The set of experiments has been conducted on healthy shaft, inverted cracked shaft and actual cracked shaft. Inverted crack methodology provides flexibility of simulating crack of any size and at any location, and it can be reconfigured for several times to obtain various set of results. Findings To derive objective of the study, steady state response analysis and transient response analysis are performed on the experiment test rig. Vibration signals are acquired from the bearing locations to detect the crack. The paper addresses the influence of the inverted crack on critical speed of the shaft and deviation of first and second harmonic component of the shaft because of introduction of inverted crack. The resultant Nyquist plots, orbit plots and frequency plots are compared with the baseline data (obtained with the healthy shaft) to identify the crack. Originality/value The present study focuses on methodology by which inverted crack is developed in the healthy shaft, which resembles the behaviour of actual crack, and it shall be used to study the changes in rotor stiffness caused by transverse crack. The experimental results obtained using the inverted crack shaft have same vibration characteristics but in reverse direction as it would have occurred with the cracked shaft.

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Journal articles on the topic 'Dynamic crack detection with photogrammetry'

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