A novel split-belt apparatus: the stress distribution and performance of its tangent split die

A novel high pressure device with a tangent split cylinder was investigated on the basis of the belt-type apparatus. The cylinder is split into several blocks and the dividing line is tangent to the inner hole. This structure of the cylinder can eliminate the tangential tensile stress due to the friction and squeeze each other on the contact surface between the divided bodies. In this paper, different split numbers of the cylinders were choosen to study the stress distribution and the pressure-bearing capacity, and compare them with the traditional belt-type die (BTD). Simulation results show that the more the number of divided bodies, the smaller the stress and the higher the pressure-bearing capacity. The experiments also indicate that the tangent split die can bear higher pressure than the BTD. The tangent split tungsten carbide cylinder has the advantages of easy manufacture, strong bearing capacity and replaceable performance.     

钢丝缠绕剖分式超高压模具等张力预紧分析

针对超高压装置大型化受限于大质量硬质合金加工困难等问题,设计了一种新型的钢丝缠绕剖分式两面顶超高压模具。该模具主要由内部的剖分式压缸和外部的预应力钢丝组成。对采用等张力钢丝缠绕模具进行了力学模型分析,并通过有限元软件对剖分式压缸和钢丝缠绕层进行研究。结果表明:加载后压缸腔体的最大等效应力出现在压缸腔体内壁;压缸腔体尺寸稳定性与钢丝缠绕层数及钢丝直径成正比;在缠绕层内部,钢丝轴向应力与钢丝直径成反比,与缠绕层数成正比。     

Study on pressure capacity of multilayer stagger-split die,using simulation-based optimization

A novel device with a large cavity is investigated with regard to pressure capacity. This device is the multilayer stagger-split die (MSSD) that employs one or more supported rings and the multilayered divided body assemblage. The divided bodies are arranged in a staggered manner between adjacent layers. The pressure capacity of this device is calculated based on different failure criteria and using the simulation-based optimization approach. The results are compared with those of the belt-type die (BTD). A comparative experiment is also carried out to verify the simulated results. We conclude that the conditionality of pressure capacity of MSSD is related to die size. And MSSD can bear higher pressure than the BTD.     

具有碳纤维材料环的超高压模具

介绍了一种使用钢环和碳纤维复合材料环共同预紧方式的两面顶超高压模具,该结构在全钢环两面顶模具的基础上,使用一层碳纤维复合材料环代替最外层钢环,得到了一种具有碳纤维复合材料环的超高压模具。这种设计避免了大直径钢环难以制造加工的问题,形成一种以钢环与复合材料环共同对压缸预紧的新型预紧方式。数值分析表明:该模具结构设计具有可行性,可以在一定程度上减小压缸的周向应力、最大剪切应力和等效应力。此外,对碳纤维复合材料环进行了失效判别。     

内表面掺硅聚苯乙烯空心微球初步研究

靶丸内表面掺杂诊断元素可以为内爆压缩界面的研究提供必要的手段。以二甲基二乙氧基硅烷为原料，利用乳液微封装技术和界面聚合技术可以实现单一内表面掺硅的空心聚苯乙烯微球的制备。X光照相和X能谱分析表明:内表面掺硅量比外表面高出2~3个数量级。均匀内表面掺硅层的厚度小于0.3μm，掺杂层厚度越小，均匀性越好。     

高压下国产六面顶压机铰链梁和工作缸的应力分析

运用有限元理论,基于ANSYS对国产六面顶压机的铰链梁、工作缸和销轴进行了接触分析。模型中首次引入销轴,约束销轴的运动,使凸耳处的载荷情况更接近实际工况,避免了对铰链梁和工作缸单独分析所进行的大量近似和简化。模拟结果表明:铰链梁上的vonMises应力峰值主要分布在凸耳内通孔处,最大应力值为348.32 MPa;工作缸上的von Mises应力峰值主要分布在工作缸底部圆弧处,最大应力值为242.87 MPa;应力峰值均低于许用应力(486.67 MPa)。模拟结果得到了大量高压实验的验证。     

轮缘密封整周模型流动与封严特性数值研究

本文通过求解SST湍流模型以及三维Unsteady Reynolds-Averaged Navier-Stokes(URANS)方程,研究了单级轴流透平轮缘密封整周模型的流动与封严特性。分析了不同冷气流量下的封严效率与压力波动的变化,并通过与仅保留静叶和仅保留动叶的简化模型比较,分析了动静叶对主流与盘腔内压力波动的影响。结果表明:盘腔内部封严效率存在周向波动但无明显周期性规律,主流与盘腔内的压力周向波动受动静叶的影响,存在明显的周期性规律,静叶下游压力波动周期数等于静叶数,动叶上游与盘腔内部压力波动周期数等于动叶数。     

Acoustic characteristics inside cylindrical structure with end plates excited at different frequencies

In order to study coupling between vibration of a structure and a sound field in contact with the structure, a cavity surrounded by a rigid cylinder having thin elastic plates at both ends is adopted as an analytical model. When excitation forces of different frequencies are applied to the respective plates, the plate vibrations and the sound field inside the cavity become aperiodic, because of the coupling between the systems. In the present investigation, distribution of the sound pressure level inside the cavity is studied in detail in order to clarify the coupling behavior. The results show that when the respective plates vibrate at the same circumferential order, the vibration modes of the plates, which effect the coupling of the plate vibrations and the sound field, cause the aperiodic nature of each system to develop. In this case, since the dominant mode exists in formation of the sound field, it significantly influences the aperiodic nature of the coupling systems. In the case of vibration modes where the plates vibrate at different circumferential orders, the behaviors of the three systems, whose coupling has been restrained, approximate a steady state. Consequently, the dominant mode does not appear in the sound field.     

Free vibration of circular cylinders of variable thickness

Flexural vibrations of finite length circular cylinders with shear diaphragm ends and symmetric circumferential wall thickness variations are described by using the Rayleigh-Ritz method. Both symmetric and asymmetric solutions are presented. Only circumferential variations in the wall radial dimension are considered; the method is amenable, however, to consideration of longitudinal variations in wall thickness as well. The cylinder wall thickness variation is described as a Fourier series and the vibration is described as a series of modes of a uniform cylinder with the same mean radius. The theory has been applied to a cylinder whose inner bore is circular but is non-concentric with the circular outer surface. The mode shapes have been investigated experimentally by using time-averaged holograms of the vibrating cylinder and the results compare well with the predictions of the theory. The frequencies of the modes agree with the theoretical predictions to within 2%.     

外部流场对激光加热运动目标影响的数值模拟

 考虑激光与运动目标相互作用的基础上，利用有限元方法分析了亚声速条件下运动目标在激光辐照全过程的温度场和热应力场的分布与演化规律。结果表明：高速流场的存在，导致了明显的冷却效应；加热过程中目标材料出现了屈服，导致激光熄灭后结构内出现残余应力和变形；激光辐照区边缘产生很高的温度梯度和应力梯度，并且由于气流影响，受辐照区域前后两端应力分布不对称。     

Laser-induced circumferential waves on hollow cylinder and their interaction with defects by finite element method

A three dimensional (3-D) finite element model for simulating laser induced circumferential wave on a hollow cylinder is developed based on the thermoelastical mechanism, which can take any laser source into account and simulate the interactions between circumferential wave and defects in the hollow cylinder. The model is verified by a control calculation. The results show that the waveforms of circumferential wave are in very good agreement with those available in literature, not only on the arrival time and shape but also on the amplitudes of A ₀, S ₀ and A₁ modes. Using the model, circumferential waves on the surfaces of two series hollow cylinders are simulated, one with same thickness but different outer radius, and the other with the same outer radius but different thickness. The results show that a new mode appears in circumferential wave, compared with Lamb wave in plate. With increase of thickness or radius, the amplitude of the new mode reduces. Another conclusion is that with increase of the thickness of the hollow cylinder, the circumferential wave evolves gradually to the cylindrical Rayleigh waveform, which results from the attenuation of the coupling effect between the outer and inner surface. Moreover, the circumferential waves generated on a hollow cylinder with a surface defect are also simulated, and the results indicate that in the circumferential waves obtained at the point beyond the defect, the amplitude of A ₀ mode decreases and its dispersion enhances. More importantly, a new bipolar waveform corresponding to the interaction of S ₀ mode with the defect appears, its amplitude is larger than three times of that of S ₀ mode. As a result, we consider that the new bipolar waveform will be the optimal feature to nondestructively detect the surface defect on the hollow cylinder.     

Moment and forces exerted on the inner cylinder in eccentric annular flow

This paper presents results of numerical modeling for analysis of the moment and forces exerted on an eccentrically positioned rotating inner cylinder due to the annular flow between two cylinders with parallel axes. Laminar stationary fully developed flows of Newtonian and power law fluid flows are considered. An impact of annulus geometry, flow regime, and fluid characteristics are studied. The study indicates that the moment exerted on the inner cylinder increases monotonically with the eccentricity. Forces acting on the inner cylinder include pressure and viscous friction. The pressure forces provide a predominant contribution. When eccentricity does not exceed a certain critical value, the radial force pushes the inner cylinder to the channel wall. When eccentricity is large enough, the radial force reverses its sign, and the inner cylinder is pushed away from the outer wall. Circumferential component of the force has always the same direction and induces precession of the inner cylinder.     

A low-temperature high-pressure apparatus with a temperature control system

Abstract

A low-temperature high-pressure apparatus was designed using commercial cryogenic equipment. Pressures up to 1 GPa and temperatures down to 40 K can be obtained in a volume of up to 30 cm³. The apparatus is of the piston-cylinder type with a piston diameter of 45 mm, and the pressure can be varied at all temperatures, An adaptive temperature control system keeps the temperature inside the pressure cylinder constant to within ±0.1 K.     

Contraction and relaxation-induced oscillations of the left ventricle of the heart during the isovolumic phases

A theoretical analysis is presented for the transient dynamical response of the left ventricle of the heart during the isovolumic contraction and relaxation phases of the cardiac cycle. Small oscillations of the left ventricular cavity pressure and wall motion are excited by the initial rates of filling and emptying of the ventricle as well as the rate of change in muscle fiber activation. The analysis applies to the genesis of the first and second heart sounds. The ventricle is modeled as a finite, thick-walled incompressible cylinder having a continuum of imbedded axial and circumferential active muscle fibers, which interacts with a fixed volume of an incompressible, ideal fluid. The solution is obtained using a two-timing asymptotic expansion procedure. The theoretical calculations of left ventricular pressure waveforms compare favorably with published recorded pressure waveforms. The amplitude spectra of computed waveforms contain information concerning the active elastic modulus of the fibers, which is a measure of cardiac contractility.     

Single-material coupling-tolerant semi-planar microresonator using Littrow diffraction

Resonators carved in a single material such as disc, rings, spheres, do not require genuine mirrors since they exploit shape resonances, but they then suffer from poor coupling to standard free-space collimated beams. Exploiting the idea of Littrow resonators combining total internal reflection and grating diffraction, we propose trapezoidal prism-type geometries that include a strong grating on one face, and total internal reflection on the other face. Resonant modes are localized within a length of the same order as the prism thickness, but are well coupled to free-space beams. The resonator core can be seen as a broad waveguide with multimode coupling of “Littrow modes”, a configuration recently pointed out for its capability to produce a “collective” slow-light regime. A more “planar” version, with a saw-tooth input-coupling grating for vertically collimated beam is also proposed.     

Effect of shroud geometry on the pressure distributed around a circular cylinder

Some results are presented of an investigation of the distribution of the mean static pressure around a circular cylinder fitted with various shrouds, for the subcritical and transition Reynolds number range. Those shrouds were chosen which suppress flow-induced vibrations and these seem to have a particular effect on the pressure distribution: namely, the flat part of the corresponding pressure coefficient curve versus the circumferential angle is reduced behind the cylinder.     

4.5 GPa静水压活塞圆筒式高压装置的压力检测分析及压力校正

 本文提供了提高现有活塞圆筒式高压装置流体静压强的一种实验方法。成功地制作了锰铜丝压力计，并利用铋丝相变准确地做了压力校正。各箍的应力检测分析和相对位移测量都表明：无论压腔空载或充液时，在0.000 1~3.08 GPa均不显示出同步箍紧作用；上下缸的压强差偏大带来高压暴露的危险。为把流体静压强提高到3.08 GPa以上，建议改进设计；（1）内箍中箍合二为一，外箍分为上下二层，将增加箍力；（2）调整各箍之间接触圆锥面的面积，将有助于同步箍紧；（3）增大密封套圈的无支承面，将减少上下缸压差，有利于安全运行。     

MRI investigation of granular interface rheology using a new cylinder shear apparatus

The rheology of granular materials near an interface is investigated through proton magnetic resonance imaging. A new cylinder shear apparatus has been inserted in the magnetic resonance imaging device, which allows the control of the radial confining pressure exerted by the outer wall on the grains and the measurement of the torque on the inner shearing cylinder. A multi-layer velocimetry sequence has been developed for the simultaneous measurement of velocity profiles in different sample zones, while the measurement of the solid fraction profile is based on static imaging of the sample. This study describes the influence of the roughness of the shearing interface and of the transverse confining walls on the granular interface rheology.     

HgCdTe256×256用制冷杜瓦集成组件的研制

介绍一种红外焦平面器件用制冷杜瓦组件,该组件用于封装256×256HgCdTe红外焦平面芯片,由直线马达驱动型斯特林制冷机冷却,制冷机与杜瓦的耦合采用IDCA方式;制冷机、杜瓦进行一体化优化设计,使得整个红外探测器组件能耗、重量大大降低,实现了红外探测器组件的小型化.     

325 MHz spoke腔的二次电子倍增效应

采用CST软件的粒子工作室模块, 对spoke超导腔中可能发生的二次电子倍增效应进行了分析研究,并采用二次电子倍增效应发生后形成稳定状态时的粒子数增长率来表征其强度。模拟计算表明:该腔存在两处二次电子倍增效应,spoke柱两端的两点一阶倍增; spoke腔两端侧壁与中心圆筒交界处的单点一阶倍增;二次电子倍增在加速腔压为0.65 MV时的增长率最高,而腔压大于1 MV时,增长率均为负,即无倍增发生。