FRICTION STIR WELDING METHOD AND DEVICE, AS WELL AS WORKPIECE COMPRISING A BUTT WELD SEAM

Abstract

A welding device (70) includes a probe assembly (90) including at least a first and second probe device (100a, 100b). A first and second part (31a, 31b) to be joined along the weld line (40) are provided, wherein the parts are each formed as a laminate (1; 1) including at least a first layer (2a, 2b) formed with a first material and a second layer (5a, 5b) formed with a second material. The first and second materials have different material properties. The method friction stir welds of the parts using the welding device, wherein simultaneously the first probe device acts on the first layers and the second probe device acts on the second layers.

Claims

1. A workpiece component of an aircraft or spacecraft comprising: a first part and a second part are each formed of a fiber metal laminate including a metal layer and a synthetic layer with embedded reinforcing fibers; a first edge of the first part next to a second edge of the second part are aligned such that the metal layer of the first part and the metal layer of the second part are aligned in a first plane and the synthetic layer of the first part and the synthetic layer of the second part are aligned in a second plane parallel to the first plane, and first and second butt weld seams between and joining the first edge of the first part and the second edge of the second part, wherein the first butt weld seam is in the first plane and is between and joins the metal layers of the first and second parts, and the second butt weld seam is in the second plane and is between and joins the synthetic layers of the first and second parts.

2. The workpiece component according to claim 1, wherein the workpiece component is configured as a vessel of a storage tank for liquefied gas on the aircraft or space craft.

3. A friction stir welding device configured to join two parts along a butt joint weld line, the friction welding device comprising: a probe assembly including a first probe and a second probe, wherein the first probe is configured to friction stir weld a first layer in each of the two parts along the butt joint weld line, wherein the second probe is configured to friction stir weld a second layers in each of the two parts along the butt joint weld line, and wherein the two parts when friction stir welded along the butt joint weld line form a laminate in which the first layers have different material properties than the second layers.

4. The friction stir welding device according to claim 3, wherein the first layers of the two parts have a different thermal conductivity than the second layers of the two parts, wherein the first probe is configured to friction stir weld a metal layer to a metal layer, and wherein the second probe is configured to stir weld a synthetic layer to a synthetic layer.

5. The friction stir welding device according to claim 3, wherein the first layers of the two parts are metal layers, and the second layers are synthetic layers are a thermoplastic matrix embedded with reinforcing fibers.

6. The friction stir welding device according to claim 3, wherein the probe assembly is configured to be moved along the butt joint weld line during the friction stir welding of the two parts and/or the first probe and the second probe are arranged coaxially.

7. The friction stir welding device according to claim 3, wherein: the first probe includes a first probe body having an axial length adapted to a thickness of the first layers of the two parts, and the second probe includes a second probe body adapted to a thickness of the second layers of the two parts.

8. The friction stir welding device according to claim 7, wherein the first probe body includes a first hollow shaft, and the second probe body includes a second shaft coaxial with and extending through the first hollow shaft.

9. The friction stir welding device according to claim 7, wherein the first probe body has a first outer diameter and the second probe body has a second outer diameter, wherein the first outer diameter is larger than the second outer diameter.

10. The friction stir welding device according to claim 7, further comprising a driver actuator configured to rotate the first probe body and simultaneously rotate the second probe at a rotational speed different than a rotational speed of the first probe body.

11. The friction stir welding device according to claim 10, wherein the first probe body and the second probe body each include a sprocket or gear configured to engage with and be driven by the driver actuator.

12. The friction stir welding device according of claim 3, further comprising a third probe with a third probe body coaxial with the first probe body and the second probe body.

Description

[0049] In the figures of the drawing, elements, features and components which are identical, functionally identical and of identical action are denoted in each case by the same reference designations unless stated otherwise. Elements of the drawings are not necessarily drawn to scale.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0050] FIG. 1 (a) and FIG. 1 (b) show a fiber metal laminate 1, configured as a hybrid layered material with two metal layers 2, 3 and an interposed synthetic layer 5 between the metal layers 2, 3. The metal layers 2, 3 are each formed from an aluminum alloy. The synthetic layer 5 comprises, in the exemplary laminate 1 of FIGS. 1 (a) and 1 (b), two synthetic sublayers 7 and 8.

[0051] In FIG. 1 (c), another exemplary fiber metal laminate 1 is illustrated, which comprises three metal layers 2, 3 and 4 with two interposed synthetic layers 5 and 6. The metal layers 2, 3, 4 and the synthetic layers 5, 6 of the laminate 1 are alternatingly arranged one upon another. The metal layers 2, 3, 4 of the laminate 1 are each formed from an aluminum alloy. In FIG. 1 (c), the synthetic layer 5 comprises two synthetic sublayers 7 and 8, and the synthetic layer 6 comprises two synthetic sublayers 9 and 10.

[0052] The aluminum alloy from which the layers 2, 3 or 2, 3 and 4 are formed may, for example, be an aluminum-magnesium-scandium alloy or AlMgSc alloy. Such AlMgSc alloys have optimal material properties at temperatures up to approximately 400 C. and can be advantageous in terms of performance, e.g. with regard to the fatigue behavior, of workpieces formed from the laminate 1 or 1.

[0053] Each of the synthetic layers 5 and 6 is formed with a matrix 13 of a thermoplastic material, in particular a high performance thermoplastic, which for example may be any of a polyphenylene sulfide or PPS, a polyimide or PI, a polyaryletherketone or PAEK. For example, the thermoplastic material used to form the matrix 13 may be a polyetherketone or PEK or a polyetheretherketone or PEEK or a polyetherketoneketone or PEKK. These thermoplastics are weldable and re-weldable.

[0054] The sublayer 7 and 8 of the synthetic layer 5 shown in FIG. 1 at (a) and (b) may be formed as thickness regions of an integral layer 5. In each sublayer 7, 8, reinforcing fibers 14 are embedded in the matrix 13. More specifically, in the first thickness region or sublayer 7, the fibers 14 extend substantially perpendicular to the plane of projection of FIG. 1 (b) and (d), while in the second thickness region or sublayer 8, the fibers 14 extend substantially parallel to that plane of projection. The exemplary configuration of the sublayers 7, 8 is shown in more detail in FIG. 1 (d). The sublayers 9, 10 of the synthetic layer 6 may be configured in the same manner. However, the fibers 14 may in other examples be arranged different from the exemplary configuration displayed in FIG. 1, in accordance with the mechanical properties of the laminate 1 or 1 that are desired, and accordingly, more or fewer sublayers may in variants be provided for the synthetic layer(s) 5 and/or 6.

[0055] FIGS. 1 (a) and (b) show two metal layers 2, 3 and a single synthetic layer 5. FIG. 1 (c) shows three metal layers 2, 3, 4 and two synthetic layers 5, 6. Different numbers of metal and/or synthetic layers are within the scope of the invention. Fiber metal laminates such as laminates 1 or 1 have less weight than comparable solid metal sheets, for example, and also display a better fatigue behavior than such solid sheets.

[0056] FIG. 2 schematically shows an arrangement for friction stir welding of two sheet-type sections or parts 31a and 31b of a workpiece, which in FIG. 2 are configured as two separate pieces that are joined by the friction stir welding process. Each part 31a and 31b is configured as a laminate formed with at least one first layer which is formed as a metal layer, and at least one second layer which is formed as a synthetic layer. In exemplary manner, each of the parts 31a, 31b may be formed from the fiber metal laminate 1 or 1 described herein above, or may be formed from a variant of laminates 1, 1 having a different number of metal and/or synthetic layers and/or a different arrangement of synthetic sublayers.

[0057] Accordingly, in exemplary manner, the first layer is formed with a first material, which is a metal such as an aluminum alloy, and the second layer is formed with a second material, which is a thermoplastic synthetic matrix 13 with embedded reinforcing fibers 14. The first layer may correspond to the metal layer 2, and the second layer may correspond to the synthetic layer 5. The parts 31a, 31b in accordance with embodiments described in the following further include a third layer corresponding to the metal layer 3, and may in variants additionally include a fourth layer corresponding to synthetic layer 6 and fifth layer corresponding to metal layer 4.

[0058] In the following, a method of friction stir welding and a welding device 70 will be described in exemplary manner and more detail with reference to the laminate 1.

[0059] The arrangement of FIG. 2 includes a friction stir welding device 70 adapted to join the two parts 31a, 31b along a butt joint weld line. The friction stir welding device 70 comprises a probe assembly 90 and a drive arrangement 60 for rotationally driving the probe assembly 90. A shoulder 95, also displayed in FIG. 2, may optionally be provided, as part of the device 70, or may be omitted. In the arrangement of FIG. 2, the friction stir welding device 70 is mounted on a robotic device 50.

[0060] In order to form a butt weld seam, the sheet-type parts 31a and 31b are arranged such that an edge 32a of part 31a faces an edge 32b of part 31b. The parts 31a, 31b are moved towards each other such that the edges 32a, 32b are substantially parallel and adjacent to each other, and in particular such that the parts 31a, 31b abut against each other along the adjacent edges 32a, 32b.

[0061] The relative positions of the parts 31a, 31b may then be fixed by one or more devices, e.g. jig(s), not shown in the Figures. Then, friction stir welding of the two pieces 31a, 31b is performed using the welding device 70, which is moved along the adjacent edges 32a, 32b by the robotic device 50.

[0062] The materials of the metal layers 2, 3, 4 and of the synthetic layers 5, 6 have material properties different from each other. In particular, the thermal conductivities of the layers 2, 3 or 2, 3 and 4 are different from those of the layers 5, 6. The friction stir welding device 70 is configured to perform friction stir welding for joining the parts 31a, 31b simultaneously through the entire thickness of the laminate, e.g. 1 or 1, from which the parts 31a, 31b are formed, in a manner which joins corresponding ones of the layers, e.g. 2, 5, 3 or 2, 5, 3, 6, 4, individually along the butt weld seam that is formed. More specifically, in this way, corresponding layers formed from the same material can be individually joined across the weld line. Using the welding device 70, this is accomplished while at the same time, the different material properties of these layers are taken into account. The configuration of the welding device 70 will now be described with reference to an exemplary embodiment, illustrated in FIGS. 3 and 4, in which the optional shoulder 95 is omitted.

[0063] The welding device 70 comprises the probe assembly 90, which includes in this embodiment a first probe device 100a, a second probe device 100b and a third probe device 100c.

[0064] The first probe device 100a comprises a probe body 101a and a central shaft 102a. The shaft 102a extends from one end face of the probe body 101a. The probe body 101a has a substantially circular outer cross-section, may be substantially cylindrical, and has an outer diameter Da as well as an axial length ta. Further, the shaft 102a may be substantially cylindrical, but has a diameter that is smaller than Da. At a first end of the shaft 102a, the shaft 102a is connected to the probe body 101a for co-rotation therewith, and in the vicinity of a second end of the shaft 102a, opposite the first end thereof, the shaft 102a is provided on an outer peripheral surface thereof with a toothing, which forms a sprocket ring or gear 103a. The probe body 101a and the shaft 102a are connected such as to be substantially coaxially arranged. The first probe device 100a comprises a central internal passage 104a which axially extends through the probe body 101a and the shaft 102a. At opposite ends of the probe device 100a, i.e. at an end face of the probe body 101a oriented away from the first end of the shaft 102a, and at the second end of the shaft 102a, the passage 104a is open towards the outside.

[0065] The second probe device 100b comprises a probe body 101b and a central shaft 102b. The shaft 102b extends from one end face of the probe body 101b. The probe body 101b has a substantially circular outer cross-section, may be substantially cylindrical, and has an outer diameter Db as well as an axial length tb. Further, the shaft 102b may be substantially cylindrical, but has a diameter that is considerably smaller than Db. At a first end of the shaft 102b, the shaft 102b is connected to the probe body 101b for co-rotation therewith, and in the vicinity of a second end of the shaft 102b, opposite the first end thereof, the shaft 102b is provided on an outer peripheral surface thereof with a toothing, which forms a sprocket ring or gear 103b. The probe body 101b and the shaft 102b are connected such as to be substantially coaxially arranged. The second probe device 100b comprises a central internal passage 104b which axially extends through the probe body 101b and the shaft 102b. At opposite ends of the probe device 100b, i.e. at an end face of the probe body 101b oriented away from the first end of the shaft 102b, and at the second end of the shaft 102b, the passage 104b is open towards the outside.

[0066] The third probe device 100c comprises a probe body 101c and a central shaft 102c. The shaft 102c extends from one end face of the probe body 101c. The probe body 101c has a substantially circular outer cross-section, may be substantially cylindrical, and has an outer diameter Dc as well as an axial length tc. Further, the shaft 102c preferably is substantially cylindrical, but has a diameter that is considerably smaller than Dc. At a first end of the shaft 102c, the shaft 102c is connected to the probe body 101c for co-rotation therewith, and in the vicinity of a second end of the shaft 102c, opposite the first end thereof, the shaft 102c is provided on an outer peripheral surface thereof with a toothing, which forms a sprocket ring or gear 103c. The probe body 101c and the shaft 102c are connected such as to be substantially coaxially arranged. The shaft 102c may be solid.

[0067] The length ta is adapted depending on a thickness t2 of the metal layer 2, the length tb is adapted depending on a thickness t5 of the synthetic layer 5, and the length tc is adapted depending on a thickness t3 of the metal layer 3, see also FIG. 4. In particular, the lengths ta, tb, tc are selected such that approximately ta=t2, tb=t5 and tc=t3.

[0068] The diameters Da, Db and Dc are individually chosen depending on the properties of the layers 2, 5 and 3, respectively, to be welded. Ideal values of Da, Db and Dc for given thicknesses and materials may be found by experiment. In the exemplary embodiment of FIGS. 3 and 4, the metal layers 2 and 3 are formed from the same aluminum alloy, and t2=t5=t3. In FIGS. 3 and 4, the diameters Da, Db and Dc as well as lengths ta, tb and tc are selected such that approximately Da=Dc and Da>Db and ta=tb=tc. In some variants, each of t2, t5 and t3 may be less than or equal to 1.0 mm. Other layer thicknesses t2, t5, t3 are conceivable.

[0069] FIG. 3 also illustrates that in order to assemble the probe assembly 90, the shaft 102b is inserted into the passage 104a and is rotatable within the passage 104a, and the shaft 102c is inserted into the passage 104b and is rotatable within the passage 104b. In an assembled state of the probe assembly 90, the probe bodies 101a, 101b and 101c abut against each other in this order, and the probe devices 100a, 100b and 100c are coaxially arranged and rotatable with respect to each other about a common axis of rotation 105, as shown in FIG. 4.

[0070] Axial lengths of the shafts 102a, 102b, 102c are chosen such that in the assembled state of the probe assembly 90, the shaft 102b outwardly protrudes from the second end of the shaft 102a, and that the shaft 102c outwardly protrudes from the second end of the shaft 102b, in such a manner that the each of the sprockets or gears 103a, 103b and 103c is accessible.

[0071] FIG. 4 shows the assembled probe assembly 90 during friction stir welding of the two parts 31a and 31b. In FIG. 4, for the parts 31a, 31b, the layers 2, 3 and 5 as well as the sublayers 7 and 8 are labelled 2a, 3a, 5a and 7a, 8a, as well as 2b, 3b, 5b and 7b, 8b, respectively. The layer thicknesses t2, t5 and t3 are indicated for the layers 2a, 5a and 3a of part 31a only, but are the same for the layers 2b, 5b and 3b of part 31b.

[0072] The drive arrangement 60 comprises several drive shafts 110a, 110b and 110c. The drive shafts 110a, 110b and 110c can each be rotatably driven. The drive shaft 110a comprises a sprocket ring or gear 111a configured to mesh with the sprocket ring or gear 103a for rotationally driving the shaft 102a and the probe body 101a. The drive shaft 110b comprises a sprocket ring or gear 111b configured to mesh with the sprocket ring or gear 103b for rotationally driving the shaft 102b and the probe body 101b. The drive shaft 110c comprises a sprocket ring or gear 111c configured to mesh with the sprocket ring or gear 103c for rotationally driving the shaft 102c and the probe body 101c. The meshing toothings provided by the sprocket rings or gears 103a and 111a, 103b and 111b, 103c and 111c, respectively, may in some embodiments be configured to provide a suitable transmission ratio, e.g. for changing the angular velocity of the shaft 102a, 102b or 102c in comparison with that of the assigned drive shaft 110a, 110b or 110c, respectively.

[0073] By the drive arrangement 60, the probe devices 100a, 100b and 100c are each simultaneously driven for rotation thereof about the common axis of rotation 105. A rotational velocity of each drive shaft 110a, 110b and 110c is preferably individually controllable and adjustable. For example, the rotational velocities of the drive shafts 110a-c may each be steplessly controllable. At least, however, the rotational velocity of the drive shaft 110b can be selected or is set in such a manner that a rotational velocity of the probe body 101b is different from rotational velocities of the probe bodies 101a and 101c, which for example may be substantially equal.

[0074] FIG. 4 also shows that during friction stir welding, each of the probe bodies 101a-c is in contact with corresponding ones of the layers 2a and 2b, 5a and 5b or 3a and 3b, respectively. In particular, each pair of corresponding layers is made from the same material. The probe devices 100a, 100b and 100c simultaneously act on the layers 2a-b, 5a-b and 3a-b, respectively. During the friction stir welding process using the welding device 70, the layers 2a and 2b are individually welded to each other, the layers 5a and 5b are individually welded to each other, and the layers 3a and 3b are individually welded to each other.

[0075] For example, for the same thickness t2=t3=15 of metal layers 2, 3 and synthetic layer 5 with thermoplastic matrix 13, due to the lower thermal conductivity of the thermoplastic, a but joint weld line within the thermoplastic layers 5a,b is preferably narrower than within the metal layers 2a,b and 3a,b, in order for the heat to penetrate this width, and hence Db<Da and Db<Dc. Moreover, an increased amount of heat may be needed in the thermoplastic layers 5a,b, and in order to generate a sufficient amount of friction in the thermoplastic layers 5a,b at the joint, the rotational velocity, i.e. angular velocity, of the probe body 101b used to weld the thermoplastic layers 5a-b is preferably higher than the rotational velocity, i.e. angular velocity, of the probe bodies 101a and 101c. Larger diameters Da, Dc and lower rotational velocities are preferable for the probe bodies 101a,c used for welding the metal layers 2a-b, 3a-b. Each probe device 100a-c is thus rotated at an individually chosen rotational velocity.

[0076] The outer diameters Da, Db, Dc and the rotational velocities of the probe bodies 101a, 101b and 101a are adapted to the requirements of the material of each layer 2, 5, 3, so that the layers 2a-b, 5a-b and 3a-b, respectively, can each be joined using optimal welding parameters adapted to the particular material, in particular to the metal material and the thermoplastic matrix 13.

[0077] The probe assembly 90 is moved as a unit along the butt joint weld line 40, defined by adjacent edges of the parts 31a, 31b, whereby a butt weld seam 45 is formed. This is shown in the perspective illustration in FIG. 5, in which the parts 31a, 31b have, in order to illustrate a further variant, each been turned by 90 degrees compared with FIG. 4, so that the fiber orientations in sublayers 7a-b, 8a-b are different from those in FIG. 4. Regarding the optional shoulder 95 shown in FIG. 2 but not present in the situation of FIG. 5, in case the shoulder 95 is optionally provided, it essentially abuts on the top faces of the adjacent parts 31a, 31b, has a diameter larger than the probe body 101a, and may be rotationally fixed or may rotate about the axis 105 during friction stir welding. Alternatively, the shoulder 95 may not be necessary and may be omitted. Such a shoulder 95, which may rotate at a lower rotational velocity than the probe device(s), e.g. 100a, or may be rotationally fixed, may be useful to maintain the contour on the top face of the material if the topmost layer is made with a thermoplastic matrix. If, as in the embodiments described with reference to FIGS. 1-5, the topmost layer is a metal layer 2, the shoulder 95 is not necessary, but a co-rotating shoulder 95 may in some variants be helpful in the case of a thicker metal layer 2.

[0078] In other embodiments, the probe assembly 90 may comprise two probe devices for welding sections or parts of a two-layer laminate, not shown in the Figures, or the probe assembly may comprise more than three probe devices, e.g. five probe devices for welding sections or parts of the laminate 1 of FIG. 1 (c). In other words, each individual layer in a great variety of fiber metal laminates can be processed in appropriate manner. Symmetry of the layer arrangement of the laminate with respect to a center main plane of extension thereof, which would be horizontal e.g. in FIG. 4, is not required. Layers, e.g. metal or synthetic layers, having different thicknesses within one laminate can be processed.

[0079] In a variant, it may be conceivable to provide a probe set, as schematically illustrated in FIG. 3, with a number of different probe devices, e.g. more than three, that can be assembled and re-assembled in various configurations of the probe assembly 90, which can then be coupled to the drive arrangement 60 for being used for friction stir welding. This may enable increased flexibility e.g. for adjusting the probe body diameters.

[0080] The method of friction stir welding and the friction stir welding device of the invention, of which embodiments are described above, in particular make it possible to obtain one or more of the following advantages:

[0081] Individual attention can be paid to the temperature requirements and heat conductivity for each material for the friction stir welding, which is made possible by enabling probes to rotate at different rotational velocities.

[0082] Individual attention can be paid to the ideal weld line width for each layer, by enabling the probes to be provided with individual probe diameters.

[0083] Efficient and fast welding of fiber metal laminates is made possible, the efficiency and speed being comparable to friction stir welding of monolithic parts from a single material.

[0084] Analogous advantages can be obtained for a workpiece having a butt weld seam created in line with the invention.

[0085] FIG. 6 shows an exemplary aircraft 200 having a fuselage 201, a nose 202, an empennage 203, wings 204 and engines 205. In exemplary manner, the aircraft 200 is configured as a passenger aeroplane. The aircraft 200 is provided with a hydrogen-based propulsion system. In particular, the engines 205 may be configured as gas turbines adapted for combustion of hydrogen with oxygen for the purpose of propulsion. Further, the aircraft 200 may be provided with one or more fuel cells 206, only schematically indicated in FIG. 1, adapted to generate electrical power using hydrogen as well as oxygen. Electrical power obtained in this way may alternatively be used for propulsion. Further, the aircraft 200 may comprise a hybrid hydrogen-based arrangement for propulsion and energy supply, including both combustion of hydrogen in the jet engines 205 as well as fuel cells 206 for generation of electricity to supply various devices in the aircraft 200. Such aircraft 200 may be considered zero emission aircraft, avoid the emission of carbon dioxide during flight, and can significantly contribute to sustainable, environment-friendly air travel, by virtue of hydrogen-combustion and/or hydrogen-electric propulsion.

[0086] While the oxygen can be obtained from the ambient air, liquid hydrogen is stored within the aircraft 200 in one or more storage tanks 207. Preferably, the hydrogen is cooled down to a temperature of 253 C. and stored in liquid form, so as to minimize the volume required to store a quantity of hydrogen with a given energy content. A storage tank 207 for liquified, cryogenic hydrogen in accordance with an embodiment of the invention is schematically shown in FIG. 7. The hydrogen-based propulsion system of the aircraft 200 is supplied with hydrogen from the storage tank 207.

[0087] The liquid hydrogen storage tank 207 of FIG. 7 has a generally elongate shape and comprises a pressure vessel 208 as well as further installations, not shown in detail, which may be provided for filling the storage tank 207 and for supplying the hydrogen from the storage tank 207 e.g. to the engines 205 or fuel cells 206. Preferably, thermal insulation may be provided as well.

[0088] The vessel 208 is elongate and comprises a substantially cylindrical center section 209 as well as two dome-shaped end sections 210. The center section 209 and the dome-shaped end sections 210 are joined at peripheral butt weld seams 211 which follow an approximately circular path. Moreover, the center section 209 comprises a longitudinal butt weld seam 212 which serves, in the example displayed, for joining ends of a sheet of material that has been bent to form a cylinder. Alternatively, for instance, the center section 209 may be formed from shell-type sections, and in this case, the center section 209 may comprise two or more longitudinal butt weld seams 212.

[0089] Within the vessel 208, the liquid, cryogenic hydrogen will be stored. The vessel 208 is adapted to be pressurized, e.g. due to evaporation of liquid hydrogen, which then fills a space inside the vessel 208 above the liquid level. For example, the vessel 208 may be configured to safely sustain an internal pressure of at least approximately 3 bar, but the vessel 208 may in variants be designed for internal pressures higher or lower than 3 bar.

[0090] A vessel wall 213 of the vessel 208 is formed, in both the center section 209 and the end sections 210, from the fiber metal laminate 1 or 1, described above with reference to FIG. 1, or from a variant of such a laminate as described above.

[0091] The butt weld seams 211 and 212 are formed in an optimized and efficient manner in the way described above with reference to FIGS. 1-5, using the friction stir welding device 70 of the embodiments explained above. In this way, a pressurizable vessel 208 having seams 211, 212 of high quality can be made in a reasonable, expedient, quick and efficient manner from a fiber metal laminate, and is advantageous with regard to its reduced weight and improved fatigue behavior compared to a vessel made from solid metal sheets. When the butt weld seams 211 and 212 are formed, sections of the laminate forming the vessel wall 213 of the vessel 208 are joined as parts 231a, 231b of a workpiece, in a manner analogous to joining the parts 31a, 31b in FIGS. 2-5. In FIG. 7, this is indicated in exemplary manner for the longitudinal butt weld seam 212.

[0092] Producing the vessel 208 as a workpiece from a fiber metal laminate using the friction stir welding process and device 70 in accordance with the invention, of which embodiments are described herein above, thus provides the following further advantages:

[0093] Particularly efficient welding of longitudinal weld seams for forming cylindrical tubes, and of peripheral seams for joining end domes to such tubes, is made possible, for instance for producing liquid hydrogen storage tanks.

[0094] Using quick and efficient friction stir welding, a cryogenic tank material can be provided which is lighter and has a better fatigue behavior than monolithic aluminum alloys, and also has better characteristics than a pure composite laminate with respect to permeation and static electricity.

[0095] Although the invention has been completely described above with reference to preferred embodiments, the invention is not limited to these embodiments but may be modified in many ways.

[0096] In particular, the friction stir welding method and device of the invention may be used to form many other kinds of workpieces, for non-structural or structural applications, beyond the field of storage tanks for liquified gas.

[0097] While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms comprise or comprising do not exclude other elements or steps, the terms a or one do not exclude a plural number, and the term or means either or both, unless the this application states otherwise. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.

LIST OF REFERENCE SIGNS

[0098] 1, 1 fiber metal laminate [0099] 2, 3, 4 metal layer [0100] 5,6 synthetic layer [0101] 7, 8, 9, 10 synthetic sublayer [0102] 13 matrix [0103] 14 reinforcing fibers [0104] 31a, 31b part [0105] 32a, 32b edge [0106] 40 butt joint weld line [0107] 45 butt weld seam [0108] 50 robotic device [0109] 60 drive arrangement [0110] 70 friction stir welding device [0111] 90 probe assembly [0112] 95 shoulder [0113] 100a first probe device [0114] 100b second probe device [0115] 100c third probe device [0116] 101a,b,c probe body [0117] 102a,b,c shaft [0118] 103a,b,c sprocket ring or gear [0119] 104a,b passage [0120] 105 axis of rotation [0121] 110a,b,c drive shaft with sprocket ring or gear [0122] 111a,b,c sprocket ring or gear [0123] 200 aircraft [0124] 201 fuselage [0125] 202 nose [0126] 203 empennage [0127] 204 wing [0128] 205 engine [0129] 206 fuel cell [0130] 207 storage tank [0131] 208 vessel [0132] 209 center section [0133] 210 dome-shaped end section [0134] 211 peripheral butt weld seam [0135] 212 longitudinal butt weld seam [0136] 213 vessel wall [0137] 231a, 231b part [0138] Da first outer diameter (probe body of first probe device) [0139] Db second outer diameter (probe body of second probe device) [0140] Dc third outer diameter (probe body of third probe device) [0141] ta, tb, tc axial length (probe body) [0142] t2, t3 layer thickness (metal layer) [0143] t5 layer thickness (synthetic layer)