准脆性材料的弹塑性各向异性损伤耦合本构模型研究

针对准脆性材料的非线性特征,在热动力学框架内,建立了准脆性材料的弹塑性与各向异性损伤耦合的本构关系.对准脆性材料的变形机理和损伤诱发的各向异性进行了诠释,并给出了损伤构形和有效构形中各物理量之间的关系.在有效应力空间内,建立了塑性屈服准则、拉压不同的塑性随动强化法则和各向同性强化法则.在损伤构形中,采用应变能释放率,建立了拉压损伤准则、拉压不同的损伤随动强化法则和各向同性强化法则.基于塑性屈服准则和损伤准则,构建了塑性势泛函和损伤势泛函,并由正交性法则,给出了塑性和损伤强化效应内变量的演化规律,同时,联立塑性屈服面和损伤加载面,给出了塑性流动和损伤演化内变量的演化法则.将损伤力学和塑性力学结合起来,建立了应变驱动的应力-应变增量本构关系,给出了本构数值积分的要点.以单轴加载-卸载往复试验识别和校准了材料常数,并对简单试验进行了预测,结果表明,所建本构模型对准脆件材料的非线性材料性能有良好的预测能力.     

空间网架结构在地震作用下的损伤累积分析

本文从连续介质损伤力学的基础理论出发，提出了弹性模量等价性假设，并在这一假设的基础上建立了考虑损伤累积效应的空间网架结构分析的有限元列式。最后，以空间网架结构在地震作用下的损伤累积分析为例，给出了本文方法的具体实施步骤。     

THE USE OF VISCO-ELASTOPLASTIC DAMAGE CONSTITUTIVE MODEL TO SIMULATE NONLINEAR BEHAVIOR OF CONCRETE

A visco-elastoplastic damage constitutive model is proposed for simulating nonlinear behavior of concrete. Based on traditional plastic theory, the irreversible deformation is simulated in effective stress space. In order to reflect different stiffness degradation mechanism of concrete under tensile and compressive loading conditions, both tensile and compressive damage variables are introduced, and then on the basis of energy release rate, the model is firmly derived within the concept of irreversible thermodynamics. The rate-dependent model is considered by introducing viscous regularization into the inelastic strain and damage variable, and combined with an additional elastic condition. Fully implicit backward-Euler algorithm is used to perform constitutive integration. Results of numerical examples using the proposed model agree well with test results for specimens under uniaxial tension and compression, biaxial loading and triaxial loading. Failure processes of single-edge-notched (SEN) beam and double-edge-notched (DEN) specimen are also simulated to further validate the proposed model.     

裂隙岩体损伤局部化破坏分岔模型及其应用

采用概率统计方法分析节理裂隙岩体的几何特征，定义了反映裂隙岩体几何特征的组构张量．基于不可逆热力学理论，通过裂纹扩展的细观分析，得出了损伤的发展机理和演化方程，把损伤演化和裂隙的几何特征的变化联系起来，建立了弹塑性损伤本构关系．为分析含有节理裂隙岩体在发生局部化破坏时的特征，通过对发生局部化时的裂隙岩体的分析。构造了适用于节理裂隙岩体局部化分析的不连续分岔模型．利用非线性规划数值解法，可以得出局部化破坏的方向特征．在有限元方法中，根据该模型给出了节理裂隙岩体相关的算例，分析表明该模型用于分析裂隙岩体的局部化破坏是有效的．     

A micromechanical damage model for rocks and concretes under triaxial compression

Based on analysis of deformation in an infinite isotropic elastic matrix containing an embedded elliptic crack, subject to far field triaxial compressive stress, the energy release rate and a mixed fracture criterion are obtained by using an energy balance approach. The additional compliance tensor induced by a single closed elliptic microcrack in a representative volume element and its in-plane growth is derived. The additional compliance tensor induced by the kinked growth of the elliptic microcrack is also obtained. The effect of the microcracks, randomly distributed both in geometric characteristics and orientations, is analyzed with the Taylor＇s scheme by introducing an appropriate probability density function. A micromechanical damage model for rocks and concretes under triaxial compression is obtained and experimentally verified.     

饱和和非饱和介质的弹塑性损伤模型

针对饱和和非饱和工程材料变形和强度特点,给出了一个具体的弹塑性损伤本构方程,该本构方程可以描述材料性质的劣化过程（即损伤和软化）以及饱和程度对材料变形强度特性的影响。此外,还讨论了该弹塑性损伤本构方程的有限元实施方法,编制了专用的有限元程序。对常规三轴试伯进行了有限元分析,得出了一些具体的结果。     

含损伤的冻土本构模型及耦合问题数值分析

从复合材料的细观力学机理出发,建立了含损伤的冻土弹性本构模型. 对于在不同冰体积 含量和不同温度下的冻结砂土,由该损伤本构模型计算的结果与实测的应力-应变曲线比较 吻合. 利用自主开发的程序,分别对渠道冻结和冻土路基的水分场、温度场、应力场3场耦 合进行数值模拟,得到了比较准确、详尽的符合实际的温度场与应力场、位移场、应变场耦 合的计算结果,与前人的计算及实测结果相符合,规律一致. 表明该程序能够计算冻土材料 的相关物理量,并能很好地描述这些相关物理量之间的关系.     

基于内时大变形弹塑性本构模型的镦粗热力耦合分析

采用一个简单机械模型得到了热力耦合的弹塑性大变形本构方程,它满足不可逆热力学的基本约束,并考虑到了储存在残余微应力场中的能量对后续变形的贡献.发展了相应的算法,对弹性压板间的圆柱镦粗进行了分析.结果表明,在镦粗过程中的塑性耗散和工件两端的热传导造成工件中温度分布的不均匀,因此导致了材料力学性能的改变.与实验结果和等温假设下的计算结果进行了比较,表明计及塑性耗散热的计算结果与实验结果更为一致.     

DAMAGE MODEL FOR HARDENING AND SOFTENING MATERIAL IN GENERAL STATE OF STRESS

The present paper is aimed to simulate progression of damage,hardeningand softening response in brittle materials such as concrete or rock in general state ofstress.Similar shape of surfaces for yield,failure and damage progressing areavailable,and softening strain is treated as plasticity.Then,the proposed model isapplied to solving several boundary value problems.     

含水合物沉积物三轴剪切试验与损伤统计分析

天然气水合物开采诱发水合物分解,削弱水合物地层强度,可能导致地层滑动和生产平台倒塌等工程地质灾害,对水合物开采安全性构成严重威胁.深入理解含水合物沉积物力学性质并建立合理的本构关系模型是水合物开采安全性评价的前提条件.在自主研发的含水合物沉积物力学性质测试实验装置上,采用饱和水海砂沉积物气体扩散法制备了含水合物沉积物样品,并开展了系列的排水三轴剪切试验,通过时域反射技术实现了样品中水合物饱和度的实时在线测量;基于复合材料的罗伊斯(Reuss)应力串联模型和沃伊特(Voigt)应变并联模型提出了含水合物沉积物等效弹性模量的细观力学混合律模型,结合损伤统计理论和摩尔-库伦破坏准则改进了含水合物沉积物的本构关系模型.结果表明:随着水合物饱和度的增加和有效围压的减小,应力-应变曲线由应变硬化型变为应变软化型,割线模量和峰值强度均随水合物饱和度与有效围压的增加而提高,黏聚力受水合物饱和度影响明显,而内摩擦角基本不变;提出的等效弹性模量细观力学混合律模型与改进的本构关系模型均具有良好的适用性,模型参数少且物理意义明确.      

混凝土静力与动力损伤本构模型研究进展述评

对混凝土材料在静力和动力载荷作用下的损伤本构关系模型进行了评述.梳理了混凝土本构关系研究的历史脉络和逻辑脉络;归纳总结了在混凝土本构关系研究发展过程中具有代表性意义、并且对重大工程建设具有参考意义的若干混凝土静力和动力损伤本构模型.基于对混凝土材料非线性及随机性的理解和诠释,阐述了混凝土静力和动力本构关系研究的发展趋势.      

节理岩体能量损伤本构模型与工程应用

本文根据Betti能量互易定理,节理岩体能量损伤演化方程,广义正交法则和塑性损伤一致性条件建立了节理岩体的能量损伤本构模型,并将该模型编制成三维非线性有限元计算程序应用于溪洛渡地下厂房洞室群施工开挖稳定性分析,获得了较为满意的计算结果。     

A DUAL-SURFACE DAMAGE MODEL AND EVALUATION FOR NATURAL SOILS WITHIN THE THERMOMECHANICAL FRAMEWORK

Naturally deposited or residual soils exhibit more complicated behavior than remolded clays. A dual-surface damage model for structured soils is developed based on the thermodynamics framework established in our first paper. The shift stresses and the transformation between the generalized dissipative stress space and actual stress space are established following a systematic procedure. The corresponding constitutive behavior of the proposed model is determined, which reflects the internal structural configuration and damage behavior for geomaterials. Four evolution variables κj^i（i=D, R;j=V, S） and the basic parameters λ, s, v and e0 are introduced to account for the progressive loss of internal structure for natural clays. A series of fully triaxial tests and isotropic compression tests are performed for structured and reconstituted samples of Beijing and Zhengzhou natural clays. The validation of the proposed model is examined by comparing the numerical results with the experimental data.     

DISSIPATION-BASED CONSISTENT RATE-DEPENDENT MODEL FOR CONCRETE

An energy-dissipation based viscoplastic consistency model is presented to describe the performance of concrete under dynamic loading. The development of plasticity is started with the thermodynamic hypotheses in order that the model may have a sound theoretical background. Independent hardening and softening and the rate dependence of concrete are described separately for tension and compression. A modified implicit backward Euler integration scheme is adopted for the numerical computation. Static and dynamic behavior of the material is illustrated with certain numerical examples at material point level and structural level, and compared with existing experimental data. Results validate the effectiveness of the model.     

UNIAXIAL COMPRESSION TEST AND DAMAGE CONSTITUTIVE MODEL FOR ANALYSIS OF FROZEN CLAY 1)

从冻土微元破坏服从Weibull随机分布的特点出发,将Mohr--Coulomb强度准则作为冻土微元统计分布变量,利用应变等价性假说,建立了单轴应力状态下冻结黏土损伤本构模型;在此基础上,讨论了模型参数和弹性模量与冻结温度的关系,对模型参数和弹性模量进行合理修正,建立了温度影响下的冻结黏土损伤本构模型,并与试验结果进行对比。分析结果表明：考虑温度效应的损伤本构模型能很好地模拟冻结黏土应力--应变全过程曲线,具有很好的适应性。     

单向应力状态下钢材高温分析的损伤模型

本文结合结构钢材火灾高温分析的特点，通过对Ｌｅｍａｉｔｒｅ关于常温下金属材料延性损伤模型和修改，提出一种适用应力状态下钢材高温分析的损伤模型，为进行钢框架在火灾高温作用下及火灾冷却后的２和损伤分析提供可能性。     

泡沫铝率相关本构模型及其在三明治夹芯板冲击吸能特性的应用研究

高孔隙率泡沫铝芯体三明治板具有轻质、高比刚度和减振吸能等优良的力学特性和物理特性,被广泛地应用于碰撞吸能部件上.近年来,高孔隙率泡沫铝在动态压缩下是否具有应变率敏感性成为广大学者的研究焦点.论文建立了横观各向同性率相关本构模型来描述高孔隙率泡沫铝的应变率效应,给出了有限元的计算步骤,基于ABAQUS/Explicit平台开发了子程序VUMAT,并在单个单元模型中验证了计算结果的稳定性和可靠性.将其作为三明治板芯体的材料属性,研究了不同率敏感系数对整个结构冲击吸能能力的影响.结果表明,随着率敏感系数的增加,芯体吸收的能量也随之增加,而底面面板的变形会越小,再一次验证了该子程序可以用来描述泡沫铝的应变率效应.采用该率相关模型及其子程序VUMAT,可以对泡沫铝夹芯三明治板的冲击力学特性进行很好的有限元模拟,对工程实际应用具有一定的指导意义.