Collapse Criterion for the CANDU 6 Calandria Vault Floor During a Severe Accident

2017 ◽  
Vol 3 (2) ◽  
Author(s):  
Robert David
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Analytical Model ◽  
Nuclear Reactor ◽  
Element Model ◽  
Severe Accident ◽  
Core Concrete

The thickness at which the calandria vault floor in a generic CANDU 6 nuclear reactor may collapse while undergoing molten core–concrete interaction (MCCI) was studied using an approximate analytical model and a finite-element model. It was confirmed that the collapse criterion of 0.45 m floor thickness that is currently used in severe accident analyses is adequate. The estimated timing of collapse is subject to uncertainty of several hours.

scholarly journals Co-Simulation of an Inverter Fed Permanent Magnet Synchronous Machine

2014 ◽  
Vol 6 (1) ◽  
pp. 19-25
Author(s):  
Gergely Máté Kiss ◽  
István Vajda
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Analytical Model ◽  
Element Model ◽  
Electrical Machine ◽  
Permanent Magnet Synchronous Machine ◽  
Variable Speed ◽  
Analytical Variable ◽  
Drive Model ◽  
The Finite Element Model

Abstract Co-simulation is a method which makes it possible to study the electric machine and its drive at once, as one system. By taking into account the actual inverter voltage waveforms in a finite element model instead of using only the fundamental, we are able to study the electrical machine's behavior in more realistic scenario. The recent increase in the use of variable speed drives justifies the research on such simulation techniques. In this paper we present the co-simulation of an inverter fed permanent magnet synchronous machine. The modelling method employs an analytical variable speed drive model and a finite element electrical machine model. By linking the analytical variable speed drive model together with a finite element model the complex simulation model enables the investigation of the electrical machine during actual operation. The methods are coupled via the results. This means that output of the finite element model serves as an input to the analytical model, and the output of the analytical model provides the input of the finite element model for a different simulation, thus enabling the finite element simulation of an inverter fed machine. The resulting speed and torque characteristics from the analytical model and the finite element model show a good agreement. The experiences with the co-simulation technique encourage further research and effort to improve the method.

Modelling of 4H-SiC VJFETs with Self-Aligned Contacts

2016 ◽  
Vol 858 ◽  
pp. 913-916 ◽  
Author(s):  
Konstantinos Zekentes ◽  
Konstantin Vassilevski ◽  
Antonis Stavrinidis ◽  
George Konstantinidis ◽  
Maria Kayambaki ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Analytical Model ◽  
Element Model ◽  
Experimental Results ◽  
Compact Model ◽  
Channel Lengths ◽  
The Finite Element Model

Purely vertical 4H-SiC JFETs have been modeled by using three different approaches: the analytical model, the finite element model and the compact model. The results of the modeling have been compared with experimental results on a series of fabricated self-aligned devices with two different channel lengths (0.3 and 1.1μm) and various channel widths (1.5, 2, 2.5, 3, 4 and 5 μm). For all the considered models I-V and C-V characteristics could be satisfactorily simulated.

Thermo-Mechanical Analysis of Instrumentation Guide Tube Failure During a Severe Accident in a Nordic Boiling Water Reactor

2020 ◽  
Author(s):  
Ying Yue ◽  
Walter Villanueva ◽  
Hongdi Wang ◽  
Dingqu Wang
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Failure Modes ◽  
Element Model ◽  
Boiling Water ◽  
Severe Accident ◽  
Boiling Water Reactor ◽  
Guide Tube ◽  
Water Reactor ◽  
Water Reactors

Abstract Vessel penetrations are important features of both pressurized water reactors and boiling water reactors. The thermal and structural behaviour of instrumentation guide tubes (IGTs) and control rod guide tubes (CRGTs) during a severe accident is vital in the assessment of the structure integrity of the reactor pressure vessel. Penetrations may fail due to welding failure, nozzle rupture, melt-through, etc. It is thus important to assess the failure mechanisms of penetrations with sufficient details. The objective of this paper is to assess the timing and failure modes of IGTs at the lower head during a severe accident in a Nordic boiling water reactor. In this study, a three-dimensional local finite element model was established using Ansys Mechanical that includes the vessel wall, the nozzle, and the weld joint. The thermo-mechanical loads of the finite element model were based on MELCOR results of a station blackout accident (SBO) combined with a large-break loss-of-coolant accident (LBLOCA) including an external vessel cooling by water as a severe accident management strategy. Given the temperature, creep strain, elastic strain, plastic strain, stress and displacement from the ANSYS simulations, the results showed the timing and failure modes of IGTs. Failure of the IGT penetration by nozzle creep is found to be the dominant failure mode of the vessel. However, it was also found that the IGT is clamped by the flow limiter before the nozzle creep, which means that IGT ejection is unlikely.

Comparison of Analytical Model for Contact Mechanics Parameters with Numerical Analysis and Experimental Results

2019 ◽  
Vol 48 (3) ◽  
pp. 168-187
Author(s):  
Sunish Vadakkeveetil ◽  
Arash Nouri ◽  
Saied Taheri
Keyword(s):  
Finite Element ◽  
Numerical Analysis ◽  
Finite Element Model ◽  
Penetration Depth ◽  
Contact Mechanics ◽  
Analytical Model ◽  
Element Model ◽  
Experimental Results ◽  
Nano Indentation ◽  
Interfacial Separation

ABSTRACT Being able to estimate tire/rubber friction is very important to tire engineers, materials developers, and pavement engineers. This is because of the need for estimating forces generated at the contact, optimizing tire and vehicle performance, and estimating tire wear. Efficient models for contact area and interfacial separation are key for accurate prediction of friction coefficient. Based on the contact mechanics and surface roughness, various models were developed that can predict real area of contact and penetration depth/interfacial separation. In the present work, we intend to compare the analytical contact mechanics models using experimental results and numerical analysis. Nano-indentation experiments are performed on the rubber compound to obtain penetration depth data. A finite element model of a rubber block in contact with a rough surface was developed and validated using the nano-indentation experimental data. Results for different operating conditions obtained from the developed finite element model are compared with analytical model results, and further model improvements are discussed.

Self-tensioning Support Post Design to Control Residual Stress in MEMS Fixed-Fixed Beams

2014 ◽  
Vol 1659 ◽  
pp. 55-61
Author(s):  
Ryan M. Pocratsky ◽  
Maarten P. de Boer
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Finite Element Model ◽  
Analytical Model ◽  
Local Stress ◽  
Element Model ◽  
3D Finite Element ◽  
3D Finite Element Model ◽  
Fixed Beam ◽  
Good Agreement

ABSTRACTFixed-fixed beams are ubiquitous MEMS structures that are integral components for sensors and actuation mechanisms. However, residual stress inherent in surface micromachining can affect the mechanical behavior of fixed-fixed structures, and even can cause buckling. A self-tensioning support post design that utilizes the compressive residual stress of trapped sacrificial oxide to control the stress state passively and locally in a fixed-fixed beam is proposed and detailed. The thickness and length of the trapped oxide affects the amount of stress in the beam. With this design, compression can be reduced or even converted into tension. An analytical model and a 3D finite element model are presented. The analytical model shows relatively good agreement with a 3D finite element model, indicating that it can be used for design purposes. A series of fixed-fixed beams were fabricated to demonstrate that the tensioning support post causes a reduction in buckling amplitude, even pulling the beam into tension. Phase shifting interferometry deflection measurements were used to confirm the trends observed from the models. Controlling residual stress allows longer fixed-fixed beams to be fabricated without buckling, which can improve the performance range of sensors. This technique can also enable local stress control, which is important for sensors.

Steady-State Kink Band Propagation in Layered Materials

2018 ◽  
Vol 85 (6) ◽  
Author(s):  
Simon P. H. Skovsgaard ◽  
Henrik Myhre Jensen
Keyword(s):  
Finite Element ◽  
Steady State ◽  
Finite Element Model ◽  
Analytical Model ◽  
Element Model ◽  
Kink Band ◽  
Layered Materials ◽  
Transcendental Equation ◽  
Experimental Findings ◽  
Good Agreement

Failure by steady-state kink band propagation in layered materials is analyzed using three substantially different models. A finite element model and an analytical model are developed and used together with a previously introduced constitutive model. A novel methodology for simulating an infinite kink band is used for the finite element model using periodic boundary conditions on a skewed mesh. The developed analytical model results in a transcendental equation for the steady-state kink band propagation state. The three models are mutually in good agreement and results obtained using the models correlate well with the previous experimental findings.

Stress-Strain Analysis of a Taper-Taper Adhesive-Bonded Joint Under Cylindrical Bending

1999 ◽  
Vol 121 (3) ◽  
pp. 374-380 ◽  
Author(s):  
Jack E. Helms ◽  
Chihdar Yang ◽  
Su-Seng Pang
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Analytical Model ◽  
Plate Theory ◽  
Element Model ◽  
Variable Coefficients ◽  
Fortran Program ◽  
Cylindrical Bending ◽  
First Order ◽  
Bonded Joint

A model of a taper-taper adhesive-bonded joint under cylindrical bending has been derived using first-order laminated plate theory. Shear correction factors were used to account for transverse shear deformation. A FORTRAN program was written to integrate the resulting system of twelve simultaneous, linear, first-order, differential equations with variable coefficients. The Linear Shooting Method was used to solve the model. A finite element model was developed using the COSMOS/M commercial finite element package to verify the analytical model for a cross-ply laminate. The analytical model results agreed well with the finite element models and predicted peak adhesive stresses within about 2% of the finite element model.

scholarly journals A New Analytical Model of the Brake Pad for Improved Calculation of the Centre of Pressure and Friction Coefficient in A Multi-Piston Disc Brake

2018 ◽  
Vol 7 (3.17) ◽  
pp. 54 ◽  
Author(s):  
Tomas Budinsky ◽  
Peter Brooks ◽  
David Barton
Keyword(s):  
Finite Element ◽  
Friction Coefficient ◽  
Finite Element Model ◽  
Analytical Model ◽  
Traditional Approach ◽  
Element Model ◽  
Disc Brake ◽  
Brake Pad ◽  
Centre Of Pressure ◽  
New Model

In recent experimental work it has been observed that the position of the centre of pressure (CoP) at the brake pad/disc interface has an influence on the onset of brake squeal. To determine the CoP during a braking event, a simple two-dimensional analytical model of the brake pad or more complex numerical finite element model of a disc brake are commonly used. This paper presents a new three-dimensional analytical model of a brake pad that determines the CoP position in both circumferential and radial directions. Due to higher complexity, this model provides more realistic clamp and friction force values, which can be used together with the more accurate radial position of the CoP for evaluation of the brake torque. The CoP position calculated using the new model was compared with the CoP evaluated by a finite-element model of an equivalent 8-piston opposed disc brake. The CoP results across the whole pad/disc interface showed a close correlation between these two approaches, giving the new analytical model a potential use in applications where an instantaneous value of the CoP with good accuracy is required. Finally, the new model was used to demonstrate possible improvement of the traditional method of the friction coefficient calculation. Due to greater accuracy the new model gives an approximately 8% larger value of the friction coefficient than the traditional approach. 

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