scholarly journals Thermo-elastic-plastic Model for Numerical Simulation of Fasteners Destruction Under Gasodynamic Impulsive Pressure

2018 ◽  
Vol 183 ◽  
pp. 01039
Author(s):  
Marina Chernobryvko ◽  
Konstantin Avramov ◽  
Boris Uspensky ◽  
Anatoly Tonkonogenko ◽  
Leopold Kruszka
Keyword(s):  
Numerical Simulation ◽  
High Speed ◽  
Failure Model ◽  
Wave Impact ◽  
Deformation And Failure ◽  
Elastic Plastic ◽  
Environment Temperature ◽  
Impact Impulse ◽  
Numerical Research ◽  
Impulsive Pressure

Modern rocketry widely employs a method of gasodynamic impulse destruction of bondings which may occur at high variety of temperatures. To design fasteners correctly it is necessary to have the ability to calculate fastener’s destruction time at a given pressure. Numerical research is an expedient approach to this problem. A mathematical model of a high-speed deformation and failure in fastening elements of special rocket structures due to gasodynamic wave-impact impulse loading is developed. A technique for numerical analysis of the deformation of fasteners and failure duration is proposed. To perform such analysis a set of factors such as: static stress-strain state due to assembling; thermo-elastic deformation of fasteners due to environment temperature; high-speed dynamical elastic-plastic failure of fastening elements are taken into consideration. The failure model due to the plastic flow considers dynamical material properties. As a criterion of failure maximum plastic deformation is chosen. The technique is implemented for several types of fasteners. Numerical simulation using finite elements method is conducted. The results of the numerical research are well-correlated with experimental data.

Experimental and Numerical Research of Small Metal Disk Driven by Explosive

2011 ◽  
Vol 673 ◽  
pp. 301-305
Author(s):  
Hideki Hamashima ◽  
Shiro Kubota ◽  
Tei Saburi ◽  
Yuji Ogata
Keyword(s):  
Numerical Simulation ◽  
High Speed ◽  
Numerical Results ◽  
Experimental Results ◽  
Basic Data ◽  
High Speed Camera ◽  
Analysis Software ◽  
Metal Disk ◽  
Numerical Research ◽  
Explosion Experiment

In order to investigate the hazard of the fragments caused by the explosion damage, the simply-simulated explosion experiment and numerical simulation were conducted. In this study, the behavior of the disk supposing the fragment driven by an explosive was investigated. In the experiment, the optical observation using a high-speed camera was performed to obtain the basic data about a disk, such as flying velocity. Moreover, numerical simulation was performed using analysis software LS-DYNA. Comparison and examination for experimental results and numerical results were reported.

Numerical simulation of high-speed civil transport inlet operability with angle of attack

AIAA Journal ◽  
1998 ◽  
Vol 36 ◽  
pp. 1223-1229
Author(s):  
Ge-Cheng Zha ◽  
Doyle Knight ◽  
Donald Smith ◽  
Martin Haas
Keyword(s):  
Numerical Simulation ◽  
High Speed ◽  
Angle Of Attack

Numerical Simulation of High-Speed Crack Propagating and Branching Phenomena

2016 ◽  
Vol 37 (7) ◽  
pp. 729-739
Author(s):  
GU Xin-bao ◽  
◽  
ZHOU Xiao-ping ◽  
XU Xiao ◽  
Keyword(s):  
Numerical Simulation ◽  
High Speed

scholarly journals Stochastic Uncertainty in a Dam-Break Experiment with Varying Gate Speeds

2021 ◽  
Vol 9 (1) ◽  
pp. 67
Author(s):  
Hiroshi Takagi ◽  
Fumitaka Furukawa
Keyword(s):  
High Speed ◽  
Pressure Sensors ◽  
Dam Break ◽  
Maximum Pressure ◽  
Vertical Acceleration ◽  
Ship Wakes ◽  
Dam Break Flow ◽  
Statistical Relationships ◽  
Flow Propagation ◽  
Impulsive Pressure

Uncertainties inherent in gate-opening speeds are rarely studied in dam-break flow experiments due to the laborious experimental procedures required. For the stochastic analysis of these mechanisms, this study involved 290 flow tests performed in a dam-break flume via varying gate speeds between 0.20 and 2.50 m/s; four pressure sensors embedded in the flume bed recorded high-frequency bottom pressures. The obtained data were processed to determine the statistical relationships between gate speed and maximum pressure. The correlations between them were found to be particularly significant at the sensors nearest to the gate (Ch1) and farthest from the gate (Ch4), with a Pearson’s coefficient r of 0.671 and −0.524, respectively. The interquartile range (IQR) suggests that the statistical variability of maximum pressure is the largest at Ch1 and smallest at Ch4. When the gate is opened faster, a higher pressure with greater uncertainty occurs near the gate. However, both the pressure magnitude and the uncertainty decrease as the dam-break flow propagates downstream. The maximum pressure appears within long-period surge-pressure phases; however, instances considered as statistical outliers appear within short and impulsive pressure phases. A few unique phenomena, which could cause significant bottom pressure variability, were also identified through visual analyses using high-speed camera images. For example, an explosive water jet increases the vertical acceleration immediately after the gate is lifted, thereby retarding dam-break flow propagation. Owing to the existence of sidewalls, two edge waves were generated, which behaved similarly to ship wakes, causing a strong horizontal mixture of the water flow.

Numerical Simulation of Flowfield around High Speed Trains Passing by each other at the same Speed

2011 ◽  
Vol 97-98 ◽  
pp. 698-701
Author(s):  
Ming Lu Zhang ◽  
Yi Ren Yang ◽  
Li Lu ◽  
Chen Guang Fan
Keyword(s):  
Numerical Simulation ◽  
Wind Tunnel ◽  
Flow Field ◽  
Point Source ◽  
High Speed ◽  
Stokes Equations ◽  
Field Structure ◽  
Vehicle Speed ◽  
Mesh Method ◽  
High Speed Trains

Large eddy simulation (LES) was made to solve the flow around two simplified CRH2 high speed trains passing by each other at the same speed base on the finite volume method and dynamic layering mesh method and three dimensional incompressible Navier-Stokes equations. Wind tunnel experimental method of resting train with relative flowing air and dynamic mesh method of moving train were compared. The results of numerical simulation show that the flow field structure around train is completely different between wind tunnel experiment and factual running. Two opposite moving couple of point source and point sink constitute the whole flow field structure during the high speed trains passing by each other. All of streamlines originate from point source (nose) and finish with the closer point sink (tail). The flow field structure around train is similar with different vehicle speed.

Stability Enhancement of Supercavitating Projectiles by Unsteady Air Injection

2005 ◽  
Author(s):  
Yasmin Khakpour ◽  
Miad Yazdani
Keyword(s):  
Numerical Simulation ◽  
Drag Reduction ◽  
High Speed ◽  
The Body ◽  
Air Injection ◽  
Cavity Surface ◽  
The Stability ◽  
Stability Enhancement

In this work, numerical simulation is used to study the stability enhancement of high speed supercavitating hydrofoils. Although supercavitation is known as one of the most effective methods for drag reduction, producing the cavity, either by ventilation or by cavitator at front of the body, may cause some instabilities on cavity surface and thus on the projectile’s motion. Therefore removing these instabilities comes as an important point of discussion. First of all, we calculate the sources of instabilities and measure respective forces and then present some approaches that significantly reduce these instabilities. One of these methods that could produce more stable supercavities is injecting of the air into the cavity unsteadily which varies through the projectile’s surface. This approach is provided by arrays of slots distributed on the projectile’s surface and unsteady injection is modeled over the surface. Furthermore, the position of ventilation, dramatically affects the stability like those in aerodynamics. In all approaches it is assumed that the supercavity covers the whole of the body, however the forces caused by the wakes, formed behind the body are taken into account. The calculation is performed at three cavitation numbers with respective velocities of 40 m/s, 50 m/s, 60 m/s.

Deformation and Failure Mechanisms of Austenitic Piping Under the Influence of Oxyhydrogen Reactions

2016 ◽  
Author(s):  
Stefan Offermanns ◽  
Stefan Weihe
Keyword(s):  
Failure Mechanisms ◽  
Shear Bands ◽  
Adiabatic Shear ◽  
Material Behavior ◽  
Inert Gas ◽  
Materials Testing ◽  
Failure Model ◽  
Adiabatic Shear Bands ◽  
Deformation And Failure ◽  
Gas Component

The present paper deals with the deformation and failure mechanisms of austenitic piping under the influence of oxyhydrogen reactions for the safety evaluation of incident scenarios in technical installations based on previous work of the author [1–5]. For the characterization of the processes, detonation tests performed at the Materials Testing Institute University of Stuttgart (MPA Stuttgart) have been used. The aim of these experiments was to study the detonation processes in head spray cooling piping of boiling water reactors. The experiments were performed on austenitic pipes with an outer diameter of O. D. = 114.3 mm and various wall thicknesses. Oxyhydrogen was used in its stoichiometric ratio of 2H2+O2 mixed with various amounts of an inert gas component. These tests have shown that less amounts of reactive gas may result in a stronger reaction of the pipe structure. This observation is attributed to the influence of the so-called overdriven detonation. Depending on the ratio of oxyhydrogen to the inert gas component and the pipe-wall thickness, adiabatic shear bands can occur in the piping structure. Adiabatic shear bands are very narrow zones with intense localized shear deformations due to the conversion of a significant portion of strain energy into heat. In order to describe this phenomenon numerically, a strain-based failure model was used which can reflect material damage over a wide range of different stress states. However, it has shown that damage of the studied material depends significantly on the Lode angle. Furthermore, no clear dependence of the failure limit on the loading rate has been found for the studied material. For the constitutive description of the material behavior under the occurring loading rates and temperatures suitable material models were selected and the required parameters have been evaluated experimentally and verified by numerical methods. With the aid of this constitutive description of the material behavior and the failure model numerical simulations of the detonation tests were carried out.

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