水工建筑物伸缩缝的破坏及渗漏问题会直接影响水工结构自身的安全稳定。本文基于南水北调穿黄隧洞工程实际背景,引入基于内聚力(Cohesive Zone Model)单元界面破坏有限元模型,进行了伸缩缝嵌缝材料在背水压作用下的仿真分析,并将其结果...水工建筑物伸缩缝的破坏及渗漏问题会直接影响水工结构自身的安全稳定。本文基于南水北调穿黄隧洞工程实际背景,引入基于内聚力(Cohesive Zone Model)单元界面破坏有限元模型,进行了伸缩缝嵌缝材料在背水压作用下的仿真分析,并将其结果与室内压水试验的应变-荷载数据进行对比,给出了适合于聚脲基复合防渗体系嵌缝内聚力单元的断裂能。同时,分析计算了伸缩缝宽度及嵌缝深度对结构抵抗水压能力的影响,证明所取参数的正确性。进一步分析了伸缩缝变形和水压力作用条件下的仿真结果,给出了伸缩缝变形、伸缩缝宽度、嵌缝深度及承载能力之间的关系。本文结果可为伸缩缝的结构设计提供指导。展开更多
针刺/缝合多尺度联锁复合材料具有优异的层间性能,在航天热结构复合材料中得到越来越多的应用,然而,缝合工艺对于针刺复合材料双切口层间剪切(DNS)性能的影响还不清楚。以石英缎纹基布、石英斜纹半切布为原料,设计制备了3种缝合矩阵、4...针刺/缝合多尺度联锁复合材料具有优异的层间性能,在航天热结构复合材料中得到越来越多的应用,然而,缝合工艺对于针刺复合材料双切口层间剪切(DNS)性能的影响还不清楚。以石英缎纹基布、石英斜纹半切布为原料,设计制备了3种缝合矩阵、4种缝合纤维束的石英纤维增强树脂基针刺/缝合多尺度联锁复合材料,测试并分析了复合材料的DNS性能。采用Micro-CT对织物内部结构进行表征,同时通过扫描电镜(SEM)观察试样断口形貌,阐明层间增强机制。使用内聚力模型(Cohesive zone model,CZM)结合Abaqus软件进一步探究针刺/缝合多尺度联锁复合材料的DNS行为,预测材料的极限破坏强度。研究结果表明:缝合工艺的引入极大地改善了复合材料的层间性能,其DNS的破坏载荷最大可达到32.73 MPa,相比针刺复合材料提升了86.46%。针刺/缝合多尺度联锁复合材料DNS的主要破坏方式是基体开裂、纤维束的脆性断裂和拔出。同时,模拟结果和针刺/缝合多尺度联锁复合材料的DNS实验结果吻合较好,误差最大不超过8%,证明本文建立的内聚力模型能够有效预测针刺/缝合多尺度联锁复合材料的层间剪切性能。展开更多
This paper examines the mechanical behavior offiber reinforced polymer(FRP)-confined concrete under cyclic compression using the 3D cohesive zone model(CZM).A numerical modeling method was developed,employing zero-thick...This paper examines the mechanical behavior offiber reinforced polymer(FRP)-confined concrete under cyclic compression using the 3D cohesive zone model(CZM).A numerical modeling method was developed,employing zero-thickness cohesive elements to represent the stress-displacement relationship of concrete potential fracture surfaces and FRP-concrete interfaces.Additionally,mixed-mode damage plastic constitutive models were pro-posed for the concrete potential fracture surfaces and FRP-concrete interface,considering interfacial friction.Furthermore,an anisotropic plastic constitutive model was developed for the FRP composite jacket.The CZM model proposed in this study was validated using experimental data from plain concrete and large rupture strain(LRS)FRP-confined concrete subjected to cyclic compression.The simulation results demonstrate that the pro-posed model accurately predicts the mechanical response of both concrete and FRP-confined concrete under cyc-lic compression.Lastly,various parametric studies were conducted to investigate the internal failure mechanism of FRP-confined concrete under cyclic loading to analyze the influence of the inner friction plasticity of different components.展开更多
针对复合结构的粘接界面断裂性能分析,在有限元软件ABAQUS中基于CZM(Cohesive Zone Model)中的cohesive单元来模拟粘接层并建立有限元模型,模拟分析了钢板和碳纤维树脂粘接界面的损伤情况,得到了碳纤维与钢I型断裂的载荷位移曲线,并通...针对复合结构的粘接界面断裂性能分析,在有限元软件ABAQUS中基于CZM(Cohesive Zone Model)中的cohesive单元来模拟粘接层并建立有限元模型,模拟分析了钢板和碳纤维树脂粘接界面的损伤情况,得到了碳纤维与钢I型断裂的载荷位移曲线,并通过双悬臂梁实验测试验证了模拟结果的准确性,为实际工程结构加固提供指导。展开更多
An appropriate coupled cohesive law for predicting the mixed mode failure is established by combining normal separation and tangential separation of surfaces in the cohesive zone model （CZM） and the cohesive element...An appropriate coupled cohesive law for predicting the mixed mode failure is established by combining normal separation and tangential separation of surfaces in the cohesive zone model （CZM） and the cohesive element method. The Xu-Needleman exponential cohesive law with the fully shear failure mechanism is one of the most popular models. Based on the proposed consistently coupled rule/principle, the Xu-Needleman law with the fully shear failure mechanism is proved to be a non-consistently coupled cohesive law by analyzing the surface separation work. It is shown that the Xu-Needleman law is only valid in the mixed mode fracture when the normal separation work equals the tangential separation work. Based on the consistently coupled principle and the modification of the Xu-Needleman law, a consistently coupled cohesive （CCC） law is given. It is shown that the proposed CCC law has already overcome the non-consistency defect of the Xu-Needleman law with great promise in mixed mode analyses.展开更多
In this paper, a selective activation strategy is studied in order to alleviate the issue of added compliance in the intrinsic cohesive zone model applied to arbitrary crack propagation. This strategy proceeds by firs...In this paper, a selective activation strategy is studied in order to alleviate the issue of added compliance in the intrinsic cohesive zone model applied to arbitrary crack propagation. This strategy proceeds by first inserting cohesive elements between bulk elements and subsequently tying the duplicated nodes across the interface using controllable multi-point constraints before the analysis begins. Then, during the analysis, a part of the multi-point constraints are selectively released, thereby reactivating the corresponding cohesive elements and allowing cracks to initiate and propagate along the bulk element boundaries. The strategy is implemented in Abaqus/Standard using a user-defined multi-point constraint subroutine. Analysis results indicate that the strategy significantly alleviates the added compliance problem and reduces the computation time.展开更多
目的找出混凝土裂缝扩展对纤维增强材料FRP与混凝土界面粘结性能的影响规律.方法基于断裂力学理论,采用商业软件ANSYS中的界面单元模型(Cohesive Zone Model CZM),模拟素混凝土梁跨中I型裂缝扩展以及FRP与混凝土界面II型裂缝的扩展过程...目的找出混凝土裂缝扩展对纤维增强材料FRP与混凝土界面粘结性能的影响规律.方法基于断裂力学理论,采用商业软件ANSYS中的界面单元模型(Cohesive Zone Model CZM),模拟素混凝土梁跨中I型裂缝扩展以及FRP与混凝土界面II型裂缝的扩展过程.结果随着混凝土裂缝的扩展,加固梁承载力出现两个峰值:第一个峰值出现在混凝土宏观裂缝扩展的起始点,此时FRP布的应力低于500 MPa,FRP与混凝土界面切应力在混凝土裂缝附近较大,其余部分切应力及界面滑移量基本为零,界面处于完全粘结状态.第二个峰值出现在FRP与混凝土界面发生剥离时刻,之后界面剥离从混凝土跨中裂缝位置向梁端部扩展,加固梁的承载力保持在第二个峰值上,FRP布应力达到1 480 MPa,界面粘结切应力及滑移量向FRP端部移动,跨中完全剥离的界面,切应力降为零,滑移量保持不变.结论计算得到的荷载随混凝土开裂的变化趋势及峰值荷载与试验值吻合较好,说明笔者提出的数值模拟方法能较准确地预测CFRP加固带缝混凝土梁的承载力.展开更多
The interface toughness of adhesively bonded structural members is one of the critical parameters for adhesive joint design. It is often assumed that the joint toughness is a material constant so that its value can be...The interface toughness of adhesively bonded structural members is one of the critical parameters for adhesive joint design. It is often assumed that the joint toughness is a material constant so that its value can be obtained from fracture tests of simple geometries such as DCB for Mode-Ⅰ, ENF for Mode-Ⅱ, using linear elastic fracture mechanics （LEFM）. However, the LEFM assumption of point-wise crack-tip fracture process is overly simplistic and may cause significant error in interpreting fracture test data. In this paper, the accuracy and applicability of various traditional beam-bending-theory based methods for fracture toughness evaluation, such as simple beam theory （SBT）, corrected beam theory （CBT） and experimental compliance method （ECM）, were assessed using the cohesive zone modelling （CZM） approach. It was demonstrated that the fracture process zone （FPZ） size has profound influence on toughness calculation and unfortunately, all the classic beam-bending theories based methods fail to include this important element and are erroneous especially when the ratio of crack length to FPZ size is relatively small （〈5.0）. It has also been demonstrated that after the FPZ size is incorporated into simple beam formulations, they provide much improved evaluation for fracture toughness. Formulation of first order estimate of FPZ size is aIso given in this paper.展开更多
Fully automatic finite element(FE) modelling of the fracture process in quasi-brittle materials such as concrete and rocks and ductile materials such as metals and alloys,is of great significance in assessing structur...Fully automatic finite element(FE) modelling of the fracture process in quasi-brittle materials such as concrete and rocks and ductile materials such as metals and alloys,is of great significance in assessing structural integrity and presents tre-mendous challenges to the engineering community. One challenge lies in the adoption of an objective and effective crack propagation criterion. This paper proposes a crack propagation criterion based on the principle of energy conservation and the cohesive zone model(CZM) . The virtual crack extension technique is used to calculate the differential terms in the criterion. A fully-automatic discrete crack modelling methodology,integrating the developed criterion,the CZM to model the crack,a simple remeshing procedure to accommodate crack propagation,the J2 flow theory implemented within the incremental plasticity framework to model the ductile materials,and a local arc-length solver to the nonlinear equation system,is developed and im-plemented in an in-house program. Three examples,i.e.,a plain concrete beam with a single shear crack,a reinforced concrete(RC) beam with multiple cracks and a compact-tension steel specimen,are simulated. Good agreement between numerical predictions and experimental data is found,which demonstrates the applicability of the criterion to both quasi-brittle and ductile materials.展开更多
文摘水工建筑物伸缩缝的破坏及渗漏问题会直接影响水工结构自身的安全稳定。本文基于南水北调穿黄隧洞工程实际背景,引入基于内聚力(Cohesive Zone Model)单元界面破坏有限元模型,进行了伸缩缝嵌缝材料在背水压作用下的仿真分析,并将其结果与室内压水试验的应变-荷载数据进行对比,给出了适合于聚脲基复合防渗体系嵌缝内聚力单元的断裂能。同时,分析计算了伸缩缝宽度及嵌缝深度对结构抵抗水压能力的影响,证明所取参数的正确性。进一步分析了伸缩缝变形和水压力作用条件下的仿真结果,给出了伸缩缝变形、伸缩缝宽度、嵌缝深度及承载能力之间的关系。本文结果可为伸缩缝的结构设计提供指导。
文摘针刺/缝合多尺度联锁复合材料具有优异的层间性能,在航天热结构复合材料中得到越来越多的应用,然而,缝合工艺对于针刺复合材料双切口层间剪切(DNS)性能的影响还不清楚。以石英缎纹基布、石英斜纹半切布为原料,设计制备了3种缝合矩阵、4种缝合纤维束的石英纤维增强树脂基针刺/缝合多尺度联锁复合材料,测试并分析了复合材料的DNS性能。采用Micro-CT对织物内部结构进行表征,同时通过扫描电镜(SEM)观察试样断口形貌,阐明层间增强机制。使用内聚力模型(Cohesive zone model,CZM)结合Abaqus软件进一步探究针刺/缝合多尺度联锁复合材料的DNS行为,预测材料的极限破坏强度。研究结果表明:缝合工艺的引入极大地改善了复合材料的层间性能,其DNS的破坏载荷最大可达到32.73 MPa,相比针刺复合材料提升了86.46%。针刺/缝合多尺度联锁复合材料DNS的主要破坏方式是基体开裂、纤维束的脆性断裂和拔出。同时,模拟结果和针刺/缝合多尺度联锁复合材料的DNS实验结果吻合较好,误差最大不超过8%,证明本文建立的内聚力模型能够有效预测针刺/缝合多尺度联锁复合材料的层间剪切性能。
基金funded by the Natural Science Foundation of Fujian Province(2023J01938)the Scientific Research Startup Foundation of Fujian University of Technology(GY-Z21026).
文摘This paper examines the mechanical behavior offiber reinforced polymer(FRP)-confined concrete under cyclic compression using the 3D cohesive zone model(CZM).A numerical modeling method was developed,employing zero-thickness cohesive elements to represent the stress-displacement relationship of concrete potential fracture surfaces and FRP-concrete interfaces.Additionally,mixed-mode damage plastic constitutive models were pro-posed for the concrete potential fracture surfaces and FRP-concrete interface,considering interfacial friction.Furthermore,an anisotropic plastic constitutive model was developed for the FRP composite jacket.The CZM model proposed in this study was validated using experimental data from plain concrete and large rupture strain(LRS)FRP-confined concrete subjected to cyclic compression.The simulation results demonstrate that the pro-posed model accurately predicts the mechanical response of both concrete and FRP-confined concrete under cyc-lic compression.Lastly,various parametric studies were conducted to investigate the internal failure mechanism of FRP-confined concrete under cyclic loading to analyze the influence of the inner friction plasticity of different components.
文摘针对复合结构的粘接界面断裂性能分析,在有限元软件ABAQUS中基于CZM(Cohesive Zone Model)中的cohesive单元来模拟粘接层并建立有限元模型,模拟分析了钢板和碳纤维树脂粘接界面的损伤情况,得到了碳纤维与钢I型断裂的载荷位移曲线,并通过双悬臂梁实验测试验证了模拟结果的准确性,为实际工程结构加固提供指导。
基金Project supported by the National Natural Science Foundation of China(Nos.50878117 and 51038006)the China Scholarship Council Project(No.M.H.HE-2009621076)the Tsinghua University Initiative Scientific Research Program(No.20101081766)
文摘An appropriate coupled cohesive law for predicting the mixed mode failure is established by combining normal separation and tangential separation of surfaces in the cohesive zone model （CZM） and the cohesive element method. The Xu-Needleman exponential cohesive law with the fully shear failure mechanism is one of the most popular models. Based on the proposed consistently coupled rule/principle, the Xu-Needleman law with the fully shear failure mechanism is proved to be a non-consistently coupled cohesive law by analyzing the surface separation work. It is shown that the Xu-Needleman law is only valid in the mixed mode fracture when the normal separation work equals the tangential separation work. Based on the consistently coupled principle and the modification of the Xu-Needleman law, a consistently coupled cohesive （CCC） law is given. It is shown that the proposed CCC law has already overcome the non-consistency defect of the Xu-Needleman law with great promise in mixed mode analyses.
文摘In this paper, a selective activation strategy is studied in order to alleviate the issue of added compliance in the intrinsic cohesive zone model applied to arbitrary crack propagation. This strategy proceeds by first inserting cohesive elements between bulk elements and subsequently tying the duplicated nodes across the interface using controllable multi-point constraints before the analysis begins. Then, during the analysis, a part of the multi-point constraints are selectively released, thereby reactivating the corresponding cohesive elements and allowing cracks to initiate and propagate along the bulk element boundaries. The strategy is implemented in Abaqus/Standard using a user-defined multi-point constraint subroutine. Analysis results indicate that the strategy significantly alleviates the added compliance problem and reduces the computation time.
文摘目的找出混凝土裂缝扩展对纤维增强材料FRP与混凝土界面粘结性能的影响规律.方法基于断裂力学理论,采用商业软件ANSYS中的界面单元模型(Cohesive Zone Model CZM),模拟素混凝土梁跨中I型裂缝扩展以及FRP与混凝土界面II型裂缝的扩展过程.结果随着混凝土裂缝的扩展,加固梁承载力出现两个峰值:第一个峰值出现在混凝土宏观裂缝扩展的起始点,此时FRP布的应力低于500 MPa,FRP与混凝土界面切应力在混凝土裂缝附近较大,其余部分切应力及界面滑移量基本为零,界面处于完全粘结状态.第二个峰值出现在FRP与混凝土界面发生剥离时刻,之后界面剥离从混凝土跨中裂缝位置向梁端部扩展,加固梁的承载力保持在第二个峰值上,FRP布应力达到1 480 MPa,界面粘结切应力及滑移量向FRP端部移动,跨中完全剥离的界面,切应力降为零,滑移量保持不变.结论计算得到的荷载随混凝土开裂的变化趋势及峰值荷载与试验值吻合较好,说明笔者提出的数值模拟方法能较准确地预测CFRP加固带缝混凝土梁的承载力.
基金Project supported by the National Natural Science Foundation of China (No. 10272088), and the Program for New Century Excellent Talents in University, China
文摘The interface toughness of adhesively bonded structural members is one of the critical parameters for adhesive joint design. It is often assumed that the joint toughness is a material constant so that its value can be obtained from fracture tests of simple geometries such as DCB for Mode-Ⅰ, ENF for Mode-Ⅱ, using linear elastic fracture mechanics （LEFM）. However, the LEFM assumption of point-wise crack-tip fracture process is overly simplistic and may cause significant error in interpreting fracture test data. In this paper, the accuracy and applicability of various traditional beam-bending-theory based methods for fracture toughness evaluation, such as simple beam theory （SBT）, corrected beam theory （CBT） and experimental compliance method （ECM）, were assessed using the cohesive zone modelling （CZM） approach. It was demonstrated that the fracture process zone （FPZ） size has profound influence on toughness calculation and unfortunately, all the classic beam-bending theories based methods fail to include this important element and are erroneous especially when the ratio of crack length to FPZ size is relatively small （〈5.0）. It has also been demonstrated that after the FPZ size is incorporated into simple beam formulations, they provide much improved evaluation for fracture toughness. Formulation of first order estimate of FPZ size is aIso given in this paper.
基金the Scientific Research Foundation for Re-turned Overseas Chinese Scholars, MOE (No. J20050924)the United Research Foundation of the National Natural Science Com-mittee and the Ertan Hydropower Development Co. Ltd., China (No. 50579081)
文摘Fully automatic finite element(FE) modelling of the fracture process in quasi-brittle materials such as concrete and rocks and ductile materials such as metals and alloys,is of great significance in assessing structural integrity and presents tre-mendous challenges to the engineering community. One challenge lies in the adoption of an objective and effective crack propagation criterion. This paper proposes a crack propagation criterion based on the principle of energy conservation and the cohesive zone model(CZM) . The virtual crack extension technique is used to calculate the differential terms in the criterion. A fully-automatic discrete crack modelling methodology,integrating the developed criterion,the CZM to model the crack,a simple remeshing procedure to accommodate crack propagation,the J2 flow theory implemented within the incremental plasticity framework to model the ductile materials,and a local arc-length solver to the nonlinear equation system,is developed and im-plemented in an in-house program. Three examples,i.e.,a plain concrete beam with a single shear crack,a reinforced concrete(RC) beam with multiple cracks and a compact-tension steel specimen,are simulated. Good agreement between numerical predictions and experimental data is found,which demonstrates the applicability of the criterion to both quasi-brittle and ductile materials.
