The present invention relates to a method for plastically deforming a body, in particular a sheet body, whereby the body is positioned in a mould cavity of a mould between a first mould section and a second mould section, and the body is subjected to a deformation force, which is directed towards a mould surface of the first mould section, in order to plastically deform the body and to conform it at least substantially to the mould surface. The invention also relates to a device for plastically deforming a body, in particular a sheet body, comprising a mould with a first mould section and a second mould section which mutually enclose a mould cavity, holding means to partly receive the deformed body in the mould cavity between both said mould sections and pressurizing means which, during operation, are capable of and equipped to subject the body to a deformation force directed toward the first mould section and to plastically conform the body to a mould surface of the first mould section facing the body.

The plastic deforming of bodies, in particular metal sheets, is employed on a large scale in mechanical manufacturing processes in order to form parts, semi-finished products and finished products. Usually this involves positioning the body in a mould and forcing it against a mould surface provided for this purpose so that it conforms to it.

For this purpose one can make use of processes which, as a rule, are referred to as static or quasi-static such as deep drawing. Thereby the mould surface extends between a first mould section and an at least almost complementary opposing mould section while enclosing the sheet body in between. Both mould sections are

(hydro)mechanically brought together under a (extremely) large force so that the body is permanently plastically deformed into a shell portion in accordance with the available mould surface. Thus a seamless three-dimensional form can be given to it. One drawback of such a deep drawing technique is the relatively high cost and depreciation of the moulds used and the machinery required for it. Nevertheless, a big advantage is the excellent control and manageability of the process, resulting in a large degree of precision.

A cheaper solution is offered by deforming techniques usually referred to as dynamic, whereby a high ambient pressure is briefly applied to a side of the body in the mould cavity which is averted from the mould surface. For this purpose a pyrolytic gas may be detonated or else, for example, an electrostatic discharge or a heat pulse of a laser may be achieved. An advantage of these techniques is the great speed with which the body can be shaped into the desired form, in addition to the relatively low installation costs of the machinery and moulds to be used. However, an important disadvantage is the relatively low process control, partly due to the turbulence which is inevitably part of this process.

The present invention inter alia aims to provide for a deformation technique which combines the mentioned advantages of both know techniques without, however, inheriting the disadvantages to an equally large extent. In order to achieve the intended goal a method of the type described in the opening paragraph is characterized in that a first fluid is admitted into the mould cavity on a side of the body, which is averted from the first mould section, whereby the first fluid comprises a gas, compressed under pressure, which has departed from a gaseous state of aggregation, and in that a second fluid is admitted into a mould cavity, which is at least partly filled with the first fluid, at a temperature above a boiling point of the first fluid in order to allow the first fluid to expand, while forming a pressure wave to force the body against the mould surface of the first mould section. The bringing together of both fluids results in an ultra rapid phase transition of the first fluid which thereby expands while forming a pressure wave. In practice this pressure wave proves to be of a sufficient magnitude to force the (sheet)body against the mould surface while plastically deforming it permanently.

By admitting both fluids in a controlled manner this expansion is to a large extent controllable and the process remains to a large extent manageable and checkable. A preferred embodiment of the method is therefore characterized in that at least one of the first and second fluid is admitted in a controlled manner via adjustable means of admission. A particular preferred embodiment of the method according to the invention is characterized in that the first fluid is admitted in at least one of a solid, wet and supercritical state of aggregation. By bringing the first fluid, while in this state, into contact with the proportionally "hot" second fluid in the mould cavity an ultra rapid phase transition is achieved bringing about a pressure wave, which is strong enough to plastically deform the material of the body.

In principle gases, i.e. matter that is usually gaseous at room temperature and atmospheric pressure, are particularly suitable as a first fluid, but in practice particularly good results can be obtained with a particular embodiment of the method, characterized in that the first fluid comprises at least one medium from a collection including carbon dioxide, argon and nitrogen.

In order to supply the first fluid with an extra amount of energy so that a faster and stronger expansion can be achieved, a further preferred embodiment of the method according to the invention is characterized in that the second fluid is heated before being admitted into the mould cavity, and furthermore in particular the second fluid includes vapour.

In order to be able to mitigate the expansion process, if desired, a further preferred embodiment of the method according to the invention is characterized in that the first fluid is guided through controllable heating means before being admitted into the mould cavity. Thus process parameters can be optimally set and chosen to control and manage the entire process adequately. Although the previously described ultra rapid phase transition and the expansion of the first fluid accompanying this is in itself sufficient for a plastic deforming of the (sheet)body, a particular embodiment of the method according to the invention is nevertheless characterized by admitting a pyrolytic gas into the mould cavity and igniting it. Thus the method can be supplemented by more conventional pyrolytic deformation, in addition to a (hydro)mechanical force which may be exercised by admitting one or both of the fluids in the mould cavity under pressure. Therefore the method offers a wide range of deformation techniques, which in practice can be selected and adapted, as one sees fit. The required pyrolytic gas or gas mixture is advantageously obtained via electrolysis or catalysis in-situ.

A device for plastically deforming a body under the influence of pressurizing means, of the type described in the opening paragraph, is characterized, according to the invention, in that the pressurizing means comprise means for generating a pressure wave, whereby the pressurizing means for this purpose comprise adjustable first means of admission for the controlled admission of a compressed first fluid into the mould cavity which are connected to compression means capable of and set up to compress a gas, in particular the first fluid, under increased pressure, to an aggregate state deviating from the gas phase, and whereby the pressurizing means for this purpose comprise adjustable second means of admission for the controlled admission of a second fluid into the mould cavity which are connected to heating means for heating the second fluid to above a boiling point of the first fluid.

For quick operation and a short repetition cycle one preferred embodiment of the device according to the invention is characterized in that the compressor comprises a buffer space in which the fluid is preservable under increased pressure and in that the adjustable means of admission of the fluid comprise adjustable atomizer means between the mould cavity and the buffer space, which open out into the mould cavity and are in open communication with the buffer vessel via an inlet. A further preferred embodiment of the device according to the present invention is characterized in that at least one part when in contact with the fluid under increased pressure or increased temperature comprises a medium selected from a group comprising titanium, silicon, aluminium or a combination thereof. A further preferred embodiment of the device according to the present invention is characterized in that a buffer vessel comprising at least one section is wire wound, in particular with a mineral wire, a metallic wire or a plastic wire.

In view of the ultra rapid inlet and pressure resistance of the means of admission a preferred embodiment of the device according to the invention is characterized in that the means of admission comprise atomizer means with a pyrolytic and/or magneto- rheological and/or electro-rheological empowered seal.

The invention will now be explained further based on an example of an embodiment and an accompanying drawing. The drawing shows:

Figure 1 a schematic reproduction of a processing plant with an example of an embodiment of a device according to the invention for execution of an example of the embodiment of the method according to the invention; Figure 2 a cross section, a mould as used in the plant in figure 1; and

Figure 3 a detailed cross section of the means of admission as used in the plant in figure 1.

Incidentally, the figures are purely schematic and not always drawn to scale. In particular, for the sake of clarity some of the dimensions may have been reproduced to a greater or lesser extent in an exaggerated manner. In general, corresponding sections in the figures are referred to with the same reference number. A work piece (body), such as a metal or plastic sheet or a profile, is positioned inside a cavity (34) or a mould. The mould comprises one or more sections which enclose said cavity and enables the body to be shaped into a hollow or otherwise profiled product. Figure 1 shows a double sided die, but in practice also a single sided die can be used to form the work piece into shape. The work piece will hereinafter be referred to as blank.

The sections (19,25) of the mould can be closed by means of a hydraulic cylinder (18) powered by a hydraulic pump (38) to apply a closing force preventing or limiting leakage between these sections. Such closing and clamping provisions are also seen in hydroforming or quick plastic forming processes. One section surrounding the cavity may have a form, shape or curvature to assist the flow of a forming medium, this is preferably the side (25) where a working fluid like gas is introduced. The closing means between the upper tool half and the lower tool half may comprise a blank holder (26). Such a blank holder acts as a clamping or gripping device to provide a pressure on the work piece other than the closing force between the sections (19,25). The cavity is connected to a gas supply (1, 2, 2a), as depicted in figure 1, by means of channels which are used for supply of gas. At least one channel is used for supply of gas at temperatures below gas specific triple-point, hereafter referred to as "cold gas". At least one channel is being used for supply of gas above gas specific triple point, hereafter referred to as "hot gas". This triple-point can be derived from phase diagrams describing the different phases.

A portion of cold gas is introduced into the cavity by means of valve operation (3). The gas flow is directed into a diverter station (7) at a pressure preferably higher than 20 bar. Inside the diverter station (7) the gas flow is directed by appropriate valve operation towards valve (36). This valve can direct the gas flow towards a feeding arrangement which is equipped to control a density of the cold gas (31). As a result cold gas will be introduced into the cavity as solid gas particles ranging from

micrometre sizes to millimetre sizes. A means of producing solid gas particles is represented. Such means could form a part of the density control section (31).

It is also possible to supply liquid gas to the cavity (34) by means of valve operation (3), for direct feeding into the diverter station (7) where a valve directs the gas flow through a compressor (24), and a recovery unit (16) where by-pass connections direct the gas flow towards a valve/pump (15) and, then, into the cavity (34).

When, instead of liquid gas, a gaseous flow is preferred, then the compressor may supply air by blowing air through a non-return valve (one-way-valve) which is present inside the recovery unit. There it meets with the liquid gas flow, whereupon mixing of cold gas at a temperature and a defined portion of air can take place. This air is generally provided at ambient temperature. The mixing of air at ambient temperature and a portion of liquid gas will result in transformation of liquid gas to a gaseous state. This gas flow can be directed to valve (15) and into the cavity.

Following the introduction of solid gas particles inside the cavity, a gas flow at far higher temperatures is introduced into the cavity. As s result a process will unfold which is commonly referred to as rapid phase transition ( PT). Such type of phase transition is able to produce pressure waves or Shockwaves under the condition that the energy transfer between the cold gas flow and hot gas flow is in balance. This is the case when the portion of hot gas is large enough for the portion of cold gas particles to sublimate at a high rate. The rate and force of this phase transition happens to be high enough to deform the work piece.

To provide the required amount of energy, a portion of gas is being heated. The temperature difference between the cold gas and hot gas may range from 20 C° to more than 1000 C°. Such high temperatures can be achieved totally through external heating prior to introducing gas into the cavity. Gas is heated inside a reactor-array (6) by means of a catalytic reaction. This gas can be supplied from a gas storage (1, 2, 2a) by means of valve operation (3) and feeding into a pump unit (4). The pump-unit may comprise a pump, temperature sensors, pressure sensors, valves, couplings, piping sections and the like.

Inside the pump unit the temperature of the gas flow is measured. Feeding to the reactor is only allowed to take place when gas temperatures are higher than the gas specific triple point. Normally, gas from the gas storage (1,2,2a) is stored at a temperature below the operational temperature of the reactor. To achieve a temperature elevation in case the initial gas temperature is too low, heating must take place. When the heater (5) reaches a temperature preferably higher than said triple point, gas is being pumped into the heater (5) by means of the pump unit (4).

After the gas has been pre-heated, it is directed through the diverter station (7) where the gas flow is being directed to the reactor (6). Inside the reactor-array (6) gas is heated to temperatures preferably higher than 150 C°. After this heating arrangement the gas flow turns back into the diverter station (7) which further comprises a high pressure pump, such as a pump for supercritical fluids. By means of this pump, the gas flow is being pumped under high pressure into an intermediate storage facility, such as a rectifier vessel (32) or high pressure container (8).

During normal operation it may be economical to re-use gas which has been used during forming-operations. In this manner, processed gas leaving the cavity through pump (15) is directed into a recovery unit (16). This recovery unit comprises of a storage container which volumetric capacity is sufficient to contain at least the volume of the cavity when filled under high pressure. The recovery unit further comprises of piping connections, a temperature and pressure sensor, a safety valve, non-return valves and a pressure regulator. The gas pressure exiting the cavity forces a non-return valve inside the recovery unit to open through which gas flows into a storage container of the recovery unit. The pump (15) only assists when the pressure exiting the cavity drops below the pressure inside the storage container of the recovery unit (16), and will operate until the gas volume inside the cavity has been evacuated. Evacuation is said to have taken place when the pressure inside the cavity has reached ambient pressure.

Once filling of the gas storage container inside the recovery unit (16) is completed, the pressure and temperature are measured. When the gas temperature is sufficient, the gas flow will be directed through the diverter station (7) and into the reactor-array (6). When used for rapid phase transition, the gas temperature exiting the cavity will be below the operating temperature of the reactor-array (6). When this temperature is below this value, then the gas flow will be directed through diverter station (7) and to valves (35) and (3). From this point the gas flow needs to follow the heater routing as described hereinbefore.

Gas may be heated and pumped into a rectifier vessel (32) or high pressure container (8), when the temperature in the rectifier vessel (32) drops more than 10% below the normal feeding temperature on leaving the reactor-array (6). The gas flow can be reheated by means of redirecting the gas flow through valve (35) and (3). From this point the gas flow needs to follow the heater routing as described before until the temperature inside the rectifier vessel has been compensated. Heat compensation can also be provided by means of direct heating of pressure vessel (8) or (32). The reactor-array (6) preferably comprises multiple reactors, and each reactor is provided with an internal structure comprising reactor channels. The diameter of these channels is preferably as small as possible to achieve a large surface area per unit volume. Because micro sized reactors may add substantial costs to the production of the reactors, also additional length of each individual channel may be provided for to obtain more reactive surface area. The maximum internal channel diameter preferably stays below 4 millimeters in order to avoid runaway reactions from the gas flow. Determination of the diameter range is highly dependent on the catalyst formulation and crystallite size, and furthermore on the initial gas flow conditions and type of gas. Appropriate diameters are ranging from 20 micrometers ranging up to 4 millimeters in diameter. Said flow takes place in an environment where flow conditions, such as pressure and volume are controlled by pressure regulators and valves. All gaseous or otherwise fluid media are transported and controlled independently in order to avoid undesired mixtures.

By passing a gas flow through a reactor a temperature elevation of the gas flow of at least beyond the specific triple-point temperature of the gas entering the reactor is achieved. Preferably a temperature rise of at least 150 C° above ambient temperature is imposed. Higher temperatures may be achieved by changing the composition of a specific catalyst formulation inside the reactor. Preferably a catalyst formulation is chosen containing metallic substances, like Magnesium, so that the maximum temperature of gas exiting the reactor-array (6) will be below a recrystallization temperature of the catalyst material. In practice a temperature even higher than 250 C° may be chosen in this manner.

Typically several reactors of the same type can be coupled parallel for initial capacity demands of the process, or incorporated later, at any time, for possible up scaling purpose. Regardless the number of reactors, it is hereafter referred to as "reactor- array".

The internal channel structure of the reactors of the reactor-array contain a material acting as a catalyst. This catalyst can be coated to the surface of the internal wal ls of the channel structure as seen in microchannel reactors, or form an homogeneous structure which can be moulded, extruded, sintered or produced otherwise as to form a solid reactor with an internal structure as seen in monolith-type of reactors. The level of catalyst activity is related to the surface area of the catalyst. This, in turn, is related to the crystallite size. A preferred catalyst features a crystallite size of at least 2 nanometers and below 70 micrometers. The catalyst may comprise a metallic material, such as magnesium or compounds thereof, or any other composition acting as catalyst inside a channel structure.

Once the gas flow enters the reactor-array, the gas acts as reactant upon contacting the surface of the internal channel-like structure of the reactor array. This reaction results in elevated gas temperature and gas pressure. The temperature and/or pressure can be measured by means of thermocouples or pressure transmitters or by other measuring methods providing the same. The signal produced by this

measurement provide information through which the flow conditions, such as pressure of the initial gas flow can be regulated/adjusted prior to reactor entry. By altering the residence-time of the gas flow within the reactor-array it is possible to control the gas temperature to an order of 0.1 C° or better.

The reactant gasses (2, 2a) are preferably nitrogen, argon and/or carbon dioxide.

These gasses are handled separately throughout the total process. Carbon dioxide offers the advantage over Nitrogen of a more practical phase conversion temperature, whereas nitrogen provides a different chemical reactivity which may be preferred during production. A drawback of using Nitrogen is its low phase conversion temperature which is costly. Using both Nitrogen and Carbon dioxide covers the desired processing bandwidth. The availability of Argon (1) in the process provide an opportunity to mix Argon with Nitrogen or Carbon dioxide prior to transporting a gas into the reactor-array. By this means the intensity of the reaction can be lowered or additionally fine tuned. This is performed by means of a gas regulator at a set pressure and a mixing orifice or a gas mixer/gas blender providing the same. This step should be avoided when re-use of gas by means of the recovery unit (16) is targeted. The mixture ratio of Argon (1) can be adjusted to a maximum of 30% in case of mixing with Carbon dioxide or Nitrogen but preferably is below 7% in order to avoid an undesired low activity between catalyst and the reactant gasses during operation. Mixing Argon is advised up to the maximum mixture ratio only when calibration takes place after replacement of reactors or during initial process start-up after equipment installation. Then the reactor activity is measured and controlled as described. The level of activity within the reactor-array is essentially arranged by changing the residence time of Nitrogen or Carbon dioxide within the reactor-array while Argon is mainly used for tempering the catalytic activity inside the reactor.

Another purpose of Argon could be to secure initial flow conditions, such as avoiding a pressure drop below a critical value during operation. Otherwise the reactor activity could rise to undesired levels due to an extended residence time of Nitrogen or Carbon dioxide inside the reactor possibly leading to premature failure of a reactor. To avoid failure, the critical temperature should stay preferably 8% below the metallurgic recrystallization temperature of the catalyst used, while the normal range of operation is preferably 12% below recrystallization temperature. The reactor-array is equipped with measurement and controlling devices, such as sensors, transmitters, and controllers and the like, to measure temperature and pressure of the gas flow passing the reactor at multiple locations. When a

temperature rise is detected through sensors with value's exceeding normal operational range, a indication can be made of failing flow conditions. A second signal is provided by means of pressure transmitters fitted at both reactor entry and reactor exit. In case of failing gas flow conditions the reactant gas flow will be terminated by means of valve operation and Argon under elevated pressure will be transferred into the reactor-array. The pressure of the Argon (1) flow may be calibrated to achieve a transit time from Argon reaching the most remote distance of the reactor preferably below 2 seconds. By this means reactant gasses are evacuated rapidly preventing the temperature to rise further. The maximum residence time of Argon inside the reactor array should preferably stay below 3 to 4 seconds to avoid thermal shock.

Thermal shock is also suppressed by preheating of Argon. This is provided for by means of a heat exchanger with a volumetric capacity of preferably 10 times the available gas volume inside the reactor-array, and a heating capacity high enough to heat said volume of Argon within two minutes from the gas temperature exiting the main Argon gas storage up to at least 50% and preferably 65% of the temperature inside the reactor-array during normal operation. The heat exchanger and thus also the Argon gas are heated primarily by means of waste gas resulting from the process taking place inside the cavity.

Argon gas, still residing after flowing through the reactor-array, will be collected and diverted to a waste gas provision. In this case the gas is directed out of the reactor- array (6), through the diverter station (7), and from there towards a scroll

expander/heat exchanger (28). The scroll expander is a provision meant for energy recovery as it will expand a gas flow meanwhile lowering its temperature and collecting electricity by means of a rotating scroll and coupling of this scroll to a generator. A heat exchanger is being used (28) to recover excess heat. This recovered heat is primarily used for heating of Argon, and subsidiary to obtain a constant temperature inside the storage containers. The waste gas provision (20) may comprise a catalyst to lower emissions once the gas leaves the exhaust (37). For large installations a gas washing device may be used to decrease emissions.

After the reactant gasses, such as nitrogen or carbon dioxide, are heated as described in

the previous steps, the gasses may be stored inside a pressure vessel. Preferably two or more pressure vessels are being used for this purpose. In that case, during operation, one vessel can be filled with gas while a second vessel is used for supplying a medium for the metal forming operations. Switching between the pressure vessels is performed by means of a valve (39). This valve is operated based on a pressure dependent signal coming from a pressure transmitter. This transmitter communicates with a control unit, such as a PLC, where a pre-set pressure activates the valve between the vessels.

The pressure containers may comprise a number of parts or sections to form a center body. The sections are preferably of a same diameter and are enclosed between cone- shaped top and bottom sections. The sections may be treaded or otherwise equipped with locking means.

The high pressure containers (8, 32) are preferably wire wound with high strength wires such as Basalt fiber or Ultra high strength steel wire. Other high temperature resistant wires can be used.

The function of wire wound vessels, especially when pre-stressed prior to winding, are primarily to enable higher pressure regions without the need of excessive wall thickness of a pressure vessel. Pre-stressing also lowers fatigue risks, and provide additional safety in case of failure. A vessel may be cooled with Nitrogen and the like prior to, and during winding. All parts subject to elevated pressures and temperatures, such as (8,9,11,19,25,26,32) may comprise Ti (titanium), Si (silicium) or Ti (titanium) and Al (Alumina). A number of sealings subject to high pressure, such as sealings used in (8,9,11,19,25,26,32) may comprise Ti (titanium) and Nb (niobium) and compounds thereof.

The high pressure containers (8,32) further comprise an opening and closing means through which gas can be filled and released. Opening of the valve (23) enables filling of the manifolds (9) equally with a portion of gas preferably in supercritical state. The temperature of the gas may vary upon preferred process conditions from gas specific triple point to over 500 C°.

Valve (23) operation offers the functionality to enable controlled filling of portions supercritical fluids to the manifolds (9). By this means filling of the manifolds (9) is established at a pressure that is possibly different from the pressure inside the pressure containers (8,32).

Each individual manifold (9) is equipped with a valve on both entrance and exit side in order to control the pressure in which each manifold (9) is filled. By this means it is possible to control the gas release mode from each manifold individually.

The release of pressurized substances, such as gasses in supercritical state, from the manifolds (9) is performed by means of valve operation on the exit side of the manifold. Upon valve operation, a gas flow is initiated into the manifold connection (72) and into the shut-off nozzle. At the same moment of operating the valve on the exit side of the manifold, actuator (66) is operated providing an open connection between the manifold (9), the manifold connection (72), through channel (62) and nozzle cavity (58), and into the gas outlet (63).

The function of the channel (62) is to provide a delay functionality for the released supercritical fluid from the manifold to reach the needle holder (57). By this means the needle (55) and the needle holder are enabled to reach a completely opened position prior to the high pressure reaches the needle holder. If necessary, calibration on this motion can be established by adjusting the needle cap (56). This calibration is not be necessary during daily operation while the opening rate can be controlled by altering the velocity with which the actuator (66) travels.

The form, shape and/or curvature of the needle holder (57) enables compensation of the pressure acting on the needle holder from the side of the channel (62) and the counteracting pressure imposed from the side of the nozzle cavity (58) during operation.

This facilitates fast opening and closing rates and thus fast reaction time of the nozzle. The magneto-rheological dampener (64) has multiple functions. The first function is to dampen the velocity just before the needle-holder and needle reach their fully opened or fully closed position. This is necessary while the force imposed on the same must be high to reach the desired rate of opening and closing. Dampening would be required during opening to avoid the needle holder of striking the C-sealing (60) at a force possible leading to damage. During closing, on the other hand, dampening would be required to prevent the needle (55) striking the front end (59) from leading to rigorous damage. The second function of the magneto-rheological dampener to control the release from supercritical fluid exiting the manifold (9). To perform this it would be required to control the opening and closing position of the needle-holder and needle, the rate of the travelling stroke, and how fast the desired final position will be reached. The magneto-rheological dampener (64) provides the desired reaction speed, dampening profile, and dampening force to provide this action.

The magneto-rheological damper (64) further offers the advantage of very low contra- directional resistance against actuation as seen in common gas-dampeners and springs.

The needle-position sensor (61) provides a signal to a control unit through which the needle position can be monitored. This control unit can be programmed by means of software and communicates with the magneto-rheological dampener to establish the exact stroke position, stroke velocity, start,- and end position, and the dampening profile. Closing of the needle is provided by means of a actuator (67) acting force on the lever (70). The needle will be kept in its maximum closing position by means of a electro- rheological clutch (65) or the magneto-rheological damper (64). The actuator (66,67) is driven by electromagnetic force resulting from discharging energy from a accumulator like a capacitor-bank.

In the scope of the invention, the activation means can also be provided by electro- hydraulic force, in this case a capacitor discharge is fluid assisted to generate the described activation means.

A person skilled in the art has the option to choose between various types of shut-off nozzles, such as the shut-off nozzle shown in figure 3 or types that prove different opening and closing rates. Other means to control the velocity in which the lever travels can be found in a electro-rheological clutch. This clutch would then be connected to the pivoting axis of the lever (70) . The advantage of such a clutch is fast response, high power density and it can be used for reversible motion. The individual manifolds (9) can be heated by external means or by heat exchanger (28) through recuperation of gas via route (28, followed by 11).

With these means additional control of the gas pressure and gas temperature inside the manifolds can be arranged. If a higher temperature is required then provided through recuperation, then heater (30) is able to heat gas from the storage container through route (1 or 2, or 2a, followed by diverting through the diverter station (7), compressor (24), heater (30). In this case a by-pass connection / piping section must be installed between (30) and (11). Once the preferred pressure, density, and temperature of the gas inside the manifold is reached, a gas flow may be initiated out of the manifolds (9), through the nozzle- sections (10,11) and into the cavity (34) by said control means. The air or gas inside the cavity (34 ) is preferably evacuated prior to releasing gas and the feeding of cold gas particles.

The air between the workpiece (40) and the die (17) may be evacuated by means of a pump, such as a vacuum pump, or at least a venting arrangement as depicted in figure 1 (42). Such an evacuation is commonly undertaken at high velocity forming processes.

Hydrogen is used to cover higher strain rate regions then normally is achieved with heavy gasses, such as nitrogen, carbon dioxide, and argon. Hydrogen is one of the lightest abundant gasses and is highly flammable. With a catalytic hydrogen reactor (13), it is possible to produce di-atomic hydrogen in-situ, which would be favoured taking into account the present storage challenges and hazards. The procedure is to supply water (12) which can be pre-treated prior to feeding the catalytic hydrogen reactor (13). Inside the reactor, the water vapour reacts with a catalyst, such as magnesium, providing di-hydrogen to valve (14).

By means of valve (14) operation, the desired amount of di-hydrogen can flow inside the cavity (34). The valve (14) is preferably equipped with a flame-arrestor and may be a non-return type of valve. Air inside the cavity (34) must be evacuated prior to feeding di-hydrogen through valve (14). The air is said to be evacuated when the pressure inside the cavity (34) has reached vacuum. High vacuum is not desirable prior to feeding di-hydrogen due to explosion risks. Air or gasses inside the cavity (34) are evacuated through port (15).

Once the desired volume of di-hydrogen gas is present inside the cavity, valve (14) is closed, trapping di-hydrogen gas inside the cavity (34). The temperature / pressure inside the cavity (34) should be below an auto-ignition temperature of the gas. Ignition of di-atomic hydrogen is occurs by means of a spark generated by a spark plug (33). This action ignites the hydrogen and the resultant energy will force the work piece into the die (17). A safety vent (27) is provided functioning to divert overpressure, this safety vent may be equipped with a flame arrestor or be connected to an exhaust provision (37).

Providing di-atomic hydrogen may also be generated by means of Electrolysis.

This could be a PEM (proton exchange membrane) electrolyser (29) or other electrolyser providing the same. As a result, a gas flow is initiated from the electrolyser (29) towards valve (14) and inside the cavity (34). After this the mentioned procedure to evacuate air and igniting hydrogen should be undertaken.

Figure 1 also shows how the whole process may be incorporated into existing processes, also known as hydroforming processes . Through water supply (12), water flows through the hydraulic pump (21). This pump forces pressurized fluid through a intensifier (22) which intensifies the pressurized fluid to the desired pressure. The chosen pressure should be sufficient to force the work piece (40) to conform to the shape of the die (17). It is also possible to use other fluids or mixtures instead of water and mixtures thereof.

Figure 2 shows a cross-section of the mould shown in figure 1.

A work piece (80) is placed above the die cavity (93), where the workpiece is being clamped by means of closing the hydraulic cylinders (83). The hydraulic cylinders are supported by platens (82) in order to spread the closing force more evenly onto the lower tooling / die cabinet (84).

In practice, a profiled surface on a blank holder (86) can be provided in order to provide a different or non-linear clamping force along the surface of the blank holder. This can be applied to impose a pressure onto the workpiece which may be different then the closing/clamping force, and hence, provide different strains.

To force a work piece (80) into conformance with the shape of the die (81), a portion of cold fluidum, such as solid gas particles is provided through the Cold fluidum supply channel (89). The pressure inside the forming chamber (87) in this example is preferably atmospheric pressure.

The air temperature inside the forming chamber (87) can be measured by means of a thermocouple (92) and can be at or around ambient temperature. A lower temperature then ambient temperature is also possible, because this functions as a delay of sublimation from the solid gas particles which is being undertaken in this procedure. The air / available gas inside the forming chamber is evacuated prior to feeding of solid gas particles through a fluid release channel (88).

The amount of solid gas particles can be controlled by means of valve operation. The size of solid gas particles preferably varies from less then 1 micrometer to 4 or 5 millimeters. The pressure in which solid gas particles are brought into the forming chamber (87) is preferably around 2 Mpa but can be performed at a different pressure

After the portion of cold gas particles is forced in to the forming chamber (87), and appropriate valve operation blocks the inflow, then a portion of hot Fluid is supplied directly through supply (91).

In this example the pressure of the hot fluid in this example is 300 Mpa and the temperature of the hot fluid is 473 K. Once the portion of hot fluid and the portion of cold fluid interact a process unfolds commonly referred to as Rapid Phase Transition. During Rapid Phase Transition, solid gas particles carrying a temperature of 194 K, will be forced to sublimate at extremely high rate. This is caused by the high temperature difference while the inflowing hot fluid, such as carbon dioxide is in supercritical state at a temperature of 473 K. The temperature differential is in this case 279 K. The high rate of sublimation can produce a pressure wave or Shockwave.

The pressure rise time inside the forming chamber cavity (95), can be controlled effectively by altering the temperature or pressure of the inflowing hot fluid, the size and amount of the solid gas particles.

Releasing only a hot fluid under high pressure inside a closed system at atmospheric pressure and ambient temperature may also lead to the formation of a pressure wave. This is caused by instant superheating upon pressure relief, also known as BLEVE Reactions (Boiling Liquid Evaporation Explosions). Providing solid gas particles in such a system changes the number of nucleation sites and is functional to delay the path of the BLEVE reaction. The strain rate, which is a decisive parameter in High Energy Rate Forming processes (HERF) is hereby controlled more effectively. Formation of a Shockwave during depressurization is based on three impulses. The first impulse is created by the blow-down itself where acceleration of gas under high pressure exits the release means at such a high velocity that a Shockwave is sent out. The strength of this Shockwave is directly proportional to the gauge pressure of gas prior to venting. The second impulse occurs when gas in supercritical phase expands explosively due to rapid homogeneous nucleation. The third impulse occurs by rapid growth of a bubble followed after instant superheating. The expansion can lead to the formation of a Shockwave.

Avoiding a Shockwave can be controlled by means of lowering the release rate of the fluid. By this means the thermodynamic path will affect the mode of homogeneous nucleation. Then the fluid will expand at a lower rate allowing time for heat transfer between any gaseous medium which may be present inside the cavity and cavity walls. This lower rate process may still be fast enough to produce a pressure wave instead of a Shockwave. The described heat transfer is effectively controlled by the amount of solid gas particles, the density and size of the particles, and furthermore also dependent on the time between filling of the solid particles and release of hot fluid.

The pressure/pressure rise time inside the forming chamber (87) is monitored on the pressure transmitter (90). The strain rate is measured by means of calculating the time difference in which the pressure transmitters (85) are being contacted by the work piece (80) while being forced into the die cavity (93). The pressure transmitters also provide a measurement of the force in which the work piece (80) contacts the die (81). When the pressure still rises further after each of the pressure transmitters (85) are contacted by the work piece (80), an indication can be made that the pressure is above the value needed to form a specific work piece in conformance with the die.

Prior to forming a work piece (80) it is commonly undertaken in high rate forming processes, also known as impulse forming, to evacuate the air present inside the die cavity (93) prior to forming. This air can be evacuated by vacuum connection (94).

This aspect may be important to avoid entrapment of air inside the die cavity, possibly leading to non-complete forming. The scope of this invention is such that the pressure rise time can be controlled more effectively then with existing impulse forming processes.

While the invention was explained with the previously described embodiments.it is obvious that the invention is not limited hereto. On the contrary, within the scope of the invention there are many variations and embodiments possible for a person skilled in the art.