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A typical MPW system includes a power supply, which contains a bank of capacitors, a fast switching system and a coil. In our research laboratory we proposed several new coiles instead of the solenoidal coil. When the eddy current is flowing, Al sheet is pressed to the Fe sheet by magnetic pressure and are heated by Joule heat .
The SEM image of the welded zone in a Aluminium alloy(A6016) and SPCC welded sample is shown as a exmple in the following pictuer. Comparison of the maximum tensile shearing strength for (a) the same Aluminum alloy combination and (b) different aluminum alloy combination:q the maximum tensile shearing strength of welded sample r the maximum tensile shearing strength of the based alloy without weld. Our experimental results show that the weld joint is always stronger than the weaker metal and in all tested combination a discontinuous or continuous pocket-type, wavy transition layer was formed without any significant heat-affected zone. Application of MPW using several types of coil :The upper shows the coil structure and the lower side shows the welded sample. Magnetic pulse welding (MPW) is a solid state welding process that uses magnetic forces to weld two workpieces together. Magnetic pulse welding is based on a very short electromagnetic pulse (<100Aµs), which is obtained by a fast discharge of capacitors through low inductance switches into a coil. During magnetic pulse welding a high plastic deformation is developed along with high shear strain and oxide disruption thanks to the jet and high temperatures near the collision zone.
Jetting condition: the collision has to be subsonic compared to the local materials speed of sound to generate a jet. High pressure regime: the impact velocity has to be sufficient to obtain a hydrodynamic regime, otherwise the parts will only be crimped or formed. No fusion during the collision: If the pressure is too high, the materials can locally melt and re-solidify. The main difference between magnetic pulse welding and explosive welding is that the collision angle and the velocity are almost constant during the explosive welding process, while in magnetic pulse welding they continuously vary. High-speed pulse lasts from 10 to 100 Aµs, the only time limitation is loading and unloading and capacitor charge time.
Magnetic Pulse Welding (MPW) is a solid-state shock welding process in which metallic bonds are created through the high-velocity impact of joining partners. However, before MPW can be brought into production, the defining parameters for optimum collision conditions that control the resulting joint quality need to be assessed. In order to achieve this, project partners with in-depth know-how concerning forming and joining (Institute of Forming Technology and Lightweight Construction at TU Dortmund, IUL) as well as joining and structures (IF) will be working in collaboration. Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING.
This paper investigated the effect of magnetic pulse welding (MPW) condition (welding power, surface scratches, and contamination) on the establishment of welding between aluminum and copper tubes, and the associated welding mechanisms. Owing to the increasing numbers of different applications, Fronius are continually adding new components that make robot welding even more interesting. Ita€™s as true here as in so many other areas: The whole is more than the sum of its parts. Indeed, some of its characteristics will only be at all effective in the context of a complete system a€“ on their own, they either wouldna€™t exist, or would be pointless.
To get this, you need to work with people who know the system, who see themselves as responsible and who can keep on providing important innovational impulses. Quantitatively speaking, the joining of steel accounts for the liona€™s share of robot welding.
Software which is mainly used for sending all the welding and telemetric data from several welding installations to one central computer where they are collected, evaluated and archived.
Collecting, visualising, evaluating and archiving the welding data from all your power sources at one central point, with WeldOffice. Quantitatively, aluminium is not as significant as steel, but it is a highly capable, versatile and light material nonetheless. Firstly, because of the oxide layer; secondly, because the soft wire is very difficult to feed, and the surface of the wire must not on any account be damaged.
The system prevents strong kinks, as the hose describes wide radii with every motion of the robot. A further advantage: It also shortens maintenance times, as the inner liner is prepared with the hose and is simply unclicked and clicked back in again with a quick-acting catch. Robacta Drive with external wire guidance: Quick changes of the inner liner, shortest possible downtimes. This is not so easy with aluminium, either, as it smears when subjected to conventional mechanical milling. Fronius has now developed a coating system for the gas nozzle that minimises the adhesion of welding spatter right from the outset.
Systems for robot welding make highly complex demands of all the individual components, and of the interplay between them all.
As this article a€“ with its overview of the latest developments in the field a€“ clearly shows, Fronius are not content to stick with the status quo but are resolutely continuing along the pathway of technological leadership. Fronius products are technologically leading ones a€“ which means that they come with all sorts of finer points that often dona€™t even get mentioned, as with Fronius theya€™re all standard equipment anyway. Method of magnetic pulse welding an end fitting to a driveshaft tube of a vehicular driveshaft - Torque-Traction Technologies, Inc. A method for securing components of a vehicular driveshaft includes disposing a neck of an end fitting into the open end of a driveshaft tube. Yablochnikov, B., “Apparatus for Magnetic Pulse Welding Large Diameter Thin-Walled Pipes”, AVT. Kojima et al., “Effect of Collision Angle on the Result of Electromagnetic Welding of Aluminum”, Transactions of the Japan Welding Society, vol. Karpouhin et al., “Magnetic Pulse Welding”, International Conference on the Joining of Materials, Helsingor, Denmark, pp.
Hardwick et al., “Some More Recent Advances in Cladding Technology”, Ninth Annual Conference on High Energy Reaction on Materials, Novosibirsk, Russia, pp. BACKGROUND OF THE INVENTIONThe present invention relates generally to a method of fabricating automotive driveshafts and more specifically, to a method of attaching metal end-fittings such as an automotive U-joint yoke and splined tube shaft to tubular shafts which rotate at speeds and transmit torque and axial forces such as when in use as a vehicle driveshaft.In general, a vehicular driveshaft transmits torque from a transmission to an axle to drive selected wheels of a vehicle. The parts to be joined are inserted into the coil, the capacitor bank is charged and the low inductance switch is triggered by a pulse trigger system and the current flows through the coil. The one-turn flat which is consisted of upper and lower H-shape plates which we call that the double layer H-shaped coil is design for thin or foils work-samples.
The depth of skin effect can be obtained by, where ?O is the angular frequency of changing field. As is evident from equation (1), for the materials with higher electrical conductivity , more eddy currents create at surface and as a result, stronger magnetic pressure p and a large amount of Joule heat are generated. It shows that the wavy morphology bond interface was formed in interface layer without any significant heat-affected zone (HAZ). The hardness measurement across the interface layer clearly shows that the hardness of intermediate layer is higher than Aluminum base metal in all points.
It can be pointed out that the sheet metals retain their original properties without the heat-affected zone (HAZ) problems during weld process and the welded zone is stronger than the weaker base metals so failure always occurred outside of welded zone for these combinations. The capability of our MPW method has been also examined for several other types of metals joint, such as T-joint, circular joint, long sheet sample (up to 500mm) successfully.
The welding mechanism is most similar to that of explosion welding.[1] Magnetic pulse welding started in the early 1970s, when the automotive industry began to use solid state welding.
The pulsed current with a very high amplitude and frequency (500kA and 15 kHz) produces a high-density magnetic field, which creates an eddy current in one of the work pieces. These factors are key in achieving a continuous and homogeneous weld, which in turn controls the joint strength. IF will be primarily responsible for the characterization of the weld joints as well as the execution of welding experiments involving high-energy pulses. The results showed that higher applied power and surface scratches in tangential direction were in favor for good weld, and oil on the surface prevented welding. A market in which Fronius has particularly good prospects, as here ita€™s all about complete systems.
This age-old philosophical statement quite neatly paraphrases the essence of a modern-day concept: Networking. Normally, this is done mechanically: The torch, together with the gas nozzle, is clamped in place and the spatter is removed by miller cutters.
This permits precision guidance of the soft aluminium wire a€“ as can also be verified at any time by taking a look inside the inner liner. This decreases friction, reduces wear-and-tear and thus prolongs the equipmenta€™s service life. When ita€™s Fronius who are responsible for the system, it can be expected to run just perfectly and without a hitch. For people who are new to Fronius, though, these things may well come as a welcome surprise.
The end fitting is held with respect to the driveshaft tube so that an annular gap is formed between the neck and the driveshaft tube. The method defined in claim 1 wherein the neck of the end fining is disposed concentrically relative to the end of the driveshaft tube. The method defined in claim 1 wherein the end of the driveshaft tube is an open end, and wherein the neck of the end fining is disposed within the end of the driveshaft tube. The method defined in claim 3 wherein the neck of the end fining is disposed concentrically within the end of the driveshaft tube. The method defined in claim 1 wherein the inductor is disposed about the neck of the end fining and the end of the driveshaft tube. The method defined in claim 1 wherein the neck of the end fining and the end of the driveshaft tube are formed from the same material.
The method defined in claim 1 wherein the neck of the end fitting and the end of the driveshaft tube are formed from different materials. A driveshaft operates through changing relative angles between the transmission and the axle. When current is applied to the coil, a high-density magnetic flux is created around the coil, and as a result an eddy current is created in the work-pieces. As a result, an electromagnetic force of i ?~B acts mainly on the Al sheet and the Al sheet is accelerated away from the coil and collides rapidly with the steel sheet. In addition, magnetic pressure will increase according to equation (2) because the depth of skin effect decreases by increasing of the electrical conductivity. The reason of this higher hardness at the intermediate can be resulted from intense plastic deformation due to high velocity collision or to fine-grain microstructure which was formed by rapid solidification of welded interface. The biggest advantage using magnetic pulse welding is that the formation of brittle intermetallic phases is avoided. To create such joints, at least one of the joining partners is accelerated very rapidly by magnetic forces. Predictive methods used for other shock welding processes, for instance explosion welding, are not fully applicable to MPW and therefore an investigation of the processes behind this joining method is necessary. IUL will be primarily responsible for the execution of welding experiments and the measurement of process parameters such as collision velocity and collision angle. And complete welding systems are exactly what Fronius has always offered, seeing itself as having overall responsibility for the process.
Leta€™s look at networking of different functions: Ita€™s only in the interplay of different functions that each separate function can evolve its capability to the full.
Furthermore, a driveshaft expands and contracts in response to road conditions when the vehicle is operated. At the moment of collision the colliding surfaces can be cleared by a large kinetic energy getting before the collision. Consequently this method is applicable to welding metal sheets with higher electrical conductivity such as aluminium and copper to dissimilar sheet metal. These so-called Lorentz forces are generated by a pulsed current of several hundred kiloampere sent through a tool coil (Fig. The purpose of this project is the development of MPW-specific prediction models and the derivation of instruments to systematically influence weld qualities. CuAl intermetallics with different atomic ratios were identified by energy dispersion spectrum (EDS) chemical analysis and by microscratching test. Or the program can send you an e-mail in good time when a medium is running short, or when an installation needs servicing, etc. Now Fronius offer a cleaning facility that is still truly unique a€“ where the gas nozzle is cleaned completely touchlessly using an electromagnetic process. The inductor is energized to generate a magnetic field for collapsing the driveshaft tube about the neck at a high velocity so that the driveshaft tube and the end fitting are welded to each other. To accomplish these functions, driveshafts include well known universal joints and slip joints connected to driveshaft tubes.A driveshaft tube includes a hollow cylindrical portion of a desired length, oftentimes terminating at one end in a tube yoke. This force can drive the work-pieces together at an extremely high rate of speed and creates an explosive or impact type of weld.
After the collision, the cleared surfaces are being pressed together by electromagnetic force and a fixture.
As eddy current pass through the sheets very fast with a short duration of about 50?Es, there is negligible heating of the metal. With magnetic pulse welding high quality welds in similar and dissimilar metals can be made in microseconds without the need for shielding gases or welding consumables. Aizenshtein, Interface Phenomena and Bonding Mechanism in Magnetic Pulse Welding, Journal of Materials Engineering and Performance, 2014.
This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
The torch is first immersed in a parting agent, and then the spatter is removed with the aid of electromagnetic pulses. The tube yoke includes a pair of opposed arms for receiving bearing cups mounted on trunnions of a cross. Therefore, in this welding method materials will not be suffered from bad influences of heat that resulted from the conventional spot or fusion welding method.
The tube yoke, cross and bearing can be combined with an end yoke to form a universal joint.
The opposite end of the driveshaft tube can terminate in a splined tube shaft designed to receive an end yoke. During the collision, it appears that the atoms of the two joining parts are pushed towards each other by such high forces that they overcome their natural repulsive forces. For achieving the successful weldment and using this process, the design of working coil is the most important factor, because working coil has to generate a high-intensity magnetic field on the surface of the workpiece during the process. Therefore, the objective of this study is to analyze the distribution of electromagnetic force of square working coil for magnetic pulse welding. Tube yokes and driveshaft tubes are conventionally formed from steel and are attached to the driveshaft tube by conventional welding processes.In order to reduce vehicular weight, obtain smooth operation and improve fuel economy, driveshaft components have been formed from lighter materials such as aluminum. For this, FE-model has been developed to analyze the distribution of electromagnetic force; after that, distribution of electromagnetic force, results of numerical analysis and experimental results for verifying the developed FE-model were compared. Pure aluminum does not make driveshaft components of acceptable strength, but alloys of aluminum have adequate strength.
While aluminum alloys have been an acceptable material because of their strength and lighter weight, problems have been experienced using conventional welding techniques with such components. The shape and material of square working coil were decided through literature surveys. For example, aluminum components have been weakened by heat generated and transferred to them during conventional welding.For the attachment of end-fittings to metal tubes, many other techniques are available with varying degree of success. For the experiment, an MPW equipment W-MPW manufactured by WELDMATE Co., Ltd. Among these other methods are the use of pins, rivets, bolts, adhesives and such mechanical methods as splines, keyways, polygon matching shapes, shrink fits and press fits. However, these attachment methods are not as economical as desired, particularly when applied to driveshafts of vehicles.In use today, with limited success, is one recent innovation known under the trademark MAGNAFORM. After the experiment, leakage test was used to verify the weldability. This technology employs a very high electromagnetic-induced force to swage aluminum tube onto a fitting, as is commonly used for non-driveshaft applications. Also weld joints were observed on longitudinal cross-section by microscope. Unfortunately, the results of such a method for attaching end fittings to driveshaft tubes have been less than satisfactory. The electromagnetic force generated was the greatest one at the center adjacent to square working coil, decreasing as moving into the edge.
Magnetic forming requires a non-circular, force-transmitting shape to transmit torque between two rotating parts. Aluminum, which is typically used in driveshafts, is a notch sensitive material, and is subject to cracking where it is stressed by being deformed into shapes having relatively large contours. These results are similar to the output data from developed electromagnetic FE-model where electromagnetic force decreases as moving into the corners of square working coil.
Also, when torque is applied to the driveshaft in the vehicle, there is a small amount of slippage between the yoke and the driveshaft tube which produces a loud and irritating sound. Besides that, magnetic pulse forming gives good mechanical strength results only as long as the torque is not too high.
But with a high level of torque, as measured with fatigue tests, the life of the driveshaft is reduced considerably.A large number of revisions have been made in order to attempt to solve those problems. There is therefore a need to provide a solution which permits the advantageous use of magnetic pulse fields for swaging a tube and the advantageous use of the welding process for joining the end-fitting and the aluminum driveshaft tube.A known prior art method of pressure welding is based on the use of interaction of magnetic fields, produced by an inductor through which an impulse of high intensity current is passed. The parts to be welded are positioned in spaced relation at an angle therebetween and the method can be used for obtaining overlapping welded joints of thin-walled parts having different thickness and made from different materials without melting.
This method is referred to as Magnetic Pulse Welding (MPW) and has been used in particular to weld the end of nuclear fuel rods and has also found application in other contexts in which the diameters of the parts to be joined are small (about 25 mm) and tubes made from mechanical strength metal.
The main parts of each apparatus are a capacitor bank, inductor and high current switching device.
The technological capability of conventional MPW apparatus is much less than what is necessary for magnetic pulse welding of driveshafts having tube diameter within the range of about 75 to 180 mm and wall thickness of 2 to 3 mm.
The contact surfaces of the insulators, the metallic housing and the electrodes are hermetically sealed to create a closed discharge chamber which is evacuated by a vacuum pump.
Introduction The car industry is currently working to accommodate the conflicting requirements of both environmental legislation and customer demands for high performance and safety by developing a light-weight vehicle [1]. Due to those features and extra-low inductance of the system connection bus bars, AMPE has minimal loss of energy in the process of discharge.In principle, AMPE should permit tubes as large as a driveshaft to be welded using MPW, but there appear four problems which must be solved before this technology can become valuable from a manufacturing point of view. So the light weight materials such as aluminum and magnesium have been applied in automation. Especially, development of aluminum space frame for automotive body structure has been carried out in recent years [2]. This cumulative jet is produced in the process of collision welding of metal when the impact velocity is high enough. However, when only light materials are used in automotive body structure, they cannot satisfy the required intensity and strong property, and it is imperative to weld light weight materials with existing used ones.


The second problem is the low strength of the welding joint between high-strength aluminum alloy tubes and the end fitting if the latter is made from steel. Accordingly, it has been required to study on welding of dissimilar metals [1] due to the different physical properties between materials.
Welding as existing fusion welding generally causes not only defects, such as solidification, cracking, porosity and oxidation, but also transformation and corrosion. For this reason, more attention has been paid to magnetic pulse welding process as a kind of solid-state welding these days.
The last two problems are connected and contradictory to each other.In the process of MPW welding, the surfaces of metal approach each other at an angle and collide with high relative velocity.
To get a strong joint or weld, it is necessary to clean this contamination from the welding surfaces.
The electrical energy stored in the magnetic pulse power source is discharged instantaneously as a high current to the working coil by a trigger discharge, and thus an induced current is generated at the conductive outer workpiece positioned within the working coil.
In the process of MPW in the area where the surfaces collide with each other at high velocity, the cumulative jet includes material from the surface sheets and contaminants from the collision surfaces.
For successful magnetic pulse welding, it is important to develop a working coil that can gain enough electromagnetic force for welding. This material carried with the cumulative jet acts to clean the welding surfaces.The cumulative jet has supersonic velocity and creates a loud sound like thunder if allowed to escape to the atmosphere. If the cumulative jet is restrained, and reflected from obstacles such as the shoulder of the end fitting or the surfaces of tooling, and directed toward the insulation elements of inductor, then the cumulative jet can create problems. In such a case, the insulation elements can be contaminated and can be destroyed within a short number (perhaps less than 100) of welding cycles. The extensive knowledge in this complicated area is not easily obtained, as the variety of experimental setups and the complicated dynamic interaction between different phenomena in the welding process are extremely difficult to describe in a closed analytical form.
Obviously this is unacceptable in a manufacturing process because breakdown of the inductor is possible.As a result of the problems described above, welding using MPW has not yet been found to produce high quality welding joints between driveshaft tubes and end fittings if the driveshaft tubes are made from high-strength aluminum alloys like 6061 and any related temper, and the end fittings are made from middle carbonic steel like EMS-40. But it is highly desirable in the manufacture of driveshafts to find a method to allow MPW of aluminum driveshaft tubes with split fitting because those fittings can only be made from steel.The problem of eliminating the aforementioned self breakdown of the switch is a basic problem in the technique of high pulse current and strong magnetic fields. This problem becomes especially complicated if the amplitude of the current achieves a level of one mega-ampere or more, if the energy of the pulse is 40 kilojoules or more, if the charge transfer is 10 coulombs or more, and if the frequency of pulses more than one per minute.Any high current switch must be able to withstand the working voltage of the capacitor bank without spontaneous breakdown.
Further, the switch should have sufficient current throughput capacity, charge transfer and long service life. Depending on the actual conditions, to these main requirements are added others such as ease of linkage with the other components of the discharge circuit, quiet running, and a sufficiently narrow interval between discharge cycles.
For magnetic pulse welding of a driveshaft, it is especially important to have such properties as a working switch with a narrow interval between discharge cycles and without spontaneous breakdown—contradictory requirements, especially for vacuum switches. The reason for the first of these properties (narrow interval) is the necessity to achieve highly productive output for driveshaft. The reason for the second (without spontaneous breakdown) is the impossibility of repairing the driveshaft in case of failure of the welding operation. This is a critical difference between the processes of magnetic pulse forming and magnetic pulse welding.
The failure of the magnetic pulse forming operation can be corrected by using repetition of the discharge pulse. But the failure of the magnetic pulse welding operation cannot be corrected by using repetition of the discharge pulse because the first pulse changes or eliminates the gap between the welded surfaces, the value of which is very critical for the success of the MPW process. It is obvious that a long service life is also necessary for MPW driveshaft under manufacturing conditions.For welding driveshafts using MPW only two types of inductor can be used. The first has a massive high-strength single-turn coil, the disadvantage of which is a gap between the leads, resulting in a nonuniform magnetic force field, and thereby providing a non-uniform weld. The other, preferred type of inductor has high strength coil comprised of a number of generally flat, closely packed but spaced-apart, nearly circular or annular electrical conductor strips, as disclosed in U.S. Consequently, the objective of this research is to develop FEmodel for square working coil in magnetic pulse welding which is a basic research for manufacturing the automotive space frame.
For this study, first, the shape and material of coil were decided through literature survey. This type of coil provides a uniformly azimuthal distribution of the magnetic field and is used in the conventional AMPE process. To weld driveshafts using MPW, both types of inductors demand very high currents (1 to 2 mega amperes and higher) and a high energy of pulse (40 to 60 kilojoule and more).The higher the amplitude of the current and the higher the energy of the pulse, the more complicated become the problems of switching that current's pulse. The comparison between the calculated and measured results was finally done to verify the developed electromagnetic FE-model. This problem becomes more and more complicated if the pulse current must be repeated with short intervals, as is necessary in an economical manufacturing process.
The best results in switching the pulse current for a conventional AMPE process is a vacuum switch. The productivity must be at least 2 to 3 times higher.The vacuum switch used in conventional AMPE has a gap between the electrodes of about 5 mm and is ready to switch if the residual pressure in the discharge chamber is lowered to about 10 to 20 Pascals. In this area of physical characteristics, the voltage of self breakdown of the switch increases inversely proportionally to the value of the residual pressure within the chamber as the pressure is being reduced. Unfortunately, this relation is true only if intervacuum surfaces of insulation elements are clean. High current discharge is accompanied by very intensive processes of electric erosion of electrodes and insulators. As a result of the deposition of these products of erosion on the elements of the vacuum switch, the switch is not capable of blocking the voltage developed across the capacitor bank if the charging starts too early.The reason that it is difficult to maintain a switch at a high level of cleanliness to avoid premature discharge is as follows. After each discharge of the stored energy from the capacitor bank, the gaseous mixture from the vacuum chamber of the switch is evacuated by the vacuum pump. However, part of the metallic vapors and drops are deposited on surfaces of the insulators, and over time they form a coating on various insulating elements, and this consequently decreases the insulating properties. A complete understanding of the sophisticated physical processes inside the discharge chambers of the vacuum switches is not known, especially when the amplitude of the current reaches millions of amperes.
But experiments found that a good vacuum in the discharge chamber is not sufficient by itself to prevent premature discharge.During a welding cycle, the time required for recovery of the insulation properties of the intervacuum insulation and the time for charging the capacitor bank takes 80 to 90 percent of the entire working cycle of AMPE, which is typically 25 to 30 seconds.
An additional disadvantage of the AMPE is that there is no guarantee that each cycle will work properly because a self breakdown is possible. A known solution to the problems of productivity and reliability of AMPE consists of separating the capacitor bank from the discharge circuit by means of special disconnectors after each switching during the time of pumping of the discharge chamber, and also measuring the breakdown voltage between electrodes.
The processes of pumping the chamber and charging the capacitor bank can take place simultaneously.
After achieving the breakdown and charging the voltages as necessary, the disconnectors are closed and switching can be done. The disadvantages of this solution are the sophisticated and large size required for the disconnectors. Also, a special hydraulic system controlled by the disconnectors is required if the design is based on a mechanical principle, and the use of mercury is required if the design is based on a liquid-metallic principle.There is therefore a need to provide a solution which permits use of MPW for joining the various elements of driveshaft assemblies to each other, including attaching an aluminum driveshaft tube to an end fitting made of the same or different metals. This system should provide high productivity and reliability, and should avoid the complex design of the AMPE.
Such a system should weld aluminum components of a vehicular driveshaft in such a manner so as not to damage the integrity or strength of the components or the final assembly.SUMMARY OF THE INVENTIONThis invention relates to a method for securing components of vehicular driveshafts.
Development of Square Working Coil 2.1. This method utilizes an electromagnetic field to force one component into another at a very high velocity, thereby causing the components to be welded to one another upon impact. Magnetic Pulse Welding The magnetic pulse welding is a solid-state, cold-welding process that is accomplished when a magnetic pulse causing a high-velocity impact between two materials, resulting in a true metallurgical bond [8]. The principle of magnetic pulse welding is based on the physical phenomena of magnetic fields induced by an electric current [9]. 1 is an exploded perspective view of an end fitting and driveshaft tube prior to welding the end fitting to the driveshaft using an inductor pursuant to the method of the present invention.FIG. It is well known that two conductors with their electric currents travelling in opposite direction repels due to the interaction of their oppositely orientated magnetic fields induced. 2 is a partial sectional view of the end fitting, driveshaft tube and conductor strip of FIG. Figure 1 shows in the initial coil, the inductor, a current impulse which in turn, generates a current of the opposite direction in the outer workpiece. 1 after the end fitting has been inserted into the driveshaft tube and the driveshaft tube has been disposed within the inductor, illustrating the forces of a magnetic field created by the welding method of the present invention.FIG. A electromagnetic force to the initial coil causes the outer workpiece to impact at a tremendous force and speed at the inner workpiece, resembling an explosion taking about 20 millionths of a second [7]. 4 is a partial sectional view of an end fitting, a cylindrical sleeve, driveshaft tube and an inductor illustrating the forces generated by the magnetic field created during the welding method of the present invention.FIG. 5 is a partial sectional view of the end fitting, cylindrical sleeve, driveshaft tube and inductor of FIG. To generate the high-current impulse an arrangement of capacitors, an arrestor-discharge and a working coil has been constituted the core of the magnetic pulse module, as shown in Figure 2 [10,11]. The capacitors, special high-voltage capacitors with extremely low self-inductance, can store charge up to a certain maximum level that is determined by the arrestor-discharge, which creates a short, highcurrent pulse in the work coil [6]. 6 is a schematic exploded view of a universal joint connected to a driveshaft tube according to the method of invention.FIG. 7 is a schematic plan view of a vehicle containing a universal joint and driveshaft tube made according to the method of the invention.FIG.
8 is a schematic cross-sectional view in elevation of the drive shaft, end fitting and a preferred inductor coil of the invention, with the end fitting having a single tapered outer surface.FIG. 12 is a schematic cross-sectional view in elevation of a portion of the drive shaft and a portion of the end fitting illustrating detail of a particular embodiment of the invention.FIG. 13 is a schematic cross-sectional view in elevation of another embodiment of the drive shaft, the inductor and the end fitting, illustrating the locating fixtures.FIGS.
14-16 are schematic cross-sectional views in elevation of a portion of the drive shaft and a portion of the end fitting illustrating the application of a very thin layer of an intermediate sleeve of transition material.FIG. 17 is a graph showing the buildup over time of the voltage of self breakdown and the buildup of the voltage charge in the capacitor bank.FIG. 18 is a timeline illustrating the sequence of steps in magnetic pulse welding according to the method of the invention.FIG. 19 is a schematic cross-sectional view illustrating a gap for collecting airborne contaminants, and a barrier for preventing outflow of contaminants into the remainder of the inductor.FIG. 20 is a schematic cross-sectional view showing the welding of a end fitting with a cylindrical surface rather than a sloped, frustoconical surface.FIG.
The principle of the magnetic pulse welding process [7].
21 is an illustration showing an end fitting having a convex surface and a slit for improved flexibility.FIG.
22 is an illustration showing an end fitting having a concave surface and slits for improved flexibility.FIGS. 23 and 24 are schematic cross-sectional views in elevation of another embodiment of the drive shaft, showing the addition of a thin transition layer.FIG. 25 is a schematic cross-sectional view in elevation of another embodiment showing the welding of the driveshaft in a one-step process with a layer of transition material.DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTNow referring to the drawings, there is illustrated in FIG.
A predetermined length of a driveshaft tube 12 is a hollow cylindrical member having at least a first open end 14. In the illustrated embodiment, driveshaft tube 12 is illustrated with a second open end 16. However, in other embodiments, the driveshaft tube 12 can include a midship tube shaft (not illustrated) or slip tube shaft (not illustrated) or other member secured at the second end 16.Preferably, the driveshaft tube 12 has a substantially constant inner diameter defining an inner surface 18 and a substantially constant outer diameter defining an outer surface 20, as shown in FIG.
The driveshaft tube 12 can be formed from any suitable material, such as aluminum, and in particular strong aluminum alloys, such as 6061T aluminum alloy. Another possibly suitable material is titanium alloys.An end fitting, in the form of tube yoke 24, is provided. Although the embodiment shown illustrates a tube yoke 24 as the end fitting, it is to be understood that any other type of end fitting desired to be secured to the open end 14 of the driveshaft tube 12 can be used. The tube yoke 24 has a body portion 26 having a pair of spaced-apart, opposed arms 28 extending therefrom.
Each of the opposed arms 28 has a cylindrical opening 30 formed therethrough which receives a respective bearing cup 32, shown in FIG. The tube yoke 24, cross 34 and an end yoke 36 cooperate to form a well known universal joint in a vehicular driveshaft. The tube yoke 24 can be formed from any suitable material, including aluminum and steel.Tubular neck 38 extends from the body portion 26 opposite the arms 28. 8, the neck 38 has a varying inner diameter defining a tapered inner surface 42 and a varying outer diameter defining a tapered outer surface 44. Other surface configurations include cylindrical, twin tapered convex and twin tapered concave, as will be explained below.The present invention includes a method for securing the end fitting, illustrated as a tube yoke 24, to the driveshaft tube 12. The neck 38 of the tube yoke 24 and the driveshaft tube 12 are sized so that an annular gap G exists between the outer surface 44 of the neck 38 and the inner surface 18 of the driveshaft tube 12 when the neck 38 is inserted into the open first end 14, as shown in FIG. Preferably the gap G is substantially uniform at every circumferential location around the neck of the tube yoke.
When the neck 38 is inserted into the open end 14 of the driveshaft tube 12 as illustrated in FIG. For purposes of clarity of illustration, the annular gap G created by the loose fit has been exaggerated in the drawings.
The tube yoke 24 and the driveshaft tube 12 can be held in position by a suitable locator fixture (not shown in FIG.
Preferably, the gap G for tube yokes having cylindrical outer surfaces has a relatively large radial span, typically within the range of from about 0.5 to about 5 mm, and preferably within the range of from about 1 to about 3 mm. For tube yokes having non-cylindrical outer surfaces, the gap will vary between about zero and about 5 mm.An inductor 46 is provided about, and preferably radially spaced from, the outer surface 20 of the driveshaft tube 12 adjacent the first end 14.
For magnetic pulse welding driveshaft tubes, which typically have diameters within the range of from about 7.5 to about 18 cm, only two types of inductor coil can be used. The single turn inductor is disadvantageous in that it has a gap or spacing between the ends or leads, resulting in a nonuniform magnetic force field surrounding the driveshaft, and thereby providing a nonuniform weld.The other, preferred type of coil is a high strength coil 48 comprised of plurality of generally flat, closely packed, but spaced-apart, nearly circular or annular electrical conductor strips 50, shown in FIG. The conductor strips 50 can be helically bent at a pitch which insures a displacement of the ends or leads of the conductor strips relative to each other. Shape and Material As I mentioned before, magnetic pulse welding uses the electromagnetic force from current discharged through the working coil which develops a repulsive force between the induced currents flowing parallel and in the opposite direction in the workpice to be welded. However, the theoretical analysis for development of perfected working coils considering various factors hasn’t been established yet. Nevertheless generally the considered factors were classified into a shape and an electric property [10].
1 is preferable over a conventional single-turn coil because it provides a uniformly azimuthal distribution of the magnetic field.The inductor 46 includes leads or terminals 53 which provide an electrical connection to the inductor coil 48. Second, distribution an electromagnetic force by the interaction between working coil and outer pipe should be investigated after selecting materials that electric resistance is low and that has enough intensity mass possible to resist electromagnetic force on processing.
One of the terminals 53 is supplied with current via the first switch connector or electrode 59, and the other of the terminals 53 is connected to the source of current by a first bus bar 60. Similarly, the second electrode 61 is connected to the source of current by a second bus bar 62.The inductor 46 is connected via discharge circuit 63 to high voltage capacitors 64. A compression coil is the solenoid type surrounding processed materials which is welded from outside direction to inside. The current required for successful welding of aluminum tubes and yokes suitable for use as vehicle driveshafts is on the order of at least several hundred thousand amps, and possibly as high as one million amps or more.
Therefore the discharge circuit must be suitable for conducting a current of great magnitude. The discharge circuit 63 includes a discharge switch 65 which when activated allows the capacitors to discharge and supply an energy spike or surge to the inductor 46. The inductor 46 creates a strong magnetic field that exerts a force against the outer surface 20 of the driveshaft tube 12, as will be explained in further detail below. The switch 65 must be suitable for handling the high currents involved in the discharge circuit 63. A plate coil which located on and under the processed material was employed in plate welding [3].
Therefore, the shape of solenoid-typed compression coil was chosen between compression coil and expansion one that are used in joining of pipes because it is located in the outside of the specimens. In addition it has no size limit as well as simple connection magnetic pulse power source. 1, where the ring-like or circular conductor or first electrode 59 is positioned close to the second electrode 61, with a gap 68 of about 5 mm between them. The use of ring-like or circular electrodes 59 and 61 for the switch 65 enables the current to flow through the discharge circuit 63 without significant losses, thereby greatly increasing the capacity or power of the magnetic pulse welding apparatus of the invention. Such high current switches are known in the art.During charging of the capacitors 64, the voltage builds up across the gap 68. To prevent premature discharge across the gap, a vacuum or partial vacuum is placed over the gap, by vacuum means, not shown, so that there will be no arcing across the switch 65. When desired, this partial vacuum can be interrupted by any means, such as a spark plug, not shown, to initiate discharge of the current through the inductor 46.
The current will arc across the gap 68 and create a momentary discharge pulse traveling through the discharge circuit 63.
The capacitors 64 can be in the form of a single capacitor, or preferably a battery of capacitors arranged in parallel circuits, as shown in FIG.
Capacitors having low inductance are preferred.The battery of capacitors 64 is connected to a source of electrical power, such as power source 70, via a charging circuit 72. Ideally, the power source and capacitors will be sized to allow a rapid buildup of the charge in the capacitors, thereby shortening the period or cycle time for each magnetic pulse welding operation. During the step when the current is arcing across the gap 68 and the discharge circuit is closed, the charging circuit is preferably disconnected from or insulated from the power source. This can be accomplished by a switch 74 in the charging circuit 72.The effect of the intense, momentary magnetic field on the metallic driveshaft 12 is to create an extremely powerful force which repels or drives away the driveshaft, radially inwardly from the inductor 46.
The magnetic field created by the pulse of current through the inductor creates strong reactive eddy currents in the aluminum driveshaft tube 12. These eddy currents create opposing magnetic fields which result in inwardly directed forces on the metallic driveshaft, as indicated by arrows 78 in FIG. These forces cause the driveshaft tube 12 to collapse about the neck 38 which such an impact that the driveshaft is welded to the neck 38, as shown in FIG. 3.The sizes and shapes of the neck 38 of the tube yoke 24 and the driveshaft 12, the size and shape of the inductor 46, and the strength and shape of the electromagnetic field are all factors determining the strength of the weld. By maintaining a relatively large annular gap G between the driveshaft tube 12 and the neck 38, the collapsing portion of the driveshaft tube 12 is permitted to accelerate to a relatively high velocity. The high impact velocity causes the inner surface 18 of the driveshaft tube 12 to become welded to the outer surface 44 of the neck 38 when they contact each other, as illustrated in FIG. 3.The velocity of the driveshaft tube 12 when it comes into contact with the outer surface 44 of the neck 38 of the end yoke is preferably at least 300 meters per second, and more preferably within the range of from about 300 to about 400 meters per second.
In contrast to the generally known method of metallic forming, sometimes referred to as a magnetic forming process, the electric pulse welding process of the invention propels the metallic work piece toward the tube yoke with a velocity sufficient to weld the driveshaft 12 to the neck of the tube yoke 24. It can be appreciated that the impact velocity of the driveshaft into contact with the neck of the tube yoke is not only a function of the magnetic driving force created by the inductor 46, but also is a function of the gap or distance G between the driveshaft tube 12 and the neck 38 of the tube yoke 24.Another factor to be taken into consideration when considering the physical layout of the magnetic pulse welding apparatus is the fact that the driveshaft 12 must respond to the magnetic field by deforming or shrinking to close the gap and allow the driveshaft to come into contact with the tube yoke.


Where the gap is too large this resistance to inward deformation may decrease the velocity of the impact of the driveshaft into the tube yoke 24 and thereby prevent the establishment of a satisfactory weld. An even more important limitation is the fact that the electromagnetic field established by the coil 50 has a gradient and weakens as the driveshaft wall moves radially inwardly, away from the inductor coil 50.
Therefore, a balance must be struck between the desire for a relatively large gap 68 to increase the impact speed, and a need for a narrow gap to maximize the force from the electromagnetic field and to minimize the forces counteracting the deformation of the drive shaft.In operation, the power source 70 charges the capacitors 64. The charging circuit is closed and the discharge circuit is open during the charging of the capacitors. When the voltage across the gap 68 increases to the desired discharge level, the switch 65 is closed, and the current arcs across the gap 68 to cause a current to flow in the discharge circuit 63. The charging circuit is open and the discharge circuit is closed during the discharging of the capacitors.
The current running through the inductor 46 establishes a strong magnetic field, which causes a rapid inward repulsion of the driveshaft 12 toward the neck 38 of the end yoke 24. Analysis Method and Procedure After shape and material of coil was chosen, electromagnetic force needed to welding should be confirmed.
The gap G between the driveshaft 12 and the neck 38 of the end yoke 24 is a distance suitable to enable a sufficient impact velocity to cause a permanent welding of the driveshaft 12 to the neck 38 of the end yoke 24.The magnetic pulse welding method of the invention enables the welding of relatively large driveshafts and tube yokes.
However, there is a limitation for electromagnetic force Table 1.
For example, driveshafts having outside diameters within the range of from about 7.5 to about 18 cm can be welded using the method of the invention, although typical driveshaft sizes are around 10 cm.
Successful welding of the end fitting to the driveshaft means that upon applying torque between the end fitting and the driveshaft, the driveshaft fails before the weld fails.The above-described method of magnetic pulse welding is suitable when the material used to form the driveshaft tube 12 is the same as the material used to form the end fitting.
In other instances, it may be desirable to form the driveshaft tube 12 from a first material, such as a high strength aluminum alloy, and the end fitting from a second material, such as steel. In such an instance, a hollow cylindrical sleeve 80 of a transition material such as 1100 series aluminum, may be disposed between the inner surface 18 of the driveshaft tube 12 and the outer surface 44 of the neck 38, as illustrated in FIG. A first substantially uniform annular gap is maintained between the driveshaft tube 12 and the sleeve 80, and a substantially uniform annular gap is maintained between the sleeve 80 and the neck 38. Preferably, for end fittings having cylindrical outer surfaces gaps have a relatively large radial spans, typically within the range of from about 1 and 3 mm. Preferably, gaps are substantially uniform at every circumferential location around the sleeve 80.When the driveshaft tube 12, sleeve 80 and neck 38 are held in desired positions by locator fittings, shown in FIG. 13, and subjected to the magnetic force of the inductor 46, the adjacent surfaces are collapsed under relatively high velocity so that welding occurs at both interfaces to secure the driveshaft tube 12 to the sleeve 80, and the sleeve 80 to the neck 38 of the end fitting, illustrated as a tube yoke 24. 4 have been exaggerated to illustrate the loose fits between the driveshaft tube 12 and the sleeve 80, and between the sleeve 80 and the neck 38.As shown in FIGS. 6 and 7, after the tube yoke is welded to the driveshaft 12, the end yoke 36 and the cross 34 can be connected with the tube yoke 24 to form a universal joint 82.
The universal joint 82 can be used in transmitting torque in a vehicle 84, as shown in FIG.
The engine 85 supplies power to the transmission 86, which provides rotative force to the rear wheels 87 via universal joint 82 and driveshaft 12.As shown in FIGS. 8-11, the outer surface of the end fitting 24 need not be cylindrical, but rather can have different configurations.
Because this force is decided by interactions of electromagnetic and workpiece model development of numerical analysis can be a useful means. 8 that the end 14 of the driveshaft tube 12 is generally axially aligned with the end 90 of the conductor strips gases surrounding.
11, however, when the end fitting outer surface is cylindrical as is outer surface 44D, the optimum position of the end 14 of the driveshaft tube 12 is in alignment with the approximate mid-point 92 of the conductor strips gases surrounding, rather than at the end 90 of the conductor strips gases surrounding. The magnetic field of the workpiece is expressed from Equations (2) to (5). This angle between the surfaces is provided to accommodate the nonuniform acceleration of the drive shaft tube 12 toward the end fitting during the welding process.
In its initial state the driveshaft is cylindrical, and the free end 14 is located at the mid-point 92 of the conductor strips gases surrounding, as shown in FIG. Usually distribution of the magnetic field along the axial length of the coil results in a maximum magnetic field strength at the midpoint 92 of the coil. To these differential relations, the constitutive relations are included from Equations (6) and (7). Owing to the magnetic field maximum at the midpoint 92, the free end 14 achieves a higher impact velocity than any other part of the driveshaft 12.
As a result of the free end 14 being positioned at the axial maximum of the magnetic forces, the free end is the first part of the driveshaft to strike the end fitting surface. This angle between the driveshaft and the end fitting is beneficial because it provides a nonuniform impact of the driveshaft against the end fitting.
The end fitting 96 is provided with a shoulder or annular step 98 which acts as a stop or locator with respect to the end 14 of the driveshaft 12.
The first surface portion is the generally cylindrical portion 102, which generally contacts the driveshaft wall and serves to center the end fitting 96 within the driveshaft tube 12. The axial outer end surface portion 104 of the end fitting inner surface 100 is tapered radially inwardly to facilitate insertion of the end fitting 96 into the driveshaft tube 12. The axial inner end surface portion 106 is tapered radially inwardly with respect to the driveshaft tube 12, resulting in a spacing between the driveshaft tube 12 and the inner end surface portion 106. This spacing enables the driveshaft tube wall to develop sufficient velocity during the welding process to produce an effective weld upon impact.As shown in FIG. 13, in a specific embodiment of the invention, the driveshaft tube 12 and end fitting 110 are positioned within the inductor 46. A locator clamp 112 is fixed to the driveshaft 12, and the axial movement of the driveshaft 12 into the inductor 46 is limited by the abutment or contact of the locator clamp 112 with the limitator or stop 114, which is fixed with respect to the inductor 46.A locator fixture 116 is provided for the end fitting 110. When a high frequency current flows through a conductor, the current tends to flow on the conductor surface.
Fixture 116 has an annular locator ring 118 that comes into contact with annular bushing 120 for a positive, predetermined axial positioning of the end fitting 110 with respect to the inductor 46.
The magnitude of the current is exponentially decreased with the depth of penetration into the conductor. In addition to axially fixing the penetration of the end fitting 110 into the inductor 46, the locator fixture 116 also provides radial centering of the end fitting with respect to the inductor and the driveshaft tube.
Figure 4 shows a schematic diagram for magnetic pulse welding this study. The annular ring 118 is preferably provided with an axial slot and an adjustment member, such as a set screw 122, to enable the annular locator ring 118 to be adjustably tied or connected to the locator fixture 116. The locator fixture 116 is fixedly connected to the end fitting 110 by end fitting connection 124. A conical grip 126 is provided to ensure proper centering of the driveshaft tube 12 in the inductor 46.EXAMPLEIn an example of a successful operation, the power source 70 provides a steady voltage of about 5,000 volts maximum, and the capacitor bank has 24 capacitors in parallel, each having a capacitance of 350 ?F at a proof voltage of 5,000 volts, for a total capacitance of 8400 ?F. Table 2 shows the material properties for working coil and outer pipe. The voltage across the gap 68 is allowed to rise to a level of about 3500 volts before the arc discharge was initiated. Current was inputted into the working coil as a sine wave function. The current flowing through the inductor is preferably greater than about one million amps, and typically about 1.3 million amps. Not only the magnitude was 500 kA a, but also the frequency was 25 kHz for the experiment.
To avoid the calculation complexity of energy transformation, current was employed as the excitation in the present analysis. This causes the driveshaft to move radially inwardly into contact with the tube yoke with a velocity sufficient to cause a permanent weld.FIGS. This transition material can be any suitable material for enhancing the bond between a driveshaft of a strong aluminum alloy and an end fitting of another material, such as steel. A blank or segment of transition material in the shape of a collar 130 is first positioned adjacent tube yoke neck, as shown in FIG.
Then the welded collar 130 is turned or shaved off to a very thin layer 130A, as shown in FIG.
It is to be understood that any applicable machining process can be used to reduce the thickness of the collar. The thinness of the layer 130A contributes to the strength of the ultimate bond between the driveshaft and the end fitting. After the transition layer has been turned to reduce its thickness, the driveshaft 12 can be welded to the transition material 130A, as shown in FIG. 16.It would seem preferable to apply a thin layer 130A to the tube yoke neck 38 rather than the thicker layer 130 which requires turning to reduce its thickness. However, a thin layer of transition material cannot be applied using energy at the same frequency used for applying a relatively thick layer. In order to avoid the necessity of using two separate machines, a thicker layer 130 is applied and then it is turned to obtain the desired thin layer 130A.
17 and 18 illustrate the timing of the various process steps during a representative MPW welding cycle of the invention. 17 and 18 merely represent one possible timing scheme, and numerous other timing and processing designs can be used with the invention. The vacuum pump, not shown, runs continuously, and starting at the beginning of the cycle the vacuum is drawn, thereby continuously decreasing the air pressure surrounding the discharge switch 65, as indicated by time bar 134 in FIG. 18.During the first second or few seconds of the cycle, the driveshaft components welded in the previous cycle are removed from the welding apparatus, as indicated by time bar 136. At approximately one second into the cycle, the charging circuit switch 74 is closed to supply voltage to the capacitor bank 64, as shown in FIG. 17, the delay in the start of the charging of the capacitor bank means that the voltage of the capacitor bank 64, as indicated by curve 140, is lower than the voltage of self breakdown 142.
The self breakdown voltage is that voltage which is sufficient to overcome the insulation associated with the apparatus, giving rise to a sudden, unwanted discharge of voltage.
The self discharge voltage is the level at which the electrical insulation is no longer sufficient to prevent discharge. To avoid premature discharge of the voltage, the charging of the capacitor bank is purposely carried out at a rate to maintain a difference or gap between the voltage of self breakdown and the voltage of the capacitor bank.
Preferably the difference in voltage between the self breakdown voltage of the discharge switch and the voltage of the capacitor is maintained at a level of at least 200 volts during the charging of the capacitor.While the capacitor bank 64 is being charged, the components to be welded are assembled and made ready to be inserted into the inductor 46, as indicated by time bar 144. After the voltage of the capacitor exceeds the minimum or threshold voltage, indicated by curve 146 in FIG.
After the threshold voltage is reached, the assembled driveshaft and end fitting components are inserted into the inductor 46, as indicated by time bar 148. After the assembled components are inserted into the inductor, the voltage in the capacitor bank 64 is discharged across the gap 68 in the discharge switch 65, and the assembled components are welded. The assembly, insertion into the inductor, and removal from the inductor can be completed either manually or by an automatic apparatus, not shown, such as a robot.
By delaying the insertion of the assembled components until the capacitor bank is fully charged, the possibility of prematurely discharging the capacitor bank and permanently ruining the driveshaft is precluded.As shown in FIG. 19, a portion of the welding surface 149 of the neck 38A of the yoke 24 is the prime welding area 152. The prime welding area is typically made of the same material as the rest of the welding surface 149 of the end fitting, but the prime welding area 152 is the zone where the maximum strength of the weld occurs. This is determined by various factors, such as the spacing or gap between the drive shaft 12 and the welding surface 149, and such as the angle and impact of the contact between the driveshaft and the welding surface 149.
While other areas of the welding surface may also be welded to the driveshaft, the prime welding area 152 provides the best possible adherence of the driveshaft 12 to the yoke 24.As described above, the welding surfaces usually have oxide films and various contaminants.
To obtain a strong joint or weld, it is necessary to clean this contamination from the welding surfaces. In the process of MPW in the area where the surfaces collide with each other at an angle and at high velocity, the resulting cumulative jet includes material from the collision surfaces. It is desirable to contain these contaminants and pressurized air to prevent them from escaping from the cavity 156. Otherwise, the contaminants could accumulate on various elements of the inductor apparatus, and the force of the contaminants and pressurized air escaping from the cavity 156 would degrade the central insulator 58 (shown in FIG.
The configuration selected for any particular welding operation well depend on such factors as the yoke shape, the required strength of the materials and of the bond, the tube diameter, and the materials to be used. Results and Discussion Figure 5 shows distributions of the magnetic flux density of the square working coil.
19, 21 and 22, the welding surface 149 need not be cylindrical, but can be on an angle (frustoconical), thereby defining, with yoke shoulder 154, a cavity 156.
Magnetic flux is increased at the upper part of a coil and concentrated in adjacent corner of coil. At the end of the cavity 156, there is provided one or more pockets 160 which act as collection points or depositories for contaminants generated during the welding process. The presence of a pocket 160 in the end yoke enables a substantial portion of the contaminants to be held in without escaping to the atmosphere, thereby promoting the efficiency of the system. Where the welding surface 149 is frustoconical, the welding process causes the driveshaft tube 12 to contact the welding surface 149 first at an initial contact portion 161 of the welding surface, then progressively along an intermediate portion 162 of the welding surface, and finally at an end portion 163 of the welding surface.
Especially, Figure 6(c) indicates the distribution of the electromagnetic force of inside square coil. The pocket is positioned near the end portion 163 of the welding surface to collect the contaminants and pressurized air. The maximum electromagnetic force generated in coil is about 951 N and in the edge about 503 N was measured.
When interaction between a square coil and Al pipe is being processed, the collision of Al pipe is caused because the electromagnetic force acts from surface to inside of the Al pipe. 19, and can be positioned on the shoulder 154, or on the welding surface 149, or on both the shoulder and the welding surface, as shown in FIG.
The pocket 160 can be of any suitable shape for collecting the contaminants and pressurized air.Another aspect of the welding process of the invention is the use of a contamination shield, such as annular plastic shield 164. These phenomena occurred because current is accumulated in the corner of the square coil compared with the solenoid coil at discharging of current. Even though the end 14 of the driveshaft tube is generally axially aligned with the shoulder 154, excessive contaminants can be emitted from the cavity 156 during the welding process. The shield 164 helps prevent excessive contaminants and pressurized air from escaping the cavity 156. As explained above, the impact of the contaminants and pressurized air forcefully ejected from the cavity 156 can damage the central insulator 58.
Preferably, the shield 164 is a single-use protective envelope located where the end 14 of the driveshaft 12 meets the shoulder 154 of the fitting neck 38A to prevent escape of contaminating gases, vapors and particulate matter during the welding process.As shown in FIG.
20, where the end fitting welding surface 149B is cylindrical rather than frustoconical, the end 14 of the driveshaft 12 is positioned near the midpoint of the inductor coil 48.
The prime welding area 152B is shown as being positioned adjacent the end 14 of the driveshaft 12. 20 is that since the end 14 contacts the welding surface first, the wave or flow of contaminants and pressurized gases is contained, and cannot escape.As shown in FIG.
21, the welding surface is a convex welding surface 149C having two prime welding areas 152C. The slot 168C is particularly advantageous where there are two prime welding areas, such as shown in FIGS. 21 and 22, because the slot gives the yoke the ability to deform slightly when necessary, thereby greatly increasing its usefulness as a component of a driveshaft assembly.
Therefore, when there are two prime welding areas, the flexibility gained by the use of the slot allows both of the welded connections to be stressed, thereby distributing the forces and producing a stronger overall weld.The slot 168C can be of any shape, such as the annular shape shown in FIG. Preferably, the slot has an orientation generally normal to the welding surface, as shown, although other orientations are possible.
Setup and Procedure To test for the developed working coil efficiency test, as show in Figure 7, the experimental employed in this study is a W-MPW manufactured by WELMATE CO., LTD.
22 improves flexibility of the end fitting in the same manner as described in connection with slot 168C shown in FIG. Additionally, a second slot 170D can also be provided on the inside surface of the end fitting 38D. A preferred slot has a width within the range of from about 2 to about 5 mm, and a depth within the range of from about 1.0 to about 10 mm. After experimenting, the (a)(b)(c) Figure 6. In addition, ultrasonic cleansing was carried out for approximately 10 minutes within acetone in order to remove grease.
And then the weldment was observed by microscopic on circumferential cross section. Results and Discussion Figure 9 shows the measured waveform while discharging the energy charged in working coil. The sin-waveform of decreasing vibration was recorded and it took about 25 us to peak current needed to welding. The weldment and section of welded part were presented at Figure 10. These results are similar to the output data from electromagnetic model that electromagnetic force decreases as moving into the corners as shown Figure 6. The maximum electromagnetic force generated in coil is about 951 N and in the edge about 503 N was measured. The generated electromagnetic force is the greatest at the centre adjacent to coil, decreasing as moving into the edge. Park, “Design of Joints for the Automotive Space frame with Electromagnetic Forming and Adhesive Bonding,” Ph.D. Thesis, Graduate School of the Seoul National University, Seoul, 2004 K. Kobayashi, “Production and Fabrication Technology Development of Aluminium Useful for Automobile Lightweights,” Advanced Engineering Materials, Vol. Yang, “Numerical Simulation of the Magnetic Pressure in tube Electromagnetic Bulging,” Journal of Materials Processing Technology, Vol. Sato, “High-Speed Forming of Metal Sheets by Electromagnetic Force,” JSME International Journal, Vol. Kapoor, “Modeling of the Electromagnetic Forming of Sheet Metals: State of the Art and Future Need,” JSME International Journal, Vol.
Barber “Magnetic Pulse Welding of Tubing: Exploring the Cold Welding Process,” Fabricator, Vol. Daehn, “Modeling of Electromagnetically Formed Sheet Metal,” Journal of Materials Processing Technology, Vol.



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