A helical-radial magnetic cumulation fast-growing current pulse generator

A design-experimental study of a magnetic cumulation generator (further referred to as generator) with flat helical is performed. This generator combines advantages of both spiral-cylindrical and disk generators. As to speed of operation, the spiral-radial generator is equivalent to the disk generator, but can operate in high-impedance loads. To calculate characteristics of spiral-radial generators, including external-excitation generators, a semiempirical procedure for determining laws of variations of the inductances and mutual inductance of helical of the generator is developed. The procedure is based on measuring the current oscillation frequency in the course of the magnetic-field compression, while the helix is loaded into a small capacitance. A satisfactory compliance of the experimental data and semiempirical calculations is obtained. The experimental effective time values of the current buildup of the spiral-radial generators do not exceed the same characteristic for spiral-cylindrical generators with an axial charge initiation of the explosive material. A possibility of further decreasing the effective time is shown for the plane-parallel throwing of liner plates.     

Magnetic cummulation generators applied for rapid charging of forming lines

We describe an off-line nanosecond charging device for a short forming line; the device has been created on the basis of an inductive energy storage unit. Energy storage is carried out by the current of an explosive magnetic cumulation generator, and the energy output to the load, by means of an electroexplosive current interrupter. The use of a two-stage, instead of a one-stage, magnetic cumulation generator, consisting of a preamplifier and a dynamic transformer, and two smaller-size generators with sequential connection of secondary windings of dynamic transformers, one of which is connected to the inductive storage unit, and the other, to the current interrupter—has made it possible to substantially increase the line charge voltage. As a result, within a time on the order of 100 ns, it was possible to charge a forming line with an electric length of 5 ns to a voltage of ≥1 MV.     

端面型槽广义对数螺旋线的通用模型与应用

为解决流体润滑端面型槽设计中经典型线形状优化受限的问题,提出一种广义对数螺旋线模型,获得了斜直线、圆弧线、抛物线和椭圆曲线等经典几何型线的广义螺旋线表达式,掌握了不同参数条件下广义对数螺旋线的几何共性及演变规律。以气体推力轴承为例,对比分析了高速条件下广义螺旋角的分布规律和变化幅值对推力轴承承载性能的影响规律,结果表明:广义对数螺旋线具有很强的几何表征能力,从外径至内径侧流道渐扩的广义对数螺旋槽端面具有最大的气膜承载力。     

新形蜗杆砂轮无轴向进给磨削圆柱齿轮技术原理

在分析空间相错轴螺旋齿轮传动实现瞬时线接触共轭的条件与方法基础上,新建立了一种齿面直线接触的蜗杆传动方式。提出了以这种蜗杆为砂轮实现无轴向进给磨削圆柱齿轮的原理与方法。论述了运用这种蜗杆原理的双蜗杆磨轮磨削圆柱齿轮的结构实现、磨削进给的实现方法等,并推导了磨削速度计算公式。这种磨削加工方法结构简单、无需轴向进给、相对滑动速度大、效率高,可以用于大批量生产中齿轮的磨削加工或者珩磨加工。     

Operation simulation of a high-voltage nanosecond multistage generator

A model of a high-voltage nanosecond multistage generator employing series voltage addition in the transmission line with stepwise adjustment of the wave impedance is described. The forming lines are coaxial to the transmission line. The generator contains three arrays of switches which are brought into operation one-by-one with a delay equal to the time in which the electromagnetic wave propagates between them, thus forming across a 2.5-kΩ load a pulse whose amplitude is five times higher than the charge voltage of the forming lines. The calculated generator efficiency on an 8.4-Ω matched load is 95%.     

A ГИН-1200 high-voltage pulse generator

The electric circuit, design, and electric and triggering characteristics of the ГИН-1200 small-sized 12-stage high-voltage pulse generator used for charging a double forming line to 1 MV for a 300-ns period are described. The generator is mounted in a metallic housing with the transformer-oil insulation. The storages in stages of the generator are KMK 100–0.017 (100 kV, 0.017 μF) capacitors with a 1-kJ total stored energy. The switches are trigatron gaps filled with a 20% SF₆ + 80% N₂ gas mixture. The gap housings are assembled into one line. The through-passing axial channel ensures spark illumination of adjacent intervals, thereby improving the triggering characteristics of the generator. The operation-time scatter of the ГИН-1200 generator at an 85-kV charging voltage and 65% electric-strength margin was ≤10 ns, and the operation delay time was ～100 ns. The ГИН-1200 generator operated ～2000 times and demonstrated reliable stable operation.     

谐波齿轮中柔轮中性层的伸缩变形规律

在波发生器作用下,柔轮的中性层变形是谐波齿轮啮合分析的基础。柔轮变形分析基于小变形和中性层不伸长假定,但几何分析计算表明：柔轮的中性层出现伸长变形。为了真实揭示柔轮在双圆盘波发生器作用下的变形特征,提出基于强制几何约束条件和力平衡方程及连续性条件的柔轮中性层变形和内力计算方法。将波发生器作用下圆环受力分为接触区和非接触区,接触区由波发生器的强制位移条件确定柔轮中性层内力和变形;非接触区的变形和内力根据弯曲微分方程及其边界条件、连续性条件来确定。利用胡克定律,基于齿圈的周向力获得柔轮中性层周向应变和伸长变形。建立壳单元的柔轮有限元模型,实例表明理论解与有限元模型结果吻合良好,验证了柔轮中性层伸缩变形计算方法的正确性。获得的双圆盘波发生器作用下柔轮中性层变形及其周向应变分布,为后续的啮合分析、共轭齿廓设计及其侧隙计算提供了更准确的理论基础。     

Effects of Boundary Condition and Helix Angle On Meshing Performance of TI Worm Gearing

To exactly describe the contact state and contact area of tooth surface of toroidal involute (TI) worm gearing, the authors introduced boundary condition into contact line analysis. With helix angle chosen as parameter, the criterion for the existence of meshing boundary line on the surface of TI worm gearing is derived. Results show that there can be four situations for meshing boundary line on the tooth surface of gear, namely, inexistence of meshing boundary line, a unique line, two lines, and two coincident lines. If the helix angle is equal to or slightly smaller than the bigger angle, which makes two meshing boundary lines superpose, a preferable meshing performance is obtained. Computer simulation proves the validity of the above conclusion. Translated from Journal of Tianjin University, 2004, 37(10)     

双头单螺杆泵定子衬套力学行为分析

为研究双头单螺杆泵定子衬套的受力状态及内轮廓线的变形规律,分析了内压、压差、材料非线性、橡胶泊松比等多种因素对定子衬套应力、应变及内轮廓线变形规律的影响,并拟合出双头单螺杆泵定子衬套在均匀内压作用下内轮廓线位移的方程式及非均匀内压下内轮廓线最大位移公式。分析结果表明：均匀压力下,衬套应力、应变呈周期性变化,内轮廓线位移呈正弦规律变化,位移与内压成线性关系;压差作用下,衬套应力、应变最大值向压差作用处转移,内轮廓线变形规律发生改变,位移及其变形幅度均增大;衬套橡胶泊松比微小的变化即会对衬套变形产生非常大的影响。因此,实际生产中应注意注胶工艺及泊松比的变化。研究结果为定子、转子过盈量的选取及线型的优化设计提供了理论基础,对提高双头单螺杆泵工作效率和使用寿命具有重要工程实际意义。     

A generator of probing pulses for EMA flaw detectors

It is shown that an increase in the power of a probing-pulse generator is a desirable way to further increase the efficiency of EMA flaw detectors. A generator with an increased power was developed. Such a generator can form radio pulses of a current with a peak value of up to 200 A at a developed voltage of at least 500 V in an EMA transducer. The new generator is mainly intended for stationary EMA flaw detectors. It can supply transducers of virtually any type.     

异型螺旋曲面数控加工运动学研究与应用

通过对加工运动学原理的研究,找出曲面上的曲线也存在着活动的特征标架这一特性,提出了模仿特征标架沿曲面曲线运动的特征加工法。并以碟形砂轮加工等螺旋角锥形铣刀刀槽作为加工异型螺旋曲面的实例,对特征加工法的应用予以说明。     

High-voltage pulsed generator for dynamic fragmentation of rocks

A portable high-voltage (HV) pulsed generator has been designed for rock fragmentation experiments. The generator can be used also for other technological applications. The installation consists of low voltage block, HV block, coaxial transmission line, fragmentation chamber, and control system block. Low voltage block of the generator, consisting of a primary capacitor bank (300?μF) and a thyristor switch, stores pulse energy and transfers it to the HV block. The primary capacitor bank stores energy of 600 J at the maximum charging voltage of 2 kV. HV block includes HV pulsed step up transformer, HV capacitive storage, and two electrode gas switch. The following technical parameters of the generator were achieved: output voltage up to 300 kV, voltage rise time of ～50?ns, current amplitude of ～6?kA with the 40?Ω active load, and ～20?kA in a rock fragmentation regime (with discharge in a rock-water mixture). Typical operation regime is a burst of 1000 pulses with a frequency of 10 Hz. The operation process can be controlled within a wide range of parameters. The entire installation (generator, transmission line, treatment chamber, and measuring probes) is designed like a continuous Faraday's cage (complete shielding) to exclude external electromagnetic perturbations.     

大型发电机局部放电在线监测仪的研究

局部放电在线监测是大型发电机绝缘诊断的重要方法。本文介绍了所研制的一套宽频局部放电在线监测系统,它可正确识别实验室模拟的几种典型局部放电。最后给出了现场监测大型发电机运行工况的实际测试结果。     

干粉砂浆储罐用搅拌叶轮设计

基于干粉砂浆搅拌加工机理,研究了搅拌和出料螺旋线模型。考虑到搅拌均匀、耐磨损和出料流畅的需求,采用圆柱螺旋线和分段螺旋升角形式,设计出叶轮参数和结构。搅拌叶轮由搅拌轴、搅拌臂、搅拌叶片等组成,采用桨叶式设计。在合理选择材料的基础上,结合三维模型,借助流体力学方法计算了叶轮所受载荷,根据强度理论校验了搅拌轴的静强度,利用Pro/Mechanica有限元工具分析了搅拌臂、搅拌轴的应力场分布,结果证明结构参数合理,强度满足设计要求。     

A Generator of Ultrashort Megavolt Pulses

A generator of voltage pulses with a duration of 3 ns and an amplitude of >1 MV across a high-resistance (450 ) load is described. The generator contains a pulse transformer with a biased core and a resonant circuit consisting of a high-voltage solenoid and capacitance of a forming line. This line contains a spark gap for switching a charge to the transmitting line with a lumped load at its end such as a vacuum diode. The results of voltage measurements of the basic units of the generator are presented.     

锥形铣刀螺旋面刀具路径策略的新思路

从运动学的角度对螺旋曲面加工进行研究,找出其曲面上的曲线上存在着活动的特征标识,提出了模仿特征标识沿曲面曲线运动的加工法。并以锥形铣刀等螺旋角刀槽作为加工实例,应用特征加工法使程序得到最大限度的简化,极大地提高编程效率,对类似零件的数控加工提供有益的参考。     

用工具斜齿条法加工斜齿非圆齿轮的啮合理论模型

介绍了斜齿非圆齿轮齿廓的形成原理,针对用工具斜齿条法加工斜齿非圆齿轮动轴线变传动比复杂的运动几何关系,建立了其理论研究的数学模型,对斜齿非圆齿轮齿廓端面截形、节曲柱面截形及瞬时接触线进行了分析。论证了斜齿非圆齿轮齿廓为直纹面,其节曲柱面截形是变导程等螺旋角的螺旋线,平行轴斜齿非圆齿轮传动的瞬时接触线是直线。     

An investigation into the influence of helix angle on the torque-thrust coupling effect in twist drills

This paper presents an experimental investigation into the torque-thrust coupling effect in twist drills. A set of cross-coupling stiffness coefficients (K_ft and K_tf) are defined. The influence of helix angle on torsional and the cross-coupling stiffnesses is studied. The coupling interaction (as measured by K_ft and K_tf) is strongly influenced by the helix angle and has a distinct maxima around 28°. Also, the magnitudes of the coefficients increase parabolically with drill diameter. The pure torsional stiffness also has a maxima around the same helix angle. Under axial restraint, the torsional stiffness increases by 10 to 25% owing to the coupling effect. The larger the torque-thrust interaction, the larger is this increase in torsional stiffness. The findings of this investigation is proposed as a probable basis for the traditional popularity of a 28 to 30° helix angle for drills.     

一种基于VHDL与CPLD器件的PWM发生器

介绍了一种自行研制的基于硬件描述语言(VHDL)和复杂可编程逻辑器件(CPLD)的PWM发生器的设计,在产生正反两路PWM波形信号的同时,实现了两路信号互锁、延时时间可调.该发生器采用数字化设计,结构简单、控制精确、可在线编程.