Patent Application
20070090155
This invention relates to friction welding and, more specifically, to friction welding of one or more structural members to form a tailored blank.
Structural devices are often formed as assemblies of a number of smaller structural members. Such assembling of individual members may be necessary to form devices that are too large or too complicated to be formed by conventional manufacturing methods. For example, such factors as casting sizes, forging sizes, available plate and block sizes, and the like can limit the size and geometry of the structural members that can be manufactured. To form larger or more complex devices, the structural members are typically assembled by joining the individual structural members using a variety of known joining techniques including, for example, mechanical fastening or welding.
Joints formed by mechanical fasteners such as rivets, screws, and bolts typically require an overlap of the structural materials at the joint. The fasteners and the overlap of material result in an increase in weight of the joint and the structural assembly. The joint can also introduce areas of increased stress, for example, around holes drilled for receiving rivets. Alternatively, weld joints can be formed to join the structural members, sometimes requiring little or no overlap of material. However, the formation of conventional weld joints, such as by arc or electron beam welding, can result in undesirable dimensional changes in the structural members. Welding can also introduce porosity or other discontinuities into the structural members or otherwise cause unwanted changes to the material properties of the structural members.
Friction welding has also been proposed as an alternative to conventional welding methods for joining members. Linear friction welding, and rotational friction welding can be used to form strong joints without reducing the mechanical characteristics of the joined materials or causing significant dimensional changes. Conventional linear friction welding and rotational friction welding require one member to be moved, i.e. oscillated or rotated, and urged against the other member.
It is known to friction weld structural members together to make a tailored blank that is later machined. Typically the tailored blank approximates the desired dimensions and configuration of the final structural assembly and therefore requires little machining or other subsequent processing to form the final structural assembly. There is a need for improvements in the art of friction welding structural members to make such tailored blanks.
The invention is directed to methods of friction welding structural elements to make tailored blanks that can be further processed into final structural assemblies. The invention is also directed to the resulting tailored blanks.
One aspect of the invention is a method of making a tailored blank comprising the following steps: (a) friction welding a first joining surface of a first structural member having a substantially non-rectangular parallelogram-shaped profile to a first portion of a surface of a substrate; and (b) concurrently linear friction welding first and second joining surfaces of a second structural member having a substantially non-rectangular parallelogram-shaped profile to a second portion of the surface of the substrate and to a second joining surface of the first structural member respectively, wherein the first and second portions of the surface of the substrate are adjacent.
Another aspect of the invention is a method of making a tailored blank comprising the following steps: (a) friction welding a first joining surface of a first structural member to a first portion of a joining surface of a substrate; and (b) concurrently linear friction welding first and second joining surfaces of a second structural member to a second portion of the surface of the substrate and to a second joining surface of the first structural member respectively, wherein the first and second portions of the surface of the substrate are adjacent, and the second joining surfaces of the first and second structural members are substantially planar, mutually substantially parallel and substantially normal to the substrate.
A further aspect of the invention is a method of making tailored blanks comprising the following steps: (a) placing a first structural member having a cross section that is substantially non-rectangular parallelogram shaped in abutting relationship with a structure comprising first and second surfaces disposed at an oblique angle, the first structural member comprising first and second surfaces that intersect at the oblique angle, a third surface substantially parallel to the first surface, and a fourth surface substantially parallel to the second surface, the first surface of the first structural member abutting a first portion of the first surface of the structure and the second surface of the first structural member abutting the second surface of the structure; (b) applying a force on the first structural member to respectively urge the first and second surfaces of the first structural member against the first and second surfaces of the structure; and (c) alternatingly displacing the first structural member in mutually opposite directions substantially parallel to the longitudinal axis of the first structural member while step (b) is being performed, causing frictional heat to be generated at a first interface where the first surfaces of the structure and the first structural member rub together and at a second interface where the second surfaces of the structure and the first structural member rub together, wherein step (c) is halted after material at the first and second interfaces becomes plasticized and while step (b) is being performed, step (b) being continued until the plasticized material at the first and second interfaces forms a weld.
Yet another aspect of the invention is a tailored blank comprising a substrate, a first structural member having a substantially non-rectangular parallelogram-shaped profile, a second structural member having the same substantially non-rectangular parallelogram-shaped profile, a first weld joint joining the first structural member to the substrate, a second weld joint joining the second structural member to the substrate, and a third weld joint joining the first structural member to the second structural member, the first and second weld joints being substantially coplanar, and the third weld joint being substantially planar and disposed at an acute angle relative to the first and second weld joints.
A further aspect of the invention is a tailored blank comprising a substrate, a first structural member having a polygonal profile, a second structural member having a substantially parallelogram-shaped profile, a first weld joint joining the structural member to the substrate, a second weld joint joining the second structural member to the substrate, and a third weld joint joining the first structural member to the second structural member, the first and second weld joints being substantially coplanar, and the third weld joint being substantially planar and disposed at an acute angle relative to the first and second weld joints.
Other aspects of the invention are disclosed and claimed below.
In a linear friction welding process, respective surfaces of two parts are placed in contact with each other to form an interface and then rubbed together in a reciprocating manner. This is accomplished by moving at least one of the parts back and forth along a line. As the parts are rubbed, compressive force is applied to place the interface under high pressure. At the interface, frictional heat is generated and material from each part plasticizes. Some of this material flows out from between the parts (flash flow), resulting in gradual decrease in the thickness, i.e. the dimension in the direction in which pressure is applied (the dimension normal to the interface) of the parts. When the process is terminated, flash flow ceases, and at the interface, the remaining plastic state material of each part forms a weld, thereby joining the two parts together.
The present invention involves a linear friction welding process wherein two non-parallel surfaces of one structural member are concurrently welded to respective surfaces of an intermediate tailored blank structure. In the embodiments disclosed herein, the intermediate tailored blank structure is itself formed by linear friction welding two structural members together. Various embodiments of the invention will be described with reference to the drawings, in which similar elements in different drawings bear the same reference numerals.
In accordance with a first embodiment of the invention, a tailored blank having a long flange or other long feature attached to a base member or substrate can be made by friction welding. The long feature in accordance with the first embodiment comprises one or more structural members in the form of a parallelepiped with two mutually opposing faces in the shape of non-rectangular parallelograms and four substantially rectangular faces. Two or more of such structural members can be welded end to end to form a long feature having a desired length.
Referring to the drawings, in accordance with the first embodiment of the invention, a base member or substrate (which terms are used interchangeably herein) 22 and structural members 24, 26, 28 (see
The structural assemblies of the present invention can be formed from any number of structural members depending on the desired dimensions and configuration of the structural assembly. Further, the configuration and material composition of the structural members can be formed and selected according to the specifications and design requirements of the final structural assembly. For example, as illustrated in
In the embodiment of a tailored blank depicted in
Advantageously, each of the base member 22 and the structural members 24, 26, 28 can be standard stock items in inventory. As is known in the art, the base and structural members 22, 24, 26, 28 can be formed from a variety of fabricating processes such as milling, casting, die or hand forging, extruding, rolling, and machining. The base and structural members 22, 24, 26, 28 can be formed from materials having high strength-to-weight ratios and good corrosion resistance. For purposes of example only and not limitation, the base and structural members 22, 24, 26, 28 may comprise aluminum, aluminum alloys, titanium, titanium alloys, steel, nickel-based alloys, copper-based alloys, beryllium-based alloys, or mixtures thereof. Further, the base and structural members 22, 24, 26, 28 can be formed from similar or dissimilar materials (provided that the dissimilar materials are of types that can be welded together).
In addition to the material composition and properties of the base and structural members 22, 24, 26, 28, the selection of the members 22, 24, 26, 28 is also based on the desired dimensions of the final structural assembly that is to be formed. More specifically, the desired dimensions of the structural assembly can be determined first, and the base and structural members 22, 24, 26, 28 can then be selected so that the resulting tailored blank 20 will correspond in configuration to the final structural assembly, i.e., the configuration of the tailored blank 20 is such that material can be machined or otherwise removed or reconfigured to achieve the dimensions of the finished structural assembly. Advantageously, by constructing tailored blanks having dimensions and configurations closely or substantially approximating the predetermined dimensions and configuration of the corresponding desired final structural assembly, machining time and material waste can be minimized, making the finished structural assemblies more economical to produce.
The finished structural assemblies manufactured by the methods disclosed herein (such as structural assembly 10 depicted in
Still referring to
Referring now to
The frequency of the reciprocating movement and the applied pressure are selected to cause the materials at the surfaces being rubbed together to plasticize, reaching a state wherein the parts will become fused together when reciprocation ceases and the plasticized material is allowed to fuse while the pressure is still being applied. More specifically, the relative motion between the structural member 24 and the base member 22 generates frictional heating that plasticizes a portion of the structural member 24 and/or a portion of the base member 22. Once sufficient plasticization has occurred, the reciprocating motion of the structural member 24 is terminated. Plasticization can be detected, for example, by mechanical or optical measurements, or friction welding can be continued for a predetermined duration based upon such factors as the type of materials being joined, the size or type of the joint to be formed, and the compressive force therebetween.
After the motion of the structural member 24 has been terminated, the compressive force between the structural member 24 and the base member 22 can be maintained by continuing to urge the structural member 24 in direction F against the base member 22, thereby forming a friction weld joint 40 (indicated in
It is appreciated that the forces and ranges of motion required for linear friction welding the structural member 24 to the base member 22 can vary according to such factors as the material of the members 22 and 24, the dimensions of the members 22 and 24, the surface finishes of the members 22 and 24, and the like. For example, in accordance with one embodiment of the present invention, in which the members 22 and 24 are formed of aluminum, the structural member 24 is urged in direction F against the base member 22 with a force sufficient to produce a pressure of about 20,000 psi between the structural member 24 and the base member 22, while the structural member 24 is reciprocated about 0.1 inch alternatingly in directions 30, 32 seen in
In other embodiments of the invention, the first structural member (e.g., structural member 24 seen in
As illustrated in
Thereafter, a second structural member 26 is concurrently joined to the base member 22 and to the structural member 24 by linear friction welding. As previously described, the side faces of the structural member 26 are substantially non-rectangular parallelogram shaped. The end faces 36 and 38 (later referred to as joining surfaces 36 and 38) of the structural member 26 are inclined relative to the substantially planar top surface of the base member 22 at the same oblique angle at which joining surface 34 of the structural member 24 is inclined.
Initially, the structural member 26 is placed between the previously described jaws 50, which grasp the structural member 26. The jaws 50 are initially positioned such that structural member 26 occupies the position shown in
Referring now to
The relative motion between the structural member 26 and the precursor structure formed by welding the structural member 24 to the base member 22 generates frictional heating that plasticizes respective portions of the structural members 24 and 26 at the interface of the joining surfaces 34 and 36, forming an inclined weld joint 44 (indicated in
Once sufficient plasticization has occurred, the reciprocating motion of the structural member 26 is terminated. Thereafter, the compressive force between the structural member 26 and the base member 22 is maintained by continuing to urge the structural member 26 in direction F against the base member 22, thereby forming friction weld joint 42 (indicated in
As illustrated in
Thereafter, a third structural member 28 is concurrently joined to the base member 22 and to the structural member 26 by linear friction welding, which operation is depicted in
Initially, the structural member 28 is placed between the previously described jaws 50, which grasp the structural member 28. The jaws 50 are initially positioned such that structural member 28 occupies the position shown in
Referring now to
Again, the relative motion between the structural member 28 and the intermediate structure formed by welding the structural members 24 and 26 to the base member 22 and to each other generates frictional heating that plasticizes respective portions of the structural members 26 and 28 at their interface and that concurrently plasticizes respective portions of the structural member 28 and the base member 22 at their interfaces. Once sufficient plasticization has occurred, the reciprocating motion of the structural member 28 is terminated. Thereafter, the compressive force between the structural member 28 and the base member 22 is maintained by continuing to urge the structural member 28 in direction F against the base member 22, thereby forming friction weld joints 46 and 48 indicated in
As illustrated in
After all of the structural members 24, 26, 28 have been welded in place, as illustrated in
For the purpose of illustration, an embodiment has been disclosed in which the substantially non-rectangular parallelogram-shaped structural members are beams or bars. Alternatively, the substantially non-rectangular parallelogram-shaped structural members can be plates. The use of substantially non-rectangular parallelogram-shaped structural members to build a long feature eliminates the need for connector pieces of the type disclosed in U.S. Patent Appln. Publ. No. US 2005/0127140 A1.
In accordance with a second embodiment of the invention, one structural member or feature can be friction welded to a base member and to another structural member or feature already welded to that base member using upset force in either two different directions or a vector combination direction. In accordance with this method, a second structural feature is joined to mutually substantially orthogonal joining surfaces of a base member and a first structural feature welded to that base member by linearly oscillating the second structural feature while first and second upset forces are being applied in mutually substantially orthogonal directions that are substantially normal to the aforementioned joining surfaces of the base member and first structural member. The second embodiment differs from the first embodiment in that the joining surfaces of the structural features are substantially normal instead of oblique relative to the substantially planar top surface of the base member, which orientation necessitates the application of an upset force or vector component thereof in a direction substantially normal to those joining surfaces.
One implementation of the second embodiment is shown in
The frequency of the reciprocating movement and the applied pressure are again selected to cause the materials at the surfaces being rubbed together to plasticize, reaching a state wherein the parts will become fused together when reciprocation ceases. After the motion of the structural member 56 has been terminated, the compressive force between the structural member 56 and the base member 22 is maintained, thereby forming a friction weld joint 40 (indicated in
Thereafter, a second structural member 60 is concurrently joined to the base member 22 and to the structural member 56 by linear friction welding with upset forces being applied in two mutually substantially orthogonal directions F1 and F2 indicated in
Initially, the structural member 60 is placed between the previously described jaws 50, which grasp the structural member 60. The jaws 50 are initially positioned such that structural member 60 occupies the position shown in
The relative motion between the structural member 60 and the precursor structure formed by welding the structural member 56 to the base member 22 generates frictional heating that plasticizes respective portions of the structural members 56 and 60 at the interface of the joining surfaces 58 and 62, forming a vertical weld joint, and that concurrently plasticizes respective portions of the structural member 60 and the base member 22 at the interface of the bottom face of the structural member 60 and the contacting portion of the top surface of the base member 22, forming a horizontal weld joint.
In accordance with a further implementation of the second embodiment shown in
Thereafter a flange portion 66 is positioned with a portion of a side face 74 of the flange portion abutting an end face 76 of the stiffener 68 and with a bottom face 70 of the flange portion 66 abutting a second portion of the substantially planar top surface of the base member 22. The faces 74 and 76 are substantially planar surfaces disposed substantially normal to the substantially planar top surface of the base member 22. Then upset forces are applied to the flange portion 66 from two directions: a first direction substantially normal to the plane of the top surface of the base member 22 and a second direction substantially normal to the plane of the end face 76 of the stiffener 68. Alternatively, a force which is the vector combination of the foregoing two upset forces is exerted on the stiffener. Then the flange portion 66 is reciprocated at high frequency in the manner previously described to generate sufficient frictional heat that the rubbing surfaces plasticize. Then the reciprocation of the flange portion 66 is terminated while maintaining the force or forces that press the faces of the flange portion 66 against the stiffener 68 and the base member 22 respectively. As a result, the flange portion 66 will be welded in place as shown in
As should be apparent to a person skilled in the art, the sequence of friction welding steps may be reversed in the example depicted in
Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. For example, the structural members can be processed before and/or after joining by friction welding. Such processing can include cleaning the joining surfaces of the structural members to remove oxidation or surface defects. Additionally, the structural members can be heat treated by aging, quenching, stretching, annealing, or solution annealing to obtain desired mechanical or chemical properties, as is known in the art. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
While the invention has been described with reference to various embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation to the teachings of the invention without departing from the essential scope thereof. Therefore it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
