Earthquake-induced rock shear through a deposition hole: Laboratory tests on bentonite-material models and modelling of three scale tests

Clay Minerals ◽  
2018 ◽  
Vol 53 (2) ◽  
pp. 213-235
Author(s):  
Lennart Börgesson ◽  
Ann Dueck ◽  
Jan Hernelind
Keyword(s):  
Finite Element ◽  
Laboratory Tests ◽  
Spent Nuclear Fuel ◽  
Material Model ◽  
Spent Fuel ◽  
Stress Strain ◽  
Element Mesh ◽  
Material Models ◽  
Bentonite Buffer ◽  
Nonlinear Stress

ABSTRACTEarthquake-induced rock shear through a bentonite-filled deposition hole in a repository for spent nuclear fuel is an important scenario for the safety analysis because it may cause substantial damage to the canister hosting the spent fuel. Appropriate tools to investigate the effects on the buffer and the canister are required.The study described here explored the laboratory tests conducted to develop a material model of the bentonite buffer to be used in the simulations, the material models that these tests have provided and finite element (FE) simulations of three scale tests of a rock shear for comparison between modelled and measured results. The results were used for validation of the material models and the calculation technique that was used for modelling different rock-shear cases.The laboratory study consisted of swelling-pressure tests and tests to determine shear strength and stress-strain properties. The material model is elastic-plastic with a nonlinear stress-strain relation which depends on the density of the bentonite buffer and is a function of the strain rate. The three scale tests were modelled using theAbaqusfinite element code. Good agreement between modelled and measured results was observed, in spite of the complexity of the models and the difficulties associated with measuring stresses and strains under the very fast shear.The modelling results thus validate the modelling of the SR-Site. The modelling technique, the element mesh and the material models used in these analyses are well fitted and useful for this type of modelling.

Cord/Rubber Material Properties

1985 ◽  
Vol 58 (4) ◽  
pp. 830-856 ◽  
Author(s):  
R. J. Cembrola ◽  
T. J. Dudek
Keyword(s):  
Finite Element ◽  
Material Model ◽  
Rubber Composites ◽  
Stress Strain ◽  
Element Analysis ◽  
Rubber Layer ◽  
Strain Behavior ◽  
Nonlinear Stress ◽  
Interlaminar Shear ◽  
Mechanics Of Composite Materials

Abstract Recent developments in nonlinear finite element methods (FEM) and mechanics of composite materials have made it possible to handle complex tire mechanics problems involving large deformations and moderate strains. The development of an accurate material model for cord/rubber composites is a necessary requirement for the application of these powerful finite element programs to practical problems but involves numerous complexities. Difficulties associated with the application of classical lamination theory to cord/rubber composites were reviewed. The complexity of the material characterization of cord/rubber composites by experimental means was also discussed. This complexity arises from the highly anisotropic properties of twisted cords and the nonlinear stress—strain behavior of the laminates. Micromechanics theories, which have been successfully applied to hard composites (i.e., graphite—epoxy) have been shown to be inadequate in predicting some of the properties of the calendered fabric ply material from the properties of the cord and rubber. Finite element models which include an interply rubber layer to account for the interlaminar shear have been shown to give a better representation of cord/rubber laminate behavior in tension and bending. The application of finite element analysis to more refined models of complex structures like tires, however, requires the development of a more realistic material model which would account for the nonlinear stress—strain properties of cord/rubber composites.

Earthquake Induced Rock Shear Through a Deposition Hole. Effect on the Canister and Buffer

2003 ◽  
Vol 807 ◽  
Author(s):  
L. Börgesson ◽  
L.-E. Johannesson ◽  
J. Hernelind
Keyword(s):  
Finite Element ◽  
Shear Rate ◽  
Laboratory Tests ◽  
Water Saturation ◽  
Shear Plane ◽  
Material Model ◽  
Shear Displacement ◽  
Element Mesh ◽  
Shear Rates ◽  
Finite Element Calculations

ABSTRACTExisting fractures crossing a deposition hole may be activated and sheared by an earthquake. The effect of such a rock shear has been investigated in a project that includes both laboratory tests and finite element calculations.A number of laboratory tests have been performed with shearing of water-saturated bentonite samples at different densities and shear rates. From those tests a material model of the buffer that takes into account the shear rate has been formulated. Shear rates up to 6 m/s have been tested.The rock shear has been modelled with finite element calculations with the code ABAQUS. A 3D finite element mesh of the buffer and the canister has been created and a number of calculations with simulation of a rock shear have been performed. The rock shear has been assumed to take place perpendicular to the canister axis in either the centre of the deposition hole or at the ¼ point. The shear calculations have been driven to a total shear of 20 cm. Buffer densities at water saturation between 1950 and 2100 kg/m3 and shear rates between 0.0001 and 1000 mm/s have been modelled. The influence of buffer density, shear plane location, the shear rate and the magnitude of the shear displacement are analysed and discussed.The results show that the influence of especially the density of the buffer and the location of the shear plane are very strong but also that the shear rate and the magnitude of the shear displacement have a significant effect.

Delamination in the scoring and folding of paperboard

TAPPI Journal ◽  
2012 ◽  
Vol 11 (1) ◽  
pp. 61-66 ◽  
Author(s):  
DOEUNG D. CHOI ◽  
SERGIY A. LAVRYKOV ◽  
BANDARU V. RAMARAO
Keyword(s):  
Finite Element ◽  
Plane Deformation ◽  
Strain Analysis ◽  
Local Strain ◽  
Uniaxial Stress ◽  
Material Model ◽  
Element Model ◽  
Plastic Behavior ◽  
Stress Strain ◽  
Strain Fields

Delamination between layers occurs during the creasing and subsequent folding of paperboard. Delamination is necessary to provide some stiffness properties, but excessive or uncontrolled delamination can weaken the fold, and therefore needs to be controlled. An understanding of the mechanics of delamination is predicated upon the availability of reliable and properly calibrated simulation tools to predict experimental observations. This paper describes a finite element simulation of paper mechanics applied to the scoring and folding of multi-ply carton board. Our goal was to provide an understanding of the mechanics of these operations and the proper models of elastic and plastic behavior of the material that enable us to simulate the deformation and delamination behavior. Our material model accounted for plasticity and sheet anisotropy in the in-plane and z-direction (ZD) dimensions. We used different ZD stress-strain curves during loading and unloading. Material parameters for in-plane deformation were obtained by fitting uniaxial stress-strain data to Ramberg-Osgood plasticity models and the ZD deformation was modeled using a modified power law. Two-dimensional strain fields resulting from loading board typical of a scoring operation were calculated. The strain field was symmetric in the initial stages, but increasing deformation led to asymmetry and heterogeneity. These regions were precursors to delamination and failure. Delamination of the layers occurred in regions of significant shear strain and resulted primarily from the development of large plastic strains. The model predictions were confirmed by experimental observation of the local strain fields using visual microscopy and linear image strain analysis. The finite element model predicted sheet delamination matching the patterns and effects that were observed in experiments.

Na/Ca selectivity coefficients of montmorillonite in perchlorate solution at different temperatures

2012 ◽  
Vol 1475 ◽  
Author(s):  
Aku Itälä ◽  
Arto Muurinen
Keyword(s):  
Cation Exchange ◽  
Spent Nuclear Fuel ◽  
Spent Fuel ◽  
Selectivity Coefficients ◽  
Crystalline Bedrock ◽  
Bentonite Buffer ◽  
Different Temperatures ◽  
C 50 ◽  
Exchange Selectivity

ABSTRACTThe Finnish spent nuclear fuel disposal is based on the Swedish KBS-3 concept in crystalline bedrock. The concept aims at long-term isolation and containment of spent fuel in copper canisters surrounded by bentonite buffer which mostly consists of montmorillonite. For the long-term modelling of the chemical processes in the buffer, the cation-exchange selectivity coefficients have to be known at different temperatures. In this work, the cation-exchange selectivity coefficients and cation-exchange isotherms were determined in batch experiments for montmorillonite at three different temperatures (25 °C, 50 °C and 75 °C). Five different ratios of NaClO4/Ca(ClO4)2 were used in the experimental solutions. After equilibration the solution and montmorillonite were separated and the solution analysed to get the desired exchange parameters. The experiments were modelled with a computational model capable of taking into account the physicochemical processes that take place in the experiment.

Parametric Variational Principle for Bi-Modulus Materials and Its Application to Nacreous Bio-Composites

2016 ◽  
Vol 08 (06) ◽  
pp. 1650082 ◽  
Author(s):  
Liang Zhang ◽  
Huiting Zhang ◽  
Jian Wu ◽  
Bo Yan ◽  
Mengkai Lu
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Variational Principle ◽  
Principal Stress ◽  
Stress Strain ◽  
Element Analysis ◽  
Parametric Variational Principle ◽  
Strain Relation ◽  
Stress Strain Relation ◽  
Nonlinear Stress

Bi-modulus materials have different moduli in tension and compression and the stress–strain relation depends on principal stress that is unknown before displacement is determined. Establishment of variational principle is important for mechanical analysis of materials. First, parametric variational principle (PVP) is proposed for static analysis of bi-modulus materials and structures. A parametric variable indicating state of principal stress is included in the potential energy formulation and the nonlinear stress–strain relation is evolved into a linear complementarity constraint. Convergence of finite element analysis is thus improved. Then the proposed variational principle is extended to a dynamic problem and the dynamic equation can be derived based on Hamilton’s principle. Finite element analysis of nacreous bio-composites is performed, in which a unilateral contact behavior between two hard mineral bricks is modeled using the bi-modulus stress–strain relation. Effective modulus of composites can be determined numerically and stress mechanism of “tension–shear chain” in nacre is revealed. A delayed effect on stress propagation is found around the “gaps” between mineral bricks, when a tension force is loaded to nacreous bio-composites dynamically.

Stress Concentration Factor Calculation for the Hooks in Lifting Appliance of Spent Fuel Well Cover

2014 ◽  
Author(s):  
Xiang Liu ◽  
Yue Li ◽  
Jinhua Wang ◽  
Bin Wu
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Spent Nuclear Fuel ◽  
Curved Beam ◽  
Spent Fuel ◽  
The Finite Element Method ◽  
High Temperature Reactor

The spent nuclear fuel of HTR-PM (High Temperature Reactor–Pebblebed Modules) will be dry stored in wells. In the mouth of each well, there is a cover weighing 11 tons. A lifting appliance with three hooks is used to open and close the covers. The hooks are L-shaped with fillet at the inside corner. The stress concentration at the corner has a significant impact on the strength and fatigue life of hooks. For optimizing the structure of the hook, the stress concentration factor related to the radius of fillet is calculated by both theoretical and numerical methods. The theoretical calculation is based on the Saint-Venant’s Principle and the analytical solution of a curved beam. The result is consistent with the numerical calculation performed by the finite element method.

Buckling of Rectangular Cross-Ply Laminated Plates With Nonlinear Stress-Strain Behavior

1979 ◽  
Vol 46 (3) ◽  
pp. 637-643 ◽  
Author(s):  
Harold S. Morgan ◽  
Robert M. Jones
Keyword(s):  
Strain Curve ◽  
Material Model ◽  
Laminated Plates ◽  
Nonlinear Material ◽  
Stress Strain ◽  
Buckling Loads ◽  
Strain Behavior ◽  
Reinforced Composite ◽  
Nonlinear Stress ◽  
Behavior Characteristic

The Jones-Nelson-Morgan nonlinear material model is used in the derivation of a buckling criterion for laminated plates with nonlinear stress-strain behavior characteristic of many fiber-reinforced composite materials. A search procedure is developed to solve this buckling criterion which is transcendental because of interdependence of the buckling load and the coefficients relating the variations in laminate forces and moments to the variations in strains and curvatures. The effect of stress-strain curve nonlinearities on laminate buckling loads is illustrated by comparing solutions of the buckling criterion to buckling loads for laminates with linear stress-strain behavior.

scholarly journals Exploratory what-if analysis of some debated canister failure modes in the review of a licence application for the construction and operation of a spent nuclear fuel repository in Sweden

2019 ◽  
Vol 49 ◽  
pp. 67-75
Author(s):  
Bo Strömberg ◽  
Lena Sonnerfelt ◽  
Henrik Öberg
Keyword(s):  
Failure Modes ◽  
Spent Nuclear Fuel ◽  
Free Water ◽  
Crystalline Rock ◽  
Spent Fuel ◽  
Creep Ductility ◽  
Regulatory Review ◽  
Bentonite Buffer ◽  
Detailed Assessment ◽  
Long Timescales

Abstract. Regulatory review of the licence application for construction and operation of a spent fuel repository at the Forsmark site in Sweden involves detailed assessment of both expected and hypothetical failure modes of the copper canister. The copper canister, which is supported by the bentonite buffer and the surrounding crystalline rock in the KBS-3 concept, is expected to provide complete containment of radioactive elements for very long timescales. Detailed assessment shows that there is a small probability on such timescales of canister failure due to corrosion following loss of buffer as well as mechanical failure due to large earthquakes. During the regulatory review process, it was proposed that canisters might also fail due to: (i) corrosion in anoxic oxygen gas free water, (ii) pitting corrosion, (iii) stress corrosion cracking, (iv) creep brittle failure, (v) hydrogen embrittlement. We here provisionally accept a number of alternative assumptions related to these processes as a basis for what-if analysis of their implications. The focus is not to determine the merit or to estimate probability of these cases, but rather to explore their potential significance in the context of the available knowledge about the repository environment. Simplified estimates are made of the consequences in terms of number and timing of canister failures as well as radiological impact. It is judged that poor creep ductility of copper would have larger potential consequences compared to localised corrosion phenomena. Potential corrosion failures are expected to be associated with the small fraction of deposition holes that are most extensively exposed to corrodants.

scholarly journals Numerical Analyses of Locomotive Impacts on a Spent Fuel Truck Cask and Trailer

2005 ◽  
Author(s):  
Doug Ammerman ◽  
Dave Stevens ◽  
Matt Barsotti
Keyword(s):  
Finite Element ◽  
High Speed ◽  
Applied Research ◽  
Spent Nuclear Fuel ◽  
Numerical Study ◽  
Numerical Approach ◽  
Finite Element Models ◽  
Spent Fuel ◽  
Physical Test ◽  
Grade Crossing

During the transportation of spent nuclear fuel by truck, the possibility exists that a train could run into the spent fuel cask at a grade crossing. Sandia National Laboratories has conducted a numerical study to assess the possibility of cask breach or material release in the event of a high-speed, broadside locomotive collision. A numerical approach has the advantage over conducting a physical test as was done in the 1970s [1] in that varying parameters can be examined. For example, one of the criticisms of the 1970s test was the height of the cask. In the test, the centerline of the cask was above the main frame-rails of the locomotive. In this study the position of the cask with respect to the locomotive was varied. The response of the cask and trailer in different collision scenarios was modeled numerically with LS-DYNA [2]. The simulations were performed as a collaborative endeavor between Sandia National Laboratories (SNL), Applied Research Associates, Inc. (ARA) and Foster-Miller, Inc (FMI). ARA developed the GA-4 Spent Fuel Cask and Cask Transporter models described in this report. These models were then combined with two existing FMI heavy freight locomotive finite element models to create the overall simulation scenarios. The modeling effort, results, and conclusions are presented in this paper.

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