Experimental study of thermo-hydro-mechanical behaviour of Callovo-Oxfordian Clay-stone

International Nuclear Information System (INIS)

Mohajerani, M.

2011-01-01

During the different phases of the exothermic radioactive waste deep disposal (excavation, operation) and after permanent closure, the host rock is submitted to various coupled mechanical, hydraulic and thermal phenomena. Hence, a thorough investigation of the thermo-hydro-mechanical behaviour of the rock is necessary to complete existing data and to better understand and model the short and long term behaviour of the Callovo-Oxfordian (COx) clay formation in Bure (Meuse/Haute-Marne - M/HM), considered by ANDRA as a potential host rock in France.In this work, the compression - swelling behaviour of the COx Clay-stone was first investigated by carrying out a series of high-pressure oedometric tests. The results, interpreted in terms of coupling between damage and swelling, showed that the magnitude of swelling was linked to the density of the fissures created during compression. In a second step, the hydro-mechanical and thermo-hydro-mechanical behaviour of the saturated Clay-stone under a mean stress close to the in situ one were investigated by using two devices with short drainage path (10 mm), namely a isotropic cell and a newly designed hollow cylinder triaxial cell with local displacement measurements. These devices helped to solve two majors problems related to testing very low permeability materials: i) a satisfactory previous sample saturation (indicated by good Skempton values) and ii) satisfactory drainage conditions. Some typical constitutive parameters (Skempton and Biot's coefficients, drained and undrained compressibility coefficients) have been determined at ambient temperature through isotropic compression tests that also confirmed the transverse isotropy of the Clay-stone. The consistency of the obtained parameters has been checked in a saturated poro-elastic framework. Two aspects of the thermo-hydro-mechanical behaviour of the COx Clay-stone have then been investigated through different heating tests and through drained and undrained isotropic

Analysis and modeling of coupled thermo-hydro-mechanical phenomena in 3D fractured media; Analyse et modelisation des phenomenes couples thermo-hydromecaniques en milieux fractures 3D

Energy Technology Data Exchange (ETDEWEB)

Canamon Valera, I

2006-11-15

This doctoral research was conducted as part of a joint France-Spain co-tutelage PhD thesis in the framework of a bilateral agreement between two universities, the Institut National Polytechnique de Toulouse (INPT) and the Universidad Politecnica de Madrid (UPM). It concerns a problem of common interest at the national and international levels, namely, the disposal of radioactive waste in deep geological repositories. The present work is devoted, more precisely, to near-field hydrogeological aspects involving mass and heat transport phenomena. The first part of the work is devoted to a specific data interpretation problem (pressures, relative humidities, temperatures) in a multi-barrier experimental system at the scale of a few meters - the 'Mock-Up Test' of the FEBEX project, conducted in Spain. Over 500 time series are characterized in terms of spatial, temporal, and/or frequency/scale-based statistical analysis techniques. The time evolution and coupling of physical phenomena during the experiment are analyzed, and conclusions are drawn concerning the behavior and reliability of the sensors. The second part of the thesis develops in more detail the 3-Dimensional (3D) modeling of coupled Thermo-Hydro-Mechanical phenomena in a fractured porous rock, this time at the scale of a hundred meters, based on the data of the 'In-Situ Test' of the FEBEX project conducted at the Grimsel Test Site in the Swiss Alps. As a first step, a reconstruction of the 3D fracture network is obtained by Monte Carlo simulation, taking into account through optimization the geomorphological data collected around the FEBEX gallery. The heterogeneous distribution of traces observed on the cylindrical wall of the tunnel is fairly well reproduced in the simulated network. In a second step, we develop a method to estimate the equivalent permeability of a many-fractured block by extending the superposition method of Ababou et al. [1994] to the case where the permeability of

Results of laboratory and in-situ measurements for the description of coupled thermo-hydro-mechanical processes in clays

Energy Technology Data Exchange (ETDEWEB)

Goebel, Ingeborg; Alheid, Hans-Joachim [BGR Hannover, Stilleweg 2, D-30655 Hannover (Germany); Jockwer, Norbert [Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH, Theodor-Heuss-Str. 4, 38122 Braunschweig (Germany); Mayor, Juan Carlos [ENRESA, Emilio Vargas 7, E-Madrid (Spain); Garcia-Sineriz, Jose Luis [AITEMIN, c/ Alenza, 1 - 28003 Madrid (Spain); Alonso, Eduardo [International Center for Numerical Methods in Engineering, CIMNE, Edificio C-1, Campus Norte UPC, C/Gran Capitan, s/n, 08034 Barcelona (Spain); Weber, Hans Peter [NAGRA, Hardstrasse 73, CH-5430 Wettingen (Switzerland); Ploetze, Michael [ETHZ, Eidgenoessische Technische Hochschule Zuerich, ETH Zentrum, HG Raemistrasse 101, CH-8092 Zuerich (Switzerland); Klubertanz, Georg [COLENCO Power Engineering Ltd, CPE, Taefern Str. 26, 5405 Baden-Daettwil (Switzerland); Ammon, Christian [Rothpletz, Lienhard, Cie AG, Schifflaendestrasse 35, 5001 Aarau (Switzerland)

2004-07-01

The Heater Experiment at the Mont Terri Underground Laboratory aims at producing a validated model of thermo-hydro-mechanically (THM) coupled processes. The experiment consists of an engineered barrier system where in a vertical borehole, a heater is embedded in bentonite blocks, surrounded by the host rock, Opalinus Clay. The experimental programme comprises permanent monitoring before, during, and after the heating phase, complemented by geotechnical, hydraulic, and seismic in-situ measurements as well as laboratory analyses of mineralogical and rock mechanics properties. After the heating, the experiment was dismantled for further investigations. Major results of the experimental findings are outlined. (authors)

Coupled thermo-hydro-mechanical processes around a bentonite buffer embedded in Opalinus Clay - Comparison between measurements and calculations

Energy Technology Data Exchange (ETDEWEB)

Goebel, Ingeborg; Alheid, Hans-Joachim [BGR Hannover, Stilleweg 2, D-30655 Hannover (Germany); Jockwer, Norbert [Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH, Theodor-Heuss-Str. 4, 38122 Braunschweig (Germany); Mayor, Juan Carlos [ENRESA, Emilio Vargas 7, E-Madrid (Spain); Garcia-Sineriz, Jose Luis [AITEMIN, c/ Alenza, 1 - 28003 Madrid (Spain); Alonso, Eduardo; Munoz, Juan Jorge [International Center for Numerical Methods in Engineering, CIMNE, Edificio C-1, Campus Norte UPC, C/Gran Capitan, s/n, 08034 Barcelona (Spain); Weber, Hans Peter [NAGRA, Hardstrasse 73, CH-5430 Wettingen (Switzerland); Ploetze, Michael [ETHZ, Eidgenoessische Technische Hochschule Zuerich, ETH Zentrum, HG Raemistrasse 101, CH-8092 Zuerich (Switzerland); Klubertanz, Georg [COLENCO Power Engineering Ltd, CPE, Taefern Str. 26, 5405 Baden-Daettwil (Switzerland); Ammon, Christian [Rothpletz, Lienhard, Cie AG, Schifflaendestrasse 35, 5001 Aarau (Switzerland)

2004-07-01

The Heater Experiment at the Mont Terri Underground Laboratory consists of an engineered barrier system composed of compacted bentonite blocks around a heater. The bentonite barrier is embedded in Opalinus Clay. The aim of the project is improved understanding of thermo-hydro mechanically (THM) coupled processes. Calculations are performed by 2 Finite-Element programs, CODE-BRIGHT and MHERLIN, the former for the near-field modeling and the latter for the rock modeling. Numerical modeling is carried out during all phases of the project to give input for design tasks such as cooling and dismantling, and to finally produce verified models of the THM coupled engineered barrier system. Results of both programs are discussed in the light of the experimental findings. (authors)

Summary report of research on evaluation of coupled thermo-hydro-mechanical behavior in the engineered barrier

International Nuclear Information System (INIS)

Chijimatsu, Masakazu; Amemiya, Kiyoshi; Yamashita, Ryo

2002-02-01

After emplacement of the engineered barrier system (EBS), it is expected that the near-field environment will be impacted by phenomena such as heat dissipation by conduction and other heat transfer mechanisms, infiltration of groundwater from the surrounding rock in to the engineered barrier system, stress imposed by the overburden pressure and generation of swelling pressure in the buffer due to water infiltration. In order to recognize and evaluate these coupled thermo-hydro-mechanical (THM) phenomena, it is necessary to make a confidence of the mathematical models and computer codes. Evaluating these coupled THM phenomena is important in order to clarify the initial transient behavior of the EBS within the near field. DECOVALEX project is an international co-operative project for the DEvelopment of COupled models and their VALidation against EXperiments in nuclear waste isolation and it is significance to participate this project and to apply the code for the validation. Therefore, we tried to apply the developed numerical code against the subjects of DECOVALEX. In the above numerical code, swelling phenomenon is modeled as the function of water potential. However it dose no evaluate the experiment results enough. Then, we try to apply the new model. (author)

Investigation research on the evaluation of a coupled thermo-hydro-mechanical-chemical phenomena. 4

International Nuclear Information System (INIS)

Ishihara, Yoshinao; Sagawa, Hiroshi; Matsuoka, Fushiki; Chijimatsu, Masakazu; Amemiya, Kiyoshi

2005-02-01

In order to realize a coupling analysis in the near field of the geological disposal system, the coupling analysis code 'COUPLYS (Coupling analysis system)' on the Thermo-Hydro-Mechanical-Chemical (THMC) phenomena by THAMES, Dtransu-3D·EL and PHREEQC, those are existing analysis code, is developed in this study. (1) We have introduced 8 nodes element for THAMES code in order to solve the coupled thermal, hydraulic and mechanical phenomena. Furthermore, in order to obtain the reliable resolution, each phenomenon is solved separately instead of full coupling. (2) In order to upgrade Dtransu-3D·EL model, we have introduced gas diffusion independent on aqueous element. (3) We have adopted surface site density for the bentonite depend on water content and CSH solid phase based on the ratio of C/S for cementitious material in the geochemistry module, and studied on the methodology of time mesh for kinetic model and separate method for pore water chemistry in the bentonite. (4) In order to develop THMC code, we have modified Multi p hreeqc to keep efficiency distributed processing for geochemical calculation and modified COUPLYS to calculate continuous treatment, and studied on the coupling module. After THAMES, Dtransu, PHREEQC and the hydraulic conductivity module were installed in COUPLYS, verification study was carried out to check basic function. (5) In order to ensure efficiency of analysis processor, we have developed supporting tool for graphic processor for THMC code and supporting tool of interpretation for geochemistry results. (author)

Research on evaluation of coupled thermo-hydro-mechanical phenomena in the near-field

International Nuclear Information System (INIS)

Chijimatsu, Masakazu; Imai, Hisashi; Fukutome, Kazuhito; Kayukawa, Koji; Sasaki, Hajime; Moro, Yoshiji

2004-02-01

After emplacement of the engineered barrier system (EBS), it is expected that the near-field environment will be impacted by phenomena such as heat dissipation by conduction and other heat transfer mechanisms, infiltration of groundwater from the surrounding rock in the engineered barrier system, stress imposed by the overburden pressure and generation of swelling pressure in the buffer due to water infiltration. In order to recognize and evaluate these coupled thermo-hydro-mechanical (THM) phenomena, it is necessary to make a confidence of the mathematical models and computer codes. Evaluating these coupled THM phenomena is important in order to clarify the initial transient behavior of the EBS within the near field. DECOVALEX project is an international co-operative project for the DEvelopment of COupled models and their VALidation against EXperiments in nuclear waste isolation and it is significance to participate this project and to apply the code for the validation. Therefore, we tried to apply the developed numerical code against the subjects of DECOVALEX. We carried out the simulation against the Task 1 (simulation of FEBEX in-situ full-scale experiment), Task 3 BMT1 (Bench Mark Test against the near field coupling phenomena) and Task 3 BMT2 (Bench Mark Test against the up-scaling of fractured rock mass). This report shows the simulation results against these tasks. Furthermore, technical investigations about the in-situ full-scale experiment (called Prototype Repository Project) in Aespoe HRL facility by SKB of Sweden were performed. In order to evaluate the coupled phenomena in the engineered barrier, we use the new swelling model based on the theoretical approach. In this paper, we introduce the modeling approach and applicability about the new model. (author)

Thermo-hydro-mechanical simulation of a 3D fractured porous rock: preliminary study of coupled matrix-fracture hydraulics

International Nuclear Information System (INIS)

Canamon, I.; Javier Elorza, F.; Ababou, R.

2007-01-01

We present a problem involving the modeling of coupled flow and elastic strain in a 3D fractured porous rock, which requires prior homogenization (up-scaling) of the fractured medium into an equivalent Darcian anisotropic continuum. The governing equations form a system of PDE's (Partial Differential Equations) and, depending on the case being considered, this system may involve two different types of 'couplings' (in a real system, both couplings (1) and (2) generally take place): 1) Hydraulic coupling in a single (no exchange) or in a dual matrix-fracture continuum (exchange); 2) Thermo-Hydro-Mechanical interactions between fluid flow, pressure, elastic stress, strain, and temperature. We present here a preliminary model and simulation results with FEMLAB R , for the hydraulic problem with anisotropic heterogeneous coefficients. The model is based on data collected at an instrumented granitic site (FEBEX project) for studying a hypothetical nuclear waste repository at the Grimsel Test Site in the Swiss Alps. (authors)

Thermo-hydro-mechanical simulation of a 3D fractured porous rock: preliminary study of coupled matrix-fracture hydraulics

Energy Technology Data Exchange (ETDEWEB)

Canamon, I.; Javier Elorza, F. [Universidad Politecnica de Madrid, Dept. de Matematica Aplicada y Metodos Informaticas, ETSI Minas (UPM) (Spain); Ababou, R. [Institut de Mecanique des Fluides de Toulouse (IMFT), 31 (France)

2007-07-01

We present a problem involving the modeling of coupled flow and elastic strain in a 3D fractured porous rock, which requires prior homogenization (up-scaling) of the fractured medium into an equivalent Darcian anisotropic continuum. The governing equations form a system of PDE's (Partial Differential Equations) and, depending on the case being considered, this system may involve two different types of 'couplings' (in a real system, both couplings (1) and (2) generally take place): 1) Hydraulic coupling in a single (no exchange) or in a dual matrix-fracture continuum (exchange); 2) Thermo-Hydro-Mechanical interactions between fluid flow, pressure, elastic stress, strain, and temperature. We present here a preliminary model and simulation results with FEMLAB{sup R}, for the hydraulic problem with anisotropic heterogeneous coefficients. The model is based on data collected at an instrumented granitic site (FEBEX project) for studying a hypothetical nuclear waste repository at the Grimsel Test Site in the Swiss Alps. (authors)

Development of finite element code for the analysis of coupled thermo-hydro-mechanical behaviors of a saturated-unsaturated medium

International Nuclear Information System (INIS)

Ohnishi, Y.; Shibata, H.; Kobsayashi, A.

1987-01-01

A model is presented which describes fully coupled thermo-hydro-mechanical behavior of a porous geologic medium. The mathematical formulation for the model utilizes the Biot theory for the consolidation and the energy balance equation. If the medium is in the condition of saturated-unsaturated flow, then the free surfaces are taken into consideration in the model. The model, incorporated in a finite element numerical procedure, was implemented in a two-dimensional computer code. The code was developed under the assumptions that the medium is poro-elastic and in the plane strain condition; that water in the ground does not change its phase; and that heat is transferred by conductive and convective flow. Analytical solutions pertaining to consolidation theory for soils and rocks, thermoelasticity for solids and hydrothermal convection theory provided verification of stress and fluid flow couplings, respectively, in the coupled model. Several types of problems are analyzed

Hydro-thermo-mechanical response of a fractured rock block

International Nuclear Information System (INIS)

Kelkar, S.; Zyvoloski, G.

1990-01-01

Hydro-thermo-mechanical effects in fractured rocks are important in many engineering applications and geophysical processes. Modeling these effects is made difficult by the fact that the governing equations are nonlinear and coupled, and the problems to be solved are three dimensional. In this paper we describe a numerical code developed for this purpose. The code is finite element based to allow for complicated geometries, and the time differencing is implicit, allowing for large time steps. The use of state-of-the-art equation solvers has resulted in a practical code. The code is capable of fully three dimensional simulations, however, in this paper we consider only the case of two dimensional heat and mass flow coupled to one dimensional deformation. Partial verification of the code is obtained by comparison with published semianalytical results. Several examples are presented to demonstrate the effects of matrix expansion, due to pore pressure and heating, on fracture opening due to fluid injection. 16 refs., 11 figs

Multi-scale modeling of the thermo-hydro- mechanical behaviour of heterogeneous materials. Application to cement-based materials under severe loads

International Nuclear Information System (INIS)

Grondin, Frederic Alain

2005-01-01

The work of modeling presented here relates to the study of the thermo-hydro- mechanical behaviour of porous materials based on hydraulic binder such as concrete, High Performance Concrete or more generally cement-based materials. This work is based on the exploitation of the Digital Concrete model, of the finite element code Symphonie developed in the Scientific and Technical Centre for Building (CSTB), in coupling with the homogenization methods to obtain macroscopic behaviour laws drawn from the Micro-Macro relations. Scales of investigation, macroscopic and microscopic, has been exploited by simulation in order to allow the comprehension fine of the behaviour of cement-based materials according to thermal, hydrous and mechanical loads. It appears necessary to take into account various scales of modeling. In order to study the behaviour of the structure, we are brought to reduce the scale of investigation to study the material more particularly. The research tasks presented suggest a new approach for the identification of the multi-physic behaviour of materials by simulation. In complement of the purely experimental approach, based on observations on the sample with measurements of the apparent parameters on the macroscopic scale, this new approach allows to obtain the fine analysis of elementary mechanisms in acting within the material. These elementary mechanisms are at the origin of the evolution of the macroscopic parameters measured in experimental tests. In this work, coefficients of the thermo-hydro-mechanical behaviour law of porous materials and the equivalent hydraulic conductivity were obtained by a multi-scales approach. Applications has been carried out on the study of the damaged behaviour of cement-based materials, in the objective to determine the elasticity tensor and the permeability tensor of a High Performance Concrete at high temperatures under a mechanical load. Also, the study of the strain evolution of cement-based materials at low

Full-scale test on coupled thermo-hydro-mechanical processes in engineered barrier system

International Nuclear Information System (INIS)

Moro, Yoshiji; Fujita, Tomoo; Kanno, Takeshi; Kobayashi, Akira.

1994-01-01

On dynamic behavior within artificial barrier in ground layer disposal of high level radioactive wastes, some phenomena such as exotherm from the wastes, penetration of groundwater from surrounding base rock, swelling pressure formation of buffer material due to penetration of groundwater, ground pressure change of the surrounding base rock, and so forth are supposed to affect each other. It is one of important problems from a viewpoint of elucidation of near field environment in the property evaluation study to evaluate such thermo-hydro-mechanical coupled phenomena. As results of the investigation from such reason and its application to actual test in accompany with execution of heating and water inserting test in the Big-Ben (Big-Bentonite facility), the following informations were obtained: (1) In heating and water inserting test, data on temperature distribution, water content ratio distribution and swelling pressure of each portion for 5 months could be obtained. (2) water migration due to water slope was divided to migrations due to steam and liquid water, of which models were made according to Fick and Darcy laws, respectively. (3) As a simulation of water migration, water diffusion coefficient due to temperature slope could be expressed almost by a model with nonlinearity to temperature. (G.K.)

Objective thermo-hydro-mechanical modelling of the damaged zone around a radioactive waste storage site

International Nuclear Information System (INIS)

Marinelli, Ferdinando

2013-01-01

We present two different approaches to describe the hydro-mechanical behaviour of geo-materials. In the first approach the porous media is studied through an equivalent continuum media where the interaction between the fluid and solid phases characterize the coupling behaviour at the macro-scale. We take into account this approach to model experimental tests performed over a hollow cylinder sample of clay rock (Boom Clay), considered for nuclear waste storage. The experimental results clearly show that the mechanical behaviour of the material is strongly anisotropic. For this reason we chose an elasto-plastic model based on Drucker-Prager criterion where the elastic part is characterized by cross anisotropy. The numerical results of boundary value problem clearly show localised strains around the inner hollow section. In order to regularize the numerical problem we consider a second gradient local continuum media with an enriched kinematic where an internal length can be introduced making the results mesh independent. The uniqueness study is carried out showing that changing the temporal discretization of the problem leads to different solutions. In the second approach we study the hydro-mechanical behaviour of a porous media that it is characterised by the microstructure of the material. The microstructure taken into account is composed by elastic grains, cohesive interfaces and a network of fluid channels. Using a periodic media a numerical homogenization (square finite element method) is considered to compute mass flux, stress and density of the mixture. In this way a pure numerical constitutive law is built from the microstructure of the media. This method has been implemented into a finite element code (Lagamine, Universite de Liege) to obtain results at the macro-scale. A validation of this implementation is performed for a pure mechanical boundary value problem and for a hydro-mechanical one. (author)

Integrated Modeling and Experiments to Characterize Coupled Thermo-hydro-geomechanical-chemical processes in Hydraulic Fracturing

Science.gov (United States)

Viswanathan, H. S.; Carey, J. W.; Karra, S.; Porter, M. L.; Rougier, E.; Kang, Q.; Makedonska, N.; Hyman, J.; Jimenez Martinez, J.; Frash, L.; Chen, L.

2015-12-01

Hydraulic fracturing phenomena involve fluid-solid interactions embedded within coupled thermo-hydro-mechanical-chemical (THMC) processes over scales from microns to tens of meters. Feedbacks between processes result in complex dynamics that must be unraveled if one is to predict and, in the case of unconventional resources, facilitate fracture propagation, fluid flow, and interfacial transport processes. The proposed work is part of a broader class of complex systems involving coupled fluid flow and fractures that are critical to subsurface energy issues, such as shale oil, geothermal, carbon sequestration, and nuclear waste disposal. We use unique LANL microfluidic and triaxial core flood experiments integrated with state-of-the-art numerical simulation to reveal the fundamental dynamics of fracture-fluid interactions to characterize the key coupled processes that impact hydrocarbon production. We are also comparing CO2-based fracturing and aqueous fluids to enhance production, greatly reduce waste water, while simultaneously sequestering CO2. We will show pore, core and reservoir scale simulations/experiments that investigate the contolling mechanisms that control hydrocarbon production.

Role of temperature and composition on the thermal-hydro-mechanical coupling of concretes

International Nuclear Information System (INIS)

Brue, Flore

2009-01-01

The French project of the storage of nuclear wastes, which is managed by the Andra, needs some experimental data on the durability of the concrete. Loadings which are taken into account are the desaturation/re-saturation processes, the heat load and the mechanical evolution. Hence this study focuses on the coupling thermo-hydro-mechanical on concretes of the research program of Andra, made with CEM I and CEM V/A cement type. The water saturation degree and shrinkages of materials, which are subjected to desiccation or re-saturation, are dependent on the imposed thermal and hydrous conditions and on their microstructural characteristics. Moreover the study of the mechanical evolution is gone further at 20 C in function of the water saturation degree. Different short-term tests highlight a hydrous damage, which determine the mechanical behaviour. The long-term study of desiccation creep shows the coupling between the durability, the mechanical evolution and the desiccation. (author)

Multi-scale modelling and simulation of the thermo-hydro-mechanical behavior of concrete with explicit representation of cracking

International Nuclear Information System (INIS)

Tognevi, Amen

2012-01-01

The concrete structures of nuclear power plants can be subjected to moderate thermo-hydric loadings characterized by temperatures of the order of hundred of degrees in service conditions as well as in accidental ones. These loadings can be at the origin of important disorders, in particular cracking which accelerate hydric transfers in the structure. In the framework of the study of durability of these structures, a coupled thermo-hydro-mechanical model denoted THMs has been developed at Laboratoire d'Etude du Comportement des Betons et des Argiles (LECBA) of CEA Saclay in order to perform simulations of the concrete behavior submitted to such loadings. In this work, we focus on the improvement in the model THMs in one hand of the assessment of the mechanical and hydro-mechanical parameters of the unsaturated micro-cracked material and in the other hand of the description of cracking in terms of opening and propagation. The first part is devoted to the development of a model based on a multi-scale description of cement-based materials starting from the scale of the main hydrated products (portlandite, ettringite, C-S-H etc.) to the macroscopic scale of the cracked material. The investigated parameters are obtained at each scale of the description by applying analytical homogenization techniques. The second part concerns a fine numerical description of cracking. To this end, we choose to use combined finite element and discrete element methods. This procedure is presented and illustrated through a series of mechanical tests in order to show the feasibility of the method and to proceed to its validation. Finally, we apply the procedure to a heated wall and the proposed method for estimating the permeability shows the interest to take into account an anisotropic permeability tensor when dealing with mass transfers in cracked concrete structures. (author) [fr

Thermo-hydro-mechanical coupling in long-term sedimentary rock response

Science.gov (United States)

Makhnenko, R. Y.; Podladchikov, Y.

2017-12-01

Storage of nuclear waste or CO2 affects the state of stress and pore pressure in the subsurface and may induce large thermal gradients in the rock formations. In general, the associated coupled thermo-hydro-mechanical effect on long-term rock deformation and fluid flow have to be studied. Principles behind mathematical models for poroviscoelastic response are reviewed, and poroviscous model parameter, the bulk viscosity, is included in the constitutive equations. Time-dependent response (creep) of fluid-filled sedimentary rocks is experimentally quantified at isotropic stress states. Three poroelastic parameters are measured by drained, undrained, and unjacketed geomechanical tests for quartz-rich Berea sandstone, calcite-rich Apulian limestone, and clay-rich Jurassic shale. The bulk viscosity is calculated from the measurements of pore pressure growth under undrained conditions, which requires time scales 104 s. The bulk viscosity is reported to be on the order of 1015 Pa•s for the sandstone, limestone, and shale. It is found to be decreasing with the increase of pore pressure despite corresponding decrease in the effective stress. Additionally, increase of temperature (from 24 ºC to 40 ºC) enhances creep, where the most pronounced effect is reported for the shale with bulk viscosity decrease by a factor of 3. Viscous compaction of fluid-filled porous media allows a generation of a special type of fluid flow instability that leads to formation of high-porosity, high-permeability domains that are able to self-propagate upwards due to interplay between buoyancy and viscous resistance of the deforming porous matrix. This instability is known as "porosity wave" and its formation is possible under conditions applicable to deep CO2 storage in reservoirs and explains creation of high-porosity channels and chimneys. The reported experiments show that the formation of high-permeability pathways is most likely to occur in low-permeable clay-rich materials (caprock

Thermo-hydro-mechanical tests of buffer material

International Nuclear Information System (INIS)

Pintado, X.; Hassan, Md. M.; Martikainen, J.

2013-10-01

MX-80 bentonite is the reference clay material for the buffer component planned to be used in the deep geological repository for the disposal of spent nuclear fuel in Finland. The buffer presents complex thermo-hydro-mechanical behavior which is modeled with different constitutive models for heat flow, water flow and stress-strain evolution in the buffer. Thermo, hydro and mechanical models need parameters to evaluate the THM-behavior. These modeling parameters were determined by performing series of laboratory experiments as follows: Water retention curve tests were performed on compacted bentonite samples, encompassing a range of initial dry density values from 1397 to 1718 kg/m 3 as the initial water content was around of 5-8 %. The water retention curve was determined by imposing different suctions to the samples and the suctions were then checked using capacitive hygrometer and chilled mirror psychrometer. Oedometer tests were performed on compacted bentonite samples, encompassing a range of initial dry density values from 1590 to 1750 kg/m 3 as the initial water content was around of 6 %. Samples were saturated with tap water, 35 or 70 g/L salt solutions. Infiltration tests were performed on compacted unsaturated bentonite samples, encompassing a range of initial dry density values from 1400 to 1720 kg/m 3 as the initial water content was approximately between 4-7 %. Samples were saturated with tap water, 0.87, 35 or 70 g/L salt solutions. Tortuosity tests were performed on bentonite samples, encompassing a range of dry density values from 1460 to 1750 kg/m 3 and the degree of saturation varied between 33-93 %. Thermal conductivity tests were performed on compacted bentonite samples, encompassing a range of dry density values from 1545 to 1715 kg/m 3 and the degree of saturation varied between 31-88 %. The measurement was performed using a thermal needle probe. The general trend of all analyzed parameters was as expected when dry density, water content, and

Thermo-hydro-mechanical tests of buffer material

Energy Technology Data Exchange (ETDEWEB)

Pintado, X.; Hassan, Md. M.; Martikainen, J. [B and Tech Oy, Helsinki (Finland)

2013-10-15

MX-80 bentonite is the reference clay material for the buffer component planned to be used in the deep geological repository for the disposal of spent nuclear fuel in Finland. The buffer presents complex thermo-hydro-mechanical behavior which is modeled with different constitutive models for heat flow, water flow and stress-strain evolution in the buffer. Thermo, hydro and mechanical models need parameters to evaluate the THM-behavior. These modeling parameters were determined by performing series of laboratory experiments as follows: Water retention curve tests were performed on compacted bentonite samples, encompassing a range of initial dry density values from 1397 to 1718 kg/m{sup 3} as the initial water content was around of 5-8 %. The water retention curve was determined by imposing different suctions to the samples and the suctions were then checked using capacitive hygrometer and chilled mirror psychrometer. Oedometer tests were performed on compacted bentonite samples, encompassing a range of initial dry density values from 1590 to 1750 kg/m{sup 3} as the initial water content was around of 6 %. Samples were saturated with tap water, 35 or 70 g/L salt solutions. Infiltration tests were performed on compacted unsaturated bentonite samples, encompassing a range of initial dry density values from 1400 to 1720 kg/m{sup 3} as the initial water content was approximately between 4-7 %. Samples were saturated with tap water, 0.87, 35 or 70 g/L salt solutions. Tortuosity tests were performed on bentonite samples, encompassing a range of dry density values from 1460 to 1750 kg/m{sup 3} and the degree of saturation varied between 33-93 %. Thermal conductivity tests were performed on compacted bentonite samples, encompassing a range of dry density values from 1545 to 1715 kg/m{sup 3} and the degree of saturation varied between 31-88 %. The measurement was performed using a thermal needle probe. The general trend of all analyzed parameters was as expected when dry

Thermo-hydro-mechanical modelling of fractured rock masses application to radioactive wastes storage

International Nuclear Information System (INIS)

Vuillod, E.

1995-01-01

This work belongs to the Decovalex project (international cooperative project for the development of coupled models and their validation against experiments in nuclear waste isolation) of thermo-hydro-mechanical (THM) modeling of fractured rock massifs inside which high level radioactive waste disposal sites are simulated. The mathematical laws controlling the behaviour of the environment are resolved analytically in the case of a continuous environment (definition of an equivalent environment) and numerically if the environment is discontinuous (modeling of joints behaviour). The coupled THM models strongly influence the behaviour of a model. Modeling performed with the UDEC code shows the importance of HM couplings depending on whether the calculations are made in permanent or transient regime, and the influence of the loading path in the case of TM modeling. The geometry of fractures also influences the behaviour of the model. Studying the connexity of a fractures network allows to determine its degree of homogeneity. The comparison between two methods, continuous environment and discontinuous environment, has been carried out by determining the permeability tensor and the stress-deformation relations on fractured test-samples. It shows the differences in behaviour between an homogenized environment and a discrete environment. Finally two exercises of THM modeling of radioactive waste disposal sites illustrate the researches carried out. A far field model has permitted to compare the results obtained with calculation codes using different logics. The second model, a near field one, focusses more on the importance played by fracturing on the behaviour of the massif. The high density of the reference network has required some mathematical developments, in order to determine the representative equivalent volume (continuous approaches), and some mathematical analyses, to correctly simplify the environment (discontinuous approaches). These methods and analyses are

Investigation research on the evaluation of a coupled thermo-hydro-mechanical-chemical phenomena. 3. Result Report

International Nuclear Information System (INIS)

Ishihara, Yoshinao; Ito, Takaya; Chijimatsu, Masakazu; Amemiya, Kiyoshi; Shiozaki, Isao

2004-02-01

In order to realize a coupling analysis in the near field of the geological disposal system, the coupling analysis code 'COUPLYS (Coupling analysis system)' on the Thermo-Hydro-Mechanical-Chemical (THMC) phenomena by THAMES, Dtransu and phreeqc, which are existing analysis code, is developed in this study. And some case analyses on THMC phenomena are carried out by this code. (1) Some supporting modules, which include the transfer of dissolution concentration and total concentration (dissolution + precipitation concentration), were prepared as a functional expansion. And in order to add on the function of treat de-gases and gases diffusion, accumulation and dilution phenomena, the mass transport analysis code was modified. (2) We have modified reactive transport module to treat ionic exchange, surface reaction and kinetic reaction in the each barrier. (3) We have prepared hydraulic conductivity module of buffer material depending on change of dry density due to chemical equilibrium (dissolution and precipitation of minerals), degradation of buffer material such as Ca-type bentonite and change of concentration of NaCl solutions. After THAMES, Dtransu, phreeqc and the hydraulic conductivity module were installed in COUPLYS (Coupling Analysis), verification study was carried out to check basic function. And we have modified COUPLYS to control coupling process. (4) In order to confirm the applicability of the developed THMC analysis code (existing analysis code and COUPLYS), we have carried out case analyses on 1-dimensional and 3-dimensional model which are including vitrified waste, over-pack, buffer material and rock in the HLW near-field. (author)

Coupled thermo-hydro-mechanical experiment at Kamaishi mine. Technical note 08-96-01. Measurement data related to excavation of the test pit

International Nuclear Information System (INIS)

Fujita, T.; Chijimatsu, M.; Sugita, Y.; Ishikawa, H.

1997-07-01

It is an important part of the near field performance assessment of nuclear waste disposal to evaluate coupled thermo-hydro-mechanical (T-H-M) phenomena, e.g., thermal effects on groundwater flow through rock matrix and water seepage into the buffer material, the generation of swelling pressure of the buffer material, and thermal stresses potentially affecting porosity and fracture apertures of the rock. An in-situ T-H-M experiment named Engineered Barrier Experiment ' has been conducted at the Kamaishi Mine, of which host rock is granodiorite, in order to establish conceptual models of the coupled T-H-M processes and to build confidence in mathematical models and computer codes. In 1995, fourteen boreholes were excavated in order to install the various sensors. After the hydraulic tests, mechanical tests were carried out to obtain the rock properties. After that, a test pit, 1.7 m in diameter and 5.0 m in depth, was excavated. During the excavation, the change of pore pressure, displacement and temperature of rock mass were measured. Furthermore, pit convergence was measured. This note shows the results of mechanical tests and measurement data during the excavation of test pit. (author)

Study of gap conductance model for thermo mechanical fully coupled finite element model

International Nuclear Information System (INIS)

Kim, Hyo Cha; Yang, Yong Sik; Kim, Dae Ho; Bang, Je Geon; Kim, Sun Ki; Koo, Yang Hyun

2012-01-01

A light water reactor (LWR) fuel rod consists of zirconium alloy cladding and uranium dioxide pellets, with a slight gap between them. Therefore, the mechanical integrity of zirconium alloy cladding is the most critical issue, as it is an important barrier for fission products released into the environment. To evaluate the stress and strain of the cladding during operation, fuel performance codes with a one-dimensional (1D) approach have been reported since the 1970s. However, it is difficult for a 1D model to simulate the stress and strain of the cladding accurately owing to a lack of degree of freedom. A LWR fuel performance code should include thermo-mechanical coupled model owing to the existence of the fuel-cladding gap. Generally, the gap that is filled with helium gas results in temperature drop along radius direction. The gap conductance that determines temperature gradient within the gap is very sensitive to gap thickness. For instance, once the gap size increases up to several microns in certain region, difference of surface temperatures increases up to 100 Kelvin. Therefore, iterative thermo-mechanical coupled analysis is required to solve temperature distribution throughout pellet and cladding. Consequently, the Finite Element (FE) module, which can simulate a higher degree of freedom numerically, is an indispensable requirement to understand the thermomechanical behavior of cladding. FRAPCON-3, which is reliable performance code, has iterative loop for thermo-mechanical coupled calculation to solve 1D gap conductance model. In FEMAXI-III, 1D thermal analysis module and FE module for stress-strain analysis were separated. 1D thermal module includes iterative analysis between them. DIONISIO code focused on thermal contact model as function of surface roughness and contact pressure when the gap is closed. In previous works, gap conductance model has been developed only for 1D model or hybrid model (1D and FE). To simulate temperature, stress and strain

Evaluation of coupled thermo-hydro-mechanical phenomena in the near field for geological disposal of high-level radioactive waste

International Nuclear Information System (INIS)

Chijimatsu, Masakazu; Fujita, Tomoo; Sugita, Yutaka; Taniguchi, Wataru

2000-01-01

, fracture survey, hydraulic test and the measurement of inflow rate into the test pit, which was excavated at the floor of the experiment drift, were conducted. In Chapter 4, hydraulic analyses were conducted using the rock properties obtained by the hydraulic test described in Chapter 3. Analyses were performed by tow kinds of methods; continuum approach and discrete approach. In Chapter 5, the results of in-situ coupled thermo-hydro-mechanical experiment at Kamaishi mine was described. The test pit, 1.7 m in diameter and 5.0 m in depth, was excavated. After the excavation of test pit, the buffer material and heater were set up in the test pit, and then coupled thermo-hydro-mechanical test was started. The duration of heating phase was 250 days and that of cooling phase was 180 days. The heater surface was controlled to be 100degC during heating phase. Measurement was carried out by a number of sensors installed in both buffer and rock mass during the test. In Chapter 6, development of coupled T-H-M model and the validation analyses of model were described. As validation, the analysis of BIG-BEN experiment at Tokai Works in JNC and the analysis of in-situ experiment at Kamaishi mine etc. were performed. In Chapter 7, the coupled T-H-M processes in the near field were simulated with fully coupled model. The material of buffer is bentonite-sand mixture and dry density is 1.6 g/cm 3 . From the results, the following results were obtained; re-saturation time of buffer is strongly dependent on the water pressure in the rock mass. However, it is not dependent on the permeability of rock mass if the intrinsic permeability of rock mass is in the 10 -13 - 10 -18 m 2 range. In the case that the intrinsic permeability of rock mass is approximately 10 -15 m 2 , the initial water content in the buffer does not exert influence on the re-saturation time of buffer. Two dimensional coupled T-H-M analysis in consideration of water drawdown due to the excavation of drift is carried our. As a

Evaluation of coupled thermo-hydro-mechanical phenomena in the near field for geological disposal of high-level radioactive waste

Energy Technology Data Exchange (ETDEWEB)

Chijimatsu, Masakazu; Fujita, Tomoo; Sugita, Yutaka; Taniguchi, Wataru [Japan Nuclear Cycle Development Inst., Tokai Works, Waste Management and Fuel Cycle Research Center, Waste Isolation Research Division, Barrier Performance Group, Tokai, Ibaraki (Japan)

2000-01-01

, fracture survey, hydraulic test and the measurement of inflow rate into the test pit, which was excavated at the floor of the experiment drift, were conducted. In Chapter 4, hydraulic analyses were conducted using the rock properties obtained by the hydraulic test described in Chapter 3. Analyses were performed by tow kinds of methods; continuum approach and discrete approach. In Chapter 5, the results of in-situ coupled thermo-hydro-mechanical experiment at Kamaishi mine was described. The test pit, 1.7 m in diameter and 5.0 m in depth, was excavated. After the excavation of test pit, the buffer material and heater were set up in the test pit, and then coupled thermo-hydro-mechanical test was started. The duration of heating phase was 250 days and that of cooling phase was 180 days. The heater surface was controlled to be 100degC during heating phase. Measurement was carried out by a number of sensors installed in both buffer and rock mass during the test. In Chapter 6, development of coupled T-H-M model and the validation analyses of model were described. As validation, the analysis of BIG-BEN experiment at Tokai Works in JNC and the analysis of in-situ experiment at Kamaishi mine etc. were performed. In Chapter 7, the coupled T-H-M processes in the near field were simulated with fully coupled model. The material of buffer is bentonite-sand mixture and dry density is 1.6 g/cm{sup 3}. From the results, the following results were obtained; re-saturation time of buffer is strongly dependent on the water pressure in the rock mass. However, it is not dependent on the permeability of rock mass if the intrinsic permeability of rock mass is in the 10{sup -13} - 10{sup -18} m{sup 2} range. In the case that the intrinsic permeability of rock mass is approximately 10{sup -15} m{sup 2}, the initial water content in the buffer does not exert influence on the re-saturation time of buffer. Two dimensional coupled T-H-M analysis in consideration of water drawdown due to the excavation

Multi-scale modelling of the hydro-mechanical behaviour of argillaceous rocks

International Nuclear Information System (INIS)

Van den Eijnden, Bram

2015-01-01

Feasibility studies for deep geological radioactive waste disposal facilities have led to an increased interest in the geomechanical modelling of its host rock. In France, a potential host rock is the Callovo-Oxfordian clay-stone. The low permeability of this material is of key importance, as the principle of deep geological disposal strongly relies on the sealing capacity of the host formation. The permeability being coupled to the mechanical material state, hydro-mechanical coupled behaviour of the clay-stone becomes important when mechanical alterations are induced by gallery excavation in the so-called excavation damaged zone (EDZ). In materials with microstructure such as the Callovo-Oxfordian clay-stone, the macroscopic behaviour has its origin in the interaction of its micromechanical constituents. In addition to the coupling between hydraulic and mechanical behaviour, a coupling between the micro (material microstructure) and macro scale will be made. By means of the development of a framework of computational homogenization for hydro-mechanical coupling, a double-scale modelling approach is formulated, for which the macro-scale constitutive relations are derived from the microscale by homogenization. An existing model for the modelling of hydro-mechanical coupling based on the distinct definition of grains and intergranular pore space is adopted and modified to enable the application of first order computational homogenization for obtaining macro-scale stress and fluid transport responses. This model is used to constitute a periodic representative elementary volume (REV) that allows the representation of the local macroscopic behaviour of the clay-stone. As a response to deformation loading, the behaviour of the REV represents the numerical equivalent of a constitutive relation at the macro-scale. For the required consistent tangent operators, the framework of computational homogenization by static condensation is extended to hydro-mechanical coupling. The

Thermo-hydro-mechanical behavior of fractured rock mass

International Nuclear Information System (INIS)

Coste, F.

1997-12-01

The purpose of this research is to model Thermo-Hydro-Mechanical behavior of fractured rock mass regarding a nuclear waste re-depository. For this, a methodology of modeling was proposed and was applied to a real underground site (EDF site at Nouvelle Romanche). This methodology consists, in a first step, to determine hydraulic and mechanical REV. Beyond the greatest of these REV, development of a finite element code allows to model all the fractures in an explicit manner. The homogenized mechanical properties are determined in drained and undrained boundary conditions by simulating triaxial tests that represent rock mass subject to loading. These simulations allow to study the evolution of hydraulic and mechanical properties as a function of stress state. Drained and undrained boundary conditions enable to discuss the validity of assimilation of a fractured rock mass to a porous medium. The simulations lead to a better understanding of the behavior of the fractured rock masses and allow to show the dominant role of the shear behavior of the fractures on the hydraulic and mechanical homogenized properties. From a thermal point of view, as long as conduction is dominant, thermal properties of the rock mass are almost the same as those the intact rock. (author)

Numerical modeling for hydro-mechanical coupled problems in the context of geo-materials

International Nuclear Information System (INIS)

Fernandes, R.

2009-01-01

The main technical purpose of this PhD Thesis is to build up and validate a regularisation method, able to remedy to the spurious mesh dependency of post localized computations, in order to make possible hydro-mechanical coupling studies for geo-materials. The proposed model is based on the framework of second gradient models and is called the micro-dilation model. It allows to predict robustly the hydro-mechanical coupled behaviors related to the degradation of natural soils and rocks. This modeling is a clear enhancement with respect to classical second gradient computations since it requires less degrees of freedom and consequently is less time consuming. Its efficiency is shown through hydro-mechanical coupled simulations of underground excavations. Finally, an algorithm to detect several solutions in the direction of singular modes associated with negative eigenvalues is presented. It allows us to deal with the non-linear nature of the irreversible behavior of soils and rocks. The scope of this bifurcation analysis is restricted to symmetrical operators. Through the simulations of homogeneous biaxial tests and underground excavations under drained conditions, it is shown that this algorithm is an efficient and robust tool not only to detect several solutions but also to overcome numerical instabilities near singular points or due to snap-back. (author)

Coupled Large Scale Hydro-mechanical Modelling for cap-rock Failure Risk Assessment of CO2 Storage in Deep Saline Aquifers

International Nuclear Information System (INIS)

Rohmer, J.; Seyedi, D.M.

2010-01-01

This work presents a numerical strategy of large scale hydro-mechanical simulations to assess the risk of damage in cap-rock formations during a CO 2 injection process. The proposed methodology is based on the development of a sequential coupling between a multiphase fluid flow (TOUGH2) and a hydro-mechanical calculation code (Code-Aster) that enables us to perform coupled hydro-mechanical simulation at a regional scale. The likelihood of different cap-rock damage mechanisms can then be evaluated based on the results of the coupled simulations. A scenario based approach is proposed to take into account the effect of the uncertainty of model parameters on damage likelihood. The developed methodology is applied for the cap-rock failure analysis of deep aquifer of the Dogger formation in the context of the Paris basin multilayered geological system as a demonstration example. The simulation is carried out at a regional scale (100 km) considering an industrial mass injection rate of CO 2 of 10 Mt/y. The assessment of the stress state after 10 years of injection is conducted through the developed sequential coupling. Two failure mechanisms have been taken into account, namely the tensile fracturing and the shear slip reactivation of pre-existing fractures. To deal with the large uncertainties due to sparse data on the layer formations, a scenario based strategy is undertaken. It consists in defining a first reference modelling scenario considering the mean values of the hydro-mechanical properties for each layer. A sensitivity analysis is then carried out and shows the importance of both the initial stress state and the reservoir hydraulic properties on the cap-rock failure tendency. On this basis, a second scenario denoted 'critical' is defined so that the most influential model parameters are taken in their worst configuration. None of these failure criteria is activated for the considered conditions. At a phenomenological level, this study points out three key

Damage mechanisms in PBT-GF30 under thermo-mechanical cyclic loading

International Nuclear Information System (INIS)

Schaaf, A.; De Monte, M.; Hoffmann, C.; Vormwald, M.; Quaresimin, M.

2014-01-01

The scope of this paper is the investigation of damage mechanisms at microscopic scale on a short glass fiber reinforced polybutylene terephthalate (PBT-GF30) under thermo-mechanical cyclic loading. In addition the principal mechanisms are verified through micro mechanical FE models. In order to investigate the fatigue behavior of the material both isothermal strain controlled fatigue (ISCF) tests at three different temperatures and thermo-mechanical fatigue (TMF) tests were conducted on plain and notched specimens, manufactured by injection molding. The goal of the work is to determine the damage mechanisms occurring under TMF conditions and to compare them with the mechanisms occurring under ISCF. For this reason fracture surfaces of TMF and ISCF samples loaded at different temperature levels were analyzed using scanning electron microscopy. Furthermore, specimens that failed under TMF were examined on microsections revealing insight into both crack initiation and crack propagation. The findings of this investigation give valuable information about the main damage mechanisms of PBT-GF30 under TMF loading and serve as basis for the development of a TMF life estimation methodology

A three-dimensional coupled thermo-hydro-mechanical model for deformable fractured geothermal systems

DEFF Research Database (Denmark)

Salimzadeh, Saeed; Paluszny, Adriana; Nick, Hamidreza M.

2018-01-01

A fully coupled thermal-hydraulic-mechanical (THM) finite element model is presented for fractured geothermal reservoirs. Fractures are modelled as surface discontinuities within a three-dimensional matrix. Non-isothermal flow through the rock matrix and fractures are defined and coupled to a mec......A fully coupled thermal-hydraulic-mechanical (THM) finite element model is presented for fractured geothermal reservoirs. Fractures are modelled as surface discontinuities within a three-dimensional matrix. Non-isothermal flow through the rock matrix and fractures are defined and coupled....... The model has been validated against several analytical solutions, and applied to study the effects of the deformable fractures on the injection of cold water in fractured geothermal systems. Results show that the creation of flow channelling due to the thermal volumetric contraction of the rock matrix...

On the use of effective stress in three-dimensional hydro-mechanical coupled model

International Nuclear Information System (INIS)

Arairo, W.; Prunier, F.; Djeran-Maigre, I.; Millard, A.

2014-01-01

In the last decades, a number of hydro-mechanical elastoplastic constitutive models for unsaturated soils have been proposed. Those models couple the hydraulic and mechanical behaviour of unsaturated soils, and take into account the effects of the degree of saturation on the stress-strain behaviour and the effects of deformation on the soil-water characteristic response with a simple reversible part for the hysteresis. In addition, the influence of the suction on the stress-strain behaviour is considered. However, until now, few models predict the stress-strain and soil-water characteristic responses of unsaturated soils in a fully three-dimensional Finite Element code. This paper presents the predictions of an unsaturated soil model in a Three-dimensional Framework, and develops a study on the effect of partial saturation on the stability of shallow foundation resting on unsaturated silty soil. Qualitative predictions of the constitutive model show that incorporating a special formulation for the effective stress into an elastoplastic coupled hydro-mechanical model opens a full range of possibilities in modelling unsaturated soil behaviour. (authors)

Numerical study of the EDZ by a thermo-hydro-mechanical damage model dedicated to unsaturated geo-materials

International Nuclear Information System (INIS)

Arson, Chloe; Gatmiri, Behrouz

2010-01-01

Document available in extended abstract form only. The design of deep nuclear waste repositories requires the modelling of the effects of thermal loadings in the Excavation Damaged Zone (EDZ). The containers are to be stored in bentonite buffers surrounded by a geological massif. These two barriers are multi-phase porous media, in which coupled mechanical, capillary and thermal phenomena occur. The aim of this study is to develop a new damage model dedicated to non-isothermal unsaturated porous media, the 'THHMD' model. Contrary to almost all of the existing damage models dedicated to non dry media, it is formulated in independent stress state variables (net stress, suction and thermal stress). The damage variable is a second-order tensor, which gives a good approximation for the representation of anisotropic cracking in three dimensions. The behaviour laws stem from the combination of phenomenological and micromechanical principles. The total strain tensor is split into three components, each of which being conjugated to a stress state variable. The Helmholtz free energy is written as the sum of damaged elastic energies and residual-strain-potentials. The concept of effective stress, frequently used in Continuum Damaged Mechanics, is extended to the three stress state variables, by using the operator of Cordebois and Sidoroff. The damaged rigidities are computed by application of the Principle of Equivalent Elastic Energy (PEEE). The non-elastic strain components depend on the increment of damage, which is determined by an associative flow rule. Fracturing is also modelled in the transfer equations. The Representative Elementary Volume (REV) is assumed to be damaged by a microcrack network, among which liquid water and vapour flows are homogenized. A damaged intrinsic conductivity, which plays the role of an internal length parameter, is introduced. The influence of damage on air and heat flows is taken into account by means of porosity, which is also

Thermo-Hydro-Micro-Mechanical 3D Modeling of a Fault Gouge During Co-seismic Slip

Science.gov (United States)

Papachristos, E.; Stefanou, I.; Sulem, J.; Donze, F. V.

2017-12-01

A coupled Thermo-Hydro-Micro-Mechanical (THMM) model based on the Discrete Elements method (DEM) is presented for studying the evolving fault gouge properties during pre- and co-seismic slip. Modeling the behavior of the fault gouge at the microscale is expected to improve our understanding on the various mechanisms that lead to slip weakening and finally control the transition from aseismic to seismic slip.The gouge is considered as a granular material of spherical particles [1]. Upon loading, the interactions between particles follow a frictional behavior and explicit dynamics. Using regular triangulation, a pore network is defined by the physical pore space between the particles. The network is saturated by a compressible fluid, and flow takes place following Stoke's equations. Particles' movement leads to pore deformation and thus to local pore pressure increase. Forces exerted from the fluid onto the particles are calculated using mid-step velocities. The fluid forces are then added to the contact forces resulting from the mechanical interactions before the next step.The same semi-implicit, two way iterative coupling is used for the heat-exchange through conduction.Simple tests have been performed to verify the model against analytical solutions and experimental results. Furthermore, the model was used to study the effect of temperature on the evolution of effective stress in the system and to highlight the role of thermal pressurization during seismic slip [2, 3].The analyses are expected to give grounds for enhancing the current state-of-the-art constitutive models regarding fault friction and shed light on the evolution of fault zone propertiesduring seismic slip.[1] Omid Dorostkar, Robert A Guyer, Paul A Johnson, Chris Marone, and Jan Carmeliet. On the role of fluids in stick-slip dynamics of saturated granular fault gouge using a coupled computational fluid dynamics-discrete element approach. Journal of Geophysical Research: Solid Earth, 122

Aespoe Pillar Stability Experiment. Final coupled 3D thermo-mechanical modeling. Preliminary particle mechanical modeling

International Nuclear Information System (INIS)

Wanne, Toivo; Johansson, Erik; Potyondy, David

2004-02-01

SKB is planning to perform a large-scale pillar stability experiment called APSE (Aespoe Pillar Stability Experiment) at Aespoe HRL. The study is focused on understanding and control of progressive rock failure in hard crystalline rock and damage caused by high stresses. The elastic thermo-mechanical modeling was carried out in three dimensions because of the complex test geometry and in-situ stress tensor by using a finite-difference modeling software FLAC3D. Cracking and damage formation were modeled in the area of interest (pillar between two large scale holes) in two dimensions by using the Particle Flow Code (PFC), which is based on particle mechanics. FLAC and PFC were coupled to minimize the computer resources and the computing time. According to the modeling the initial temperature rises from 15 deg C to about 65 deg C in the pillar area during the heating period of 120 days. The rising temperature due to thermal expansion induces stresses in the pillar area and after 120 days heating the stresses have increased about 33% from the excavation induced maximum stress of 150 MPa to 200 MPa in the end of the heating period. The results from FLAC3D model showed that only regions where the crack initiation stress has exceeded were identified and they extended to about two meters down the hole wall. These could be considered the areas where damage may occur during the in-situ test. When the other hole is pressurized with a 0.8 MPa confining pressure it yields that 5 MPa more stress is needed to damage the rock than without confining pressure. This makes the damaged area in some degree smaller. High compressive stresses in addition to some tensile stresses might induce some AE (acoustic emission) activity in the upper part of the hole from the very beginning of the test and are thus potential areas where AE activities may be detected. Monitoring like acoustic emissions will be measured during the test execution. The 2D coupled PFC-FLAC modeling indicated that

Aespoe Pillar Stability Experiment. Final coupled 3D thermo-mechanical modeling. Preliminary particle mechanical modeling

Energy Technology Data Exchange (ETDEWEB)

Wanne, Toivo; Johansson, Erik; Potyondy, David [Saanio and Riekkola Oy, Helsinki (Finland)

2004-02-01

SKB is planning to perform a large-scale pillar stability experiment called APSE (Aespoe Pillar Stability Experiment) at Aespoe HRL. The study is focused on understanding and control of progressive rock failure in hard crystalline rock and damage caused by high stresses. The elastic thermo-mechanical modeling was carried out in three dimensions because of the complex test geometry and in-situ stress tensor by using a finite-difference modeling software FLAC3D. Cracking and damage formation were modeled in the area of interest (pillar between two large scale holes) in two dimensions by using the Particle Flow Code (PFC), which is based on particle mechanics. FLAC and PFC were coupled to minimize the computer resources and the computing time. According to the modeling the initial temperature rises from 15 deg C to about 65 deg C in the pillar area during the heating period of 120 days. The rising temperature due to thermal expansion induces stresses in the pillar area and after 120 days heating the stresses have increased about 33% from the excavation induced maximum stress of 150 MPa to 200 MPa in the end of the heating period. The results from FLAC3D model showed that only regions where the crack initiation stress has exceeded were identified and they extended to about two meters down the hole wall. These could be considered the areas where damage may occur during the in-situ test. When the other hole is pressurized with a 0.8 MPa confining pressure it yields that 5 MPa more stress is needed to damage the rock than without confining pressure. This makes the damaged area in some degree smaller. High compressive stresses in addition to some tensile stresses might induce some AE (acoustic emission) activity in the upper part of the hole from the very beginning of the test and are thus potential areas where AE activities may be detected. Monitoring like acoustic emissions will be measured during the test execution. The 2D coupled PFC-FLAC modeling indicated that

Two-scale modelling for hydro-mechanical damage

International Nuclear Information System (INIS)

Frey, J.; Chambon, R.; Dascalu, C.

2010-01-01

Document available in extended abstract form only. Excavation works for underground storage create a damage zone for the rock nearby and affect its hydraulics properties. This degradation, already observed by laboratory tests, can create a leading path for fluids. The micro fracture phenomenon, which occur at a smaller scale and affect the rock permeability, must be fully understood to minimize the transfer process. Many methods can be used in order to take into account the microstructure of heterogeneous materials. Among them a method has been developed recently. Instead of using a constitutive equation obtained by phenomenological considerations or by some homogenization techniques, the representative elementary volume (R.E.V.) is modelled as a structure and the links between a prescribed kinematics and the corresponding dual forces are deduced numerically. This yields the so called Finite Element square method (FE2). In a numerical point of view, a finite element model is used at the macroscopic level, and for each Gauss point, computations on the microstructure gives the usual results of a constitutive law. This numerical approach is now classical in order to properly model some materials such as composites and the efficiency of such numerical homogenization process has been shown, and allows numerical modelling of deformation processes associated with various micro-structural changes. The aim of this work is to describe trough such a method, damage of the rock with a two scale hydro-mechanical model. The rock damage at the macroscopic scale is directly link with an analysis on the microstructure. At the macroscopic scale a two phase's problem is studied. A solid skeleton is filled up by a filtrating fluid. It is necessary to enforce two balance equation and two mass conservation equations. A classical way to deal with such a problem is to work with the balance equation of the whole mixture, and the mass fluid conservation written in a weak form, the mass

Contribution to the numerical study of concrete behaviour and of reinforced concrete structures submitted to coupled thermal and mechanical solicitations: a damageable thermo-elasto-plastic approach

International Nuclear Information System (INIS)

Nechnech, W.

2000-12-01

The aim of this research is the development of an Finite Element model for the analysis of reinforced concrete structures under thermal, mechanical loadings or any combination of them. An available synthesis of results on the concrete behavior under thermal solicitation is exposed. The different behavior of concrete that can be founded notably in thermo-mechanical analysis (Damage, unilateral phenomenon, thermo-mechanical interaction,...) are underlined. The various families of modeling are analyzed thereafter while underlining the important aspects of the behavior that each one can re-transcribe. A new thermo-plastic damage model for plain concrete subjected to combined thermal and cyclic loading is developed using the concept of plastic-work-hardening and stiffness degradation in continuum damage mechanics. Two damage variables are used: the first one for mechanical action and the second one for thermal action. Further, thermo-mechanical interaction strains have been introduced to describe the influence of mechanical loading on the physical process of thermal expansion of concrete. The constitutive relations for elastoplastic responses are decoupled from the degradation damage responses by using the effective stress concept. This method provides advantages in the numerical implementation. A simple and thermodynamically consistent scalar degradation model is introduced to simulate the effect of damage on elastic stiffness and its recovery during crack opening and closing. Efficient computational algorithms for the proposed model are subsequently explored and performance of this model is demonstrated with numerical examples. (author)

Application of a new thermo-mechanical model for the study of the nuclear waste disposal in clay rocks

International Nuclear Information System (INIS)

Dizier, A.; Li, X.L.; Francois, B.; Collin, F.; Charlier, R.

2012-01-01

(LY curve (Loading Yield)). This one may be considered analogous with the LC curve (Loading Collapse) met in the Barcelona Basic Model dedicated to unsaturated soil mechanics. This thermo-mechanical law has been used to model the PRACLAY experiment and particularly to analyse the evolution of the damaged zone with temperature. In this study, the damaged zone is considered as the sum of two plastic strain components, a deviatoric and a volumetric one. The deviatoric strains are induced when the internal friction criterion is reached while the volumetric strains are a consequence of the Cam - Clay model or the TY curve. The results of the evolution of the deviatoric strain show that the magnitude of this strain is modified near the wall but the extension of the size of the plastic deviatoric zone is not affected by temperature. The modification of the deviatoric strain near the wall can be explained by hydro-mechanical coupling caused by thermally induced excess pore water pressure which permits the stress path to reach the internal friction criterion. Concerning the volumetric plastic strains, these follow the effect of the thermal load and the size of the zone affected by these strains correspond to the zone affected by the temperature. On the contrary the magnitude of the strain depends on the state of stress of the clay as observed near the wall. Indeed, the stresses near the wall are reduced due to the process of excavation and the state of stress exhibits a kind of over-consolidation effect where only thermal dilation is possible. In that modelling, the set of parameters chosen doesn't allow the activation of the LY curve. Finally the results obtained with this new thermo-mechanical law have been compared with results obtained with other thermo-mechanical law, that is to say with ACMEG-T which is a thermo-plastic law developed at EPFL and a classical thermo-elastic law. The comparison shows that the results obtained with the two thermo-plastic constitutive laws

A multi-scale computational scheme for anisotropic hydro-mechanical couplings in saturated heterogeneous porous media

NARCIS (Netherlands)

Mercatoris, B.C.N.; Massart, T.J.; Sluys, L.J.

2013-01-01

This contribution discusses a coupled two-scale framework for hydro-mechanical problems in saturated heterogeneous porous geomaterials. The heterogeneous nature of such materials can lead to an anisotropy of the hydro-mechanical couplings and non-linear effects. Based on an assumed model of the

FEBEX Full-Scalle Engineered Barriers Experiment in Crystalline Host Rock Preoperational Thermo-Hydro-Mechanical (THM) Modelling of the Mock Up Test

International Nuclear Information System (INIS)

1998-01-01

The object of this report is to present and discuss the results of a series of 1-D and 2-D coupled thermo-hydro-mechanical (THM) and 2-D coupled thermo-hydro-mechanical (THM) analyses modelling the FEBEX mock-up test. The analyses have been carried out during the preoperational storage of the test and attempt to incorporate all available information obtained from laboratory characterisation work. The aim is not only to offer the best estimate of test performance using current models and information but also to provide a basis for future model improvements. Both the theoretical framework adopted in the analysis and the computer code employed are briefly described. The set of parameters used in the computation is then presented with particular reference to the source from which they have been derived. Initial and boundary condition are also defined. The results of a 1-D radially symmetric analysis are used to examine the basic patterns of thermal, hydraulic and mechanical behaviour of the test. A set of sensitivity analyses has been carried out in order to check the effects that the variation of a number of important parameters has on test results. Only in this way it is possible to acquire a proper understanding of the internal structure of the problem and of the interactions between the various phenomena occurring in the buffer. A better reproduction of the geometry of the test is achieved by means of a 2-D mesh representing and axisymmetric longitudinal section. Due to two-dimensional effects, the analyses carried out using this geometry exhibit some differences when compared with the results of the 1-D case, but the basic test behaviour is very similar. The test was started with an initial flooding stage with the purpose of closing the gaps between bentonite blocks. A limited number of compilations using recently developed joint elements have been performed to assess approximately the effect of this initial step on subsequent test behaviour. The analyses reported

The importance of Thermo-Hydro-Mechanical couplings and microstructure to strain localization in 3D continua with application to seismic faults. Part I: Theory and linear stability analysis

Science.gov (United States)

Rattez, Hadrien; Stefanou, Ioannis; Sulem, Jean

2018-06-01

A Thermo-Hydro-Mechanical (THM) model for Cosserat continua is developed to explore the influence of frictional heating and thermal pore fluid pressurization on the strain localization phenomenon. A general framework is presented to conduct a bifurcation analysis for elasto-plastic Cosserat continua with THM couplings and predict the onset of instability. The presence of internal lengths in Cosserat continua enables to estimate the thickness of the localization zone. This is done by performing a linear stability analysis of the system and looking for the selected wavelength corresponding to the instability mode with fastest finite growth coefficient. These concepts are applied to the study of fault zones under fast shearing. For doing so, we consider a model of a sheared saturated infinite granular layer. The influence of THM couplings on the bifurcation state and the shear band width is investigated. Taking representative parameters for a centroidal fault gouge, the evolution of the thickness of the localized zone under continuous shear is studied. Furthermore, the effect of grain crushing inside the shear band is explored by varying the internal length of the constitutive law.

The hydro-mechanical modeling of the fractured media

International Nuclear Information System (INIS)

Kadiri, I.

2002-10-01

analyzed with the aim to catch the nature of hydro-mechanical coupling. The modeling of Coaraze allowed to reproduce in situ measurements and to give an opinion on the problems of the hydro-mechanical coupling in the fractured mediums. (author)

Modelling the hydro-mechanical behaviour of swelling unsaturated soils; Modelisation du comportement hydromecanique des sols gonflants non satures

Energy Technology Data Exchange (ETDEWEB)

Mrad, M

2005-10-15

The use of compacted swelling soils in engineering practice is very widely spread, especially in geotechnical and environmental engineering. After their setup, these materials are likely to be subject to complex suction/stress paths involving significant variations of their hydro-mechanical properties which can affect their initial behaviour. It is important to be able to predict the hydro-mechanical behaviour of these materials taking into account the significant applications for which they are intended. Barcelona team developed a finite-element code (Code-Bright) for the thermo-hydro-mechanical coupling (THM) integrating the BBM elastoplastic model for unsaturated soils based on the independent variables approach. This model is recognized to correctly describe the hydro-mechanical behaviour of unsaturated soils but fails to take into account some particular observed aspects on swelling soils. A second model BExM was then proposed to address these aspects. The objective of this study is: (i) to implement the elastoplastic model BExM for the unsaturated swelling soils in the finite-element code (Code-Bright); (ii) to check the numerical model validity through the numerical simulation of laboratory tests made on swelling soils; and (iii) to apply this model to some practical problems. For this purpose, a new family of numerical procedures adapted to the BExM model was introduced into the code. The equation of the yield surface of this model for a given deviatoric stress states was given in a manner to facilitate calculations of its derivatives. The model was checked by the numerical simulation of suction-controlled odometric tests made on three different swelling soils. The simulation results showed that the numerical model is able to correctly reproduce the experimental data. Lastly, the model was applied to two practical problems: radioactive waste repository in deep geological layers and a shallow footing under the action of a swelling soil. The results obtained

Effect of hydro mechanical coupling on natural fracture network formation in sedimentary basins

Science.gov (United States)

Ouraga, Zady; Guy, Nicolas; Pouya, Amade

2018-05-01

In sedimentary basin context, numerous phenomena, depending on the geological time span, can result in natural fracture network formation. In this paper, fracture network and dynamic fracture spacing triggered by significant sedimentation rate are studied considering mode I fracture propagation using a coupled hydro-mechanical numerical methods. The focus is put on synthetic geological structure under a constant sedimentation rate on its top. This model contains vertical fracture network initially closed and homogeneously distributed. The fractures are modelled with cohesive zone model undergoing damage and the flow is described by Poiseuille's law. The effect of the behaviour of the rock is studied and the analysis leads to a pattern of fracture network and fracture spacing in the geological layer.

Thermo-hydro-mechanical behavior of argillite

International Nuclear Information System (INIS)

Tran, Duy Thuong; Dormieux, Luc; Lemarchand, Eric; Skoczylas, Frederic

2012-01-01

Document available in extended abstract form only. Argillite is a very low permeability geo-material widely encountered: that is the reason why it is an excellent candidate for the storage of long-term nuclear waste depositories. This study focuses on argillites from Meuse-Haute-Marne (East of France) which forms a geological layer located approximately 400 m and 500 m depth. We know that this material is made up of a mixture of shale, quartz and calcite phases. The multi-scale definition of this material suggests the derivation of micro-mechanics reasonings in order to better account for the mechanisms occurring at the local (nano and micro-) scale and controlling the macroscopic mechanical behavior. In this work, up-scaling techniques are used in the context of thermo-hydro-mechanical couplings. The first step consists in clarifying the morphology of the microstructure at the relevant scales (particles arrangement, pore size distribution) and identifying the mechanisms that take place at those scales. These local informations provide the input data of micro-mechanics based models. Schematic picture of the microstructure where the argillite material behaves as a dual-porosity, with liquid in both micro-pores and interlayer space in between clay solid platelets, seems a reasonable starting point for this micro-mechanical modelling of clay. This allows us to link the physical phenomena (swelling clays) and the mechanical properties (elastic moduli, Poisson's ratio). At the pressure applied by the fluid on the solid platelets appears as the sum of the uniform pressure in the micro-pores and of a swelling overpressure depending on the distance between platelets and on the ion concentration in the micro-pores. The latter is proved to be responsible for a local elastic modulus of physical origin. This additional elastic component may strongly be influenced by both relative humidity and temperature. A first contribution of this study is to analysing this local elastic

Experiments on thermo-hydro-mechanical behaviour of Opalinus Clay at Mont Terri rock laboratory, Switzerland

Directory of Open Access Journals (Sweden)

Paul Bossart

2017-06-01

Full Text Available Repositories for deep geological disposal of radioactive waste rely on multi-barrier systems to isolate waste from the biosphere. A multi-barrier system typically comprises the natural geological barrier provided by the repository host rock – in our case the Opalinus Clay – and an engineered barrier system (EBS. The Swiss repository concept for spent fuel and vitrified high-level waste (HLW consists of waste canisters, which are emplaced horizontally in the middle of an emplacement gallery and are separated from the gallery wall by granular backfill material (GBM. We describe here a selection of five in-situ experiments where characteristic hydro-mechanical (HM and thermo-hydro-mechanical (THM processes have been observed. The first example is a coupled HM and mine-by test where the evolution of the excavation damaged zone (EDZ was monitored around a gallery in the Opalinus Clay (ED-B experiment. Measurements of pore-water pressures and convergences due to stress redistribution during excavation highlighted the HM behaviour. The same measurements were subsequently carried out in a heater test (HE-D where we were able to characterise the Opalinus Clay in terms of its THM behaviour. These yielded detailed data to better understand the THM behaviours of the granular backfill and the natural host rock. For a presentation of the Swiss concept for HLW storage, we designed three demonstration experiments that were subsequently implemented in the Mont Terri rock laboratory: (1 the engineered barrier (EB experiment, (2 the in-situ heater test on key-THM processes and parameters (HE-E experiment, and (3 the full-scale emplacement (FE experiment. The first demonstration experiment has been dismantled, but the last two ones are on-going.

Regional-scale geomechanical impact assessment of underground coal gasification by coupled 3D thermo-mechanical modeling

Science.gov (United States)

Otto, Christopher; Kempka, Thomas; Kapusta, Krzysztof; Stańczyk, Krzysztof

2016-04-01

Underground coal gasification (UCG) has the potential to increase the world-wide coal reserves by utilization of coal deposits not mineable by conventional methods. The UCG process involves combusting coal in situ to produce a high-calorific synthesis gas, which can be applied for electricity generation or chemical feedstock production. Apart from its high economic potentials, UCG may induce site-specific environmental impacts such as fault reactivation, induced seismicity and ground subsidence, potentially inducing groundwater pollution. Changes overburden hydraulic conductivity resulting from thermo-mechanical effects may introduce migration pathways for UCG contaminants. Due to the financial efforts associated with UCG field trials, numerical modeling has been an important methodology to study coupled processes considering UCG performance. Almost all previous UCG studies applied 1D or 2D models for that purpose, that do not allow to predict the performance of a commercial-scale UCG operation. Considering our previous findings, demonstrating that far-field models can be run at a higher computational efficiency by using temperature-independent thermo-mechanical parameters, representative coupled simulations based on complex 3D regional-scale models were employed in the present study. For that purpose, a coupled thermo-mechanical 3D model has been developed to investigate the environmental impacts of UCG based on a regional-scale of the Polish Wieczorek mine located in the Upper Silesian Coal Basin. The model size is 10 km × 10 km × 5 km with ten dipping lithological layers, a double fault and 25 UCG reactors. Six different numerical simulation scenarios were investigated, considering the transpressive stress regime present in that part of the Upper Silesian Coal Basin. Our simulation results demonstrate that the minimum distance between the UCG reactors is about the six-fold of the coal seam thickness to avoid hydraulic communication between the single UCG

On a morphological approach of the meso-structure for the multi-scale analysis of the thermo-hydro-mechanical behaviour of cementitious materials

International Nuclear Information System (INIS)

Le, T.T.H.

2011-01-01

The investigation of the behavior of heated concrete is a major research topic which concerns the assessment of safety level of structures when exposed to high temperatures, for instance during a fire. For this purpose, several modeling approaches were developed within thermo-hydro-mechanical (THM) frameworks in order to take into account the involved physic-chemical and mechanical processes that affect stability of heated concrete. However, existing models often do note account explicitly for the heterogeneity of the material: concrete is composite material that may be schematized as an assembly of inclusions (aggregates) embedded in a cementitious matrix (cement paste). This latter may be described as a partially saturated open porous medium. The aggregates are characterized by their mineralogical nature together with their morphology and size distribution. The material heterogeneity bring an additional complexity: the need to take into account the microstructure in order to quantify the effect of matrix-inclusion thermal, hygral and mechanical incompatibilities on the THM behavior of concrete. This work is a first step in this direction. For this purpose, a three-dimensional (3D) multi-scale finite element model is developed. It allows affecting specific behaviors to matrix and inclusions. For the former, where mass transports occur within the connected porous network, a three-fluids approach (liquid water, vapor and dry air) is adopted and is coupled to a poro-mechanical damage based approach. For inclusions (aggregates) no hygral component arises a pure thermo-mechanical model is considered. The developed model is then used to investigate, either by 2D or 3D numerical simulations, effects of mineralogical nature, morphology and distribution of aggregates. Studied effects have mainly concerned the influence of these parameters on local fluctuations of simulated temperature, gas pressure and damage fields with regard to experimentally observed dispersion. The

A 3D coupled hydro-mechanical granular model for the prediction of hot tearing formation

International Nuclear Information System (INIS)

Sistaninia, M; Drezet, J-M; Rappaz, M; Phillion, A B

2012-01-01

A new 3D coupled hydro-mechanical granular model that simulates hot tearing formation in metallic alloys is presented. The hydro-mechanical model consists of four separate 3D modules. (I) The Solidification Module (SM) is used for generating the initial solid-liquid geometry. Based on a Voronoi tessellation of randomly distributed nucleation centers, this module computes solidification within each polyhedron using a finite element based solute diffusion calculation for each element within the tessellation. (II) The Fluid Flow Module (FFM) calculates the solidification shrinkage and deformation-induced pressure drop within the intergranular liquid. (III) The Semi-solid Deformation Module (SDM) is used to simulate deformation of the granular structure via a combined finite element / discrete element method. In this module, deformation of the solid grains is modeled using an elasto-viscoplastic constitutive law. (IV) The Failure Module (FM) is used to simulate crack initiation and propagation with the fracture criterion estimated from the overpressure required to overcome the capillary forces at the liquid-gas interface. The FFM, SDM, and FM are coupled processes since solid deformation, intergranular flow, and crack initiation are deeply linked together. The granular model predictions have been validated against bulk data measured experimentally and calculated with averaging techniques.

Training and Research on Probabilistic Hydro-Thermo-Mechanical Modeling of Carbon Dioxide Geological Sequestration in Fractured Porous Rocks

Energy Technology Data Exchange (ETDEWEB)

Gutierrez, Marte

2013-05-31

Colorado School of Mines conducted research and training in the development and validation of an advanced CO{sub 2} GS (Geological Sequestration) probabilistic simulation and risk assessment model. CO{sub 2} GS simulation and risk assessment is used to develop advanced numerical simulation models of the subsurface to forecast CO2 behavior and transport; optimize site operational practices; ensure site safety; and refine site monitoring, verification, and accounting efforts. As simulation models are refined with new data, the uncertainty surrounding the identified risks decrease, thereby providing more accurate risk assessment. The models considered the full coupling of multiple physical processes (geomechanical and fluid flow) and describe the effects of stochastic hydro-mechanical (H-M) parameters on the modeling of CO{sub 2} flow and transport in fractured porous rocks. Graduate students were involved in the development and validation of the model that can be used to predict the fate, movement, and storage of CO{sub 2} in subsurface formations, and to evaluate the risk of potential leakage to the atmosphere and underground aquifers. The main major contributions from the project include the development of: 1) an improved procedure to rigorously couple the simulations of hydro-thermomechanical (H-M) processes involved in CO{sub 2} GS; 2) models for the hydro-mechanical behavior of fractured porous rocks with random fracture patterns; and 3) probabilistic methods to account for the effects of stochastic fluid flow and geomechanical properties on flow, transport, storage and leakage associated with CO{sub 2} GS. The research project provided the means to educate and train graduate students in the science and technology of CO{sub 2} GS, with a focus on geologic storage. Specifically, the training included the investigation of an advanced CO{sub 2} GS simulation and risk assessment model that can be used to predict the fate, movement, and storage of CO{sub 2} in

An efficient hydro-mechanical model for coupled multi-porosity and discrete fracture porous media

Science.gov (United States)

Yan, Xia; Huang, Zhaoqin; Yao, Jun; Li, Yang; Fan, Dongyan; Zhang, Kai

2018-02-01

In this paper, a numerical model is developed for coupled analysis of deforming fractured porous media with multiscale fractures. In this model, the macro-fractures are modeled explicitly by the embedded discrete fracture model, and the supporting effects of fluid and fillings in these fractures are represented explicitly in the geomechanics model. On the other hand, matrix and micro-fractures are modeled by a multi-porosity model, which aims to accurately describe the transient matrix-fracture fluid exchange process. A stabilized extended finite element method scheme is developed based on the polynomial pressure projection technique to address the displacement oscillation along macro-fracture boundaries. After that, the mixed space discretization and modified fixed stress sequential implicit methods based on non-matching grids are applied to solve the coupling model. Finally, we demonstrate the accuracy and application of the proposed method to capture the coupled hydro-mechanical impacts of multiscale fractures on fractured porous media.

Numerical analysis of thermal impact on hydro-mechanical properties of clay

Directory of Open Access Journals (Sweden)

Xuerui Wang

2014-10-01

Full Text Available As is known, high-level radioactive waste (HLW is commonly heat-emitting. Heat output from HLW will dissipate through the surrounding rocks and induce complex thermo-hydro-mechanical-chemical (THMC processes. In highly consolidated clayey rocks, thermal effects are particularly significant because of their very low permeability and water-saturated state. Thermal impact on the integrity of the geological barriers is of most importance with regard to the long-term safety of repositories. This study focuses on numerical analysis of thermal effects on hydro-mechanical properties of clayey rock using a coupled thermo-mechanical multiphase flow (TH2M model which is implemented in the finite element programme OpenGeoSys (OGS. The material properties of the numerical model are characterised by a transversal isotropic elastic model based on Hooke's law, a non-isothermal multiphase flow model based on van Genuchten function and Darcy's law, and a transversal isotropic heat transport model based on Fourier's law. In the numerical approaches, special attention has been paid to the thermal expansion of three different phases: gas, fluid and solid, which could induce changes in pore pressure and porosity. Furthermore, the strong swelling and shrinkage behaviours of clayey material are also considered in the present model. The model has been applied to simulate a laboratory heating experiment on claystone. The numerical model gives a satisfactory representation of the observed material behaviour in the laboratory experiment. The comparison of the calculated results with the laboratory findings verifies that the simulation with the present numerical model could provide a deeper understanding of the observed effects.

Thermo-mechanical ratcheting in jointed rock masses

KAUST Repository

Pasten, C.

2015-09-01

Thermo-mechanical coupling takes place in jointed rock masses subjected to large thermal oscillations. Examples range from exposed surfaces under daily and seasonal thermal fluctuations to subsurface rock masses affected by engineered systems such as geothermal operations. Experimental, numerical and analytical results show that thermo-mechanical coupling can lead to wedging and ratcheting mechanisms that result in deformation accumulation when the rock mass is subjected to a biased static-force condition. Analytical and numerical models help in identifying the parameter domain where thermo-mechanical ratcheting can take place.

Thermo-mechanical ratcheting in jointed rock masses

KAUST Repository

Pasten, C.; Garcí a, M.; Santamarina, Carlos

2015-01-01

Thermo-mechanical coupling takes place in jointed rock masses subjected to large thermal oscillations. Examples range from exposed surfaces under daily and seasonal thermal fluctuations to subsurface rock masses affected by engineered systems such as geothermal operations. Experimental, numerical and analytical results show that thermo-mechanical coupling can lead to wedging and ratcheting mechanisms that result in deformation accumulation when the rock mass is subjected to a biased static-force condition. Analytical and numerical models help in identifying the parameter domain where thermo-mechanical ratcheting can take place.

High-performance coupled poro-hydro-mechanical models to resolve fluid escape pipes

Science.gov (United States)

Räss, Ludovic; Makhnenko, Roman; Podladchikov, Yury

2017-04-01

Field observations and laboratory experiments exhibit inelastic deformation features arising in many coupled settings relevant to geo-applications. These irreversible deformations and their specific patterns suggest a rather ductile or brittle mechanism, such as viscous creep or micro cracks, taking place on both geological (long) and human (short) timescales. In order to understand the underlying mechanisms responsible for these deformation features, there is a current need to accurately resolve the non-linearities inherent to strongly coupled physical processes. Among the large variety of modelling tools and softwares available nowadays in the community, very few are capable to efficiently solve coupled systems with high accuracy in both space and time and run efficiently on modern hardware. Here, we propose a robust framework to solve coupled multi-physics hydro-mechanical processes on very high spatial and temporal resolution in both two and three dimensions. Our software relies on the Finite-Difference Method and a pseudo-transient scheme is used to converge to the implicit solution of the system of poro-visco-elasto-plastic equations at each physical time step. The rheology including viscosity estimates for major reservoir rock types is inferred from novel lab experiments and confirms the ease of flow of sedimentary rocks. Our results propose a physical mechanism responsible for the generation of high permeability pathways in fluid saturated porous media and predict their propagation in rates observable on operational timescales. Finally, our software scales linearly on more than 5000 GPUs.

Fully-coupled hydro-mechanical modelling of the D-holes and validation drift inflow

International Nuclear Information System (INIS)

Monsen, K.; Barton, N.; Makurat, A.

1992-02-01

This report presents the results from fully-coupled hydro-mechanical modelling of the D-hole and drift inflows. Joints represented in Harwells stochastically generated 8m x 8m x 8m cubes were used to select two possible joint geometries for two-dimensional rock mechanics simulations of the 2.8 x 2.2m validation drift, and the rock mass response to its excavation. The joints intersecting the four end faces of these cubes were set up in distinct element UDEC-BB models and loaded with boundary stresses of 10 MPa vertically and 14 MPa horizontally. In numerical models 5 and 8, which were run first as mechanical response (M) models (TR 91-05), full H-M coupling was performed, with calculations of inflow. In general, response to excavation was a little stronger than in hte un-coupled mechanical response (M) modelling. In the D-hole simulations, however, channel development int he disturbed zone could not occur due to less displacement taking place in the rock mass. For this reason, the stress levels were also generally much more moderate, preventing the joints from closing as much as in the drift simulations. Consequently, the D-hole model had a much better radial connectivity. It was possible to observe that the radial inflow to the D-holes was significantly higher than the flow into the drift models. However, due to the extremely small joint apertures involved (<1μm), time steps and calculation times were very slow in the H-M models, and although mechanical behaviour appeared to have reached equilibrium, there was evidence of continued transients in some of the flow regions. The drift excavation caused nearly total closing of critical joints due to local normal stress inceases. Near-blockage of fluid transportation routes was demonstrated. (au)

Damage evolution of TBC system under in-phase thermo-mechanical tests

International Nuclear Information System (INIS)

Kitazawa, R.; Tanaka, M.; Kagawa, Y.; Liu, Y.F.

2010-01-01

In-phase thermo-mechanical tests (TMF) of EB-PVD Y 2 O 3 -ZrO 2 thermal barrier coating (TBC) system (8 wt% Y 2 O 3 -ZrO 2 /CoNiCrAlY/IN-738 substrate) were done under a through-the-thick-direction thermal gradient from TBC surface temperature at 1150 deg. C to substrate temperature at 1000 deg. C. Deformation and failure behaviors of the TBC system were observed at the macroscopic and microscopic scales and damage evolution of the system under in-phase thermo-mechanical test was discussed. Special attention was paid to TBC layer cracking, thermally grown oxide (TGO) layer formation and void formation in bond coat and substrate. Effect of TMF conditions on the damage evolution behaviors was also discussed.

Fractures inside crystalline rocks. Effects of deformations on fluid circulations

International Nuclear Information System (INIS)

Gentier, S.

2005-01-01

The modeling of fluid flows inside granite massifs is an important task for the evaluation of the feasibility of radioactive waste storage inside such formations. This document makes a synthesis of the works carried out since about 15 years, in particular by the French bureau of geological and mining research (BRGM), about the hydro-mechanical behaviour of a fracture and about the hydrodynamical characterization of fracture networks inside crystalline rocks: 1 - introduction; 2 - hydro-mechanical behaviour under normal stress: experimental results (hydro-mechanical behaviour, flow regimes, mechanical behaviour, test protocol, complementary tests, influence of samples size), geometrical interpretation of experimental results (relation with walls geometry, relation with voids geometry, relation with contacts geometry), hydro-mechanical modeling (hydraulic modeling, mechanical modeling); 3 - from the hydro-mechanical behaviour under normal stress to the coupling with heat transfers and chemistry: experiment for the study of the chemo-thermo-hydro-mechanical coupling (experimental results, relation with walls morphology), thermo-hydro-mechanical experiments, thermo-hydro-chemical experiments with fractures, conclusions; 4 - hydro-mechanical behaviour during shear: experimental results, geometrical interpretation (relation with the geometry of damaged zones, relation with voids geometry, relation with walls geometry), hydro-mechanical modeling (mechanical modeling, hydro-mechanical modeling of the behaviour during shear). (J.S.)

Fractures inside crystalline rocks. Effects of deformations on fluid circulations; Fractures dans les roches cristallines. Effets des deformations sur les circulations de fluides

Energy Technology Data Exchange (ETDEWEB)

Gentier, S

2005-07-01

The modeling of fluid flows inside granite massifs is an important task for the evaluation of the feasibility of radioactive waste storage inside such formations. This document makes a synthesis of the works carried out since about 15 years, in particular by the French bureau of geological and mining research (BRGM), about the hydro-mechanical behaviour of a fracture and about the hydrodynamical characterization of fracture networks inside crystalline rocks: 1 - introduction; 2 - hydro-mechanical behaviour under normal stress: experimental results (hydro-mechanical behaviour, flow regimes, mechanical behaviour, test protocol, complementary tests, influence of samples size), geometrical interpretation of experimental results (relation with walls geometry, relation with voids geometry, relation with contacts geometry), hydro-mechanical modeling (hydraulic modeling, mechanical modeling); 3 - from the hydro-mechanical behaviour under normal stress to the coupling with heat transfers and chemistry: experiment for the study of the chemo-thermo-hydro-mechanical coupling (experimental results, relation with walls morphology), thermo-hydro-mechanical experiments, thermo-hydro-chemical experiments with fractures, conclusions; 4 - hydro-mechanical behaviour during shear: experimental results, geometrical interpretation (relation with the geometry of damaged zones, relation with voids geometry, relation with walls geometry), hydro-mechanical modeling (mechanical modeling, hydro-mechanical modeling of the behaviour during shear). (J.S.)

Aespoe Pillar Stability Experiment. Final 2D coupled thermo-mechanical modelling

Energy Technology Data Exchange (ETDEWEB)

Fredriksson, Anders; Staub, Isabelle; Outters, Nils [Golder Associates AB, Uppsala (Sweden)

2004-02-01

A site scale Pillar Stability Experiment is planned in the Aespoe Hard Rock Laboratory. One of the experiment's aims is to demonstrate the possibilities of predicting spalling in the fractured rock mass. In order to investigate the probability and conditions for spalling in the pillar 'prior to experiment' numerical simulations have been undertaken. This report presents the results obtained from 2D coupled thermo-mechanical numerical simulations that have been done with the Finite Element based programme JobFem. The 2D numerical simulations were conducted at two different depth levels, 0.5 and 1.5 m below tunnel floor. The in situ stresses have been confirmed with convergence measurements during the excavation of the tunnel. After updating the mechanical and thermal properties of the rock mass the final simulations have been undertaken. According to the modelling results the temperature in the pillar will increase from the initial 15.2 deg up to 58 deg after 120 days of heating. Based on these numerical simulations and on the thermal induced stresses the total stresses are expected to exceed 210 MPa at the border of the pillar for the level at 0.5 m below tunnel floor and might reach 180-182 MPa for the level at 1.5 m below tunnel floor. The stresses are slightly higher at the border of the confined hole. Upon these results and according to the rock mechanical properties the Crack Initiation Stress is exceeded at the border of the pillar already after the excavation phase. These results also illustrate that the Crack Damage Stress is exceeded only for the level at 0.5 m below tunnel floor and after at least 80 days of heating. The interpretation of the results shows that the required level of stress for spalling can be reached in the pillar.

A geometrical multi-scale numerical method for coupled hygro-thermo-mechanical problems in photovoltaic laminates.

Science.gov (United States)

Lenarda, P; Paggi, M

A comprehensive computational framework based on the finite element method for the simulation of coupled hygro-thermo-mechanical problems in photovoltaic laminates is herein proposed. While the thermo-mechanical problem takes place in the three-dimensional space of the laminate, moisture diffusion occurs in a two-dimensional domain represented by the polymeric layers and by the vertical channel cracks in the solar cells. Therefore, a geometrical multi-scale solution strategy is pursued by solving the partial differential equations governing heat transfer and thermo-elasticity in the three-dimensional space, and the partial differential equation for moisture diffusion in the two dimensional domains. By exploiting a staggered scheme, the thermo-mechanical problem is solved first via a fully implicit solution scheme in space and time, with a specific treatment of the polymeric layers as zero-thickness interfaces whose constitutive response is governed by a novel thermo-visco-elastic cohesive zone model based on fractional calculus. Temperature and relative displacements along the domains where moisture diffusion takes place are then projected to the finite element model of diffusion, coupled with the thermo-mechanical problem by the temperature and crack opening dependent diffusion coefficient. The application of the proposed method to photovoltaic modules pinpoints two important physical aspects: (i) moisture diffusion in humidity freeze tests with a temperature dependent diffusivity is a much slower process than in the case of a constant diffusion coefficient; (ii) channel cracks through Silicon solar cells significantly enhance moisture diffusion and electric degradation, as confirmed by experimental tests.

Theoretical and numerical study of thermo-hydro-mechanical damage in unsaturated porous media

International Nuclear Information System (INIS)

Arson, Ch.

2009-09-01

Nuclear waste disposals are designed in multi-phase porous media. A new damage model, formulated in independent state variables (net stress, suction and thermal stress), is proposed for such geo-materials. The damage variable is a second-order tensor, which principal values grow with tensile strains. The stress/strain relations are derived from a postulated expression of the free energy. The degraded rigidities are computed by applying the Principle of Equivalent Elastic Energy for each stress state variable. Cracking effects are taken into account in transfers by introducing internal length parameters in the expressions of moisture conductivities. The damage model has been implemented in Θ-Stock Finite Element code. The mechanical model has been validated by comparing numerical results to experimental data and theoretical predictions. The qualitative evolutions given by the model in the parametric studies performed on realistic complex configurations show good trends. (author)

Damage evolution of TBC system under in-phase thermo-mechanical tests

Energy Technology Data Exchange (ETDEWEB)

Kitazawa, R.; Tanaka, M.; Kagawa, Y. [Research Center for Advanced Science and Technology, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904 (Japan); Liu, Y.F., E-mail: yfliu@hyper.rcast.u-tokyo.ac.jp [Research Center for Advanced Science and Technology, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904 (Japan)

2010-10-15

In-phase thermo-mechanical tests (TMF) of EB-PVD Y{sub 2}O{sub 3}-ZrO{sub 2} thermal barrier coating (TBC) system (8 wt% Y{sub 2}O{sub 3}-ZrO{sub 2}/CoNiCrAlY/IN-738 substrate) were done under a through-the-thick-direction thermal gradient from TBC surface temperature at 1150 deg. C to substrate temperature at 1000 deg. C. Deformation and failure behaviors of the TBC system were observed at the macroscopic and microscopic scales and damage evolution of the system under in-phase thermo-mechanical test was discussed. Special attention was paid to TBC layer cracking, thermally grown oxide (TGO) layer formation and void formation in bond coat and substrate. Effect of TMF conditions on the damage evolution behaviors was also discussed.

OpenGeoSys: An open-source initiative for numerical simulation of thermo-hydro-mechanical/chemical (THM/C) processes in porous media

DEFF Research Database (Denmark)

Kolditz, O.; Bauer, S.; Bilke, L.

In this paper we describe the OpenGeoSys (OGS) project, which is a scientific open-source initiative for numerical simulation of thermo-hydro-mechanical/chemical processes in porous media. The basic concept is to provide a flexible numerical framework (using primarily the Finite Element Method (FEM...

Gross greenhouse gas fluxes from hydro-power reservoir compared to thermo-power plants

International Nuclear Information System (INIS)

Santos, Marco Aurelio dos; Pinguelli Rosa, Luiz; Sikar, Bohdan; Sikar, Elizabeth; Santos, Ednaldo Oliveira dos

2006-01-01

This paper presents the findings of gross carbon dioxide and methane emissions measurements in several Brazilian hydro-reservoirs, compared to thermo power generation. The term 'gross emissions' means gas flux measurements from the reservoir surface without natural pre-impoundment emissions by natural bodies such as the river channel, seasonal flooding and terrestrial ecosystems. The net emissions result from deducting pre-existing emissions by the reservoir. A power dam emits biogenic gases such as CO 2 and CH 4 . However, studies comparing gas emissions (gross emissions) from the reservoir surface with emissions by thermo-power generation technologies show that the hydro-based option presents better results in most cases analyzed. In this study, measurements were carried in the Miranda, Barra Bonita, Segredo, Tres Marias, Xingo, and Samuel and Tucurui reservoirs, located in two different climatological regimes. Additional data were used here from measurements taken at the Itaipu and Serra da Mesa reservoirs. Comparisons were also made between emissions from hydro-power plants and their thermo-based equivalents. Bearing in mind that the estimated values for hydro-power plants include emissions that are not totally anthropogenic, the hydro-power plants studied generally posted lower emissions than their equivalent thermo-based counterparts. Hydro-power complexes with greater power densities (capacity/area flooded-W/m 2 ), such as Itaipu, Xingo, Segredo and Miranda, have the best performance, well above thermo-power plants using state-of-the-art technology: combined cycle fueled by natural gas, with 50% efficiency. On the other hand, some hydro-power complexes with low-power density perform only slightly better or even worse than their thermo-power counterparts

Numerical analysis of thermo-hydro-mechanical (THM) processes in the clay based material

Energy Technology Data Exchange (ETDEWEB)

Wang, Xuerui

2016-10-06

Clay formations are investigated worldwide as potential host rock for the deep geological disposal of high-level radioactive waste (HLW). Usually bentonite is preferred as the buffer and backfill material in the disposal system. In the disposal of HLW, heat emission is one of the most important issues as it can generate a series of complex thermo-hydro-mechanical (THM) processes in the surrounding materials and thus change the material properties. In the context of safety assessment, it is important to understand the thermally induced THM interactions and the associated change in material properties. In this work, the thermally induced coupled THM behaviours in the clay host rock and in the bentonite buffer as well as the corresponding coupling effects among the relevant material properties are numerically analysed. A coupled non-isothermal Richards flow mechanical model and a non-isothermal multiphase flow model were developed based on the scientific computer codes OpenGeoSys (OGS). Heat transfer in the porous media is governed by thermal conduction and advective flow of the pore fluids. Within the hydraulic processes, evaporation, vapour diffusion, and the unsaturated flow field are considered. Darcy's law is used to describe the advective flux of gas and liquid phases. The relative permeability of each phase is considered. The elastic deformation process is modelled by the generalized Hooke's law complemented with additional strain caused by swelling/shrinkage behaviour and by temperature change. In this study, special attention has been paid to the analysis of the thermally induced changes in material properties. The strong mechanical and hydraulic anisotropic properties of clay rock are described by a transversely isotropic mechanical model and by a transversely isotropic permeability tensor, respectively. The thermal anisotropy is described by adoption of the bedding-orientation-dependent thermal conductivity. The dependency of the thermal

Numerical analysis of thermo-hydro-mechanical (THM) processes in the clay based material

International Nuclear Information System (INIS)

Wang, Xuerui

2016-01-01

Clay formations are investigated worldwide as potential host rock for the deep geological disposal of high-level radioactive waste (HLW). Usually bentonite is preferred as the buffer and backfill material in the disposal system. In the disposal of HLW, heat emission is one of the most important issues as it can generate a series of complex thermo-hydro-mechanical (THM) processes in the surrounding materials and thus change the material properties. In the context of safety assessment, it is important to understand the thermally induced THM interactions and the associated change in material properties. In this work, the thermally induced coupled THM behaviours in the clay host rock and in the bentonite buffer as well as the corresponding coupling effects among the relevant material properties are numerically analysed. A coupled non-isothermal Richards flow mechanical model and a non-isothermal multiphase flow model were developed based on the scientific computer codes OpenGeoSys (OGS). Heat transfer in the porous media is governed by thermal conduction and advective flow of the pore fluids. Within the hydraulic processes, evaporation, vapour diffusion, and the unsaturated flow field are considered. Darcy's law is used to describe the advective flux of gas and liquid phases. The relative permeability of each phase is considered. The elastic deformation process is modelled by the generalized Hooke's law complemented with additional strain caused by swelling/shrinkage behaviour and by temperature change. In this study, special attention has been paid to the analysis of the thermally induced changes in material properties. The strong mechanical and hydraulic anisotropic properties of clay rock are described by a transversely isotropic mechanical model and by a transversely isotropic permeability tensor, respectively. The thermal anisotropy is described by adoption of the bedding-orientation-dependent thermal conductivity. The dependency of the thermal

Basic rock properties for the thermo-hydro-mechanical analysis of a high-level radioactive waste repository

Energy Technology Data Exchange (ETDEWEB)

Kim, Jhin Wung; Kang, Chul Hyung

1999-04-01

Deep geological radioactive waste disposal is generally based on the isolation of the waste from the biosphere by multiple barriers. The host rock is one of these barriers which should provide a stable mechanical and chemical environment for the engineered barriers. In the evaluation of the safety of the high-level radioactive waste disposal systems, an important part of the safety analysis is an assessment of the coupling or interaction between thermal, hydrological, and mechanical effects. In order to do this assessment, adequate data on the characteristics of different host rocks are necessary. The properties of the rock and rock discontinuity are very complex and their values vary in a wide range. The accuracy of the result of the assessment depends on the values of these properties used. The present study is an attempt to bring together and condense data for the basic properties of various rock masses, which are needed in the thermo-hydro-mechanical analysis for the deep geological radioactive waste repository. The testing and measurement methods for these basic properties are also presented. Domestic data for deep geological media should be supplemented in the future, due to the insufficiency and the lack of accuracy of the data available at present. (author). 28 refs., 21 figs.

Basic rock properties for the thermo-hydro-mechanical analysis of a high-level radioactive waste repository

International Nuclear Information System (INIS)

Kim, Jhin Wung; Kang, Chul Hyung

1999-04-01

Deep geological radioactive waste disposal is generally based on the isolation of the waste from the biosphere by multiple barriers. The host rock is one of these barriers which should provide a stable mechanical and chemical environment for the engineered barriers. In the evaluation of the safety of the high-level radioactive waste disposal systems, an important part of the safety analysis is an assessment of the coupling or interaction between thermal, hydrological, and mechanical effects. In order to do this assessment, adequate data on the characteristics of different host rocks are necessary. The properties of the rock and rock discontinuity are very complex and their values vary in a wide range. The accuracy of the result of the assessment depends on the values of these properties used. The present study is an attempt to bring together and condense data for the basic properties of various rock masses, which are needed in the thermo-hydro-mechanical analysis for the deep geological radioactive waste repository. The testing and measurement methods for these basic properties are also presented. Domestic data for deep geological media should be supplemented in the future, due to the insufficiency and the lack of accuracy of the data available at present. (author). 28 refs., 21 figs

Thermo-mechanical simulations of early-age concrete cracking with durability predictions

Science.gov (United States)

Havlásek, Petr; Šmilauer, Vít; Hájková, Karolina; Baquerizo, Luis

2017-09-01

Concrete performance is strongly affected by mix design, thermal boundary conditions, its evolving mechanical properties, and internal/external restraints with consequences to possible cracking with impaired durability. Thermo-mechanical simulations are able to capture those relevant phenomena and boundary conditions for predicting temperature, strains, stresses or cracking in reinforced concrete structures. In this paper, we propose a weakly coupled thermo-mechanical model for early age concrete with an affinity-based hydration model for thermal part, taking into account concrete mix design, cement type and thermal boundary conditions. The mechanical part uses B3/B4 model for concrete creep and shrinkage with isotropic damage model for cracking, able to predict a crack width. All models have been implemented in an open-source OOFEM software package. Validations of thermo-mechanical simulations will be presented on several massive concrete structures, showing excellent temperature predictions. Likewise, strain validation demonstrates good predictions on a restrained reinforced concrete wall and concrete beam. Durability predictions stem from induction time of reinforcement corrosion, caused by carbonation and/or chloride ingress influenced by crack width. Reinforcement corrosion in concrete struts of a bridge will serve for validation.

Sensitivity analysis of a coupled hydro-mechanical paleo-climate model of density-dependent groundwater flow in discretely fractured crystalline rock

International Nuclear Information System (INIS)

Normani, S.D.; Sykes, J.F.

2011-01-01

A high resolution three-dimensional sub-regional scale (104 km 2 ) density-dependent, discretely fractured groundwater flow model with hydro-mechanical coupling and pseudo-permafrost was developed from a larger 5734 km 2 regional-scale groundwater flow model of a Canadian Shield setting. The objective of the work is to determine the sensitivity of modelled groundwater system evolution to the hydro-mechanical parameters. The discrete fracture dual continuum numerical model FRAC3DVS-OPG was used for all simulations. A discrete fracture network model delineated from surface features was superimposed onto an approximate 790 000 element domain mesh with approximately 850 000 nodes. Orthogonal fracture faces (between adjacent finite element grid blocks) were used to best represent the irregular discrete fracture zone network. Interconnectivity of the permeable fracture zones is an important pathway for the possible migration and subsequent reduction in groundwater and contaminant residence times. The crystalline rock matrix between these structural discontinuities was assigned mechanical and flow properties characteristic of those reported for the Canadian Shield. The variation of total dissolved solids with depth was assigned using literature data for the Canadian Shield. Performance measures for the sensitivity analysis include equivalent freshwater heads, environmental heads, linear velocities, and depth of penetration by conservative non-decaying tracers released at the surface. A 121 000 year North American continental scale paleo-climate simulation was applied to the domain with ice-sheet histories estimated by the University of Toronto Glacial Systems Model (UofT GSM). Hydro-mechanical coupling between the rock matrix and the pore fluid, due to the ice sheet normal stress, was included in the simulations. The flow model included the influence of vertical strain and assumed that areal loads were homogeneous. Permafrost depth was applied as a permeability reduction

DECOVALEX III PROJECT. Thermal-Hydro-Mechanical Coupled Processes in Safety Assessments. Report of Task 4

International Nuclear Information System (INIS)

Andersson, Johan

2005-02-01

A part (Task 4) of the International DECOVALEX III project on coupled thermo-hydro-mechanical (T-H-M) processes focuses on T-H-M modelling applications in safety and performance assessment of deep geological nuclear waste repositories. A previous phase, DECOVALEX II, saw a need to improve such modelling. In order to address this need Task 4 of DECOVALEX III has: Analysed two major T-H-M experiments (Task 1 and Task 2) and three different Bench Mark Tests (Task 3) set-up to explore the significance of T-H-M in some potentially important safety assessment applications. Compiled and evaluated the use of T-H-M modelling in safety assessments at the time of the year 2000. Organised a forum a forum of interchange between PA-analysts and THM modelers at each DECOVALEX III workshop. Based on this information the current report discusses the findings and strives for reaching recommendations as regards good practices in addressing coupled T-H-M issues in safety assessments. The full development of T-H-M modelling is still at an early stage and it is not evident whether current codes provide the information that is required. However, although the geosphere is a system of fully coupled processes, this does not directly imply that all existing coupled mechanisms must be represented numerically. Modelling is conducted for specific purposes and the required confidence level should be considered. It is necessary to match the confidence level with the modelling objective. Coupled THM modelling has to incorporate uncertainties. These uncertainties mainly concern uncertainties in the conceptual model and uncertainty in data. Assessing data uncertainty is important when judging the need to model coupled processes. Often data uncertainty is more significant than the coupled effects. The emphasis on the need for THM modelling differs among disciplines. For geological radioactive waste disposal in crystalline and other similar hard rock formations DECOVALEX III shows it is essential to

DECOVALEX III PROJECT. Thermal-Hydro-Mechanical Coupled Processes in Safety Assessments. Report of Task 4

Energy Technology Data Exchange (ETDEWEB)

Andersson, Johan [JA Streamflow AB, Aelvsjoe (Sweden)

2005-02-15

A part (Task 4) of the International DECOVALEX III project on coupled thermo-hydro-mechanical (T-H-M) processes focuses on T-H-M modelling applications in safety and performance assessment of deep geological nuclear waste repositories. A previous phase, DECOVALEX II, saw a need to improve such modelling. In order to address this need Task 4 of DECOVALEX III has: Analysed two major T-H-M experiments (Task 1 and Task 2) and three different Bench Mark Tests (Task 3) set-up to explore the significance of T-H-M in some potentially important safety assessment applications. Compiled and evaluated the use of T-H-M modelling in safety assessments at the time of the year 2000. Organised a forum a forum of interchange between PA-analysts and THM modelers at each DECOVALEX III workshop. Based on this information the current report discusses the findings and strives for reaching recommendations as regards good practices in addressing coupled T-H-M issues in safety assessments. The full development of T-H-M modelling is still at an early stage and it is not evident whether current codes provide the information that is required. However, although the geosphere is a system of fully coupled processes, this does not directly imply that all existing coupled mechanisms must be represented numerically. Modelling is conducted for specific purposes and the required confidence level should be considered. It is necessary to match the confidence level with the modelling objective. Coupled THM modelling has to incorporate uncertainties. These uncertainties mainly concern uncertainties in the conceptual model and uncertainty in data. Assessing data uncertainty is important when judging the need to model coupled processes. Often data uncertainty is more significant than the coupled effects. The emphasis on the need for THM modelling differs among disciplines. For geological radioactive waste disposal in crystalline and other similar hard rock formations DECOVALEX III shows it is essential to

Study of the water retention and the consolidation of partially saturated soils in a thermo-hydro-mechanical framework

International Nuclear Information System (INIS)

Salager, Simon

2007-01-01

This work is concerned with the study of water retention and consolidation of unsaturated soils in a thermo-hydro-mechanical framework. It is organized into two parts which deal respectively with deformation and temperature effects on hydric behaviour, and suction and temperature effects on mechanical behaviour. In the first part, we point out the relevance of the characteristic surface concept for soils as opposed to the retention curve, which has limited modelling power in the case of deformable media. The characteristic surface concept is experimentally illustrated for the example of a clayey silty sand. Its modelling is based on a large sample of experimental investigations with about 240 measurements of the triplet void ratio, water content, suction. In addition, a thermo-hydric behaviour model is proposed in order to determine the characteristic surface and the retention curve for a given temperature. This model is validated for the case of two materials: a ceramic and a clayey silty sand through direct testing, and for other materials on the basis of an analysis of the literature. Finally, we present an application to the determination of the permeability of unsaturated soils taking into account deformation and temperature. In the second part, temperature and suction effects on the mechanical behaviour are studied through consolidation tests on 'Sion' silt. These tests are performed for different temperatures and suctions. For each test, swelling and compression indexes, as well as the pre-consolidation pressure are measured. The influence of temperature and suction on these essential parameters of mechanical behaviour is determined. Finally, we propose a theoretical model which account for pre-consolidation pressure as a function of temperature and suction. (author)

The hydro-mechanical modeling of the fractured media; Modelisation hydromecanique des milieux fractures

Energy Technology Data Exchange (ETDEWEB)

Kadiri, I

2002-10-15

analyzed with the aim to catch the nature of hydro-mechanical coupling. The modeling of Coaraze allowed to reproduce in situ measurements and to give an opinion on the problems of the hydro-mechanical coupling in the fractured mediums. (author)

Computational thermo-hydro-mechanics for freezing and thawing multiphase geological media in the finite deformation range

Science.gov (United States)

Sun, W.; Na, S.

2017-12-01

A stabilized thermo-hydro-mechanical (THM) finite element model is introduced to investigate the freeze-thaw action of frozen porous media in the finite deformation range. By applying the mixture theory, frozen soil is idealized as a composite consisting of three phases, i.e., solid grain, unfrozen water and ice crystal. A generalized hardening rule at finite strain is adopted to replicate how the elasto-plastic responses and critical state evolve under the influence of phase transitions and heat transfer. The enhanced particle interlocking and ice strengthening during the freezing processes and the thawing-induced consolidation at the geometrical nonlinear regimes are both replicated in numerical examples. The numerical issues due to lack of two-fold inf-sup condition and ill-conditioning of the system of equations are addressed. Numerical examples for engineering applications at cold region are analyzed via the proposed model to predict the impacts of changing climate on infrastructure at cold regions.

Numerical Analysis of a Class of THM Coupled Model for Porous Materials

Science.gov (United States)

Liu, Tangwei; Zhou, Jingying; Lu, Hongzhi

2018-01-01

We consider the coupled models of the Thermo-hydro-mechanical (THM) problem for porous materials which arises in many engineering applications. Firstly, mathematical models of the THM coupled problem for porous materials were discussed. Secondly, for different cases, some numerical difference schemes of coupled model were constructed, respectively. Finally, aassuming that the original water vapour effect is neglectable and that the volume fraction of liquid phase and the solid phase are constants, the nonlinear equations can be reduced to linear equations. The discrete equations corresponding to the linear equations were solved by the Arnodli method.

Thermo-mechanical modelling of salt caverns due to fluctuating loading conditions.

Science.gov (United States)

Böttcher, N.

2015-12-01

This work summarizes the development and application of a numerical model for the thermo-mechanical behaviour of salt caverns during cyclic gas storage. Artificial salt caverns are used for short term energy storage, such as power-to-gas or compressed air energy storage. Those applications are characterized by highly fluctuating operation pressures due to the unsteady power levels of power plants based on renewable energy. Compression and expansion of the storage gases during loading and unloading stages lead to rapidly changing temperatures in the host rock of the caverns. This affects the material behaviour of the host rock within a zone that extends several meters into the rock mass adjacent to the cavern wall, and induces thermo-mechanical stresses and alters the creep response.The proposed model features the thermodynamic behaviour of the storage medium, conductive heat transport in the host rock, as well as temperature dependent material properties of rock salt using different thermo-viscoplastic material models. The utilized constitutive models are well known and state-of-the-art in various salt mechanics applications. The model has been implemented into the open-source software platform OpenGeoSys. Thermal and mechanical processes are solved using a finite element approach, coupled via a staggered coupling scheme. The simulation results allow the conclusion, that the cavern convergence rate (and thus the efficiency of the cavern) is highly influenced by the loading cycle frequency and the resulting gas temperatures. The model therefore allows to analyse the influence of operation modes on the cavern host rock or on neighbouring facilities.

Numerical modelling of ductile damage mechanics coupled with an unconventional plasticity model

Directory of Open Access Journals (Sweden)

R. Fincato

2016-10-01

Full Text Available Ductility in metals includes the material’s capability to tolerate plastic deformations before partial or total degradation of its mechanical properties. Modelling this parameter is important in structure and component design because it can be used to estimate material failure under a generic multi-axial stress state. Previous work has attempted to provide accurate descriptions of the mechanical property degradation resulting from the formation, growth, and coalescence of microvoids in the medium. Experimentally, ductile damage is inherently linked with the accumulation of plastic strain; therefore, coupling damage and elastoplasticity is necessary for describing this phenomenon accurately. In this paper, we combine the approach proposed by Lemaitre with the features of an unconventional plasticity model, the extended subloading surface model, to predict material fatigue even for loading conditions below the yield stress

Rôles de la température et de la composition sur le couplage thermo-hydro-mécanique des bétons

OpenAIRE

Brue , Flore

2009-01-01

The French project of the storage of nuclear wastes, which is managed by the Andra, needs some experimental data on the durability of the concrete. Loadings which are taken into account are the desaturation/resaturation processes, the heat load and the mechanical evolution. Hence this study focuses on the coupling thermo-hydro-mechanical on concretes of the research program of Andra, made with CEM I and CEM V/A cement type. The water saturation degree and shrinkages of materials, which are su...

A Dual-Continuum Model for Brine Migration in Salt Associated with Heat-Generating Nuclear Waste: Fully Coupled Thermal-Hydro-Mechanical Analysis

Science.gov (United States)

Hu, M.; Rutqvist, J.

2017-12-01

The disposal of heat-generating nuclear waste in salt host rock establishes a thermal gradient around the waste package that may cause brine inclusions in the salt grains to migrate toward the waste package. In this study, a dual-continuum model is developed to analyze such a phenomenon. This model is based on the Finite Volume Method (FVM), and it is fully thermal-hydro-mechanical (THM) coupled. For fluid flow, the dual-continuum model considers flow in the interconnected pore space and also in the salt grains. The mass balance of salt and water in these two continua is separately established, and their coupling is represented by flux associated with brine migration. Together with energy balance, such a system produces a coupled TH model with strongly nonlinear features. For mechanical analysis, a new formulation is developed based on the Voronoi tessellated mesh. By relating each cell to several connected triangles, first-order approximation is constructed. The coupling between thermal and mechanical fields is only considered in terms of thermal expansion. And the coupling between the hydraulic and mechanical fields in terms of pore-volume effects is consistent with Biot's theory. Therefore, a fully coupled THM model is developed. Several demonstration examples are provided to verify the model. Last the new model is applied to analyze coupled THM behavior and the results are compared with experimental data.

Finite element implementation of a thermo-damage-viscoelastic constitutive model for hydroxyl-terminated polybutadiene composite propellant

Science.gov (United States)

Xu, Jinsheng; Han, Long; Zheng, Jian; Chen, Xiong; Zhou, Changsheng

2017-11-01

A thermo-damage-viscoelastic model for hydroxyl-terminated polybutadiene (HTPB) composite propellant with consideration for the effect of temperature was implemented in ABAQUS. The damage evolution law of the model has the same form as the crack growth equation for viscoelastic materials, and only a single damage variable S is considered. The HTPB propellant was considered as an isotropic material, and the deviatoric and volumetric strain-stress relations are decoupled and described by the bulk and shear relaxation moduli, respectively. The stress update equations were expressed by the principal stresses σ_{ii}R and the rotation tensor M, the Jacobian matrix in the global coordinate system J_{ijkl} was obtained according to the fourth-order tensor transformation rules. Two models having complex stress states were used to verify the accuracy of the constitutive model. The test results showed good agreement with the strain responses of characteristic points measured by a contactless optical deformation test system, which illustrates that the thermo-damage-viscoelastic model perform well at describing the mechanical properties of an HTPB propellant.

Near-field NanoThermoMechanical memory

International Nuclear Information System (INIS)

Elzouka, Mahmoud; Ndao, Sidy

2014-01-01

In this letter, we introduce the concept of NanoThermoMechanical Memory. Unlike electronic memory, a NanoThermoMechanical memory device uses heat instead of electricity to record, store, and recover data. Memory function is achieved through the coupling of near-field thermal radiation and thermal expansion resulting in negative differential thermal resistance and thermal latching. Here, we demonstrate theoretically via numerical modeling the concept of near-field thermal radiation enabled negative differential thermal resistance that achieves bistable states. Design and implementation of a practical silicon based NanoThermoMechanical memory device are proposed along with a study of its dynamic response under write/read cycles. With more than 50% of the world's energy losses being in the form of heat along with the ever increasing need to develop computer technologies which can operate in harsh environments (e.g., very high temperatures), NanoThermoMechanical memory and logic devices may hold the answer

From fracture mechanics to damage mechanics: how to model structural deterioration

International Nuclear Information System (INIS)

Nicolet, S.; Lorentz, E.; Barbier, G.

1998-01-01

Modelling of structural deteriorations of thermo-mechanical origin is highly enhanced when using damage mechanics. Indeed, the latter offers both a fine description of the material behaviour and an ability to deal with any loading conditions, moving away the current limits of fracture mechanics. But new difficulties can arise, depending on the examined problem: if forecasts of rack initiation are well mastered, the study of crack propagation remains more complex and needs sophisticated modelizations, which are nevertheless on the point of being well understood too. (authors)

Well-Posedness of a fully coupled thermo-chemo-poroelastic system with applications to petroleum rock mechanics

Directory of Open Access Journals (Sweden)

Tetyana Malysheva

2017-05-01

Full Text Available We consider a system of fully coupled parabolic and elliptic equations constituting the general model of chemical thermo-poroelasticity for a fluid-saturated porous media. The main result of this paper is the developed well-posedness theory for the corresponding initial-boundary problem arising from petroleum rock mechanics applications. Using the proposed pseudo-decoupling method, we establish, subject to some natural assumptions imposed on matrices of diffusion coefficients, the existence, uniqueness, and continuous dependence on initial and boundary data of a weak solution to the problem. Numerical experiments confirm the applicability of the obtained well-posedness results for thermo-chemo-poroelastic models with real-data parameters.

Effect of the heating rate on residual thermo-hydro-mechanical properties of a high-strength concrete in the context of nuclear waste storage

International Nuclear Information System (INIS)

Galle, C.; Pin, M.; Ranc, G.; Rodrigues, S.

2003-01-01

Concrete is likely to be used in massive structures for nuclear waste long-term storage facilities in France. In the framework of vitrified waste and spent fuel management, these structures could be submitted to high temperatures. In standard conditions, ambient temperature should not exceed 60 degC but in case of failure of a cooling system, concretes could be temporarily exposed to temperatures up to 250 degC. Depending on the temperature rise kinetics, concretes could be damaged to a greater or lesser extent. In this context, an experimental study on the effect of heating rate on concrete thermo-hydro-mechanical properties exposed to high temperatures (110 - 250 degC) was carried out at the French Atomic Energy Commission (CEA). Data analysis and interpretation provided enough arguments to conclude that, at local scale, the impact of heating rate on residual properties was real though relatively limited. (author)

A coupled mechanical and chemical damage model for concrete affected by alkali–silica reaction

Energy Technology Data Exchange (ETDEWEB)

Pignatelli, Rossella, E-mail: rossellapignatelli@gmail.com [Department of Civil and Environmental Engineering, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano (Italy); Lombardi Ingegneria S.r.l., Via Giotto 36, 20145 Milano (Italy); Comi, Claudia, E-mail: comi@stru.polimi.it [Department of Civil and Environmental Engineering, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano (Italy); Monteiro, Paulo J.M., E-mail: monteiro@ce.berkeley.edu [Department of Civil and Environmental Engineering, University of California, Berkeley, CA 94720 (United States)

2013-11-15

To model the complex degradation phenomena occurring in concrete affected by alkali–silica reaction (ASR), we formulate a poro-mechanical model with two isotropic internal variables: the chemical and the mechanical damage. The chemical damage, related to the evolution of the reaction, is caused by the pressure generated by the expanding ASR gel on the solid concrete skeleton. The mechanical damage describes the strength and stiffness degradation induced by the external loads. As suggested by experimental results, degradation due to ASR is considered to be localized around reactive sites. The effect of the degree of saturation and of the temperature on the reaction development is also modeled. The chemical damage evolution is calibrated using the value of the gel pressure estimated by applying the electrical diffuse double-layer theory to experimental values of the surface charge density in ASR gel specimens reported in the literature. The chemo-damage model is first validated by simulating expansion tests on reactive specimens and beams; the coupled chemo-mechanical damage model is then employed to simulate compression and flexure tests results also taken from the literature. -- Highlights: •Concrete degradation due to ASR in variable environmental conditions is modeled. •Two isotropic internal variables – chemical and mechanical damage – are introduced. •The value of the swelling pressure is estimated by the diffuse double layer theory. •A simplified scheme is proposed to relate macro- and microscopic properties. •The chemo-mechanical damage model is validated by simulating tests in literature.

FEBEX II Project Final report on thermo-hydro-mechanical laboratory tests

International Nuclear Information System (INIS)

Lloret, A.; Romero, E.; Villar, M. V.

2004-01-01

The results of the thermo-hydro-mechanical (THM) study of the FEBEX bentonite performed during FEBEX II are presented. The laboratory test program continued in part with the works carried out during FEBEX I, particularly in activities related to tests aimed to the calibration of the models, the acquisition of parameters by back-analysis and the improvement of the knowledge on the behaviour of expansive clays. But the program has also included tests on new areas: investigations about the influence of the microstructure changes in bentonite, of temperature and of the solute concentration on the behaviour of clay. Besides, several tests were proposed in order to understand the unexpected behaviour observed in the mock-up test, towards the end of year 2. Temperature effects on water retention curves in confined and unconfined conditions were determined, and swelling pressure, hydraulic conductivity and swelling and consolidation strains as a function of temperature were successfully measured. Different experimental techniques and equipments were developed to study thermal induced changes under partially saturated states, covering a wide range of suctions. FEBEX bentonite remains suitable as a sealing material in HLW repositories (from the hydro- mechanical point of view) for temperatures of up to 80 C, as it keeps its high water retention capacity, low permeability and self-healing ability. The extrapolation of results points out to the preservation of properties for at least up to 100 C. Mercury intrusion porosimetry and environmental scanning electron microscopy provided promising results in order to characterise the bentonite microstructure and to give information about the mechanisms influencing pore size distribution changes on high active clays. The use of digital imaging techniques allowed verifying that at micro-scale level, where chemical phenomena prevail, strains are almost reversible as it is considered in the two-level elasto-plastic models. The swelling

FEBEX II Project Final report on thermo-hydro-mechanical laboratory tests

Energy Technology Data Exchange (ETDEWEB)

Lloret, A.; Romero, E.; Villar, M. V.

2004-07-01

The results of the thermo-hydro-mechanical (THM) study of the FEBEX bentonite performed during FEBEX II are presented. The laboratory test program continued in part with the works carried out during FEBEX I, particularly in activities related to tests aimed to the calibration of the models, the acquisition of parameters by back-analysis and the improvement of the knowledge on the behaviour of expansive clays. But the program has also included tests on new areas: investigations about the influence of the microstructure changes in bentonite, of temperature and of the solute concentration on the behaviour of clay. Besides, several tests were proposed in order to understand the unexpected behaviour observed in the mock-up test, towards the end of year 2. Temperature effects on water retention curves in confined and unconfined conditions were determined, and swelling pressure, hydraulic conductivity and swelling and consolidation strains as a function of temperature were successfully measured. Different experimental techniques and equipments were developed to study thermal induced changes under partially saturated states, covering a wide range of suctions. FEBEX bentonite remains suitable as a sealing material in HLW repositories (from the hydro- mechanical point of view) for temperatures of up to 80 C, as it keeps its high water retention capacity, low permeability and self-healing ability. The extrapolation of results points out to the preservation of properties for at least up to 100 C. Mercury intrusion porosimetry and environmental scanning electron microscopy provided promising results in order to characterise the bentonite microstructure and to give information about the mechanisms influencing pore size distribution changes on high active clays. The use of digital imaging techniques allowed verifying that at micro-scale level, where chemical phenomena prevail, strains are almost reversible as it is considered in the two-level elasto-plastic models. The swelling

The importance of Thermo-Hydro-Mechanical couplings and microstructure to strain localization in 3D continua with application to seismic faults. Part II: Numerical implementation and post-bifurcation analysis

Science.gov (United States)

Rattez, Hadrien; Stefanou, Ioannis; Sulem, Jean; Veveakis, Manolis; Poulet, Thomas

2018-06-01

In this paper we study the phenomenon of localization of deformation in fault gouges during seismic slip. This process is of key importance to understand frictional heating and energy budget during an earthquake. A infinite layer of fault gouge is modeled as a Cosserat continuum taking into account Thermo-Hydro-Mechanical (THM) couplings. The theoretical aspects of the problem are presented in the companion paper (Rattez et al., 2017a), together with a linear stability analysis to determine the conditions of localization and estimate the shear band thickness. In this Part II of the study, we investigate the post-bifurcation evolution of the system by integrating numerically the full system of non-linear equations using the method of Finite Elements. The problem is formulated in the framework of Cosserat theory. It enables to introduce information about the microstructure of the material in the constitutive equations and to regularize the mathematical problem in the post-localization regime. We emphasize the influence of the size of the microstructure and of the softening law on the material response and the strain localization process. The weakening effect of pore fluid thermal pressurization induced by shear heating is examined and quantified. It enhances the weakening process and contributes to the narrowing of shear band thickness. Moreover, due to THM couplings an apparent rate-dependency is observed, even for rate-independent material behavior. Finally, comparisons show that when the perturbed field of shear deformation dominates, the estimation of the shear band thickness obtained from linear stability analysis differs from the one obtained from the finite element computations, demonstrating the importance of post-localization numerical simulations.

Bonding Strength Effects in Hydro-Mechanical Coupling Transport in Granular Porous Media by Pore-Scale Modeling

Directory of Open Access Journals (Sweden)

Zhiqiang Chen

2016-03-01

Full Text Available The hydro-mechanical coupling transport process of sand production is numerically investigated with special attention paid to the bonding effect between sand grains. By coupling the lattice Boltzmann method (LBM and the discrete element method (DEM, we are able to capture particles movements and fluid flows simultaneously. In order to account for the bonding effects on sand production, a contact bond model is introduced into the LBM-DEM framework. Our simulations first examine the experimental observation of “initial sand production is evoked by localized failure” and then show that the bonding or cement plays an important role in sand production. Lower bonding strength will lead to more sand production than higher bonding strength. It is also found that the influence of flow rate on sand production depends on the bonding strength in cemented granular media, and for low bonding strength sample, the higher the flow rate is, the more severe the erosion found in localized failure zone becomes.

A Thermo-Hydro-Mechanical coupled Numerical modeling of Injection-induced seismicity on a pre-existing fault

Science.gov (United States)

Kim, Jongchan; Archer, Rosalind

2017-04-01

In terms of energy development (oil, gas and geothermal field) and environmental improvement (carbon dioxide sequestration), fluid injection into subsurface has been dramatically increased. As a side effect of these operations, a number of injection-induced seismic activities have also significantly risen. It is known that the main causes of induced seismicity are changes in local shear and normal stresses and pore pressure as well. This mechanism leads to increase in the probability of earthquake occurrence on permeable pre-existing fault zones predominantly. In this 2D fully coupled THM geothermal reservoir numerical simulation of injection-induced seismicity, we investigate the thermal, hydraulic and mechanical behavior of the fracture zone, considering a variety of 1) fault permeability, 2) injection rate and 3) injection temperature to identify major contributing parameters to induced seismic activity. We also calculate spatiotemporal variation of the Coulomb stress which is a combination of shear stress, normal stress and pore pressure and lastly forecast the seismicity rate on the fault zone by computing the seismic prediction model of Dieterich (1994).

Developing confidence in a coupled TH model based on the results of experiment by using engineering scale test facility, 'COUPLE'

International Nuclear Information System (INIS)

Fujisaki, Kiyoshi; Suzuki, Hideaki; Fujita, Tomoo

2008-03-01

It is necessary to understand quantitative changes of near-field conditions and processes over time and space for modeling the near-field evolution after emplacement of engineered barriers. However, the coupled phenomena in near-field are complicated because thermo-, hydro-, mechanical, chemical processes will interact each other. The question is, therefore, whether the applied model will represent the coupled behavior adequately or not. In order to develop confidence in the modeling, it is necessary to compare with results of coupled behavior experiments in laboratory or in site. In this report, we evaluated the applicability of a coupled T-H model under the conditions of simulated near-field for the results of coupled T-H experiment in laboratory. As a result, it has been shown that the fitting by the modeling with the measured data is reasonable under this condition. (author)

Thermo-mechanical Modelling of Pebble Beds in Fusion Blankets and its Implementation by a Return-Mapping Algorithm

International Nuclear Information System (INIS)

Gan, Yixiang; Kamlah, Marc

2008-01-01

In this investigation, a thermo-mechanical model of pebble beds is adopted and developed based on experiments by Dr. Reimann at Forschungszentrum Karlsruhe (FZK). The framework of the present material model is composed of a non-linear elastic law, the Drucker-Prager-Cap theory, and a modified creep law. Furthermore, the volumetric inelastic strain dependent thermal conductivity of beryllium pebble beds is taken into account and full thermo-mechanical coupling is considered. Investigation showed that the Drucker-Prager-Cap model implemented in ABAQUS can not fulfill the requirements of both the prediction of large creep strains and the hardening behaviour caused by creep, which are of importance with respect to the application of pebble beds in fusion blankets. Therefore, UMAT (user defined material's mechanical behaviour) and UMATHT (user defined material's thermal behaviour) routines are used to re-implement the present thermo-mechanical model in ABAQUS. An elastic predictor radial return mapping algorithm is used to solve the non-associated plasticity iteratively, and a proper tangent stiffness matrix is obtained for cost-efficiency in the calculation. An explicit creep mechanism is adopted for the prediction of time-dependent behaviour in order to represent large creep strains in high temperature. Finally, the thermo-mechanical interactions are implemented in a UMATHT routine for the coupled analysis. The oedometric compression tests and creep tests of pebble beds at different temperatures are simulated with the help of the present UMAT and UMATHT routines, and the comparison between the simulation and the experiments is made. (authors)

Hydro-mechanically coupled finite-element analysis of the stability of a fractured-rock slope using the equivalent continuum approach: a case study of planned reservoir banks in Blaubeuren, Germany

Science.gov (United States)

Song, Jie; Dong, Mei; Koltuk, Serdar; Hu, Hui; Zhang, Luqing; Azzam, Rafig

2018-05-01

Construction works associated with the building of reservoirs in mountain areas can damage the stability of adjacent valley slopes. Seepage processes caused by the filling and drawdown operations of reservoirs also affect the stability of the reservoir banks over time. The presented study investigates the stability of a fractured-rock slope subjected to seepage forces in the lower basin of a planned pumped-storage hydropower (PSH) plant in Blaubeuren, Germany. The investigation uses a hydro-mechanically coupled finite-element analyses. For this purpose, an equivalent continuum model is developed by using a representative elementary volume (REV) approach. To determine the minimum required REV size, a large number of discrete fracture networks are generated using Monte Carlo simulations. These analyses give a REV size of 28 × 28 m, which is sufficient to represent the equivalent hydraulic and mechanical properties of the investigated fractured-rock mass. The hydro-mechanically coupled analyses performed using this REV size show that the reservoir operations in the examined PSH plant have negligible effect on the adjacent valley slope.

Hydro-mechanically coupled finite-element analysis of the stability of a fractured-rock slope using the equivalent continuum approach: a case study of planned reservoir banks in Blaubeuren, Germany

Science.gov (United States)

Song, Jie; Dong, Mei; Koltuk, Serdar; Hu, Hui; Zhang, Luqing; Azzam, Rafig

2017-12-01

Construction works associated with the building of reservoirs in mountain areas can damage the stability of adjacent valley slopes. Seepage processes caused by the filling and drawdown operations of reservoirs also affect the stability of the reservoir banks over time. The presented study investigates the stability of a fractured-rock slope subjected to seepage forces in the lower basin of a planned pumped-storage hydropower (PSH) plant in Blaubeuren, Germany. The investigation uses a hydro-mechanically coupled finite-element analyses. For this purpose, an equivalent continuum model is developed by using a representative elementary volume (REV) approach. To determine the minimum required REV size, a large number of discrete fracture networks are generated using Monte Carlo simulations. These analyses give a REV size of 28 × 28 m, which is sufficient to represent the equivalent hydraulic and mechanical properties of the investigated fractured-rock mass. The hydro-mechanically coupled analyses performed using this REV size show that the reservoir operations in the examined PSH plant have negligible effect on the adjacent valley slope.

Thermo-magneto-elastoplastic coupling model of metal magnetic memory testing method for ferromagnetic materials

Science.gov (United States)

Shi, Pengpeng; Zhang, Pengcheng; Jin, Ke; Chen, Zhenmao; Zheng, Xiaojing

2018-04-01

Metal magnetic memory (MMM) testing (also known as micro-magnetic testing) is a new non-destructive electromagnetic testing method that can diagnose ferromagnetic materials at an early stage by measuring the MMM signal directly on the material surface. Previous experiments have shown that many factors affect MMM signals, in particular, the temperature, the elastoplastic state, and the complex environmental magnetic field. However, the fact that there have been only a few studies of either how these factors affect the signals or the physical coupling mechanisms among them seriously limits the industrial applications of MMM testing. In this paper, a nonlinear constitutive relation for a ferromagnetic material considering the influences of temperature and elastoplastic state is established under a weak magnetic field and is used to establish a nonlinear thermo-magneto-elastoplastic coupling model of MMM testing. Comparing with experimental data verifies that the proposed theoretical model can accurately describe the thermo-magneto-elastoplastic coupling influence on MMM signals. The proposed theoretical model can predict the MMM signals in a complex environment and so is expected to provide a theoretical basis for improving the degree of quantification in MMM testing.

Thermal stress analysis and thermo-mechanical fatigue for gas turbine blade

International Nuclear Information System (INIS)

Hyun, J. S.; Kim, B. S.; Kang, M. S.; Ha, J. S.; Lee, Y. S.

2002-01-01

The numerical analysis for gas turbine blades were carried out under several conditions by compounding temperature field, velocity field, thermal conduction of blade, and cooling heat transfer. The three types of 1,100 deg. C class 1st-stage gas turbine blades were analyzed. The analysis results are applied to the study on evaluating the remaining life for thermo-mechanical fatigue life. The thermo-mechanical fatigue experiments under out-of-phase and in-phase have been performed. The physical-based life prediction models which considered the contribution of different damage mechanisms have been applied. These models were applied to the temperature and strain rate dependences of isothermal cycling fatigue lives, and the strain-temperature history effect on the thermo-mechanical fatigue lives

Hydro-mechanical modelling of an excavation in an underground research laboratory with an elasto-viscoplastic behaviour law and regularization by second gradient of dilation

International Nuclear Information System (INIS)

Plassart, Roland; Giraud, Albert; Hoxha, Dashnor; Laigle, Francois

2013-01-01

In the context of nuclear waste disposals, this paper deals with hydro-mechanical modelling in saturated conditions in deep geological formation, using a specific elasto-viscoplastic model hereafter called the L and K model. While classical Biot's framework is followed for the hydro-mechanical coupling, the mechanical L and K model offers a coupling between instantaneous and delayed behaviour and a variation of dilation of ten related to softening. These volumetric strains are especially highlighted in coupled hydro-mechanical conditions. In order to avoid mesh dependency and numerical localized solutions, this type of modelling needs the use of a regularization method which is here referred to as the second gradient dilation model. After describing the numeric tools, we use them for simulating a gallery of the underground research laboratory of Bure. The approach is validated by the good general agreement found between numeric results and in situ measures for both hydraulic pressure and displacement. (authors)

Progressive damage analysis of carbon/epoxy laminates under couple laser and mechanical loading

Directory of Open Access Journals (Sweden)

Wanlei Liu

Full Text Available A multiscale model based bridge theory is proposed for the progressive damage analysis of carbon/epoxy laminates under couple laser and mechanical loading. The ablation model is adopted to calculate ablation temperature changing and ablation surface degradation. The polynomial strengthening model of matrix is used to improve bridging model for reducing parameter input. Stiffness degradation methods of bridging model are also improved in order to analyze the stress redistribution more accurately when the damage occurs. Thermal-mechanical analyses of the composite plate are performed using the ABAQUS/Explicit program with the developed model implemented in the VUMAT. The simulation results show that this model can be used to proclaim the mesoscale damage mechanism of composite laminates under coupled loading. Keywords: Laser irradiation, Multiscale analysis, Bridge model, Thermal-mechanical

A nonlinear magneto-thermo-elastic coupled hysteretic constitutive model for magnetostrictive alloys

International Nuclear Information System (INIS)

Jin Ke; Kou Yong; Zheng Xiaojing

2012-01-01

This paper presents a general hysteretic constitutive law of nonlinear magneto-thermo-elastic coupling for magnetostrictive alloys. The model considered here is thermodynamically motivated and based on the Gibbs free energy function. A nonlinear part of the elastic strain arising from magnetic domain rotation induced by the pre-stress is taken into account. Furthermore, the movement of the domain walls is incorporated to describe hysteresis based on Jiles–Atherton's model. Then a set of closed and analytical expressions of the constitutive law for the magnetostrictive rods and films are obtained, and the parameters appearing in the model can be determined by those measurable experiments in mechanics and physics. Comparing this model with other existing models in this field, the quantitative results show that the relationships obtained here are more effective to describe the effects of the pre-stress or in-plane residual stress and ambient temperature on the magnetization or the magnetostriction hysteresis loops. - Highlights: ► A general hysteretic constitutive law of nonlinear magneto-thermo-elastic coupling for magnetostrictive materials is proposed. ► Model is thermodynamically motivated and the reversible magnetic domain rotation and irreversible domain wall motion are taken. ► The predictions are in good accordance with the experimental data including both rods and films. ► Magnetostrictive alloys are sensitive to environment temperature and pre-stress or residual stress.

A Rock Mechanics and Coupled Hydro mechanical Analysis of Geological Repository of High Level Nuclear Waste in Fractured Rocks

International Nuclear Information System (INIS)

Min, Kibok

2011-01-01

This paper introduces a few case studies on fractured hard rock based on geological data from Sweden, Korea is one of a few countries where crystalline rock is the most promising rock formation as a candidate site of geological repository of high level nuclear waste. Despite the progress made in the area of rock mechanics and coupled hydro mechanics, extensive site specific study on multiple candidate sites is essential in order to choose the optimal site. For many countries concerned about the safe isolation of nuclear wastes from the biosphere, disposal in a deep geological formation is considered an attractive option. In geological repository, thermal loading continuously disturbs the repository system in addition to disturbances a recent development in rock mechanics and coupled hydro mechanical study using DFN(Discrete Fracture Network) - DEM(Discrete Element Method) approach mainly applied in hard, crystalline rock containing numerous fracture which are main sources of deformation and groundwater flow

Study of the hydro-mechanical behaviour of expanded graphite gaskets; Etude du comportement et de l`etancheite de joints en graphite expnase

Energy Technology Data Exchange (ETDEWEB)

Patron, E. [Electricite de France (EDF), Direction des Etudes et Recherches, 92 - Clamart (France)

1997-12-31

The poro-mechanical behaviour models developed by O. Coussy permit to consider various phenomena observed experimentally: thermo-hydro-mechanical couplings, plasticity, etc. The aim of this study is to implement the simplest poro-mechanical model (i.e. the isotropic linear poro-elastic model) to model the gasket hydro-mechanical behaviour. First, isotropic poro-elastic characteristics of expanded graphite have been estimated from these tests conducted at Departement Mecanique et Technologie des Composants (MTC) and data from literature. Then, analytical solutions of the tightness tests developed at the MTC Department have been carried out. These calculations provide a first estimation of porosity variations during a tightness tests with metal/metal contact or in elastic recovery, and during a `hot thermal transient`. Thickness controlled numerical calculations have proved the analytical calculations relevance. With regard to simulation of tests with metal/metal contact or `hot thermal transient`, stress controlled numerical calculations have pointed out: - a greater vertical displacement on the inner side of the graphite ring and - a z dependence of the radial displacement and thus a porous differential variation between the upper and lower faces of the ring. (author). 21 refs.

Modelling the Thermo-Mechanical Behavior of Magnesium Alloys during Indirect Extrusion

International Nuclear Information System (INIS)

Steglich, D.; Ertuerk, S.; Bohlen, J.; Letzig, D.; Brocks, W.

2010-01-01

One of the basic metal forming process for semi-finished products is extrusion. Since extrusion involves complex thermo-mechanical and multiaxial loading conditions resulting in large strains, high strain rates and an increase in temperature due to deformation, a proper yield criterion and hardening law should be used in the numerical modelling of the process. A phenomenological model based on a plastic potential has been proposed that takes strain, strain rate and temperature dependency on flow behaviour into consideration. A hybrid methodology of experiment and finite element simulation has been adopted in order to obtain necessary model parameters. The anisotropy/asymmetry in yielding was quantified by tensile and compression tests of specimens prepared from different directions. The identification of the corresponding model parameters was performed by a genetic algorithm. A fully coupled thermo-mechanical analysis has been used in extrusion simulations for calculation of the temperature field by considering heat fluxes and heat generated due to plastic deformation. The results of the approach adopted in this study appeared to be successful showing promising predictions of the experiments and thus may be extended to be applicable to other magnesium alloys or even other hcp metals.

An Explicit Approach Toward Modeling Thermo-Coupled Deformation Behaviors of SMPs

Directory of Open Access Journals (Sweden)

Hao Li

2017-03-01

Full Text Available A new elastoplastic J 2 -flow models with thermal effects is proposed toward simulating thermo-coupled finite deformation behaviors of shape memory polymers. In this new model, an elastic potential evolving with development of plastic flow is incorporated to characterize the stress-softening effect at unloading and, moreover, thermo-induced plastic flow is introduced to represent the strain recovery effect at heating. It is shown that any given test data for both effects may be accurately simulated by means of direct and explicit procedures. Numerical examples for model predictions compare well with test data in literature.

Thermo-hydro-mechanical mode of canister retrieval test

International Nuclear Information System (INIS)

Zandarin, M.T.; Olivella, S.; Gens', A.; Alonso, E.E.

2010-01-01

Document available in extended abstract form only. The Canister Retrieval Tests (CRT) is a full scale in situ experiment performed by SKB at Aespoe Laboratory. The experiment involves placing a canister equipped with electrical heaters inside of a deposition hole bored in Aespoe diorite. The deposition hole is 8.55 metres deep and has a diameter of 1.76 metres. The space between canister and the hole is filled with a MX-80 bentonite buffer. The bentonite buffer was installed in form of blocks and rings of bentonite. At the top of the canister bentonite bricks occupy the volume between the canister top surface and the bottom surface of the plug. Due to the bentonite ring size there are two gaps; once between canister and buffer which was left empty and another one between buffer and rock that was filled with bentonite pellets. The top of the hole was sealed with a retaining plug composed of concrete and a steel plate. The plug was secured against heave caused by the swelling clay with nine cables anchored in the rock. An artificial pressurised saturation system was used because the supply of water from the rock was judged to be insufficient for saturating the buffer in a feasible time. A large number of instruments were installed to monitor the test as follows: - Canister - temperature and strain. - Rock mass - temperature and stress. - Retaining system - force and displacement. - Buffer - temperature, relative humidity, pore pressure and total pressure. After dismantling the tests the final dry density and water content of bentonite and pellets were measured. The comprehensive record of the Thermo-Hydro-Mechanical (THM) processes in the buffer give the possibility to investigate theoretical formulations and models, since the results of THM analyses can be checked against experimental data. As part of the European project THERESA, a 2-D axisymmetric model simulation of CRT bas been carried out. Some of the main objectives of this simulation are the study of the

Numerical modelling of crack initiation and propagation in concrete structure under hydro-mechanical loading

International Nuclear Information System (INIS)

Bian, H.B.; Jia, Y.; Shao, J.F.

2012-01-01

Document available in extended abstract form only. This subject is devoted to numerical analysis of crack initiation and propagation in concrete structures due to hydro-mechanical coupling processes. When the structures subjected to the variation in hydraulic conditions, fractures occur as a consequence of coalescence of diffuse damage. Consequently, the mechanical behaviour of concrete is described by an isotropic damage model. Once the damage reaches a critical value, a macroscopic crack is initiated. In the framework of extended Finite Element Method (XFEM), the propagation of localized crack is studied in this paper. Each crack is then considered as a discontinuity surface of displacement. According to the determination of crack propagation orientations, a tensile stress-based criterion is used. Furthermore, spatial variations of mechanical properties of concrete are also taken into account using the Weibull distribution function. Finally, the proposed model is applied to numerical analysis of a concrete liner in the context of feasibility studies for geological storage of radioactive wastes. The numerical results show that the proposed approach is capable to reproduce correctly the initiation and propagation crack process until the complete failure of concrete structures during hydro-mechanical loading. The concrete is most widely used construction material in many engineering applications. It is generally submitted to various environmental loading: such as the mechanical loading, the variation of relative humidity and the exposure to chemical risk, etc. In order to evaluate the safety and durability of concrete structures, it is necessary to get a good knowledge on the influence of loading path on the concrete behaviour. The objective of this paper is to study numerically the crack propagation in concrete structure under hydro-mechanical loading,.i.e. the mechanical behaviour of concrete subjected to drying process. The drying process leads to desiccation

Electro-chemo-hydro-mechanical coupling in clayey media

International Nuclear Information System (INIS)

Lemaire, Th.

2004-12-01

The aim of this study is to understand coupled phenomena that occur in swelling porous materials like clays. Electro-chemo-hydro-mechanical contributions are taken into account to analyze transfers in such minerals. In a first part, a general discussion is proposed to introduce mineralogical and physico- chemical considerations of clayey media. An important objective of this chapter is to show the crucial role of the microstructure. In a second part is presented an imbibition test in a MX80 bentonite powder. The hydraulic diffusivity versus water content curve's decrease is explained thanks to a double porosity model that shows the progressive collapse of meso-pores due to swelling effects at the micro-scale. Thus a multi-scale analysis is necessary to well describe clayey media behaviour. The third chapter exposes such a multi-scale modelling (periodic homogenization). It is based on the double-layer theory and introduces an innovative concept of virtual electrolyte solution. First numerical results are given in a simple geometry (parallel platelets). In the next part are proposed numerical simulations of two kinds: response of the system to a chemical gradient and simulation of electro-osmosis. The end of this chapter puts into relief the necessity to integrate pH effects in the model. In the last part, chemical surface exchanges are incorporated in the modelling to understand pH and ionic force roles in electro-osmotic process. (author)

Thermo-mechanical modeling of laser treatment on titanium cold-spray coatings

Science.gov (United States)

Paradiso, V.; Rubino, F.; Tucci, F.; Astarita, A.; Carlone, P.

2018-05-01

Titanium coatings are very attractive to several industrial fields, especially aeronautics, due to the enhanced corrosion resistance and wear properties as well as improved compatibility with carbon fiber reinforced plastic (CFRP) materials. Cold sprayed titanium coatings, among the others deposition processes, are finding a widespread use in high performance applications, whereas post-deposition treatments are often used to modify the microstructure of the cold-sprayed layer. Laser treatments allow one to noticeably increase the superficial properties of titanium coatings when the process parameters are properly set. On the other hand, the high heat input required to melt titanium particles may result in excessive temperature increase even in the substrate. This paper introduces a thermo-mechanical model to simulate the laser treatment effects on a cold sprayed titanium coating as well as the aluminium substrate. The proposed thermo-mechanical finite element model considers the transient temperature field due to the laser source and applied boundary conditions using them as input loads for the subsequent stress-strain analysis. Numerical outcomes highlighted the relevance of thermal gradients and thermally induced stresses and strains in promoting the damage of the coating.

Comparative modelling approaches of hydro-mechanical processes in sealing experiments at the Tournemire URL

Czech Academy of Sciences Publication Activity Database

Millard, A.; Mokni, N.; Barnichon, J. D.; Thatcher, K. E.; Bond, A.; Fraser-Harris, A.; Mc Dermott, C.; Blaheta, Radim; Michalec, Zdeněk; Hasal, Martin; Nguyen, T.; Nasir, O.; Yi, H.; Kolditz, O.

2017-01-01

Roč. 76, č. 2 (2017), č. článku 78. ISSN 1866-6280 Institutional support: RVO:68145535 Keywords : hydro-mechanical (HM) coupling * numerical modelling * sealing systems * compacted bentonite–sand mixture Subject RIV: BA - General Mathematics OBOR OECD: Applied mathematics Impact factor: 1.569, year: 2016 https://link.springer.com/article/10.1007/s12665-016-6324-8

Coupled thermo-hydro-mechanical calculations of the water saturation phase of a KBS-3 deposition hole. Influence of hydraulic rock properties on the water saturation phase

International Nuclear Information System (INIS)

Boergesson, Lennart; Hernelind, J.

1999-12-01

The wetting process in deposition holes designed according to the KBS-3-concept has been simulated with finite element calculations of the thermo-hydro-mechanical processes in the buffer, backfill and surrounding rock. The buffer material has been modelled according to the preliminary material models developed for swelling clay. The properties of the rock have been varied in order to investigate the influence of the rock properties and the hydraulic conditions on the wetting processes. In the modelling of the test holes the permeability of the rock matrix, the water supply from the backfill, the water pressure in the surrounding rock, the permeability of the disturbed zone around the deposition hole, the water retention properties of the rock, and the transmissivity of two fractures intersecting the deposition hole have been varied. The calculations indicate that the wetting takes about 5 years if the water pressure in the rock is high and if the permeability of the rock is so high that the properties of the bentonite determine the wetting rate. However, it may take considerably more than 30 years if the rock is very tight and the water pressure in the rock is low. The calculations also show that the influence of the rock structure is rather large except for the influence of the transmissivity T of the fractures, which turned out to be insignificant for the values used in the calculations

The Numerical Simulation of Coupling Behavior of Soil with Chemical Pollutant Effects

Science.gov (United States)

Liu, Z. J.; Li, X. K.; Tang, L. Q.

2010-05-01

The coupling behavior of clay plays a role in the integrity of clay barriers used in landfills. The clay barriers are subjected to mechanical and thermal effects coupled with hydraulic behavior, also, if the leachates become in contact with the clay liner, chemical effects may lead to some drastic changes in the properties of the clay. A numerical method to simulate the coupling behavior of soil with chemical pollutant effects is presented. Within the framework of Gens-Alonso model describing the constitutive behavior of unsaturated clay presented in reference[1], basing on the work of Wu[2] and Hueckel[3], a constitutive model describing the chemo-thermo-hydro-mechanical(CTHM) coupling behavior of clays in contact with a single organic contaminant is presented. The thermical softening and chemical softening is considered in the presented model. The strain arising in the material due to chemical and thermical effects can be decomposed into two parts: elastic expansion and plastic compaction. The chemical effects are described in terms of the mass concentration of the contaminant. The increases in temperature and contaminant concentration cause decreases of the pre-consolidation pressure and the cohesion. The mechanisms are called thermical softening and chemical softening. The presented coupled CTHM constitutive model has been integrated into the coupled thermo-hydro-mechanical mathematical model including contaminant transport in porous media. To solve the equilibrium equations, the grogram of finite element methods is developed with a stagger algorithm. The mechanisms taking place due to the coupling behaviour of the clay with a single contaminant solute are analysed with the presented numerical method.

Hydro-methane and methanol combined production from hydroelectricity and biomass: Thermo-economic analysis in Paraguay

International Nuclear Information System (INIS)

Rivarolo, M.; Bellotti, D.; Mendieta, A.; Massardo, A.F.

2014-01-01

Highlights: • We investigate H 2 /O 2 production from large hydraulic plant by water electrolysis. • We produce methanol and hydro-methane from H 2 /O 2 obtained. • We investigate two different configurations of the plant. • We perform a thermo-economic analysis for three scenarios in Paraguay. • We find plants optimal size using a time-dependent thermo-economic approach. - Abstract: A thermo-economic analysis regarding large scale hydro-methane and methanol production from renewable sources (biomass and renewable electricity) is performed. The study is carried out investigating hydrogen and oxygen generation by water electrolysis, mainly employing the hydraulic energy produced from the 14 GW Itaipu Binacional Plant, owned by Paraguay and Brazil. Oxygen is employed in biomass gasification to synthesize methanol; the significant amount of CO 2 separated in the process is mixed with hydrogen produced by electrolysis in chemical reactors to produce hydro-methane. Hydro-methane is employed to supply natural gas vehicles in Paraguay, methanol is sold to Brazil, that is the largest consumer in South America. The analysis is performed employing time-dependent hydraulic energy related to the water that would normally not be used by the plant, named “spilled energy”, when available; in the remaining periods, electricity is acquired at higher cost by the national grid. For the different plant lay-outs, a thermo-economic analysis has been performed employing two different software, one for the design point and one for the time-dependent one entire year optimization, since spilled energy is strongly variable throughout the year. Optimal sizes for the generation plants have been determined, investigating the influence of electricity cost, size and plant configuration

Modelling of pavement materials on steel decks using the five-point bending test: Thermo mechanical evolution and fatigue damage

International Nuclear Information System (INIS)

Arnaud, L; Houel, A

2010-01-01

This paper deals with the modelling of wearing courses on steel orthotropic decks such as the Millau viaduct in France. This is of great importance when dealing with durability: due to the softness of such a support, the pavement is subjected to considerable strains that may generate top-down cracks in the layer at right angles of the orthotropic plate stiffeners and shear cracks at the interface between pavement and steel. Therefore, a five-point bending fatigue test was developed and improved since 2003 at the ENTPE laboratory, to test different asphalt concrete mixes. This study aims at modelling the mechanical behavior of the wearing course throughout the fatigue test by a finite element method (Comsol Multiphysics software). Each material - steel, sealing sheet, asphalt concrete layer - is considered and modelled. The modelling of asphalt concrete is complex since it is a heterogeneous material, a viscoelastic medium and it thermosensitive. The actual characteristics of the asphalt concrete (thermo physical parameter and viscoelastic complex modulus) are determined experimentally on cylindrical cores. Moreover, a damage law based on Miner's damage is included in the model. The modelling of the fatigue test leads to encouraging results. Finally, results from the model are compared to the experimental data obtained from the five-point bending fatigue test device. The experimental data are very consistent with the numerical simulation.

DECOVALEX - Mathematical models of coupled T-H-M processes for nuclear waste repositories. Executive summary for Phases I,II and III

International Nuclear Information System (INIS)

Jing, L.; Stephansson, O.; Tsang, C.F.; Kautsky, F.

1996-06-01

This executive summary presents the motivation, structure, objectives, methodologies and results of the first stage of the international DECOVALEX project - DECOVALEX I (1992-1995). The acronym stands for Development of Coupled Models and their Validation against Experiment in Nuclear Waste Isolation, and the project is an international effort to develop mathematical models, numerical methods and computer codes for coupled thermo-hydro-mechanical processes in fractured rocks and buffer materials for geological isolation of spent nuclear fuel and other radioactive wastes, and validate them against laboratory and field experiments. 24 refs

Modeling the Coupled Chemo-Thermo-Mechanical Behavior of Amorphous Polymer Networks.

Energy Technology Data Exchange (ETDEWEB)

Zimmerman, Jonathan A. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Nguyen, Thao D. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Xiao, Rui [Sandia National Lab. (SNL-CA), Livermore, CA (United States)

2015-02-01

Amorphous polymers exhibit a rich landscape of time-dependent behavior including viscoelasticity, structural relaxation, and viscoplasticity. These time-dependent mechanisms can be exploited to achieve shape-memory behavior, which allows the material to store a programmed deformed shape indefinitely and to recover entirely the undeformed shape in response to specific environmental stimulus. The shape-memory performance of amorphous polymers depends on the coordination of multiple physical mechanisms, and considerable opportunities exist to tailor the polymer structure and shape-memory programming procedure to achieve the desired performance. The goal of this project was to use a combination of theoretical, numerical and experimental methods to investigate the effect of shape memory programming, thermo-mechanical properties, and physical and environmental aging on the shape memory performance. Physical and environmental aging occurs during storage and through exposure to solvents, such as water, and can significantly alter the viscoelastic behavior and shape memory behavior of amorphous polymers. This project – executed primarily by Professor Thao Nguyen and Graduate Student Rui Xiao at Johns Hopkins University in support of a DOE/NNSA Presidential Early Career Award in Science and Engineering (PECASE) – developed a theoretical framework for chemothermo- mechanical behavior of amorphous polymers to model the effects of physical aging and solvent-induced environmental factors on their thermoviscoelastic behavior.

FEBEX Full-Scalle Engineered barriers experiment in crystalline host rock Preoperational thermo-hydro-mechanical (THM) modelling of the in situ test

International Nuclear Information System (INIS)

1998-01-01

This report contains the results of a set of 1-D and 2-D coupled thermo-hydro-mechanical (THM) analyses carried out during the preoperational stage simulating the in situ FEBEX test. The analyses incorporate available information concerning rock and bentonite properties as well as the final test layout and conditions. The main goals are: -To provide the best estimate of test performance given current models and information - To define a basis for future model improvements. The theoretical bases of the analyses and the computer code used are reviewed. Special reference is made to the process of parameter estimation that tries to incorporate available information on material behaviour obtained in the characterisation work carried out both in the laboratory and in the field. Data obtained in the characterisation stage is also used to define initial and boundary conditions. The results of the 1-D THM Base Case analysis are used to gain a good understanding of expected test behaviour concerning thermal, hydraulic and mechanical problems. A quite extensive programme of sensitivity analyses is also reported in which the effect of a number of parameters and boundary conditions are examined. The results of the sensitivity analyses place an appropriate context the information obtained from the Base Case showing, for instance, that rock desaturation and degree of buffer hydration depend on some critical parameters in a complex way. Two-dimensional effects are discussed on the basis of the results of 2-D axisymmetric THM analysis performed using a longitudinal section that provides a better representation of real test geometry. Quantitative but not qualitative differences are found with respect to the 1-D results. Finally, a 2-D THM cross section analysis has been performed under plane strain conditions. No specific 2-D effects are observed in this case as quasi-axisymmetric conditions have been prescribed. The models employed in the analyses included in this report have not

A phase field approach for the fully coupled thermo-electro-mechanical dynamics of nanoscale ferroelectric actuators

Science.gov (United States)

Wang, Dan; Du, Haoyuan; Wang, Linxiang; Melnik, Roderick

2018-05-01

The fully coupled thermo-electro-mechanical properties of nanoscale ferroelectric actuators are investigated by a phase field model. Firstly, the thermal effect is incorporated into the commonly-used phase field model for ferroelectric materials in a thermodynamic consistent way and the governing equation for the temperature field is derived. Afterwards, the modified model is numerically implemented to study a selected prototype of the ferroelectric actuators, where strain associated with electric field-induced non-180° domain switching is employed. The temperature variation and energy flow in the actuation process are presented, which enhances our understanding of the working mechanism of the actuators. Furthermore, the influences of the input voltage frequency and the thermal boundary condition on the temperature variation are demonstrated and carefully discussed in the context of thermal management for real applications.

Effective Hydro-Mechanical Properties of Fluid-Saturated Fracture Networks

Science.gov (United States)

Pollmann, N.; Vinci, C.; Renner, J.; Steeb, H.

2015-12-01

Consideration of hydro-mechanical processes is essential for the characterization of liquid-resources as well as for many engineering applications. Furthermore, the modeling of seismic waves in fractured porous media finds application not only in geophysical exploration but also reservoir management. Fractures exhibit high-aspect-ratio geometries, i.e. they constitute thin and long hydraulic conduits. Motivated by this peculiar geometry, the investigation of the hydro-mechanically coupled processes is performed by means of a hybrid-dimensional modeling approach. The effective material behavior of domains including complex fracture patterns in a porous rock is assessed by investigating the fluid pressure and the solid displacement of the skeleton saturated by compressible fluids. Classical balance equations are combined with a Poiseuille-type flow in the dimensionally reduced fracture. In the porous surrounding rock, the classical Biot-theory is applied. For simple geometries, our findings show that two main fluid-flow processes occur, leak-off from fractures to the surrounding rock and fracture flow within and between the connected fractures. The separation of critical frequencies of the two flow processes is not straightforward, in particular for systems containing a large number of fractures. Our aim is to model three dimensional hydro-mechanically coupled processes within complex fracture patterns and in particular determine the frequency-dependent attenuation characteristics. Furthermore, the effect of asperities of the fracture surfaces on the fracture stiffness and on the hydraulic conductivity will be added to the approach.

Comparative modelling of laboratory experiments for the hydro-mechanical behaviour of a compacted bentonite–sand\

Czech Academy of Sciences Publication Activity Database

Millard, A.; Mokni, N.; Barnichon, J. D.; Tatcher, K. E.; Bond, A.; Mc Dermott, C.; Blaheta, Radim; Michalec, Zdeněk; Hasal, Martin; Nguyen, T. S.; Nasir, O.; Fedors, S.; Yi, H.; Kolditz, O.

2016-01-01

Roč. 75, č. 20 (2016), s. 1311-1327 ISSN 1866-6280. [DECOVALEX 2015 /8./. Wakkanai, 13.10.2015-16.10.2015] Institutional support: RVO:68145535 Keywords : hydro-mechanical (hm) coupling * numerical modelling * sealing system s * compacted bentonite–sand mixture Subject RIV: DB - Geology ; Mineralogy Impact factor: 1.569, year: 2016 http://link.springer.com/article/10.1007/s12665-016-6118-z

Thermo-hydro-mechanical processes in the nearfield around a HLW repository in argillaceous formations. Vol. II. In-situ-investigations and interpretative modelling. May 2007 to May 2013

Energy Technology Data Exchange (ETDEWEB)

Zhang, Chun-Liang; Czaikowski, Oliver; Komischke, Michael; Wieczorek, Klaus

2014-06-15

Deep disposal of heat-emitting high-level radioactive waste (HLW) in clay formations will inevitably induce thermo-hydro-mechanical-chemical disturbances to the host rock and engineered barriers over very long periods of time. The responses and resulting property changes of the natural and engineered barriers are to be well understood, characterized, and predicted for assessing the long-term performance and safety of the repositories. In accordance with the R and D programme defined by the German Federal Ministry of Economics and Technology (BMWi), GRS has intensively performed site-independent research work on argillaceous rocks during the last decade. Most of the investigations have been carried out on the Callovo-Oxfordian argillite and the Opalinus clay by par-ticipation in international research projects conducted at the underground research laboratories at Bure in France (MHM-URL) and Mont-Terri in Switzerland (MT-URL). The THM-TON project, which was funded by BMWi under contract number 02E10377, in-vestigated the THM behaviours of the clay host rock and clay-based backfill/sealing materials with laboratory tests, in situ experiments and numerical modelling.

Hollow Cylinder Tests on Boom Clay: Modelling of Strain Localization in the Anisotropic Excavation Damaged Zone

Science.gov (United States)

François, Bertrand; Labiouse, Vincent; Dizier, Arnaud; Marinelli, Ferdinando; Charlier, Robert; Collin, Frédéric

2014-01-01

Boom Clay is extensively studied as a potential candidate to host underground nuclear waste disposal in Belgium. To guarantee the safety of such a disposal, the mechanical behaviour of the clay during gallery excavation must be properly predicted. In that purpose, a hollow cylinder experiment on Boom Clay has been designed to reproduce, in a small-scale test, the Excavation Damaged Zone (EDZ) as experienced during the excavation of a disposal gallery in the underground. In this article, the focus is made on the hydro-mechanical constitutive interpretation of the displacement (experimentally obtained by medium resolution X-ray tomography scanning). The coupled hydro-mechanical response of Boom Clay in this experiment is addressed through finite element computations with a constitutive model including strain hardening/softening, elastic and plastic cross-anisotropy and a regularization method for the modelling of strain localization processes. The obtained results evidence the directional dependency of the mechanical response of the clay. The softening behaviour induces transient strain localization processes, addressed through a hydro-mechanical second grade model. The shape of the obtained damaged zone is clearly affected by the anisotropy of the materials, evidencing an eye-shaped EDZ. The modelling results agree with experiments not only qualitatively (in terms of the shape of the induced damaged zone), but also quantitatively (for the obtained displacement in three particular radial directions).

裂隙岩体水-冰相变及低温温度场-渗流场-应力场耦合研究%WATER-ICE PHASE TRANSITION AND THERMO-HYDRO-MECHANICAL COUPLING AT LOW TEMPERATURE IN FRACTURED ROCK

Institute of Scientific and Technical Information of China (English)

刘泉声; 康永水; 刘滨; 朱元广

2011-01-01

The problem of freezing-thawing damage of rock mass involves thermo-hydro-mechanic al(THM) coupling at low temperature. Based on the phase transition theory and the energy conservation principle, the expression of frozen ratio is derived. Using the dual-porosity medium theory, the governing equations of THM coupling of freezing rock are obtained according to the law of mass conservation, the law of energy conservation and the principle of static equilibrium. Finally, considering the influence of freezing process on permeability, an example of fractured tunnel is given to reveal the distribution of temperature field, stress field and pore pressure under THM coupling condition by using the method of equivalent thermal expansion coefficient.%岩体冻融损伤涉及低温环境下温度场、渗流场和应力场的耦合问题.基于水-冰相变理论和能量守恒原理,得出冻结率表达式.运用双重孔隙介质模型理论,根据质量守恒定律、能量守恒定律及静力平衡原理,得出冻结条件下裂隙岩体的温度场-渗流场-应力场(THM)耦合控制方程.最后,通过1个含裂隙隧道低温THM耦合算例,将围岩当作岩块与裂隙介质组成的系统,采用等效热膨胀系数法对夹冰(含水)裂隙的冻胀效应进行模拟,并考虑冻结过程对岩体渗透系数的影响,研究低温THM耦合条件下的温度场、应力场及孔隙压力等的分布规律.

Experimental and Modelling Investigations of the Coupled Elastoplastic Damage of a Quasi-brittle Rock

Science.gov (United States)

Zhang, Jiu-Chang

2018-02-01

Triaxial compression tests are conducted on a quasi-brittle rock, limestone. The analyses show that elastoplastic deformation is coupled with damage. Based on the experimental investigation, a coupled elastoplastic damage model is developed within the framework of irreversible thermodynamics. The coupling effects between the plastic and damage dissipations are described by introducing an isotropic damage variable into the elastic stiffness and yield criterion. The novelty of the model is in the description of the thermodynamic force associated with damage, which is formulated as a state function of both elastic and plastic strain energies. The latter gives a full consideration on the comprehensive effects of plastic strain and stress changing processes in rock material on the development of damage. The damage criterion and potential are constructed to determine the onset and evolution of damage variable. The return mapping algorithms of the coupled model are deduced for three different inelastic corrections. Comparisons between test data and numerical simulations show that the coupled elastoplastic damage model is capable of describing the main mechanical behaviours of the quasi-brittle rock.

Application of an enriched FEM technique in thermo-mechanical contact problems

Science.gov (United States)

Khoei, A. R.; Bahmani, B.

2018-02-01

In this paper, an enriched FEM technique is employed for thermo-mechanical contact problem based on the extended finite element method. A fully coupled thermo-mechanical contact formulation is presented in the framework of X-FEM technique that takes into account the deformable continuum mechanics and the transient heat transfer analysis. The Coulomb frictional law is applied for the mechanical contact problem and a pressure dependent thermal contact model is employed through an explicit formulation in the weak form of X-FEM method. The equilibrium equations are discretized by the Newmark time splitting method and the final set of non-linear equations are solved based on the Newton-Raphson method using a staggered algorithm. Finally, in order to illustrate the capability of the proposed computational model several numerical examples are solved and the results are compared with those reported in literature.

Modeling of Coupled Thermo-Hydro-Mechanical-Chemical Processes for Bentonite in a Clay-rock Repository for Heat-generating Nuclear Waste

Science.gov (United States)

Xu, H.; Rutqvist, J.; Zheng, L.; Birkholzer, J. T.

2016-12-01

Engineered Barrier Systems (EBS) that include a bentonite-based buffer are designed to isolate the high-level radioactive waste emplaced in tunnels in deep geological formations. The heat emanated from the waste can drive the moisture flow transport and induce strongly coupled Thermal (T), Hydrological (H), Mechanical (M) and Chemical (C) processes within the bentonite buffer and may also impact the evolution of the excavation disturbed zone and the sealing between the buffer and walls of an emplacement tunnel The flow and contaminant transport potential along the disturbed zone can be minimized by backfilling the tunnels with bentonite, if it provides enough swelling stress when hydrated by the host rock. The swelling capability of clay minerals within the bentonite is important for sealing gaps between bentonite block, and between the EBS and the surrounding host rock. However, a high temperature could result in chemical alteration of bentonite-based buffer and backfill materials through illitization, which may compromise the function of these EBS components by reducing their plasticity and capability to swell under wetting. Therefore, an adequate THMC coupling scheme is required to understand and to predict the changes of bentonite for identifying whether EBS bentonite can sustain higher temperatures. More comprehensive links between chemistry and mechanics, taking advantage of the framework provided by a dual-structure model, named Barcelona Expansive Model (BExM), was implemented in TOUGHREACT-FLAC3D and is used to simulate the response of EBS bentonite in in clay formation for a generic case. The current work is to evaluate the chemical changes in EBS bentonite and the effects on the bentonite swelling stress under high temperature. This work sheds light on the interaction between THMC processes, evaluates the potential deterioration of EBS bentonite and supports the decision making in the design of a nuclear waste repository in light of the maximum allowance

Development of coupled models and their validation against experiments -DECOVALEX project

International Nuclear Information System (INIS)

Stephansson, O.; Jing, L.; Kautsky, F.

1995-01-01

DECOVALEX is an international co-operative research project for theoretical and experimental studies of coupled thermal, hydrological and mechanical processes in hard rocks. Different mathematical models and computer codes have been developed by research teams from different countries. These models and codes are used to study the so-called Bench Mark Test and Test Case problems developed within this project. Bench-Mark Tests are defined as hypothetical initial-boundary value problems of a generic nature, and Test Cases are experimental investigations of part or full aspects of coupled thermo-hydro-mechanical processes in hard rocks. Analytical and semi-analytical solutions related to coupled T-H-M processes are also developed for problems with simpler geometry and initial-boundary conditions. These solutions are developed to verify algorithms and their computer implementations. In this contribution the motivation, organization and approaches and current status of the project are presented, together with definitions of Bench-Mark Tests and Test Case problems. The definition and part of results for a BMT problem (BMT3) for a near-field repository model are described as an example. (authors). 3 refs., 11 figs., 3 tabs

Long term thermo-hydro-mechanical interaction behavior study of the saturated, discontinuous granitic rock mass around the radwaste repository using a steady state flow algorithm

Energy Technology Data Exchange (ETDEWEB)

Kim, Jhin Wung; Bae, Dae Suk; Kang, Chul Hyung; Choi, Jong Won [Korea Atomic Energy Research Institute, Taejeon (Korea)

2002-02-01

The objective of the present study is to understand the long term (500 years) thermo-hydro-mechanical interaction behavior of the 500 m depth underground radwaste repository in the saturated, discontinuous granitic rock mass using a steady state flow algorithm. The numerical model includes a saturated granitic rock mass with joints around the repository and a 45 .deg. C fault passing through the tunnel roof-wall intersection, and a canister with PWR spent fuels surrounded by the compacted bentonite and mixed-bentonite. Barton-Bandis joint constitutive model from the UDEC code is used for the joints. For the hydraulic analysis, a steady state flow algorithm is used for the groundwater flow through the rock joints. For the thermal analysis, heat transfer is modeled as isotropic conduction and heat decays exponentially with time. The results show that the variations of the hydraulic aperture, hydraulic conductivity, normal stress, normal displacements, and shear displacements of the joints are high in the vicinity of the repository and stay fairly constant on the region away from the repository. 14 refs., 15 figs., 11 tabs. (Author)

Couplings in multiphasic geo-materials: temperature and chemistry effects

International Nuclear Information System (INIS)

Ghasemzadeh, H.

2006-05-01

Transport of chemical components in soil through water is the major cause of pollution of the soil. This transport takes place around landfills and nuclear waste storage areas, tailings and mine wastes, and so on. A great number of these sites are unsaturated of water and in some cases heat can change the fate of chemical species, that lead us to a coupled problem. In this dissertation, numerical simulation with an existent thermo-hydro-mechanical model and theoretical modeling and numerical simulation of transport and interactions of one chemical species in multiphase media are presented. Integrated THM model in the Code-Aster is presented. Excavation, engineering barrier and thermal load of waste nuclear storage well are modeled. Verification of model is presented with these simulations. A thermo-hydro-mechanical behaviour coupled with chemical phenomena is presented with a fully coupled method that water, gas, chemical species and soil skeleton were considered as constituents and corresponding unknowns are temperature, water pressure, gas pressure, chemical concentration and displacements. For each constituent, mass balance equation and linear momentum equation are written and solved simultaneously to find related unknowns. The results of this model have been compared with the theoretical and experimental results existing in the literature. Furthermore, results of some applications of this model are included. Some areas where further work is required are identified. In particular, there is a need to perform experiments to obtain necessary soil parameters to permit accurate modelling of the heat and contaminant transport in unsaturated soils. (author)

BENCHPAR PROJECT. How to Incorporate ThermaI-Hydro-Mechanical Coupled Processes into Performance Assessments and Design Studies for Radioactive Waste Disposal in Geological Formations. Guidance Document

International Nuclear Information System (INIS)

Stephansson, O.; Andersson, Johan

2005-02-01

The objective of this Guidance Document is to provide advice on how to incorporate thermo-hydro-mechanical (THM) coupled processes into Performance Assessments (PAS) and design studies for radioactive waste disposal in geological formations to be experienced in a European context. The document has been generated by the EU research project BENCHPAR: Benchmark Tests and Guidance on Coupled Processes for Performance Assessment of Nuclear Waste Repositories. The document starts in Section 1 with an explanation of why numerical analyses incorporating THM mechanisms are required for radioactive waste studies and provides background material on the subject. Then, the THM processes and their interactions are explained in Section 2. Three case examples of THM numerical analysis are presented in Section 3 to illustrate the type of work that can be conducted to study the near-field, upscaling, and the far-field. For the three cases, there is discussion on the main findings, the relevance to a safety case, the relative importance of the different couplings, and the uncertainties involved. The importance and priority of the THM couplings are then summarized in Section 4. It is especially important to be able to technically audit the numerical analyses in order to establish that all the relevant variables, parameters and mechanisms have been included in the modelling and hence that the numerical model adequately represents the rock and engineering reality. Accordingly, recommended soft and hard auditing procedures are presented in Section 5. In this Guidance Document, we emphasize especially that the most important step in numerical modelling is not executing the calculations per se, but the earlier conceptualization of the problem regarding the dominant processes, the material properties and parameters, the engineering perturbations, and their mathematical presentations. The associated modelling component of addressing the uncertainties and estimating their influence on the

Lead transport in intra-oceanic subduction zones: 2D geochemical-thermo-mechanical modeling of isotopic signatures

NARCIS (Netherlands)

Baitsch-Ghirardello, B.; Stracke, A.; Connolly, J.A.D.; Nikolaeva, K.M.; Gerya, T.V.

2014-01-01

Understanding the physical-chemical mechanisms and pathways of geochemical transport in subduction zones remains a long-standing goal of subduction-related research. In this study, we perform fully coupled geochemical-thermo-mechanical (GcTM) numerical simulations to investigate Pb isotopic

Thermo-Hydro Mechanical Characteristics and Processes in the Clay Barrier of a High Level Radioactive Waste Repository. State of the Art Report

International Nuclear Information System (INIS)

Villar, M. V.

2004-01-01

This document is a summary of the available information on the thermo-hydro-mechanical properties of the bentonite barrier of a high-level radioactive waste repository and of the processes taking place in it during the successive repository operation phases. Mainly the thermal properties, the volume change processes (swelling and consolidation), the permeability and the water retention capacity are analysed. A review is made of the existing experimental knowledge on the modification of the these properties by the effect of temperature, water salinity, humidity and density of the bentonite, and their foreseen evolution as a consequence of the processes expected in the repository. The compiled evolution refers mostly to the FEBEX (Spain), the MX-80 (USA) and the FoCa (France) bentonite, considered as reference barrier materials in several European disposal concepts. (Author) 102 refs

Thermo-Hydro Mechanical Characteristics and Processes in the Clay Barrier of a High Level Radioactive Waste Repository. State of the Art Report

Energy Technology Data Exchange (ETDEWEB)

Villar, M. V.

2004-07-01

This document is a summary of the available information on the thermo-hydro-mechanical properties of the bentonite barrier of a high-level radioactive waste repository and of the processes taking place in it during the successive repository operation phases. Mainly the thermal properties, the volume change processes (swelling and consolidation), the permeability and the water retention capacity are analysed. A review is made of the existing experimental knowledge on the modification of the these properties by the effect of temperature, water salinity, humidity and density of the bentonite, and their foreseen evolution as a consequence of the processes expected in the repository. The compiled evolution refers mostly to the FEBEX (Spain), the MX-80 (US) and the FoCa (France) bentonite, considered as reference barrier materials in several European disposal concepts. (Author) 102 refs.

A Lattice-Misfit-Dependent Damage Model for Non-linear Damage Accumulations Under Monotonous Creep in Single Crystal Superalloys

Science.gov (United States)

le Graverend, J.-B.

2018-05-01

A lattice-misfit-dependent damage density function is developed to predict the non-linear accumulation of damage when a thermal jump from 1050 °C to 1200 °C is introduced somewhere in the creep life. Furthermore, a phenomenological model aimed at describing the evolution of the constrained lattice misfit during monotonous creep load is also formulated. The response of the lattice-misfit-dependent plasticity-coupled damage model is compared with the experimental results obtained at 140 and 160 MPa on the first generation Ni-based single crystal superalloy MC2. The comparison reveals that the damage model is well suited at 160 MPa and less at 140 MPa because the transfer of stress to the γ' phase occurs for stresses above 150 MPa which leads to larger variations and, therefore, larger effects of the constrained lattice misfit on the lifetime during thermo-mechanical loading.

Role of HHM coupling mechanisms on the evolution of rock masses around nuclear waste disposals in the context of gas generation

International Nuclear Information System (INIS)

Hoxha, D.; Do, D.-P.; Wendling, J.; Poutrel, A.

2010-01-01

Document available in extended abstract form only. This paper aims at modelling of long term evolution of hydro-mechanical state of rock masses around sealing nuclear waste disposals. In the principles of nuclear waste disposals the geological barrier must play a long term confining role in respect with nuclide transport. In terms of hydro-mechanical properties this calls for managing the damage around the underground workings of the waste disposals. In particular the seal buffers and barrier rock will support the generation of hydrogen of different origins, mainly from the corrosion of steals used in various elements of a nuclear waste disposal. This generation would generate gas pressures sufficiently high to partially dry seal or barrier rock leading to a redistribution of stress around underground openings, to a reactivation of the rock damage and finally could put in question the concept of geological barrier itself. The object of this paper is to shed light in the mechanisms of HHM coupling in rocks around a repository by comparative numerical analyses. Basically, we chose two configurations to proceed with analyses: one in plan strain conditions and the other an axial symmetric configuration. The goal of the first configuration is the assessment of gas pressure evolution in the openings of a repository. The principal input of the problem is the kinetics of gas generation (H 2 generation) given by a step-wise function of time describing the gas generation of one single nuclear waste coli. Then known the repository architecture one could easily calculate the mass of gas generated on one access gallery. Since extreme scenario is studied, we suppose that the gas generated by the set of alveoli is fully located in the access gallery and only a radial gas flux is possible.The hydro mechanical properties of rocks up to the surface were taken into account. For the callovo-Oxfordian clay that constitutes barrier rock in immediate neighbouring of the gallery a model

A dissolution-diffusion sliding model for soft rock grains with hydro-mechanical effect

Directory of Open Access Journals (Sweden)

Z. Liu

2018-06-01

Full Text Available The deformation and failure of soft rock affected by hydro-mechanical (HM effect are one of the most concerns in geotechnical engineering, which are basically attributed to the grain sliding of soft rock. This study tried to develop a dissolution-diffusion sliding model for the typical red bed soft rock in South China. Based on hydration film, mineral dissolution and diffusion theory, and geochemical thermodynamics, a dissolution-diffusion sliding model with the HM effect was established to account for the sliding rate. Combined with the digital image processing technology, the relationship between the grain size of soft rock and the amplitude of sliding surface was presented. An equation for the strain rate of soft rocks under steady state was also derived. The reliability of the dissolution-diffusion sliding model was verified by triaxial creep tests on the soft rock with the HM coupling effect and by the relationship between the inversion average disjoining pressure and the average thickness of the hydration film. The results showed that the sliding rate of the soft rock grains was affected significantly by the waviness of sliding surface, the shear stress, and the average thickness of hydration film. The average grain size is essential for controlling the steady-state creep rate of soft rock. This study provides a new idea for investigating the deformation and failure of soft rock with the HM effect. Keywords: Soft rock, Hydro-mechanical (HM effect, Mineral dissolution-diffusion, Grain sliding model

Coupled thermo-mechanical analysis of granite for high-level radioactive waste repository

International Nuclear Information System (INIS)

Liu Wengang; Wang Ju; Zhou Hongwei; Jiang Pengfei; Yang Chunhe

2008-01-01

High-level radioactive wastes (HLW) repository is a special deep underground engineering, and in the stages of site selection, designing, constructing ,the stability evaluation, lots of important rock mechanics problems need to be resolved. During the decay of nuclear waste, enormous thermal energy was released and temperature variation caused dynamic distribution of stress and deformation field of surrounding rock of repository. BeiShan region of Gansu province was selected to be the repository field in the future, it is of practical significance to do research on granite in this region. Based on the concept model of HLW repository, this thesis calculates temperature field, stress field and deformation field of HLW repository surrounding rock under the condition of TM coupled with applying the finite difference FLAC 3D . From this study, thermo-mechanical characteristic of granite is obtained primarily under given canister heat source and given decay law function. And these results show that the reasonable space between disposal hole is 8 m-12 m, and the peak temperature of the canister surface is 130 ℃, the centerline temperature between pits is about 40 ℃ which is maintained for about hundreds of years under given heating output at -500 m depth. (authors)

Panel report on coupled thermo-mechanical-hydro-chemical processes associated with a nuclear waste repository

International Nuclear Information System (INIS)

Tsang, C.F.; Mangold, D.C.

1984-07-01

Four basic physical processes, thermal, hydrological, mechanical and chemical, are likely to occur in 11 different types of coupling during the service life of an underground nuclear waste repository. A great number of coupled processes with various degrees of importance for geological repositories were identified and arranged into these 11 types. A qualitative description of these processes and a tentative evaluation of their significance and the degree of uncertainty in prediction is given. Suggestions for methods of investigation generally include, besides theoretical work, laboratory and large scale field testing. Great efforts of a multidisciplinary nature are needed to elucidate details of several coupled processes under different temperature conditions in different geological formations. It was suggested that by limiting the maximum temperature to 100 0 C in the backfill and in the host rock during the whole service life of the repository the uncertainties in prediction of long-term repository behavior might be considerably reduced

Panel report on coupled thermo-mechanical-hydro-chemical processes associated with a nuclear waste repository

Energy Technology Data Exchange (ETDEWEB)

Tsang, C.F.; Mangold, D.C. (eds.)

1984-07-01

Four basic physical processes, thermal, hydrological, mechanical and chemical, are likely to occur in 11 different types of coupling during the service life of an underground nuclear waste repository. A great number of coupled processes with various degrees of importance for geological repositories were identified and arranged into these 11 types. A qualitative description of these processes and a tentative evaluation of their significance and the degree of uncertainty in prediction is given. Suggestions for methods of investigation generally include, besides theoretical work, laboratory and large scale field testing. Great efforts of a multidisciplinary nature are needed to elucidate details of several coupled processes under different temperature conditions in different geological formations. It was suggested that by limiting the maximum temperature to 100{sup 0}C in the backfill and in the host rock during the whole service life of the repository the uncertainties in prediction of long-term repository behavior might be considerably reduced.

Electro-chemo-hydro-mechanical coupling in clayey media; Couplage electro-chimio-hydro-mecaniques dans les milieux argileux

Energy Technology Data Exchange (ETDEWEB)

Lemaire, Th

2004-12-15

The aim of this study is to understand coupled phenomena that occur in swelling porous materials like clays. Electro-chemo-hydro-mechanical contributions are taken into account to analyze transfers in such minerals. In a first part, a general discussion is proposed to introduce mineralogical and physico- chemical considerations of clayey media. An important objective of this chapter is to show the crucial role of the microstructure. In a second part is presented an imbibition test in a MX80 bentonite powder. The hydraulic diffusivity versus water content curve's decrease is explained thanks to a double porosity model that shows the progressive collapse of meso-pores due to swelling effects at the micro-scale. Thus a multi-scale analysis is necessary to well describe clayey media behaviour. The third chapter exposes such a multi-scale modelling (periodic homogenization). It is based on the double-layer theory and introduces an innovative concept of virtual electrolyte solution. First numerical results are given in a simple geometry (parallel platelets). In the next part are proposed numerical simulations of two kinds: response of the system to a chemical gradient and simulation of electro-osmosis. The end of this chapter puts into relief the necessity to integrate pH effects in the model. In the last part, chemical surface exchanges are incorporated in the modelling to understand pH and ionic force roles in electro-osmotic process. (author)

Monitoring and modelling of thermo-hydro-mechanical processes - main results of a heater experiment at the Mont Terri underground rock laboratory

Energy Technology Data Exchange (ETDEWEB)

Ingeborg, G.; Alheid, H.J. [BGR - Federal Institute for Geosciences and Natural Resources, Hannover (Germany); Jockwerz, N. [Gesellschaft fur Anlagen- und Reaktorsicherheit (GRS) - Final Repository Research Division, Braunschweig (Germany); Mayor, J.C. [ENRESA - Empresa Nacional des Residuos Radioactivos, Madrid (Spain); Garcia-Siner, J.L. [AITEMIN -Asociacion para la Investigacion y Desarrollo Industrial de los Recursos Naturales, Madrid, (Spain); Alonso, E. [CIMNE - Centre Internacional de Metodos Numerics en Ingenyeria, UPC, Barcelona (Spain); Weber, H.P. [NAGRA - National Cooperative for the Disposal of Radioactive Waste, Wettingen (Switzerland); Plotze, M. [ETHZ - Swiss Federal Institute of Technology Zurich, IGT, Zurich, (Switzerland); Klubertanz, G. [COLENCO Power Engineering Ltd., Baden (Switzerland)

2005-07-01

The long-term safety of permanent underground repositories relies on a combination of engineered and geological barriers, so that the interactions between the barriers in response to conditions expected in a high-level waste repository need to be identified and fully understood. Co-financed by the European Community, a heater experiment was realized on a pilot plant scale at the underground laboratory in Mont Terri, Switzerland. The experiment was accompanied by an extensive programme of continuous monitoring, experimental investigations on-site as well as in laboratories, and numerical modelling of the coupled thermo-hydro-mechanical processes. Heat-producing waste was simulated by a heater element of 10 cm diameter, held at a constant surface temperature of 100 C. The heater element (length 2 m) operated in a vertical borehole of 7 m depth at 4 to 6 m depth. It was embedded in a geotechnical barrier of pre-compacted bentonite blocks (outer diameter 30 cm) that were irrigated for 35 months before the heating phase (duration 18 months) began. The host rock is a highly consolidated stiff Jurassic clay stone (Opalinus Clay). After the heating phase, the vicinity of the heater element was explored by seismic, hydraulic, and geotechnical tests to investigate if the heating had induced changes in the Opalinus Clay. Additionally, rock mechanic specimens were tested in the laboratory. Finally, the experiment was dismantled to provide laboratory specimens of post - heating buffer and host rock material. The bentonite blocks were thoroughly wetted at the time of the dismantling. The volume increase amounted to 5 to 9% and was thus below the bentonite potential. Geo-electrical measurements showed no decrease of the water content in the vicinity of the heater during the heating phase. Decreasing energy input to the heater element over time suggests hence, that the bentonite dried leading to a decrease of its thermal conductivity. Gas release during the heating period occurred

Contribution to the modeling of the anisotropic damage and the variation of the permeability of the brittle rocks

International Nuclear Information System (INIS)

Zhou, J.

2006-03-01

This work deals with a modeling of the mechanical and hydro-mechanical behaviour of saturated rocks taking into account the variation of the permeability with damage. At first is established a function of the free enthalpy by a direct micro-mechanical approach in taking into account the distribution of the microcrack length. The opening of the closed microcracks due to the tangential gliding is taken into account because of the roughness of the cracks surfaces. This opening contributes directly to the volume expansion and to the variation of the macroscopic permeability of the material. A phenomenological approach with an approximation by a damage tensor of two order is shown too. Then, an extension of the model is proposed for describing the poro-mechanical behaviour of saturated rocks. The poro-mechanical answers in drained and undrained conditions of the Vosges sandstone have been studied. In the last part, a coupled model describing the behaviour of the coupling between the induced damage and the variation of the rocks permeability is proposed. (O.M.)

Flexible parallel implicit modelling of coupled thermal-hydraulic-mechanical processes in fractured rocks

Science.gov (United States)

Cacace, Mauro; Jacquey, Antoine B.

2017-09-01

Theory and numerical implementation describing groundwater flow and the transport of heat and solute mass in fully saturated fractured rocks with elasto-plastic mechanical feedbacks are developed. In our formulation, fractures are considered as being of lower dimension than the hosting deformable porous rock and we consider their hydraulic and mechanical apertures as scaling parameters to ensure continuous exchange of fluid mass and energy within the fracture-solid matrix system. The coupled system of equations is implemented in a new simulator code that makes use of a Galerkin finite-element technique. The code builds on a flexible, object-oriented numerical framework (MOOSE, Multiphysics Object Oriented Simulation Environment) which provides an extensive scalable parallel and implicit coupling to solve for the multiphysics problem. The governing equations of groundwater flow, heat and mass transport, and rock deformation are solved in a weak sense (either by classical Newton-Raphson or by free Jacobian inexact Newton-Krylow schemes) on an underlying unstructured mesh. Nonlinear feedbacks among the active processes are enforced by considering evolving fluid and rock properties depending on the thermo-hydro-mechanical state of the system and the local structure, i.e. degree of connectivity, of the fracture system. A suite of applications is presented to illustrate the flexibility and capability of the new simulator to address problems of increasing complexity and occurring at different spatial (from centimetres to tens of kilometres) and temporal scales (from minutes to hundreds of years).

Flexible parallel implicit modelling of coupled thermal–hydraulic–mechanical processes in fractured rocks

Directory of Open Access Journals (Sweden)

M. Cacace

2017-09-01

Full Text Available Theory and numerical implementation describing groundwater flow and the transport of heat and solute mass in fully saturated fractured rocks with elasto-plastic mechanical feedbacks are developed. In our formulation, fractures are considered as being of lower dimension than the hosting deformable porous rock and we consider their hydraulic and mechanical apertures as scaling parameters to ensure continuous exchange of fluid mass and energy within the fracture–solid matrix system. The coupled system of equations is implemented in a new simulator code that makes use of a Galerkin finite-element technique. The code builds on a flexible, object-oriented numerical framework (MOOSE, Multiphysics Object Oriented Simulation Environment which provides an extensive scalable parallel and implicit coupling to solve for the multiphysics problem. The governing equations of groundwater flow, heat and mass transport, and rock deformation are solved in a weak sense (either by classical Newton–Raphson or by free Jacobian inexact Newton–Krylow schemes on an underlying unstructured mesh. Nonlinear feedbacks among the active processes are enforced by considering evolving fluid and rock properties depending on the thermo-hydro-mechanical state of the system and the local structure, i.e. degree of connectivity, of the fracture system. A suite of applications is presented to illustrate the flexibility and capability of the new simulator to address problems of increasing complexity and occurring at different spatial (from centimetres to tens of kilometres and temporal scales (from minutes to hundreds of years.

Research on borehole stability of shale based on seepage-stress-damage coupling model

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Xiaofeng Ran

2014-01-01

Full Text Available In oil drilling, one of the most complicated problems is borehole stability of shale. Based on the theory of continuum damage mechanics, a modified Mohr-Coulomb failure criterion according to plastic damage evolution and the seepage-stress coupling is established. Meanwhile, the damage evolution equation which is based on equivalent plastic strain and the permeability evolution equation of shale are proposed in this paper. The physical model of borehole rock for a well in China western oilfield is set up to analyze the distribution of damage, permeability, stress, plastic strain and displacement. In the calculation process, the influence of rock damage to elastic modulus, cohesion and permeability is involved by writing a subroutine for ABAQUS. The results show that the rock damage evolution has a significant effect to the plastic strain and stress in plastic zone. Different drilling fluid density will produce different damage in its value, range and type. This study improves the theory of mechanical mechanism of borehole collapse and fracture, and provides a reference for the further research of seepage-stress-chemical-damage coupling of wall rock.

Temperature buffer test. Hydro-mechanical and chemical/ mineralogical characterizations

International Nuclear Information System (INIS)

Aakesson, Mattias; Olsson, Siv; Dueck, Ann; Nilsson, Ulf; Karnland, Ola; Kiviranta, Leena; Kumpulainen, Sirpa; Linden, Johan

2012-01-01

The Temperature Buffer Test (TBT) is a joint project between SKB/ANDRA and supported by ENRESA (modeling) and DBE (instrumentation), which aims at improving the understanding and to model the thermo-hydro-mechanical behavior of buffers made of swelling clay submitted to high temperatures (over 100 deg C) during the water saturation process. The test has been carried out in a KBS-3 deposition hole at Aspo HRL. It was installed during the spring of 2003. Two steel heaters (3 m long, 0.6 m diameter) and two buffer arrangements have been investigated: the lower heater was surrounded by rings of compacted Wyoming bentonite only, whereas the upper heater was surrounded by a composite barrier, with a sand shield between the heater and the bentonite. The test was dismantled and sampled during the winter of 2009/2010. This report presents the hydro-mechanical and chemical/mineralogical characterization program which was launched subsequent to the dismantling operation. The main goal has been to investigate if any significant differences could be observed between material from the field experiment and the reference material. The field samples were mainly taken from Ring 4 (located at the mid-section around the lower heater), in which the temperature in the innermost part reached 155 deg C. The following hydro-mechanical properties have been determined for the material (test technique within brackets): hydraulic conductivity (swelling pressure device), swelling pressure (swelling pressure device), unconfined compression strength (mechanical press), shear strength (triaxial cell) and retention properties (jar method). The following chemical/mineralogical properties (methods within brackets) were determined: anion analysis of water leachates (IC), chemical composition (ICP/AES+MS, EGA), cation exchange capacity (CEC, Cu-trien method) and exchangeable cations (exchange with NH4, ICPAES), mineralogical composition (XRD and FTIR), element distribution and microstructure (SEM and

Sufficient conditions for Hadamard well-posedness of a coupled thermo-chemo-poroelastic system

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Tetyana Malysheva

2016-01-01

Full Text Available This article addresses the well-posedness of a coupled parabolic-elliptic system modeling fully coupled thermal, chemical, hydraulic, and mechanical processes in porous formations that impact drilling and borehole stability. The underlying thermo-chemo-poroelastic model is a system of time-dependent parabolic equations describing thermal, solute, and fluid diffusions coupled with Navier-type elliptic equations that attempt to capture the elastic behavior of rock around a borehole. An existence and uniqueness theory for a corresponding initial-boundary value problem is an open problem in the field. We give sufficient conditions for the well-posedness in the sense of Hadamard of a weak solution to a fully coupled parabolic-elliptic initial-boundary value problem describing homogeneous and isotropic media.

Deformation and damage modes of deep argillaceous rocks under hydro-mechanical stresses

International Nuclear Information System (INIS)

Vales, F.

2008-12-01

An experimental identification of the hydro-mechanical behaviour of an argillite rock is proposed within a multi-scale approach. In particular, interest is focused on the spatial and temporal localization of strain and damage in a specimen during hydro-mechanical loading. Firstly, we describe the techniques used to follow the rock evolutions under loading, and in particular Digital Images Correlation (DIC), Acoustic Emission, microscopy and mercury intrusion porosimetry. Measurement errors and device limitations are discussed. The studied material is the Callovo-Oxfordian indurated argillaceous rock (or argillite) of the Bure site where ANDRA has built an underground research laboratory to study the radioactive waste storage. Petrophysical characterizations and microstructural observations by optical and scanning electron microscopy provide an identification of the constitutive phase and a characterization of their spatial distribution and typical sizes. Argillite can be described as a composite structure with a continuous clay matrix and embedded mineral particles, essentially quartz and carbonates. The typical size of these particles ranges from a few micrometers to a few hundreds micrometers, with an average close to 50 μ.m. The general experimental procedure combines two steps: in a fist time, imposed suctions bring samples to a given degree of water saturation, and, in a second time, uniaxial mechanical compression tests are performed. To understand the evolutions of the material under hydric and mechanical loading, samples are instrumented with standard measurement techniques, but also with Digital Image Correlation, at both the global scale of the sample and the local scale of the composite microstructure, and with Acoustic Emissions recording. Moisture transfers are imposed by controlled suctions on the range of 150 to 2.8 MPa, corresponding to the relative humidity range of 32 to 98%RH. During pure hydric solicitation, the changes in physical parameters

Coupling methodology within the software platform alliances

Energy Technology Data Exchange (ETDEWEB)

Montarnal, Ph; Deville, E; Adam, E; Bengaouer, A [CEA Saclay, Dept. de Modelisation des Systemes et Structures 91 - Gif-sur-Yvette (France); Dimier, A; Gaombalet, J; Loth, L [Agence Nationale pour la Gestion des Dechets Radioactifs (ANDRA), 92 - Chatenay Malabry (France); Chavant, C [Electricite de France (EDF), 92 - Clamart (France)

2005-07-01

CEA, ANDRA and EDF are jointly developing the software platform ALLIANCES which aim is to produce a tool for the simulation of nuclear waste storage and disposal repository. This type of simulations deals with highly coupled thermo-hydro-mechanical and chemical (T-H-M-C) processes. A key objective of Alliances is to give the capability for coupling algorithms development between existing codes. The aim of this paper is to present coupling methodology use in the context of this software platform. (author)

Coupling methodology within the software platform alliances

International Nuclear Information System (INIS)

Montarnal, Ph.; Deville, E.; Adam, E.; Bengaouer, A.; Dimier, A.; Gaombalet, J.; Loth, L.; Chavant, C.

2005-01-01

CEA, ANDRA and EDF are jointly developing the software platform ALLIANCES which aim is to produce a tool for the simulation of nuclear waste storage and disposal repository. This type of simulations deals with highly coupled thermo-hydro-mechanical and chemical (T-H-M-C) processes. A key objective of Alliances is to give the capability for coupling algorithms development between existing codes. The aim of this paper is to present coupling methodology use in the context of this software platform. (author)

Hydro-Mechanical Modelling of Slow Slip Phenomena at the Subduction Interface.

Science.gov (United States)

Petrini, C.; Gerya, T.; Madonna, C.; van Dinther, Y.

2016-12-01

Subduction zones experience a spectrum of slip phenomena, ranging from large devastating megathrust earthquakes to aseismic slow slip events. Slow slip events, lasting hours to years and being perceptible only by instruments, are believed to have the capability to induce large earthquakes. It is also repeatedly proposed that such slow events are controlled by fluid-rock interactions along the subduction interface, thus calling for development of fully coupled seismo-hydro-mechanical modeling approaches to identify their physics and controlling parameters. We present a newly developed finite difference visco-elasto-plastic numerical code with marker-in-cell technique, which fully couples mechanical deformation and fluid flow. We use this to investigate how the presence of fluids in the pore space of a (de)compacting rock matrix affects elastic stress accumulation and release along a fluid-bearing subduction interface. The model simulates the spontaneous occurrence of quasi-periodic slow slip phenomena along self-consistently forming highly localized shearbands, which accommodate shear displacement between two plates. The produced elastic rebound events show a slip velocity on the order of cm/yr, which is in good agreement with measured data. The governing gradual strength decrease along the slowly propagating shear bands is related to a drop in total pressure caused by shear localization at nearly constant (slightly decreasing) fluid pressure. Gradual reduction of the difference between the total and fluid pressure decreases brittle/plastic strength of fluid-bearing rocks along the shear bands, thus providing a dynamic feedback mechanism for the accumulated elastic stress release at the subduction interface.

FE Analysis of Rock with Hydraulic-Mechanical Coupling Based on Continuum Damage Evolution

Directory of Open Access Journals (Sweden)

Yongliang Wang

2016-01-01

Full Text Available A numerical finite element (FE analysis technology is presented for efficient and reliable solutions of rock with hydraulic-mechanical (HM coupling, researching the seepage characteristics and simulating the damage evolution of rock. To be in accord with the actual situation, the rock is naturally viewed as heterogeneous material, in which Young’s modulus, permeability, and strength property obey the typical Weibull distribution function. The classic Biot constitutive relation for rock as porous medium is introduced to establish a set of equations coupling with elastic solid deformation and seepage flow. The rock is subsequently developed into a novel conceptual and practical model considering the damage evolution of Young’s modulus and permeability, in which comprehensive utilization of several other auxiliary technologies, for example, the Drucker-Prager strength criterion, the statistical strength theory, and the continuum damage evolution, yields the damage variable calculating technology. To this end, an effective and reliable numerical FE analysis strategy is established. Numerical examples are given to show that the proposed method can establish heterogeneous rock model and be suitable for different load conditions and furthermore to demonstrate the effectiveness and reliability in the seepage and damage characteristics analysis for rock.

A novel thermo-hydraulic coupling model to investigate the crater formation in electrical discharge machining

Science.gov (United States)

Tang, Jiajing; Yang, Xiaodong

2017-09-01

A novel thermo-hydraulic coupling model was proposed in this study to investigate the crater formation in electrical discharge machining (EDM). The temperature distribution of workpiece materials was included, and the crater formation process was explained from the perspective of hydrodynamic characteristics of the molten region. To better track the morphology of the crater and the movement of debris, the level-set method was introduced in this study. Simulation results showed that the crater appears shortly after the ignition of the discharge, and the molten material is removed by vaporizing in the initial stage, then by splashing at the following time. The driving force for the detachment of debris in the splashing removal stage comes from the extremely large pressure difference in the upper part of the molten region, and the morphology of the crater is also influenced by the shearing flow of molten material. It was found that the removal ratio of molten material is only about 7.63% under the studied conditions, leaving most to form the re-solidification layer on the surface of the crater. The size of the crater reaches the maximum at the end of discharge duration then experiences a slight reduction because of the reflux of molten material after the discharge. The results of single pulse discharge experiments showed that the morphologies and sizes between the simulation crater and actual crater are good at agreement, verifying the feasibility of the proposed thermo-hydraulic coupling model in explaining the mechanisms of crater formation in EDM.

Hydro-mechanical coupled simulation of hydraulic fracturing using the eXtended Finite Element Method (XFEM)

Science.gov (United States)

Youn, Dong Joon

This thesis presents the development and validation of an advanced hydro-mechanical coupled finite element program analyzing hydraulic fracture propagation within unconventional hydrocarbon formations under various conditions. The realistic modeling of hydraulic fracturing is necessarily required to improve the understanding and efficiency of the stimulation technique. Such modeling remains highly challenging, however, due to factors including the complexity of fracture propagation mechanisms, the coupled behavior of fracture displacement and fluid pressure, the interactions between pre-existing natural and initiated hydraulic fractures and the formation heterogeneity of the target reservoir. In this research, an eXtended Finite Element Method (XFEM) scheme is developed allowing for representation of single or multiple fracture propagations without any need for re-meshing. Also, the coupled flows through the fracture are considered in the program to account for their influence on stresses and deformations along the hydraulic fracture. In this research, a sequential coupling scheme is applied to estimate fracture aperture and fluid pressure with the XFEM. Later, the coupled XFEM program is used to estimate wellbore bottomhole pressure during fracture propagation, and the pressure variations are analyzed to determine the geometry and performance of the hydraulic fracturing as pressure leak-off test. Finally, material heterogeneity is included into the XFEM program to check the effect of random formation property distributions to the hydraulic fracture geometry. Random field theory is used to create the random realization of the material heterogeneity with the consideration of mean, standard deviation, and property correlation length. These analyses lead to probabilistic information on the response of unconventional reservoirs and offer a more scientific approach regarding risk management for the unconventional reservoir stimulation. The new stochastic approach

A coupled thermo-mechanical pseudo inverse approach for preform design in forging

Science.gov (United States)

Thomas, Anoop Ebey; Abbes, Boussad; Li, Yu Ming; Abbes, Fazilay; Guo, Ying-Qiao; Duval, Jean-Louis

2017-10-01

Hot forging is a process used to form difficult to form materials as well as to achieve complex geometries. This is possible due to the reduction of yield stress at high temperatures and a subsequent increase in formability. Numerical methods have been used to predict the material yield and the stress/strain states of the final product. Pseudo Inverse Approach (PIA) developed in the context of cold forming provides a quick estimate of the stress and strain fields in the final product for a given initial shape. In this paper, PIA is extended to include the thermal effects on the forging process. A Johnson-Cook thermo-viscoplastic material law is considered and a staggered scheme is employed for the coupling between the mechanical and thermal problems. The results are compared with available commercial codes to show the efficiency and the limitations of PIA.

Microscale experimental investigation of deformation and damage of argillaceous rocks under cyclic hydric and mechanical loads

International Nuclear Information System (INIS)

Wang, Linlin; Yang, Diansen; Heripre, Eva; Chanchole, Serge; Bornert, Michel; Pouya, Ahmad; Halphen, Bernard

2012-01-01

Document available in abstract form only. Argillaceous rocks are possible host rocks for underground nuclear waste repositories. They exhibit complex coupled thermo-hydro-chemo-mechanical behavior, the description of which would strongly benefit from an improved experimental insight on their deformation and damage mechanisms at microscale. We present some recent observations of the evolution of these rocks at the scale of their composite microstructure, essentially made of a clay matrix with embedded carbonates and quartz particles with sizes ranging from a few to several tens of micrometers, when they are subjected to cyclic variations of relative humidity and mechanical loading. They are based on the combination of high definition and high resolution imaging in an environmental scanning electron microscope (ESEM), in situ hydro-mechanical loading of the samples, and digital image correlation techniques. Samples, several millimeters in diameter, are held at a constant temperature of 2 deg. Celsius while the vapor pressure in the ESEM chamber is varied from a few to several hundreds of Pascals, generating a relative humidity ranging from about 10% up to 90%. Results show a strongly heterogeneous deformation field at microscale, which is the result of complex hydro-mechanical interactions. In particular, it can be shown that local swelling incompatibilities can generate irreversible deformations in the clay matrix, even if the overall hydric deformations seem reversible. In addition, local damage can be generated, in the form of a network of microcracks, located in the bulk of the clay matrix and/or at the interface between clay and other mineral particles. The morphology of this network, described in terms of crack length, orientation and preferred location, has been observed to be dependent on the speed of the variation of the relative humidity, and is different in a saturation or desaturation process. Besides studying the deformation and damage under hydric

Investigation of cold extrusion process using coupled thermo-mechanical FEM analysis and adaptive friction modeling

Science.gov (United States)

Görtan, Mehmet Okan

2017-10-01

Cold extrusion processes are known for their excellent material usage as well as high efficiency in the production of large batches. Although the process starts at room temperature, workpiece temperatures may rise above 200°C. Moreover, contact normal stresses can exceed 2500 MPa, whereas surface enlargement values can reach up to 30. These changes affects friction coefficients in cold extrusion processes. In the current study, friction coefficients between a plain carbon steel C4C (1.0303) and a tool steel (1.2379) are determined dependent on temperature and contact pressure using the sliding compression test (SCT). In order to represent contact normal stress and temperature effects on friction coefficients, an empirical adaptive friction model has been proposed. The validity of the model has been tested with experiments and finite element simulations for a cold forward extrusion process. By using the proposed adaptive friction model together with thermo-mechanical analysis, the deviation in the process loads between numerical simulations and model experiments could be reduced from 18.6% to 3.3%.

A coupled carbonation-rust formation mechanical damage model for steel corrosion in reinforced concrete

International Nuclear Information System (INIS)

Nguyen, Huyen; Bary, B.; L'Hostis, Valerie; DeLarrard, T.

2014-01-01

This paper aims at presenting a strategy to simulate the corrosion of steel reinforcement due to carbonation of concrete in atmospheric environment. We propose a model coupling drying, carbonation, diffusion of oxygen, formation of rust and mechanics to describe these phenomena. The rust layer is assumed to be composed of two sub-layers with different elastic modulus. An unstable layer with a low modulus (from 0.1 to 5 GPa) is located next to the transformed medium, and another more stable one with a higher modulus (from 100 to 150 GPa) at the interface with steel reinforcement. This model is applied to a numerical meso-structure composed of 4 phases: mortar matrix, randomly distributed aggregates, steel rebar and rust layers to underline the effect of aggregates on damage initiation and corresponding crack pattern of concrete cover. (authors)

Modeling Lightning Impact Thermo-Mechanical Damage on Composite Materials

Science.gov (United States)

Muñoz, Raúl; Delgado, Sofía; González, Carlos; López-Romano, Bernardo; Wang, De-Yi; LLorca, Javier

2014-02-01

Carbon fiber-reinforced polymers, used in primary structures for aircraft due to an excellent strength-to-weight ratio when compared with conventional aluminium alloy counterparts, may nowadays be considered as mature structural materials. Their use has been extended in recent decades, with several aircraft manufacturers delivering fuselages entirely manufactured with carbon composites and using advanced processing technologies. However, one of the main drawbacks of using such composites entails their poor electrical conductivity when compared with aluminium alloy competitors that leads to lightning strikes being considered a significant threat during the service life of the aircraft. Traditionally, this problem was overcome with the use of a protective copper/bronze mesh that added additional weight and reduced the effectiveness of use of the material. Moreover, this traditional sizing method is based on vast experimental campaigns carried out by subjecting composite panels to simulated lightning strike events. While this method has proven its validity, and is necessary for certification of the structure, it may be optimized with the aid provided by physically based numerical models. This paper presents a model based on the finite element method that includes the sources of damage observed in a lightning strike, such as thermal damage caused by Joule overheating and electromagnetic/acoustic pressures induced by the arc around the attachment points. The results of the model are compared with lightning strike experiments carried out in a carbon woven composite.

DECOVALEX I - Bench-Mark Test 3: Thermo-hydro-mechanical modelling

International Nuclear Information System (INIS)

Israelsson, J.

1995-12-01

The bench-mark test concerns the excavation of a tunnel, located 500 m below the ground surface, and the establishment of mechanical equilibrium and steady-state fluid flow. Following this, a thermal heating due to the nuclear waste, stored in a borehole below the tunnel, was simulated. The results are reported at (1) 30 days after tunnel excavation, (2) steady state, (3) one year after thermal loading, and (4) at the time of maximum temperature. The problem specification included the excavation and waste geometry, materials properties for intact rock and joints, location of more than 6500 joints observed in the 50 by 50 m area, and calculated hydraulic conductivities. However, due to the large number of joints and the lack of dominating orientations, it was decided to treat the problem as a continuum using the computer code FLAC. The problem was modeled using a vertical symmetry plane through the tunnel and the borehole. Flow equilibrium was obtained approx. 40 days after the opening of the tunnel. Since the hydraulic conductivity was set to be stress dependent, a noticeable difference in the horizontal and vertical conductivity and flow was observed. After 40 days, an oedometer-type consolidation of the model was observed. Approx. 4 years after the initiation of the heat source, a maximum temperature of 171 C was obtained. The stress-dependent hydraulic conductivity and the temperature-dependent dynamic viscosity caused minor changes to the flow pattern. The specified mechanical boundary conditions imply that the tunnel is part of a system of parallel tunnels. However, the fixed temperature at the top boundary maintains the temperature below the temperature anticipated for an equivalent repository. The combination of mechanical and hydraulic boundary conditions cause the model to behave like an oedometer test in which the consolidation rate goes asymptotically to zero. 17 refs, 55 figs, 22 tabs

A thermo-electro-mechanical simulation model for hot wire cutting of EPS foam

DEFF Research Database (Denmark)

Petkov, Kiril; Hattel, Jesper Henri

2016-01-01

A one-dimensional thermo-electro-mechanical mathematical model describing the effects taking place within a Ni-Cr20% wire used in a hot-wire cutting process for free forming and rapid prototyping of expanded polystyrene (EPS) is investigated and simulated. The model implements and solves three semi...... cutting of EPS in contact with a cutting tool made of an electrically heated metal wire attached to a robot device. The finite difference method is used to solve the coupled equations in the two environments (domains) in which the hot-wire operates, namely air and EPS. The model is calibrated against...... experimentally obtained data. Novel findings are a transient temperature-dependent kerfwidth prediction and a relation between kerfwidth and the cutting angle as measured from the horizontal direction. These are important relations in the aim for higher geometrical accuracy of the hot-wire cutting process. (C...

Thermo-mechanical properties and integrity of metallic interconnects in microelectronics

Science.gov (United States)

Ege, Efe Sinan

In this dissertation, combined numerical (Finite Element Method) and experimental efforts were undertaken to study thermo-mechanical behavior in microelectronic devices. Interconnects, including chip-level metallization and package-level solder joints, are used to join many of the circuit parts in modern equipment. The dissertation is structured into six independent studies after the introductory chapter. The first two studies focus on thermo-mechanical fatigue of solder joints. Thermo-mechanical fatigue, in the form of damage along a microstructurally coarsened region in tin-lead solder, is analyzed along with the effects of intermetallic morphology. Also, lap-shear testing is modeled to characterize the joint and to investigate the validity of experimental data from different solder and substrate geometries. In the third study, the effects of pre-machined holes on strain localization and overall ductility in bulk eutectic tin-lead alloy is examined. Finite element analyses, taking into account the viscoplastic response, were carried out to provide a mechanistic rationale to corroborate the experimental findings. The fourth study concerns chip-level copper interconnects. Various combinations of oxide and polymer-based low-k dielectric schemes, with and without the thin barrier layers surrounding the Cu line, are considered. Attention is devoted to the thermal stress and strain fields and their dependency on material properties, geometry, and modeling details. This study is followed by a chapter on atomistics of interface-mediated plasticity in thin metallic films. The objective is to gain fundamental insight into the underlying mechanisms affecting the mechanical response of nanoscale thin films. The final study investigates the effect of microstructural heterogeneity on indentation response, for the purpose of raising awareness of the uncertainties involved in applying indentation techniques in probing mechanical properties of miniaturized devices.

Thermo-Mechanical Modeling of Laser-Mig Hybrid Welding (lmhw)

Science.gov (United States)

Kounde, Ludovic; Engel, Thierry; Bergheau, Jean-Michel; Boisselier, Didier

2011-01-01

Hybrid welding is a combination of two different technologies such as laser (Nd: YAG, CO2…) and electric arc welding (MIG, MAG / TIG …) developed to assemble thick metal sheets (over 3 mm) in order to reduce the required laser power. As a matter of fact, hybrid welding is a lso used in the welding of thin materials to benefit from process, deep penetration and gap limit. But the thermo-mechanical behaviour of thin parts assembled by LMHW technology for railway cars production is far from being controlled the modeling and simulation contribute to the assessment of the causes and effects of the thermo mechanical behaviour in the assembled parts. In order to reproduce the morphology of melted and heat-affected zones, two analytic functions were combined to model the heat source of LMHW. On one hand, we applied a so-called "diaboloïd" (DB) which is a modified hyperboloid, based on experimental parameters and the analysis of the macrographs of the welds. On the other hand, we used a so-called "double ellipsoïd" (DE) which takes the MIG only contribution including the bead into account. The comparison between experimental result and numerical result shows a good agreement.

Coupled thermo-hydro-mechanical analysis for the conceptual repository of high-level radioactive waste in China

International Nuclear Information System (INIS)

Lin, Y.M.; Wang, J.; Ke, D.; Cai, M.F.

2010-01-01

In order to safely dispose of the high-level radioactive waste (HLW), RD guide of HLW disposal was published in February 2006 in China. The spent fuel from nuclear power plants will be reprocessed first, followed by verification and final disposal. A conceptual repository 3D configuration comprises a single vertical borehole in a continuous and homogeneous hard rock, containing a canister surrounded by an over-pack and a bentonite layer, and the backfilled upper portion of the gallery using FLAC3D. To take into account in situ stress, geothermal gradient and groundwater of Beishan area, thermal relief of HLW and swelling pressure of buffer/backfill material made by GMZ01 bentonite, the TM, HM and THM evolution of the whole configuration is simulated over a period of 100 years. The results demonstrate that temperature is hardly affected by the couplings. In contrast, the influence of the couplings on the mechanical stresses is considerable. The repository has long-term stability in fully THM coupling action condition. (authors)

Contribution to a hydro-chemo-mechanical multi-mechanisms model based on the multi-scale and multi components structure of Callovo-Oxfordian argillites: experiments and modelling

International Nuclear Information System (INIS)

Robinet, J.C.; Trinh, M.H.; Imbert, C.

2010-01-01

show an increase of porosity from 12% up to 20% associated with the creation of macro-pores (mercury intrusion porosimetry). - X ray micro tomography observations and pictures analysis made on successive sections of sample argillite and 3D rebuilding of calcite organisation. Mechanical conceptual model of argillite Independently of its origin, the strong density associated with some inclusions like calcite, quartz grains and fibres shaped calcite resulting of the filling of the macro porosity is considered to explain: (i) localized damage occurring on extension paths and/or (ii) diffuse and localized damage, on compression path. Damage is characterized by creation of localized and/or diffuse macro-porosity that confers plasticity to argillite and allows development of classical hydro-chemo-mechanical mechanisms of clays, hydro-mechanical consolidation, swelling, and viscosity (creep) that are responsible of long term deformations. Irreversible strains and weak macro porosity observed on the tests with cored samples could be a consequence of the mechanical and hydraulic discharges. Laboratory tests after a controlled damage produced by a thermal cycle at constant volume highlighted the existence of some mechanisms: - swelling of the argillite samples (attributed to smectite swelling), - increase of the swelling potential with the proportion of macro pores, - decrease of the oedometric modulus with the proportion of macro pores. The existence of a transient phase after damage induced by the brutal creation of a macro porosity partially saturated (cavitations phenomenon) because of low permeability of argillite is due to the water re-saturation of the macro pores. Different mechanical laboratory tests conducted on Bure argillite, for instance drained and undrained triaxial tests, are compared to numerical simulation. The simulation of the behaviour of the galleries and shafts in the Callovian-Oxfordian formation have been realised with the previous model integrated in the

A coupled interface-body nonlocal damage model for the analysis of FRP strengthening detachment from cohesive material

Directory of Open Access Journals (Sweden)

J. Toti

2011-10-01

Full Text Available In the present work, a new model of the FRP-concrete or masonry interface, which accounts for the coupling occurring between the degradation of the cohesive material and the FRP detachment, is presented; in particular, a coupled interface-body nonlocal damage model is proposed. A nonlocal damage and plasticity model is developed for the quasi-brittle material. For the interface, a model which accounts for the mode I, mode II and mixed mode of damage and for the unilateral contact and friction effects is developed. Two different ways of performing the coupling between the body damage and the interface damage are proposed and compared. Some numerical applications are carried out in order to assess the performances of the proposed model in reproducing the mechanical behavior of the masonry elements strengthened with external FRP reinforcements.

Hydro-mechanical coupling and transport in Meuse/Haute-Marne argillite: experimental and multi-scale approaches

International Nuclear Information System (INIS)

Cariou, S.

2010-07-01

This thesis deals with the hydro-mechanical behaviour of argillite. Classical Biot theory is shown to be badly adapted to the case of argillite. An original state equation is then built by use of homogenization tools, and takes into account the microstructure of argillite as well as physical phenomena happening inside the material, like the swelling overpressure inside the clay particles or the capillary effects in the porous network. This state equation explains some experiments which were not by the classical Biot theory. It is then improved by integrating the experimental data that are the dependency of the elasticity tensor with the saturation degree and the existence of a porosity surrounding the inclusions. Combined with the monitoring of length variation under hydric loading, this relevant state equation permits one to determine the Biot tensor of argillite. Since this state equation is coupled with the hydric state of the material, one is interested in modelling the variation of the saturation degree during a drying process. Two transport models are studied and compared, then a model for the porous network is proposed in order to explain the unusual permeability measurements. (author)

Evolution of mechanical behavior of 6XXX aluminium alloy due to the precipitation state during a thermo-mechanical process

International Nuclear Information System (INIS)

Bardel, Didier; Perez, Michel; Nelias, Daniel; Chaise, Thibaut; Garnier, Jerome; Bourlier, Florent

2014-01-01

The aim of this research is to link the microstructural state and the mechanical properties of an age hardening alloy during a fast heat treatment such as encountered during welding. A coupled model between precipitation state and mechanical properties is used to predict the yield strength and hardening behavior that can be observed experimentally. The method permits the identification of the kinematic and isotropic contributions in the hardening model. The methodology is applied to a 6061-T6 aluminium alloy which is used in the Jules Horowitz reactor vessel. The general idea of this methodology is to couple an efficient microstructural model to a mechanical one based on the dislocation theory and ad'hoc experiments. The theoretical background is based on the work of Kampmann and Wagner, known as the KWN model, to account for nucleation, growth/dissolution and coarsening of precipitates. This analysis requires transient thermo-mechanical experimental data. The efficiency of these models and their coupling are shown for a series 6XXX aluminium alloy which contains β'' and β' precipitates. Ultimately these models are coupled to a FEA model and allows to predict the distribution of precipitates within each element of the mesh, and subsequently its mechanical behavior. (authors)

Coupled Flow and Mechanics in Porous and Fractured Media*

Science.gov (United States)

Martinez, M. J.; Newell, P.; Bishop, J.

2012-12-01

Numerical models describing subsurface flow through deformable porous materials are important for understanding and enabling energy security and climate security. Some applications of current interest come from such diverse areas as geologic sequestration of anthropogenic CO2, hydro-fracturing for stimulation of hydrocarbon reservoirs, and modeling electrochemistry-induced swelling of fluid-filled porous electrodes. Induced stress fields in any of these applications can lead to structural failure and fracture. The ultimate goal of this research is to model evolving faults and fracture networks and flow within the networks while coupling to flow and mechanics within the intact porous structure. We report here on a new computational capability for coupling of multiphase porous flow with geomechanics including assessment of over-pressure-induced structural damage. The geomechanics is coupled to the flow via the variation in the fluid pore pressures, whereas the flow problem is coupled to mechanics by the concomitant material strains which alter the pore volume (porosity field) and hence the permeability field. For linear elastic solid mechanics a monolithic coupling strategy is utilized. For nonlinear elastic/plastic and fractured media, a segregated coupling is presented. To facilitate coupling with disparate flow and mechanics time scales, the coupling strategy allows for different time steps in the flow solve compared to the mechanics solve. If time steps are synchronized, the controller allows user-specified intra-time-step iterations. The iterative coupling is dynamically controlled based on a norm measuring the degree of variation in the deformed porosity. The model is applied for evaluation of the integrity of jointed caprock systems during CO2 sequestration operations. Creation or reactivation of joints can lead to enhanced pathways for leakage. Similarly, over-pressures can induce flow along faults. Fluid flow rates in fractures are strongly dependent on the

Thermo-mechanical constitutive modeling of unsaturated clays based on the critical state concepts

OpenAIRE

Tourchi, Saeed; Hamidi, Amir

2015-01-01

A thermo-mechanical constitutive model for unsaturated clays is constructed based on the existing model for saturated clays originally proposed by the authors. The saturated clays model was formulated in the framework of critical state soil mechanics and modified Cam-clay model. The existing model has been generalized to simulate the experimentally observed behavior of unsaturated clays by introducing Bishop's stress and suction as independent stress parameters and modifying the hardening rul...

Modeling of fluid injection and withdrawal induced fault activation using discrete element based hydro-mechanical and dynamic coupled simulator

Science.gov (United States)

Yoon, Jeoung Seok; Zang, Arno; Zimmermann, Günter; Stephansson, Ove

2016-04-01

Operation of fluid injection into and withdrawal from the subsurface for various purposes has been known to induce earthquakes. Such operations include hydraulic fracturing for shale gas extraction, hydraulic stimulation for Enhanced Geothermal System development and waste water disposal. Among these, several damaging earthquakes have been reported in the USA in particular in the areas of high-rate massive amount of wastewater injection [1] mostly with natural fault systems. Oil and gas production have been known to induce earthquake where pore fluid pressure decreases in some cases by several tens of Mega Pascal. One recent seismic event occurred in November 2013 near Azle, Texas where a series of earthquakes began along a mapped ancient fault system [2]. It was studied that a combination of brine production and waste water injection near the fault generated subsurface pressures sufficient to induced earthquakes on near-critically stressed faults. This numerical study aims at investigating the occurrence mechanisms of such earthquakes induced by fluid injection [3] and withdrawal by using hydro-geomechanical coupled dynamic simulator (Itasca's Particle Flow Code 2D). Generic models are setup to investigate the sensitivity of several parameters which include fault orientation, frictional properties, distance from the injection well to the fault, amount of fluid withdrawal around the injection well, to the response of the fault systems and the activation magnitude. Fault slip movement over time in relation to the diffusion of pore pressure is analyzed in detail. Moreover, correlations between the spatial distribution of pore pressure change and the locations of induced seismic events and fault slip rate are investigated. References [1] Keranen KM, Weingarten M, Albers GA, Bekins BA, Ge S, 2014. Sharp increase in central Oklahoma seismicity since 2008 induced by massive wastewater injection, Science 345, 448, DOI: 10.1126/science.1255802. [2] Hornbach MJ, DeShon HR

FEM Analyses for T-H-M-M Coupling Processes in Dual-Porosity Rock Mass under Stress Corrosion and Pressure Solution

Directory of Open Access Journals (Sweden)

Yu-Jun Zhang

2012-01-01

Full Text Available The models of stress corrosion and pressure solution established by Yasuhara et al. were introduced into the 2D FEM code of thermo-hydro-mechanical-migratory coupling analysis for dual-porosity medium developed by the authors. Aiming at a hypothetical model for geological disposal of nuclear waste in an unsaturated rock mass from which there is a nuclide leak, two computation conditions were designed. Then the corresponding two-dimensional numerical simulation for the coupled thermo-hydro-mechanical-migratory processes were carried out, and the states of temperatures, rates and magnitudes of aperture closure, pore and fracture pressures, flow velocities, nuclide concentrations and stresses in the rock mass were investigated. The results show: the aperture closure rates caused by stress corrosion are almost six orders higher than those caused by pressure solution, and the two kinds of closure rates climb up and then decline, furthermore tend towards stability; when the effects of stress corrosion and pressure solution are considered, the negative fracture pressures in near field rise very highly; the fracture aperture and porosity are decreases in the case 1, so the relative permeability coefficients reduce, therefore the nuclide concentrations in pore and fracture in this case are higher than those in case 2.

Coupled hygrothermal, electrochemical, and mechanical modelling for deterioration prediction in reinforced cementitious materials

DEFF Research Database (Denmark)

Michel, Alexander; Geiker, Mette Rica; Lepech, M.

2017-01-01

In this paper a coupled hygrothermal, electrochemical, and mechanical modelling approach for the deterioration prediction in cementitious materials is briefly outlined. Deterioration prediction is thereby based on coupled modelling of (i) chemical processes including among others transport of hea......, i.e. information, such as such as corrosion current density, damage state of concrete cover, etc., are constantly exchanged between the models....... and matter as well as phase assemblage on the nano and micro scale, (ii) corrosion of steel including electrochemical processes at the reinforcement surface, and (iii) material performance including corrosion- and load-induced damages on the meso and macro scale. The individual FEM models are fully coupled...

Analysing hydro-mechanical behaviour of reinforced slopes through centrifuge modelling

Science.gov (United States)

Veenhof, Rick; Wu, Wei

2017-04-01

Every year, slope instability is causing casualties and damage to properties and the environment. The behaviour of slopes during and after these kind of events is complex and depends on meteorological conditions, slope geometry, hydro-mechanical soil properties, boundary conditions and the initial state of the soils. This study describes the effects of adding reinforcement, consisting of randomly distributed polyolefin monofilament fibres or Ryegrass (Lolium), on the behaviour of medium-fine sand in loose and medium dense conditions. Direct shear tests were performed on sand specimens with different void ratios, water content and fibre or root density, respectively. To simulate the stress state of real scale field situations, centrifuge model tests were conducted on sand specimens with different slope angles, thickness of the reinforced layer, fibre density, void ratio and water content. An increase in peak shear strength is observed in all reinforced cases. Centrifuge tests show that for slopes that are reinforced the period until failure is extended. The location of shear band formation and patch displacement behaviour indicate that the design of slope reinforcement has a significant effect on the failure behaviour. Future research will focus on the effect of plant water uptake on soil cohesion.

A Coupled Plastic Damage Model for Concrete considering the Effect of Damage on Plastic Flow

OpenAIRE

Zhou, Feng; Cheng, Guangxu

2015-01-01

A coupled plastic damage model with two damage scalars is proposed to describe the nonlinear features of concrete. The constitutive formulations are developed by assuming that damage can be represented effectively in the material compliance tensor. Damage evolution law and plastic damage coupling are described using the framework of irreversible thermodynamics. The plasticity part is developed without using the effective stress concept. A plastic yield function based on the true stress is ado...

Thermo-mechanically coupled fracture analysis of shape memory alloys using the extended finite element method

Science.gov (United States)

Hatefi Ardakani, S.; Ahmadian, H.; Mohammadi, S.

2015-04-01

In this paper, the extended finite element method is used for fracture analysis of shape memory alloys for both cases of super elastic and shape memory effects. Heat generation during the forward and reverse phase transformations can lead to temperature variation in the material because of strong thermo-mechanical coupling, which significantly influences the SMA mechanical behavior. First, the stationary crack mode is studied and the effects of loading rate on material behavior in the crack tip are examined. Then, the crack propagation analysis is performed in the presence of an initial crack by adopting a weighted averaging criterion, where the direction of crack propagation is determined by weighted averaging of effective stresses at all the integration points in the vicinity of the crack tip. Finally, several numerical examples are analyzed and the obtained results are compared with the available reference results.

Rock Failure Analysis Based on a Coupled Elastoplastic-Logarithmic Damage Model

Science.gov (United States)

Abdia, M.; Molladavoodi, H.; Salarirad, H.

2017-12-01

The rock materials surrounding the underground excavations typically demonstrate nonlinear mechanical response and irreversible behavior in particular under high in-situ stress states. The dominant causes of irreversible behavior are plastic flow and damage process. The plastic flow is controlled by the presence of local shear stresses which cause the frictional sliding. During this process, the net number of bonds remains unchanged practically. The overall macroscopic consequence of plastic flow is that the elastic properties (e.g. the stiffness of the material) are insensitive to this type of irreversible change. The main cause of irreversible changes in quasi-brittle materials such as rock is the damage process occurring within the material. From a microscopic viewpoint, damage initiates with the nucleation and growth of microcracks. When the microcracks length reaches a critical value, the coalescence of them occurs and finally, the localized meso-cracks appear. The macroscopic and phenomenological consequence of damage process is stiffness degradation, dilatation and softening response. In this paper, a coupled elastoplastic-logarithmic damage model was used to simulate the irreversible deformations and stiffness degradation of rock materials under loading. In this model, damage evolution & plastic flow rules were formulated in the framework of irreversible thermodynamics principles. To take into account the stiffness degradation and softening on post-peak region, logarithmic damage variable was implemented. Also, a plastic model with Drucker-Prager yield function was used to model plastic strains. Then, an algorithm was proposed to calculate the numerical steps based on the proposed coupled plastic and damage constitutive model. The developed model has been programmed in VC++ environment. Then, it was used as a separate and new constitutive model in DEM code (UDEC). Finally, the experimental Oolitic limestone rock behavior was simulated based on the developed

H, HM, and THM-C processes in natural barriers

Energy Technology Data Exchange (ETDEWEB)

Javeri, V.; Le, T.T.; Cui, Y.J.; Delage, P.; Li, X.J.; Wieczorek, K.; Jockwer, N.; Romero, E.; Lima, A.; Gens, A.; Li, X.L.; Francois, B.; Nuth, M.; Laloui, L.; Chen, W.; Jia, S.; Yu, H.; Wu, G.; Li, X.; Bernier, F.; Tan, X.; Wu, G.; Jia, S.; Giot, R.; Hoxha, D.; Giraud, A.; Homand, F.; Su, K.; Chavant, C.; Duveau, G.; Jia, Y.; Shao, J.F.; Peron, H.; Laloui, L.; Hueckel, T.; Hu, L.B.; Auvray, C.; Lequiller, B.; Cuisinier, O.; Ferber, V.; Cui, Y.J.; Deneele, D.; Uhlig, L.; Jobmann, M.; Polster, M.; Vaunat, J.; Garrite, B.; Wileveau, Y.; Sato, H.; Jacinto, A.; Sanchez, M.; Ledesma, A.; Morel, J.; Balland, C.; Armand, G.; Nguyen Minh, D.; Vales, F.; Pham, Q.T.; Gharbi, H.; Mokni, N.; Olivella, S.; Li, X.; Smets, St.; Valcke, E.; Karnland, O.; Nilsson, U.; Olsson, S.; Sellin, P.; Fernandez, A.M.; Melon, A.M.; Villar, M.V.; Turrero, M.J.; Garitte, B.; Guimaraes, L.D.N.; Gens, A.; Mayor, J.C.; Koliji, A.; Laloui, L.; Vulliet, L.; Hamdi, N.; Marzouki, A.; Srasra, E.; Cuss, R.J.; Harrington, J.F.; Noy, D.J.; Birchall, D.J.; Marschall, P.; Mallet, A.; Ababou, R.; Matray, J.M.; Renaud, V.; Maison, T.; Enachescu, C.; Frieg, B.; Rohs, St.; Paris, B.; Robinet, J.C.; Bui, T.D.; Barnichon, J.D.; Plas, F.; Klubertanz, G.; Folly, M.; Hufschmied, P.; Frank, E

2007-07-01

This session gathers 30 articles (posters) dealing with: the three Dimensional analyses of combined gas, heat and nuclide transport in a repository considering coupled thermo-hydro geomechanical processes; the experimental study on the thermo-hydro-mechanical behaviour of boom clay; hydraulic in-situ measurements in the Opalinus clay in the frame of a heater test performed at the Mont Terri URL; the hydro-mechanical behaviour of natural boom clay in controlled-suction tests; a constitutive approach to address the thermal and hydric impacts in the concept of deep radioactive waste repositories; the numerical analysis on stability of boom clay tunnel by shield construction; a thermo-hydro-mechanical model for clay in unsaturated conditions; the 3D modelling of TER experiment accounting for fully anisotropic thermo-poro-elastic behaviour; the hydro-mechanical modeling of shaft excavation in Meuse/Haute-Marne laboratory; the modelling of drying damage in engineered and natural clay barriers for nuclear waste disposal; the elasto-viscoplastic behaviour of Meuse/Haute-Marne argillite: laboratory tests and modelling; the long-term behaviour of a lime treated soil under percolation conditions; the stress redistribution and hydro-mechanical effects due to excavation and drilling operations in TER experiment; a thermodynamic model on swelling of bentonite buffer and backfill materials; the 3D analysis of a heating test in the Opalinus clay; the THM analysis of a 'mock-up' laboratory experiment using a double-structure expansive model; the measurement of the effect of re-confinement on rock properties around a slot; a laboratory Study of desaturation - re-saturation effects on a clay-stone; the deformation induced by dissolution of salts in porous media; the bentonite swelling pressure in pure water and saline solutions; the mineralogy and sealing properties of various bentonites and smectite-rich clay materials; the evaluation of the geochemical processes occurring

The Numerical Nuclear Reactor for High-Fidelity Integrated Simulation of Neutronic, Thermal-Hydraulic, and Thermo-Mechanical Phenomena

Energy Technology Data Exchange (ETDEWEB)

Kim, K. S.; Ju, H. G.; Jeon, T. H. and others

2005-03-15

A comprehensive high fidelity reactor core modeling capability has been developed for detailed analysis of current and advanced reactor designs as part of a US-ROK collaborative I-NERI project. High fidelity was accomplished by integrating highly refined solution modules for the coupled neutronic, thermal-hydraulic, and thermo-mechanical phenomena. Each solution module employs methods and models that are formulated faithfully to the first-principles governing the physics, real geometry, and constituents. Specifically, the critical analysis elements that are incorporated in the coupled code capability are whole-core neutron transport solution, ultra-fine-mesh computational fluid dynamics/heat transfer solution, and finite-element-based thermo-mechanics solution, all obtained with explicit (fuel pin cell level) heterogeneous representations of the components of the core. The vast computational problem resulting from such highly refined modeling is solved on massively parallel computers, and serves as the 'numerical nuclear reactor'. Relaxation of modeling parameters were also pursued to make problems run on clusters of workstations and PCs for smaller scale applications as well.

The Numerical Nuclear Reactor for High-Fidelity Integrated Simulation of Neutronic, Thermal-Hydraulic, and Thermo-Mechanical Phenomena

International Nuclear Information System (INIS)

Kim, K. S.; Ju, H. G.; Jeon, T. H. and others

2005-03-01

A comprehensive high fidelity reactor core modeling capability has been developed for detailed analysis of current and advanced reactor designs as part of a US-ROK collaborative I-NERI project. High fidelity was accomplished by integrating highly refined solution modules for the coupled neutronic, thermal-hydraulic, and thermo-mechanical phenomena. Each solution module employs methods and models that are formulated faithfully to the first-principles governing the physics, real geometry, and constituents. Specifically, the critical analysis elements that are incorporated in the coupled code capability are whole-core neutron transport solution, ultra-fine-mesh computational fluid dynamics/heat transfer solution, and finite-element-based thermo-mechanics solution, all obtained with explicit (fuel pin cell level) heterogeneous representations of the components of the core. The vast computational problem resulting from such highly refined modeling is solved on massively parallel computers, and serves as the 'numerical nuclear reactor'. Relaxation of modeling parameters were also pursued to make problems run on clusters of workstations and PCs for smaller scale applications as well

Couplings in multiphasic geo-materials: temperature and chemistry effects; Couplages dans les geomateriaux multiphasiques: effets de la temperature et de la chimie

Energy Technology Data Exchange (ETDEWEB)

Ghasemzadeh, H.

2006-05-15

Transport of chemical components in soil through water is the major cause of pollution of the soil. This transport takes place around landfills and nuclear waste storage areas, tailings and mine wastes, and so on. A great number of these sites are unsaturated of water and in some cases heat can change the fate of chemical species, that lead us to a coupled problem. In this dissertation, numerical simulation with an existent thermo-hydro-mechanical model and theoretical modeling and numerical simulation of transport and interactions of one chemical species in multiphase media are presented. Integrated THM model in the Code-Aster is presented. Excavation, engineering barrier and thermal load of waste nuclear storage well are modeled. Verification of model is presented with these simulations. A thermo-hydro-mechanical behaviour coupled with chemical phenomena is presented with a fully coupled method that water, gas, chemical species and soil skeleton were considered as constituents and corresponding unknowns are temperature, water pressure, gas pressure, chemical concentration and displacements. For each constituent, mass balance equation and linear momentum equation are written and solved simultaneously to find related unknowns. The results of this model have been compared with the theoretical and experimental results existing in the literature. Furthermore, results of some applications of this model are included. Some areas where further work is required are identified. In particular, there is a need to perform experiments to obtain necessary soil parameters to permit accurate modelling of the heat and contaminant transport in unsaturated soils. (author)

Hydro-chemo-mechanical coupling in sediments: Localized mineral dissolution

KAUST Repository

Cha, Minsu; Santamarina, Carlos

2016-01-01

Mineral dissolution is inherently a chemo-hydro-mechanical coupled process. Field evidence and laboratory results show that dissolution may localize and form open conduits in cohesive media such as carbonate rocks. This study focuses on the evolution of localized dissolution in soils (i.e., frictional and non-cohesive granular materials) under effective confining stresses. Experimental results show the development of localized dissolution (“pipe”) when a carbonate-quartz sand is subjected to reactive fluid flow: only loosely packed quartz grains remain within pipes, and the number of pipes decreases away from the inlet port. Concurrent shear wave velocity measurements show a decrease in stiffness during dissolution due to stress and fabric changes, and more complex signal codas anticipate the development of internal heterogeneity. The discrete element method is used to simulate localized vertical dissolution features in granular materials, under constant vertical stress and zero lateral strain far-field boundaries. As porosity increases along dissolution pipes, vertical load is transferred to the surrounding soils and marked force chains develop. In terms of equivalent stress, principal stress rotation takes place within pipes and the sediment reaches the Coulomb failure condition inside pipes and in the surrounding medium. Dissolution pipes alter the geo-plumbing of the subsurface, enhance fluid transport but limit the long term performance of storage systems, alter the fluid pressure and effective stress fields, soften the sediment and may trigger shear failures.

Hydro-chemo-mechanical coupling in sediments: Localized mineral dissolution

KAUST Repository

Cha, Minsu

2016-06-11

Mineral dissolution is inherently a chemo-hydro-mechanical coupled process. Field evidence and laboratory results show that dissolution may localize and form open conduits in cohesive media such as carbonate rocks. This study focuses on the evolution of localized dissolution in soils (i.e., frictional and non-cohesive granular materials) under effective confining stresses. Experimental results show the development of localized dissolution (“pipe”) when a carbonate-quartz sand is subjected to reactive fluid flow: only loosely packed quartz grains remain within pipes, and the number of pipes decreases away from the inlet port. Concurrent shear wave velocity measurements show a decrease in stiffness during dissolution due to stress and fabric changes, and more complex signal codas anticipate the development of internal heterogeneity. The discrete element method is used to simulate localized vertical dissolution features in granular materials, under constant vertical stress and zero lateral strain far-field boundaries. As porosity increases along dissolution pipes, vertical load is transferred to the surrounding soils and marked force chains develop. In terms of equivalent stress, principal stress rotation takes place within pipes and the sediment reaches the Coulomb failure condition inside pipes and in the surrounding medium. Dissolution pipes alter the geo-plumbing of the subsurface, enhance fluid transport but limit the long term performance of storage systems, alter the fluid pressure and effective stress fields, soften the sediment and may trigger shear failures.

Effect of Pore Pressure on Slip Failure of an Impermeable Fault: A Coupled Micro Hydro-Geomechanical Model

Science.gov (United States)

Yang, Z.; Juanes, R.

2015-12-01

The geomechanical processes associated with subsurface fluid injection/extraction is of central importance for many industrial operations related to energy and water resources. However, the mechanisms controlling the stability and slip motion of a preexisting geologic fault remain poorly understood and are critical for the assessment of seismic risk. In this work, we develop a coupled hydro-geomechanical model to investigate the effect of fluid injection induced pressure perturbation on the slip behavior of a sealing fault. The model couples single-phase flow in the pores and mechanics of the solid phase. Granular packs (see example in Fig. 1a) are numerically generated where the grains can be either bonded or not, depending on the degree of cementation. A pore network is extracted for each granular pack with pore body volumes and pore throat conductivities calculated rigorously based on geometry of the local pore space. The pore fluid pressure is solved via an explicit scheme, taking into account the effect of deformation of the solid matrix. The mechanics part of the model is solved using the discrete element method (DEM). We first test the validity of the model with regard to the classical one-dimensional consolidation problem where an analytical solution exists. We then demonstrate the ability of the coupled model to reproduce rock deformation behavior measured in triaxial laboratory tests under the influence of pore pressure. We proceed to study the fault stability in presence of a pressure discontinuity across the impermeable fault which is implemented as a plane with its intersected pore throats being deactivated and thus obstructing fluid flow (Fig. 1b, c). We focus on the onset of shear failure along preexisting faults. We discuss the fault stability criterion in light of the numerical results obtained from the DEM simulations coupled with pore fluid flow. The implication on how should faults be treated in a large-scale continuum model is also presented.

Development of a new code to solve hydro-mechanical coupling, shear failure and tensile failure due to hydraulic fracturing operations.

Science.gov (United States)

María Gómez Castro, Berta; De Simone, Silvia; Carrera, Jesús

2016-04-01

Nowadays, there are still some unsolved relevant questions which must be faced if we want to proceed to the hydraulic fracturing in a safe way. How much will the fracture propagate? This is one of the most important questions that have to be solved in order to avoid the formation of pathways leading to aquifer targets and atmospheric release. Will the fracture failure provoke a microseismic event? Probably this is the biggest fear that people have in fracking. The aim of this work (developed as a part of the EU - FracRisk project) is to understand the hydro-mechanical coupling that controls the shear of existing fractures and their propagation during a hydraulic fracturing operation, in order to identify the key parameters that dominate these processes and answer the mentioned questions. This investigation focuses on the development of a new C++ code which simulates hydro-mechanical coupling, shear movement and propagation of a fracture. The framework employed, called Kratos, uses the Finite Element Method and the fractures are represented with an interface element which is zero thickness. This means that both sides of the element lie together in the initial configuration (it seems a 1D element in a 2D domain, and a 2D element in a 3D domain) and separate as the adjacent matrix elements deform. Since we are working in hard, fragile rocks, we can assume an elastic matrix and impose irreversible displacements in fractures when rock failure occurs. The formulation used to simulate shear and tensile failures is based on the analytical solution proposed by Okada, 1992 and it is part of an iterative process. In conclusion, the objective of this work is to employ the new code developed to analyze the main uncertainties related with the hydro-mechanical behavior of fractures derived from the hydraulic fracturing operations.

Thermo-mechanical modeling of the obduction process based on the Oman ophiolite case

OpenAIRE

Duretz , Thibault; Agard , Philippe; Yamato , Philippe; Ducassou , Céline; Burov , Evgenii ,; Gerya , T. V.

2016-01-01

International audience; Obduction emplaces regional-scale fragments of oceanic lithosphere (ophiolites) over continental lithosphere margins of much lower density. For this reason, the mechanisms responsible for obduction remain enigmatic in the framework of plate tectonics. We present two-dimensional (2D) thermo-mechanical models of obduction and investigate possible dynamics and physical controls of this process. Model geometry and boundary conditions are based on available geological and g...

Investigation of multi-stage cold forward extrusion process using coupled thermo-mechanical finite element analysis

Science.gov (United States)

Görtan, Mehmet Okan

2018-05-01

Cold extrusion processes are distinguished by their low material usage as well as great efficiency in the production of mid-range and large component series. Although majority of the cold extruded parts are produced using die systems containing multiple forming stages, this subject has rarely been investigated so far. Therefore, the characteristics of multi-stage cold forward rod extrusion is studied in the current work using thermo-mechanically coupled finite element (FE) analysis. A case hardening steel, 16MnCr5 (1.7131) was used as experimental material. Its strain, strain rate and temperature dependent mechanical characteristics were determined using compression testing and modeled in FE simulations via a Johnson-Cook material model. Friction coefficients for the same material while in contact with a tool steel (1.2379) were determined dependent on temperature and contact pressure using sliding compression test (SCT) and modeled by an adaptive friction model developed by the author. In the first set of simulations, rod material with a diameter of 14.9 mm was extruded down to a diameter of 9.6 mm in a single step using three different die opening angles (2α); 20°, 40° and 60°. In the second set of investigations, the same rod was reduced first to 12 mm and then to 9.6 mm in two steps within the same forming die. Press forces, contact normal stresses between extruded material and forming die, material temperature and axial stresses are compared in these two set of simulations and the differences are discussed.

Multi-scale modelling of the physicochemical-mechanical coupling of fuel behaviour at high temperature in pressurized water reactors

International Nuclear Information System (INIS)

Julien, Jerome

2008-01-01

Within the frame of the problematic of pellet-sheath interaction in a nuclear fuel rod, a good description of the fuel thermo-mechanical behaviour is required. This research thesis reports the coupling of physics-chemistry (simulation of gas transfers between different cavities) and mechanics (assessment of fuel viscoplastic strains). A new micromechanical model is developed which uses a multi-scale approach to describe the evolution of the double population of cavities (cavities with two different scales) while taking internal pressures as well as the fuel macroscopic viscoplastic behaviour into account. The author finally describes how to couple this micromechanical mode to physics-chemistry models [fr

On nonlinear thermo-electro-elasticity.

Science.gov (United States)

Mehnert, Markus; Hossain, Mokarram; Steinmann, Paul

2016-06-01

Electro-active polymers (EAPs) for large actuations are nowadays well-known and promising candidates for producing sensors, actuators and generators. In general, polymeric materials are sensitive to differential temperature histories. During experimental characterizations of EAPs under electro-mechanically coupled loads, it is difficult to maintain constant temperature not only because of an external differential temperature history but also because of the changes in internal temperature caused by the application of high electric loads. In this contribution, a thermo-electro-mechanically coupled constitutive framework is proposed based on the total energy approach. Departing from relevant laws of thermodynamics, thermodynamically consistent constitutive equations are formulated. To demonstrate the performance of the proposed thermo-electro-mechanically coupled framework, a frequently used non-homogeneous boundary-value problem, i.e. the extension and inflation of a cylindrical tube, is solved analytically. The results illustrate the influence of various thermo-electro-mechanical couplings.

Thermo-Hydro-Mechanical Characterisation of the Bentonite of a Simulated HLW Repository after Five Years Operation ( In Situ Test of the FEBEX Project)

Energy Technology Data Exchange (ETDEWEB)

Villar, M. V.

2004-07-01

After five years of operation, heater 1 of the FEBEX experimental at the Grimsel Test Sites was switched off in February 2002. Following cooling of the system, the bentonite barrier was dismantled and the heater extracted. During dismantling many bentonite samples were taken. Several determinations were carried out in these samples with the aim of: (1) characterise the actual state of the bentonite and (2) determine the possible changes in its properties occurred during the experiment. The results of the thermo-hydro-mechanical characterisation performed at CIEMAT are reported and analysed. The distribution of water content and dry density of the bentonite in vertical sections presents axial symmetry. The construction gaps of the barrier have been filled by the expansion of the bentonite. The water retention capacity, the hydraulic conductivity and the swelling capacity of the samples from Grimsel have not irreversible changed. The pre consolidation pressure of the Grimsel samples has decreased due to the microstructural changes associated to the volume increase experienced during hydration. The thermal conductivity is higher for the bentonite blocks of the external ring of the barrier. (Author)

Thermo-Hydro-Mechanical Characterisation of the Bentonite of a Simulated HLW Repository after Five Years Operation ( In Situ Test of the FEBEX Project)

International Nuclear Information System (INIS)

Villar, M. V.

2004-01-01

After five years of operation, heater 1 of the FEBEX experimental at the Grimsel Test Sites was switched off in February 2002. Following cooling of the system, the bentonite barrier was dismantled and the heater extracted. During dismantling many bentonite samples were taken. Several determinations were carried out in these samples with the aim of: (1) characterise the actual state of the bentonite and (2) determine the possible changes in its properties occurred during the experiment. The results of the thermo-hydro-mechanical characterisation performed at CIEMAT are reported and analysed. The distribution of water content and dry density of the bentonite in vertical sections presents axial symmetry. The construction gaps of the barrier have been filled by the expansion of the bentonite. The water retention capaciaty, the hydraulic conductivity and the swelling capacity of the samples from Grimsel have not irreversible changed. The preconsolidation pressure of the Grimsel samples has decreased due to the microstructural changes asswociated to the volume increase experienced during hydration. The thermal conductivity is higher for the bentonite blocks of the external ring of the barrier. (Author)

Simulated evolution of fractures and fracture networks subject to thermal cooling: A coupled discrete element and heat conduction model

Energy Technology Data Exchange (ETDEWEB)

Huang, Hai; Plummer, Mitchell; Podgorney, Robert

2013-02-01

Advancement of EGS requires improved prediction of fracture development and growth during reservoir stimulation and long-term operation. This, in turn, requires better understanding of the dynamics of the strongly coupled thermo-hydro-mechanical (THM) processes within fractured rocks. We have developed a physically based rock deformation and fracture propagation simulator by using a quasi-static discrete element model (DEM) to model mechanical rock deformation and fracture propagation induced by thermal stress and fluid pressure changes. We also developed a network model to simulate fluid flow and heat transport in both fractures and porous rock. In this paper, we describe results of simulations in which the DEM model and network flow & heat transport model are coupled together to provide realistic simulation of the changes of apertures and permeability of fractures and fracture networks induced by thermal cooling and fluid pressure changes within fractures. Various processes, such as Stokes flow in low velocity pores, convection-dominated heat transport in fractures, heat exchange between fluid-filled fractures and solid rock, heat conduction through low-permeability matrices and associated mechanical deformations are all incorporated into the coupled model. The effects of confining stresses, developing thermal stress and injection pressure on the permeability evolution of fracture and fracture networks are systematically investigated. Results are summarized in terms of implications for the development and evolution of fracture distribution during hydrofracturing and thermal stimulation for EGS.

Fundamental Processes of Coupled Radiation Damage and Mechanical Behavior in Nuclear Fuel Materials for High Temperature Reactors

Energy Technology Data Exchange (ETDEWEB)

Phillpot, Simon; Tulenko, James

2011-09-08

The objective of this work has been to elucidate the relationship among microstructure, radiation damage and mechanical properties for nuclear fuel materials. As representative nuclear materials, we have taken an hcp metal (Mg as a generic metal, and Ti alloys for fast reactors) and UO2 (representing fuel). The degradation of the thermo-mechanical behavior of nuclear fuels under irradiation, both the fissionable material itself and its cladding, is a longstanding issue of critical importance to the nuclear industry. There are experimental indications that nanocrystalline metals and ceramics may be more resistant to radiation damage than their coarse-grained counterparts. The objective of this project look at the effect of microstructure on radiation damage and mechanical behavior in these materials. The approach to be taken was state-of-the-art, large-scale atomic-level simulation. This systematic simulation program of the effects of irradiation on the structure and mechanical properties of polycrystalline Ti and UO2 identified radiation damage mechanisms. Moreover, it will provided important insights into behavior that can be expected in nanocrystalline microstructures and, by extension, nanocomposites. The fundamental insights from this work can be expected to help in the design microstructures that are less susceptible to radiation damage and thermomechanical degradation.

Fundamental Processes of Coupled Radiation Damage and Mechanical Behavior in Nuclear Fuel Materials for High Temperature Reactors

International Nuclear Information System (INIS)

Phillpot, Simon; Tulenko, James

2011-01-01

The objective of this work has been to elucidate the relationship among microstructure, radiation damage and mechanical properties for nuclear fuel materials. As representative nuclear materials, we have taken an hcp metal (Mg as a generic metal, and Ti alloys for fast reactors) and UO2 (representing fuel). The degradation of the thermo-mechanical behavior of nuclear fuels under irradiation, both the fissionable material itself and its cladding, is a longstanding issue of critical importance to the nuclear industry. There are experimental indications that nanocrystalline metals and ceramics may be more resistant to radiation damage than their coarse-grained counterparts. The objective of this project look at the effect of microstructure on radiation damage and mechanical behavior in these materials. The approach to be taken was state-of-the-art, large-scale atomic-level simulation. This systematic simulation program of the effects of irradiation on the structure and mechanical properties of polycrystalline Ti and UO2 identified radiation damage mechanisms. Moreover, it will provided important insights into behavior that can be expected in nanocrystalline microstructures and, by extension, nanocomposites. The fundamental insights from this work can be expected to help in the design microstructures that are less susceptible to radiation damage and thermomechanical degradation.

The numerical high cycle fatigue damage model of fillet weld joint under weld-induced residual stresses

Science.gov (United States)

Nguyen Van Do, Vuong

2018-04-01

In this study, a development of nonlinear continuum damage mechanics (CDM) model for multiaxial high cycle fatigue is proposed in which the cyclic plasticity constitutive model has been incorporated in the finite element (FE) framework. T-joint FE simulation of fillet welding is implemented to characterize sequentially coupled three-dimensional (3-D) of thermo-mechanical FE formulation and simulate the welding residual stresses. The high cycle fatigue damage model is then taken account into the fillet weld joints under the various cyclic fatigue load types to calculate the fatigue life considering the residual stresses. The fatigue crack initiation and the propagation in the present model estimated for the total fatigue is compared with the experimental results. The FE results illustrated that the proposed high cycle fatigue damage model in this study could become a powerful tool to effectively predict the fatigue life of the welds. Parametric studies in this work are also demonstrated that the welding residual stresses cannot be ignored in the computation of the fatigue life of welded structures.

A new coupled elastoplastic damage model for clay-stone and its parameter identification

International Nuclear Information System (INIS)

Jia, S.P.; Chen, W.Z.; Yu, H.D.; Li, X.L.; Sillen, X.

2010-01-01

Document available in extended abstract form only. In Belgium, the Boom Clay is considered as a potential host rock for the geological disposal of the high level nuclear waste and is intensively studied from hydro-mechanical point of view. Laboratory tests on Boom clay shown that the Boom clay presents very complex stress strain behaviour. Undrained triaxial tests indicated often a hardening behaviour at small deformation and softening at larger deformation. It is not easy to give an explicit function to describe the stress-strain behaviour under triaxial stress state. The mechanical characteristics are obviously affected by the porosity, fractures growth, water content, and stress, etc., four stages can be usually distinguished from the stress-strain curve of Boom Clay, named as OA, AB, BC and CD. 1) Stage OA, the relation between stress and strain is linear. This stage is elastic state, and point A is called as yield strength σ c0 . 2) Stage AB, the weak fractures in the rock appear, develop and cumulate gradually. Point B is called peak strength σ cu . 3) Stage BC, peak strength is reached and stress reduces with the increasing of strain, up to the residual strength. This stage is called strain softening and point C is the residual strength σ cr . The axial pressure causes the fracture developing and strength reducing. 4) Stage CD, the final strength doesn't reduce obviously with the development of plastic deformation. This stage is called plastic flow. Obviously, The conventional elasto-plastic constitutive model can not describe the mechanical behaviours of Boom Clay. Based on damage mechanics theory, an new elasto-plastic damage constitutive model is put forward and applied to Boom Clay, which can describe the complex stress-strain behaviour of clay. It is described as follows: stage OA with an elastic model, stage AB with elastic damage model, stage BC and stage CD with plastic damage model. The complete process curve of stress-strain can be divided

Analysis of Thermo-Acoustic Emission from Damage in Composite Laminates under Thermal Cyclic Loading

International Nuclear Information System (INIS)

Kim, Young Bok; Min, Dae Hong; Lee, Deok Bo; Choi, Nak Sam

2001-01-01

An investigation on nondestructive evaluation of thermal stress-reduced damage in the composite laminates (3mm in thickness and [+45 6 /-45 6 ] S lay-up angles) has been performed using the thermo-acoustic emission technique. Reduction of thermo-AE events due to repetitive thermal load cycles showed a Kaiser effect. An analysis of the thermo-AE behavior determined the stress free temperature of composite laminates. Fiber fracture and matrix cracks were observed using the optical microscopy, scanning electron microscopy and ultrasonic C-sean. Short-Time Fourier Transform of thermo-AE signals offered the time-frequency characteristics which might classify the thermo-AE as three different types to estimate the damage processes of the composites

Modeling of excavation induced coupled hydraulic-mechanical processes in claystone

Energy Technology Data Exchange (ETDEWEB)

Massmann, Jobst

2009-07-01

Concepts for the numerical modeling of excavation induced processes in claystone are investigated. The study has been motivated by the international discussion on the adequacy of claystone as a potential host rock for a final repository of radioactive waste. The processes, which could impact the safety of such a repository, are manifold and strongly interacting. Thus, a multiphysics approach is needed, regarding solid mechanics and fluid mechanics within a geological context. A coupled modeling concept is therefore indispensable. Based on observations and measurements at an argillaceous test site (the underground laboratory Tournemire, operated by the Institute of Radioprotection and Nuclear Safety, France) the modeling concept is developed. Two main processes constitute the basis of the applied model: deformation (linear elasticity considering damage) and fluid flow (unsaturated one-phase flow). Several coupling phenomena are considered: Terzaghi 's effective stress concept, mass conservation of the liquid in a deformable porous media, drying induced shrinkage, and a permeability which depends on deformation and damage. In addition, transversely isotropic material behavior is considered. The numerical simulations are done with the finite element code RockFlow, which is extended to include: an orthotropic non-linear shrinkage model, a continuum damage model, and an orthotropic permeability model. For these new methods the theory and a literature review are presented, followed by applications, which illustrate the capability to model excavation induced processes in principle. In a comprehensive case study, the modeling concept is used to simulate the response of the Tournemire argillite to excavation. The results are compared with observations and measurements of three different excavations (century old tunnel, two galleries excavated in 1996 and 2003). In summary, it can be concluded that the developed model concept provides a prediction of the excavation induced

Modeling of excavation induced coupled hydraulic-mechanical processes in claystone

International Nuclear Information System (INIS)

Massmann, Jobst

2009-01-01

Concepts for the numerical modeling of excavation induced processes in claystone are investigated. The study has been motivated by the international discussion on the adequacy of claystone as a potential host rock for a final repository of radioactive waste. The processes, which could impact the safety of such a repository, are manifold and strongly interacting. Thus, a multiphysics approach is needed, regarding solid mechanics and fluid mechanics within a geological context. A coupled modeling concept is therefore indispensable. Based on observations and measurements at an argillaceous test site (the underground laboratory Tournemire, operated by the Institute of Radioprotection and Nuclear Safety, France) the modeling concept is developed. Two main processes constitute the basis of the applied model: deformation (linear elasticity considering damage) and fluid flow (unsaturated one-phase flow). Several coupling phenomena are considered: Terzaghi 's effective stress concept, mass conservation of the liquid in a deformable porous media, drying induced shrinkage, and a permeability which depends on deformation and damage. In addition, transversely isotropic material behavior is considered. The numerical simulations are done with the finite element code RockFlow, which is extended to include: an orthotropic non-linear shrinkage model, a continuum damage model, and an orthotropic permeability model. For these new methods the theory and a literature review are presented, followed by applications, which illustrate the capability to model excavation induced processes in principle. In a comprehensive case study, the modeling concept is used to simulate the response of the Tournemire argillite to excavation. The results are compared with observations and measurements of three different excavations (century old tunnel, two galleries excavated in 1996 and 2003). In summary, it can be concluded that the developed model concept provides a prediction of the excavation induced

Modeling of excavation induced coupled hydraulic-mechanical processes in claystone

Energy Technology Data Exchange (ETDEWEB)

Massmann, Jobst

2009-07-01

Concepts for the numerical modeling of excavation induced processes in claystone are investigated. The study has been motivated by the international discussion on the adequacy of claystone as a potential host rock for a final repository of radioactive waste. The processes, which could impact the safety of such a repository, are manifold and strongly interacting. Thus, a multiphysics approach is needed, regarding solid mechanics and fluid mechanics within a geological context. A coupled modeling concept is therefore indispensable. Based on observations and measurements at an argillaceous test site (the underground laboratory Tournemire, operated by the Institute of Radioprotection and Nuclear Safety, France) the modeling concept is developed. Two main processes constitute the basis of the applied model: deformation (linear elasticity considering damage) and fluid flow (unsaturated one-phase flow). Several coupling phenomena are considered: Terzaghi 's effective stress concept, mass conservation of the liquid in a deformable porous media, drying induced shrinkage, and a permeability which depends on deformation and damage. In addition, transversely isotropic material behavior is considered. The numerical simulations are done with the finite element code RockFlow, which is extended to include: an orthotropic non-linear shrinkage model, a continuum damage model, and an orthotropic permeability model. For these new methods the theory and a literature review are presented, followed by applications, which illustrate the capability to model excavation induced processes in principle. In a comprehensive case study, the modeling concept is used to simulate the response of the Tournemire argillite to excavation. The results are compared with observations and measurements of three different excavations (century old tunnel, two galleries excavated in 1996 and 2003). In summary, it can be concluded that the developed model concept provides a prediction of the excavation

Characterisation of Ground Thermal and Thermo-Mechanical Behaviour for Shallow Geothermal Energy Applications

Directory of Open Access Journals (Sweden)

Ana Vieira

2017-12-01

Full Text Available Increasing use of the ground as a thermal reservoir is expected in the near future. Shallow geothermal energy (SGE systems have proved to be sustainable alternative solutions for buildings and infrastructure conditioning in many areas across the globe in the past decades. Recently novel solutions, including energy geostructures, where SGE systems are coupled with foundation heat exchangers, have also been developed. The performance of these systems is dependent on a series of factors, among which the thermal properties of the soil play a major role. The purpose of this paper is to present, in an integrated manner, the main methods and procedures to assess ground thermal properties for SGE systems and to carry out a critical review of the methods. In particular, laboratory testing through either steady-state or transient methods are discussed and a new synthesis comparing results for different techniques is presented. In situ testing including all variations of the thermal response test is presented in detail, including a first comparison between new and traditional approaches. The issue of different scales between laboratory and in situ measurements is then analysed in detail. Finally, the thermo-hydro-mechanical behaviour of soil is introduced and discussed. These coupled processes are important for confirming the structural integrity of energy geostructures, but routine methods for parameter determination are still lacking.

Electro-thermo-mechanical coupling analysis of deep drawing with resistance heating for aluminum matrix composites sheet

Science.gov (United States)

Zhang, Kaifeng; Zhang, Tuoda; Wang, Bo

2013-05-01

Recently, electro-plastic forming to be a focus of attention in materials hot processing research area, because it is a sort of energy-saving, high efficient and green manufacturing technology. An electro-thermo-mechanical model can be adopted to carry out the sequence simulation of aluminum matrix composites sheet deep drawing via electro-thermal coupling and thermal-mechanical coupling method. The first step of process is resistance heating of sheet, then turn off the power, and the second step is deep drawing. Temperature distribution of SiCp/2024Al composite sheet by resistance heating and sheet deep drawing deformation were analyzed. During the simulation, effect of contact resistances, temperature coefficient of resistance for electrode material and SiCp/2024Al composite on temperature distribution were integrally considered. The simulation results demonstrate that Sicp/2024Al composite sheet can be rapidly heated to 400° in 30s using resistances heating and the sheet temperature can be controlled by adjusting the current density. Physical properties of the electrode materials can significantly affect the composite sheet temperature distribution. The temperature difference between the center and the side of the sheet is proportional to the thermal conductivity of the electrode, the principal cause of which is that the heat transfers from the sheet to the electrode. SiCp/2024Al thin-wall part can be intactly manufactured at strain rate of 0.08s-1 and the sheet thickness thinning rate is limited within 20%, which corresponds well to the experimental result.

Coupled transient thermo-fluid/thermal-stress analysis approach in a VTBM setting

International Nuclear Information System (INIS)

Ying, A.; Narula, M.; Zhang, H.; Abdou, M.

2008-01-01

A virtual test blanket module (VTBM) has been envisioned as a utility to aid in streamlining and optimizing the US ITER TBM design effort by providing an integrated multi-code, multi-physics modeling environment. Within this effort, an integrated simulation approach is being developed for TBM design calculations and performance evaluation. Particularly, integrated thermo-fluid/thermal-stress analysis is important for enabling TBM design and performance calculations. In this paper, procedures involved in transient coupled thermo-fluid/thermal-stress analysis are investigated. The established procedure is applied to study the impact of pulsed operational phenomenon on the thermal-stress response of the TBM first wall. A two-way coupling between the thermal strain and temperature field is also studied, in the context of a change in thermal conductivity of the beryllium pebble bed in a solid breeder blanket TBM due to thermal strain. The temperature field determines the thermal strain in beryllium, which in turn changes the temperature field. Iterative thermo-fluid/thermal strain calculations have been applied to both steady-state and pulsed operation conditions. All calculations have been carried out in three dimensions with representative MCAD models, including all the TBM components in their entirety

Chemo-hydro-mechanical behaviour of unsaturated clays

International Nuclear Information System (INIS)

Mokni, N.; Olivella, S.; Alonso, E.E.; Romero, E.

2010-01-01

Document available in extended abstract form only. Understanding of the chemical effects on clays is essential for many problems ranging from pollution studies and waste-containment. Several studies examined the effect of changes in pore fluid composition on the mechanical and hydraulic properties. Volume changes (contraction/ expansion) have been measured on clay specimens upon exposure to salt solutions or permeation with organic liquids. Moreover, it was shown that permeation of clay with brine induces an increase of the shear strength. In addition, several models have been proposed to describe the chemo-mechanical behaviour of saturated clays under saturated conditions. A new chemo-hydro-mechanical model for unsaturated clays is under development. The chemo-mechanical effects are described within an elasto-plastic framework using the concept that chemical effects act on the plastic properties by increasing or decreasing the pre-consolidation stress. The model is based on the distinction within the material of a microstructural and a macro-structural levels. Chemical loading has a significant effect on the microstructure. The negative pressure associated with the capillary water plays its role in the interconnected macro pores. By adopting simple assumptions concerning the coupling between the two levels it is intended to reproduce the features of the behaviour of unsaturated clays when there is a change in pore fluid composition (increase or decrease of concentration). A yield surface which defines the set of yield pre-consolidation stress values, for each associated capillary suction and concentration of pore fluid should be defined. In addition, the behaviour of clays under unsaturated condition and the behaviour at full saturation under chemical loading represent two limiting cases of the framework. Studies on the compatibility of Boom Clay with large amounts of nitrate- bearing bituminized radioactive waste have recently raised a particular interest on the

Optimization in Friction Stir Welding - With Emphasis on Thermo-mechanical Aspects

DEFF Research Database (Denmark)

Tutum, Cem Celal

combined with classical single-objective and evolutionary multi-objective optimization algorithms (i.e. SQP and NSGA-II), to find the optimum process parameters (heat input, rotational and traverse welding speeds) that would result in favorable thermo-mechanical conditions for the process.......This book deals with the challenging multidisciplinary task of combining variant thermal and thermo-mechanical simulations for the manufacturing process of friction stir welding (FSW) with numerical optimization techniques in the search for optimal process parameters. The FSW process...... is characterized by multiphysics involving solid material flow, heat transfer, thermal softening, recrystallization and the formation of residual stresses. Initially, the thermal models were addressed since they in essence constitute the basis of all other models of FSW. Following this, several integrated thermo-mechanical...

Coupling of a reservoir model and of a poro-mechanical model. Application to the study of the compaction of petroleum reservoirs and of the associated subsidence; Couplage d'un modele de gisement et d'un modele mecanique. Application a l'etude de la compaction des reservoirs petroliers et de la subsidence associee

Energy Technology Data Exchange (ETDEWEB)

Bevillon, D.

2000-11-30

The aim of this study is to provide a better description of the rock contribution to fluid flows in petroleum reservoirs. The production of oil/gas in soft highly compacting reservoirs induces important reduction of the pore volume, which increases oil productivity. This compaction leads to undesirable effects such as surface subsidence or damage of well equipment. Analysis of compaction and subsidence can be performed using either engineering reservoir models or coupled poro-mechanical models. Poro-mechanical model offers a rigorous mechanical framework, but does not permit a complete description of the fluids. The reservoir model gives a good description of the fluid phases, but the description of the mechanic phenomenon is then simplified. To satisfy the set of equations (mechanical equilibrium and diffusivity equations), two simulators can be used together sequentially. Each of the two simulators solves its own system independently, and information passed both directions between simulators. This technique is usually referred to the partially coupled scheme. In this study, reservoir and hydro-mechanical simulations show that reservoir theory is not a rigorous framework to represent the evolution of the high porous rocks strains. Then, we introduce a partially coupled scheme that is shown to be consistent and unconditionally stable, which permits to describe correctly poro-mechanical theory in reservoir models. (author)

Comparative analysis of coupled creep-damage model implementations and application

International Nuclear Information System (INIS)

Bhandari, S.; Feral, X.; Bergheau, J.M.; Mottet, G.; Dupas, P.; Nicolas, L.

1998-01-01

Creep rupture of a reactor pressure vessel in a severe accident occurs after complex load and temperature histories leading to interactions between creep deformations, stress relaxation, material damaging and plastic instability. The concepts of continuous damage introduced by Kachanov and Robotnov allow to formulate models coupling elasto-visco-plasticity and damage. However, the integration of such models in a finite element code creates some difficulties related to the strong non-linearity of the constitutive equations. It was feared that different methods of implementation of such a model might lead to different results which, consequently, might limit the application and usefulness of such a model. The Commissariat a l'Energie Atomique (CEA), Electricite de France (EDF) and Framasoft (FRA) have worked out numerical solutions to implement such a model in respectively CASTEM 2000, ASTER and SYSTUS codes. A ''benchmark'' was set up, chosen on the basis of a cylinder studied in the programme ''RUPTHER''. The aim of this paper is not to enter into the numerical details of the implementation of the model, but to present the results of the comparative study made using the three codes mentioned above, on a case of engineering interest. The results of the coupled model will also be compared to an uncoupled model to evaluate differences one can obtain between a simple uncoupled model and a more sophisticated coupled model. The main conclusion drawn from this study is that the different numerical implementations used for the coupled damage-visco-plasticity model give quite consistent results. The numerical difficulty inherent to the integration of the strongly non-linear constitutive equations have been resolved using Runge-Kutta or mid-point rule. The usefulness of the coupled model comes from the fact the uncoupled model leads to too conservative results, at least in the example treated and in particular for the uncoupled analysis under the hypothesis of the small

Development of Hydro-Mechanical Deep Drawing

DEFF Research Database (Denmark)

Zhang, Shi-Hong; Danckert, Joachim

1998-01-01

The hydro-mechanical deep-drawing process is reviewed in this article. The process principles and features are introduced and the developments of the hydro-mechanical deep-drawing process in process performances, in theory and in numerical simulation are described. The applications are summarized....... Some other related hydraulic forming processes are also dealt with as a comparison....

Hydro-mechanical processes

Energy Technology Data Exchange (ETDEWEB)

Laouafa, F.; Kazmierczak, J.B. [Institut National de l' Environnement Industriel et des Risques (INERIS), Parc Technologique ALATA, 60 - Verneuil en Halatte (France); Armand, G. [Agence Nationale pour la Gestion des Dechets Radioactifs, Lab. de Souterrain de Meuse/Haute-Marne, 55 - Bure (France); Vaunat, J. [Catalonia UPC- Technical Univ., Barcelona (Spain); Jobmann, M.; Polster, M. [DBETEC- DBE Technology GmbH, Peine (Germany); Su, K.; Lebon, P.; Plas, F.; Armand, G.; Abou-Chakra Guery, A.; Cormery, F.; Shao, J.F.; Kondo, D. [ANDRA - Agence Nationale pour la Gestion des Dechets Radioactifs, 92 - Chatenay Malabry (France); Souley, M. [Institut National de l' Environnement Industriel et des Risques (INERIS), 54 - Nancy (France); Coll, C.; Charlier, R.; Collin, F.; Gerard, P. [Liege Univ., Dept. ArGEnCo (Belgium); Xiang Ling, Li [ESV EURIDICE, SCK.CEN, Belgian Nuclear Research Centre, Mol (Belgium); Collin, F. [Liege Univ., Charge de Recherches FNRS (Belgium); Pellet, F.L.; Fabre, G. [University Joseph Fourier, Laboratory 3S-R, 38 - Grenoble (France); Garcia-Sineriz, J.L.; Rey, M. [AITEMIN - Asociacion para la Investigacion y Desarrollo Industrial de los Recursos Naturales, Madrid (Spain); Mayor, J.C. [ENRESA - Empresa Nacional des Residuos Radioactivos, Madrid (Spain); Castellanos, E.; Romero, E.; Lloret, A.; Gens, A. [Catalunya Univ. Politecnica, UPC (Spain); Villar, M.V. [CIEMAT - Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas, Madrid (Spain); Chambon, R. [Laboratoire 3S, UJF-INPG-CNRS, 38 - Grenoble (France); Czaikowski, O.; Lux, K.H. [Clausthal Univ. of Technology, Professorship for Waste Disposal and Geomechanics, Clausthal-Zellerfeld (Germany); Van Geet, M.; Bastiaens, W.; Volckaert, G.; Weetjens, E.; Sillen, X. [SCK-CEN, Waste and Disposal dept., Mol (Belgium); ONDRAF/NIRAS, Brussel (Belgium); Imbert, Ch. [CEA Saclay, Dept. de Physico-Chimie (DPC/SCCME/LECBA), 91 - Gif sur Yvette (France)] [and others

2007-07-01

This session gathers 13 articles dealing with: three-dimensional and time stepping modelling of the whole Meuse/Haute-Marne ANDRA URL (F. Laouafa, J.B. Kazmierczak, G. Armand, J. Vaunat, M. Jobmann, M. Polster); a constitutive model for a deep argillaceous rock using Hoek-Brown criteria (K. Su, C. Chavant, M. Souley); the long term behaviour of the Boom clay: influence of viscosity on the pore pressure distribution (C. Coll, R. Charlier, X.L. Li, F. Collin); the microstructural changes induced by viscoplastic deformations in argillaceous rocks (F.L. Pellet, G. Fabre, K. Su, P. Lebon); the engineered barrier experiment at Mont Terri rock laboratory (J.L. Garcia-Sineriz, M. Rey, J.C. Mayor); the chemical influence on the Hydro-Mechanical behaviour of high-density FEBEX bentonite (E. Castellanos, M.V. Villar, E. Romero, A. Lloret, A. Gens); the influence of water exchanges on the gallery convergence (P. Gerard, R. Charlier, R. Chambon, F. Collin); a new method for ageing resistant storage of argillaceous rock samples to achieve reproducible experimental results even after long intermediate storage times (O. Czaikowski, K.H. Lux); the installation and evaluation of a large-scale in-situ shaft seal experiment in Boom clay the RESEAL project M. Van Geet, W. Bastiaens, G. Volckaert, E. Weetjens, X. Sillen, A. Gens, M.V. Villar, Ch. Imbert, M. Filippi, F. Plas); the hydro-Mechanical response of the Callovo-Oxfordian mud-stone around a deep vertical drift (J. Vaunat, B. Garitte, A. Gens, K. Su, G. Armand); the sensitivity of total stress to changes in externally applied water pressure in KBS-3 buffer bentonite (J.F. Harrington, D.J. Birchall, P. Sellin); the comparison of the poro-elastic behavior of Meuse/Haute Marne and Tournemire argillites: effect of loading and saturation states (E. Bemer, A. Noiret, F. Homand, A. Rejeb); and the multi-scale modelling of the argillites mechanical behaviour (A. Abou-Chakra Guery, F. Cormery, K. Su, J.F. Shao, D. Kondo)

Thermo-mechanical constitutive modeling of unsaturated clays based on the critical state concepts

Directory of Open Access Journals (Sweden)

Saeed Tourchi

2015-04-01

Full Text Available A thermo-mechanical constitutive model for unsaturated clays is constructed based on the existing model for saturated clays originally proposed by the authors. The saturated clays model was formulated in the framework of critical state soil mechanics and modified Cam-clay model. The existing model has been generalized to simulate the experimentally observed behavior of unsaturated clays by introducing Bishop's stress and suction as independent stress parameters and modifying the hardening rule and yield criterion to take into account the role of suction. Also, according to previous studies, an increase in temperature causes a reduction in specific volume. A reduction in suction (wetting for a given confining stress may induce an irreversible volumetric compression (collapse. Thus an increase in suction (drying raises a specific volume i.e. the movement of normal consolidation line (NCL to higher values of void ratio. However, some experimental data confirm the assumption that this reduction is dependent on the stress level of soil element. A generalized approach considering the effect of stress level on the magnitude of clays thermal dependency in compression plane is proposed in this study. The number of modeling parameters is kept to a minimum, and they all have clear physical interpretations, to facilitate the usefulness of model for practical applications. A step-by-step procedure used for parameter calibration is also described. The model is finally evaluated using a comprehensive set of experimental data for the thermo-mechanical behavior of unsaturated soils.

Effect of Nb2O5 doping on improving the thermo-mechanical stability of sealing interfaces for solid oxide fuel cells.

Science.gov (United States)

Zhang, Qi; Du, Xinhang; Tan, Shengwei; Tang, Dian; Chen, Kongfa; Zhang, Teng

2017-07-13

Nb 2 O 5 is added to a borosilicate sealing system to improve the thermo-mechanical stability of the sealing interface between the glass and Fe-Cr metallic interconnect (Crofer 22APU) in solid oxide fuel cells (SOFCs). The thermo-mechanical stability of the glass/metal interface is evaluated experimentally as well as by using a finite element analysis (FEA) method. The sealing glass doped with 4 mol.% Nb 2 O 5 shows the best thermo-mechanical stability, and the sealing couple of Crofer 22APU/glass/GDC (Gd 0.2 Ce 0.8 O 1.9 ) remains intact after 50 thermal cycles. In addition, all sealing couples show good joining after being held at 750 °C for 1000 h. Moreover, the possible mechanism on the thermo-mechanical stability of sealing interface is investigated in terms of stress-based and energy-based perspectives.

An approach for the modeling of interface-body coupled nonlocal damage

Directory of Open Access Journals (Sweden)

J. Toti

2010-04-01

Full Text Available Fiber Reinforced Plastic (FRP can be used for strengthening concrete or masonry constructions. One of the main problem in the use of FRP is the possible detachment of the reinforcement from the support material. This paper deals with the modeling of the FRP-concrete or masonry damage interface, accounting for the coupling occurring between the degradation of the cohesive material and the FRP detachment. To this end, a damage model is considered for the quasi-brittle material. In order to prevent strain localization and strong mesh sensitivity of the solution, an integral-type of nonlocal model based on the weighted spatial averaging of a strain-like quantity is developed. Regarding the interface, the damage is governed by the relative displacement occurring at bond. A suitable interface model which accounts for the mode I, mode II and mixed mode of damage is developed. The coupling between the body damage and the interface damage is performed computing the body damage on the bond surface. Numerical examples are presented.

Multiphasic fluid models and multicomponents reactive transport in porous media

International Nuclear Information System (INIS)

Juncosa, R.

2001-01-01

The design and construction of repositories for toxic waste, such as radioactive waste of medium and high activity, require tools, that will enable us to predict how the system will behave. The rational behind this Dissertation is based precisely on developing numerical models to study and predict coupled thermal, mechanical, hydrodynamic and geochemical behavior of clays intended to be used as engineered barriers in radioactive waste repository. In order to meet the requirements of the FEBEX Project (Full Scale Engineered Barriers Experiment) it was necessary to develop thermo-hydro-geochemical conceptual and numerical models (THG). For this purpose a THG code was developed to simulate and predict the THG behavior of the clay barrier. The code was created after considering two options. a) The development of a completely new code, or b) the coupling of existing codes. In this Dissertation we chose the second option, and developed a new program (FADES-CORE), which was obtained by using the FADES thermo-hydro-mechanical code (Navarro, 1997) and the CORE-LE code (Samper et al., 1998). This process entailed the modification of FADES, the addition of new subroutines for the calculation of solute transport, the modification of CORE-LE and the introduction of additional geochemical and transport processes. (Author)

Characterizing and modelling the excavation damaged zone (EDZ) in crystalline rock in the context of radioactive waste disposal

International Nuclear Information System (INIS)

Hudson, J.A.; Backstrom, A.; Rutqvist, J.; Jing, L.; Backers, T.; Chijimatsu, M.; Christiansson, R.; Feng, X.-T.; Kobayashi, A.; Koyama, T.; Lee, H.-S.; Neretnieks, I.; Pan, P.Z.; Rinne, M.; Shen, B.-T.

2008-01-01

This paper describes current knowledge about the nature of and potential for thermo-hydro-mechanical-chemical modelling of the Excavation Damaged Zone (EDZ) around the excavations for an underground radioactive waste repository. In the first part of the paper, the disturbances associated with excavation are explained, together with reviews of Workshops that have been held on the subject. In the second part of the paper, the results of a DECOVALEX research programme on modelling the EDZ are presented. Four research teams used four different models to simulate the complete stress-strain curve for Avro granite from the Swedish Aespoe Hard Rock Laboratory. Subsequent research extended the work to computer simulation of the evolution of the repository using a 'wall block model' and a 'near-field model'. This included assessing the evolution of stress, failure and permeability and time dependent effects during repository evolution. As discussed, all the computer models are well suited to sensitivity studies for evaluating the influence of their respective supporting parameters on the complete stress-strain curve for rock and for modelling the EDZ

Characterising and modelling the excavation damaged zone (EDZ) in crystalline rock in the context of radioactive waste disposal

Energy Technology Data Exchange (ETDEWEB)

Hudson, J.A.; Backstrom, A.; Rutqvist, J.; Jing, L.; Backers, T.; Chijimatsu, M.; Christiansson, R.; Feng, X.-T.; Kobayashi, A.; Koyama, T.; Lee, H.-S.; Neretnieks, I.; Pan, P.Z.; Rinne, M.; Shen, B.-T.

2008-10-01

This paper describes current knowledge about the nature of and potential for thermo-hydro-mechanical-chemical modelling of the Excavation Damaged Zone (EDZ) around the excavations for an underground radioactive waste repository. In the first part of the paper, the disturbances associated with excavation are explained, together with reviews of Workshops that have been held on the subject. In the second part of the paper, the results of a DECOVALEX research programme on modelling the EDZ are presented. Four research teams used four different models to simulate the complete stress-strain curve for Avro granite from the Swedish Aespoe Hard Rock Laboratory. Subsequent research extended the work to computer simulation of the evolution of the repository using a 'wall block model' and a 'near-field model'. This included assessing the evolution of stress, failure and permeability and time dependent effects during repository evolution. As discussed, all the computer models are well suited to sensitivity studies for evaluating the influence of their respective supporting parameters on the complete stress-strain curve for rock and for modelling the EDZ.

Hydro mechanical coupling for non linear behaviour laws. Application to petroleum problems; Couplage hydromecanique pour des lois de comportement non lineaires Application a des problemes petroliers

Energy Technology Data Exchange (ETDEWEB)

Longuemare, P.

1996-11-28

The aim of this study is to provide a better description of the rock contribution to fluid flows in sedimentary basins and petroleum reservoirs. After a study of the mechanical behaviour of high porosity chalks and shales, we present the elaboration of an elastoplastic constitutive model for the description of their behaviour under various strain and stress paths. This model is introduced in a coupled poro-mechanical approach and used to study the advantages of a good description of strain and stress paths in petroleum reservoirs and sedimentary basins studies. Hydro-mechanical modelling of the behaviour of petroleum reservoir allowed us to analyse the influence of boundary limit conditions on stress paths recovery rates. The study of sedimentary basins showed the importance of the consideration of the evolution of the porosity with time due to the time-scale difference between the laboratory and the field data. (author) 58 refs.

Relationship between permeability and damage in concretes at high temperature

International Nuclear Information System (INIS)

Dal Pont, St.

2004-09-01

Due to its technical and economical advantages, concrete is nowadays the most used building material in civil engineering. Even if its use is known since nearly two centuries, its behavior has not been yet completely explained due to the complexity of its porous microstructure. This fact is quite evident under particular conditions such as, by instance, during an elevation of temperature. This condition can mainly occur in two cases: due to a casualty (e.g. a fire) or in normal use conditions (e.g. storage of nuclear rejects). This work aims at contributing to the study of the phenomena that can be observed in concrete exposed to high temperatures and, in particular, focuses on the study of the evolution of intrinsic permeability. The characterisation of permeability (which is hardly measurable in hot conditions) is necessary for describing and modelling transport phenomena which occur in porous media. An experimental study has been made in collaboration with the CEA. A real-scale hollow cylinder has been instrumented with gauges for studying the evolution of temperature and gas pressure fields inside concrete. Later, the cylinder has been then numerically modelled by means of a thermo-hydro-chemical (THC) and a thermo-hydro-chemo-mechanical (THCM) model. The THC model, implemented by means of the finite volume method, has allowed a first, qualitative study of the behaviour of concrete submitted to high temperature. This model, which, for sake of simplicity, has neglected all mechanical effects, has allowed the description of the main phenomena occurring inside concrete: mass transport, phase changes, microstructure evolution. Later, the modelling has been completed by means of the THCM model using the Hitecosp code, implemented by means of the finite element method at the university of Padua. This code allows a very complete description of the phenomena occurring inside concrete and takes into consideration the mechanical behavior of concrete by means of an

Mont Terri Project - Heater experiment : rock and bentonite thermo-hydro-mechanical (THM) processes in the near field of a thermal source for development of deep underground high level radioactive waste repositories

Energy Technology Data Exchange (ETDEWEB)

Goebel, I.; Alheid, H.-J.; Kaufhold, St.; Naumann, M.; Pletsch, Th.; Plischke, I.; Schnier, H.; Schuster, K.; Sprado, K. [Bundesanstalt fuer Geowissenschaften und Rohstoffe (BGR), Hannover (Germany); Meyer, T.; Miehe, R.; Wieczorek, K. [Gesellschaft fuer Anlagen und Reaktorsicherheit mbH (GRS), Braunschweig (Germany); Mayor, J.C. [Empresa Nacional de Residuos Radioactivos SA (ENRESA), Madrid (Spain); Garcia-Sineriz, J.; Rey, M. [Asociacion para la Investigacion y Desarollo Industrial de los Recursos Naturales (AITEMIN), Madrid (Spain); Alonso, E.; Lloret, A.; Munoz, J.J. [Centre Internacional de Metodos Numerics en Ingenyeria (CIMNE), Barcelona (Spain); Weber, H. [National Cooperative for the Disposal of Radioactive Waste (Nagra), Wettingen (Switzerland); Ploetze, M. [Eidgenoessische Technische Hochschule Zuerich, Institut fuer Geotechnik, Zuerich (Switzerland); Klubertanz, G. [Colenco Power Engineering Ltd, Baden (Switzerland); Ammon, Ch. [Rothpletz Lienhard und Cie AG, Aarau (Switzerland); Graf, A.; Nussbaum, Ch.; Zingg, A. [Goetechnical Institute Ltd, Saint-Ursanne (Switzerland); Bossart, P. [Federal Office of Topography (swisstopo), Wabern (Switzerland); Buehler, Ch.; Kech, M.; Trick, Th. [Solexperts AG, Moenchaltorf (Switzerland); Emmerich, K. [ITC-WGT, Karlsruhe (Germany); Fernandez, A. M. [Ciemat, Madrid (Spain)

2007-07-01

The long-term safety of underground permanent repositories for radioactive waste relies on a combination of several engineered and geological barriers. The interactions between a host rock formation of the type 'Opalinus Clay' and an engineered barrier of the type 'bentonite buffer' are observed in the Heater Experiment (HE) during a hydration and a heating phase. The objective of the experiment is an improved understanding of the coupled thermo-hydro-mechanical (THM) processes in a host rock-buffer system achieved by experimental observations as well as numerical modelling. The basic objectives are in detail: a) Long-term monitoring in the vicinity of the heater during hydration and heating; especially observation and study of coupled THM processes in the near field, i.e. continuous measurements of temperatures, pore pressures, displacements, electric conductivity, and analysis of the gases and water released into the rock by effect of heating; b) Determination of the properties of barrier and host rock done mainly by laboratory and in situ experiments, i.e. general mechanical and mineralogical properties, mechanical state in-situ, and changes induced by the experiment; c) Study of the interaction between host rock and bentonite buffer as well as validation and refinement of existing tools for modelling THM processes; d) Study of the behaviour and reliability of instrumentation and measuring techniques, i.e. inspection of sensors after dismantling the experimental setting. To achieve the objectives, the experiment was accompanied by an extensive programme of continuous monitoring, experimental investigations on-site as well as in laboratories, and numerical modelling of the coupled THM processes. Finally, the experiment was dismantled to provide laboratory specimens of post-heating buffer and host rock material. The continuous monitoring of the experiment by a multitude of sensors (for temperature, pore pressure, total pressure, relative

Dynamic contact problem with adhesion and damage between thermo-electro-elasto-viscoplastic bodies

Science.gov (United States)

Hadj ammar, Tedjani; Saïdi, Abdelkader; Azeb Ahmed, Abdelaziz

2017-05-01

We study of a dynamic contact problem between two thermo-electro-elasto-viscoplastic bodies with damage and adhesion. The contact is frictionless and is modeled with normal compliance condition. We derive variational formulation for the model and prove an existence and uniqueness result of the weak solution. The proof is based on arguments of evolutionary variational inequalities, parabolic inequalities, differential equations, and fixed point theorem.

Thermo-mechanical analysis of PWR bolts susceptible to IASCC

International Nuclear Information System (INIS)

Matteoli, C.; Hannink, M.H.C.; Blom, F.J.; Marck, S.C. van der; Charpin-Jacobs, F.

2015-01-01

Irradiation Assisted Stress Corrosion Cracking (IASCC) is considered a primary ageing issue for the Reactor Pressure Vessel (RPV) internals of Pressurized Water Reactors (PWR). In particular, this complex phenomenon which develops in an environment featuring thermal and mechanical stresses, interaction with corrosive compounds and irradiation, is affecting the bolts connecting the baffles and the formers in the Nuclear Power Plants' RPVs. The baffle-former assembly is the structure that borders the fuel assemblies region, contributing to keep them in position and separating in the radial direction, the core region from the downcomer region. An evaluation of the stresses and temperatures reached in the baffle-former bolts during normal operation was performed by means of a coupled thermo-mechanical study which uses reactor physics calculations to obtain the fluence in the reactor core and as a consequence the heat deposition in the RPV internals. The heat deposition data are coupled with a finite element model of the bolts and the RPV internals in order to perform a complete analysis taking in account thermal, mechanical and radiation loadings. The study is first carried out focusing on a section of the RPV internals, showing a single row of baffle-former bolts. Then the work is extended to the full core height. The model set up in this work, includes an in-depth study of the behavior of the core internals, in particular baffle-former bolts. The model has the capability of understanding the mechanical and thermal behavior of essential internal components in a PWR. (authors)

Modelling the influence of water content on the mechanical behaviour of Callovo-Oxfordian argillite

International Nuclear Information System (INIS)

Jia, Y.; Zhang, F.; Shao, J.F.

2010-01-01

hydro-mechanical response of Callovo-Oxfordian argillite, a stiff, layered Mesozoic clay, located at 500 m depth in Eastern France. Thanks to its low permeability, significant retardation properties for solute transport, high mechanical strength and self-healing capacity when fracture, the Callovo-Oxfordian argillite is studied as potential geological barrier for radioactive wastes and an underground research laboratory, called M/HM URL is under construction.Various experimental studies have been performed to study the different aspects of rock behaviour. Meanwhile, different constitutive model have been proposed for this material. Among recently proposed models for argillites, the contributions Zhou et al. (2008) and Jia et al. (2009) are of direct interest to this paper. Zhou et al. (2008) have proposed a unified approach for modelling of elastic-plastic and viscoplastic behaviour coupled with induced damage in Callovo-Oxfordian argillite. Both instantaneous and differ plastic deformations are described within the unique constitutive model. Material damage induced by microcrack is coupled with plastic deformation. Jia et al. (2009) have developed a constitutive model, where the plastic deformation was considered as the principal mechanism, to consider coupling between plastic deformations and damage and evolution of mechanical properties with water content. In addition, a special attention is paid on the residual state of rocks after peak strength and the shrinkage/swelling deformation during the desaturation/re-saturation processes. However, the influence of water content on the elastic proprieties and the long term mechanical behaviour of argillite are not dealt with in these models. These two phenomena will be studied in this paper. Firstly, a synthesis of experimental study on the poro-mechanical behavior of argillites is presented. Special attention is given to the influence of water content on the long term mechanical aspects of the clay behaviour. In the second

Seismo-thermo-mechanical modeling of subduction zone seismicity

Energy Technology Data Exchange (ETDEWEB)

Dinther van, Y.

2013-07-01

The catastrophic occurrence of the 2004 M9.2 Sumatra and 2011 M9.0 Tohoku earthquakes illustrated the disastrous impact of megathrust earthquakes on society. They also emphasized our limited understanding of where and when these 'big ones' may strike. The necessary improvement of long-term seismic hazard assessment requires a better physical understanding of the seismic cycle at these seismically active subduction zones. Models have the potential to overcome the restricted, direct observations in space and time. Currently, however, no model exists to explore the relation between long-term subduction dynamics and relating deformation and short-term seismogenesis. The development, validation and initial application of such a physically consistent seismo-thermo-mechanical numerical model is the main objective of this thesis. First, I present a novel analog modeling tool that simulates cycling of megathrust earthquakes in a visco-elastic gelatin wedge. A comparison with natural observations shows interseismic and coseismic physics are captured in a robust, albeit simplified, way. This tool is used to validate that a continuum-mechanics based, visco-elasto-plastic numerical approach, typically used for large-scale geodynamic problems, can be extended to study the short-term seismogenesis of megathrust earthquakes. To generate frictional instabilities and match laboratory source parameters, a local invariant implementation of a strongly slip rate-dependent friction formulation is required. The resulting continuum approach captures several interesting dynamic features, including inter-, co- and postseismic deformation that agrees qualitatively with GPS measurements and dynamic rupture features, including cracks, self-healing pulses and fault re-rupturing. To facilitate a comparison to natural settings, I consider a more realistic setup of the Southern Chilean margin in terms of geometry and physical processes. Results agree with seismological, geodetic and

Seismo-thermo-mechanical modeling of subduction zone seismicity

International Nuclear Information System (INIS)

Dinther van, Y.

2013-01-01

The catastrophic occurrence of the 2004 M9.2 Sumatra and 2011 M9.0 Tohoku earthquakes illustrated the disastrous impact of megathrust earthquakes on society. They also emphasized our limited understanding of where and when these 'big ones' may strike. The necessary improvement of long-term seismic hazard assessment requires a better physical understanding of the seismic cycle at these seismically active subduction zones. Models have the potential to overcome the restricted, direct observations in space and time. Currently, however, no model exists to explore the relation between long-term subduction dynamics and relating deformation and short-term seismogenesis. The development, validation and initial application of such a physically consistent seismo-thermo-mechanical numerical model is the main objective of this thesis. First, I present a novel analog modeling tool that simulates cycling of megathrust earthquakes in a visco-elastic gelatin wedge. A comparison with natural observations shows interseismic and coseismic physics are captured in a robust, albeit simplified, way. This tool is used to validate that a continuum-mechanics based, visco-elasto-plastic numerical approach, typically used for large-scale geodynamic problems, can be extended to study the short-term seismogenesis of megathrust earthquakes. To generate frictional instabilities and match laboratory source parameters, a local invariant implementation of a strongly slip rate-dependent friction formulation is required. The resulting continuum approach captures several interesting dynamic features, including inter-, co- and postseismic deformation that agrees qualitatively with GPS measurements and dynamic rupture features, including cracks, self-healing pulses and fault re-rupturing. To facilitate a comparison to natural settings, I consider a more realistic setup of the Southern Chilean margin in terms of geometry and physical processes. Results agree with seismological, geodetic and geological

Computational implementation of the multi-mechanism deformation coupled fracture model for salt

International Nuclear Information System (INIS)

Koteras, J.R.; Munson, D.E.

1996-01-01

The Multi-Mechanism Deformation (M-D) model for creep in rock salt has been used in three-dimensional computations for the Waste Isolation Pilot Plant (WIPP), a potential waste, repository. These computational studies are relied upon to make key predictions about long-term behavior of the repository. Recently, the M-D model was extended to include creep-induced damage. The extended model, the Multi-Mechanism Deformation Coupled Fracture (MDCF) model, is considerably more complicated than the M-D model and required a different technology from that of the M-D model for a computational implementation

Chemo-mechanical coupling behaviour of leached concrete

International Nuclear Information System (INIS)

Nguyen, V.H.; Nedjar, B.; Torrenti, J.M.

2007-01-01

The paper is concerned with a coupled chemo-mechanical model describing the interaction between the calcium leaching and the mechanical damage in concrete materials. On the one hand, the phenomenological chemistry is described by the nowadays well-known simplified calcium leaching approach. It is based on the dissolution-diffusion process together with the chemical equilibrium relating the calcium concentration of the solid's skeleton and the calcium in the pore solution. For concrete, a homogenization approach using asymptotic expansions is used to take into account the influence of the presence of the aggregates leading to an equivalent homogeneous medium. On the other hand, the continuum damage mechanics is used to describe the mechanical degradation of concrete. The modelling accounts for the fact that concrete becomes more and more ductile as the leaching process grows. The model also predicts the inelastic irreversible deformation as damage evolves. The growth of inelastic strains observed during the mechanical tests is described by means of an elastoplastic-like model. The coupled nonlinear problem at hand is addressed within the context of the finite element method. And finally, numerical simulations are compared with the experimental results of first part of this work

A new coupling of the 3D thermal-hydraulic code THYC and the thermo-mechanical code CYRANO3 for PWR calculations

Energy Technology Data Exchange (ETDEWEB)

Marguet, S.D. [Electricite de France (EDF), 92 - Clamart (France)

1997-12-31

Among all parameters, the fuel temperature has a significant influence on the reactivity of the core, because of the Doppler effect on cross-sections. Most neutronic codes use a straightforward method to calculate an average fuel temperature used in their specific feed-back models. For instance, EDF`s neutronic code COCCINELLE uses the Rowland`s formula using the temperatures of the center and the surface of the pellet. COCCINELLE is coupled to the 3D thermal-hydraulic code THYC with calculates TDoppler with is standard thermal model. In order to improve the accuracy of such calculations, we have developed the coupling of our two latest codes in thermal-hydraulics (THYC) and thermo-mechanics (CYRANO3). THYC calculates two-phase flows in pipes or rod bundles and is used for transient calculations such as steam-line break, boron dilution accidents, DNB predictions, steam generator and condenser studies. CYRANO3 calculates most of the phenomena that take place in the fuel such as: 1) heat transfer induced by nuclear power; 2) thermal expansion of the fuel and the cladding; 3) release of gaseous fission`s products; 4) mechanical interaction between the pellet and the cladding. These two codes are now qualified in their own field and the coupling, using Parallel Virtual Machine (PVM) libraries customized in an home-made-easy-to-use package called CALCIUM, has been validated on `low` configurations (no thermal expansion, constant thermal characteristics) and used on accidental transients such as rod ejection and loss of coolant accident. (K.A.) 7 refs.

A new coupling of the 3D thermal-hydraulic code THYC and the thermo-mechanical code CYRANO3 for PWR calculations

International Nuclear Information System (INIS)

Marguet, S.D.

1997-01-01

Among all parameters, the fuel temperature has a significant influence on the reactivity of the core, because of the Doppler effect on cross-sections. Most neutronic codes use a straightforward method to calculate an average fuel temperature used in their specific feed-back models. For instance, EDF's neutronic code COCCINELLE uses the Rowland's formula using the temperatures of the center and the surface of the pellet. COCCINELLE is coupled to the 3D thermal-hydraulic code THYC with calculates TDoppler with is standard thermal model. In order to improve the accuracy of such calculations, we have developed the coupling of our two latest codes in thermal-hydraulics (THYC) and thermo-mechanics (CYRANO3). THYC calculates two-phase flows in pipes or rod bundles and is used for transient calculations such as steam-line break, boron dilution accidents, DNB predictions, steam generator and condenser studies. CYRANO3 calculates most of the phenomena that take place in the fuel such as: 1) heat transfer induced by nuclear power; 2) thermal expansion of the fuel and the cladding; 3) release of gaseous fission's products; 4) mechanical interaction between the pellet and the cladding. These two codes are now qualified in their own field and the coupling, using Parallel Virtual Machine (PVM) libraries customized in an home-made-easy-to-use package called CALCIUM, has been validated on 'low' configurations (no thermal expansion, constant thermal characteristics) and used on accidental transients such as rod ejection and loss of coolant accident. (K.A.)

Finite Element Modeling of Dieless Tube Drawing of Strain Rate Sensitive Material with Coupled Thermo-Mechanical Analysis

Science.gov (United States)

Furushima, Tsuyoshi; Sakai, Takashi; Manabe, Ken-ichi

2004-06-01

Dieless drawing is a unique deformation process without conventional dies, which can achieve a great reduction of wire and tube metals in single pass by means of local heating and cooling approach. In this study, for microtube forming, the dieless drawing process applying superplastic behavior was analyzed by finite element method (FEM) in order to clarify the effect of dieless tube drawing conditions such as tensile speed, moving speed of heating and cooling system, and material properties on deformation behavior of the tube. In the calculation, the material properties were dealt in a special subroutine, whose constitutive equation was defined as σ = Kɛnɛ˙m, and was linked to the solver. A coupled thermo-mechanical analysis was performed for the dieless tube drawing using the FEM. In the thermal analysis of dieless tube drawing, heat transfer was introduced to calculate the heat flux between heating coil and tube surface, and heat conduction in a tube. The influence of dieless tube drawing conditions on deformation behavior was clarified. As a result, for the strain rate sensitive material, the maximum reduction of area and the minimum outer diameter in single pass attain to 90.9% and 2.56mm, respectively. From the result, it is concluded that the dieless tube drawing is essential to produce an extrafine microtube by reason of keeping cylindrical tube diameter ratio constant with extremely high reduction.

Thermo-mechanical design of the Plasma Driver Plate for the MITICA ion source

Energy Technology Data Exchange (ETDEWEB)

Pavei, Mauro, E-mail: mauro.pavei@igi.cnr.it [Consorzio RFX, EURATOM-ENEA Association, Corso Stati Uniti 4, I-35127 Padova (Italy); Palma, Mauro Dalla; Marcuzzi, Diego [Consorzio RFX, EURATOM-ENEA Association, Corso Stati Uniti 4, I-35127 Padova (Italy)

2010-12-15

In the framework of the activities for the development of the Neutral Beam Injector (NBI) for ITER, the detailed design of the Radio-Frequency (RF) negative ion source has been carried out. One of the most heated components of the RF source is the rear vertical plate, named Plasma Driver Plate (PDP), where the Back-Streaming positive Ions (BSI+) generated from stripping losses in the accelerator and back scattered on the plasma source impinge on. The heat loads that result are huge and concentrated, with first estimate of the power densities up to 60 MW/m{sup 2}. The breakdowns that occur into the accelerator cause such heat loads to act cyclically, so that the PDP is thermo-mechanically fatigue loaded. Moreover, the surface of the PDP facing the plasma is functionally required to be temperature controlled and to be molybdenum or tungsten coated. The thermo-hydraulic design of the plate has been carried out considering active cooling with ultra-pure water. Different heat sink materials, hydraulic circuit layout and manufacturing processes have been considered. The heat exhaust has been optimized by changing the channels geometry, the path of the heat flux in the heat sink, the thickness of the plate and maximizing the Heat Transfer Coefficient. Such optimization has been carried out by utilizing 3D Finite Element (FE) models. Afterwards all the suitable mechanical (aging, structural monotonic and cyclic) verifications have been carried out post-processing the results of the thermo-mechanical 3D FE analyses in accordance to specific procedures for nuclear components exposed to high temperature. The effect of sputtering phenomenon due to the high energy BSI+ impinging on the plate has been considered and combined with fatigue damage for the mechanical verification of the PDP. Alternative solutions having molybdenum (or tungsten coatings) facing the plasma, aiming to reduce the sputtering rate and the consequent plasma pollution, have been evaluated and related 3D FE

Elastoplastic simulation coupled to the induced anisotropic damage for argilites

International Nuclear Information System (INIS)

Chiarelli, A.S.; Shao, J.F.

2002-01-01

A constitutive model coupling plastic deformation and induced damage is proposed to describe the mechanical behaviour of a shale rock, the argilites of East. The plastic behaviour is produced by a typical cohesive-frictional model. The material damage is represented by a second rank symmetric tensor. The damage criterion and evolution rate is related to tensile strains. The damage effect on plastic flow is also considered by an anisotropic transformation. The model formulation and a simple procedure for the determination of model parameters from standards tests is proposed. The validity of the model is checked against experimental data in various loading conditions. (author)

On phase transformation models for thermo-mechanically coupled response of Nitinol

KAUST Repository

Sengupta, Arkaprabha

2011-03-31

Fully coupled thermomechanical models for Nitinol at the grain level are developed in this work to capture the inter-dependence between deformation and temperature under non-isothermal conditions. The martensite transformation equations are solved using a novel algorithm which imposes all relevant constraints on the volume fractions. The numerical implementation of the resulting models within the finite element method is effected by the monolithic solution of the momentum and energy equations. Validation of the models is achieved by means of thin-tube experiments at different strain rates. © 2011 Springer-Verlag.

Computer code HYDRO-ACE for analyzing thermo-hydraulic phenomena in the BWR core

International Nuclear Information System (INIS)

Abe, Kiyoharu; Naito, Yoshitaka

1979-10-01

A computer code HYDRO-ACE has been developed for analyzing thermo-hydraulic phenomena in the BWR core under forced or natural circulation of cooling water. The code is composed of two main calculation routines for single channels such as riser, separator, and downcommer and multiple channels such as the reactor core with a heated zone. Functionally the code is divided into many subroutines to be connected straightforwardly, and so that the user can choose a given course freely by simply arranging the subroutines. In the program, void fraction is calculated by Maurer's method, two-phase frictional pressure drop by Maltinelli-Nelson's, and critical heat flux ratio by Hench-Levy's. The coolant flow distributions in the JPDR-II core calculated by the code are in good agreement with those measured. (author)

Thermo-mechanical stress analysis of cryopreservation in cryobags and the potential benefit of nanowarming.

Science.gov (United States)

Solanki, Prem K; Bischof, John C; Rabin, Yoed

2017-06-01

Cryopreservation by vitrification is the only promising solution for long-term organ preservation which can save tens of thousands of lives across the world every year. One of the challenges in cryopreservation of large-size tissues and organs is to prevent fracture formation due to the tendency of the material to contract with temperature. The current study focuses on a pillow-like shape of a cryobag, while exploring various strategies to reduce thermo-mechanical stress during the rewarming phase of the cryopreservation protocol, where maximum stresses are typically found. It is demonstrated in this study that while the level of stress may generally increase with the increasing amount of CPA filled in the cryobag, the ratio between width and length of the cryobag play a significant role. Counterintuitively, the overall maximum stress is not found when the bag is filled to its maximum capacity (when the filled cryobag resembles a sphere). Parametric investigation suggests that reducing the initial rewarming rate between the storage temperature and the glass transition temperature may dramatically decrease the thermo-mechanical stress. Adding a temperature hold during rewarming at the glass transition temperature may reduce the thermo-mechanical stress in some cases, but may have an adverse effect in other cases. Finally, it is demonstrated that careful incorporation of volumetric heating by means on nanoparticles in an alternating magnetic field, or nanowarming, can dramatically reduce the resulting thermo-mechanical stress. These observations display the potential benefit of a thermo-mechanical design of the cryopreservation protocols in order to prevent structural damage. Copyright © 2017 Elsevier Inc. All rights reserved.

Coupled Hydro-Mechanical Simulations of CO2 Storage Supported by Pressure Management Demonstrate Synergy Benefits from Simultaneous Formation Fluid Extraction

Directory of Open Access Journals (Sweden)

Kempka Thomas

2015-04-01

Full Text Available We assessed the synergetic benefits of simultaneous formation fluid extraction during CO2 injection for reservoir pressure management by coupled hydro-mechanical simulations at the prospective Vedsted storage site located in northern Denmark. Effectiveness of reservoir pressure management was investigated by simulation of CO2 storage without any fluid extraction as well as with 66% and 100% equivalent volume formation fluid extraction from four wells positioned for geothermal heat recovery. Simulation results demonstrate that a total pressure reduction of up to about 1.1 MPa can be achieved at the injection well. Furthermore, the areal pressure perturbation in the storage reservoir can be significantly decreased compared to the simulation scenario without any formation fluid extraction. Following a stress regime analysis, two stress regimes were considered in the coupled hydro-mechanical simulations indicating that the maximum ground surface uplift is about 0.24 m in the absence of any reservoir pressure management. However, a ground uplift mitigation of up to 37.3% (from 0.24 m to 0.15 m can be achieved at the injection well by 100% equivalent volume formation fluid extraction. Well-based adaptation of fluid extraction rates can support achieving zero displacements at the proposed formation fluid extraction wells located close to urban infrastructure. Since shear and tensile failure do not occur under both stress regimes for all investigated scenarios, it is concluded that a safe operation of CO2 injection with simultaneous formation fluid extraction for geothermal heat recovery can be implemented at the Vedsted site.

HCPB TBM thermo mechanical design: Assessment with respect codes and standards and DEMO relevancy

International Nuclear Information System (INIS)

Cismondi, F.; Kecskes, S.; Aiello, G.

2011-01-01

In the frame of the activities of the European TBM Consortium of Associates the Helium Cooled Pebble Bed Test Blanket Module (HCPB-TBM) is developed in Karlsruhe Institute of Technology (KIT). After performing detailed thermal and fluid dynamic analyses of the preliminary HCPB TBM design, the thermo mechanical behaviour of the TBM under typical ITER loads has to be assessed. A synthesis of the different design options proposed has been realized building two different assemblies of the HCPB-TBM: these two assemblies and the analyses performed on them are presented in this paper. Finite Element thermo-mechanical analyses of two detailed 1/4 scaled models of the HCPB-TBM assemblies proposed have been performed, with the aim of verifying the accordance of the mechanical behaviour with the criteria of the design codes and standards. The structural design limits specified in the codes and standard are discussed in relation with the EUROFER available data and possible damage modes. Solutions to improve the weak structural points of the present design are identified and the DEMO relevancy of the present thermal and structural design parameters is discussed.

Effective thermo-mechanical properties and shape memory effect of CNT/SMP composites

Science.gov (United States)

Yang, Qingsheng; Liu, Xia; Leng, Fangfang

2009-07-01

Shape memory polymer (SMP) has been applied in many fields as intelligent sensors and actuators. In order to improve the mechanical properties and recovery force of SMP, the addition of minor amounts of carbon nanotubes (CNT) into SMP has attracted wide attention. A micromechanical model and thermo-mechanical properties of CNT/SMP composites were studied in this paper. The thermo-mechanical constitutive relation of intellectual composites with isotropic and transversely isotropic CNT was obtained. Moreover, the shape memory effect of CNT/SMP composites and the effect of temperature and the volume fraction of CNT were discussed. The work shows that CNT/SMP composites exhibit excellent macroscopic thermo-mechanical properties and shape memory effect, while both of them can be affected remarkably by temperature and the microstructure parameters.

Analysis of unsaturated clayey materials hydration incorporating the effect of thermo-osmotic flow

International Nuclear Information System (INIS)

Sanchez, M.; Arson, C.

2012-01-01

past, for example Soler (2001) studied the impact of coupled phenomena on the long-term behavior of radioactive waste repositories in saturated argillaceous rock. Bing (2006) proposed an analytical solution in the half-space for the thermal consolidation of layered saturated soils, including the influences of thermo-osmosis and thermal filtration. Chen et al. (2009) recently proposed a coupled Thermo-Hydro-Mechanical (THM) formulation which accounts for the flow of water and air driven by temperature gradients. The aim of this work is to explore the impact of thermo-osmosis on the hydration of clayey soils and rocks generally used in the design of nuclear waste disposals. Both small scale experiments and large scale problems are analyzed. A coupled THM formulation has been extended to deal with thermal osmosis in porous media. Special emphasis is put on the study of thermo-osmotic flow in unsaturated low permeability clays. A simple model was implemented in Theta-Stock program to study thermo-osmotic effects in the performance of a nuclear waste repository. The thermo-osmotic conductivity K fT is assumed to be a scalar (k T ). The permeability of the liquid phase in the initial state is around 5*10-13 m.s -1 . The thermo-osmotic coefficient k T is taken 100 times higher than the typical permeability of the massif: k T = 5*10 -11 m.s -1 . Containers are assumed to be stored in a 100- meter depth horizontal gallery. The ground water is located at 500 meters depth. The initial saturation degree of the ground mass was 0.15. The response of the unsaturated tuff is studied over 1000 years. The material parameters, related to fluid and temperature effects, are taken from the data given by Pollock (1986). Up to 200 years of heating, the trends of the saturation degree are the same in both models. But the magnitudes are different around the heating source, between 80 meters and 140 meters deep. With the model accounting for thermo-osmotic effects, the saturation degree is

Thermo-mechanical behaviour modelling of particle fuels using a multi-scale approach

International Nuclear Information System (INIS)

Blanc, V.

2009-12-01

Particle fuels are made of a few thousand spheres, one millimeter diameter large, compound of uranium oxide coated by confinement layers which are embedded in a graphite matrix to form the fuel element. The aim of this study is to develop a new simulation tool for thermo-mechanical behaviour of those fuels under radiations which is able to predict finely local loadings on the particles. We choose to use the square finite element method, in which two different discretization scales are used: a macroscopic homogeneous structure whose properties in each integration point are computed on a second heterogeneous microstructure, the Representative Volume Element (RVE). First part of this works is concerned by the definition of this RVE. A morphological indicator based in the minimal distance between spheres centers permit to select random sets of microstructures. The elastic macroscopic response of RVE, computed by finite element has been compared to an analytical model. Thermal and mechanical representativeness indicators of local loadings has been built from the particle failure modes. A statistical study of those criteria on a hundred of RVE showed the significance of choose a representative microstructure. In this perspective, a empirical model binding morphological indicator to mechanical indicator has been developed. Second part of the work deals with the two transition scale method which are based on the periodic homogenization. Considering a linear thermal problem with heat source in permanent condition, one showed that the heterogeneity of the heat source involve to use a second order method to localized finely the thermal field. The mechanical non-linear problem has been treats by using the iterative Cast3M algorithm, substituting to integration of the behavior law a finite element computation on the RVE. This algorithm has been validated, and coupled with thermal resolution in order to compute a radiation loading. A computation on a complete fuel element

Adaptive coupling between damage mechanics and peridynamics: a route for objective simulation of material degradation up to complete failure

KAUST Repository

Han, Fei

2016-05-17

The objective (mesh-independent) simulation of evolving discontinuities, such as cracks, remains a challenge. Current techniques are highly complex or involve intractable computational costs, making simulations up to complete failure difficult. We propose a framework as a new route toward solving this problem that adaptively couples local-continuum damage mechanics with peridynamics to objectively simulate all the steps that lead to material failure: damage nucleation, crack formation and propagation. Local-continuum damage mechanics successfully describes the degradation related to dispersed microdefects before the formation of a macrocrack. However, when damage localizes, it suffers spurious mesh dependency, making the simulation of macrocracks challenging. On the other hand, the peridynamic theory is promising for the simulation of fractures, as it naturally allows discontinuities in the displacement field. Here, we present a hybrid local-continuum damage/peridynamic model. Local-continuum damage mechanics is used to describe “volume” damage before localization. Once localization is detected at a point, the remaining part of the energy is dissipated through an adaptive peridynamic model capable of the transition to a “surface” degradation, typically a crack. We believe that this framework, which actually mimics the real physical process of crack formation, is the first bridge between continuum damage theories and peridynamics. Two-dimensional numerical examples are used to illustrate that an objective simulation of material failure can be achieved by this method.

Adaptive coupling between damage mechanics and peridynamics: a route for objective simulation of material degradation up to complete failure

KAUST Repository

Han, Fei; Lubineau, Gilles; Azdoud, Yan

2016-01-01

The objective (mesh-independent) simulation of evolving discontinuities, such as cracks, remains a challenge. Current techniques are highly complex or involve intractable computational costs, making simulations up to complete failure difficult. We propose a framework as a new route toward solving this problem that adaptively couples local-continuum damage mechanics with peridynamics to objectively simulate all the steps that lead to material failure: damage nucleation, crack formation and propagation. Local-continuum damage mechanics successfully describes the degradation related to dispersed microdefects before the formation of a macrocrack. However, when damage localizes, it suffers spurious mesh dependency, making the simulation of macrocracks challenging. On the other hand, the peridynamic theory is promising for the simulation of fractures, as it naturally allows discontinuities in the displacement field. Here, we present a hybrid local-continuum damage/peridynamic model. Local-continuum damage mechanics is used to describe “volume” damage before localization. Once localization is detected at a point, the remaining part of the energy is dissipated through an adaptive peridynamic model capable of the transition to a “surface” degradation, typically a crack. We believe that this framework, which actually mimics the real physical process of crack formation, is the first bridge between continuum damage theories and peridynamics. Two-dimensional numerical examples are used to illustrate that an objective simulation of material failure can be achieved by this method.

Improved cyberinfrastructure for integrated hydrometeorological predictions within the fully-coupled WRF-Hydro modeling system

Science.gov (United States)

gochis, David; hooper, Rick; parodi, Antonio; Jha, Shantenu; Yu, Wei; Zaslavsky, Ilya; Ganapati, Dinesh

2014-05-01

The community WRF-Hydro system is currently being used in a variety of flood prediction and regional hydroclimate impacts assessment applications around the world. Despite its increasingly wide use certain cyberinfrastructure bottlenecks exist in the setup, execution and post-processing of WRF-Hydro model runs. These bottlenecks result in wasted time, labor, data transfer bandwidth and computational resource use. Appropriate development and use of cyberinfrastructure to setup and manage WRF-Hydro modeling applications will streamline the entire workflow of hydrologic model predictions. This talk will present recent advances in the development and use of new open-source cyberinfrastructure tools for the WRF-Hydro architecture. These tools include new web-accessible pre-processing applications, supercomputer job management applications and automated verification and visualization applications. The tools will be described successively and then demonstrated in a set of flash flood use cases for recent destructive flood events in the U.S. and in Europe. Throughout, an emphasis on the implementation and use of community data standards for data exchange is made.

Predictive FEM simulation of thermal shock damage in the refractory lining of steelmaking installations

NARCIS (Netherlands)

Damhof, F.; Brekelmans, W.A.M.; Geers, M.G.D.

2011-01-01

Thermal shock damage in the refractory lining of steelmaking installations is modelled using an experimentally validated constitutive damage framework which is coupled incrementally with a thermo-elastic FE package. Both non-local elasticity-based damage induced by temperature gradients and thermal

Thermo-mechanical design of the SINGAP accelerator grids for ITER NB Injectors

International Nuclear Information System (INIS)

Agostinetti, P.; Dal Bello, S.; Palma, M.D.; Zaccaria, P.

2006-01-01

The SINGle Aperture - SINgle GAP (SINGAP) accelerator for ITER neutral beam injector foresees four grids for the extraction and acceleration of negative ions, instead of the seven grids of the Multi Aperture Multi Grid (MAMuG) reference configuration. Optimized geometry of the SINGAP grids (plasma, extraction, pre-acceleration, and grounded grid) was identified by CEA Association considering specific requirements for ions extraction and beam generation referring to experimental data and code simulations. This paper focuses on the thermo-hydraulic and thermo-mechanical design of the grids carried out by Consorzio RFX for the design of the first ITER NB Injector and the ITER NB Test Facility. The cooling circuit design (position and shape of the channels) and the cooling parameters (water coolant temperatures, pressure and velocity) were optimized with thermo-hydraulic and thermo-mechanical sensitivity analyses in order to satisfy the grid functional requirements (temperatures, in plane and out of plane deformations). A complete and detailed thermo-structural design assessment of the SINGAP grids was accomplished applying the structural design rules for ITER in-vessel components and considering both the reference load conditions and the maximum load provided by the power supplies. The design required a complete modelling of the grids and their support frames by means of 3D FE and CAD models. The grids were finally integrated with the support and cooling systems inside the beam source vessel. The main results of the thermo-hydraulic and thermo-mechanical analyses are presented. The open issues are then reported, mainly regarding the material properties characterization (static and fatigue tests) and the qualification of technologies for OFHC copper electro-deposition, brazing, and welding of heterogeneous materials. (author)

Microwave propagation and absorption and its thermo-mechanical consequences in heterogeneous rocks.

Science.gov (United States)

Meisels, R; Toifl, M; Hartlieb, P; Kuchar, F; Antretter, T

2015-02-10

A numerical analysis in a two-component model rock is presented including the propagation and absorption of a microwave beam as well as the microwave-induced temperature and stress distributions in a consistent way. The analyses are two-dimensional and consider absorbing inclusions (discs) in a non-absorbing matrix representing the model of a heterogeneous rock. The microwave analysis (finite difference time domain - FDTD) is performed with values of the dielectric permittivity typical for hard rocks. Reflections at the discs/matrix interfaces and absorption in the discs lead to diffuse scattering with up to 20% changes of the intensity in the main beam compared to a homogeneous model rock. The subsequent thermo-mechanical finite element (FE) analysis indicates that the stresses become large enough to initiate damage. The results are supported by preliminary experiments on hard rock performed at 2.45 GHz.

Main outcomes from in situ thermo-hydro-mechanical experiments programme to demonstrate feasibility of radioactive high-level waste disposal in the Callovo-Oxfordian claystone

Directory of Open Access Journals (Sweden)

G. Armand

2017-06-01

Full Text Available In the context of radioactive waste disposal, an underground research laboratory (URL is a facility in which experiments are conducted to demonstrate the feasibility of constructing and operating a radioactive waste disposal facility within a geological formation. The Meuse/Haute-Marne URL is a site-specific facility planned to study the feasibility of a radioactive waste disposal in the Callovo-Oxfordian (COx claystone. The thermo-hydro-mechanical (THM behaviour of the host rock is significant for the design of the underground nuclear waste disposal facility and for its long-term safety. The French National Radioactive Waste Management Agency (Andra has begun a research programme aiming to demonstrate the relevancy of the French high-level waste (HLW concept. This paper presents the programme implemented from small-scale (small diameter boreholes to full-scale demonstration experiments to study the THM effects of the thermal transient on the COx claystone and the strategy implemented in this new programme to demonstrate and optimise current disposal facility components for HLW. It shows that the French high-level waste concept is feasible and working in the COx claystone. It also exhibits that, as for other plastic clay or claystone, heating-induced pore pressure increases and that the THM behaviour is anisotropic.

Analysis of the thermo-mechanical behaviour of the DEMO Water-Cooled Lithium Lead breeding blanket module under normal operation steady state conditions

Energy Technology Data Exchange (ETDEWEB)

Di Maio, P.A.; Arena, P. [Dipartimento di Energia, Ingegneria dell’Informazione e Modelli Matematici, Università di Palermo, Viale delle Scienze, 90128 Palermo (Italy); Aubert, J. [CEA Saclay, DEN/DANS/DM2S/SEMT, 91191 Gif sur Yvette Cedex (France); Bongiovì, G. [Dipartimento di Energia, Ingegneria dell’Informazione e Modelli Matematici, Università di Palermo, Viale delle Scienze, 90128 Palermo (Italy); Chiovaro, P., E-mail: pierluigi.chiovaro@unipa.it [Dipartimento di Energia, Ingegneria dell’Informazione e Modelli Matematici, Università di Palermo, Viale delle Scienze, 90128 Palermo (Italy); Giammusso, R. [ENEA – C.R. Brasimone, 40032 Camugnano (Italy); Li Puma, A. [CEA Saclay, DEN/DANS/DM2S/SEMT, 91191 Gif sur Yvette Cedex (France); Tincani, A. [ENEA – C.R. Brasimone, 40032 Camugnano (Italy)

2015-10-15

Highlights: • A DEMO WCLL blanket module thermo-mechanical behaviour has been investigated. • Two models of the WCLL blanket module have been set-up adopting a code based on FEM. • The water flow domain in the module has been considered. • A set of uncoupled steady state thermo-mechanical analyses has been carried out. • Critical temperature is not overcome. Safety verifications are generally satisfied. - Abstract: Within the framework of DEMO R&D activities, a research cooperation has been launched between ENEA, the University of Palermo and CEA to investigate the thermo-mechanical behaviour of the outboard equatorial module of the DEMO1 Water-Cooled Lithium Lead (WCLL) blanket under normal operation steady state scenario. The research campaign has been carried out following a theoretical–computational approach based on the Finite Element Method (FEM) and adopting a qualified commercial FEM code. In particular, two different 3D FEM models (Model 1 and Model 2), reproducing respectively the central and the lateral poloidal–radial slices of the WCLL blanket module, have been set up. A particular attention has been paid to the modelling of water flow domain, within both the segment box channels and the breeder zone tubes, to simulate realistically the coolant-box thermal coupling. Results obtained are herewith reported and critically discussed.

Modeling of thermo-mechanical and irradiation behavior of mixed oxide fuel for sodium fast reactors

International Nuclear Information System (INIS)

Karahan, Aydin; Buongiorno, Jacopo

2010-01-01

An engineering code to model the irradiation behavior of UO 2 -PuO 2 mixed oxide fuel pins in sodium-cooled fast reactors was developed. The code was named fuel engineering and structural analysis tool (FEAST-OXIDE). FEAST-OXIDE has several modules working in coupled form with an explicit numerical algorithm. These modules describe: (1) fission gas release and swelling, (2) fuel chemistry and restructuring, (3) temperature distribution, (4) fuel-clad chemical interaction and (5) fuel-clad mechanical analysis. Given the fuel pin geometry, composition and irradiation history, FEAST-OXIDE can analyze fuel and cladding thermo-mechanical behavior at both steady-state and design-basis transient scenarios. The code was written in FORTRAN-90 program language. The mechanical analysis module implements the LIFE algorithm. Fission gas release and swelling behavior is described by the OGRES and NEFIG models. However, the original OGRES model has been extended to include the effects of joint oxide gain (JOG) formation on fission gas release and swelling. A detailed fuel chemistry model has been included to describe the cesium radial migration and JOG formation, oxygen and plutonium radial distribution and the axial migration of cesium. The fuel restructuring model includes the effects of as-fabricated porosity migration, irradiation-induced fuel densification, grain growth, hot pressing and fuel cracking and relocation. Finally, a kinetics model is included to predict the clad wastage formation. FEAST-OXIDE predictions have been compared to the available FFTF, EBR-II and JOYO databases, as well as the LIFE-4 code predictions. The agreement was found to be satisfactory for steady-state and slow-ramp over-power accidents.

Modeling of thermo-mechanical and irradiation behavior of mixed oxide fuel for sodium fast reactors

Energy Technology Data Exchange (ETDEWEB)

Karahan, Aydin, E-mail: karahan@mit.ed [Center for Advanced Nuclear Energy Systems, Nuclear Science and Engineering Department, Massachusetts Institute of Technology, MA (United States); Buongiorno, Jacopo [Center for Advanced Nuclear Energy Systems, Nuclear Science and Engineering Department, Massachusetts Institute of Technology, MA (United States)

2010-01-31

An engineering code to model the irradiation behavior of UO{sub 2}-PuO{sub 2} mixed oxide fuel pins in sodium-cooled fast reactors was developed. The code was named fuel engineering and structural analysis tool (FEAST-OXIDE). FEAST-OXIDE has several modules working in coupled form with an explicit numerical algorithm. These modules describe: (1) fission gas release and swelling, (2) fuel chemistry and restructuring, (3) temperature distribution, (4) fuel-clad chemical interaction and (5) fuel-clad mechanical analysis. Given the fuel pin geometry, composition and irradiation history, FEAST-OXIDE can analyze fuel and cladding thermo-mechanical behavior at both steady-state and design-basis transient scenarios. The code was written in FORTRAN-90 program language. The mechanical analysis module implements the LIFE algorithm. Fission gas release and swelling behavior is described by the OGRES and NEFIG models. However, the original OGRES model has been extended to include the effects of joint oxide gain (JOG) formation on fission gas release and swelling. A detailed fuel chemistry model has been included to describe the cesium radial migration and JOG formation, oxygen and plutonium radial distribution and the axial migration of cesium. The fuel restructuring model includes the effects of as-fabricated porosity migration, irradiation-induced fuel densification, grain growth, hot pressing and fuel cracking and relocation. Finally, a kinetics model is included to predict the clad wastage formation. FEAST-OXIDE predictions have been compared to the available FFTF, EBR-II and JOYO databases, as well as the LIFE-4 code predictions. The agreement was found to be satisfactory for steady-state and slow-ramp over-power accidents.

Numerical modelling of levee stability based on coupled mechanical, thermal and hydrogeological processes

Directory of Open Access Journals (Sweden)

Dwornik Maciej

2016-01-01

Full Text Available The numerical modelling of coupled mechanical, thermal and hydrogeological processes for a soil levee is presented in the paper. The modelling was performed for a real levee that was built in Poland as a part of the ISMOP project. Only four parameters were changed to build different flood waves: the water level, period of water increase, period of water decrease, and period of low water level after the experiment. Results of numerical modelling shows that it is possible and advisable to calculate simultaneously changes of thermal and hydro-mechanical fields. The presented results show that it is also possible to use thermal sensors in place of more expensive pore pressure sensors, with some limitations. The results of stability analysis show that the levee is less stable when the water level decreases, after which factor of safety decreases significantly. For all flooding wave parameters described in the paper, the levee is very stable and factor of safety variations for any particular stage were not very large.

Large scale hydro-economic modelling for policy support

Science.gov (United States)

de Roo, Ad; Burek, Peter; Bouraoui, Faycal; Reynaud, Arnaud; Udias, Angel; Pistocchi, Alberto; Lanzanova, Denis; Trichakis, Ioannis; Beck, Hylke; Bernhard, Jeroen

2014-05-01

To support European Union water policy making and policy monitoring, a hydro-economic modelling environment has been developed to assess optimum combinations of water retention measures, water savings measures, and nutrient reduction measures for continental Europe. This modelling environment consists of linking the agricultural CAPRI model, the LUMP land use model, the LISFLOOD water quantity model, the EPIC water quality model, the LISQUAL combined water quantity, quality and hydro-economic model, and a multi-criteria optimisation routine. With this modelling environment, river basin scale simulations are carried out to assess the effects of water-retention measures, water-saving measures, and nutrient-reduction measures on several hydro-chemical indicators, such as the Water Exploitation Index (WEI), Nitrate and Phosphate concentrations in rivers, the 50-year return period river discharge as an indicator for flooding, and economic losses due to water scarcity for the agricultural sector, the manufacturing-industry sector, the energy-production sector and the domestic sector, as well as the economic loss due to flood damage. Recently, this model environment is being extended with a groundwater model to evaluate the effects of measures on the average groundwater table and available resources. Also, water allocation rules are addressed, while having environmental flow included as a minimum requirement for the environment. Economic functions are currently being updated as well. Recent development and examples will be shown and discussed, as well as open challenges.

Multiphasic fluid models and multicomponents reactive transport in porous media; Modelos de flujo multifasico no isotermo y de transporte reactivo multicomponente en medios porosos

Energy Technology Data Exchange (ETDEWEB)

Juncosa, R [Universidad Politecnica de Madrid (Spain)

2001-07-01

The design and construction of repositories for toxic waste, such as radioactive waste of medium and high activity, require tools, that will enable us to predict how the system will behave. The rational behind this Dissertation is based precisely on developing numerical models to study and predict coupled thermal, mechanical, hydrodynamic and geochemical behavior of clays intended to be used as engineered barriers in radioactive waste repository. In order to meet the requirements of the FEBEX Project (Full Scale Engineered Barriers Experiment) it was necessary to develop thermo-hydro-geochemical conceptual and numerical models (THG). For this purpose a THG code was developed to simulate and predict the THG behavior of the clay barrier. The code was created after considering two options. (a) The development of a completely new code, or (b) the coupling of existing codes. In this Dissertation we chose the second option, and developed a new program (FADES-CORE), which was obtained by using the FADES thermo-hydro-mechanical code (Navarro, 1997) and the CORE-LE code (Samper et al., 1998). This process entailed the modification of FADES, the addition of new subroutines for the calculation of solute transport, the modification of CORE-LE and the introduction of additional geochemical and transport processes. (Author)

DECOVALEX III PROJECT. Mathematical Models of Coupled Thermal-Hydro-Mechanical Processes for Nuclear Waste Repositories. Executive Summary

Energy Technology Data Exchange (ETDEWEB)

Jing, L.; Stephansson, O. [Royal Inst. of Technology, Stockholm (Sweden). Engineering Geology; Tsang, C.F. [Lawrence Berkely National Laboratory, Berkeley, CA (United States). Earth Science Div.; Mayor, J.C. [ENRESA, Madrid (Spain); Kautzky, F. [Swedish Nuclear Power Inspectorate, Stockholm (Sweden)] (eds.)

2005-02-15

DECOVALEX is an international consortium of governmental agencies associated with the disposal of high-level nuclear waste in a number of countries. The consortium's mission is the DEvelopment of COupled models and their VALidation against EXperiments. Hence the acronym/name DECOVALEX. Currently, agencies from Canada, Finland, France, Germany, Japan, Spain, Switzerland, Sweden, United Kingdom, and the United States are in DECOVALEX. Emplacement of nuclear waste in a repository in geologic media causes a number of physical processes to be intensified in the surrounding rock mass due to the decay heat from the waste. The four main processes of concern are thermal, hydrological, mechanical and chemical. Interactions or coupling between these heat-driven processes must be taken into account in modeling the performance of the repository for such modeling to be meaningful and reliable. DECOVALEX III is organized around four tasks. The FEBEX (Full-scale Engineered Barriers EXperiment) in situ experiment being conducted at the Grimsel site in Switzerland is to be simulated and analyzed in Task 1. Task 2, centered around the Drift Scale Test (DST) at Yucca Mountain in Nevada, USA, has several sub-tasks (Task 2A, Task 2B, Task 2C and Task 2D) to investigate a number of the coupled processes in the DST. Task 3 studies three benchmark problems: a) the effects of thermal-hydrologic-mechanical (THM) coupling on the performance of the near-field of a nuclear waste repository (BMT1); b) the effect of upscaling THM processes on the results of performance assessment (BMT2); and c) the effect of glaciation on rock mass behavior (BMT3). Task 4 is on the direct application of THM coupled process modeling in the performance assessment of nuclear waste repositories in geologic media. This executive summary presents the motivation, structure, objectives, approaches, and the highlights of the main achievements and outstanding issues of the tasks studied in the DECOVALEX III project

DECOVALEX III PROJECT. Mathematical Models of Coupled Thermal-Hydro-Mechanical Processes for Nuclear Waste Repositories. Executive Summary

International Nuclear Information System (INIS)

Jing, L.; Stephansson, O.; Kautzky, F.

2005-02-01

DECOVALEX is an international consortium of governmental agencies associated with the disposal of high-level nuclear waste in a number of countries. The consortium's mission is the DEvelopment of COupled models and their VALidation against EXperiments. Hence the acronym/name DECOVALEX. Currently, agencies from Canada, Finland, France, Germany, Japan, Spain, Switzerland, Sweden, United Kingdom, and the United States are in DECOVALEX. Emplacement of nuclear waste in a repository in geologic media causes a number of physical processes to be intensified in the surrounding rock mass due to the decay heat from the waste. The four main processes of concern are thermal, hydrological, mechanical and chemical. Interactions or coupling between these heat-driven processes must be taken into account in modeling the performance of the repository for such modeling to be meaningful and reliable. DECOVALEX III is organized around four tasks. The FEBEX (Full-scale Engineered Barriers EXperiment) in situ experiment being conducted at the Grimsel site in Switzerland is to be simulated and analyzed in Task 1. Task 2, centered around the Drift Scale Test (DST) at Yucca Mountain in Nevada, USA, has several sub-tasks (Task 2A, Task 2B, Task 2C and Task 2D) to investigate a number of the coupled processes in the DST. Task 3 studies three benchmark problems: a) the effects of thermal-hydrologic-mechanical (THM) coupling on the performance of the near-field of a nuclear waste repository (BMT1); b) the effect of upscaling THM processes on the results of performance assessment (BMT2); and c) the effect of glaciation on rock mass behavior (BMT3). Task 4 is on the direct application of THM coupled process modeling in the performance assessment of nuclear waste repositories in geologic media. This executive summary presents the motivation, structure, objectives, approaches, and the highlights of the main achievements and outstanding issues of the tasks studied in the DECOVALEX III project. The

Numerical simulation for the coupled thermo-mechanical performance of a lined rock cavern for underground compressed air energy storage

Science.gov (United States)

Zhou, Shu-Wei; Xia, Cai-Chu; Zhao, Hai-Bin; Mei, Song-Hua; Zhou, Yu

2017-12-01

Compressed air energy storage (CAES) is a technology that uses compressed air to store surplus electricity generated from low power consumption time for use at peak times. This paper presents a thermo-mechanical modeling for the thermodynamic and mechanical responses of a lined rock cavern used for CAES. The simulation was accomplished in COMSOL Multiphysics and comparisons of the numerical simulation and some analytical solutions validated the thermo-mechanical modeling. Air pressure and temperatures in the sealing layer and concrete lining exhibited a similar trend of ‘up-down-down-up’ in one cycle. Significant temperature fluctuation occurred only in the concrete lining and sealing layer, and no strong fluctuation was observed in the host rock. In the case of steel sealing, principal stresses in the sealing layer were larger than those in the concrete and host rock. The maximum compressive stresses of the three layers and the displacement on the cavern surface increased with the increase of cycle number. However, the maximum tensile stresses exhibited the opposite trend. Polymer sealing achieved a relatively larger air temperature and pressure compared with steel and air-tight concrete sealing. For concrete layer thicknesses of 0 and 0.1 m and an initial air pressure of 4.5 MPa, the maximum rock temperature could reach 135 °C and 123 °C respectively in a 30 day simulation.

Decomposition mechanism of melamine borate in pyrolytic and thermo-oxidative conditions

Energy Technology Data Exchange (ETDEWEB)

Hoffendahl, Carmen; Duquesne, Sophie; Fontaine, Gaëlle; Bourbigot, Serge, E-mail: serge.bourbigot@ensc-lille.fr

2014-08-20

Highlights: • Decomposition of melamine borate in pyrolytic and thermo-oxidative conditions was investigated. • With increasing temperature, orthoboric acid forms boron oxide releasing water. • Melamine decomposes evolving melamine, ammonia and other fragments. • Boron oxide is transformed into boron nitride and boron nitride-oxide structures through presence of ammonia. - Abstract: Decomposition mechanism of melamine borate (MB) in pyrolytic and thermo-oxidative conditions is investigated in the condensed and gas phases using solid state NMR ({sup 13}C and {sup 11}B), X-ray photoelectron spectroscopy (XPS), pyrolysis-gas chromatography–mass spectrometry (py-GCMS) and thermogravimetric analysis coupled with a Fourier transform infrared spectrometer (TGA–FTIR). It is evidenced that orthoboric acid dehydrates to metaboric and then to boron oxide. The melamine is partially sublimated. At the same time, melamine condensates, i.e., melem and melon are formed. Melon is only formed in thermo-oxidative conditions. At higher temperature, melem and melon decompose releasing ammonia which reacts with the boron oxide to form boron nitride (BN) and BNO structures.

Thermodynamic restrictions on linear reversible and irreversible thermo-electro-magneto-mechanical processes

Directory of Open Access Journals (Sweden)

Sushma Santapuri

2016-10-01

Full Text Available A unified thermodynamic framework for the characterization of functional materials is developed. This framework encompasses linear reversible and irreversible processes with thermal, electrical, magnetic, and/or mechanical effects coupled. The comprehensive framework combines the principles of classical equilibrium and non-equilibrium thermodynamics with electrodynamics of continua in the infinitesimal strain regime.In the first part of this paper, linear Thermo-Electro-Magneto-Mechanical (TEMM quasistatic processes are characterized. Thermodynamic stability conditions are further imposed on the linear constitutive model and restrictions on the corresponding material constants are derived. The framework is then extended to irreversible transport phenomena including thermoelectric, thermomagnetic and the state-of-the-art spintronic and spin caloritronic effects. Using Onsager's reciprocity relationships and the dissipation inequality, restrictions on the kinetic coefficients corresponding to charge, heat and spin transport processes are derived. All the constitutive models are accompanied by multiphysics interaction diagrams that highlight the various processes that can be characterized using this framework. Keywords: Applied mathematics, Materials science, Thermodynamics

Effect of thermo-coupled processes on the behaviour of a clay barrier submitted to heating and hydration

Directory of Open Access Journals (Sweden)

Marcelo Sánchez

2010-03-01

Full Text Available The storage of high level radioactive waste is still an unresolved problem of the nuclear industry, being geological disposal the most favoured option and, naturally, the one requiring the strongest geo-mechanical input. Most conceptual designs for the deep geological disposal of nuclear waste envisage placing the canisters containing the waste in horizontal drifts or vertical boreholes. The empty space surrounding the canisters is filled by an engineered barrier often made up of compacted swelling clay. Inthebarrierandthenearfield,significantthermo-hydro-mechanical(THM phenomena take place that interact in a complex way. A good understanding of THM issues is, therefore, necessary to ensure a correct performance of engineered barriers and seals. The conditions of the bentonite in an engineered barrier for high-level radioactive waste disposal are being simulated in a mock-up heating test at almost scale, at the premises of CIEMAT in Madrid. The evolution of the main Thermo-Hydro-Mechanical (THM variables of this test are analysed in this paper by using a fully coupled THM formulation and the corresponding finite element code. Special emphasis has been placed on the study of the effect of thermo-osmotic flow in the hydration of the clay barrier at an advanced staged of the experiment.O armazenamento de rejeitos altamente radioativos é ainda um problema em aberto na área de engenharia nuclear sendo os sítios geológicos ainda a opção mais favorável e naturalmente aquela que demanda maior conhecimento na área de geomecânica. A maioria dos projetos conceituais de armazenamento do lixo nuclear objetiva a alocação de cilindros que contêm os rejeitos em poços verticais ou horizontais. O espaço vazio que circunda os cilindros é preenchido por uma barreirade engenharia na maioria dos casos composta por uma argila expansiva. Na barreira e na vizinhança fenômenos significativos de acoplamento termo-hidro-mecânico(THM tomam lugar e

Thermo-acoustic coupling in can-annular combustors : A numerical investigation

NARCIS (Netherlands)

Farisco, Federica; Panek, Lukasz; Kok, Jim B.W.; Pent, Jared; Rajaram, Rajesh

2015-01-01

Thermo-acoustic instabilities in modern, high power density gas turbines need to be predicted and understood in order to avoid unexpected damage and engine failure. While the annular combustor design is expected to suffer from the occurrence of transverse waves and burner-to-burner acoustic

Joint atmospheric-terrestrial water balances for East Africa: a WRF-Hydro case study for the upper Tana River basin

Science.gov (United States)

Kerandi, Noah; Arnault, Joel; Laux, Patrick; Wagner, Sven; Kitheka, Johnson; Kunstmann, Harald

2018-02-01

For an improved understanding of the hydrometeorological conditions of the Tana River basin of Kenya, East Africa, its joint atmospheric-terrestrial water balances are investigated. This is achieved through the application of the Weather Research and Forecasting (WRF) and the fully coupled WRF-Hydro modeling system over the Mathioya-Sagana subcatchment (3279 km2) and its surroundings in the upper Tana River basin for 4 years (2011-2014). The model setup consists of an outer domain at 25 km (East Africa) and an inner one at 5-km (Mathioya-Sagana subcatchment) horizontal resolution. The WRF-Hydro inner domain is enhanced with hydrological routing at 500-m horizontal resolution. The results from the fully coupled modeling system are compared to those of the WRF-only model. The coupled WRF-Hydro slightly reduces precipitation, evapotranspiration, and the soil water storage but increases runoff. The total precipitation from March to May and October to December for WRF-only (974 mm/year) and coupled WRF-Hydro (940 mm/year) is closer to that derived from the Climate Hazards Group Infrared Precipitation with Stations (CHIRPS) data (989 mm/year) than from the TRMM (795 mm/year) precipitation product. The coupled WRF-Hydro-accumulated discharge (323 mm/year) is close to that observed (333 mm/year). However, the coupled WRF-Hydro underestimates the observed peak flows registering low but acceptable NSE (0.02) and RSR (0.99) at daily time step. The precipitation recycling and efficiency measures between WRF-only and coupled WRF-Hydro are very close and small. This suggests that most of precipitation in the region comes from moisture advection from the outside of the analysis domain, indicating a minor impact of potential land-precipitation feedback mechanisms in this case. The coupled WRF-Hydro nonetheless serves as a tool in quantifying the atmospheric-terrestrial water balance in this region.

Hydro-mechanical behaviour of a heterogeneous compacted soil: experimental observations and modelling

International Nuclear Information System (INIS)

Gens, A.; Vallejan, B.; Sanchez, M.; Imbert, C.; Villar, M.V.; Van Geet, M.

2011-01-01

The paper describes a theoretical and experimental study of the coupled hydro-mechanical behaviour of a compacted mixture of bentonite powder and bentonite pellets intended as sealing material in underground repositories for nuclear waste. One of the main advantages of the use of powder/pellets mixtures is the reduction of the compaction effort required to achieve the value of average dry density necessary to attain the required swelling potential. However, the heterogeneous fabric of the material requires special approaches in order to describe adequately its behaviour during hydration. A double porosity formulation is presented to account for the presence of two distinct structural levels in the material. Hydraulic equilibrium between the two porosities is not assumed; instead a water exchange term between them is postulated. The formulation is applied to the modelling of a number of one-dimensional swelling pressure tests performed in the CEA (Commissariat a l'Energie Atomique, France) and CIEMAT (Spain) laboratories. A very satisfactory quantitative description of the experimental observations is obtained that includes a number of complex behaviour features such as size effects and non-monotonic development of swelling pressures. Some micro-fabric observations using X-ray tomography and mercury intrusion porosimetry lend support to the conceptual approach adopted. The formulation is then applied to the analysis of a long-term large-scale sealing test performed at the Hades underground facility in Belgium, using the same set of hydraulic and mechanical parameters employed in the modelling of the laboratory tests. Although the field observations exhibit a much higher degree of scatter, the basic behaviour of the field sealing test is satisfactorily simulated. A formulation that incorporates basic features of the micro-fabric of the mixture is thus able to span successfully over a large range of space and time scales. (authors)

THM-issues in repository rock. Thermal, mechanical, thermo-mechanical and hydro-mechanical evolution of the rock at the Forsmark and Laxemar sites

Energy Technology Data Exchange (ETDEWEB)

Hoekmark, Harald; Loennqvist, Margareta; Faelth, Billy (Clay Technology AB, Lund (Sweden))

2010-05-15

The present report addresses aspects of the Thermo-Hydro-Mechanical (THM) evolution of the repository host rock that are of potential importance to the SR-Site safety assessment of a KBS-3 type spent nuclear fuel repository. The report covers the evolution of rock temperatures, rock stresses, pore pressures and fracture transmissivities during the excavation and operational phase, the temperate phase and a glacial cycle on different scales. The glacial cycle is assumed to include a period of pre-glacial permafrost with lowered temperatures and with increased pore pressures in the rock beneath the impermeable permafrost layer. The report also addresses the question of the peak temperature reached during the early temperate phase in the bentonite buffer surrounding the spent fuel canisters. The main text is devoted exclusively to the projected THM evolution of the rock at the Forsmark site in central Sweden. The focus is on the potential for stress-induced failures, i.e. spalling, in the walls of the deposition holes and on changes in the transmissivity of fractures and deformation zones. All analyses are conducted by a combination of numerical tools (3DEC) and analytical solutions. All phases are treated separately and independently of each other, although in reality construction will overlap with heat generation because of the step-by-step excavation/deposition approach with some 50 years between deposition of the first and last canisters. It is demonstrated here that the thermal and thermo-mechanical evolution of the near-field will be independent of heat generated by canisters that were deposited in the past, provided that deposition is made in an orderly fashion, deposition area by deposition area. Peak temperatures and near-field stresses can, consequently, be calculated as if all canisters were deposited simultaneously. The canister and tunnel spacing is specified such that the peak buffer temperature will not exceed 100 deg C in any deposition hole, i.e. not

Deformation and damage modes of deep argillaceous rocks under hydro-mechanical stresses; Modes de deformation et d'endommagement de roches argileuses profondes sous sollicitations hydro-mecaniques

Energy Technology Data Exchange (ETDEWEB)

Vales, F.

2008-12-15

An experimental identification of the hydro-mechanical behaviour of an argillite rock is proposed within a multi-scale approach. In particular, interest is focused on the spatial and temporal localization of strain and damage in a specimen during hydro-mechanical loading. Firstly, we describe the techniques used to follow the rock evolutions under loading, and in particular Digital Images Correlation (DIC), Acoustic Emission, microscopy and mercury intrusion porosimetry. Measurement errors and device limitations are discussed. The studied material is the Callovo-Oxfordian indurated argillaceous rock (or argillite) of the Bure site where ANDRA has built an underground research laboratory to study the radioactive waste storage. Petrophysical characterizations and microstructural observations by optical and scanning electron microscopy provide an identification of the constitutive phase and a characterization of their spatial distribution and typical sizes. Argillite can be described as a composite structure with a continuous clay matrix and embedded mineral particles, essentially quartz and carbonates. The typical size of these particles ranges from a few micrometers to a few hundreds micrometers, with an average close to 50 {mu}.m. The general experimental procedure combines two steps: in a fist time, imposed suctions bring samples to a given degree of water saturation, and, in a second time, uniaxial mechanical compression tests are performed. To understand the evolutions of the material under hydric and mechanical loading, samples are instrumented with standard measurement techniques, but also with Digital Image Correlation, at both the global scale of the sample and the local scale of the composite microstructure, and with Acoustic Emissions recording. Moisture transfers are imposed by controlled suctions on the range of 150 to 2.8 MPa, corresponding to the relative humidity range of 32 to 98%RH. During pure hydric solicitation, the changes in physical parameters

3-D thermo-mechanical laboratory modeling of plate-tectonics: modeling scheme, technique and first experiments

Directory of Open Access Journals (Sweden)

D. Boutelier

2011-05-01

Full Text Available We present an experimental apparatus for 3-D thermo-mechanical analogue modeling of plate tectonic processes such as oceanic and continental subductions, arc-continent or continental collisions. The model lithosphere, made of temperature-sensitive elasto-plastic analogue materials with strain softening, is submitted to a constant temperature gradient causing a strength reduction with depth in each layer. The surface temperature is imposed using infrared emitters, which allows maintaining an unobstructed view of the model surface and the use of a high resolution optical strain monitoring technique (Particle Imaging Velocimetry. Subduction experiments illustrate how the stress conditions on the interplate zone can be estimated using a force sensor attached to the back of the upper plate and adjusted via the density and strength of the subducting lithosphere or the lubrication of the plate boundary. The first experimental results reveal the potential of the experimental set-up to investigate the three-dimensional solid-mechanics interactions of lithospheric plates in multiple natural situations.

Thermo-mechanical design of the SINGAP accelerator grids for ITER NB injectors

Energy Technology Data Exchange (ETDEWEB)

Agostinetti, P. [Consorzio RFX, Euratom-ENEA Association, Corso Stati Uniti 4, I35127 Padova (Italy)], E-mail: piero.agostinetti@igi.cnr.it; Dal Bello, S.; Dalla Palma, M.; Zaccaria, P. [Consorzio RFX, Euratom-ENEA Association, Corso Stati Uniti 4, I35127 Padova (Italy)

2007-10-15

The SINGle Aperture-SINgle GAP (SINGAP) accelerator for ITER neutral beam injector foresees four grids for the extraction and acceleration of negative ions, instead of the seven grids of the Multi-Aperture Multi-Grid (MAMuG) reference configuration. The grids have to fulfil specific requirements coming from ion extraction, beam optics and thermo-mechanical issues. This paper focuses on the thermo-hydraulic and thermo-mechanical design of the grids carried out by Consorzio RFX for the design of the first ITER NB injector and the ITER NB Test Facility. The cooling circuit design (position and shape of the channels) and the cooling parameters (water coolant temperatures, pressure and velocity) were optimized with sensitivity analyses in order to satisfy the grid functional requirements (temperatures, stresses, in plane and out of plane deformations). The design required a complete modelling of the grids and their support frames by means of 3D FE and CAD models.

Continuum Damage Mechanics Models for the Analysis of Progressive Failure in Open-Hole Tension Laminates

Science.gov (United States)

Song, Kyonchan; Li, Yingyong; Rose, Cheryl A.

2011-01-01

The performance of a state-of-the-art continuum damage mechanics model for interlaminar damage, coupled with a cohesive zone model for delamination is examined for failure prediction of quasi-isotropic open-hole tension laminates. Limitations of continuum representations of intra-ply damage and the effect of mesh orientation on the analysis predictions are discussed. It is shown that accurate prediction of matrix crack paths and stress redistribution after cracking requires a mesh aligned with the fiber orientation. Based on these results, an aligned mesh is proposed for analysis of the open-hole tension specimens consisting of different meshes within the individual plies, such that the element edges are aligned with the ply fiber direction. The modeling approach is assessed by comparison of analysis predictions to experimental data for specimen configurations in which failure is dominated by complex interactions between matrix cracks and delaminations. It is shown that the different failure mechanisms observed in the tests are well predicted. In addition, the modeling approach is demonstrated to predict proper trends in the effect of scaling on strength and failure mechanisms of quasi-isotropic open-hole tension laminates.

Thermo-mechanical efficiency of the bimetallic strip heat engine at the macro-scale and micro-scale

International Nuclear Information System (INIS)

Arnaud, A; Boughaleb, J; Monfray, S; Boeuf, F; Skotnicki, T; Cugat, O

2015-01-01

Bimetallic strip heat engines are energy harvesters that exploit the thermo-mechanical properties of bistable bimetallic membranes to convert heat into mechanical energy. They thus represent a solution to transform low-grade heat into electrical energy if the bimetallic membrane is coupled with an electro-mechanical transducer. The simplicity of these devices allows us to consider their miniaturization using MEMS fabrication techniques. In order to design and optimize these devices at the macro-scale and micro-scale, this article proposes an explanation of the origin of the thermal snap-through by giving the expressions of the constitutive equations of composite beams. This allows us to evaluate the capability of bimetallic strips to convert heat into mechanical energy whatever their size is, and to give the theoretical thermo-mechanical efficiencies which can be obtained with these harvesters. (paper)

Incorporating damage mechanics into explosion simulation models

International Nuclear Information System (INIS)

Sammis, C.G.

1993-01-01

The source region of an underground explosion is commonly modeled as a nested series of shells. In the innermost open-quotes hydrodynamic regimeclose quotes pressures and temperatures are sufficiently high that the rock deforms as a fluid and may be described using a PVT equation of state. Just beyond the hydrodynamic regime, is the open-quotes non-linear regimeclose quotes in which the rock has shear strength but the deformation is nonlinear. This regime extends out to the open-quotes elastic radiusclose quotes beyond which the deformation is linear. In this paper, we develop a model for the non-linear regime in crystalline source rock where the nonlinearity is mostly due to fractures. We divide the non-linear regime into a open-quotes damage regimeclose quotes in which the stresses are sufficiently high to nucleate new fractures from preexisting ones and a open-quotes crack-slidingclose quotes regime where motion on preexisting cracks produces amplitude dependent attenuation and other non-linear effects, but no new cracks are nucleated. The boundary between these two regimes is called the open-quotes damage radius.close quotes The micromechanical damage mechanics recently developed by Ashby and Sammis (1990) is used to write an analytic expression for the damage radius in terms of the initial fracture spectrum of the source rock, and to develop an algorithm which may be used to incorporate damage mechanics into computer source models for the damage regime. Effects of water saturation and loading rate are also discussed

Numerical Modelling and Damage Assessment of Rotary Wing Aircraft Cabin Door Using Continuum Damage Mechanics Model

Science.gov (United States)

Boyina, Gangadhara Rao T.; Rayavarapu, Vijaya Kumar; V. V., Subba Rao

2017-02-01

The prediction of ultimate strength remains the main challenge in the simulation of the mechanical response of composite structures. This paper examines continuum damage model to predict the strength and size effects for deformation and failure response of polymer composite laminates when subjected to complex state of stress. The paper also considers how the overall results of the exercise can be applied in design applications. The continuum damage model is described and the resulting prediction of size effects are compared against the standard benchmark solutions. The stress analysis for strength prediction of rotary wing aircraft cabin door is carried out. The goal of this study is to extend the proposed continuum damage model such that it can be accurately predict the failure around stress concentration regions. The finite element-based continuum damage mechanics model can be applied to the structures and components of arbitrary configurations where analytical solutions could not be developed.

On the Effects of Thermal History on the Development and Relaxation of Thermo-Mechanical Stress in Cryopreservation.

Science.gov (United States)

Eisenberg, David P; Steif, Paul S; Rabin, Yoed

2014-01-01

This study investigates the effects of the thermal protocol on the development and relaxation of thermo-mechanical stress in cryopreservation by means of glass formation, also known as vitrification. The cryopreserved medium is modeled as a homogeneous viscoelastic domain, constrained within either a stiff cylindrical container or a highly compliant bag. Annealing effects during the cooling phase of the cryopreservation protocol are analyzed. Results demonstrate that an intermediate temperature-hold period can significantly reduce the maximum tensile stress, thereby decreasing the potential for structural damage. It is also demonstrated that annealing at temperatures close to glass transition significantly weakens the dependency of thermo-mechanical stress on the cooling rate. Furthermore, a slower initial rewarming rate after cryogenic storage may drastically reduce the maximum tensile stress in the material, which supports previous experimental observations on the likelihood of fracture at this stage. This study discusses the dependency of the various stress components on the storage temperature. Finally, it is demonstrated that the stiffness of the container wall can affect the location of maximum stress, with implications on the development of cryopreservation protocols.

Thermal and thermo-mechanical simulation of laser assisted machining

International Nuclear Information System (INIS)

Germain, G.; Dal Santo, P.; Lebrun, J. L.; Bellett, D.; Robert, P.

2007-01-01

Laser Assisted Machining (LAM) improves the machinability of materials by locally heating the workpiece just prior to cutting. The heat input is provided by a high power laser focused several millimeters in front of the cutting tool. Experimental investigations have confirmed that the cutting force can be decreased, by as much as 40%, for various materials (tool steel, titanium alloys and nickel alloys). The laser heat input is essentially superficial and results in non-uniform temperature profiles within the depth of the workpiece. The temperature field in the cutting zone is therefore influenced by many parameters. In order to understand the effect of the laser on chip formation and on the temperature fields in the different deformation zones, thermo-mechanical simulation were undertaken. A thermo-mechanical model for chip formation with and without the laser was also undertaken for different cutting parameters. Experimental tests for the orthogonal cutting of 42CrMo4 steel were used to validate the simulation via the prediction of the cutting force with and without the laser. The thermo-mechanical model then allowed us to highlight the differences in the temperature fields in the cutting zone with and without the laser. In particular, it was shown that for LAM the auto-heating of the material in the primary shear zone is less important and that the friction between the tool and chip also generates less heat. The temperature fields allow us to explain the reduction in the cutting force and the resulting residual stress fields in the workpiece

Thermo-mechanical properties of SOFC components investigated by a combined method

DEFF Research Database (Denmark)

Teocoli, Francesca; Esposito, Vincenzo; Ramousse, Severine

, and differential thermo-mechanical behavior at each layer. The combination of such factors can have a critical effect on the final shape and microstructure, and on the mechanical integrity. Thermo-mechanical properties and sintering mechanisms of important SOFC materials (CGO, YSZ, ScYSZ) were systematically...

Global thermo-mechanical effects from a KBS-3 type repository

International Nuclear Information System (INIS)

Hakami, E.; Olofsson, Stig-Olof

1998-01-01

The objective of this study has been to identify the global thermo-mechanical effects in the bedrock hosting a nuclear waste repository. Numerical thermo-mechanical modeling using distinct element models was performed. The number of fracture zones, the heat intensity of the waste, the material properties of the rock mass and the boundary conditions of the models were varied. Different models for multi-level repositories were also analyzed and compared to the main single-level case. Further, the global influence from the excavation of repository tunnels and deposition holes was examined by introducing weaker rock mass material properties in the repository region of one model. The maximum compression stress obtained for the main model is 44 MPa and occurs at the repository level after about 100 years of deposition. Due to thermal expansion, the rock mass displaces upward, and the maximum heave at the ground surface after 1000 years is calculated to be 16 cm. In the area close to the ground surface the horizontal stresses reduce, causing the rock to yield in tension down to a depth of about 80 meters. The fracture zones show opening displacements at shallow depths and closing and shearing at the repository level. The maximum displacements are 0.3-2.5 cm for closing, 0.0-0.8 cm for opening and 0.2-2.2 cm for shearing. The resultant stresses and displacements depend in large part on the assumptions made concerning the heat intensity of the waste. In the main model, an initial heat intensity of 10 W/m 2 is assumed, which gives larger effects than the case with 6 W/m 2 . Another important input parameter for the analysis is the Young's modulus of the rock mass. In the main model, a value of 30 GPa is assumed. Higher values of Young's modulus give larger thermo-mechanical effects. All multi-level repository layouts give rise to higher temperatures than the single-level layout, causing the compressive stresses to increase more at the repository level. The multi

Report on Thermo-Hydro-Mechanical Laboratory Tests Performed by CIEMAT on Febex Bentonite 2004-2008

International Nuclear Information System (INIS)

Villar, M. V.; Gomez-Espina, R.

2009-01-01

The results of the laboratory studies performed by CIEMAT with the FEBEX bentonite in the context of WP3.2 of the NF-PRO Project and of the Agreement ENRESA-CIEMAT Anexo V are presented and analysed in this report. They refer to the effect of the hydraulic gradient on the permeability of bentonite, the effect of the thermal gradient on the hydration kinetics of bentonite, and the repercussion of temperature on the hydro-mechanical properties of bentonite (swelling, permeability and water retention capacity). In all the cases the bentonite has been used compacted to densities expected in the engineered barrier of a high-level radioactive waste repository. The existence of threshold and critical hydraulic gradients has been observed, both of them dependent on bentonite density and water pressures. After more than seven years of hydration, the 40-cm high bentonite columns are far from full saturation, the thermal gradient additionally delaying the process, which is very slow. Temperatures below 100 degree centigrade slightly decrease the swelling and the water retention capacity of the bentonite and increase its permeability. The information obtained improves the knowledge on the behaviour of expansive clay and will help the development of constitutive models and the interpretation of the results obtained in the mock-up and the in situ tests. (Author) 35 refs

Report on Thermo-Hydro-Mechanical Laboratory Tests Performed by CIEMAT on Febex Bentonite 2004-2008

Energy Technology Data Exchange (ETDEWEB)

Villar, M. V.; Gomez-Espina, R.

2009-11-25

The results of the laboratory studies performed by CIEMAT with the FEBEX bentonite in the context of WP3.2 of the NF-PRO Project and of the Agreement ENRESA-CIEMAT Anexo V are presented and analysed in this report. They refer to the effect of the hydraulic gradient on the permeability of bentonite, the effect of the thermal gradient on the hydration kinetics of bentonite, and the repercussion of temperature on the hydro-mechanical properties of bentonite (swelling, permeability and water retention capacity). In all the cases the bentonite has been used compacted to densities expected in the engineered barrier of a high-level radioactive waste repository. The existence of threshold and critical hydraulic gradients has been observed, both of them dependent on bentonite density and water pressures. After more than seven years of hydration, the 40-cm high bentonite columns are far from full saturation, the thermal gradient additionally delaying the process, which is very slow. Temperatures below 100 degree centigrade slightly decrease the swelling and the water retention capacity of the bentonite and increase its permeability. The information obtained improves the knowledge on the behaviour of expansive clay and will help the development of constitutive models and the interpretation of the results obtained in the mock-up and the in situ tests. (Author) 35 refs.

Thermo-mechanical analysis of RMP coil system for EAST tokamak

International Nuclear Information System (INIS)

Wang, Songke; Ji, Xiang; Song, Yuntao; Zhang, Shanwen; Wang, Zhongwei; Sun, Youwen; Qi, Minzhong; Liu, Xufeng; Wang, Shengming; Yao, Damao

2014-01-01

Highlights: • Thermal design requirements for EAST RMP coils are summarized. • Cooling parameters based on both theoretical and numerical solutions are determined. • Compromise between thermal design and structural design is made on number of turns. • Thermo-mechanical calculations are made to validate its structural performance. - Abstract: Resonant magnetic perturbation (RMP) has been proved to be an efficient approach on edge localized modes (ELMs) control, resistive wall mode (RWM) control, and error field correction (EFC), RMP coil system under design in EAST tokamak will realize the above-mentioned multi-functions. This paper focuses on the thermo-mechanical analysis of EAST RMP coil system on the basis of sensitivity analysis, both normal and off-normal working conditions are considered. The most characteristic set of coil system is chosen with a complete modelling by means of three-dimensional (3D) finite element method, thermo-hydraulic and thermal-structural performances are investigated adequately, both locally and globally. The compromise is made between thermal performance and structural design requirements, and the results indicate that the optimized design is feasible and reasonable

Thermo-mechanical models of obduction applied to the Oman ophiolite

Science.gov (United States)

Thibault, Duretz; Philippe, Agard; Philippe, Yamato; Céline, Ducassou; Taras, Gerya; Evguenii, Burov

2015-04-01

During obduction regional-scale fragments of oceanic lithosphere (ophiolites) are emplaced somewhat enigmatically on top of lighter continental lithosphere. We herein use two-dimensional thermo-mechanical models to investigate the feasibility and controlling parameters of obduction. The models are designed using available geological data from the Oman (Semail) ophiolite. Initial and boundary conditions are constrained by plate kinematic and geochronological data and modeling results are validated against petrological and structural observations. The reference model consists of three distinct stages: (1) initiation of oceanic subduction initiation away from Arabian margin, (2) emplacement of the Oman Ophiolite atop the Arabian margin, (2) dome-like exhumation of the subducted Arabian margin beneath the overlying ophiolite. A parametric study suggests that 350-400 km of shortening allows to best fit both the peak P-T conditions of the subducted margin (1.5-2.5 GPa / 450-600°C) and the dimensions of the ophiolite (~170 km width), in agreement with previous estimations. Our results further confirm that the locus of obduction initiation is close to the eastern edge of the Arabian margin (~100 km) and indicate that obduction is facilitated by a strong continental basement rheology.

A constitutive model for representing coupled creep, fracture, and healing in rock salt

International Nuclear Information System (INIS)

Chan, K.S.; Bodner, S.R.; Munson, D.E.; Fossum, A.F.

1996-01-01

The development of a constitutive model for representing inelastic flow due to coupled creep, damage, and healing in rock salt is present in this paper. This model, referred to as Multimechanism Deformation Coupled Fracture model, has been formulated by considering individual mechanisms that include dislocation creep, shear damage, tensile damage, and damage healing. Applications of the model to representing the inelastic flow and fracture behavior of WIPP salt subjected to creep, quasi-static loading, and damage healing conditions are illustrated with comparisons of model calculations against experimental creep curves, stress-strain curves, strain recovery curves, time-to-rupture data, and fracture mechanism maps

Modeling of the thermo-mechanical behaviour of the PWR fuel

International Nuclear Information System (INIS)

Mailhe, P.

2014-01-01

This article reviews the various physical phenomena that take place in an irradiated fuel rod and presents the development of the thermo-mechanical codes able to simulate them. Though technically simple the fuel rod is the place where appear 4 types of process: thermal, gas behaviour, mechanical and corrosion that combine involving 5 elements: the fuel pellet, the fuel clad, the fuel-clad gap, the inside volume and the coolant. For instance the pellet is the place where the following mechanical processes took place: thermal dilatation, elastic deformation, creep deformation, densification, solid swelling, gaseous swelling and cracking. The first industrial code simulating the behaviour of the fuel rod was COCCINEL, it was developed by AREVA teams from the American PAD code that was included in the Westinghouse license. Today the GALILEO code has replaced the COPERNIC code that was developed in the beginning of the 2000 years. GALILEO is a synthesis of the state of the art of the different models used in the codes validated for PWR and BWR. GALILEO has been validated on more than 1500 fuel rods concerning PWR, BWR and specific reactors like Siloe, Osiris, HFR, Halden, Studsvik, BR2/3,...) and also for extended burn-ups. (A.C.)

Coupled thermo-mechanical creep analysis for boiling water reactor pressure vessel lower head

International Nuclear Information System (INIS)

Villanueva, Walter; Tran, Chi-Thanh; Kudinov, Pavel

2012-01-01

Highlights: ► We consider a severe accident in a BWR with melt pool formation in the lower head. ► We study the influence of pool depth on vessel failure mode with creep analysis. ► There are two modes of failure; ballooning of vessel bottom and a localized creep. ► External vessel cooling can suppress creep and subsequently prevent vessel failure. - Abstract: In this paper we consider a hypothetical severe accident in a Nordic-type boiling water reactor (BWR) at the stage of relocation of molten core materials to the lower head and subsequent debris bed and then melt pool formation. Nordic BWRs rely on reactor cavity flooding as a means for ex-vessel melt coolability and ultimate termination of the accident progression. However, different modes of vessel failure may result in different regimes of melt release from the vessel, which determine initial conditions for melt coolant interaction and eventually coolability of the debris bed. The goal of this study is to define if retention of decay-heated melt inside the reactor pressure vessel is possible and investigate modes of the vessel wall failure otherwise. The mode of failure is contingent upon the ultimate mechanical strength of the vessel structures under given mechanical and thermal loads and applied cooling measures. The influence of pool depth and respective transient thermal loads on the reactor vessel failure mode is studied with coupled thermo-mechanical creep analysis. Efficacy of control rod guide tube (CRGT) cooling and external vessel wall cooling as potential severe accident management measures is investigated. First, only CRGT cooling is considered in simulations revealing two different modes of vessel failure: (i) a ‘ballooning’ of the vessel bottom and (ii) a ‘localized creep’ concentrated within the vicinity of the top surface of the melt pool. Second, possibility of in-vessel retention with CRGT and external vessel cooling is investigated. We found that the external vessel

Simulation of thermo-mechanical effect in bulk-silicon FinFETs

OpenAIRE

Burenkov, Alex; Lorenz, Jürgen

2016-01-01

The thermo-mechanical effect in bulk-silicon FinFETs of the 14 nm CMOS technology node is studied by means of numerical simulation. The electrical performance of such devices is significantly enhanced by the intentional introduction of mechanical stress during the device processing. The thermo-mechanical effect modifies the mechanical stress distribution in active regions of the transistors when they are heated. This can lead to a modification of the electrical performance. Numerical simulati...

Thermo-mechanical response and fatigue behavior of shape memory alloy

Energy Technology Data Exchange (ETDEWEB)

Kusagawa, Masaki; Asada, Yasuhide; Nakamura, Toshiya [Tokyo Univ. (Japan). Dept. of Mechanical Engineering

1998-11-01

Mechanical, thermo-mechanical and fatigue behaviors of Ni-Ti-Nb shape memory alloy (SMA) have been studied to prepare material data for a design purpose. Presented are testing devices, testing procedure and test results of monotonic tensile, recovery of inelastic deformation due to post heating (thermo-mechanical recovery) and fatigue for future use of the SMA as a structural material of nuclear incore structures. (orig.)

Thermo-mechanical response and fatigue behavior of shape memory alloy

International Nuclear Information System (INIS)

Kusagawa, Masaki; Asada, Yasuhide; Nakamura, Toshiya

1998-01-01

Mechanical, thermo-mechanical and fatigue behaviors of Ni-Ti-Nb shape memory alloy (SMA) have been studied to prepare material data for a design purpose. Presented are testing devices, testing procedure and test results of monotonic tensile, recovery of inelastic deformation due to post heating (thermo-mechanical recovery) and fatigue for future use of the SMA as a structural material of nuclear incore structures. (orig.)

Development of a numerical code for the prediction of the long-term behavior of the underground facilities for the high-level radioactive waste disposal

International Nuclear Information System (INIS)

Sawada, Masataka; Okada, Tetsuji; Hasegawa, Takuma

2006-01-01

Complicated phenomena originated by thermo-hydro-mechanical coupling behavior will occur in the near-field of geological disposal of nuclear waste. Development of a numerical evaluation method for such phenomena is important in order to make a reasonable repository design and a safety assessment. In order to achieve the objective above, a numerical model using the equations which can evaluate the swelling characteristics of buffer materials based on the diffusive double layer theory is proposed, and a numerical scheme for the thermo-hydro-mechanical coupled analysis including the swelling model is constructed. The proposed swelling model can reproduce the behavior observed during both swelling pressure tests and swelling deformation tests. When the developed numerical code is applied to the laboratory heater test using a bentonite specimen, it can reproduce the thermal gradient, the distribution of saturation rate and the variation of porosity. The developed numerical code will be applied to well-controlled laboratory tests and full-scale in-situ tests in the future work. In order to apply to the various geochemical conditions around the engineered barrier, chemical component will be coupled to the present numerical code. (author)

Numerical modelling of the long term mechanical behaviour of a storage cell for high level nuclear wastes

International Nuclear Information System (INIS)

Bian, H.B.; Jia, Y.; Duveau, G.; Shao, J.F.; Poutrel, A.

2010-01-01

the various important processes in the storage structures, the coupling between the corrosion/strain processes and the Callovo-Oxfordian clay formation is death with in this study. The principal objective is to establish a numerical method capable to reproduce correctly the evolutionary interface between the metallic container and clay formation taking into account the decrease of mechanical resistance and the generated supplementary volume. Special attention is paid on the evolution of the interface of steel and rock, the amplitude of possible overpressure and stress and the evolution of the EDZ (Excavation Damaged Zone). In the numerical analyses, different materials are taken into account: limestone, argillite, steel and air. Firstly, a brief presentation of the constitutive models for the Callovo-Oxfordian clay is given. For the sake of simplicity, a poro-elastic model is used for limestone and an elasto-plasticity model using a Mises type criterion is applied to the steel. Then a series of parametric studies is performed in order to study the mechanical resistance of corroded steel.. Finally, a storage cell of High-Level Wastes is simulated. In the numerical model, the wastes cell is taken as a circular borehole. The loading path is composed of the following three steps: the excavation phase, the waiting phase for the installation of waste package, and the evolution phase after the backfilling of the storage cell. The proposed model is able to describe the main features of poro-mechanical behaviour for the clay formation: such as plastic deformation, material damage by microcracks, transition of volumetric compressibility/dilatancy and the viscoplastic strain. In spite of the simplifications used, the numerical results allow us to obtain some quantitative results describing the mechanical behaviour and the coupled thermo-hydro-mechanical processes for a short and long-term in the storage cell. (authors)

Assessment of thermo-mechanical behavior in CLAM steel first wall structures

International Nuclear Information System (INIS)

Liu Fubin; Yao Man

2012-01-01

Highlights: ► China Low Activation Martensitic steel (CLAM) as FW the structural material. ► The thermo-mechanical behavior of the FW was analyzed under the condition of normal ITER operation combined effect of plasma heat flux and neutron heating. ► The temperature dependence of the material physical properties of CLAM is summarized. - Abstract: The temperature and strain distributions of the mockup with distinct structural material (SS316L or China Low Activation Martensitic steel (CLAM)) in two-dimensional model were calculated and analyzed, based on a high heat flux (HHF) test recently reported with heat flux of 3.2 MW/m 2 . The calculated temperature and strain results in the first wall (FW), in which SS316L is as the structural material, showed good agreement with HHF test. By substituting CLAM steel for SS316L the contrast analysis indicates that the thermo-mechanical property for CLAM steel is better than that of SS316 at the same condition. Furthermore, the thermo-mechanical behavior of the FW was analyzed under the condition of normal ITER operation combined effect of plasma heat flux and neutron heating.

Assessment of thermo-mechanical behavior in CLAM steel first wall structures

Energy Technology Data Exchange (ETDEWEB)

Liu Fubin, E-mail: liufubin_1216@126.com [School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, Liaoning (China); Yao Man, E-mail: yaoman@dlut.edu.cn [School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, Liaoning (China)

2012-01-15

Highlights: Black-Right-Pointing-Pointer China Low Activation Martensitic steel (CLAM) as FW the structural material. Black-Right-Pointing-Pointer The thermo-mechanical behavior of the FW was analyzed under the condition of normal ITER operation combined effect of plasma heat flux and neutron heating. Black-Right-Pointing-Pointer The temperature dependence of the material physical properties of CLAM is summarized. - Abstract: The temperature and strain distributions of the mockup with distinct structural material (SS316L or China Low Activation Martensitic steel (CLAM)) in two-dimensional model were calculated and analyzed, based on a high heat flux (HHF) test recently reported with heat flux of 3.2 MW/m{sup 2}. The calculated temperature and strain results in the first wall (FW), in which SS316L is as the structural material, showed good agreement with HHF test. By substituting CLAM steel for SS316L the contrast analysis indicates that the thermo-mechanical property for CLAM steel is better than that of SS316 at the same condition. Furthermore, the thermo-mechanical behavior of the FW was analyzed under the condition of normal ITER operation combined effect of plasma heat flux and neutron heating.

Coupling X-band dual-polarized mini-radars and hydro-meteorological forecast models: the HYDRORAD project

Directory of Open Access Journals (Sweden)

E. Picciotti

2013-05-01

Full Text Available Hydro-meteorological hazards like convective outbreaks leading to torrential rain and floods are among the most critical environmental issues world-wide. In that context weather radar observations have proven to be very useful in providing information on the spatial distribution of rainfall that can support early warning of floods. However, quantitative precipitation estimation by radar is subjected to many limitations and uncertainties. The use of dual-polarization at high frequency (i.e. X-band has proven particularly useful for mitigating some of the limitation of operational systems, by exploiting the benefit of easiness to transport and deploy and the high spatial and temporal resolution achievable at small antenna sizes. New developments on X-band dual-polarization technology in recent years have received the interest of scientific and operational communities in these systems. New enterprises are focusing on the advancement of cost-efficient mini-radar network technology, based on high-frequency (mainly X-band and low-power weather radar systems for weather monitoring and hydro-meteorological forecasting. Within the above context, the main objective of the HYDRORAD project was the development of an innovative mbox{integrated} decision support tool for weather monitoring and hydro-meteorological applications. The integrated system tool is based on a polarimetric X-band mini-radar network which is the core of the decision support tool, a novel radar products generator and a hydro-meteorological forecast modelling system that ingests mini-radar rainfall products to forecast precipitation and floods. The radar products generator includes algorithms for attenuation correction, hydrometeor classification, a vertical profile reflectivity correction, a new polarimetric rainfall estimators developed for mini-radar observations, and short-term nowcasting of convective cells. The hydro-meteorological modelling system includes the Mesoscale Model 5

Thermo-mechanical fatigue behavior of the intermetallic gamma-TiAl alloy TNB-V5 with different microstructures

International Nuclear Information System (INIS)

Roth, M; Biermann, H

2010-01-01

The cyclic deformation and fatigue behavior of the γ-TiAl alloy TNB-V5 is studied under thermo-mechanical load for the three technically important microstructures Fully-Lamellar (FL), Near-Gamma (NG) and Duplex (DP), respectively. Thus, thermo-mechanical fatigue (TMF) tests were carried out with different temperature-strain cycles, different temperature ranges from 400 0 C to 800 0 C and with two different strain ranges. Cyclic deformation curves, stress-strain hysteresis loops and fatigue lives are presented. The type of microstructure shows a surprisingly small influence on the cyclic deformation and fatigue behavior under TMF conditions. For a general life prediction the damage parameter of Smith, Watson and Topper P SWT is well suitable, if the testing and the application temperature ranges, respectively, include temperatures above the ductile-brittle transition temperature (approx. 750 0 C). If the maximum temperature is below that temperature, the brittle materials' behavior yields a high scatter of fatigue lives and a low slope of the fatigue life curve and therefore the damage parameter P SWT cannot be applied for the live prediction.

Enhanced thermo-mechanical performance and strain-induced ...

Indian Academy of Sciences (India)

Enhanced thermo-mechanical performance and strain-induced band gap reduction of TiO2@PVC nanocomposite films ... School of Chemical Engineering, Yeungnam University, Gyeongsan 712-749, Republic of Korea; School of Mechanical Engineering, Yeungnam University, Gyeongsan 712-749, Republic of Korea ...

Experimental Hydro-Mechanical Characterization of Full Load Pressure Surge in Francis Turbines

Science.gov (United States)

Müller, A.; Favrel, A.; Landry, C.; Yamamoto, K.; Avellan, F.

2017-04-01

Full load pressure surge limits the operating range of hydro-electric generating units by causing significant power output swings and by compromising the safety of the plant. It appears during the off-design operation of hydraulic machines, which is increasingly required to regulate the broad integration of volatile renewable energy sources into the existing power network. The underlying causes and governing physical mechanisms of this instability were investigated in the frame of a large European research project and this paper documents the main findings from two experimental campaigns on a reduced scale model of a Francis turbine. The multi-phase flow in the draft tube is characterized by Particle Image Velocimetry, Laser Doppler Velocimetry and high-speed visualizations, along with synchronized measurements of the relevant hydro-mechanical quantities. The final result is a comprehensive overview of how the unsteady draft tube flow and the mechanical torque on the runner shaft behave during one mean period of the pressure oscillation, thus defining the unstable fluid-structure interaction responsible for the power swings. A discussion of the root cause is initiated, based on the state of the art. Finally, the latest results will enable a validation of recent RANS flow simulations used for determining the key parameters of hydro-acoustic stability models.

A THM stress-strain framework for modelling the performance of argillaceous materials in deep repositories for radioactive waste

International Nuclear Information System (INIS)

Laloui, L.; Francois, B.

2007-01-01

In the scenarios for deep, geological nuclear-waste repositories, clayey soils will be hydrated, heated, cooled and dried. The numerical modelling of these mechanical processes is a key issue. Performance assessment of deep repositories for heat-generating radioactive waste would benefit from improvements in mechanical stress-strain constitutive modelling of the coupled thermo-hydro-mechanical behaviour. The presented framework allows progress in understanding the most involved phenomena relevant to nuclear-waste repositories and their coupled nature. It could be used both in the design and in the performance assessment of repositories. It may be applied to disposal in clay formations and to hard-rock repositories where artificially compacted clay is to be used as buffer and backfill. Such a constitutive framework may help in understanding some unexplained or controversial behaviours and in defining experimental programmes to answer key questions. (author)

Relationship between permeability and damage in concretes at high temperature; Lien entre la permeabilite et l'endommagement dans les betons a haute temperature

Energy Technology Data Exchange (ETDEWEB)

Dal Pont, St

2004-09-15

Due to its technical and economical advantages, concrete is nowadays the most used building material in civil engineering. Even if its use is known since nearly two centuries, its behavior has not been yet completely explained due to the complexity of its porous microstructure. This fact is quite evident under particular conditions such as, by instance, during an elevation of temperature. This condition can mainly occur in two cases: due to a casualty (e.g. a fire) or in normal use conditions (e.g. storage of nuclear rejects). This work aims at contributing to the study of the phenomena that can be observed in concrete exposed to high temperatures and, in particular, focuses on the study of the evolution of intrinsic permeability. The characterisation of permeability (which is hardly measurable in hot conditions) is necessary for describing and modelling transport phenomena which occur in porous media. An experimental study has been made in collaboration with the CEA. A real-scale hollow cylinder has been instrumented with gauges for studying the evolution of temperature and gas pressure fields inside concrete. Later, the cylinder has been then numerically modelled by means of a thermo-hydro-chemical (THC) and a thermo-hydro-chemo-mechanical (THCM) model. The THC model, implemented by means of the finite volume method, has allowed a first, qualitative study of the behaviour of concrete submitted to high temperature. This model, which, for sake of simplicity, has neglected all mechanical effects, has allowed the description of the main phenomena occurring inside concrete: mass transport, phase changes, microstructure evolution. Later, the modelling has been completed by means of the THCM model using the Hitecosp code, implemented by means of the finite element method at the university of Padua. This code allows a very complete description of the phenomena occurring inside concrete and takes into consideration the mechanical behavior of concrete by means of an

Hydro-mechanical coupling and transport in Meuse/Haute-Marne argillite: experimental and multi-scale approaches; Couplage hydro-me canique et transfert dans l'argilite de Meuse/Haute-Marne: approches experimentale et multi-echelle

Energy Technology Data Exchange (ETDEWEB)

Cariou, S.

2010-07-15

This thesis deals with the hydro-mechanical behaviour of argillite. Classical Biot theory is shown to be badly adapted to the case of argillite. An original state equation is then built by use of homogenization tools, and takes into account the microstructure of argillite as well as physical phenomena happening inside the material, like the swelling overpressure inside the clay particles or the capillary effects in the porous network. This state equation explains some experiments which were not by the classical Biot theory. It is then improved by integrating the experimental data that are the dependency of the elasticity tensor with the saturation degree and the existence of a porosity surrounding the inclusions. Combined with the monitoring of length variation under hydric loading, this relevant state equation permits one to determine the Biot tensor of argillite. Since this state equation is coupled with the hydric state of the material, one is interested in modelling the variation of the saturation degree during a drying process. Two transport models are studied and compared, then a model for the porous network is proposed in order to explain the unusual permeability measurements. (author)

A Micromechanics-Based Elastoplastic Damage Model for Rocks with a Brittle-Ductile Transition in Mechanical Response

Science.gov (United States)

Hu, Kun; Zhu, Qi-zhi; Chen, Liang; Shao, Jian-fu; Liu, Jian

2018-06-01

As confining pressure increases, crystalline rocks of moderate porosity usually undergo a transition in failure mode from localized brittle fracture to diffused damage and ductile failure. This transition has been widely reported experimentally for several decades; however, satisfactory modeling is still lacking. The present paper aims at modeling the brittle-ductile transition process of rocks under conventional triaxial compression. Based on quantitative analyses of experimental results, it is found that there is a quite satisfactory linearity between the axial inelastic strain at failure and the confining pressure prescribed. A micromechanics-based frictional damage model is then formulated using an associated plastic flow rule and a strain energy release rate-based damage criterion. The analytical solution to the strong plasticity-damage coupling problem is provided and applied to simulate the nonlinear mechanical behaviors of Tennessee marble, Indiana limestone and Jinping marble, each presenting a brittle-ductile transition in stress-strain curves.

Relationship between permeability and damage in concretes at high temperature; Lien entre la permeabilite et l'endommagement dans les betons a haute temperature

Energy Technology Data Exchange (ETDEWEB)

Dal Pont, St

2004-09-15

Due to its technical and economical advantages, concrete is nowadays the most used building material in civil engineering. Even if its use is known since nearly two centuries, its behavior has not been yet completely explained due to the complexity of its porous microstructure. This fact is quite evident under particular conditions such as, by instance, during an elevation of temperature. This condition can mainly occur in two cases: due to a casualty (e.g. a fire) or in normal use conditions (e.g. storage of nuclear rejects). This work aims at contributing to the study of the phenomena that can be observed in concrete exposed to high temperatures and, in particular, focuses on the study of the evolution of intrinsic permeability. The characterisation of permeability (which is hardly measurable in hot conditions) is necessary for describing and modelling transport phenomena which occur in porous media. An experimental study has been made in collaboration with the CEA. A real-scale hollow cylinder has been instrumented with gauges for studying the evolution of temperature and gas pressure fields inside concrete. Later, the cylinder has been then numerically modelled by means of a thermo-hydro-chemical (THC) and a thermo-hydro-chemo-mechanical (THCM) model. The THC model, implemented by means of the finite volume method, has allowed a first, qualitative study of the behaviour of concrete submitted to high temperature. This model, which, for sake of simplicity, has neglected all mechanical effects, has allowed the description of the main phenomena occurring inside concrete: mass transport, phase changes, microstructure evolution. Later, the modelling has been completed by means of the THCM model using the Hitecosp code, implemented by means of the finite element method at the university of Padua. This code allows a very complete description of the phenomena occurring inside concrete and takes into consideration the mechanical behavior of concrete by means of an

Normal Mode Analysis to a Poroelastic Half-Space Problem under Generalized Thermoelasticity

Directory of Open Access Journals (Sweden)

Chunbao Xiong

Full Text Available Abstract The thermo-hydro-mechanical problems associated with a poroelastic half-space soil medium with variable properties under generalized thermoelasticity theory were investigated in this study. By remaining faithful to Biot’s theory of dynamic poroelasticity, we idealized the foundation material as a uniform, fully saturated, poroelastic half-space medium. We first subjected this medium to time harmonic loads consisting of normal or thermal loads, then investigated the differences between the coupled thermohydro-mechanical dynamic models and the thermo-elastic dynamic models. We used normal mode analysis to solve the resulting non-dimensional coupled equations, then investigated the effects that non-dimensional vertical displacement, excess pore water pressure, vertical stress, and temperature distribution exerted on the poroelastic half-space medium and represented them graphically.

Coupled numerical modeling of gas hydrates bearing sediments from laboratory to field-scale conditions

Science.gov (United States)

Sanchez, M. J.; Santamarina, C.; Gai, X., Sr.; Teymouri, M., Sr.

2017-12-01

Stability and behavior of Hydrate Bearing Sediments (HBS) are characterized by the metastable character of the gas hydrate structure which strongly depends on thermo-hydro-chemo-mechanical (THCM) actions. Hydrate formation, dissociation and methane production from hydrate bearing sediments are coupled THCM processes that involve, amongst other, exothermic formation and endothermic dissociation of hydrate and ice phases, mixed fluid flow and large changes in fluid pressure. The analysis of available data from past field and laboratory experiments, and the optimization of future field production studies require a formal and robust numerical framework able to capture the very complex behavior of this type of soil. A comprehensive fully coupled THCM formulation has been developed and implemented into a finite element code to tackle problems involving gas hydrates sediments. Special attention is paid to the geomechanical behavior of HBS, and particularly to their response upon hydrate dissociation under loading. The numerical framework has been validated against recent experiments conducted under controlled conditions in the laboratory that challenge the proposed approach and highlight the complex interaction among THCM processes in HBS. The performance of the models in these case studies is highly satisfactory. Finally, the numerical code is applied to analyze the behavior of gas hydrate soils under field-scale conditions exploring different features of material behavior under possible reservoir conditions.

Axisymmetric alternating direction explicit scheme for efficient coupled simulation of hydro-mechanical interaction in geotechnical engineering—Application to circular footing and deep tunnel in saturated ground

Directory of Open Access Journals (Sweden)

Simon Heru Prassetyo

2018-04-01

Full Text Available Explicit solution techniques have been widely used in geotechnical engineering for simulating the coupled hydro-mechanical (H-M interaction of fluid flow and deformation induced by structures built above and under saturated ground, i.e. circular footing and deep tunnel. However, the technique is only conditionally stable and requires small time steps, portending its inefficiency for simulating large-scale H-M problems. To improve its efficiency, the unconditionally stable alternating direction explicit (ADE scheme could be used to solve the flow problem. The standard ADE scheme, however, is only moderately accurate and is restricted to uniform grids and plane strain flow conditions. This paper aims to remove these drawbacks by developing a novel high-order ADE scheme capable of solving flow problems in non-uniform grids and under axisymmetric conditions. The new scheme is derived by performing a fourth-order finite difference (FD approximation to the spatial derivatives of the axisymmetric fluid–diffusion equation in a non-uniform grid configuration. The implicit Crank-Nicolson technique is then applied to the resulting approximation, and the subsequent equation is split into two alternating direction sweeps, giving rise to a new axisymmetric ADE scheme. The pore pressure solutions from the new scheme are then sequentially coupled with an existing geomechanical simulator in the computer code fast Lagrangian analysis of continua (FLAC. This coupling procedure is called the sequentially-explicit coupling technique based on the fourth-order axisymmetric ADE scheme or SEA-4-AXI. Application of SEA-4-AXI for solving axisymmetric consolidation of a circular footing and of advancing tunnel in deep saturated ground shows that SEA-4-AXI reduces computer runtime up to 42%–50% that of FLAC's basic scheme without numerical instability. In addition, it produces high numerical accuracy of the H-M solutions with average percentage difference of only 0.5%�

Experimental study on the thermo-mechanical behaviour of stiff clay under non-isotropic stress state

International Nuclear Information System (INIS)

Tang, Anh Minh; Cui, Yu-Jun; Li, Xiang-Ling

2012-01-01

Document available in extended abstract form only. Stiff clay is usually considered as possible host-rock for geological radioactive waste disposal due to its low permeability and its self-sealing capacity. Boom Clay, for instance, is one of the clays currently considered by the Belgian radioactive waste management agency Ondraf/Niras as a potential host for a geological repository. In order to analyse the performance of this material, it is important to understand its behaviour under the coupled thermo-hydro-mechanical solicitations. In laboratory, several studies have been performed to study the volume change of clay under coupled thermomechanical loading. The results show that heating under drained conditions can induce thermal dilation at low confining stress and thermal contraction at high confining stress. On the other hand, compression tests performed at constant temperature show that the compressibility parameters of soil can be modified by temperature change. These features are now well considered in constitutive laws based on the framework of elasto-plasticity. Under undrained conditions, heating can increase pore-water pressure and this behaviour can be simulated using the theoretical thermo-poro-elastic framework. The temperature effect on the soil behaviour under triaxial compression is also often considered. It is commonly accepted that heating decreases the shear strength of clay but this softening can be hidden by the thermal contraction that occurs during heating which can induce at the same time soil hardening. In spite of these existing works, laboratory tests considering the thermo-mechanical loading path that the soil can be subjected to are still rare. Actually, in the case of geological radioactive waste disposal, after the installation of waste canisters, the soil is expected to be heated under non-isotropic stress state. Most of the existing laboratory works show heating tests in odometer cell or triaxial cell under isotropic stress

Time dependent mechanical modeling for polymers based on network theory

Energy Technology Data Exchange (ETDEWEB)

Billon, Noëlle [MINES ParisTech, PSL-Research University, CEMEF – Centre de mise en forme des matériaux, CNRS UMR 7635, CS 10207 rue Claude Daunesse 06904 Sophia Antipolis Cedex (France)

2016-05-18

Despite of a lot of attempts during recent years, complex mechanical behaviour of polymers remains incompletely modelled, making industrial design of structures under complex, cyclic and hard loadings not totally reliable. The non linear and dissipative viscoelastic, viscoplastic behaviour of those materials impose to take into account non linear and combined effects of mechanical and thermal phenomena. In this view, a visco-hyperelastic, viscoplastic model, based on network description of the material has recently been developed and designed in a complete thermodynamic frame in order to take into account those main thermo-mechanical couplings. Also, a way to account for coupled effects of strain-rate and temperature was suggested. First experimental validations conducted in the 1D limit on amorphous rubbery like PMMA in isothermal conditions led to pretty goods results. In this paper a more complete formalism is presented and validated in the case of a semi crystalline polymer, a PA66 and a PET (either amorphous or semi crystalline) are used. Protocol for identification of constitutive parameters is described. It is concluded that this new approach should be the route to accurately model thermo-mechanical behaviour of polymers using a reduced number of parameters of some physical meaning.

Fracture mechanics in new designed power module under thermo-mechanical loads

Directory of Open Access Journals (Sweden)

Durand Camille

2014-06-01

Full Text Available Thermo-mechanically induced failure is a major reliability issue in the microelectronic industry. On this account, a new type of Assembly Interconnected Technology used to connect MOSFETs in power modules has been developed. The reliability is increased by using a copper clip soldered on the top side of the chip, avoiding the use of aluminium wire bonds, often responsible for the failure of the device. Thus the new designed MOSFET package does not follow the same failure mechanisms as standard modules. Thermal and power cycling tests were performed on these new packages and resulting failures were analyzed. Thermo-mechanical simulations including cracks in the aluminium metallization and intermetallics (IMC were performed using Finite Element Analysis in order to better understand crack propagation and module behaviour.

RATDAMPER - A Numerical Model for Coupling Mechanical and Hydrological Properties within the Disturbed Rock Zone at the Waste Isolation Pilot Plant

International Nuclear Information System (INIS)

RATH, JONATHAN S.; PFEIFLE, T.W.; HUNSCHE, U.

2000-01-01

A numerical model for predicting damage and permeability in the disturbed rock zone (DRZ) has been developed. The semi-empirical model predicts damage based on a function of stress tensor invariant. For a wide class of problems hydrologic/mechanical coupling is necessary for proper analysis. The RATDAMPER model incorporates dilatant volumetric strain and permeability. The RATDAMPER model has been implemented in a weakly coupled code, which combines a finite element structural code and a finite difference multi-phase fluid flow code. Using the development of inelastic volumetric strain, a value of permeability can be assigned. This flexibility allows empirical permeability functional relationships to be evaluated

Multiphysics modelling and experimental validation of an air-coupled array of PMUTs with residual stresses

Science.gov (United States)

Massimino, G.; Colombo, A.; D'Alessandro, L.; Procopio, F.; Ardito, R.; Ferrera, M.; Corigliano, A.

2018-05-01

In this paper a complete multiphysics modelling via the finite element method (FEM) of an air-coupled array of piezoelectric micromachined ultrasonic transducers (PMUT) and its experimental validation are presented. Two numerical models are described for the single transducer, axisymmetric and 3D, with the following features: the presence of fabrication induced residual stresses, which determine a non-linear initial deformed configuration of the diaphragm and a substantial fundamental mode frequency shift; the multiple coupling between different physics, namely electro-mechanical coupling for the piezo-electric model, thermo-acoustic-structural interaction and thermo-acoustic-pressure interaction for the waves propagation in the surrounding fluid. The model for the single transducer is enhanced considering the full set of PMUTs belonging to the silicon dye in a 4 × 4 array configuration. The results of the numerical multiphysics models are compared with experimental ones in terms of the initial static pre-deflection, of the diaphragm central point spectrum and of the sound intensity at 3.5 cm on the vertical direction along the axis of the diaphragm.

micro-mechanical experimental investigation and modelling of strain and damage of argillaceous rocks under combined hydric and mechanical loads

International Nuclear Information System (INIS)

Wang, L.

2012-01-01

The hydro-mechanical behavior of argillaceous rocks, which are possible host rocks for underground radioactive nuclear waste storage, is investigated by means of micro-mechanical experimental investigations and modellings. Strain fields at the micrometric scale of the composite structure of this rock, are measured by the combination of environmental scanning electron microscopy, in situ testing and digital image correlation technique. The evolution of argillaceous rocks under pure hydric loading is first investigated. The strain field is strongly heterogeneous and manifests anisotropy. The observed nonlinear deformation at high relative humidity (RH) is related not only to damage, but also to the nonlinear swelling of the clay mineral itself, controlled by different local mechanisms depending on RH. Irreversible deformations are observed during hydric cycles, as well as a network of microcracks located in the bulk of the clay matrix and/or at the inclusion-matrix interface. Second, the local deformation field of the material under combined hydric and mechanical loadings is quantified. Three types of deformation bands are evidenced under mechanical loading, either normal to stress direction (compaction), parallel (microcracking) or inclined (shear). Moreover, they are strongly controlled by the water content of the material: shear bands are in particular prone to appear at high RH states. In view of understanding the mechanical interactions a local scale, the material is modeled as a composite made of non-swelling elastic inclusions embedded in an elastic swelling clay matrix. The internal stress field induced by swelling strain incompatibilities between inclusions and matrix, as well as the overall deformation, is numerically computed at equilibrium but also during the transient stage associated with a moisture gradient. An analytical micro-mechanical model based on Eshelby's solution is proposed. In addition, 2D finite element computations are performed. Results

An example of coupling behaviour-damage-environment in polycrystals. Application to Pellet-Cladding Interaction

International Nuclear Information System (INIS)

Diard, Olivier

2001-01-01

Zircaloy-4 cladding is the first containment barrier for fission products, and its integrity must therefore be ensured in nominal and accidental situations. However, stress corrosion induced cracks may appear due to a strong pellet-cladding interaction. It is therefore important to model this interaction and crack growth and propagation to establish non-damage criteria. Thus, this research thesis aims at developing a modelling covering both issues (pellet-cladding interaction, and stress corrosion cracking) and allowing macroscopic and microscopic scales to be coupled. After a bibliographical synthesis on iodine-induced stress corrosion cracking and similar phenomena, the author presents the model proposed for the pellet-cladding interaction: phenomena to be taken into account, phenomenological and macroscopic behaviour laws used respectively for pellet and cladding. An extended version of an existing cladding viscoplastic model is proposed. Stress and strain fields in the cladding are obtained, notably in the contact zone. In the next part, the author presents various numerical tools developed or used to model multi-crystalline aggregates, and the model of crystalline plasticity used to simulate cladding behaviour at the microstructure scale. Effects of mesh density, element types and anisotropic elasticity are also discussed. The next chapter addresses the mechanical-chemical coupling. Some coupling formulas are presented for simple cases in order to define the effective diffusion coefficient. The last part reports the modelling of intergranular damage: definition of a damage criterion at the granular scale, assessment of stresses at grain boundaries, and effect of crystallographic neighbouring. A model of grain boundary damage is also proposed. This model is assessed on Failure Mechanics test samples and on simple microstructures. The application of the whole numerical model is reported [fr

Hydro-mechanical analysis of results acquired by video-observations and deformation measurements performed in boreholes in the Opalinus clay of the URL Mont Terri supported by laboratory investigations on the hydro-mechanical behaviour of Opalinus clay

International Nuclear Information System (INIS)

Seeska, R.; Rutenberg, M.; Lux, K.H.

2012-01-01

also be detected. Furthermore, a significant influence of the hydraulic behaviour on the load-bearing and deformation behaviour of the investigated boreholes was observed. Therefore, laboratory investigations regarding the hydraulic sensitivity of Opalinus Clay have been performed in the TUC rock mechanic laboratory on rock samples from the URL Mont Terri in addition to the in-situ observations. To investigate the hydraulic sensitivity and the hydro-mechanically coupled behaviour of the clay-stone samples, a series of uniaxial strength tests with precisely controlled relative humidity and temperature of the air surrounding the specimen inside the test rig has been performed. Eventually, an attempt has been made to hydro-mechanically model the observed borehole behaviour by using a three-dimensional model covering a drift section and a borehole within the near field of the drift. The numerical simulations have been performed using an elastoplastic constitutive model named ubiquitous joint. Implemented in the FLAC3D software code, the constitutive model ubiquitous joint is capable of modelling the mechanical behaviour of the rock matrix as well as the highly anisotropic mechanical behaviour of the bedding planes. Furthermore, effects like time dependent desaturation of the rock mass, a reduction of strength in the damaged zones around the drift and the borehole, and the increase of hydraulic permeability within the damaged zones have also been taken into consideration when performing the numerical simulations. Figure 2 exemplarily shows the calculated pore pressure distribution around the drift and the borehole in a cross section along the borehole's longitudinal axis. The presentation includes a brief discussion of the results obtained by the logging tool and the discussion of the borehole videos that were recorded by the axial borehole camera as well as a discussion of the laboratory results before in the concluding part the results of the numerical simulations will be

Thermo-mechanical fatigue behavior of the intermetallic gamma-TiAl alloy TNB-V5 with different microstructures

Energy Technology Data Exchange (ETDEWEB)

Roth, M [now at IAV GmbH, Kauffahrtei 25, D-09120 Chemnitz (Germany); Biermann, H, E-mail: marcel.roth@iav.d [TU Bergakademie Freiberg, Institute for Materials Engineering, Gustav-Zeuner-Strasse 5, D-09599 Freiberg (Germany)

2010-07-01

The cyclic deformation and fatigue behavior of the {gamma}-TiAl alloy TNB-V5 is studied under thermo-mechanical load for the three technically important microstructures Fully-Lamellar (FL), Near-Gamma (NG) and Duplex (DP), respectively. Thus, thermo-mechanical fatigue (TMF) tests were carried out with different temperature-strain cycles, different temperature ranges from 400{sup 0}C to 800{sup 0}C and with two different strain ranges. Cyclic deformation curves, stress-strain hysteresis loops and fatigue lives are presented. The type of microstructure shows a surprisingly small influence on the cyclic deformation and fatigue behavior under TMF conditions. For a general life prediction the damage parameter of Smith, Watson and Topper P{sub SWT} is well suitable, if the testing and the application temperature ranges, respectively, include temperatures above the ductile-brittle transition temperature (approx. 750{sup 0}C). If the maximum temperature is below that temperature, the brittle materials' behavior yields a high scatter of fatigue lives and a low slope of the fatigue life curve and therefore the damage parameter P{sub SWT} cannot be applied for the live prediction.

A damage mechanics based general purpose interface/contact element

Science.gov (United States)

Yan, Chengyong

Most of the microelectronics packaging structures consist of layered substrates connected with bonding materials, such as solder or epoxy. Predicting the thermomechanical behavior of these multilayered structures is a challenging task in electronic packaging engineering. In a layered structure the most complex part is always the interfaces between the strates. Simulating the thermo-mechanical behavior of such interfaces, is the main theme of this dissertation. The most commonly used solder material, Pb-Sn alloy, has a very low melting temperature 180sp°C, so that the material demonstrates a highly viscous behavior. And, creep usually dominates the failure mechanism. Hence, the theory of viscoplasticity is adapted to describe the constitutive behavior. In a multilayered assembly each layer has a different coefficient of thermal expansion. Under thermal cycling, due to heat dissipated from circuits, interfaces and interconnects experience low cycle fatigue. Presently, the state-of-the art damage mechanics model used for fatigue life predictions is based on Kachanov (1986) continuum damage model. This model uses plastic strain as a damage criterion. Since plastic strain is a stress path dependent value, the criterion does not yield unique damage values for the same state of stress. In this dissertation a new damage evolution equation based on the second law of thermodynamic is proposed. The new criterion is based on the entropy of the system and it yields unique damage values for all stress paths to the final state of stress. In the electronics industry, there is a strong desire to develop fatigue free interconnections. The proposed interface/contact element can also simulate the behavior of the fatigue free Z-direction thin film interconnections as well as traditional layered interconnects. The proposed interface element can simulate behavior of a bonded interface or unbonded sliding interface, also called contact element. The proposed element was verified against

Temperature buffer test. Hydro-mechanical and chemical/ mineralogical characterizations

Energy Technology Data Exchange (ETDEWEB)

Aakesson, Mattias; Olsson, Siv; Dueck, Ann; Nilsson, Ulf; Karnland, Ola [Clay Technology AB, Lund (Sweden); Kiviranta, Leena; Kumpulainen, Sirpa [BandTech Oy, Helsinki (Finland); Linden, Johan [Aabo Akademi, Aabo (Finland)

2012-01-15

The Temperature Buffer Test (TBT) is a joint project between SKB/ANDRA and supported by ENRESA (modeling) and DBE (instrumentation), which aims at improving the understanding and to model the thermo-hydro-mechanical behavior of buffers made of swelling clay submitted to high temperatures (over 100 deg C) during the water saturation process. The test has been carried out in a KBS-3 deposition hole at Aspo HRL. It was installed during the spring of 2003. Two steel heaters (3 m long, 0.6 m diameter) and two buffer arrangements have been investigated: the lower heater was surrounded by rings of compacted Wyoming bentonite only, whereas the upper heater was surrounded by a composite barrier, with a sand shield between the heater and the bentonite. The test was dismantled and sampled during the winter of 2009/2010. This report presents the hydro-mechanical and chemical/mineralogical characterization program which was launched subsequent to the dismantling operation. The main goal has been to investigate if any significant differences could be observed between material from the field experiment and the reference material. The field samples were mainly taken from Ring 4 (located at the mid-section around the lower heater), in which the temperature in the innermost part reached 155 deg C. The following hydro-mechanical properties have been determined for the material (test technique within brackets): hydraulic conductivity (swelling pressure device), swelling pressure (swelling pressure device), unconfined compression strength (mechanical press), shear strength (triaxial cell) and retention properties (jar method). The following chemical/mineralogical properties (methods within brackets) were determined: anion analysis of water leachates (IC), chemical composition (ICP/AES+MS, EGA), cation exchange capacity (CEC, Cu-trien method) and exchangeable cations (exchange with NH4, ICPAES), mineralogical composition (XRD and FTIR), element distribution and microstructure (SEM and

Coupled HM modelling of the mine-by test at Meuse-Haute-Marne (MHM) URL France

International Nuclear Information System (INIS)

Yildizdag, K.; Shao, H.; Hesser, J.; Soennke, J.; Noiret, A.

2012-01-01

calculated and measured pore pressure values was obtained in the near field by using a 2D damage model (Figure 2). Discussion: Increased understanding of the complex hydro-mechanical responses to the excavation process in clay-stone is gained through coupled HM models and damage process. Comprehensive analyses revealed that observed long-term deformation and pore pressure development result in change of near field material properties mainly induced by damage, e.g. reduction of stiffness and increasing of permeability. (authors)

Environmental flows in hydro-economic models

Science.gov (United States)

Pereau, Jean-Christophe; Pryet, Alexandre

2018-03-01

The protection of environmental flows, as a management objective for a regulating agency, needs to be consistent with the aquifer water balance and the degree of resource renewability. A stylized hydro-economic model is used where natural recharge, which sustains environmental flows, is considered both in the aquifer water budget and in the welfare function as ecosystem damage. Groundwater recharge and the associated natural drainage may be neglected for aquifers containing fossil water, where the groundwater is mined. However, when dealing with an aquifer that constitutes a renewable resource, for which recharge is not negligible, natural drainage should explicitly appear in the water budget. In doing so, the optimum path of net extraction rate does not necessarily converge to the recharge rate, but depends on the costs associated with ecosystem damages. The optimal paths and equilibrium values for the water volume and water extraction are analytically derived, and numerical simulations based on the Western La Mancha aquifer (southwest Spain) illustrate the theoretical results of the study.

A hydro-thermo-mechanics analyze of the thermal fatigue in the mixing tee junction

International Nuclear Information System (INIS)

Gourdin, C.; Chapuliot, S.; Magnaud, J.P.; Payen, T.

2003-01-01

Work presented here, has been achieved at Cea, and is related to the comprehension of the mechanisms leading to cracking under thermal loading in the zones of mixing. The main objective of this work is to analyze, by computation, the thermal loading induced by the turbulent mixing following a tee junction and to explain how it can create cracking, from the internal skin of the component to a leakage, as it was observed in Civaux Power Plant in 1998. The phenomenon is still today not completely understood. One of the principal reasons to this partial incomprehension undoubtedly resides in the multi-field aspect of the loading and of the associated damage, utilizing three different and complementary scientific disciplines: thermohydraulics, thermomechanics and material science. The presentation proposed here, consists in connecting the analyses resulting from these various fields. The first part concentrates on thermohydraulics simulations. The choice of an adequate modeling is discussed on the basis of observed cracking in order to highlight phenomena of large scale beats, which are supposed one of the major causes leading to the failure of the structures. The second part deals with the use of the temperature fields obtained in the first part in order to carry out thermomechanical simulations. All these simulations are 3-dimensional and represent the complex geometry of Civaux RRA piping line, including a tee junction and elbows, water flow velocity. Mean and temperatures variations, mean and stresses variations are also presented. As final results make it possible to determine a map of the damage associated with these complex thermal loading. (authors)

Thermo-mechanical modelling and experimental validation of CLIC prototype module type 0

CERN Document Server

Kortelainen, Lauri; Koivurova, Hannu; Riddone, Germana; Österberg, Kenneth

Micron level stability of the two-meter repetitive modules constituting the two main linacs is one of the most important requirements to achieve the luminosity goal for the Compact Linear Collider. Structural deformations due to thermal loads and related to the RF power dissipated inside the modules affect the alignment of the linacs and therefore the resulting luminosity performance. A CLIC prototype module has been assembled in a dedicated laboratory and a thermal test program has been started in order to study its thermo-mechanical behaviour. This thesis focuses on the finite elements modelling of the first CLIC prototype module 0. The aim of the modelling is to examine the temperature distributions and the resulting deformations of the module in different operating conditions defined in the thermal test program. The theoretical results have been compared to the experimental ones; the comparison shows that the results are in good agreement both for the thermal behaviour of the module and for the resulting ...

Computational Modelling of Fracture Propagation in Rocks Using a Coupled Elastic-Plasticity-Damage Model

Directory of Open Access Journals (Sweden)

Isa Kolo

2016-01-01

Full Text Available A coupled elastic-plasticity-damage constitutive model, AK Model, is applied to predict fracture propagation in rocks. The quasi-brittle material model captures anisotropic effects and the distinct behavior of rocks in tension and compression. Calibration of the constitutive model is realized using experimental data for Carrara marble. Through the Weibull distribution function, heterogeneity effect is captured by spatially varying the elastic properties of the rock. Favorable comparison between model predictions and experiments for single-flawed specimens reveal that the AK Model is reliable and accurate for modelling fracture propagation in rocks.

A Plastic Damage Mechanics Model for Engineered Cementitious Composites

DEFF Research Database (Denmark)

Dick-Nielsen, Lars; Stang, Henrik; Poulsen, Peter Noe

2007-01-01

This paper discusses the establishment of a plasticity-based damage mechanics model for Engineered Cementitious Composites (ECC). The present model differs from existing models by combining a matrix and fiber description in order to describe the behavior of the ECC material. The model provides...

Heater test in the Opalinus Clay of the Mont Terri URL. Gas release and water redistribution - Contribution to heater experiment (HE); Rock and bentonite thermo-hydro-mechanical (THM) processes in the nearfield

International Nuclear Information System (INIS)

Jockwer, N.; Wieczorek, K.

2006-06-01

Beside salt and granite, clay formations are investigated as potential host rocks for disposing radioactive waste. In Switzerland in the canton Jura close to the city of St. Ursanne, an underground laboratory was built in the vicinity of the reconnaissance gallery of a motorway tunnel. Since 1995, a consortium of 12 international organisations is running this laboratory for investigating the suitability of the Opalinus clay formation with regard to disposal of radioactive waste. In 1999, the Heater Experiment B (HE-B) was started for investigating the coupled thermo-hydro-mechanical (THM) processes of the Opalinus clay in interaction with the bentonite buffer. The principal contractors of this project were the Bundesanstalt fuer Geowissenschaften und Rohstoffe (BGR), the Empresa Nacional de Residuos Radiactivos S. A. (ENRESA), the Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH, and the National Cooperative for the Disposal of Radioactive Waste (NAGRA). GRS participated in that experiment for determining the subjects of gas generation, gas release, water content, and water redistribution in the Opalinus clay during heating. This was achieved by analysing gas and water samples from the test field before, during, and after the heating period and by performing geoelectric tomography measurements in the heated region. The in-situ measurements were supported by an additional laboratory programme. This report deals with the work of GRS performed in this project during the years 1999 to 2005. All the results obtained in the frame of the project are presented. Additional laboratory measurements conducted by the Pore Water Laboratory at CIEMAT in Madrid are also presented. The participation of GRS was funded by German Ministry of Economics and Labour (BMWA) under the contract No. 02 E 9602 and by the Commission of the European Communities under the contract No. FIKW.CT-2001-00132. (orig.)

Modelling of the Thermo-Mechanical Behavior of the Two-Beam Module for the Compact Linear Collider

CERN Document Server

Raatikainen, Riku; Österberg, K; Lehtovaara, A; Pajunen, S

2011-01-01

To fulfil the mechanical requirements set by the luminosity goals of the compact linear collider, the 2-m long two-beam modules, the shortest repetitive elements in the main linear accelerator, have to be controlled at micrometer level. At the same time these modules are exposed to high power dissipation that varies while the accelerator is ramped up to nominal power and when the mode of the accelerator operation is modified. These variations will give rise to inevitable temperature transients driving mechanical distortions in and between different module components. Therefore, the thermo-mechanical behaviour of the module is of a high importance. This thesis describes a finite element method model for the two-beam compact linear collider module. The components are described in detail compared to earlier models, which should result in a realistic description of the module. Due to the complexity of the modules, the modelling is divided into several phases from geometrical simplification and modification to the...

Ultra-compact and wide-spectrum-range thermo-optic switch based on silicon coupled photonic crystal microcavities

International Nuclear Information System (INIS)

Zhang, Xingyu; Chung, Chi-Jui; Pan, Zeyu; Yan, Hai; Chakravarty, Swapnajit; Chen, Ray T.

2015-01-01

We design, fabricate, and experimentally demonstrate a compact thermo-optic gate switch comprising a 3.78 μm-long coupled L0-type photonic crystal microcavities on a silicon-on-insulator substrate. A nanohole is inserted in the center of each individual L0 photonic crystal microcavity. Coupling between identical microcavities gives rise to bonding and anti-bonding states of the coupled photonic molecules. The coupled photonic crystal microcavities are numerically simulated and experimentally verified with a 6 nm-wide flat-bottom resonance in its transmission spectrum, which enables wider operational spectrum range than microring resonators. An integrated micro-heater is in direct contact with the silicon core to efficiently drive the device. The thermo-optic switch is measured with an optical extinction ratio of 20 dB, an on-off switching power of 18.2 mW, a thermo-optic tuning efficiency of 0.63 nm/mW, a rise time of 14.8 μs, and a fall time of 18.5 μs. The measured on-chip loss on the transmission band is as low as 1 dB

Combined meso-scale modeling and experimental investigation of the effect of mechanical damage on the transport properties of cementitious composites

Science.gov (United States)

Raghavan, Balaji; Niknezhad, Davood; Bernard, Fabrice; Kamali-Bernard, Siham

2016-09-01

The transport properties of cementitious composites such as concrete are important indicators of their durability, and are known to be heavily influenced by mechanical loading. In the current work, we use meso-scale hygro-mechanical modeling with a morphological 3D two phase mortar-aggregate model, in conjunction with experimentally obtained properties, to investigate the coupling between mechanical loading and damage and the permeability of the composite. The increase in permeability of a cylindrical test specimen at 28% aggregate fraction during a uniaxial displacement-controlled compression test at 85% of the peak load was measured using a gas permeameter. The mortar's mechanical behavior is assumed to follow the well-known compression damaged plasticity (CDP) model with isotropic damage, at varying thresholds, and obtained from different envelope curves. The damaged intrinsic permeability of the mortar evolves according to a logarithmic matching law with progressive loading. We fit the matching law parameters to the experimental result for the test specimen by inverse identification using our meso-scale model. We then subject a series of virtual composite specimens to quasi-static uniaxial compressive loading with varying boundary conditions to obtain the simulated damage and strain evolutions, and use the damage data and the previously identified parameters to determine the evolution of the macroscopic permeability tensor for the specimens, using a network model. We conduct a full parameter study by varying aggregate volume fraction, granulometric distribution, loading/boundary conditions and "matching law" parameters, as well as for different strain-damage thresholds and uniaxial loading envelope curves. Based on this study, we propose Avrami equation-based upper and lower bounds for the evolution of the damaged permeability of the composite.

Multi-scale modeling of the thermo-mechanical behavior of particle-based composites

International Nuclear Information System (INIS)

Di Paola, F.

2010-01-01

The aim of this work was to perform numerical simulations of the thermal and mechanical behavior of a particle-based nuclear fuel. This is a refractory composite material made of UO 2 spherical particles which are coated with two layers of pyrocarbon and embedded in a graphite matrix at a high volume fraction (45%). The objective was to develop a multi-scale modeling of this composite material which can estimate its mean behavior as well as the heterogeneity of the local mechanical variables. The first part of this work was dedicated to the modeling of the microstructure in 3D. To do this, we developed tools to generate random distributions of spheres, meshes and to characterize the morphology of the microstructure towards the finite element code Cast3M. A hundred of numerical samples of the composite were created. The second part was devoted to the characterization of the thermo-elastic behavior by the finite element modeling of the samples. We studied the influence of different modeling parameters, one of them is the boundary conditions. We proposed a method to vanish the boundary conditions effects from the computed solution by analyzing it on an internal sub-volume of the sample obtained by erosion. Then, we determined the effective properties (elastic moduli, thermal conductivity and thermal expansion) and the stress distribution within the matrix. Finally, in the third part we proposed a multi-scale modeling to determine the mean values and the variance and covariance of the local mechanical variables for any macroscopic load. This statistical approach have been used to estimate the intra-phase distribution of these variables in the composite material. (author) [fr

Multi-scale modeling of the thermo-mechanical behavior of particle-based composites

International Nuclear Information System (INIS)

Di Paola, F.

2010-11-01

The aim of this work was to perform numerical simulations of the thermal and mechanical behavior of a particle-based nuclear fuel. This is a refractory composite material made of UO 2 spherical particles which are coated with two layers of pyrocarbon and embedded in a graphite matrix at a high volume fraction (45 %). The objective was to develop a multi-scale modeling of this composite material which can estimate its mean behavior as well as the heterogeneity of the local mechanical variables. The first part of this work was dedicated to the modeling of the microstructure in 3D. To do this, we developed tools to generate random distributions of spheres, meshes and to characterize the morphology of the microstructure towards the finite element code Cast3M. A hundred of numerical samples of the composite were created. The second part was devoted to the characterization of the thermo-elastic behavior by the finite element modeling of the samples. We studied the influence of different modeling parameters, one of them is the boundary conditions. We proposed a method to vanish the boundary conditions effects from the computed solution by analyzing it on an internal sub-volume of the sample obtained by erosion. Then, we determined the effective properties (elastic moduli, thermal conductivity and thermal expansion) and the stress distribution within the matrix. Finally, in the third part we proposed a multi-scale modeling to determine the mean values and the variance and covariance of the local mechanical variables for any macroscopic load. This statistical approach have been used to estimate the intra-phase distribution of these variables in the composite material. (author)

Non-destructive thermo-mechanical behavior assessment of glass-ceramics for dental applications

Science.gov (United States)

Kordatos, E. Z.; Abdulkadhim, Z.; Feteira, A. M.

2017-05-01

Every year millions of people seek dental treatment to either repair damaged, unaesthetic and dysfunctional teeth or replace missing natural teeth. Several dental materials have been developed to meet the stringent requirements in terms of mechanical properties, aesthetics and chemical durability in the oral environment. Glass-ceramics exhibit a suitable combination of these properties for dental restorations. This research is focused on the assessment of the thermomechanical behavior of bio-ceramics and particularly lithium aluminosilicate glass-ceramics (LAS glass-ceramics). Specifically, methodologies based on Infrared Thermography (IRT) have been applied in order the structure - property relationship to be evaluated. Non-crystallized, partially crystallized and fully crystallized glass-ceramic samples have been non-destructively assessed in order their thermo-mechanical behavior to be associated with their micro-structural features.

Learnings from investigations on SG divider plates: Coupling field characterizations with numerical mechanical simulation

International Nuclear Information System (INIS)

Rossillon, F.; Depradeux, L.; Miloudi, S.; Deforge, D.; Lemaire, E.; Massoud, J.P.

2014-01-01

Nickel based alloys stress corrosion cracking (SCC) has been a major concern for the nuclear power plant utilities since the 1970s. Since 2002, SCC indications have been found on steam generator (SG) divider plates made of alloy 600 on French PWRs (pressurized water reactors) 900 MWe units. Although integrity is not questioned, many studies have been conducted to deepen understanding of the phenomenon. Among numerous studies to investigate the SCC damage phenomena, advanced mechanical analysis has been performed to improve the knowledge of the in-service loadings of the SG 900 MWe partition stub and divider plate. Manufacturing steps are taken into account, such as welding and the first hydro-test, to have a more precise description of the mechanical states in the vicinity of the welds where SCC is likely to occur. Recently, EDF hot laboratories made destructive examinations of a decommissioned SG. To fulfil the analyses computations have been carried out on the dedicated configuration. A 3D FE model, including the simulation of the welding and hydro-test, has been set up. Comparisons with experimental investigations on the divider plate of decommissioned SG have shown a good agreement between experimental and numerical results. These results emphasize the redistribution of weld residual stresses after the first hydro-test, and the effect of hydro-testing on the plastic deformation of the stub only in some specific cases of 900 MWe SG

Learnings from investigations on SG divider plates: Coupling field characterizations with numerical mechanical simulation

Energy Technology Data Exchange (ETDEWEB)

Rossillon, F., E-mail: frederique.rossillon@edf.fr [EDF SEPTEN, 12-14 Avenue Dutrievoz, Villeurbanne (France); Depradeux, L. [EC2-MS, 66 Bd Niels Bohr, Villeurbanne (France); Miloudi, S. [EDF CEIDRE, CNPE de Chinon, Avoine (France); Deforge, D. [EDF CEIDRE, 2 Rue Ampère, Saint Denis (France); Lemaire, E. [EDF UNIE, Cap Ampère, Saint Denis (France); Massoud, J.P. [EDF SEPTEN, 12-14 Avenue Dutrievoz, Villeurbanne (France)

2014-04-01

Nickel based alloys stress corrosion cracking (SCC) has been a major concern for the nuclear power plant utilities since the 1970s. Since 2002, SCC indications have been found on steam generator (SG) divider plates made of alloy 600 on French PWRs (pressurized water reactors) 900 MWe units. Although integrity is not questioned, many studies have been conducted to deepen understanding of the phenomenon. Among numerous studies to investigate the SCC damage phenomena, advanced mechanical analysis has been performed to improve the knowledge of the in-service loadings of the SG 900 MWe partition stub and divider plate. Manufacturing steps are taken into account, such as welding and the first hydro-test, to have a more precise description of the mechanical states in the vicinity of the welds where SCC is likely to occur. Recently, EDF hot laboratories made destructive examinations of a decommissioned SG. To fulfil the analyses computations have been carried out on the dedicated configuration. A 3D FE model, including the simulation of the welding and hydro-test, has been set up. Comparisons with experimental investigations on the divider plate of decommissioned SG have shown a good agreement between experimental and numerical results. These results emphasize the redistribution of weld residual stresses after the first hydro-test, and the effect of hydro-testing on the plastic deformation of the stub only in some specific cases of 900 MWe SG.

Efficient modeling of metallic interconnects for thermo-mechanical simulation of SOFC stacks: homogenized behaviors and effect of contact

DEFF Research Database (Denmark)

Tadesse Molla, Tesfaye; Kwok, Kawai; Frandsen, Henrik Lund

2016-01-01

temperature, deformations involving the elastic, creep as well as effect of changes in the geometry due to contact should be accounted for. The constitutive law can be applied using 3D modeling, but for simple presentation of the theory, 2D plane strain formulation is used to model the corrugated metallic......Currently thermo-mechanical analysis of the entire solid oxide fuel cell (SOFC) stack at operational conditions is computationally challenging if the geometry of metallic interconnects is considered explicitly. This is particularly the case when creep deformations in the interconnect are considered...... model to calculate the homogenized mechanical response of corrugated metallic interconnects at high temperatures.Thereafter, a constitutive law for the homogenized structure (effective material law) is developed. In order to properly describe the mechanical behavior of the interconnect at high...

Migration of Gas in Water Saturated Clays by Coupled Hydraulic-Mechanical Model

Directory of Open Access Journals (Sweden)

Aliaksei Pazdniakou

2018-01-01

Full Text Available Understanding the gas migration in highly water saturated sedimentary rock formations is of great importance for safety of radioactive waste repositories which may use these host rocks as barrier. Recent experiments on drainage in argillite samples have demonstrated that they cannot be represented in terms of standard two-phase flow Darcy model. It has been suggested that gas flows along highly localized dilatant pathways. Due to very small pore size and the opacity of the material, it is not possible to observe this two-phase flow directly. In order to better understand the gas transport, a numerical coupled hydraulic-mechanical model at the pore scale is proposed. The model is formulated in terms of Smoothed Particle Hydrodynamics (SPH and is applied to simulate drainage within a sample reconstructed from the Focused Ion Beam (FIB images of Callovo-Oxfordian claystone. A damage model is incorporated to take into account the degradation of elastic solid properties due to local conditions, which may lead to formation of new pathways and thus to modifications of fluid transport. The influence of the damage model as well as the possible importance of rigid inclusions is demonstrated and discussed.

Micro-mechanics based damage mechanics for 3D Orthogonal Woven Composites: Experiment and Numerical Modelling

KAUST Repository

Saleh, Mohamed Nasr; Lubineau, Gilles; Potluri, Prasad; Withers, Philip; Soutis, Constantinos

2016-01-01

Damage initiation and evolution of three-dimensional (3D) orthogonal woven carbon fibre composite (3DOWC) is investigated experimentally and numerically. Meso-scale homogenisation of the representative volume element (RVE) is utilised to predict the elastic properties, simulate damage initiation and evolution when loaded in tension. The effect of intra-yarns transverse cracking and shear diffused damage on the in-plane transverse modulus and shear modulus is investigated while one failure criterion is introduced to simulate the matrix damage. The proposed model is based on two major assumptions. First, the effect of the binder yarns, on the in-plane properties, is neglected, so the 3DOWC unit cell can be approximated as a (0o/90o) cross-ply laminate. Second, a micro-mechanics based damage approach is used at the meso-scale, so damage indicators can be correlated, explicitly, to the density of cracks within the material. Results from the simulated RVE are validated against experimental results along the warp (0o direction) and weft (90o direction). This approach paves the road for more predictive models as damage evolution laws are obtained from micro mechanical considerations and rely on few well-defined material parameters. This largely differs from classical damage mechanics approaches in which the evolution law is obtained by retrofitting experimental observations.

Micro-mechanics based damage mechanics for 3D Orthogonal Woven Composites: Experiment and Numerical Modelling

KAUST Repository

Saleh, Mohamed Nasr

2016-01-08

Damage initiation and evolution of three-dimensional (3D) orthogonal woven carbon fibre composite (3DOWC) is investigated experimentally and numerically. Meso-scale homogenisation of the representative volume element (RVE) is utilised to predict the elastic properties, simulate damage initiation and evolution when loaded in tension. The effect of intra-yarns transverse cracking and shear diffused damage on the in-plane transverse modulus and shear modulus is investigated while one failure criterion is introduced to simulate the matrix damage. The proposed model is based on two major assumptions. First, the effect of the binder yarns, on the in-plane properties, is neglected, so the 3DOWC unit cell can be approximated as a (0o/90o) cross-ply laminate. Second, a micro-mechanics based damage approach is used at the meso-scale, so damage indicators can be correlated, explicitly, to the density of cracks within the material. Results from the simulated RVE are validated against experimental results along the warp (0o direction) and weft (90o direction). This approach paves the road for more predictive models as damage evolution laws are obtained from micro mechanical considerations and rely on few well-defined material parameters. This largely differs from classical damage mechanics approaches in which the evolution law is obtained by retrofitting experimental observations.

Geomechanical/Geochemical Modeling Studies Conducted within the International DECOVALEX Project

International Nuclear Information System (INIS)

Birkholzer, J.T.; Rutqvist, J.; Sonnenthal, E.L.; Barr, D.; Chijimatsu, M.; Kolditz, O.; Liu, Q.; Oda, Y.; Wang, W.; Xie, M.; Zhang, C.

2005-01-01

The DECOVALEX project is an international cooperative project initiated by SKI, the Swedish Nuclear Power Inspectorate, with participation of about 10 international organizations. The general goal of this project is to encourage multidisciplinary interactive and cooperative research on modeling coupled thermo-hydro-mechanical-chemical (THMC) processes in geologic formations in support of the performance assessment for underground storage of radioactive waste. One of the research tasks, initiated in 2004 by the U.S. Department of Energy (DOE), addresses the long-term impact of geomechanical and geochemical processes on the flow conditions near waste emplacement tunnels. Within this task, four international research teams conduct predictive analysis of the coupled processes in two generic repositories, using multiple approaches and different computer codes. Below, we give an overview of the research task and report its current status

Geomechanical/Geochemical Modeling Studies Conducted Within the International DECOVALEX Project

International Nuclear Information System (INIS)

J.T. Birkholzer; J. Rutqvist; E.L. Sonnenthal; D. Barr; M.Chijimatsu; O. Kolditz; Q. Liu; Y. Oda; W. Wang; M. Xie; C. Zhang

2006-01-01

The DECOVALEX project is an international cooperative project initiated by SKI, the Swedish Nuclear Power Inspectorate, with participation of about 10 international organizations. The general goal of this project is to encourage multidisciplinary interactive and cooperative research on modeling coupled thermo-hydro-mechanical-chemical (THMC) processes in geologic formations in support of the performance assessment for underground storage of radioactive waste. One of the research tasks, initiated in 2004 by the U.S. Department of Energy (DOE), addresses the long-term impact of geomechanical and geochemical processes on the flow conditions near waste emplacement tunnels. Within this task, four international research teams conduct predictive analysis of the coupled processes in two generic repositories, using multiple approaches and different computer codes. Below, we give an overview of the research task and report its current status

Nuclear, thermo-mechanical and tritium release analysis of ITER breeding blanket

International Nuclear Information System (INIS)

Kosaku, Yasuo; Kuroda, Toshimasa; Enoeda, Mikio; Hatano, Toshihisa; Sato, Satoshi; Miki, Nobuharu; Akiba, Masato

2003-06-01

The design of the breeding blanket in ITER applies pebble bed breeder in tube (BIT) surrounded by multiplier pebble bed. It is assumed to use the same module support mechanism and coolant manifolds and coolant system as the shielding blankets. This work focuses on the verification of the design of the breeding blanket, from the viewpoints which is especially unique to the pebble bed type breeding blanket, such as, tritium breeding performance, tritium inventory and release behavior and thermo-mechanical performance of the ITER breeding blanket. With respect to the neutronics analysis, the detailed analyses of the distribution of the nuclear heating rate and TBR have been performed in 2D model using MCNP to clarify the input data for the tritium inventory and release rate analyses and thermo-mechanical analyses. With respect to the tritium inventory and release behavior analysis, the parametric analyses for selection of purge gas flow rate were carried out from the view point of pressure drop and the tritium inventory/release performance for Li 2 TiO 3 breeder. The analysis result concluded that purge gas flow rate can be set to conventional flow rate setting (88 l/min per module) to 1/10 of that to save the purge gas flow and minimize the size of purge gas pipe. However, it is necessary to note that more tritium is transformed to HTO (chemical form of water) in case of Li 2 TiO 3 compared to other breeder materials. With respect to the thermo-mechanical analyses of the pebble bed blanket structure, the analyses have been performed by ABAQUS with 2D model derived from one of eight facets of a blanket module, based on the reference design. Analyses were performed to identify the temperature distribution incorporating the pebble bed mechanical simulation and influence of mechanical behavior to the thermal behavior. The result showed that the maximum temperature in the breeding material was 617degC in the first row of breeding rods and the minimum temperature was 328

Coupling a 1D Dual-permeability Model with an Infinite Slope Stability Approach to Quantify the Influence of Preferential Flow on Slope Stability

NARCIS (Netherlands)

Shao, W.; Bogaard, T.A.; Su, Y.; Bakker, M.

2016-01-01

In this study, a 1D hydro-mechanical model was developed by coupling a dual-permeability model with an infinite slope stability approach to investigate the influence of preferential flow on pressure propagation and slope stability. The dual-permeability model used two modified Darcy-Richards

MX-80 Bentonite. Thermal-Hydro-Mechanical Characterisation Performed at CIEMAT in the Context of the Prototype Project

International Nuclear Information System (INIS)

Villar, M. V.

2005-01-01

This document details the results of the thermo-hydro-mechanical (THM) characterisation of the commercial MX-80 bentonite performed by CIEMAT from 2001 to 2004 in the context of a project carried out at the AEspoe Hard Rock Laboratory (Sweden), the Prototype Repository. The swelling pressure and the permeability of the bentonite compacted to different dry densities has been determined, as well as the influence of the permeant salinity on hydraulic conductivity. The influence of salinity on the retention capacity of the compacted bentonite has been studied. For that, a new methodology has been designed. Water retention curves have been determined at temperatures of 20 and 60 0 C. Suction controlled odometer tests have been performed at 20oC. Finally, the behaviour of the MX-80 bentonite has been compared to that of the Spanish FEBEX bentonite. (Author) 13 refs

MX-80 Bentonite. thermal-Hydro-Mechanical Characterisation Performed at CIEMAT in the Context of the Prototype Project

Energy Technology Data Exchange (ETDEWEB)

Villar, M. V.

2005-07-01

This document details the results of the thermo-hydro-mechanical (THM) characterisation of the commercial MX-80 bentonite performed by CIEMAT from 2001 to 2004 in the context of a project carried out at the AEspoe Hard Rock Laboratory (Sweden), the Prototype Repository. The swelling pressure and the permeability of the bentonite compacted to different dry densities has been determined, as well as the influence of the permeant salinity on hydraulic conductivity. The influence of salinity on the retention capacity of the compacted bentonite has been studied. For that, a new methodology has been designed. Water retention curves have been determined at temperatures of 20 and 60oC. Suction controlled odometer tests have been performed at 20oC. Finally, the behaviour of the MX-80 bentonite has been compared to that of the Spanish FEBEX bentonite. (Author) 13 refs.

Fully coupled thermal-mechanical-fluid flow model for nonliner geologic systems

International Nuclear Information System (INIS)

Hart, R.D.

1981-01-01

A single model is presented which describes fully coupled thermal-mechanical-fluid flow behavior of highly nonlinear, dynamic or quasistatic, porous geologic systems. The mathematical formulation for the model utilizes the continuum theory of mixtures to describe the multiphase nature of the system, and incremental linear constitutive theory to describe the path dependency of nonlinear material behavior. The model, incorporated in an explicit finite difference numerical procedure, was implemented in two different computer codes. A special-purpose one-dimensional code, SNEAKY, was written for initial validation of the coupling mechanisms and testing of the coupled model logic. A general purpose commercially available code, STEALTH, developed for modeling dynamic nonlinear thermomechanical processes, was modified to include fluid flow behavior and the coupling constitutive model. The fully explicit approach in the coupled calculation facilitated the inclusion of the coupling mechanisms and complex constitutive behavior. Analytical solutions pertaining to consolidation theory for soils, thermoelasticity for solids, and hydrothermal convection theory provided verification of stress and fluid flow, stress and conductive heat transfer, and heat transfer and fluid flow couplings, respectively, in the coupled model. A limited validation of the adequacy of the coupling constitutive assumptions was also performed by comparison with the physical response from two laboratory tests. Finally, the full potential of the coupled model is illustrated for geotechnical applications in energy-resource related areas. Examples in the areas of nuclear waste isolation and cut-and-fill mining are cited

Radiation damage evaluation on concrete within a facility for Selective Production of Exotic Species (SPES Project), Italy

International Nuclear Information System (INIS)

Pomaro, B.; Salomoni, V.A.; Gramegna, F.; Prete, G.; Majorana, C.E.

2011-01-01

Highlights: → We present the effect of radiation on concrete as shielding material. → The coupling between hydro-thermal-mechanical fields and radiation damage is shown. → Attention is focused on numerical modelling of concrete in 3D domains. → A new estimate of the radiation damage parameter is given. → A risk assessment of concrete-radiation interactions is developed. - Abstract: Concrete is commonly used as a biological shield against nuclear radiation. As long as, in the design of nuclear facilities, its load carrying capacity is required together with its shielding properties, changes in the mechanical properties due to nuclear radiation are of particular significance and may have to be taken into account in such circumstances. The study presented here allows for reaching first evidences on the behavior of concrete when exposed to nuclear radiation in order to evaluate the consequent effect on the mechanical field, by means of a proper definition of the radiation damage, strictly connected with the strength properties of the building material. Experimental evidences on the decay of the mechanical modulus of concrete have allowed for implementing the required damage law within a 3D F.E. research code which accounts for the coupling among moisture, heat transfer and the mechanical field in concrete treated as a fully coupled porous medium. The development of the damage front in a concrete shielding wall is analyzed under neutron radiation and results within the wall thickness are reported for long-term radiation spans and several concrete mixtures in order to discuss the resulting shielding properties.

Examination of the Thermo-mechanical Properties of E-Glass/Carbon Composites

Directory of Open Access Journals (Sweden)

Hande Sezgin

2017-12-01

Full Text Available Eight-ply E-glass, carbon and E-glass/carbon fabric-reinforced polyester based hybrid composites were manufactured in this study. A vacuum infusion system was used as the production method. Dynamic mechanical analysis, thermogravimetric analysis and differential scanning calorimetry analysis were conducted to examine the thermo-mechanical properties of composite samples. The effect of reinforcement type and different stacking sequences of fabric plies on the thermo-mechanical properties of composite samples were also investigated. Results showed that the type and alignment of reinforcement material has a signifi cant effect on the dynamic mechanical properties of composite samples.

The Community WRF-Hydro Modeling System Version 4 Updates: Merging Toward Capabilities of the National Water Model

Science.gov (United States)

McAllister, M.; Gochis, D.; Dugger, A. L.; Karsten, L. R.; McCreight, J. L.; Pan, L.; Rafieeinasab, A.; Read, L. K.; Sampson, K. M.; Yu, W.

2017-12-01

The community WRF-Hydro modeling system is publicly available and provides researchers and operational forecasters a flexible and extensible capability for performing multi-scale, multi-physics options for hydrologic modeling that can be run independent or fully-interactive with the WRF atmospheric model. The core WRF-Hydro physics model contains very high-resolution descriptions of terrestrial hydrologic process representations such as land-atmosphere exchanges of energy and moisture, snowpack evolution, infiltration, terrain routing, channel routing, basic reservoir representation and hydrologic data assimilation. Complementing the core physics components of WRF-Hydro are an ecosystem of pre- and post-processing tools that facilitate the preparation of terrain and meteorological input data, an open-source hydrologic model evaluation toolset (Rwrfhydro), hydrologic data assimilation capabilities with DART and advanced model visualization capabilities. The National Center for Atmospheric Research (NCAR), through collaborative support from the National Science Foundation and other funding partners, provides community support for the entire WRF-Hydro system through a variety of mechanisms. This presentation summarizes the enhanced user support capabilities that are being developed for the community WRF-Hydro modeling system. These products and services include a new website, open-source code repositories, documentation and user guides, test cases, online training materials, live, hands-on training sessions, an email list serve, and individual user support via email through a new help desk ticketing system. The WRF-Hydro modeling system and supporting tools which now include re-gridding scripts and model calibration have recently been updated to Version 4 and are merging toward capabilities of the National Water Model.

Thermo-mechanical design and testing of a microbalance for space applications

Science.gov (United States)

Scaccabarozzi, Diego; Saggin, Bortolino; Tarabini, Marco; Palomba, Ernesto; Longobardo, Andrea; Zampetti, Emiliano

2014-12-01

This work focuses on the thermo-mechanical design of the microbalance used for the VISTA (Volatile In Situ Thermogravimetry Analyzer) sensor. VISTA has been designed to operate in situ in different space environments (asteroids, Mars, icy satellites). In this paper we focus on its application on Mars, where the expected environmental conditions are the most challenging for the thermo-mechanical design. The microbalance holding system has been designed to ensure piezoelectric crystal integrity against the high vibration levels during launch and landing and to cope with the unavoidable thermo-elastic differential displacements due to CTE and temperature differences between the microbalance elements. The crystal holding system, based on three symmetrical titanium supports, provides also the electrical connections needed for crystal actuation, microbalance heating and temperature measurement on the electrode area. On the microbalance crystal surfaces the electrodes, a micro film heater (optimized to perform thermo-gravimetric analysis up to 400 °C) and a resistive thermometer are deposited through a vacuum sputtering process. A mockup of the system has been manufactured and tested at the expected vibration levels and the thermal control effectiveness has been verified in thermo-vacuum environment.

Sensitivity analysis of a new dual-porosity hydroloigcal model coupled with the SOSlope model for the numerical simulations of rainfall triggered shallow landslides.

Science.gov (United States)

Schwarz, Massimiliano; Cohen, Denis

2017-04-01

Morphology and extent of hydrological pathways, in combination with the spatio-temporal variability of rainfall events and the heterogeneities of hydro-mechanical properties of soils, has a major impact on the hydrological conditions that locally determine the triggering of shallow landslides. The coupling of these processes at different spatial scales is an enormous challenge for slope stability modeling at the catchment scale. In this work we present a sensitivity analysis of a new dual-porosity hydrological model implemented in the hydro-mechanical model SOSlope for the modeling of shallow landslides on vegetated hillslopes. The proposed model links the calculation of the saturation dynamic of preferential flow-paths based on hydrological and topographical characteristics of the landscape to the hydro-mechanical behavior of the soil along a potential failure surface due to the changes of soil matrix saturation. Furthermore, the hydro-mechanical changes of soil conditions are linked to the local stress-strain properties of the (rooted-)soil that ultimately determine the force redistribution and related deformations at the hillslope scale. The model considers forces to be redistributed through three types of solicitations: tension, compression, and shearing. The present analysis shows how the conditions of deformation due to the passive earth pressure mobilized at the toe of the landslide are particularly important in defining the timing and extension of shallow landslides. The model also shows that, in densely rooted hillslopes, lateral force redistribution under tension through the root-network may substantially contribute to stabilizing slopes, avoiding crack formation and large deformations. The results of the sensitivity analysis are discussed in the context of protection forest management and bioengineering techniques.

A Coupled Damage and Reaction Model for Simulating Energetic Material Response to Impact Hazards

International Nuclear Information System (INIS)

BAER, MELVIN R.; DRUMHELLER, D.S.; MATHESON, E.R.

1999-01-01

The Baer-Nunziato multiphase reactive theory for a granulated bed of energetic material is extended to allow for dynamic damage processes, that generate new surfaces as well as porosity. The Second Law of Thermodynamics is employed to constrain the constitutive forms of the mass, momentum, and energy exchange functions as well as those for the mechanical damage model ensuring that the models will be dissipative. The focus here is on the constitutive forms of the exchange functions. The mechanical constitutive modeling is discussed in a companion paper. The mechanical damage model provides dynamic surface area and porosity information needed by the exchange functions to compute combustion rates and interphase momentum and energy exchange rates. The models are implemented in the CTH shock physics code and used to simulate delayed detonations due to impacts in a bed of granulated energetic material and an undamaged cylindrical sample

Hydrological Modeling in Alaska with WRF-Hydro

Science.gov (United States)

Elmer, N. J.; Zavodsky, B.; Molthan, A.

2017-12-01

The operational National Water Model (NWM), implemented in August 2016, is an instantiation of the Weather Research and Forecasting hydrological extension package (WRF-Hydro). Currently, the NWM only covers the contiguous United States, but will be expanded to include an Alaska domain in the future. It is well known that Alaska presents several hydrological modeling challenges, including unique arctic/sub-arctic hydrological processes not observed elsewhere in the United States and a severe lack of in-situ observations for model initialization. This project sets up an experimental version of WRF-Hydro in Alaska mimicking the NWM to gauge the ability of WRF-Hydro to represent hydrological processes in Alaska and identify model calibration challenges. Recent and upcoming launches of hydrology-focused NASA satellite missions such as the Soil Moisture Active Passive (SMAP) and Surface Water Ocean Topography (SWOT) expand the spatial and temporal coverage of observations in Alaska, so this study also lays the groundwork for assimilating these NASA datasets into WRF-Hydro in the future.

Forced synchronization and asynchronous quenching in a thermo-acoustic system

Science.gov (United States)

Mondal, Sirshendu; Pawar, Samadhan A.; Sujith, Raman

2017-11-01

Forced synchronization, which has been extensively studied in theory and experiments, occurs through two different mechanisms known as phase locking and asynchronous quenching. The latter indicates the suppression of oscillation amplitude. In most practical combustion systems such as gas turbine engines, the main concern is high amplitude pressure oscillations, known as thermo-acoustic instability. Thermo-acoustic instability is undesirable and needs to be suppressed because of its damaging consequences to an engine. In the present study, a systematic experimental investigation of forced synchronization is performed in a prototypical thermo-acoustic system, a Rijke tube, in its limit cycle operation. Further, we show a qualitatively similar behavior using a reduced order model. In the phase locking region, the simultaneous occurrence of synchronization and resonant amplification leads to high amplitude pressure oscillations. However, a reduction in the amplitude of natural oscillations by about 78% of the unforced amplitude is observed when the forcing frequency is far lower than the natural frequency. This shows the possibility of suppression of the oscillation amplitude through asynchronous quenching in thermo-acoustic systems.

A simple analytical thermo-mechanical model for liquid crystal elastomer bilayer structures

Directory of Open Access Journals (Sweden)

Yun Cui

2018-02-01

Full Text Available The bilayer structure consisting of thermal-responsive liquid crystal elastomers (LCEs and other polymer materials with stretchable heaters has attracted much attention in applications of soft actuators and soft robots due to its ability to generate large deformations when subjected to heat stimuli. A simple analytical thermo-mechanical model, accounting for the non-uniform feature of the temperature/strain distribution along the thickness direction, is established for this type of bilayer structure. The analytical predictions of the temperature and bending curvature radius agree well with finite element analysis and experiments. The influences of the LCE thickness and the heat generation power on the bending deformation of the bilayer structure are fully investigated. It is shown that a thinner LCE layer and a higher heat generation power could yield more bending deformation. These results may help the design of soft actuators and soft robots involving thermal responsive LCEs.

Hydromechanical modeling of clay rock including fracture damage

Science.gov (United States)

Asahina, D.; Houseworth, J. E.; Birkholzer, J. T.

2012-12-01

Argillaceous rock typically acts as a flow barrier, but under certain conditions significant and potentially conductive fractures may be present. Fracture formation is well-known to occur in the vicinity of underground excavations in a region known as the excavation disturbed zone. Such problems are of particular importance for low-permeability, mechanically weak rock such as clays and shales because fractures can be relatively transient as a result of fracture self-sealing processes. Perhaps not as well appreciated is the fact that natural fractures can form in argillaceous rock as a result of hydraulic overpressure caused by phenomena such as disequlibrium compaction, changes in tectonic stress, and mineral dehydration. Overpressure conditions can cause hydraulic fracturing if the fluid pressure leads to tensile effective stresses that exceed the tensile strength of the material. Quantitative modeling of this type of process requires coupling between hydrogeologic processes and geomechanical processes including fracture initiation and propagation. Here we present a computational method for three-dimensional, hydromechanical coupled processes including fracture damage. Fractures are represented as discrete features in a fracture network that interact with a porous rock matrix. Fracture configurations are mapped onto an unstructured, three-dimensonal, Voronoi grid, which is based on a random set of spatial points. Discrete fracture networks (DFN) are represented by the connections of the edges of a Voronoi cells. This methodology has the advantage that fractures can be more easily introduced in response to coupled hydro-mechanical processes and generally eliminates several potential issues associated with the geometry of DFN and numerical gridding. A geomechanical and fracture-damage model is developed here using the Rigid-Body-Spring-Network (RBSN) numerical method. The hydrogelogic and geomechanical models share the same geometrical information from a 3D Voronoi

Prediction of thermo-mechanical reliability of wafer backend processes

NARCIS (Netherlands)

Gonda, V.; Toonder, den J.M.J.; Beijer, J.G.J.; Zhang, G.Q.; van Driel, W.D.; Hoofman, R.J.O.M.; Ernst, L.J.

2004-01-01

More than 65% of IC failures are related to thermal and mechanical problems. For wafer backend processes, thermo-mechanical failure is one of the major bottlenecks. The ongoing technological trends like miniaturization, introduction of new materials, and function/product integration will increase

Prediction of thermo-mechanical integrity of wafer backend processes

NARCIS (Netherlands)

Gonda, V.; Toonder, den J.M.J.; Beijer, J.G.J.; Zhang, G.Q.; Hoofman, R.J.O.M.; Ernst, L.J.; Ernst, L.J.

2003-01-01

More than 65% of IC failures are related to thermal and mechanical problems. For wafer backend processes, thermo-mechanical failure is one of the major bottlenecks. The ongoing technological trends like miniaturization, introduction of new materials, and function/product integration will increase

Well-posedness of a thermo-mechanical model for shape memory alloys under tension

Czech Academy of Sciences Publication Activity Database

Krejčí, Pavel; Stefanelli, U.

2010-01-01

Roč. 44, č. 6 (2010), s. 1239-1253 ISSN 0764-583X R&D Projects: GA ČR GAP201/10/2315 Institutional research plan: CEZ:AV0Z10190503 Keywords : shape memory alloys * thermo-mechanics * well-posedness * hysteresis operator Subject RIV: BA - General Mathematics Impact factor: 1.202, year: 2010 http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8129335

Simulation of the Mechanical Response of the 11T Magnet by Means of COMSOL-MpCCI-ANSYS Coupling

CERN Document Server

Wilczek, Michal

2017-01-01

This report covers the work during my Summer Student internship at CERN as a part of the STEAM group (Simulation of Transient Effects in Accelerator Magnets) in the Technology Department, Machine Protection and Electrical Integrity group. I was responsible for the development of the ANSYS APDL model of the 11T superconducting magnet serving as a proof of concept for magneto-thermo-mechanical co-simulations of quench propagation in COMSOL and ANSYS software. The aforementioned co-simulation estimates the magnetic, thermal, and mechanical response of the magnet during the discharge process, while protected by a recently developed method, called Coupling-Loss Induced Quench (CLIQ). The already existing STEAM framework performs field/circuit coupling of a magneto-thermal field models previously developed by the STEAM. The next task of the group aimed at combining magneto-thermal field solution with the mechanical simulations. Such a coupling is of interest for the High-Luminosity upgrade of the Large Hadron Colli...

Characterisation of Ground Thermal and Thermo-Mechanical Behaviour for Shallow Geothermal Energy Applications

DEFF Research Database (Denmark)

Vieira, Ana; Alberdi-Pagola, Maria; Christodoulides, Paul

2017-01-01

Increasing use of the ground as a thermal reservoir is expected in the near future. Shallow geothermal energy (SGE) systems have proved to be sustainable alternative solutions for buildings and infrastructure conditioning in many areas across the globe in the past decades. Recently novel solutions......-hydro-mechanical behaviour of soil is introduced and discussed. These coupled processes are important for confirming the structural integrity of energy geostructures, but routine methods for parameter determination are still lacking (Energies). Keywords: shallow geothermal systems; soil thermal behaviour; laboratory testing......, including energy geostructures, where SGE systems are coupled with foundation heat exchangers, have also been developed. The performance of these systems is dependent on a series of factors, among which the thermal properties of the soil play a major role. The purpose of this paper is to present...

Theory and modeling of cylindrical thermo-acoustic transduction

Energy Technology Data Exchange (ETDEWEB)

Tong, Lihong, E-mail: lhtong@ecjtu.edu.cn [School of Civil Engineering and Architecture, East China Jiaotong University, Nanchang, Jiangxi (China); Lim, C.W. [Department of Architecture and Civil Engineering, City University of Hong Kong, Kowloon, Hong Kong SAR (China); Zhao, Xiushao; Geng, Daxing [School of Civil Engineering and Architecture, East China Jiaotong University, Nanchang, Jiangxi (China)

2016-06-03

Models both for solid and thinfilm-solid cylindrical thermo-acoustic transductions are proposed and the corresponding acoustic pressure solutions are obtained. The acoustic pressure for an individual carbon nanotube (CNT) as a function of input power is investigated analytically and it is verified by comparing with the published experimental data. Further numerical analysis on the acoustic pressure response and characteristics for varying input frequency and distance are also examined both for solid and thinfilm-solid cylindrical thermo-acoustic transductions. Through detailed theoretical and numerical studies on the acoustic pressure solution for thinfilm-solid cylindrical transduction, it is concluded that a solid with smaller thermal conductivity favors to improve the acoustic performance. In general, the proposed models are applicable to a variety of cylindrical thermo-acoustic devices performing in different gaseous media. - Highlights: • Theory and modeling both for solid and thinfilm-solid cylindrical thermo-acoustic transductions are proposed. • The modeling is verified by comparing with the published experimental data. • Acoustic response characteristics of cylindrical thermo-acoustic transductions are predicted by the proposed model.

Damage and service life of nickel-base alloys under thermal-mechanical fatigue stress at different phase positions; Schaedigung und Lebensdauer von Nickelbasislegierungen unter thermisch-mechanischer Ermuedungsbeanspruchung bei verschiedenen Phasenlagen

Energy Technology Data Exchange (ETDEWEB)

Guth, Stefan

2016-07-01

This work considers the behaviour of two nickel-base alloys (NiCr22Co12Mo9 and MAR-M247 LC) under thermo-mechanical fatigue loading with varying phase angles between mechanical strain and temperature. The investigations focus on the characterisation of microstructures and damage mechanisms as a function of the phase angle. Based on the results, a life prediction model is proposed.

Damage Modeling Of Injection-Molded Short- And Long-Fiber Thermoplastics

International Nuclear Information System (INIS)

Nguyen, Ba Nghiep; Kunc, Vlastimil; Bapanapalli, Satish K.; Phelps, Jay; Tucker, Charles L. III

2009-01-01