A ductile fracture criterion with Zener-Hollomon parameter of pure molybdenum sheet in thermal forming

Directory of Open Access Journals (Sweden)

Wang Chu

2015-01-01

Full Text Available Formability of pure molybdenum in thermal forming process has been greatly improved, but it is still hard to avoid the generation of rupture and other quality defects. In this paper, a ductile fracture criterion of pure molybdenum sheet in thermal forming was established by considering the plastic deformation capacity of material and stress states, which can be used to describe fracture behaviour and critical rupture prediction of pure molybdenum sheet during hot forming process. Based on the isothermal uniaxial tensile tests which performed at 993 to 1143 K with strain rate range from 0.0005 to 0.2 s−1, the material parameters are calculated by the combination method of experiment with FEsimulation. Based on the observation, new fracture criteria can be expressed as a function of Zener-Hollomon parameter. The critical fracture value that calculated by Oyane-Sato criterion increases with increasing temperature and decreasing strain rate. The ductile fracture criterion with Zener-Hollomon parameter of pure molybdenum in thermal forming is proposed.

Effects of heat transfer coefficient treatments on thermal shock fracture prediction for LWR fuel claddings in water quenching

Energy Technology Data Exchange (ETDEWEB)

Lee, Youho; Lee, Jeong Ik; Cheon, Hee [KAIST, Daejeon (Korea, Republic of)

2015-05-15

Accurate modeling of thermal shock induced stresses has become ever most important to emerging accident-tolerant ceramic cladding concepts, such as silicon carbide (SiC) and SiC coated zircaloy. Since fractures of ceramic (entirely ceramic or coated) occur by excessive tensile stresses with linear elasticity, modeling transient stress distribution in the material provides a direct indication of the structural integrity. Indeed, even for the current zircaloy cladding material, the oxide layer formed on the surface - where cracks starts to develop upon water quenching - essentially behaves as a brittle ceramic. Hence, enhanced understanding of thermal shock fracture of a brittle material would fundamentally contribute to safety of nuclear reactors for both the current fuel design and that of the coming future. Understanding thermal shock fracture of a brittle material requires heat transfer rate between the solid and the fluid for transient temperature fields of the solid, and structural response of the solid under the obtained transient temperature fields. In water quenching, a solid experiences dynamic time-varying heat transfer rates with phase changes of the fluid over a short quenching period. Yet, such a dynamic change of heat transfer rates during the water quenching transience has been overlooked in assessments of mechanisms, predictability, and uncertainties for thermal shock fracture. Rather, a time-constant heat transfer coefficient, named 'effective heat transfer coefficient' has become a conventional input to thermal shock fracture analysis. No single constant heat transfer could suffice to depict the actual stress evolution subject to dynamic heat transfer coefficient changes with fluid phase changes. Use of the surface temperature dependent heat transfer coefficient will remarkably increase predictability of thermal shock fracture of brittle materials and complete the picture of stress evolution in the quenched solid. The presented result

Proposed rule package on fracture toughness and thermal annealing requirements and guidance for light water reactor vessels

International Nuclear Information System (INIS)

Allen Hiser, J.R.

1993-01-01

In the framework of updating and clarification of the fracture toughness and thermal annealing requirements and guidance for light water reactor pressure vessels, proposed revisions concerning the pressurized thermal shock rule, fracture toughness requirements and reactor vessel material surveillance program requirements, are described. A new rule concerning thermal annealing requirements and a draft regulatory guide on 'Format and Content of Application for Approval for Thermal Annealing of RPV' are also proposed

Proposed rule package on fracture toughness and thermal annealing requirements and guidance for light water reactor vessels

Energy Technology Data Exchange (ETDEWEB)

Allen Hiser, J R [UKAEA Harwell Lab. (United Kingdom). Engineering Div.

1994-12-31

In the framework of updating and clarification of the fracture toughness and thermal annealing requirements and guidance for light water reactor pressure vessels, proposed revisions concerning the pressurized thermal shock rule, fracture toughness requirements and reactor vessel material surveillance program requirements, are described. A new rule concerning thermal annealing requirements and a draft regulatory guide on `Format and Content of Application for Approval for Thermal Annealing of RPV` are also proposed.

Investigation of Mode I fracture toughness of red Verona marble after thermal treatment

Directory of Open Access Journals (Sweden)

Daniela Scorza

2015-10-01

Full Text Available The present paper aims to assess the effect of freeze/thaw cycles on fracture behaviour of a natural stone: the red Verona marble. A wide variety of specimen types and methods to determine Mode I fracture toughness of natural stones are available in the literature and, in this context, the model originally proposed for plain concrete, i.e. the Two-Parameter Model (TPM, is adopted. Such a method is able to take into account the slow nonlinear crack growth occurring before the peak load, typical of quasi-brittle materials, with the advantage of easy specimen preparation and simple test configuration. In the present paper, the atmospheric ageing is simulated by means of thermal pre-treatments consisting of freeze/thaw cycles. Experimental tests are carried out using three-point bending Single-Edge Notched (SEN specimens, according to the TPM procedure. The effects of thermal treatment on both mechanical and fracture parameters are examined in terms of elastic modulus and fracture toughness, respectively

A fully coupled finite element framework for thermal fracturing simulation in subsurface cold CO2 injection

Directory of Open Access Journals (Sweden)

Shunde Yin

2018-03-01

Simulation of thermal fracturing during cold CO2 injection involves the coupled processes of heat transfer, mass transport, rock deforming as well as fracture propagation. To model such a complex coupled system, a fully coupled finite element framework for thermal fracturing simulation is presented. This framework is based on the theory of non-isothermal multiphase flow in fracturing porous media. It takes advantage of recent advances in stabilized finite element and extended finite element methods. The stabilized finite element method overcomes the numerical instability encountered when the traditional finite element method is used to solve the convection dominated heat transfer equation, while the extended finite element method overcomes the limitation with traditional finite element method that a model has to be remeshed when a fracture is initiated or propagating and fracturing paths have to be aligned with element boundaries.

Tensile fracture and thermal conductivity characterization of toughened epoxy/CNT nanocomposites

Energy Technology Data Exchange (ETDEWEB)

Balakrishnan, Anandh [School of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK 73019 (United States); Saha, Mrinal C., E-mail: msaha@ou.edu [School of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK 73019 (United States)

2011-01-25

Rubber toughened epoxy/CNT nanocomposites were manufactured at different weight percents between 0 and 1% of multiwall carbon nanotube (MWNT) using a high intensity ultrasonic liquid processor with a titanium probe. Mechanical properties of manufactured dog bone samples were measured in tension and the results indicated a maximum of 23% increase in the elastic modulus at 0.6% by weight of MWNT. However, the fracture strength showed a maximum decrease of about 11% as a function of increasing MWNT loading. Scanning Electron Microscopy (SEM) images from the neat samples revealed a distinct circular pit at the top left edge of the specimen with an overall tearing deformation causing the fracture paths. Comparatively, all nanocomposite samples on an average seemed to show a prominent brittle fracture with little or no evidence of circular pit formation. The amount of tearing deformation seemed to be enhanced in the nanocomposite specimens as compare to the neat ones. Finally, Transmission Electron Microscopy images indicated that different states of dispersion exist in all of the nanocomposite samples. The data showed that agglomeration of nanotubes increases as a function of weight percent. In addition to mechanical property characterization, thermal conductivity of all the samples was determined as a function of temperature between 30 deg. C and 100 deg. C using the 3{omega} method. The tested samples showed an almost 16% increase in thermal conductivity. The minimal enhancement in thermal conductivity has been analyzed from the standpoint of the Effective Medium Theory. Interfacial thermal resistances exhibit no order of magnitude changes explaining the conductivity results.

Tensile fracture and thermal conductivity characterization of toughened epoxy/CNT nanocomposites

International Nuclear Information System (INIS)

Balakrishnan, Anandh; Saha, Mrinal C.

2011-01-01

Rubber toughened epoxy/CNT nanocomposites were manufactured at different weight percents between 0 and 1% of multiwall carbon nanotube (MWNT) using a high intensity ultrasonic liquid processor with a titanium probe. Mechanical properties of manufactured dog bone samples were measured in tension and the results indicated a maximum of 23% increase in the elastic modulus at 0.6% by weight of MWNT. However, the fracture strength showed a maximum decrease of about 11% as a function of increasing MWNT loading. Scanning Electron Microscopy (SEM) images from the neat samples revealed a distinct circular pit at the top left edge of the specimen with an overall tearing deformation causing the fracture paths. Comparatively, all nanocomposite samples on an average seemed to show a prominent brittle fracture with little or no evidence of circular pit formation. The amount of tearing deformation seemed to be enhanced in the nanocomposite specimens as compare to the neat ones. Finally, Transmission Electron Microscopy images indicated that different states of dispersion exist in all of the nanocomposite samples. The data showed that agglomeration of nanotubes increases as a function of weight percent. In addition to mechanical property characterization, thermal conductivity of all the samples was determined as a function of temperature between 30 deg. C and 100 deg. C using the 3ω method. The tested samples showed an almost 16% increase in thermal conductivity. The minimal enhancement in thermal conductivity has been analyzed from the standpoint of the Effective Medium Theory. Interfacial thermal resistances exhibit no order of magnitude changes explaining the conductivity results.

Fast fracture: an adiabatic restriction on thermally activated crack propagation

Energy Technology Data Exchange (ETDEWEB)

Burns, S.J.

1978-01-01

Slow, isothermal, crack propagation is widely suspected to be rate controlled by thermally activated plastic deformation in the crack tip region. Adiabatic conditions are generally established in the fracture modified material at the tip of a crack during fast fracture. The temperature of this material is not the temperature of the specimen and is generally not measured during fast fracture. Thus, a complete thermodynamic description of adiabatic crack propagation data can not be made. When the slow, isothermal, crack propagation mechanisms are assumed to be operative during adiabatic crack propagation then certain predictions can be made. For example: the changes in the driving force due to temperature and rate are always in the opposite sense; there is no minimum in the driving force versus crack velocity without a change in mechanism; the temperature rise in the crack tip fracture modified material is determined mainly by the activation enthalpy for crack propagation; the interpretation of fast fracture structural steel data from simple plastic models is suspect since these materials have dissimilar isothermal temperature dependencies.

Thermal shock fracture of graphite armor plate under the heat load of plasma disruption

International Nuclear Information System (INIS)

Horie, Tomoyoshi; Seki, Masahiro; Ohmori, Junji

1989-01-01

Experiments on the thermal shock brittle fracture of graphite plates were performed. Thermal loading which simulated a plasma disruption was produced by an electron beam facility. Pre-cracks produced on the surface propagated to the inside of the specimen even if the thermal stress on the surface was compressive. Two mechanisms are possible to produce tensile stress around the crack tip under thermal shock conditions. Temperature, thermal stress, and the stress intensity factor for the specimen were analyzed based on the finite element method for various heating conditions. The trend of experimental results under the asymmetric heating agrees qualitatively with the analytical results. This phenomenon is important for the design of plasma facing components made of graphite. Establishment of a lifetime prediction procedure including fatigue, fatigue crack growth, and brittle fracture is needed for graphite armors. (orig.)

Thermal conductive heating in fractured bedrock: Screening calculations to assess the effect of groundwater influx

Science.gov (United States)

Baston, Daniel P.; Kueper, Bernard H.

2009-02-01

A two-dimensional semi-analytical heat transfer solution is developed and a parameter sensitivity analysis performed to determine the relative importance of rock material properties (density, thermal conductivity and heat capacity) and hydrogeological properties (hydraulic gradient, fracture aperture, fracture spacing) on the ability to heat fractured rock using thermal conductive heating (TCH). The solution is developed using a Green's function approach in which an integral equation is constructed for the temperature in the fracture. Subsurface temperature distributions are far more sensitive to hydrogeological properties than material properties. The bulk ground water influx ( q) can provide a good estimate of the extent of influx cooling when influx is low to moderate, allowing the prediction of temperatures during heating without specific knowledge of the aperture and spacing of fractures. Target temperatures may not be reached or may be significantly delayed when the groundwater influx is large.

Fracture of thermally loaded disks of materials in elastic-brittle state

International Nuclear Information System (INIS)

Egorov, V.S.; Lanin, A.G.; Fedik, I.I.

1981-01-01

Fracture kinetics and limiting supporting power were studied in a solid thin disk axisymmetrically cooled from the periphery depending on the deqree of the stressed state nonuniformity and crack interaction. Basing on a strength approach of fracture linear mechanism it has become possible to obtain limit equilibrium curves and to evaluate thermoelastic stress redistribution on the boundary of the disk with one, two and four symmetrical radial cracks. Calculated data are confirmed by the results of the experiments performed with zirconium carbide water-cooled disks. It is shown that while determining the limit supporting power of a thermally loaded body, the loading history and fracture kinetics should be taken into account

Fracture mechanics evaluation for the cast duplex stainless steel after thermal aging

Energy Technology Data Exchange (ETDEWEB)

Urata, Shigeru [Kansai Electric Power Co., Inc., Osaka (Japan)

1998-12-31

For the primary coolant piping of PWRs in Japan, cast duplex stainless steel which is excellent in terms of strength, corrosion resistance, and weldability has conventionally been used. The cast duplex stainless steel contains the ferrite phase in the austenite matrix and thermal aging after long term service is known to change its material characteristics. It is considered appropriate to apply the methodology of elastic plastic fracture mechanics for an evaluation of the integrity of the primary coolant piping after thermal aging. Therefore, we evaluated the integrity of the primary coolant piping for an initial PWR plant in Japan by means of elastic plastic fracture mechanics. The evaluation results show that the crack will not grow into an unstable fracture and the integrity of the piping will be secured, even when such through wall crack length is assumed to equal the fatigue crack growth length for a service period of up to 60 years. (author)

Multi-Scale Thermal Heat Tracer Tests for Characterizing Transport Processes and Flow Channelling in Fractured Media: Theory and Field Experiments

Science.gov (United States)

de La Bernardie, J.; Klepikova, M.; Bour, O.; Le Borgne, T.; Dentz, M.; Guihéneuf, N.; Gerard, M. F.; Lavenant, N.

2017-12-01

The characterization of flow and transport in fractured media is particularly challenging because hydraulic conductivity and transport properties are often strongly dependent on the geometric structure of the fracture surfaces. Here we show how thermal tracer tests may be an excellent complement to conservative solute tracer tests to infer fracture geometry and flow channeling. We performed a series of thermal tracer tests at different scales in a crystalline rock aquifer at the experimental site of Ploemeur (H+ observatory network). The first type of thermal tracer tests are push-pull tracer tests at different scales. The temporal and spatial scaling of heat recovery, measured from thermal breakthrough curves, shows a clear signature of flow channeling. In particular, the late time tailing of heat recovery under channeled flow is shown to diverge from the T(t) α t-1,5 behavior expected for the classical parallel plate model and follow the scaling T(t) α 1/t(logt)2 for a simple channel modeled as a tube. Flow channeling is also manifested on the spatial scaling of heat recovery as flow channeling affects the decay of the thermal breakthrough peak amplitude and the increase of the peak time with scale. The second type of thermal tracer tests are flow-through tracer tests where a pulse of hot water was injected in a fracture isolated by a double straddle packer while pumping at the same flow rate in another fracture at a distance of about 10 meters to create a dipole flow field. Comparison with a solute tracer test performed under the same conditions also present a clear signature of flow channeling. We derive analytical expressions for the retardation and decay of the thermal breakthrough peak amplitude for different fracture geometries and show that the observed differences between thermal and solute breakthrough can be explained only by channelized flow. These results suggest that heat transport is much more sensitive to fracture heterogeneity and flow

Shallow crack effect on brittle fracture of RPV during pressurised thermal shock

International Nuclear Information System (INIS)

Ikonen, K.

1995-12-01

This report describes the study on behaviour of postulated shallow surface cracks in embrittled reactor pressure vessel subjected to pressurised thermal shock loading in an emergency core cooling. The study is related to the pressure vessel of a VVER-440 type reactor. Instead of a conventional fracture parameter like stress intensity factor or J integral the maximum principal stress distribution on a crack tip area is used as a fracture criteria. The postulated cracks locate circumferentially at the inner surface of the reactor pressure wall and they penetrate the cladding layer and open to the inner surface. Axisymmetric and semielliptical crack shapes were studied. Load is formed of an internal pressure acting also on crack faces and of a thermal gradient in the pressure vessel wall. Physical properties of material and loading data correspond real conditions in VVER-440 RPV. The study was carried out by making lot of 2D- and 3D- finite element calculations. Analysing principles and computer programs are explained. Except of studying the shallow crack effect, one objective of the study has also been to develop further expertise and the in-house developed computing system to make effectively elastic-plastic fracture mechanical analyses for real structures under complicated loads. Though the study concerns VVER-440 RPV, the results are of more general interest especially related to thermal loads. (orig.) (11 refs.)

Fracture mechanics evaluation of cast duplex stainless steel after thermal aging

International Nuclear Information System (INIS)

Tujikura, Y.; Urata, S.

1999-01-01

For the primary coolant piping of PWRs in Japan, cast duplex stainless steel, which is excellent in terms of strength, corrosion resistance and weldability, has conventionally been used. Cast duplex stainless steel contains the ferrite phase in the austenite matrix, and thermal aging after long-term service is known to decrease fracture toughness. Therefore, we evaluated the integrity of the primary coolant piping for an initial PWR plant in Japan by means of elastic plastic fracture mechanics. The evaluation results show that the crack will not grow into an unstable fracture and the integrity of the piping will be secure, even when such through-wall crack length is assumed to be as large as the fatigue crack length grown for a service period of up to 60 years. (orig.)

Fracture mechanics evaluation of cast duplex stainless steel after thermal aging

Energy Technology Data Exchange (ETDEWEB)

Tujikura, Y.; Urata, S. [Kansai Electr. Power Co., Inc., Osaka (Japan). General Office of Nucl. and Fossil Power Production

1999-07-01

For the primary coolant piping of PWRs in Japan, cast duplex stainless steel, which is excellent in terms of strength, corrosion resistance and weldability, has conventionally been used. Cast duplex stainless steel contains the ferrite phase in the austenite matrix, and thermal aging after long-term service is known to decrease fracture toughness. Therefore, we evaluated the integrity of the primary coolant piping for an initial PWR plant in Japan by means of elastic plastic fracture mechanics. The evaluation results show that the crack will not grow into an unstable fracture and the integrity of the piping will be secure, even when such through-wall crack length is assumed to be as large as the fatigue crack length grown for a service period of up to 60 years. (orig.)

Fracture resistance of metal-free composite crowns-effects of fiber reinforcement, thermal cycling, and cementation technique.

Science.gov (United States)

Lehmann, Franziska; Eickemeyer, Grit; Rammelsberg, Peter

2004-09-01

The improved mechanical properties of contemporary composites have resulted in their extensive use for the restoration of posterior teeth. However, the influence of fiber reinforcement, cementation technique, and physical stress on the fracture resistance of metal-free crowns is unknown. This in vitro study evaluated the effect of fiber reinforcement, physical stress, and cementation methods on the fracture resistance of posterior metal-free Sinfony crowns. Ninety-six extracted human third molars received a standardized tooth preparation: 0.5-mm chamfer preparation and occlusal reduction of 1.3 to 1.5 mm. Sinfony (nonreinforced crowns, n=48) and Sinfony-Vectris (reinforced crowns, n=48) crowns restoring original tooth contour were prepared. Twenty-four specimens of each crown type were cemented, using either glass ionomer cement (GIC) or resin cement. Thirty-two crowns (one third) were stored in humidity for 48 hours. Another third was exposed to 10,000 thermal cycles (TC) between 5 degrees C and 55 degrees C. The remaining third was treated with thermal cycling and mechanical loading (TCML), consisting of 1.2 million axial loads of 50 N. The artificial crowns were then vertically loaded with a steel sphere until failure occurred. Significant differences in fracture resistance (N) between experimental groups were assessed by nonparametric Mann-Whitney U-test (alpha=.05). Fifty percent of the Sinfony and Sinfony-Vectris crowns cemented with glass ionomer cement loosened after thermal cycling. Thermal cycling resulted in a significant reduction in the mean fracture resistance for Sinfony crowns cemented with GIC, from 2037 N to 1282 N (P=.004). Additional fatigue produced no further effects. Fiber reinforcement significantly increased fracture resistance, from 1555 N to 2326 N (P=.001). The minimal fracture resistance was above 600 N for all combinations of material, cement and loading. Fracture resistance of metal-free Sinfony crowns was significantly increased by

Prediction of minimum UO2 particle size based on thermal stress initiated fracture model

International Nuclear Information System (INIS)

Corradini, M.

1976-08-01

An analytic study was employed to determine the minimum UO 2 particle size that could survive fragmentation induced by thermal stresses in a UO 2 -Na Fuel Coolant Interaction (FCI). A brittle fracture mechanics approach was the basis of the study whereby stress intensity factors K/sub I/ were compared to the fracture toughness K/sub IC/ to determine if the particle could fracture. Solid and liquid UO 2 droplets were considered each with two possible interface contact conditions; perfect wetting by the sodium or a finite heat transfer coefficient. The analysis indicated that particles below the range of 50 microns in radius could survive a UO 2 -Na fuel coolant interaction under the most severe temperature conditions without thermal stress fragmentation. Environmental conditions of the fuel-coolant interaction were varied to determine the effects upon K/sub I/ and possible fragmentation. The underlying assumptions of the analysis were investigated in light of the analytic results. It was concluded that the analytic study seemed to verify the experimental observations as to the range of the minimum particle size due to thermal stress fragmentation by FCI. However the method used when the results are viewed in light of the basic assumptions indicates that the analysis is crude at best, and can be viewed as only a rough order of magnitude analysis. The basic complexities in fracture mechanics make further investigation in this area interesting but not necessarily fruitful for the immediate future

Potential effect of fracture technology on IPTS [Integrated Pressurized Thermal Shock] analysis (Fracture toughness: Kla and Klc and warm prestressing)

International Nuclear Information System (INIS)

Dickson, T.L.

1990-01-01

A major nuclear plant life extension issue to be confronted in the 1990's is pressure vessel integrity for the pressurized thermal shock (PTS) loading condition. Governing criteria associated with PTS are included in ''The PTS Rule'' (10 CFR 50.61) and Regulatory Guide 1.154: Format and Content of Plant-Specific Pressurized Thermal Shock Safety Analysis Reports for Pressurized Water Reactors. The results of the Integrated Pressurized Water Reactors. The results of the Integrated Pressurized Thermal Shock (IPTS) Program, along with risk assessments and fracture analyses performed by the NRC and reactor system vendors, contributed to the derivation of the PTS Rule. Over the last several years, the Heavy Section Steel Technology (HSST) Program at the Oak Ridge National Laboratory (ORNL) has performed a series of large-scale fracture-mechanics experiments. The Thermal Shock Experiments (TSE), Pressurized Thermal Shock Experiments (PTSE), and Wide Plate Experiments (WPE) produced K IC and K Ia data that suggest increased mean K IC and K Ia curves relative to the ones used in the IPTS study. Also, the PTSE and WPE have demonstrated that prototypical nuclear reactor pressure vessel steels are capable of arresting a propagating crack at K I values considerably above 220 MPa√m, the implicit limit of the ASME Code and the limit used in the IPTS studies. This document provides a discussion of the results of these experiments

Kinetic and energetic approaches to analysis of scabbing fracture of structural steels under thermal shock

International Nuclear Information System (INIS)

Molitvin, A.M.

2002-01-01

The regularities of the scabbing fracture of nine brands of structural steels under the conditions of the impact of the nuclear explosion X-ray irradiation are studied. The time dependences of the scabbing strength of the structural materials under thermal shock, initiated by the X-ray irradiation, are established within the frames of the approach to the problem on the scabbing fracture. The time dependences of the critical specific energy of the steels fracture under the conditions of the X-ray irradiation effect are determined within the frames of the energetic approach to the problem on the scabbing fracture, based on the comparison of the sample energy reserve and fracture work [ru

Underground disposal for radioactive wastes: study of the thermal impact in a fractured medium

International Nuclear Information System (INIS)

Coudrain, A.; Hosanski, J.M.; Ledoux, E.; Vouille, G.

1982-01-01

Radioactive waste storage in deep geologic formations, like granitic rocks, is one of the solutions studied for long-life radioactive wastes disposal. The study, presented in this document, has been developed in five stages: (1) theorical analysis of heat transfer in a fractured medium; bench-scale experiments (2) to study the convection in an artificial fracture with a punctual heat source, and, (3) in a real fracture with a spread heat source; (4) influence of the thermal stresses on the permeability of a fracture; (5) and finally, the mathematical model, validated in laboratory, used to simulate water and heat transfer, allows to discuss the radionuclides migration from an hydrodynamical point of view

Phase field modelling of dynamic thermal fracture in the context of irradiation damage

CERN Document Server

Schlüter, Alexander; Müller, Ralf; Tomut, Marilena; Trautmann , Christina; Weick, Helmut; Plate, Carolin

2015-01-01

This work presents a continuum mechanics approach to model fracturing processes in brittle materials that are subjected to rapidly applied high-temperature gradients. Such a type of loading typically occurs when a solid is exposed to an intense high-energy particle beam that deposits a large amount of energy into a small sample volume. Given the rapid energy deposition leading to a fast temperature increase, dynamic effects have to be considered. Our existing phase field model for dynamic fracture is thus extended in a way that allows modelling of thermally induced fracture. A finite element scheme is employed to solve the governing partial differential equations numerically. Finally, the functionality of our model is illustrated by two examples.

Hydrological and thermal issues concerning a nuclear waste repository in fractured rocks

International Nuclear Information System (INIS)

Wang, J.S.Y.

1991-12-01

The characterization of the ambient conditions of a potential site and the assessment of the perturbations induced by a nuclear waste repository require hydrological and thermal investigations of the geological formations at different spatial and temporal scales. For high-level wastes, the near-field impacts depend on the heat power of waste packages and the far-field long-term perturbations depend on the cumulative heat released by the emplaced wastes. Surface interim storage of wastes for several decades could lower the near-field impacts but would have relatively small long-term effects if spent fuels were the waste forms for the repository. One major uncertainty in the assessment of repository impacts is from the variation of hydrological properties in heterogeneous media, including the effects of fractures as high-permeability flow paths for containment migration. Under stress, a natural fracture cannot be represented by the parallel plate model. The rock surface roughness, the contact area, and the saturation state in the rock matrix could significantly change the fracture flow. In recent years, the concern of fast flow through fractures in saturated media has extended to the unsaturated zones. The interactions at different scales between fractures and matrix, between fractured matrix unites and porous units, and between formations and faults are discussed

Potential impact of enhanced fracture-toughness data on pressurized-thermal-shock analysis

International Nuclear Information System (INIS)

Dickson, T.L.; Theiss, T.J.

1990-01-01

The Heavy Section Steel Technology (HSST) Program is involved with the generation of ''enhanced'' fracture-initiation toughness and fracture-arrest toughness data of prototypic nuclear reactor vessel steels. These two sets of data are enhanced because they have distinguishing characteristics that could potentially impact PWR pressure vessel integrity assessments for the pressurized-thermal shock (PTS) loading condition which is a major plant-life extension issue to be confronted in the 1990's. Currently, the HSST Program is planning experiments to verify and quantify, for A533B steel, the distinguishing characteristic of elevated initiation-fracture toughness for shallow flaws which has been observed for other steels. Deterministic and probabilistic fracture-mechanics analyses were performed to examine the influence of the enhanced initiation and arrest fracture-toughness data on the cleavage fracture response of a nuclear reactor pressure vessel subjected to PTS loading. The results of the analyses indicated that application of the enhanced K Ia data does reduce the conditional probability of failure P(F|E); however, it does not appear to have the potential to significantly impact the results of PTS analyses. The application of enhanced fracture-initiation-toughness data for shallow flaws also reduces P(F|E), but it does appear to have a potential for significantly affecting the results of PTS analyses. The effect of including Type I warm prestress in probabilistic fracture-mechanics analyses is beneficial. The benefit is transient dependent and, in some cases, can be quite significant. 19 refs., 12 figs., 1 tab

Elastic-plastic Fracture Mechanics Assessment of nozzle corners submitted to thermal shock loading

International Nuclear Information System (INIS)

Chapuliot, S.; Marie, S.

2016-01-01

This paper focuses on the development of a simplified analytical scheme for the elastic-plastic Fracture Mechanics Assessment of large nozzle corners. Within that frame, following the specific numerical effort performed for the definition of a Stress Intensity Factor compendium, complementary elastic-plastic developments are proposed here for the consideration of the thermal shock loading in the elastic-plastic domain: this type of loading is a major loading for massive structures such as nozzle corners of large components. Thus, an important numerical was performed in order to extend the applicability domain of existing analytical schemes to those complex geometries. The final formulation is a simple one, applicable to a large variety of materials and geometrical configurations as long as the structure is large and the defect remains small in comparison to the internal radius of the nozzle. - Highlights: • Fracture Mechanics Assessment of large nozzle corners. • Elastic-plastic Stress Intensity Factor determination under thermal shock loading. • Semi-analytical schemes for J calculation.

Numerical modelling of fracture displacements due to thermal load from a KBS-3 repository

Energy Technology Data Exchange (ETDEWEB)

Hakami, Eva; Olofsson, Stig-Olof [Itasca Geomekanik AB, Stockholm (Sweden)

2002-01-01

The objective of the project has been to estimate the largest shear displacements that could be expected on a pre-existing fracture located in the repository area, due to the heat release from the deposited waste. Two-dimensional numerical analyses using the 'Universal Distinct Element Code' (UDEC) have been performed. The UDEC models represent a vertical cross section of a KBS-3 type repository with a large planar fracture intersecting a deposition hole at the repository centre. The extension, dip and mechanical properties of the fracture were changed in different models to evaluate the influence of these parameters on fracture shear displacements. The fracture was modelled using a Coulomb slip criterion with no cohesion and no dilation. The rock mass surrounding the fracture was modelled as a homogeneous, isotropic and elastic material, with a Young's modulus of 40 GPa. The initial heat release per unit repository area was assumed to be 8W/m{sup 2} (total power/total repository area). The shear displacements occur due to the thermal expansion of the rock surrounding the heat generating canisters. The rock mass is almost free to expand vertically, but is constrained horizontally, which gives a temperature-induced addition of shear stresses in the plane of the fracture. The shear movement of the fracture therefore follows the temperature development in the surrounding rock and the maximum shear displacement develops about 200 years after the waste deposition. Altogether, twenty cases are analysed. The maximum shear displacement, which occurs at the fracture centre, amounts to 0.2-13.8 cm depending on the fracture parameters. Among the analysed cases, the largest shear values, about 13 cm, was calculated for the cases with about 700 m long fractures with a shear stiffness of 0.005 GPa/m. Also, for large fractures with a higher shear stiffness of 5 GPa/m, but with a low friction angle (15 deg), the shear displacement reaches similar magnitudes, about

Probabilistic fracture mechanics analysis of reactor vessel for pressurized thermal shock: the effect of residual stress and fracture toughness

International Nuclear Information System (INIS)

Jung, Sung Gyu; Jin, Tae Eun; Jhung, Myung Jo; Choi, Young Hwan

2003-01-01

The structural integrity of the reactor vessel with the approaching end of life must be assured for pressurized thermal shock. The regulation specifies the screening criteria for this and requires that specific analysis be performed for the reactor vessel which is anticipated to exceed the screening criteria at the end of plant life. In case the screening criteria is exceeded by the deterministic analysis, probabilistic analysis must be performed to show that failure probability is within the limit. In this study, probabilistic fracture mechanics analysis of the reactor vessel for pressurized thermal shock is performed and the effects of residual stress and master curve on the failure probability are investigated

Effect of Thermal Aging and Test Temperatures on Fracture Toughness of SS 316(N) Welds

Science.gov (United States)

Dutt, B. Shashank; Babu, M. Nani; Shanthi, G.; Moitra, A.; Sasikala, G.

2018-03-01

The effect of thermal aging and test temperatures on fracture toughness (J 0.2) of SS 316(N) weld material has been studied based on J-R curve evaluations. The aging of the welds was carried out at temperatures 370, 475 and 550 °C and for durations varying from 1000 to 20,000 h. The fracture toughness (J-R curve) tests were carried out at 380 and 550 °C for specimens after all aging conditions, including as-weld condition. The initiation fracture toughness (J 0.2) of the SS 316(N) weld material has shown degradation after 20,000-h aging durations and is reflected in all the test temperatures and aging temperatures. The fracture toughness after different aging conditions and test temperatures, including as-weld condition, was higher than the minimum specified value for this class of welds.

The mechanics and physics of fracturing: application to thermal aspects of crack propagation and to fracking.

Science.gov (United States)

Cherepanov, Genady P

2015-03-28

By way of introduction, the general invariant integral (GI) based on the energy conservation law is presented, with mention of cosmic, gravitational, mass, elastic, thermal and electromagnetic energy of matter application to demonstrate the approach, including Coulomb's Law generalized for moving electric charges, Newton's Law generalized for coupled gravitational/cosmic field, the new Archimedes' Law accounting for gravitational and surface energy, and others. Then using this approach the temperature track behind a moving crack is found, and the coupling of elastic and thermal energies is set up in fracturing. For porous materials saturated with a fluid or gas, the notion of binary continuum is used to introduce the corresponding GIs. As applied to the horizontal drilling and fracturing of boreholes, the field of pressure and flow rate as well as the fluid output from both a horizontal borehole and a fracture are derived in the fluid extraction regime. The theory of fracking in shale gas reservoirs is suggested for three basic regimes of the drill mud permeation, with calculating the shape and volume of the local region of the multiply fractured rock in terms of the pressures of rock, drill mud and shale gas. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

The effect of thermal treatment on the fracture properties of alloy X-750 in aqueous environments

International Nuclear Information System (INIS)

Ballinger, R.; Elliott, C.S.; Hwang, I.S.; Prybylowski, J.

1993-05-01

Alloy X-750 is a high strength, age hardenable nickel-base alloy used in light water nuclear reactors. The excellent corrosion resistance and high temperature strength of alloy X-750 make it suitable for use in a variety of structure components in both pressurized water reactors and boiling water reactors. These applications involve exposure of highly stressed material to aqueous media. Operational stresses are subject to low frequency thermally induced fluctuations and high frequency flow induced fluctuations. In general, alloy X-750 has performed well in light water reactors. However, an economically significant number of components have failed unexpectedly due to localized forms of attack such as corrosion fatigue and stress corrosion cracking. Thermal processing history is known to play a significant role in the fracture properties of alloy X-750 in aqueous environments. While thermal treatments have been developed recently to improve performance, in many cases the reason for improved performance remains unclear. Therefore, identification of the mechanisms responsible for the degradation of fracture properties in aqueous environments is necessary. As a corollary it is necessary to achieve an understanding of how thermal treatment influences microstructure and, in turn, how microstructure influences fracture properties in aqueous environments. This report discusses five thermal treatments which were studied: (1) SA-1 hr at 1093 degree C, (2) AH - 24 hr at 885 degree C + 20 hr at 704 degree C, (3) HTH - 1 hr at 1093 degree C + 20 hr at 704 degree C, (4) AHTH - 1 hr at 1093 degree C + 24 hr at 885 degree C + 20 hr at 704 degree C, and (5) HOA - 1 hr at 1093 degree C + 100 hrs at 760 degree C. Microstructural characterization of these materials was accomplished through the use of optical microscopy, transmission electron microscopy,scanning transmission electron microscopy, energy dispersive x-ray spectroscopy, and x-ray diffractometry

Thermal analysis of fractures at Cerberus Fossae, Mars: Detection of air convection in the porous debris apron

Science.gov (United States)

Antoine, R.; Lopez, T.; Baratoux, D.; Rabinowicz, M.; Kurita, K.

2011-08-01

This study investigates the cause of high nighttime temperatures within Cerberus Fossae, a system of fractures affecting the Central Elysium Planitia. The inner parts (walls and floor) of the fractures are up to 40 K warmer than the surrounding plains. However, several temperature profiles exhibit a local temperature minima occurring in the central part of the fractures. We examined first the influence of cooling efficiency at night in the case of a strong reduction of the sky proportion induced by the fracture's geometry. However, the lack of correlation between temperature and sky proportion, calculated from extracted Mars Orbiter Laser Altimeter (MOLA) profiles argues against this hypothesis. Albedo variations were considered but appear to be limited within the fractures, and are generally not correlated with the temperatures. Variations of the thermal properties of bedrocks exposures, debris aprons and sand dunes inferred from high-resolution images do not either correlate with temperature variations within the fractures. As none of these factors taken alone, or combined, can satisfactorily explain the temperature variations within and near the fracture, we suggest that geothermal heat transported by air convection within the porous debris aprons may contribute to explain high temperatures at night and the local minima on the fracture floor. The conditions for the occurrence of the suggested phenomenon and the consequences on the surface temperature are numerically explored. A conservative geothermal gradient of 20 mW/m 2 was used in the simulations, this value being consistent with either inferred lithosphere elastic thicknesses below the shield volcanoes of the Tharsis dome or values predicted from numerical simulations of the thermal evolution of Mars. The model results indicate that temperature differences of 10-20 K between the central and upper parts of the fracture are explained in the case of high Darcy velocities which require high permeability values

Thermal fracturing on comets. Applications to 67P/Churyumov-Gerasimenko

Science.gov (United States)

Attree, N.; Groussin, O.; Jorda, L.; Rodionov, S.; Auger, A.-T.; Thomas, N.; Brouet, Y.; Poch, O.; Kührt, E.; Knapmeyer, M.; Preusker, F.; Scholten, F.; Knollenberg, J.; Hviid, S.; Hartogh, P.

2018-03-01

We simulate the stresses induced by temperature changes in a putative hard layer near the surface of comet 67P/Churyumov-Gerasimenko with a thermo-viscoelastic model. Such a layer could be formed by the recondensation or sintering of water ice (and dust grains), as suggested by laboratory experiments and computer simulations, and would explain the high compressive strength encountered by experiments on board the Philae lander. Changes in temperature from seasonal insolation variation penetrate into the comet's surface to depths controlled by the thermal inertia, causing the material to expand and contract. Modelling this with a Maxwellian viscoelastic response on a spherical nucleus, we show that a hard, icy layer with similar properties to Martian permafrost will experience high stresses: up to tens of MPa, which exceed its material strength (a few MPa), down to depths of centimetres to a metre. The stress distribution with latitude is confirmed qualitatively when taking into account the comet's complex shape but neglecting thermal inertia. Stress is found to be comparable to the material strength everywhere for sufficient thermal inertia (≳50 J m-2 K-1 s-1/2) and ice content (≳45% at the equator). In this case, stresses penetrate to a typical depth of 0.25 m, consistent with the detection of metre-scale thermal contraction crack polygons all over the comet. Thermal fracturing may be an important erosion process on cometary surfaces which breaks down material and weakens cliffs.

Prevention against fragile fracture in PWR pressure vessel in the presence of pressurized thermal shock

International Nuclear Information System (INIS)

Carmo, E.G.D. do; Oliveira, L.F.S. de; Roberty, N.C.

1984-01-01

A method for the determination of operational limit curves (primary pressure versus temperature) for PWR is presented. Such curves give the operators indications related to the safety status of the plant concerning the possibility of a pressurized thermal shock. The method begins by a thermal analysis for several postulated transients, followed by the determination of the thermomechanical stresses in the vessel and finally it makes use of the linear elasticity fracture mechanics. Curves are shown for a typical PWR. (Author) [pt

Fracture mechanics assessment of thermal aged nuclear piping based on the Leak-Before-Break concept

Energy Technology Data Exchange (ETDEWEB)

Chen, Mingya, E-mail: chenmingya@cgnpc.com.cn [Suzhou Nuclear Power Research Institute, Suzhou, Jiangsu Province (China); Yu, Weiwei [Suzhou Nuclear Power Research Institute, Suzhou, Jiangsu Province (China); Qian, Guian [Paul Scherrer Institute, Nuclear Energy and Safety Department, Villigen PSI (Switzerland); Wang, Rongshan; Lu, Feng; Zhang, Guodong; Xue, Fei; Chen, Zhilin [Suzhou Nuclear Power Research Institute, Suzhou, Jiangsu Province (China)

2016-05-15

Highlights: • The effects of thermal aging on crack unstable tearing are studied. • The critical size of crack unstable tearing is calculated by different methods. • The critical failure models are compared. • The conservatism of J–T diagram is shown. - Abstract: The Leak-Before-Break (LBB) concept has been accepted to design the primary piping system of the pressurized water reactor (PWR). Due to thermal aging of long term operation, the cast stainless steels (CSSs) which are used for the primary piping of PWR, suffer a significant loss of fracture toughness, and as a consequence the safety margin of the thermal aged pipe decreases. Therefore, the aged piping should be analyzed and validated by the LBB concept. In this paper, elastic–plastic fracture mechanics (EPFM) assessments of the thermal aged piping are presented according to the LBB concept. The critical break size of crack unstable tearing is calculated by the EPFM method. The crack driving force diagram (J–a diagram), the stability assessment diagram (J–T diagram) and a numerical method are applied to calculate the critical crack size of crack break. The effects of thermal aging on the plastic limit load, J–T diagram, critical crack size of the EPFM and the critical failure mode are studied. The results show that the thermal aging effect decreases the maximum allowed J-integral at a certain ductile tearing modulus by more than 50% and it increases the flow stress and plastic limit load by 11.78%. The results based on the J–T diagram are about 40% conservative than those based on the direct numerical method for the high loading case. For the thermal aged piping, it is important to consider the competition failure modes between plastic collapse and unstable ductile tearing.

Preliminary analysis of the potential for thermally-induced rock fracture around high-level waste containers

International Nuclear Information System (INIS)

Ratigan, J.L.

1976-01-01

The major results are: the development of parametric formulations relating the potential for thermally induced fracturing in the high-level radioactive waste repository concept to the elastic and thermal properties of the site rock and the depth of the excavation, and the recognition of a need to determine the actual ''failure envelope'' for any potential site rock in the laboratory and adjust the parametric relations appropriately. Analysis of five rock types indicated that none would experience elastic/brittle failure due to the thermal stresses induced by the introduction of a 5 kW heat source. However, the rock strengths and elastic properties are laboratory values and not in situ values

FAVOR: A new fracture mechanics code for reactor pressure vessels subjected to pressurized thermal shock

International Nuclear Information System (INIS)

Dickson, T.L.

1993-01-01

This report discusses probabilistic fracture mechanics (PFM) analysis which is a major element of the comprehensive probabilistic methodology endorsed by the NRC for evaluation of the integrity of Pressurized Water Reactor (PWR) pressure vessels subjected to pressurized-thermal-shock (PTS) transients. It is anticipated that there will be an increasing need for an improved and validated PTS PFM code which is accepted by the NRC and utilities, as more plants approach the PTS screening criteria and are required to perform plant-specific analyses. The NRC funded Heavy Section Steel Technology (HSST) Program at Oak Ridge National Laboratories is currently developing the FAVOR (Fracture Analysis of Vessels: Oak Ridge) PTS PFM code, which is intended to meet this need. The FAVOR code incorporates the most important features of both OCA-P and VISA-II and contains some new capabilities such as PFM global modeling methodology, the capability to approximate the effects of thermal streaming on circumferential flaws located inside a plume region created by fluid and thermal stratification, a library of stress intensity factor influence coefficients, generated by the NQA-1 certified ABAQUS computer code, for an adequate range of two and three dimensional inside surface flaws, the flexibility to generate a variety of output reports, and user friendliness

Thermal stability and fracture toughness of epoxy resins modified with epoxidized castor oil and Al2O3 nanoparticles

International Nuclear Information System (INIS)

Zhu, Lin; Jin, Fanlong; Park, Soojin

2012-01-01

This study examined the effects of the epoxidized castor oil (ECO) and Al 2 O 3 content on the thermal stability and fracture toughness of the diglycidylether of bisphenol-A (DGEBA)/ECO/Al 2 O 3 ternary composites using a range of techniques. The thermal stability of the composites was decreased by the addition of ECO and Al 2 O 3 nanoparticles. The fracture toughness of the composites was improved significantly by the addition of ECO and Al 2 O 3 nanoparticles. The composite containing 3 wt % Al 2 O 3 nanoparticles showed the maximum flexural strength. Scanning electron microscopy (SEM) revealed tortuous cracks in the DGEBA/ECO/Al 2 O 3 composites, which prevented deformation and crack propagation

Coupled processes in single fractures, double fractures and fractured porous media

International Nuclear Information System (INIS)

Tsang, C.F.

1986-12-01

The emplacement of a nuclear waste repository in a fractured porous medium provides a heat source of large dimensions over an extended period of time. It also creates a large cavity in the rock mass, changing significantly the stress field. Such major changes induce various coupled thermohydraulic, hydromechanic and hydrochemical transport processes in the environment around a nuclear waste repository. The present paper gives, first, a general overview of the coupled processes involving thermal, mechanical, hydrological and chemical effects. Then investigations of a number of specific coupled processes are described in the context of fluid flow and transport in a single fracture, two intersecting fractures and a fractured porous medium near a nuclear waste repository. The results are presented and discussed

Structure, thermal and fracture mechanical properties of benzoxazine-modified amine-cured DGEBA epoxy resins

Directory of Open Access Journals (Sweden)

2011-03-01

Full Text Available First, traditional diamine hardeners of epoxy resins (EP were checked as potential accelerators for the benzoxazine (BOX homopolymerization. It was established that the acceleration effect depends on both the type and amount of the diamine compounds. In the follow-up work amine-curable diglycidyl ether bisphenol A (DGEBA type EP was modified with BOX keeping the EP/BOX ratio constant (75/25 wt.%. The amine hardeners, added in the EP in stoichiometric amounts, were of aliphatic and aromatic nature, viz. diethylenetriamine (DETA, 4,4'-diaminodiphenyl methane (DDM, and their 1/1 mixture. The thermal, viscoelastic, flexural and fracture mechanical properties of the EP/BOX hybrids were determined and compared to those of the reference EPs. Based on dynamic-mechanical thermal analysis and atomic force microscopy the formation of co-network between EP and BOX was concluded. Homopolymerized BOX was built in the network in nanoscaled inclusions and it was associated with internal antiplasticization. Incorporation of BOX improved the charring, enhanced the flexural modulus and strength, and reduced the glass transition of the parent EP. The fracture toughness and energy were not improved by hybridization with BOX.

Evidence for tectonic, lithologic, and thermal controls on fracture system geometries in an andesitic high-temperature geothermal field

Science.gov (United States)

Massiot, Cécile; Nicol, Andrew; McNamara, David D.; Townend, John

2017-08-01

Analysis of fracture orientation, spacing, and thickness from acoustic borehole televiewer (BHTV) logs and cores in the andesite-hosted Rotokawa geothermal reservoir (New Zealand) highlights potential controls on the geometry of the fracture system. Cluster analysis of fracture orientations indicates four fracture sets. Probability distributions of fracture spacing and thickness measured on BHTV logs are estimated for each fracture set, using maximum likelihood estimations applied to truncated size distributions to account for sampling bias. Fracture spacing is dominantly lognormal, though two subordinate fracture sets have a power law spacing. This difference in spacing distributions may reflect the influence of the andesitic sequence stratification (lognormal) and tectonic faults (power law). Fracture thicknesses of 9-30 mm observed in BHTV logs, and 1-3 mm in cores, are interpreted to follow a power law. Fractures in thin sections (˜5 μm thick) do not fit this power law distribution, which, together with their orientation, reflect a change of controls on fracture thickness from uniform (such as thermal) controls at thin section scale to anisotropic (tectonic) at core and BHTV scales of observation. However, the ˜5% volumetric percentage of fractures within the rock at all three scales suggests a self-similar behavior in 3-D. Power law thickness distributions potentially associated with power law fluid flow rates, and increased connectivity where fracture sets intersect, may cause the large permeability variations that occur at hundred meter scales in the reservoir. The described fracture geometries can be incorporated into fracture and flow models to explore the roles of fracture connectivity, stress, and mineral precipitation/dissolution on permeability in such andesite-hosted geothermal systems.

The application of linear elastic fracture mechanics to thermally stressed welded components

International Nuclear Information System (INIS)

Green, D.

1981-01-01

Linear Elastic Fracture Mechanics techniques are applied to components constructed from brittle materials and operating at low or ambient temperatures. It is argued that these techniques can justifiably be applied to components at high temperature provided that stresses are thermally induced, self-equilibrating and cyclic. Such loading conditions occur for example in an LMFBR and a simple welded detail containing a crevice is taken as an example. Theoretical and experimental estimates of crack growth in this component are compared and good agreement is shown. (author)

Tee-junction of LMFR secondary circuit involving thermal, thermomechanical and fracture mechanics assessment on a striping phenomenon

International Nuclear Information System (INIS)

Lee, H.-Y.; Kim, J.-B.; Yoo, B.

2002-01-01

This paper presents the thermomechanical and fracture mechanics evaluation procedure of thermal striping damage on the secondary piping of LMFR using Green's function method and standard FEM. The thermohydraulic loading conditions used in the present analysis are simplified sinusoidal thermal loads and the random type thermal loads. The thermomechanical fatigue damage was evaluated according to ASME code subsection NH. The results of fatigue analysis for the sinusoidal and random type load cases showed that fatigue failure would occur at a welded joint during 90 000 hours of operation. The assessment for the fracture behavior of the welded joint showed that the crack would be initiated at an early stage of the operation. The fatigue crack was evaluated to propagate up to 5 mm along the thickness direction during the first 940.7 and 42 698.9 hours of operation for the sinusoidal and the random loading cases, respectively. However, it was evaluated that the crack would be arrested because of the low level of the primary stresses. The fatigue and crack propagation analyses for the random type loads were performed by Green's function method. (author)

Electroperturbation of human stratum corneum fine structure by high voltage pulses: a freeze-fracture electron microscopy and differential thermal analysis study.

Science.gov (United States)

Jadoul, A; Tanojo, H; Préat, V; Bouwstra, J A; Spies, F; Boddé, H E

1998-08-01

Application of high voltage pulses (HVP) to the skin has been shown to promote the transdermal drug delivery by a mechanism involving skin electroporation. The aim of this study was to detect potential changes in lipid phase and ultrastructure induced in human stratum corneum by various HVP protocols, using differential thermal analysis and freeze-fracture electron microscopy. Due to the time involved between the moment the electric field is switched off and the analysis, only "secondary" phenomena rather than primary events could be observed. A decrease in enthalpies for the phase transitions observed at 70 degrees C and 85 degrees C was detected by differential thermal analysis after HVP treatment. No changes in transition temperature could be seen. The freeze-fracture electron microscopy study revealed a dramatic perturbation of the lamellar ordering of the intercellular lipid after application of HVP. Most of the planes displayed rough surfaces. The lipid lamellae exhibited rounded off steps or a vanished stepwise order. There was no evidence for perturbation of the corneocytes content. In conclusion, the freeze-fracture electron microscopy and differential thermal analysis studies suggest that HVP application induces a general perturbation of the stratum corneum lipid ultrastructure.

Effects of low upper shelf fracture toughness on reactor vessel integrity during pressurized thermal shock events

International Nuclear Information System (INIS)

Bamford, W.H.; Heinecke, C.C.; Balkey, K.R.

1988-01-01

For the past decade, significant attention has been focused on the subject of nuclear rector vessel integrity during pressurized thermal shock (PTS) events. The issue of low upper shelf fracture toughness at operating temperatures has been a consideration for some reactor vessel materials since the early 1970's. Deterministic and probabilistic fracture mechanics sensitivity studies have been completed to evaluate the interaction between the PTS and lower upper shelf toughness issues that result from neutron embrittlement of the critical beltline region materials. This paper presents the results of these studies to show the interdependency of these fracture considerations in certain instances and to identify parameters that need to be carefully treated in reactor vessel integrity evaluations for these subjects. This issue is of great importance to those vessels which have low upper shelf toughness, both for demonstrating safety during the original design life and in life extension assessments

Thermal Exposure and Environment Effects on Tension, Fracture and Fatigue of 5XXX Alloys Tested in Different Orientations

Science.gov (United States)

2017-12-27

Thermal Exposure and Environment Effects on Tension, Fracture and Fatigue of 5XXX Alloys Tested in Different Orientations Sb. GRANT NUMBER ONR-N000 14...e.g.Hl31, HI 16, HI 28), thermal exposure conditions (i .e. time, temperature), and environment (e.g. dry air, humid air, solutions) on the... environmental cracking susceptibility at different load ing rates in both the S-T and L-T orientations. Experiments were conducted using slow strain rate

Estimation of fracture toughness of cast stainless steels during thermal aging in LWR systems-revision 1

International Nuclear Information System (INIS)

Chopra, O.K.

1994-08-01

This report presents a revision of the procedure and correlations presented earlier in NUREG/CR-4513, ANL-90/42 (June 1991) for predicting the change in mechanical properties of cast stainless steel components due to thermal aging during service in light water reactors at 280-330 degrees C (535-625 degrees F). The correlations presented in this report are based on an expanded data base and have been optimized with mechanical-property data on cast stainless steels aged up to ∼58,000 h at 290-350 degrees C (554-633 degrees F). The fracture toughness J-R curve, tensile stress, and Charpy-impact energy of aged cast stainless steels are estimated from known material information. Mechanical properties of a specific cast stainless steel are estimated from the extent and kinetics of thermal embrittlement. Embrittlement of cast stainless steels is characterized in terms of room-temperature Charpy-impact energy. Charpy-impact energy as a function of time and temperature of reactor service is estimated from the kinetics of thermal embrittlement, which are also determined from the chemical composition. The initial impact energy of the unaged steel is required for these estimations. Initial tensile flow stress is needed for estimating the flow stress of the aged material. The fracture toughness J-R curve for the material is then obtained by correlating room-temperature Charpy-impact energy with fracture toughness parameters. The values of J IC are determined from the estimated J-R curve and flow stress. A common open-quotes predicted lower-boundclose quotes J-R curve for cast stainless steels of unknown chemical composition is also defined for a given grade of steel, range of ferrite content, and temperature. Examples of estimating mechanical properties of cast stainless steel components during reactor service are presented

Documentation of probabilistic fracture mechanics codes used for reactor pressure vessels subjected to pressurized thermal shock loading: Parts 1 and 2. Final report

International Nuclear Information System (INIS)

Balkey, K.; Witt, F.J.; Bishop, B.A.

1995-06-01

Significant attention has been focused on the issue of reactor vessel pressurized thermal shock (PTS) for many years. Pressurized thermal shock transient events are characterized by a rapid cooldown at potentially high pressure levels that could lead to a reactor vessel integrity concern for some pressurized water reactors. As a result of regulatory and industry efforts in the early 1980's, a probabilistic risk assessment methodology has been established to address this concern. Probabilistic fracture mechanics analyses are performed as part of this methodology to determine conditional probability of significant flaw extension for given pressurized thermal shock events. While recent industry efforts are underway to benchmark probabilistic fracture mechanics computer codes that are currently used by the nuclear industry, Part I of this report describes the comparison of two independent computer codes used at the time of the development of the original U.S. Nuclear Regulatory Commission (NRC) pressurized thermal shock rule. The work that was originally performed in 1982 and 1983 to compare the U.S. NRC - VISA and Westinghouse (W) - PFM computer codes has been documented and is provided in Part I of this report. Part II of this report describes the results of more recent industry efforts to benchmark PFM computer codes used by the nuclear industry. This study was conducted as part of the USNRC-EPRI Coordinated Research Program for reviewing the technical basis for pressurized thermal shock (PTS) analyses of the reactor pressure vessel. The work focused on the probabilistic fracture mechanics (PFM) analysis codes and methods used to perform the PTS calculations. An in-depth review of the methodologies was performed to verify the accuracy and adequacy of the various different codes. The review was structured around a series of benchmark sample problems to provide a specific context for discussion and examination of the fracture mechanics methodology

Pressurized thermal shock probabilistic fracture mechanics sensitivity analysis for Yankee Rowe reactor pressure vessel

International Nuclear Information System (INIS)

Dickson, T.L.; Cheverton, R.D.; Bryson, J.W.; Bass, B.R.; Shum, D.K.M.; Keeney, J.A.

1993-08-01

The Nuclear Regulatory Commission (NRC) requested Oak Ridge National Laboratory (ORNL) to perform a pressurized-thermal-shock (PTS) probabilistic fracture mechanics (PFM) sensitivity analysis for the Yankee Rowe reactor pressure vessel, for the fluences corresponding to the end of operating cycle 22, using a specific small-break-loss- of-coolant transient as the loading condition. Regions of the vessel with distinguishing features were to be treated individually -- upper axial weld, lower axial weld, circumferential weld, upper plate spot welds, upper plate regions between the spot welds, lower plate spot welds, and the lower plate regions between the spot welds. The fracture analysis methods used in the analysis of through-clad surface flaws were those contained in the established OCA-P computer code, which was developed during the Integrated Pressurized Thermal Shock (IPTS) Program. The NRC request specified that the OCA-P code be enhanced for this study to also calculate the conditional probabilities of failure for subclad flaws and embedded flaws. The results of this sensitivity analysis provide the NRC with (1) data that could be used to assess the relative influence of a number of key input parameters in the Yankee Rowe PTS analysis and (2) data that can be used for readily determining the probability of vessel failure once a more accurate indication of vessel embrittlement becomes available. This report is designated as HSST report No. 117

Phase stability and fracture toughness of t' ZrO2 stabilised with MO1.5 (M=Yb and Gd) for thermal barrier application

International Nuclear Information System (INIS)

Loganathan, Archana; Gandhi, Ashutosh S.

2010-01-01

Thermal Barrier coatings (TBC's) protect the gas turbine blades at high temperature exposure. The t' phase is metastable and slowly transforms to the high-temperature equilibrium state consisting of tetragonal (t) and cubic (c) during high temperature exposure. Nanometric grain size also influences the fracture toughness and t' stability. A comparative study of the phase stability and fracture toughness evolution of Yb and Gd stabilized zirconia with composition 8 mol%MO 1.5 . The t' ZrO 2 -8mol% MO 1.5 (M = Yb and Gd) were prepared by co-precipitation method with crystallite size ∼ 20nm. Spark plasma sintering at 1250 deg C for 10 min was carried out to produce compacts with ∼ 96% relative density for fracture toughness measurements. The dense compacts were heat treated at 1250 deg C upto 192h. XRD studies revealed the partitioning of t' to t+c. No spontaneous monoclinic phase formed during cooling, except after 192h exposure. The fracture toughness of the sintered pellets with various time intervals of thermal exposure was measured. The results were analysed in terms of the effect of phase constitution on fracture toughness. The role of ferroelastic toughening in these materials was explored. (author)

The role of ductile ligaments and warm prestress on the re-initiation of fracture from a crack arrested during thermal shock

International Nuclear Information System (INIS)

Smith, E.

1982-01-01

The protection offered by warm prestress can be important for preserving a nuclear pressure vessel's integrity during a postulated emergency condition involving a loss of coolant, when the emergency core cooling water subjects the pressure vessel to a thermal shock. There are two aspects to the problem: (a) the initial extension of a defect into the vessel wall, and (b) the subsequent re-initiation of fracture at an arrested crack tip. This note considers the effect of warm prestress on the re-initiation of fracture from an arrested crack, and emphasizes the role of ductile ligaments. It is argued that the warm prestress concept is applicable, thus complementing the limited experimental results provided by the HSST Thermal Shock experimental programme. (orig.)

Impacts of transient heat transfer modeling on prediction of advanced cladding fracture during LWR LBLOCA

Energy Technology Data Exchange (ETDEWEB)

Lee, Youho, E-mail: euo@kaist.ac.kr; Lee, Jeong Ik, E-mail: jeongiklee@kaist.ac.kr; NO, Hee Cheon, E-mail: hcno@kaist.ac.kr

2016-03-15

Highlights: • Use of constant heat transfer coefficient for fracture analysis is not sound. • On-time heat transfer coefficient should be used for thermal fracture prediction. • ∼90% of the actual fracture stresses were predicted with the on-time transient h. • Thermal-hydraulic codes can be used to better predict brittle cladding fracture. • Effects of surface oxides on thermal shock fracture should be accounted by h. - Abstract: This study presents the importance of coherency in modeling thermal-hydraulics and mechanical behavior of a solid for an advanced prediction of cladding thermal shock fracture. In water quenching, a solid experiences dynamic heat transfer rate evolutions with phase changes of the fluid over a short quenching period. Yet, such a dynamic change of heat transfer rates has been overlooked in the analysis of thermal shock fracture. In this study, we are presenting quantitative evidence against the prevailing use of a constant heat transfer coefficient for thermal shock fracture analysis in water. We conclude that no single constant heat transfer could suffice to depict the actual stress evolution subject to dynamic fluid phase changes. Use of the surface temperature dependent heat transfer coefficient will remarkably increase predictability of thermal shock fracture of brittle materials. The presented results show a remarkable stress prediction improvement up to 80–90% of the actual stress with the use of the surface temperature dependent heat transfer coefficient. For thermal shock fracture analysis of brittle fuel cladding such as oxidized zirconium-based alloy or silicon carbide during LWR reflood, transient subchannel heat transfer coefficients obtained from a thermal-hydraulics code should be used as input for stress analysis. Such efforts will lead to a fundamental improvement in thermal shock fracture predictability over the current experimental empiricism for cladding fracture analysis during reflood.

Fracture Toughness Evaluation of Space Shuttle External Tank Thermal Protection System Polyurethane Foam Insulation Materials

Science.gov (United States)

McGill, Preston; Wells, Doug; Morgan, Kristin

2006-01-01

Experimental evaluation of the basic fracture properties of Thermal Protection System (TPS) polyurethane foam insulation materials was conducted to validate the methodology used in estimating critical defect sizes in TPS applications on the Space Shuttle External Fuel Tank. The polyurethane foam found on the External Tank (ET) is manufactured by mixing liquid constituents and allowing them to react and expand upwards - a process which creates component cells that are generally elongated in the foam rise direction and gives rise to mechanical anisotropy. Similarly, the application of successive foam layers to the ET produces cohesive foam interfaces (knitlines) which may lead to local variations in mechanical properties. This study reports the fracture toughness of BX-265, NCFI 24-124, and PDL-1034 closed-cell polyurethane foam as a function of ambient and cryogenic temperatures and knitline/cellular orientation at ambient pressure.

Special problems: LBB, thermal effects

International Nuclear Information System (INIS)

Lin Chiwen

2001-01-01

This section presents the discussion of special problems in the reactor coolant system design, including LBB and thermal effects. First, the categories of fracture mechanics technology applicable to LBB is discussed. Two categories of fracture mechanics, namely: linear-elastic fracture mechanics (LEFM) and elastic-plastic fracture mechanics (EPFM) are discussed specifically. Next, basic concepts of LEFM are discussed. This will be followed by a discussion of EPFM, with more specific discussion of the methodology currently acceptable to NRC, with the emphasis on the J-integral approach. This is followed by a discussion of the NRC position and recommendations and basic requirements laid out by NRC. A specific example of LBB application to WPWR piping is used to identify the key steps to be followed, in order to satisfy the recommendations and requirements of NRC. An application of LBB to the WPWR reactor coolant loop piping is provided as further illustration of the methodology. This section focuses on the thermal effects which have not been addressed earlier, and the thermal effects which have caused particular concerns on potential reactor degradations, such as pressurized thermal shocks. The organization of this section is divided into the following subsections: linear-elastic fracture mechanics (LEFM); elastic-plastic fracture mechanics (EPFM); J concepts; NRC recommendations and requirements on the application of LBB; two specific applications of LBB to WPWR piping; PWR internals degradation; thermal fatigue considerations; a case study of pressurized thermal shock

Fracture during cooling of cast borosilicate glass containing nuclear wastes

International Nuclear Information System (INIS)

Smith, P.K.; Baxter, C.A.

1981-09-01

Procedures and techniques were evaluated to mitigate thermal stress fracture in waste glass as the glass cools after casting. The two principal causes of fracture identified in small-scale testing are internal thermal stresses arising from excessive thermal gradients when cooled too fast, and shear fracturing in the surface of the glass because the stainless steel canister shrinks faster than the glass on cooling. Acoustic emission and ceramographic techniques were used to outline an annealing schedule that requires at least three weeks of controlled cooling below 550 0 C to avoid excessive thermal gradients and corresponding stresses. Fracture arising from canister interactions cannot be relieved by slow cooling, but can be eliminated for stainless steel canisters by using ceramic paper, ceramic or graphite paste linings, or by choosing a canister material with a thermal expansion coefficient comparable to, or less than, that of the glass

Pressure vessel fracture studies pertaining to a PWR LOCA-ECC thermal shock: experiments TSE-1 and TSE-2

International Nuclear Information System (INIS)

Cheverton, R.D.

1976-09-01

The LOCA-ECC Thermal Shock Program was established to investigate the potential for flaw propagation in pressurized-water reactor (PWR) vessels during injection of emergency core coolant following a loss-of-coolant accident. Studies thus far have included fracture mechanics analyses of typical PWRs, the design and construction of a thermal shock test facility, determination of material properties for test specimens, and two thermal shock experiments with 0.53-m-OD (21-in.) by 0.15-m-wall (6-in.) cylindrical test specimens. The PWR calculations indicated that under some circumstances crack propagation could be expected and that experiments should be conducted for cracks that would have the potential for propagation at least halfway through the wall

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...

Numerical simulation of the heat extraction in EGS with thermal-hydraulic-mechanical coupling method based on discrete fractures model

International Nuclear Information System (INIS)

Sun, Zhi-xue; Zhang, Xu; Xu, Yi; Yao, Jun; Wang, Hao-xuan; Lv, Shuhuan; Sun, Zhi-lei; Huang, Yong; Cai, Ming-yu; Huang, Xiaoxue

2017-01-01

The Enhanced Geothermal System (EGS) creates an artificial geothermal reservoir by hydraulic fracturing which allows heat transmission through the fractures by the circulating fluids as they extract heat from Hot Dry Rock (HDR). The technique involves complex thermal–hydraulic–mechanical (THM) coupling process. A numerical approach is presented in this paper to simulate and analyze the heat extraction process in EGS. The reservoir is regarded as fractured porous media consisting of rock matrix blocks and discrete fracture networks. Based on thermal non-equilibrium theory, the mathematical model of THM coupling process in fractured rock mass is used. The proposed model is validated by comparing it with several analytical solutions. An EGS case from Cooper Basin, Australia is simulated with 2D stochastically generated fracture model to study the characteristics of fluid flow, heat transfer and mechanical response in geothermal reservoir. The main parameters controlling the outlet temperature of EGS are also studied by sensitivity analysis. The results shows the significance of taking into account the THM coupling effects when investigating the efficiency and performance of EGS. - Highlights: • EGS reservoir comprising discrete fracture networks and matrix rock is modeled. • A THM coupling model is proposed for simulating the heat extraction in EGS. • The numerical model is validated by comparing with several analytical solutions. • A case study is presented for understanding the main characteristics of EGS. • The THM coupling effects are shown to be significant factors to EGS's running performance.

Hydraulic fracturing in granite under geothermal conditions

Science.gov (United States)

Solberg, P.; Lockner, D.; Byerlee, J.D.

1980-01-01

The experimental hydraulic fracturing of granite under geothermal conditions produces tensile fracture at rapid fluid injection rates and shear fracture at slow injection rates and elevated differential stress levels. A sudden burst of acoustic emission activity accompanies tensile fracture formation whereas the acoustic emission rate increases exponentially prior to shear fracture. Temperature does not significantly affect the failure mechanism, and the experimental results have not demonstrated the occurrence of thermal fracturing. A critical result of these experiments is that fluid injection at intermediate rates and elevated differential stress levels increases permeability by more than an order of magnitude without producing macroscopic fractures, and low-level acoustic emission activity occurs simultaneously near the borehole and propagates outward into the specimen with time. Permeability measurements conducted at atmospheric pressure both before and after these experiments show that increased permeability is produced by permanent structural changes in the rock. Although results of this study have not demonstrated the occurrence of thermal fracturing, they suggest that fluid injection at certain rates in situ may markedly increase local permeability. This could prove critical to increasing the efficiency of heat exchange for geothermal energy extraction from hot dry rock. ?? 1980.

Quantifying voids effecting delamination in carbon/epoxy composites: static and fatigue fracture behavior

Science.gov (United States)

Hakim, I.; May, D.; Abo Ras, M.; Meyendorf, N.; Donaldson, S.

2016-04-01

On the present work, samples of carbon fiber/epoxy composites with different void levels were fabricated using hand layup vacuum bagging process by varying the pressure. Thermal nondestructive methods: thermal conductivity measurement, pulse thermography, pulse phase thermography and lock-in-thermography, and mechanical testing: modes I and II interlaminar fracture toughness were conducted. Comparing the parameters resulted from the thermal nondestructive testing revealed that voids lead to reductions in thermal properties in all directions of composites. The results of mode I and mode II interlaminar fracture toughness showed that voids lead to reductions in interlaminar fracture toughness. The parameters resulted from thermal nondestructive testing were correlated to the results of mode I and mode II interlaminar fracture toughness and voids were quantified.

Time-dependent fracture of materials at elevated temperature for solar thermal power systems

International Nuclear Information System (INIS)

Gupta, G.D.

1979-01-01

Various Solar Thermal Power Systems are briefly described. The components of solar power systems in which time-dependent fracture problems become important are identified. Typical materials of interest, temperature ranges, and stress states are developed; and the number of cycles during the design life of these systems are indicated. The ASME Code procedures used by designers to predict the life of these components are briefly described. Some of the major problems associated with the use of these ASME procedures in the design of solar components are indicated. Finally, a number of test and development needs are identified which would enable the designers to predict the life of the solar power system components with a reasonable degree of confidence

Evaluation of fracture mechanics analyses used in RPV integrity assessment regarding brittle fracture

International Nuclear Information System (INIS)

Moinereau, D.; Faidy, C.; Valeta, M.P.; Bhandari, S.; Guichard, D.

1997-01-01

Electricite de France has conducted during these last years some experimental and numerical research programmes in order to evaluate fracture mechanics analyses used in nuclear reactor pressure vessels structural integrity assessment, regarding the risk of brittle fracture. These programmes included cleavage fracture tests on large scale cladded specimens containing subclad flaws with their interpretations by 2D and 3D numerical computations, and validation of finite element codes for pressurized thermal shocks analyses. Four cladded specimens made of ferritic steel A508 C13 with stainless steel cladding, and containing shallow subclad flaws, have been tested in four point bending at very low temperature in order to obtain cleavage failure. The specimen failure was obtained in each case in base metal by cleavage fracture. These tests have been interpreted by two-dimensional and three-dimensional finite element computations using different fracture mechanics approaches (elastic analysis with specific plasticity corrections, elastic-plastic analysis, local approach to cleavage fracture). The failure of specimens are conservatively predicted by different analyses. The comparison between the elastic analyses and elastic-plastic analyses shows the conservatism of specific plasticity corrections used in French RPV elastic analyses. Numerous finite element calculations have also been performed between EDF, CEA and Framatome in order to compare and validate several fracture mechanics post processors implemented in finite element programmes used in pressurized thermal shock analyses. This work includes two-dimensional numerical computations on specimens with different geometries and loadings. The comparisons show a rather good agreement on main results, allowing to validate the finite element codes and their post-processors. (author). 11 refs, 24 figs, 3 tabs

Evaluation of fracture mechanics analyses used in RPV integrity assessment regarding brittle fracture

Energy Technology Data Exchange (ETDEWEB)

Moinereau, D [Electricite de France, Dept. MTC, Moret-sur-Loing (France); Faidy, C [Electricite de France, SEPTEN, Villeurbanne (France); Valeta, M P [Commisariat a l` Energie Atomique, Dept. DMT, Gif-sur-Yvette (France); Bhandari, S; Guichard, D [Societe Franco-Americaine de Constructions Atomiques (FRAMATOME), 92 - Paris-La-Defense (France)

1997-09-01

Electricite de France has conducted during these last years some experimental and numerical research programmes in order to evaluate fracture mechanics analyses used in nuclear reactor pressure vessels structural integrity assessment, regarding the risk of brittle fracture. These programmes included cleavage fracture tests on large scale cladded specimens containing subclad flaws with their interpretations by 2D and 3D numerical computations, and validation of finite element codes for pressurized thermal shocks analyses. Four cladded specimens made of ferritic steel A508 C13 with stainless steel cladding, and containing shallow subclad flaws, have been tested in four point bending at very low temperature in order to obtain cleavage failure. The specimen failure was obtained in each case in base metal by cleavage fracture. These tests have been interpreted by two-dimensional and three-dimensional finite element computations using different fracture mechanics approaches (elastic analysis with specific plasticity corrections, elastic-plastic analysis, local approach to cleavage fracture). The failure of specimens are conservatively predicted by different analyses. The comparison between the elastic analyses and elastic-plastic analyses shows the conservatism of specific plasticity corrections used in French RPV elastic analyses. Numerous finite element calculations have also been performed between EDF, CEA and Framatome in order to compare and validate several fracture mechanics post processors implemented in finite element programmes used in pressurized thermal shock analyses. This work includes two-dimensional numerical computations on specimens with different geometries and loadings. The comparisons show a rather good agreement on main results, allowing to validate the finite element codes and their post-processors. (author). 11 refs, 24 figs, 3 tabs.

Geothermal-Related Thermo-Elastic Fracture Analysis by Numerical Manifold Method

Directory of Open Access Journals (Sweden)

Jun He

2018-05-01

Full Text Available One significant factor influencing geothermal energy exploitation is the variation of the mechanical properties of rock in high temperature environments. Since rock is typically a heterogeneous granular material, thermal fracturing frequently occurs in the rock when the ambient temperature changes, which can greatly influence the geothermal energy exploitation. A numerical method based on the numerical manifold method (NMM is developed in this study to simulate the thermo-elastic fracturing of rocklike granular materials. The Voronoi tessellation is incorporated into the pre-processor of NMM to represent the grain structure. A contact-based heat transfer model is developed to reflect heat interaction among grains. Based on the model, the transient thermal conduction algorithm for granular materials is established. To simulate the cohesion effects among grains and the fracturing process between grains, a damage-based contact fracture model is developed to improve the contact algorithm of NMM. In the developed numerical method, the heat interaction among grains as well as the heat transfer inside each solid grain are both simulated. Additionally, as damage evolution and fracturing at grain interfaces are also considered, the developed numerical method is applicable to simulate the geothermal-related thermal fracturing process.

Estimation of fracture conditions of ceramics by thermal shock with laser beams based on the maximum compressive stress criterion

International Nuclear Information System (INIS)

Akiyama, Shigeru; Amada, Shigeyasu.

1992-01-01

Structural ceramics are attracting attention in the development of space planes, aircraft and nuclear fusion reactors because they have excellent wear-resistant and heat-resistant characteristics. However, in some applications it is anticipated that they will be exposed to very-high-temperature environments of the order of thousands of degrees. Therefore, it is very important to investigate their thermal shock characteristics. In this report, the distributions of temperatures and thermal stresses of cylindrically shaped ceramics under irradiation by laser beams are discussed using the finite-element computer code (MARC) with arbitrary quadrilateral axisymmetric ring elements. The relationships between spot diameters of laser beams and maximum values of compressive thermal stresses are derived for various power densities. From these relationships, a critical fracture curve is obtained, and it is compared with the experimental results. (author)

Microscale fracture mechanisms of a Cr3C2-NiCr HVOF coating

International Nuclear Information System (INIS)

Robertson, Andrew L.; White, Ken W.

2017-01-01

Thermal spray coatings, often composed of heterogeneous, multiphase microstructures, may, consequently, exhibit complex fracture behavior. For such coating structures, conventional mechanical evaluation methods fail to isolate the contribution of microstructural features to the overall fracture behavior. For this reason, this study employed focused ion beam machined (FIB) microcantilever beams and FIB sectioning methods to study the fracture mechanisms important at the scale of the heterogeneous Cr 3 C 2 -NiCr thermal spray coating. We found three fracture modes, namely, intergranular matrix fracture, matrix/carbide interfacial fracture, and carbide cleavage. By comparison, microindentation-induced cracks, the frequency of crack deflection around carbides is significantly more prevalent at this much larger crack dimension. This mechanistic variation provides some insight into the specific role and limitations of the microcantilever beam technique for fracture characterization of composite microstructures.

The influence of chemistry concentration on the fracture risk of a reactor pressure vessel subjected to pressurized thermal shocks

Energy Technology Data Exchange (ETDEWEB)

Huang, Pin-Chiun [Institute of Nuclear Engineering and Science, National Tsing-Hua University, Hsinchu 30013, Taiwan, ROC (China); Chou, Hsoung-Wei, E-mail: hwchou@iner.gov.tw [Institute of Nuclear Energy Research, Taoyuan 32546, Taiwan, ROC (China); Ferng, Yuh-Ming [Institute of Nuclear Engineering and Science, National Tsing-Hua University, Hsinchu 30013, Taiwan, ROC (China)

2016-02-15

Highlights: • Probabilistic fracture mechanics method was used to analyze a reactor pressure vessel. • Effects of copper and nickel contents on RPV fracture probability under PTS were investigated and discussed. • Representative PTS transients of Beaver Valley nuclear power plant were utilized. • The range of copper and nickel contents of the RPV materials were suggested. • With different embrittlement levels the dominated PTS category is different. - Abstract: The radiation embrittlement behavior of reactor pressure vessel shell is influenced by the chemistry concentration of metal materials. This paper aims to study the effects of copper and nickel content variations on the fracture risk of pressurized water reactor (PWR) pressure vessel subjected to pressurized thermal shock (PTS) transients. The probabilistic fracture mechanics (PFM) code, FAVOR, which was developed by the Oak Ridge National Laboratory in the United States, is employed to perform the analyses. A Taiwan domestic PWR pressure vessel assumed with varied copper and nickel contents of beltline region welds and plates is investigated in the study. Some PTS transients analyzed from Beaver Valley Unit 1 for establishing the U.S. NRC's new PTS rule are applied as the loading condition. It is found that the content variation of copper and nickel will significantly affect the radiation embrittlement and the fracture probability of PWR pressure vessels. The results can be regarded as the risk incremental factors for comparison with the safety regulation requirements on vessel degradation as well as a reference for the operation of PWR plants in Taiwan.

A fracture mechanics method of evaluating structural integrity of a reactor vessel due to thermal shock effects following LOCA condition

International Nuclear Information System (INIS)

Ramani, D.T.

1977-01-01

The importance of knowledge of structural integrity of a reactor vessel due to thermal shock effects, is related to safety and operational requirements in assessing the adequacy and flawless functioing of the nuclear power systems. Followig a loss-of-coolant accident (LOCA) condition the integrity of the reactor vessel due to a sudden thermal shock induced by actuation of emergency core cooling system (ECCS), must be maintained to ensure safe and orderly shutdown of the reactor and its components. The paper encompasses criteria underlaying a fracture mechanics method of analysis to evaluate structural integrity of a typical 950 MWe PWR vessel as a result of very drastic changes in thermal and mechanical stress levels in the reactor vessel wall. The main object of this investigation therefore consists in assessing the capability of a PWR vessel to withstand the most critical thermal shock without inpairing its ability to conserve vital coolant owing to probable crack propagation. (Auth.)

Thermally induced delamination of multilayers

DEFF Research Database (Denmark)

Sørensen, Bent F.; Sarraute, S.; Jørgensen, O.

1998-01-01

Steady-state delamination of multilayered structures, caused by stresses arising during processing due to thermal expansion mismatch, is analyzed by a fracture mechanics model based on laminate theory. It is found that inserting just a few interlayers with intermediate thermal expansion coefficie...... coefficients may be an effective way of reducing the delamination energy release rate. Uneven layer thickness and increasing elastic mismatch are shown to raise the energy release rate. Experimental work confirms important trends of the model.......Steady-state delamination of multilayered structures, caused by stresses arising during processing due to thermal expansion mismatch, is analyzed by a fracture mechanics model based on laminate theory. It is found that inserting just a few interlayers with intermediate thermal expansion...

Inclusion-initiated fracture model for ceramics

International Nuclear Information System (INIS)

Sung, J.; Nicholson, P.S.

1990-01-01

The fracture of ceramics initiating from a typical inclusion is analyzed. The inclusion is considered to have a thermal expansion coefficient and fracture toughness lower than those of the matrix and a Young's modulus higher than that of the matrix. Inclusion-initiated fracture is modeled for a spherical inclusion using a weight function method to compute the residual stress intensity factor for a part-through elliptical crack. The results are applied to an α-Al 2 O 3 inclusion embedded in a tetragonal ZrO 2 ceramic. The strength predictions agree well with experimental data

Fracture risk assessment for the pressurized water reactor pressure vessel under pressurized thermal shock events

International Nuclear Information System (INIS)

Chou, Hsoung-Wei; Huang, Chin-Cheng

2016-01-01

Highlight: • The PTS loading conditions consistent with the USNRC's new PTS rule are applied as the loading condition for a Taiwan domestic PWR. • The state-of-the-art PFM technique is employed to analyze a reactor pressure vessel. • Novel flaw model and embrittlement correlation are considered in the study. • The RT-based regression formula of NUREG-1874 was also utilized to evaluate the failure risks of RPV. • For slightly embrittled RPV, the SO-1 type PTSs play more important role than other types of PTS. - Abstract: The fracture risk of the pressurized water reactor pressure vessel of a Taiwan domestic nuclear power plant has been evaluated according to the technical basis of the U.S.NRC's new pressurized thermal shock (PTS) screening criteria. The ORNL's FAVOR code and the PNNL's flaw models were employed to perform the probabilistic fracture mechanics analysis associated with plant specific parameters of the domestic reactor pressure vessel. Meanwhile, the PTS thermal hydraulic and probabilistic risk assessment data analyzed from a similar nuclear power plant in the United States for establishing the new PTS rule were applied as the loading conditions. Besides, an RT-based regression formula derived by the U.S.NRC was also utilized to verify the through-wall cracking frequencies. It is found that the through-wall cracking of the analyzed reactor pressure vessel only occurs during the PTS events resulted from the stuck-open primary safety relief valves that later reclose, but with only an insignificant failure risk. The results indicate that the Taiwan domestic PWR pressure vessel has sufficient structural margin for the PTS attack until either the current license expiration dates or during the proposed extended operation periods.

Fracture analyses of WWER reactor pressure vessels

International Nuclear Information System (INIS)

Sievers, J.; Liu, X.

1997-01-01

In the paper first the methodology of fracture assessment based on finite element (FE) calculations is described and compared with simplified methods. The FE based methodology was verified by analyses of large scale thermal shock experiments in the framework of the international comparative study FALSIRE (Fracture Analyses of Large Scale Experiments) organized by GRS and ORNL. Furthermore, selected results from fracture analyses of different WWER type RPVs with postulated cracks under different loading transients are presented. 11 refs, 13 figs, 1 tab

Fracture analyses of WWER reactor pressure vessels

Energy Technology Data Exchange (ETDEWEB)

Sievers, J; Liu, X [Gesellschaft fuer Anlagen- und Reaktorsicherheit mbH (GRS), Koeln (Germany)

1997-09-01

In the paper first the methodology of fracture assessment based on finite element (FE) calculations is described and compared with simplified methods. The FE based methodology was verified by analyses of large scale thermal shock experiments in the framework of the international comparative study FALSIRE (Fracture Analyses of Large Scale Experiments) organized by GRS and ORNL. Furthermore, selected results from fracture analyses of different WWER type RPVs with postulated cracks under different loading transients are presented. 11 refs, 13 figs, 1 tab.

Fracture toughness and stress relief response of irradiated Type 347/348 stainless steel

International Nuclear Information System (INIS)

Haggag, F.M.

1985-01-01

A test program has experimentally determined: (1) The fracture toughness of Type 347/348 stainless steel (SS) specimens with high values of irradiation fluence (2.3 to 4.8 x 10 22 n/cm 2 , E > 1.0 MeV) and experiencing different levels of irradiation creep (0.0, 0.6, 1.1, 1.8%), (2) the effect of thermal stress relief on fracture toughness recovery for the highly irradiated material, and (3) the mechanisms associated with fracture toughness recovery due to thermal stress relief. The postirradiation fracture toughness tests and tensile tests were conducted at 427 0 C

Some advances in fracture studies under the heavy-section steel technology program

International Nuclear Information System (INIS)

Pugh, C.E.; Corwin, W.R.; Bryan, R.H.; Bass, B.R.

1985-01-01

Recent results are summarized from HSST studies in three major areas that relate to assessing nuclear reactor pressure vessel integrity under pressurized-thermal-shock (PTS) conditions: irradiation effects on the fracture properties of stainless steel cladding, crack run-arrest behavior under nonisothermal conditions, and fracture behavior of a thick-wall vessel under combined thermal and pressure loadings

Fracture mechanics analysis of reactor pressure vessel under pressurized thermal shock - The effect of elastic-plastic behavior and stainless steel cladding -

International Nuclear Information System (INIS)

Joo, Jae Hwang; Kang, Ki Ju; Jhung, Myung Jo

2002-01-01

Performed here is an assessment study for deterministic fracture mechanics analysis of a pressurized thermal shock (PTS). The PTS event means an event or transient in pressurized water reactors (PWRs) causing severe overcooling (thermal shock) concurrent with or followed by significant pressure in the reactor vessel. The problems consisting of two transients and 10 cracks are solved and maximum stress intensity factors and maximum allowable nil-ductility reference temperatures are calculated. Their results are compared each other to address the general characteristics between transients, crack types and analysis methods. The effects of elastic-plastic material behavior and clad coating on the inner surface are explored

Pressurized Thermal Shock, Pts

International Nuclear Information System (INIS)

Boyd, C.

2008-01-01

Pressurized Thermal Shock (Pts) refers to a condition that challenges the integrity of the reactor pressure vessel. The root cause of this problem is the radiation embrittlement of the reactor vessel. This embrittlement leads to an increase in the reference temperature for nil ductility transition (RTNDT). RTNDT can increase to the point where the reactor vessel material can loose fracture toughness during overcooling events. The analysis of the risk of having a Pts for a specific plant is a multi-disciplinary problem involving probabilistic risk analysis (PRA), thermal-hydraulic analysis, and ultimately a structural and fracture analysis of the vessel wall. The PRA effort involves the postulation of overcooling events and ultimately leads to an integrated risk analysis. The thermal-hydraulic effort involves the difficult task of predicting the system behavior during a postulated overcooling scenario with a special emphasis on predicting the thermal and mechanic loadings on the reactor pressure vessel wall. The structural and fracture analysis of the reactor vessel wall relies on the thermal-hydraulic conditions as boundary conditions. The US experience has indicated that medium and large diameter primary system breaks dominate the risk of Pts along with scenarios that involve a stuck open valve (and associated system cooldown) that recloses resulting in system re-pressurization while the vessel wall is cool.

Essential work of fracture analysis for starch filled poly(propylene carbonate) composites

International Nuclear Information System (INIS)

Wang, X.L.; Li, R.K.Y.; Cao, Y.X.; Meng, Y.Z.

2007-01-01

Starch filled poly(propylene carbonate) composites are environmental friendly materials. In this study, the fracture toughness of composites under mode I loading was determined by the essential work of fracture concept. The specific essential fracture work of the poly(propylene carbonate)/starch composites decreases with increasing the starch content, while the non-essential work term, βw p increases with increasing the starch content. In addition, the morphologies, thermal properties, thermo-mechanical properties were studied by scanning electron microscope, thermogravimetric analysis, dynamic mechanical analysis, and differential scanning calorimetry, respectively. The thermal and thermo-mechanical measurements revealed that increasing starch content led to an increase in glass transition temperature and thermal stability. Morphology observation indicates that poly(propylene carbonate) and starch have weak interfacial adhesion

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)

Microscale fracture mechanisms of a Cr{sub 3}C{sub 2}-NiCr HVOF coating

Energy Technology Data Exchange (ETDEWEB)

Robertson, Andrew L., E-mail: Andrew.robertson99987@gmail.com; White, Ken W.

2017-03-14

Thermal spray coatings, often composed of heterogeneous, multiphase microstructures, may, consequently, exhibit complex fracture behavior. For such coating structures, conventional mechanical evaluation methods fail to isolate the contribution of microstructural features to the overall fracture behavior. For this reason, this study employed focused ion beam machined (FIB) microcantilever beams and FIB sectioning methods to study the fracture mechanisms important at the scale of the heterogeneous Cr{sub 3}C{sub 2}-NiCr thermal spray coating. We found three fracture modes, namely, intergranular matrix fracture, matrix/carbide interfacial fracture, and carbide cleavage. By comparison, microindentation-induced cracks, the frequency of crack deflection around carbides is significantly more prevalent at this much larger crack dimension. This mechanistic variation provides some insight into the specific role and limitations of the microcantilever beam technique for fracture characterization of composite microstructures.

Effect of temperature and moisture on the fracture energy and the thermal properties of concrete

International Nuclear Information System (INIS)

Kallel, H.; Carre, H.; Laborderie, C.; Masson, B.; Tran, N.C.

2015-01-01

In nuclear power plants, during a severe accident the containment building undergoes an increase of pressure, temperature and relative humidity that can reach respectively 5 bars, 140 C. degrees and the saturation of water vapor. Beyond the regulatory calculations, a suitable knowledge of the thermal and mechanical behaviour of the materials and more specifically of the concrete is required to carry out accurate numerical simulations. An experimental apparatus has been designed to assess the fracture energy (G f ) evolutions for concrete under various experimental conditions in terms of temperature and relative humidity of the concrete. Mechanical tests have been performed under different controlled conditions in terms of temperature (T=30 C. degrees ) and liquid water degree of saturation S w (four target values of 50, 70, 90 and 100%). These values of liquid water degree of saturation have been obtained by conditioning the relative humidity of the sealed environment where specimens have been left for the equalisation process by using potassium salt solutions. DCT (Disk-shape Compact Tension) test has been chosen for determining G f . In comparison with three points bending test, the typology of the test, the equipment and all test devices have been validated. Test results show clearly the decreasing of the fracture energy as saturation degree increases. This evolution has a linear trend for S w ranging from 36 % to 97 %

Morphology Analysis of Cu Film Fractures in Sandwiched Methylmethacrylate Plates

Directory of Open Access Journals (Sweden)

Cristiano Fidani

2015-06-01

Full Text Available Thin films of Cu were evaporated on solid plates of polymethylmethacrylate (PMMA. A polymerization process was made to realize sandwiched structure to protect the Cu films. Fracturing of the metal film surface was observed with several morphologies showing two different fracture systems. Surface film morphology was analysed in terms of the distribution area of the islands and contour fractal dimension. The island areas showed a maximum corresponding to 42 nm of the Cu thickness, it was also the threshold to observe the second fracture system. The fractures pattern resulted to be scale invariant with fractal dimensions between 1.55 and 1.7. The minimum fractal dimension also occurred at the film thickness corresponding to the maximum island area. The reported effects can be understood on the basis of different thermal expansion coefficients of the two materials and their thermally induced adhesion.DOI: http://dx.doi.org/10.5755/j01.ms.21.2.6518

Thermal shock behavior of toughened gadolinium zirconate/YSZ double-ceramic-layered thermal barrier coating

International Nuclear Information System (INIS)

Zhong, Xinghua; Zhao, Huayu; Zhou, Xiaming; Liu, Chenguang; Wang, Liang; Shao, Fang; Yang, Kai; Tao, Shunyan; Ding, Chuanxian

2014-01-01

Highlights: • Gd 2 Zr 2 O 7 /YSZ DCL thermal barrier coating was designed and fabricated. • The Gd 2 Zr 2 O 7 top ceramic layer was toughened by addition of nanostructured 3YSZ. • Remarkable improvement in thermal shock resistance of the DCL coating was achieved. - Abstract: Double-ceramic-layered (DCL) thermal barrier coating system comprising of toughened Gadolinium zirconate (Gd 2 Zr 2 O 7 , GZ) as the top ceramic layer and 4.5 mol% Y 2 O 3 partially-stabilized ZrO 2 (4.5YSZ) as the bottom ceramic layer was fabricated by plasma spraying and thermal shock behavior of the DCL coating was investigated. The GZ top ceramic layer was toughened by addition of nanostructured 3 mol% Y 2 O 3 partially-stabilized ZrO 2 (3YSZ) to improve fracture toughness of the matrix. The thermal shock resistance of the DCL coating was enhanced significantly compared to that of single-ceramic-layered (SCL) GZ-3YSZ composite coating, which is believed to be primarily attributed to the two factors: (i) the increase in fracture toughness of the top ceramic layer by incorporating nanostructured YSZ particles and (ii) the improvement in strain tolerance through the utilization of 4.5YSZ as the bottom ceramic layer. In addition, the failure mechanisms are mainly attributed to the still low fracture toughness of the top ceramic layer and oxidation of the bond-coat

Coupled hydro-thermo-mechanical modeling of hydraulic fracturing in quasi-brittle rocks using BPM-DEM

Directory of Open Access Journals (Sweden)

Ingrid Tomac

2017-02-01

Full Text Available This paper presents an improved understanding of coupled hydro-thermo-mechanical (HTM hydraulic fracturing of quasi-brittle rock using the bonded particle model (BPM within the discrete element method (DEM. BPM has been recently extended by the authors to account for coupled convective–conductive heat flow and transport, and to enable full hydro-thermal fluid–solid coupled modeling. The application of the work is on enhanced geothermal systems (EGSs, and hydraulic fracturing of hot dry rock (HDR is studied in terms of the impact of temperature difference between rock and a flowing fracturing fluid. Micro-mechanical investigation of temperature and fracturing fluid effects on hydraulic fracturing damage in rocks is presented. It was found that fracture is shorter with pronounced secondary microcracking along the main fracture for the case when the convective–conductive thermal heat exchange is considered. First, the convection heat exchange during low-viscosity fluid infiltration in permeable rock around the wellbore causes significant rock cooling, where a finger-like fluid infiltration was observed. Second, fluid infiltration inhibits pressure rise during pumping and delays fracture initiation and propagation. Additionally, thermal damage occurs in the whole area around the wellbore due to rock cooling and cold fluid infiltration. The size of a damaged area around the wellbore increases with decreasing fluid dynamic viscosity. Fluid and rock compressibility ratio was found to have significant effect on the fracture propagation velocity.

Buoyancy flow in fractures intersecting a nuclear waste repository

International Nuclear Information System (INIS)

Wang, J.S.Y.; Tsang, C.F.

1980-07-01

The thermally induced buoyancy flow in fractured rocks around a nuclear waste repository is of major concern in the evaluation of the regional, long-term impact of nuclear waste disposal in geological formation. In this study, buoyancy flow and the development of convective cells are calculated in vertical fractures passing through or positioned near a repository. Interaction between buoyancy flow and regional hydraulic gradient is studied as a function of time, and the interference of intersecting fractures with each other is also discussed

Natural convection and dispersion in a tilted fracture

International Nuclear Information System (INIS)

Woods, A.W.; Linz, S.J.

1992-01-01

In many geophysical situations, fluid is contained in long narrow fractures embedded within an impermeable medium of different thermal conductivity; and there may be a uniform vertical temperature gradient imposed upon the system. We show that whenever the slot is tilted to the vertical, convection develops in the fluid, even if the background temperature increases with height. Using typical values for the physical properties of a water-filled fracture, we show that the Earth's geothermal gradient produces a convective flow in a fracture; this has an associated dispersion coefficient D T ∼10 2 -10 3 D in fractures about a centimetre wide. We show that this shear dispersion could transport radioactive material, of half-life 10 4 years, tens of metres along the fracture within one half-life; without this dispersion, the material would only diffuse a few metres along the fracture within one half-life. (author)

Oil recovery from naturally fractured reservoirs by steam injection methods. Final report

Energy Technology Data Exchange (ETDEWEB)

Reis, J.C.; Miller, M.A.

1995-05-01

Oil recovery by steam injection is a proven, successful technology for nonfractured reservoirs, but has received only limited study for fractured reservoirs. Preliminary studies suggest recovery efficiencies in fractured reservoirs may be increased by as much as 50% with the application of steam relative to that of low temperature processes. The key mechanisms enhancing oil production at high temperature are the differential thermal expansion between oil and the pore volume, and the generation of gases within matrix blocks. Other mechanisms may also contribute to increased production. These mechanisms are relatively independent of oil gravity, making steam injection into naturally fractured reservoirs equally attractive to light and heavy oil deposits. The objectives of this research program are to quantify the amount of oil expelled by these recovery mechanisms and to develop a numerical model for predicting oil recovery in naturally fractured reservoirs during steam injection. The experimental study consists of constructing and operating several apparatuses to isolate each of these mechanisms. The first measures thermal expansion and capillary imbibition rates at relatively low temperature, but for various lithologies and matrix block shapes. The second apparatus measures the same parameters, but at high temperatures and for only one shape. A third experimental apparatus measures the maximum gas saturations that could build up within a matrix block. A fourth apparatus measures thermal conductivity and diffusivity of porous media. The numerical study consists of developing transfer functions for oil expulsion from matrix blocks to fractures at high temperatures and incorporating them, along with the energy equation, into a dual porosity thermal reservoir simulator. This simulator can be utilized to make predictions for steam injection processes in naturally-fractured reservoirs. Analytical models for capillary imbibition have also been developed.

CSNI Project for Fracture Analyses of Large-Scale International Reference Experiments (FALSIRE II)

Energy Technology Data Exchange (ETDEWEB)

Bass, B.R.; Pugh, C.E.; Keeney, J. [Oak Ridge National Lab., TN (United States); Schulz, H.; Sievers, J. [Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH, Koeln (Gemany)

1996-11-01

A summary of Phase II of the Project for FALSIRE is presented. FALSIRE was created by the Fracture Assessment Group (FAG) of the OECD/NEA`s Committee on the Safety of Nuclear Installations (CNSI) Principal Working Group No. 3. FALSIRE I in 1988 assessed fracture methods through interpretive analyses of 6 large-scale fracture experiments in reactor pressure vessel (RPV) steels under pressurized- thermal-shock (PTS) loading. In FALSIRE II, experiments examined cleavage fracture in RPV steels for a wide range of materials, crack geometries, and constraint and loading conditions. The cracks were relatively shallow, in the transition temperature region. Included were cracks showing either unstable extension or two stages of extensions under transient thermal and mechanical loads. Crack initiation was also investigated in connection with clad surfaces and with biaxial load. Within FALSIRE II, comparative assessments were performed for 7 reference fracture experiments based on 45 analyses received from 22 organizations representing 12 countries. Temperature distributions in thermal shock loaded samples were approximated with high accuracy and small scatter bands. Structural response was predicted reasonably well; discrepancies could usually be traced to the assumed material models and approximated material properties. Almost all participants elected to use the finite element method.

CSNI Project for Fracture Analyses of Large-Scale International Reference Experiments (FALSIRE II)

International Nuclear Information System (INIS)

Bass, B.R.; Pugh, C.E.; Keeney, J.; Schulz, H.; Sievers, J.

1996-11-01

A summary of Phase II of the Project for FALSIRE is presented. FALSIRE was created by the Fracture Assessment Group (FAG) of the OECD/NEA's Committee on the Safety of Nuclear Installations (CNSI) Principal Working Group No. 3. FALSIRE I in 1988 assessed fracture methods through interpretive analyses of 6 large-scale fracture experiments in reactor pressure vessel (RPV) steels under pressurized- thermal-shock (PTS) loading. In FALSIRE II, experiments examined cleavage fracture in RPV steels for a wide range of materials, crack geometries, and constraint and loading conditions. The cracks were relatively shallow, in the transition temperature region. Included were cracks showing either unstable extension or two stages of extensions under transient thermal and mechanical loads. Crack initiation was also investigated in connection with clad surfaces and with biaxial load. Within FALSIRE II, comparative assessments were performed for 7 reference fracture experiments based on 45 analyses received from 22 organizations representing 12 countries. Temperature distributions in thermal shock loaded samples were approximated with high accuracy and small scatter bands. Structural response was predicted reasonably well; discrepancies could usually be traced to the assumed material models and approximated material properties. Almost all participants elected to use the finite element method

Grain boundary phosphorus segregation under thermal aging in low alloy steels

International Nuclear Information System (INIS)

Nakata, Hayato; Fujii, Katsuhiko; Fukuya, Koji; Kasada, Ryuta; Kimura, Akihiko

2007-01-01

Intergranular embrittlement due to grain boundary segregation of phosphorus is recognized as one of the potential degradation factors in irradiated reactor low alloy steels at high neutron fluence. In this study, low alloy steels thermally aged at 400-500degC were investigated to evaluate the correlation between phosphorus segregation and intergranular embrittlement. Phosphorus segregation determined using Auger electron spectroscopy increased after thermal aging above 450degC and was in good agreement with the calculated value based on McLean's model. No influence of thermal aging on tensile properties or hardness was observed. The ductile brittle transition temperature determined using a one-third size Charpy impact test increased at a P/Fe peak ratio of 0.14. These results indicated that there is a threshold level of phosphorus segregation for non-hardening embrittlement. DBTT increased with the proportion of intergranular fracture, so this result shows that there is a relationship between DBTT and the properties of intergranular fracture. The fracture stress decreases due to non-hardening embrittlement on the thermally aged material with high proportion of intergranular fracture. (author)

Three-Dimensional Modeling of Fracture Clusters in Geothermal Reservoirs

Energy Technology Data Exchange (ETDEWEB)

Ghassemi, Ahmad [Univ. of Oklahoma, Norman, OK (United States)

2017-08-11

The objective of this is to develop a 3-D numerical model for simulating mode I, II, and III (tensile, shear, and out-of-plane) propagation of multiple fractures and fracture clusters to accurately predict geothermal reservoir stimulation using the virtual multi-dimensional internal bond (VMIB). Effective development of enhanced geothermal systems can significantly benefit from improved modeling of hydraulic fracturing. In geothermal reservoirs, where the temperature can reach or exceed 350oC, thermal and poro-mechanical processes play an important role in fracture initiation and propagation. In this project hydraulic fracturing of hot subsurface rock mass will be numerically modeled by extending the virtual multiple internal bond theory and implementing it in a finite element code, WARP3D, a three-dimensional finite element code for solid mechanics. The new constitutive model along with the poro-thermoelastic computational algorithms will allow modeling the initiation and propagation of clusters of fractures, and extension of pre-existing fractures. The work will enable the industry to realistically model stimulation of geothermal reservoirs. The project addresses the Geothermal Technologies Office objective of accurately predicting geothermal reservoir stimulation (GTO technology priority item). The project goal will be attained by: (i) development of the VMIB method for application to 3D analysis of fracture clusters; (ii) development of poro- and thermoelastic material sub-routines for use in 3D finite element code WARP3D; (iii) implementation of VMIB and the new material routines in WARP3D to enable simulation of clusters of fractures while accounting for the effects of the pore pressure, thermal stress and inelastic deformation; (iv) simulation of 3D fracture propagation and coalescence and formation of clusters, and comparison with laboratory compression tests; and (v) application of the model to interpretation of injection experiments (planned by our

Fracture in Phenolic Impregnated Carbon Ablator

Science.gov (United States)

Agrawal, Parul; Chavez-Garcia, Jose; Pham, John

2013-01-01

This paper describes the development of a novel technique to understand the failure mechanisms inside thermal protection materials. The focus of this research is on the class of materials known as phenolic impregnated carbon ablators. It has successfully flown on the Stardust spacecraft and is the thermal protection system material chosen for the Mars Science Laboratory and SpaceX Dragon spacecraft. Although it has good thermal properties, structurally, it is a weak material. To understand failure mechanisms in carbon ablators, fracture tests were performed on FiberForm(Registered TradeMark) (precursor), virgin, and charred ablator materials. Several samples of these materials were tested to investigate failure mechanisms at a microstructural scale. Stress-strain data were obtained simultaneously to estimate the tensile strength and toughness. It was observed that cracks initiated and grew in the FiberForm when a critical stress limit was reached such that the carbon fibers separated from the binder. However, both for virgin and charred carbon ablators, crack initiation and growth occurred in the matrix (phenolic) phase. Both virgin and charred carbon ablators showed greater strength values compared with FiberForm samples, confirming that the presence of the porous matrix helps in absorbing the fracture energy.

Coupled Thermo-Hydro-Mechanical-Chemical Modeling of Water Leak-Off Process during Hydraulic Fracturing in Shale Gas Reservoirs

Directory of Open Access Journals (Sweden)

Fei Wang

2017-11-01

Full Text Available The water leak-off during hydraulic fracturing in shale gas reservoirs is a complicated transport behavior involving thermal (T, hydrodynamic (H, mechanical (M and chemical (C processes. Although many leak-off models have been published, none of the models fully coupled the transient fluid flow modeling with heat transfer, chemical-potential equilibrium and natural-fracture dilation phenomena. In this paper, a coupled thermo-hydro-mechanical-chemical (THMC model based on non-equilibrium thermodynamics, hydrodynamics, thermo-poroelastic rock mechanics, and non-isothermal chemical-potential equations is presented to simulate the water leak-off process in shale gas reservoirs. The THMC model takes into account a triple-porosity medium, which includes hydraulic fractures, natural fractures and shale matrix. The leak-off simulation with the THMC model involves all the important processes in this triple-porosity medium, including: (1 water transport driven by hydraulic, capillary, chemical and thermal osmotic convections; (2 gas transport induced by both hydraulic pressure driven convection and adsorption; (3 heat transport driven by thermal convection and conduction; and (4 natural-fracture dilation considered as a thermo-poroelastic rock deformation. The fluid and heat transport, coupled with rock deformation, are described by a set of partial differential equations resulting from the conservation of mass, momentum, and energy. The semi-implicit finite-difference algorithm is proposed to solve these equations. The evolution of pressure, temperature, saturation and salinity profiles of hydraulic fractures, natural fractures and matrix is calculated, revealing the multi-field coupled water leak-off process in shale gas reservoirs. The influences of hydraulic pressure, natural-fracture dilation, chemical osmosis and thermal osmosis on water leak-off are investigated. Results from this study are expected to provide a better understanding of the

Cracking behavior of thermally aged and irradiated CF-8 cast austenitic stainless steel

Energy Technology Data Exchange (ETDEWEB)

Chen, Y., E-mail: Yiren_Chen@anl.gov [Argonne National Laboratory, 9700 S. Cass Ave, Argonne, IL 60439 (United States); Alexandreanu, B.; Chen, W.-Y.; Natesan, K. [Argonne National Laboratory, 9700 S. Cass Ave, Argonne, IL 60439 (United States); Li, Z.; Yang, Y. [University of Florida, Gainesville, FL 32611 (United States); Rao, A.S. [US Nuclear Regulatory Commission, 11545 Rockville Pike, Rockville, MD 20852 (United States)

2015-11-15

To assess the combined effect of thermal aging and neutron irradiation on the cracking behavior of CF-8 cast austenitic stainless steel, crack growth rate (CGR) and fracture toughness J-R curve tests were carried out on compact-tension specimens in high-purity water with low dissolved oxygen. Both unaged and thermally aged specimens were irradiated at ∼320 °C to 0.08 dpa. Thermal aging at 400 °C for 10,000 h apparently had no effect on the corrosion fatigue and stress corrosion cracking behavior in the test environment. The cracking susceptibility of CF-8 was not elevated significantly by neutron irradiation at 0.08 dpa. Transgranular cleavage-like cracking was the main fracture mode during the CGR tests, and a brittle morphology of delta ferrite was often seen on the fracture surfaces at the end of CGR tests. The fracture toughness J-R curve tests showed that both thermal aging and neutron irradiation can induce significant embrittlement. The loss of fracture toughness due to neutron irradiation was more pronounced in the unaged than aged specimens. After neutron irradiation, the fracture toughness values of the unaged and aged specimens were reduced to a similar level. G-phase precipitates were observed in the aged and irradiated specimens with or without prior aging. The similar microstructural changes resulting from thermal aging and irradiation suggest a common microstructural mechanism of inducing embrittlement in CF-8.

Pressurized thermal shock evaluation of RPV-Stade

International Nuclear Information System (INIS)

Blauel, J.G.; Hodulak, L.; Siegele, D.; Nagel, G.; Hertlein, D.

1997-01-01

The presentation overviews the following issues: thermal shock analysis (thermohydraulics, temperatures and stresses, crack tip field parameters, cladding influence, methodology of fracture mechanics assessment); EOL safety evaluation for RPV Stade (initial conditions and input data, fracture toughness, load path diagrams, warm prestress effect, crack arrest, remaining load carrying capacity)

Pressurized thermal shock evaluation of RPV-Stade

Energy Technology Data Exchange (ETDEWEB)

Blauel, J G; Hodulak, L; Siegele, D [Fraunhofer-Institut fuer Werkstoffmechanik, Freiburg im Breisgau (Germany); Nagel, G [PreussenElektra AG, Hannover (Germany); Hertlein, D [Siemens AG Unternehmensbereich KWU, Erlangen (Germany)

1997-09-01

The presentation overviews the following issues: thermal shock analysis (thermohydraulics, temperatures and stresses, crack tip field parameters, cladding influence, methodology of fracture mechanics assessment); EOL safety evaluation for RPV Stade (initial conditions and input data, fracture toughness, load path diagrams, warm prestress effect, crack arrest, remaining load carrying capacity).

Relationship between microstructure and fracture types in a UNS S32205 duplex stainless steel

Directory of Open Access Journals (Sweden)

Maria Victoria Biezma

2013-01-01

Full Text Available Duplex stainless steels are susceptible to the formation of sigma phase at high temperature which could potentially be responsible for catastrophic service failure of components. Thermal treatments were applied to duplex stainless steels in order to promote the precipitation of different fractions of sigma phase into a ferrite-austenite microstructure. Quantitative image analysis was employed to characterize the microstructure and Charpy impact tests were used in order to evaluate the mechanical degradation caused by sigma phase presence. The fracture morphology of the Charpy test specimens were thoroughly observed in SEM, looking for a correlation between the microstructure and the fracture types in UNS S32205 duplex stainless steel. The main conclusion is the strong embrittlement effect of sigma phase since it is possible to observe a transition from transgranular fracture to intergranular fracture as increases the percentage of sigma phase. Thus, the mixed modes of fracture are predominant in the present study with high dependence on sigma phase percentages obtained by different thermal treatments.

Fuel pellet fracture and relocation

International Nuclear Information System (INIS)

Walton, L.A.; Husser, D.L.

1983-01-01

The model used to describe fuel pellet fracture and relocation is an important feature of a fuel performance computer code. This model becomes especially important if the computer code is principally to be used for the evaluation of pellet clad interaction. The fracture and relocation model being developed for the B and W fuel performance code FUMAC was derived from an extensive data base. Cross sections of irradiated fuel rods were photographically magnified and measured to determine the configuration of the fragments of the fractured fuel pellets. Data, representing a wide range of LWR fuel designs and as-manufactured mechanical configurations, were catalogued and systematically reduced and then correlated as a function of the likely independent variables. These correlations define the key phenomenological behavior patterns which the relocation model must duplicate and indicate which mechanistic approaches are viable explanations of this behavior. The data base covers the burnup range from approximately one to 35 GWd/mtU and linear heat rates from less than 100 to nearly 700 W/Cm. This paper presents the correlated data base and the methods used to derive and interpret it. It was determined from this data base that pellet cracking is initially both power level and burnup dependent but tends to saturate eventually with continued steady irradiation. Fuel pellet relocation was found to be much more extensive than would be deduced from thermal considerations alone. Even at very low burnups fuel fragments were found to move outward until restrained by the cladding. The results also suggest that changes in internal resistance to heat flow within the pellets due to the opening of cracks may be as important as peripheral gap changes to the thermal modeler. The transient response and thermal implications of this model are recommended as primary areas for future investigation

Spalling fracture of metals and alloys under intense x-radiation

International Nuclear Information System (INIS)

Molitvin, A.M.

2001-01-01

Creation of different power and irradiating installations assisted in studying mechanical properties of structural materials under the effect of high-power radiation fluxes: laser, electron, X-ray, ion beam etc. There are being widely investigated such phenomena as surface and deep hardening of metals and alloys under irradiation, generation of elastic and shock waves, materials failure under thermal shock etc.In the paper there are discussed the results of long researches of spalling fracture of materials and alloys under intense X-radiation. Model assemblies with consequently arranged samples (foils) of metals and alloys under investigation underwent pulse X-radiation. The energy flux of X-radiation was weakened to the needed value by dose filters intensively absorbing soft spectrum of X-radiation. At carrying out the researches the foils of copper, nickel, titanium, brass, bronze, molybdenum, tungsten, tantalum, cadmium, lead, zinc, silver and steels 0.005-1 mm thick were used as objects under investigation. The samples diameter (10-16 mm) was chosen to be quite large as compared to their thickness so that the side load does not affect the central part of the samples and the front (looking the source of X-radiation) and back (shadow) surfaces of the samples are free what makes it possible to consider the processes of spalling fracture in one-dimensional approximation. Within the frames of kinetic approach to the problem of solid states spalling fracture under pulse loading that considers fracture as progressing in time process there were found spalling fracture time dependencies of lead, cadmium, zinc, silver, copper, brass, bronze, nickel, titanium, molybdenum, tungsten, tantalum and steels under thermal shock initiated by X-radiation. It was demonstrated that longevity of metals and alloys under thermal shock exponentially decreases with the growth of rupture stresses amplitude and can be described in terms of kinetic concept of strength.Within the frames of

Measurements of interface fracture properties of composite materials

International Nuclear Information System (INIS)

Ashkenazi, D.; Bank-Sills, L.; Travitzky, N.; Eliasi, R.

1998-01-01

In this investigation, interface Fracture properties are measured. To this end, glass/epoxy Brazilian disk specimens are studied. In order to calibrate the specimen, a numerical procedure is used. The finite element method is employed to derive stress intensity factors as a function of loading angle and crack length. By means of the weight friction method together with finite elements, a correction to the stress intensity factors for residual thermal stresses is obtained. These are combined to determine the critical interface energy release rate as a function of phase angle Tom the measured load and crack length at Fracture. A series of tests on a glass/epoxy material pair were carried out. It may be observed from the results that the residual thermal stresses resulting from the material mismatch greatly affect the interface toughness values

Heavy-Section Steel Technology program fracture issues

International Nuclear Information System (INIS)

Pennell, W.E.

1989-10-01

Large scale fracture mechanics tests have resulted in the identification of a number of fracture technology issues. Identification of additional issues has come from the reactor vessel materials irradiation test program and from reactor operating experience. This paper provides a review of fracture issues with an emphasis on their potential impact on a reactor vessel pressurized thermal shock (PTS) analysis. Mixed mode crack propagation emerges as a major issue, due in large measure to the poor performance of existing models for the prediction of ductile tearing. Rectification of ductile tearing technology deficiencies may require extending the technology to include a more complete treatment of stress state and loading history effects. The effect of cladding on vessel fracture remains uncertain to the point that it is not possible to determine at this time if the net effect will be positive or negative. Enhanced fracture toughness for shallow flaws has been demonstrated for low strength structural steels. Demonstration of a similar effect in reactor pressure vessel steels could have a significant beneficial effect on the probabilistic analysis of reactor vessel fracture. Further development of existing fracture mechanics models and concepts is required to meet the special requirements for fracture evaluation of circumferential flaws in the welds of ring forged vessels. Fracture technology advances required to address the issues discussed in this paper are the major objective for the ongoing Heavy Section Steel Technology (HSST) program at ORNL. 24 refs., 18 figs

Heavy-section steel technology program: Fracture issues

International Nuclear Information System (INIS)

Pennell, W.E.

1992-01-01

Large-scale fracture mechanics tests have resulted in the identification of a number of fracture technology issues. Identification of additional issues has come from the reactor vessel materials irradiation test program and from reactor operating experience. This paper provides a review of fracture issues with an emphasis on their potential impact on a reactor vessel pressurized thermal shock (PTS) analysis. Mixed mode crack propagation emerges as a major issue, due in large measure to the poor performance of existing models for the prediction of ductile tearing. Rectification of ductile tearing technology deficiencies may require extending the technology to include a more complete treatment of stress state and loading history effects. The effect of cladding on vessel fracture remains uncertain to the point that it is not possible to determine at this time if the net effect will be positive or negative. Enhanced fracture toughness for shallow flaws has been demonstrated for low-strength structural steels. Demonstration of a similar effect in reactor pressure vessel steels could have a significant beneficial effect on the probabilistic analysis of reactor vessel fracture. Further development of existing fracture mechanics models and concepts is required to meet the special requirements for fracture evaluation of circumferential flaws in the welds of ring-forged vessels. Fracture technology advances required to address the issues discussed in this paper are the major objective for the ongoing Heavy Section Steel Technology (HSST) program at ORNL

A numerical study of water percolation through an unsaturated variable aperture fracture under coupled thermomechanical effects

International Nuclear Information System (INIS)

Tsang, C.F.; Noorishad, J.; Hale, F.V.

1991-12-01

In calculation of ground water travel times associated with performance assessment of a nuclear waste repository, the role of fractures may turn out to be very important. There are two aspects related to fracture flow that have not been fully resolved. The first is the effect of coupled thermomechanical impact on fracture apertures due to the thermal output of the nuclear waste repository. The second is the effect of the variable aperture nature of the fractures. The present paper is an exploratory study of the impact of these two effects on water percolation through unsaturated fractures. The paper is divided into two main sections. the first section describes a calculation of the thermomechanical behavior of the geologic formation around a waste repository. In this exploratory study we assume two major fractures, one vertical and one horizontal through the repository center. Temperatures and thermally induced stress fields are calculated. The second part of the paper considers the unsaturated case and describes a study of water infiltration from the land surface through the vertical fracture to the repository

Fracture mechanics evaluation for at typical PWR primary coolant pipe

Energy Technology Data Exchange (ETDEWEB)

Tanaka, T. [Kansai Electric Power Company, Osaka (Japan); Shimizu, S.; Ogata, Y. [Mitsubishi Heavy Industries, Ltd., Kobe (Japan)

1997-04-01

For the primary coolant piping of PWRs in Japan, cast duplex stainless steel which is excellent in terms of strength, corrosion resistance, and weldability has conventionally been used. The cast duplex stainless steel contains the ferrite phase in the austenite matrix and thermal aging after long term service is known to change its material characteristics. It is considered appropriate to apply the methodology of elastic plastic fracture mechanics for an evaluation of the integrity of the primary coolant piping after thermal aging. Therefore we evaluated the integrity of the primary coolant piping for an initial PWR plant in Japan by means of elastic plastic fracture mechanics. The evaluation results show that the crack will not grow into an unstable fracture and the integrity of the piping will be secured, even when such through wall crack length is assumed to equal the fatigue crack growth length for a service period of up to 60 years.

Fracture mechanics evaluation for at typical PWR primary coolant pipe

International Nuclear Information System (INIS)

Tanaka, T.; Shimizu, S.; Ogata, Y.

1997-01-01

For the primary coolant piping of PWRs in Japan, cast duplex stainless steel which is excellent in terms of strength, corrosion resistance, and weldability has conventionally been used. The cast duplex stainless steel contains the ferrite phase in the austenite matrix and thermal aging after long term service is known to change its material characteristics. It is considered appropriate to apply the methodology of elastic plastic fracture mechanics for an evaluation of the integrity of the primary coolant piping after thermal aging. Therefore we evaluated the integrity of the primary coolant piping for an initial PWR plant in Japan by means of elastic plastic fracture mechanics. The evaluation results show that the crack will not grow into an unstable fracture and the integrity of the piping will be secured, even when such through wall crack length is assumed to equal the fatigue crack growth length for a service period of up to 60 years

Thermal shock resistances of a bonding material of C/C composite and copper

International Nuclear Information System (INIS)

Kurumada, Akira; Oku, Tatsuo; Kawamata, Kiyohiro; Motojima, Osamu; Noda, Nobuaki; McEnaney, B.

1997-01-01

The purpose of this study is to contribute to the development and the safety design of plasma facing components for fusion reactor devices. We evaluated the thermal shock resistance and the thermal shock fracture toughness of a bonding material which was jointed a carbon-fiber-reinforced carbon composite (C/C composite) to oxygen-free copper. We also examined the microstructures of the bonding layers using a scanning electron microscope before and after thermal shock tests. The bonding material did not fracture during thermal shock tests. However, thermal cracks and delamination cracks were observed in the bonding layers. (author)

Factors influencing the thermally-induced strength degradation of B/Al composites

International Nuclear Information System (INIS)

Dicarlo, J.A.

1983-01-01

Literature data related to the thermally-induced strength degradation of B/Al composites were examined in the light of fracture theories based on reaction-controlled fiber weakening. Under the assumption of a parabolic time-dependent growth for the interfacial reaction product, a Griffith-type fracture model was found to yield simple equations whose predictions were in good agreement with data for boron fiber average strength and for B/Al axial fracture strain. The only variables in these equations were the time and temperature of the thermal exposure and an empirical factor related to fiber surface smoothness prior to composite consolidation. Such variables as fiber diameter and aluminum alloy composition were found to have little influence. The basic and practical implications of the fracture model equations are discussed

Thermal-shock experiments with flawed clad cylinders

International Nuclear Information System (INIS)

Cheverton, R.D.; Bryson, J.W.; Alexander, D.J.

1989-01-01

The life expectancy of LWR pressure vessels is influenced by a reduction in fracture toughness that is the result of radiation damage. As the fracture toughness decreases, the probability of propagation of preexisting flaws (sharp, crack-like defects) in the wall of the vessel increases. The probability of propagation is also influenced by the type of loading condition and the type of flaws that might exist. A loading condition of particular concern is referred to as pressurized thermal shock (PTS), and a flaw of particular concern for PTS loading conditions is a shallow surface flaw. A sudden cooling (thermal shock) of the inner surface of the vessel results in relatively high tensile stresses and relatively low fracture toughness at the inner surface. In addition, the attenuation of the fast-neutron fluence also results in relatively low fracture toughness at the inner surface. Under some circumstances, this combination of high stress and low toughness at the inner surface makes it possible for very shallow surface flaws to propagate. The PTS issue has been under investigation for quite some time, but thus far possible beneficial effects, other than thermal resistance, of the cladding on the inner surface of the vessel have not been included in the analysis of flaw behavior. This document discusses this effect of cladding on surface flaws and crack propagation

Insights to Engineered Geothermal System Performance Using Gringarten-Witherspoon-Ohnishi Analytical Solutions and Fracture Network Models

Science.gov (United States)

Doe, T.; McLaren, R.; Finilla, A.

2017-12-01

An enduring legacy of Paul Witherspoon and his students and colleagues has been both the development of geothermal energy and the bases of modern fractured-rock hydrogeology. One of the seminal contributions to the geothermal field was Gringarten, Witherspoon, and Ohnishi's analytical models for enhanced geothermal systems. Although discrete fracture network (DFN) modeling developed somewhat independently in the late 1970s, Paul Witherspoon's foresight in promoting underground in situ testing at the Stripa Mine in Sweden was a major driver in Lawrence Berkeley Laboratory's contributions to its development.This presentation looks extensions of Gringarten's analytical model into discrete fracture network modeling as a basis for providing further insights into the challenges and opportunities of engineered geothermal systems. The analytical solution itself has many insightful applications beyond those presented in the original paper. The definition of dimensionless time by itself shows that thermal breakthrough has a second power dependence on surface area and on flow rate. The fracture intensity also plays a strong role, as it both increases the surface area and decrease his flow rate per fracture. The improvement of EGS performance with fracture intensity reaches a limit where thermal depletion of the rock lags only slightly behind the thermal breakthrough of cold water in the fracture network.Simple network models, which couple a DFN generator (FracMan) with a hydrothermally coupled flow solver (HydroGeoSphere) expand on Gringarten's concepts to show that realistic heterogeneity of spacing and transmissivity significantly degrades EGS performance. EGS production in networks of stimulated fractures initially follows Gringarten's type curves, with a later deviation is the smaller rock blocks thermally deplete and the entire stimulated volume acts as a single sink. Three-dimensional models of EGS performance show the critical importance of the relative magnitudes of

Geothermal-Related Thermo-Elastic Fracture Analysis by Numerical Manifold Method

OpenAIRE

Jun He; Quansheng Liu; Zhijun Wu; Yalong Jiang

2018-01-01

One significant factor influencing geothermal energy exploitation is the variation of the mechanical properties of rock in high temperature environments. Since rock is typically a heterogeneous granular material, thermal fracturing frequently occurs in the rock when the ambient temperature changes, which can greatly influence the geothermal energy exploitation. A numerical method based on the numerical manifold method (NMM) is developed in this study to simulate the thermo-elastic fracturing ...

FAVOR: A new fracture mechanics code for reactor pressure vessels subjected to pressurized thermal shock

International Nuclear Information System (INIS)

Dickson, T.L.

1993-01-01

Probabilistic fracture mechanics (PFM) analysis is a major element of the comprehensive probabilistic methodology endorsed by the Nuclear Regulatory Commission (NRC) for evaluation of the integrity of pressurized water reactor pressure vessels subjected to pressurized-thermal-shock (PTS) transients. OCA-P and VISA-II are PTS PFM computer codes that are currently referenced in Regulatory Guide 1.154 as acceptable codes for performing plant-specific analyses. These codes perform PFM analyses to estimate the increase in vessel failure probability as the vessel accumulates radiation damage over the operating life of the vessel. Experience with the application of these codes in the last few years has provided insights into areas where they could be improved. As more plants approach the PTS screening criteria and are required to perform plant-specific analyses, there will be an increasing need for an improved and validated PTS PFM code that is accepted by the NRC and utilities. The NRC funded Heavy Section Steel Technology Program (HSST) at the Oak Ridge National Laboratory is currently developing the FAVOR (Fracture Analysis of Vessels: Oak Ridge) code, which is expected to meet this need. The FAVOR code incorporates the most important features of both OCA-P and VISA-II and contains some new capabilities such as (1) a PFM global modeling methodology; (2) the calculation of the axial stress component associated with coolant streaming beneath an inlet nozzle; (3) a library of stress intensity factor influence coefficients, generated by the NQA-1 certified ABAQUS computer code, for an appropriate range of two and three dimensional inner-surface flaws; (4) the flexibility to generate a variety of output reports; and (5) enhanced user friendliness

Microfracture spacing distributions and the evolution of fracture patterns in sandstones

Science.gov (United States)

Hooker, J. N.; Laubach, S. E.; Marrett, R.

2018-03-01

Natural fracture patterns in sandstone were sampled using scanning electron microscope-based cathodoluminescence (SEM-CL) imaging. All fractures are opening-mode and are fully or partially sealed by quartz cement. Most sampled fractures are too small to be height-restricted by sedimentary layers. At very low strains ( 100) datasets show spacings that are best fit by log-normal size distributions, compared to exponential, power law, or normal distributions. The clustering of fractures suggests that the locations of natural factures are not determined by a random process. To investigate natural fracture localization, we reconstructed the opening history of a cluster of fractures within the Huizachal Group in northeastern Mexico, using fluid inclusions from synkinematic cements and thermal-history constraints. The largest fracture, which is the only fracture in the cluster visible to the naked eye, among 101 present, opened relatively late in the sequence. This result suggests that the growth of sets of fractures is a self-organized process, in which small, initially isolated fractures grow and progressively interact, with preferential growth of a subset of fractures developing at the expense of growth of the rest. Size-dependent sealing of fractures within sets suggests that synkinematic cementation may contribute to fracture clustering.

Shear-induced Fracture Slip and Permeability Change. Implications for Long-term Performance of a Deep Geological Repository

International Nuclear Information System (INIS)

Min, Ki-Bok; Stephansson, Ove

2009-03-01

Opening of fractures induced by shear dilation or normal deformation can be a significant source of fracture permeability change in jointed rock, which is important for the performance assessment of geological repositories for spent nuclear fuel. As the repository generates heat and later cools the fluid-carrying ability of the rocks becomes a dynamic variable during the lifespan of the repository. Heating causes expansion of the rock close to the repository and, at the same time, contraction close to the surface. During the cooling phase of the repository, the opposite takes place. Heating and cooling together with the virgin stress can induce shear dilation of fractures and deformation zones and change the flow field around the repository. The objectives of this project are to examine the contribution of thermal stress to the shear slip of fracture in mid- and far-field around a KBS-3 type of repository and to investigate the effect of evolution of stress on the rock mass permeability. The first part of the study is about the evolution of thermal stresses in the rock during the lifetime of the repository. Critical sections of heat generated stresses around the repository are selected and classified. Fracture data from Forsmark is used to establish fracture network models (DFN) and the models are subjected to the sum of virgin stress and thermal stresses and the shear slip and related permeability change are studied. In the first part of this study, zones of fracture shear slip were examined by conducting a three-dimensional, thermo-mechanical analysis of a spent fuel repository model. Stress evolutions of importance for fracture shear slip are: (1) comparatively high horizontal compressive thermal stress at the repository level, (2) generation of vertical tensile thermal stress right above the repository, (3) horizontal tensile stress near the surface, which can induce tensile failure, and generation of shear stresses at the corners of the repository. In the

Shear-induced Fracture Slip and Permeability Change. Implications for Long-term Performance of a Deep Geological Repository

Energy Technology Data Exchange (ETDEWEB)

Min, Ki-Bok (School of Civil, Environmental and Mining Engineering, Univ. of Adelaide, Adelaide (Australia)); Stephansson, Ove (Steph Rock Consulting AB, Berlin (Germany))

2009-03-15

Opening of fractures induced by shear dilation or normal deformation can be a significant source of fracture permeability change in jointed rock, which is important for the performance assessment of geological repositories for spent nuclear fuel. As the repository generates heat and later cools the fluid-carrying ability of the rocks becomes a dynamic variable during the lifespan of the repository. Heating causes expansion of the rock close to the repository and, at the same time, contraction close to the surface. During the cooling phase of the repository, the opposite takes place. Heating and cooling together with the virgin stress can induce shear dilation of fractures and deformation zones and change the flow field around the repository. The objectives of this project are to examine the contribution of thermal stress to the shear slip of fracture in mid- and far-field around a KBS-3 type of repository and to investigate the effect of evolution of stress on the rock mass permeability. The first part of the study is about the evolution of thermal stresses in the rock during the lifetime of the repository. Critical sections of heat generated stresses around the repository are selected and classified. Fracture data from Forsmark is used to establish fracture network models (DFN) and the models are subjected to the sum of virgin stress and thermal stresses and the shear slip and related permeability change are studied. In the first part of this study, zones of fracture shear slip were examined by conducting a three-dimensional, thermo-mechanical analysis of a spent fuel repository model. Stress evolutions of importance for fracture shear slip are: (1) comparatively high horizontal compressive thermal stress at the repository level, (2) generation of vertical tensile thermal stress right above the repository, (3) horizontal tensile stress near the surface, which can induce tensile failure, and generation of shear stresses at the corners of the repository. In the

Factors influencing the thermally-induced strength degradation of B/Al composites

Science.gov (United States)

Dicarlo, J. A.

1983-01-01

Literature data related to the thermally-induced strength degradation of B/Al composites were examined in the light of fracture theories based on reaction-controlled fiber weakening. Under the assumption of a parabolic time-dependent growth for the interfacial reaction product, a Griffith-type fracture model was found to yield simple equations whose predictions were in good agreement with data for boron fiber average strength and for B/Al axial fracture strain. The only variables in these equations were the time and temperature of the thermal exposure and an empirical factor related to fiber surface smoothness prior to composite consolidation. Such variables as fiber diameter and aluminum alloy composition were found to have little influence. The basic and practical implications of the fracture model equations are discussed. Previously announced in STAR as N82-24297

Probabilistic fracture mechanics analysis of reactor vessels with low upper-shelf fracture toughness

International Nuclear Information System (INIS)

Yoon, K.K.

1993-01-01

A class of submerged-arc welds used in fabricating early reactor vessels has relatively high copper contents. Studies have shown that when such vessels are irradiated, the copper contributes to lowering the Charpy upper-shelf energy level. To address this concern, 10CFR50, Appendix G requires a fracture mechanics analysis to demonstrate an adequate margin of safety for continued service. The B and W Owners Group (B and WOG) has been accumulating J-resistance fracture toughness data for these weld metals. Based on a mathematical model derived from this B and WOG data base, the first Appendix G analysis was performed. Another important issue affecting reactor vessel integrity is pressurized thermal shock (PIS) transients. In the early 1980s, probabilistic fracture mechanics analyses were performed on a reactor vessel to determine the probability of failure under postulated accident scenarios. Results of such analyses were used by the Nuclear Regulatory Commission (NRC) to establish the screening criteria for assessing reactor vessel integrity under PTS transient loads. This paper addresses the effect of low upper-shelf toughness on the probability of failure of reactor vessels under PTS loads. Probabilistic fracture mechanics codes were modified to include the low upper-shelf toughness model used in a reference and a series of analyses was performed using plant-specific material conditions and realistic PTS scenarios. The results indicate that low upper-shelf toughness has an insignificant effect on the probability of reactor vessel failures. This is mostly due to PTS transients being susceptible to crack initiation at low temperatures and not affected by upper-shelf fracture toughness

Laboratory experiments on heat-drive two-phase flows in natural and artificial rock fractures

International Nuclear Information System (INIS)

Kneafsey, Timothy J.; Pruess, Karsten

1998-01-01

Water flow in partially saturated fractures under thermal drive may lead to fast flow along preferential localized pathways and heat pipe conditions. At the potential high-level nuclear waste repository at Yucca Mountain, water flowing in fast pathways may ultimately contact waste packages and transport radionuclides to the accessible environment. Sixteen experiments were conducted to visualize heat-driven liquid flow in fracture models that included (1) assemblies of roughened glass plates, (2) epoxy replicas of rock fractures, and (3) a fractured specimen of Topopah Spring tuff. Continuous rivulet flow was observed for high liquid flow rates, intermittent rivulet flow and drop flow for intermediate flow rates, and film flow for lower flow rates and wide apertures. Heat pipe conditions (vapor-liquid counterflow with phase change) were identified in five of the seven experiments in which spatially resolved thermal monitoring was performed but not when vapor-liquid counterflow was hindered by very narrow apertures and when an inadequate working fluid volume was used

Coupled Analysis of Change in Fracture Permeability during the Cooling Phase of the Yucca Mountain Drift Scale Test

International Nuclear Information System (INIS)

Rutqvist, Jonny; Rutqvist, J.; Freifeld, B.; Tsang, Y.W.; Min, K.B.; Elsworth, D.

2008-01-01

This paper presents results from a coupled thermal, hydrological and mechanical analysis of thermally-induced permeability changes during heating and cooling of fractured volcanic rock at the Drift Scale Test at Yucca Mountain, Nevada. The analysis extends the previous analysis of the four-year heating phase to include newly available data from the subsequent four year cooling phase. The new analysis of the cooling phase shows that the measured changes in fracture permeability follows that of a thermo-hydro-elastic model on average, but at several locations the measured permeability indicates (inelastic) irreversible behavior. At the end of the cooling phase, the air-permeability had decreased at some locations (to as low as 0.2 of initial), whereas it had increased at other locations (to as high as 1.8 of initial). Our analysis shows that such irreversible changes in fracture permeability are consistent with either inelastic fracture shear dilation (where permeability increased) or inelastic fracture surface asperity shortening (where permeability decreased). These data are important for bounding model predictions of potential thermally-induced changes in rock-mass permeability at a future repository at Yucca Mountain

Properties of fracture surfaces of glassy polymers: chain scission versus chain pullout

NARCIS (Netherlands)

Fischer, H.R.

2010-01-01

Fresh fracture surfaces formed by tensile failure of craze in molded polystyrene (PS) bars have been compared with the molded surfaces of the same bars, using an atomic force microscope with a thermal probe and operated in local thermal analysis. The results indicate that molecular weight is much

Permeability testing of fractures in climax stock granite at the Nevada Test Site

International Nuclear Information System (INIS)

Murray, W.A.

1980-01-01

Permeability tests conducted in the Climax stock granitic rock mass indicate that the bulk rock permeability can be highly variable. If moderately to highly fractured zones are encountered, the permeability values may lie in the range of 10 -4 to 10 -1 darcies. If, on the other hand, only intact rock or healed fractures are encountered, the permeability is found to be less than 10 -9 darcies. In order to assess the thermomechanical effect on fracture permeability, discrete fractures will be packed off and tested periodically throughout the thermal cycle caused by the emplacement of spent nuclear fuel in the Climax stock

Implementation of nondestructive testing and mechanical performance approaches to assess low temperature fracture properties of asphalt binders

Directory of Open Access Journals (Sweden)

Salman Hakimzadeh

2017-05-01

Full Text Available In the present work, three different asphalt binders were studied to assess their fracture behavior at low temperatures. Fracture properties of asphalt materials were obtained through conducting the compact tension [C(T] and indirect tensile [ID(T] strength tests. Mechanical fracture tests were followed by performing acoustic emissions test to determine the “embrittlement temperature” of binders which was used in evaluation of thermally induced microdamages in binders. Results showed that both nondestructive and mechanical testing approaches could successfully capture low-temperature cracking behavior of asphalt materials. It was also observed that using GTR as the binder modifier significantly improved thermal cracking resistance of PG64-22 binder. The overall trends of AE test results were consistent with those of mechanical tests. Keywords: Thermal cracking, Indirect tensile strength test, Compact tension test, Nondestructive approach, Acoustic emission test, Embrittlement temperature

Kertész line of thermally activated breakdown phenomena

KAUST Repository

Yoshioka, Naoki

2010-11-12

Based on a fiber bundle model we substantially extend the phase-transition analogy of thermally activated breakdown of homogeneous materials. We show that the competition of breaking due to stress enhancement and due to thermal fluctuations leads to an astonishing complexity of the phase space of the system: varying the load and the temperature a phase boundary emerges, separating a Griffith-type regime of abrupt failure analogous to first-order phase transitions from disorder dominated fracture where a spanning cluster of cracks emerges. We demonstrate that the phase boundary is the Kertész line of the system along which thermally activated fracture appears as a continuous phase transition analogous to percolation. The Kertész line has technological relevance setting the boundary of safe operation for construction components under high thermal loads. © 2010 The American Physical Society.

Influence of the preparation design and artificial aging on the fracture resistance of monolithic zirconia crowns.

Science.gov (United States)

Mitov, Gergo; Anastassova-Yoshida, Yana; Nothdurft, Frank Phillip; von See, Constantin; Pospiech, Peter

2016-02-01

The aim of this study was to evaluate the fracture resistance and fracture behavior of monolithic zirconia crowns in accordance with the preparation design and aging simulation method. An upper first molar was prepared sequentially with three different preparation designs: shoulderless preparation, 0.4 mm chamfer and 0.8 mm chamfer preparation. For each preparation design, 30 monolithic zirconia crowns were fabricated. After cementation on Cr-Co alloy dies, the following artificial aging procedures were performed: (1) thermal cycling and mechanical loading (TCML): 5000 cycles of thermal cycling 5℃-55℃ and chewing simulation (1,200,000 cycles, 50 N); (2) Low Temperature Degradation simulation (LTD): autoclave treatment at 137℃, 2 bar for 3 hours and chewing simulation; and (3) no pre-treatment (control group). After artificial aging, the crowns were loaded until fracture. The mean values of fracture resistance varied between 3414 N (LTD; 0.8 mm chamfer preparation) and 5712 N (control group; shoulderless preparation). Two-way ANOVA analysis showed a significantly higher fracture loads for the shoulderless preparation, whereas no difference was found between the chamfer preparations. In contrast to TCML, after LTD simulation the fracture strength of monolithic zirconia crowns decreased significantly. The monolithic crowns tested in this study showed generally high fracture load values. Preparation design and LTD simulation had a significant influence on the fracture strength of monolithic zirconia crowns.

Effect of Random Natural Fractures on Hydraulic Fracture Propagation Geometry in Fractured Carbonate Rocks

Science.gov (United States)

Liu, Zhiyuan; Wang, Shijie; Zhao, Haiyang; Wang, Lei; Li, Wei; Geng, Yudi; Tao, Shan; Zhang, Guangqing; Chen, Mian

2018-02-01

Natural fractures have a significant influence on the propagation geometry of hydraulic fractures in fractured reservoirs. True triaxial volumetric fracturing experiments, in which random natural fractures are created by placing cement blocks of different dimensions in a cuboid mold and filling the mold with additional cement to create the final test specimen, were used to study the factors that influence the hydraulic fracture propagation geometry. These factors include the presence of natural fractures around the wellbore, the dimension and volumetric density of random natural fractures and the horizontal differential stress. The results show that volumetric fractures preferentially formed when natural fractures occurred around the wellbore, the natural fractures are medium to long and have a volumetric density of 6-9%, and the stress difference is less than 11 MPa. The volumetric fracture geometries are mainly major multi-branch fractures with fracture networks or major multi-branch fractures (2-4 fractures). The angles between the major fractures and the maximum horizontal in situ stress are 30°-45°, and fracture networks are located at the intersections of major multi-branch fractures. Short natural fractures rarely led to the formation of fracture networks. Thus, the interaction between hydraulic fractures and short natural fractures has little engineering significance. The conclusions are important for field applications and for gaining a deeper understanding of the formation process of volumetric fractures.

Photoelastic stress analysis assisted evaluation of fracture toughness in hydrothermally aged epoxies

Directory of Open Access Journals (Sweden)

G. Pitarresi

2014-10-01

Full Text Available The present work has investigated the fracture toughness of a model DGEBA epoxy system subject to Hidro-Thermal aging. A Photoelastic Stress Analysis technique has been implemented, showing the evolution of stresses arising throughout the water uptake process due to the non-uniform swelling of the material. Gravimetric and Dynamic Mechanical Thermal Analyses have further complemented the characterization, showing the onset of plasticization effects with aging. The correlation of all previous characterizations has allowed to conclude that an increase of KIC fracture toughness is obtained at the fully saturated condition. In particular Photoelasticity has also revealed the onset of relevant swelling induced stresses during the first stages of water absorption, leading to an increase of fracture toughness due to compressive stresses settling near the crack tip. A stress free condition is instead reestablished at the later stages of absorption, suggesting that the increased toughness of the saturated material is an effect of the modifications induced by aging on the polymer structure.

Pressurized-thermal-shock technology

International Nuclear Information System (INIS)

Dickson, T.L.

1991-01-01

It was recognized at the time the original Issues on Pressurized Thermal Shock (IPTS) studies were conducted that distinct vertical plumes of cooling water form beneath the cold leg inlet nozzles during those particular transients that exhibit fluid/thermal stratification. The formation of these plumes (referred to as thermal streaming) induces a time-dependent circumferential temperature variation on the inner surface of the Reactor Pressure Vessel (RPV) wall that creates an axial stress component. This axial stress component is in addition to the axial stress components induced by time-dependent radial temperature variation through the wall thickness and the time-dependent pressure transient. This additional axial stress component will result in a larger axial stress resultant that results in a larger stress-intensity factor acting on circumferential flaws, thus reducing the fracture margin for circumferential flaws. Although this was recognized at the time of the original IPTS study, the contribution appeared to be relatively small; therefore, it was neglected. The original IPTS studies were performed with OCA-P, a computer program developed at ORNL to analyze the cleavage fracture response of a nuclear RPV subjected to PTS loading. OCA-P is a one-dimensional (1-D) finite-element code that analyzes the stresses and stress-intensity factors (axial and tangential) resulting from the pressure and the radial temperature variation through the wall thickness only. The HSST Program is investigating the potential effects of thermal-streaming-induced stresses in circumferential welds on the reactor vessel PTS analyses. The initial phase of this investigation focused on an evaluation of the available thermal-hydraulic data and analyses results. The objective for the initial phase of the investigation is to evaluate thermal-streaming behavior under conditions relevant to the operation of U.S. PWRs and chracterize any predicted thermal-streaming plumes

Thermally stable diamond brazing

Science.gov (United States)

Radtke, Robert P [Kingwood, TX

2009-02-10

A cutting element and a method for forming a cutting element is described and shown. The cutting element includes a substrate, a TSP diamond layer, a metal interlayer between the substrate and the diamond layer, and a braze joint securing the diamond layer to the substrate. The thickness of the metal interlayer is determined according to a formula. The formula takes into account the thickness and modulus of elasticity of the metal interlayer and the thickness of the TSP diamond. This prevents the use of a too thin or too thick metal interlayer. A metal interlayer that is too thin is not capable of absorbing enough energy to prevent the TSP diamond from fracturing. A metal interlayer that is too thick may allow the TSP diamond to fracture by reason of bending stress. A coating may be provided between the TSP diamond layer and the metal interlayer. This coating serves as a thermal barrier and to control residual thermal stress.

Thermal shock behavior of nano-sized SiC particulate reinforced AlON composites

Energy Technology Data Exchange (ETDEWEB)

Zhao, X.J. [Department of Materials Science and Engineering, School of Materials and Metallurgy, Northeastern University, Shenyang, Liaoning 110004 (China); Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, Ontario M5B 2K3 (Canada); Ru, H.Q., E-mail: ruhq@smm.neu.edu.cn [Department of Materials Science and Engineering, School of Materials and Metallurgy, Northeastern University, Shenyang, Liaoning 110004 (China); Chen, D.L., E-mail: dchen@ryerson.ca [Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, Ontario M5B 2K3 (Canada); Zhang, N.; Liang, B. [Key Laboratory of Advanced Materials Manufacturing Technology of Liaoning Province, Shenyang University, Shenyang, Liaoning 110044 (China)

2012-03-25

Highlights: Black-Right-Pointing-Pointer Addition of nano-SiC particles enhances residual strength and critical temperature. Black-Right-Pointing-Pointer Young's modulus decreases with increasing quenching temperature. Black-Right-Pointing-Pointer Linear relationship between residual strength and thermal shock times is obtained. Black-Right-Pointing-Pointer Rougher fracture surfaces in the SiC-AlON composites are observed. - Abstract: Aluminum oxynitride (AlON) has been considered as a potential ceramic material for high-performance structural and advanced refractory applications. Thermal shock resistance is a major concern and an important performance index of high-temperature ceramics. While silicon carbide (SiC) particles have been proven to improve mechanical properties of AlON ceramic, the high-temperature thermal shock behavior was unknown. The aim of this investigation was to identify the thermal shock resistance and underlying mechanisms of AlON ceramic and 8 wt% SiC-AlON composites over a temperature range between 175 Degree-Sign C and 275 Degree-Sign C. The residual strength and Young's modulus after thermal shock decreased with increasing quenching temperature and thermal shock times due to large temperature gradients and thermal stresses caused by abrupt water-quenching. A linear relationship between the residual strength and thermal shock times was observed in both pure AlON and SiC-AlON composites. The addition of nano-sized SiC particles increased both residual strength and critical temperature from 200 Degree-Sign C in the monolithic AlON to 225 Degree-Sign C in the SiC-AlON composites due to the toughening effect, the lower coefficient of thermal expansion and higher thermal conductivity of SiC. The enhancement of the thermal shock resistance in the SiC-AlON composites was directly related to the change of fracture mode from intergranular cracking along with cleavage-type fracture in the AlON to a rougher fracture surface with ridge

Role of MRI in hip fractures, including stress fractures, occult fractures, avulsion fractures

International Nuclear Information System (INIS)

Nachtrab, O.; Cassar-Pullicino, V.N.; Lalam, R.; Tins, B.; Tyrrell, P.N.M.; Singh, J.

2012-01-01

MR imaging plays a vital role in the diagnosis and management of hip fractures in all age groups, in a large spectrum of patient groups spanning the elderly and sporting population. It allows a confident exclusion of fracture, differentiation of bony from soft tissue injury and an early confident detection of fractures. There is a spectrum of MR findings which in part is dictated by the type and cause of the fracture which the radiologist needs to be familiar with. Judicious but prompt utilisation of MR in patients with suspected hip fractures has a positive therapeutic impact with healthcare cost benefits as well as social care benefits.

Paratrooper's ankle fracture: posterior malleolar fracture.

Science.gov (United States)

Young, Ki Won; Kim, Jin-su; Cho, Jae Ho; Kim, Hyung Seuk; Cho, Hun Ki; Lee, Kyung Tai

2015-03-01

We assessed the frequency and types of ankle fractures that frequently occur during parachute landings of special operation unit personnel and analyzed the causes. Fifty-six members of the special force brigade of the military who had sustained ankle fractures during parachute landings between January 2005 and April 2010 were retrospectively analyzed. The injury sites and fracture sites were identified and the fracture types were categorized by the Lauge-Hansen and Weber classifications. Follow-up surveys were performed with respect to the American Orthopedic Foot and Ankle Society ankle-hindfoot score, patient satisfaction, and return to preinjury activity. The patients were all males with a mean age of 23.6 years. There were 28 right and 28 left ankle fractures. Twenty-two patients had simple fractures and 34 patients had comminuted fractures. The average number of injury and fractures sites per person was 2.07 (116 injuries including a syndesmosis injury and a deltoid injury) and 1.75 (98 fracture sites), respectively. Twenty-three cases (41.07%) were accompanied by posterior malleolar fractures. Fifty-five patients underwent surgery; of these, 30 had plate internal fixations. Weber type A, B, and C fractures were found in 4, 38, and 14 cases, respectively. Based on the Lauge-Hansen classification, supination-external rotation injuries were found in 20 cases, supination-adduction injuries in 22 cases, pronation-external rotation injuries in 11 cases, tibiofibular fractures in 2 cases, and simple medial malleolar fractures in 2 cases. The mean follow-up period was 23.8 months, and the average follow-up American Orthopedic Foot and Ankle Society ankle-hindfoot score was 85.42. Forty-five patients (80.36%) reported excellent or good satisfaction with the outcome. Posterior malleolar fractures occurred in 41.07% of ankle fractures sustained in parachute landings. Because most of the ankle fractures in parachute injuries were compound fractures, most cases had to

Fracture mechanics analyses of ceramic/veneer interface under mixed-mode loading.

Science.gov (United States)

Wang, Gaoqi; Zhang, Song; Bian, Cuirong; Kong, Hui

2014-11-01

Few studies have focused on the interface fracture performance of zirconia/veneer bilayered structure, which plays an important role in dental all-ceramic restorations. The purpose of this study was to evaluate the fracture mechanics performance of zirconia/veneer interface in a wide range of mode-mixities (at phase angles ranging from 0° to 90°), and to examine the effect of mechanical properties of the materials and the interface on the fracture initiation and crack path of an interfacial crack. A modified sandwich test configuration with an oblique interfacial crack was proposed and calibrated to choose the appropriate geometry dimensions by means of finite element analysis. The specimens with different interface inclination angles were tested to failure under three-point bending configuration. Interface fracture parameters were obtained with finite element analyses. Based on the interfacial fracture mechanics, three fracture criteria for crack kinking were used to predict crack initiation and propagation. In addition, the effects of residual stresses due to coefficient of thermal expansion mismatch between zirconia and veneer on the crack behavior were evaluated. The crack initiation and propagation were well predicted by the three fracture criteria. For specimens at phase angle of 0, the cracks propagated in the interface; whereas for all the other specimens the cracks kinked into the veneer. Compressive residual stresses in the veneer can improve the toughness of the interface structure. The results suggest that, in zirconia/veneer bilayered structure the veneer is weaker than the interface, which can be used to explain the clinical phenomenon that veneer chipping rate is larger than interface delamination rate. Consequently, a veneer material with larger fracture toughness is needed to decrease the failure rate of all-ceramic restorations. And the coefficient of thermal expansion mismatch of the substrates can be larger to produce larger compressive

Fracture Mechanics

International Nuclear Information System (INIS)

Jang, Dong Il; Jeong, Gyeong Seop; Han, Min Gu

1992-08-01

This book introduces basic theory and analytical solution of fracture mechanics, linear fracture mechanics, non-linear fracture mechanics, dynamic fracture mechanics, environmental fracture and fatigue fracture, application on design fracture mechanics, application on analysis of structural safety, engineering approach method on fracture mechanics, stochastic fracture mechanics, numerical analysis code and fracture toughness test and fracture toughness data. It gives descriptions of fracture mechanics to theory and analysis from application of engineering.

Fracture toughness of irradiated wrought and cast austenitic stainless steels in BWR environment

International Nuclear Information System (INIS)

Chopra, O.K.; Gruber, E.E.; Shack, W.J.

2007-01-01

Experimental data are presented on the fracture toughness of wrought and cast austenitic stainless steels (SSs) that were irradiated to a fluence of ∼ 1.5 x 10 21 n/cm 2 (E > 1 MeV) * (∼ 2.3 dpa) at 296-305 o C. To evaluate the possible effects of test environment and crack morphology on the fracture toughness of these steels, all tests were conducted in normal-water-chemistry boiling water reactor (BWR) environments at ∼ 289 o C. Companion tests were also conducted in air on the same material for comparison. The fracture toughness J-R curves for SS weld heat-affected-zone materials in BWR water were found to be comparable to those in air. However, the results of tests on sensitized Type 304 SS and thermally aged cast CF-8M steel suggested a possible effect of water environment. The available fracture toughness data on irradiated austenitic SSs were reviewed to assess the potential for radiation embrittlement of reactor-core internal components. The synergistic effects of thermal and radiation embrittlement of cast austenitic SS internal components are also discussed. (author)

Fracture mechanisms in lead zirconate titanate ceramics

International Nuclear Information System (INIS)

Freiman, S.W.; Chuck, L.; Mecholsky, J.J.; Shelleman, D.L.

1986-01-01

Lead Zirconate Titanate (PZT) ceramics can be formed over a wide range of PbTiO 3 /PbZrO 3 ratios and exist in a number of crystal structures. This study involved the use of various fracture mechanics techniques to determine critical fracture toughness, K /SUB IC/ , as a function of composition, microstructure, temperature, and electrical and thermal history. The results of these experiments indicate that variations in K /SUB IC/ are related to phase transformations in the material as well as to other toughening mechanisms such as twinning and microcracking. In addition, the strength and fracture toughness of selected PZT ceramics were determined using specimens in which a crack was introduced by a Vicker's hardness indentor. The variation of K /SUB IC/ with composition and microstructure was related to the extent of twin-crack interaction. Comparison of the plot of strength as a function of indentation load with that predicted from indentation fracture models indicates the presence of internal stresses which contribute to failure. The magnitude of these internal stresses has been correlated with electrical properties of the ceramic. Fractographic analysis was used to determine the magnitude of internal stresses in specimens failing from ''natural flaws.''

Vaporizing Flow in Hot Fractures: Observations from Laboratory Experiments

International Nuclear Information System (INIS)

Kneafsey, T.; Pruess, K.

1998-01-01

Understanding water seepage in hot fractured rock is important in a number of fields including geothermal energy recovery and nuclear waste disposal. Heat-generating high-level nuclear waste packages which will be emplaced in the partially saturated fractured tuffs at the potential high-level nuclear waste repository at Yucca Mountain, Nevada, if it becomes a high-level nuclear waste repository, will cause significant impacts on moisture distribution and migration. Liquid water, which occupies anywhere from 30 to 100% of the porespace, will be vaporized as the temperature reaches the boiling temperature. Flowing primarily in fractures, the vapor will condense where it encounters cooler rock, generating mobile water. This water will flow under gravitational and capillary forces and may flow back to the vicinity of the emplaced waste where it may partially escape vaporization. Water flowing down (sub-) vertical fractures may migrate considerable distances through fractured rock that is at above-boiling temperatures; thus, flowing condensate may contact waste packages, and provide a pathway for the transport of water-soluble radionuclides downward to the saturated zone. Thermally-driven flow processes induced by repository heat may be as important or even more important for repository performance than natural infiltration. For a nominal thermal loading of 57 kW/acre, vaporization may generate an average equivalent percolation flux from condensate of 23.1 mm/yr over 1,000 years, and 5.2 mm/yr over 10,000 years. These numbers are comparable to or larger than current estimates of net infiltration at Yucca Mountain. This condensate, which is generated in the immediate vicinity (meters) of the waste packages, will likely have a larger impact on waste package and repository performance than a similar amount of water introduced at the land surface

Fracture toughness and flexural strength of Sm(Co,Fe,Cu,Zr)7-8 magnetic alloys

International Nuclear Information System (INIS)

Ren, Libo.; Hadjipanayis, George C.; Parvizi-Majidi, Azar

2003-01-01

This paper presents the results of a parametric investigation of the strength and fracture toughness of Sm 2 Co 17 type permanent magnets in the Sm(Co,Fe,Cu,Zr) 7-8 family of alloys. The strength and fracture toughness of the as-received materials were characterized as a function of temperature, loading direction, and magnetization. Since these magnets are candidates for applications with service temperatures up to 450 deg. C, the effect of thermal exposure on the mechanical properties was determined by characterizing the properties after a thermal treatment of 40 h at 450 deg. C

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).

Fracture mechanics of thin wall cylindrical pressure vessels: an interim review

International Nuclear Information System (INIS)

Kurtz, R.J.; Olson, N.J.

1977-08-01

The report is a result of activities in the LMFBR Fuel Rod Transient Performance Program sponsored by the LMFBR Branch of the Division of Project Management, U.S. Nuclear Regulatory Commission. One of the objectives is to develop predictions relative to the length, direction, and rate of growth of cladding rips subsequent to (or concurrent with) the initial cladding breach during unprotected transients. To provide a basis for evaluation, Battelle, Pacific Northwest Laboratories has reviewed most available fracture mechanics assessments relative to thin-wall cylindrical pressure vessels. The purpose of the report is to review the various fracture mechanics models and to describe the pertinent fracture parameters. It is intended to provide a formal basis for assessing future analytical predictions of fracture behavior of materials exposed to transient LMFBR thermal and mechanical loading conditions. In addition, the report is expected to provide reference material for evaluating or developing experimental programs required to properly address the problem of predicting fracture behavior of materials during transient events

Large-Scale True Triaxial Apparatus for Geophysical Studies in Fractured Rock

KAUST Repository

Garcia, A. V.

2018-05-12

The study of fractured rock masses in the laboratory remains challenging because of the large specimen sizes and bulky loading systems that are required. This article presents the design, structural analysis, and operation of a compact and self-reacting true triaxial device for fractured rock. The frame subjects a 50 cm by 50 cm by 50 cm fractured rock specimen to a maximum stress of 3 MPa along three independent axes. Concurrent measurements include long-wavelength P-wave propagation, passive acoustic emission monitoring, deformations, and thermal measurements. The device can accommodate diverse research, from rock mass properties and geophysical fractured rock characterizations, to coupled hydro-chemo-thermo-mechanical processes, drilling, and grouting. Preliminary wave propagation data gathered under isotropic and anisotropic stress conditions for an assembly of 4,000 rock blocks demonstrate the system’s versatility and provide unprecedented information related to long-wavelength propagation in fractured rock under various stress anisotropies.

Large-Scale True Triaxial Apparatus for Geophysical Studies in Fractured Rock

KAUST Repository

Garcia, A. V.; Rached, R. M.; Santamarina, Carlos

2018-01-01

The study of fractured rock masses in the laboratory remains challenging because of the large specimen sizes and bulky loading systems that are required. This article presents the design, structural analysis, and operation of a compact and self-reacting true triaxial device for fractured rock. The frame subjects a 50 cm by 50 cm by 50 cm fractured rock specimen to a maximum stress of 3 MPa along three independent axes. Concurrent measurements include long-wavelength P-wave propagation, passive acoustic emission monitoring, deformations, and thermal measurements. The device can accommodate diverse research, from rock mass properties and geophysical fractured rock characterizations, to coupled hydro-chemo-thermo-mechanical processes, drilling, and grouting. Preliminary wave propagation data gathered under isotropic and anisotropic stress conditions for an assembly of 4,000 rock blocks demonstrate the system’s versatility and provide unprecedented information related to long-wavelength propagation in fractured rock under various stress anisotropies.

Fracture strengths of chair‑side‑generated veneers cemented with ...

African Journals Online (AJOL)

2014-06-09

Jun 9, 2014 ... Group 1), CAD/CAM‑fabricated veneers cemented with a glass fiber ... specimens were tested with a universal testing machine after thermal cycling treatment. ... The purpose of the current in vitro study is to determine the ..... fracture resistance of fiber reinforced cups‑replacing composite restorations.

LNG cascading damage study. Volume I, fracture testing report.

Energy Technology Data Exchange (ETDEWEB)

Petti, Jason P.; Kalan, Robert J.

2011-12-01

As part of the liquefied natural gas (LNG) Cascading Damage Study, a series of structural tests were conducted to investigate the thermal induced fracture of steel plate structures. The thermal stresses were achieved by applying liquid nitrogen (LN{sub 2}) onto sections of each steel plate. In addition to inducing large thermal stresses, the lowering of the steel temperature simultaneously reduced the fracture toughness. Liquid nitrogen was used as a surrogate for LNG due to safety concerns and since the temperature of LN{sub 2} is similar (-190 C) to LNG (-161 C). The use of LN{sub 2} ensured that the tests could achieve cryogenic temperatures in the range an actual vessel would encounter during a LNG spill. There were four phases to this test series. Phase I was the initial exploratory stage, which was used to develop the testing process. In the Phase II series of tests, larger plates were used and tested until fracture. The plate sizes ranged from 4 ft square pieces to 6 ft square sections with thicknesses from 1/4 inches to 3/4 inches. This phase investigated the cooling rates on larger plates and the effect of different notch geometries (stress concentrations used to initiate brittle fracture). Phase II was divided into two sections, Phase II-A and Phase II-B. Phase II-A used standard A36 steel, while Phase II-B used marine grade steels. In Phase III, the test structures were significantly larger, in the range of 12 ft by 12 ft by 3 ft high. These structures were designed with more complex geometries to include features similar to those on LNG vessels. The final test phase, Phase IV, investigated differences in the heat transfer (cooling rates) between LNG and LN{sub 2}. All of the tests conducted in this study are used in subsequent parts of the LNG Cascading Damage Study, specifically the computational analyses.

Simulating Dynamic Fracture in Oxide Fuel Pellets Using Cohesive Zone Models

Energy Technology Data Exchange (ETDEWEB)

R. L. Williamson

2009-08-01

It is well known that oxide fuels crack during the first rise to power, with continued fracture occurring during steady operation and especially during power ramps or accidental transients. Fractures have a very strong influence on the stress state in the fuel which, in turn, drives critical phenomena such as fission gas release, fuel creep, and eventual fuel/clad mechanical interaction. Recently, interest has been expressed in discrete fracture methods, such as the cohesive zone approach. Such models are attractive from a mechanistic and physical standpoint, since they reflect the localized nature of cracking. The precise locations where fractures initiate, as well as the crack evolution characteristics, are determined as part of the solution. This paper explores the use of finite element cohesive zone concepts to predict dynamic crack behavior in oxide fuel pellets during power-up, steady operation, and power ramping. The aim of this work is first to provide an assessment of cohesive zone models for application to fuel cracking and explore important numerical issues associated with this fracture approach. A further objective is to provide basic insight into where and when cracks form, how they interact, and how cracking effects the stress field in a fuel pellet. The ABAQUS commercial finite element code, which includes powerful cohesive zone capabilities, was used for this study. Fully-coupled thermo-mechanical behavior is employed, including the effects of thermal expansion, swelling due to solid and gaseous fission products, and thermal creep. Crack initiation is determined by a temperature-dependent maximum stress criterion, based on measured fracture strengths for UO2. Damage evolution is governed by a traction-separation relation, calibrated to data from temperature and burn-up dependent fracture toughness measurements. Numerical models are first developed in 2D based on both axisymmetric (to explore axial cracking) and plane strain (to explore radial

Stress generation and hierarchical fracturing in reactive systems

Science.gov (United States)

Jamtveit, B.; Iyer, K.; Royne, A.; Malthe-Sorenssen, A.; Mathiesen, J.; Feder, J.

2007-12-01

Hierarchical fracture patterns are the result of a slowly driven fracturing process that successively divides the rocks into smaller domains. In quasi-2D systems, such fracture patterns are characterized by four sided domains, and T-junctions where new fractures stop at right angles to pre-existing fractures. We describe fracturing of mm to dm thick enstatite layers in a dunite matrix from the Leka ophiolite complex in Norway. The fracturing process is driven by expansion of the dunite matrix during serpentinization. The cumulative distributions of fracture lengths show a scaling behavior that lies between a log - normal and power law (fractal) distribution. This is consistent with a simple fragmentation model in which domains are divided according to a 'top hat' distribution of new fracture positions within unfractured domains. Reaction-assisted hierarchical fracturing is also likely to be responsible for other (3-D) structures commonly observed in serpentinized ultramafic rocks, including the mesh-textures observed in individual olivine grains, and the high abundance of rectangular domains at a wide range of scales. Spectacular examples of 3-D hierarchical fracture patterns also form during the weathering of basaltic intrusions (dolerites). Incipient chemical weathering of dolerites in the Karoo Basin in South Africa occurs around water- filled fractures, originally produced by thermal contraction or by externally imposed stresses. This chemical weathering causes local expansion of the rock matrix and generates elastic stresses. On a mm to cm scale, these stresses lead to mechanical layer-by-layer spalling, producing the characteristic spheroidal weathering patterns. However, our field observations and computer simulations demonstrate that in confined environments, the spalling process alone is unable to relieve the elastic stresses. In such cases, chemical weathering drives a much larger scale hierarchical fracturing process in which fresh dolerite undergoes a

Fracture behaviour of a self-healing microcapsule-loaded epoxy system

Directory of Open Access Journals (Sweden)

2011-03-01

Full Text Available The effect of temperature on the fracture behaviour of a microcapsule-loaded epoxy matrix was investigated. Microencapsulated epoxy and mercaptan-derivative healing agents were incorporated into an epoxy matrix to produce a polymer composite capable of self-healing. Maximum fracture loads were measured using the double-torsion method. Thermal aging at 55 and 110°C for 17 hours [hrs] was applied to heal the pre-cracked samples. The addition of microcapsules appeared to increase significantly the load carrying capacity of the epoxy after healing. Once healed, the composites achieved as much as 93–171% of its virgin maximum fracture load at 18, 55 and 110°C. The fracture behavior of the microcapsule- loaded epoxy matrix was influenced by the healing temperature. The high self-healing efficiency may be attributed to the result of the subsurface micro-crack pinning or deviation, and to a stronger microencapsulated epoxy and mercaptanderivative binder than that of the bulk epoxy. The results show that the healing temperature has a significant effect on recovery of load transferring capability after fracture.

Hot and Steamy Fractures in the Philippines: The Geological Characterization and Permeability Evaluation of Fractures in the Southern Negros Geothermal Field, Philippines

Science.gov (United States)

Pastoriza, L. R.; Holdsworth, R.; McCaffrey, K. J. W.; Dempsey, E. D.; Walker, R. J.; Gluyas, J.; Reyes, J. K.

2016-12-01

Fluid flow pathway characterization is critical to geothermal exploration and exploitation. It requires a good understanding of the structural evolution, fault distribution and fluid flow properties. A dominantly fieldwork-based approach has been used to evaluate the potential fracture permeability characteristics of a typical high-temperature geothermal reservoir in the Southern Negros Geothermal Field, Philippines. This is a liquid-dominated geothermal resource hosted in the andesitic to dacitic Quaternary Cuernos de Negros Volcano in Negros Island. Fieldwork reveals two main fracture groups based on fault rock characteristics, alteration type, relative age of deformation, and associated thermal manifestation, with the younger fractures mainly related to the development of the modern geothermal system. Palaeostress analyses of cross-cutting fault and fracture arrays reveal a progressive counterclockwise rotation of stress axes from the (?)Pliocene up to the present-day, which is consistent with the regional tectonic models. A combined slip and dilation tendency analysis of the mapped faults indicates that NW-SE structures should be particularly promising drilling targets. Frequency versus length and aperture plots of fractures across six to eight orders of magnitude show power-law relationships with a change in scaling exponent in the region of 100 to 500m length-scales. Finally, evaluation of the topology of the fracture branches shows the dominance of Y-nodes that are mostly doubly connected suggesting good connectivity and permeability within the fracture networks. The results obtained in this study illustrate the value of methods that can be globally applied during exploration to better characterize fracture systems in geothermal reservoirs using multiscale datasets.

Pressure vessel fracture studies pertaining to a PWR LOCA-ECC thermal shock: experiments TSE-3 and TSE-4 and update of TSE-1 and TSE-2 analysis

International Nuclear Information System (INIS)

Cheverton, R.D.; Bolt, S.E.

1977-01-01

The LOCA-ECC Thermal Shock Program was established to investigate the potential for flaw propagation in pressurized-water reactor (PWR) vessels during injection of emergency core coolant following a loss-of-coolant accident. Studies thus far have included fracture mechanics analyses of typical PWRs, the design and construction of a thermal shock test facility, determination of material properties for test specimens, and four thermal shock experiments with 0.53-m-OD (21-in.) by 0.15-m-wall (6-in.) cylindrical test specimens. In the first experiment, initiation was not expected and did not occur, although there was a small amount of subcritical crack growth. In the second experiment, initiation of a semicircular flaw took place as expected; the final length along the surface was about four times the initial length, but there was no radial growth. The third and fourth experiments were similar, and the long axial flaw initiated in good agreement with predictions

Geology and fracture system at Stripa. Technical information report No. 21

International Nuclear Information System (INIS)

Olkiewicz, A.; Gale, J.E.; Thorpe, R.; Paulsson, B.

1979-02-01

The Stripa test site has been excavated in granitic rock between 338 m and 360 m below the ground surface, and is located under the north limb of an ENE-plunging synclinal structure. The granitic rocks, in the areas mapped, are of Archean age and are dominated by a reddish, medium-grained, massive monzogranite that shows varying degrees of deformation. The granitic rocks have been intruded by diabase (dolerite) and pegmatite dikes. Surface and subsurface mapping shows that the Stripa granite is highly fractured and that there are at least four joint sets in the area of the test excavations. In addition to the joints, the rock mass contains fissures, fracture zones, and small-scale shear zones, representing the complete spectrum of the fracture family. Most of the fractures are lined with chlorite, occasionally with calcite. Many of the small-scale shear fractures are filled or coated with epidote. Offsets of pegmatite dikes formed by these fractures are usually limited to one to two meters. Water seepage is observed only as drops from fractures or moist fracture surfaces. It was found that reconstruction of the local three-dimensional fracture system is the heater-experiment sites was difficult, and in some cases subjective. Such reconstruction is a prerequisite to accurate interpretation of thermal and mechanical data from such sites

Modeling thermal stress propagation during hydraulic stimulation of geothermal wells

Science.gov (United States)

Jansen, Gunnar; Miller, Stephen A.

2017-04-01

A large fraction of the world's water and energy resources are located in naturally fractured reservoirs within the earth's crust. Depending on the lithology and tectonic history of a formation, fracture networks can range from dense and homogeneous highly fractured networks to single large scale fractures dominating the flow behavior. Understanding the dynamics of such reservoirs in terms of flow and transport is crucial to successful application of engineered geothermal systems (also known as enhanced geothermal systems or EGS) for geothermal energy production in the future. Fractured reservoirs are considered to consist of two distinct separate media, namely the fracture and matrix space respectively. Fractures are generally thin, highly conductive containing only small amounts of fluid, whereas the matrix rock provides high fluid storage but typically has much smaller permeability. Simulation of flow and transport through fractured porous media is challenging due to the high permeability contrast between the fractures and the surrounding rock matrix. However, accurate and efficient simulation of flow through a fracture network is crucial in order to understand, optimize and engineer reservoirs. It has been a research topic for several decades and is still under active research. Accurate fluid flow simulations through field-scale fractured reservoirs are still limited by the power of current computer processing units (CPU). We present an efficient implementation of the embedded discrete fracture model, which is a promising new technique in modeling the behavior of enhanced geothermal systems. An efficient coupling strategy is determined for numerical performance of the model. We provide new insight into the coupled modeling of fluid flow, heat transport of engineered geothermal reservoirs with focus on the thermal stress changes during the stimulation process. We further investigate the interplay of thermal and poro-elastic stress changes in the reservoir

Synthesis report on thermally driven coupled processes

International Nuclear Information System (INIS)

Hardin, E.L.

1997-01-01

The main purpose of this report is to document observations and data on thermally coupled processes for conditions that are expected to occur within and around a repository at Yucca Mountain. Some attempt is made to summarize values of properties (e.g., thermal properties, hydrologic properties) that can be measured in the laboratory on intact samples of the rock matrix. Variation of these properties with temperature, or with conditions likely to be encountered at elevated temperature in the host rock, is of particular interest. However, the main emphasis of this report is on direct observation of thermally coupled processes at various scales. Direct phenomenological observations are vitally important in developing and testing conceptual models. If the mathematical implementation of a conceptual model predicts a consequence that is not observed, either (1) the parameters or the boundary conditions used in the calculation are incorrect or (2) the conceptual basis of the model does not fit the experiment; in either case, the model must be revised. For example, the effective continuum model that has been used in thermohydrology studies combines matrix and fracture flow in a way that is equivalent to an assumption that water is imbibed instantaneously from fractures into adjacent, partially saturated matrix. Based on this approximation, the continuum-flow response that is analogous to fracture flow will not occur until the effective continuum is almost completely saturated. This approximation is not entirely consistent with some of the experimental data presented in this report. This report documents laboratory work and field studies undertaken in FY96 and FY97 to investigate thermally coupled processes such as heat pipes and fracture-matrix coupling. In addition, relevant activities from past years, and work undertaken outside the Yucca Mountain project are summarized and discussed. Natural and artificial analogs are also discussed to provide a convenient source of

On metal fracture induced by laser radiation and impact pinched plasma

International Nuclear Information System (INIS)

Sultanov, M.A.; Olejnikov, V.P.

1980-01-01

Dependences of erosion of metals (Mo, W, Fe, Ta, Cr, Cd and etc.) on thermal physical properties and the place of laser radiation focusing are investigated. The radiation output energy has reached 10G, the impulse durability - 10 -3 sec. It is shown that the lense focus shift causes the change in the form and dimensions of a crater fracture. It is noted that there are shock waves in the laser plasma structure of fracture products, which are indicative of supersonic velocities of outflow of plasma microjets. A greater fracture degree of refractory metals (W, Mo, Ta) under the investigated conditions is noted. The erosion parameters of a great number of the metals under investigation are given

Reactor pressure vessel thermal annealing

International Nuclear Information System (INIS)

Lee, A.D.

1997-01-01

The steel plates and/or forgings and welds in the beltline region of a reactor pressure vessel (RPV) are subject to embrittlement from neutron irradiation. This embrittlement causes the fracture toughness of the beltline materials to be less than the fracture toughness of the unirradiated material. Material properties of RPVs that have been irradiated and embrittled are recoverable through thermal annealing of the vessel. The amount of recovery primarily depends on the level of the irradiation embrittlement, the chemical composition of the steel, and the annealing temperature and time. Since annealing is an option for extending the service lives of RPVs or establishing less restrictive pressure-temperature (P-T) limits; the industry, the Department of Energy (DOE) and the Nuclear Regulatory Commission (NRC) have assisted in efforts to determine the viability of thermal annealing for embrittlement recovery. General guidance for in-service annealing is provided in American Society for Testing and Materials (ASTM) Standard E 509-86. In addition, the American Society of Mechanical Engineers (ASME) Code Case N-557 addresses annealing conditions (temperature and duration), temperature monitoring, evaluation of loadings, and non-destructive examination techniques. The NRC thermal annealing rule (10 CFR 50.66) was approved by the Commission and published in the Federal Register on December 19, 1995. The Regulatory Guide on thermal annealing (RG 1.162) was processed in parallel with the rule package and was published on February 15, 1996. RG 1.162 contains a listing of issues that need to be addressed for thermal annealing of an RPV. The RG also provides alternatives for predicting re-embrittlement trends after the thermal anneal has been completed. This paper gives an overview of methodology and recent technical references that are associated with thermal annealing. Results from the DOE annealing prototype demonstration project, as well as NRC activities related to the

Model of T-Type Fracture in Coal Fracturing and Analysis of Influence Factors of Fracture Morphology

Directory of Open Access Journals (Sweden)

Yuwei Li

2018-05-01

Full Text Available Special T-type fractures can be formed when coal is hydraulically fractured and there is currently no relevant theoretical model to calculate and describe them. This paper first establishes the height calculation model of vertical fractures in multi-layered formations and deduces the stress intensity factor (SIF at the upper and lower sides of the fracture in the process of vertical fracture extension. Combined with the fracture tip stress analysis method of fracture mechanics theory, the horizontal bedding is taken into account for tensile and shear failure, and the critical mechanical conditions for the formation of horizontal fracture in coal are obtained. Finally, the model of T-type fracture in coal fracturing is established, and it is verified by fracturing simulation experiments. The model calculation result shows that the increase of vertical fracture height facilitates the increase of horizontal fracture length. The fracture toughness of coal has a significant influence on the length of horizontal fracture and there is a threshold. When the fracture toughness is less than the threshold, the length of horizontal fracture remains unchanged, otherwise, the length of horizontal fracture increases rapidly with the increase of fracture toughness. When the shear strength of the interface between the coalbed and the interlayer increases, the length of the horizontal fracture of the T-type fracture rapidly decreases.

STAFAN, Fluid Flow, Mechanical Stress in Fractured Rock of Nuclear Waste Repository

International Nuclear Information System (INIS)

Huyakorn, P.; Golis, M.J.

1989-01-01

1 - Description of program or function: STAFAN (Stress And Flow Analysis) is a two-dimensional, finite-element code designed to model fluid flow and the interaction of fluid pressure and mechanical stresses in a fractured rock surrounding a nuclear waste repository. STAFAN considers flow behavior of a deformable fractured system with fracture-porous matrix interactions, the coupling effects of fluid pressure and mechanical stresses in a medium containing discrete joints, and the inelastic response of the individual joints of the rock mass subject to the combined fluid pressure and mechanical loading. 2 - Restrictions on the complexity of the problem: STAFAN does not presently contain thermal coupling, and it is unable to simulate inelastic deformation of the rock mass and variably saturated or two-phase flow in the fractured porous medium system

Microstructural, mechanical, and thermal characteristics of recycled cellulose fiber-halloysite-epoxy hybrid nanocomposites

KAUST Repository

Alamri, H.

2012-02-26

Epoxy hybrid-nanocomposites reinforced with recycled cellulose fibers (RCF) and halloysite nanotubes (HNTs) have been fabricated and investigated. The dispersion of HNTs was studied by synchrotron radiation diffraction (SRD) and transmission electron microscopy (TEM). The influences of RCF/HNTs dispersion on the mechanical properties and thermal properties of these composites have been characterized in terms of flexural strength, flexural modulus, fracture toughness, impact toughness, impact strength, and thermogravimetric analysis. The fracture surface morphology and toughness mechanisms were investigated by SEM. Results indicated that mechanical properties increased because of the addition of HNTs into the epoxy matrix. Flexural strength, flexural modulus, fracture toughness, and impact toughness increased by 20.8, 72.8, 56.5, and 25.0%, respectively, at 1 wt% HNTs load. The presence of RCF dramatically enhanced flexural strength, fracture toughness, impact strength, and impact toughness of the composites by 160%, 350%, 444%, and 263%, respectively. However, adding HNTs to RCF/epoxy showed only slight enhancements in flexural strength and fracture toughness. The inclusion of 5 wt% HNTs into RCF/epoxy ecocomposites increased the impact toughness by 27.6%. The presence of either HNTs or RCF accelerated the thermal degradation of neat epoxy. However, at high temperature, samples reinforced with RCF and HNTs displayed better thermal stability with increased char residue than neat resin. © 2012 Society of Plastics Engineers.

Enhancement of Fracture Toughness of Epoxy Nanocomposites by Combining Nanotubes and Nanosheets as Fillers.

Science.gov (United States)

Domun, Nadiim; Paton, Keith R; Hadavinia, Homayoun; Sainsbury, Toby; Zhang, Tao; Mohamud, Hibaaq

2017-10-19

In this work the fracture toughness of epoxy resin has been improved through the addition of low loading of single part and hybrid nanofiller materials. Functionalised multi-walled carbon nanotubes (f-MWCNTs) was used as single filler, increased the critical strain energy release rate, G IC , by 57% compared to the neat epoxy, at only 0.1 wt% filler content. Importantly, no degradation in the tensile or thermal properties of the nanocomposite was observed compared to the neat epoxy. When two-dimensional boron nitride nanosheets (BNNS) were added along with the one-dimensional f-MWCNTs, the fracture toughness increased further to 71.6% higher than that of the neat epoxy. Interestingly, when functionalised graphene nanoplatelets (f-GNPs) and boron nitride nanotubes (BNNTs) were used as hybrid filler, the fracture toughness of neat epoxy is improved by 91.9%. In neither of these hybrid filler systems the tensile properties were degraded, but the thermal properties of the nanocomposites containing boron nitride materials deteriorated slightly.

Enhancement of Fracture Toughness of Epoxy Nanocomposites by Combining Nanotubes and Nanosheets as Fillers

Directory of Open Access Journals (Sweden)

Nadiim Domun

2017-10-01

Full Text Available In this work the fracture toughness of epoxy resin has been improved through the addition of low loading of single part and hybrid nanofiller materials. Functionalised multi-walled carbon nanotubes (f-MWCNTs was used as single filler, increased the critical strain energy release rate, GIC, by 57% compared to the neat epoxy, at only 0.1 wt% filler content. Importantly, no degradation in the tensile or thermal properties of the nanocomposite was observed compared to the neat epoxy. When two-dimensional boron nitride nanosheets (BNNS were added along with the one-dimensional f-MWCNTs, the fracture toughness increased further to 71.6% higher than that of the neat epoxy. Interestingly, when functionalised graphene nanoplatelets (f-GNPs and boron nitride nanotubes (BNNTs were used as hybrid filler, the fracture toughness of neat epoxy is improved by 91.9%. In neither of these hybrid filler systems the tensile properties were degraded, but the thermal properties of the nanocomposites containing boron nitride materials deteriorated slightly.

Fracture toughness and flexural strength of Sm(Co,Fe,Cu,Zr){sub 7-8} magnetic alloys

Energy Technology Data Exchange (ETDEWEB)

Ren, Libo. E-mail: ren@me.udel.edu; Hadjipanayis, George C.; Parvizi-Majidi, Azar

2003-02-01

This paper presents the results of a parametric investigation of the strength and fracture toughness of Sm{sub 2}Co{sub 17} type permanent magnets in the Sm(Co,Fe,Cu,Zr){sub 7-8} family of alloys. The strength and fracture toughness of the as-received materials were characterized as a function of temperature, loading direction, and magnetization. Since these magnets are candidates for applications with service temperatures up to 450 deg. C, the effect of thermal exposure on the mechanical properties was determined by characterizing the properties after a thermal treatment of 40 h at 450 deg. C00.

The application of fracture mechanics in thermally stressed structures

International Nuclear Information System (INIS)

Cesari, F.; Maitan, A.; Hellen, T.K.

1981-03-01

There is considerable interest in calculating stress intensity factors at crack tips in thermally stressed structures, particularly in the power generation industry where the safe operation of both conventional and nuclear plant is founded on rigorous safety cases. Analytical methods to study such problems are of limited scope, although they can be extended by introducing numerical techniques. Purpose built numerical methods, however, offer a much greater and more accurate solution capability and in particular the finite element method is well advanced. Such methods are described, including how stress intensity factors can be obtained from the finite element results. They are then applied to a range of thermally stressed problems including plates with central cracks and cylinders with axial and circumferential cracks. Both steady state and transient temperature distributions arising from typical thermal shocks are considered. (author)

Performance reliability prediction for thermal aging based on kalman filtering

International Nuclear Information System (INIS)

Ren Shuhong; Wen Zhenhua; Xue Fei; Zhao Wensheng

2015-01-01

The performance reliability of the nuclear power plant main pipeline that failed due to thermal aging was studied by the performance degradation theory. Firstly, through the data obtained from the accelerated thermal aging experiments, the degradation process of the impact strength and fracture toughness of austenitic stainless steel material of the main pipeline was analyzed. The time-varying performance degradation model based on the state space method was built, and the performance trends were predicted by using Kalman filtering. Then, the multi-parameter and real-time performance reliability prediction model for the main pipeline thermal aging was developed by considering the correlation between the impact properties and fracture toughness, and by using the stochastic process theory. Thus, the thermal aging performance reliability and reliability life of the main pipeline with multi-parameter were obtained, which provides the scientific basis for the optimization management of the aging maintenance decision making for nuclear power plant main pipelines. (authors)

Parallel, Multigrid Finite Element Simulator for Fractured/Faulted and Other Complex Reservoirs based on Common Component Architecture (CCA)

Energy Technology Data Exchange (ETDEWEB)

Milind Deo; Chung-Kan Huang; Huabing Wang

2008-08-31

Black-oil, compositional and thermal simulators have been developed to address different physical processes in reservoir simulation. A number of different types of discretization methods have also been proposed to address issues related to representing the complex reservoir geometry. These methods are more significant for fractured reservoirs where the geometry can be particularly challenging. In this project, a general modular framework for reservoir simulation was developed, wherein the physical models were efficiently decoupled from the discretization methods. This made it possible to couple any discretization method with different physical models. Oil characterization methods are becoming increasingly sophisticated, and it is possible to construct geologically constrained models of faulted/fractured reservoirs. Discrete Fracture Network (DFN) simulation provides the option of performing multiphase calculations on spatially explicit, geologically feasible fracture sets. Multiphase DFN simulations of and sensitivity studies on a wide variety of fracture networks created using fracture creation/simulation programs was undertaken in the first part of this project. This involved creating interfaces to seamlessly convert the fracture characterization information into simulator input, grid the complex geometry, perform the simulations, and analyze and visualize results. Benchmarking and comparison with conventional simulators was also a component of this work. After demonstration of the fact that multiphase simulations can be carried out on complex fracture networks, quantitative effects of the heterogeneity of fracture properties were evaluated. Reservoirs are populated with fractures of several different scales and properties. A multiscale fracture modeling study was undertaken and the effects of heterogeneity and storage on water displacement dynamics in fractured basements were investigated. In gravity-dominated systems, more oil could be recovered at a given pore

Effect of thermal fatigue on the structure and properties of Ni3Al-based alloy single crystals

Science.gov (United States)

Povarova, K. B.; Drozdov, A. A.; Bazyleva, O. A.; Bulakhtina, M. A.; Alad'ev, N. A.; Antonova, A. V.; Arginbaeva, E. G.; Morozov, A. E.

2014-05-01

The effect of thermal fatigue during tests of and single crystals according to the schedules 100 ai 850°C, 100 ai 1050°C, 100 ai 1100°C at a peak-to-peak stress Δσtc = 700-1000 MPa (sum of the maximum tensile and compressive stresses in a thermal cycle) on the structure, the fracture, and the fatigue life of an Ni3Al-based VKNA-1V alloy is studied. It is found that, at 103 thermal cycles, the single crystals have the maximum thermal fatigue resistance at the maximum cycle temperature of 850 and 1050°C, and the properties of the and samples are almost the same at the maximum thermal cycle temperature of 1100°C. After thermal cycling at the maximum temperature of 850°C, the γ layers in the two-phase γ' + γ region in dendrites remain a single-phase structure, as in the as-cast material, and the layer thickness is 100-150 nm. When the maximum thermal cycle temperature increases to 1050 or 1100°C, the discontinuous γ-phase layers in the γ'(Ni3Al) matrix change their morphology and become shorter and wider (their thickness is 300-700 nm). The nickel-based supersaturated solid solution in these layers decomposes with the formation of secondary γ'(Ni3Al)-phase (γ'sec) precipitates in the form of cuboids 50 and 100 nm in size at the maximum cycle temperature of 1050 and 1100°C, respectively. The alternating stresses that appear during thermal cycling cause plastic deformation. As in nickel superalloys, this deformation at the first stage proceeds via the slip of screw dislocations along octahedral {111} planes. Networks of 60° dislocation segments form at γ'/γ interfaces in this case. Fracture begins at the lines of intersection of the slip planes of the {111} octahedron with the sample surface. During fractional, a crack passes from one octahedral plane to another and forms terraces and steps (crystallographic fracture); as a result, the fracture surface bends and becomes curved. In all cases, the fracture surfaces have a mixed brittle-ductile character

Development of probabilistic fracture mechanics code PASCAL and user's manual

Energy Technology Data Exchange (ETDEWEB)

Shibata, Katsuyuki; Onizawa, Kunio [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Li, Yinsheng; Kato, Daisuke [Fuji Research Institute Corporation, Tokyo (Japan)

2001-03-01

As a part of the aging and structural integrity research for LWR components, a new PFM (Probabilistic Fracture Mechanics) code PASCAL (PFM Analysis of Structural Components in Aging LWR) has been developed since FY1996. This code evaluates the failure probability of an aged reactor pressure vessel subjected to transient loading such as PTS (Pressurized Thermal Shock). The development of the code has been aimed to improve the accuracy and reliability of analysis by introducing new analysis methodologies and algorithms considering the recent development in the fracture mechanics methodologies and computer performance. The code has some new functions in optimized sampling and cell dividing procedure in stratified Monte Carlo simulation, elastic-plastic fracture criterion of R6 method, extension analysis models in semi-elliptical crack, evaluation of effect of thermal annealing and etc. In addition, an input data generator of temperature and stress distribution time histories was also prepared in the code. Functions and performance of the code have been confirmed based on the verification analyses and some case studies on the influence parameters. The present phase of the development will be completed in FY2000. Thus this report provides the user's manual and theoretical background of the code. (author)

Hot and steamy fractures in the Philippines: the characterisation and permeability evaluation of fractures of the Southern Negros Geothermal Field, Negros Oriental, Philippines

Science.gov (United States)

Pastoriza, Loraine; Holdsworth, Robert; McCaffrey, Kenneth; Dempsey, Eddie; Walker, Richard; Gluyas, Jon; Reyes, Jonathan

2017-04-01

Fluid flow pathway characterisation is critical to geothermal exploration and exploitation. It requires a good understanding of the structural evolution, fault distribution and fluid flow properties. A dominantly fieldwork-based approach has been used to evaluate the potential fracture permeability characteristics of a typical high-temperature geothermal reservoir in the Southern Negros Geothermal Field, Philippines. This is a liquid-dominated geothermal resource hosted in the andesitic to dacitic Quaternary Cuernos de Negros Volcano in Negros Island. Fieldwork reveals two main fracture groups based on fault rock characteristics, alteration type, relative age of deformation, and associated thermal manifestation, with the younger fractures mainly related to the development of the modern geothermal system. Palaeostress analyses of cross-cutting fault and fracture arrays reveal a progressive counterclockwise rotation of stress axes from the (?)Pliocene up to the present-day, which is consistent with the regional tectonic models. A combined slip and dilation tendency analysis of the mapped faults indicates that NW-SE structures should be particularly promising drilling targets. Frequency versus length and aperture plots of fractures across six to eight orders of magnitude show power-law relationships with a change in scaling exponent in the region of 100 to 500m length-scales. Finally, evaluation of the topology of the fracture branches shows the dominance of Y-nodes that are mostly doubly connected suggesting good connectivity and permeability within the fracture networks. The results obtained in this study illustrate the value of methods that can be globally applied during exploration to better characterize fracture systems in geothermal reservoirs using multiscale datasets.

Some aspects of fracture assessment diagrams, plastic zone size corrections and contour integrals in post-yield fracture mechanics

International Nuclear Information System (INIS)

Ainsworth, R.A.

1981-03-01

The CEGB failure assessment route is briefly described and is shown to be consistent with a plastic zone size correction method. Modifications to the assessment route which have recently been suggested for describing the effects of thermal and residual stresses are examined. It is shown that the plastic zone size correction method may be used to include local thermal and residual stresses in the assessment route in a simple manner. The assessment route is compared with finite-element solutions for a thermal stress problem and with strip-yield model solutions for a residual stress problem. In using finite-element solutions there are different contour integral methods available for calculating a post-yield fracture parameter. The J-integral of Rice and the J*-integral of Blackburn are examined and compared and the appropriate parameter is identified. (author)

On the Fracture Response of Shape Memory Alloy Actuators

Science.gov (United States)

Jape, Sameer; Parrinello, Antonino; Baxevanis, Theocharis; Lagoudas, Dimitris C.

In this paper, the effect of global thermo-mechanically-induced phase transformation on the driving force for crack growth in polycrystalline shape memory alloys is analyzed in an infinite center-cracked plate subjected to thermal actuation under isobaric, plane strain, mode I loading. Finite element calculations are carried out to determine the mechanical fields near the static crack and the crack-tip energy release rate using the virtual crack closure technique. Analysis of the static crack shows that, as compared to constant mechanical loading, the energy release rate during cooling increases by approximately an order of magnitude. This increase is attributed to the stress redistribution at the crack-tip induced by global phase transformation during cooling. Crack growth during actuation is assumed to occur when the crack-tip energy release rate reaches a material specific critical value. Fracture toughening behavior is observed during crack growth and is mainly associated with the energy dissipated by the progressively occurring phase transformation close to the moving crack tip. Lastly, the effect of crack configuration on fracture toughness enhancement in the large-scale transformation problem is studied. Numerical results for static cracks in compact tensile and three-point bending SMA specimens are reported and a comparison of fracture toughening during thermal actuation in the semi-infinite crack configuration with the compact tensile and three-point bending geometries is presented.

Environmental controls on micro fracture processes in shelf ice

Science.gov (United States)

Sammonds, Peter

2013-04-01

The recent retreat and collapse of the ice shelves on the Antarctic Peninsula has been associated with regional atmospheric warming, oceanic warming, increased summer melt and shelf flexure. Although the cause of collapse is a matter of active discussion, the process is that of fracture of a creep-brittle material, close to its melting point. The environmental controls on how fracturing initiates, at a micro-scale, strongly determine the macroscopic disintegration of ice shelves. In particular the shelf temperature profile controls the plasticity of the ice shelf; the densification of shelf ice due to melting and re-freezing affects the crack tip stress intensity; the accretion of marine ice at the bottom of the shelf imposes a thermal/mechanical discontinuity; saline environments control crack tip stress corrosion; cyclic loading promotes sub-critical crack propagation. These strong environmental controls on shelf ice fracture means that assessing shelf stability is a non-deterministic problem. How these factors may be parameterized in ice shelf models, through the use of fracture mechanisms maps, is discussed. The findings are discussed in relation to the stability of Larsen C.

Thermal Site Descriptive Model. A strategy for the model development during site investigations. Version 1.0

International Nuclear Information System (INIS)

Sundberg, Jan

2003-04-01

Site investigations are in progress for the siting of a deep repository for spent nuclear fuel. As part of the planning work, strategies are developed for site descriptive modelling regarding different disciplines, amongst them the thermal conditions. The objective of the strategy for a thermal site descriptive model is to guide the practical implementation of evaluating site specific data during the site investigations. It is understood that further development may be needed. The model describes the thermal properties and other thermal parameters of intact rock, fractures and fracture zones, and of the rock mass. The methodology is based on estimation of thermal properties of intact rock and discontinuities, using both empirical and theoretical/numerical approaches, and estimation of thermal processes using mathematical modelling. The methodology will be used and evaluated for the thermal site descriptive modelling at the Aespoe Hard Rock Laboratory

Dynamic Response and Fracture of Composite Gun Tubes

Directory of Open Access Journals (Sweden)

Jerome T. Tzeng

2001-01-01

Full Text Available The fracture behavior due to dynamic response in a composite gun tube subjected to a moving pressure has been investigated. The resonance of stress waves result in very high amplitude and frequency strains in the tube at the instant and location of pressure front passage as the velocity of the projectile approaches a critical value. The cyclic stresses can accelerate crack propagation in the gun tube with an existing imperfection and significantly shorten the fatigue life of gun tubes. The fracture mechanism induced by dynamic amplification effects is particularly critical for composite overwrap barrels because of a multi-material construction, anisotropic material properties, and the potential of thermal degradation.

Bimalleolar ankle fracture with proximal fibular fracture

NARCIS (Netherlands)

Colenbrander, R. J.; Struijs, P. A. A.; Ultee, J. M.

2005-01-01

A 56-year-old female patient suffered a bimalleolar ankle fracture with an additional proximal fibular fracture. This is an unusual fracture type, seldom reported in literature. It was operatively treated by open reduction and internal fixation of the lateral malleolar fracture. The proximal fibular

UK modelling of thermal effects on leakage from hard rock depositories

International Nuclear Information System (INIS)

Bourke, P.J.

1980-01-01

Thermally induced stress through and around depositories have been calculated assuming the rock to have constant mechanical properties obtained from laboratory measurements and ignoring the effects of existing fractures. After allowing for probable values of the natural stress field, regions of net tension and high shear stress which might cause new fractures were found. This analysis is, however, not yet considered to be reliable because of uncertainty about the above assumptions. Further, even if it is accurate, it is incomplete because it is still not possible to relate quantitatively calculated stresses to changes in permeability and porosity due to changes in existing fractures or initiation of new ones. Accordingly, further theoretical work is being done to plan an underground study of the effects of heating on a well defined fracture. Measurements of strain and modulus will be made to investigate the validity of the mechanical assumptions and hydraulic data will be obtained to relate stress to resistance to flow. It is hoped that further analysis will then allow an assessment of the importance of thermal stress around a depository to be made

Correlation of Hip Fracture with Other Fracture Types: Toward a Rational Composite Hip Fracture Endpoint

Science.gov (United States)

Colón-Emeric, Cathleen; Pieper, Carl F.; Grubber, Janet; Van Scoyoc, Lynn; Schnell, Merritt L; Van Houtven, Courtney Harold; Pearson, Megan; Lafleur, Joanne; Lyles, Kenneth W.; Adler, Robert A.

2016-01-01

Purpose With ethical requirements to the enrollment of lower risk subjects, osteoporosis trials are underpowered to detect reduction in hip fractures. Different skeletal sites have different levels of fracture risk and response to treatment. We sought to identify fracture sites which cluster with hip fracture at higher than expected frequency; if these sites respond to treatment similarly, then a composite fracture endpoint could provide a better estimate of hip fracture reduction. Methods Cohort study using Veterans Affairs and Medicare administrative data. Male Veterans (n=5,036,536) aged 50-99 years receiving VA primary care between1999-2009 were included. Fractures were ascertained using ICD9 and CPT codes and classified by skeletal site. Pearson correlation coefficients, logistic regression and kappa statistics, were used to describe the correlation between each fracture type and hip fracture within individuals, without regards to the timing of the events. Results 595,579 (11.8%) men suffered 1 or more fractures and 179,597 (3.6%) suffered 2 or more fractures during the time under study. Of those with one or more fractures, rib was the most common site (29%), followed by spine (22%), hip (21%) and femur (20%). The fracture types most highly correlated with hip fracture were pelvic/acetabular (Pearson correlation coefficient 0.25, p<0.0001), femur (0.15, p<0.0001), and shoulder (0.11, p<0.0001). Conclusions Pelvic, acetabular, femur, and shoulder fractures cluster with hip fractures within individuals at greater than expected frequency. If we observe similar treatment risk reductions within that cluster, subsequent trials could consider use of a composite endpoint to better estimate hip fracture risk. PMID:26151123

Initial Probabilistic Evaluation of Reactor Pressure Vessel Fracture with Grizzly and Raven

Energy Technology Data Exchange (ETDEWEB)

Spencer, Benjamin [Idaho National Lab. (INL), Idaho Falls, ID (United States); Hoffman, William [Univ. of Idaho, Moscow, ID (United States); Sen, Sonat [Idaho National Lab. (INL), Idaho Falls, ID (United States); Rabiti, Cristian [Idaho National Lab. (INL), Idaho Falls, ID (United States); Dickson, Terry [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Bass, Richard [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2015-10-01

The Grizzly code is being developed with the goal of creating a general tool that can be applied to study a variety of degradation mechanisms in nuclear power plant components. The first application of Grizzly has been to study fracture in embrittled reactor pressure vessels (RPVs). Grizzly can be used to model the thermal/mechanical response of an RPV under transient conditions that would be observed in a pressurized thermal shock (PTS) scenario. The global response of the vessel provides boundary conditions for local models of the material in the vicinity of a flaw. Fracture domain integrals are computed to obtain stress intensity factors, which can in turn be used to assess whether a fracture would initiate at a pre-existing flaw. These capabilities have been demonstrated previously. A typical RPV is likely to contain a large population of pre-existing flaws introduced during the manufacturing process. This flaw population is characterized stastistically through probability density functions of the flaw distributions. The use of probabilistic techniques is necessary to assess the likelihood of crack initiation during a transient event. This report documents initial work to perform probabilistic analysis of RPV fracture during a PTS event using a combination of the RAVEN risk analysis code and Grizzly. This work is limited in scope, considering only a single flaw with deterministic geometry, but with uncertainty introduced in the parameters that influence fracture toughness. These results are benchmarked against equivalent models run in the FAVOR code. When fully developed, the RAVEN/Grizzly methodology for modeling probabilistic fracture in RPVs will provide a general capability that can be used to consider a wider variety of vessel and flaw conditions that are difficult to consider with current tools. In addition, this will provide access to advanced probabilistic techniques provided by RAVEN, including adaptive sampling and parallelism, which can dramatically

Thermal fatigue behavior of thermal barrier coatings by air plasma spray

Energy Technology Data Exchange (ETDEWEB)

Lee, Han Sang; Kim, Eui Hyun [Korea Electric Power Research Institute, Daejeon (Korea, Republic of); Lee, Jung Hyuk [Korea Plant Service and Engineering Co. Ltd., Incheon (Korea, Republic of)

2008-06-15

Effects of top coat morphology and thickness on thermal fatigue behavior of Thermal Barrier Coatings (TBC) were investigated in this study. Thermal fatigue tests were conducted on three coating specimens with different top coat morphology and thickness, and then the test data were compared via microstructures, cycles to failure, and fracture surfaces. In the air plasma spray specimens (APS1, APS2), top coat were 200 and 300 {mu}m respectively. The thickness of top coat was about 700 {mu}m in the Perpendicular Cracked Specimen (PCS). Under thermal fatigue condition at 1,100 .deg. C, the cycles to top coat failure of APS1, APS2, and PCS were 350, 560 and 480 cycles, respectively. The cracks were initiated at the interface of top coat and Thermally Grown Oxide (TGO) and propagated into TGO or top coat as the number of thermal fatigue cycles increased. For the PCS specimen, additive cracks were initiated and propagated at the starting points of perpendicular cracks in the top coat. Also, the thickness of TGO and the decrease of aluminium concentration in bond coat do not affect the cycles to failure.

Length scale of secondary stresses in fracture and fatigue

International Nuclear Information System (INIS)

Dong, P.

2008-01-01

In an attempt to provide a consistent framework for the analysis and treatment of secondary stresses associated with welding and thermal loading in the context of fracture mechanics, this paper starts with an effective stress characterization procedure by introducing a length-scale concept. With it, a traction-based stress separation procedure is then presented to provide a consistent characterization of stresses from various sources based on their length scale. Their relative contributions to fracture driving force are then quantified in terms of their characteristic length scales. Special attention is given to the implications of the length-scale argument on both analysis and treatment of welding residual stresses in fracture assessment. A series of examples is provided to demonstrate how the present developments can be applied for treating not only secondary stresses but also externally applied stresses, as well as their combined effects on the structural integrity of engineering components

Microscopic observation and statics consideration of tensile fracture of TiC coating on stainless steel

International Nuclear Information System (INIS)

Okawa, Akira; Hasiguti, Ryukiti

1986-01-01

We have measured the tensile fracture properties of the TiC coated SUS316L stainless steel, applying a stress perpendicular to the plane of interface between the coating and the substrate. The fracture of the as grown or non-annealed specimens occurred partially within the TiC layer. A tensile fracture of the TiC coated specimens after vacuum annealing at about 1373 K (1100 deg C) presented arc-shape curved fracture surfaces which can be understood by statics consideration taking into account the maximum stress plane theory and the residual thermal stress. The strengths of non-annealed and annealed specimens are 34.4 MPa (350 kgf/cm 2 ) and 30.2 MPa (308 kgf/cm 2 ), respectively, expressed in terms of Weibull's 50 % fracture stresses. (author)

Foal Fractures: Osteochondral Fragmentation, Proximal Sesamoid Bone Fractures/Sesamoiditis, and Distal Phalanx Fractures.

Science.gov (United States)

Reesink, Heidi L

2017-08-01

Foals are susceptible to many of the same types of fractures as adult horses, often secondary to external sources of trauma. In addition, some types of fractures are specific to foals and occur routinely in horses under 1 year of age. These foal-specific fractures may be due to the unique musculoskeletal properties of the developing animal and may present with distinct clinical signs. Treatment plans and prognoses are tailored specifically to young animals. Common fractures not affecting the long bones in foals are discussed in this article, including osteochondral fragmentation, proximal sesamoid bone fractures/sesamoiditis, and distal phalanx fractures. Copyright © 2017 Elsevier Inc. All rights reserved.

Effect of ion implantation on thermal shock resistance of magnesia and glass

International Nuclear Information System (INIS)

Gurarie, V.N.; Williams, J.S.; Watt, A.J.

1995-01-01

Monocrystals of magnesia together with glass samples have been subjected to ion implantation prior to thermal shock testing in an impulse plasma of continuously varied intensity. Measurements of the separation between fragments have been used to estimate the surface temperature. Fracture and deformation characteristics of the surface layer are measured in ion implanted and unimplanted samples using optical and scanning electron microscopy. Implantation-induced near-surface damage is analysed by ion channeling using 2 MeV He + ions. Ion implantation is shown to modify the near-surface structure of magnesia samples by introducing damage, which makes crack initiation easier under thermal stresses. The fracture threshold and maximum crack density are shifted towards the lower temperature range. Ion implanted MgO crystals show a ten fold increase in surface crack density. An increased crack density results in a decreased degree of damage characterised by the depth of crack penetration. The thermal stress resistance parameter of glass samples is increased at relatively small doses and decreased at higher doses. The results suggest that crack density and the degree of fracture damage in brittle ceramics operating under thermal shock conditions can be effectively controlled by ion implantation which provides crack initiating defects in the near-surface region. 23 refs., 7 figs

X-231A demonstration of in-situ remediation of DNAPL compounds in low permeability media by soil fracturing with thermally enhanced mass recovery or reactive barrier destruction

International Nuclear Information System (INIS)

Siegrist, R.L.; Slack, W.W.; Houk, T.C.

1998-03-01

The overall goal of the program of activities is to demonstrate robust and cost-effective technologies for in situ remediation of DNAPL compounds in low permeability media (LPM), including adaptations and enhancements of conventional technologies to achieve improved performance for DNAPLs in LPM. The technologies sought should be potential for application at simple, small sites (e.g., gasoline underground storage tanks) as well as at complex, larger sites (e.g., DOE land treatment units). The technologies involved in the X-231A demonstration at Portsmouth Gaseous Diffusion Plant (PORTS) utilized subsurface manipulation of the LPM through soil fracturing with thermally enhanced mass recovery or horizontal barrier in place destruction. To enable field evaluation of these approaches, a set of four test cells was established at the X-231A land treatment unit at the DOE PORTS plant in August 1996 and a series of demonstration field activities occurred through December 1997. The principal objectives of the PORTS X-231A demonstration were to: determine and compare the operational features of hydraulic fractures as an enabling technology for steam and hot air enhanced soil vapor extraction and mass recovery, in situ interception and reductive destruction by zero valent iron, and in situ interception and oxidative destruction by potassium permanganate; determine the interaction of the delivered agents with the LPM matrix adjacent to the fracture and within the fractured zone and assess the beneficial modifications to the transport and/or reaction properties of the LPM deposit; and determine the remediation efficiency achieved by each of the technology strategies

Crack formation and crack propagation under multiaxial mechanical and thermal stresses. Proceedings

International Nuclear Information System (INIS)

1993-01-01

The 25th meeting of the DV Fracture Group was held on 16/17 February 1993 at Karlsruhe Technical University. The main topic, ''Crack formation and crack propagation under multiaxial mechanical and thermal stresses'', was discussed by five invited papers (by K.J. Miller, D. Loehe, H.A. Richard, W. Brocks, A. Brueckner-Foit) and 23 short papers. The other 21 papers were devoted to various domains of fracture mechanics, with emphasis on elastoplastic fracture mechanics. (orig./MM) [de

Role of Austenite in Brittle Fracture of Bond Region of Super Duplex Stainless Steel

Science.gov (United States)

Kitagawa, Yoshihiko; Ikeuchi, Kenji; Kuroda, Toshio

Weld simulation of heat-affected zone (HAZ) was performed to investigate the mechanism by which austenite affects the toughness of super duplex stainless steel. Thermal cycles of various peak temperatures in the range from 1373 K to 1673 K corresponding to the HAZ were applied to SAF2507 super duplex stainless steel specimens. Charpy impact test was carried out using the specimens after the weld simulation, and the fracture surfaces were observed by SEM using three-dimensionally reconstruction technique. Austenite content decreased with increasing the peak temperature when the peak temperature exceeded 1473 K and the impact value decreased with increasing the peak temperature and decreasing the austenite content. The thermal cycle of the peak temperature of 1673 K corresponding to weld bond region caused decreasing of austenite content which was 22% lower than that of the base metal. The ductile-brittle transition temperature was measured. As a result the temperature increased rapidly in the weld bond region, the peak temperature of which exceeded 1623 K by the grain growth of ferrite matrix occurring subsequently to the completely dissolution of austenite. The morphology of the fracture surfaces after impact testing at 77 K showed cleavage fracture of ferrite. The {100} orientations of cleavage fracture facets were measured using three-dimensional images of the fracture surfaces and the results were visualized as the orientation color maps. The results showed that there were cleavage fractures consisting of a few facets parallel to each other. It was considered that a few facets existed in one ferrite grain. It was concluded that Widmanstätten austenite divided the large fracture into smaller cleavage facets in a ferrite grain and then suppressed the degradation of bond toughness of duplex stainless steel.

Radial cracks and fracture mechanism of radially oriented ring 2:17 type SmCo magnets

International Nuclear Information System (INIS)

Tian Jianjun; Pan Dean; Zhou Hao; Yin Fuzheng; Tao Siwu; Zhang Shengen; Qu Xuanhui

2009-01-01

Radially oriented ring 2:17 type SmCo magnets have different microstructure in the radial direction (easy magnetization) and axial direction (hard magnetization). The structure of the cross-section in radial direction is close-packed atomic plane, which shows cellular microstructure. The microstructure of the cross-section in axial direction consists of a mixture of rhombic microstructure and parallel lamella phases. So the magnets have obvious anisotropy of thermal expansion in different directions. The difference of the thermal expansion coefficients reaches the maximum value at 830-860 deg. C, which leads to radial cracks during quenching. The magnets have high brittlement because there are fewer slip systems in crystal structure. The fracture is brittle cleavage fracture.

Gradient effects on the fracture of inhomogeneous materials

Energy Technology Data Exchange (ETDEWEB)

Becker, Terrence Lee [Univ. of California, Berkeley, CA (United States)

2000-05-01

Functionally Graded Materials (FGMs) have a spatial variation in physical properties that can be tailored to meet the needs of a specific application and/or to minimize internal stresses arising from thermal and elastic mismatch. Modeling these materials as inhomogeneous continua allows assessment of the role of the gradient without requiring detailed knowledge of the microstructure. Motivated by the relative difficulty of obtaining analytical solutions to boundary value problems for FGMs, an accurate finite-element code is developed for obtaining numerical planar and axisymmetric linear thermoelastic solutions. In addition an approximate analytical technique for mapping homogeneous-modulus solutions to those for FGMs is assessed and classes of problems to which it applies accurately are identified. The fracture mechanics analysis of FGMs can be characterized by the classic stress intensities, KI and KII, but there has been scarce progress in understanding the role of the modulus gradient in determining fracture initiation and propagation. To address this question, a statistical fracture model is used to correlate near-tip stresses with brittle fracture initiation behavior. This describes the behavior of a material experiencing fracture initiation away from the crack tip. Widely dispersed zones of fracture initiation sites are expected. Finite-length kinks are analyzed to describe the crack path for continuous crack growth. For kink lengths much shorter than the gradient dimension, a parallel stress term describes the deviation of the kinking angle from that for homogeneous materials. For longer kinks there is a divergence of the kink angle predicted by the maximum energy release rate and the pure opening mode criteria.

Acetabular Fracture

Directory of Open Access Journals (Sweden)

Chad Correa

2017-09-01

Full Text Available History of present illness: A 77-year-old female presented to her primary care physician (PCP with right hip pain after a mechanical fall. She did not lose consciousness or have any other traumatic injuries. She was unable to ambulate post-fall, so X-rays were ordered by her PCP. Her X-rays were concerning for a right acetabular fracture (see purple arrows, so the patient was referred to the emergency department where a computed tomography (CT scan was ordered. Significant findings: The non-contrast CT images show a minimally displaced comminuted fracture of the right acetabulum involving the acetabular roof, medial and anterior walls (red arrows, with associated obturator muscle hematoma (blue oval. Discussion: Acetabular fractures are quite rare. There are 37 pelvic fractures per 100,000 people in the United States annually, and only 10% of these involve the acetabulum. They occur more frequently in the elderly totaling an estimated 4,000 per year. High-energy trauma is the primary cause of acetabular fractures in younger individuals and these fractures are commonly associated with other fractures and pelvic ring disruptions. Fractures secondary to moderate or minimal trauma are increasingly of concern in patients of advanced age.1 Classification of acetabular fractures can be challenging. However, the approach can be simplified by remembering the three basic types of acetabular fractures (column, transverse, and wall and their corresponding radiologic views. First, column fractures should be evaluated with coronally oriented CT images. This type of fracture demonstrates a coronal fracture line running caudad to craniad, essentially breaking the acetabulum into two halves: a front half and a back half. Secondly, transverse fractures should be evaluated by sagittally oriented CT images. By definition, a transverse fracture separates the acetabulum into superior and inferior halves with the fracture line extending from anterior to posterior

Report on the Fracture Analysis of HfB(sub 2)-SiC and ZrB(sub 2)-SiC Composites; TOPICAL

International Nuclear Information System (INIS)

MECHOLSKY, JR. JOHN J.

2001-01-01

Hafnium diboride-silicon carbide (HS) and zirconium diboride-silicon carbide (ZS) composites are potential materials for high temperature, thermal shock applications such as for components on re-entry vehicles. In order to establish material constants necessary for evaluation of in situ fracture, bars fractured in four-point flexure were examined using fractographic principles. The fracture toughness was determined from measurements of the critical crack sizes and the strength values and the crack branching constants were established to use in forensic fractography for future in-flight tests. The fracture toughnesses range from about 13 MPam(sup 1/2) at room temperature to about 6 MPam(sup 1/2) at 1400 C for ZrB(sub 2)-Sic composites and from about 13 MPam(sup 1/2) at room temperature to about 4 MPam(sup 1/2) at 1400 C for HfB(sub 2)-SiC composites. Thus, the toughnesses of either the HS or ZS composites have the potential for use in thermal shock applications. Processing and manufacturing defects limited the strength of the test bars. However, examination of the microstructure on the fracture surfaces shows that the processing of these composites can be improved. There is potential for high toughness composites with high strength to be used in thermal shock conditions if the processing and handling are controlled

Associations of early premenopausal fractures with subsequent fractures vary by sites and mechanisms of fractures.

Science.gov (United States)

Honkanen, R; Tuppurainen, M; Kroger, H; Alhava, E; Puntila, E

1997-04-01

In a retrospective population-based study we assessed whether and how self-reported former fractures sustained at the ages of 20-34 are associated with subsequent fractures sustained at the ages of 35-57. The 12,162 women who responded to fracture questions of the baseline postal enquiry (in 1989) of the Kuopio Osteoporosis Study, Finland formed the study population. They reported 589 former and 2092 subsequent fractures. The hazard ratio (HR), with 95% confidence interval (CI), of a subsequent fracture was 1.9 (1.6-2.3) in women with the history of a former fracture compared with women without such a history. A former low-energy wrist fracture was related to subsequent low-energy wrist [HR = 3.7 (2.0-6.8)] and high-energy nonwrist [HR = 2.4 (1.3-4.4)] fractures, whereas former high-energy nonwrist fractures were related only to subsequent high-energy nonwrist [HR = 2.8 (1.9-4.1)] but not to low-energy wrist [HR = 0.7 (0.3-1.8)] fractures. The analysis of bone mineral density (BMD) data of a subsample of premenopausal women who underwent dual x-ray absorptiometry (DXA) during 1989-91 revealed that those with a wrist fracture due to a fall on the same level at the age of 20-34 recorded 6.5% lower spinal (P = 0.140) and 10.5% lower femoral (P = 0.026) BMD than nonfractured women, whereas the corresponding differences for women with a former nonwrist fracture due to high-energy trauma were -1.8% (P = 0.721) and -2.4% (P = 0. 616), respectively. Our results suggest that an early premenopausal, low-energy wrist fracture is an indicator of low peak BMD which predisposes to subsequent fractures in general, whereas early high-energy fractures are mainly indicators of other and more specific extraskeletal factors which mainly predispose to same types of subsequent fractures only.

Fracturing of simulated high-level waste glass in canisters

International Nuclear Information System (INIS)

Peters, R.D.; Slate, S.C.

1981-09-01

Waste-glass castings generated from engineering-scale developmental processes at the Pacific Northwest Laboratory are generally found to have significant levels of cracks. The causes and extent of fracturing in full-scale canisters of waste glass as a result of cooling and accidental impact are discussed. Although the effects of cracking on waste-form performance in a repository are not well understood, cracks in waste forms can potentially increase leaching surface area. If cracks are minimized or absent in the waste-glass canisters, the potential for radionuclide release from the canister package can be reduced. Additional work on the effects of cracks on leaching of glass is needed. In addition to investigating the extent of fracturing of glass in waste-glass canisters, methods to reduce cracking by controlling cooling conditions were explored. Overall, the study shows that the extent of glass cracking in full-scale, passively-cooled, continuous melting-produced canisters is strongly dependent on the cooling rate. This observation agrees with results of previously reported Pacific Northwest Laboratory experiments on bench-scale annealed canisters. Thus, the cause of cracking is principally bulk thermal stresses. Fracture damage resulting from shearing at the glass/metal interface also contributes to cracking, more so in stainless steel canisters than in carbon steel canisters. This effect can be reduced or eliminated with a graphite coating applied to the inside of the canister. Thermal fracturing can be controlled by using a fixed amount of insulation for filling and cooling of canisters. In order to maintain production rates, a small amount of additional facility space is needed to accomodate slow-cooling canisters. Alternatively, faster cooling can be achieved using the multi-staged approach. Additional development is needed before this approach can be used on full-scale (60-cm) canisters

Thermal Fatigue Behavior of Air-Plasma Sprayed Thermal Barrier Coating with Bond Coat Species in Cyclic Thermal Exposure

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Ungyu Paik

2013-08-01

Full Text Available The effects of the bond coat species on the delamination or fracture behavior in thermal barrier coatings (TBCs was investigated using the yclic thermal fatigue and thermal-shock tests. The interface microstructures of each TBC showed a good condition without cracking or delamination after flame thermal fatigue (FTF for 1429 cycles. The TBC with the bond coat prepared by the air-plasma spray (APS method showed a good condition at the interface between the top and bond coats after cyclic furnace thermal fatigue (CFTF for 1429 cycles, whereas the TBCs with the bond coats prepared by the high-velocity oxygen fuel (HVOF and low-pressure plasma spray (LPPS methods showed a partial cracking (and/or delamination and a delamination after 780 cycles, respectively. The TBCs with the bond coats prepared by the APS, HVOF and LPPS methods were fully delaminated (>50% after 159, 36, and 46 cycles, respectively, during the thermal-shock tests. The TGO thickness in the TBCs was strongly dependent on the both exposure time and temperature difference tested. The hardness values were found to be increased only after the CFTF, and the TBC with the bond coat prepared by the APS showed the highest adhesive strength before and after the FTF.

On the evaluation of steam assisted gravity drainage in naturally fractured oil reservoirs

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Seyed Morteza Tohidi Hosseini

2017-06-01

Full Text Available Steam Assisted Gravity Drainage (SAGD as a successful enhanced oil recovery (EOR process has been applied to extract heavy and extra heavy oils. Huge amount of global heavy oil resources exists in carbonate reservoirs which are mostly naturally fractured reservoirs. Unlike clastic reservoirs, few studies were carried out to determine the performance of SAGD in carbonate reservoirs. Even though SAGD is a highly promising technique, several uncertainties and unanswered questions still exist and they should be clarified for expansion of SAGD methods to world wide applications especially in naturally fractured reservoirs. In this communication, the effects of some operational and reservoir parameters on SAGD processes were investigated in a naturally fractured reservoir with oil wet rock using CMG-STARS thermal simulator. The purpose of this study was to investigate the role of fracture properties including fracture orientation, fracture spacing and fracture permeability on the SAGD performance in naturally fractured reservoirs. Moreover, one operational parameter was also studied; one new well configuration, staggered well pair was evaluated. Results indicated that fracture orientation influences steam expansion and oil production from the horizontal well pairs. It was also found that horizontal fractures have unfavorable effects on oil production, while vertical fractures increase the production rate for the horizontal well. Moreover, an increase in fracture spacing results in more oil production, because in higher fracture spacing model, steam will have more time to diffuse into matrices and heat up the entire reservoir. Furthermore, an increase in fracture permeability results in process enhancement and ultimate recovery improvement. Besides, diagonal change in the location of injection wells (staggered model increases the recovery efficiency in long-term production plan.

Ductile fracture behavior of cast structure containing voids

Energy Technology Data Exchange (ETDEWEB)

Gilles, Ph.; Migne, C. [FRAMATOME ANP, 92 - Paris-La-Defence (France); Chapuliot, S. [CEA Saclay, 91 - Gif-sur-Yvette (France). Dept. de Mecanique et de Technologie

2001-07-01

In pressurized water reactors, the primary loop contains cast-piping components made of duplex stainless steel. Due to the presence of ferrite, such steels are susceptible to thermal aging embrittlement, which decrease their fracture resistance. The cast process induces shrinkage cavities, therefore all these components are submitted to liquid penetrant examination and all surface defects are repaired. EDF, CEA and Framatome have conducted experimental and analytical analysis of fatigue and fracture behavior of aged cast stainless steel structures containing shrinkage cavities. The present study considers only ductile tearing and is based on specimen test results and a fracture mechanics model of the interaction between shrinkage cavities. The experimental results presented here show that large groups of shrinkage cavities have almost no influence on the global behavior of the structure. Only for the specimen with the largest reduction of area, a significant reduction of strength has been registered. Using elementary fracture mechanics models, it has been evidenced that failure mechanism of structures containing shrinkage cavities consists in 3 phases: local initiation, macro-crack formation by coalescence and failure by crack instability or collapse depending if J resistance is low or not. No significant changes in global behavior appear in the first phase. (A.C.)

Ductile fracture behavior of cast structure containing voids

International Nuclear Information System (INIS)

Gilles, Ph.; Migne, C.; Chapuliot, S.

2001-01-01

In pressurized water reactors, the primary loop contains cast-piping components made of duplex stainless steel. Due to the presence of ferrite, such steels are susceptible to thermal aging embrittlement, which decrease their fracture resistance. The cast process induces shrinkage cavities, therefore all these components are submitted to liquid penetrant examination and all surface defects are repaired. EDF, CEA and Framatome have conducted experimental and analytical analysis of fatigue and fracture behavior of aged cast stainless steel structures containing shrinkage cavities. The present study considers only ductile tearing and is based on specimen test results and a fracture mechanics model of the interaction between shrinkage cavities. The experimental results presented here show that large groups of shrinkage cavities have almost no influence on the global behavior of the structure. Only for the specimen with the largest reduction of area, a significant reduction of strength has been registered. Using elementary fracture mechanics models, it has been evidenced that failure mechanism of structures containing shrinkage cavities consists in 3 phases: local initiation, macro-crack formation by coalescence and failure by crack instability or collapse depending if J resistance is low or not. No significant changes in global behavior appear in the first phase. (A.C.)

Numerical Fracture Analysis of Cryogenically Treated Alloy Steel Weldments

International Nuclear Information System (INIS)

Rasool Mohideen, S; Thamizhmanii, S; Muhammed Abdul Fatah, M.M; Saidin, W. Najmuddin W.

2016-01-01

Cryogenic treatment is being used commercially in the industries in the last two decades for improving the life of many engineering component such as bearings and cutting tools. Though their influence in improving the wear resistance of tool materials is well established, the effect of treatment on weldments is not much investigated. In the present work, a two dimensional finite element analysis was carried out on the compact tension specimen model for simulating the treatment process and to study the fracture behaviour. The weldments were modelled by thermo- mechanical coupled field analysis for simulating he temperature distribution in the model during weld pool cooling and introducing thermal stresses due to uneven contraction and cooling. The model was subjected to cryogenic treatment by adopting radiation effect. The fracture analysis was carried out using Rice's J- Integral approach. The analysis produced a similar outcome of experimental results i.e. Increase in the fracture toughness of the specimen after cryogenic treatment in the heat affected zone of weldment. (paper)

Fracture toughness study of new Zr-based Be-bearing bulk metallic glasses

OpenAIRE

Kim, C. Paul; Suh, Jin-Yoo; Wiest, Aaron; Lind, Mary Laura; Conner, R. Dale; Johnson, William L.

2009-01-01

Three new compositional variants of the Zr–Ti–Be–LTM (late transition metal) family of metallic glasses are discussed. Thermal stability, ΔT = T_x−T_g, was increased from 82 °C for Zr_(41.2)Ti_(13.8)Cu_(12.5)Ni_(10)Be_(22.5) (Viterloy 1) to 141 °C for Zr_(44)Ti_(11)Cu_(20)Be_(25). It is found that fracture toughness is the most distinguishing parameter characterizing the alloys in contrast to other mechanical properties. Quaternary alloys consistently had fracture toughness values exceeding 8...

Heat treatments and low temperature fracture toughness of a Ti-6A1-4V alloy

International Nuclear Information System (INIS)

Nagai, K.; Hiraga, K.; Ishikawa, K.; Ogata, T.

1984-01-01

Titanium alloy is one of the reliable structural materials for cryogenic use owing to its high strength, high specific strength and low thermal conductivity. Heat treatment is one method of controlling the normally poor fracture toughness of this alloy at ambient temperature. However, there have been few attempts to improve the low temperature fracture toughness by heat treatment. This study was conducted to elucidate the effects of heat treatments on the low temperature fracture toughness in a Ti-6A1-4V alloy. The effects of the heat treatments were as follows: the beta treatment was a very feasible method to improve the low temperature fracture properties; the alpha+beta treatment was favorable for the increment in the low temperature ductility but did not largely improve the fracture toughness; the double treatment yielded good ductility but was not useful for improving the fracture toughness

Mechanical strength and analysis of fracture of titanium joining submitted to laser and tig welding

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Ana Cláudia Gabrielli Piveta

2012-12-01

Full Text Available This study compared the tensile strength and fracture mechanism of tungsten inert gas (TIG welds in cylindrical rods of commercially pure titanium (cp Ti with those of laser welds and intact samples. Thirty dumbbell-shaped samples were developed by using brass rods as patterns. The samples were invested in casings, subjected to thermal cycles, and positioned in a plasma arc welding machine under argon atmosphere and vacuum, and titanium was injected under vacuum/pressure. The samples were X-rayed to detect possible welding flaws and randomly assigned to three groups to test the tensile strength and the fracture mechanism: intact, laser welding, and TIG welding. The tensile test results were investigated using ANOVA, which indicated that the samples were statistically similar. The fracture analysis showed that the cpTi samples subjected to laser welding exhibited brittle fracture and those subjected to TIG welding exhibited mixed brittle/ductile fracture with a predominance of ductile fracture with the presence of microcavities and cleavage areas. Intact samples presented the characteristic straightening in the fracture areas, indicating the ductility of the material.

Ballistic fractures: indirect fracture to bone.

Science.gov (United States)

Dougherty, Paul J; Sherman, Don; Dau, Nathan; Bir, Cynthia

2011-11-01

Two mechanisms of injury, the temporary cavity and the sonic wave, have been proposed to produce indirect fractures as a projectile passes nearby in tissue. The purpose of this study is to evaluate the temporal relationship of pressure waves using strain gauge technology and high-speed video to elucidate whether the sonic wave, the temporary cavity, or both are responsible for the formation of indirect fractures. Twenty-eight fresh frozen cadaveric diaphyseal tibia (2) and femurs (26) were implanted into ordnance gelatin blocks. Shots were fired using 9- and 5.56-mm bullets traversing through the gelatin only, passing close to the edge of the bone, but not touching, to produce an indirect fracture. High-speed video of the impact event was collected at 20,000 frames/s. Acquisition of the strain data were synchronized with the video at 20,000 Hz. The exact time of fracture was determined by analyzing and comparing the strain gauge output and video. Twenty-eight shots were fired, 2 with 9-mm bullets and 26 with 5.56-mm bullets. Eight indirect fractures that occurred were of a simple (oblique or wedge) pattern. Comparison of the average distance of the projectile from the bone was 9.68 mm (range, 3-20 mm) for fractured specimens and 15.15 mm (range, 7-28 mm) for nonfractured specimens (Student's t test, p = 0.036). In this study, indirect fractures were produced after passage of the projectile. Thus, the temporary cavity, not the sonic wave, was responsible for the indirect fractures.

Hydraulic fracture propagation modeling and data-based fracture identification

Science.gov (United States)

Zhou, Jing

Successful shale gas and tight oil production is enabled by the engineering innovation of horizontal drilling and hydraulic fracturing. Hydraulically induced fractures will most likely deviate from the bi-wing planar pattern and generate complex fracture networks due to mechanical interactions and reservoir heterogeneity, both of which render the conventional fracture simulators insufficient to characterize the fractured reservoir. Moreover, in reservoirs with ultra-low permeability, the natural fractures are widely distributed, which will result in hydraulic fractures branching and merging at the interface and consequently lead to the creation of more complex fracture networks. Thus, developing a reliable hydraulic fracturing simulator, including both mechanical interaction and fluid flow, is critical in maximizing hydrocarbon recovery and optimizing fracture/well design and completion strategy in multistage horizontal wells. A novel fully coupled reservoir flow and geomechanics model based on the dual-lattice system is developed to simulate multiple nonplanar fractures' propagation in both homogeneous and heterogeneous reservoirs with or without pre-existing natural fractures. Initiation, growth, and coalescence of the microcracks will lead to the generation of macroscopic fractures, which is explicitly mimicked by failure and removal of bonds between particles from the discrete element network. This physics-based modeling approach leads to realistic fracture patterns without using the empirical rock failure and fracture propagation criteria required in conventional continuum methods. Based on this model, a sensitivity study is performed to investigate the effects of perforation spacing, in-situ stress anisotropy, rock properties (Young's modulus, Poisson's ratio, and compressive strength), fluid properties, and natural fracture properties on hydraulic fracture propagation. In addition, since reservoirs are buried thousands of feet below the surface, the

Microstructure analysis and damage patterns of thermally cycled Ti–49.7Ni (at.%) wires

International Nuclear Information System (INIS)

Karhu, Marjaana; Lindroos, Tomi

2012-01-01

Long-term behaviour and fatigue endurance are the key issues in the utilization of SMA actuators, but systematic research work is still needed in this field. This study concentrates on the effects of three major design parameters on the long-term behaviour of binary Ti–49.7Ni-based actuators: the effect of the temperature interval used on thermal cycling, the effect of the stress level used and the effect of the heat-treatment state of the wire used. The long-term behaviour of the wires was studied in a custom-built fatigue test frame in which the wires were thermally cycled under a constant stress level. Before the fatigue testing, a series of heat treatments was carried out to generate optimal actuator properties for the wires. This paper concentrates on the systematic fractographic analysis of the fatigue fractured Ti–49.7Ni wires. The aim was to discover the relationships between the macro-scale behaviour and the microstructural changes of the material. During thermal cycling the surfaces of the Ti–49.7Ni wires were examined with an optical microscope. Clear connections between the detected surface defects and fracture nucleation sites were not established. Multiple cracks were initiated and grew during thermal cycling. SEM examinations showed that the fracture surfaces can be divided into different and separate zones: a smooth surface region with radial marks indicating the fatigue crack propagation area, a rougher ductile fracture surface region area and the roughest surface region on the interface of these two surfaces. It was detected that the size of the crack propagation area is related to the fatigue lives of the thermally cycled wires. Surface cracking and subsequent crack growth proved to be responsible for the accumulation of fatigue damage in the studied wires. It was detected from the fracture surface cross-sections that cracks were not initiated at the oxide layer. The major factor for nucleating the surface cracking and then shortening the

Fatigue and fracture of fibre metal laminates

CERN Document Server

Alderliesten, René

2017-01-01

This book contributes to the field of hybrid technology, describing the current state of knowledge concerning the hybrid material concept of laminated metallic and composite sheets for primary aeronautical structural applications. It is the only book to date on fatigue and fracture of fibre metal laminates (FMLs). The first section of the book provides a general background of the FML technology, highlighting the major FML types developed and studied over the past decades in conjunction with an overview of industrial developments based on filed patents. In turn, the second section discusses the mechanical response to quasi-static loading, together with the fracture phenomena during quasi-static and cyclic loading. To consider the durability aspects related to strength justification and certification of primary aircraft structures, the third section discusses thermal aspects related to FMLs and their mechanical response to various environmental and acoustic conditions.

Effects of Heating Rate on the Dynamic Tensile Mechanical Properties of Coal Sandstone during Thermal Treatment

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Ming Li

2017-01-01

Full Text Available The effects of coal layered combustion and the heat injection rate on adjacent rock were examined in the process of underground coal gasification and coal-bed methane mining. Dynamic Brazilian disk tests were conducted on coal sandstone at 800°C and slow cooling from different heating rates by means of a Split Hopkinson Pressure Bar (SHPB test system. It was discovered that thermal conditions had significant effects on the physical and mechanical properties of the sandstone including longitudinal wave velocity, density, and dynamic linear tensile strength; as the heating rates increased, the thermal expansion of the sandstone was enhanced and the damage degree increased. Compared with sandstone at ambient temperature, the fracture process of heat-treated sandstone was more complicated. After thermal treatment, the specimen had a large crack in the center and cracks on both sides caused by loading; the original cracks grew and mineral particle cracks, internal pore geometry, and other defects gradually appeared. With increasing heating rates, the microscopic fracture mode transformed from ductile fracture to subbrittle fracture. It was concluded that changes in the macroscopic mechanical properties of the sandstone were result from changes in the composition and microstructure.

Heat induced fracturing of rock in an existing uniaxial stress field

International Nuclear Information System (INIS)

Mathis, J.; Stephansson, O.; Bjarnason, B.; Hakami, H.; Herdocia, A.; Mattila, U.; Singh, U.

1986-01-01

This study was initiated under the premise that it may be possible to determine the state of stress in the earth's crust by heat induced fracturing of the rock surrounding a borehole. The theory involved is superficially simple, involving the superposition of the stress field around a borehole due to the existing virgin stresses and the uniform stress field of thermally loaded rock as induced by a heater. Since the heat stress field is uniform, varying only in magnitude and gradient as a function of heater input, fracturing should be controlled by the non-uniform virgin stress field. To determine if the method was, in fact, feasible, a series of laboratory test were conducted. These tests consisted of physically loading center drilled cubes of rock, 0.3 m on a side, uniaxially from 0 to 25 MPa. The blocks were then thermally loaded with a nominally rated 3.7 kW heater until failure occurred. Results from these laboratory tests were then compared to analytical studies of the problem, i.e., finite element and discrete theoretical analysis. Overall, results were such that the method is likely eliminated as a stress measurement technique. The immediate development of a thermal compressive zone on the borehole wall overlaps the tensile zone created by the uniaxial stress field, forcing the failure is thus controlled largely by the power input of the heater, being retarded by the small compressive stresses genrated by the uniaxial stress field. This small retardation effect is of such low magnitude that the retardation effect is of such low magnitude that the fracture time is relatively insensitive to the local virgin stress field. (authors)

Crack assessment of pipe under combined thermal and mechanical load

International Nuclear Information System (INIS)

Song, Tae Kwang; Kim, Yun Jae

2009-01-01

In this paper, J-integral and transient C(t)-integral, which were key parameters in low temperature and high temperature fracture mechanics, under combined thermal and mechanical load were estimated via 3-dimensional finite element analyses. Various type of thermal and mechanical load, material hardening were considered to decrease conservatism in existing solutions. As a results, V-factor and redistribution time for combined thermal and mechanical load were proposed to calculate J-integral and C(t)-integral, respectively.

Distinguishing stress fractures from pathologic fractures: a multimodality approach

International Nuclear Information System (INIS)

Fayad, Laura M.; Kamel, Ihab R.; Kawamoto, Satomi; Bluemke, David A.; Fishman, Elliot K.; Frassica, Frank J.

2005-01-01

Whereas stress fractures occur in normal or metabolically weakened bones, pathologic fractures occur at the site of a bone tumor. Unfortunately, stress fractures may share imaging features with pathologic fractures on plain radiography, and therefore other modalities are commonly utilized to distinguish these entities. Additional cross-sectional imaging with CT or MRI as well as scintigraphy and PET scanning is often performed for further evaluation. For the detailed assessment of a fracture site, CT offers a high-resolution view of the bone cortex and periosteum which aids the diagnosis of a pathologic fracture. The character of underlying bone marrow patterns of destruction can also be ascertained along with evidence of a soft tissue mass. MRI, however, is a more sensitive technique for the detection of underlying bone marrow lesions at a fracture site. In addition, the surrounding soft tissues, including possible involvement of adjacent muscle, can be well evaluated with MRI. While bone scintigraphy and FDG-PET are not specific, they offer a whole-body screen for metastases in the case of a suspected malignant pathologic fracture. In this review, we present select examples of fractures that underscore imaging features that help distinguish stress fractures from pathologic fractures, since accurate differentiation of these entities is paramount. (orig.)

Double segmental tibial fractures - an unusual fracture pattern

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Bali Kamal

2012-02-01

Full Text Available 【Abstract】A case of a 50-year-old pedestrian who was hit by a bike and suffered fractures of both bones of his right leg was presented. Complete clinical and radiographic assessment showed double segmental fractures of the tibia and multisegmental fractures of the fibula. Review of the literature revealed that this fracture pattern was unique and only a single case was reported so far. Moreover, we discussed the possible mechanisms which can lead to such an injury. We also discussed the management of segmental tibial fracture and the difficulties encountered with them. This case was managed by modern osteosynthesis tech- nique with a pleasing outcome. Key words: Fracture, bone; Tibia; Fibula; Nails

Fracture coatings in Topopah Spring Tuff along drill hole wash

International Nuclear Information System (INIS)

Carlos, B.A.; Chipera, S.J.; Bish, D.L.

1994-01-01

Fracture-lining minerals are being studied as part of site characterization to determine the suitability of Yucca Mountain, Nevada as a potential high level nuclear waste repository. Fracture coatings in the Paintbrush Group provide information on potential flow paths above the water table both toward and away from the potential repository and provide information on the distribution of fracture-lining minerals needed to model thermal effects of waste emplacement. Fracture coatings within the predominantly non-zeolitic Paintbrush Group vary both with depth and laterally across Yucca Mountain, whereas fracture coatings in tuffs below the Paintbrush Group are related to the mineralogy of the tuffs and follow a consistent pattern of distribution with predominantly quartz, calcite, and manganese oxides in the devitrified intervals and mordenite and clinoptilolite in the zeolitic intervals. The zeolites stellerite and heulandite are more abundant in fractures in the Topopah Spring Tuff in drill holes USW G-1 and UE-25 a number-sign l, located along Drill Hole Wash (at the northern end of Yucca Mountain) than in core from other parts of Yucca Mountain. Buesch et al. (2) present evidence for a complex fault system along Drill Hole Wash. To investigate the possibility that the abundant fracture-lining zeolites in USW G-1 and UE-25 a number-sign 1 are related to the Drill Hole Wash fault, the Topopah Spring Tuff was examined in drill cores from USW UZ-14, USW G-1, USW NRG-7/7a, and UE-25 a number-sign l

Ankle fracture spur sign is pathognomonic for a variant ankle fracture.

Science.gov (United States)

Hinds, Richard M; Garner, Matthew R; Lazaro, Lionel E; Warner, Stephen J; Loftus, Michael L; Birnbaum, Jacqueline F; Burket, Jayme C; Lorich, Dean G

2015-02-01

The hyperplantarflexion variant ankle fracture is composed of a posterior tibial lip fracture with posterolateral and posteromedial fracture fragments separated by a vertical fracture line. This infrequently reported injury pattern often includes an associated "spur sign" or double cortical density at the inferomedial tibial metaphysis. The objective of this study was to quantitatively establish the association of the ankle fracture spur sign with the hyperplantarflexion variant ankle fracture. Our clinical database of operative ankle fractures was retrospectively reviewed for the incidence of hyperplantarflexion variant and nonvariant ankle fractures as determined by assessment of injury radiographs, preoperative advanced imaging, and intraoperative observation. Injury radiographs were then evaluated for the presence of the spur sign, and association between the spur sign and variant fractures was analyzed. The incidence of the hyperplantarflexion variant fracture among all ankle fractures was 6.7% (43/640). The spur sign was present in 79% (34/43) of variant fractures and absent in all nonvariant fractures, conferring a specificity of 100% in identifying variant fractures. Positive predictive value and negative predictive value were 100% and 99%, respectively. The ankle fracture spur sign was pathognomonic for the hyperplantarflexion variant ankle fracture. It is important to identify variant fractures preoperatively as patient positioning, operative approach, and fixation construct of variant fractures often differ from those employed for osteosynthesis of nonvariant fractures. Identification of the spur sign should prompt acquisition of advanced imaging to formulate an appropriate operative plan to address the variant fracture pattern. Level III, retrospective comparative study. © The Author(s) 2014.

Association of Ipsilateral Rib Fractures With Displacement of Midshaft Clavicle Fractures.

Science.gov (United States)

Stahl, Daniel; Ellington, Matthew; Brennan, Kindyle; Brennan, Michael

2017-04-01

To determine whether the presence of ipsilateral rib fractures affects the rate of a clavicle fracture being unstable (>100% displacement). A retrospective review from 2002-2013 performed at a single level 1 trauma center evaluated 243 midshaft clavicle fractures. Single Level 1 trauma center. These fractures were subdivided into those with ipsilateral rib fractures (CIR; n = 149) and those without ipsilateral rib fractures (CnIR; n = 94). The amount of displacement was measured on the initial injury radiograph and subsequent follow-up radiographs. Fractures were classified into either 100% displacement, based on anteroposterior radiographs. Ipsilateral rib fractures were recorded based on which number rib was fractured and the total number of fractured ribs. One hundred sixteen (78%) of the CIR group and 51 (54%) of the CnIR group were found to have >100% displacement at follow-up (P = 0.0047). Seventy-two percent of the CIR group demonstrated progression from 100% displacement of the fracture compared with only 54% of the CnIR group (P fracture to >100% was 4.08 (P = 0.000194) when ribs 1-4 were fractured and not significant for rib fractures 5-8 or 9-12. The presence of concomitant ipsilateral rib fractures significantly increases the rate of midshaft clavicle fractures being >100% displaced. In addition, a fracture involving the upper one-third of the ribs significantly increases the rate of the clavicle fracture being >100% displaced on early follow-up. Clavicle fractures with associated ipsilateral rib fractures tend to demonstrate an increased amount of displacement on follow-up radiographs compared with those without ipsilateral rib fractures. Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Deformation and velocity measurements at elevated temperature in a fractured 0.5 M block of tuff

International Nuclear Information System (INIS)

Blair, S.C.; Berge, P.A.

1996-01-01

This paper presents preliminary results of laboratory tests conducted on small block samples of Topopah Spring tuff, in support of the Yucca Mountain Site Characterization Project. The overall objective of these tests is to investigate the thermal-mechanical, thermal-hydrological, and thermal-chemical response of the rock to conditions similar to the near-field environment (NFE) of a potential nuclear waste repository. We present preliminary results of deformation and elastic wave velocity measurements on a 0.5-m-scale block of Topopah Spring tuff tested in uniaxial compression to 8.5 MPa and at temperatures to 85 degree C. The Young's modulus was found to be about 7 to 31 GPa for vertical measurements parallel to the stress direction across parts of the block containing no fractures or a few fractures, and 0.5 to 0.9 GPA for measurements across individual fractures, at ambient temperature and 8.5 MPa maximum stress. During stress cycles between 5 and 8.5 MPa, the deformation modulus values for the matrix with fractures were near 15-20 GPa at ambient temperature but dropped to about 10 GPa at 85 degree C. Compressional wave velocities were found to be about 3.6 to 4.7 km/s at ambient temperature and stress. After the stress was cycled, velocities dropped to values as low as 2.6 km/s in the south end of the block where vertical cracks developed. Heating the block to about 85 degree C raised velocities to as much as 5.6 km/s in the upper third of the block

Development of probabilistic fracture mechanics code PASCAL and user's manual

Energy Technology Data Exchange (ETDEWEB)

Shibata, Katsuyuki; Onizawa, Kunio [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Li, Yinsheng; Kato, Daisuke [Fuji Research Institute Corporation, Tokyo (Japan)

2001-03-01

As a part of the aging and structural integrity research for LWR components, a new PFM (Probabilistic Fracture Mechanics) code PASCAL (PFM Analysis of Structural Components in Aging LWR) has been developed since FY1996. This code evaluates the failure probability of an aged reactor pressure vessel subjected to transient loading such as PTS (Pressurized Thermal Shock). The development of the code has been aimed to improve the accuracy and reliability of analysis by introducing new analysis methodologies and algorithms considering the recent development in the fracture mechanics methodologies and computer performance. The code has some new functions in optimized sampling and cell dividing procedure in stratified Monte Carlo simulation, elastic-plastic fracture criterion of R6 method, extension analysis models in semi-elliptical crack, evaluation of effect of thermal annealing and etc. In addition, an input data generator of temperature and stress distribution time histories was also prepared in the code. Functions and performance of the code have been confirmed based on the verification analyses and some case studies on the influence parameters. The present phase of the development will be completed in FY2000. Thus this report provides the user's manual and theoretical background of the code. (author)

Failure mechanism for thermal fatigue of thermal barrier coating systems

Energy Technology Data Exchange (ETDEWEB)

Giolli, C.; Scrivani, A.; Rizzi, G. [Turbocoating S.p.A., Rubbiano di Solignano (Italy); Borgioli, F. [Firenze Univ., Sesto Fiorentino (Italy); Bolelli, G.; Lusvarghi, L. [Univ. di Modena e Reggio Emilia, Modena (Italy)

2008-07-01

High temperature thermal fatigue causes the failure of Thermal Barrier Coating (TBC) systems. Due to the difference in thickness and microstructure between thick TBCs and traditional thin TBCs, they cannot be assumed a-priori to possess the same failure mechanisms. Thick TBCs, consisting of a CoNiCrAlY bond coat and Yttria Partially Stabilised Zirconia top coat with different values of porosity, were produced by Air Plasma Spray. Thermal fatigue resistance limit of TBCs was tested by Furnace Cycling Tests (FCT) according to the specifications of an Original Equipment Manufacturer (OEM). TBC systems were analyzed before and after FCT. The morphological and chemical evolution of CoNiCrAlY/TGO microstructure was studied. Sintering effect, residual stress, phase transformation and fracture toughness were evaluated in the ceramic Top Coat. All the tested samples passed FCT according to the specification of an important OEM. Thermal fatigue resistance increases with the amount of porosity in the top coat. The compressive in-plane stresses increase in the TBC systems after thermal cycling, nevertheless the increasing rate has a trend contrary to the porosity level of top coat. The data suggest that the spallation happens at the TGO/Top Coat interface. The failure mechanism of thick TBCs subjected to thermal fatigue was eventually found to be similar to the failure mechanism of thin TBC systems made by APS. (orig.)

Thermal theory of autowave processes in low-temperature solid-phase radiochemical reactions

International Nuclear Information System (INIS)

Barelko, V.V.; Barkalov, I.M.; Vaganov, D.A.; Zanin, A.M.; Kiryukhin, D.P.

1982-01-01

A new phenomenon in radiation cryochemistry concerning the class of autowave processes was previously discovered. It was observed in halogenation and hydrohalogenation of hydrocarbons and consisted of spontaneous, laminar propagation of a chemical transformation wave based on a frozen mixture of reagents previously irradiated with 60 Co γ-rays. The effect of the positive inverse correlation between the chemical conversion and brittle fracture of a solid sample of reagents is the phenomenological basis of the phenomenon; formation of fractures triggers a reactive process which takes place on their active surface (or in the layer adjacent to it), and the chemical reaction, in turn, stimulates the subsequent development of the process of decomposition. As a result, a single brittle fracture and chemical conversion wave which moves along the solid sample arises. Different mechanisms of generation of fracture surfaces under the effect of the reaction are possible. A difference in the densities of the initial reagents and the products of the reaction could be one of the causes of brittle fracture, and the thermal stresses induced by the exothermicity of the chemical processes could be another cause. The present work concerns the analysis of the features of the wave process which occurs based on the second, thermal mechanism. The analysis was conducted within the framework of a phenomenological approach which does not require specific definition of the nature of the chemical activation of the system during its brittle fracture

Lateral extrusion of a thermally weakened pluton overburden (Campiglia Marittima, Tuscany)

Science.gov (United States)

Vezzoni, Simone; Rocchi, Sergio; Dini, Andrea

2017-10-01

The ascent and emplacement of magmas in the upper crust modify the local pre-existing thermal and rheological settings. Such changes have important effects in producing anomalous structures, mass extrusion, rock fracturing, and in some conditions, hydrothermal mineralizations. In the Campiglia Marittima area, detailed field mapping led to the reconstruction of a local deformation history that overlaps, chronologically and spatially, with regional extension. This local deformation was triggered at the Miocene-Pliocene boundary by the intrusion of a monzogranitic pluton beneath a carbonate sedimentary sequence. The emplacement of the pluton produced a perturbation in the rheological behaviour of the carbonate host rocks, producing transient ductile conditions in the very shallow crust. The carbonate rocks were thermally weakened and flowed laterally, accumulating downslope of the pluton roof, mainly toward the east. As the thermal anomaly was decaying, the brittle-ductile boundary moved progressively back towards the pluton, and large tension gash-shaped volumes of fractured marble were generated. These fractured volumes were exploited by rising hydrothermal fluids generating sigmoidal skarn bodies and ore shoots. This work presents the Campiglia Marittima case study as a prime example of structural interference between regional extensional structures and local, lateral mass extrusion in a transient ductile rheological regime triggered by pluton emplacement.

Orientation dependence of the thermal fatigue of nickel alloy single crystals

Energy Technology Data Exchange (ETDEWEB)

Dul' nev, R A; Svetlov, I L; Bychkov, N G; Rybina, T V; Sukhanov, N N

1988-11-01

The orientation dependence of the thermal stability and the thermal fatigue fracture characteristics of single crystals of MAR-M200 nickel alloy are investigated experimentally using X-ray diffraction analysis and optical and scanning electron microscopy. It is found that specimens with the 111-line orientation have the highest thermal stability and fatigue strength. Under similar test conditions, the thermal fatigue life of single crystals is shown to be a factor of 1.5-2 higher than that of the directionally solidified and equiaxed alloys. 6 references.

Flow characteristics through a single fracture of artificial fracture system

International Nuclear Information System (INIS)

Park, Byoung Yoon; Bae, Dae Seok; Kim, Chun Soo; Kim, Kyung Su; Koh, Young Kwon; Jeon, Seok Won

2001-04-01

Fracture flow in rock masses is one of the most important issues in petroleum engineering, geology, and hydrogeology. Especially, in case of the HLW disposal, groundwater flow in fractures is an important factor in the performance assessment of the repository because the radionuclides move along the flowing groundwater through fractures. Recently, the characterization of fractures and the modeling of fluid flow in fractures are studied by a great number of researchers. Among those studies, the hydraulic behavior in a single fracture is one of the basic issues for understanding of fracture flow in rockmass. In this study, a fluid flow test in the single fracture made of transparent epoxy replica was carried out to obtain the practical exponent values proposed from the Cubic law and to estimate the flow rates through a single fracture. Not only the relationship between flow rates and the geometry of fracture was studied, but also the various statistical parameters of fracture geometry were compared to the effective transmissivity data obtained from computer simulation.

Fracture mechanics assessment of surface and sub-surface cracks in the RPV under non-symmetric PTS loading

Energy Technology Data Exchange (ETDEWEB)

Keim, E; Shoepper, A; Fricke, S [Siemens AG Unternehmensbereich KWU, Erlangen (Germany)

1997-09-01

One of the most severe loading conditions of a reactor pressure vessel (rpv) under operation is the loss of coolant accident (LOCA) condition. Cold water is injected through nozzles in the downcomer of the rpv, while the internal pressure may remain at a high level. Complex thermal hydraulic situations occur and the fluid and downcomer temperatures as well as the fluid to wall heat transfer coefficient at the inner surface are highly non-linear. Due to this non-symmetric conditions, the problem is investigated by three-dimensional non-linear finite element analyses, which allow for an accurate assessment of the postulated flaws. Transient heat transfer analyses are carried out to analyze the effect of non-symmetrical cooling of the inner surface of the pressure vessel. In a following uncoupled stress analysis the thermal shock effects for different types of defects, surface flaws and sub-surface flaws are investigated for linear elastic and elastic-plastic material behaviour. The obtained fracture parameters are calculated along the crack fronts. By a fast fracture analysis the fracture parameters at different positions along the crack front are compared to the material resistance. Safety margins are pointed out in an assessment diagram of the fracture parameters and the fracture resistance versus the transient temperature at the crack tip position. (author). 4 refs, 10 figs.

Hydrogeologic characterization of a fractured granitic rock aquifer, Raymond, California

Energy Technology Data Exchange (ETDEWEB)

Cohen, Andrew J.B. [Univ. of California, Berkeley, CA (United States)

1993-10-01

The hydrogeologic properties of a shallow, fractured granitic rock aquifer in the foothills of the Sierra Nevada, California were investigated via the analysis of borehole geophysical logs and pumping tests. The drawdowns produced during these tests are not indicative of any simple conceptual aquifer model, and borehole logs show that the granite is intensely fractured. These observations are suggestive of a complex fracture-flow geometry which is extremely difficult to decipher. However, through the measurement of orientations of individual subsurface fractures from acoustic televiewer logs, and correlation between particular fractures and electrical resistivity and thermal-pulse flowmeter logs, it was found that the aquifer is, in general, comprised of two subhorizontal and nearly parallel zones of unloading fractures. Downhole flowmeter measurements taken in several wells provide further evidence for the inferred dual-layer structure of the aquifer, as well as yield quantitative measures of the contribution of flow from each zone. Analysis of drawdowns in pumped wells reveals that there are zones of relatively high transmissivity immediately around them. It was found that these properties, as well as a nearby zone of lower transmissivity, can account for their observed drawdowns. A numerical model was constructed to test whether these major heterogeneities could also account for the drawdowns in observation wells. This stepwise analysis of both the geophysical and hydrological data resulted in the formulation of a conceptual model of the aquifer which is consistent with observations, and which can account for its behavior when subjected to pumping.

A Rare Nasal Bone Fracture: Anterior Nasal Spine Fracture

Directory of Open Access Journals (Sweden)

Egemen Kucuk

2014-04-01

Full Text Available Anterior nasal spine fractures are a quite rare type of nasal bone fractures. Associated cervical spine injuries are more dangerous than the nasal bone fracture. A case of the anterior nasal spine fracture, in a 18-year-old male was presented. Fracture of the anterior nasal spine, should be considered in the differential diagnosis of the midface injuries and also accompanying cervical spine injury should not be ignored.

Flaw evaluation of thermally aged cast stainless steel in light-water reactor applications

International Nuclear Information System (INIS)

Lee, S.; Kuo, P.T.; Wichman, K.; Chopra, O.

1997-01-01

Cast stainless steel may be used in the fabrication of the primary loop piping, fittings, valve bodies, and pump casings in light-water reactors. However, this material is subject to embrittlement due to thermal aging at the reactor temperature, that is 290 o C (550 o F). The Argonne National Laboratory (ANL) recently completed a research program and the results indicate that the lower-bound fracture toughness of thermally aged cast stainless steel is similar to that of submerged arc welds (SAWs). Thus, the US Nuclear Regulatory Commission (NRC) staff has accepted the use of SAW flaw evaluation procedures in IWB-3640 of Section XI of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code to evaluate flaws in thermally aged cast stainless steel for a license renewal evaluation. Alternatively, utilities may estimate component-specific fracture toughness of thermally aged cast stainless steel using procedures developed at ANL for a case-by-case flaw evaluation. (Author)

Experimental investigation of transient thermoelastic effects in dynamic fracture

International Nuclear Information System (INIS)

Rittel, D.

1997-01-01

Thermoelastic effects in fracture are generally considered to be negligible at the benefit of the conversion of plastic work into heat. For the case of dynamic crack initiation, the experimental and theoretical emphasis has been put on the temperature rise associated with crack-tip plasticity. Nevertheless, earlier experimental work with polymers has shown that thermoelastic cooling precedes the temperature rise at the tip of a propagating crack (Fuller et al., 1975). Transient thermoelastic effects at the tip of a dynamically loaded crack have been theoretically assessed and shown to be significant when thermal conductivity is initially neglected. However, the fundamental question of the relation between crack initiation and thermal fields, both of transient nature, is still open. In this paper, we present an experimental investigation of the thermoelastic effect at the tip of fatigue cracks subjected to mixed-mode (dominant mode 1) dynamic loading. The material is commercial polymethylmethacrylate as an example of 'brittle' material. The applied loads, crack-tip temperatures and fracture time are simultaneously monitored to provide a more complete image of dynamic crack initiation. The corresponding evolution of the stress intensity factors is calculated by a hybrid-experimental numerical model. The results show that substantial crack-tip cooling develops initially to an extent which corroborates theoretical estimates. This effect is followed by a temperature rise. Fracture is shown to initiate during the early cooling phase, thus emphasizing the relevance of the phenomenon to dynamic crack initiation in this material as probably in other materials. (author)

Assessment of structural, thermal, and mechanical properties of portlandite through molecular dynamics simulations

Energy Technology Data Exchange (ETDEWEB)

Hajilar, Shahin, E-mail: shajilar@iastate.edu [Department of Civil, Construction and Environmental Engineering, Iowa State University, Ames, IA 50011-1066 (United States); Shafei, Behrouz, E-mail: shafei@iastate.edu [Department of Civil, Construction and Environmental Engineering, Department of Materials Science and Engineering, Iowa State University, Ames, IA 50011-1066 (United States)

2016-12-15

The structural, thermal, and mechanical properties of portlandite, the primary solid phase of ordinary hydrated cement paste, are investigated using the molecular dynamics method. To understand the effects of temperature on the structural properties of portlandite, the coefficients of thermal expansion of portlandite are determined in the current study and validated with what reported from the experimental tests. The atomic structure of portlandite equilibrated at various temperatures is then subjected to uniaxial tensile strains in the three orthogonal directions and the stress-strain curves are developed. Based on the obtained results, the effect of the direction of straining on the mechanical properties of portlandite is investigated in detail. Structural damage analysis is performed to reveal the failure mechanisms in different directions. The energies of the fractured surfaces are calculated in different directions and compared to those of the ideal surfaces available in the literature. The key mechanical properties, including tensile strength, Young's modulus, and fracture strain, are extracted from the stress-strain curves. The sensitivity of the obtained mechanical properties to temperature and strain rate is then explored in a systematic way. This leads to valuable information on how the structural and mechanical properties of portlandite are affected under various exposure conditions and loading rates. - Graphical abstract: Fracture mechanism of portlandite under uniaxial strain in the z-direction. - Highlights: • The structural, thermal, and mechanical properties of portlandite are investigated. • The coefficients of thermal expansion are determined. • The stress-strain relationships are studied in three orthogonal directions. • The effects of temperature and strain rate on mechanical properties are examined. • The plastic energy required for fracture in the crystalline structure is reported.

Fracture of the styloid process associated with the mandible fracture

Directory of Open Access Journals (Sweden)

K N Dubey

2013-01-01

Full Text Available Fracture of the styloid process (SP of temporal bone is an uncommon injuries. Fracture of the SP can be associated with the facial injuries including mandible fracture. However, injury to the SP may be concealed and missed diagnosis may lead to the improper or various unnecessary treatments. A rare case of SP fracture associated with the ipsilateral mandibular fracture and also the diagnostic and management considerations of the SP fracture are discussed.

Facial Fractures.

Science.gov (United States)

Ghosh, Rajarshi; Gopalkrishnan, Kulandaswamy

2018-06-01

The aim of this study is to retrospectively analyze the incidence of facial fractures along with age, gender predilection, etiology, commonest site, associated dental injuries, and any complications of patients operated in Craniofacial Unit of SDM College of Dental Sciences and Hospital. This retrospective study was conducted at the Department of OMFS, SDM College of Dental Sciences, Dharwad from January 2003 to December 2013. Data were recorded for the cause of injury, age and gender distribution, frequency and type of injury, localization and frequency of soft tissue injuries, dentoalveolar trauma, facial bone fractures, complications, concomitant injuries, and different treatment protocols.All the data were analyzed using statistical analysis that is chi-squared test. A total of 1146 patients reported at our unit with facial fractures during these 10 years. Males accounted for a higher frequency of facial fractures (88.8%). Mandible was the commonest bone to be fractured among all the facial bones (71.2%). Maxillary central incisors were the most common teeth to be injured (33.8%) and avulsion was the most common type of injury (44.6%). Commonest postoperative complication was plate infection (11%) leading to plate removal. Other injuries associated with facial fractures were rib fractures, head injuries, upper and lower limb fractures, etc., among these rib fractures were seen most frequently (21.6%). This study was performed to compare the different etiologic factors leading to diverse facial fracture patterns. By statistical analysis of this record the authors come to know about the relationship of facial fractures with gender, age, associated comorbidities, etc.

Tensile and fracture toughness test results of neutron irradiated beryllium

Energy Technology Data Exchange (ETDEWEB)

Chaouadi, R.; Moons, F.; Puzzolante, J.L. [Centre d`Etude de l`Energie Nucleaire, Mol (Belgium)

1998-01-01

Tensile and fracture toughness test results of four Beryllium grades are reported here. The flow and fracture properties are investigated by using small size tensile and round compact tension specimens. Irradiation was performed at the BR2 material testing reactor which allows various temperature and irradiation conditions. The fast neutron fluence (>1 MeV) ranges between 0.65 and 2.45 10{sup 21} n/cm{sup 2}. In the meantime, un-irradiated specimens were aged at the irradiation temperatures to separate if any the effect of temperature from irradiation damage. Test results are analyzed and discussed, in particular in terms of the effects of material grade, test temperature, thermal ageing and neutron irradiation. (author)

Chance Fracture Secondary to a Healed Kyphotic Compression Osteoporotic Fracture

Directory of Open Access Journals (Sweden)

Teh KK

2009-11-01

Full Text Available Chance fracture is an unstable vertebral fracture, which usually results from a high velocity injury. An elderly lady with a previously healed osteoporotic fracture of the T12 and L1 vertebra which resulted in a severe kyphotic deformity subsequently sustained a Chance fracture of the adjacent L2 vertebrae after a minor fall. The previously fracture left her with a deformity which resulted in significant sagittal imbalance therefore predisposing her to this fracture. This case highlights the importance of aggressive treatment of osteoporotic fractures in order to prevent significant sagittal imbalance from resultant (i.e. kyphotic deformity.

Hip Fracture

Science.gov (United States)

... hip fractures in people of all ages. In older adults, a hip fracture is most often a result of a fall from a standing height. In people with very weak bones, a hip fracture can occur simply by standing on the leg and twisting. Risk factors The rate of hip fractures increases substantially with ...

Ankle fractures have features of an osteoporotic fracture.

Science.gov (United States)

Lee, K M; Chung, C Y; Kwon, S S; Won, S H; Lee, S Y; Chung, M K; Park, M S

2013-11-01

We report the bone attenuation of ankle joint measured on computed tomography (CT) and the cause of injury in patients with ankle fractures. The results showed age- and gender-dependent low bone attenuation and low-energy trauma in elderly females, which suggest the osteoporotic features of ankle fractures. This study was performed to investigate the osteoporotic features of ankle fracture in terms of bone attenuation and cause of injury. One hundred ninety-four patients (mean age 51.0 years, standard deviation 15.8 years; 98 males and 96 females) with ankle fracture were included. All patients underwent CT examination, and causes of injury (high/low-energy trauma) were recorded. Mean bone attenuations of the talus, medial malleolus, lateral malleolus, and distal tibial metaphysis were measured on CT images. Patients were divided into younger age (fractures than the younger age group. With increasing age, bone attenuations tended to decrease and the difference of bone attenuation between the genders tended to increase in the talus, medial malleolus, lateral malleolus, and distal tibial metaphysis. Ankle fracture had features of osteoporotic fracture that is characterized by age- and gender-dependent low bone attenuation. Ankle fracture should not be excluded from the clinical and research interest as well as from the benefit of osteoporosis management.

The understanding of the R7T7 glass blocks long term behavior: chemical and transport coupling in fractured media

International Nuclear Information System (INIS)

Chomat, L.

2008-04-01

The long term behavior of nuclear waste glass blocks depends highly on chemical reactions which occur at the surface in contact with water. Studies carried out on inactive fractured glass blocks show that fracture networks play a significant part in reactive surface area. Nevertheless, the complexity of results interpretation, due to a weak knowledge of fracture networks and local lixiviation conditions, does not allow us to comprehend the physical and chemical mechanisms involved. Model cracks are a key step to study chemical and transport coupling in fractured media. Crack lixiviation in aggressive conditions (pH≥11) show that the crack's position (horizontal or vertical) determines the dominant transport mechanism (respectively diffusion or convection induced by gravity). This gravity driven flow seems to be negligible in lower pH conditions. The convective velocity is estimated by a 1D model of reactive transport. Two other parameters are studied: the influence of thermal gradient and the influence of interconnected cracks on alteration. A strong retroactive effect of convection, due to thermal gradient, on the alteration kinetic is observed inside the crack. These works lead to a complete alteration experiment of a 163 crack network subject to a thermal gradient. The use of the geochemical software, HYTEC, within the framework of this study shows the potential of the software which is however limited by the kinetics law used. (author)

A Rare Entity: Bilateral First Rib Fractures Accompanying Bilateral Scapular Fractures

OpenAIRE

Gulbahar, Gultekin; Kaplan, Tevfik; Turker, Hasan Bozkurt; Gundogdu, Ahmet Gokhan; Han, Serdar

2015-01-01

First rib fractures are scarce due to their well-protected anatomic locations. Bilateral first rib fractures accompanying bilateral scapular fractures are very rare, although they may be together with scapular and clavicular fractures. According to our knowledge, no case of bilateral first rib fractures accompanying bilateral scapular fractures has been reported, so we herein discussed the diagnosis, treatment, and complications of bone fractures due to thoracic trauma in bias of this rare en...

A Rare Entity: Bilateral First Rib Fractures Accompanying Bilateral Scapular Fractures.

Science.gov (United States)

Gulbahar, Gultekin; Kaplan, Tevfik; Turker, Hasan Bozkurt; Gundogdu, Ahmet Gokhan; Han, Serdar

2015-01-01

First rib fractures are scarce due to their well-protected anatomic locations. Bilateral first rib fractures accompanying bilateral scapular fractures are very rare, although they may be together with scapular and clavicular fractures. According to our knowledge, no case of bilateral first rib fractures accompanying bilateral scapular fractures has been reported, so we herein discussed the diagnosis, treatment, and complications of bone fractures due to thoracic trauma in bias of this rare entity.

Three-dimensional modelling of thermal stress in floating zone silicon crystal growth

Science.gov (United States)

Plate, Matiss; Krauze, Armands; Virbulis, Jānis

2018-05-01

During the growth of large diameter silicon single crystals with the industrial floating zone method, undesirable level of thermal stress in the crystal is easily reached due to the inhomogeneous expansion as the crystal cools down. Shapes of the phase boundaries, temperature field and elastic material properties determine the thermal stress distribution in the solid mono crystalline silicon during cylindrical growth. Excessive stress can lead to fracture, generation of dislocations and altered distribution of intrinsic point defects. Although appearance of ridges on the crystal surface is the decisive factor of a dislocation-free growth, the influence of these ridges on the stress field is not completely clear. Here we present the results of thermal stress analysis for 4” and 5” diameter crystals using a quasi-stationary three dimensional mathematical model including the material anisotropy and the presence of experimentally observed ridges which cannot be addressed with axis-symmetric models. The ridge has a local but relatively strong influence on thermal stress therefore its relation to the origin of fracture is hypothesized. In addition, thermal stresses at the crystal rim are found to increase for a particular position of the crystal radiation reflector.

Validation studies for assessing unsaturated flow and transport through fractured rock

International Nuclear Information System (INIS)

Bassett, R.L.; Neuman, S.P.; Rasmussen, T.C.; Guzman, A.; Davidson, G.R.; Lohrstorfer, C.F.

1994-08-01

*The objectives of this contract are to examine hypotheses and conceptual models concerning unsaturated flow and transport through heterogeneous fractured rock and to design and execute confirmatory field and laboratory experiments to test these hypotheses and conceptual models. Important new information is presented such as the application and evaluation of procedures for estimating hydraulic, pneumatic, and solute transport coefficients for a range of thermal regimes. A field heater experiment was designed that focused on identifying the suitability of existing monitoring equipment to obtain required data. A reliable method was developed for conducting and interpreting tests for air permeability using a straddle-packer arrangement. Detailed studies of fracture flow from Queen Creek into the Magina Copper Company ore haulage tunnel have been initiated. These studies will provide data on travel time for transport of water and solute in unsaturated tuff. The collection of rainfall runoff, and infiltration data at two small watersheds at the Apache Leap Tuff Site enabled us to evaluate the quantity and rate of water infiltrating into the subsurface via either fractures or matrix. Characterization methods for hydraulic parameters relevant to Weigh-level waste transport, including fracture apertures, transmissivity, matrix porosity, and fracture wetting front propagation velocities, were developed

Validation studies for assessing unsaturated flow and transport through fractured rock

Energy Technology Data Exchange (ETDEWEB)

Bassett, R.L.; Neuman, S.P.; Rasmussen, T.C.; Guzman, A.; Davidson, G.R.; Lohrstorfer, C.F. [Arizona Univ., Tucson, AZ (United States). Dept. of Hydrology and Water Resources

1994-08-01

*The objectives of this contract are to examine hypotheses and conceptual models concerning unsaturated flow and transport through heterogeneous fractured rock and to design and execute confirmatory field and laboratory experiments to test these hypotheses and conceptual models. Important new information is presented such as the application and evaluation of procedures for estimating hydraulic, pneumatic, and solute transport coefficients for a range of thermal regimes. A field heater experiment was designed that focused on identifying the suitability of existing monitoring equipment to obtain required data. A reliable method was developed for conducting and interpreting tests for air permeability using a straddle-packer arrangement. Detailed studies of fracture flow from Queen Creek into the Magina Copper Company ore haulage tunnel have been initiated. These studies will provide data on travel time for transport of water and solute in unsaturated tuff. The collection of rainfall runoff, and infiltration data at two small watersheds at the Apache Leap Tuff Site enabled us to evaluate the quantity and rate of water infiltrating into the subsurface via either fractures or matrix. Characterization methods for hydraulic parameters relevant to Weigh-level waste transport, including fracture apertures, transmissivity, matrix porosity, and fracture wetting front propagation velocities, were developed.

Influence of grain boundaries on the fracture toughness of tungsten alloys

International Nuclear Information System (INIS)

Gludovatz, B.; Faleschini, M.; Pippan, R.; Hoffmann, A.

2007-01-01

Full text of publication follows: Tungsten and tungsten alloys are possible candidates for future fusion reactors because of their high melting points, high thermal conductivity and their high erosion resistance. Since these materials have a body-centered cubic (bcc) structure, they show a typical change in fracture behaviour from brittle at low temperatures to ductile at high temperatures. For that reason the fracture behaviour of pure tungsten (W), potassium doped tungsten (AKS) and tungsten with 1 wt% La 2 O 3 (WL10) was studied, taking into account the influence of temperature and fabrication condition. Especially AKS has been studied to investigate the longitudinal splitting of the AKS-wires, the crack propagation direction with the lowest fracture toughness. This alloy subjected to intense deformation leads to a material with an elongated grain structure after recrystallization because of the potassium bubbles. Fracture toughness has been investigated by means of 3-point bending (3PB) specimens, double cantilever beam (DCB) specimens and compact tension (CT) specimens. Tests were performed in the range -196 deg. C to more than 1000 deg. C. Though all these materials show an expected increase in fracture toughness with increasing temperature, influences like texture, chemical composition, grain boundary segregation and dislocation density seem to have an extreme influence on the obtained results. These influences can especially be seen in the fracture behaviour and morphology, where two kinds of fracture can occur: on one hand the trans-crystalline and on the other hand the intercrystalline fracture. Therefore techniques like electron backscatter diffraction, auger electron spectroscopy and X-ray line profile analysis were used to determine the parameter influencing fracture toughness. Also new testing techniques have been devised and successfully applied. Additional tests like an 'in-situ EBSD' technique for investigating the formation of dislocations during

Relationships between fractures

Science.gov (United States)

Peacock, D. C. P.; Sanderson, D. J.; Rotevatn, A.

2018-01-01

Fracture systems comprise many fractures that may be grouped into sets based on their orientation, type and relative age. The fractures are often arranged in a network that involves fracture branches that interact with one another. Interacting fractures are termed geometrically coupled when they share an intersection line and/or kinematically coupled when the displacements, stresses and strains of one fracture influences those of the other. Fracture interactions are characterised in terms of the following. 1) Fracture type: for example, whether they have opening (e.g., joints, veins, dykes), closing (stylolites, compaction bands), shearing (e.g., faults, deformation bands) or mixed-mode displacements. 2) Geometry (e.g., relative orientations) and topology (the arrangement of the fractures, including their connectivity). 3) Chronology: the relative ages of the fractures. 4) Kinematics: the displacement distributions of the interacting fractures. It is also suggested that interaction can be characterised in terms of mechanics, e.g., the effects of the interaction on the stress field. It is insufficient to describe only the components of a fracture network, with fuller understanding coming from determining the interactions between the different components of the network.

A Rare Entity: Bilateral First Rib Fractures Accompanying Bilateral Scapular Fractures

Directory of Open Access Journals (Sweden)

Gultekin Gulbahar

2015-01-01

Full Text Available First rib fractures are scarce due to their well-protected anatomic locations. Bilateral first rib fractures accompanying bilateral scapular fractures are very rare, although they may be together with scapular and clavicular fractures. According to our knowledge, no case of bilateral first rib fractures accompanying bilateral scapular fractures has been reported, so we herein discussed the diagnosis, treatment, and complications of bone fractures due to thoracic trauma in bias of this rare entity.

Proximal femoral fractures.

Science.gov (United States)

Webb, Lawrence X

2002-01-01

Fractures of the proximal femur include fractures of the head, neck, intertrochanteric, and subtrochanteric regions. Head fractures commonly accompany dislocations. Neck fractures and intertrochanteric fractures occur with greatest frequency in elderly patients with a low bone mineral density and are produced by low-energy mechanisms. Subtrochanteric fractures occur in a predominantly strong cortical osseous region which is exposed to large compressive stresses. Implants used to address these fractures must be able to accommodate significant loads while the fractures consolidate. Complications secondary to these injuries produce significant morbidity and include infection, nonunion, malunion, decubitus ulcers, fat emboli, deep venous thrombosis, pulmonary embolus, pneumonia, myocardial infarction, stroke, and death.

Fracture mechanisms and fracture control in composite structures

Science.gov (United States)

Kim, Wone-Chul

Four basic failure modes--delamination, delamination buckling of composite sandwich panels, first-ply failure in cross-ply laminates, and compression failure--are analyzed using linear elastic fracture mechanics (LEFM) and the J-integral method. Structural failures, including those at the micromechanical level, are investigated with the aid of the models developed, and the critical strains for crack propagation for each mode are obtained. In the structural fracture analyses area, the fracture control schemes for delamination in a composite rib stiffener and delamination buckling in composite sandwich panels subjected to in-plane compression are determined. The critical fracture strains were predicted with the aid of LEFM for delamination and the J-integral method for delamination buckling. The use of toughened matrix systems has been recommended for improved damage tolerant design for delamination crack propagation. An experimental study was conducted to determine the onset of delamination buckling in composite sandwich panel containing flaws. The critical fracture loads computed using the proposed theoretical model and a numerical computational scheme closely followed the experimental measurements made on sandwich panel specimens of graphite/epoxy faceskins and aluminum honeycomb core with varying faceskin thicknesses and core sizes. Micromechanical models of fracture in composites are explored to predict transverse cracking of cross-ply laminates and compression fracture of unidirectional composites. A modified shear lag model which takes into account the important role of interlaminar shear zones between the 0 degree and 90 degree piles in cross-ply laminate is proposed and criteria for transverse cracking have been developed. For compressive failure of unidirectional composites, pre-existing defects play an important role. Using anisotropic elasticity, the stress state around a defect under a remotely applied compressive load is obtained. The experimentally

Effects of Thermal Aging on Material Properties, Stress Corrosion Cracking, and Fracture Toughness of AISI 316L Weld Metal

Science.gov (United States)

Lucas, Timothy; Forsström, Antti; Saukkonen, Tapio; Ballinger, Ronald; Hänninen, Hannu

2016-08-01

Thermal aging and consequent embrittlement of materials are ongoing issues in cast stainless steels, as well as duplex, and high-Cr ferritic stainless steels. Spinodal decomposition is largely responsible for the well-known "748 K (475 °C) embrittlement" that results in drastic reductions in ductility and toughness in these materials. This process is also operative in welds of either cast or wrought stainless steels where δ-ferrite is present. While the embrittlement can occur after several hundred hours of aging at 748 K (475 °C), the process is also operative at lower temperatures, at the 561 K (288 °C) operating temperature of a boiling water reactor (BWR), for example, where ductility reductions have been observed after several tens of thousands of hours of exposure. An experimental program was carried out in order to understand how spinodal decomposition may affect changes in material properties in Type 316L BWR piping weld metals. The study included material characterization, nanoindentation hardness, double-loop electrochemical potentiokinetic reactivation (DL-EPR), Charpy-V, tensile, SCC crack growth, and in situ fracture toughness testing as a function of δ-ferrite content, aging time, and temperature. SCC crack growth rates of Type 316L stainless steel weld metal under simulated BWR conditions showed an approximate 2 times increase in crack growth rate over that of the unaged as-welded material. In situ fracture toughness measurements indicate that environmental exposure can result in a reduction of toughness by up to 40 pct over the corresponding at-temperature air-tested values. Material characterization results suggest that spinodal decomposition is responsible for the degradation of material properties measured in air, and that degradation of the in situ properties may be a result of hydrogen absorbed during exposure to the high-temperature water environment.

Pressurized-thermal-shock experiments: PTSE-1 results and PTSE-2 plans

International Nuclear Information System (INIS)

Bryan, R.H.; Nanstad, R.K.; Wanner, R.; Merkle, J.G.; Robinson, G.C.; Whitman, G.D.

1985-01-01

The first pressurized-thermal-shock experiment (PTSE-1) was performed with a vessel with a 1-m-long flaw in a plug of specially tempered steel having the composition of SA-508 forging steel. The second experiment (PTSE-2) will have a similar arrangement, but the material in which the flaw will be implanted is being prepared to have low tearing resistance. Special tempering of a 2 1/4 Cr - 1 Mo steel plate has been shown to induce a low Charpy impact energy in the upper-shelf temperature range. The purpose of PTSE-2 is to investigate the fracture behavior of low-upper-shelf material in a vessel under the combined loading of concurrent pressure and thermal shock. The primary objective of the experimental plan is to induce a rapidly propagating cleavage fracture under conditions that are likely to induce a ductile tearing instability at the time of arrest of the cleavage fracture. The secondary objective of the test is to extend the range of the investigation of warm prestressing. 11 figs

Dating fractures and fracture movement in the Lac du Bonnet Batholith

International Nuclear Information System (INIS)

Gascoyne, M.; Brown, A.; Ejeckam, R.B.; Everitt, R.A.

1997-04-01

This report examines and summarizes all work that has been done from 1980 to the present in determining the age of rock crystallization, fracture initiation, fracture reactivation and rates of fracture movement in the Lac du Bonnet Batholith to provide information for Atomic Energy of Canada Limited's (AECL) Canadian Nuclear Fuel Waste Management Program. Geological and petrographical indicators of relative age (e.g. cross-cutting relationships, sequences of fracture infilling minerals, P-T characteristics of primary and secondary minerals) are calibrated with radiometric age determinations on minerals and whole rock samples, using 87 Rb- 87 Sr, 40 K- 39 Ar, 40 Ar- 39 Ar and fission track methods. Most fractures and fracture zones inclined at low angles are found to be ancient features, first formed in the Early Proterozoic under conditions of deuteric alteration. Following some movement on fractures in the Late Proterozoic and Early Paleozoic, reactivation of fractures during the Pleistocene is established from uranium-series dating methods and use of stable isotopic contents of fracture infilling minerals (mainly calcite). Some indication of movement on fracture zones during the Pleistocene is given by electron spin resonance dating techniques on fault gouge. The slow rate of propagation of fractures is indicated by mineral infillings, their P-T characteristics and U-series calcite ages in a fracture in sparsely fractured rock, accessible from AECL's Underground Research Laboratory. These results collectively indicate that deep fractures observed in the batholith are ancient features and the fracturing and jointing in the upper 200 m is relatively recent (< 1 Ma) and largely a result of stress release. (author)

Investigation of statistical relationship between dynamic modulus and thermal strength of asphalt concrete

International Nuclear Information System (INIS)

Qadir, A.; Gular, M.

2011-01-01

Dynamic modulus is a performance indicator for asphalt concrete and is used to qualify asphalt mixtures based on stress-strain characteristics under repeated loading. Moreover, the low temperature cracking of asphalt concrete mixes are measured in terms of fracture strength and fracture temperature. Dynamic modulus test was selected as one of the simple performance tests in the AASHTO 2002 guidelines to rate mixtures according to permanent deformation performance. However, AASHTO 2002 guidelines is silent in relating dynamic modulus values to low temperature cracking, probably because of weak correlations reported between these two properties. The present study investigates the relation between these two properties under the influence of aggregate type and mix gradation. Mixtures were prepared with two types of aggregate and gradations, while maintaining the binder type and air voids constant. The mixtures were later tested for dynamic modulus and fracture strength using thermal stress restrained specimen test (TSRST). Results indicate that there exists a fair correlation between the thermal fracture strength and stiffness at a selected test temperature and frequency level. These correlations are highly dependent upon the type of aggregate and mix gradation. (author)

Ion beam modification of thermal stress resistance of MgO single crystals with different crystallographic faces

International Nuclear Information System (INIS)

Gurarie, V.N.; Otsuka, P.H.; Williams, J.S.; Conway, M.J.

2000-01-01

Ion beam modification of thermal shock stress resistance of MgO single crystals with various crystallographic faces is investigated. The most stable crystal faces in terms of stress and damage resistance are established. Ion implantation is shown to reduce the temperature threshold of fracture for all crystal faces tested. The (111) face is demonstrated to be of highest stability compared to (110) and (100) faces in both implanted and unimplanted crystals. At the same time ion implantation substantially increases the microcrack density for all the faces tested and reduces the degree of fracture damage following thermal shock. The theoretical resistance parameters for various crystal faces are calculated using the continuum mechanics approach. The results are discussed on the basis of fracture mechanics principles and the effect of the implantation-induced lattice damage on crack nucleation

Nanobioceramic Composites: A Study of Mechanical, Morphological, and Thermal Properties

Directory of Open Access Journals (Sweden)

Sivabalan Sasthiryar

2013-12-01

Full Text Available The aim of this study was to explore the incorporation of biomass carbon nanofillers (CNF into advanced ceramic. Biomass from bamboo, bagasse (remains of sugarcane after pressing, and oil palm ash was used as the predecessor for producing carbon black nanofillers. Furnace pyrolysis was carried out at 1000 °C and was followed by ball-mill processing to obtain carbon nanofillers in the range of 50 nm to 100 nm. CNFs were added to alumina in varying weight fractions and the resulting mixture was subjected to vacuum sintering at 1400 °C to produce nanobioceramic composites. The ceramic composites were characterized for mechanical, thermal, and morphological properties. A high-resolution Charge-coupled device (CCD camera was used to study the fracture impact and the failure mechanism. An increase in the loading percentage of CNFs in the alumna decreased the specific gravity, vickers hardness (HV, and fracture toughness values of the composite materials. Furthermore, the thermal conductivity and the thermal stability of the ceramic composite increased as compared to the pristine alumina.

The fracture toughness of Type 316 steel and weld metal

International Nuclear Information System (INIS)

Picker, C.

This paper describes the results of fracture toughness tests on Type 316 steel and Manual Metal Arc (MMA) weld metal over a range of temperatures from 20 deg. C to 550 deg. C, and includes the effects on toughness of specimen size, post weld heat treatment and thermal ageing. The conclusions reached are that Type 316 steel possesses a superior toughness to the weld metal in the as-welded or stress relieved conditions but the toughness of the steel is degraded to a level similar to that of the weld metal following thermal ageing at temperatures over 600 deg. C. Relatively short term thermal ageing in the temperature range 370 deg. C to 450 deg. C does not appear to affect the toughness of either Type 316 steel or weld metal. (author)

Interlamellar cracking of thermal barrier coatings with TGOs by non-standard four-point bending tests

Energy Technology Data Exchange (ETDEWEB)

Zhao, P.F. [State Key Laboratory for Strength and Vibration, Department of Engineering Mechanics, Xi' an Jiaotong University, Xi' an (China); Li, X.D. [State Key Laboratory for Strength and Vibration, Department of Engineering Mechanics, Xi' an Jiaotong University, Xi' an (China); Aircraft Strength Research Institute of China, Xi' an, 710065 (China); Shang, F.L., E-mail: shangfl@mail.xjtu.edu.cn [State Key Laboratory for Strength and Vibration, Department of Engineering Mechanics, Xi' an Jiaotong University, Xi' an (China); Li, C.J. [State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi' an Jiaotong University, Xi' an (China)

2011-09-25

Highlights: {yields} A non-standard modified four-point bending specimen is adopted for delamination test. {yields} Typical failure mode of the TBC system with TGO layer is demonstrated. {yields} Fracture toughness of 8YSZ on a cold-sprayed MCrAlY coating is evaluated theoretically. - Abstract: This work concerns the failure mode and fracture toughness of plasma-sprayed 8 wt% yttria-stabilized zirconia (8YSZ) deposited on a cold-sprayed MCrAlY bond coat (BC) after thermal oxidation. Upon high-temperature exposure, a thermally grown oxide (TGO) layer was formed along the interface between the BC layer and YSZ ceramic coating layer through oxidation of the bond coat. By utilizing a non-standard modified four-point bending specimen, in conjunction with fractured surface examinations by scanning electron microscope and energy disperse spectroscope, the failure mode of this thermal barrier coating (TBC) system has been checked experimentally. It is shown that delamination cracks firstly initiate at the YSZ/BC interface edge, and then propagate along a wavy path near the interface, not only through the TBC but also within the TGO and along the interlamellar interfaces. Through a theoretical analysis of the bending specimen, the fracture toughness of this TBC system, in terms of strain energy release rate, has been determined from the load-displacement curves which were recorded during the tests.

Physical fracture properties (fracture surfaces as information sources; crackgrowth and fracture mechanisms; exemples of cracks)

International Nuclear Information System (INIS)

Meny, Lucienne.

1979-06-01

Fracture surfaces are considered as a useful source of informations: an introduction to fractography is presented; the fracture surface may be observed through X ray microanalysis, and other physical methods such as Auger electron spectroscopy or secundary ion emission. The mechanisms of macroscopic and microscopic crackgrowth and fracture are described, in the case of unstable fracture (cleavage, ductile with shear, intergranular brittleness) and of progressive crack propagation (creep, fatigue). Exemples of cracks are presented in the last chapter [fr

Thermal aspects of radioactive waste disposal in hard rock

International Nuclear Information System (INIS)

Beale, H.; Bourke, P.J.; Hodgkinson, D.P.

1980-01-01

Buried heat emitting radioactive waste will appreciably raise the temperature of the surrounding rock over distances of several hundred metres for many centuries. This paper describes continuing research at Harwell aimed at understanding how this heating affects the design of hard rock depositories for the waste. It also considers how water-borne leakage of radionuclides from a depository to the surface might be increased by thermal convection currents through the rock mass and by thermally induced changes in its permeability and porosity. A conceptual design for a three-dimensional depository with an array of vitrified waste blocks placed in vertical boreholes is described. The maximum permissible power outputs of individual blocks and the minimum permissible separations between blocks to limit the local and bulk average rock temperatures will be determined by heat transfer through the rock and are reviewed. Interim results of a field heating experiment to study transient heat transfer through granite are discussed subsequently. Field experiments are now being started to measure the fracture permeability and porosity over large distances in virgin granite and to investigate their variation on heating and cooling the rock. Theoretical estimates of the temperatures, thermal stresses and thermal convection currents around a depository are next presented. The implications for water-borne leakage are that the induced stresses could change the fracture permeability and porosity, and thermal convection could cause substantial water movement vertically towards the surface. Finally some conclusions from the work are presented. (author)

Stress Fractures

Science.gov (United States)

Stress fractures Overview Stress fractures are tiny cracks in a bone. They're caused by repetitive force, often from overuse — such as repeatedly jumping up and down or running long distances. Stress fractures can also arise from normal use of ...

Transstyloid, transscaphoid, transcapitate fracture: a variant of scaphocapitate fractures.

LENUS (Irish Health Repository)

Burke, Neil G

2014-01-01

Transstyloid, transscaphoid, transcapitate fractures are uncommon. We report the case of a 28-year-old man who sustained this fracture following direct trauma. The patient was successfully treated by open reduction internal fixation of the scaphoid and proximal capitate fragment, with a good clinical outcome at 1-year follow-up. This pattern is a new variant of scaphocapitate fracture as involves a fracture of the radial styloid as well.

Normalizing treatment influence on the forged steel SAE 8620 fracture properties

Directory of Open Access Journals (Sweden)

Paulo de Tarso Vida Gomes

2005-03-01

Full Text Available In a PWR nuclear power plant, the reactor pressure vessel (RPV contains the fuel assemblies and reactor vessels internals and keeps the coolant at high temperature and high pressure during normal operation. The RPV integrity must be assured all along its useful life to protect the general public against a significant radiation liberation damage. One of the critical issues relative to the VPR structural integrity refers to the pressurized thermal shock (PTS accident evaluation. To better understand the effects of this kind of event, a PTS experiment has been planned using an RPV prototype. The RPV material fracture behavior characterization in the ductile-brittle transition region represents one of the most important aspects of the structural assessment process of RPV's under PTS. This work presents the results of fracture toughness tests carried out to characterize the RPV prototype material behavior. The test data includes Charpy energy curves, T0 reference temperatures for definition of master curves, and fracture surfaces observed in electronic microscope. The results are given for the vessel steel in the "as received" and normalized conditions. This way, the influence of the normalizing treatment on the fracture properties of the steel could be evaluated.

Preliminary test results from the HSST shallow-crack fracture toughness program

International Nuclear Information System (INIS)

Theiss, T.J.; Robinson, G.C.; Rolfe, S.T.

1991-01-01

The Heavy Section Steel Technology (HSST) Program under sponsorship of the Nuclear Regulatory Commission (NRC) is investigating the influence of crack depth on the fracture toughness of reactor pressure vessel steel. The ultimate goal of the investigation is the generation of a limited data base of elastic-plastic fracture toughness values appropriate for shallow flaws in a reactor pressure vessel and the application of this data to reactor vessel life assessments. It has been shown that shallow-flaws play a dominant role in the probabilistic fracture mechanics analysis of reactor pressure vessels during a pressurized-thermal-shock event. In addition, recent research has shown that the crack initiation toughness measured using specimens with shallow flaws is greater that the toughness determined with conventional, deeply notched specimens at temperatures within the transition region for non-nuclear steels. The influence of crack depth on the elastic-plastic fracture toughness for prototypic reactor material is being investigated. Preliminary results indicate a significant increase in the toughness associated with shallow-flaws which has the potential to significantly impact the conditional probability of vessel failure. 8 refs., 4 figs., 1 tab

Numerical methods for coupled fracture problems

Science.gov (United States)

Viesca, Robert C.; Garagash, Dmitry I.

2018-04-01

We consider numerical solutions in which the linear elastic response to an opening- or sliding-mode fracture couples with one or more processes. Classic examples of such problems include traction-free cracks leading to stress singularities or cracks with cohesive-zone strength requirements leading to non-singular stress distributions. These classical problems have characteristic square-root asymptotic behavior for stress, relative displacement, or their derivatives. Prior work has shown that such asymptotics lead to a natural quadrature of the singular integrals at roots of Chebyhsev polynomials of the first, second, third, or fourth kind. We show that such quadratures lead to convenient techniques for interpolation, differentiation, and integration, with the potential for spectral accuracy. We further show that these techniques, with slight amendment, may continue to be used for non-classical problems which lack the classical asymptotic behavior. We consider solutions to example problems of both the classical and non-classical variety (e.g., fluid-driven opening-mode fracture and fault shear rupture driven by thermal weakening), with comparisons to analytical solutions or asymptotes, where available.

Elastic response of thermal spray deposits under indentation tests

International Nuclear Information System (INIS)

Leigh, S.H.; Lin, C.K.; Berndt, C.C.

1997-01-01

The elastic response behavior of thermal spray deposits at Knoop indentations has been investigated using indentation techniques. The ration of hardness to elastic modulus, which is an important prerequisite for the evaluation of indentation fracture toughness, is determined by measuring the elastic recovery of the in-surface dimensions of Knoop indentations. The elastic moduli of thermal spray deposits are in the range of 12%--78% of the comparable bulk materials and reveal the anisotropic behavior of thermal spray deposits. A variety of thermal spray deposits has been examined, including Al 2 O 3 , yttria-stabilized ZrO 2 (YSZ), and NiAl. Statistical tools have been used to evaluate the error estimates of the data

Risk of hip fracture after osteoporosis fractures. 451 women with fracture of lumbar spine, olecranon, knee or ankle

DEFF Research Database (Denmark)

Lauritzen, J B; Lund, B

1993-01-01

In a follow-up study during 1976-1984, the risk of a subsequent hip fracture was investigated in women aged 60-99 years, hospitalized for the following fractures: lumbar spine (n 70), olecranon (n 52), knee (n 129) and ankle (n 200). Follow-up ranged from 0 to 9 years. Observation time of the 4...... different fractures were 241, 180, 469, and 779, person-years, respectively. In women aged 60-79 years with one of the following fractures the relative risk of a subsequent hip fracture was increased by 4.8 (lumbar spine), 4.1 (olecranon), 3.5 (knee) and 1.5 (ankle). The relative risk of hip fracture showed...... a tendency to level off 3 years after the primary fracture....

ORNL probabilistic fracture-mechanics code OCA-P

International Nuclear Information System (INIS)

Cheverton, R.D.; Ball, D.G.

1984-01-01

The computer code OCA-P was developed at the request of the USNRC for the purpose of helping to evaluate the integrity of PWR pressure vessels during overcooling accidents (OCA's). The code can be used for both deterministic and probabilistic fracture-mechanics calculations, and consists essentially of OCA-II and a Monte Carlo routine similar to that developed by Strosnider et al. In the probabilistic mode OCA-P generates a large number of vessels (10 6 more or less), each with a different combination of the various values of the different parameters involved in the analysis of flaw behavior. For each of these vessels a deterministic fracture-mechanics analysis is performed (calculation of K/sub I/, K/sub Ic/, K/sub Ia/) to determine whether vessel failure takes place. The conditional probability of failure is simply the number of vessels that fail divided by the number of vessels generated. OCA-II is used for the deterministic analysis. Basic input to OCA-II includes, among other things, the primry-system pressure transient and the temperature transient for the coolant in the reactor-vessel downcomer. With this and additional information available OCA-II performs a one-dimensional thermal analysis to obtain the temperature distribution in the wall as a function of time and then a one-dimensional linear-elastic stress analysis. OCA-P has been checked against similar codes and is presently being used in the Integrated Pressurized Thermal Shock Program for specific PWR plants

An integrated methodology for characterizing flow and transport processes in fractured rock

International Nuclear Information System (INIS)

Wu, Yu-Shu

2007-01-01

To investigate the coupled processes involved in fluid and heat flow and chemical transport in the highly heterogeneous, unsaturated-zone (UZ) fractured rock of Yucca Mountain, we present an integrated modeling methodology. This approach integrates a wide variety of moisture, pneumatic, thermal, and geochemical isotopic field data into a comprehensive three-dimensional numerical model for modeling analyses. The results of field applications of the methodology show that moisture data, such as water potential and liquid saturation, are not sufficient to determine in situ percolation flux, whereas temperature and geochemical isotopic data provide better constraints to net infiltration rates and flow patterns. In addition, pneumatic data are found to be extremely valuable in estimating large-scale fracture permeability. The integration of hydrologic, pneumatic, temperature, and geochemical data into modeling analyses is thereby demonstrated to provide a practical modeling approach for characterizing flow and transport processes in complex fractured formations

High prevalence of simultaneous rib and vertebral fractures in patients with hip fracture.

Science.gov (United States)

Lee, Bong-Gun; Sung, Yoon-Kyoung; Kim, Dam; Choi, Yun Young; Kim, Hunchul; Kim, Yeesuk

2017-02-01

The purpose was to evaluate the prevalence and location of simultaneous fracture using bone scans in patients with hip fracture and to determine the risk factors associated with simultaneous fracture. One hundred eighty two patients with hip fracture were reviewed for this study. Clinical parameters and bone mineral density (BMD) of the lumbar vertebra and femoral neck were investigated. To identify acute simultaneous fracture, a bone scan was performed at 15.4±4.1days after hip fracture. The prevalence and location of simultaneous fracture were evaluated, and multivariate logistic regression analysis was performed to determine the risk factors. Simultaneous fracture was observed in 102 of 182 patients, a prevalence of 56.0%. Rib fracture was the most common type of simultaneous fracture followed by rib with vertebral fracture. The BMD of the lumbar vertebra was significantly lower in patients with simultaneous fracture (p=0.044) and was identified as an independent risk factor (odds ratio: OR 0.05, 95% confidence interval: CI 0.01-0.57). The prevalence of simultaneous fracture was relatively high among patients with hip fracture, and BMD was significantly lower in patients with simultaneous fracture than in patients without it. Surgeons should be aware of the possibility of simultaneous fracture in patients with hip fracture. Copyright © 2016 Elsevier Ltd. All rights reserved.

External fixation of tibial pilon fractures and fracture healing.

Science.gov (United States)

Ristiniemi, Jukka

2007-06-01

Distal tibial fractures are rare and difficult to treat because the bones are subcutaneous. External fixation is commonly used, but the method often results in delayed union. The aim of the present study was to find out the factors that affect fracture union in tibial pilon fractures. For this purpose, prospective data collection of tibial pilon fractures was carried out in 1998-2004, resulting in 159 fractures, of which 83 were treated with external fixation. Additionally, 23 open tibial fractures with significant > 3 cm bone defect that were treated with a staged method in 2000-2004 were retrospectively evaluated. The specific questions to be answered were: What are the risk factors for delayed union associated with two-ring hybrid external fixation? Does human recombinant BMP-7 accelerate healing? What is the role of temporary ankle-spanning external fixation? What is the healing potential of distal tibial bone loss treated with a staged method using antibiotic beads and subsequent autogenous cancellous grafting compared to other locations of the tibia? The following risk factors for delayed healing after external fixation were identified: post-reduction fracture gap of >3 mm and fixation of the associated fibula fracture. Fracture displacement could be better controlled with initial temporary external fixation than with early definitive fixation, but it had no significant effect on healing time, functional outcome or complication rate. Osteoinduction with rhBMP-7 was found to accelerate fracture healing and to shorten the sick leave. A staged method using antibiotic beads and subsequent autogenous cancellous grafting proved to be effective in the treatment of tibial bone loss. Healing potential of the bone loss in distal tibia was at least equally good as in other locations of the tibia.

Ion beam modification of thermal stress resistance of MgO single crystals with different crystallographic faces

International Nuclear Information System (INIS)

Gurarie, V.N.; Otsuka, P.H.; Jamieson, D.N.; Williams, J.S.; Conway, M.

1999-01-01

Ion beam modification of thermal shock stress and damage resistance of MgO single crystals with various crystallographic faces is investigated. The most stable crystal faces in terms of stress and damage resistance are established. Ion implantation is shown to reduce the temperature threshold of fracture for all crystal faces tested. The (111) face is demonstrated to be of highest stability compared to (110) and (100) faces in both implanted and unimplanted crystals. At the same time ion implantation substantially increases the microcrack density for the faces tested and reduces the degree of fracture damage following thermal shock. The microcrack density is found to be highest in the crystals with (110) face in comparison with the (001) and (111) faces. The effect is analysed using fracture mechanics principles and discussed in terms of the implantation-induced lattice damage

Radiographic anatomy of the proximal femur: femoral neck fracture vs. transtrochanteric fracture

Directory of Open Access Journals (Sweden)

Ana Lecia Carneiro Leão de Araújo Lima

Full Text Available ABSTRACT OBJECTIVE: To evaluate the correlation between radiographic parameters of the proximal femur with femoral neck fractures or transtrochanteric fractures. METHODS: Cervicodiaphyseal angle (CDA, femoral neck width (FNW, hip axis length (HAL, and acetabular tear drop distance (ATD were analyzed in 30 pelvis anteroposterior view X-rays of patients with femoral neck fractures (n = 15 and transtrochanteric fractures (n = 15. The analysis was performed by comparing the results of the X-rays with femoral neck fractures and with transtrochanteric fractures. RESULTS: No statistically significant differences between samples were observed. CONCLUSION: There was no correlation between radiographic parameters evaluated and specific occurrence of femoral neck fractures or transtrochanteric fractures.

Thermal image analysis of plastic deformation and fracture behavior by a thermo-video measurement system

International Nuclear Information System (INIS)

Ohbuchi, Yoshifumi; Sakamoto, Hidetoshi; Nagatomo, Nobuaki

2016-01-01

The visualization of the plastic region and the measurement of its size are necessary and indispensable to evaluate the deformation and fracture behavior of a material. In order to evaluate the plastic deformation and fracture behavior in a structural member with some flaws, the authors paid attention to the surface temperature which is generated by plastic strain energy. The visualization of the plastic deformation was developed by analyzing the relationship between the extension of the plastic deformation range and the surface temperature distribution, which was obtained by an infrared thermo-video system. Furthermore, FEM elasto-plastic analysis was carried out with the experiment, and the effectiveness of this non-contact measurement system of the plastic deformation and fracture process by a thermography system was discussed. The evaluation method using an infrared imaging device proposed in this research has a feature which does not exist in the current evaluation method, i.e. the heat distribution on the surface of the material has been measured widely by noncontact at 2D at high speed. The new measuring technique proposed here can measure the macroscopic plastic deformation distribution on the material surface widely and precisely as a 2D image, and at high speed, by calculation from the heat generation and the heat propagation distribution. (paper)

Ductile fracture prediction of an axially cracked pressure vessel under pressurized thermal shock

International Nuclear Information System (INIS)

Takahashi, Jun; Okamura, Hiroyuki

1991-01-01

In this paper, the J-value of an axially cracked cylinder under several PTS conditions are evaluated using a simple estimation scheme which we proposed. Results obtained are summerized as follow: (1) Under any PTS conditions, the effect of internal pressure is so predominant upon the J-value and dJ/da that it is very important to grasp the transient of internal pressure under any imaginable accident from the viewpoint of structural integrity. (2) Under any IP, TS, and PTS conditions, J - a/W relation shows that the J-value reaches its maximum at a certain crack depth, then drops to zero at a/W ≅ 0.9. Though the effect of inertia is not taken into account, this fact may explain the phenomena of crack arrest qualitatively. (3) The compliance of a cylindrical shell plays an important role in the fracture prediction of a pressure vessel. (4) Under typical PTS conditions, the region at the crack tip dominated by the Hutchinson-Rice-Rosengren singularity is substantially large enough to apply the J-based criterion to predict unstable ductile fracture. (author)

Prior nonhip limb fracture predicts subsequent hip fracture in institutionalized elderly people.

Science.gov (United States)

Nakamura, K; Takahashi, S; Oyama, M; Oshiki, R; Kobayashi, R; Saito, T; Yoshizawa, Y; Tsuchiya, Y

2010-08-01

This 1-year cohort study of nursing home residents revealed that historical fractures of upper limbs or nonhip lower limbs were associated with hip fracture (hazard ratio = 2.14), independent of activities of daily living (ADL), mobility, dementia, weight, and type of nursing home. Prior nonhip fractures are useful for predicting of hip fracture in institutional settings. The aim of this study was to evaluate the utility of fracture history for the prediction of hip fracture in nursing home residents. This was a cohort study with a 1-year follow-up. Subjects were 8,905 residents of nursing homes in Niigata, Japan (mean age, 84.3 years). Fracture histories were obtained from nursing home medical records. ADL levels were assessed by caregivers. Hip fracture diagnosis was based on hospital medical records. Subjects had fracture histories of upper limbs (5.0%), hip (14.0%), and nonhip lower limbs (4.6%). Among historical single fractures, only prior nonhip lower limbs significantly predicted subsequent fracture (adjusted hazard ratio, 2.43; 95% confidence interval (CI), 1.30-4.57). The stepwise method selected the best model, in which a combined historical fracture at upper limbs or nonhip lower limbs (adjusted hazard ratio, 2.14; 95% CI, 1.30-3.52), dependence, ADL levels, mobility, dementia, weight, and type of nursing home independently predicted subsequent hip fracture. A fracture history at upper or nonhip lower limbs, in combination with other known risk factors, is useful for the prediction of future hip fracture in institutional settings.

Laboratory study of fracture healing in Topopah Spring tuff: Implications for near field hydrology

International Nuclear Information System (INIS)

Lin, Wunan; Daily, W.D.

1989-09-01

Seven Topopah Spring tuff samples were studied to determine water permeability in this rock under pressure and temperature conditions similar to those expected in the near field of a nuclear waste package. Six of the seven samples were studied under isothermal condition; the other was subjected to a thermal gradient. Four of the six fractured samples contained a reopened, healed, natural fracture; one contained an induced tensile fracture and the other contained a saw-cut. The fracture surfaces were examined using scanning electron microscope (SEM) before and after the experiments and the water that flowed through the samples was sampled for chemical analysis. The experimental durations ranged from about 3 months to almost 6 months. Water permeability of the fractured samples was found to decrease by more than three orders of magnitude when the sample temperature increased to 150 degree C. The sharpest decrease in permeability occurred when the temperature was increased above 90 degree C. Permeability of the intact sample did not change significantly under the similar experimental conditions. When the temperature returned to room conditions, the water permeability did not recover. The mechanical strength of one healed sample was about half that of the intact rock. SEM studies of the fracture surfaces and water chemical analysis of the water suggested that both dissolution and deposition occurred on the fracture surfaces. Smoothing of fracture asperities because of dissolution and deposition was probably the main cause of the permeability decrease. Deposition of dissolved silica was probably the main cause of fracture healing. 12 refs., 6 figs., 1 tab

Fracture assessment of shallow-flaw cruciform beams tested under uniaxial and biaxial loading conditions

International Nuclear Information System (INIS)

Bass, B.R.; McAfee, W.J.; Williams, P.T.; Pennell, W.E.

1999-01-01

A technology to determine shallow-flaw fracture toughness of reactor pressure vessel (RPV) steels is being developed for application to the safety assessment of RPVs containing postulated shallow surface flaws. Matrices of cruciform beam tests were developed to investigate and quantify the effects of temperature, biaxial loading, and specimen size on fracture initiation toughness of two-dimensional (constant depth), shallow, surface flaws. The cruciform beam specimens were developed at Oak Ridge National Laboratory (ORNL) to introduce a far-field, out-of-plane biaxial stress component in the test section that approximates the nonlinear stresses resulting from pressurized-thermal-shock or pressure-temperature loading of an RPV. Tests were conducted under biaxial load ratios ranging from uniaxial to equibiaxial. These tests demonstrated that biaxial loading can have a pronounced effect on shallow-flaw fracture toughness in the lower transition temperature region for an RPV material. The cruciform fracture toughness data were used to evaluate fracture methodologies for predicting the observed effects of biaxial loading on shallow-flaw fracture toughness. Initial emphasis was placed on assessment of stress-based methodologies, namely, the J-Q formulation, the Dodds-Anderson toughness scaling model, and the Weibull approach. Applications of these methodologies based on the hydrostatic stress fracture criterion indicated an effect of loading-biaxiality on fracture toughness; the conventional maximum principal stress criterion indicated no effect. A three-parameter Weibull model based on the hydrostatic stress criterion is shown to correlate with the experimentally observed biaxial effect on cleavage fracture toughness by providing a scaling mechanism between uniaxial and biaxial loading states. (orig.)

Mandible Fractures.

Science.gov (United States)

Pickrell, Brent B; Serebrakian, Arman T; Maricevich, Renata S

2017-05-01

Mandible fractures account for a significant portion of maxillofacial injuries and the evaluation, diagnosis, and management of these fractures remain challenging despite improved imaging technology and fixation techniques. Understanding appropriate surgical management can prevent complications such as malocclusion, pain, and revision procedures. Depending on the type and location of the fractures, various open and closed surgical reduction techniques can be utilized. In this article, the authors review the diagnostic evaluation, treatment options, and common complications of mandible fractures. Special considerations are described for pediatric and atrophic mandibles.

Experimental and statistical study on fracture boundary of non-irradiated Zircaloy-4 cladding tube under LOCA conditions

Science.gov (United States)

Narukawa, Takafumi; Yamaguchi, Akira; Jang, Sunghyon; Amaya, Masaki

2018-02-01

For estimating fracture probability of fuel cladding tube under loss-of-coolant accident conditions of light-water-reactors, laboratory-scale integral thermal shock tests were conducted on non-irradiated Zircaloy-4 cladding tube specimens. Then, the obtained binary data with respect to fracture or non-fracture of the cladding tube specimen were analyzed statistically. A method to obtain the fracture probability curve as a function of equivalent cladding reacted (ECR) was proposed using Bayesian inference for generalized linear models: probit, logit, and log-probit models. Then, model selection was performed in terms of physical characteristics and information criteria, a widely applicable information criterion and a widely applicable Bayesian information criterion. As a result, it was clarified that the log-probit model was the best among the three models to estimate the fracture probability in terms of the degree of prediction accuracy for both next data to be obtained and the true model. Using the log-probit model, it was shown that 20% ECR corresponded to a 5% probability level with a 95% confidence of fracture of the cladding tube specimens.

Recognizing and reporting vertebral fractures: reducing the risk of future osteoporotic fractures

International Nuclear Information System (INIS)

Lentle, B.C.; Brown, J.P.; Khan, A.

2007-01-01

Given the increasing evidence that vertebral fractures are underdiagnosed and not acted on, Osteoporosis Canada and the Canadian Association of Radiologists initiated a project to develop and publish a set of recommendations to promote and facilitate the diagnosis and reporting of vertebral fractures. The identification of spinal fractures is not uniform. More than 65% of vertebral fractures cause no symptoms. It is also apparent that vertebral fractures are inadequately recognized when the opportunity for diagnosis arises fortuitously. It is to patients' benefit that radiologists report vertebral fractures evident on a chest or other radiograph, no matter how incidental to the immediate clinical indication for the examination. The present recommendations can help to close the gap in care in recognizing and treating vertebral fractures, to prevent future fractures and thus reduce the burden of osteoporosis-related morbidity and mortality, as well as fracture-related costs to the health care system. Several studies indicate that a gap exists in regard to the diagnosis of vertebral fractures and the clinical response following such diagnosis. All recommendations presented here are based on consensus. These recommendations were developed by a multidisciplinary working group under the auspices of the Scientific Advisory Council of Osteoporosis Canada and the Canadian Association of Radiologists. Prevalent vertebral fractures have important clinical implications in terms of future fracture risk. Recognizing and reporting fractures incidental to radiologic examinations done for other reasons has the potential to reduce health care costs by initiating further steps in osteoporosis diagnosis and appropriate therapy. Physicians should be aware of the importance of vertebral fracture diagnosis in assessing future osteoporotic fracture risk. Vertebral fractures incidental to radiologic examinations done for other reasons should be identified and reported. Vertebral fractures

Investigation of the local fracture toughness and the elastic-plastic fracture behavior of NiAl and tungsten by means of micro-cantilever tests

International Nuclear Information System (INIS)

Ast, Johannes

2016-01-01

is linked to the thermally activated dislocation mobility which is more constrained in those samples. Investigations on plastically predeformed samples were performed in order to study the influence of the dislocation density on the fracture behavior. It was found that the fracture toughness was again not affected but that the predeformed samples failed at an earlier stage at lower J-integrals. This is due to the lower mobility of the dislocations emitted from the crack tip in consequence of the high amount of strain hardening and the higher flow stress in those samples. Experiments in ultrafine-grained tungsten revealed a fracture behavior which was more brittle than expected. A single grain at the crack front with its crystallographic orientation being prone to cleavage failure can decisively influence the fracture behavior at the micro scale. [de

Influence of crack depth on the fracture toughness of reactor pressure vessel steel

International Nuclear Information System (INIS)

Theiss, T.J.; Bryson, J.W.

1991-01-01

The Heavy Section Steel Technology Program (HSST) at Oak Ridge National Laboratory (ORNL) is investigating the influence of flaw depth on the fracture toughness of reactor pressure vessel (RPV) steel. Recently, it has been shown that, in notched beam testing, shallow cracks tend to exhibit an elevated toughness as a result of a loss of constraint at the crack tip. The loss of constraint takes place when interaction occurs between the elastic-plastic crack-tip stress field and the specimen surface nearest the crack tip. An increased shallow-crack fracture toughness is of interest to the nuclear industry because probabilistic fracture-mechanics evaluations show that shallow flaws play a dominant role in the probability of vessel failure during postulated pressurized-thermal-shock (PTS) events. Tests have been performed on beam specimens loaded in 3-point bending using unirradiated reactor pressure vessel material (A533 B). Testing has been conducted using specimens with a constant beam depth (W = 94 mm) and within the lower transition region of the toughness curve for A533 B. Test results indicate a significantly higher fracture toughness associated with the shallow flaw specimens compared to the fracture toughness determined using deep-crack (a/W = 0.5) specimens. Test data also show little influence of thickness on the fracture toughness for the current test temperature (-60 degree C). 21 refs., 5 figs., 3 tabs

Fracture Propagation and Permeability Change under Poro-thermoelastic Loads & Silica Reactivity in Enhanced Geothermal Systems

Energy Technology Data Exchange (ETDEWEB)

Ahmad Ghassemi

2009-10-01

/dissolution, as well as the variation in fracture aperture and pressure. Also, a three-dimensional model of injection/extraction has been developed to consider the impact poro- and thermoelastic stresses on fracture slip and injection pressure. These investigations shed light on the processes involved in the observed phenomenon of injection pressure variation (e.g., in Coso), and allow the assessment of the potential of thermal and chemical stimulation strategies.

Simulation of complex fracture networks influenced by natural fractures in shale gas reservoir

Directory of Open Access Journals (Sweden)

Zhao Jinzhou

2014-10-01

Full Text Available When hydraulic fractures intersect with natural fractures, the geometry and complexity of a fracture network are determined by the initiation and propagation pattern which is affected by a number of factors. Based on the fracture mechanics, the criterion for initiation and propagation of a fracture was introduced to analyze the tendency of a propagating angle and factors affecting propagating pressure. On this basis, a mathematic model with a complex fracture network was established to investigate how the fracture network form changes with different parameters, including rock mechanics, in-situ stress distribution, fracture properties, and frac treatment parameters. The solving process of this model was accelerated by classifying the calculation nodes on the extending direction of the fracture by equal pressure gradients, and solving the geometrical parameters prior to the iteration fitting flow distribution. With the initiation and propagation criterion as the bases for the propagation of branch fractures, this method decreased the iteration times through eliminating the fitting of the fracture length in conventional 3D fracture simulation. The simulation results indicated that the formation with abundant natural fractures and smaller in-situ stress difference is sufficient conditions for fracture network development. If the pressure in the hydraulic fractures can be kept at a high level by temporary sealing or diversion, the branch fractures will propagate further with minor curvature radius, thus enlarging the reservoir stimulation area. The simulated shape of fracture network can be well matched with the field microseismic mapping in data point range and distribution density, validating the accuracy of this model.

Mechanical and thermal properties of bulk ZrB{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Nakamori, Fumihiro [Graduate School of Engineering, Osaka University (Japan); Ohishi, Yuji, E-mail: ohishi@ms.see.eng.osaka-u.ac.jp [Graduate School of Engineering, Osaka University (Japan); Muta, Hiroaki; Kurosaki, Ken [Graduate School of Engineering, Osaka University (Japan); Fukumoto, Ken-ichi [Research Institute of Nuclear Engineering, University of Fukui (Japan); Yamanaka, Shinsuke [Graduate School of Engineering, Osaka University (Japan); Research Institute of Nuclear Engineering, University of Fukui (Japan)

2015-12-15

ZrB{sub 2} appears to have formed in the fuel debris at the Fukushima Daiichi nuclear disaster site, through the reaction between Zircaloy cladding materials and the control rod material B{sub 4}C. Since ZrB{sub 2} has a high melting point of 3518 K, the ceramic has been widely studied as a heat-resistant material. Although various studies on the thermochemical and thermophysical properties have been performed for ZrB{sub 2}, significant differences exist in the data, possibly due to impurities or the porosity within the studied samples. In the present study, we have prepared a ZrB{sub 2} bulk sample with 93.1% theoretical density by sintering ZrB{sub 2} powder. On this sample, we have comprehensively examined the thermal and mechanical properties of ZrB{sub 2} by the measurement of specific heat, ultrasonic sound velocities, thermal diffusivity, and thermal expansion. Vickers hardness and fracture toughness were also measured and found to be 13–23 GPa and 1.8–2.8 MPa m{sup 0.5}, respectively. The relationships between these properties were carefully examined in the present study. - Highlights: • A ZrB{sub 2} bulk sample with 93.1% theoretical density was prepared by sintering ZrB{sub 2} powder. • We have evaluated mechanical and thermal properties such as Vickers hardness, fracture toughness and thermal conductivity. • The relationships between these properties were carefully examined.

Development of a finite element based thermal cracking performance prediction model.

Science.gov (United States)

2009-09-15

Low-temperature cracking of hot-mix asphalt (HMA) pavements continues to be a leading cause of : premature pavement deterioration in regions of cold climate and/or where significant thermal cycling : occurs. Recent advances in fracture testing and mo...

Experimental and numerical simulation of dissolution and precipitation: implications for fracture sealing at Yucca Mountain, Nevada

Science.gov (United States)

Dobson, Patrick F.; Kneafsey, Timothy J.; Sonnenthal, Eric L.; Spycher, Nicolas; Apps, John A.

2003-05-01

Plugging of flow paths caused by mineral precipitation in fractures above the potential repository at Yucca Mountain, Nevada could reduce the probability of water seeping into the repository. As part of an ongoing effort to evaluate thermal-hydrological-chemical (THC) effects on flow in fractured media, we performed a laboratory experiment and numerical simulations to investigate mineral dissolution and precipitation under anticipated temperature and pressure conditions in the repository. To replicate mineral dissolution by vapor condensate in fractured tuff, water was flowed through crushed Yucca Mountain tuff at 94 °C. The resulting steady-state fluid composition had a total dissolved solids content of about 140 mg/l; silica was the dominant dissolved constituent. A portion of the steady-state mineralized water was flowed into a vertically oriented planar fracture in a block of welded Topopah Spring Tuff that was maintained at 80 °C at the top and 130 °C at the bottom. The fracture began to seal with amorphous silica within 5 days. A 1-D plug-flow numerical model was used to simulate mineral dissolution, and a similar model was developed to simulate the flow of mineralized water through a planar fracture, where boiling conditions led to mineral precipitation. Predicted concentrations of the major dissolved constituents for the tuff dissolution were within a factor of 2 of the measured average steady-state compositions. The mineral precipitation simulations predicted the precipitation of amorphous silica at the base of the boiling front, leading to a greater than 50-fold decrease in fracture permeability in 5 days, consistent with the laboratory experiment. These results help validate the use of a numerical model to simulate THC processes at Yucca Mountain. The experiment and simulations indicated that boiling and concomitant precipitation of amorphous silica could cause significant reductions in fracture porosity and permeability on a local scale. However

Numerical analysis of thermal-hydrological conditions in the single heater test at Yucca Mountain

International Nuclear Information System (INIS)

Birkholzer, Jens T.; Tsang, Yvonne W.

1998-01-01

The Single Heater Test (SHT) is one of two in-situ thermal tests included in the site characterization program for the potential underground nuclear waste repository at Yucca Mountain. The heating phase of the SHT started in August 1996, and was completed in May 1997 after 9 months of heating. The coupled processes in the unsaturated fractured rock mass around the heater were monitored by numerous sensors for thermal, hydrological, mechanical and chemical data. In addition to passive monitoring, active testing of the rock mass moisture content was performed using geophysical methods and air injection testing. The extensive data set available from this test gives a unique opportunity to improve the understanding of the thermal-hydrological situation in the natural setting of the repository rocks. The present paper focuses on the 3-D numerical simulation of the thermal-hydrological processes in the SHT using TOUGH2. In the comparative analysis, they are particularly interested in the accuracy of different fracture-matrix-interaction concepts such as the Effective Continuum (ECM), the Dual Continuum (DKM), and the Multiple Interacting Continua (MINC) method

Radiotherapy of pathologic fractures and skeletal lesions bearing the risk of fracture

International Nuclear Information System (INIS)

Rieden, K.; Kober, B.; Mende, U.; Zum Winkel, K.

1986-01-01

Radiotherapy is of great importance in the treatment of pathologic fractures and skeletal lesions bearing the risk of fracture which are induced by malignomas, especially if these are in an advanced stage. In dependence on site and extent of skeletal destruction as well as on the general tumor dissemination, it can be distinguished between palliative radiotherapy and curative radiotherapy aiming at analgesia and remineralization. A retrospective analysis of 27 pathologic fractures and 56 skeletal lesions bearing the risk of fracture in malignoma patients showed an analgetic effect obtained by radiotherapy in 67% of pathological fractures and in 80% of skeletal lesions bearing the risk of fracture, whereas a remineralization could be demonstrated for 33% of pathological fractures and 50% of destructions bearing the risk of fracture. A stabilization of destructions progressing before therapy was found in 55% of pathological fractures and 40% of skeletal lesions bearing the risk of fracture. Thus a partial loading, supported by orthopedic prostheses, was possible for more than 50% of all patients. (orig.) [de

[Trochanteric femoral fractures].

Science.gov (United States)

Douša, P; Čech, O; Weissinger, M; Džupa, V

2013-01-01

At the present time proximal femoral fractures account for 30% of all fractures referred to hospitals for treatment. Our population is ageing, the proportion of patients with post-menopausal or senile osteoporosis is increasing and therefore the number of proximal femoral fractures requiring urgent treatment is growing too. In the age category of 50 years and older, the incidence of these fractures has increased exponentially. Our department serves as a trauma centre for half of Prague and part of the Central Bohemia Region with a population of 1 150 000. Prague in particular has a high number of elderly citizens. Our experience is based on extensive clinical data obtained from the Register of Proximal Femoral Fractures established in 1997. During 14 years, 4280 patients, 3112 women and 1168 men, were admitted to our department for treatment of proximal femoral fractures. All patients were followed up until healing or development of complications. In the group under study, 82% were patients older than 70 years; 72% of those requiring surgery were in their seventies and eighties. Men were significantly younger than women (pfractures were 2.3-times more frequent in women than in men. In the category under 60 years, men significantly outnumbered women (pfractures were, on the average, eight years older than the patients with intertrochanteric fractures, which is a significant difference (pTrochanteric fractures accounted for 54.7% and femoral neck fractures for 45.3% of all fractures. The inter-annual increase was 5.9%, with more trochanteric than femoral neck fractures. There was a non-significant decrease in intertrochanteric (AO 31-A3) fractures. On the other hand, the number of pertrochanteric (AO 31-A1+2) fractures increased significantly (pfractures were treated with a proximal femoral nail; a short nail was used in 1260 and a long nail in 134 of them. A dynamic hip screw (DHS) was employed to treat 947 fractures. Distinguishing between pertrochanteric (21-A1

Jogger's fracture and other stress fractures of the lumbo-sacral spine

International Nuclear Information System (INIS)

Abel, M.S.

1985-01-01

The posterior rings of the lower lumbo-sacral vertebrae are subject to stress fractures at any part - pedicle, pars, or lamina. The site of fracture is apparently determined by the axis of weight bearing. The three illustrative clinical examples cited include a jogger with a laminar fracture, a ballet dancer with pedicle fractures, and a nine-year-old boy with fractures of pars and lamina. Chronic low back pain is the typical complaint with stress fractures of the lower lumbo-sacral spine. Special imaging techniques are usually needed to demonstrate these lesions, including vertebral arch views, multi-directional tomography, and computed tomography (CT). (orig.)

Improvement of the fracture toughness matrix cured by electron beam radiation, by incorporation of thermoplastic

International Nuclear Information System (INIS)

Chauray, E.

2003-07-01

The aim of the present study is to improve the fracture toughness of a vinyl-ester matrix cured by electron beam radiation, by incorporation of a thermoplastic polymer. The ultimate plan is to improve the fracture toughness of the composite material made of this reinforced matrix and carbon fibres. The first step deals with the study of an epoxy matrix reinforced by a polyether-sulfone. This well-known material, as it is used in industrial formulation, allowed us to characterize all the parameters needed to obtain a good reinforcement as for instance the morphology, and also to compare two kinds of processes: thermal and electron beam curing. In fact, we are really interested in increasing fracture toughness of a vinyl-ester matrix that is not miscible with polyether-sulfone. So a copolymer which has a similar structure as polyether-sulfone is synthesized in order to obtain a miscible blend. The corresponding material has good fracture toughness, with an increase of 80 % for 15 % addition of thermoplastic. (author)

Characterization of ductile fracture properties of quench-hardenable boron steel: Influence of microstructure and processing conditions

International Nuclear Information System (INIS)

Golling, Stefan; Östlund, Rickard; Oldenburg, Mats

2016-01-01

Developments of the hot stamping technology have enabled the production of components with differential microstructure composition and mechanical properties. These can increase the performance of certain crash-relevant automotive structures by combining high intrusion protection and energy absorption. This paper presents a comprehensive experimental investigation on the flow and ductile fracture properties of boron-alloyed steel with a wide range of different microstructure compositions. Three types of dual phase microstructures at three different volume fractions, and one triple phase grade, were generated by thermal treatment. Flow curves extending beyond necking and the equivalent plastic strain to fracture for each grade was determined by tensile testing using full-field measurements. The influence of phase composition and microstructural parameters were further investigated by means of a multi-scale modeling approach based on mean-field homogenization in combination with local fracture criteria. Inter-phase and intra-phase fracture mechanisms were considered by adopting two separate fracture criteria formulated in terms of the local average stress field. The micromechanical model captures with useful accuracy the strong influence of microstructure and processing conditions on the flow and fracture properties, implying promising prospects of mean-field homogenization for the constitutive modeling of hot stamped components.

Characterization of ductile fracture properties of quench-hardenable boron steel: Influence of microstructure and processing conditions

Energy Technology Data Exchange (ETDEWEB)

Golling, Stefan, E-mail: stefan.golling@ltu.se [Luleå University of Technology, SE 971 87 Luleå (Sweden); Östlund, Rickard [Gestamp HardTech, Ektjärnsvägen 5, SE 973 45 Luleå (Sweden); Oldenburg, Mats [Luleå University of Technology, SE 971 87 Luleå (Sweden)

2016-03-21

Developments of the hot stamping technology have enabled the production of components with differential microstructure composition and mechanical properties. These can increase the performance of certain crash-relevant automotive structures by combining high intrusion protection and energy absorption. This paper presents a comprehensive experimental investigation on the flow and ductile fracture properties of boron-alloyed steel with a wide range of different microstructure compositions. Three types of dual phase microstructures at three different volume fractions, and one triple phase grade, were generated by thermal treatment. Flow curves extending beyond necking and the equivalent plastic strain to fracture for each grade was determined by tensile testing using full-field measurements. The influence of phase composition and microstructural parameters were further investigated by means of a multi-scale modeling approach based on mean-field homogenization in combination with local fracture criteria. Inter-phase and intra-phase fracture mechanisms were considered by adopting two separate fracture criteria formulated in terms of the local average stress field. The micromechanical model captures with useful accuracy the strong influence of microstructure and processing conditions on the flow and fracture properties, implying promising prospects of mean-field homogenization for the constitutive modeling of hot stamped components.

Ablation of musculoskeletal metastases: pain palliation, fracture risk reduction, and oligometastatic disease.

Science.gov (United States)

Kurup, Anil Nicholas; Callstrom, Matthew R

2013-12-01

Thermal ablation is an effective, minimally invasive alternative to conventional therapies in the palliation of painful musculoskeletal metastases and an emerging approach to obtain local tumor control in the setting of limited metastatic disease. Various thermal ablation technologies have been applied to bone and soft tissue tumors and may be used in combination with percutaneous cement instillation for skeletal lesions with or at risk for pathologic fracture. This article reviews current practices of percutaneous ablation of musculoskeletal metastases with an emphasis on radiofrequency ablation and cryoablation of painful skeletal metastases. © 2013 Elsevier Inc. All rights reserved.

Imaging of insufficiency fractures

Energy Technology Data Exchange (ETDEWEB)

Krestan, Christian [Department of Radiology, Medical University of Vienna, Vienna General Hospital, Waehringerstr. 18-20, 1090 Vienna (Austria)], E-mail: christian.krestan@meduniwien.ac.at; Hojreh, Azadeh [Department of Radiology, Medical University of Vienna, Vienna General Hospital, Waehringerstr. 18-20, 1090 Vienna (Austria)

2009-09-15

This review focuses on the occurrence, imaging and differential diagnosis of insufficiency fractures. Prevalence, the most common sites of insufficiency fractures and their clinical implications are discussed. Insufficiency fractures occur with normal stress exerted on weakened bone. Postmenopausal osteoporosis is the most common cause of insufficiency fractures. Other conditions which affect bone turnover include osteomalacia, hyperparathyroidism, chronic renal failure and high-dose glucocorticoid therapy. It is a challenge for the radiologist to detect and diagnose insufficiency fractures, and to differentiate them from other bone lesions. Radiographs are still the most widely used imaging method for identification of insufficiency fractures, but sensitivity is limited, depending on the location of the fractures. Magnetic resonance imaging (MRI) is a very sensitive tool to visualize bone marrow abnormalities associated with insufficiency fractures. Thin section, multi-detector computed tomography (MDCT) depicts subtle fracture lines allowing direct visualization of cortical and trabecular bone. Bone scintigraphy still plays a role in detecting fractures, with good sensitivity but limited specificity. The most important differential diagnosis is underlying malignant disease leading to pathologic fractures. Bone densitometry and clinical history may also be helpful in confirming the diagnosis of insufficiency fractures.

Influence of structures on fracture and fracture toughness of cemented tungsten carbides

International Nuclear Information System (INIS)

Zhao, W.; Zhang, X.

1987-01-01

A study was made of the influence of structures on fracture and fracture toughness of cemented tungsten carbides with different compositions and grain sizes. The measurement of the fracture toughness of cemented tungsten carbide was carried out using single edge notched beam. The microstructural parameters and the proportion for each fracture mode on the fracture surface were obtained. The brittle fracture of the alloy is mainly due to the interfacial decohesion fracture following the interface of the carbide crystals. It has been observed that there are localized fractures region ahead of the crack tip. The morphology of the crack propagation path as well as the slip structure in the cobalt phase of the deformed region have been investigated. In addition, a study of the correlation between the plane strain fracture toughness and microstructural parameters, such as mean free path of the cobalt phase, tungsten carbide grain size and the contiguity of tungsten carbide crystals was also made

Post-depositional fracturing and subsidence of pumice flow deposits: Lascar Volcano, Chile.

Science.gov (United States)

Whelley, Patrick L; Jay, J; Calder, E S; Pritchard, M E; Cassidy, N J; Alcaraz, S; Pavez, A

Unconsolidated pyroclastic flow deposits of the 1993 eruption of Lascar Volcano, Chile, have, with time, become increasingly dissected by a network of deeply penetrating fractures. The fracture network comprises orthogonal sets of decimeter-wide linear voids that form a pseudo-polygonal grid visible on the deposit surface. In this work, we combine shallow surface geophysical imaging tools with remote sensing observations and direct field measurements of the deposit to investigate these fractures and their underlying causal mechanisms. Based on ground penetrating radar images, the fractures are observed to have propagated to depths of up to 10 m. In addition, orbiting radar interferometry shows that deposit subsidence of up to 1 cm/year -1 occurred between 1993 and 1996 with continued subsidence occurring at a slower rate thereafter. In situ measurements show that 1 m below the surface, the 1993 deposits remain 5°C to 15°C hotter, 18 years after emplacement, than adjacent deposits. Based on the observed subsidence as well as estimated cooling rates, the fractures are inferred to be the combined result of deaeration, thermal contraction, and sedimentary compaction in the months to years following deposition. Significant environmental factors, including regional earthquakes in 1995 and 2007, accelerated settling at punctuated moments in time. The spatially variable fracture pattern relates to surface slope and lithofacies variations as well as substrate lithology. Similar fractures have been reported in other ignimbrites but are generally exposed only in cross section and are often attributed to formation by external forces. Here we suggest that such interpretations should be invoked with caution, and deformation including post-emplacement subsidence and fracturing of loosely packed ash-rich deposits in the months to years post-emplacement is a process inherent in the settling of pyroclastic material.

Percolation cooling of the Three Mile Island Unit 2 lower head by way of thermal cracking and gap formation

DEFF Research Database (Denmark)

Thomsen, K.L.

2002-01-01

Two partial models have been developed to elucidate the Three Mile Island Unit 2 lower head coolability by water percolation from above into the thermally cracking debris bed and into a gap between the debris and the wall The bulk permeability of the cracked top crust is estimated based on simple...... fracture mechanics and application of Poiseuille's law to the fractures. The gap is considered as an abstraction representing an initially rugged interface, which probably expanded by thermal deformation and cracking in connection with the water ingress. The coupled flow and heat conduction problem...

Rib fractures predict incident limb fractures: results from the European prospective osteoporosis study.

Science.gov (United States)

Ismail, A A; Silman, A J; Reeve, J; Kaptoge, S; O'Neill, T W

2006-01-01

Population studies suggest that rib fractures are associated with a reduction in bone mass. While much is known about the predictive risk of hip, spine and distal forearm fracture on the risk of future fracture, little is known about the impact of rib fracture. The aim of this study was to determine whether a recalled history of rib fracture was associated with an increased risk of future limb fracture. Men and women aged 50 years and over were recruited from population registers in 31 European centres for participation in a screening survey of osteoporosis (European Prospective Osteoporosis Study). Subjects were invited to complete an interviewer-administered questionnaire that included questions about previous fractures including rib fracture, the age of their first fracture and also the level of trauma. Lateral spine radiographs were performed and the presence of vertebral deformity was determined morphometrically. Following the baseline survey, subjects were followed prospectively by annual postal questionnaire to determine the occurrence of clinical fractures. The subjects included 6,344 men, with a mean age of 64.2 years, and 6,788 women, with a mean age of 63.6 years, who were followed for a median of 3 years (range 0.4-5.9 years), of whom 135 men (2.3%) and 101 women (1.6%) reported a previous low trauma rib fracture. In total, 138 men and 391 women sustained a limb fracture during follow-up. In women, after age adjustment, those with a recalled history of low trauma rib fracture had an increased risk of sustaining 'any' limb fracture [relative hazard (RH)=2.3; 95% CI 1.3, 4.0]. When stratified by fracture type the predictive risk was more marked for hip (RH=7.7; 95% CI 2.3, 25.9) and humerus fracture (RH=4.5; 95% CI 1.4, 14.6) than other sites (RH=1.6; 95% CI 0.6, 4.3). Additional adjustment for prevalent vertebral deformity and previous (non-rib) low trauma fractures at other sites slightly reduced the strength of the association between rib fracture and

Hip fracture - discharge

Science.gov (United States)

... neck fracture repair - discharge; Trochanteric fracture repair - discharge; Hip pinning surgery - discharge ... in the hospital for surgery to repair a hip fracture, a break in the upper part of ...

Quantifying Discrete Fracture Network Connectivity in Hydraulic Fracturing Stimulation

Science.gov (United States)

Urbancic, T.; Ardakani, E. P.; Baig, A.

2017-12-01

Hydraulic fracture stimulations generally result in microseismicity that is associated with the activation or extension of pre-existing microfractures and discontinuities. Microseismic events acquired under 3D downhole sensor coverage provide accurate event locations outlining hydraulic fracture growth. Combined with source characteristics, these events provide a high quality input for seismic moment tensor inversion and eventually constructing the representative discrete fracture network (DFN). In this study, we investigate the strain and stress state, identified fracture orientation, and DFN connectivity and performance for example stages in a multistage perf and plug completion in a North American shale play. We use topology, the familiar concept in many areas of structural geology, to further describe the relationships between the activated fractures and their effectiveness in enhancing permeability. We explore how local perturbations of stress state lead to the activation of different fractures sets and how that effects the DFN interaction and complexity. In particular, we observe that a more heterogeneous stress state shows a higher percentage of sub-horizontal fractures or bedding plane slips. Based on topology, the fractures are evenly distributed from the injection point, with decreasing numbers of connections by distance. The dimensionless measure of connection per branch and connection per line are used for quantifying the DFN connectivity. In order to connect the concept of connectivity back to productive volume and stimulation efficiency, the connectivity is compared with the character of deformation in the reservoir as deduced from the collective behavior of microseismicity using robustly determined source parameters.

Change of Charpy impact fracture behavior of precracked ferritic specimens due to thermal aging in sodium

International Nuclear Information System (INIS)

Hu, W.L.

1985-12-01

A series of tests were conducted to evaluate the effect of sodium on the impact fracture behavior of precracked Charpy specimens made of HT-9 weldment. One set of samples was precracked prior to sodium aging and the other set was precracked after aging in sodium. Both set of specimens exhibited the same DBTT. Samples precracked prior to sodium exposure, however, showed a 40% reduction in the upper shelf energy (USE) as compared to the set precracked after aging. The results suggest that the fracture toughness of the material may be reduced if an existing crack was soaked in sodium at elevated temperature for a period of time

Thermal shock considerations for the TFCX limiter and first wall

International Nuclear Information System (INIS)

Haines, J.R.; Fuller, G.M.

1983-01-01

Resistance to thermal shock fracture of limiter and first wall surface material candidates during plasma disruption heating conditions is evaluated. A simple, figure-of-merit type thermal shock parameter which provides a mechanism to rank material candidates is derived. Combining this figure-of-merit parameter with the parameters defining specific heating conditions yields a non-dimensional thermal shock parameter. For values of this parameter below a critical value, a given material is expected to undergo thermal shock damage. Prediction of thermal shock damage with this parameter is shown to exhibit good agreement with test data. Applying this critical parameter value approach, all materials examined in this study are expected to experience thermal shock damage for nominal TFCX plasma disruption conditions. Since the extent of this damage is not clear, tests which explore the range of expected conditions for TFCX are recommended

Fracture network growth for prediction of fracture characteristics and connectivity in tight reservoir rocks

NARCIS (Netherlands)

Barnhoorn, A.; Cox, S.F.

2012-01-01

Fracturing experiments on very low-porosity dolomite rocks shows a difference in growth of fracture networks by stress-driven fracturing and fluid-driven fracturing. Stress-driven fracture growth, in the absence of fluid pressure, initially forms fractures randomly throughout the rocks followed by

Residual Tensile Property of Plain Woven Jute Fiber/Poly(Lactic Acid) Green Composites during Thermal Cycling.

Science.gov (United States)

Katogi, Hideaki; Takemura, Kenichi; Akiyama, Motoki

2016-07-14

This study investigated the residual tensile properties of plain woven jute fiber reinforced poly(lactic acid) (PLA) during thermal cycling. Temperature ranges of thermal cycling tests were 35-45 °C and 35-55 °C. The maximum number of cycles was 10³ cycles. The quasi-static tensile tests of jute fiber, PLA, and composite were conducted after thermal cycling tests. Thermal mechanical analyses of jute fiber and PLA were conducted after thermal cycling tests. Results led to the following conclusions. For temperatures of 35-45 °C, tensile strength of composite at 10³ cycles decreased 10% compared to that of composite at 0 cycles. For temperatures of 35-55 °C, tensile strength and Young's modulus of composite at 10³ cycles decreased 15% and 10%, respectively, compared to that of composite at 0 cycles. Tensile properties and the coefficient of linear expansion of PLA and jute fiber remained almost unchanged after thermal cycling tests. From observation of a fracture surface, the length of fiber pull out in the fracture surface of composite at 10³ cycles was longer than that of composite at 0 cycles. Therefore, tensile properties of the composite during thermal cycling were decreased, probably because of the decrease of interfacial adhesion between the fiber and resin.

In vitro comparison of fracture load of implant-supported, zirconia-based, porcelain- and composite-layered restorations after artificial aging.

Science.gov (United States)

Komine, Futoshi; Taguchi, Kohei; Fushiki, Ryosuke; Kamio, Shingo; Iwasaki, Taro; Matsumura, Hideo

2014-01-01

This study evaluated fracture load of single-tooth, implant-supported, zirconia-based, porcelain- and indirect composite-layered restorations after artificial aging. Forty-four zirconia-based molar restorations were fabricated on implant abutments and divided into four groups, namely, zirconia-based all-ceramic restorations (ZAC group) and three types of zirconia-based composite-layered restorations (ZIC-P, ZIC-E, and ZIC groups). Before layering an indirect composite material, the zirconia copings in the ZIC-P and ZIC-E groups were primed with Clearfil Photo Bond and Estenia Opaque Primer, respectively. All restorations were cemented on the abutments with glass-ionomer cement and then subjected to thermal cycling and cyclic loading. All specimens survived thermal cycling and cyclic loading. The fracture load of the ZIC-P group (2.72 kN) was not significantly different from that of the ZAC group (3.05 kN). The fracture load of the zirconia-based composite-layered restoration primed with Clearfil Photo Bond (ZIC-P) was comparable to that of the zirconia-based all-ceramic restoration (ZAC) after artificial aging.

Scaphoid Fracture

Directory of Open Access Journals (Sweden)

Esther Kim, BS

2018-04-01

Full Text Available History of present illness: A 25-year-old, right-handed male presented to the emergency department with left wrist pain after falling from a skateboard onto an outstretched hand two-weeks prior. He otherwise had no additional concerns, including no complaints of weakness or loss of sensation. On physical exam, there was tenderness to palpation within the anatomical snuff box. The neurovascular exam was intact. Plain films of the left wrist and hand were obtained. Significant findings: The anteroposterior (AP plain film of this patient demonstrates a full thickness fracture through the middle third of the scaphoid (red arrow, with some apparent displacement (yellow lines and subtle angulation of the fracture fragments (blue line. Discussion: The scaphoid bone is the most commonly fractured carpal bone accounting for 70%-80% of carpal fractures.1 Classically, it is sustained following a fall onto an outstretched hand (FOOSH. Patients should be evaluated for tenderness with palpation over the anatomical snuffbox, which has a sensitivity of 100% and specificity of 40%.2 Plain films are the initial diagnostic modality of choice and have a sensitivity of 70%, but are commonly falsely negative in the first two to six weeks of injury (false negative of 20%.3 The Mayo classification organizes scaphoid fractures as involving the proximal, mid, and distal portions of the scaphoid bone with mid-fractures being the most common.3 The proximal scaphoid is highly susceptible to vascular compromise because it depends on retrograde blood flow from the radial artery. Therefore, disruption can lead to serious sequelae including osteonecrosis, arthrosis, and functional impairment. Thus, a low threshold should be maintained for neurovascular evaluation and surgical referral. Patients with non-displaced scaphoid fractures should be placed in a thumb spica splint.3 Patients with even suspected scaphoid fractures should be placed in a thumb spica splint and re

Surrogate-based optimization of hydraulic fracturing in pre-existing fracture networks

Science.gov (United States)

Chen, Mingjie; Sun, Yunwei; Fu, Pengcheng; Carrigan, Charles R.; Lu, Zhiming; Tong, Charles H.; Buscheck, Thomas A.

2013-08-01

Hydraulic fracturing has been used widely to stimulate production of oil, natural gas, and geothermal energy in formations with low natural permeability. Numerical optimization of fracture stimulation often requires a large number of evaluations of objective functions and constraints from forward hydraulic fracturing models, which are computationally expensive and even prohibitive in some situations. Moreover, there are a variety of uncertainties associated with the pre-existing fracture distributions and rock mechanical properties, which affect the optimized decisions for hydraulic fracturing. In this study, a surrogate-based approach is developed for efficient optimization of hydraulic fracturing well design in the presence of natural-system uncertainties. The fractal dimension is derived from the simulated fracturing network as the objective for maximizing energy recovery sweep efficiency. The surrogate model, which is constructed using training data from high-fidelity fracturing models for mapping the relationship between uncertain input parameters and the fractal dimension, provides fast approximation of the objective functions and constraints. A suite of surrogate models constructed using different fitting methods is evaluated and validated for fast predictions. Global sensitivity analysis is conducted to gain insights into the impact of the input variables on the output of interest, and further used for parameter screening. The high efficiency of the surrogate-based approach is demonstrated for three optimization scenarios with different and uncertain ambient conditions. Our results suggest the critical importance of considering uncertain pre-existing fracture networks in optimization studies of hydraulic fracturing.

XFEM modeling of hydraulic fracture in porous rocks with natural fractures

Science.gov (United States)

Wang, Tao; Liu, ZhanLi; Zeng, QingLei; Gao, Yue; Zhuang, Zhuo

2017-08-01

Hydraulic fracture (HF) in porous rocks is a complex multi-physics coupling process which involves fluid flow, diffusion and solid deformation. In this paper, the extended finite element method (XFEM) coupling with Biot theory is developed to study the HF in permeable rocks with natural fractures (NFs). In the recent XFEM based computational HF models, the fluid flow in fractures and interstitials of the porous media are mostly solved separately, which brings difficulties in dealing with complex fracture morphology. In our new model the fluid flow is solved in a unified framework by considering the fractures as a kind of special porous media and introducing Poiseuille-type flow inside them instead of Darcy-type flow. The most advantage is that it is very convenient to deal with fluid flow inside the complex fracture network, which is important in shale gas extraction. The weak formulation for the new coupled model is derived based on virtual work principle, which includes the XFEM formulation for multiple fractures and fractures intersection in porous media and finite element formulation for the unified fluid flow. Then the plane strain Kristianovic-Geertsma-de Klerk (KGD) model and the fluid flow inside the fracture network are simulated to validate the accuracy and applicability of this method. The numerical results show that large injection rate, low rock permeability and isotropic in-situ stresses tend to lead to a more uniform and productive fracture network.

Measurement of interfacial shear mechanical properties in thermal barrier coating systems by a barb pullout method

International Nuclear Information System (INIS)

Guo, S.Q.; Mumm, D.R.; Karlsson, A.M.; Kagawa, Y.

2005-01-01

A test technique has been developed to facilitate evaluation of the fracture characteristics of coatings and interfaces in thermal barrier coating (TBC) systems. The methodology has particular application in analyzing delamination crack growth, where crack propagation occurs under predominantly mode II loading. The technique has been demonstrated by quantitatively measuring the effective delamination fracture resistance of an electron-beam physical vapor deposition TBC

Analysis of the Slab Temperature, Thermal Stresses and Fractures Computed with the Implementation of Local and Average Boundary Conditions in the Secondary Cooling Zones

Directory of Open Access Journals (Sweden)

Hadała B.

2016-12-01

Full Text Available The numerical simulations of the temperature fields have been accomplished for slab casting made of a low carbon steel. The casting process of slab of 1500 mm in width and 225 mm in height has been modeled. Two types of boundary condition models of heat transfer have been employed in numerical simulations. The heat transfer coefficient in the first boundary condition model was calculated from the formula which takes into account the slab surface temperature and water flow rate in each secondary cooling zone. The second boundary condition model defines the heat transfer coefficient around each water spray nozzle. The temperature fields resulting from the average in zones water flow rate and from the nozzles arrangement have been compared. The thermal stresses and deformations resulted from such temperature field have given higher values of fracture criterion at slab corners.

Mortality Following Periprosthetic Proximal Femoral Fractures Versus Native Hip Fractures.

Science.gov (United States)

Boylan, Matthew R; Riesgo, Aldo M; Paulino, Carl B; Slover, James D; Zuckerman, Joseph D; Egol, Kenneth A

2018-04-04

The number of periprosthetic proximal femoral fractures is expected to increase with the increasing prevalence of hip arthroplasties. While native hip fractures have a well-known association with mortality, there are currently limited data on this outcome among the subset of patients with periprosthetic proximal femoral fractures. Using the New York Statewide Planning and Research Cooperative System, we identified patients from 60 to 99 years old who were admitted to a hospital in the state with a periprosthetic proximal femoral fracture (n = 1,655) or a native hip (femoral neck or intertrochanteric) fracture (n = 97,231) between 2006 and 2014. Within the periprosthetic fracture cohort, the indication for the existing implant was not available in the data set. We used mixed-effects regression models to compare mortality at 1 and 6 months and 1 year for periprosthetic compared with native hip fractures. The risk of mortality for patients who sustained a periprosthetic proximal femoral fracture was no different from that for patients who sustained a native hip fracture at 1 month after injury (3.2% versus 4.6%; odds ratio [OR], 0.90; 95% confidence interval [CI], 0.68 to 1.19; p = 0.446), but was lower at 6 months (3.8% versus 6.5%; OR, 0.74; 95% CI, 0.57 to 0.95; p = 0.020) and 1 year (9.7% versus 15.9%; OR, 0.71; 95% CI, 0.60 to 0.85; p accounting for age and comorbidities. Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Assessment of fracture risk

International Nuclear Information System (INIS)

Kanis, John A.; Johansson, Helena; Oden, Anders; McCloskey, Eugene V.

2009-01-01

Fractures are a common complication of osteoporosis. Although osteoporosis is defined by bone mineral density at the femoral neck, other sites and validated techniques can be used for fracture prediction. Several clinical risk factors contribute to fracture risk independently of BMD. These include age, prior fragility fracture, smoking, excess alcohol, family history of hip fracture, rheumatoid arthritis and the use of oral glucocorticoids. These risk factors in conjunction with BMD can be integrated to provide estimates of fracture probability using the FRAX tool. Fracture probability rather than BMD alone can be used to fashion strategies for the assessment and treatment of osteoporosis.

Overview and Evaluation of the NESC Projects for Fracture Assessments of Nuclear Components

International Nuclear Information System (INIS)

Sattari-Far, Iradj; Lorentzon, Mikael

2011-02-01

The overall objective of the NESC network has been to examine the reliability of the entire process of structural integrity assessment within an international framework. Within this network, six projects were conducted under the period of 1993-2008. The main targets of these projects were: NESC-I: This project evaluated the interactions among various technical disciplines applied to the integrity assessment of a large-scale thermally shocked spinning cylinder experiment. The cylinder test was designed to simulate selected conditions associated with an ageing flawed reactor pressure vessel. NESC-II: This project was on brittle crack initiation, propagation and arrest of shallow cracks in clad vessels under PTS loading. The results of this project underlined the conservatism of existing defects assessment procedures for shallow RPV flaws. NESC-III: This project was to quantify the accuracy of structural integrity assessment procedures for defects in dissimilar welds. The project was built around the conducted ADIMEW-project to share its overall objectives and to provide additional input. NESC-IV: This project was an experimental/analytical program to develop validated analysis methods for transferring fracture toughness data generated on standard test specimens to shallow flaws in reactor pressure vessel welds subject to biaxial loading in the lower-transition temperature region. NESC-V: This project aimed to develop a European multi-level procedure for handling of thermal fatigue phenomena in the nuclear power plant components. It also aimed to create a database of service and mock-up data for better understanding of thermal fatigue damage mechanisms. NESC-VI: This project was an extension of the NESC-IV project. Embedded subclad racks in beam specimens under uniaxial loading were studied to study the transferability of fracture toughness data between different crack configurations. This report gives an overview report of these six NESC projects. The reports cover

The radiation swelling effect on fracture properties and fracture mechanisms of irradiated austenitic steels. Part I. Ductility and fracture toughness

Energy Technology Data Exchange (ETDEWEB)

Margolin, B., E-mail: mail@crism.ru; Sorokin, A.; Shvetsova, V.; Minkin, A.; Potapova, V.; Smirnov, V.

2016-11-15

The radiation swelling effect on the fracture properties of irradiated austenitic steels under static loading has been studied and analyzed from the mechanical and physical viewpoints. Experimental data on the stress-strain curves, fracture strain, fracture toughness and fracture mechanisms have been represented for austenitic steel of 18Cr-10Ni-Ti grade (Russian analog of AISI 321 steel) irradiated up to neutron dose of 150 dpa with various swelling. Some phenomena in mechanical behaviour of irradiated austenitic steels have been revealed and explained as follows: a sharp decrease of fracture toughness with swelling growth; untypical large increase of fracture toughness with decrease of the test temperature; some increase of fracture toughness after preliminary cyclic loading. Role of channel deformation and channel fracture has been clarified in the properties of irradiated austenitic steel and different tendencies to channel deformation have been shown and explained for the same austenitic steel irradiated at different temperatures and neutron doses.

Fast fracture of a zirconium alloy pressure tube: cause and implications

International Nuclear Information System (INIS)

Price, E.G.; Cheadle, B.A.

1985-12-01

The cause of the unstable fracture of a Zircaloy-2 pressure tube in the core of a CANDU reactor is reviewed. Failure was associated with the presence of brittle zones of zirconium hydride which developed as a result of thermal gradient induced hydrogen diffusion. Unstable fracture occurred when the partial thickness crack reached an unstable length and the crack ran 2 meters along the tube and terminated by circumferential tearing. The partial thickness defect initiated and propagated to an unstable length by delayed hydride cracking is high compared to fatigue progression and increases exponentially with temperature. Delayed hydride cracking can be prevented by reducing residual stresses to a minimum and by high standards of non-destructive testing that ensures freedom from unacceptable defects. Future prevention of fast fracture is based upon the inspection of a limited number of fuel channels for the presence of defects and for conditions which can cause hydride build-up together with the periodic removal of Zr-2.5wt% Nb tubes to monitor their condition

Simulation of counter-current imbibition in water-wet fractured reservoirs based on discrete-fracture model

Directory of Open Access Journals (Sweden)

Wang Yueying

2017-08-01

Full Text Available Isolated fractures usually exist in fractured media systems, where the capillary pressure in the fracture is lower than that of the matrix, causing the discrepancy in oil recoveries between fractured and non-fractured porous media. Experiments, analytical solutions and conventional simulation methods based on the continuum model approach are incompetent or insufficient in describing media containing isolated fractures. In this paper, the simulation of the counter-current imbibition in fractured media is based on the discrete-fracture model (DFM. The interlocking or arrangement of matrix and fracture system within the model resembles the traditional discrete fracture network model and the hybrid-mixed-finite-element method is employed to solve the associated equations. The Behbahani experimental data validates our simulation solution for consistency. The simulation results of the fractured media show that the isolated-fractures affect the imbibition in the matrix block. Moreover, the isolated fracture parameters such as fracture length and fracture location influence the trend of the recovery curves. Thus, the counter-current imbibition behavior of media with isolated fractures can be predicted using this method based on the discrete-fracture model.

Fracture characteristics in Japanese rock

International Nuclear Information System (INIS)

Ijiri, Yuji; Sawada, Atsushi; Akahori, Kuniaki

1999-11-01

It is crucial for the performance assessment of geosphere to evaluate the characteristics of fractures that can be dominant radionuclide migration pathways from a repository to biosphere. This report summarizes the characteristics of fractures obtained from broad literature surveys and the fields surveys at the Kamaishi mine in northern Japan and at outcrops and galleries throughout the country. The characteristics of fractures described in this report are fracture orientation, fracture shape, fracture frequency, fracture distribution in space, transmissivity of fracture, fracture aperture, fracture fillings, alteration halo along fracture, flow-wetted surface area in fracture, and the correlation among these characteristics. Since granitic rock is considered the archetype fractured media, a large amount of fracture data is available in literature. In addition, granitic rock has been treated as a potential host rock in many overseas programs, and has JNC performed a number of field observations and experiments in granodiorite at the Kamaishi mine. Therefore, the characteristics of fractures in granitic rock are qualitatively and quantitatively clarified to some extent in this report, while the characteristics of fractures in another rock types are not clarified. (author)

Cough-induced rib fractures.

Science.gov (United States)

Hanak, Viktor; Hartman, Thomas E; Ryu, Jay H

2005-07-01

To define the demographic, clinical, and radiological features of patients with cough-induced rib fractures and to assess potential risk factors. For this retrospective, single-center study, we identified all cases of cough-induced rib fractures diagnosed at the Mayo Clinic in Rochester, Minn, over a 9-year period between January 1, 1996, and January 31, 2005. Bone densitometry data from patients' medical records were analyzed, and T scores were used to classify patients into bone density categories. The mean +/- SD age of the 54 study patients at presentation was 55+/-17 years, and 42 patients (78%) were female. Patients presented with chest wall pain after onset of cough. Rib fracture was associated with chronic cough (> or =3 weeks' duration) in 85% of patients. Rib fractures were documented by chest radiography, rib radiography, computed tomography, or bone scan. Chest radiography had been performed in 52 patients and revealed rib fracture in 30 (58%). There were 112 fractured ribs in 54 patients. One half of patients had more than one fractured rib. Right-sided rib fractures alone were present in 17 patients (26 fractured ribs), left-sided in 23 patients (35 fractured ribs), and bilateral in 14 patients (51 fractured ribs). The most commonly fractured rib on both sides was rib 6. The fractures were most common at the lateral aspect of the rib cage. Bone densitometry was done in 26 patients and revealed osteopenia or osteoporosis in 17 (65%). Cough-induced rib fractures occur primarily in women with chronic cough. Middle ribs along the lateral aspect of the rib cage are affected most commonly. Although reduced bone density is likely a risk factor, cough-induced rib fractures can occur in the presence of normal bone density.

Influence of perforation erosion on multiple growing hydraulic fractures in multi-stage fracturing

Directory of Open Access Journals (Sweden)

Yongming Li

2018-02-01

Full Text Available In multi-stage hydraulic fracturing, the limited-entry method is widely used to promote uniform growth of multiple fractures. However, this method's effectiveness may be lost because the perforations will be eroded gradually during the fracturing period. In order to study the influence of perforation erosion on multiple growing hydraulic fractures, we combined the solid–fluid coupled model of hydraulic fracture growth with an empirical model of perforation erosion to implement numerical simulation. The simulations show clearly that the erosion of perforation will significantly deteriorate the non-uniform growth of multiple fractures. Based on the numerical model, we also studied the influences of proppant concentration and injection rates on perforation erosion in multi-stage hydraulic fracturing. The results indicate that the initial erosion rates become higher with the rising proppant concentration, but the growth of multiple hydraulic fractures is not sensitive to the varied proppant concentration. In addition, higher injection rates are beneficial significantly to the limited-entry design, leading to more uniform growth of fractures. Thus, in multi-stage hydraulic fracturing enough high injection rates are proposed to keep uniform growths. Keywords: Unconventional oil and gas reservoir, Horizontal well, Perforation friction, Perforation erosion, Multi-stage hydraulic fracturing, Numerical simulation, Mathematic model, Uniform growth of fractures

Characteristic fracture spacing in primary and secondary recovery for naturally fractured reservoirs

NARCIS (Netherlands)

Gong, J.; Rossen, W.R.

2018-01-01

If the aperture distribution is broad enough in a naturally fractured reservoir, even one where the fracture network is highly inter-connected, most fractures can be eliminated without significantly affecting the flow through the fracture network. During a waterflood or enhanced-oil-recovery

Fracture strengths of chair-side-generated veneers cemented with glass fibers.

Science.gov (United States)

Turkaslan, S; Bagis, B; Akan, E; Mutluay, M M; Vallittu, P K

2015-01-01

CAD/CAM (computer-aided design and computer-aided manufacturing) systems have refreshed the idea of chair-side production of restorations, but the fracture of ceramic veneers remains a problem. Cementation with glass fibers may improve the fracture strengths and affect the failure modes of CAD/CAM-generated ceramic veneers. Therefore, this study compared the fracture strengths of ceramic veneers produced at chair side and cemented with or without glass fibers with those of composite veneers. Thirty intact mandibular incisors were randomly divided into three groups ( n = 10) and treated with CAD/CAM-fabricated veneers cemented with dual-cure composite resin luting cement (CRLC; Group 1), CAD/CAM-fabricated veneers cemented with a glass fiber network (GFN) and dual-cure CRLC (Group 2), and a direct particulate filler composite veneer constructed utilizing fiber and a restorative composite resin (Group 3). The specimens were tested with a universal testing machine after thermal cycling treatment. The loads at the start of fracture were the lowest for traditionally fabricated composite veneers and higher for CAD/CAM-generated. Veneers cemented either without or with the GFN. The failure initiation loads (N) for the veneers were 798.92 for Group 1, 836.27 for Group 2, and 585.93 for Group 3. The predominant failure mode is adhesive failure between the laminates and teeth for Group 1, cohesive failure in the luting layer for Group 2, and cohesive laminate failure for Group 3, which showed chipping and small fractures. Ceramic material is a reliable alternative for veneer construction at chair side. Fibers at the cementation interface may improve the clinical longevity and provide higher fracture strength values.

Fracture mechanical materials characterisation

International Nuclear Information System (INIS)

Wallin, K.; Planman, T.; Nevalainen, M.

1998-01-01

The experimental fracture mechanics development has been focused on the determination of reliable lower-bound fracture toughness estimates from small and miniature specimens, in particular considering the statistical aspects and loading rate effects of fracture mechanical material properties. Additionally, materials aspects in fracture assessment of surface cracks, with emphasis on the transferability of fracture toughness data to structures with surface flaws have been investigated. Further a modified crack-arrest fracture toughness test method, to increase the effectiveness of testing, has been developed. (orig.)

Pressurized Thermal Shock Analysis for OPR1000 Pressure Vessel

Energy Technology Data Exchange (ETDEWEB)

Bhowmik, P. K.; Shamim, J. A.; Gairola, A.; Suh, Kune Y. [Seoul National Univ., Seoul (Korea, Republic of)

2014-10-15

The study provides a brief understanding of the analysis procedure and techniques using ANSYS, such as the acceptance criteria, selection and categorization of events, thermal analysis, structural analysis including fracture mechanics assessment, crack propagation and evaluation of material properties. PTS may result from instrumentation and control malfunction, inadvertent steam dump, and postulated accidents such as smallbreak (SB) LOCA, large-break (LB) LOCA, main steam line break (MSLB), feedwater line breaks and steam generator overfill. In this study our main focus is to consider only the LB LOCA due to a cold leg break of the Optimized Power Reactor 1000 MWe (OPR1000). Consideration is given as well to the emergency core cooling system (ECCS) specific sequence with the operating parameters like pressure, temperature and time sequences. The static structural and thermal analysis to investigate the effects of PTS on RPV is the main motivation of this study. Specific surface crack effects and its propagation is also considered to measure the integrity of the RPV. This study describes the procedure for pressurized thermal shock analysis due to a loss of coolant accidental condition and emergency core cooling system operation for reactor pressure vessel.. Different accidental events that cause pressurized thermal shock to nuclear RPV that can also be analyzed in the same way. Considering the limitations of low speed computer only the static analysis is conducted. The modified LBLOCA phases and simplified geometry can is utilized to analyze the effect of PTS on RPV for general understanding not for specific specialized purpose. However, by integrating the disciplines of thermal and structural analysis, and fracture mechanics analysis a clearer understanding of the total aspect of the PTS problem has resulted. By adopting the CFD, thermal hydraulics, uncertainties and risk analysis for different type of accidental conditions, events and sequences with proper

Fracture Mechanics

CERN Document Server

Zehnder, Alan T

2012-01-01

Fracture mechanics is a vast and growing field. This book develops the basic elements needed for both fracture research and engineering practice. The emphasis is on continuum mechanics models for energy flows and crack-tip stress- and deformation fields in elastic and elastic-plastic materials. In addition to a brief discussion of computational fracture methods, the text includes practical sections on fracture criteria, fracture toughness testing, and methods for measuring stress intensity factors and energy release rates. Class-tested at Cornell, this book is designed for students, researchers and practitioners interested in understanding and contributing to a diverse and vital field of knowledge. Alan Zehnder joined the faculty at Cornell University in 1988. Since then he has served in a number of leadership roles including Chair of the Department of Theoretical and Applied Mechanics, and Director of the Sibley School of Mechanical and Aerospace Engineering.  He teaches applied mechanics and his research t...

Fractures and fracture infillings of the Eye-Dashwa Lakes pluton, Atikokan, Ontario

International Nuclear Information System (INIS)

Stone, Denver; Kamineni, D.C.

1982-01-01

Fractures in the Eye-Dashwa pluton near Atikokan, Ontario can be subdivided on the basis of their filling materials. These materials include aplite, epidote, chlorite, and gypsum-carbonate-clay, listed in order of decreasing age established from crosscutting relations. Textues indicate that infilling occurred during fracture growth. Continuous cooling of the pluton during fracturing is inferred from the expected crystallization temperatures of fillings. Fracturing began before the pluton was completely solidified (650-600 0 C) and continued to temperatures below 100 0 C. Many fractures appear to have been sealed by the filling materials after initiation but were subsequently sheared and filled by lower temperatue materials. Apparently the majority of fractures formed during or immediately after pluton solidification and new fractures became smaller and more restricted in location as cooling progressed. Fractures and filling materials are seen as important features in assessing the possibility of movement of radionuclides in aqueous solutions away from a nuclear fuel waste repository

DECOVALEX III/BENCHPAR PROJECTS. Evaluation of the Impact of Thermal-Hydro-Mechanical Couplings in Bentonite and Near-Field Rock Barriers on a Nuclear Waste Repository in a Sparsely Fractured Hard Rock. Report of BMT1C/WP2

International Nuclear Information System (INIS)

Jing, L.

2005-02-01

This report presents the works performed for the third, also the last, phase (BMT1C) of BMT1 of the DECOVALEX III project for the period of 1999-2002. The works of BMT1 is divided into three phases: BMT1A, BMT1B and BMT1C. The BMT1A concerns with calibration of the computer codes with a reference Thermal (T), Hydrological (H) and Mechanical (M) experiment at Kamaishi Mine, Japan. The objective is to validate the numerical approaches, computer codes and material models, so that the teams simulating tools are at a comparable level of maturity and sophistication. The BMT1B uses the calibrated codes to perform scoping calculations, considering varying degrees of THM coupling and varying permeability values of the surrounding rock for a reference generic repository design without fractures. The aim is to identify the coupling mechanisms of importance for construction, performance and safety of the repository. BMT1C concerns with scoping calculations with different coupling combinations for the case where a horizontal fracture intersects the deposition hole and a vertical fracture zone divides two adjacent deposition tunnel/hole system. A hydrostatic condition is applied along the vertical fracture as a hydraulic boundary condition. In addition, the SKI/KTH team performed an additional calculation case of a highly fractured rock mass with two orthogonal sets of fractures with a spacing of 0.5 m. The chosen measures for evaluating the long term safety and performance of the repository are the maximal temperature created by the thermal loading from the emplaced wastes, the time for resaturation of the buffer, the maximal swelling stress developed in the buffer, the structural integrity of the rock mass and the permeability evolution in the rock mass. The analyses fro BMT1C were conducted by four research teams: SKI/KTH (Sweden), CNSC (Canada), IRSN/CEA(France) and JNC (Japan), using FEM approach with different computer codes. From the results, it is clear that the

DECOVALEX III/BENCHPAR PROJECTS. Evaluation of the Impact of Thermal-Hydro-Mechanical Couplings in Bentonite and Near-Field Rock Barriers on a Nuclear Waste Repository in a Sparsely Fractured Hard Rock. Report of BMT1C/WP2

Energy Technology Data Exchange (ETDEWEB)

Jing, L. [Royal Inst. of Technology, Stockholm (Sweden). Engineering Geology; Nguyen, T.S. [Canadian Nuclear Safety Commission, Ottawa, ON (Canada)] (eds.)

2005-02-15

This report presents the works performed for the third, also the last, phase (BMT1C) of BMT1 of the DECOVALEX III project for the period of 1999-2002. The works of BMT1 is divided into three phases: BMT1A, BMT1B and BMT1C. The BMT1A concerns with calibration of the computer codes with a reference Thermal (T), Hydrological (H) and Mechanical (M) experiment at Kamaishi Mine, Japan. The objective is to validate the numerical approaches, computer codes and material models, so that the teams simulating tools are at a comparable level of maturity and sophistication. The BMT1B uses the calibrated codes to perform scoping calculations, considering varying degrees of THM coupling and varying permeability values of the surrounding rock for a reference generic repository design without fractures. The aim is to identify the coupling mechanisms of importance for construction, performance and safety of the repository. BMT1C concerns with scoping calculations with different coupling combinations for the case where a horizontal fracture intersects the deposition hole and a vertical fracture zone divides two adjacent deposition tunnel/hole system. A hydrostatic condition is applied along the vertical fracture as a hydraulic boundary condition. In addition, the SKI/KTH team performed an additional calculation case of a highly fractured rock mass with two orthogonal sets of fractures with a spacing of 0.5 m. The chosen measures for evaluating the long term safety and performance of the repository are the maximal temperature created by the thermal loading from the emplaced wastes, the time for resaturation of the buffer, the maximal swelling stress developed in the buffer, the structural integrity of the rock mass and the permeability evolution in the rock mass. The analyses fro BMT1C were conducted by four research teams: SKI/KTH (Sweden), CNSC (Canada), IRSN/CEA(France) and JNC (Japan), using FEM approach with different computer codes. From the results, it is clear that the

Computed tomograms of blowout fracture

International Nuclear Information System (INIS)

Ito, Haruhide; Hayashi, Minoru; Shoin, Katsuo; Hwang, Wen-Zern; Yamamoto, Shinjiro; Yonemura, Taizo.

1985-01-01

We studied 18 cases of orbital fractures, excluding optic canal fracture. There were 11 cases of pure blowout fracture and 3 of the impure type. The other 4 cases were orbital fractures without blowout fracture. The cardinal syndromes were diplopia, enophthalmos, and sensory disturbances of the trigeminal nerve in the pure type of blowout fracture. Many cases of the impure type of blowout fracture or of orbital fracture showed black eyes or a swelling of the eyelids which masked enophthalmos. Axial and coronal CT scans demonstrated: 1) the orbital fracture, 2) the degree of enophthalmos, 3) intraorbital soft tissue, such as incarcerated or prolapsed ocular muscles, 4) intraorbital hemorrhage, 5) the anatomical relation of the orbital fracture to the lacrimal canal, the trochlea, and the trigeminal nerve, and 6) the lesions of the paranasal sinus and the intracranial cavity. CT scans play an important role in determining what surgical procedures might best be employed. Pure blowout fractures were classified by CT scans into these four types: 1) incarcerating linear fracture, 2) trapdoor fracture, 3) punched-out fracture, and 4) broad fracture. Cases with severe head injury should be examined to see whether or not blowout fracture is present. If the patients are to hope to return to society, a blowout fracture should be treated as soon as possible. (author)

Computed tomograms of blowout fracture

Energy Technology Data Exchange (ETDEWEB)

Ito, Haruhide; Hayashi, Minoru; Shoin, Katsuo; Hwang, Wen-Zern; Yamamoto, Shinjiro; Yonemura, Taizo

1985-02-01

We studied 18 cases of orbital fractures, excluding optic canal fracture. There were 11 cases of pure blowout fracture and 3 of the impure type. The other 4 cases were orbital fractures without blowout fracture. The cardinal syndromes were diplopia, enophthalmos, and sensory disturbances of the trigeminal nerve in the pure type of blowout fracture. Many cases of the impure type of blowout fracture or of orbital fracture showed black eyes or a swelling of the eyelids which masked enophthalmos. Axial and coronal CT scans demonstrated: 1) the orbital fracture, 2) the degree of enophthalmos, 3) intraorbital soft tissue, such as incarcerated or prolapsed ocular muscles, 4) intraorbital hemorrhage, 5) the anatomical relation of the orbital fracture to the lacrimal canal, the trochlea, and the trigeminal nerve, and 6) the lesions of the paranasal sinus and the intracranial cavity. CT scans play an important role in determining what surgical procedures might best be employed. Pure blowout fractures were classified by CT scans into these four types: 1) incarcerating linear fracture, 2) trapdoor fracture, 3) punched-out fracture, and 4) broad fracture. Cases with severe head injury should be examined to see whether or not blowout fracture is present. If the patients are to hope to return to society, a blowout fracture should be treated as soon as possible. (author).

Viscoplastic-dynamic analyses of small-scale fracture tests to obtain crack arrest toughness values for PTS conditions

International Nuclear Information System (INIS)

Kanninen, M.F.; Hudak, S.J. Jr; Dexter, R.J.; Couque, H.; O'Donoghue, P.E.; Polch, E.Z.

1988-01-01

Reliable predictions of crack arrest at the high upper shelf toughness conditions involved in postulated pressurized thermal shock (PTS) events require procedures beyond those utilized in conventional fracture mechanics treatments. To develop such a procedure, viscoplastic-dynamic fracture mechanics finite element analyses, viscoplastic material characterization testing, and small-scale crack propagation and arrest experimentation are being combines in this research. The approach couples SwRI's viscoplastic-dynamic fracture mechanics finite element code VISCRK with experiments using duplex 4340/A533B steel compact specimens. The experiments are simulated by VISCRK computations employing the Bodner-Partom viscoplastic constitutive relation and the nonlinear fracture mechanics parameter T. The goal is to develop temperature-dependent crack arrest toughness values for A533B steel. While only room temperature K Ia values have been obtained so far, these have been found to agree closely with those obtained from wide plate tests. (author)

Facial Fractures.

Science.gov (United States)

Ricketts, Sophie; Gill, Hameet S; Fialkov, Jeffery A; Matic, Damir B; Antonyshyn, Oleh M

2016-02-01

After reading this article, the participant should be able to: 1. Demonstrate an understanding of some of the changes in aspects of facial fracture management. 2. Assess a patient presenting with facial fractures. 3. Understand indications and timing of surgery. 4. Recognize exposures of the craniomaxillofacial skeleton. 5. Identify methods for repair of typical facial fracture patterns. 6. Discuss the common complications seen with facial fractures. Restoration of the facial skeleton and associated soft tissues after trauma involves accurate clinical and radiologic assessment to effectively plan a management approach for these injuries. When surgical intervention is necessary, timing, exposure, sequencing, and execution of repair are all integral to achieving the best long-term outcomes for these patients.

In situ changes in the moisture content of heated, welded tuff based on thermal neutron measurements

International Nuclear Information System (INIS)

Ramirez, A.L.; Carlson, R.C.; Buscheck, T.A.

1991-07-01

Thermal neutron logs were collected to monitor changes in moisture content within a welded tuff rock mass heated from a borehole containing an electrical heater which remained energized for 195 days. Thermal neutron measurements were made in sampling boreholes before, during and after heating. The results generally corroborated our conceptual understanding of hydrothermal flow as well as most of the numerical modeling conducting for this study. Conceptual models have been developed in conjunction with the numerical model calculations to explain differences in the drying and re-wetting behavior above and below the heater. Numerical modeling indicated that the re-wetting of the dried-out zone was dominated by the binary diffusion of water vapor through fractures. Saturation gradients in the rock matrix resulted in relative humidity gradients which drove water vapor (primarily along fractures) back to the dried-out zone where it condensed along the fracture walls and was imbibed by the matrix. 4 refs., 28 figs

The effect of Al substitution on thermal and mechanical properties of Fe-based bulk metallic glass

International Nuclear Information System (INIS)

Ma, R.D.; Zhang, H.F.; Yu, H.S.; Hu, Z.Q.

2008-01-01

In this paper, a systematic investigation about the effect of Al substitution on properties of Fe-Cr-Mo-Er-C-B amorphous material, including glass-forming ability (GFA), thermal properties, and mechanical properties was presented. It was found out by X-ray diffraction (XRD) that the glass-forming ability decreased with the increase of Al, when Al reached 7 at%, fully amorphous specimen was not obtained. With regard to thermal parameters, such as glass transition temperature T g , crystallization temperature T x , supercooled liquid region ΔT x , and reduced glass temperature T rg were checked by differential scanning calorimeter. A rather wide supercooled liquid region more than 40 K was found. During compression test, results showed Al substitution slightly improved the fracture strength from 3.4 to 3.7 GPa. The fracture morphology was observed by scanning electron microscopy. Micrographs showed the same cleavage-like fracture in spite of different Al substitution

Distinct element method modeling of fracture behavior in near field rock

International Nuclear Information System (INIS)

Hoekmark, H.

1990-12-01

This report concerns the numerical calculations of the behavior of the near field of a nuclear waste repository. The calculations were performed using the two-dimensional distinct element code UDEC. The distinct element method accounts specifically for discontinuities, e.g. fractures that intersect the model region. It is shown that, if an appropriate joint constitutive relation is applied, the calculated joint behavior can be brought in close agreement with empirically derived stress-strain relations. Three basic geometries are studied, namely a vertical tunnel section, a horizontal borehole section and a combination, i.e. a vertical section of tunnel and deposition hole. The effects of different processes and activities are investigated, e.g. effects of excavations, of thermal loads, of internal tunnel pressures and of pore pressures and fracture flow resulting from the hydraulic ground water pressure. The interpretation of the results concerns in particular joint behavior, especially joint openings, in the nearest surroundings of excavations and of thermally affected regions. The calculations show that joint shear and joint normal displacements induced by excavation and by thermal processes may be considerable, and that thermal cycles may result in residual joint aperture changes, especially in systems with loosely bound rock blocks. It is concluded that the UDEC code, when applied to problems that have a two-dimensional character, gives results that are probably quantitatively correct. The results appear to be strongly dependant on the detailed joint structure close to free boundaries such as tunnel walls, which indicated that the 3-D situation regarding joint orientation might have to be considered. It is recommended that 3-D calculations should be performed to verify and quantitatively interpret the 2-D results and to analyze situations that are actually three-dimensional. (au)

Resistance of heat resisting steels and alloys to thermal and mechanical low-cycle fatigue

International Nuclear Information System (INIS)

Tulyakov, G.A.

1980-01-01

Carried out is a comparative evalUation of resistance of different materials to thermocyclic deformation and fracture on the base of the experimental data on thermal and mechanical low-cycle fatigUe. Considered are peculiarities of thermal fatigue resistance depending on strength and ductility of the material. It is shown, that in the range of the cycle small numbers before the fracture preference is given to the high-ductility cyclically strengthening austenitic steels of 18Cr-10Ni type with slight relation of yield strength to the σsub(0.2)/σsub(B) tensile strength Highly alloyed strength chromium-nickel steels, as well as cyclically destrengthening perlitic and ferritic steels with stronger σsub(0.2)/σsub(B) relation as compared with simple austenitic steels turn to be more long-lived in the range of the cycle great numbers berore fracture. Perlitic steels are stated to have the lowest parameter values of the K crack growth intensity under the similar limiting conditions of the experiment, while steels and alloys with austenite structure-higher values of the K parameter

Mechanics of Hydraulic Fractures

Science.gov (United States)

Detournay, Emmanuel

2016-01-01

Hydraulic fractures represent a particular class of tensile fractures that propagate in solid media under pre-existing compressive stresses as a result of internal pressurization by an injected viscous fluid. The main application of engineered hydraulic fractures is the stimulation of oil and gas wells to increase production. Several physical processes affect the propagation of these fractures, including the flow of viscous fluid, creation of solid surfaces, and leak-off of fracturing fluid. The interplay and the competition between these processes lead to multiple length scales and timescales in the system, which reveal the shifting influence of the far-field stress, viscous dissipation, fracture energy, and leak-off as the fracture propagates.

Fracture in Soft Materials

DEFF Research Database (Denmark)

Hassager, Ole

Fracture is a phenomenon that is generally associated with solids. A key element in fracture theory is the so-called weakest link idea that fracture initiates from the largest pre-existing material imperfection. However, recent work has demonstrated that fracture can also happen in liquids, where...... surface tension will act to suppress such imperfections. Therefore, the weakest link idea does not seem immediately applicable to fracture in liquids. This presentation will review fracture in liquids and argue that fracture in soft liquids is a material property independent of pre-existing imperfections....... The following questions then emerge: What is the material description needed to predict crack initiation, crack speed and crack shape in soft materials and liquids....

Unsaturated flow and transport through fractured rock related to high-level waste repositories

International Nuclear Information System (INIS)

Evans, D.D.; Rasmussen, T.C.

1991-01-01

Research results are summarized for a US Nuclear Regulatory Commission contract with the University of Arizona focusing on field and laboratory methods for characterizing unsaturated fluid flow and solute transport related to high-level radioactive waste repositories. Characterization activities are presented for the Apache Leap Tuff field site. The field site is located in unsaturated, fractured tuff in central Arizona. Hydraulic, pneumatic, and thermal characteristics of the tuff are summarized, along with methodologies employed to monitor and sample hydrologic and geochemical processes at the field site. Thermohydrologic experiments are reported which provide laboratory and field data related to the effects conditions and flow and transport in unsaturated, fractured rock. 29 refs., 17 figs., 21 tabs

The use of thermally expandable microcapsules for increasing the toughness and heal structural adhesives

Directory of Open Access Journals (Sweden)

Chiaki Sato

2011-04-01

Full Text Available In this research, the effect of thermally expandable microcapsules (TEMs on mode I fracture toughness of structural adhesives were investigated. The single-edge-notch bending (SENB test was used. Firstly, a standard toughness test was performed on adhesives with microcapsules. Secondly, since TEMs start their expansion at approximately 60ºC, the next specimens were fatigue tested expecting a local heating in the notch leading to the desired expansion before being statically loaded for fracture toughness determination. Thirdly, a manual local heating at 90ºC was applied in the notch before the fracture static test. The experimental results were successfully cross-checked through a numerical analysis using the virtual crack closure technique (VCCT based on linear elastic fracture mechanics (LEFM. The major conclusion is that fracture toughness of the modified adhesives increased as the mass fraction of the TEMs increased.

Fracture Characteristics of C/SiC Composites for Rocket Nozzle at Elevated Temperature

Energy Technology Data Exchange (ETDEWEB)

Yoon, Dong Hyun; Lee, Jeong Won; Kim, Jae Hoon [Chungnam Nat’l Univ., Daejeon (Korea, Republic of); Sihn, Ihn Cheol; Lim, Byung Joo [Dai-Yang Industries Co., Daejeon (Korea, Republic of)

2016-11-15

In a solid propulsion system, the rocket nozzle is exposed to high temperature combustion gas. Hence, choosing an appropriate material that could demonstrate adequate performance at high temperature is important. As advanced materials, carbon/silicon carbide composites (C/SiC) have been studied with the aim of using them for the rocket nozzle throat. However, when compared with typical structural materials, C/SiC composites are relatively weak in terms of both strength and toughness, owing to their quasi-brittle behavior and oxidation at high temperatures. Therefore, it is important to evaluate the thermal and mechanical properties of this material before using it in this application. This study presents an experimental method to investigate the fracture behavior of C/SiC composite material manufactured using liquid silicon infiltration (LSI) method at elevated temperatures. In particular, the effects of major parameters, such as temperature, loading, oxidation conditions, and fiber direction on strength and fracture characteristics were investigated. Fractography analysis of the fractured specimens was performed using an SEM.

Seismic characteristics of tensile fracture growth induced by hydraulic fracturing

Science.gov (United States)

Eaton, D. W. S.; Van der Baan, M.; Boroumand, N.

2014-12-01

Hydraulic fracturing is a process of injecting high-pressure slurry into a rockmass to enhance its permeability. Variants of this process are used for unconventional oil and gas development, engineered geothermal systems and block-cave mining; similar processes occur within volcanic systems. Opening of hydraulic fractures is well documented by mineback trials and tiltmeter monitoring and is a physical requirement to accommodate the volume of injected fluid. Numerous microseismic monitoring investigations acquired in the audio-frequency band are interpreted to show a prevalence of shear-dominated failure mechanisms surrounding the tensile fracture. Moreover, the radiated seismic energy in the audio-frequency band appears to be a miniscule fraction (<< 1%) of the net injected energy, i.e., the integral of the product of fluid pressure and injection rate. We use a simple penny-shaped crack model as a predictive framework to describe seismic characteristics of tensile opening during hydraulic fracturing. This model provides a useful scaling relation that links seismic moment to effective fluid pressure within the crack. Based on downhole recordings corrected for attenuation, a significant fraction of observed microseismic events are characterized by S/P amplitude ratio < 5. Despite the relatively small aperture of the monitoring arrays, which precludes both full moment-tensor analysis and definitive identification of nodal planes or axes, this ratio provides a strong indication that observed microseismic source mechanisms have a component of tensile failure. In addition, we find some instances of periodic spectral notches that can be explained by an opening/closing failure mechanism, in which fracture propagation outpaces fluid velocity within the crack. Finally, aseismic growth of tensile fractures may be indicative of a scenario in which injected energy is consumed to create new fracture surfaces. Taken together, our observations and modeling provide evidence that

Falsire: CSNI project for fracture analyses of large-scale international reference experiments (Phase 1). Comparison report

International Nuclear Information System (INIS)

1994-01-01

A summary of the recently completed Phase I of the Project for Fracture Analysis of Large-Scale International Reference Experiments (Project FALSIRE) is presented. Project FALSIRE was created by the Fracture Assessment Group (FAG) of Principal Working Group No. 3 (PWG/3) of the OECD/NEA Committee on the Safety of Nuclear Installations (CSNI), formed to evaluate fracture prediction capabilities currently used in safety assessments of nuclear vessel components. The aim of the Project FALSIRE was to assess various fracture methodologies through interpretive analyses of selected large-scale fracture experiments. The six experiments used in Project FALSIRE (performed in the Federal Republic of Germany, Japan, the United Kingdom, and the U.S.A.) were designed to examine various aspects of crack growth in reactor pressure vessel (RPV) steels under pressurized-thermal-shock (PTS) loading conditions. The analysis techniques employed by the participants included engineering and finite-element methods, which were combined with Jr fracture methodology and the French local approach. For each experiment, analysis results provided estimates of variables such as crack growth, crack-mouth-opening displacement, temperature, stress, strain, and applied J and K values. A comparative assessment and discussion of the analysis results are presented; also, the current status of the entire results data base is summarized. Some conclusions concerning predictive capabilities of selected ductile fracture methodologies, as applied to RPVs subjected to PTS loading, are given, and recommendations for future development of fracture methodologies are made

Temperature dependence of thermal pressure for NaCl

Science.gov (United States)

Singh, Chandra K.; Pande, Brijesh K.; Pandey, Anjani K.

2018-05-01

Engineering applications of the materials can be explored upto the desired limit of accuracy with the better knowledge of its mechanical and thermal properties such as ductility, brittleness and Thermal Pressure. For the resistance to fracture (K) and plastic deformation (G) the ratio K/G is treated as an indication of ductile or brittle character of solids. In the present work we have tested the condition of ductility and brittleness with the calculated values of K/G for the NaCl. It is concluded that the nature of NaCl can be predicted upto high temperature simply with the knowledge of its elastic stiffness constant only. Thermoelastic properties of materials at high temperature is directly related to thermal pressure and volume expansion of the materials. An expression for the temperature dependence of thermal pressure is formulated using basic thermodynamic identities. It is observed that thermal pressure ΔPth calculated for NaCl by using Kushwah formulation is in good agreement with the experimental values also the thermal pressure increases with the increase in temperature.

Fracture assessment of HSST Plate 14 shallow-flaw cruciform bend specimens tested under biaxial loading conditions

Energy Technology Data Exchange (ETDEWEB)

Bass, B.R.; McAfee, W.J.; Williams, P.T.; Pennell, W.E.

1998-06-01

A technology to determine shallow-flaw fracture toughness of reactor pressure vessel (RPV) steels is being developed for application to the safety assessment of RPVs containing postulated shallow surface flaws. Matrices of cruciform beam tests were developed to investigate and quantify the effects of temperature, biaxial loading, and specimen size on fracture initiation toughness of two-dimensional (constant depth), shallow, surface flaws. The cruciform beam specimens were developed at Oak Ridge National Laboratory (ORNL) to introduce a far-field, out-of-plane biaxial stress component in the test section that approximates the nonlinear stresses resulting from pressurized-thermal-shock or pressure-temperature loading of an RPV. Tests were conducted under biaxial load ratios ranging from uniaxial to equibiaxial. These tests demonstrated that biaxial loading can have a pronounced effect on shallow-flaw fracture toughness in the lower transition temperature region for an RPV material. The cruciform fracture toughness data were used to evaluate fracture methodologies for predicting the observed effects of biaxial loading on shallow-flaw fracture toughness. Initial emphasis was placed on assessment of stress-based methodologies, namely, the J-Q formulation, the Dodds-Anderson toughness scaling model, and the Weibull approach. Applications of these methodologies based on the hydrostatic stress fracture criterion indicated an effect of loading-biaxiality on fracture toughness; the conventional maximum principal stress criterion indicated no effect. A three-parameter Weibull model based on the hydrostatic stress criterion is shown to correlate the experimentally observed biaxial effect on cleavage fracture toughness by providing a scaling mechanism between uniaxial and biaxial loading states.

Pathological fractures in children

Science.gov (United States)

De Mattos, C. B. R.; Binitie, O.; Dormans, J. P.

2012-01-01

Pathological fractures in children can occur as a result of a variety of conditions, ranging from metabolic diseases and infection to tumours. Fractures through benign and malignant bone tumours should be recognised and managed appropriately by the treating orthopaedic surgeon. The most common benign bone tumours that cause pathological fractures in children are unicameral bone cysts, aneurysmal bone cysts, non-ossifying fibromas and fibrous dysplasia. Although pathological fractures through a primary bone malignancy are rare, these should be recognised quickly in order to achieve better outcomes. A thorough history, physical examination and review of plain radiographs are crucial to determine the cause and guide treatment. In most benign cases the fracture will heal and the lesion can be addressed at the time of the fracture, or after the fracture is healed. A step-wise and multidisciplinary approach is necessary in caring for paediatric patients with malignancies. Pathological fractures do not have to be treated by amputation; these fractures can heal and limb salvage can be performed when indicated. PMID:23610658

Coupled Fracture and Flow in Shale in Hydraulic Fracturing

Science.gov (United States)

Carey, J. W.; Mori, H.; Viswanathan, H.

2014-12-01

Production of hydrocarbon from shale requires creation and maintenance of fracture permeability in an otherwise impermeable shale matrix. In this study, we use a combination of triaxial coreflood experiments and x-ray tomography characterization to investigate the fracture-permeability behavior of Utica shale at in situ reservoir conditions (25-50 oC and 35-120 bars). Initially impermeable shale core was placed between flat anvils (compression) or between split anvils (pure shear) and loaded until failure in the triaxial device. Permeability was monitored continuously during this process. Significant deformation (>1%) was required to generate a transmissive fracture system. Permeability generally peaked at the point of a distinct failure event and then dropped by a factor of 2-6 when the system returned to hydrostatic failure. Permeability was very small in compression experiments (fashion as pressure increased. We also observed that permeability decreased with increasing fluid flow rate indicating that flow did not follow Darcy's Law, possibly due to non-laminar flow conditions, and conformed to Forscheimer's law. The coupled deformation and flow behavior of Utica shale, particularly the large deformation required to initiate flow, indicates the probable importance of activation of existing fractures in hydraulic fracturing and that these fractures can have adequate permeability for the production of hydrocarbon.

FRACTURED PETROLEUM RESERVOIRS

Energy Technology Data Exchange (ETDEWEB)

Abbas Firoozabadi

1999-06-11

The four chapters that are described in this report cover a variety of subjects that not only give insight into the understanding of multiphase flow in fractured porous media, but they provide also major contribution towards the understanding of flow processes with in-situ phase formation. In the following, a summary of all the chapters will be provided. Chapter I addresses issues related to water injection in water-wet fractured porous media. There are two parts in this chapter. Part I covers extensive set of measurements for water injection in water-wet fractured porous media. Both single matrix block and multiple matrix blocks tests are covered. There are two major findings from these experiments: (1) co-current imbibition can be more efficient than counter-current imbibition due to lower residual oil saturation and higher oil mobility, and (2) tight fractured porous media can be more efficient than a permeable porous media when subjected to water injection. These findings are directly related to the type of tests one can perform in the laboratory and to decide on the fate of water injection in fractured reservoirs. Part II of Chapter I presents modeling of water injection in water-wet fractured media by modifying the Buckley-Leverett Theory. A major element of the new model is the multiplication of the transfer flux by the fractured saturation with a power of 1/2. This simple model can account for both co-current and counter-current imbibition and computationally it is very efficient. It can be orders of magnitude faster than a conventional dual-porosity model. Part II also presents the results of water injection tests in very tight rocks of some 0.01 md permeability. Oil recovery from water imbibition tests from such at tight rock can be as high as 25 percent. Chapter II discusses solution gas-drive for cold production from heavy-oil reservoirs. The impetus for this work is the study of new gas phase formation from in-situ process which can be significantly

Fluid-driven fracture propagation in heterogeneous media: Probability distributions of fracture trajectories.

Science.gov (United States)

Santillán, David; Mosquera, Juan-Carlos; Cueto-Felgueroso, Luis

2017-11-01

Hydraulic fracture trajectories in rocks and other materials are highly affected by spatial heterogeneity in their mechanical properties. Understanding the complexity and structure of fluid-driven fractures and their deviation from the predictions of homogenized theories is a practical problem in engineering and geoscience. We conduct a Monte Carlo simulation study to characterize the influence of heterogeneous mechanical properties on the trajectories of hydraulic fractures propagating in elastic media. We generate a large number of random fields of mechanical properties and simulate pressure-driven fracture propagation using a phase-field model. We model the mechanical response of the material as that of an elastic isotropic material with heterogeneous Young modulus and Griffith energy release rate, assuming that fractures propagate in the toughness-dominated regime. Our study shows that the variance and the spatial covariance of the mechanical properties are controlling factors in the tortuousness of the fracture paths. We characterize the deviation of fracture paths from the homogenous case statistically, and conclude that the maximum deviation grows linearly with the distance from the injection point. Additionally, fracture path deviations seem to be normally distributed, suggesting that fracture propagation in the toughness-dominated regime may be described as a random walk.

Traumatic thoracolumbar spine fractures

NARCIS (Netherlands)

J. Siebenga (Jan)

2013-01-01

textabstractTraumatic spinal fractures have the lowest functional outcomes and the lowest rates of return to work after injury of all major organ systems.1 This thesis will cover traumatic thoracolumbar spine fractures and not osteoporotic spine fractures because of the difference in fracture

Fracture resistance of asphalt concrete modified with crumb rubber at low temperatures

Directory of Open Access Journals (Sweden)

A. Razmi

2018-05-01

Full Text Available The main objective of this study is to obtain fracture toughness of asphalt concrete modified by Crumb Rubber (CR and Sasobit at low temperatures. First, Bending Beam Rheometer (BBR test was performed on unmodified binder (binder 60/70, binder 60/70 + 3%Sasobit and 20%CR + 3%Sasobit modified asphalt binder to find how each modifier affect asphalt binder stiffness and relaxation rate at low temperatures. Mixed mode I/II fracture tests were conducted by cracked Semi-Circular Bending (SCB specimens and the critical stress intensity factors were calculated for pure mode I, mixed mode I/II and pure mode II conditions. Results of BBR tests indicated that 20%CR + 3%Sasobit reduces stiffness and the m-value increase at low temperatures. As a result, 20%CR + 3%Sasobit has positive effect on low temperatures performance by improving thermal cracking resistance. Also, according to the fracture toughness test results, the Warm Mix Asphalt (WMA mixture containing 20% CR, shows higher resistance against crack growth than WMA mixture. It was found that mixed mode I/II can be more detrimental than pure mode I and II conditions. Keywords: Crumb rubber, Asphalt concrete, Bending Beam Rheometer, Fracture resistance, Semi-circular bending test

Decoding flow unit evolution upon annealing from fracture morphology in metallic glasses

Energy Technology Data Exchange (ETDEWEB)

Gao, M., E-mail: gaomeng10@hotmail.com; Cao, X.F.; Ding, D.W.; Wang, B.B.; Wang, W.H., E-mail: whw@iphy.ac.cn

2017-02-16

The intrinsic correlation between the fracture morphology evolution and the structural heterogeneity of flow units in a typical Zr{sub 52.5}Ti{sub 5}Cu{sub 17.9}Ni{sub 14.6}Al{sub 10} (vit105) metallic glass (MG) upon annealing was investigated. By systematically tuning the annealing time at temperature below the glass transition temperature, a series of dimple-like fracture morphology were obtained, which is the unique fingerprint-like pattern for every annealing state. Based on the structural relaxation model of flow units, the evolution of the typical dimple sizes, the largest and smallest dimple size, with annealing were well fitted. Then the evolution of flow unit density was estimated from the fracture morphology evolution, which displays the same evolution trend with that measured from thermal relaxation. A stochastic dynamic model considering the interaction of activated flow units was proposed to analyze the effect of the initial flow unit density and the flow unit interaction intensity on the dynamic evolution of dimple distribution. Our work may provide a novel scheme to investigate the structural fingerprint information on flow units from fracture morphology, and enlighten the microscopic structural origin of the ductile-to-brittle transition during structural relaxation in MGs.

Epidemiology of rib fractures in older men: Osteoporotic Fractures in Men (MrOS) prospective cohort study.

Science.gov (United States)

Barrett-Connor, Elizabeth; Nielson, Carrie M; Orwoll, Eric; Bauer, Douglas C; Cauley, Jane A

2010-03-15

To study the causes and consequences of radiologically confirmed rib fractures (seldom considered in the context of osteoporosis) in community dwelling older men. Prospective cohort study (Osteoporotic Fractures in Men (MrOS) Study). 5995 men aged 65 or over recruited in 2000-2 from six US sites; 99% answered mailed questionnaires about falls and fractures every four months for a mean 6.2 (SD 1.3) year follow-up. New fractures validated by radiology reports; multivariate Cox proportional hazard ratios were used to evaluate factors independently associated with time to incident rib fracture; associations between baseline rib fracture and incident hip and wrist fracture were also evaluated. The incidence of rib fracture was 3.5/1000 person years, and 24% (126/522) of all incident non-spine fractures were rib fractures. Nearly half of new rib fractures (48%; n=61) followed falling from standing height or lower. Independent risk factors for an incident rib fracture were age 80 or above, low bone density, difficulty with instrumental activities of daily living, and a baseline history of rib/chest fracture. Men with a history of rib/chest fracture had at least a twofold increased risk of an incident rib fracture (adjusted hazard ratio 2.71, 95% confidence interval 1.86 to 3.95), hip fracture (2.05, 1.33 to 3.15), and wrist fracture (2.06, 1.14 to 3.70). Only 14/82 of men reported being treated with bone specific drugs after their incident rib fracture. Rib fracture, the most common incident clinical fracture in men, was associated with classic risk markers for osteoporosis, including old age, low hip bone mineral density, and history of fracture. A history of rib fracture predicted a more than twofold increased risk of future fracture of the rib, hip, or wrist, independent of bone density and other covariates. Rib fractures should be considered to be osteoporotic fractures in the evaluation of older men for treatment to prevent future fracture.

The inclusion of weld residual stress in fracture margin assessments of embrittled nuclear reactor pressure vessels

International Nuclear Information System (INIS)

Dickson, T.L.; Bass, B.R.; McAfee, W.J.

1998-01-01

Analyses were performed to determine the impact of weld residual stresses in a reactor pressure vessel (RPV) on (1) the generation of pressure temperature (P-T) curves required for maintaining specified fracture prevention margins during nuclear plant startup and shutdown, and (2) the conditional probability of vessel failure due to pressurized thermal shock (PTS) loading. The through wall residual stress distribution in an axially oriented weld was derived using measurements taken from a shell segment of a canceled RPV and finite element thermal stress analyses. The P-T curve derived from the best estimate load analysis and a t / 8 deep flaw, based on K Ic , was less limiting than the one derived from the current methodology prescribed in the ASME Boiler and Pressure Vessel Code. The inclusion of the weld residual stresses increased the conditional probability of cleavage fracture due to PTS loading by a factor ranging from 2 to 4

Analysis of fracture patterns and local stress field variations in fractured reservoirs

Science.gov (United States)

Deckert, Hagen; Drews, Michael; Fremgen, Dominik; Wellmann, J. Florian

2010-05-01

A meaningful qualitative evaluation of permeabilities in fractured reservoirs in geothermal or hydrocarbon industry requires the spatial description of the existing discontinuity pattern within the area of interest and an analysis how these fractures might behave under given stress fields. This combined information can then be used for better estimating preferred fluid pathway directions within the reservoir, which is of particular interest for defining potential drilling sites. A description of the spatial fracture pattern mainly includes the orientation of rock discontinuities, spacing relationships between single fractures and their lateral extent. We have examined and quantified fracture patterns in several outcrops of granite at the Costa Brava, Spain, and in the Black Forest, Germany, for describing reservoir characteristics. For our analysis of fracture patterns we have used photogrammetric methods to create high-resolution georeferenced digital 3D images of outcrop walls. The advantage of this approach, compared to conventional methods for fracture analysis, is that it provides a better 3D description of the fracture geometry as the entity of position, extent and orientation of single fractures with respect to their surrounding neighbors is conserved. Hence for instance, the method allows generating fracture density maps, which can be used for a better description of the spatial distribution of discontinuities in a given outcrop. Using photogrammetric techniques also has the advantage to acquire very large data sets providing statistically sound results. To assess whether the recorded discontinuities might act as fluid pathways information on the stress field is needed. A 3D model of the regional tectonic structure was created and the geometry of the faults was put into a mechanical 3D Boundary Element (BE) Model. The model takes into account the elastic material properties of the geological units and the orientation of single fault segments. The

Radiological classification of mandibular fractures

International Nuclear Information System (INIS)

Mihailova, H.

2009-01-01

Mandibular fractures present the biggest part (up to 97%) of the facial bone fractures. Method of choice for diagnosing of mandibular fractures is conventional radiography. The aim of the issue is to present an unified radiological classification of mandibular fractures for the clinical practice. This classification includes only those clinical symptoms of mandibular fracture which could be radiologically objectified: exact anatomical localization (F1-F6), teeth in fracture line (Ta,Tb), grade of dislocation (D I, D II), occlusal disturbances (O(+), O(-)). Radiological symptoms expressed by letter and number symbols are systematized in a formula - FTDO of mandibular fractures similar to TNM formula for tumours. FTDO formula expresses radiological diagnose of each mandibular fracture but it doesn't include neither the site (left or right) of the fracture, nor the kind and number of fractures. In order to express topography and number of fractures the radiological formula is transformed into a decimal fraction. The symbols (FTD) of right mandible fracture are written in the numerator and those of the left site - in the denominator. For double and multiple fractures between the symbols for each fracture we put '+'. Symbols for occlusal disturbances are put down opposite, the fractional line. So topographo-anatomical formula (FTD/FTD)xO is formed. In this way the whole radiological information for unilateral, bilateral, single or multiple fractures of the mandible is expressed. The information in the radiological topography anatomic formula, resp. from the unified topography-anatomic classification ensures a quick and exact X-ray diagnose of mandibular fracture. In this way contributes to get better, make easier and faster X-ray diagnostic process concerning mandibular fractures. And all these is a precondition for prevention of retardation of the diagnosis mandibular fracture. (author)

An unusual stress fracture: Bilateral posterior longitudinal stress fracture of tibia.

Science.gov (United States)

Malkoc, Melih; Korkmaz, Ozgur; Ormeci, Tugrul; Oltulu, Ismail; Isyar, Mehmet; Mahirogulları, Mahir

2014-01-01

Stress fractures (SF) occur when healthy bone is subjected to cyclic loading, which the normal carrying range capacity is exceeded. Usually, stress fractures occur at the metatarsal bones, calcaneus, proximal or distal tibia and tends to be unilateral. This article presents a 58-year-old male patient with bilateral posterior longitudinal tibial stress fractures. A 58 years old male suffering for persistent left calf pain and decreased walking distance for last one month and after imaging studies posterior longitudinal tibial stress fracture was detected on his left tibia. After six months the patient was admitted to our clinic with the same type of complaints in his right leg. All imaging modalities and blood counts were performed and as a result longitudinal posterior tibial stress fractures were detected on his right tibia. Treatment of tibial stress fracture includes rest and modified activity, followed by a graded return to activity commensurate with bony healing. We have applied the same treatment protocol and our results were acceptable but our follow up time short for this reason our study is restricted for separate stress fractures of the posterior tibia. Although the main localization of tibial stress fractures were unilateral, anterior and transverse pattern, rarely, like in our case, the unusual bilateral posterior localization and longitudinal pattern can be seen. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

Residual Tensile Property of Plain Woven Jute Fiber/Poly(Lactic Acid Green Composites during Thermal Cycling

Directory of Open Access Journals (Sweden)

Hideaki Katogi

2016-07-01

Full Text Available This study investigated the residual tensile properties of plain woven jute fiber reinforced poly(lactic acid (PLA during thermal cycling. Temperature ranges of thermal cycling tests were 35–45 °C and 35–55 °C. The maximum number of cycles was 103 cycles. The quasi-static tensile tests of jute fiber, PLA, and composite were conducted after thermal cycling tests. Thermal mechanical analyses of jute fiber and PLA were conducted after thermal cycling tests. Results led to the following conclusions. For temperatures of 35–45 °C, tensile strength of composite at 103 cycles decreased 10% compared to that of composite at 0 cycles. For temperatures of 35–55 °C, tensile strength and Young’s modulus of composite at 103 cycles decreased 15% and 10%, respectively, compared to that of composite at 0 cycles. Tensile properties and the coefficient of linear expansion of PLA and jute fiber remained almost unchanged after thermal cycling tests. From observation of a fracture surface, the length of fiber pull out in the fracture surface of composite at 103 cycles was longer than that of composite at 0 cycles. Therefore, tensile properties of the composite during thermal cycling were decreased, probably because of the decrease of interfacial adhesion between the fiber and resin.

Permeability in fractured rocks from deep geothermal boreholes in the Upper Rhine Graben

Science.gov (United States)

Vidal, Jeanne; Whitechurch, Hubert; Genter, Albert; Schmittbuhl, Jean; Baujard, Clément

2015-04-01

Permeability in fractured rocks from deep geothermal boreholes in the Upper Rhine Graben Vidal J.1, Whitechurch H.1, Genter A.2, Schmittbuhl J.1, Baujard C.2 1 EOST, Université de Strasbourg 2 ES-Géothermie, Strasbourg The thermal regime of the Upper Rhine Graben (URG) is characterized by a series of geothermal anomalies on its French part near Soultz-sous-Forêts, Rittershoffen and in the surrounding area of Strasbourg. Sedimentary formations of these areas host oil field widely exploited in the past which exhibit exceptionally high temperature gradients. Thus, geothermal anomalies are superimposed to the oil fields which are interpreted as natural brine advection occurring inside a nearly vertical multi-scale fracture system cross-cutting both deep-seated Triassic sediments and Paleozoic crystalline basement. The sediments-basement interface is therefore very challenging for geothermal industry because most of the geothermal resource is trapped there within natural fractures. Several deep geothermal projects exploit local geothermal energy to use the heat or produce electricity and thus target permeable fractured rocks at this interface. In 1980, a geothermal exploration well was drilled close to Strasbourg down to the Permian sediments at 3220 m depth. Bottom hole temperature was estimated to 148°C but the natural flow rate was too low for an economic profitability (geothermal site by drilling five boreholes, three of which extend to 5 km depth. They identified a temperature of 200° C at 5 km depth in the granitic basement but with a variable flow rate. Hydraulic and chemical stimulation operations were applied in order to increase the initial low permeability by reactivating and dissolving sealed fractures in basement. The productivity was considerably improved and allows geothermal exploitation at 165° C and 20 L/s. Recent studies revealed the occurrences of permeable fractures in the limestones of Muschelkalk and the sandstones of Buntsandstein also. For

Thermal-vacuum facility with in-situ mechanical loading. [for testing space construction materials

Science.gov (United States)

Tennyson, R. C.; Hansen, J. S.; Holzer, R. P.; Uffen, B.; Mabson, G.

1978-01-01

The paper describes a thermal-vacuum space simulator used to assess property changes of fiber-reinforced polymer composite systems. The facility can achieve a vacuum of approximately .0000001 torr with temperatures ranging from -200 to +300 F. Some preliminary experimental results are presented for materials subjected to thermal loading up to 200 F. The tests conducted include the evaluation of matrix modulus and strength, coefficients of thermal expansion, and fracture toughness. Though the experimental program is at an early stage, the data appear to indicate that these parameters are influenced by hard vacuum.

Evaluation of Fibular Fracture Type vs Location of Tibial Fixation of Pilon Fractures.

Science.gov (United States)

Busel, Gennadiy A; Watson, J Tracy; Israel, Heidi

2017-06-01

Comminuted fibular fractures can occur with pilon fractures as a result of valgus stress. Transverse fibular fractures can occur with varus deformation. No definitive guide for determining the proper location of tibial fixation exists. The purpose of this study was to identify optimal plate location for fixation of pilon fractures based on the orientation of the fibular fracture. One hundred two patients with 103 pilon fractures were identified who were definitively treated at our institution from 2004 to 2013. Pilon fractures were classified using the AO/OTA classification and included 43-A through 43-C fractures. Inclusion criteria were age of at least 18 years, associated fibular fracture, and definitive tibial plating. Patients were grouped based on the fibular component fracture type (comminuted vs transverse), and the location of plate fixation (medial vs lateral) was noted. Radiographic outcomes were assessed for mechanical failures. Forty fractures were a result of varus force as evidenced by transverse fracture of the fibula and 63 were due to valgus force with a comminuted fibula. For the transverse fibula group, 14.3% mechanical complications were noted for medially placed plate vs 80% for lateral plating ( P = .006). For the comminuted fibular group, 36.4% of medially placed plates demonstrated mechanical complications vs 16.7% for laterally based plates ( P = .156). Time to weight bearing as tolerated was also noted to be significant between groups plated medially and laterally for the comminuted group ( P = .013). Correctly assessing the fibular component for pilon fractures provides valuable information regarding deforming forces. To limit mechanical complications, tibial plates should be applied in such a way as to resist the original deforming forces. Level of Evidence Level III, comparative study.

Fractures in multiple sclerosis

DEFF Research Database (Denmark)

Stenager, E; Jensen, K

1991-01-01

In a cross-sectional study of 299 MS patients 22 have had fractures and of these 17 after onset of MS. The fractures most frequently involved the femoral neck and trochanter (41%). Three patients had had more than one fracture. Only 1 patient had osteoporosis. The percentage of fractures increase...

TIBIAL SHAFT FRACTURES.

Science.gov (United States)

Kojima, Kodi Edson; Ferreira, Ramon Venzon

2011-01-01

The long-bone fractures occur most frequently in the tibial shaft. Adequate treatment of such fractures avoids consolidation failure, skewed consolidation and reoperation. To classify these fractures, the AO/OTA classification method is still used, but it is worthwhile getting to know the Ellis classification method, which also includes assessment of soft-tissue injuries. There is often an association with compartmental syndrome, and early diagnosis can be achieved through evaluating clinical parameters and constant clinical monitoring. Once the diagnosis has been made, fasciotomy should be performed. It is always difficult to assess consolidation, but the RUST method may help in this. Radiography is assessed in two projections, and points are scored for the presence of the fracture line and a visible bone callus. Today, the dogma of six hours for cleaning the exposed fracture is under discussion. It is considered that an early start to intravenous antibiotic therapy and the lesion severity are very important. The question of early or late closure of the lesion in an exposed fracture has gone through several phases: sometimes early closure has been indicated and sometimes late closure. Currently, whenever possible, early closure of the lesion is recommended, since this diminishes the risk of infection. Milling of the canal when the intramedullary nail is introduced is still a controversial subject. Despite strong personal positions in favor of milling, studies have shown that there may be some advantage in relation to closed fractures, but not in exposed fractures.

Treatment of mandibular symphyseal fracture combined with dislocated intracapsular condylar fractures.

Science.gov (United States)

Xu, Xiaofeng; Shi, Jun; Xu, Bing; Dai, Jiewen; Zhang, Shilei

2015-03-01

To evaluate the treatment methods of mandibular symphyseal fracture combined with dislocated intracapsular condylar fractures (MSF&DICF) and to compare the effect of different treatment methods of condylar fractures. Twenty-eight patients with MSF&DICF were included in this study. Twenty-two sites were treated by open reduction, and all the medial condylar fragments were fixed with titanium screws; whereas the other 22 sites underwent close treatment. The surgical effect between these 2 groups was compared based on clinical examination and radiographic examination results. Seventeen of 22 condyle fractures were repositioned in the surgery group, whereas 4 of 22 condyle fractures were repositioned in the close treatment group. Statistical difference was observed between these 2 groups (P condyle fractures should be treated by surgical reduction with the maintenance of the attachment of lateral pterygoid muscle, which is beneficial to repositioning the dislocated condyle to its original physiological position, to closure of the mandibular lingual gap, to restore the mandibular width.

Classification of Porcine Cranial Fracture Patterns Using a Fracture Printing Interface,.

Science.gov (United States)

Wei, Feng; Bucak, Serhat Selçuk; Vollner, Jennifer M; Fenton, Todd W; Jain, Anil K; Haut, Roger C

2017-01-01

Distinguishing between accidental and abusive head trauma in children can be difficult, as there is a lack of baseline data for pediatric cranial fracture patterns. A porcine head model has recently been developed and utilized in a series of studies to investigate the effects of impact energy level, surface type, and constraint condition on cranial fracture patterns. In the current study, an automated pattern recognition method, or a fracture printing interface (FPI), was developed to classify cranial fracture patterns that were associated with different impact scenarios documented in previous experiments. The FPI accurately predicted the energy level when the impact surface type was rigid. Additionally, the FPI was exceedingly successful in determining fractures caused by skulls being dropped with a high-level energy (97% accuracy). The FPI, currently developed on the porcine data, may in the future be transformed to the task of cranial fracture pattern classification for human infant skulls. © 2016 American Academy of Forensic Sciences.

An alternative method for performing pressurized thermal shock analysis

International Nuclear Information System (INIS)

Bishop, B.A.; Meyer, T.A.; Carter, R.G.; Gamble, R.M.

1997-01-01

This paper describes how Probability of Crack Initiation and acceptable Pressurized Thermal Shock frequency were correlated with a c and summarizes several example applications, including evaluation of potential plant modifications. Plans for an industry supported pilot-plant application of the alternative Probabilistic Fracture Mechanics method for RG 1.154 are also discussed. 9 refs, 4 figs, 1 tab

Response of neutron-irradiated RPV steels to thermal annealing

International Nuclear Information System (INIS)

Iskander, S.K.; Sokolov, M.A.; Nanstad, R.K.

1997-01-01

One of the options to mitigate the effects of irradiation on reactor pressure vessels (RPVs) is to thermally anneal them to restore the fracture toughness properties that have been degraded by neutron irradiation. This paper summarizes experimental results of work performed at the Oak Ridge National Laboratory (ORNL) to study the annealing response of several irradiated RPV steels

An alternative method for performing pressurized thermal shock analysis

Energy Technology Data Exchange (ETDEWEB)

Bishop, B A; Meyer, T A [Westinghouse Energy Systems, Pittsburgh, PA (United States); Carter, R G [Electric Power Research Inst., Charlotte, NC (United States); Gamble, R M [Sartrex Corp., Rockville, MD (United States)

1997-09-01

This paper describes how Probability of Crack Initiation and acceptable Pressurized Thermal Shock frequency were correlated with a{sub c} and summarizes several example applications, including evaluation of potential plant modifications. Plans for an industry supported pilot-plant application of the alternative Probabilistic Fracture Mechanics method for RG 1.154 are also discussed. 9 refs, 4 figs, 1 tab.

Hydrajet fracturing: an effective method for placing many fractures in openhole horizontal wells

Energy Technology Data Exchange (ETDEWEB)

Surjaatmadja, J. B.; Grundmann, S. R.; McDaniel, B.; Deeg, W. F. J.; Brumley, J. L.; Swor, L. C.

1998-12-31

A new method for openhole horizontal well fracturing that combines hydrajetting and fracturing techniques, which was developed on the basis of Bernoulli`s theorem, is described. This theorem has been effectively proven in many applications such as jet pumps, additive injection systems and jet aircraft engines. By using this method, operators can position a jetting tool, without the use of sealing elements, at the exact point where fracture is required. The method also permits the use of multiple fractures in the same well, which can be spaced evenly or unevenly as prescribed by the fracturing program. Damage can be avoided by placing hundreds of small fractures in a long horizontal section, or operators can use acid and/or propped sand techniques to place a combination of two fracture types in the well. The paper describes the basic principles of horizontal hydrajet fracturing, and elements of a laboratory model which was developed to demonstrate the effectiveness of the method.

Characterisation of hydraulically-active fractures in a fractured ...

African Journals Online (AJOL)

... in the initial stage of a site investigation to select the optimal site location or to evaluate the hydrogeological properties of fractures in underground exploration studies, such as those related geothermal reservoir evaluation and radioactive waste disposal. Keywords: self-potential method, hydraulically-conductive fractures, ...

Fracture propagation in sandstone and slate – Laboratory experiments, acoustic emissions and fracture mechanics

Directory of Open Access Journals (Sweden)

Ferdinand Stoeckhert

2015-06-01

Full Text Available Fracturing of highly anisotropic rocks is a problem often encountered in the stimulation of unconventional hydrocarbon or geothermal reservoirs by hydraulic fracturing. Fracture propagation in isotropic material is well understood but strictly isotropic rocks are rarely found in nature. This study aims at the examination of fracture initiation and propagation processes in a highly anisotropic rock, specifically slate. We performed a series of tensile fracturing laboratory experiments under uniaxial as well as triaxial loading. Cubic specimens with edge lengths of 150 mm and a central borehole with a diameter of 13 mm were prepared from Fredeburg slate. An experiment using the rather isotropic Bebertal sandstone as a rather isotropic rock was also performed for comparison. Tensile fractures were generated using the sleeve fracturing technique, in which a polymer tube placed inside the borehole is pressurized to generate tensile fractures emanating from the borehole. In the uniaxial test series, the loading was varied in order to observe the transition from strength-dominated fracture propagation at low loading magnitudes to stress-dominated fracture propagation at high loading magnitudes.

Rib Fractures

Science.gov (United States)

... Video) Achilles Tendon Tear Additional Content Medical News Rib Fractures By Thomas G. Weiser, MD, MPH, Associate Professor, ... Tamponade Hemothorax Injury to the Aorta Pulmonary Contusion Rib Fractures Tension Pneumothorax Traumatic Pneumothorax (See also Introduction to ...

Orbital fractures: a review

Directory of Open Access Journals (Sweden)

Jeffrey M Joseph

2011-01-01

Full Text Available Jeffrey M Joseph, Ioannis P GlavasDivision of Ophthalmic Plastic and Reconstructive Surgery, Department of Ophthalmology, School of Medicine, New York University, New York, NY, USA; Manhattan Eye, Ear, and Throat Hospital, New York, NY, USAAbstract: This review of orbital fractures has three goals: 1 to understand the clinically relevant orbital anatomy with regard to periorbital trauma and orbital fractures, 2 to explain how to assess and examine a patient after periorbital trauma, and 3 to understand the medical and surgical management of orbital fractures. The article aims to summarize the evaluation and management of commonly encountered orbital fractures from the ophthalmologic perspective and to provide an overview for all practicing ophthalmologists and ophthalmologists in training.Keywords: orbit, trauma, fracture, orbital floor, medial wall, zygomatic, zygomatic complex, zmc fracture, zygomaticomaxillary complex fractures 

Orbital wall fractures

International Nuclear Information System (INIS)

Iinuma, Toshitaka; Ishio, Ken-ichirou; Yoshinami, Hiroyoshi; Kuriyama, Jun-ichi; Hirota, Yoshiharu.

1993-01-01

A total of 59 cases of mild facial fractures (simple orbital wall fractures, 34 cases, other facial fractures, 25 cases) with the clinical suspects of orbital wall fractures were evaluated both by conventional views (Waters' and Caldwell views) and coronal CT scans. Conventional views were obtained, as an average, after 4 days and CT after 7 days of injuries. Both the medial wall and the floor were evaluated at two sites, i.e., anterior and posterior. The ethmoid-maxillary plate was also included in the study. The degree of fractures was classified as, no fractures, fractures of discontinuity, dislocation and fragmentation. The coronal CT images in bone window condition was used as reference and the findings were compared between conventional views and CT. The correct diagnosis was obtained as follows: orbital floor (anterior, 78%, posterior, 73%), medial orbital wall (anterior, 72%, posterior, 72%) and ethmoid-maxillary plate (64%). The false positive diagnosis was as follows: orbital floor (anterior only, 13%), medial orbital wall (anterior only, 7%) and ethmoid-maxillary plate (11%). The false negative diagnosis was as follows: orbital floor (anterior, 9%, posterior, 10%), medial orbital wall (anterior, 21%, posterior, 28%) and ethmoid-maxillary plate (21%). The results were compared with those of others in the past. (author)

Alpha radiation and in-pile annealing effects on the fracture properties of a sintered alumino borosilicate glass

International Nuclear Information System (INIS)

Bevilacqua, Arturo M.; Prado, Miguel O.; Messi de Bernasconi, Norma B.; Heredia, Arturo D.; Sanfilippo, Miguel

1999-01-01

The alpha radiation and the in-pile during irradiation effects on the hardness, the crack nucleation and the fracture toughness of the German alumino borosilicate glass SG7 were investigated by using the Vickers indentation. Cold pressed and sintered samples were irradiated with thermal neutrons, in the Argentine nuclear reactors RA-3 and RA-6, to produce alpha particles in the whole volume of the glass by means of the (n, alpha)-reaction with B-10. The Vickers hardness, the crack nucleation, as 50 percent fracture probability load, plotted as the Weibull's fracture probability distribution function and the fracture toughness, as critical stress intensity factor K Ic , were correlated to the four cumulative disintegration values. It was ascertained that: a) the Vickers hardness decreases from 5.6 GPa for the non-irradiated sample up to 4.7 GPa for the sample irradiated 70 h at the lower neutron flux (4.0 x 10 - sup 18 - alpha disintegration per cm - sup 3 -), b) the 50 % fracture probability load increases from 1.4 N for the non-irradiated sample up to 4.7 g for the sample irradiated 22 h at the higher flux (6.8 x 10 - sup 18 - alpha disintegration per cm - sup 3 -), and c) the stress intensity factor increases from 0.80 MPa.m - sup 1/2 - for the non irradiated sample up to 0.86 MPa.m - sup 1/2 - for the sample mentioned in b). The in-pile annealing was analyzed by comparing the crack nucleation after irradiation with data obtained by heavy ion irradiation followed by thermal annealing. Results for the SG7 glass were compared to those for soda-lime and borosilicate glasses. (author)

Multi-zone coupling productivity of horizontal well fracturing with complex fracture networks in shale gas reservoirs

Directory of Open Access Journals (Sweden)

Weiyao Zhu

2018-02-01

Full Text Available In this paper, a series of specific studies were carried out to investigate the complex form of fracture networks and figure out the multi-scale flowing laws of nano/micro pores–complex fracture networks–wellbore during the development of shale reservoirs by means of horizontal well fracturing. First, hydraulic fractures were induced by means of Brazilian splitting tests. Second, the forms of the hydraulic fractures inside the rock samples were observed by means of X-ray CT scanning to measure the opening of hydraulic fractures. Third, based on the multi-scale unified flowing model, morphological description of fractures and gas flowing mechanism in the matrix–complex fracture network–wellbore, the productivity equation of single-stage horizontal well fracturing which includes diffusion, slipping and desorption was established. And fourthly, a productivity prediction model of horizontal well multi-stage fracturing in the shale reservoir was established considering the interference between the multi-stage fracturing zones and the pressure drop in the horizontal wellbore. The following results were obtained. First, hydraulic fractures are in the form of a complex network. Second, the measured opening of hydraulic fractures is in the range of 4.25–453 μm, averaging 112 μm. Third, shale gas flowing in different shapes of fracture networks follows different nonlinear flowing laws. Forth, as the fracture density in the strongly stimulated zones rises and the distribution range of the hydraulic fractures in strongly/weakly stimulated zones enlarges, gas production increases gradually. As the interference occurs in the flowing zones of fracture networks between fractured sections, the increasing amplitude of gas production rates decreases. Fifth, when the length of a simulated horizontal well is 1500 m and the half length of a fracture network in the strongly stimulated zone is 100 m, the productivity effect of stage 10 fracturing is the

Epidemiology of metatarsal stress fractures versus tibial and femoral stress fractures during elite training.

Science.gov (United States)

Finestone, Aharon; Milgrom, Charles; Wolf, Omer; Petrov, Kaloyan; Evans, Rachel; Moran, Daniel

2011-01-01

The training of elite infantry recruits takes a year or more. Stress fractures are known to be endemic in their basic training and the clinical presentation of tibial, femoral, and metatarsal stress fractures are different. Stress fracture incidence during the subsequent progressively more demanding training is not known. The study hypothesis was that after an adaptation period, the incidence of stress fractures during the course of 1 year of elite infantry training would fall in spite of the increasingly demanding training. Seventy-six male elite infantry recruits were followed for the development of stress fractures during a progressively more difficult training program composed of basic training (1 to 14 weeks), advanced training (14 to 26 weeks), and unit training (26 to 52 weeks). Subjects were reviewed regularly and those with clinical suspicion of stress fracture were assessed using bone scan and X-rays. The incidence of stress fractures was 20% during basic training, 14% during advanced training and 23% during unit training. There was a statistically significant difference in the incidence of tibial and femoral stress fractures versus metatarsal stress fractures before and after the completion of phase II training at week 26 (p=0.0001). Seventy-eight percent of the stress fractures during phases I and II training were either tibial or femoral, while 91% of the stress fractures in phase III training were metatarsal. Prior participation in ball sports (p=0.02) and greater tibial length (p=0.05) were protective factors for stress fracture. The study hypothesis that after a period of soldier adaptation, the incidence of stress fractures would decrease in spite of the increasingly demanding elite infantry training was found to be true for tibial and femoral fractures after 6 months of training but not for metatarsal stress fractures. Further studies are required to understand the mechanism of this difference but physicians and others treating stress fractures

Fracture behavior of reaction layers in W and SiC joint system

International Nuclear Information System (INIS)

Son, S.J.; Kohyama, A.; Yu, I.K.; Cho, S.

2007-01-01

Full text of publication follows: SiC and SiC/SiC composites are considering as attractive structural materials for fusion reactors, because of their excellent physical, chemical and nuclear properties in fusion environments. For the application of these materials to gas-cooled fusion blanket systems, they have to satisfy specific requirements, such as hermeticity and surface features, in addition to baseline thermo-mechanical and irradiation properties. One of the critical issues for a fusion technology is a plasma facing material, which is considered in the connection with joining, heat transfer control and protection from helium gas in high temperature components. Tungsten as a coating material for SiC-based plasma-facing components has excellent advantages, such as a small mismatch in coefficient of thermal expansion, a very low sputtering yield, inherent heat resistance and high thermal conductivity. Therefore, tungsten and its alloys are promising as potential coating materials for divertor and first wall applications. In the present work, by using micron-sized tungsten and nano-SiC powders, W-SiC joints were prepared by simultaneous and sequential hot-pressing process. Various reaction products in the tungsten-SiC system were revealed by microstructural analyses. The interfacial phases and thickness were strongly depended on the temperature and time of hot pressing. The fracture characteristics of the reaction layers determine the robustness of W/SiC systems. Therefore, in this work, fracture behaviors by analyzing the indentation induced cracks in each phase and mechanical properties of W/SiC joints were examined. The most high shear strength was obtained in the joints fabricated at the conditions of 1780 deg. C, 20 MPa, 1 hr holding time. Easy crack extension was confirmed in the region of WC phase. The fracture of 1870 deg. C fabrication samples, which showed comparatively low shear strength, occurred at the wide region of reaction phases (WC+W 5 Si 3 +W

Thermal Testing and Quality Assurance of BGA LCC & QFN Electronic Packages

Energy Technology Data Exchange (ETDEWEB)

Kuper, Cameron Mathias [Univ. of New Mexico, Albuquerque, NM (United States)

2015-12-10

The purpose of this project is to experimentally validate the thermal fatigue life of solder interconnects for a variety of surface mount electronic packages. Over the years, there has been a significant amount of research and analysis in the fracture of solder joints on printed circuit boards. Solder is important in the mechanical and electronic functionality of the component. It is important throughout the life of the product that the solder remains crack and fracture free. The specific type of solder used in this experiment is a 63Sn37Pb eutectic alloy. Each package was surrounded conformal coating or underfill material.

User's manual and analysis methodology of probabilistic fracture mechanics analysis code PASCAL Ver.2 for reactor pressure vessel (Contract research)

International Nuclear Information System (INIS)

Osakabe, Kazuya; Onizawa, Kunio; Shibata, Katsuyuki; Kato, Daisuke

2006-09-01

As a part of the aging structural integrity research for LWR components, the probabilistic fracture mechanics (PFM) analysis code PASCAL (PFM Analysis of Structural Components in Aging LWR) has been developed in JAEA. This code evaluates the conditional probabilities of crack initiation and fracture of a reactor pressure vessel (RPV) under transient conditions such as pressurized thermal shock (PTS). The development of the code has been aimed to improve the accuracy and reliability of analysis by introducing new analysis methodologies and algorithms considering the recent development in the fracture mechanics and computer performance. PASCAL Ver.1 has functions of optimized sampling in the stratified Monte Carlo simulation, elastic-plastic fracture criterion of the R6 method, crack growth analysis models for a semi-elliptical crack, recovery of fracture toughness due to thermal annealing and so on. Since then, under the contract between the Ministry of Economy, Trading and Industry of Japan and JAEA, we have continued to develop and introduce new functions into PASCAL Ver.2 such as the evaluation method for an embedded crack, K I database for a semi-elliptical crack considering stress discontinuity at the base/cladding interface, PTS transient database, and others. A generalized analysis method is proposed on the basis of the development of PASCAL Ver.2 and results of sensitivity analyses. Graphical user interface (GUI) including a generalized method as default values has been also developed for PASCAL Ver.2. This report provides the user's manual and theoretical background of PASCAL Ver.2. (author)

Size Scaling and Bursting Activity in Thermally Activated Breakdown of Fiber Bundles

KAUST Repository

Yoshioka, Naoki

2008-10-03

We study subcritical fracture driven by thermally activated damage accumulation in the framework of fiber bundle models. We show that in the presence of stress inhomogeneities, thermally activated cracking results in an anomalous size effect; i.e., the average lifetime tf decreases as a power law of the system size tf ∼L-z, where the exponent z depends on the external load σ and on the temperature T in the form z∼f(σ/T3/2). We propose a modified form of the Arrhenius law which provides a comprehensive description of thermally activated breakdown. Thermal fluctuations trigger bursts of breakings which have a power law size distribution. © 2008 The American Physical Society.

Reduction of femoral fractures in long-term care facilities: the Bavarian fracture prevention study.

Directory of Open Access Journals (Sweden)

Clemens Becker

Full Text Available BACKGROUND: Hip fractures are a major public health burden. In industrialized countries about 20% of all femoral fractures occur in care dependent persons living in nursing care and assisted living facilities. Preventive strategies for these groups are needed as the access to medical services differs from independent home dwelling older persons at risk of osteoporotic fractures. It was the objective of the study to evaluate the effect of a fall and fracture prevention program on the incidence of femoral fracture in nursing homes in Bavaria, Germany. METHODS: In a translational intervention study a fall prevention program was introduced in 256 nursing homes with 13,653 residents. The control group consisted of 893 nursing homes with 31,668 residents. The intervention consisted of staff education on fall and fracture prevention strategies, progressive strength and balance training, and on institutional advice on environmental adaptations. Incident femoral fractures served as outcome measure. RESULTS: In the years before the intervention risk of a femoral fracture did not differ between the intervention group (IG and control group (CG. During the one-year intervention period femoral fracture rates were 33.6 (IG and 41.0/1000 person years (CG, respectively. The adjusted relative risk of a femoral fracture was 0.82 (95% CI 0.72-0.93 in residents exposed to the fall and fracture prevention program compared to residents from CG. CONCLUSIONS: The state-wide dissemination of a multi-factorial fall and fracture prevention program was able to reduce femoral fractures in residents of nursing homes.

Pre-fracture individual characteristics associated with high total health care costs after hip fracture.

Science.gov (United States)

Schousboe, J T; Paudel, M L; Taylor, B C; Kats, A M; Virnig, B A; Dowd, B E; Langsetmo, L; Ensrud, K E

2017-03-01

Older women with pre-fracture slow walk speed, high body mass index, and/or a high level of multimorbidity have significantly higher health care costs after hip fracture compared to those without those characteristics. Studies to investigate if targeted health care interventions for these individuals can reduce hip fracture costs are warranted. The aim of this study is to estimate the associations of individual pre-fracture characteristics with total health care costs after hip fracture, using Study of Osteoporotic Fractures (SOF) cohort data linked to Medicare claims. Our study population was 738 women age 70 and older enrolled in Medicare Fee for Service (FFS) who experienced an incident hip fracture between January 1, 1992 and December 31, 2009. We assessed pre-fracture individual characteristics at SOF study visits and estimated costs of hospitalizations, skilled nursing facility and inpatient rehabilitation stays, home health care visits, and outpatient utilization from Medicare FFS claims. We used generalized linear models to estimate the associations of predictor variables with total health care costs (2010 US dollars) after hip fracture. Median total health care costs for 1 year after hip fracture were $35,536 (inter-quartile range $24,830 to $50,903). Multivariable-adjusted total health care costs for 1 year after hip fracture were 14 % higher ($5256, 95 % CI $156 to $10,356) in those with walk speed total health care costs after hip fracture in older women. Studies to investigate if targeted health care interventions for these individuals can reduce the costs of hip fractures are warranted.

Numerical simulation of multiple-physical fields coupling for thermal anomalies before earthquakes: A case study of the 2008 Wenchuan Ms8.0 earthquake in southwest China

Science.gov (United States)

Deng, Z.

2017-12-01

It has become a highly focused issue that thermal anomalies appear before major earthquakes. There are various hypotheses about the mechanism of thermal anomalies. Because of lacking of enough evidences, the mechanism is still require to be further researched. Gestation and occurrence of a major earthquake is related with the interaction of multi-physical fields. The underground fluid surging out the surface is very likely to be the reason for the thermal anomaly. This study tries to answer some question, such as how the geothermal energy transfer to the surface, and how the multiple-physical fields interacted. The 2008 Wenchuan Ms8.0 earthquake, is one of the largest evens in the last decade in China mainland. Remote sensing studies indicate that distinguishable thermal anomalies occurred several days before the earthquake. The heat anomaly value is more than 3 times the average in normal time and distributes along the Longmen Shan fault zone. Based on geological and geophysical data, 2D dynamic model of coupled stress, seepage and thermal fields (HTM model) is constructed. Then using the COMSOL multi-physics filed software, this work tries to reveal the generation process and distribution patterns of thermal anomalies prior to thrust-type major earthquakes. The simulation get the results: (1)Before the micro rupture, with the increase of compression, the heat current flows to the fault in the footwall on the whole, while in the hanging wall of the fault, particularly near the ground surface, the heat flow upward. In the fault zone, heat flow upward along the fracture surface, heat flux in the fracture zone is slightly larger than the wall rock;, but the value is all very small. (2)After the occurrence of the micro fracture, the heat flow rapidly collects to the faults. In the fault zones, the heat flow accelerates up along the fracture surfaces, the heat flux increases suddenly, and the vertical heat flux reaches to the maximum. The heat flux in the 3 fracture

Prediction of thermal fatigue life of ceramics

International Nuclear Information System (INIS)

Kamiya, N.; Kamigaito, O.

1979-01-01

On the assumption that the thermal fatigue life of ceramics is determined mainly by the duration over which a crack reaches a small critical length, a prediction of the life was made by application of fracture mechanics to ceramics based on subcritical crack growth. Approximated formulae were derived. Experimental examination showed that the formulae proved to be valid for glass, sintered mullite under moderate shock severity, and zirconia. Data given by other authors also prove their validity. The deviation of the life from the formulae for sintered mullite under a thermal shock of extremely low severty, suggests that a certain mechanism, for example strengthening, is needed to understand the life of the sintered mullite. (author)

Heavy-oil recovery in naturally fractured reservoirs with varying wettability by steam solvent co-injection

Energy Technology Data Exchange (ETDEWEB)

Al Bahlani, A. [Alberta Univ., Edmonton, AB (Canada); Babadagli, T. [Society of Petroleum Engineers, Canadian Section, Calgary, AB (Canada)]|[Alberta Univ., Edmonton, AB (Canada)

2008-10-15

Steam injection may not be an efficient oil recovery process in certain circumstances, such as in deep reservoirs, where steam injection may be ineffective because of hot-water flooding due to excessive heat loss. Steam injection may also be ineffective in oil-wet fractured carbonates, where steam channels through fracture zones without effectively sweeping the matrix oil. Steam flooding is one of the many solutions for heavy oil recovery in unconsolidated sandstones that is in commercial production. However, heavy-oil fractured carbonates are more challenging, where the recovery is generally limited only to matrix oil drainage gravity due to unfavorable wettability or thermal expansion if heat is introduced during the process. This paper proposed a new approach to improve steam/hot-water injection and efficiency for heavy-oil fractured carbonate reservoirs. The paper provided background information on oil recovery from fractured carbonates and provided a statement of the problem. Three phases were described, including steam/hot-waterflooding phase (spontaneous imbibition); miscible flooding phase (diffusion); and steam/hot-waterflooding phase (spontaneous imbibition or solvent retention). The paper also discussed core preparation and saturation procedures. It was concluded that efficient oil recovery is possible using alternate injection of steam/hot water and solvent. 43 refs., 1 tab., 13 figs.

A fracture mechanics study of tungsten failure under high heat flux loads

International Nuclear Information System (INIS)

Li, Muyuan

2015-01-01

The performance of fusion devices is highly dependent on plasma-facing components. Tungsten is the most promising candidate material for armors in plasma-facing components in ITER and DEMO. However, the brittleness of tungsten below the ductile-to-brittle transition temperature is very critical to the reliability of plasma-facing components. In this work, thermo-mechanical and fracture behaviors of tungsten are predicted numerically under fusion relevant thermal loadings.

Fracture mechanics

CERN Document Server

Perez, Nestor

2017-01-01

The second edition of this textbook includes a refined presentation of concepts in each chapter, additional examples; new problems and sections, such as conformal mapping and mechanical behavior of wood; while retaining all the features of the original book. The material included in this book is based upon the development of analytical and numerical procedures pertinent to particular fields of linear elastic fracture mechanics (LEFM) and plastic fracture mechanics (PFM), including mixed-mode-loading interaction. The mathematical approach undertaken herein is coupled with a brief review of several fracture theories available in cited references, along with many color images and figures. Dynamic fracture mechanics is included through the field of fatigue and Charpy impact testing. Explains computational and engineering approaches for solving crack-related problems using straightforward mathematics that facilitate comprehension of the physical meaning of crack growth processes; Expands computational understandin...

On the estimation of durability during thermal fatigue tests

International Nuclear Information System (INIS)

Vashunin, A.I.; Kotov, P.I.

1981-01-01

It is shown that during thermal fatigue tests under conditions of varying loading rigidity the value of stored one-sided deformation in a fracture zone tends to the limit value of material ductility. Holding at Tsub(max) is semicycle of compression increases irreversible deformation on value of Atausub(confer)sup(a), which does not depend on loading rigidity. It is established that the Use of curves of thermal fatigue as basic ones for determination of resistance of non-isothermal low-cycle fatigue is possible only at values of stored quasistatical damage, constituting less than 5% from available ductility [ru

Root fractures

DEFF Research Database (Denmark)

Andreasen, Jens Ove; Christensen, Søren Steno Ahrensburg; Tsilingaridis, Georgios

2012-01-01

The purpose of this study was to analyze tooth loss after root fractures and to assess the influence of the type of healing and the location of the root fracture. Furthermore, the actual cause of tooth loss was analyzed....

Progress Toward a Thermal-Hydrological-Mechanical-Chemical-Biological (THMCB) Experiment in the Homestake Mine Deep Underground Science and Engineering Laboratory

Science.gov (United States)

Sonnenthal, E. L.; Maher, K.; Elsworth, D.; Lowell, R. P.; Uzunlar, N.; Mailloux, B. J.; Conrad, M. E.; Olsen, N. J.; Jones, T. L.; Cruz, M. F.; Torchinsky, A.

2011-12-01

The purpose of performing a long-term hydrothermal experiment in a deep mine is to gain a scientific understanding of the coupled physical, chemical, and biological processes taking place in fractured rock under the influence of mechanical stress, thermal effects, and fluid flow. Only in a controlled experiment in a well-characterized rock mass, can a fractured rock be probed in 3-D through geophysical imaging, in situ measurements, geochemical/biological sampling, and numerical modeling. Our project is focused on the feasibility of a THMCB experiment in the Homestake Mine, South Dakota to study the long-term evolution (10+ years) of a perturbed heterogeneous rock mass. In addition to the experiment as a laboratory for studying crustal processes, it has direct application to Enhanced Geothermal Systems, carbon sequestration, and contaminant transport. Field activities have focused on fracture and feature mapping, flux measurements from flowing fractures, and collection of water and rock samples for geochemical, biological, and isotopic analyses. Fracture mapping and seepage measurements are being used to develop estimates of permeability and fluxes at different length scales and design the location and orientation of the heater array. Fluxes measured up to several liters/minute indicate localized regions of very high fracture permeability, likely in excess of 10-10 m2. Isotopic measurements indicate heterogeneity in the fracture network on the scale of tens of meters in addition to the large-scale geochemical heterogeneity observed in the mine. New methods for sampling and filtering water samples were developed and tested with the goal of performing radiocarbon analyses in DNA and phospholipid fatty acids. Analytical and numerical models of the thermal perturbation have been used to design the heater orientation and spacing. Reaction path and THC simulations were performed to assess geochemical and porosity/permeability changes as a function of the heat input

Fracturing process and effect of fracturing degree on wave velocity of a crystalline rock