• Title/Summary/Keyword: crack-repair

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Non-destructive Testing Methods to Evaluate the Effectiveness of Crack Repair Using Expoxy and Microcement (균열 주입부의 비파괴 검사에 의한 주입효과 판정에 관한 연구)

  • 최홍식;이시우;이호범;송영철;방기성
    • Proceedings of the Korea Concrete Institute Conference
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    • 2002.05a
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    • pp.841-846
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    • 2002
  • Development on non-destructive testing methods were performed to evaluate the effectiveness of crack repair for test beams induced a crack. Cracked beams are repaired with expoxy and microcement, and then they are tested by two methods, the ultrasonic pulse velocity method and the transfer function method. It is proved that the ultrasonic pulse velocity method is very valid for the evaluation of the effectiveness on expoxy repair, and the transfer function method is very applicable to evaluate the effectiveness on microcement repair.

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3-D fracture analysis of cracked aluminum plates repaired with single and double composite patches using XFEM

  • Jamal-Omidi, Majid;Falah, Mehdi;Taherifar, Davood
    • Structural Engineering and Mechanics
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    • v.50 no.4
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    • pp.525-539
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    • 2014
  • Bonded composite-patch repair has been widely used to restore or extend the service life of damaged structures due to its effectiveness as a mechanical repair technique. In this paper using extended finite element method (XFEM), three-dimensional crack models are developed to examine the fracture behavior of centrally cracked aluminum plates repaired with single and double sided composite patches. Stress intensity factor (SIF) at the crack tip is used as the fracture criterion. In this regard, the effects of the crack lengths, patch materials, orientation of plies, adhesive and patch thickness are examined to estimate the SIF of the repaired plate and the repair performance. The obtained results show that composite patches have significant effect on reduction of the SIF at the crack tip. It is also proved that using double symmetric repair, in comparison to single one, reduces considerably SIF at the crack tip. Hence, the residual strength can be improved significantly as well as fatigue life of the structure. Investigation of ply orientation effects shows SIF increase as the ply orientation is changed from $0^{\circ}$ (perpendicular to the advancing crack) to $90^{\circ}$ (parallel to the crack line). However, the effectiveness of the ply orientation depends on the loading direction and the crack direction.

Effects of Outside Repair Welding on the Crack Growth in the Surge Nozzle Weld on the Hot Leg Side in a Nuclear Power Plant (외면 보수 용접이 원전 고온관 밀림노즐에서의 결함성장에 미치는 영향)

  • Na, Kyung-Hwan;Yun, Eun-Sub;Park, Young-Sheop
    • Journal of Welding and Joining
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    • v.29 no.2
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    • pp.34-39
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    • 2011
  • Nickel-based austenitic alloys such as Alloy 82 and 182 had been employed as the weld metals in nuclear power plants (NPPs) due to their high corrosion resistance as well as good mechanical properties. However, since the 2000s, the occurrence of primary water stress corrosion cracking has been reported in conjunction with these alloys in domestic and oversea NPPs. In the present work, we assumed an imaginary crack at the inner surface of a surge nozzle weld that had previously experienced the outside repair welding, and constructed its finite element model. Finite element analysis was performed with respect to the heat transfer, and then to the residual stress for obtaining the total applied stress distributions. These stress distributions were finally converted to the stress intensity factors for estimating crack growth rate. From the comparison of crack growth rate curves for the cases of no repair welding and outside repair welding, it was found that the outside repair welding did not exhibit negative effect on the crack growth for the surge nozzle under consideration in this work; in both cases, the cracks stopped growing before they became the through-wall cracks.

When mend piercing crack of large size mat basis, study of perforation and vottom repair that use water jet (대형매트기초의 관통균열 보수시 WATER JET을 이용한 천공과 저면보수에 관한 연구)

  • 박성우;한송수;이상헌;박찬규
    • Proceedings of the Korea Concrete Institute Conference
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    • 2003.11a
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    • pp.577-580
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    • 2003
  • Problem of repairing by boring is that it deteriorates stabelety and durability of structure by permeation of seawater from underneath after damage and repair of reinforcing rod regarding of spot. The purpose of this study is to improve the porblem by using the repair method of general boring to mend the of large mat basis. Direction of thes experiment is to apply the new repair material and the method to control the blazing fire factor caused by the crack from the foundation of large mat and also to estimate it's integrity. New method of construction is method of contruction that do speace scurity in vertical drilling and bottom useing water jet. New material used bantonite and rubberized asphalt. Test result existent repair method of construction large size mat basis perforation is difficult and reinforcing rod can be damaged coule there were a lot of problems with re-water leakage of crack repair region, but overcomes existent short coming by method that apply in this study.

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Characterization of Fracture Behavior in Repaired Skin/Stiffener Structure with an Inclined Central Crack

  • Chung, Ki-Hyun;Yang, Won-Ho;Heo, Sung-Pil
    • Journal of Mechanical Science and Technology
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    • v.16 no.5
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    • pp.599-608
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    • 2002
  • Finite element analysis for the stress intensity factor (SIF) at the skin/stiffener structure with inclined central crack repaired by composite stiffened panels is developed. A numerical investigation was conducted to characterize the fracture behavior and crack growth behavior at the inclined crack. In order to investigate the crack growth direction, maximum tangential stress (MTS) criterion are used. Also, this paper is to study the performance of the effective bonded composite patch repair of a plate containing an inclined central through-crack. The main objective of this research is the validation of the inclined crack patching design. In this paper, the reduction of stress intensity factors at the crack-tip and prediction of crack growth direction are determined to evaluate the effects of various non-dimensional design parameter including; composite patch thickness and stiffener distance. We report the results of finite element analysis on the stiffener locations and crack slant angles and discuss them in this paper. The research on cracked structure subjected to mixed mode loading is accomplished and concludes that more work using a different approaches is necessary. The authors hope the present study will aid those who are responsible for the repair of damaged aircraft structures and also provide general repair guidelines.

Evaluation of Injection Property of Crack Repair Method by Right Angle Drill Method with Packer (직각천공방식으로 패커를 설치한 균열보수공법의 보수재 주입특성)

  • 고진수;이성복;서치호
    • Proceedings of the Korea Concrete Institute Conference
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    • 2003.11a
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    • pp.581-586
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    • 2003
  • The objective of this study is to evaluate the injection performance of crack repair method in concrete structure. To improve the quality of the concrete structure caulking material was injected into the crack of building that were planned to be demolished and injection properties of various repair method were compared and assessed according to type of crack. Results from the test showed that when cracks and injection port were integrated and the injection port wasn't blocked repair material was able to be injected even below around 40㎏/㎠ pressure. Moreover, effective pressure each type of packer showed wide range varying from 200-400㎏/㎠. As for drill method for injection port, core drill method has shown to be more effective compared to the air pump method

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A Study on the Viscosity and Compaction of Polymer-Cement Composites According to Types of Polymer for Crack Repair (균열보수용 폴리머 시멘트 복합체의 폴리머 종류에 따른 점도와 충전성에 관한 연구)

  • Park, Dong-Yeop;Kwon, Woo-Chan;Jo, Young-Kug
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2022.11a
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    • pp.161-162
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    • 2022
  • The purpose of this study is to determine the viscosity of the polymer-cement composites(PCCs) for crack repair of RC structures and to investigate its compaction. According to the study on the viscosity and compaction property of PCCs for crack repair, the viscosity of PCCs varies greatly depending on the polymer type and polymer cement ratio, and by mixing silica fume into PCCs, appropriate viscosity and excellent flow can be controlled without separation of cement and water. As a result of this study, basic data on the viscosity, fluidity, and compaction properties of PCCs for crack repair of RC structure can be obtained.

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Development of Crack Monitoring System for Self-healing Repair Mortar Surface Using Image Processing Technique (이미지 처리 기법을 이용한 자기치유 보수 모르타르 시공표면의 균열 모니터링 시스템 개발)

  • Oh, Sang-Hyuk;Moon, Dae-Jung;Lee, Kwang-Myong
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.9 no.3
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    • pp.359-366
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    • 2021
  • In this study, It was developed an monitoring cracks system based on image processing techniques in order to measure cracks, which are major damages in concrete, and to convert them into a database. The crack monitoring system consists of crack image captured equipment and a crack detection and analysis software. This system provides objective and quantitative data by replacing the conventional visual inspection. The crack detection algorithm w as verified through an indoor test using virtual cracks, and the amount of crack detection and crack width change was monitored by applying it to the self-healing repair mortar construction site. In the case of the crack width detected through image analysis, the maximum difference from the actual crack width was 0.0334mm. It was possible to detect microcracks of 0.1mm or less, and the effect of crack healing over time of the self-healing repair mortar was confirmed trough the field test.

Study on a rational repair and reinforcement by analysis of crack density in OO subway (지하철 터널 균열밀도 분석을 통한 합리적인 보수보강 방안 연구)

  • Yoon Tae-Gook;Shin Yong-Suk;Ahn Sang-Ro;Lee Song
    • 한국터널공학회:학술대회논문집
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    • 2005.04a
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    • pp.262-269
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    • 2005
  • The priority order about a rational repair and reinforcement is generally decided by subjective decision of engineer. An appearance investigation by tunnel scanner that is widely used in foreign nation was carried out to decide about a rational repair and reinforcement through systematic and objective analysis in box and NATM tunnel. We have decided on the order of priority of an rational repair and reinforcement through the crack density analysis by span, distance and location with the result of tunnel scanner.

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Fatigue Crack Growth Behavior of the Thin-to-Thick Type Stiffened Panels with Bonded Patch (접착 패칭된 박-후판 결합형 보강판의 피로균열성장 거동)

  • Rhee, Hwan-Woo;Kim, Seung-Hyun
    • Journal of Ocean Engineering and Technology
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    • v.22 no.3
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    • pp.89-95
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    • 2008
  • Fatigue cracked components often needs to be repaired during service. Standard repair schemes involve strengthening the component by connecting reinforcing members by means of rivets or welding by reducing the crack-tip stress intensity factors. Recent technological advances in fiber reinforced composite materials and adhesive bonding have led to the development of efficient repair schemes. In this study, the influence of various shape parameters on fatigue crack growth in the CCT type uniform thickness plates and the thin-ta-thick type stiffened panels repaired with woven fabric type Kevlar-Epoxy composite patch are studied experimentally.