bluuebunny/crossref_metadata_2025 huggingface dataset:
Simplified Calculation Method of Seismic Response Energy of Mechanical System
Authors: Aoki Shigeru
Published: August 2008

When the mechanical systems are subjected to seismic excitation, the responses are nonstationary random process, since seismic excitation has nonstationary characteristics. Mean square response is a representative value of the statistical properties of the response. Seismic response energy which is integral of mean square response is used to evaluate absorbed energy and cumulative damage of mechanical system. Theoretical method for obtaining nonstationary mean square response of the secondary system is very complicated and time consuming. Thus, some approximate methods are sometimes used. In this paper, an approximate method for calculation method of seismic response energy using statistical properties of stationary response is proposed. As input excitation, nonstationary white noise is used. The input is defined by product of stationary white noise and envelope function. Mean square response of absolute acceleration of the mechanical system, relative velocity of the mechanical system to the ground and relative displacement are obtained. Some numerical results are shown. It is found that the proposed method gives exact values of seismic response energy independent of the damping ratio, mass ratio and the natural period.
Seismic Evaluation of Existing Structures Supporting Loading-Arms in LNG Receiving Terminal
Authors: Oshima Masami , Kase Takashi
Published: August 2008

After Hyogo South Area earthquake, a new seismic design method considering non-elastic deformation behavior is established against Level 2 earthquake (Safety Shutdown Earthquake) in the Seismic Design Code of High-pressure Gas Facilities in Japan. In this paper, this method is applied for an evaluation of existing structures supporting loading-arms in LNG Receiving Terminal. A procedure of pre-earthquake seismic upgrading and modification of the structures that are supported by platforms and supporting loading-arms is introduced. In this evaluation, the seismic loads taking into account of interaction among platforms, structures, and loading-arms are analyzed as total systems. And yield strength design method is applied. Then for the seismic design of loading-arms, floor response spectrums on the installation level are presented. After upgrading the platforms in this case, seismic evaluation of loading-arms based on this study will be performed. So the effect of changing its stiffness is studied. Also to evaluate the dynamic loads subjected to the loading-arms, they are compared with seismic loads that are derived from modified static coefficient method of the seismic design code. Thus with studies of vibration characteristics as total systems, it is possible to make effective and economical countermeasures for pre-earthquake seismic upgrading and modification of the structures and loading-arms.
Using Limit Analysis for Seismic Evaluation of Component Located in Nuclear Power Plants
Authors: Zeman Petr
Published: August 2008

Using limit analysis for evaluation of the seismic resistance of the components located in NPPs is compared with the standard evaluation method. This comparison is based on the procedure specified in American Society of Mechanical Engineers Boiler and Pressure Vessel Code, Section III. Subsection NC, version 1992 standard. The limit analysis uses perfectly plastic behavior of the material. The seismic load is restricted when using limit analysis to the pseudo-static load. The possibility of building of more realistic non-linear model including contacts is another advantage of limit analysis. Using limit analysis is the way to move the evaluation method closer to the real collapse load and to reduce conservatism.
Generation of Spectrum-Compatible Earthquake Motion Using Wavelet Transform
Authors: Masuda Arata , Sone Akira
Published: August 2008

In this paper, a new method for generating artificial earthquake motions is proposed, in which one can explicitly design the time-frequency characteristics of the earthquake as well as its response spectra. First, it is shown that the velocity response spectrum at a specific period can be interpreted as the maximum amplitude of the wavelet transform in which the velocity impulse response function of a single-degree-of-freedom system is used as the analyzing wavelet. Using this relationship, a spectrum-compatible artificial earthquake motion with the desirable time-frequency characteristics is generated in the wavelet domain by an iterative correction-projection scheme. Some illustrative examples are investigated to demonstrate the capability and the practicability of the proposed scheme.
Dynamic Stress Concentration of a Cylindrical Cavity Buried in an Elastic Half-Plane Subjected to a Standing Goodier-Bishop Stress Wave
Authors: Yeh C. S. , Teng T. J. , Liao W. I. , Shyu W. S.
Published: August 2008

In this paper, based on a expansion technique proposed by Yeh et al. (1995), the dynamic stress concentration of a cylindrical cavity buried in an elastic half-plane is studied. The cavity and the half-plane are excited by a harmonic standing Goodier-Bishop stress wave which, as a result of taking the normalized frequency tends to zero, is equivalent to a simple uniform static tension parallel to the ground surface. In the formulation, the scattered waves are represented by series expansion and their associated modal fields of the expansion satisfy the boundary conditions on the ground surface as well as the radiation condition at infinity, thus the scattering problem is reduced to the determination of the expansion coefficients by matching the boundary conditions on the cavity. Some numerical results for the dynamic hoop stresses around the wall of the cavity as well as the dynamic stress concentration factors with various buried depth and excitation frequencies are presented.
The Current Development of Seismic Design Code of Highway Bridges in Taiwan
Authors: Liao W. I. , Loh C. H. , Chai J. F.
Published: August 2008

This paper describes the development of seismic design provisions of highway bridges will be revised in Taiwan reflecting the destructive damage in the 1999 Chi-Chi earthquake. After the Chi-Chi earthquake, the revised seismic design force and other related requirements in the seismic design code for highway bridges are developed in Taiwan. In addition to the conventional force based design, a capacity checking level is considered for the near-fault sites by limiting the ultimate capacity to exceed the maximum possible seismic demand. The development of seismic design force and the capacity check method are described.
Experimental Study for a New Energy Dissipation Device: Multiple-Direction Damper
Authors: Tsai C. S. , Chung L. L. , Chiang T. C. , Chen B. J. , Chen W. S.
Published: August 2008

The way of passive control technologies has been recognized as an excellent method to mitigate seismic responses of structures during seismic excitations. In general, the energy dissipation devices based on their own mechanical property can be divided into two categories, which are velocity-dependent and displacement-dependent devices. In this study, a new displacement-dependent device which is called multiple-direction damper is proposed. The proposed damper has numerous advantages: (1) the fabrication of this energy-absorbing device is effortless; (2) the construction of the energy-absorbing system is easy; (3) it is simple to install the device into a structure; (4) the material used for this damper is easy to obtain; and (5) if any damage occurs in this damper during strong excitations, this energy-absorbing device can be replaced easily to recover its energy dissipation capacity. Experimental results from component tests show that the proposed damper provides significant energy-absorbing capacity. Furthermore, the multiple-direction dampers have also been equipped into a 5-story steel structure to demonstrate its efficiency on seismic mitigation. The experimental results from shaking table tests indicate that most of earthquake-induced energy imparted into the structure is dissipated by the proposed dampers. In the meanwhile, the seismic loadings imposing on the structure with devices can be reduced effectively as compared with those of the bare structure. Therefore, the multiple-direction damper can be recognized as an effective tool to assure the safety of structure under strong ground motions.
Seismic Analyses of Viscously-Damped Structures With an Unbounded Foundation
Authors: Tsai C. S. , Chiang T. C. , Chen B. J. , Cheng C. K.
Published: August 2008

The method of supplemental damping for dissipating seismic energy has been recognized as an effective and attractive way to reduce the seismic response of structures under seismic loadings. In recent years, an extensive number of structural control devices have been proposed to mitigate the vibration response of structures subjected to wind load and earthquake excitations. However, rare publications regarding the interactions between the soil and seismically damped structure have been unfolded. In order to ensure the safety of structures equipped with viscous fluid damper devices under seismic loadings, it is required to take into account the effects of radiation damping and the flexibility resulting from the unbounded soil media. In this study, two numerical methods, the consistent-infinitesimal finite element cell method and the quiet boundary method, have been proposed to simulate the radiation damping effects of far-field unbounded media. The numerical results show that the differences in seismic responses with or without unbounded media are significant. Therefore, it is illustrated that the radiation damping resulting form unbounded media should be taken into special consideration in seismic analyses.
Design Implications of Structural Irregularity
Authors: Pong Wenshen , Nesbet David
Published: August 2008

Irregular building designs present special problems to the structural engineer due to their uneven distributions of mass, stiffness, and strength. Because of these factors, irregular structures may have significantly different dynamic performance than a regular structure, which can lead to unanticipated force concentrations, deflections, and subsequent stresses on building members. Irregular building designs, while often more visually and architecturally interesting, are significantly more challenging to engineer for seismic loads. Discontinuities and irregularities in mass, configuration, and form can create many unwanted and unexpected effects when a structure is subjected to seismic forces. The Uniform Building Code (UBC) 1997 edition has addressed this concern by requiring dynamic analysis of irregular building designs greater than five stories in areas with greater seismic activity (seismic zones 3 and 4). The UBC’s requirement of a dynamic lateral force analysis, along with the requirement of a higher base shear force for irregular building designs (regular buildings are given a 10% base shear reduction bonus when dynamic analysis is performed), has made irregular building designs unattractive to structural engineers. Some structural engineers may question whether the UBC provisions are unnecessarily punitive to irregular building analysis, particularly for smaller buildings. To test this hypothesis, this study compares the results of using much simpler static seismic loading analysis with the results obtained from a dynamic analysis on two steel-frame six-story irregular building designs. The first building is irregular due to a type 3 vertical geometric irregularity (specifically a 3-story tower asymmetrically located above the remaining 3 stories). The second building is irregular due to a plan structural irregularity (a large central courtyard which creates diaphragm discontinuities in the top three stories). Both buildings are considered to be located in seismic zone 4, with a forcing input based on the 1997 UBC figure 16-3 used for the dynamic analysis. This study aims to present the design implications of structural irregularity. It seeks to investigate the differences in the calculated seismic forces, deflections, and stresses due to the two different methods of analysis.
Testing and Analysis of a New Lead-Extrusion Damper
Authors: Tsai C. S. , Lai W. S. , Chang C. W. , Li M. C.
Published: August 2008

The purpose of this study is to test and explore the characteristics of the new lead-extrusion damper (LED), which is manufactured in the department of Civil Engineering of Feng-Chia University. The Stroke of the tested damper is ±10 mm and the maximum movement of the laboratory test is ±5mm, which is provided by the MTS (machine with a maximum capacity of 25tons). The test results have proved that the new LED possesses excellent capability for energy absorption. The hysteresis loop behaves like “plastic solids” or “coulomb dampers”. The internal force and the speed of the movement are correlated while the damper is subjected to sin wave type of loadings. By comparing the numerical results obtained from the proposed analytical model with experimental results under various displacements and frequencies, it is concluded that a good agreement between the computational and experimental results has been achieved.
RADAS Device Technology for Retrofitting Damaged Structures in 921 Chi-Chi Earthquake
Authors: Tsai C. S. , Chen C. S. , Chen B. J. , Pong W. S.
Published: August 2008

The 921 Chi-Chi earthquake was the most destructive earthquake for Taiwan in the twentieth century. The earthquake caused severe damage or collapse to residential and public structures. In addition to the use of traditional earthquake-resistant technologies for retrofitting damaged structures, new structural control technologies have been also adopted. The RADAS (Reinforced Added Damping and Stiffness) device is a new type of earthquake-proof technology. The RADAS device has been proved as a very reliable energy-absorbing device for seismic hazard mitigation through shaking table tests. In this paper, we will present the application of RADAS devices to damaged structures in the 921 Chi-Chi earthquake. It is also illustrated in this study that new structures equipped with RADAS Devices can enhance seismic resistibility, even if earthquakes exceed ML 7.3 magnitude on the Richter scale. Therefore, it is a sensible choice to use RADAS devices to retrofit damaged structures and to enhance the earthquake-resistant capacity of new structures.
About the Design Criteria for Piping Under Extreme Loading Conditions: Analysis and Design
Authors: Lazzeri L.
Published: August 2008

The aim of this paper is to propose and discuss some design criteria for piping under extreme design conditions; the basic criteria are as follows: • the different failure scenarios are identified; • such scenarios are correlated to the value of the L and Y parameters; • Both analytical and experimental data are used to correlate the collapse to the ZPA/Y parameter. The analysis involves the recalculation of experimental data as well as other models. A design criterion is finally proposed.
Piping Seismic Stress Limits: A Critical Review
Authors: Slagis Gerry C.
Published: August 2008

Seismic stress limits for nuclear piping were published by the Section III code in 1994. Because of concerns on the technical bases for the rules, NRC has not approved their use. Modifications to the rules have been made in 2001. The 1994 seismic stress limits are reduced, and one type of joint now has a seismic stress limit that is less that the static load limit. A limit for seismic that is less than the limit for a static load contradicts the test data. Most of the technical concerns were valid. The 1994 rules are based on the premise that collapse is not a potential failure mode for a seismic event. However, collapse occurred in two of the EPRI component tests. Seismic margins in the component tests were overestimated. Revisions to the seismic margin data do not support the higher stress limits. A different approach has been taken to justify the 2001 rules. A probability approach is used where seismic capacity is related to a strength factor. The strength factor is based on the measured ultimate moment in the component tests. The capacity is the strength factor multiplied by a nonlinear dynamic factor. A small nonlinear dynamic factor is used because of concerns with off-resonance margin in stiff components. In contrast, the tests demonstrate large nonlinear dynamic factors. The intent of the new rules is to limit piping response to the SSE to the linear elastic range.
About the Design Criteria for Piping Under Extreme Loading Conditions: Appendix — Detailed Analyses
Authors: Lazzeri L.
Published: August 2008

The aim of this paper is to report on some detailed analyses used in the companion paper to formulate a simplified design concept for the seismic analysis of piping. The analyses include: • Revisiting EPRI tests on elbows (in particular tests 37; • Test 40 on reducer; • The analysis of a flexible pipeline; • The analysis of a pipe-work similar to ETEC test.
Approximate Analytic Method of Piping Systems With Elasto-Plastic Damper
Authors: Aoki Shigeru , Watanabe Takeshi
Published: August 2008

An elasto-plastic damper is one of the vibration absorbers in which energy is absorbed by elasto-plastic deformation of the hysteretic type damper. It is used for the piping system. The piping system is continuous system. Since it is difficult to find the analytical solution of the equation of motion for the system with elasto-plastic damper, the equation of motion is treated by various approximate methods in which the system is usually considered as a single- or a multiple-degree-of-freedom system, but not as a continuous system. In order to analyze the response of a nonlinear continuous system, however, it is necessary to consider the system as a continuous system. In this paper, the nonlinear steady-state response of the piping system with elasto-plastic damper is undertaken by approximate solutions, which are easily obtained by a simple procedure and are more practical than the exact solutions. As a continuous model of the piping system, a beam simply supported or clamped at one end, with elasto-plastic damper at the other end is used. The restoring force is modeled as hysteresis loop characteristics in order to consider the energy loss in the damper. In the analysis, the restoring force is expanded into the Fourier series, and only fundamental terms are considered. The resonance curves and mode shapes of the beam are obtained from the approximate solution. And effect of elasto-plastic damper on the forced response of continuous system is examined.
Simultaneous Prediction of Solid Stress, Heat Transfer and Fluid Flow by a Single Algorithm
Authors: Spalding D. B.
Published: August 2008

It is frequently required to simulate fluid-flow and heat-transfer processes in and around solids which are, partly as a consequence of the flow, subject to thermal and mechanical stresses. Often, indeed, it is the stresses which are of major concern, while the fluid and heat flows are of only secondary interest. Engineering examples of fluid/heat/stress interactions include: • Gas-turbine blades under transient conditions; • “Residual stresses” resulting from casting or welding; • Thermal stresses in nuclear reactors during emergency shut-down; • Manufacture of bricks and ceramics; • Stresses in the cylinder blocks of diesel engines; • The failure of steel-frame buildings during fires. It has been customary for two computer codes to be used for the solution of such problems, one for the fluid flow and the other for the stresses. Iterative interaction between the two codes is then employed, often with considerable inconvenience. It is often believed that FLUID-FLOW and SOLID-STRESS problems must be solved by different methods and different computer programs. This is not true, if the solid-stress problems are formulated in terms of DISPLACEMENTS. The lecture exemplifies and explains how both DISPLACEMENTS and VELOCITIES can be calculated at the same time. Also described, incidentally, are economical methods of simulating: thermal RADIATION between solids immersed in fluids; and TURBULENT CONVECTION at low Reynolds numbers in the same situation.
Plume and Crosswind Interaction, Prediction and Validation
Authors: Green J. A.
Published: August 2008

The prediction of the behaviour of a jet in a crossflow using computational fluid dynamics (CFD) methods is an important area of study, with many applications in industry. The methods by which the CFD code solves the kinetic equations of fluid flow, greatly affects the accuracy of the solution. As the use of CFD becomes increasingly relied upon in industry, it is necessary to investigate different modelling techniques, and to provide validation of the techniques used. This paper describes work to develop an effective means of predicting the behaviour of a subsonic jet in a crossflow using a modified version of a commercial CFD code. The effect of mesh resolution and distribution on the accuracy of the results was studied, along with the discretisation and solution methods used to solve the Navier-Stokes equations. This was done with the aim of establishing a modelling strategy for future applications, and to appraise current methods. The treatment of species and heat transport was examined. The effect of buoyancy was modelled and found to be negligible. The results from these modelling approaches were then compared to experimental data. This revealed a reasonably high level of confidence in the usefulness of CFD as a tool for predicting jet plume and crosswind interactions.
Initial CFD Simulations of High Aspect Ratio Jets
Authors: Profe-Bracht Jan , Wakes Sarah J.
Published: August 2008

High aspect ratio jets are significant in many industrial settings and can be crucial to safety and performance. As more of these flows are being modelled it is therefore essential that the behaviour of these jets is understood and if necessary modelled correctly. Failure to do so could result in jeopardising human life and have considerable environmental implications. Upon an offshore superstructure there exists many high pressure pipelines carrying hydrocarbons often at high temperature. Much safety work before the commissioning of offshore superstructures is done numerically and it is therefore of vital importance to have confidence in the assumptions and models used. This paper concentrates on the numerical modelling of the release of gas at high pressures into the atmosphere and is based on existing experimental work. Initial numerical work with the k-ε two-equation turbulence model was undertaken to compare against this existing experimental data. In revisiting the use of the standard k-ε turbulence model with an elliptical solver replacing the parabolic used in the past for a complex flow and validating it against experimental data could have implications for the CFD modelling of complex flows.
Modeling of Flow Around a Circular Cylinder in Sub-Critical Flow Regime With the Use of Dynamic Grid Adaptation
Authors: de With Govert , Holdo̸ Arne E. , Huld Thomas A.
Published: August 2008

In the present study a Dynamic Grid Adaptation (DGA) algorithm is used for predicting flow around a circular cylinder in sub-critical flow regime at a Reynolds number of 1.4·105. The reason for adopting a DGA algorithm is to use the flow field as a driving criteria for mesh refinement rather then the geometry of the computational domain or the judgment of the CFD user as common in conventional mesh. It is demonstrated how DGA reduces the mesh size significantly and also makes time consuming mesh testing unnecessary. The concept being adopted is to concentrate mesh refinement in regions with high gradients and high turbulent viscosity, while in the region further downstream where the flow is fully developed a coarser mesh will develop and turbulence is modeled with the Large Eddy Simulation (LES) turbulence model. The aim of the study is to present an appropriate variable for mesh refinement, which accomplishes a high rate of mesh refinement in the region with high gradients. The new variable is a product of the local mesh cell size and the rate of strain and includes two additional variables to allow control over the refinement behaviour.
The Prediction of Flow Patterns Below a Fixed Bed Media
Authors: Platt Steve , Cantwell Alan , Wakes Sarah J.
Published: August 2008

This paper is concerned with studying the flow within a wastewater treatment tank. Brightwater Engineering Ltd has implemented a program of numerical studies investigating the constituent components of the treatment process with an aim to improve and fully understand the fluidic element. This paper concentrates on the bottom mixing layer of the flow in the tank and follows on from previous work on flow through the inlets ports. The work highlights the sensitivity of the flow within this region to small changes in velocity and distribution of the flow. This could have importance within the next stage, the flow within the treatment media.
Solution Adaptive Grids Applied to Low Reynolds Number Flow
Authors: de With Govert , Holdo̸ Arne E. , Huld Thomas A.
Published: August 2008

A numerical study has been undertaken to investigate the use of a solution adaptive grid for flow around a cylinder in the laminar flow regime. The main purpose of this work is twofold. The first aim is to investigate the suitability of a grid adaptation algorithm and the reduction in mesh size that can be obtained. Secondly, the uniform asymmetric flow structures are ideal to validate the mesh structures due to mesh refinement and consequently the selected refinement criteria. The refinement criteria in this work are derived from turbulent viscosity, which is not applied to the flow simulation, but instead used as a measure for grid refinement.
Investigating Flow Inside a Commercial Aircraft Cabin
Authors: Calay Rajnish K. , Harris Simon D.
Published: August 2008

The Computational Fluid Dynamics (CFD) has been used in the Aerospace Industry as a major tool in designing and manufacturing aircraft, however, for the ventilation flows its use is yet to be established. Modern commercial aeroplanes operate in a physically hostile environment. These airplanes contain a complex Environment control and thermal comfort. Therefore there are several numerical modeling issues regarding simulating flows dominated by thermal and convective currents. The ventilation airflow behaviour of the interior of a Boeing 737 is investigated in this paper using CFD.
CFD-Tool for Thermal-Hydraulics Pressurised Thermal Shock Analysis: Qualification of the Code_Saturne
Authors: Martin A. , Bellet S.
Published: August 2008

This paper explains the numerical program concerning the new thermalhydraulic Code_Saturne qualification for Safety Injection studies. Within the frame of the plant life time project, an analysis has shown that the most severe loading conditions are generated by a pressurised injection of cold water in the downcomer of a Reactor Pressure Vessel. For this kind of transients, a thermal hydraulics study has to be carried out in order to better adjust the accurate distribution of the fluid temperature in the downcomer. For that, the numerical tools have to be able to simulate the physical phenomena present during the Pressurised Thermal Shock. (PTS). For this qualification task, we have investigated one configuration related to an injection of cold water particularly in cold leg but also in a downcomer. One experiment test case has been studied and this paper gives a comparison between experiment and numerical results in terms of temperature field.
Fluid Structure Interaction in LS-DYNA: Industrial Applications
Authors: Souli M’hamed , Olovson Lars , Do Ian
Published: August 2008

A new Fluid Sructure coulping algorithms basesd on the penalty method is dpresented in thi spaper. The coupling algorithm and improved multi-material ALE-capabilities have made LS-DYNA an efficient tool for analyzing large deformation processes, such as bird strike events, forging operations and penetration problems and airbag simumations. This paper contains five example problems that illustrate the current features of the code.
A Beam Embedded Element for Numerical Modelling of Geo-Composites Structures
Authors: Sadek Machhour , Shahrour Isam , Mroueh Hussein
Published: August 2008

This paper concerns the elaboration of an embedded beam element for the calculation of reinforced structures. The paper is composed of three parts. The first part discusses the need for the development of a beam element which can be easily incorporated in existing meshes. The second part describes the mathematical formulation of this element. The last part deals with the verification of this element on various examples.
Design of Tunnels in Swelling Soils: Determination of Swelling Soil Properties
Authors: Windal Timothe´e , Shahrour Isam
Published: August 2008

This paper includes a study of soil swelling for tunnels projects. It is performed using a flexible odometer which authorizes a lateral deformation of the soil sample during swelling and allows the measurement of the lateral swell pressure. The paper is composed of three parts. The first one concerns analysis of swelling phenomenon in tunnel projects. The second one presents the swelling odometer which was used in this work. The last one presents results obtained on clay and discusses the influence of the swelling condition on both axial and lateral soils expansion.
Deformation and Collision Process of Metal Plate on Explosive Welding Using Underwater Shock Wave
Authors: Iyama Hirofumi , Fujita Masahiro , Raghukandan K. , Hokamoto Kazuyuki , Itoh Shigeru
Published: August 2008

Explosive welding using underwater shock wave has been conducted. This technique is a new method of explosive welding and can weld a steel plate with an amorphous film, multi-layer of thin copper plates and so on. The conventional method of usual explosive welding cannot weld these combinations of material. It is possible to change shock pressure acting on the flyer plate easily, because the equipment for this method can change the inclined angle and distance between the explosive and flyer plate. However, we have to understand the mechanism of this method to seek the most suitable for set-up condition. Therefore, the numerical simulation of this method was made. The simulation method was FDM using Lagrangean scheme and it can express the detonation process of explosive, propagation process of underwater shock wave, deformation process of metal plate and collision process of between flyer and base plates. In this paper, these simulation results are discussed.
Fluid-Structure Interaction for Hydrodynamic Problems: Impact Between a Tanker Bow Flare and a Submarine
Authors: Aquelet N. , Lesourne H. , Souli M.
Published: August 2008

A methodology to predict the capacity of a nuclear submarine hull to act as a protective container and energy absorber under impact by an another underwater structure is needed. Principia Marine, company of Research in Shipbuilding (formerly IRCN, Institut de Recherche en Construction Navale), is responding to this need by developing an underwater impact crash prediction methodology based upon LS-DYNA3D software. Several physical phenomena with their own characteristic times follow one another at the time of the shock. So different but complementary tasks to develop this methodology were worked individually. This paper deals with contribution to this ongoing program that breaks up into two objectives. The first goal aims to highlight the effect of water on the structural deformation at the time of the collision between a nuclear submarine and a tanker ram bow, which is generally plane. The two-dimensional modelling of this collision uses an Eulerian formulation for the fluid and a Lagrangian formulation for the structure. The fluid-structure interaction is treated by an Euler/Lagrange penalty coupling. This method of coupling, which makes it possible to transmit the efforts in pressure of the Eulerian grid to the Lagrangian grid and conversely, is relatively a recent algorithmic development. It was successfully used in many scientific and industrial applications: the modelling of the attack of birds on the fuselage of a Jet for the Boeing Corporation, the underwater explosion shaking the oil platforms, and airbag simulation… The requirements of modelling for this algorithm are increasingly pointed. Thus, the second objective of this paper is to compare the results in pressures and velocities near the bulb for two cases, in the first one, the bulb is modelled by a slip boundary condition, in the second one, the bulb is a rigid Lagrangian structure, which involves the use of the Euler/Lagrange penalty coupling.
Simulation of a CH-47 Water Crash Event
Authors: Gabrys Jonathan W. , Schatz Joshua K.
Published: August 2008

According to a Naval Aircraft Crash Report for 1972 to 1981, 45.3 % of helicopter mishaps occurred on water. For these incidents, the landing gear would not be effective. Instead, the lower portion of the helicopter is directly involved. Understanding how a helicopter reacts to such loading is critical for designing them to survive these incidents. This analysis investigates a CH-47 water crash event for various impact-speeds and predicts pilot accelerations during each event. The finite element analysis package LS-DYNA was used to simulate the fluid structure event between a full CH-47 model and water.
ALE Multi-Material Formulation of High Explosive Detonation Using LS-DYNA3D
Authors: Mahmadi K. , Aquelet N. , Souli M. , Gabrys J.
Published: August 2008

The simulation of problems in continuum mechanics involving highly transient phenomena and large deformations such as blast, shock wave propagation and reflection presents significant challenges in computational mechanics. Several models have been developed which allow some visualization of blast propagation. In this article, the numerical tool used for the blast modeling is an Eulerian multi-material formulation. The multi-material formulation has already been used with success in the simulation of fluid with large motion such as the tank sloshing modeling or the simulation of metal cutting processes. This paper describes an air blast simulation with a multi-material Eulerian formulation implemented in an explicit finite elements code, LSDYNA3D. Experimental results give the pressure histories to a distance of 5 feets from the point of initial detonation of C4-explosive. A first purpose is to prove the ALE capabilities to correlate numerical results with the experimental results. An experimental pressure history at the same point is measured when the blast shock is reflected by a ground. The second aim of this paper is to compare the experimental pressure history and the numerical pressure history for the same point.
Fluid-Structure Interaction of Stirrers in Mixing Vessels: Part I — Development of the Mechanical Model
Authors: Fischer Michael , Strohmeier Klaus
Published: August 2008

Mixing stirrers are subject to severe damages when the rotational speed approaches the Eigenfrequency. Damping due to fluid-structure interaction between the mixing stirrer and the fluid in the vessel has major influence on the Eigenfrequency. Therefore coupled analysis of the flow field within a mixing vessel and the structural dynamic response of the stirrer should be conducted in order to evaluate vibrational amplitudes to guarantee life time safety for the stirrer. In some previous works at our institute CFD analysis of mixing stirrers has been carried out for both one-phase and two-phase flow. In this paper a simplified numerical model based on Newmark’s integration scheme is developed for the stirrer dynamics that is suitable to be implemented in the CFD code as a user subroutine. Results in terms of Eigenfrequencies are compared to results of analytical formulae and FEM results and show excellent agreement. In the second part of the paper the fully fluid-structure coupled analysis is presented (Part II).
Fluid-Structure Interaction of Stirrers in Mixing Vessels: Part II — Fully Coupled Simulation
Authors: Berger Thomas , Eckl Bernhard , Strohmeier Klaus
Published: August 2008

Mixing Stirrers are subjected to severe damages [Strohmeier (1996), Strohmeier and Ho¨lzl (1998)] when the rotational speed approaches the critical rotational speed nkrit (eigenfrequency). Because of resonant vibrations, the stirrer deflection approaches infinity (no damping case). The possibilities of an accurate design of mixing stirrers with analytical calculations [Fischer and Strohmeier (2000)] are often very unsatisfactional, due to the complex effects of the fluid medium on the structure (impeller), and consequently its critical speed and its vibrational amplitudes cannot be readily defined. To consider transient fluid effects and out-of-balance forces, it is necessary to implement a coupled analysis of flow field and structural dynamic response of the stirrer in the CFD code as a user subroutine. As a new aspect, a rotating grid (sliding mesh) was combined with a deformable grid to simulate the impeller movement. The results are compared to experimental and analytical data and show good agreement.
Integrity of a Curved Divider Plate in Steam Generators of Pressurized Water Reactors Due to Dynamic Pressure Loading Considering Fluid Structure Interaction
Authors: Schramm Konrad
Published: August 2008

A non-linear analysis procedure has been developed to investigate the plastic behavior of the divider (or partition) plate in Steam Generators (SG) of Pressurized Water Reactors (PWRs). The integrity of the divider plate in the primary channel head of a Steam Generator of a Pressurized Water Reactor has to be verified for a postulated loss of coolant accident (LOCA). Primary stresses due to differential pressure Δp have to be analyzed for faulted conditions. A static elastic-plastic finite element analysis for the divider plate was performed showing unrealistically high plastic deformation due to the high differential pressure loading resulting from the assumption of rigid walls in the fluid analysis. Therefore the LOCA is analyzed in a Fluid Structure Interaction Analysis (FSIA), representing the divider plate as a single degree of freedom system (SDOFS) acting like a piston. The present paper explains how the Δp across the plate was correlated with an equivalent displacement ve and how the mass of the plate is considered. In the FSIA a realistic dynamic response of the divider plate is considered now, with a significant reduction of differential pressure Δp. The analysis results proved the resistance of the divider plate with sufficient margin.
Characteristics of the Flying Metal Plate System Using Overdriven Detonation
Authors: Itoh Shigeru , Morimoto Hideyuki , Nagano Shiro , Otsuka Masahiko , Hida Eiji , Kuroki Kenji , Liu Zhi-Yue
Published: August 2008

The pressure occured by an explosive is limited by its own property and its own performance. This pressure is called “C-J pressure”. If the pressure that is higher than C-J pressure can occur, it is very effective for a development field of new materials. So, Overdriven Detonation phenomenon in explosive is considered, that brings out higher detonation pressures than C-J pressure of an explosive. In this study, the flying metal plate accelerated by driver explosive impact against driven explosive, and Overdriven Detonation phenomenon occurs, the relation between driver explosive and driven explosive and the work on the front of the explosive is reported.
An Overview of Vapor Cloud Explosions and Their Relationship to Equipment and Piping Configurations
Authors: Pierorazio Adrian J.
Published: August 2008

Pressure vessel and piping layout is usually focused on minimizing construction costs and ensuring safety from an equipment failure standpoint. When the equipment contains flammable gases, a leak or rupture may result in a vapor cloud explosion (VCE). The severity of the resulting explosion is a function of the material reactivity, the equipment density, and the presence of structures that restrict the free expansion of the combusting cloud. This paper provides an overview of existing vapor cloud explosion prediction methodologies, with an emphasis on the effects of process equipment and piping spacing on the severity of a VCE.
A Method for Producing Extra-High Dynamic Pressure Due to the Efficient Use of High Explosive
Authors: Liu Zhi-Yue , Tanaka Katsumi , Itoh Shigeru
Published: August 2008

In the material processing such as shock synthesis and powder consolidation by shock waves the method for generating dynamic pressure is of very importance for the final recovered materials. A general and convenient way for producing shock wave needed in such field is to take advantage of the explosion effect from high explosive. Therefore, it becomes an interest subject how to produce dynamic pressure as high as possible under the given high explosive. Starting from this motivation, we put forward a method of high-pressure generation by using the overdriven detonation of high explosive. The basic configuration for this device is summarized in the following. A metal flyer accelerated by the high explosive is used to impact another layer of high explosive to incur an overdriven detonation in this layer of explosive. The overdriven detonation of high explosive acts on the powder materials, providing the high dynamic pressure for it. To examine the efficiency of this combination, a numerical computation is performed to this system. The details on the illustration of this system and numerical treatment will be given.
On Study of Free Metal Forming Using Underwater Shock Wave
Authors: Itoh Shigeru , Iyama Hirofumi , Raghukandan K. , Nagano Shiro , Matsumura Ryo , Muramoto Satoshi
Published: August 2008

In the material processing such as shock synthesis and powder consolidation by shock waves the method for generating dynamic pressure is of very importance for the final recovered materials. A general and convenient way for producing shock wave needed in such field is to take advantage of the explosion effect from high explosive. Therefore, it becomes an interest subject how to produce dynamic pressure as high as possible under the given high explosive. Starting from this motivation, we put forward a method of high-pressure generation by using the overdriven detonation of high explosive. The basic configuration for this device is summarized in the following. A metal flyer accelerated by the high explosive is used to impact another layer of high explosive to incur an overdriven detonation in this layer of explosive. The overdriven detonation of high explosive acts on the powder materials, providing the high dynamic pressure for it. To examine the efficiency of this combination, a numerical computation is performed to this system. The details on the illustration of this system and numerical treatment will be given.
Flow Characteristics of a Shaft Driven Lift Engine
Authors: Palmer Chris , Holdo̸ Arne E.
Published: August 2008

The investigation consisted of an experimental study into the effect of a cavity connecting the upper and lower surfaces of an aerofoil on the flow over the aerofoil. Such cavities are considered for locating a Lift Engine within an aircraft to provide Vertical Short Take-Off and Landing (V/STOL) capability. Whilst the concept of a Lift Engine has undergone considerable research in recent years, there remains a need to investigate transitional flight, where the provision of lift changes from the wing aerodynamics to the Lift Engine. Within this range, it is important to understand the aerodynamic effect of the cavity. The experiments were carried out at various angles of attack and freestream velocities to enable both the static pressure field over the aerofoil and around the cavity, and the velocity and direction of the air through the cavity to be characterised.
Optimisation of Loads in Piping Systems by Realistic Calculation Method Applying FSI and Dynamic Friction
Authors: Diesselhorst Tilman , Neumann Ulrich
Published: August 2008

To reduce costs and to extend the lifetime of piping systems their design loads due to valve action have to be optimised. To get the best effect the results of the fluiddynamic and structural calculations should be realistic as far as possible. Therefore the calculation programs were coupled to consider the fluid structure interaction and the effect of dynamic fluid friction was introduced to get realistic results of oscillations due to pressure surges. Detailed modelling of check valve behaviour allows to minimise the pressure surge loading by improving the valve function and adapting it to the system behaviour. The method was validated at measurements of load cases in power plant piping systems. Results with different load cases show the effectiveness of reducing the fluid forces on piping. Examples are given to prove the reduction of supports.
Metal Pipe Forming Using Underwater Shock Wave
Authors: Iyama Hirofumi , Raghukandan K. , Nagano Shiro , Muramoto Satoshi , Itoh Shigeru
Published: August 2008

Recently, many metal pipes have been manufactured and used as various mechanical parts. Cross section of these parts has circular and oval shape. And then, a lot of kinds, but a small quantity production of these metal pipe increases. However, commonly, very expensive metal die are used in that case. Therefore, we considered the metal pipe forming method so that we can obtain the required deformation shape of metal pipes using the underwater shock wave generated by underwater explosion of explosive. We did some experiments of the metal pipe forming by that method. We used detonating cord as the explosive. The metal pipe and explosive was submerged into water and the detonating cord was detonated by electric detonator. We made some experiments by changing the explosive set-up position and inside the metal pipe filled with water, soil, air, and so on. In this paper, we have discussed these experimental results. And then, we have done the numerical simulation to this method and those results are also discussed.
Continuous Computation in Apparatus Engineering
Authors: Pilhar Simon , Strohmeier Klaus , Zirkel Manfred , Vajna Sandor
Published: August 2008

Within the scope of this lecture, the results of a teamwork project of the co-operating institutes are to be presented. The aim of the project is the optimization of the apparatus design by the development of an integrated computer support on the basis of a feature-based product model for apparatus engineering. For this reason the optimization on the one hand consists in the development of a computer-aided method for apparatus engineering and the corresponding tools and on the other hand, in the integration of the partial solutions into the commercial CAD systems AutoCAD and SolidEDGE. Due to the division into application and data model, the system can easily be adapted to user specific requirements without the need of programming the entire system again. With the aid of this system, the apparatus designer can be freed from routine activities and is able to dedicate more time for design according to safety precautions and load requirements.
CFD Simulation of Soil Flow Over Augers
Authors: Davison Joel , Calay Rajnish , Sands Tim , England Melvin
Published: August 2008

The modelling of soil as an engineering material is confined, in the most part, to the investigation of how it behaves under loading and unloading. A key assumption made in existing models is that the soil is similar in behaviour to a solid and is generally elastic-perfectly plastic and has a linear stress strain relationship. The rapid displacement of soil, such as flow, has been studied far less. The aim of this paper is to study such behaviour and present the initial results of the flow around a rotating auger assuming the soil acts as a fluid. These initial simulations rely on the governing equations of fluid flow assuming Newtonian viscosity. Although evidence points to soil not having constant coefficient of viscosity, this study and a further study by Tardos [1] shows that for loose soils with a low angle of internal friction, such as liquefied sand, the Newtonian viscosity is an acceptable assumption. The patterns of soil movement around the auger are shown over two different drilling tools. Visual and numerical results of soil movement are presented.