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Experimental and numerical evaluation on debonding of fully grouted rockbolt under pull‑out loading

International Journal of Coal Science & Technology 2022年第1期9卷 84-98页

作者： Shuisheng Yu Wancheng Zhu Leilei Niu Center for Rock Instability and Seismicity Research Department of Mining EngineeringSchool of Resource and Civil EngineeringNortheastern UniversityShenyang 110819China School of Architectural Engineering Zhongyuan University of TechnologyZhengzhou 450007China

The axial loading in rockbolts changes due to stress redistribution and rheology in the country rock *** a change may lead to debonding at rockbolt to grout interface or rupture of the *** this study,based on laboratory experiments,ultrasonic guided wave propagation in fully grouted rockbolt under different pull-out loads was investigated in order to examine the resultant debonding of *** signals obtained from the ultrasonic monitoring during the pull-out test were processed using wavelet multi-scale analysis and frequency spectrum analysis,the signal amplitude and the amplitude ratio(Q)of low frequency to high frequency were defined to quantify the debonding of *** addition to the laboratory test,numerical simulation on the effect of the embedment lengths on ultrasonic guided wave propagation in rockbolt was conducted by using a damage-based model,and the debonding between rockbolt and cement mortar was numerically *** was confirmed that the ultrasonic guided wave propagation in rockbolt was very sensitive to the debonding because of pull-out load,therefore,the critical bond length could be calculated based on the propagation of guided wave in the grouted *** time domain,the signal amplitude in rockbolt increased with pull-out load from 0 to 100 kN until the completely debonding,thus quantifying the debonding under the different pull-out *** the frequency domain,as the Q value increased,the debonding length of rockbolt decreased *** numerical results confirmed that the guided wave propagation in the fully grouted rockbolt was effective in detecting and quantifying the debonding of rockbolt under pull-out load.

关键词： Fully grouted rockbolt debonding Pull-out load Ultrasonic guided wave propagation

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An optimized perforation clusters spacing model based on the frictional shale layer’s debonding

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Science China(Physics,Mechanics & Astronomy) 2019年第11期62卷 142-145页

作者： Tao Wang Xuan Ye ZhanLi Liu Yue Gao Zhuo Zhuang School of Aerospace Engineering Tsinghua University

The success of hydraulic fracturing for shale gas recovery has motivated much research interest in understanding the underlying mechanisms (1-3)When hydraulic fractures (HFs) expand, multiple cracks and crack branches... 详细信息

关键词： An optimized perforation clusters spacing model based on the frictional shale layer’s debonding SRV

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Fracture analysis of cortical bone under the condition of cement line debonding and osteon pullout

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International Journal of Biomathematics 2018年第2期11卷 175-188页

作者： Yaogeng Chen Wenshuai Wang Xing Li School of Mathematics and Statistics Ningxia University Yinchuan Ningxia 750021 P. R. China School of Science Ningxia Medical University Yinchuan Ningxia 750004 P. R. China

Cortical bone consists of osteons embedded in interstitial bone tissue and there is a thin amorphous interface, named cement line, between osteon and interstitial bone. Due to fatigue and cyclic loading, the pullout or debonding phenomenon often occurs in osteonal and interstitial tissue bone. The study aims to construct a fiber-reinforced composite material debonding model for cortical bone, in which the bonding condition along the osteon, cement line and interstitial tissue bone are assumed to be imperfect. In the study, we used the complex variable method to obtain series representations for stress fields in the osteon, cement line and the interstitial tissue bone with a radial crack. The effects of material properties of osteon and cement line, crack position, and varying degrees of debonding on the fracture behavior were investigated by computing the stress intensity factor （SIF） in the vicinity of the microcrack tips. The investigation results indicated that the cement line was important for controlling the fracture toughening mechanisms and that the level of imperfect bonding among osteon, cement line and interstitial tissue bone had a pronounced effect on the crack behavior and should not be ignored.

关键词： Cortical bone debonding cement line complex variables method.

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Mechanical Characterisation of Interface for Steel/Polymer Composite Using Pull-out Test: Shear-Lag and Frictional Analysis

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Journal of Materials Science & Technology 2006年第4期22卷 552-558页

作者： Mohamed KHARRAT Maher DAMMAK Amine CHARFI Institut Préparatoire aux Etudes d'Ingénieurs de Sfax Tunisia Laboratoire des Systèmes ElectromécaniquesEcole Nationale d'Ingénieurs de SfaxTunisia Laboratoire des Systèmes Electromécaniques Ecole Nationale d'Ingénieurs de SfaxTunisia

Fibre-matrix interface is known to have contribution to the mechanical performance of fibre-reinforced composite by its potential for load transfer between the fibre and the matrix. Such load transfer is of great importance in dentistry when a post is used for fixing a ceramic crown on the tooth. In this study, a pull-out test was carried out to analyse the interfacial properties of a steel fibre embedded in a polyester and epoxy matrices. It was found that the fibre-matrix interface is debonded on the whole embedded length when the fibre stress reached the debonding stress. Then, the fibre stress fell down to the initial extraction stress required to pulling out the debonded fibre from the matrix. Both debonding stress and initial extraction stress initiated a linear increase with the implantation length after the debonding stress reached horizontal asymptotes. To analyse the fibre-matrix load transfer before debonding, an analytical shear-lag model was adopted to in this test conditions. Fitting the experimental results with the analytical model provided the interfacial shear strength. By considering the Coulomb friction at the fibre-matrix interface during the fibre extraction process, an analytical model which considers Poisson＇s effects on both fibre and matrix, was developed. In this model, knowledge of the initial extraction stress of the fibre provides the residual normal stress at the fibre-matrix interface.

关键词： Fibre Matrix Interface Pull-out Shear-lag debonding Friction

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A Comparative Study on the Post-Buckling Behavior of Reinforced Thermoplastic Pipes(RTPs)Under External Pressure Considering Progressive Failure

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China Ocean Engineering 2024年第2期38卷 233-246页

作者： DING Xin-dong WANG Shu-qing LIU Wen-cheng YE Xiao-han College of Engineering Ocean University of ChinaQingdao 266100China Shandong Provincial Key Laboratory of Ocean Engineering Ocean University of ChinaQingdao 266100China Department of Marine Technology Norwegian University of Science and Technology(NTNU)Trondheim NO-7491Norway

The collapse pressure is a key parameter when RTPs are applied in harsh deep-water *** investigate the collapse of RTPs,numerical simulations and hydrostatic pressure tests are *** the numerical simulations,the eigenvalue analysis and Riks analysis are combined,in which the Hashin failure criterion and fracture energy stiffness degradation model are used to simulate the progressive failure of composites,and the“infinite”boundary conditions are applied to eliminate the boundary *** for the hydrostatic pressure tests,RTP specimens were placed in a hydrostatic chamber after filled with *** has been observed that the cross-section of the middle part collapses when it reaches the maximum *** collapse pressure obtained from the numerical simulations agrees well with that in the ***,the applicability of NASA SP-8007 formula on the collapse pressure prediction was also *** has a relatively greater difference because of the ignorance of the progressive failure of *** the parametric study,it is found that RTPs have much higher first-ply-failure pressure when the winding angles are between 50°and 70°.Besides,the effect of debonding and initial ovality,and the contribution of the liner and coating are also discussed.

关键词： reinforced thermoplastic pipes post-buckling behavior progressive failure of composites debonding initial ovality

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INTERFACIAL BEHAVIOR OF PIPE JOINTS UNDER TORSION LOADS

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Acta Mechanica Solida Sinica 2015年第5期28卷 521-535页

作者： Jun Han Hong Yuan Jiayu Wu MOE Key Lab of Disaster and Control in Engineering Institute of Applied Mechanics Jinan University

The interfacial behavior of pipe joints is studied in this paper. Firstly, through nonlinear fracture mechanics, the analytical expressions of interfacial shear stress and the load- displacement relationship at loaded end of pipe joints under torsion loads are obtained. Thus the shear stress propagation and the debonding process of the whole interface for different bond lengths can be predicted. Secondly, through the analytical solutions, the influences of different bond lengths on the load-displacement curve and the ultimate load are studied. The stress trans- fer mechanism, the interface crack propagation and the ductility behavior of the joints can be explained.

关键词： interface failure mechanism softening debonding torsion pipe joints

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Micro-annulus generation under downhole conditions: Insights from three-dimensional staged finite element analysis of cement hardening and wellbore operations

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Journal of Rock Mechanics and Geotechnical Engineering 2020年第6期12卷 1185-1200页

作者： Weicheng Zhang Andreas Eckert Department of Geosciences and Geological and Petroleum Engineering Missouri University of Science and TechnologyRollaMOUSA

A micro-annulus(MA)is defined as a high permeability zone or gap initiating/occurring at the casingcement and cement-formation interfaces during the wellbore life *** MA can significantly compromise wellbore integrity by establishing enhanced fluid flow *** study uses a staged finite element approach to simulate wellbore integrity during various loading steps of wellbore operations under downhole *** emphasis is placed on the processes of cement poro-elastic property evolution,volume variation,and pore pressure variation as part of the cement hardening *** resulting state of stress during the life cycle of a typical injection well(***,completion,and injection)is analyzed to assess the onset and evolution of micro-annuli at various interfaces of the composite wellbore system under downhole *** results show that cement shear failure is observed at the casing-cement interface during pressure testing(excessive wellbore pressure);and tensile debonding failure initiates at the cement-formation interface due to cement shrinkage during hardening and injection-related cooling(thermal cycling).Sensitivity analyses considering several parameters show that:(1)the degree of poro-elastic bulk shrinkage has significant implications for both shear and tensile failure initiation e the less the cement shrinks,the less likely the failure initiation is;(2)cement integrity increases with increasing depth;(3)cement pore pressure evolution has significant implications for tensile failure e if cement pore pressure decreases more,higher temperature differences can be sustained before an MA occurs;and(4)cement temperature fluctuations during hardening promote initiation of debonding *** summary,the results presented indicate that establishing downhole conditions to quantitatively analyze MA generation is *** results are different compared to laboratory studies without considering/simulating downhole *** kno

关键词： Micro-annulus debonding Staged finite element analysis Cement hardening Poro-elastic bulk shrinkage Pore pressure Temperature fluctuation

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Effect of Interfacial Strength on the Flexural Behavior of Glass Fiber Reinforced Polymer(GFRP) Reinforced Concrete Beam

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Journal of Wuhan University of Technology(Materials Science) 2015年第5期30卷 1001-1007页

作者：张亚芳 YANG Wenlong LIU Hao CHEN Peiran LIU Feng Faculty of Civil Engineering Guangzhou University

The reinforcement/matrix interfacial strength has been considered as the key factor when glass fiber reinforced polymer(GFRP) bar is mixed with concrete. In this paper, based on micromechanics, fourpoint bending numerical models with and without glass fiber of different interfacial strength have been set up to simulate the damage process of GFRP reinforced concrete beam. The results show that the higher the interfacial strength is, the higher the ultimate bearing capacity of beams, and the less the opening width and height of cracks will be reached. Furthermore, mixing of glass fibers has less influence on the damage process when the interfacial strength is weak, however, it can help to improve the ultimate bearing capacity of the beams, retard the expansion of cracks and improve the toughness when the interfacial strength is high.

关键词： interfacial strength GFRP damage process debonding numerical simulation

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Quality evaluation of rubber-to-metal bonded structures based on shearography

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Science China(Physics,Mechanics & Astronomy) 2015年第7期58卷 49-56页

作者： LIU Bin GUO XingMing QI GongJin ZHANG DongSheng Shanghai Institute of Applied Mathematics and Mechanics Shanghai Key Laboratory of Mechanics in Energy Engineering Beijing Aeronautical Technology Research Center Department of Mechanics Shanghai University

The quality of bonding is often a concern in rubber-to-metal bonded parts with regard to the integrity and stability of the structure. In this study, shearography has been used to detect the out-of-plane deformation of the defects caused by thermal and vacuum stresses. A sample of the vulcanized styrene-butadiene rubber bonded to steel with known artificial voids was prepared and during bonding process a region was glued with thick adhesives. The rubber surface of the sample was inspected in thermal radiation and vacuum modes respectively with a self-designed shearography device. Meanwhile, a numerical simulation was conducted to predict the out-of-plane deformation of the rubber surface in these two stress modes. Results from the numerical simulation and the experiments indicated that the debonding defects could be inspected in both loading modes. In the thermal radiation mode the region with thick adhesives could be identified successfully. This study provides a guideline for quality control of rubber-to-metal structures using an optical method.

关键词： shearography optical mechanics debonding

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MECHANICAL PERFORMANCE OF NANO-CaCO_3 FILLED POLYSTYRENE COMPOSITES

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Acta Mechanica Solida Sinica 2009年第6期22卷 555-562页

作者： Yun Gao Luqi Liu Zhong Zhang National Center for Nanoscience and Technology Beijing 100190 China

Nano-CaCO3 incorporated polystyrene composites are compounded by twin-screw extrusion. Tensile and compact tensile tests show that the strength and toughness of polystyrene are decreased after the addition of nano-CaCO3 particles. Fracture surface analysis suggests that the defects induced by interfacial debonding and nano-filler agglomerations would be the key factors responsible for the declined strength and toughness. Nevertheless, it has to be stated, if the applied stress is lower than the ultimate strength, the rigid nanoparticles would still stiffen the polymer molecules, and resist polymer chain mobility. Hence, the improved tensile modulus and creep resistance can be obtained with the increasing contents of nanoparticles.

关键词： nanocomposites nanoparticles polymers mechanical properties debonding

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