This paper concentrates on simulating fracture in thin walled single-lap joints connected by resistance spot-welding(RSW)process which were subjected to tensile loading.For this purpose,three sets of lap-joints with d...This paper concentrates on simulating fracture in thin walled single-lap joints connected by resistance spot-welding(RSW)process which were subjected to tensile loading.For this purpose,three sets of lap-joints with different spot configurations were tested to achieve the joints’tensile behavior.To simulate the joints tensile behavior,firstly a 2D axisymmetric finite element(FE)model was used to calculate residual stresses induced during the welding process.Then the results were transferred to 3D models as pre-stress.In this step,cohesive zone model(CZM)technique was used to simulate fracture in the models under tensile load.Cohesive zone parameters were extracted using coach-peel and shear lap specimens.The results were employed to simulate deformation and failure in single lap spot weld samples.It has been shown that considering the residual stresses in simulating deformation and fracture load enables quite accurate predictions.展开更多
A new test method was proposed to evaluate the cohesive strength of composite laminates. Cohesive strength and the critical strain energy for Mode-II interlamiar fracture of E-glass/epoxy woven fabrication were determ...A new test method was proposed to evaluate the cohesive strength of composite laminates. Cohesive strength and the critical strain energy for Mode-II interlamiar fracture of E-glass/epoxy woven fabrication were determined from the single lap joint(SLJ) and end notch flexure(ENF) test, respectively. In order to verify their adequacy, a cohesive zone model simulation based on interface finite elements was performed. A closed form solution for determination of the penalty stiffness parameter was proposed. Modified form of Park-Paulino-Roesler traction-separation law was provided and conducted altogether with trapezoidal and bilinear mixed-mode damage models to simulate damage using Abaqus cohesive elements. It was observed that accurate damage prediction and numerical convergence were obtained using the proposed penalty stiffness. Comparison between three damage models reveals that good simulation of fracture process zone and delamination prediction were obtained using the modified PPR model as damage model. Cohesive zone length as a material property was determined. To ensure the sufficient dissipation of energy, it was recommended that at least 4 elements should span cohesive zone length.展开更多
The key parameters of the adhesive layer of a reinforcing patch are of great significance and affect the ability to suppress crack propagation in an Al–Li alloy patch-reinforced structure.This paper proposes a method...The key parameters of the adhesive layer of a reinforcing patch are of great significance and affect the ability to suppress crack propagation in an Al–Li alloy patch-reinforced structure.This paper proposes a method to determine the key parameters of the adhesive layer of adhesively bonded joints in the Al–Li alloy patch-reinforced structure.A zero-thickness cohesive zone model(CZM)was selected to simulate the adhesive layer’s fracture process,and an orthogonal simulation was designed to compare against the test results.A three-dimensional progressive damage model of an Al–Li alloy patch-reinforced structure with single-lap adhesively bonded joints was developed.The simulation’s results closely agree with the test results,demonstrating that this method of determining the key parameters is likely accurate.The results also verify the correctness of the cohesive strength and fracture energy,the two key parameters of the cohesive zone model.The model can accurately predict the strength and fracture process of adhesively bonded joints,and can be used in research to suppress crack propagation in Al–Li alloy patch-reinforced structures.展开更多
以2195铝锂合金搅拌摩擦焊接头为研究对象,开展基于相场法的脆性断裂数值模拟研究.相场法以Francfort-Marigo变分原理为理论基础,在系统总势能中考虑断裂能,并考虑应变能的拉伸和压缩分解.引入弥散裂纹模型近似非光滑的裂纹拓扑关系,以...以2195铝锂合金搅拌摩擦焊接头为研究对象,开展基于相场法的脆性断裂数值模拟研究.相场法以Francfort-Marigo变分原理为理论基础,在系统总势能中考虑断裂能,并考虑应变能的拉伸和压缩分解.引入弥散裂纹模型近似非光滑的裂纹拓扑关系,以序参量表征材料损伤.基于Abaqus软件联合用户自定义元素子程序(user element subroutine,UEL),采用交替解法实现位移场和相场的耦合,进而求解脆性断裂问题.通过与试验结果对比,基于相场法的紧凑拉伸试件焊接区脆性断裂的裂纹扩展路径模拟吻合较好,且最大载荷值误差仅为0.46%.文中进一步研究增量步步长△u、相场特征宽度Lc与网格尺寸h对相场法模拟结果的影响,并将相场法与扩展有限元法(extended finite element method,XFEM)和内聚力模型(cohesive zone model,CZM)进行对比.研究表明,当分析增量步为1×10-4时,分析结果收敛. Lc与裂纹h存在2倍的关系时,模拟结果较为准确.相场法可以准确模拟2195铝锂合金搅拌摩擦焊接头脆性断裂演化过程.展开更多
为了探究装配式风电混塔胶黏拼缝的黏结性能以及塔筒整体的承载力,开展了混凝土-结构胶黏结界面的法向拉伸和切向剪切试验。针对混凝土黏结界面位置的裂纹开展以及破坏模式进行了详细考察,明确了黏结界面的法向以及切向的内聚力本构模...为了探究装配式风电混塔胶黏拼缝的黏结性能以及塔筒整体的承载力,开展了混凝土-结构胶黏结界面的法向拉伸和切向剪切试验。针对混凝土黏结界面位置的裂纹开展以及破坏模式进行了详细考察,明确了黏结界面的法向以及切向的内聚力本构模型。基于试验得到的内聚力本构模型建立了6节段的装配式风电混塔简化模型,开展了装配式塔筒在纯扭及弯扭荷载工况下的承载能力研究,探究了竖缝结构胶对于装配式混塔承载力的影响。研究表明:混凝土-结构胶-混凝土黏结试件的剪切破坏模式以黏结界面破坏为主,抗剪性能会弱于混凝土本身;而法向拉伸破坏模式以混凝土基材破坏为主,抗拉性能会强于混凝土本身;通过数值模拟计算结果发现,相比于摩擦接触模型,竖缝内聚力模型(cohesive zone model,CZM)的抗扭承载能力有显著提升,但扭矩持续加载导致竖缝内聚力单元破坏后,其抗扭承载力和摩擦接触模型相近。展开更多
文摘This paper concentrates on simulating fracture in thin walled single-lap joints connected by resistance spot-welding(RSW)process which were subjected to tensile loading.For this purpose,three sets of lap-joints with different spot configurations were tested to achieve the joints’tensile behavior.To simulate the joints tensile behavior,firstly a 2D axisymmetric finite element(FE)model was used to calculate residual stresses induced during the welding process.Then the results were transferred to 3D models as pre-stress.In this step,cohesive zone model(CZM)technique was used to simulate fracture in the models under tensile load.Cohesive zone parameters were extracted using coach-peel and shear lap specimens.The results were employed to simulate deformation and failure in single lap spot weld samples.It has been shown that considering the residual stresses in simulating deformation and fracture load enables quite accurate predictions.
文摘A new test method was proposed to evaluate the cohesive strength of composite laminates. Cohesive strength and the critical strain energy for Mode-II interlamiar fracture of E-glass/epoxy woven fabrication were determined from the single lap joint(SLJ) and end notch flexure(ENF) test, respectively. In order to verify their adequacy, a cohesive zone model simulation based on interface finite elements was performed. A closed form solution for determination of the penalty stiffness parameter was proposed. Modified form of Park-Paulino-Roesler traction-separation law was provided and conducted altogether with trapezoidal and bilinear mixed-mode damage models to simulate damage using Abaqus cohesive elements. It was observed that accurate damage prediction and numerical convergence were obtained using the proposed penalty stiffness. Comparison between three damage models reveals that good simulation of fracture process zone and delamination prediction were obtained using the modified PPR model as damage model. Cohesive zone length as a material property was determined. To ensure the sufficient dissipation of energy, it was recommended that at least 4 elements should span cohesive zone length.
基金Project(51575535)supported by the National Natural Science Foundation of ChinaProject(2015CX002)supported by the Innovation-driven Plan in Central South University,China+2 种基金Project(zzyjkt2013-09B)supported by the Fund of the State Key Laboratory of High Performance Manufacturing,ChinaProject(2017zzts638)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(2016RS2015)supported by the Scientific and Technological Leading Talent Projects of Hunan Province,China
文摘The key parameters of the adhesive layer of a reinforcing patch are of great significance and affect the ability to suppress crack propagation in an Al–Li alloy patch-reinforced structure.This paper proposes a method to determine the key parameters of the adhesive layer of adhesively bonded joints in the Al–Li alloy patch-reinforced structure.A zero-thickness cohesive zone model(CZM)was selected to simulate the adhesive layer’s fracture process,and an orthogonal simulation was designed to compare against the test results.A three-dimensional progressive damage model of an Al–Li alloy patch-reinforced structure with single-lap adhesively bonded joints was developed.The simulation’s results closely agree with the test results,demonstrating that this method of determining the key parameters is likely accurate.The results also verify the correctness of the cohesive strength and fracture energy,the two key parameters of the cohesive zone model.The model can accurately predict the strength and fracture process of adhesively bonded joints,and can be used in research to suppress crack propagation in Al–Li alloy patch-reinforced structures.
文摘以2195铝锂合金搅拌摩擦焊接头为研究对象,开展基于相场法的脆性断裂数值模拟研究.相场法以Francfort-Marigo变分原理为理论基础,在系统总势能中考虑断裂能,并考虑应变能的拉伸和压缩分解.引入弥散裂纹模型近似非光滑的裂纹拓扑关系,以序参量表征材料损伤.基于Abaqus软件联合用户自定义元素子程序(user element subroutine,UEL),采用交替解法实现位移场和相场的耦合,进而求解脆性断裂问题.通过与试验结果对比,基于相场法的紧凑拉伸试件焊接区脆性断裂的裂纹扩展路径模拟吻合较好,且最大载荷值误差仅为0.46%.文中进一步研究增量步步长△u、相场特征宽度Lc与网格尺寸h对相场法模拟结果的影响,并将相场法与扩展有限元法(extended finite element method,XFEM)和内聚力模型(cohesive zone model,CZM)进行对比.研究表明,当分析增量步为1×10-4时,分析结果收敛. Lc与裂纹h存在2倍的关系时,模拟结果较为准确.相场法可以准确模拟2195铝锂合金搅拌摩擦焊接头脆性断裂演化过程.
文摘为了探究装配式风电混塔胶黏拼缝的黏结性能以及塔筒整体的承载力,开展了混凝土-结构胶黏结界面的法向拉伸和切向剪切试验。针对混凝土黏结界面位置的裂纹开展以及破坏模式进行了详细考察,明确了黏结界面的法向以及切向的内聚力本构模型。基于试验得到的内聚力本构模型建立了6节段的装配式风电混塔简化模型,开展了装配式塔筒在纯扭及弯扭荷载工况下的承载能力研究,探究了竖缝结构胶对于装配式混塔承载力的影响。研究表明:混凝土-结构胶-混凝土黏结试件的剪切破坏模式以黏结界面破坏为主,抗剪性能会弱于混凝土本身;而法向拉伸破坏模式以混凝土基材破坏为主,抗拉性能会强于混凝土本身;通过数值模拟计算结果发现,相比于摩擦接触模型,竖缝内聚力模型(cohesive zone model,CZM)的抗扭承载能力有显著提升,但扭矩持续加载导致竖缝内聚力单元破坏后,其抗扭承载力和摩擦接触模型相近。
