The isotope effect of gaseous hydrogen under shock compression

The shock compression method has been used to measure the Hugoniot data and shock temperature for gaseous hydrogen samples, covering the pressure range of 55-140 MPa and the temperature range of 3400-4500 K and with the initial conditions of P ₀ = 0.6 MPa, 1.2 MPa and T ₀ at room temperature. Spectral radiance histories emitted from shocked D ₂ and H ₂ + D ₂ (equimolar mixture) are monitored by a pyrometer system with seven wavelength channels. Theoretical calculations based on the Saha model with Debye-Hückel correction for the shock compression behavior of shocked gaseous samples are in good agreement with the measured Hugoniot data, but show slightly higher values for the shock temperature when comparing with experiments. An isotope effect relevant to these shocked hydrogen species has been found in the linear shock velocity vs particle velocity relation, in which the correlation factor between these hydrogen isotopes or hydrogen mixtures is simply of initial density dependence.Received: 8 December 2002, Accepted: 8 May 2003, Published online: 2 September 2003PACS: 62.50 + p, 31.30.GS, 51.90. + r     

Linear relationship between Hugoniot temperature and shock Mach number

It is the purpose of this publication to discuss further the apparent validity of a linear relationship between the Hugoniot temperature and the shock Mach number, when used as an independent variable in the thermodynamics of very high pressures. Additional evidence for seventeen different materials is presented. Some of the materials discussed might present phase transitions within the ranges of pressure and temperature here studied. The case of molybdenum is discussed in particular because experimental data on phase transitions are available within the ranges of pressure and temperature considered. Equation of state results for a few materials, obtained using an exact analytical equation of state, are compared with those computed employing an approximate form of the equation, consequence of the linear relationship between the Hugoniot temperature and shock Mach number. The excellent agreement shows that this approximate and very simple equation of state can be very reliable and useful. Received 17 June 1997 / Accepted 4 November 1997     

[100]LiF单晶在60 GPa以内冲击加载下的高压屈服强度特性

获取光学窗口自身的高压强度特性是开展材料高压高应变率冲击响应行为精密测量和数据反演的重要基础。利用平板撞击和双屈服面法,通过冲击-卸载、冲击-再加载原位粒子速度剖面精细测量和数据反演,获得了约60 GPa范围内[100]LiF屈服强度特性随冲击压力的变化规律。结果表明:在实验压力范围内,[100]LiF的屈服强度随加载压力的提高而显著提高,压力硬化效应显著;同时,LiF在冲击加载下的屈服强度高于磁驱准等熵加载结果,应变率硬化效应强于热软化效应。采用Huang-Asay模型确定了可描述冲击加载[100]LiF强度特性的本构模型参数,为LiF在强度、相变、层断裂等加窗测量实验中的深入应用和数据准确解读提供了重要支撑。     

Nano-particle sizing by laser-induced-incandescence (LII) in a shock wave reactor

Abstract. Laser-Induced Incandescence (LII) is a relatively new optical diagnostic for particle sizing which is currently used in combustion science. Its advantage against light extinction and light scattering methods is the possibility of getting size information with high time and space resolution even for nano-particles. LII is mostly applied to particle formation or particle removal in reactive stationary flows, but it can also be used in shock-induced reactive flows. This is demonstrated in three examples: soot particle formation during high temperature pyrolysis of benzene, iron particle formation from iron pentacarbonyl, and formation of carbon-coated iron particles. From the principles of LII, it is not possible to obtain a complete particle growth curve from one individual shock tube experiment. Therefore, the kinetics of particle growth evolution must be determined from several “identical” shock tube experiments with a delayed triggering of the heat-up laser. The principles of LII, the in-situ measurement of particle size, and the comparison to beam-collected particles, which were visualized by a high resolution transmission electron microscope (HRTEM), are demonstrated. It was found that the energy accommodation coefficient during the particle cooling is for a soot surface but is significantly lower e.g. for an iron surface. Received 30 April 2002 / Accepted 9 December 2002 Published online 4 February 2003 Correspondence to: R. Starke (e-mail: starke@ivg.uni-duisburg.de)     

Ultrafast high repetition rate absorption spectroscopy of polymer shock compression

A dual-beam transient absorption spectrometer for high repetition rate (80 shocks per second) studies of shock compressed materials is described. The apparatus time response is 100 ps, so the time resolution of the shock compression process is generally limited by the shock transit time across the sample. In turn the sample thickness is limited by the sensitivity of the spectrometer. Using 400 nm thick samples of R640 dye aggregates in \textit{poly} methyl methacrylate (PMMA) and a 4.2 GPa laser-driven shock, transient absorption spectra show a shock induced absorption redshift occurring in 500 ps, considerably longer than the 200 ps shock front transit time (round trip) through the sample. This noninstantaneous shock compression is consistent with the $\sim 300$ ps viscoelastic response of PMMA at 4.2 GPa. Received 30 July 2001 / Accepted 13 March 2002 – Published online 17 June 2002     

Microwave detection of molecules formed by shock wave induced reactions

The paper describes experimental investigations in a shock tube concerning the formation of new molecules using He as a driver gas and a mixture of Kr, CH and NH as driven gas, where Kr serves as diluant. By microwave absorption technique it was possible to detect HCN, CHO and CHNH as reaction products. Obviously, these molecules were formed in the plasma behind the shock wave. In addition, the “swan bands” of C have been observed with optical methods. Received 16 November 1997 / Accepted 7 May 1998     

Detonation and deflagration initiation at the focusing of shock waves in combustible gaseous mixture

Abstract. Detonation and deflagration initiation under focusing conditions in a lean hydrogen-air mixture was experimentally investigated. The experiments were carried out in a shock tube equipped with the laser schlieren system and pressure transducers. Two-dimensional wedges (53° and 90°), semi-cylinder and parabola, were used as the focusing elements. The peculiarities of mild and strong ignition inside the reflector cavity were visualized. A hydrogen-nitrogen mixture was taken for comparison between reactive and inert mixture. It was found that mild ignition inside the reflector cavity can lead to detonation initiation outside the cavity. Schlieren pictures of the process were obtained and the dependence of the distance of detonation initiation on Mach number of the incident shock wave was established. Received 30 August 1999 / Accepted 23 February 2000     

The formation of a secondary shock wave behind a shock wave diffracting at a convex corner

This paper deals with the formation of a secondary shock wave behind the shock wave diffracting at a two-dimensional convex corner for incident shock Mach numbers ranging from 1.03 to 1.74 in air. Experiments were carried out using a 60 mm 150 mm shock tube equipped with holographic interferometry. The threshold incident shock wave Mach number () at which a secondary shock wave appeared was found to be = 1.32 at an 81° corner and = 1.33 at a 120° corner. These secondary shock waves are formed due to the existence of a locally supersonic flow behind the diffracting shock wave. Behind the diffracting shock wave, the subsonic flow is accelerated and eventually becomes locally supersonic. A simple unsteady flow analysis revealed that for gases with specific heats ratio the threshold shock wave Mach number was = 1.346. When the value of is less than this, the vortex is formed at the corner without any discontinuous waves accompanying above the slip line. The viscosity was found to be less effective on the threshold of the secondary shock wave, although it attenuated the pressure jump at the secondary shock wave. This is well understood by the consideration of the effect of the wall friction in one-dimensional duct flows. In order to interpret the experimental results a numerical simulation using a shock adaptive unstructured grid Eulerian solver was also carried out. Received 1 May 1996 / Accepted 12 September 1996     

Shock reaction of hexane at 77, 193, and 273 K with special reference to shock pressure

Shock waves generated by projectile impacts were transmitted into hexane and the shocked hexane was analyzed by TCD-GC, FID-GC, GCMS, and FABMS for produced aliphatic hydrocarbons. The projectile length and its velocity were varied from 10 to 40 mm and from 220 to 1040 m/s, respectively. The initial temperature of the hexane was 77, 193 and 273 K. The major products detected throughout the reactions were hydrogen, light alkanes from C to C, and light alkenes from C to C. The minor products were heavy alkanes from C to C and soot-like materials. Experiments with varied projectile length revealed that the shock reaction occurred only while the shock wave was transmitted through hexane (about seconds). This short reaction time may be responsible for a lower yield of branched products in the shock reaction compared with yield produced by hexane pyrolysis in previous studies. In the shock reaction of hexane, the dehydrogenation was one of the important reactions and the recombination of hexyl radicals might play a role in the formation of -C. Experiments with varied initial temperature suggested that the molar yield of products depends not on the shock temperature but on the shock pressure, and that the reaction mechanisms for solid hexane and for liquid hexane are not identical. As the shock pressure increased, the relative yield of heavy products increased while that of light products decreased. This could be interpreted mainly by considering the activation volumes of the reaction involved. Received 12 September 1997 / Accepted 14 October 1997     

高温高密度液氦冲击压缩特性理论研究

选择高密度液氦作为研究对象,采用F.H.Ree修正的WCA状态方程和改进的分子流体微扰变分统计理论（MCRSR）,并且考虑液氦体系低温量子力学效应,计算了一次和二次冲击压力在0～108 GPa、对应温度为471～32 790 K范围内的高压物态方程。在确定体系分子间相互作用时,通过实验数据拟合选取了较合理的指数6势参数。理论计算结果与实验数据吻合较好。     

Experimental studies of ignition and transition to detonation induced by the reflection and diffraction of shock waves

This paper presents results from a program of experimental studies of ignition induced by the interaction of an initially planar shock wave with an obstacle in its path. With the aid of pressure measurements, spark schlieren photography and smoked foil techniques it is shown how, given favourable initial conditions, the two-dimensional multiple shock reflection and diffraction can promote ignition and transition to detonation in reactive gaseous mixtures. Comparison of the results with those of a non-reactive gas distinguishes the gas dynamic and chemical processes involved, and experimentally determined detonation cell sizes are compared with values predicted using chemical kinetic rate data. The systems investigated were argon, air, propane-air, propane-oxygen-argon and ethylene-oxygen-argon. Received: 3 December 1998 / Accepted: 27 October 1999     

斜波压缩下HMX晶体的弹塑性行为

开展了（010）、（011）晶向HMX晶体的斜波压缩实验,获得了约15 GPa压力下的速度响应剖面。实验结果表明,HMX单晶存在明显弹塑性转变行为,且速度波形有下降趋势,这是材料的黏性效应导致,材料的弹性极限随着样品厚度增加而变化,不同晶向的材料动力学特性存在差异。结合Hobenemser-Prager黏弹塑性本构关系和三阶Birch-Murnaghan物态方程开展了HMX晶体斜波压缩物理过程的数值模拟,计算结果可以很好地描述HMX晶体的弹塑性转变这一物理过程。     

初始堆积对发射药床底部挤压应力的影响

为给发射装药发射安全性的评估提供关键数据,对不同初始堆积发射药床进行了挤压破碎实验,测得了发射药床底部的挤压应力。利用离散单元法,建立了发射装药挤压破碎动力学模型,对发射药床的挤压应力进行了计算。实验结果和计算结果吻合较好。随机堆积药床底部的挤压应力较一致,竖排堆积药床底部的挤压应力差异较大。     

固体材料高功率激光斜波压缩研究进展

利用高功率激光诱导的应力波对固体材料进行高应变率斜波压缩,是近年来快速发展的新型动高压实验技术。与传统加载手段不同,它可以在数ns时间内以极高的应变率(106~109 s-1)将薄样品平滑加载到数千万大气压,并仍然保持其固体状态。结合多种先进的诊断技术,可以测得样品材料的热力学、动力学参数和原位微观结构特性,是研究动高压物理、物态方程和高应变率动力学问题的先进途径。本文梳理了这种技术的发展历程,对其加载和诊断技术以及已取得的主要结果进行综述,并展望了其发展前景。     

Visualization of shock-wave formation processes during shock reflection at obstacles with multiple steps

According to standard textbooks on compressible fluid dynamics, a shock wave is formed by an accumulation of compression waves. However, the process by which an accumulated compression wave grows into a shock wave has never been visualized. In the present paper, the authors tried to visualize this process using a model wedge with multiple steps. This model is useful for generating a series of compression waves and can simulate a compression process that occurs in a shock tube. By estimating the triple-point trajectory angle, we demonstrated visually that an accumulated compression wave grows into a shock wave. Further reflection experiments over a rough-surface wedge confirmed the tendency for the triple point trajectory angle to reach the asymptotic value _s in the end.This work was first presented at the Symposium on Shock Waves, Japan 2002     

Transformations of graphite and boron nitride in shock waves

Peculiarities of shock adiabat of graphite are attributed to the graphite–diamond transformation. However only a very small amount of diamond can be recovered from pure shocked graphite with a density approaching the theoretical value. In order to interpret this fact, accessible data concerning the behaviour of graphite under static and dynamic load have been analysed. An additional peculiarity of the shock adiabat of graphite has been found at 12 GPa by analysing compressibility data. It has been attributed to shearing in the basal planes that paves the way for deformation of the planes. An isotherm of cold compression of graphite can be constructed on the basis of the results from theoretical modelling published in the literature. Another isotherm, fitting experimental data, has been proposed. An isotherm for graphitic boron nitride has been also proposed. The isotherms have been used in the interpretation of the peculiarities of shock adiabats. It has been shown that the so-called “mixed-phase” region is an apparent compressibility curve. Energy evaluations based on the isotherms have proved that the peculiarities of the shock adiabat of graphite correspond to the formation of hexagonal instead of cubic diamond. Similarly the formation of the wurtzite modification of BN is responsible for the peculiarities of the shock adiabat of BN. Literature data concerning the mechanism of the polymorphous transformations of graphite and BN in shock waves have been reviewed. On the basis of proposed isotherms of cold compression, the activation energy has been appraised and an equation of kinetics proposed. The equation has been analysed by comparing results of theoretical modelling and accessible experimental data. Received 11 March 1993 / Accepted 15 September 1993     

Wave pattern characteristics of a two-phase nozzle flow by shock propagation

In this paper, the wave pattern characteristics of shock-induced two-phase nozzle flows with the quiescent or moving dusty gas ahead of the incident-shock front has been investigated by using high-resolution numerical method. As compared with the corresponding results in single-phase nozzle flows of the pure gas, obvious differences between these two kinds of flows can be obtained. Received 14 June 1996 / Accepted 19 October 1996     

Constitutive behaviour of anisotropic materials under shock loading

Thermodynamically and mathematically consistent constitutive equations suitable for shock wave propagation in an anisotropic material are presented in this paper. Two fundamental tensors α_ij and β_ij which represent anisotropic material properties are defined and can be considered as generalisations of the Kronecker delta symbol, which plays the main role in the theory of isotropic materials. Using two fundamental tensors α_ij and β_ij, the concept of total generalised “pressure” and pressure corresponding to the thermodynamic (equation of state) response are redefined. The equation of state represents mathematical and physical generalisation of the classical Mie–Grüneisen equation of state for isotropic material and reduces to the Mie–Grüneisen equation of state in the limit of isotropy. Based on the generalised decomposition of the stress tensor, the modified equation of state for anisotropic materials, and the modified Hill criteria, combined with the associated flow rule, a system of constitutive equations suitable for shock wave propagation is formulated. The behaviour of aluminium alloy 7010-T6 under shock loading conditions is considered. A comparison of numerical simulations with existing experimental data shows good agreement of the general pulse shape, Hugoniot Elastic Limits (HELs), and Hugoniot stress levels, and suggests that the constitutive equations are performing satisfactorily. The results are presented and discussed, and future studies are outlined.     

Aerodynamic calibration of TCM2 facility and study of a bow shock layer by emission and laser spectroscopy

Flow properties in the TCM2 free piston shock tube/tunnel are determined by time-resolved pressure and heat flux measurements in numerous points of the shock tube and the nozzle, and in the free flow for two stagnation enthalpy conditions (3.5 and 11 MJ/kg). These measurements demonstrate the homogeneity of the flow during more than 1 ms. The cleanness of the useful test time is shown with time-resolved emission measurements at critical wavelengths. NO fluorescence profiles are established with local and planar laser-induced fluorescence in the shock layer around a cylindrical model. It allows to determine the shock stand-off distance for both enthalpy conditions. The problems of quenching and amplified spontaneous emission are considered. The importance of atomic oxygen and atomic nitrogen densities as well as temperature effects is also shown. Evaluation of the temperatures behind the shock front through spectroscopic data agrees with calculations. The proof of the presence of vibrationally excited NO ahead of the shock layer is given. Received 14 March 2000 / Accepted 18 June 2001