Underwater Wire Research Articles

“Water bath” effect during the electrical underwater wire explosion

The results of a simulation of underwater electrical wire explosion at a current density >109A∕cm2, total discharge current of ∼3MA, and rise time of the current of ∼100ns are presented. The electrical wire explosion was simulated using a one-dimensional radiation-magnetohydrodynamic model. It is shown that the radiation of the exploded wire produces a thin conducting plasma shell in the water in the vicinity of the exploding wire surface. It was found that this plasma shell catches up to 30% of the discharge current. Nevertheless, it was shown that the pressure and temperature of the wire material remain unchanged as compared with the idealized case of the electrical wire explosion in vacuum. This result is explained by a “water bath” effect.

Strongly coupled copper plasma generated by underwater electrical wire explosion

A number of theoretical approaches to the analysis of the parameters of a discharge channel consisting of strongly coupled plasma generated in the process of underwater electrical wire explosion are presented. The analysis is based on experimental results obtained from discharges employing Cu wire. The obtained experimental data included electrical measurements and optical observations from which information about the dynamics of the water flow was extrapolated. Numerical calculation based on a 1D magnetohydrodynamic model was used to simulate the process of underwater wire explosion. A wide range conductivity model was applied in this calculation and good agreement with a set of experimental data was obtained. A method of determining the average temperature of the discharge channel based on this model and experimental results is proposed, and the limits of this method's applicability are discussed.

Simplified model of underwater electrical discharge.

A model of the underwater discharge with initiating wire is presented. The model reveals the nature of similarity parameters which have been phenomenologically introduced in earlier experimental research in order to predict behavior of different discharges. It is shown that these parameters naturally appear as a result of the normalization of differential equations, which determines the process of underwater wire initiated discharge. In these equations the energy conservation law for wire material evaporation and the dependence of plasma conductivity on the energy dissipated in the discharge are implied to calculate the time varying resistance of the discharge gap. The comparison of calculations with the experimental results shows that good agreement is achieved when modification of these parameters is introduced. These new similarity parameters are functions of the original similarity parameters, hence the law of the similarity of underwater electrical discharge is preserved.

Experimental investigation of bublles by underwater wire exploding

The pulsation of bubbles generated by underwater wire exploding is studied by means of high-speed photography. We discovered that mechanical parameters of the b ubbles are mainly determined by the total discharge energy and related not much to the voltage and the capacitance. Boundary influence is also not too large in the experiment. The energy of pulsation occupies 20%—40% of the total discharg e energy, and the proportion between the pulsation energies of the first time an d the second time is about this value. The bursting forth phenomenon is the main reason of the decline of bubble's energy.

THE PHENOMENON OF DISCHARGING INTWICE OF UNDERWATER WIRE EXPLODING

The phenomenon of discharging in twice of underwater wire exploding is discovered-by investigating the time characteristics of pulsed discharging current and voltage. Pictures taking by high-speed shadow photography and streak camera have testified the existence of the phenomenon. Parameters related to the phenomenon are presented in this paper.

Propagation of fuel-coolant interactions in multi-jet experiments with molten tin

Abstract A study of the propagation of fuel-coolant interactions (FCI) has been carried out, using a so called droplet curtain arrangement of molten tin in the water. To create the two-dimensional arrangement of the droplet curtain, the melt was heated up in a rectangular crucible with an exchangeable steel plate in which holes were bored with the desired diameter at corresponding distances. By tilting the crucible, multi-jets of hot molten tin flow through the holes side by side into a container filled with water and the jets disintegrate into several smaller jets of droplets. An interaction was triggeres in the water container at the first drop chain by a shock wave generated by an underwater bridge wire explosion. A propagation of interactions from edge to edge took place for instance with the following parameter combination: tin temperature 650°C, water temperature 70°C, hole diameter 5 mm and the distance between holes 25 mm. This parameter combination yielded an average propagation velocity in the horizontal direction of 2.7 m/s and in the vertical direction of 2.1 m/s.

Metal Forming by Underwater Wire Explosions : 2. Experiments on Bulging of Circular Aluminum Sheets by Copper Wire Explosions

Experiments on high speed bulging are presented under various die diameters and sheet thicknesses, and the results are compared with the analytical results of the first report. The final deflections of the sheets can be estimated by the impulse of the pressure pulse measured by Hopkinson pressure bar. The process of the bulging measured by a high speed camera differs from the analytical one; the differences between them are discussed by the theory on wave propagation and reflection. Supplementary experiments on two dimensional bulging of rectangular sheets are made and the effect of the cavitation beneath the sheet on the bulging is examined.

Metal Forming by Underwater Wire Explosions : 2nd Report, Experiments of Bulging of Circular Aluminum Sheets by Copper Wire Explosions

Metal Forming by Underwater Wire Explosions : 2nd Report, Experiments of Bulging of Circular Aluminum Sheets by Copper Wire Explosions

Pressure Pulses Produced by Underwater Wire Explosions in Electric Discharge Metal Forming

The impulsive pressure pulses arising from copper wire explosions are measured using Hopkinson pressure bar technique under various charging voltages up to 63 kV, charging energies up to 2.6 kJ, natural frequencies of the discharge circuit from 10 kHz to 50 kHz and various wire dimensions, and impulses which are defined as time integral of the pressure pulse are obtained. The decays of a pressure pulse and an impulse during propagation are represented by the ratio of stand-off distance to length of the wires. Taken together with the previous paper, the dependencies of peak values and impulses of the pressure pulses upon the energies consumed in exploding wires are obtained. It is also shown that, when charging energies are held constant, low voltage (and thus large capacity) and high voltage (and thus small capacity) are equally efficient provided that the optimum wire dimensions are chosen for each case.

Metal Forming by Underwater Wire Explosion : 1. An Analysis of Plastic Deformation of Circular Membranes Under Impulsive Loading

The plastic deformation of circular membranes of a strain-rate dependent, work-hardening metal is analyzed based on the strain increment theory. Numerical solutions for aluminum membranes are obtained under various types of loading as well as impulsive pressure pulses caused by underwater wire explosions. When the duration of a loading pulse is less than one-third of the time required to finish the deformation of the membrane, the deflection of a deformed membrane depends almost only on the impulse of the loading pulse and the instantaneous profile of the membrane is found to be trapezoidal during deformation. The relation between impulse of loading and deflection is calculated and illustrated. The forming limit due to peripheral necking is discussed. The neglect of strain-rate dependency of material leads to a notable underestimation of the forming limit.

Metal Forming by Underwater Wire Explosion : 1st Report, An Analysis of Plastic Deformation of Circular Diaphragms under Impulsive Loading

Metal Forming by Underwater Wire Explosion : 1st Report, An Analysis of Plastic Deformation of Circular Diaphragms under Impulsive Loading

Pressure Waves Produced by Underwater Wire Explosions in Electric Discharge Metal Fonning

Pressure Waves Produced by Underwater Wire Explosions in Electric Discharge Metal Fonning

Über die Ausbreitung von Stoßwellen elektrischer Drahtexplosionen in Wasser

Abstract Pressure profiles of shod: waves of underwater wire explosions are recorded by means of piezoresistive pressure probes at different distances from the wire. Basing on an expansion of the theory of Brinkley and Kirkwood the time behaviour of characteristic quantities of the shock waves for a large intervall of the travelling distance can be determined by only a few measured values. In this way also statements may be made about the behaviour of the shock wave at those distances at which direct measurements are not possible. Furthermore, conclusions on the conditions for the formation of the shock wave can be made.