Dynamics Simulations of a Graphite Block Under Longitudinal Impact

2010 ◽  
Author(s):  
Gyeongho Kim ◽  
DongOk Kim ◽  
Woo-Seok Choi ◽  
Ji Ho Kang ◽  
Jae Man Noh
Keyword(s):  
Structural Integrity ◽  
Seismic Analysis ◽  
Mesh Size ◽  
Contact Dynamics ◽  
Longitudinal Impact ◽  
Graphite Block ◽  
Time Step ◽  
Core Components ◽  
Dynamics Simulations ◽  
Step Contact

Graphite blocks are important core components of the high temperature gas-cooled reactor. As these blocks are simply stacked in array, collisions among neighboring components may occur during earthquakes or accidents. Thus, it is important to develop a reliable seismic model of the stacked graphite blocks and have them designed to maintain their structural integrity during the anticipated occurrences. Various aspects involved in modeling and calculating impact-contact dynamics can affect the resulting behavior of the graphite block. These include mesh size, time step, contact behavior, mechanical constraint formulation of impact-contact analysis, etc. This work is dedicated to perform comparative studies and the effects of these parameters will be identified. The insights obtained through these studies will help build a realistic impact-contact model of the graphite block, from which a lumped or reduced dynamics model will be developed for the seismic analysis of the reactor including these graphite components.

Dynamics Simulations of a Graphite Block Under Longitudinal Impact

2010 ◽  
Vol 133 (5) ◽  
Author(s):  
Gyeongho Kim ◽  
Dong Ok Kim ◽  
Woo-Seok Choi ◽  
Ji Ho Kang ◽  
Jae Man Noh
Keyword(s):  
Structural Integrity ◽  
Seismic Analysis ◽  
Mesh Size ◽  
Contact Dynamics ◽  
Longitudinal Impact ◽  
Graphite Block ◽  
Time Step ◽  
Core Components ◽  
Dynamics Simulations ◽  
Step Contact

Graphite blocks are important core components of the high temperature gas-cooled reactor. As these blocks are simply stacked in array, collisions among neighboring components may occur during earthquakes or accidents. Thus, it is important to develop a reliable seismic model of the stacked graphite blocks and have them designed to maintain their structural integrity during the anticipated occurrences. Various aspects involved in modeling and calculating impact-contact dynamics can affect the resulting behavior of the graphite block. These include mesh size, time step, contact behavior, mechanical constraint formulation of impact-contact analysis, etc. This work is dedicated to perform comparative studies and the effects of these parameters will be identified. The insights obtained through these studies will help build a realistic impact-contact model of the graphite block from which a lumped or reduced dynamics model will be developed for the seismic analysis of the reactor including these graphite components.

A Safety Evaluation of HTTR Core Components Against 2011 Tohoku Earthquake

2013 ◽  
Author(s):  
Kazuhiko Iigaki ◽  
Masato Ono ◽  
Yosuke Shimazaki ◽  
Daisuke Tochio ◽  
Atsushi Shimizu ◽  
...  
Keyword(s):  
Structural Integrity ◽  
Seismic Analysis ◽  
Reactor Core ◽  
Safety Evaluation ◽  
Tohoku Earthquake ◽  
Reactor Power ◽  
2011 Tohoku Earthquake ◽  
The 2011 Tohoku Earthquake ◽  
Maximum Acceleration ◽  
Core Components

On March 11th, 2011, the 2011 Tohoku Earthquake which is one of the largest earthquakes in japan occurred and the maximum acceleration in observed seismic wave in the HTTR exceeded the design value in a part of input seismic motions. Therefore, a visual inspection, a seismic analysis and a performance confirmation test of facilities were carried out in order to confirm the integrity of facility after the earthquake. The seismic analysis was carried out for the reactor core structures by using the response magnification factor method. As the results of the evaluation, the generated stress in the graphite blocks in the reactor core at the earthquake were well below the allowable values of safety criteria, and thus the structural integrity of the reactor core was confirmed. The integrity of reactor core was also supported by the visual inspections of facilities and the operation without reactor power in cold conditions of HTTR.

Core Seismic Experiment and Analysis of a Large Number of Element Models for Fast Reactor

2017 ◽  
Author(s):  
Akihisa Iwasaki ◽  
Shinichiro Matsubara ◽  
Tomohiko Yamamoto ◽  
Seiji Kitamura ◽  
Shigeki Okamura
Keyword(s):  
Fast Reactor ◽  
Structural Integrity ◽  
Impact Force ◽  
Seismic Analysis ◽  
Reactor Core ◽  
Horizontal Displacement ◽  
Vertical Displacement ◽  
Three Dimensions ◽  
Core Element ◽  
Core Components

To design fast reactor (FR) core components, seismic response must be evaluated in order to ensure structural integrity. Generally, the fast reactor core is made of several hundred core elements in hexagonal arrangement. When a big earthquake occurs, large horizontal displacement, vertical displacement (rising) and impact force of each core element may cause a trouble for control rod insertability, reactivity insertion and core element intensity. Therefore, a seismic analysis method of a fast reactor core considering three-dimensional nonlinear behavior, such as bouncing, impact, fluid-structure interaction, etc. was developed. Validation of the core element vibration analysis code in three dimensions (REVIAN-3D) was conducted by 1/1.5 scale 32 core element mock-ups one-row test and 1/2.5 scale 313 core element mock-ups hexagonal-matrix test. In this verification, the applicability of the result obtained on a single model test or a small number of scale tests is verified when the number of core components increases. The vertical behavior (rising displacement) and horizontal behavior (Impact force, horizontal response) as a single core element of the analysis result agreed very well with the experiments.

How to Select the Optimized Time Step and Mesh Size for FEM Thermal Transients Simulations of PWR Vessels and Nozzles by Means of Artificial Neural Networks

2019 ◽  
Author(s):  
Nicolas Santucho ◽  
Martin Chimenti ◽  
Jose Duo
Keyword(s):  
Data Base ◽  
Structural Integrity ◽  
Mesh Size ◽  
Time Step ◽  
Thermal Transients ◽  
Element Size ◽  
Mechanical Models ◽  
Allowable Error ◽  
Artificial Neural ◽  
Definition Of

Abstract This paper describes the development of a data base and associated interpolation tool used to perform the validation of FEA thermo-mechanical models designed to verify the structural integrity of a self-pressurized modular Reactor Pressure Vessel (RPV) and its nozzles under service transient thermal loads. The main goal is to assess the element’s size and time steps that provide a confidence level on the obtained solutions. The validation process implies the definition of the geometry under study, its material’s properties, thermal load conditions and type of mesh element. With all this information, the program gives the user a set of curves for maximum time steps vs. temperature change rates for each typical thickness section in the modeled geometry for a chosen element size. Any point located below those curves assures a solution underneath a user specified allowable error (e.g.: 5%). All calculations are processed using dimensionless variables in order to create a universal data base enabling the analysis of many different situations of geometries, materials and loads. To improve performance, an Artificial Neural Network algorithm was developed. The resulting application significantly reduces the convergence study time and efforts.

Model Reduction of Contact Dynamics Simulation Using Modified Lyapunov Balancing Method

2011 ◽  
Author(s):  
Jianxun Liang ◽  
Ou Ma
Keyword(s):  
Finite Element ◽  
Model Reduction ◽  
Contact Stiffness ◽  
Influential Factors ◽  
Contact Dynamics ◽  
Dynamics Simulation ◽  
Integration Time ◽  
Time Step ◽  
Reduction Techniques ◽  
Dynamics Simulations

Finite element models can accurately simulate impact-contact dynamics response of a multibody dynamical system. However, such a simulation remains very inefficient because very small integration time step must be used when solving the involved differential equations. Although many model reduction techniques can be used to improve the efficiency of finite element based simulations, most of these techniques cannot be readily applied to contact dynamics simulations due to the high nonlinearity of the contact dynamics model. This paper presents a model reduction approach for finite-element based multibody contact dynamics simulation, based on a modified Lyapunov balanced truncation method. An example is presented to demonstrate that, by applying the model reduction the simulation process is significantly speeded up and the resulting error is bounded within an acceptable level. The performance of the method with respect to some influential factors such as element size, shape and contact stiffness is also investigated.

Assessing the Antimalarial Potentials of Phytochemicals: Virtual Screening, Molecular Dynamics and In-Vitro Investigations

2019 ◽  
Vol 16 (3) ◽  
pp. 291-300
Author(s):  
Saumya K. Patel ◽  
Mohd Athar ◽  
Prakash C. Jha ◽  
Vijay M. Khedkar ◽  
Yogesh Jasrai ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Structural Integrity ◽  
Md Simulations ◽  
Tylophora Indica ◽  
Multidrug Resistance Protein 1 ◽  
Receptor Complexes ◽  
Resistance Protein ◽  
Dynamics Simulations ◽  
Stable Trajectory

Background: Combined in-silico and in-vitro approaches were adopted to investigate the antiplasmodial activity of Catharanthus roseus and Tylophora indica plant extracts as well as their isolated components (vinblastine, vincristine and tylophorine). </P><P> Methods: We employed molecular docking to prioritize phytochemicals from a library of 26 compounds against Plasmodium falciparum multidrug-resistance protein 1 (PfMDR1). Furthermore, Molecular Dynamics (MD) simulations were performed for a duration of 10 ns to estimate the dynamical structural integrity of ligand-receptor complexes. </P><P> Results: The retrieved bioactive compounds viz. tylophorine, vinblastin and vincristine were found to exhibit significant interacting behaviour; as validated by in-vitro studies on chloroquine sensitive (3D7) as well as chloroquine resistant (RKL9) strain. Moreover, they also displayed stable trajectory (RMSD, RMSF) and molecular properties with consistent interaction profile in molecular dynamics simulations. </P><P> Conclusion: We anticipate that the retrieved phytochemicals can serve as the potential hits and presented findings would be helpful for the designing of malarial therapeutics.

Fractal Characteristics of Sandstone Cutting Fracture under Mechanical Shock Loading Conditions

2012 ◽  
Vol 226-228 ◽  
pp. 1789-1794 ◽  
Author(s):  
Shu Ren Wang ◽  
Paul Hagan ◽  
Yan Cheng
Keyword(s):  
Fractal Dimension ◽  
Size Distribution ◽  
Structural Integrity ◽  
Theoretical Calculations ◽  
Mesh Size ◽  
Rock Cutting ◽  
Weight Percent ◽  
Rock Breaking ◽  
Engineering Practice ◽  
Mechanical Shock

It is the key to guide rock-breaking design and engineering practice for how to obtain a reasonable test indicator to assess the cuttability of the rock. Some sandstone samples were tested by using the linear rock cutting machine in the school of mining engineering, University of New South Wales (UNSW), Australia. The curves characteristics for the weight percent of the broken debris with the mesh size distribution were obtained through the screening statistics. Furthermore, the fractal dimension of the specimen broken debris was derived through theoretical calculations and statistical analysis. The results showed that the rock cutting fragmentation is of significant fractal features under the mechanical shock loads. The broken debris fractal dimension of the structural integrity specimens is bigger, the range of the fractal dimension is smaller and the broken debris size distribution is more even than that of the poor structural integrity specimens. The fractal dimension is the ideal test indicator to assess and analysis the rock-breaking degree.

Numerical simulation of fairing separation test for hypersonic air breathing vehicle

2016 ◽  
Vol 231 (2) ◽  
pp. 319-325 ◽  
Author(s):  
Ankit Raj ◽  
K Anandhanarayanan ◽  
R Krishnamurthy ◽  
Debasis Chakraborty
Keyword(s):  
Structural Integrity ◽  
Test Results ◽  
Air Breathing ◽  
Aerodynamic Loads ◽  
Pressure Distributions ◽  
Ground Test ◽  
Computational Fluid Dynamics Simulations ◽  
Euler Solver ◽  
Dynamics Simulations ◽  
Flight Hardware

Fairings are provided to cover hypersonic air breathing vehicle to protect it from adverse aerodynamic loading and kinetic heating. Separation dynamics of fairings is an important event in the launch of vehicle. Extensive computational fluid dynamics simulations are carried out for the design of fairings and vehicle and selection of time sequences of various separation events. A ground test of fairing separation is conducted in the sled facility to check the structural integrity and functionality of various separation mechanisms and flight hardware. Simulations have been carried out to study the separation dynamics of fairings at test conditions using grid-free Euler solver to get the aerodynamic loads and the loads are integrated to get the trajectory of fairings. The aerodynamic loads are provided to verify the structural integrity of various components and the trajectory of panels is used in the test planning. The pressure distributions on the vehicle are compared with the test results.

scholarly journals Numerical Method of Fabric Dynamics Using Front Tracking and Spring Model

2013 ◽  
Vol 14 (5) ◽  
pp. 1228-1251 ◽  
Author(s):  
Yan Li ◽  
I-Liang Chern ◽  
Joung-Dong Kim ◽  
Xiaolin Li
Keyword(s):  
Upper Bound ◽  
Mesh Size ◽  
Front Tracking ◽  
Time Step ◽  
Mass System ◽  
Ode System ◽  
Spring System ◽  
Fabric Surface ◽  
Mass Spring ◽  
Eigen Frequency

AbstractWe use front tracking data structures and functions to model the dynamic evolution of fabric surface. We represent the fabric surface by a triangulated mesh with preset equilibrium side length. The stretching and wrinkling of the surface are modeled by the mass-spring system. The external driving force is added to the fabric motion through the “Impulse method” which computes the velocity of the point mass by superposition of momentum. The mass-spring system is a nonlinear ODE system. Added by the numerical and computational analysis, we show that the spring system has an upper bound of the eigen frequency. We analyzed the system by considering two spring models and we proved in one case that all eigenvalues are imaginary and there exists an upper bound for the eigen-frequency This upper bound plays an important role in determining the numerical stability and accuracy of the ODE system. Based on this analysis, we analyzed the numerical accuracy and stability of the nonlinear spring mass system for fabric surface and its tangential and normal motion. We used the fourth order Runge-Kutta method to solve the ODE system and showed that the time step is linearly dependent on the mesh size for the system.

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