Repair Scheme Research Articles

Experimental and Numerical Analysis of Bolted Repair for Composite Laminates with Delamination Damage

Composite materials are widely used in aircraft due to the urgent need for high-quality structures in aerospace engineering. In order to verify the effectiveness of complex bolt repairs on composite structures, compression tests have been performed on three types (intact, damaged, and repaired) of composite plate specimens, and finite element simulation results of these three types’ specimens were obtained. The experimental results show that for damaged composite laminates, the strength recovery after bolt repair can reach an impressive 107%, and the delamination propagation caused by over-buckling deformation is considered to be the main cause of failure, which also suggests that although bolt repair can improve the strength of the specimens, it has a limited ability to inhibit delamination propagation. The simulation results of the finite element model in this paper are in good agreement with the actual experimental results, and the maximum error does not exceed 7.9%. In conclusion, this paper verifies the suitability of the proposed repair scheme in engineering applications and the correctness of the modeling method for repaired composite laminates.

Experimental investigation of buckling and post-buckling behaviour of repaired composite laminates under in-plane shear loading

The performance of Ramped Scarf (RS) and Stepped Scarf (SS) repair schemes for highly loaded composite structures has been extensively studied under compressive, tensile, and flexural loadings. However, there is a lack of research on the buckling and post-buckling behaviour of RS and SS repairs under in-plane shear loading, which is critical for aerostructures. This paper addresses this gap by investigating the buckling and post-buckling performance of these repair schemes. Pristine (P) laminates, RS repairs with a scarf angle of 3°, and SS repairs with an overlap step length of 1/60 were manufactured and tested. The quality of the scarf repairs was inspected using artificial intelligence-based machine vision. Mechanical in-plane shear testing was conducted to evaluate the buckling and post-buckling behaviour of P, RS, and SS laminates. The experimental results indicate that RS repairs demonstrated an average of 35 % higher maximum displacement and 12 % higher failure load compared to pristine laminates. SS repairs showed 19 % higher maximum displacement, and 5 % higher failure load compared to pristine laminates. RS repairs excelled in all key mechanical performance indicators, including buckling load, Hooke's stiffness, maximum displacement, and failure load, compared to SS repairs. The failure modes of P, RS, and SS laminates were similar. However, RS repairs exhibited greater susceptibility to repair patch detachment compared to SS repairs.

An Integrated Method Using a Convolutional Autoencoder, Thresholding Techniques, and a Residual Network for Anomaly Detection on Heritage Roof Surfaces

The roofs of heritage buildings are subject to long-term degradation, resulting in poor heat insulation, heat regulation, and water leakage prevention. Researchers have predominantly employed feature-based traditional machine learning methods or individual deep learning techniques for the detection of natural deterioration and human-made damage on the surfaces of heritage building roofs for preservation. Despite their success, balancing accuracy, efficiency, timeliness, and cost remains a challenge, hindering practical application. The paper proposes an integrated method that employs a convolutional autoencoder, thresholding techniques, and a residual network to automatically detect anomalies on heritage roof surfaces. Firstly, unmanned aerial vehicles (UAVs) were employed to collect the image data of the heritage building roofs. Subsequently, an artificial intelligence (AI)-based system was developed to detect, extract, and classify anomalies on heritage roof surfaces by integrating a convolutional autoencoder, threshold techniques, and residual networks (ResNets). A heritage building project was selected as a case study. The experiments demonstrate that the proposed approach improved the detection accuracy and efficiency when compared with a single detection method. The proposed method addresses certain limitations of existing approaches, especially the reliance on extensive data labeling. It is anticipated that this approach will provide a basis for the formulation of repair schemes and timely maintenance for preventive conservation, enhancing the actual benefits of heritage building restoration.

Nondisassembly Repair of Degraded LiFePO4 Cells via Lithium Restoration from the Solid Electrolyte Interphase.

The disposal of degraded batteries will be a severe challenge with the expanding market demand for lithium iron phosphate (LiFePO4 or LFP) batteries. However, due to a lack of economic and technical viability, conventional metal extraction and material regeneration are hindered from practical application. Herein, we propose a nondisassembly repair strategy for degraded cells through a lithium restoration method based on deep discharge, which can elevate the anodic potential to result in the selective oxidative decomposition and thinning of the solid electrolyte interphase (SEI) on the graphite anode. The decomposed SEI acts as a lithium source to compensate for the Li loss and eliminate Li-Fe antisite defects for degraded LFP. Through this design, the repaired pouch cells show improved kinetic characteristics, significant capacity restoration, and an extended lifespan. This proposed repair scheme relying on SEI rejuvenation is of great significance for extending the service life and promoting the secondary use of degraded cells.

A clearance control and interference repair method for ship rib plate assembly based on reverse engineering

Due to the influence of manufacturing errors, welding deformation of ship parts and other factors, interference often occurs due to out-of-tolerance assembly clearance for ship rib plate assembly using the pull-in method. To solve the problem, a clearance control and interference repair method for ship rib plate assembly is proposed. Firstly, the factors causing ship rib assembly errors were analyzed, and an accurate model of the ship rib with manufacturing errors was built based on a 3D scanning point cloud. Secondly, the fit clearances between multiple components during the motion process were calculated based on simulation. Finally, the assembly clearances were redistributed through pose coordination technology to autonomously control the assembly clearance, allocate excess clearances to interference areas and quantitatively complete the subsequent interference processing. The case study results show that the proposed method can achieve quantitative prediction of assembly clearances and generate a precise repair scheme. The interference for ship rib plate assembly is reduced by 50%, and the efficiency is increased by 24%.

Energy-Efficient and Highly Reliable Geographic Routing Based on Link Detection and Node Collaborative Scheduling in WSN.

Energy efficiency and data reliability are important indicators to measure network performance in wireless sensor networks. In existing research schemes of routing protocols, the impact of node coverage on the network is often ignored, and the possibility that multiple sensor nodes may sense the same spatial point is not taken into account, which results in a waste of network resources, especially in large-scale networks. Apart from that, the blindness of geographic routing in data transmission has been troubling researchers, which means that the nodes are unable to determine the validity of data transmission. In order to solve the above problems, this paper innovatively combines the routing protocol with the coverage control technique and proposes the node collaborative scheduling algorithm, which fully considers the correlation characteristics between sensor nodes to reduce the number of active working nodes and the number of packets generated, to further reduce energy consumption and network delay and improve packet delivery rate. In order to solve the problem of unreliability of geographic routing, a highly reliable link detection and repair scheme is proposed to check the communication link status and repair the invalid link, which can greatly improve the packet delivery rate and throughput of the network, and has good robustness. A large number of experiments demonstrate the effectiveness and superiority of our proposed scheme and algorithm.

Experimental and numerical studies on compressive failure behaviors of stepped-scarf repaired composite stiffened panels

Composite materials have been widely used in aerospace and other fields due to their superior mechanical properties. The repair of composite structures has received increasing attention in recent decades. In this work, the compressive failure behaviors of intact, defective and stepped-scarf repaired composite stiffened panels are analyzed experimentally and numerically. The evaluation of repair schemes of composite stiffened panels based on finite element (FE) analysis is investigated by comparison with experimental results. The maximum absolute value of error in load-carrying capacity between the numerical and experimental results does not exceed 3.65%. Progressive failure analysis model and cohesive zone model are utilized to reveal the damage evolution of multilayered composites and adhesive film. The failure modes obtained from FE analysis are in good agreement with the experimental observations. Moreover, the influence of the stepped-scarf ratio and repair patch angle deviation on the compressive strength is investigated to determine optimum repair parameters based on the established FE models. On the basis of the conducted studies, the results provide valuable insights into the evaluation and validation of repair schemes for composite stiffened panels with high accuracy and cost-effectiveness.

A time-varying competitive swarm optimizer for integrated flight recovery with multi-objective and priority considerations

Integrating aircraft and crew recovery is a growing topic in providing an efficient recovery system after a disruption. Most existing models only conduct from airline perspective and treat all disturbed flights homogeneously. However, in a realistic operation, the decision objectives are multiple with the interplay of stakeholders. Moreover, flights with first-aid items hold special priority. Thus, this paper presents a new Integrated Aircraft and Crew Recovery with Multi-objective and Priority, namely IACR_MP. To solve IACR_MP efficiently, an ad-hoc particle swarm optimization-based optimizer is designed. Time-varying tri-competition with different evolutionary mechanisms is developed to achieve a balance between exploitation and exploration capacities. Three repair schemes are built to prevent low feasibility caused by high constraints, and a self-exploration strategy is used to detect the potential zones of contemporary non-dominated solutions. Finally, six instances with different scales are used for algorithm performance analyses. Results illustrate that our algorithm has good solution quality and significantly outperforms its competitors in solving the IACR_MP. Moreover, our framework can provide a series of specific recovery schemes, providing decision support with more choices to airline managers.

Ultimate strength of hybrid repaired offshore pipelines with various slenderness ratio subjected to through-thickness pitting corrosion under axial compressive loading

Offshore pipelines are susceptible to various types of corrosions where pitting corrosion is generally considered the most severe. This study aims to study the effect of ratio of Carbon Fiber Reinforced Polymer to Glass Fiber Reinforced Polymer and wrapping patterns on the repair performance of composite repair system for offshore pipelines subjected to pitting corrosion. Four sets of samples with different slenderness ratios are subjected to axial compression, where the peak loads are recorded as the performance indicator of different repair schemes. Based on the experimental results, the average repair index, which is the ratio of repaired strength to intact strength, increases from 1.06 to 1.40 as the ratio of CFRP to GFRP increases. However, 1G3C repair schemes experience brittle failure while other repair schemes show different extents of ductility upon failure. Longitudinal wrapping pattern achieves the average repair index of 1.19 while Alternate and Horizontal yields the average repair index of 1.18 and 1.15 respectively. Furthermore, Longitudinal wrapping pattern exhibits the highest rigidity followed by Alternate and Horizontal. A higher slenderness ratio can contribute to a lower repair index where the cross-sectional properties have a more prominent effect compared to sample length. The theoretical results calculated based on equations provided in ASME PCC-2 show good agreement with the experimental results as there is only a percentage difference of 5.5% between them.

Effects of Clearfil SE Bond 2 on restoring deciduous anterior teeth with ring caries and analysis of caries risk factors in children aged 3-8 years.

To investigate the impact of various self-acid corrosion adhesives in restoring ring caries in anterior deciduous teeth and the influencing factors of childhood caries. This study retrospectively analyzed the repair effect of two kinds of restoration schemes on the annular caries of children's deciduous anterior teeth. According to the repair scheme, 54 children with caries were divided into two groups. The children with 3M single bond repair were set as the control group, and the children with Clearfil SE Bond 2 repair were set as the study group. The repair effect of 6 months and 12 months of treatment and the treatment satisfaction of children were compared. Additionally, 50 children with no oral abnormalities were included as a healthy control group to analyze dental caries risk factors comparatively. The retention of dental restorations, marginal adaptation to dentin, and dental pulp vitality scores in the study group were significantly lower than those in the control group at both 6 and 12 months post-treatment, with statistically significant differences (p < 0.05). Moreover, satisfaction levels in the study group notably exceeded those in the control group (92.59% vs. 70.37%). Fisher exact test yielded a p value of 0.041. Binary logistic regression analysis revealed that daily tooth brushing habits and parental supervision were protective against dental caries occurrence. Conversely, plaque, dental calculus, proficiency in tooth brushing techniques, and post-brushing bedtime snacking emerged as independent risk factors for dental caries (p < 0.05). Compared to the conventional self-etching dentin adhesive filling regimen, the novel blended adhesive and composite resin filling significantly enhanced dental caries restoration outcomes and increased children's satisfaction. Notably, this approach was well-received by both children and their families. Further proactive measures targeting children with identified risk factors are warranted to reduce the incidence of dental caries.

The role of Perforation Repair Technology in Extending the Life Cycle of Oil Fields

Perforation repair technology plays an important role in prolonging the life cycle of oil fields. However, the traditional perforation repair method can no longer meet the needs of modern oilfield development. With the continuous growth of artificial intelligence technology, the optimization algorithm based on data analysis and model has achieved remarkable success in many fields. In this paper, an optimization algorithm based on artificial neural network (ANN) is proposed to improve the performance of perforation repair and oil recovery. The algorithm can predict the oil field output under different perforation repair schemes according to the information of geological data, production data and historical data of the oil field, and get the optimal perforation repair scheme through optimization. The results show that this algorithm has obvious advantages compared with the traditional support vector machine (SVM) algorithm, and the error is reduced by 24.58%. By comparing the reservoir state prediction results of SVM algorithm, it is found that the prediction results of ANN are closer to the actual value and can better reflect the actual situation. This method provides new ideas and methods for the optimization and improvement of oil field perforation repair technology, and shows broad prospects for the application of machine learning technology in petroleum engineering.

A Formula for the I/O Cost of Linear Repair Schemes and Application to Reed-Solomon Codes

A Formula for the I/O Cost of Linear Repair Schemes and Application to Reed-Solomon Codes

Understanding the Factors and Consequences of Gas Deflagration Accident in Metro Shield Tunnel: Site Investigation and Numerical Analysis

This study aims to investigate the factors and consequences of gas deflagration accidents in metro shield tunnels based on on-site investigation and numerical analysis. We built a numerical model and detection process for an underground shield tunnel subjected to an internal explosion from an actual accident. The tunnel geometry under consideration is the same as that used for the metro line. Concerning the limitations of research on the failure and recovery mechanism of shield segmental linings under the action of internal explosion load, an explosion accident of a shield segmental lining under construction caused by the shield tunneling machine destroying natural gas pipelines was discussed, in which the structure failure characteristics during the explosion and the structure repair method after the explosion were investigated. An interval repair scheme was proposed, which provides experience for the treatment of similar engineering accidents. To investigate the gas explosion within the tunnel during the accident, the finite element software Ansys LS-DYNA with the arbitrary Lagrangian–Eulerian (ALE) technique was employed to simulate the explosion scenario. Dynamic analyses were carried out to reproduce the blast scenario. The stress distribution within the segmental lining as well as the lining’s deformation were calculated. The potential applications of the treatment and planning of comparable engineering mishaps were discussed in the study.

Analysis of adhesive scarf repairs on composite sandwich beams under three-point bending loading

The efficiency of a repair strategy applied to a honeycomb/carbon-epoxy sandwich beam was analyzed in this work. Experimental tests were performed considering three-point bending loading of undamaged, damaged and repaired specimens. In the damaged case, the central part of the core and of one of the skins were removed. The repair scheme consists of bonding a plug of honeycomb into the core and repairing the carbon-epoxy skin considering a scarf patch. A finite element analysis incorporating cohesive zone mixed-mode I + II analysis was performed. The resultant load-displacement numerical curves were compared with the experimental ones. It was verified that the repair procedure is efficient regarding recovery of the initial stiffness and strength of the undamaged case, and it was concluded that the proposed numerical model is a valid tool to deal with repair of sandwich beams.

Recycling of spent lithium–ion battery graphite anodes via a targeted repair scheme

When lithium–ion batteries (LIBs) reach the end of their life, a lot of hazardous wastes will be generated. Unfortunately, the recovery of spent graphite (SG) anodes is always neglected despite the rather high production cost of battery–grade graphite. In this work, we for the first time propose a novel targeted repair scheme by systematically characterizing and analyzing the structure and composition of SG. The results show that the repair scheme achieves effective SG repair and the repaired graphite anode displays excellent lithium storage performance, which can be comparable to that of commercial graphite. In addition, the scheme is evaluated to reduce energy consumption by 79 % and harmful pollutant emission by 90 % as compared to previously reported solutions. Obviously, our work provides a feasible solution for the recovery of graphite anodes from spent LIBs by understanding the failure characteristics of graphite anodes.

A Note on Bandwidth-Optimal Repair Scheme for Reed-Solomon Codes With Low Repair Locality

A Note on Bandwidth-Optimal Repair Scheme for Reed-Solomon Codes With Low Repair Locality

Fatigue improvement of rib‐to‐deck welded joints using adhesively bonded steel patches ‐ LEFM‐based parametric study

AbstractRib‐to‐deck welded joints in orthotropic steel decks of bridges are prone to develop fatigue cracks. Repairing such cracks allows for prolonging the life of the infrastructure, provided that structural safety is guaranteed. Among others, the repair technique of adhesively bonded steel patches is relatively simple and inexpensive. Moreover, it has the advantage that the original structure is not altered, e.g. as in the case of crack stop holes. This technique has been used in other details like the diaphragm of steel bridges. However, limited information is available when applied to rib‐to‐deck joints, which are the most common joint type in orthotropic steel decks. This study proposes two repair schemes using adhesively bonded steel patches for the rib‐to‐deck joints. A 3‐D finite element model which takes account of the crack size is established. Based on linear elastic fracture mechanics (LEFM), a parametric study is performed to investigate the effect of patch geometry and adhesive thickness on the performance of repair schemes.

Repair and Retrofit of Bridge structural elements: New Cementitious Materials

AbstractThe condition of infrastructure, the constant need to repair and maintain them and the increasing costs associated with the maintenance has led to the search for replacements for steel in new concrete infrastructure around the world. Further, alternatives for repair and strengthening of existing concrete structures ranging from the use of FRP as plates or fabrics wraps to the use of ultra‐high‐performance concrete (UHPC) elements as external reinforcements to achieve requisite strength and serviceability requirements are being attempted. The present study evaluates the performance of repaired/retrofitted structural concrete elements and sub‐assemblages damaged in flexure or shear using different repair schemes including those based on use of FRP plates or wraps, UHPC elements, etc., to restore the capacity of damaged structural concrete elements. An ANSYS based finite element model that accounts for both the constitutive properties of the primary structure in its damaged state and the repair material is used in this study to assess the different repair schemes. The analysis is shown to predict the test results very well. The importance of considering bond slip between rebar and surrounding concrete in the analysis is highlighted. Likewise, the consequence of bond between repair material and the primary structure on the overall structural performance is clearly seen. Performance of normal and high performance of concrete under high temperature resulting in spalling and significant damage from a fire and its rehabilitation with geopolymer concrete will be shown in lab scale tests and simulations. Finally, a field application of load testing of a defunct masonry arch bridge, its retrofit strategy and subsequent deployment with cementitious mixes as a repair to operationalise the bridge with significant cost saving will be illustrated.

Novel Repair Scheme for the Edge Delaminated Composites

Edge delamination refers to those delaminations, which arise at the free edge of a laminate. Although edge delamination in advanced laminated composites is a well-documented phenomenon, the repair of edge delamination is still a gray area. This paper presents an effective novel repair approach to repair edge delamination. Special repair tools have been designed and fabricated for this purpose. It also highlights the fabrication of artificially edge delaminated Carbon Fiber Reinforced (CFRP) specimens. Repair strengths have been evaluated by compression tests and Ultrasonic C-scan is used for validation of the repair scheme. From the tests it has been observed that the repair scheme has no bearing on the location of edge delamination and stacking sequence.

A comprehensive repair scheme for distributed storage systems

Modern data storage systems apply erasure codes to provide data reliability efficiently. Previous studies proposed a series of techniques to weigh repair/storage costs, reduce codec complexity, minimize repair time, improve fault tolerance, and enforce system-level service level agreement. These techniques have been designed in isolation, leading to performance limitations. We explore the potential advantages of combining these techniques to meet data storage systems’ requirements better and provide superior system performance. This work proposes a comprehensive repair scheme for fault data in distributed storage systems. First, we tailor design erasure codes in the presence of heterogeneity of storage devices. The core idea is to monitor device performance (e.g., access speed, reliability), compute two coefficients for each device, and use them to select the appropriate devices to create stripes of erasure codes. Second, we leverage the system hierarchy to perform intermediary repair operations, further minimizing cross-rack repair bandwidth. Finally, we propose a new repair scheme adapted to the skew of data access. To demonstrate the effectiveness of our comprehensive repair scheme, we evaluate various erasure codes via mathematical analysis and experiments in the Ceph cluster. In the mise-en-scène of traditional re-encoding methods and more recent adaptive erasure codes, our scheme stands out with significant savings in recovery bandwidth, code-switching bandwidth, repair time, and code-switching time.