The present invention relates to a device and a method for the mechanical treatment of conductive and non-conductive surfaces including impact treatment, cyclic deformation, surface polishing, oxide removal, electromagnetic forming and electromagnetic welding by tensile and compressive stresses with the ability of adjusting the direction and the amplitude of the applied force vector. The device and method can also be used for non-destructive determination of the stress tensor distribution in materials subject to treatment.
Mechanical treatment is used for tailoring the mechanical properties of a material subject to treatment with a scope of obtaining an approved profile of stress tensor distribution thereof. Such treatment has been historically performed mainly by thermal techniques as illustrated for example in U.S. Pat. Nos. 5,108,520 and in 3,480,486. Heating the material with consequent annealing (stress relief) or quenching (rapid cooling) methods, may result in reaching the desired levels of stress tensor distribution. One particular heat treatment method is the inductive heating with certain advantages in terms of time and contactless operation as disclosed in U.S. Pat. No. 2,446,202. The non-contact ability is the main advantage of these thermal techniques while their major disadvantage is the large uncertainty of the stress tensor distribution after the thermal treatment.
Apart from thermal treatment, mechanical methods have recently been developed and implemented in industrial applications. Ultrasonic Impact Treatment, as for example illustrated in U.S. Pat. No. 6,171,415, Laser Peening as for example illustrated in U.S. Pat. Nos. 4,937,421 and in 6,410,884 and Low Plasticity Burnishing as for example illustrated in U.S. Pat. No. 5,826,453, are the currently most widely accepted processes, which by introducing a certain amount of plastic deformation, produce a level of residual stress so as to improve damage tolerance and fatigue or stress-corrosion performance. The main advantage of all these techniques is their ability to precisely control the local surface stress tensor distribution, while their main disadvantages are the extensive time needed for such treatment and the requirement of a contacting means of treatment in some applications thereof.
Regarding cyclic deformation by the imposition of cyclic stresses in order to provide defect healing and microstructural strengthening, as for example in [Zhang-Jie Wang et al, Cyclic deformation leads to defect healing and strengthening of small-volume metal crystals, PNAS, 3, 112, 44, pp 13502-13507, 2015], poses the requirement of a method and a device for performing such treatment in an industrial scale.
As far as surface polishing and oxide removal is concerned, most treatments involve the implementation of dangerous chemicals and ultrasonic vibrations. The combination of ultrasonic, heat, and cleaning solutions is usually the preferred strategy. These applications present several disadvantages such as the necessity for tanks (in which the process takes place) and the use of solvents (subject to Health & Safety limitations). Aqueous solutions are also used, nevertheless are far less efficient.
Apart from the above, an electromagnetic hammer device has currently been used in an electromagnetic forming operation, as by way of example is illustrated in U.S. Pat. No. 3,426,564 and in an electromagnetic welding operation as by way of example is illustrated in U.S. Pat. No. 8,668,802. These electromagnetic hammer devices have employed the transmission of a pulsed electric current through a conductor (e.g. a solenoid) that is provided around the material subject to treatment, thereby giving rise to an inductive counter-acting response within the material. However, such an electromagnetic hammer device of the prior art can perform only a few mechanical treatment processes such as those referred to hereinabove since it might only supply compressive forces onto the material subject to treatment in a single direction, i.e. perpendicularly onto the material. Moreover, this electromagnetic hammer device requires excessive amounts of energy due to the substantially inferior magnitude of the inductive current within the material as compared to the current being supplied at the exterior thereof that eventually leads to the requirement of enhanced supply of current in order to obtain an adequate magnitude of the induced current and therefore be capable to properly perform such an electromagnetic forming or welding process.
Furthermore, none of the devices of the prior art provides for the non-destructive inspection of complex geometries and novel materials, e.g. sandwich structures that have always been a challenge, leading to new techniques based on laser-induced resonant frequencies, thus determining characteristic signatures of healthy structures. Possible defects alter or destroy the expected frequency signatures, leading to their detection. The excitation is offered by lasers which add great cost to the process.
Thus, the object of the present invention is to develop an electromagnetic hammer device for performing non-contact mechanical treatment of conductive and non-conductive surfaces, wherein such device and method may be universally applied to perform mechanical treatment operations of all kinds including impact treatment, cyclic deformation, surface polishing, oxide removal, electromagnetic forming and electromagnetic welding, as well as to perform measurement of the stress tensor distribution, the device being adapted to deliver both tensile and/or compressive forces with the ability of adjusting the direction and the amplitude of the applied force vector in a faster, better and cheaper way than any of the devices and methods of the prior art.
The electromagnetic hammer device of the invention adapted to provide mechanical treatment of a material comprises a first conductor arranged to transmit pulsed current through a predetermined path within the material subject to treatment and a second conductor lined on top of said first conductor, wherein said first conductor is supplied with a first pulsed current (I1) and said second conductor is supplied with a second pulsed current (I2), a layer of insulating material of a thickness (t) lined intermediately between said first and second conductor, wherein a simultaneous application of said first and second pulsed currents in the same direction results in applying a tensile force and exerting a pull effect onto the material subject to treatment and application of said first and second pulsed currents in opposite directions results in applying a compressive force and exerting a push effect onto the material subject to treatment, said force (F) being exerted perpendicularly onto the material subject to treatment and provided by:
where (L) stands for the length of the predetermined path within the material subject to treatment whereupon the force is applied, (μ) is the relative permeability of said layer of insulating material and (μ0) is the vacuum permeability.
According to one preferred embodiment of the invention, the electromagnetic hammer is adapted to provide mechanical treatment of a linear strip or planar surface segment of the material subject to treatment, whereby the second conductor is configured as a longitudinal strip having a length and a width equivalent or smaller than a length and width of the linear strip or planar surface segment of the material subject to treatment.
According to another preferred embodiment of the invention the electromagnetic hammer is adapted to provide mechanical treatment of incremental volumes of the material subject to treatment, whereby the second conductor is a V-shaped conductor and therefore the device is adapted to provide a mechanical treatment, such treatment being sequentially performed in incremental volumes of selected spots necessitating the mechanical treatment in the material subject to treatment.
According to further embodiments of the invention a pair of auxiliary conductors configured as longitudinal strips or as V-shaped conductors is provided on each side of the second conductor that is correspondingly configured as longitudinal strips or as V-shaped conductor, such auxiliary conductors providing the ability of exerting forces onto the material subject to treatment at selected angular directions.
Further embodiments disclose use of the electromagnetic hammer device of the invention in performing a desired mechanical treatment in a cylindrical or tubular material subject to treatment.
In accordance with another embodiment of the invention the electromagnetic hammer is adapted to provide mechanical treatment of linear strips or planar areas or incremental volumes of a non-conductive material subject to treatment, whereby the non-conductive material subject to treatment is covered by a layer of a conductive material adapted to receive the abovementioned first conductor and be covered by a film of insulating material, thereafter the second conductor being provided above the film of insulating material in a direction parallel to the underlying first conductor.
Finally, the same electromagnetic hammer device may be used to monitor and provide measurement of the stress tensor distribution in materials of all kinds.
Benefits and advantages of the present invention will become apparent after a careful reading of the detailed description with appropriate reference to the accompanying drawings.
The invention will hereinafter be presented with reference to the illustrative embodiments shown in the accompanying drawings, wherein are disclosed devices for applying different modes of stresses on the material subject to treatment.
The main object of the invention is to disclose an electromagnetic hammer device for applying tensile and/or compressive forces on the material to be treated, with the ability to act thereupon at appropriately selected angular directions.
In accordance with a first preferred embodiment of the invention the electromagnetic hammer device is adapted to provide mechanical treatment of a linear strip or a planar surface and of the volume underlying the same and determined by the skin effect of a conductive material subject to such treatment through applying tensile or compressive forces, exerted perpendicularly thereupon. In this respect, as shown in
The electromagnetic hammer device shown in
The parameters of the transmitted pulsed electric current, including frequency, duty cycle, period and amplitude can be controlled. In this way, the depth of the mechanically treated volume 6 pertaining to the skin effect of the conductive material subject to treatment 1 can be determined by controlling the frequency bandwidth of the first pulsed electric current supplied to the first conductor 2 that is arranged to pass through the linear strip or planar surface segment 3 of the conductive material subject to treatment 1. Thus if, in accordance with a preferred embodiment, the electromagnetic hammer device of the invention is provided with means of controlling the frequency bandwidth of the pulsed electric current passing through the linear strip or planar surface segment 3 of the conductive material subject to treatment 1, the effective depth of the linear strip or planar surface segment 3 of the conductive material subject to treatment 1 can be appropriately regulated, wherein, in particular as the frequency bandwidth is increased, the effective depth of the mechanically treated volume 6 pertaining to the skin effect is decreased and vice versa. It is herein noted that the duration of the action of the electromagnetic hammer on the mechanically treated volume 6 is determined by the period of simultaneous transmission of the abovementioned first and second pulsed electric currents through the mechanically treated volume 6 of the conductive material subject to treatment 1.
The mechanically treated volume 6, subject to treatment, where pulsed electric current passes, is covered by a thin insulating film 5 of a thickness t. Thus, the tensile or compressive force F acting on the mechanically treated volume 6 follows Ampere's law and is therefore provided by the following formula:
where L stands for the length of the mechanically treated volume 6 whereupon the force is applied, μ and μ0 are the relative permeability of the insulating means 5 and the vacuum permeability respectively and I1, I2, t stand for the aforementioned first and second pulsed currents and their distance t (thickness of the insulating means 5) respectively.
It is herein noted that force F is amplified if the insulating film 5 is magnetic with a magnetic permeability μ>1.
In case that currents I1 and I2 are of an equal amplitude I, force F becomes:
The sign of the force F indicates the character of the force being applied, i.e. it is an indication of such force being either tensile or compressive resulting from the aforementioned first and second currents being supplied in the same and in the opposite direction respectively.
In accordance with a further preferred embodiment, the electromagnetic hammer device of the invention is further provided with a pair of auxiliary conductors 7 and 8 as illustrated in
The auxiliary conductors 7 and 8 depicted in
Furthermore, if the pulsed currents in the auxiliary conductors 7 and 8 are supplied in a direction opposing the current of the electric conductor 4, the width of the area corresponding to the mechanically treated volume 6 is narrowed.
In this way, a non-contact push-pull multidirectional electromagnetic hammer is provided that can be used for impact or cyclic deformation treatment.
In conclusion, the electromagnetic hammer arrangement of
A further preferred embodiment of the electromagnetic hammer device of the invention appropriate for providing the desired effect onto an area under treatment is depicted in
Another preferred application of such impact or cyclic deformation treatment refers to the treatment of steady-state conductive cylinders.
Another preferred application of such impact or cyclic deformation treatment refers to the treatment of steady-state conductive tubes.
Mechanical treatment with the electromagnetic hammer of the invention can also be performed in a non-conductive material 18, such as that shown in
The electromagnetic hammer device shown in
The method can be used for oxide removal due to the ability to generate local force excess; additionally, electromagnetic forming and electromagnetic welding can be substantially improved with the present electromagnetic hammer device wherein a pulsed current passes through the material subject to treatment. Various planar, cylindrical or tubular surfaces of conductive materials can successfully be subjected to necessary mechanical treatment using the electromagnetic hammer of the invention. Appropriate mechanical treatment can also be provided in non-conductive materials by means of covering them with conductive elements. In this particular case, only compressive stresses can be applied on the surface of the material subject to treatment, but if such conductive materials are fixedly adhered thereupon tensile stresses might also be applied.
The described method and devices can be used for the non-contact mechanical treatment of conductive and non-conductive surfaces including impact treatment, cyclic deformation, surface polishing, as well as contactless and efficient removal of surface oxidation due to the aforementioned generated tensile and/or compressive forces with the ability of adjusting the direction and the amplitude of the applied force vector.
The electromagnetic hammer device of the invention may also be employed to measure the stress tensor distribution in the material subject to treatment, thereby the device being adapted to operate as a stress sensing element, by means of generating considerably smaller tensile and/or compressive forces, which, instead of treating the material, generate elastic waves, their shape and size determining the stress level of the corresponding area of elastic wave generation, propagation and detection.
All herein described embodiments of the electromagnetic hammer device of the invention may alternatively be employed to suit specific configurations of materials subjected to mechanical treatments, such as impact treatment, cyclic deformation, electromagnetic forming and electromagnetic welding, whilst mechanical treatments, such as surface polishing, oxide removal and mechanical machining are mainly being obtained with the electromagnetic hammer devices depicted in
An all-inclusive electromagnetic hammer device is provided that comprises conductors being configured in the form of linear strips and V-shaped conductors including auxiliary conductors in the form of linear strips and V-shaped conductors, wherein a case-specific arrangement of conductors is used to provide the aforementioned all-inclusive types of mechanical treatment in all types of planar or curved surfaces, such all-inclusive electromagnetic hammer device further comprising a power supply means and a computer provided with the appropriate software for arranging the frequency bandwidth and the magnitude and direction of the pulsed currents being supplied in each particular case to serve the scope of the intended mechanical treatment.
Accordingly a method for the mechanical treatment of conductive materials is provided that includes the steps of:
supplying a first pulsed electric current in a first conductor (2) through a predetermined path within the material (1, 13, 16) subject to treatment, and
supplying a second electric current in a second conductor (4, 10, 14, 17) lined on top of a layer of insulating material (5) separating said first conductor (2) from said second conductor (4, 10, 14, 17), wherein a simultaneous application of said first and second pulsed currents in the same direction results in applying a tensile force and exerting a pull effect onto the material (1, 13, 16) subject to treatment and application of said first and second pulsed currents in opposite directions results in applying a compressive force and exerting a push effect onto the material (1, 13, 16) subject to treatment, said force (F) being exerted perpendicularly onto the material subject to treatment.
In accordance with a further embodiment a further step of supplying a third and a fourth pulsed electric current in a third and fourth conductor (7, 8) or (11, 12) disposed on each side of the second conductor (4) or (10) respectively, thereby providing an enhanced resultant force being exerted onto the material subject to treatment and a capacity of controlling the angle in which this resultant force is being applied onto the material subject to treatment through varying the magnitude of the abovementioned third and fourth pulsed electric currents.
Filing Document | Filing Date | Country | Kind |
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PCT/GR2016/000028 | 6/13/2016 | WO | 00 |