US3680397A - Method of forming workpieces by means of underwater impact pressure - Google Patents

Method of forming workpieces by means of underwater impact pressure Download PDF

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Publication number
US3680397A
US3680397A US16736A US3680397DA US3680397A US 3680397 A US3680397 A US 3680397A US 16736 A US16736 A US 16736A US 3680397D A US3680397D A US 3680397DA US 3680397 A US3680397 A US 3680397A
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United States
Prior art keywords
ignition
discharge
capacitor battery
wire
occurs
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Expired - Lifetime
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US16736A
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English (en)
Inventor
Jochen Haeusler
Gunther Marz
Helmut Seiffert
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Siemens AG
Siemens Corp
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Siemens Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D26/00—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces
    • B21D26/02—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces by applying fluid pressure
    • B21D26/06—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces by applying fluid pressure by shock waves
    • B21D26/10—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces by applying fluid pressure by shock waves generated by evaporation, e.g. of wire, of liquids

Definitions

  • the invention relates to a method of forming workpieces by means of underwater impact pressure which occurs during an explosion-like evaporation of an ignition wire clamped between electrodes defining an underwater spark gap.
  • the explosion-like evaporation is produced by an underwater spark discharge of a capacitor battery.
  • the method increases the degree of effectiveness by avoiding the so-called dark interval.
  • a capacitor battery is discharged via a spark gap which is located in a liquid such as water.
  • the sparkover between the spark gap electrodes causes the formation of a vapor column maintained under high pressure.
  • the expanding vapor column drives the pressure wave, in form of impact waves, through the liquid.
  • the impact waves strike and form the workpiece.
  • the wires which evaporate explosion-like in response to a capacitor discharge, must frequently be selected to have a length sufficient to produce impact pressures thereby rendering the occurrence of a dark interval or dead time unavoidable.
  • the dark interval there is an interruption of the discharge of the capacitor and thus an interruption of the conversion of the stored energy, as happens, for example, during the forming operation performed on a workpiece.
  • the occurrence of the dark interval is explained as follows.
  • the ignition wire becomes so quickly heated, molten and evaporated, that a metal vapor column forms under extremely high pressure.
  • the column occurs because the mediumsurrounding the wire, for example water, impedes the free expansion of wire material because of its mass inertia.
  • the high pressure does not permit impact ionization in the metal vapor, wherein a metallic conductor is no longer feasible, because the atomic spacing is too great. This renders the wire material, that at first bridges the electrode gap, non-conductive within a few microseconds, thereby interrupting the discharge.
  • the use of underwater pressure impact produced by wire explosion led to the discovery, in forming technology, that the impact pressure which occurs with the first discharge pulse, performs the main share of the forming work.
  • This can be easily understood in connection with discharges where a reignition does not occur, for example, because the dark interval has a longer duration that the conductive state of the high-voltage switch.
  • the high-voltage switch serves to connect the capacitor battery to the discharge channel. During such discharges, more than 90 percent of the stored energy may remain in the capacitor battery, so that the processing may be carried out only with minimal effectiveness.
  • the discharge channel which is apparently very low ohmic or of very low resistance following the reignition, absorbs only a small amount of the remaining energy still stored following the dark interval, while the principal portion of the residual energy is dissipated in the unavoidable connecting lead resistance following reignition.
  • the capacitor battery is discharged in time-sequential discharge steps via a plurality of ignition wires and in such a manner that upon the occurrence of a dark interval, the ignition wire of the discharge channel which is connected first to the capacitor battery, is connected in parallel with another discharge channel.
  • the invention offers a fundamentally new improvement in the effectiveness due to geometrical adjustment, in addition to the already known improvements in the degree of efiiciency, whereby the improvement according to the invention lies in avoiding the dark interval by means of discharge channels ignited in sequence.
  • FIG. la illustrates the known arrangement and basic circuit diagram for the expansion of a tube by means of underwater wire explosion
  • FIG. lb shows the discharge curve which occurs during the discharge according to FIG. In;
  • FIG. 2a illustrates a basic circuit arrangement for carrying out the method of our invention wherein three tubes are arranged for expansion by means of underwater wire explosion;
  • FIG. 2b shows the discharge curve which occurs during the discharge sequence according to the invention.
  • FIG. 3 is a schematic diagram for an arrangement for the expansion of a tub according to the method of the invention.
  • FIG. 1a shows how, with an underwater wire explosion, an elongated tube is expanded in a conventional manner by discharging a capacitor battery.
  • Reference numeral 11 denotes the capacitor battery, 12 the tube to be processed, 13a and 13b the insulating parts, 14 the ignition wire, 15 the water and 16 a three electrode spark gap, as a high-voltage switch.
  • the tube or pipe 12 is sealed in a known manner by insulating portions 13, through which the ignition wire 14 leads into the interior of the tube.
  • the tube 12 is filled with water 15.
  • FIG. lb illustrates the discharge curve which occurs during the switch-on of the spark gap 16.
  • the abscissa represents the time t and the ordinate represents the discharge voltage U and the discharge current 11,.
  • the broken line 17 shows the load voltage U of the capacitor battery 1 l.
  • the curve 18 indicates the voltage curve during the discharge of the capacitor battery 11. From FIG. lb, it is evident that the degree of efficiency obtained during the forming process is limited by the fact that during the first current pulse 1'01, only a slight discharge occurs in the time interval t -t and that the second current pulse i performs no forming work following the reignition in the ignition wire 14 subsequent to the dark interval DP.
  • FIG. 2a shows a basic circuit arrangement illustrating how three tubes can be expanded with a stepwise discharge sequence according to the method of our invention.
  • the stepwise discharge utilizes the energy stored in a capacitor battery in such a manner that each pipe or tube is provided with a separate discharge channel and with its own high-voltage switch.
  • Reference numeral 21 depicts the capacitor battery; 22, 23 and 24 are the tubes to be expanded, for example steel tubes; 25, 26 and 27 are ignition wires; 28a, 28b and 28c, 28d and 28e, 28f indicate the insulating parts and 29, 210 and 211 denote three electrode spark gaps which perform as high-voltage switches.
  • the tubes 22, 23 and 24 are sealed in a known manner by insulating parts 28a to 28f through which the corresponding wires 25, 26 and 27 lead into the interior of each tube and each tube is filled with a medium 212a, 212b and 212e, such as water.
  • FIG. 2b illustrates the discharge curve U which occurs during the performance of the method of FIG. 2a.
  • the abscissa represents the time t and the ordinate represents the discharge voltage U and the discharge current i.
  • U depicts the load voltage of the capacitor battery 21.
  • U U and U are the voltage curves occurring with the respective closings of the high voltage switches.
  • the three electrode spark gap 29 is ignited and the discharge process is thereby initiated via 7 the ignition wire 25.
  • the wire 25 is heated up so fast, melted and vaporized that a vapor column develops under extremely high pressure.
  • the high pressure does not permit any impact ionization in the metal vapor.
  • the wire material which first bridges the electrode gap becomes non-conductive within a few microseconds and the discharge is interrupted.
  • the three electrode spark gap 210 isignited whereby the discharge via wire 26 occurs.
  • the dark interval sets in here, too, following the decay of the current pulse i at a time the next three electrode spark gap 211 is ignited and the discharge current pulse i is continued via the ignition wire 27. This may be continued during the distribution of the discharge to a plurality of workpiece processes for so long as the impact pressures, the energy of which decreases, suffice for a given forming operation.
  • FIG. 3 illustrates that the improvement in effectiveness obtained with the method of the invention by means of a sequential supply of discharge channels that optimally convert the energy discharged by a capacitor, is not necessarily dependent on providing several faster high-voltage switches, such as spark gaps or ignitrons. Rather, the mechanical action of the pressure waves which were already produced by the preceding discharge, may be utilized as a mechanically operating switch, or the thermal effect of the first discharge can release new discharge channels which convert the energy to a maximum, by means of planned insulation damage.
  • FIG. 3 illustrates such an arrangement for expanding a tube.
  • the reference numeral 31 denotes the capacitor battery; 32 the three electrode spark gap; 33 the high-voltage electrode; 34 the ground electrode; 35 and 36 the ignition wires; 37 an insulation tube; 38 the tube to be processed; 39a and 39b the insulation parts; 310 the transport disc and 311 the pressure channels.
  • the ignition wires 35 and 36 are guided in the insulating portions 39a and 39b through the bored electrodes 33, 34.
  • the ignition wire 35 has contact with the high-voltage electrode 33 and with the ground electrode 34, so that following the ignition of the spark gap 32 at the time t the discharge of the capacitor battery 31 is initiated.
  • the ignition wire 36 is connected only to the ground electrode 34 and is, moreover, covered by the insulating tube 37, which has less thermal and mechanical stability but more resistance to high voltages.
  • the tube 37 may comprise foils of low pressure polyethyls of about 0.3 mm wall thickness, the foils being particularly well suited therefor.
  • the insulating tube 37 becomes mechanically or thermally destroyed, especially in the high voltage electrode 33, after the start of the dark interval in the ignition wire 35, the discharge may be continued over the ignition wire 36.
  • the high-voltage electrode 33 is so constructed that in addition to the aforedescribed damage to the insulation, the impact pressure issuing from the ignition wire 35 can establish contact between the high-voltage electrode 33 and the ignition wire 36 in still another manner.
  • the insulating tube 37 is constructed in two parts with both parts overlapping at 312. The shorter portion, which is the upper part in FIG. 3, of the tube 37 is affixed to a transport disc 310, which disc is in the high voltage electrode 33.
  • a transport disc 310 which disc is in the high voltage electrode 33.
  • the accelerated transport disc 310 carries along the end of the insulating tube 37 attached thereto and closes the connection between the high-voltage electrode 33 and the ignition wire 36.
  • the switching-on of new discharge channels through planned insulation damage can also be realized by an ignition means, having conductive and insulating layers disposed in an alternating sequence in a concentric arrangement, so that the respective discharges weaken, by means of a conducting layer, the insulation layer disposed adjacent thereto to such an extent that the voltage which remains during the dark interval punctures the insulation layer and continues the discharge via the next-succeeding conductive layer.
  • a method of forming workpieces by undersurface pressure waves generated by an explosion-like vaporization of an ignition wire initiated by an undersurface spark discharge of a capacitor battery, the ignition wire being tensioned between the electrodes of an undersurface spark gap which method includes the step of continuously discharging a charged capacitor battery by sequentially applying the charged capacitor battery across a plurality of ignition wires, so that each successive ignition occurs at a time when the current in the next preceding ignition wire material ceases to flow, whereby a continuous conversion of the energy stored in the capacitor battery occurs.
  • the capacitor battery is connected across a plurality of ignition wires through a single high-voltage switch, and wherein the method includes the step of closing the switch to sequentially apply the battery to each of said ignition wires, so that each successive ignition occurs at a time when the current in the immediately preceding ignition wire material substantially ceases to flow.

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  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
US16736A 1969-03-06 1970-03-05 Method of forming workpieces by means of underwater impact pressure Expired - Lifetime US3680397A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE19691911424 DE1911424A1 (de) 1969-03-06 1969-03-06 Verfahren zum Bearbeiten von Werkstuecken mittels Unterwasser-Druckstoessen

Publications (1)

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US3680397A true US3680397A (en) 1972-08-01

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US16736A Expired - Lifetime US3680397A (en) 1969-03-06 1970-03-05 Method of forming workpieces by means of underwater impact pressure

Country Status (6)

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US (1) US3680397A (de)
AT (1) AT298208B (de)
CH (1) CH497930A (de)
DE (1) DE1911424A1 (de)
FR (1) FR2037677A5 (de)
GB (1) GB1294240A (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4030329A (en) * 1976-07-12 1977-06-21 Viktor Nikolaevich Chachin Device for electrical discharge forming
US6383152B1 (en) * 1997-01-24 2002-05-07 Siemens Aktiengesellschaft Apparatus for producing shock waves for technical, preferably medical applications
US20050185356A1 (en) * 2004-02-23 2005-08-25 Phoenix Contact Gmbh And Co. Kg Overvoltage protection element and ignition element for an overvoltage protection element

Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2435301A1 (fr) * 1978-09-05 1980-04-04 Barras Provence Procedes et dispositifs hydro-electriques pour fixer simultanement de facon etanche plusieurs tubes d'un faisceau sur une plaque
US4635840A (en) * 1980-07-07 1987-01-13 Matija Cenanovic Forming method using an electromagnetically exploded filament
DE3170485D1 (en) * 1980-07-07 1985-06-20 Matija Cenanovic Pipe repair methods and apparatus using an electromagnetically exploded filament
RU2125496C1 (ru) * 1997-10-08 1999-01-27 Волгоградский государственный технический университет Электрогидроимпульсный способ запрессовки труб в труднодоступных местах
RU2167734C2 (ru) * 1998-12-07 2001-05-27 Научно-исследовательский институт высоких напряжений при Томском политехническом университете Устройство для электрогидравлической развальцовки трубок
US7827838B2 (en) 2008-05-05 2010-11-09 Ford Global Technologies, Llc Pulsed electro-hydraulic calibration of stamped panels
US7802457B2 (en) 2008-05-05 2010-09-28 Ford Global Technologies, Llc Electrohydraulic forming tool and method of forming sheet metal blank with the same
US7516634B1 (en) 2008-05-05 2009-04-14 Ford Global Technologies, Llc Electrohydraulic forming tool
US7810366B2 (en) 2008-05-05 2010-10-12 Ford Global Technologies, Llc Electrohydraulic trimming, flanging, and hemming of blanks
US8534106B2 (en) 2009-10-19 2013-09-17 Ford Global Technologies, Llc Hydromechanical drawing process and machine

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3203212A (en) * 1963-03-01 1965-08-31 Lockheed Aircraft Corp Explosive forming by electrical discharge method and apparatus
US3208254A (en) * 1960-04-23 1965-09-28 Inoue Kiyoshi High pressure generating apparatus
US3228221A (en) * 1961-09-18 1966-01-11 Aerojet General Co Apparatus for forming material
US3232086A (en) * 1962-12-07 1966-02-01 Inoue Kiyoshi Spark pressure shaping

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3208254A (en) * 1960-04-23 1965-09-28 Inoue Kiyoshi High pressure generating apparatus
US3228221A (en) * 1961-09-18 1966-01-11 Aerojet General Co Apparatus for forming material
US3232086A (en) * 1962-12-07 1966-02-01 Inoue Kiyoshi Spark pressure shaping
US3203212A (en) * 1963-03-01 1965-08-31 Lockheed Aircraft Corp Explosive forming by electrical discharge method and apparatus

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4030329A (en) * 1976-07-12 1977-06-21 Viktor Nikolaevich Chachin Device for electrical discharge forming
US6383152B1 (en) * 1997-01-24 2002-05-07 Siemens Aktiengesellschaft Apparatus for producing shock waves for technical, preferably medical applications
US20050185356A1 (en) * 2004-02-23 2005-08-25 Phoenix Contact Gmbh And Co. Kg Overvoltage protection element and ignition element for an overvoltage protection element
US7817395B2 (en) * 2004-02-23 2010-10-19 Phoenix Contact Gmbh & Co. Kg Overvoltage protection element and ignition element for an overvoltage protection element

Also Published As

Publication number Publication date
DE1911424A1 (de) 1970-09-24
CH497930A (de) 1970-10-31
AT298208B (de) 1972-04-25
GB1294240A (en) 1972-10-25
FR2037677A5 (de) 1970-12-31

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