Mechanics of Cohesive-frictional Materials最新文献_第6页

Adaptivity based on error estimation for viscoplastic softening materials 基于误差估计的粘塑性软化材料的自适应性

Mechanics of Cohesive-frictional Materials

Pub Date : 2000-03-01 DOI: 10.1002/(SICI)1099-1484(200002)5:2<87::AID-CFM86>3.0.CO;2-W

Pedro Díez, Marino Arroyo, Antonio Huerta

This paper focuses on the numerical simulation of strain softening mechanical problems. Two problems arise: (1) the constitutive model has to be regular and (2) the numerical technique must be able to capture the two scales of the problem (the macroscopic geometrical representation and the microscopic behaviour in the localization bands). The Perzyna viscoplastic model is used in order to obtain a regularized softening model allowing to simulate strain localization phenomena. This model is applied to quasistatic examples. The viscous regularization of quasistatic processes is also discussed: in quasistatics, the internal length associated with the obtained band width is no longer only a function of the material parameters but also depends on the boundary value problem (geometry and loads, specially loading velocity).

An adaptive computation is applied to softening viscoplastic materials showing strain localization. As the key ingredient of the adaptive strategy, a residual-type error estimator is generalized to deal with such highly non-linear material model.

In several numerical examples the adaptive process is able to detect complex collapse modes that are not captured by a first, even if fine, mesh. Consequently, adaptive strategies are found to be essential to detect the collapse mechanism and to assess the optimal location of the elements in the mesh. Copyright © 2000 John Wiley & Sons, Ltd.

本文主要研究应变软化力学问题的数值模拟。出现了两个问题：（1）本构模型必须是规则的；（2）数值技术必须能够捕捉问题的两个尺度（宏观几何表示和局部化带中的微观行为）。Perzyna粘塑性模型用于获得正则化软化模型，从而模拟应变局部化现象。该模型应用于准静态实例。还讨论了拟静态过程的粘性正则化：在拟静态中，与所获得的带宽相关的内部长度不再仅仅是材料参数的函数，而是取决于边值问题（几何和载荷，特别是加载速度）。将自适应计算应用于显示应变局部化的软化粘塑性材料。残差型误差估计器作为自适应策略的关键组成部分，被推广用于处理这种高度非线性的材料模型。在几个数值示例中，自适应过程能够检测第一网格（即使是精细网格）未捕捉到的复杂塌陷模式。因此，发现自适应策略对于检测塌陷机制和评估网格中元素的最佳位置至关重要。版权所有©2000 John Wiley&；有限公司。

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引用次数: 51

The effect of volumetric strain on elastic parameters for rock salt 体积应变对岩盐弹性参数的影响

Mechanics of Cohesive-frictional Materials

Pub Date : 2000-03-01 DOI: 10.1002/(SICI)1099-1484(200002)5:2<113::AID-CFM84>3.0.CO;2-8

A. Matei, N. D. Cristescu

An experimental program aimed at characterizing the elastic response of rock salt under both quasi-static and dynamic conditions has been performed. The program includes uniaxial short-term tests and uniaxial creep tests. During axial loading, the travel times of longitudinal and transverse elastic waves propagating in the specimen were simultaneously recorded, together with the strain state. The test results show that in uniaxial, short-term tests, the dynamically determined elastic parameters vary in a similar way as does the irreversible volumetric strain, i.e. they increase in the compressibility domain, are nearly constant in the transition zone from compressibility to dilatancy, and decrease in the dilatancy domain. In creep tests, the variation is more complicated: the elastic parameters vary immediately after stress application, but continue to vary slowly in time when stress is kept constant. Moreover, both G and K increase with time when ϵ^I_ν increases and vice versa (superscript I stands for ‘irreversible’ and subscript ν for ‘volumetric’). It appears that the elastic parameters depend on the strain history or, perhaps on some other type of damage parameters. Thus, the non-constant elastic parameters governing the ‘instantaneous’ response in an elastic/ viscoplastic constitutive equation that describes compressibility and/or dilatancy and damage (as the total energy released by microcracking during dilatancy) were determined. Copyright © 2000 John Wiley & Sons, Ltd.

已经执行了一个旨在表征岩盐在准静态和动态条件下的弹性响应的实验程序。该程序包括单轴短期试验和单轴蠕变试验。在轴向加载过程中，同时记录在试样中传播的纵向和横向弹性波的传播时间以及应变状态。试验结果表明，在单轴短期试验中，动态确定的弹性参数的变化方式与不可逆体积应变的变化方式相似，即它们在压缩性域增加，在从压缩性到剪胀性的过渡区几乎不变，在剪胀性域减小。在蠕变试验中，变化更为复杂：施加应力后，弹性参数立即变化，但当应力保持不变时，弹性参数继续缓慢变化。此外，G和K都随着时间的推移而增加，当ΓIΓ增加时，反之亦然（上标I代表“不可逆”，下标Γ代表“体积”）。弹性参数似乎取决于应变历史，或者可能取决于其他类型的损伤参数。因此，确定了控制弹性/粘塑性本构方程中“瞬时”响应的非恒定弹性参数，该方程描述了压缩性和/或剪胀和损伤（作为剪胀过程中微裂纹释放的总能量）。版权所有©2000 John Wiley&；有限公司。

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引用次数: 9

Adaptivity based on error estimation for viscoplastic softening materials 基于误差估计的粘塑性软化材料自适应研究

Mechanics of Cohesive-frictional Materials

Pub Date : 2000-02-01 DOI: 10.1002/(SICI)1099-1484(200002)5:2<87::AID-CFM86>3.0.CO;2-W

P. Díez, M. Arroyo, A. Huerta

This paper focuses on the numerical simulation of strain softening mechanical problems. Two problems arise: (1) the constitutive model has to be regular and (2) the numerical technique must be able to capture the two scales of the problem (the macroscopic geometrical representation and the microscopic behaviour in the localization bands). The Perzyna viscoplastic model is used in order to obtain a regularized softening model allowing to simulate strain localization phenomena. This model is applied to quasistatic examples. The viscous regularization of quasistatic processes is also discussed: in quasistatics, the internal length associated with the obtained band width is no longer only a function of the material parameters but also depends on the boundary value problem (geometry and loads, specially loading velocity). An adaptive computation is applied to softening viscoplastic materials showing strain localization. As the key ingredient of the adaptive strategy, a residual-type error estimator is generalized to deal with such highly non-linear material model. In several numerical examples the adaptive process is able to detect complex collapse modes that are not captured by a first, even if fine, mesh. Consequently, adaptive strategies are found to be essential to detect the collapse mechanism and to assess the optimal location of the elements in the mesh. Copyright © 2000 John Wiley & Sons, Ltd.

本文主要研究应变软化力学问题的数值模拟。出现了两个问题:(1)本构模型必须是规则的;(2)数值技术必须能够捕获问题的两个尺度(宏观几何表示和局部化带中的微观行为)。采用Perzyna粘塑性模型，得到了一个正则化软化模型，可以模拟应变局部化现象。该模型应用于准静态算例。本文还讨论了准静态过程的粘性正则化问题:在准静态过程中，与获得的带宽相关的内长度不再仅仅是材料参数的函数，而且还取决于边值问题(几何和载荷，特别是加载速度)。对表现应变局部化的软化粘塑性材料，应用自适应计算。作为自适应策略的关键组成部分，推广了残差型误差估计器来处理这种高度非线性的材料模型。在几个数值例子中，自适应过程能够检测到复杂的折叠模式，这些模式即使是精细网格也不能被第一网格捕获。因此，发现自适应策略对于检测崩溃机制和评估网格中元素的最佳位置至关重要。版权所有©2000约翰威利父子有限公司

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引用次数: 51

The effect of volumetric strain on elastic parameters for rock salt 体积应变对岩盐弹性参数的影响

Mechanics of Cohesive-frictional Materials

Pub Date : 2000-02-01 DOI: 10.1002/(SICI)1099-1484(200002)5:2<113::AID-CFM84>3.0.CO;2-8

Ani Matei, N. Cristescu

An experimental program aimed at characterizing the elastic response of rock salt under both quasi-static and dynamic conditions has been performed. The program includes uniaxial short-term tests and uniaxial creep tests. During axial loading, the travel times of longitudinal and transverse elastic waves propagating in the specimen were simultaneously recorded, together with the strain state. The test results show that in uniaxial, short-term tests, the dynamically determined elastic parameters vary in a similar way as does the irreversible volumetric strain, i.e. they increase in the compressibility domain, are nearly constant in the transition zone from compressibility to dilatancy, and decrease in the dilatancy domain. In creep tests, the variation is more complicated: the elastic parameters vary immediately after stress application, but continue to vary slowly in time when stress is kept constant. Moreover, both G and K increase with time when ϵIν increases and vice versa (superscript I stands for ‘irreversible’ and subscript ν for ‘volumetric’). It appears that the elastic parameters depend on the strain history or, perhaps on some other type of damage parameters. Thus, the non-constant elastic parameters governing the ‘instantaneous’ response in an elastic/ viscoplastic constitutive equation that describes compressibility and/or dilatancy and damage (as the total energy released by microcracking during dilatancy) were determined. Copyright © 2000 John Wiley & Sons, Ltd.

对岩盐在准静态和动态两种条件下的弹性响应进行了实验研究。该程序包括单轴短期试验和单轴蠕变试验。在轴向加载过程中，同时记录了纵波和横波在试件中的传播时间，并记录了应变状态。试验结果表明，在单轴短期试验中，动态确定的弹性参数与不可逆体积应变的变化规律相似，即在压缩域中增加，在压缩到剪胀的过渡区基本不变，在剪胀域中减小。在蠕变试验中，弹性参数的变化更为复杂，在施加应力后，弹性参数立即发生变化，而在保持应力不变的情况下，弹性参数随时间继续缓慢变化。此外，当ϵIν增加时，G和K都随时间增加，反之亦然(上标I代表“不可逆”，下标ν代表“体积”)。看来，弹性参数取决于应变历史，或者可能是一些其他类型的损伤参数。这样，就确定了控制弹性/粘塑性本构方程中“瞬时”响应的非恒定弹性参数，该本构方程描述了压缩性和/或剪胀性和损伤(作为剪胀期间微裂纹释放的总能量)。版权所有©2000约翰威利父子有限公司

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引用次数: 9

Conditions for embedding Casagrande's critical states into hypoplasticity 将卡萨格兰德临界状态嵌入低塑性的条件

Mechanics of Cohesive-frictional Materials

Pub Date : 2000-02-01 DOI: 10.1002/(SICI)1099-1484(200002)5:2<125::AID-CFM85>3.0.CO;2-0

E. Bauer

引用次数: 84

Study of poroelasticity material coefficients as response of microstructure 孔隙弹性材料系数作为微观结构响应的研究

Mechanics of Cohesive-frictional Materials

Pub Date : 2000-02-01 DOI: 10.1002/(SICI)1099-1484(200002)5:2<149::AID-CFM89>3.0.CO;2-F

D. Lydzba, J. Shao

Using an asymptotic homogenization method, the effect of the porous medium microstructure on the values of poroelastic coefficients is studied in this paper. First, the Biot’s poroelasticity theory and general relations linking the macroscopic poroelastic coefficients with the averaged micromechanical solutions are recalled. Considering a variational formulation of appropriate boundary values problems stated for the representative volume element, microstructural parameters affecting the values of poroelastic coefficients are identified. In order to clarify specific roles of some relevant microstructure parameters, numerical investigations for some simplified pores geometries are presented. The numerical results obtained clearly show a strong dependence of the poroelastic coefficients on the internal geometry of pores as well as on the global porosity of the medium. In the last part, based on the micromechanics analysis, the definition of initial plastic yield condition for saturated porous media is introduced and a new interpretation of the effective stress concept in inelastic domain is proposed. Copyright © 2000 John Wiley & Sons, Ltd.

采用渐近均匀化方法，研究了多孔介质微观结构对孔隙弹性系数取值的影响。首先，回顾了Biot的孔隙弹性理论以及宏观孔隙弹性系数与平均微观力学解之间的一般关系。考虑具有代表性的体积元的适当边值问题的变分公式，确定了影响孔隙弹性系数值的微观结构参数。为了明确一些相关微观结构参数的具体作用，对一些简化的孔隙几何形状进行了数值研究。数值结果清楚地表明，孔隙弹性系数与孔隙的内部几何形状以及介质的整体孔隙度密切相关。最后，在细观力学分析的基础上，引入了饱和多孔介质初始塑性屈服条件的定义，提出了非弹性域有效应力概念的新解释。版权所有©2000约翰威利父子有限公司

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引用次数: 72

Localization criteria for non-linear constitutive equations of geomaterials 岩土材料非线性本构方程的局部化准则

Mechanics of Cohesive-frictional Materials

Pub Date : 2000-01-01 DOI: 10.1002/(SICI)1099-1484(200001)5:1<61::AID-CFM83>3.0.CO;2-M

René Chambon, Stéphane Crochepeyre, Jacques Desrues

This paper is devoted to two specific aspects of shear band analysis for geomaterials, which are basically, non-standard materials. Problems arising from incremental non-linearity (multilinear or thoroughly non-linear models) and consequences of discontinuities of the constitutive equations with respect to loading parameters, are especially investigated. Copyright © 2000 John Wiley & Sons, Ltd.

引用次数: 71

Microstructural approach and transfer water modelling in highly compacted unsaturated swelling clays 高度压实非饱和膨胀粘土的微观结构方法和输水模型

Mechanics of Cohesive-frictional Materials

Pub Date : 2000-01-01 DOI: 10.1002/(SICI)1099-1484(200001)5:1<41::AID-CFM75>3.0.CO;2-N

N. Saiyouri, P. Y. Hicher, D. Tessier

A compacted smectite clay was studied in order to understand the swelling phenomenon. The influence of the sample initial state on the swelling mechanisms was demonstrated. A complete physical–chemical and mineralogical characterization of the clay was achieved using X-ray by reflexion and thermal methods. The X-ray diffraction by transmission method allowed to describe the various levels of the hydrated clay organization and the microstructure evolution. The pore distribution and the water partition are shown. Other important parameters: water retention, inter-layer distances, particle size, number of layers per particle were examined. This information gives the ability to follow the swelling which occurred in two steps, and to calculate the swelling potential versus the water content, or the void ratio. In application to this study, a water transfer in unsaturated clay was studied with the laws of continuous medium mechanics. A finite difference program was used to examine two cases: prevented and free swelling in an oedometer. In order to take into account the material deformation, the swelling potential was introduced in the diffusion coefficients. The simulation results of the water transfer obtained on this basis, were in good agreement with the experiments. Copyright © 2000 John Wiley & Sons, Ltd.

研究了压实蒙脱石粘土的膨胀现象。证明了样品初始状态对溶胀机制的影响。使用X射线反射法和热法对粘土进行了完整的物理-化学和矿物学表征。透射法的X射线衍射可以描述不同水平的水化粘土组织和微观结构的演变。显示了孔隙分布和水分分配。检查了其他重要参数：保水性、层间距离、颗粒尺寸、每个颗粒的层数。该信息提供了跟踪在两个步骤中发生的溶胀的能力，并计算溶胀势与含水量或空隙率的关系。在本研究中，应用连续介质力学定律研究了非饱和粘土中的水分传输。有限差分程序用于检查两种情况：水肿仪中的预防性肿胀和游离性肿胀。为了考虑材料的变形，在扩散系数中引入了膨胀势。在此基础上得到的输水模拟结果与实验结果吻合较好。版权所有©2000 John Wiley&；有限公司。

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引用次数: 127

THE FINITE ELEMENT METHOD IN THE STATIC AND DYNAMIC DEFORMATION AND CONSOLIDATION OF POROUS MEDIA, 2nd edn, R. W. Lewis and B. A. Schrefler, Wiley, Chichester, 1998. ISBN 0-471-92809-7. GB£75.00. 多孔介质静态和动态变形与固结的有限元方法，第2版，R.W.Lewis和B.A.Schrefler，Wiley，Chichester，1998。是0-471-92809-7。GB 75.00英镑。

Mechanics of Cohesive-frictional Materials

Pub Date : 2000-01-01 DOI: 10.1002/(SICI)1099-1484(200001)5:1<85::AID-CFM94>3.0.CO;2-8

Roberto Nova

引用次数: 0

Constitutive testing of Red Wildmoor sandstone Red Wildmoor砂岩的本构试验

Mechanics of Cohesive-frictional Materials

Pub Date : 2000-01-01 DOI: 10.1002/(SICI)1099-1484(200001)5:1<1::AID-CFM74>3.0.CO;2-H

E. Papamichos, J. Tronvoll, I. Vardoulakis, J. F. Labuz, A. Skjærstein, T. E. Unander, J. Sulem

The first objective of this research was to improve the experimental measurements for the constitutive behaviour of Red Wildmoor sandstone by optimizing the boundary conditions and specimen geometry, and improving the triaxial test instrumentation. The uniformity of deformation of the rock specimen was improved by minimizing specimen bulging due to specimen slenderness and end-surface frictional constraints. The improvements in the instrumentation were aimed at improving the monitoring of the applied forces, axial and radial deformations, and macroscopic rock failure through use of high precision LVDTs and cantilever gauges, acoustic emission measurements and acoustic pulse transmission velocities. The second objective was to obtain test data for the constitutive modelling and calibration of Red Wildmoor sandstone under various saturating conditions and saturation fluids. An additional task was an experi mental study for the improvement of the uniaxial compression test as an index text for rock mechanics applications. The performed modifications allowed the reliable collection of post-peak stress test data of material softening behaviour, and the identification of the point of macroscopic failure of the specimen beyond which the test data cannot be used directly for continuum modelling of material behaviour. © 2000 John Wiley & Sons, Ltd.

本研究的第一个目标是通过优化边界条件和试样几何形状，以及改进三轴试验仪器，改进Red Wildmoor砂岩本构行为的实验测量。由于试件的长细比和端面摩擦约束，通过最小化试件的膨胀，提高了岩石试件变形的均匀性。仪器的改进旨在通过使用高精度LVDT和悬臂测量仪、声发射测量和声脉冲传输速度，改进对作用力、轴向和径向变形以及宏观岩石破坏的监测。第二个目标是获得用于Red Wildmoor砂岩在各种饱和条件和饱和流体下的本构模型和校准的测试数据。另一项任务是改进单轴压缩试验的实验研究，作为岩石力学应用的索引文本。所进行的修改允许可靠地收集材料软化行为的峰后应力测试数据，并识别试样的宏观失效点，超过该点的测试数据不能直接用于材料行为的连续建模。©2000 John Wiley&；有限公司。

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引用次数: 39