Journal articles: 'Crack measurement'

1

Lin, Bin, Hong Tao Zhu, Hui Wu, Z. F. Wang, and S. Y. Yu. "Evaluation and Measurement of Surface/Subsurface Crack Damage of Ground Ceramics." Materials Science Forum 471-472 (December 2004): 47–51. http://dx.doi.org/10.4028/www.scientific.net/msf.471-472.47.

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While be ground, ceramic is prone to engender surface/subsurface crack damage layer because of great grinding force and high brittle of the material. The crack damage layer was investigated in this research. In experiment, it is observed that the surface/subsurface crack damage layer consists of three kinds of cracks: surface micro-cracks, surface macro-cracks and subsurface crack system. To evaluate expediently the degree of damage to the machined components, the index of surface/subsurface crack damage - Dc, is defined.

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Wong, R. H. C., Y. S. H. Guo, K. T. Chau, Wei Shen Zhu, and Shu Cai Li. "The Crack Growth Mechanism from 3-D Surface Flaw with Strain and Acoustic Emission Measurement under Axial Compression." Key Engineering Materials 353-358 (September 2007): 2357–60. http://dx.doi.org/10.4028/www.scientific.net/kem.353-358.2357.

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This paper presents the crack growth mechanism from a 3-D surface flaw on gabbro specimens using strain measurement and acoustic emission (AE) technique. Based on the results of strain and AE measurement, microcracks initiated inside the rock and extend to the surface of the specimen. With the observation from the measurements, four types of crack patterns initiate wing crack, anti-wing crack (opposite direction of wing crack), petal crack and compressive crack. The strain values of anti-wing cracks are larger 1 to 2 times than that of wing crack. The AE energy release from anti-wing crack is higher 2.5 times than that of wing crack, while the energy release form wing crack is the least but the compressive crack is the highest. Thus, the appearance of initiation and propagation of the anti-wing crack and compressive crack are very actively than that of the wing crack. The strain and AE measurement is not only to provide a clear concept on the mechanisms of crack growth form a 3-D surface flaw but also to provide useful knowledge on the AE property of the crack patterns.

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Yuan, Yingtao, Zhendong Ge, Xin Su, Xiang Guo, Tao Suo, Yan Liu, and Qifeng Yu. "Crack Length Measurement Using Convolutional Neural Networks and Image Processing." Sensors 21, no. 17 (September 1, 2021): 5894. http://dx.doi.org/10.3390/s21175894.

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Fatigue failure is a significant problem in the structural safety of engineering structures. Human inspection is the most widely used approach for fatigue failure detection, which is time consuming and subjective. Traditional vision-based methods are insufficient in distinguishing cracks from noises and detecting crack tips. In this paper, a new framework based on convolutional neural networks (CNN) and digital image processing is proposed to monitor crack propagation length. Convolutional neural networks were first applied to robustly detect the location of cracks with the interference of scratch and edges. Then, a crack tip-detection algorithm was established to accurately locate the crack tip and was used to calculate the length of the crack. The effectiveness and precision of the proposed approach were validated through conducting fatigue experiments. The results demonstrated that the proposed approach could robustly identify a fatigue crack surrounded by crack-like noises and locate the crack tip accurately. Furthermore, crack length could be measured with submillimeter accuracy.

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Jung, Ju-Yeong, Hyuk-Jin Yoon, and Hyun-Woo Cho. "A Study on Crack Depth Measurement in Steel Structures Using Image-Based Intensity Differences." Advances in Civil Engineering 2018 (2018): 1–10. http://dx.doi.org/10.1155/2018/7530943.

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This paper seeks to propose an image-based noncontact testing method in crack depth measurement. To this end, it predicted the crack depth using the intensity values of cracks and verified its validity. To analyze the intensity values of cracks, eight stainless steel specimens with an increase in crack depths ranging from 0 to 17.5 mm at an average of 2.5 mm were fabricated, and a contrast index was attached to the center of the crack of the specimens painted with black matte spray for accurate analysis. Through various experiments, it was found that the intensity values of the cracks which decrease with the depth of the cracks were inductively formulated, and the average error was about 15% when the crack depth predicted by the empirical equation was compared with the actual crack depth. In addition, the validation of the intensity reduction equation obtained by the inductive method was verified, and it was confirmed that the crack depth can be predicted by the intensity value of the crack.

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Sekhar, A. S., and P. Balaji Prasad. "Crack Identification in a Cantilever Beam Using Coupled Response Measurements." Journal of Engineering for Gas Turbines and Power 120, no. 4 (October 1, 1998): 775–77. http://dx.doi.org/10.1115/1.2818466.

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Identification of crack location and magnitude through measurement in changes in system characteristics, such as modal measurements, has been studied by various researchers. In the present work based on the new method proposed by Gounaris et al. (1996) for crack detection through coupled response measurements, experiments were carried out on a cracked cantilever beam for eigenfrequencies, bending, and axial response measurements. It has been observed that the rate of change of direct response (bending) is much less at small cracks, while that of the coupled response (axial) changes substantially, which allows for diagnoses of smaller cracks.

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Yang, Hao, and Xiangyang Xu. "Intelligent crack extraction based on terrestrial laser scanning measurement." Measurement and Control 53, no. 3-4 (January 7, 2020): 416–26. http://dx.doi.org/10.1177/0020294019877490.

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The hazards of cracks, which could badly decrease reliability and safety of structures, are receiving increasing attention with the popularity of tunnel constructions. Traditional crack inspection relies on visual examination, which is time-, cost- and labor-intensive. Therefore, how to identify and measure cracks intelligently is significantly essential. The paper focuses on the Canny method to extract cracks of tunnel structures by the intensity value of reflectivity. We propose and investigate a novel method which combines dilation and the Canny algorithm to identify and extract the cracks automatically and intelligently based on the point cloud data of terrestrial laser scanning measurement. In order for measurement of cracks, the projection of summed edge pixels is adopted, where a synthesis is carried out on the detection results with all sampling parameters. Based on the synthesized image, vertical crack presents two sharp peaks where the space of the peaks indicates the average width of the crack, as well as its position. The advantage of the method is that it does not require determination of Canny detector parameters. The deviation between manual measurement and Canny detection is 2.92%.

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Sarker, M. M., T. A. Ali, A. Abdelfatah, S. Yehia, and A. Elaksher. "A COST-EFFECTIVE METHOD FOR CRACK DETECTION AND MEASUREMENT ON CONCRETE SURFACE." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2/W8 (November 14, 2017): 237–41. http://dx.doi.org/10.5194/isprs-archives-xlii-2-w8-237-2017.

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Crack detection and measurement in the surface of concrete structures is currently carried out manually or through Non-Destructive Testing (NDT) such as imaging or scanning. The recent developments in depth (stereo) cameras have presented an opportunity for cost-effective, reliable crack detection and measurement. This study aimed at evaluating the feasibility of the new inexpensive depth camera (ZED) for crack detection and measurement. This depth camera with its lightweight and portable nature produces a 3D data file of the imaged surface. The ZED camera was utilized to image a concrete surface and the 3D file was processed to detect and analyse cracks. This article describes the outcome of the experiment carried out with the ZED camera as well as the processing tools used for crack detection and analysis. Crack properties that were also of interest were length, orientation, and width. The use of the ZED camera allowed for distinction between surface and concrete cracks. The ZED high-resolution capability and point cloud capture technology helped in generating a dense 3D data in low-lighting conditions. The results showed the ability of the ZED camera to capture the crack depth changes between surface (render) cracks, and crack that form in the concrete itself.

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Garami, Tamás, Oliver Krammer, Gábor Harsányi, and Péter Martinek. "Method for validating CT length measurement of cracks inside solder joints." Soldering & Surface Mount Technology 28, no. 1 (February 1, 2016): 13–17. http://dx.doi.org/10.1108/ssmt-10-2015-0029.

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Purpose – This paper aims to develop a method to measure the length of cracks inside solder joints, which enables the validation of computed tomography (CT) crack length measurements. Design/methodology/approach – Cracks were formed inside solder joints intentionally by aging solder joints of 0603 size resistors with thermal shock (TS) test (−40 to +140°C, 2,000 cycles), and CT images were captured about them with different rotational increment (1/4, 1/2 and 1°) of sample projection. The length of cracks was also measured with our method, which is based on capturing high-resolution radiography X-ray images about the cracks in two perpendicular projection planes. The radiography results were compared to the CT measurements. The percentage error for the different CT rotational increment settings was calculated, and the optimal CT settings have been determined. Findings – The results have proven that reducing the rotational increment increases the sharpness of the captured images and the accuracy of crack length measurements. Nevertheless, the accuracy compared to high-resolution radiography measurements is only slightly better at 1/4° rotational increment than in the case of 1/2° rotational increment. It should be also noted that the 1/4° increment requires twice as much time for capturing the images as the 1/2° increment. So, the 1/2° rotational increment of sample projection is the optimal setting in our investigated case for measuring crack lengths. Practical implications – The developed method is applicable to find the optimal settings for CT crack length measurements, which provides faster analysation of large quantity samples used, e.g. at life-time tests. Originality/value – There is a lack of information in the literature regarding the optimisation of CT measurement set-up, e.g. a slightly larger value of the sample rotational increment can provide acceptable resolution with much faster processing time. Thus, the authors developed a method and performed research about optimising CT measurement parameters.

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Cobb, A. C., J. E. Michaels, and T. E. Michaels. "An integrated approach to local ultrasonic monitoring of fastener hole fatigue cracks." Aeronautical Journal 113, no. 1150 (December 2009): 775–88. http://dx.doi.org/10.1017/s0001924000003432.

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Abstract Ultrasonic nondestructive evaluation methods are routinely used to detect and size fatigue cracks near fastener holes in aircraft structures as a part of scheduled maintenance. In contrast, statistical crack propagation models provide an estimate of the expected fatigue life assuming a known crack size and future fatigue loadings. Here an integrated approach for in situ diagnosis and prognosis of fastener hole fatigue cracks is proposed and implemented that incorporates both ultrasonic monitoring and crack growth laws. The sensing method is an ultrasonic angle beam technique, and cracks are automatically detected from the ultrasonic response. An extended Kalman filter is applied to combine ultrasonically estimated crack sizes with a crack growth law, effectively using the time history of the ultrasonic results rather than only the most recent measurement. A natural extension of this method is fatigue life prognosis. Results from fatigue tests on 7075-T651 aluminium coupons show improved crack size estimates as compared to those obtained from ultrasonic measurements alone, and also demonstrate the capability of predicting the remaining life. This approach for fatigue crack detection, sizing and prognosis is an example of a general strategy for in situ monitoring of structural damage whereby improved results are achieved from the integration of noisy measurements with imperfect crack growth models.

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Reisgen, Uwe, Christoph Geffers, Rahul Sharma, and Jana von der Heydt. "In Situ Measurement of Thermal Strain during Fusion Welding." Materials Science Forum 768-769 (September 2013): 644–51. http://dx.doi.org/10.4028/www.scientific.net/msf.768-769.644.

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Temperature-induced strain with, at the same time, reduced formability is, among other things, responsible for crack development in the range of high temperatures. For a more detailed examination of these so-called hot cracks, experimental measurements of the strain during the welding process have been carried out using neutron diffraction. The measurement of strain is important since it exerts decisive influence on the development of cracks.

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Shuang-rui, Chen, Shi Zheng, and Yan Quan-sheng. "Concrete Crack Width Detecting System for Android Platform." Open Civil Engineering Journal 9, no. 1 (October 13, 2015): 846–51. http://dx.doi.org/10.2174/1874149501509010846.

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In order to measure crack width accurately and automatically, an Android-based Automatic Crack Width Measuring System (ACWMS) has been developed, taking advantage of the high portability of Android devices. After capturing the image using mobile phone camera, the image is processed by image processing techniques, including graying, binaryzation, denoising and edge recognition. A specified algorithm is executed to calculate the crack width according to the provided edge data. Measurements has been done to each of the 10 cracks in the same concrete beam, using Samsung Galaxy S3 mobile phone and WYSX-40X Crack detector, respectively. Test result shows that the maximum crack width accuracy reaches 95.26%, which satisfies the construction needs. Therefore, this system can greatly improve the efficiency and accuracy during crack width measurement.

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12

Fan, Zhun, Chong Li, Ying Chen, Paola Di Mascio, Xiaopeng Chen, Guijie Zhu, and Giuseppe Loprencipe. "Ensemble of Deep Convolutional Neural Networks for Automatic Pavement Crack Detection and Measurement." Coatings 10, no. 2 (February 8, 2020): 152. http://dx.doi.org/10.3390/coatings10020152.

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Automated pavement crack detection and measurement are important road issues. Agencies have to guarantee the improvement of road safety. Conventional crack detection and measurement algorithms can be extremely time-consuming and low efficiency. Therefore, recently, innovative algorithms have received increased attention from researchers. In this paper, we propose an ensemble of convolutional neural networks (without a pooling layer) based on probability fusion for automated pavement crack detection and measurement. Specifically, an ensemble of convolutional neural networks was employed to identify the structure of small cracks with raw images. Secondly, outputs of the individual convolutional neural network model for the ensemble were averaged to produce the final crack probability value of each pixel, which can obtain a predicted probability map. Finally, the predicted morphological features of the cracks were measured by using the skeleton extraction algorithm. To validate the proposed method, some experiments were performed on two public crack databases (CFD and AigleRN) and the results of the different state-of-the-art methods were compared. To evaluate the efficiency of crack detection methods, three parameters were considered: precision (Pr), recall (Re) and F1 score (F1). For the two public databases of pavement images, the proposed method obtained the highest values of the three evaluation parameters: for the CFD database, Pr = 0.9552, Re = 0.9521 and F1 = 0.9533 (which reach values up to 0.5175 higher than the values obtained on the same database with the other methods), for the AigleRN database, Pr = 0.9302, Re = 0.9166 and F1 = 0.9238 (which reach values up to 0.7313 higher than the values obtained on the same database with the other methods). The experimental results show that the proposed method outperforms the other methods. For crack measurement, the crack length and width can be measure based on different crack types (complex, common, thin, and intersecting cracks.). The results show that the proposed algorithm can be effectively applied for crack measurement.

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Reisgen, Uwe, Rahul Sharma, and Jana von der Heydt. "Neutron Diffraction Strain Measurement during TIG Welding." Advanced Materials Research 996 (August 2014): 424–30. http://dx.doi.org/10.4028/www.scientific.net/amr.996.424.

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Development of hot cracks during welding of austenitic materials is a challenge which must be coped with when a suitable welding method is to be chosen. Boundary conditions about hot crack formation are not sufficiently known. One factor is the state of strain during welding. Therefore strain is determined via neutron diffractometry next to the fusion line during welding. This evaluation shall allow to draw conclusions about the influence of the state of thermal strain on the hot crack formation.

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Zehnder, Alan T., and Ares J. Rosakis. "Experimental Measurement of the Temperature Rise Generated During Dynamic Crack Growth in Metals." Applied Mechanics Reviews 43, no. 5S (May 1, 1990): S260—S265. http://dx.doi.org/10.1115/1.3120822.

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During the high speed propagation of cracks, large temperature increases occur at the crack tip due to the intense dissipation of plastic work there. This increased temperature may have a significant effect of the material’s dynamic fracture toughness. An experimental investigation of the temperature fields at the tip of dynamically propagating cracks in 4340 steel was performed using a focused array of high speed, infrared detectors. Temperature fields were measured for cracks growing at speeds from 700m/s to 1900m/s. Maximum temperature increases were as high as 465°C. The temperature fields were differentiated to determine the plastic work rate distribution at the crack tip and to estimate the plastic strain rate. Effects of crack tip heating on dynamic fracture toughness are discussed.

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WOO, SANG-KYUN, YOUNG-CHUL SONG, and HONG-CHUL RHIM. "MEASUREMENT OF CRACK DEPTH LOCATED UNDER REINFORCEMENT IN REINFORCED CONCRETE SPECIMENS USING ULTRASONIC METHOD." Modern Physics Letters B 22, no. 11 (May 10, 2008): 1019–24. http://dx.doi.org/10.1142/s0217984908015772.

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The objective of this study is to determine crack depth located under reinforcement in concrete specimens using ultrasonic method. Experimental studies were performed on concrete specimens containing vertical and inclined surface-opening cracks with known depths. Experimental results have shown that the crack depth can be effectively measured when the distance between the probes is less than the crack depth. The effect of reinforcement on crack depth estimation is studied through a model by considering P-wave diffraction at the tip of crack and reinforcement. In addition, experimental results show that the ultrasonic method is one of useful methods to evaluate the crack depth in reinforced concrete.

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KONDO, Yoshiyuki, and Seishiro TOMIOKA. "Automatic Crack Length Measurement Using Crack Tip Singularity." Transactions of the Japan Society of Mechanical Engineers Series A 57, no. 539 (1991): 1502–5. http://dx.doi.org/10.1299/kikaia.57.1502.

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Bär, Jürgen. "Crack Detection and Crack Length Measurement with the DC Potential Drop Method–Possibilities, Challenges and New Developments." Applied Sciences 10, no. 23 (November 29, 2020): 8559. http://dx.doi.org/10.3390/app10238559.

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The direct current potential drop method (DCPDM) is widely used to determine the crack length in fatigue experiments. In practice, some special features of this method must be considered. Aside from general information on the experimental setup and calibration, some special features of the method, such as the influence of the ambient atmosphere and the application of the method to ferromagnetic materials, are presented and discussed. In addition, with the multiple potential drop measurement, a method is presented which improves the resolution of the DCPDM for detection of cracks and allows to determine crack initiation sites. The capabilities provided by this method are demonstrated on the basis of measurements undertaken on notched round bars and single edged notched specimens.

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Shi, Bei-xiao, Cheng-feng Zheng, and Jin-kun Wu. "Research Progress on Expansive Soil Cracks under Changing Environment." Scientific World Journal 2014 (2014): 1–6. http://dx.doi.org/10.1155/2014/816759.

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Engineering problems shunned previously rise to the surface gradually with the activities of reforming the natural world in depth, the problem of expansive soil crack under the changing environment becoming a control factor of expansive soil slope stability. The problem of expansive soil crack has gradually become a research hotspot, elaborates the occurrence and development of cracks from the basic properties of expansive soil, and points out the role of controlling the crack of expansive soil strength. We summarize the existing research methods and results of expansive soil crack characteristics. Improving crack measurement and calculation method and researching the crack depth measurement, statistical analysis method, crack depth and surface feature relationship will be the future direction.

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Anandika, R., J. Lundberg, and C. Stenström. "Phased array ultrasonic inspection of near-surface cracks in a railhead and its verification with rail slicing." Insight - Non-Destructive Testing and Condition Monitoring 62, no. 7 (July 1, 2020): 387–95. http://dx.doi.org/10.1784/insi.2020.62.7.387.

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In this study, near-surface cracks in a railhead are inspected thoroughly using phased array ultrasonic testing (PAUT). This research finds an alternative technique to inspect for near-surface cracks because the conventional non-destructive testing method for rail inspection lacks the capacity to inspect the near-surface crack profile. This study shows that PAUT can determine not only the crack depth but also the near-surface crack profile, so that the inspector can estimate the stage of crack growth and how the crack propagates. This information is valuable to the rail maintainer as one of the considerations for deciding the thickness of metal to remove when grinding the rail. In this study, after the measurement, the inspected region of the cracked railhead is sliced into thin pieces so that crack network information can be extracted. A 3D image reconstruction of the surface cracks based on the crack marks from all of the sliced rail pieces is performed. This image is then used as a reference to confirm the PAUT results. The results show that PAUT can clearly deliver crack profile estimation and provide an accurate estimation of a 3.51 mm crack-tip depth with an absolute error range of 8%-18%. The results also suggest that PAUT is a potential method for installation in a measurement train for near-surface crack inspection.

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Sener, Ummu S., and Sebahattin Eker. "Nondestructive Approach for Complex-Shaped Cracks in Concrete Structures by Electromagnetic Waves with FDTD Technique." Mathematical Problems in Engineering 2021 (June 1, 2021): 1–14. http://dx.doi.org/10.1155/2021/6624982.

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Concrete cracks have no specific shape and do not show linearity. Since the natural occurrences of concrete cracks make simulation identification difficult, rectangular step function and a dynamic geometry are used to define a concrete surface crack in the natural process. A novel interior crack expression is obtained by accepting the area between two curves as a crack filled by air in concrete and modeling this area like a Riemann integral domain. Taking the partition of this integral domain, the most realistic definition of the crack is made. Electromagnetic (EM) waves are utilized for numerical simulation after identifying the defects, cracks, rebars, and geometry of concrete. Three different simulation setups with complex geometries with two different surface cracks and one internal crack are simulated using a finite-difference time-domain (FDTD) method with Gaussian pulse wave excitation. Simulations are obtained using both transverse electric (TEz) waves and transverse magnetic (TMz) waves and the results are compared with each other. Air-dried concrete specimens are molded following simulation setups with surface cracks and measurements are made nondestructively with a Vivaldi antenna array in the frequency range of 0.4–4.0 GHz. The reflection and transmission coefficients are validated by comparing the data obtained using the measurement with the results obtained from numerical simulation.

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Tanaka, Keisuke, Takahisa Shobu, and Hiroshi Kimachi. "Hybrid Measurement of CT and Strain Distribution of Internal Crack Using Synchrotron High-Energy Monochromatic X-Rays." Materials Science Forum 652 (May 2010): 202–9. http://dx.doi.org/10.4028/www.scientific.net/msf.652.202.

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Using high-energy monochromatic X-rays of energy 66.4keV from the synchrotron radiation source, SPring-8, we have developed a system to perform a hybrid measurement of imaging of cracks and strain distribution around cracks. This system was applied to a fatigue crack made in a round bar made of carbon steel with a diameter of 4 mm. Computed tomography of the specimen gave the three-dimensional shape of a thumb-nail crack. High tensile strain ahead of the crack was measured at the applied maximum stress, while the strain on the crack face was low because of stress relief due to crack opening. The full width at half maximum (FWHM) increased near the crack tip under loading, and then decreased after unloading. The recoverable part of FWHM by unloading was caused by the steep distribution of the applied stress in the vicinity of the crack tip. The FWHM increased by plastic deformation does not change when unloaded. The measured distributions of the lattice strain and FWHM agreed well with those of the elastic and plastic strains calculated by the finite element method, respectively.

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Liu, H., M. Saka, H. Abe', I. Komura, and H. Sakamoto. "Analysis of Interaction of Multiple Cracks in a Direct Current Field and Nondestructive Evaluation." Journal of Applied Mechanics 66, no. 2 (June 1, 1999): 468–75. http://dx.doi.org/10.1115/1.2791071.

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A method of analysis is proposed for nondestructive evaluation of multiple cracks by means of the d.c. (direct current) potential drop technique. Two and three-dimensional multiple cracks are treated. A methodology for considering interaction of cracks based on the equation for an isolated crack is given to calculate the potential drop between both sides of a crack in multiple cracking in a plate. The inverse problem to evaluate the crack depth is analyzed by comparing the potential drop calculated in this way with the measurement. It is shown that the evaluated crack depth is in good agreement with the actual one.

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Jia, Jun, Haifeng Hu, Limin Tao, and Yongpan Hu. "In situ measurement of fatigue crack opening stresses by nonlinear vibro-acoustic modulation testing." Advances in Mechanical Engineering 9, no. 7 (July 2017): 168781401770626. http://dx.doi.org/10.1177/1687814017706265.

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The difficulty of accurately measuring crack closure regions has hindered measurements of opening or closure stresses, and ultrasonic methods have shown great potentialities in evaluating closure area. Many recent researches have confirmed the advantages of nonclassical nonlinear acoustic approaches in detecting short cracks and even micro- or meso-cracks. However, there are few reports on using nonclassical nonlinear acoustic approaches to measure crack closure. The aim of this article is to verify the applicability of vibro-acoustic modulation approach in estimating opening stresses of fatigue cracks. A procedure of approximating the opening stress by the applied tensile load of the inflection point of the modulation intensity curve is proposed. To study the performance of this measuring method experimentally, in situ vibro-acoustic modulation tests were carried out on a central cracked 5052-H32 aluminum alloy fatigue sample. The experimental estimations match well with other researches. Analysis of the experimental results suggests that the vibro-acoustic modulation technology is not only capable of measuring the fatigue cracks opening stresses, but also capable of analyzing the crack closure behavior, even for physically short cracks.

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Akiniwa, Yoshiaki, Keisuke Tanaka, and Hidehiko Kimura. "Measurement of Stress Distribution Near Fatigue Crack in Ultra-Fine Grained Steel by Synchrotron Radiation." Materials Science Forum 490-491 (July 2005): 118–23. http://dx.doi.org/10.4028/www.scientific.net/msf.490-491.118.

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Single-edge-notched specimens of ultrafine-grained steel were fatigued. The mean grain size of the steel is about 2 micrometers. Propagation behavior of fatigue cracks was observed with the crack closure. The resistance of the crack propagation of ultrafine-grained steel was larger than that of conventional steels. The crack closure acted as an important role for the larger resistance of fatigue crack propagation. After fatigue tests, stress distribution near the fatigue crack was measured by monochromatic X-rays from synchrotron radiation. The irradiated area was 100 µm x 100 µm. Residual and loading stress distributions ahead of the crack tip and on the crack wake was measured at the maximum stress intensity factor and zero applied load. The stress was determined by sin2ψ method. The measured stress was compared with the value calculated by FEM and the fatigue crack propagation model. The stress distribution at the maximum load and residual stresses agreed very well with the calculated results. The crack opening stress calculated by the residual stresses agreed with the experimental result.

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Liu, Tingjin, Honghao Huang, and Yubing Yang. "Crack Detection of Reinforced Concrete Member Using Rayleigh-Based Distributed Optic Fiber Strain Sensing System." Advances in Civil Engineering 2020 (July 25, 2020): 1–11. http://dx.doi.org/10.1155/2020/8312487.

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Early detection of crack is critical for the maintenance of reinforced concrete (RC) structures. In this study, a distributed optical fiber (DOF) sensing system with Rayleigh Optical Frequency Domain Reflectometry (OFDR) technique was deployed to a member of RC structure in a full-scale laboratory experiment, which was subjected to a monotonic lateral load. With the aid of a high space resolution (up to 1 mm) and measurement accuracy (±1 micro strain) interrogator (OSI-S by Semicon), continuous strain measurements inside of the RC member are elaborately implemented. The result of crack detection by the analysis of the measured tensile strain profiles is in excellent agreement with the visually observable cracks mapped during the test. This confirms the ability of the optical fiber inside of RC members to capture cracks on concrete surface. Moreover, the recognition of crack orientation and depth is accomplished by comparing strain measurements of optical fibers installed at multiple locations.

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Xu, Xiangyang, and Hao Yang. "Intelligent crack extraction and analysis for tunnel structures with terrestrial laser scanning measurement." Advances in Mechanical Engineering 11, no. 9 (September 2019): 168781401987265. http://dx.doi.org/10.1177/1687814019872650.

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An automatic and intelligent method for crack detection is significantly important, considering the popularity of large constructions. How to identify the cracks intelligently from massive point cloud data has become increasingly crucial. Terrestrial laser scanning is a measurement technique for three-dimensional information acquisition which can obtain coordinates and intensity values of the laser reflectivity of a dense point cloud quickly and accurately. In this article, we focus on the optimal parameter of Gaussian filtering to balance the efficiency of crack identification and the accuracy of crack analysis. The innovation of this article is that we propose a novel view of the signal-to-noise ratio gradient for Gaussian filtering to identify and extract the cracks automatically from the point cloud data of the terrestrial laser scanning measurement.

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Barter, S., P. White, and M. Burchill. "Fatigue crack path manipulation for crack growth rate measurement." Engineering Fracture Mechanics 167 (November 2016): 224–38. http://dx.doi.org/10.1016/j.engfracmech.2016.04.020.

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Xu, Song, Xiao Ming Tang, Ming Chen, Yuan Da Su, Yu Ping Qian, Dianqiang Sun, and Carlos Torres-Verdín. "Estimation of directional crack density and fluid properties from well logs in vertical wells." GEOPHYSICS 86, no. 4 (June 15, 2021): D113—D124. http://dx.doi.org/10.1190/geo2020-0710.1.

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The study of elastic properties of fractured/cracked rocks has been an important subject of interest in seismology and geophysical exploration. Downhole logging provides a direct measurement of fractured rock properties in terms of elastic wave velocities and anisotropy. Most existing studies only provide qualitative descriptions of fracture properties as evidenced from the acquired measurements. To better use downhole measurements, we have derived a comprehensive theoretical analysis and developed an inversion technique to characterize fracture properties. Theoretical results for cracked rocks show that crack density, crack alignment direction, and crack filling materials are the three main fracture parameters that strongly affect the elastic wave properties of fractured rocks. Furthermore, a detailed analysis of the crack effects on elastic properties shows that the measured elastic moduli can be used to evaluate the crack parameters of cracked rocks. We assume that cracks with any orientational distribution can be divided into two parts: horizontal and vertical. Based on the theoretical analysis, we develop an inversion method to estimate fracture parameters from well logs acquired in a vertical borehole. We assume a rock-physics model for rocks that adds effective horizontal and vertical cracks that are filled with liquid in an isotropic background, the elastic and fluid properties of which are inverted from the measured logs. The inversion method enables the quantification of the directional crack density and crack-filling material when applied to field logging measurements acquired in fractured formations. Theoretically predicted fracture properties are validated with formation microresistivity scan logging data and are consistent with the interpretation results.

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Brueckner-Foit, Angelika, Pascal Pitz, Frank Zeismann, and Lisa Zellmer. "Influence of Martensitic Phase on Microcrack Propagation in a Ferritic-Martensitic Steel." Advanced Materials Research 891-892 (March 2014): 301–6. http://dx.doi.org/10.4028/www.scientific.net/amr.891-892.301.

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Hard phases such as martensite regions affect micro-crack extension by blocking the plastic zone ahead of the crack tip, but also by changing the crack opening which can be taken as loading quantity for cracks. This paper deals with the measurement of crack opening for microcracks in a ferrite/martensite dual phase steel. The methods used are in-situ testing in the SEM, X-ray tomography, and digital image correlation. It was found that martensite regions affect the relative displacement of the crack phases both at the crack tip and in the crack wake.

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Wu, Ziling, Ting Yang, Zhifei Deng, Baokun Huang, Han Liu, Yu Wang, Yuan Chen, Mary Caswell Stoddard, Ling Li, and Yunhui Zhu. "Automatic Crack Detection and Analysis for Biological Cellular Materials in X-Ray In Situ Tomography Measurements." Integrating Materials and Manufacturing Innovation 8, no. 4 (November 25, 2019): 559–69. http://dx.doi.org/10.1007/s40192-019-00162-3.

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AbstractWe introduce a novel methodology, based on in situ X-ray tomography measurements, to quantify and analyze 3D crack morphologies in biological cellular materials during damage process. Damage characterization in cellular materials is challenging due to the difficulty of identifying and registering cracks from the complicated 3D network structure. In this paper, we develop a pipeline of computer vision algorithms to extract crack patterns from a large volumetric dataset of in situ X-ray tomography measurement obtained during a compression test. Based on a hybrid approach using both model-based feature filtering and data-driven machine learning, the proposed method shows high efficiency and accuracy in identifying the crack pattern from the complex cellular structures and tomography reconstruction artifacts. The identified cracks are registered as 3D tilted planes, where 3D morphology descriptors including crack location, crack opening width, and crack plane orientation are registered to provide quantitative data for future mechanical analysis. This method is applied to two different biological materials with different levels of porosity, i.e., sea urchin (Heterocentrotus mamillatus) spines and emu (Dromaius novaehollandiae) eggshells. The results are verified by experienced human image readers. The methodology presented in this paper can be utilized for crack analysis in many other cellular solids, including both synthetic and natural materials.

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Černý, Ivo. "Measurement of Local Initiation, Early Growth and Retardation of Physically Short Fatigue Cracks Using Amended DCPD Method." Key Engineering Materials 586 (September 2013): 19–22. http://dx.doi.org/10.4028/www.scientific.net/kem.586.19.

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Different experimental methods are being used in laboratories for automatic measurement of fatigue crack growth rates and threshold values. Such data belong to mechanical properties essential for an assessment of residual life of components and structures containing cracks of length more than several millimetres. However, if the material contains small crack-like defects like inclusions or pores, knowledge about local resistance against fatigue growth of physically short cracks becomes very important. Damage mechanisms are even more complicated in case of a presence of subsurface residual stress field, e.g. due to technological effects. Experimental difficulties connected with investigation of short fatigue crack growth (FCG) can be reduced in case of use of automatic indirect methods. The aim of the work described in this paper was to explore possibilities and limits of the use of DCPD (direct current potential drop) method for physically short crack measurement and to use the optimised method for an evaluation of local damage process of initiation and early growth of short fatigue crack in residual stress field induced by shot peening.

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Sakaue, Kenichi, and Shinichi Suzuki. "OS01W0279 Measurement of the crack opening displacement of rapidly bifurcating crack on both surfaces of PMMA specimens." Abstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics 2003.2 (2003): _OS01W0279. http://dx.doi.org/10.1299/jsmeatem.2003.2._os01w0279.

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Lee, Yung-Chun, and Shi Hoa Kuo. "Depth Measurement of Surface-Breaking Cracks Using Point-Source/Point-Receiver Acoustic Transducer." Journal of Mechanics 19, no. 4 (December 2003): 425–29. http://dx.doi.org/10.1017/s1727719100003270.

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ABSTRACTA newly developed point-source/point-receiver (PS/PR) acoustic transducer is used for measuring the depth of surface-breaking cracks. The transducer consists of two miniature conical PZT elements which form a transmitter/receiver pair for generating and detecting surface waves. A tone-burst measurement system operates the PS/PR transducer at a fixed frequency. When a surface-breaking crack is present in between the transmitter and receiver, the change in time-of-flight of surface wave propagation caused by the crack is measured and used to estimate the crack depth. To verify the feasibility of this method, machined slots on a carbon steel sample are tested by the PS/PR transducer for crack depth determination. Good experimental results are obtained. Future applications and improvements on the PS/PR transducer system are addressed.

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Liew, Chi Hoe, Foo Wei Lee, Yee Ling Lee, and Ming Han Lim. "Behavioural Study of Concrete Surface Crack Filling Conditions on Surface Rayleigh Wave." MATEC Web of Conferences 278 (2019): 01013. http://dx.doi.org/10.1051/matecconf/201927801013.

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In the recent studies of concrete surface crack non-destructive test (NDT), the environmental factors are seldom to be taken into assessment consideration using Rayleigh wave (R-wave) propagation method. Dust, fine sand or water that accumulated in the concrete surface cracks might potentially affect the behaviour of R-wave when it propagated through the cracks. In this study, the effects of filling conditions in concrete surface crack to the properties of R-wave were examined. The targeted parameters that used for studying the behaviour of R-wave are the arrival time of R-wave and its corresponding amplitude. Numerical simulations were conducted for determining the changes of R-wave amplitudes and arrival time when it propagated through a concrete model with a surface crack which containing various filling conditions. Sand and charcoal powder were the materials used for filling the concrete cracks. The results of numerical simulations were then justified by experimental measurements. The comparison between the results of numerical simulation and experimental measurement generated a conclusion where R-wave arrival time and its corresponding amplitude is independent from the predefined filling conditions of concrete surface crack.

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McGuire, S. M., M. E. Fine, O. Buck, and J. D. Achenbach. "Nondestructive detection of fatigue cracks in PM 304 stainless steel by internal friction and elasticity." Journal of Materials Research 8, no. 9 (September 1993): 2216–23. http://dx.doi.org/10.1557/jmr.1993.2216.

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A resonant frequency mechanical vibration method was used to nondestructively detect fatigue crack initiation in notched 304 stainless steel samples prepared by powder metallurgy. This method allowed the determination of an effective elastic modulus and the direct measurement of internal friction. Changes in the modulus and internal friction were found to correlate well with the presence of 50 μm long fatigue cracks. The length of the through cracks initiated at the notch was measured using surface replicas, which were examined in a scanning electron microscope. Small crack growth rate data were also obtained and plotted versus the stress intensity factor. The crack growth rates were compared with long crack data performed on compact tension samples of this material. The short cracks grew at intensity factors below the long crack threshold stress intensity factor.

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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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Xu, Xiangyang, and Hao Yang. "Vision Measurement of Tunnel Structures with Robust Modelling and Deep Learning Algorithms." Sensors 20, no. 17 (September 1, 2020): 4945. http://dx.doi.org/10.3390/s20174945.

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The health monitoring of tunnel structures is vital to the safe operation of railway transportation systems. With the increasing mileage of tunnels, regular inspection and health monitoring are urgently demanded for the tunnel structures, especially for information regarding deformation and damage. However, traditional methods of tunnel inspection are time-consuming, expensive and highly dependent on human subjectivity. In this paper, an automatic tunnel monitoring method is investigated based on image data which is collected through the moving vision measurement unit consisting of camera array. Furthermore, geometric modelling and crack inspection algorithms are proposed where a robust three-dimensional tunnel model is reconstructed utilizing a B-spline method and crack identification is conducted by means of a Mask R-CNN network. The innovation of this investigation is that we combine the robust modelling which could be applied for the deformation analysis and the crack detection where a deep learning method is employed to recognize the tunnel cracks intelligently based on image sensors. In this study, experiments were conducted on a subway tunnel structure several kilometers long, and a robust three-dimensional model is generated and the cracks are identified automatically with the image data. The superiority of this proposal is that the comprehensive information of geometry deformation and crack damage can ensure the reliability and improve the accuracy of health monitoring.

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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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Goto, Masahiro, Takaei Yamamoto, Junichi Kitamura, Seung Zeon Han, R. Takanami, Terutoshi Yakushiji, and J. H. Lee. "Growth Rate of Small Surface-Cracks in Age Hardening Cu-Ni-Si Alloy under Cyclic Stressing." Key Engineering Materials 827 (December 2019): 216–21. http://dx.doi.org/10.4028/www.scientific.net/kem.827.216.

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Stress-controlled fatigue tests were conducted on round-bar specimens to understand the fatigue behavior of precipitate-strengthened Cu–6Ni–1.5Si alloy. The cracks were initiated at the grain boundaries, followed by growth along the crystallographic slip planes in the adjacent grains. The crack growth data of plain specimens exhibited a large scatter, resulting in a difficulty of the measurement of crack growth rate. To evaluate the small-crack growth rate of the alloy, the plain specimens with a small blind hole as the crack starter were fatigued. The crack growth rate of small cracks from the hole was uniquely determined by a term σanl and the material constant, n, was 5.3. The term σanl with n = 5.3 was applied to the plain specimen, showing good applicability of the term to small cracks in the plain specimen.

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Renshaw, Jeremy, Stephen D. Holland, and R. Bruce Thompson. "Measurement of crack opening stresses and crack closure stress profiles from heat generation in vibrating cracks." Applied Physics Letters 93, no. 8 (August 25, 2008): 081914. http://dx.doi.org/10.1063/1.2976310.

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Toda, Hiroyuki, Shin Yamamoto, Kentaro Uesugi, Masakazu Kobayashi, and Toshiro Kobayashi. "OS16-2-5 3-D measurement of crack-tip opening displacement along crack front line via synchrotron microtomography." Abstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics 2007.6 (2007): _OS16–2–5——_OS16–2–5—. http://dx.doi.org/10.1299/jsmeatem.2007.6._os16-2-5-.

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Shimizu, Kenichi, Yoshiki Natsumeda, and Hiroaki Chikaishi. "OS12F123 Evaluation of Fatigue Crack Propagation Behavior in Copper Films Based on Measurement of Crack Opening Displacement Distribution." Abstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics 2011.10 (2011): _OS12F123——_OS12F123—. http://dx.doi.org/10.1299/jsmeatem.2011.10._os12f123-.

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Yang, Chang, and Wu. "Damage Indexing Method for Shear Critical Tubular Reinforced Concrete Structures based on Crack Image Analysis." Sensors 19, no. 19 (October 4, 2019): 4304. http://dx.doi.org/10.3390/s19194304.

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Image analysis techniques have been applied to measure the displacements, strain field, and crack distribution of structures in the laboratory environment, and present strong potential for use in structural health monitoring applications. Compared with accelerometers, image analysis is good at monitoring area-based responses, such as crack patterns at critical regions of reinforced concrete (RC) structures. While the quantitative relationship between cracks and structural damage depends on many factors, cracks need to be detected and quantified in an automatic manner for further investigation into structural health monitoring. This work proposes a damage-indexing method by integrating an image-based crack measurement method and a crack quantification method. The image-based crack measurement method identifies cracks locations, opening widths, and orientations. Fractal dimension analysis gives the flexural cracks and shear cracks an overall damage index ranging between 0 and 1. According to the orientations of the cracks analyzed by image analysis, the cracks can be classified as either shear or flexural, and the overall damage index can be separated into shear and flexural damage indices. These damage indices not only quantify the damage of an RC structure, but also the contents of shear and flexural failures. While the engineering significance of the damage indices is structure dependent, when the damage indexing method is used for structural health monitoring, the damage indices safety thresholds can further be defined based on the structure type under consideration. Finally, this paper demonstrates this method by using the results of two experiments on RC tubular containment vessel structures.

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Suzuki, Shinichi, and Kenichi Sakaue. "OS01W0244 Measurement of crack opening displacement and energy release rate of rapidly bifurcating cracks by high-speed holographic microscopy." Abstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics 2003.2 (2003): _OS01W0244. http://dx.doi.org/10.1299/jsmeatem.2003.2._os01w0244.

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Rajic, Nik, and Chris Brooks. "Automated Crack Detection and Crack Growth Rate Measurement Using Thermoelasticity." Procedia Engineering 188 (2017): 463–70. http://dx.doi.org/10.1016/j.proeng.2017.04.509.

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Greve, Anna K., R. Ian Acworth, and Bryce F. Kelly. "Detection of subsurface soil cracks by vertical anisotropy profiles of apparent electrical resistivity." GEOPHYSICS 75, no. 4 (July 2010): WA85—WA93. http://dx.doi.org/10.1190/1.3474590.

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To date, an understanding of crack dynamics has been fundamentally hampered by the lack of available techniques to observe or monitor crack dynamics below the soil surface. A new technique relates the growth of soil cracks to a progressive increase in the electrical anisotropy of the soil. Although a single measurement of anisotropy is possible using a surface array of electrodes, the use of four strings of electrodes installed vertically at the corners of a square provides a valuable picture of the crack pattern at depth. In addition, time-lapse electrical surveys allow the growth of cracks to be clearly monitored. The electrical anisotropy is defined as the ratio of the [Formula: see text]-to-[Formula: see text] apparent resistivity for the square array and is determined for each coplanar set of four electrodesusing one electrode from each of the four vertical strings. In a laboratory, we measured the electrical anisotropy in a sand-filled lysimeter with a plastic sheet, introduced to represent an electrically insulating crack. Measurements were then repeated in a cracking-soil-filled lysimeter. Finally, measurements were made in a field where a flood-irrigated sorghum crop was grown on cracking soil. Measurements under all three conditions demonstrate that the lateral and vertical extents of cracking in a soil profile strongly influence the electrical anisotropy. The larger the cumulative cracking volume, the higher the electrical anisotropy. Soil-moisture changes after crack closure have a minor influence on the measured anisotropy, as have sorghum roots. These experiments demonstrate that electrical-anisotropy profiles are a valuable tool for monitoring crack dynamics within a soil profile.

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Ikiades, Aris A. "Strain Measurement on Cracks Using Fiber Bragg Gratings for Use in Aircraft Composite Skin Repairs." Aerospace 7, no. 9 (September 22, 2020): 138. http://dx.doi.org/10.3390/aerospace7090138.

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Fiber Bragg grating (FBG) sensors have been widely used for measurements of strain and temperature in a host of different applications, including aerospace in composite wings, fuselage structures, and other critical components. Here, we report on a method to measure highly localized intense stress fields, generated at the initialization point of a crack, or crack-tip, using Fiber Bragg Gratings (FBG) inscribed in highly photosensitive hydrogenated germanium and boron co-doped fiber. From the spectral characteristics of short and long FBGs, bonded on a test aluminum coupon with a crack, which simulated damaged skins of an aircraft, the local stresses near the cracks were measured and assessed. As a case study, bespoke composite repair patches were designed and bonded on a coupon, incorporating a number of gratings to monitor the stress distribution with applied force in the composite patch, near the crack.

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Lai, M. O., and C. K. Ng. "Measurement of crack-profiles using AC field measurement method." Journal of Nondestructive Evaluation 13, no. 4 (December 1994): 155–63. http://dx.doi.org/10.1007/bf00742581.

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Song, Qingsong, Yu Chen, Elias Abdoli Oskoui, Zheng Fang, Todd Taylor, Guangwu Tang, Xiangmo Zhao, and Farhad Ansari. "Micro-crack detection method of steel beam surface using stacked autoencoders on massive full-scale sensing strains." Structural Health Monitoring 19, no. 4 (October 10, 2019): 1175–87. http://dx.doi.org/10.1177/1475921719879965.

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Accurate micro-crack detections on the whole surface of civil structures have great significance. Distributed optical fiber sensor based on Brillouin optical time-domain analysis technology exhibits great facility to measure strain distributions along the whole surface of structures with a high spatial resolution, thus providing a potential and competitive solution to the detection problem. However, mainly due to low signal-to-noise ratio in measurements, such sensor system is still limited in crack detection–based structural health monitoring applications. How to extract high-quality micro-crack feature representations from the low signal-to-noise ratio–distributed strain measurements is crucial to solve the problem. It has been demonstrated in field of pattern recognition that deep learning can automatically extract high-quality noise-robust feature representations from mass chaos data. Therefore, a micro-crack detection method is proposed herein based on deep learning to analyze the full-scale strain measurements. Each measurement is normalized and segmented into a set of equal-length subsequences. Autoencoders, a typical kind of building block of deep neural network, are stacked layer-wise into a deep network and then exploited to automatically extract feature representations from the subsequences. Each extracted feature representation is labeled as one of the two categories by a Softmax regression. One category originates in the subsequences acquired from structure sections with crack defects and another from sections without any cracks. The micro-crack detections are achieved by solving such a crack/non-crack binary classification problem. A 15-m-long steel I-beam with artifact crack defects is built up in laboratory to verify the proposed method. Experimental results demonstrate that the minimum size of detectable crack opening width reaches to 23 μm, and besides, the proposed method is significantly better than traditional Fisher linear discriminant analysis method and classical support vector machine on the detection accuracy.

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AKANDA, M. A. Salam, and Masumi SAKA. "Ultrasonic Measurement of Crack Closure Stress." Proceedings of the JSME annual meeting 2002.2 (2002): 147–48. http://dx.doi.org/10.1299/jsmemecjo.2002.2.0_147.

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Journal articles on the topic 'Crack measurement'

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