Charging of an inductive accumulator from an explosive-type magnetic generator through an electrical explosive-type current breaker

Analytical investigations were made of electromagnetic processes with the work of an explosive-type magnetic generator, in a series-connected inductive-type accumulator and a current breaker based on an exploding wire. A solution is obtained in dimensionless form for a model of a current breaker based on an ohmic resistance, whose value rises linearly with the temperature. The conditions are determined under which an inductive load can be connected in parallel to the current breaker; under these circumstances, the current of the load branch remains small during the whole charging stage.     

Separation of chemical elements in the discharge channel of an inductive plasma gun

Zones of separation of chemical elements in the air plasma flow in the discharge channel of the VGU-4 100-kW inductive plasma gun with a sonic nozzle of the Institute for Problems in Mechanics of the Russian Academy of Sciences are determined from an analysis of numerical solutions obtained within the framework of the Navier-Stokes equations. The occurrence of these zones and their possible influence on heat transfer to bodies in underexpanded jet flows in physical experiments are explained.     

Energy transfer from an inductive storage by means of an explosive current disconnect

Energy transfer from an inductive storage is considered for two types of systems: a disconnect with an intrinsic parasitic inductance for an inductive load and a purely resistive disconnect for a resistive load. Solutions are obtained for the voltage, power, and energy transferred to the load. The dependence of the efficiency of the device on its parameters is established.     

Transient multi-physics behavior of an insert high temperature superconducting no-insulation coil in hybrid superconducting magnets with inductive coupling

A transient multi-physics model incorporated with an electromagneto-thermomechanical coupling is developed to capture the multi-field behavior of a single-pancake (SP) insert no-insulation (NI) coil in a hybrid magnet during the charging and discharging processes. The coupled problem is resolved by means of the finite element method (FEM) for the magneto-thermo-elastic behaviors and the Runge-Kutta method for the transient responses of the electrical circuits of the hybrid superconducting magnet system. The results reveal that the transient multi-physics responses of the insert NI coil primarily depend on the charging/discharging procedure of the hybrid magnet. Moreover, a reverse azimuthal current and a compressive hoop stress are induced in the insert NI coil during the charging process, while a forward azimuthal current and a tensile hoop stress are observed during the discharging process. The induced voltages in the insert NI coil can drive the currents flowing across the radial turns where the contact resistance exists. Therefore, it brings forth significant Joule heat, causing a temperature rise and a uniform distribution of this heat in the coil turns. Accordingly, a thermally/mechanically unstable or quenching event may be encountered when a high operating current is flowing in the insert NI coil. It is numerically predicted that a quick charging will induce a compressive hoop stress which may bring a risk of buckling instability in the coil, while a discharging will not. The simulations provide an insight of hybrid superconducting magnets under transient start-up or shutdown phases which are inevitably encountered in practical applications.     

The inductive iris double discontinuity

Summary The reflection coefficient of a double discontinuity consisting of two closely spaced inductive irises in a rectangular waveguide is found. Standard transmission line techniques are no longer valid when the irises lie close together. Instead, the solution must include effects of interaction of the higher order modes excited by each iris. A variational expression for the reflection coefficient including the effects of the higher order modes is derived in terms of integrals of the induced current on one of the irises. The solution shows how more higher order mode terms become significant in determining the reflection coefficient as the iris spacing decreases. A numerical example is presented using only a few of the higher order mode factors. The results follow measured values of the reflection coefficient with spacings as close as 1/32 of a waveguide wavelength. More terms in the solution are required for closer spacings. The numerical example correctly predicts the spacing (3/16 of a waveguide wavelength) at which the higher order mode interaction becomes significant and the transmission line solution deteriorates.     

A novel inductive technique for microcantilever displacement detection

A novel inductive technique for the detection of microcantilever displacement for sensing applications was presented. We highlight the basic structure and evaluate its characteristics with the aid of modeling and simulation. Results generated by numerical simulations using ANSOFT are compared with those obtained from an equivalent circuit model using PSPICE. There are indications that the sensitivity of the inductive cantilever is about one order of magnitude higher as compared to piezoresistive silicon cantilevers of the same dimension under the same cantilever bending.     

An automated dynamic viscometer with air bearing and inductive transducers for angular displacement detection

A dynamic viscometer is described, with which the dynamic moduli in the frequency range from 2 × 10^–3 to 10 Hz can be determined for liquids with 10^–3 Pa< |G ^* | <10² Pa. Due to the application of an air bearing and inductive transducers for the detection of the angular displacement of both the drive and the measuring cylinder a sensitive apparatus has been made. Very small strains (₀ 10^–3) can be applied and only a small amount of sample (4 ml) is needed. The operation of the apparatus is fully computer-controlled, thus, long runs at various frequencies and temperatures are possible without operator intervention. The theoretical background, calibration procedure, and operation window are described. A presentation of some measurements on two polyisoprene/polystyrene triblock copolymer solutions concludes the work.     

Bending of an Anisotropic Elliptic Plate on an Elastic Foundation

An approach is proposed to solve a stress–strain problem for anisotropic rigidly fixed plates on an elastic foundation. The problem is solved by the method of successive approximations. At each approximation, the deflection is represented as polynomials whose coefficients are determined from a system of linear algebraic equations. Study is made of the influence of the reinforcement angle and the modulus of subgrade reaction on the deflections and the bending moments in an orthotropic plate.     

Unsteady Behavior of an Elastic Beam Floating on the Surface of an Infinitely Deep Fluid

The effect of initial disturbances and unsteady external loading on an elastic beam of finite length which floats freely on the surface of an ideal incompressible fluid is studied in a linear treatment. The fluid flow is considered potential. The beam deflection is sought in the form of an expansion in the eigenfunctions of beam vibrations in vacuum with time-dependent amplitudes. The problem reduces to solving an infinite system of integrodifferential equations for unknown amplitudes. The memory functions entering this system are determined by solving the radiation problem. The beam behavior is studied for various loads with and without allowance for the weight of the fluid. The effect of fluid depth on beam deformation was determined by comparing with the previously obtained solutions of the unsteady problem for a beam floating in shallow water. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 1, pp. 85–94, January–February, 2006.     

Theory of nonequilibrium inductive high-frequency discharge in a gas flow

The global nonequilibrium flow in the discharge chamber of an induction plasma generator is modeled. The problem for an equilibrium discharge was considered in [2, 3]. Here, on the basis of a numerical solution of the combined system of Navier-Stokes, Maxwell, energy, ionization kinetics and electron-gas energy balance equations, the structure of the nonequilibrium discharge is analyzed and the results obtained within the framework of the local one-dimensional approach [1] and on the basis of global numerical modeling of the flow are compared. As distinct from [2, 3], in finding the electromagnetic field distribution in the discharge chamber the boundary-value problem for the two-dimensional Maxwell equations is solved.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 153–160, March–April, 1991.The author is grateful to V. V. Lunev and G. N. Zalogin for their constant interest and useful discussions.     

Arbitrary motion of an elongated body in an ideal fluid

A method is considered which permits the use of a computer to calculate the fluid velocity on the surface of a solid body moving in an ideal fluid and to calculate the added mass. The method of [1, 2], developed for bodies of revolution, in which the flow is simulated by a system of sources and sinks distributed continuously over the body surface, is extended to the case of an arbitrary body. In contrast with the analogous work of Hess and Smith [3], where the fluid velocities on the surface of an arbitrary body were determined for translational motions, in the present case the basic integral equation of the problem is solved by the method of successive approximations without preliminary approximation of the equation by a system of linear algebraic equations of high order, which leads to a shortening of the computations.The results of the calculations are compared with the known exact values of the velocities and the added mass for a triaxial ellipsoid, and also with the results of the experimental determination of the pressures on the surface of an elongated body.     

Trajectories of charged solid particles in an air jet under the influence of an electrostatic field

Among modern coating techniques electrostatic powder spraying is one of the most attractive. In this method the plastic particles are charged by a high voltage electrode inside a coating gun. The charged particles are entrained by an air jet and directed towards the object to be coated, which is electrically grounded.In the present paper experimental trajectories of particles emerging from an electrostatic gun are determined. The equations of motion of particles in a jet are written in Lagrangean coordinates and solved numerically. Results are compared with the experimental data.     

Shaped charge with an axial channel

A shaped charge with an axial channel is considered. The charge is initiated by an impact of an annular plate. As a result, the shaped charge is initiated at all points of the domain shaped as a ring. The impact plate material and parameters (velocity, thickness, width, and distance covered by the plate) that ensure stable penetration of the shaped charge are determined. The results obtained can be used to develop a composite (e.g., “tandem”) shaped charge of the “base-head” type (the charge located farther from the target is first initiated, followed by initiation of the charge located closer to the target).     

Lift Force of an Airfoil in the Form of an Arc with a Sink

The problem of maximizing the lift force of an airfoil in the form of an arc with a sink modeling flow removal is studied within the framework of the classical model of a steady ideal incompressible liquid flow. For a sink with a fixed flow rate, an optimal position on the upper surface of the arc is found, which ensures the greatest increase in the lift force. It is shown that, in the presence of a sink, the optimal shape of the arc with a limited curvature and chord length coincides with the optimal shape of the arc without a sink, which was designed by M. A. Lavrent'ev (an arc of a circle). The flow rate corresponding to the maximum lift force is determined, and the mechanism of the influence of flow removal on the lift force is examined.     

Scattering of love waves by an interface crack between a piezoelectric layer and an elastic substrate

The scattering of Love waves by an interface crack between a piezoelectric layer and an elastic substrate is investigated by using the integral transform and singular integral equation techniques. The dynamic stress intensity factors of the left and the right crack tips are determined. It is found from numerical calculation that the dynamic response of the system depends significantly on the crack configuration, the material combination and the propagating direction of the incident wave. It is expected that specifying an appropriate material combination may retard the growth of the crack for a certain crack configuration. Project supported by the National Natural Science Foundation of China (No. 19891180), the Fundamental Research Foundation of Tsinghua University (JZ 2000.007) and the Fund of the Education Ministry of China.     

Study on particle removal efficiency of an impinging jet by an image-processing method

 An image-processing method is proposed to obtain the distribution of the removal efficiency of particles on a plate by an air jet. This method can be used to measure particle removal from a flat surface by processing the image of the reflected light from the surface. Factors affecting the particle removal efficiency such as air pressure, distance between the nozzle and the impinging surface and the impinging angle are discussed. Optimal conditions are determined to obtain the most effective particle removal by the air jet. Received: 10 April 2001 / Accepted: 2 August 2001     

Stress Analysis of Laminated Shells of Revolution with an Imperfect Interlayer Contact

An approach is proposed to solve problems on the contact interaction of layers in structurally inhomogeneous shells of revolution with allowance for both the normal and tangential stresses in the contact zones. A system of algebraic equations is constructed by using a method for solution of static problems for arbitrary shells of revolution. From this system, the contact zones and contact stresses are determined by the iteration method. The restricted behavior of the adhesion layer in cleavage and shear is taken into account. As an example, the stress state of a two-layer cylindrical shell under a concentrated load is determined     

Nonstationary Displacements in an Axisymmetric Problem for an Elastic Half-Space Under Mixed Boundary Conditions*

International Applied Mechanics - The strain state of an elastic half-space under a non-stationary normal load acting on its boundary is determined. A mixed boundary-value problem is stated. Its...     

Elastoplastic antiplane strain in an incompressible body

Antiplane strain in an incompressible cylindrical body is studied within the framework of a nonlinear model. The system of equations is reduced to a second-order nonlinear equation for the displacement. It is shown that the type of the equation is determined by the strain potential and can be mixed. An example of the strain in a hollow elliptic cylinder is considered, for which a displacement of the screw dislocation type is found and the corresponding stresses and load are studied.     

Hydrodynamic drag of an ellipsoidal droplet at small Reynolds numbers

At present, there is an absence of the accurate data on the influence of the shape of a droplet on its hydrodynamic drag and mass transfer without which the design of mass transfer apparatus is impossible [1–3]. Most often it is assumed that the drag of an ellipsoidal liquid droplet as it moves along the axis of symmetry is determined by the product of the drag of a spherical liquid droplet and a coefficient which takes into account the shape and is determined from the drag of a solid ellipsoid for which the exact solutions are known. It is shown below that this assumption is not always valid.Translated from Tzvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 4–8, May–June, 1987.