scholarly journals Sizing of Refractory Castable Gas-Burner Using Thermomechanical Simulations

2010 ◽  
Vol 70 ◽  
pp. 173-178
Author(s):  
Fabien Nazaret ◽  
Thierry Cutard ◽  
Olivier Barrau
Keyword(s):  
Damage Model ◽  
Peak Stress ◽  
Internal Length ◽  
Damage Level ◽  
Refractory Castables ◽  
Before And After ◽  
Tension And Compression ◽  
Material Choice ◽  
Gas Burner ◽  
Refractory Structures

Damage is a crucial characteristic of refractory castables and has to be considered to simulate correctly the behaviour of refractory structures. But, damage modelling by finite element simulations remains difficult. Indeed, the use of a continuum damage model with softening leads to strain localization phenomena. Numerical results depend on the mesh. Several numerical methods allow solving this meshing dependence by introducing an internal length in the material constitutive laws. In this paper, a regularization method has been applied with the damage plasticity model, considering a scalar value for damage. This model enables to take into account permanent strains due to plasticity and damage before and after the peak stress in tension and compression. Thermomechanical simulations are performed with this model to predict damage in a gas-burner. The damage level is evaluated after a thermal simulation generating high temperature gradients. Interests to take into account damage in the refractory structures are discussed. Sensitivity of results to material properties is studied. This work gives an example of using thermomechanical simulations to improve the design of refractory castable structures and to help in the material choice.

Cyclic Loading of Beams Based on Kinematics Hardening Behavior Coupled With Isotropic Damage

2006 ◽  
Author(s):  
Ali Nayebi ◽  
Kourosh H. Shirazi
Keyword(s):  
Cyclic Loading ◽  
Strain Hardening ◽  
Kinematic Hardening ◽  
Damage Model ◽  
Mapping Algorithm ◽  
Return Mapping ◽  
Tension And Compression ◽  
Computational Aspects ◽  
Isotropic Damage ◽  
Path Dependent

The kinematic hardening theory of plasticity based on the Prager model and incremental isotropic damage is used to evaluate the cyclic loading behavior of a beam under the axial, bending, and thermal loads. This allows damage to be path-dependent. The damage and inelastic deformation are incorporated and they are used for the analysis of the beam. The beam material is assumed to follow linear strain hardening property coupled with isotropic damage. The material strain hardening curves in tension and compression are assumed to be both identical for the isotropic material. Computational aspects of rate independent model is discussed and the constitutive equation of the rate independent plasticity coupled with the damage model are decomposed into the elastic, plastic and damage parts. Return Mapping Algorithm method is used for the correction of the elastoplastic state and for the damage model the algorithm is used according to the governed damage constitutive relation. The effect of the damage phenomenon coupled with the elastoplastic kinematic hardening is studied for deformation and load control loadings.

Elastic–plastic-damage model of nano-indentation of the ion-irradiated 6061 aluminium alloy

2020 ◽  
Vol 29 (8) ◽  
pp. 1271-1305
Author(s):  
A Ustrzycka ◽  
B Skoczeń ◽  
M Nowak ◽  
Ł Kurpaska ◽  
E Wyszkowska ◽  
...  
Keyword(s):  
Damage Evolution ◽  
Damage Mechanics ◽  
Ion Irradiation ◽  
Damage Model ◽  
Indentation Test ◽  
Gtn Model ◽  
Damage Level ◽  
Nano Indentation ◽  
Wide Range ◽  
Radiation Induced

The paper presents experimental and numerical characterization of damage evolution for ion-irradiated materials subjected to plastic deformation during nano-indentation. Ion irradiation technique belongs to the methods where creation of radiation-induced defects is controlled with a high accuracy (including both, concentration and depth distribution control), and allows to obtain materials having a wide range of damage level, usually expressed in terms of displacements per atom (dpa) scale. Ion affected layers are usually thin, typically less than 1 micrometer thick. Such a low thickness requires to use nano-indentation technique to measure the mechanical properties of the irradiated layers. The He or Ar ion penetration depth reaches approximately 150 nm, which is sufficient to perform several loading-partial-unloading cycles at increasing forces. Damage evolution is reflected by the force-displacement diagram, that is backed by the stress–strain relation including damage. In this work the following approach is applied: dpa is obtained from physics (irradiation mechanisms), afterwards, the radiation-induced damage is defined in the framework of continuum damage mechanics to solve the problem of further evolution of damage fields under mechanical loads. The nature of radiation-induced damage is close to porosity because of formation of clusters of vacancies. The new mathematical relation between radiation damage (dpa) and porosity parameter is proposed. Deformation process experienced by the ion irradiated materials during the nano-indentation test is then numerically simulated by using extended Gurson–Tvergaard–Needleman (GTN) model, that accounts for the damage effects. The corresponding numerical results are validated by means of the experimental measurements. It turns out, that the GTN model quite successfully reflects closure of voids, and increase of material density during the nano-indentation.

scholarly journals Resistivity and AE Response Characteristics in the Failure Process of CGB under Uniaxial Loading

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Tingye Qi ◽  
Guorui Feng
Keyword(s):  
Failure Process ◽  
Peak Stress ◽  
Uniaxial Loading ◽  
Energy Curve ◽  
Cumulative Energy ◽  
Response Characteristics ◽  
Before And After ◽  
The Difference ◽  
Linear Slope ◽  
The Stability

To understand the characteristics of the acoustic emission (AE) and electrical resistivity of cemented coal gangue backfill (CGB) under uniaxial compression, the variations in these characteristics at 1 day, 3 days, and 7 days are analyzed by means of a stress-strain-resistivity-AE test, and the microperformances are investigated. The research results indicate that the AE can reflect the initiation and propagation of cracks and later explain the variation of the resistivity of the specimens under the uniaxial loading. The cumulative energy curve of AE is approximately two straight lines corresponding to the peak stress, and the difference in the linear slope gradually decreased with the increasing curing time due to the lower pore solution content and the compact pore structure. The relationships between the stress and resistivity and the loading condition before and after the peak stress at different curing times were established. Therefore, it is of great significance to predict the stability of the filling body by monitoring the AE and resistivity variations of the filling body. In addition, it is possible to calculate the roof stress using the relation equation between the resistivity and stress.

Corrosion barriers for silver-based telescope mirrors comparing PEALD and PVD of AlOx

2015 ◽  
Vol 1805 ◽  
Author(s):  
David M. Fryauf ◽  
Andrew C. Phillips ◽  
Nobuhiko P. Kobayashi
Keyword(s):  
Physical Vapor Deposition ◽  
Accelerated Aging ◽  
Atomic Layer ◽  
Chemical Corrosion ◽  
Environmental Testing ◽  
High Reflectivity ◽  
Before And After ◽  
Material Choice ◽  
Telescope Mirrors ◽  
Set Up

ABSTRACTAstronomical telescopes continue to demand high-endurance high-reflectivity silver mirrors that can withstand years of exposure in earth-based observatory environments. The University of California Observatories Astronomical Coatings Lab has undertaken development of protected silver coatings suitable for telescope mirrors that maintain high reflectivity at wavelengths from 340 nm through the mid-infrared spectrum. We present promising results of enhanced corrosion barriers using plasma-enhanced atomic layer deposition (PEALD) of aluminum oxide (AlOx) as a top barrier layer. Novel coating recipes developed with ion-assisted electron beam deposition (IAEBD) of materials including yttrium fluoride and oxides of yttrium, tantalum, and silicon are used to compare the endurance of physical vapor deposition-grown barriers with PEALD-grown barriers of similar thickness. Samples of these mirror coatings were covered with conformal layers of AlOx deposited by PEALD using trimethylaluminum as a metal precursor and plasma-activated oxygen as an oxidant gas. Samples of coating recipes with and without PEALD oxide undergo aggressive high temperature/high humidity (HTHH) environmental testing in which samples are exposed to an environment of 80% humidity at 80°C for ten days in a simple test set-up. HTHH testing show visible results suggesting that the PEALD oxide offers enhanced robust protection against chemical corrosion and moisture from an accelerated aging environment. Mirror samples are further characterized by reflectivity/absorption before and after deposition of oxide coatings. AlOx is suitable for many applications and has been the initial material choice for this study.

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

2016 ◽  
Vol 2016 ◽  
pp. 1-15 ◽  
Author(s):  
Isa Kolo ◽  
Rashid K. Abu Al-Rub ◽  
Rita L. Sousa
Keyword(s):  
Constitutive Model ◽  
Damage Model ◽  
Computational Modelling ◽  
Fracture Propagation ◽  
Material Model ◽  
Model Predictions ◽  
Tension And Compression ◽  
Damage Constitutive Model ◽  
Ak Model ◽  
Spatially Varying

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

SEISMIC PROTECTION OF EXISTING RC BUILDINGS USING FUSE ELEMENTS

2012 ◽  
Vol 06 (02) ◽  
pp. 1250009 ◽  
Author(s):  
WAIEL MOWRTAGE (VAIL KARAKALE)
Keyword(s):  
Electric Circuit ◽  
Skilled Workers ◽  
Rc Buildings ◽  
Reinforced Concrete Frame ◽  
Damage Level ◽  
Concrete Frame ◽  
Rc Frames ◽  
Before And After ◽  
Earthquake Research ◽  
Steel Panels

This paper presents a new concept on collapse prevention of existing RC buildings during a seismic event. The idea is to install steel panels in specified locations in the structure to reduce inter-story drifts. The panels are expected to work as a fuse in an electric circuit when a major earthquake occurs; the panels will attract the seismic forces and they may totally damaged but they will prevent severe damage in the main structural system. The proposed panels are light-weight, easy to handle, and can be constructed very quickly. Moreover, they are cheap and do not need formwork or skilled workers. To test the concept, a half-scale, single-story 3D reinforced concrete frame specimen was constructed at the shake-table laboratories of the Kandilli Observatory and Earthquake Research Institute of Bogazici University, and subjected to recorded real earthquake base accelerations. The amplitudes of base accelerations were increased until a moderate damage level is reached. Then, the damaged RC frames was retrofitted by means of steel panels and tested under the same earthquake. The seismic performance of the specimen before and after the retrofit was evaluated using FEMA356 standards, and the results were compared in terms of stiffness, strength, and deformability. The results have confirmed effectiveness of the proposed retrofit scheme.

scholarly journals A Multicomponent Thermal Fluid Numerical Simulation Method considering Formation Damage

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Xinan Yu ◽  
Xiaoping Li ◽  
Shuoliang Wang ◽  
Yi Luo
Keyword(s):  
Numerical Simulation ◽  
Oil Recovery ◽  
Heavy Oil ◽  
Physical Simulation ◽  
Damage Model ◽  
Simulation Method ◽  
Formation Damage ◽  
Thermal Fluids ◽  
Before And After ◽  
Control Equation

Multicomponent thermal fluid huff and puff is an innovative heavy oil development technology for heavy oil reservoirs, which has been widely used in offshore oilfields in China and has proved to be a promising method for enhancing oil recovery. Components of multicomponent thermal fluids contain many components, including carbon dioxide, nitrogen, and steam. Under high temperature and high pressure conditions, the complex physical and chemical reactions between multicomponent thermal fluids and reservoir rocks occur, which damage the pore structure and permeability of core. In this paper, the authors set up a reservoir damage experimental device, tested the formation permeability before and after the injection of multiple-component thermal fluids, and obtained the formation damage model. The multicomponent thermal fluid formation damage model is embedded in the component control equation, the finite difference method is used to discretize the control equation, and a new multielement thermal fluid numerical simulator is established. The physical simulation experiment of multicomponent thermal fluid huff and puff is carried out by using the actual sand-packed model. By comparing the experimental results with the numerical simulation results, it is proved that the new numerical simulation model considering formation damage proposed in this paper is accurate and reliable.

Fracability evaluation of lacustrine shale by integrating brittleness and fracture toughness

2019 ◽  
Vol 7 (2) ◽  
pp. T363-T372
Author(s):  
Cheng Huang ◽  
Chao Yang ◽  
Feng Shen
Keyword(s):  
Fracture Toughness ◽  
Plastic Strain ◽  
Strain Energy ◽  
Evaluation Method ◽  
Peak Stress ◽  
Brittleness Index ◽  
Before And After ◽  
Lacustrine Shale ◽  
The Difference ◽  
The Impact

Rock brittleness and fracture toughness are important parameters for evaluating rock fracability. The stress-strain curves indicate that the lacustrine shale is strongly brittle. Brittle failure occurs rapidly when the stress of the lacustrine shale reaches its peak value. In addition, the lacustrine shale has different plastic strains before and after peak stress; this can relax the stress concentration of the crack tips. Therefore, the plastic strain that occurs before and after the peak stress can cause decreasing brittleness, which can be used to distinguish the brittleness and fracability in the formation of the lacustrine shale clearly. Moreover, this further enlarges the difference in the brittleness index. Based on the influence of plastic strain on brittleness, we have developed a new brittleness evaluation method that uses the ratio of linear elastic strain energy to the total strain energy before complete rock failure, which can indicate the difference of the lacustrine shale clearly. Fracture toughness is another important parameter that impacts the fracture extension and influences fracability. Based on the impact of brittleness and fracture toughness on the fracability, we have developed a new fracability evaluation method. The brittleness index increases with increases in the quartz content, and it decreases with increases in the albite feldspar and calcite contents. The fracture toughness decreases with increases in the quartz and clay contents, and it increases with increases in the siderite content. In addition, we established an empirical formula that can evaluate the brittleness index and the fracture toughness using mineral contents obtained from elemental logging. Using the new fracability evaluation method to optimize the fracturing stage, the preliminary field test indicates that the new approach was effective in the lacustrine shale formation.

Force Exertion during Lifting with Light Loads

1974 ◽  
Vol 18 (4) ◽  
pp. 393-396
Author(s):  
Ronald Perkins ◽  
Stephan Konz
Keyword(s):  
Male Subject ◽  
Peak Stress ◽  
Lateral Force ◽  
The Body ◽  
Vertical Force ◽  
Final Position ◽  
Single Male ◽  
Object Weight ◽  
Before And After ◽  
Body Center

A single male subject lifted a tote box 12 times at each of 24 conditions while standing on a force platform. The 24 conditions were 6 combinations of initial and final position (floor to 12,24 and 36 in. shelf, floor plus 12 in. to 24 and 36 in. shelf, and floor plus 24 in. to 36 in. shelf) x 2 box weights (11 and 22 lbs.) and 2 distances of the box from the body center of gravity (16 and 20 in.). Averaged over all 24 conditions, peak vertical force was 46 lbs., frontal force was 6 lbs., lateral force was 2 lbs., somersault torque was 417 in.-lbs., cartwheel torque was 75 in.-lbs., twist torque was 59 in.-lbs. and peak box acceleration was .3 g. For lifting with light loads, object weight has much less effect on stress than might be expected. Peak forces occurred in the .5 sec. before and after grasping the box. In fact, peak stress occurred before the box was grasped in 66% of the lifts.

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