A New Physical Metallurgy Phenomenon—the Shock Wave Nanocrystallization of Amorphous Alloys

Some results of amorphous alloy nanocrystallization by shock wave are presented.Compared with the well known annealing crystallization,these results seem novel and are very difficult to be explained by the diffusion theory,such as nucleation and growth mechanism in the solid state phase transitions.The shock wave crystallization of amorphous alloy is a new metallurgical phenomenon with possibilities for improving the crystallization theory in physics.     

Pressure-jump X-ray studies of liquid crystal transitions in lipids

In this paper, we give an overview of our studies by static and time-resolved X-ray diffraction of inverse cubic phases and phase transitions in lipids. In [section sign] 1, we briefly discuss the lyotropic phase behaviour of lipids, focusing attention on non-lamellar structures, and their geometric/topological relationship to fusion processes in lipid membranes. Possible pathways for transitions between different cubic phases are also outlined. In [section sign] 2, we discuss the effects of hydrostatic pressure on lipid membranes and lipid phase transitions, and describe how the parameters required to predict the pressure dependence of lipid phase transition temperatures can be conveniently measured. We review some earlier results of inverse bicontinuous cubic phases from our laboratory, showing effects such as pressure-induced formation and swelling. In [section sign] 3, we describe the technique of pressure-jump synchrotron X-ray diffraction. We present results that have been obtained from the lipid system 1:2 dilauroylphosphatidylcholine/lauric acid for cubic-inverse hexagonal, cubic-cubic and lamellar-cubic transitions. The rate of transition was found to increase with the amplitude of the pressure-jump and with increasing temperature. Evidence for intermediate structures occurring transiently during the transitions was also obtained. In [section sign] 4, we describe an IDL-based 'AXcess' software package being developed in our laboratory to permit batch processing and analysis of the large X-ray datasets produced by pressure-jump synchrotron experiments. In [section sign] 5, we present some recent results on the fluid lamellar-Pn3m cubic phase transition of the single-chain lipid 1-monoelaidin, which we have studied both by pressure-jump and temperature-jump X-ray diffraction. Finally, in [section sign] 6, we give a few indicators of future directions of this research. We anticipate that the most useful technical advance will be the development of pressure-jump apparatus on the microsecond time-scale, which will involve the use of a stack of piezoelectric pressure actuators. The pressure-jump technique is not restricted to lipid phase transitions, but can be used to study a wide range of soft matter transitions, ranging from protein unfolding and DNA unwinding and transitions, to phase transitions in thermotropic liquid crystals, surfactants and block copolymers.     

碎石机的聚焦冲击波研究和测量

一个椭球反射体的第一焦点水下火花放电产生球面波可以聚焦在第二焦点,产生的脉冲压力可达１００×１０６Ｐａ,本文指出了不同反射体的形状、尺寸和材料对聚焦效果、脉冲形状和焦斑的影响。为了定量研究水下聚焦冲击波,我们研制了一种特殊的冲击波压力传感器（探头）,用这种探头已对国内大部分厂家的碎石机进行电声性能的测试,效果很好。     

松香对膨化铵油炸药冲击波感度的影响

利用升降法研究了油相中松香含量对膨化铵油炸药冲击波感度(50%爆轰距离)的影响,测试结果表明膨化铵油炸药具有较高的冲击波感度,松香含量显著影响该类炸药的冲击波感度.在一定的范围内,松香具有增敏作用,过量的松香会起到钝化作用.研究表明,油相配方、混药温度是影响膨化铵油炸药冲击波感度的2个重要因素,而铵油炸药的配方和混药时间成为次要因素.     

The effect of specimen thickness on the shock propagation along the in-fibre direction of an aerospace-grade CFRP laminate

In-fibre measurements of the Hugoniot have been carried out on a carbon fibre-reinforced polymer composite. For this material, we have shown at high shock stresses, a two component wave was formed consisting of a fast moving ramped portion and a slower moving shock wave. Changing the thickness of test specimen for a given shock stress resulted in a change in the magnitude and duration of the ramped portion of the wave front. As the shock stress imparted to the target was reduced, or the thickness of the target was increased, the steep shock wave in the rear surface gauge was no longer apparent. Instead a relatively slow rising wave was measured. Consequently, to establish a Hugoniot at lower shock stress levels, relatively thin specimens of target material are required.     

激波与障碍物作用加速衰减的数值研究

强激波在管道内传播时与障碍物作用会发生绕射和反射,同时还会生成膨胀波等复杂波系结构。初步研究表明,若障碍物形状合适,则可导致激波强度衰减,但其衰减程度与障碍物形状的关系则仍待进一步研究。该文利用高阶数值格式结合沉浸边界法(IBM)以及自适应网格加密(AMR)技术,对激波在管道内与不同迎风面角度的障碍物作用过程进行了数值模拟,对激波与障碍物作用衰减的机理进行了分析,并对三种障碍物对激波衰减的效果进行了对比分析,结果表明,迎风面斜率为负的障碍物相对于其他两种障碍物具有最佳激波衰减效果。另外,与目前隧道中常用的壁面为矩形障碍物的模型为算例进行了对比,结果表明,该三角形模型比矩形障碍物具有更显著的激波衰减效果。     

Kinetics of phase transitions in block copolymers

A rich variety of equilibrium phases have been identified in block copolymer melts. In this paper we study the kinetics of phase transitions from one equilibrium state to another, from both experimental and theoretical points of view. The formation of ordered phases is often mediated by non-equilibrium intermediate states. In addition the phase transitions can proceed by either conventional nucleation, or by spinodal decomposition.     

Modeling the dynamics of several particles behind a propagating shock wave

The interaction of a shock wave in a gas phase with a system of particles moving in this gas has been numerically simulated. The wave pattern of the nonstationary interaction of the propagating shock wave with these particles is described in detail. The mathematical model and computational technology employed is compared with experimental data on the dynamics of particles behind the shock wave. It is established that the approximate model of separate particles used to calculate relaxation of their velocities unsatisfactorily operates in the presence of a mutual influence of particles, whereby one particle can occur in the aerodynamic shadow of an adjacent particle.     

Some peculiarities of nematic-isotropic liquid phase transitions in monomorphic and polymorphic mesogens

In this study, the dynamics of the changes of the morphological properties in the nematic mesophase and in the heterophase regions of the phase transitions between the nematic mesophase and the isotropic liquid for the thermotropic mesogens have been investigated. Experimentally, we have obtained the thermal hysteresis for the investigated phase transitions. For the analysis of the phase transition temperatures and the peculiarities of the heterophase regions, the mean field theory has been used.     

The use of models of mixture for analysis of shock-wave experiments with incomplete phase transformation

It is suggested to use the known models of mixture for determining phase concentrations and temperature by the data of shock-wave experiments with incomplete phase transformation. Calculation results are given for the case of some known experiments involving graphite and C₆₀ fullerite, and the dependence of the accuracy of calculation on the error of measurement is studied. The possibility is discussed of using the obtained degree of phase transformation in shock wave for constructing hydrodynamic models of kinetics of phase transitions at high pressures and temperatures, which adequately fit the experiment.     

Temperature-dependent phase transitions in zeptoliter volumes of a complex biological membrane

Phase transitions in purple membrane have been a topic of debate for the past two decades. In this work we present studies of a reversible transition of purple membrane in the 50-60?°C range in zeptoliter volumes under different heating regimes (global heating and local heating). The temperature of the reversible phase transition is 52 ± 5?°C for both local and global heating, supporting the hypothesis that this transition is mainly due to a structural rearrangement of bR molecules and trimers. To achieve high resolution measurements of temperature-dependent phase transitions, a new scanning probe microscopy-based method was developed. We believe that our new technique can be extended to other biological systems and can contribute to the understanding of inhomogeneous phase transitions in complex systems.     

Velocities and Displacements of Shrapnel and a Shock Wave during Blast

It is important to minimize the destruction of defense works when blasted. In our opinion,information in the available literature is very deficient. We now present our research results on better and simpler formulas for calculating the velocities and displacements of shrapnel and a shock wave;these formulas are indispensable for understanding the destruction of blast. Formulas now available in China are too complicated. In this paper, we derive Equation (13) as the formula for calculating the velocity of shrapnel and Equation (18) as that for calculating the velocity of a shock wave. We used the test data of Denver Research Institute, as reported in Reference 4, as numerical example and found that our Equations (13) and (18) give calculated results that agree well with their test data in two respects: (1) both test data and our calculations show that at first a shock wave is ahead of shrapnel,then their displacements are equal, and finally shrapnel is ahead of the shock wave; (2) when the displacements of shrapnel and shock wave are equal, the time is 0.34 s according to test data and 0.31 s according to our calculations.     

Shocks and high velocity deformation

The shock Hugoniot curves of a large number of materials up to a few Mbar have been obtained experimentally. Metallurgical examination and physical measurements on metallic and other samples recovered after shock loading up to several 100 kbar indicate the existence of large concentrations of point, line and planar defects. Dislocation mechanisms have been invoked to explain shock wave propagation and the phenomena related to the quick homogenisation of stress and strain behind the shock front. Computer simulation models using molecular dynamics calculations have also been used to understand some aspects of shock wave propagation at an atomistic level. For very strong shocks, the material is expected to melt under shock heating, but the experimental evidence regarding this is inconclusive. A combination of shock temperature measurement and theory may be able to answer this question.     

燃料空气炸药爆炸压力场测试系统误差分析

结合燃料空气炸药武器野外爆炸试验的实际情况,运用误差理论,分析了自由场冲击波压力测试系统的误差传递规律,得到了冲击波超压的相对误差计算式。研究表明,用算术平均偏差估算FAE武器爆炸状态场冲击波侧向超压的测量误差比用标准差更切合实际。     

Quantum Griffiths Effects and Smeared Phase Transitions in Metals: Theory and Experiment

In this paper, we review theoretical and experimental research on rare region effects at quantum phase transitions in disordered itinerant electron systems. After summarizing a few basic concepts about phase transitions in the presence of quenched randomness, we introduce the idea of rare regions and discuss their importance. We then analyze in detail the different phenomena that can arise at magnetic quantum phase transitions in disordered metals, including quantum Griffiths singularities, smeared phase transitions, and cluster-glass formation. For each scenario, we discuss the resulting phase diagram and summarize the behavior of various observables. We then review several recent experiments that provide examples of these rare region phenomena. We conclude by discussing limitations of current approaches and open questions.     

Refracting and birefringent properties of lyotropic nematic mesophases

In this work, we investigated refracting, birefringent and thermotropic properties of lyotropic nematic mesophases. In particular, the morphological properties of nematic-calamitic and nematic-discotic lyotropic mesophases have been investigated in the heterophase regions at lyotropic nematic-isotropic liquid phase transitions.The changes in isotropic, mean refractive index, and anisotropic, birefringence, optical properties of the nematic mesophases by the changes in temperature have been observed to have fluctuational character in the heterophase regions of lyotropic nematic-isotropic liquid phase transitions. This character reflects the character of changes in shapes and sizes of micelles and in symmetries of the mesophases in the heterophase region.     

含h-BN复相陶瓷制备及性能研究进展

陶瓷材料密度低、抗腐蚀性及耐磨性良好,但是其硬而脆导致加工困难、抗热震性差。h-BN具有弹性模量低、硬度低的特点,其可加工性能和抗热震性能优异。将h-BN引入陶瓷基体制备含h-BN复相陶瓷,能够有效改善陶瓷材料的可加工性能和抗热震性。对含h-BN复相陶瓷的材料体系、制备工艺和性能的研究一直备受关注。本文以h-BN的引入方式为分类依据较全面地总结了含h-BN复相陶瓷的制备方法。本文对引入h-BN后所制备的含h-BN复相陶瓷的常规力学性能、抗热震性、可加工性、透波性、摩擦磨损等性能的影响进行了综述;对含h-BN复相陶瓷的制备及性能研究中存在的问题进行了概括,并对该材料体系的研究方向提出了建议。     

水下钻孔爆破水中冲击波试验研究

通过海边浅层水中钻孔爆破试验,实测得到了水中冲击波波形曲线及压力数据;分析了水下钻孔爆破水中冲击波的特性和传播衰减规律,并给出了水中冲击波的半理论半经验公式,验证并总结出部分相关结论,为进一步的研究积累了经验。     

Measurement of explosively induced movement and spalling of granite model blocks

Charges of high explosives have been buried (countersunk) in granite blocks and detonated. This article describes the measurement and evaluation of the shock wave propagating through the granite blocks. It also demonstrates how the shock wave data can be used to improve computer simulations of granite's behaviour. The overall goal has been to investigate how granite withstands penetrating weapons, that first penetrate the ground and then detonates within the created cavity. Several variables have been investigated. It is shown that water content of the granite can increase the shock wave amplitude with up to a factor 2, and a crack in the granite often attenuates the shock wave amplitude with a factor 4 or more. Also, the granite block thickness needed to prevent internal crack formation has been investigated.     

爆炸冲击波信号处理方法比较

空中爆炸冲击波的实测信号中,常有幅值很大的瞬时干扰信号,冲击波超压峰值的获取往往需要采用后期信号处理的方法。针对模爆器产生的爆炸冲击波超压的特点,采用"经验拟合"和"数字滤波"2种不同的处理方法进行信号的消噪处理,通过对试验测试结果的比较研究,肯定了传统的经验公式拟合方法在爆炸冲击波信号处理中的适用性。