Crack Patching Research Articles

Surface crack treatment of concrete via nano-modified microbial carbonate precipitation

As a new concrete crack patching technology, microbial self-healing slurries offer favourable characteristics including non-pollution, ecological sustainability and good compatibility with concrete. In this paper, a nano-sio2-modified microbial bacteria liquid, combined with sodium alginate and polyvinyl alcohol, was used to prepare a nano-modified microbial self-healing slurry. This slurry was used to coat concrete under negative pressure in order to verify its restoration effect, and the micromorphology of the resulting microbial mineralization products was observed. The results revealed that patching the concrete using the nano-modified microbial slurry significantly improved its permeability, and increased its carbonization resistance by three times in comparison with the control group. Through a combination of Scanning electron microscopy (SEM) and X-ray diffraction (XRD) observation, it was determined that the microbial mineralization reaction products were mainly calcite crystals, which, integrated with the nano-sio2, sodium alginate and polyvinyl alcohol at the microscopic level, filled the internal pores of concrete, thus improving its durability.

TransCrack: revisiting fine-grained road crack detection with a transformer design.

Prior convolution-based road crack detectors typically learn more abstract visual representation with increasing receptive field via an encoder-decoder architecture. Despite the promising accuracy, progressive spatial resolution reduction causes semantic feature blurring, leading to coarse and incontiguous distress detection. To these ends, an alternative sequence-to-sequence perspective with atransformer network termed TransCrack is introduced for road crack detection. Specifically, an image is decomposed into a grid of fixed-size crack patches, which is flattened with position embedding into a sequence. We further propose a pure transformer-based encoder with multi-head reduced self-attention modules and feed-forward networks for explicitly modelling long-range dependencies from the sequential input in a global receptive field. More importantly, a simple decoder with cross-layer aggregation architecture is developed to incorporate global with local attentions across different regions for detailed feature recovery and pixel-wise crack mask prediction. Empirical studies are conducted on three publicly available damage detection benchmarks. The proposed TransCrack achieves a state-of-the-art performance over all counterparts by a substantialmargin, and qualitative results further demonstrate its superiority in contiguous crack recognition and fine-grained profile extraction. This article is part of the theme issue 'Artificial intelligence in failure analysis of transportation infrastructure and materials'.

Numerical analysis of cracked aluminium panel repaired with functionally graded adhesively bonded patch

Aircraft maintenance is becoming more important as a means of enhancing structural integrity and prolonging the service life of older aircraft. The bonded composite repair is the most popular among the various repair processes because of its ability to join similar and dissimilar materials. In the present research, the performance of a single sided functionally graded adhesively bonded patch on a centre crack aluminium panel was evaluated using 3D FE analysis. The integrity of a graded crack patch repair system is investigated using the fracture mechanics principle. The strain energy release rate (SERR) GI is used to analyse damage/crack growth and evaluated by utilising the virtual crack closure technique (VCCT), which is based on the concept of linear elastic fracture mechanics (LEFM). The gradation of patch is carried out with linear profile with different modulus ratios in the preferred direction such that using more flexible adhesive at centre of crack and stiffer adhesive ahead of crack/damage. From exhaustive finite element analyses, substantial reduction in crack growth driving forces (SERR) is observed in functionally graded crack-patch repair system. Effect of different modulus ratios on SERR has been also studied. In view of above, graded crack-patch repair system can be recommended for designer.

Integrated pixel-level CNN-FCN crack detection via photogrammetric 3D texture mapping of concrete structures

Although multiple learning-based crack detection systems show promising results in detecting cracks with pixel accuracy on individual images, few effectively enable inspection of larger structures. This paper thereby proposes an advanced inspection reporting system based on an integrated CNN-FCN crack detection system applied on the texture space of a footing, enabling crack inspection and display for larger structures. The system, a Convolutional Neural Network (CNN) and a Fully Convolutional Network (FCN), segments cracks at the pixel-level on the texture space, acquired from a 3D model created with photogrammetry techniques. Firstly, the trained CNN is employed to detect crack patches, then imported to the trained FCN system to segment cracks at the pixel-level, and a crack map is then generated which is projected onto a 3D model. This system indicates promising results for footing textures as represented by: Accuracy (99.88%), Precision (82.2%), Recall (90.2%), and F1 Score (86.01%).

An Improved Nondestructive Semantic Segmentation Method for Concrete Dam Surface Crack Images with High Resolution

To nondestructive semantic segment the crack pixels in the image with high resolution, previous methods often use sliding window and the crack patches to train the FCNs, and then use the trained FCNs for crack recognition. However, the FCNs will produce a higher proportion of false crack predictions with messy distributions in the high-resolution image. A CNN-to-FCN method is proposed to solve this problem. The CNN is trained by all the patches for large-scale crack and background recognition, and the screened crack predictions are then segmented by the FCN. A real-world concrete dam surface crack image database is firstly established to verify the improved method. The results indicated that (1) the improved method can extremely avoid the higher proportion of false crack predictions and their messy distributions in the high-resolution image through the full utilization of background patches and large-scale background recognition; (2) the ResNetv2 backbone and DeepLabv3 architecture recommended by the improved method can be further modified by reducing the bottleneck channels and adding a DUC module to achieve better performance; (3) the improved method can also reduce the prediction time when the image has low proportion of crack patches, which becomes more practicable for the engineering applications.

A triple-thresholds pavement crack detection method leveraging random structured forest

Automatic pavement crack detection has attracted increasing attention in the field of national infrastructure maintenance and rehabilitation. However, due to inhomogeneous crack pixel value, miscellaneous crack topology, noisy texture surrounding and multifarious illumination condition, automatic pavement crack detection is still a challenging problem. In this paper, a triple-thresholds pavement crack detection method is proposed leveraging random structured forest. Specifically, channel features and pairwise difference features are exploited to enrich the information of patches that comprise the crack image. We tackle the task of predicting local crack patches in a structured learning framework leveraging random structured forest. After that, a crack score map is generated where each position shows the score of crack in the corresponding position of the original image. Then, a triple-thresholds method is introduced to obtain the preliminary crack detection result from the crack score map as well as suppress the noise. Finally, a new morphological operation is proposed to enhance the continuity of the crack on premise of maintaining crack width of the given tolerance margin. Our approach is evaluated by comparing with six state-of-the-art crack detection algorithms using public data-set CFD. Experimental results show that our method outperforms the counterparts since it achieves 95.95%, 90.59% and 92.59% of precision, recall and F1-score, respectively.

Research on Plant Core, Patch Repair Method of Huizhou Traditional Architecture Timber

Huizhou traditional architecture design method of repair beams is one of the hot spots in the present study of ancient architecture. Based on the basis of a large number of data collection and on-the-spot investigation, research and combined with the national regulations of the traditional building repair method of reinforcement beams, analysis of the Huizhou traditional architecture in timber frame beams damaged reasons, summed up the ancient building timber strength, stiffness the degree of the calculation formula and the core of planting of Huizhou traditional architecture beams by the finite element method, the crack patching reinforcement method is analyzed by numerical simulation. The results show that: when the damaged section beam strength and stiffness, through strengthening after the renovation has been improved; through the core and damaged beams, crack patching reinforcement method after repair is to meet the requirements of the standard. Through theoretical calculation and numerical analysis of beams, the calculation results are consistent, repair reinforcement design verification of Huizhou traditional architecture wooden frame beams The feasibility and feasibility of this method can be used as a reference for the protection and renovation of ancient buildings in Huizhou.

A novel hybrid approach for crack detection

Vision-based crack detection is of crucial importance in various industries, and it is very challenging due to weak signals in noisy backgrounds. In this paper, we propose a novel hybrid approach for crack detection in raw images, which combines deep learning models and Bayesian probabilistic analysis for robust crack detection. First, we re-train a state-of-the-art object detector (e.g. a Faster R-CNN) to detect crack patches of suitable SNR (signal-noise-ratio). We design a semi-automatic method to generate ground truths of crack patches along crack lines for training. To further improve the accuracy of crack detections over the whole image, we propose a Bayesian integration algorithm to suppress false detections. Specifically, we use a deep CNN to recognize the orientation of the crack segment in each detected patch. Then, a Bayesian probability is computed on the accumulated evidence from detected adjacent patches within a neighborhood based on spatial proximity, orientation consistency and alignment consistency. The patch which lacks local supports is suppressed as false detection. An algorithm to learn the parameters of Bayesian integration is also derived. Extensive experiments and evaluations are performed on a new comprehensive dataset of crack images. The results show that our approach outperforms the state-of-the-art baseline approach on deep CNN classifier. Ablation experiments are also conducted to show the effectiveness of proposed techniques.

EA-9320 접착제와 알루미늄 합금의 접착강도 특성에 관한 실험적 연구

The paste-type adhesive can be stored for a certain period of time and can be cured at room temperature. So it is mainly used for crack patching repair of aircraft airframe structures. This study analysed the influence of environmental factors and evaluated the adherence strength characteristics according to the adherence delay time of the paste-type adhesive. The test specimens were made of aluminum alloy(AL 2024-T3) with reference to ASTM D1002 which is generally performed to measure the adherence strength of the adhesive used for metal bonding. As a result of analysing the influence of temperature and humidity, it was found that the optimal temperature range is 24.5±0.5℃ and the optimal humidity range is 71±1% for maintenance work of the aircraft using EA-9320 adhesive. In addition, the adherence strength did not decrease with the inherent application time of the EA-9320, but it was found that the adherence strength dropped rapidly when the applied time exceeded the inherent application time of it.

Overgrazing leads to soil cracking that later triggers the severe degradation of alpine meadows on the Tibetan Plateau

AbstractSoil cracking is an important process and feature of degradation in terrestrial ecosystems. However, the patterns and causes of cracks related to alpine rangeland overgrazing have not been reported. In this study, we used a multiscale approach to investigate the distribution of soil‐cracking areas at a landscape scale (217 survey sites), selected the grazing‐induced parameter that was closely related to the cracks at a small scale (2013–2017), and evaluated the water infiltration due to mosaic cracking at a microscale. The results showed that cracks only formed in the alpine meadow after overstocking. Soil compaction and water content explained 89.0% of the total variance in the crack characteristics, and soil compaction was closely related to cracking. The initial infiltration rate and steady infiltration rate of the healed cracks were significantly higher than those in the raised areas in the centre of the mosaic crack patches (p < .001). We propose a new model of alpine meadow degradation considering the cracking phenomenon due to overgrazing and provide key and easy‐to‐measure indicators to prevent overgrazing and cracking: a residual biomass greater than 65 g m−2 and a height greater than 6 cm, and the soil compaction should be lower than 1,044.26 ± 188.88 kPa. These safeguard thresholds warn rangeland managers to reduce the stocking rate or improve grazing management. We suggest that the cracking stage of alpine rangelands is the most critical turning point in the process of rangeland degradation and that rangeland managers should pay more attention to crack phenomena to prevent severe degradation.

NB-CNN: Deep Learning-Based Crack Detection Using Convolutional Neural Network and Naïve Bayes Data Fusion

Regular inspection of nuclear power plant components is important to guarantee safe operations. However, current practice is time consuming, tedious, and subjective, which involves human technicians reviewing the inspection videos and identifying cracks on reactors. A few vision-based crack detection approaches have been developed for metallic surfaces, and they typically perform poorly when used for analyzing nuclear inspection videos. Detecting these cracks is a challenging task since they are tiny, and noisy patterns exist on the components’ surfaces. This study proposes a deep learning framework, based on a convolutional neural network (CNN) and a Naive Bayes data fusion scheme, called NB-CNN, to analyze individual video frames for crack detection while a novel data fusion scheme is proposed to aggregate the information extracted from each video frame to enhance the overall performance and robustness of the system. To this end, a CNN is proposed to detect crack patches in each video frame, while the proposed data fusion scheme maintains the spatiotemporal coherence of cracks in videos, and the Naive Bayes decision making discards false positives effectively. The proposed framework achieves a 98.3% hit rate against 0.1 false positives per frame that is significantly higher than state-of-the-art approaches as presented in this paper.

Fracture Analysis of Double-Side Adhesively Bonded Composite Repairs to Cracked Aluminium Plate Using Line Spring Model

A line spring model is developed for analyzing the fracture problem of cracked metallic plate repaired with the double-sided adhesively bonded composite patch. The restraining action of the bonded patch is modeled as continuous distributed linear springs bridging the crack faces provided that the cracked plate is subjected to extensional load. The effective spring constant is determined from 1-D bonded joint theory. The hyper-singular integral equation (HSIE), which can be solved using the second kind Chebyshev polynomial expansion method, is applied to determine the crack opening displacements (COD) and the crack tip stress intensity factors (SIF) of the repaired cracked plate. The numerical result of SIF for the crack-tip correlates very well with the finite element (FE) computations based on the virtual crack closure technique (VCCT). The present analysis approaches and mathematical techniques are critical to the successful design, analysis and implementation of crack patching.

A finite element method with mesh‐separation‐based approximation technique and its application in modeling crack propagation with adaptive mesh refinement

SUMMARYThis paper presents a FEM with mesh‐separation‐based approximation technique that separates a standard element into three geometrically independent elements. A dual mapping scheme is introduced to couple them seamlessly and to derive the element approximation. The novel technique makes it very easy for mesh generation of problems with complex or solution‐dependent, varying geometry. It offers a flexible way to construct displacement approximations and provides a unified framework for the FEM to enjoy some of the key advantages of the Hansbo and Hansbo method, the meshfree methods, the semi‐analytical FEMs, and the smoothed FEM. For problems with evolving discontinuities, the method enables the devising of an efficient crack‐tip adaptive mesh refinement strategy to improve the accuracy of crack‐tip fields. Both the discontinuities due to intra‐element cracking and the incompatibility due to hanging nodes resulted from the element refinement can be treated at the elemental level. The effectiveness and robustness of the present method are benchmarked with several numerical examples. The numerical results also demonstrate that a high precision integral scheme is critical to pass the crack patch test, and it is essential to apply local adaptive mesh refinement for low fracture energy problems. Copyright © 2014 John Wiley & Sons, Ltd.

Christchurch City Council lifelines

On 22 February 2011 an earthquake measuring 6.3 on the Richter Scale occurred in Christchurch City resulting in widespread damage to buildings and infrastructure.
 Christchurch City Council (CCC) has an extensive potable water supply network including bulk storage and service reservoirs which provide water to approximately 320,000 residents. Inspections undertaken, following the 22 February earthquake, on 43 concrete reservoirs located on the Port Hills and Cashmere Hills areas noted varying extents of damage from nil through to major. Damaged roof to wall connections were observed in many reservoirs with damage to walls, base-slabs and internal columns limited to a few reservoirs only. Of the 43 reservoirs, complete functional failure occurred in only one, with reduced function and operation at other sites resulting from excessive leakage, necessity for emergency repairs, or associated pipe work damage. Those reservoirs currently out of operation for reinstatement, including Christchurch’s largest, account for approximately 40% of the network’s storage capacity.
 Overall, given the magnitude of earthquake accelerations that occurred on 22 February 2011, the reservoirs are considered to have performed remarkably well. Those in the Port Hills area nearest the earthquake epicentre, have expectedly, incurred the most damage.
 Reinstatement works, varying from minor crack injection and patch repair through to reconstruction and retrofit, have been developed appropriate to the extent of damage. CCC has prioritised reservoir repair to maximise available water supply for the 2011-2012 summer demand and this has required, in some instances, staging and deferring of reinstatement works.
 A summary of structural and functional performance, results of physical investigations and detailed seismic assessments, and common damage areas observed are presented in this paper along with the reinstatement options developed.

Analysis on the effective position of a reinforcement patch used as crack arrest for plates with mixed-mode (I/II) cracks

Rectangular patches are usually used as the temporary crack stoppers ahead of the tips of macro cracks. As mixed-mode cracks are usually initiated in engineering structures, the relative position of reinforcement patches to crack tips should be carefully considered. There will be many directions around crack tips for allocating reinforcement patches and the effectiveness of reinforcement patches should be quite dependent on their allocation positions, which can be expressed by the distance between the crack tip and patch, and also the direction of the patch relative to the crack line. The present paper will aim to examine the proper position for allocating the reinforcement patch by comparing the reduction level of the stress intensity factors. Finite element analysis will be conducted for this purpose. The optimum position for allocating the reinforcement patch will be determined, which will be further compared with crack propagation direction determined by strain energy density theory for an elastic cracked body. The conclusion is drawn that the patch with proper stiffness should be allocated in the direction of initial crack propagation near the crack tips. Its effectiveness will not be satisfactory when allocated away from the region.

모서리균열이 있는 알루미늄판의 복합재 패치보수시 수명예측 연구

노후항공기의 균열보수 방법 중 복합재를 이용한 균열보수 방법을 이용하여 항공기 알루미늄 재료의 피로수명 예측을 위해 유한요소해석을 이용 하였다. 패치보수의 해석 시에는 접착제 층이 매우 얇기 때문에 모델링의 어려움이 있는데, 본 연구에서는 3층 기법을 이용하여 해석을 수행하였다. 피로수명의 예측 시에는 Paris의 법칙을 적용하였고, 효율적 수명예측을 위해 수정된 균열닫힘법을 적용하였다. 해석에 의한 수명예측 결과는 실험치를 잘 모사할 수 있었으며, 항공기의 피로수명 예측이나 수명연장기법으로 활용될 수 있을 것으로 생각된다. One of the hot issues in composite patching is to reduce the thermal residual stresses between composite patch and aluminum surface which occurs after bonding of composite patch. In this study, the edge crack patching is adopted for different curing cycles. For the analysis, three layer Mindlin plate elements are used, and Paris' law is adopted to predict the fatigue life of composite patch plate. The analysis results show a good agreement with the experimental fatigue life and this technique can be applied for the prediction of fatigue life of aircraft structures.

Crack patching revisited

This paper presents the generic relationship between crack length and fatigue life for cracks repaired with an externally bonded composite patch. We then show that the crack growth rate follows the generalised Frost–Dugdale growth law. A simple methodology for predicting crack growth is also presented and validated by comparison with experimental data.

Cubical Marching Squares: Adaptive Feature Preserving Surface Extraction from Volume Data

Computer Graphics ForumVolume 24, Issue 3 p. 537-545 Cubical Marching Squares: Adaptive Feature Preserving Surface Extraction from Volume Data Chien.-Chang Ho, Chien.-Chang Ho National Taiwan University † e-mail: {murphyho, joyce}@cmlab.csie.ntu.edu.twSearch for more papers by this authorFu-Che Wu, Fu-Che Wu National Taiwan University † e-mail: {murphyho, joyce}@cmlab.csie.ntu.edu.twSearch for more papers by this authorBing-Yu Chen, Bing-Yu Chen National Taiwan University ‡ e-mail: robin@ntu.edu.twSearch for more papers by this authorYung-Yu Chuang, Yung-Yu Chuang National Taiwan University § e-mail: {cyy, ming}@csie.ntu.edu.twSearch for more papers by this authorMing Ouhyoung, Ming Ouhyoung National Taiwan University § e-mail: {cyy, ming}@csie.ntu.edu.twSearch for more papers by this author Chien.-Chang Ho, Chien.-Chang Ho National Taiwan University † e-mail: {murphyho, joyce}@cmlab.csie.ntu.edu.twSearch for more papers by this authorFu-Che Wu, Fu-Che Wu National Taiwan University † e-mail: {murphyho, joyce}@cmlab.csie.ntu.edu.twSearch for more papers by this authorBing-Yu Chen, Bing-Yu Chen National Taiwan University ‡ e-mail: robin@ntu.edu.twSearch for more papers by this authorYung-Yu Chuang, Yung-Yu Chuang National Taiwan University § e-mail: {cyy, ming}@csie.ntu.edu.twSearch for more papers by this authorMing Ouhyoung, Ming Ouhyoung National Taiwan University § e-mail: {cyy, ming}@csie.ntu.edu.twSearch for more papers by this author First published: 07 October 2005 https://doi.org/10.1111/j.1467-8659.2005.00879.xCitations: 38 † http://graphics.csie.ntu.edu.tw/CMS/ Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume24, Issue3September 2005Pages 537-545 RelatedInformation

Crack patching: an experimental evaluation of fatigue crack growth

This paper examines the crack growth history of a range of test specimen and service cracking, for cracks repaired with a composite patch and shows that for small to medium crack lengths there is a linear relationship between the log of the crack length and the service history (number of cycles).

Comparison of double and single bonded repairs to symmetric composite structures: a numerical analysis

Owing to the importance of crack patching in fracture mechanics analysis, the aim of this study is to analyse numerically by the finite element method the advantage of the use of the bonded symmetric composite patch for repairing cracks in metallic sheets in mode I and mixed mode. The obtained results show that there is a considerable reduction of the asymptotic value of the stress intensity factor at the crack tip in the case of the use of the double symmetric patch compared with the single patch. In addition the gain of the composite thickness obtained by the double patch is also considerable in both mode one and mixed mode.