Simulations of Fully-Flexible Fuel Bundle Response due to Turbulence Excitation

2019 ◽  
Author(s):  
Osama Elbanhawy ◽  
Marwan Hassan ◽  
Atef Mohany
Keyword(s):  
Numerical Model ◽  
Single Point ◽  
Point Contact ◽  
Vibration Response ◽  
Pressure Tube ◽  
Contact Method ◽  
Impact Forces ◽  
Fuel Bundle ◽  
System Components ◽  
Fuel Elements

Abstract This work presents a numerical model for a fully-flexible CANDU fuel bundle to predict the vibration response due to turbulence excitation. The model includes 37 fuel elements and two endplates. The contact between system components such as fuel-to-fuel and fuel-to-pressure tube is modeled using the single point contact method (SPC). A range of flow velocities was examined, and the associated impact forces and work rates were calculated. In addition, the stresses on the endplates due to vibration of the fuel elements were predicted.

Analyzing Fuel Bundle Deformation Using the Finite Element Method

2017 ◽  
Author(s):  
Rabia Soni ◽  
Paul K. Chan ◽  
Diane Wowk ◽  
Anthony Williams
Keyword(s):  
Finite Element ◽  
Fuel Element ◽  
Deformation Behaviour ◽  
Flow Distribution ◽  
Element Model ◽  
Pressure Tube ◽  
The Finite Element Method ◽  
Fuel Bundle ◽  
Channel Temperature ◽  
Fuel Elements

During off-normal conditions, the temperature transient experienced by a CANDU fuel bundle may lead to deformation of the bundle via fuel element bowing between the spacer pads due to sub-channel temperature gradients, or fuel element sagging under gravity. The resulting deformation could impact the coolant flow distribution through the bundle, causing further degradation of the fuel cooling. Moreover, the deformation of the fuel elements may also lead to contact with the pressure tube, leading to localized heating that may compromise the integrity of the pressure tube. The objective of this work is to create a 3D finite element model to analyze bundle deformation behaviour under transient conditions. The methodology and preliminary results are presented herein.

Creep Forces Effect on the Ride of Empty Indian Freight Wagon

2017 ◽  
Vol 9 (3) ◽  
Author(s):  
N.K. Kanoje ◽  
S.C. Sharma ◽  
S.P. Harsha
Keyword(s):  
Numerical Model ◽  
Numerical Study ◽  
Single Point ◽  
Point Contact ◽  
Friction Model ◽  
Creep Model ◽  
Nonlinear Creep ◽  
Optimum Parameters ◽  
Coulomb Friction Model ◽  
Secondary Suspension

Indian Freight system is facing huge competition. The average speed of wagons at 40-50 kmph for empty wagons faces huge hunting problem. In these paper Indian parameters are studied using a numerical model The numerical model is consist of a whole wagon with two conventional three-piece bogie running on wheelsets. The wheel-rail contact is considered with heuristic nonlinear creep model for both single point and two point contact. Coulomb friction model is considered for contact between the truck and bolster. The present study concentrates on the critical hunting which is mainly depending on primary and secondary suspension parameters. A numerical study is run in Matlab to obtain the optimum parameters for increasing critical speed to stabilize wagon for both increased speed and at loaded vehicle.

scholarly journals Electromigration-induced directional steps towards the formation of single atomic Ag contacts

2020 ◽  
Vol 11 ◽  
pp. 680-687
Author(s):  
Atasi Chatterjee ◽  
Christoph Tegenkamp ◽  
Herbert Pfnür
Keyword(s):  
Fourier Transforms ◽  
Single Point ◽  
Point Contact ◽  
Single Atom ◽  
Point Contacts ◽  
Cross Sectional ◽  
Shell Effects ◽  
Theoretical Approaches ◽  
Average Grain Size ◽  
Thinning Process

Even though there have been many experimental attempts and theoretical approaches to understand the process of electromigration (EM), it has not been quantitatively understood for ultrathin structures and at grain boundaries. Nevertheless, we showed recently that it can be used reliably for the formation of single atomic point contacts after careful pre-structuring of the initial Ag nanostructures. The process of formation of nanocontacts by EM down to a single-atom point contact was investigated for ultrathin (5 nm) Ag structures at 100 K by measuring the conductance as a function of the time during EM. In this paper, we compare the process of thinning by EM of structures with constrictions below the average grain size of Ag layers (15 nm) with that of structures with much larger initial constrictions of around 150 nm having multiple grains at the centre constriction prior to the formation of a point contact. Even though clear morphological differences exist between both types of structures, quantized conductance plateaus showing the formation of single point contacts have been observed for both. Here we put emphasis on the thinning process by EM, just before a point contact is formed. To understand this thinning process, the semi-classical regime before the contact reaches the quantum regime was analyzed in detail. For this purpose, we used experimental conductance histograms in the range between 2G 0 and 15G 0 and their corresponding Fourier transforms (FTs). The FT analysis of the conductance histograms exhibits a clear preference for thinning along the [100] direction. Using well-established models, both atom-by-atom steps and ranges of stability, presumably caused by electronic shell effects, can be discriminated. Although the directional motion of atoms during EM leads to specific properties such as the instabilities mentioned, similarities to mechanically opened contacts with respect to cross-sectional stability were found.

Wheel-Rail Multi-Point Contact Method for Railway Turnouts

2011 ◽  
Vol 97-98 ◽  
pp. 378-381
Author(s):  
Zhi Wei Chen ◽  
Linan Li ◽  
Shi Gang Sun ◽  
Jun Long Zhou
Keyword(s):  
Calculation Method ◽  
Normal Force ◽  
Contact Point ◽  
Point Contact ◽  
Contact Model ◽  
Contact Method ◽  
Elastic Contact ◽  
Simulation Calculation ◽  
Acute Change

A calculation method of wheel-rail multi-point contact based on the elastic contact model is introduced. Moreover, the simulation calculation of vehicles passing through branch lines of No.18 turnouts is carried out. The result showed that the acute change of wheel-rail normal force caused by the transfers of wheel-rail contact point between two rails can be avoid by wheel-rail multi-point contact method, and the transfers of wheel-rail normal force between two rails is smoother. The validity of wheel-rail multi-point contact method is verified.

Engineering Relation for Dependence of Threshold Stress Intensity Factor for Delayed Hydride Cracking on Crack Orientation

2008 ◽  
Author(s):  
Douglas A. Scarth ◽  
Gordon K. Shek ◽  
Steven X. Xu
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Threshold Stress ◽  
Pressure Tube ◽  
Threshold Stress Intensity ◽  
Tube Material ◽  
Fuel Bundle ◽  
Threshold Stress Intensity Factor ◽  
Cold Worked

Delayed Hydride Cracking (DHC) in cold-worked Zr-2.5 Nb pressure tubes is of interest to the CANDU industry in the context of the potential to initiate DHC at an in-service flaw. Examples of in-service flaws are fuel bundle scratches, crevice corrosion marks, fuel bundle bearing pad fretting flaws and debris fretting flaws. To date, experience with fretting flaws has been favourable, and crack growth from an in-service fretting flaw has not been detected. However, postulated DHC growth from these flaws can result in severe restrictions on the allowable number of reactor Heatup/Cooldown cycles prior to re-inspection of the flaw, and it is important to reduce any unnecessary conservatism in the evaluation of DHC from the flaw. One method to reduce conservatism is to take credit for the increase in the isothermal threshold stress intensity factor for DHC initiation at a crack, KIH, as the flaw orientation changes from an axial flaw to a circumferential flaw in the pressure tube. This increase in KIH is due to the texture of the pressure tube material. An engineering relation that provides the value of KIH as a function of the orientation of the flaw relative to the axial direction in the pressure tube has been developed as described in this paper. The engineering relation for KIH has been validated against results from DHC initiation experiments on unirradiated cold-worked Zr-2.5 Nb pressure tube material.

Resolving the Unique Invariant Slip-Direction in Rigid Three-Dimensional Multi-Point Impacts at Stick-Slip Transitions

2018 ◽  
Author(s):  
Abhishek Chatterjee ◽  
Alan Bowling
Keyword(s):  
Single Point ◽  
Three Dimensional ◽  
Impact Behavior ◽  
Slip Direction ◽  
Stick Slip ◽  
Impact Forces ◽  
Post Impact ◽  
Impact Problems ◽  
Slip Transition ◽  
The Impact

This work presents a new approach for resolving the unique invariant slip direction at Stick-Slip Transition during impact. The solution method presented in this work is applicable to both single-point and multi-point impact problems. The proposed method utilizes rigid body constraints to resolve the impact forces at all collision points in terms of a single independent impact forces parameter. This work also uses an energetic coefficient of restitution to terminate impact events, thereby yielding energetically consistent post-impact behavior.

An Improved Design of Microchannel Fuel Processors

2005 ◽  
Author(s):  
Hye-Mi Jung ◽  
Sung-Dae Yim ◽  
Sukkee Um ◽  
Young-Gi Yoon ◽  
Gu-Gon Park ◽  
...  
Keyword(s):  
Numerical Model ◽  
Steam Reforming ◽  
Kinetic Equations ◽  
Methanol Conversion ◽  
Steel Plates ◽  
Catalyst Loading ◽  
Contact Method ◽  
Micro Channel ◽  
Catalytic Combustor ◽  
Improved Design

This paper focuses on a new systematic configuration of micro-channel fuel processors, particularly designed for portable applications. An alternative integration method of the micro-channel fuel processors is attempted to overcome the serious thermal unbalance and to minimize the system volume by introducing the direct contact method of the sub-components. An integrated micro-channel methanol processor was developed by assembling unit reactors, which were fabricated by stacking and bounding micro-channel patterned stainless steel plates, including fuel vaporizer, catalytic combustor and steam reformer. Commercially available Cu/ZnO/Al2O3 catalyst (ICI Synetix 33-5) was coated inside micro-channel of the unit reactor for steam reforming. The steam reforming reaction was conducted in the temperature range of 200°C to 260°C in the basis of reformer side end-plate and the temperature was controlled by varying methanol feeding into the combustor. More than 99% of methanol was converted at 240°C of reformer side temperature. A mechanism-based numerical model aimed at enhancing physical understanding and optimizing designs has been developed for improved micro-channel fuel processors. A two-dimensional numerical model in the reformer section created to model the phenomena of species transport and reaction occurring at the catalyst surface. The mass, momentum, and species equations were employed with kinetic equations that describe the chemical reaction characteristics to solve flow-field, methanol conversion rate, and species concentration variations along the micro-channel. This mechanism-based model was validated against the experimental data from the literature and then applied to various layouts of the micro-channel fuel processors targeted for the optimal catalyst loading and fuel reforming purpose. The computer-aided models developed in this study can be greatly utilized for the design of advanced fast-paced micro-channel fuel processors research.

Application of the finite element submodeling technique in a single point contact and wear problem

2018 ◽  
Vol 116 (10-11) ◽  
pp. 708-722 ◽  
Author(s):  
Cristina Curreli ◽  
Francesca Di Puccio ◽  
Lorenza Mattei
Keyword(s):  
Finite Element ◽  
Single Point ◽  
Point Contact

A nonlinear dynamic vibration model of a defective bearing: the importance of modelling the angle of the leading and trailing edges of a defect

2020 ◽  
pp. 147592172096395
Author(s):  
Francesco Larizza ◽  
Carl Q Howard ◽  
Steven Grainger ◽  
Wenyi Wang
Keyword(s):  
Numerical Model ◽  
Surface Defects ◽  
Vibration Response ◽  
Rolling Element Bearing ◽  
Analytical Models ◽  
Bearing Defect ◽  
Defect Profile ◽  
Vibration Model ◽  
Trailing Edges ◽  
Rolling Element

Rolling element bearings eventually become worn and fail by developing surface defects, such as spalls, dents and pits. Previous researchers have tested bearings with defects that have sharp [Formula: see text] rectangular edges that were used to develop analytical models of a defective bearing. These models have limitations that require smooth surfaces and constant curvature of the bearing components; as well as assuming the defect profile. A method has been created to capture the surface topography of a bearing defect. A numerical model has been developed for a rolling element bearing that uses the measured defect profile and removes the limitations of models by previous researchers that use analytical expressions for contact area and force. The predicted vibration response of a bearing with a defect that has sloped leading and trailing edges on the outer and inner raceway was compared with experimental results. It was found that the new numerical model was able to predict the vibration response of a defective bearing. The defect topographies and the developed model have been made publicly available.

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