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Showing papers on "Shock (mechanics) published in 2002"


Book
31 Mar 2002
TL;DR: In this paper, the authors discuss the physics of gas dynamics and classical theory of shock waves, including thermal radiation and radiant heat exchange in a medium, and some self-similar processes in gas dynamics.
Abstract: : Contents: Elements of gas dynamics and classical theory of shock waves; thermal radiation and radiant heat exchange in a medium; thermodynamic properties of gases at high temperatures; shock tubes; absorption and emission of radiation in gases at high temperatures; speed of relaxation processes in gases; structure of front of shock waves in gases; physico-chemical kinetics in hydrodynamic processes; light phenomena in shock waves and during strong explosion in air; thermal waves; shock waves in solids; certain self-similar processes in gas dynamics.

3,685 citations



Journal ArticleDOI
31 May 2002-Science
TL;DR: Multimillion-atom molecular-dynamics simulations are used to investigate the shock-induced phase transformation of solid iron, finding that the dynamics and orientation of the developing close-packed grains depend on the shock strength and especially on the crystallographic shock direction.
Abstract: Multimillion-atom molecular-dynamics simulations are used to investigate the shock-induced phase transformation of solid iron. Above a critical shock strength, many small close-packed grains nucleate in the shock-compressed body-centered cubic crystal growing on a picosecond time scale to form larger, energetically favored grains. A split two-wave shock structure is observed immediately above this threshold, with an elastic precursor ahead of the lagging transformation wave. For even higher shock strengths, a single, overdriven wave is obtained. The dynamics and orientation of the developing close-packed grains depend on the shock strength and especially on the crystallographic shock direction. Orientational relations between the unshocked and shocked regions are similar to those found for the temperature-driven martensitic transformation in iron and its alloys.

413 citations


Journal ArticleDOI
TL;DR: In this article, the authors analyze the mechanical response of a large class of shock loaded microsystems and formulate failure criteria for these microstructures, which correlate well with the experimentally observed responses of different MEMS devices.
Abstract: As a first step toward formulating guidelines for the design of dynamically reliable MEMS, we analyze the mechanical response of, and formulate failure criteria for, a large class of shock loaded microsystems. MEMS are modeled as microstructures attached to elastic substrates, and the shocks are modeled as pulses of acceleration applied to the substrate over a finite time duration. The relevant time scales in the analysis are the acoustic transit time, the time period of vibrations, and the duration of the applied shock load. For many MEMS structures and shock loads (with durations in the range 50-5000 /spl mu/s), the substrates respond as rigid bodies and are expected to be immune to stress-wave-induced damage. Time-domain criteria, obtained to distinguish between the impulse, resonant, and quasistatic responses of the microstructures, correlate well with the experimentally observed responses of different MEMS devices. The formulation of displacement-based and stress-based failure criteria is discussed, along with their sensitivity to the applied strain rate. A case study, in which these results are applied to evaluate the reliability of a packaged surface-micromachined device, is presented.

207 citations


Journal ArticleDOI
TL;DR: In this article, laser shock processing of copper using focused laser beam size about ten microns is investigated for its feasibility and capability to impart desirable residual stress distributions into the target material in order to improve the fatigue life of the material.
Abstract: Laser shock processing of copper using focused laser beam size about ten microns is investigated for its feasibility and capability to impart desirable residual stress distributions into the target material in order to improve the fatigue life of the material. Shock pressure and strain/stress are properly modeled to reflect the micro scale involved, and the high strain rate and ultrahigh pressure involved. Numerical solutions of the model are experimentally validated in terms of the geometry of the shock-generated plastic deformation on target material surfaces as well as the average in-depth strains under various conditions. The residual stress distributions can be further influenced by shocking at different locations with certain spacing. The potential of applying the technique to micro components, such as micro gears fabricated using MEMS is demonstrated. The investigation also lays groundwork for possible combination of the micro scale laser shock processing with laser micromachining processes to offset the undesirable residual stress often induced by such machining processes.

178 citations


Journal ArticleDOI
TL;DR: In this article, the dynamic compressive characteristics of a closed cell aluminium alloy foam (manufactured by Hydro Aluminium AS, Norway) have been studied experimentally by using a direct impact technique for a range of velocities up to 210 m s-1.
Abstract: The dynamic compressive characteristics of a closed cell aluminium alloy foam (manufactured by Hydro Aluminium AS, Norway) have been studied experimentally by using a direct impact technique for a range of velocities up to 210 m s–1. Experimental data on the dynamic initial crushing and plateau stresses are compared for two average cell sizes of approximately 4 and 14 mm. The data reveal significant dynamic enhancements of the initial crushing strengths throughout the range of velocities used. The dynamic plateau stresses are insensitive to impact velocity below the values of 50 and 100 m s–1 for the large and small cell foams respectively. Beyond a critical velocity value of ~ 100 m s–1, the crushing wave front propagates through the foam with shock like characteristics. The inertia effects associated with the dynamic localisation of crushing and the microinertia of the cell wall/edge material on the dynamic strength enhancement are discussed. A one-dimensional shock model based on a rate indepen...

172 citations


Journal ArticleDOI
TL;DR: Lin et al. as discussed by the authors used Web of Science Record created on 2007-05-22, modified on 2016-08-08 for the purpose of obtaining a record of the paper.
Abstract: Reference LIN-ARTICLE-2002-008View record in Web of Science Record created on 2007-05-22, modified on 2016-08-08

165 citations


Journal ArticleDOI
Pasquale Blasi1
TL;DR: In this article, a semi-analytical model was proposed to deal with non-linear effects in particle acceleration in a quantitative way, which is compatible with the previous simplified results and also provides a satisfactory description of the results of numerical simulations of shock acceleration.

152 citations


Proceedings ArticleDOI
01 Jan 2002
TL;DR: In this paper, a series of five different designs of transonic fans is analyzed by CFD and it is found that the 3D features have remarkably little effect on the shock pattern near the tip where the shock must remain perpendicular to the casing.
Abstract: The aerodynamics of transonic fans is discussed with emphasis on the use of three-dimensional design techniques, such as blade sweep and lean, to improve their performance. In order to study the interaction of these 3D features with the shock pattern a series of five different designs is produced and analysed by CFD. It is found that the 3D features have remarkably little effect on the shock pattern near the tip where the shock must remain perpendicular to the casing. Lower down the blade significant shock sweep, and hence reduced shock loss, can be induced by 3D design but this is usually at the expense of reduced stall margin and increased loss elsewhere along the blade span. Overall, very little change in peak efficiency or pressure ratio is produced by blade sweep or lean. However, there are significant effects on stall margin with forwards sweep producing a better stall margin and maintaining a high efficiency over a wider range.Copyright © 2002 by ASME

143 citations


Journal ArticleDOI
TL;DR: In this paper, a shock-capturing numerical scheme for the one-dimensional Savage-Hutter theory of granular flow is employed to describe the phenomenon of supercritical flow merging into a region of subcritical flow.

138 citations


Book ChapterDOI
28 May 2002
TL;DR: This work addresses the issue of regularizing Osher and Rudin's shock filter, used for image deblurring, and proposes an original solution of adding a complex diffusion term to the shock equation to smooth out noise and indicate inflection points simultaneously.
Abstract: We address the issue of regularizing Osher and Rudin's shock filter, used for image deblurring, in order to allow processes that are more robust against noise. Previous solutions to the problem suggested adding some sort of diffusion term to the shock equation. We analyze and prove some properties of coupled shock and diffusion processes. Finally we propose an original solution of adding a complex diffusion term to the shock equation. This new term is used to smooth out noise and indicate inflection points simultaneously. The imaginary value, which is an approximated smoothed second derivative scaled by time, is used to control the process. This results in a robust deblurring process that performs well also on noisy signals.

Journal ArticleDOI
TL;DR: In this article, the ejecta particle size distributions for shocked Al and Sn metals were measured using an in-line Fraunhofer holography technique, and the size of the ejected particles was then measured using the size distribution method.
Abstract: When a shock wave interacts at a metal vacuum interface “ejected particulates” (ejecta) can be emitted from the surface. The mass, size, shape, and velocity of the ejecta varies depending on the initial shock conditions and the material properties of the metal sample. To understand this phenomena, experiments have been conducted at the Pegasus Pulsed Power Facility located at Los Alamos National Laboratory. For the experiments reported in this article, the facility is used to implode a cylinder to a velocity of 3.4 mm/μs. When this cylinder impacts a smaller diameter target cylinder, shock pressures of 30 and 40 GPa can be obtained in Al and Sn metals, respectively. Ejecta formation proceeds as the shock wave in the metal sample interacts at the metal vacuum interface. The size of the ejected particles is then measured using an in-line Fraunhofer holography technique. In this report, ejecta particle size distributions will be presented for shocked Al and Sn metals. The measured particle size distributions...

Journal ArticleDOI
TL;DR: In this article, the characteristics of compressive shock wave propagation in the solid phase of a cellular material were studied using a one-dimensional mass-spring model, which leads to several interesting observations on the characteristic of one dimensional stress wave transmission.

Journal ArticleDOI
TL;DR: In this paper, the transition from free shock separation to restricted shock separation in a parabolic nozzles was analyzed and the cap-shock pattern was identified to be the cause of this transition.
Abstract: Uncontrolled flow separation in nozzles of rocket engines is not desired because it can lead to dangerous lateral forces. Different origins for side loads were identified in the past. Meanwhile, it is proven that in thrust-optimized or parabolic nozzles, a major side load occurs as a result of the transition of separation pattern from free shock separation to restricted shock separation and vice versa. Reasons for the transition between the separation patterns are discussed, and the cap-shock pattern, which is identified to be the cause of this transition, is closely analyzed. It turns out that this pattern can be interpreted as an inverse Mach reflection of the internal shock at the nozzle axis. To prove the transition effect as main side-load driver, a subscale test campaign has been performed. Two different nozzle contours, a thrust-optimized and a truncated ideal nozzle with equal performance data, were tested. Highest side loads were measured in the thrust-optimized nozzle, when the separation pattern changes from free to restricted shock separation. Side loads measured in the truncated ideal nozzle were only about one-third as high as in the thrust-optimized nozzle.

Journal ArticleDOI
TL;DR: In this paper, the phase diagram for calcite (CaCO3) is re-evaluated in relation to dynamic compression and following release from shock, and it is shown that CO2 from naturally shocked carbonates to the atmosphere is (grossly) overestimated if based on the calcite phase diagram constructed from thermodynamic equilibrium conditions.

Journal ArticleDOI
TL;DR: In this paper, the authors used smoothed particle hydrodynamics (SPH) to simulate water mitigation problems in large deformation explosion events with significant inhomogeneities.
Abstract: It is very difficult for traditional numerical methods to simulate the problems of water mitigation which has been increasingly used to reduce blast effects. This paper studies water mitigation problems by using smoothed particle hydrodynamics (SPH), which is a meshless, Lagrangian method appealing in treating large deformation explosion events with significant inhomogeneities. Numerical verifications considering high explosive detonation and underwater explosion shock waves have demonstrated the effectiveness of the SPH method, the solution procedure and the code. Contact and non-contact water mitigation simulations have been carried out and are compared with the case without mitigation. For either contact or non-contact water shield, the peak shock pressure and the equilibrium gas pressure are reduced to different levels according to the relevant geometry of the system setup. An optimum contact water shield thickness is found to produce the best mitigation effect for a given high explosive charge, while the non-contact water shield, if properly designed, can result in further reduction of the peak shock pressure and the equilibrium gas pressure.

Journal ArticleDOI
Salvatore Mancuso1, John C. Raymond1, J. L. Kohl1, Yuan-Kuen Ko1, M. Uzzo1, R. Wu1 
TL;DR: In this article, the authors reported the observation of a 1100 km s - 1 CME-driven shock with the UltraViolet Coronagraph Spectrometer (UVCS) telescope operating on board SOHO.
Abstract: We report the observation of a 1100 km s - 1 CME-driven shock with the UltraViolet Coronagraph Spectrometer (UVCS) telescope operating on board SOHO on March 3, 2000. The shock speed was derived from the type II radio burst drift rate and from UVCS observations that can yield the density profile just before the passage of the shock. A CME projected speed of 920 km s - 1 was deduced from the Large Angle Spectrometric Coronagraph (LASCO) white light images, indicating that the CME leading edge was lagging behind at about 20% of the shock speed. The spectral profiles of both the O VI and Lya lines were Doppler dimmed and broadened at the passage of the shock by the emission from shocked material along the line of sight. The observed line broadening for both protons and oxygen ions was modeled by adopting a mechanism in which the heating is due to the nondeflection of the ions at the shock ramp in a quasi-perpendicular shock wave. This specific ion heating model was able to reproduce the observed spectroscopic properties of the shocked plasma.

Proceedings ArticleDOI
07 Aug 2002
TL;DR: In this article, a drop impact response of portable electronic products at different impact orientations and drop heights is examined, and the impact force and the strain and level of shock induced at the printed circuit board (PCB) during impact is measured.
Abstract: One of the most common causes of failure for portable electronic products is from drop impact. Impact and shock to such products can cause significant functional and physical damage. They can cause external housing, internal electronic component or package-to-board interconnection failure. This paper examines the drop impact response of portable electronic products at different impact orientations and drop heights. A method whereby actual drop test using a cellular phone as an example is proposed. Of interest is the measurement of the level of shock experienced by the electronic components on the printed circuit board (PCB) during impact. A patent pending drop tester which allows drop impact of the cellular phone at any orientation and drop height is used. A high-speed video camera is also utilized to verify the impact orientation. The drop impact responses examined are the impact force and the strains and level of shock induced at the PCB. A better understanding of the shock induced at the electronic components and packages in the products can assist manufacturers not only in designing better components and electronic packages but also products which are more robust and reliable, to handle shock and impact loading.

Journal ArticleDOI
TL;DR: In this paper, a new experimental procedure was proposed to detect the shock wave front sensitively, which makes it possible to measure shock Hugoniot in higher precision than the previous method.
Abstract: A shock Hugoniot compression curve for water has been measured up to less than 1 GPa. A plane and steady shock wave is produced in water by the flat plate impact of a projectile accelerated by a compressed gas gun. A new experimental procedure was proposed to detect the shock wave front sensitively, which makes it possible to measure shock Hugoniot in higher precision than the previous method. The present method is based on the very large pressure dependence of the refractive index of water upon compression. By using this method, the shock compression curve was determined within the precision of 2% to 3% of the estimated shock pressure. The precision is better than that of the previous data. It was confirmed that within the pressure range covered in this experiment, the shock-particle velocity Hugoniot can be described by a linear relation with a large slope. Shock Hugoniot states on the pressure–temperature plane were calculated by using the obtained Hugoniot data combined with the values of thermodynamical variables. Thermodynamic analysis of the shock compression process was developed to estimate the contributions of irreversible heating by shock compression.

01 Jan 2002
TL;DR: The optical flash accompanying GRB 990123 is believed to be powered by the reverse shock of a thin shell as discussed by the authors, and the theoretical peak flux of the optical flash accounts for only 3×10-4 of the observed.
Abstract: The optical flash accompanying GRB 990123 is believed to be powered by the reverse shock of a thin shell. With the best-fit physical parameters forGRB 990123 and the assumption that the parameters in the optical flash are the same as in the afterglow, we show that: 1) the shell is thick rather than thin, and we have provided the light curve for the thick shell case which coincides with the observation; 2) the theoretical peak flux of the optical flash accounts for only 3×10-4 of the observed. In order to remove this discrepancy, the physical parameters, the electron energy and magnetic ratios, ∈e and ∈B, should be 0.61 and 0.39, which are very different from their values for the late afterglow.

Journal ArticleDOI
TL;DR: In this paper, the authors present the current status of kinetic research with emphasis on the diagnostic techniques and highlight the use of the shock tube as high temperature wave reactor for gas phase material synthesis.

Journal ArticleDOI
TL;DR: In this paper, an initial compressional wave with a ramp shape steepens to form oscillations at the leading part due to dispersion and becomes an oscillatory shock wave when the dust is mixed in the plasma and the density of the dust grains is smaller than a critical value.
Abstract: Dust ion-acoustic shock waves have been investigated experimentally in a homogeneous unmagnetized dusty double-plasma device. An initial compressional wave with a ramp shape steepens to form oscillations at the leading part due to dispersion. The oscillation develops to a train of solitons when the plasma contains no dust grain. The wave becomes an oscillatory shock wave when the dust is mixed in the plasma and the density of the dust grains is smaller than a critical value. When the dust density is larger than the critical value, only steepening is observed at the leading part of the wave and a monotonic shock structure is observed. The velocity and width of the shock waves are measured and compared with results of numerical integrations of the modified Korteweg–de Vries–Burgers equation.

Journal ArticleDOI
TL;DR: The first-order Fermi acceleration process at an ultra-relativistic shock wave is expected to create a particle spectrum with the unique asymptotic spectral index 1 2:2 as discussed by the authors.
Abstract: The first-order Fermi acceleration process at an ultra-relativistic shock wave is expected to create a particle spectrum with the unique asymptotic spectral index 1 2:2. Below, we discuss this result and dierences in its various derivations, which - explicitly or implicitly - always require highly turbulent conditions downstream of the shock. In the presence of medium amplitude turbulence the generated particle spectrum can be much steeper than the above asymptotic one. We also note problems with application of the pitch angle diusion model for particle transport near the ultra-relativistic shocks.

Journal ArticleDOI
TL;DR: In this paper, a finite element model of a disk-suspension-slider air bearing system is developed and modified, and it is used to obtain the dynamic normal load and moments applied to the air bearing slider.
Abstract: As non-traditional applications of hard disk drives emerge, their mechanical robustness during the operating state is of greater concern. A procedure for simulating the shock responses of a disk-suspension-slider air bearing system is proposed in this paper. A finite element model of the system is developed and modified, and it is used to obtain the dynamic normal load and moments applied to the air bearing slider. The dynamic load and moments are then used as input data for the air bearing dynamic simulator to calculate the dynamic flying attitudes. We obtain not only the responses of the structural components, but also the responses of the air bearing slider. The procedure is convenient for practical application, because it separates the work into two essentially uncoupled steps. It is used to simulate the shock response of a drive. The system modeled is linear if the load dimple of the suspension maintains contact with the slider, but it is non-linear if the dimple separates due to a strong shock. The air bearing has different responses for upward and downward shocks. Slider-asperity contacts occur when a strong shock is applied.

Journal ArticleDOI
TL;DR: In this article, a zirconium-based bulk metallic glass, Zr41.2Ti13.8Cu12.5Ni10Be22.5 (Vit 1), and its composite Zr56.3Ti14.9Ni5.6Nb5.0Be12.
Abstract: A zirconium-based bulk metallic glass, Zr41.2Ti13.8Cu12.5Ni10Be22.5 (Vit 1), and its composite, Zr56.3Ti13.8Cu6.9Ni5.6Nb5.0Be12.5 (beta-Vit), were subjected to planar impact loading. A surprisingly low amplitude elastic precursor and bulk wave, corresponding to the elastic response of the "frozen structure" of the intact metallic glasses, were observed to precede the rate-dependent large deformation shock wave. A concave downward curvature after the initial increase of the U-s-U-p shock Hugoniots suggests that a phase-change-like transition occurred during shock compression. Further, compression damage occurred due to the shear localization. The spalling in Vit 1 was induced by shear localization, while in beta-Vit, it was due to debonding of the beta-phase boundary from the matrix. The spall strengths at strain rate of 2x10(6) s(-1) were determined to be 2.35 and 2.11 GPa for Vit 1 and beta-Vit, respectively.

Journal ArticleDOI
TL;DR: In this paper, the Lighthill-Whitham-Richards kinematic wave traffic flow model was extended to describe traffic with different types of vehicles, in which all vehicles are completely mixed and travel at the same group velocity.
Abstract: The Lighthill-Whitham-Richards kinematic wave traffic flow model was extended to describe traffic with different types of vehicles, in which all types of vehicles are completely mixed and travel at the same group velocity. A study of such a model with two vehicle classes (e.g., passenger cars and trucks) showed that when both classes of traffic have identical free-flow speeds, the model (a) satisfies the first-in-first-out rule, (b) is anisotropic, and (c) has the usual shock and expansion waves and a family of contact waves. Different compositions of vehicle classes in this model propagate along contact waves. Such models can be used to study traffic evolution on long crowded highways where low-performance vehicles entrap high-performance ones.

Journal ArticleDOI
TL;DR: Soures et al. as discussed by the authors investigated the propagation of a structured shock front within a radiation-driven target assembly, the formation of a supersonic jet of material, and the subsequent interaction of this jet with an ambient medium in which a second, ablatively driven shock wave is propagating.
Abstract: Supersonic fluid flow and the interaction of strong shock waves to produce jets of material are ubiquitous features of inertial confinement fusion (ICF), astrophysics, and other fields of high energy-density science. The availability of large laser systems provides an opportunity to investigate such hydrodynamic systems in the laboratory, and to test their modeling by radiation hydrocodes. We describe experiments to investigate the propagation of a structured shock front within a radiation-driven target assembly, the formation of a supersonic jet of material, and the subsequent interaction of this jet with an ambient medium in which a second, ablatively driven shock wave is propagating. The density distribution within the jet, the Kelvin–Helmholz roll-up at the tip of the jet, and the jet’s interaction with the counterpropagating shock are investigated by x-ray backlighting. The experiments were designed and modeled using radiation hydrocodes developed by Los Alamos National Laboratory, AWE, and Lawrence Livermore National Laboratory. The same hydrocodes are being used to model a large number of other ICF and high energy-density physics experiments. Excellent agreement between the different simulations and the experimental data is obtained, but only when the full geometry of the experiment, including both laser-heated hohlraum targets (driving the jet and counter-propagating shock), is included. The experiments were carried out at the University of Rochester’s Omega laser [J. M. Soures et al., Phys. Plasmas 3, 2108 (1996)].

Journal ArticleDOI
TL;DR: In this article, experimental data on the compression of solid deuterium at a pressure of ∼60 GPa were presented and compared with the data of shock experiments obtained on a Nova laser facility and an electrodynamic EPBF-Z plant.
Abstract: Experimental data on the compression of solid deuterium at a pressure of ∼60 GPa are presented. The data were obtained on a generator of powerful converging spherical shock waves. The results are compared with the data of shock experiments obtained on a Nova laser facility and an electrodynamic EPBF-Z plant.

Journal ArticleDOI
TL;DR: In this article, the response of an epoxy resin to plate impact was investigated using the methods of plate impact to generate planar shock waves, and the results indicated that shear strength increases with longitudinal stress in the range investigated.
Abstract: The response of an epoxy resin has been investigated using the methods of plate impact to generate planar shock waves. In particular, the Hugoniot, both in stress–particle velocity and shock velocity–particle velocity space, and the variation of shear strength with impact stress, have been investigated. Comparison of the results of this investigation with those of previous workers shows good agreement. Measurements of lateral stress, which have been used to determine the shear strength have indicated that shear strength increases with longitudinal stress in the range investigated. Further, lateral stresses have been shown to decrease behind the shock front, implying an increase of strength of this material during shock loading. It would seem possible that this is a manifestation of the viscoplastic nature of epoxy based resins.

Journal ArticleDOI
TL;DR: In this paper, the magnetic field at the four Cluster spacecraft, typically separated by ∼600 km, during bow shock crossings are used to estimate the orientation and motion of the quasiperpendicular bow shocks.
Abstract: [1] Measurements of the magnetic field at the four Cluster spacecraft, typically separated by ∼600 km, during bow shock crossings allow the orientation and motion of this structure to be estimated. Results from 48 clean and steady quasiperpendicular crossings during 2000 and 2001, covering local times from 0600 to 1700, reveal the bow shock normal to be remarkably stable, under a wide range of steady upstream conditions. Nearly 80% of normals lay within 10° of those of two bow shock models, suggesting that the timing method is accurate to around 10°, and possibly better, and therefore that four spacecraft timings are a useful estimator of the orientation and motion of quasiperpendicular bow shocks. These results show that models provide a good approximation to the bow shock surface and can therefore be used when four spacecraft data are not available. In contrast, only 19% of magnetic coplanarity vectors were within 10° of the model normal. The mean deviation of the coplanarity vector from the timing-derived normal for shocks with θBN < 70° was 22 ± 4°. Typical shock velocities were ∼35 km s−1, although the fastest measured shock was traveling outbound at nearly 150 km s−1.