US 2815535 A
Description (OCR text may contain errors)
A. G. DENE, JR
Filed June 35, 1953 INVBVTOR.
SONIC WTHGD MR PGWDEWD EETAL MOLDING Albert G. Bodine, in, Van Nuys, Calit. Awlication lune 26, 1953, sum No. SMAM 10 cm (Cl. Sid-49.2)
This invention relates generally to the art of powdered metallurgy, and more particularly to the application of sound waves to the powdered metal being molded to improve the quality of the product.
In the molding of products from powdered metal, the powdered metal is subjected to high pressme within the mold. To the present time, however, it has not been possible to adequately pressurize the material in pockets and undercuts in the mold, and the process has accordingly not heretofore been successful in the production of high precision parts of complicated shapes.
The primary object of the invention is accormngly the provision of methods for assuring complete filling and compacting of the powdered metal within molds having pockets, undercuts and the like.
A further object is the provision of methods for more tightly compacting the powder in predetermined local'rcgions of the part where'locally incrmsed density and strength is desirable, for example, in the gear tooth region of a gear.
In molding of parts from powdered metal, the powdered metal is placed in the mold, and then subjected to great pressure, as is known. The minute metal particlw are forced into tight iuterengagement and a shape is so formed which, after removal from the mold, is aintered at a moderate high temperature, such as approximately 19$? C., but depending upon the metal.
According to the present invention, the metal powder in the mold is subjected to sound waves during the com pression operation. By sound waves, I do not refer to audible sound waves in air, nor do I confine myself to the audible spectrum of sound wave frequencies. Instead, the term refers more broadly to alternating waves of compression and raretaction in the transmitting media, which may include first, the vibratory elmtic rod or other transducer through which the sound waves may be transmitted to the powdered metal body, and second, the powdered metal body itself. These waves may be of any frequency efiective in accomplishing my purposes, though the range up to 20-50 kilocycles per second is presently preferred, being within the range readily achieved with suitable known wave generating devices such as magnetostriction and piezoelectric, generators.
The alternating compressions and rarefactions pro duced in the powdered metal body occur with reference to a mean pressure which is the molding pressure exerted within the mold. These compressions and raretactions agitate the metal particles and cause them to flow into all portions of the mold, including complicated pockets and undercuts. A feature of the invention is the creation within the body of powdered metal of a pressure antinode zone of a sonic standing wave, thus subjecting the material in said zone to a periodic stress or pressure cycle, which is very efiective in compacting the material. This sonic standing wave may be set up primarily in an elastic bar, which is arranged so that a pressure antinode region thereof is in engagement with the body of material, canaingthelattertoacousticallycoupleinaudpartakeot 23%,535 Patented Dec. id, lbb? ice the same stress cycle as that in the engaging portion of the bar. In another form, a condition of resonance may be set up in the body of material itself, creating a sound wave pattern with definitely located pressure antinodes and velocity antinodes, and the high amplitude pressure cycle at the pressure antinode regions gives those regions of the product increased compactness and density.
The wave energy expended in the powdered metal body is considerable, and is of course dissipated as heat. This heat is generated at the points of contact between interengam'ng particles, and causes sutiicient local heating at those points to cause the particles to become bonded or welded to one another by localized melting at the contacting areas. The article coming from the mold is consequentiy an integrated body of increased ruggedness, capable of withstanding considerable handling without crumbling.
In the process according to the invention the sound waves radiated into the powdered metal body at first cause individual particles of the metal to vibrate or oscillate as independent bodies. The impacts between individual particles cause some degree of elastic deformation of in dividual particles. These types of vibratory agitation promote the free flow of the particles into the various pockets, crevices or undercuts of the mold. As pressure is maintained or gradually increased during this vibration, the particles are compressed more tightly together, and finally are no longer capable of free and independent vibration. By the time this stage is reached, the various pockets and undercuts of the mold have been completely filled and the material therewithin pressurized to a degree not heretofore possible, and if the sound waves were then stopped, a. greatly improved product would be obtained. However, as the particles are pressed into interengagement, they gradually form an integrated body having properties of mass and elastically permitting it to undergo cyclic elastic deformation at minute amplitude. Sustaining the operation under these conditions further compacts and integrates the particles into a body of high density.
The invention will be better understood by referring now to the following detailed description of several present illustrative embodiments thereof, reference for this purpose being bad to the accompanying drawings, in which:
Fig. l is a view partly in section and partly in elevation showing a powdered metal press and a sound wave driver, the ram of the press functioning also as the bar through which sound waves are transmitted to the product;
Fig. 2 is a view similar to a portion of Fig. l, but show ing a modification;
Fig. 3 shows a standing wave pattern which may be set up in the mold of Fig. 2;
Fig. 4 is a view similar to Fig. 1 but showing a modification; and
Fig. 5 is a fragmentary view similar to a portion of Figs. 1 and 2, but showing another modification.
in Fig. 1 of the drawings, numeral 10 designates generally a suitable press, usually hydraulic, and comprising base 13, standard 12 and head 13in which plunger 14 is mounted for vertical movement under hydraulic or mechanical pressure exerted through conventional means and not necessary to illustrate herein. Mounted on base ti, and secured in position as by means of set screw 15, are upper and lower mold blocks 16 and 17 respectively, having horizontal parting plane 18 and mold cavity 19 extending above and below said plane, as indicated. Upper block 16 has a vertical bore 20 to slidably receive ram 21, and this bore fill-opens into the top of cavity 19 as shown. The cavity 19 may have undercuts such as indicated at 22.
The ram 21 is vertically aligned with press plunger 14, and mounted between the two is a coupling member 24 having low acoustic impedance, i. e., substantial deforms I tlon amplitude under the cyclic driving force exerted thereagamst, as later described. A rubber block, as shown, or a spnng, will serve for this coupling element 24. in the case of a spring, it must of course be designed with suflicient strength to transmit the pressure exerted by the press. A sleeve 25 mounted on plunger 14 extends downwardly around element 24 and receives the top end portion of ram 21. The design is such that when plunger is elevated, the lower end of this sleeve 25 clears the upper end of ram 21 to permit the assembly of ram and die blocks to be installed in or removed from the press.
As will be seen, downward movement of press plunger b 14 transmits force through element 24 to the upper end of ram 21, and the latter transmits the pressure of the press to the body B of powdered metal-which has been filled into the die cavity 19.
The ram 21 functions additionally to transmit sound waves to and into the body B, and in the apparatus of Fig. 1, this is accomplished by using the ram 21 also as the rod of a magneto-striction vibrator 30. For this purpose, the rod 21 is made of a nickel-iron alloy having magneto-sanction properties, i. e., the ability to vibrate longitudinally at high frequency in response to a periodic magnetic field. The field is produced by coil 31 surroundmg the rod, and this coil may carry an alternating current of suitable frequency, superimposed on a direct current employed for polarizing purposes, as in conventional practice. A separate polarizing coil may alternatively be used, and there may also be used two coils whichare in the plate and grid circuits of an oscillator tube, all. as well understood in the magneto-striction art. The coil arrangements are merely diagrammatically indicated in Fig. l, and the generator for energizing the coil is also omitted from the drawings since it may also be of conventional character. It may here be mentioned, however, that the use of a power oscillator, auto-resonant at the resonant frequency of the load viewed by the coil 31, permits operation at the resonant frequency of the load without manual attention by the operator. 0n the other hand, it is also possible to use an oscillator and amplifier for the drive of the coil 31, and in' this case, resonant operation is easiest achieved by manual adjustment of the oscillator, guided by a current meter in the circuit feed ing the coil 31. Even without such an indicating instrument, the operator will readily become sufficiently familiar with the process and apparatus to adjust to resonant operation guided by the visual and audible evidence of the behaviour of the system.
The apparatus as thus broadly described may be designed for operation in several different ways.
First, the bar or rod 21 may be designed for high Q," meaning low energy dissipation and a sharp resonance peak, with a strong tendency to influence the entire oscillatory system to operate at its own natural resonant frequency. A solid bar 21 will have relatively high Q. For low Q, the bar 21 may be laminated, which introduces frictional energy dissipation, and thus broadens the hump of the resonance curve. The high Q bar is said to have sharp tuning, the low Q bar broad tuning. An auto-resonant power oscillator may be employed, and such an oscillator will deliver an alternating current of frequency governed by the resonant frequency of the bar.
The article being molded is coupled into the system, but if it is acted upon by a high Q bar, its own natural period will not greatly influence the operating frequency of the system as a whole.
Operation of the system as thus described is as follows: The alternating magnetic field of coil 30 sets up oscillatory forces longitudinally of rod 21 causing said rod to alternately lengthen and shorten. At the start, the bar 21 behaves as a half wavelength free-free bar, and vibrates in the longitudinal mode characteristic thereof. This means that the center of the bar stands substantially stationary, while the two end portions thereof move equally and oppositely to one another along the longi tudinal axis of the bar at the natural resonant frequency of the bar governed by its length and the velocity of sound in the material of the bar. The lower end portion of the bar thus moves up and down at this resonant frequency in contact with the powdered metal in the cavity 19, vibrating the body of powdered metal particles accordingly.
As earlier explained, in this beginning stage of operation, prior to application of substantial pressure by means of the bar 21, the metal particles tend to vibrate independently of one another. The press 10 is then operated to exert an increasing downward force through plunger 14, coupling element 19, to the bar 21 and thence against the body of powdered metal. As the pressure increases on the body of powdered metal, the particles thereof are more and more strongly independently vibrated, and the resulting agitation causes them to flow and pack more deeply into the mold cavity, filling all small pockets, crevices and undercuts as the pressure is increased. When the mold cavity has finally become substantially completely filled and the material relatively compacted therein. two changes occur. The particles no longer undergo independent oscillatory motion, and instead, the entire compacted body of metal particles tends more and more to elastically vibrate, i. e., compress and expand, as a unitary elastic body. In this phase, sound waves (elastic waves of tension and compression) are set up in the body, and their travel therein causes periodic elastic deformation of the body, without, of course, necessitating any vibratory acceleration or displacement of its center of gravity. And as this takes place, the impedance of the compacted body materially increases, with the result that the amplitude of vertical oscillation of the lower end of the bar 21 is materially reduced, while at the same time the oscillatory force with which the lower end of the bar vibrates the compacted body of metal particles is correspondingly increased. In effect, the bar 21 gradually undergoes a transition from half wave operation to quarter wave operation. That is to say, the lower end portion of the bar undergoes a transition from a velocity antinode region to a pressure antinode region, the vibration amplitude of the lower end portion of the bar approaching. but not quite reaching, zero amplitude, while the upper end por tion of the bar continues as a velocity antinode region. The low impedance coupling element 19 operates throughout to transmit the pressure of the plunger 14 to the rod 21 while still permitting vibration of the upper end portion of the bar relative to the plunger.
in this conversion from half wave operation to quarter wave operation, the natural resonant frequency of the bar 21 is substantially reduced. If the change from half wave operation to quarter wave operation were to run its full course, the frequency would of course be reduced by one-half. In practice, this will never be achieved because body B does not exhibit infinite mass, but the frequency reduction may be regarded as approaching a limit of one-half its original frequency. As earlier explained, a power oscillator having auto-resonant characteristics may be employed for energizing of the driving coil 31, and its frequency or operation accordingly follows the described gradually reducing resonant frequency of the bar 21.
From what has now been said, it will be understood that as the pressure exerted by the press 10 through bar 21 onto the body of powdered metal is increased to its maximum, the lower end of the bar gradually approaches pressure antinode behaviour, and exerts a maximized pressure cycle on the body B. Under these conditions of operation, the sound wave action induced in the body B causes it to be alternately elastically compressed and permitted to expand. Under ordinary conditions, the body B then experiences the stress conditions characteristics of a pressure antinode, and these are maximum pressure cycle with minimum amplitude of vibration. These conditions are highly favorable to the production h of a very dense body E, of substantially unitcrm density throughout.
Assuming application of the pressure cycle for a sufficient period of time, the ry energy dissipated within the body B results in suificient l heating of the points of contact between interengagement particles as to accomplish a sort of welding of the particles to one another.
Another type of operation is also possible, akin to that described above in all respects excepting that the fre quency of vibration of the bar, either fundamental or some higher order harmonic, gives a wave pattern in body B. This frequency can be adjusted to correspond with a resonant frequency of the body B itself. This could be accomplished either by g the bar 211 of a length which is small relative to the dimensions of the body B, or by relying on an overtone frequency of the bar 21. For instance, if the length of the bar 21 is roughly comparable with 0.4 diameter of the body B, its fundamental frequency as a hall wave bar may correspond to a desirable resonant frequency of the body B. Or, in view or the fact that bar It vibrated as described will have not only a fundamental frequency, but will also vibrate at various harmonics, one of these harmonics may, by suitable design of the bar 21, be caused to correspond with a resonant frequency of the body E.
In either case, the body 3, instead of elastically contracting and expanding as a whole, may develop its own resonant acoustic standing wave pattern within its dimensions, with both pressure and velocity nntinode regions. In such cases, the pressure antinode regions are subjected to maximum pressure cycle and will become most strongly compacted and of greatest density, while the velocity antinode regions will be thoroughly agitated during the process and so brought to a condition of uniform density, but the density may not the value reached at the pressure antinode regions. For some purposes, this is a distinct advantage, and Em'ther description of such wave patterns within the body B will be given hereinafter.
Assume next that the mtem is as described in the foregoing, excepting that a bar 21 of low Q is employcd, as descrilmi earlier. Operation in this case is in general quite similar to that for the first case, with the exception that the system is much more strongly influenced by any natural resonant frequency of the body B. That is to say, the system is much less sharply tuned to the natural resonant frequency dictated by the length and speed of sound in the bar 231, and touch more strongly conscious of resonant frequency tendency in the body B. If, therefore, the body B is so shaped og. =rlimensioned as to possess a natural resonant frequency for acoustic waves anywhere in the general region of the natural frequency of operation of the bar 21, the system will tend to oscillate at a resonant frequency approaching that of the body B. Thus, in the event that resonant wave patterns should be desired in the body B, then, preferably, a bar 21 of relatively low Q is employed, so that the system can resonate easily at a frequency approaching the resonant hequency ot' bodyB.
As a third case, let it be assumed that the system is powered not by an auto-resonant power oscillator, but by oscillator and power amplifier of a conventional type which does not readily or automatically follow the resonant frequency of the rod. In such a system, manual tuning adjustments are provided by which the oscillator may be tuned to resonance with any output load. The situatlsn in this case is that the operator must be relied on to vary the frequency of the generator system in accordarlce with or so as to follow the behaviour of the bar 2L and body B. By proper manual adjustment, the frequency of the generator can be varied to follow the lowering frequency characteristic of the bar 21 as pressure is increased against the body 18, and also, particularly with a bar of low Q. adjus can be e to eed complish resonance and the desired acoustic wave pattern within the body B.
Fig. 2 shows a modification of the lower portion of Fig. 1, designed for a case in which a specific wave pattern is desired in the body of material, and in this case, two die blocks 40 and 41 are employed, shown as resting on the base 13. of the same press as shown in Fig. 1. The upper die block 40 has a bore 42 to receive the vibratory bar 21.1: which will be understood to be similar to the bar 21 of the apparatus previously described. The die cavity 43 formed between the blocks 40 and 41 is in the shape of a simple spur gear, and the lower die block 41 is formed with an upwardly extending mandrel M which is received within a socket 45 formed in the lower end of the bar 21a. The mandrel it thus forms a hole in the center of the gear and the cavity is shaped to provide the gear with a hub portion 47, a web portion 48, and a toothed rim 49.
Fig. 3 shows a standing wave pattern such as may be established in the material in the cavity of Fig. 2. The wave pattern shown in Fig. 3 is a common pattern found in cylindrical cavities, and is the third resonant mode. its characteristic is an inner pressure antinode designated by the letter P, an annular velocity antinode region, designated by the letter V, and an outer peripheral pressure antinode region designated by the letter F. Such a pattern is readily excited by the bar 21a bearing on the central hub portion of the gear-shaped body of metal particles within the cavity.
As earlier explained, it is necessary that the system be designed to operate at a frequency which can develop this desired acoustic wave pattern, and this can be accomplished'in various ways as heretofore noted, but is most easily accomplished by use of a bar 21a of low Q, driven by an auto-resonant power oscillator, having the necessary frequency range. The low Q bar readily finds and vibrates at the natural third resonant frequency at which material in the mold cavity tends to resonate. With a high Q" bar, it is further necessary that the bar 211 have a resonant frequency corresponding with the third resonant frequency of the cavity (assuming, of course, that the wave pattern of Fig. 3 is desired). The result of this practice of the invention is that both the hub and toothed rim portions of the gear are formed under the high pressure cycle conditions characteristic of a pressure antinode, and are accordingly highly compacted, whereas the web portion 48 is not so greatly compacted and is of lesser density in the final product. The gear resulting from this practice of the invention is accordingly highly dense and wear resistant in its rim and hub portions, where maximum loads exist, and having good grain for damping characteristics elsewhere.
Pig. 4 shows a modified form of apparatus, using a. press 50 with base 51 and standard 52, the base supporting die blocks 53 and 54 of the same nature as those shown in Fig. 1. Thus the die blocks are formed with a cavity 55, and the upper die block has bore 56 to slidably receive cylindrical bar 57.
The bar 57 has intermediate its ends a piston 58 working in a hydraulic cylinder 59, the latter provided with upper and lower liquid connections 60 and 61, respectively. The upper end of the bar carries a vibrator 645 only conventionally illustrated, but understood to be any suitable electrically driven vibrator, such as a piezo-' electric crystal or any other found suitable.
In this case, increasing hydraulic pressure is exerted on the body of metal particles by introducing hydraulic liquid under pressure to the cylinder above piston 58. The bar 57 is at the same time subjected to longitudinal elastic vibration, accomplished in this instance, however, by means of vibrator 64 mounted on its upper end. As is well known, the bar supported near its middle, as is the bar 57, is readily excited to its half wave mode of 10m gitudinal vibration by means of a vibrator mounted on one end, as is the case in the apparatus of Fig. 4. As-
3] suming use of an electrically driven crystal type ct" vibrator or transducer, the vibrator may again be either of low or high Q characteristics, depending upon the type of crystal or other vibrator employed. If a simple conventional voice coil type of vibrator is employed, such as used in loud speakers, a very low Q is provided. The apparatus of Fig. 4 behaves essentially, in all material respects, as does that of Fig. l, and is subject to operation in all of the various modes described in connection with Fig. 1. Thus, the bar 57 is excited at first to operate at half wavelength, in the nature of a free-free bar. As the powdered metal in die cavity is compacted, the behaviour converts gradually to onequarter wavelength operation, with pressure antinode conditions towards the lower end of the bar, and a velocity antinode condition remaining at the top. No further description of the embodiment of Fig. 4 is deemed necessary since that heretofore given in connection with Fig. 1 fully applies, and it is only necessary to point out that the system of Fig. 4 is of some advantage over that of Fig. 1, since the embodiment of Fig. 1 presents some problem of applying pressure from the pressv to the upper velocity antinode region of the vibratory bar 21, whereas in Fig. 4, the hydraulic pressure is easily applied to the Zubsta'ntially non-vibratory center or lower section of the Fig. 5 shows one further embodiment, and may be rcgarded as a modification of either Fig. l or Fig. 4. Upper and lower die blocks 65 and 66 are to be understood as mounted on the base of a suitable press, and ntnncral 67 designates the cylindrical ram of such press, entering upper die block through here 68. In this case, the sound wave vibrations are not transmitted to the material through the same member 67 by which the main compressive force is exerted on the body of powdered metal within the die cavity but rather a separate vibrator 69 is employed. This vibrator, which is typically ylin- :drical in form, is here shown to enter the lower die block in a lateral direction through a bore 70, its inner end being shaped to engage the body of material B in the die cavity and to, in effect, form one defining surface of the die cavity. Combined with vibrator 69 is vibration generator 71, and this may again be of a crystal type, or any other found suitable. Alternatively, as will be apparent, the magneto-striction type of vibration generator can be employed by using a body of magneto-suictivc material, for the member 69, surrounded by a suitably energized coil. To hold the vibrator 69 up to the body 3 under the high compression exerted thereon by ram 67, a clamp 73 is secured to die block 66 and engages over a flange 74 mounted on the vibrator 69, a ring or washer 75 of resilient material being used between the clamp and fiange 74. It is evident that a suitable vibration generator can act directly upon the body B, without requiring an intervening rod in all cases. Actually, the vibrator can be of the direct acting type, so that the clastic vibrations are in the body B only. Member 69 end thus be an electro-mechanical transducer, such as a mag.- neto-strictive vibrator as described above, or it may "be a barium titanate ceramic driven by an electrostatic field in the conventional manner, employing the necessary high voltage connections to a conventional condenser type of coupler which may be designated by member 71. There are many other well known forms of vibrators, all of which can generate the desired elastic or wave vibratiou in body B. If a vibrator is acoustically matched to body 13 so that the impedanccs are of the same order of magnitude a very etiective sonic vibration can be generated in body B even though there be no elastic vibration in the vibrator.
The operation of the modification of Fig. 5 will be self-evident, the only departure from the types of operation previously described being that sound wave vibrations are transmitted to the body B through a vibrator which is separate of the ram 67 through which the compressive pressure is exerted.
Various illustrative embodiments of the invention have now been described. It is to be understood, however, that these are for illustrative purposes only, and that the invention may take various other forms coming within the scope of the appended claims.
l. The process of forming separate portions of a fusible material into a consolidated body, that comprises: holding separate portions of material in pressural contact with one another, transmitting sonic waves through said portions of material so held in pressural contact, in such manner as to produce in said portions of material alternating half cycles of increase and decrease in compression with reference to the pressure level at which they are held in contact with one another, and sustaining said sonic wave transmission until said portions of material are worked thereby into intimate mechanical juncture at a multiplicity of points of surface contact, and until said portions of material heat and fuse to one another at said points of contact by conversion of absorbed sonic energy into sufiicient heat to attain the fusion temperature of the material.
2. The process of forming separate portions of a fu- Bible material into a consolidated body, that comprises: introducing the portions of material into a closed mold cavity, exerting a compressive pressure on said material within said cavity, transmitting sonic waves through the portions of pressurized material in the cavity, in such manner as to produce in said portions of material alternating half cycles of increase and decrease in compression with reference to said compressive pressure, and sustaining said sonic wave transmission until said portions of material are worked thereby into intimate mechanical juncture at a multiplicity of points of surface contact, and until said portions of material heat and fuse to one another at said points of contact by conversion of absorbed sonic energy into sutiicient heat to attain the fusion temperature of the material.
3. The process of forming fusible granular material into a consolidated body, that compirses: introducing the granular material into a closed mold cavity, exerting and sustaining a comp essive pressure on said material within said cavity, transmitting sonic waves through the pressurized granular material in the cavity, in such manner as to produce first in settling and consolidation of the material and a filling of the material into all existing corners, undercuts or crevices of the mold cavity. and then to maintain elastic waves in the consolidated material characterized by alternating half cycles of increase and decrease in compression with reference to the compressive level at which said material is held, and sustaining said sonic wave transmission until the granules of said material are worked thereby into intimate mechanical juncture at a multiplicity of points of surface contact, and until said granules of material heat and fuse to one another at said points of contact by conversion of absorbed sonic energy into suificient heat to attain the fusion temperature of the material.
4. The process of forming powdered metal material intoia compact self-sustaining consolidated body that comprises: introducing the powdered metal into a closed mold cavity, exerting and sustaining a compressive force on said powdered metal material in said cavity, transmitting sonic waves through the pressurized powdered metal in the cavity, in such manner as to produce first a settling and consolidation of the powdered metal material and u filling of the material into existing corners, undercuts or crevices of the mold cavity. and then to maintain elastic waves in the consolidated material characterized by ulternating half cycles of increase and decrease in compression with reference to the compressive level at which said material is held, and sustaining said sonic wave transmission until the metal particles of the mutcrial are worked and keyed thereby into intimate mechanical luncture with one another at a multiplicity of points of surface contact within the material such that a dense and highly compact, self-sustaining body is produced.
5. The process of forming powdered metal material into a compact self-sustaining consolidated body that comprises: introducing the powdered metal into a closed mold cavity, exerting and gradually increasing a compressive force on said powdered metal material in said cavity, and while so doing, transmitting sonic waves through the pressurized powdered metal in the cavity in such manner as to produce first a settling and consolidation of the powdered metal material and a filling of the material into existing corners, undercuts or crevices of the mold cavity, and then to maintain elastic waves in the consolidated material characterized by alternating half cycles of increase and decrease in compression with reference to the compressive level at which said material is held, and sustaining said sonic wave transmission until the metal particles of the material are worked and keyed thereby into intimate mechanical juncture with one are other at a multiplicity of points of surface contact within the material such that a dense and highly compact selfsustaining body is produced.
6. 'lhe process of forming powdered metal material into a compact self-sustaining consolidated body that comprises: introducing the powdered metal into a closed mold cavity, exerting and sustaining a compressive force on said powdered metal material in said cavity, transmitting sonic waves through the pressurized powdered metal in the cavity in such manner as to produce first a settling and consolidation of the powdered metal material and a filling of the material into existing corners, undercuts or crevices of the mold cavity, and then to maintain elastic waves in the consolidated material characterized by alternating half cycles of increase and decrease in compression with reference to the compressive level at which said material is held, and sustaining said sonic wave transmission until the metal particles of the material are worked and keyed thereby into intimate mechanical juncture with one another at a multiplicity of points of surface contact within the material, and until the metal particles heat and fuse to one another at said points of contact by conversion of absorbed sonic energy into sufi cient heat to attain the fusion temperature of the material.
7. The process of forming powdered metal material into a compact self-sustaining consolidated body that comprises: introducing the powdered metal into a closed mold cavity, exerting and sustaining a compressive force on said powdered metal material in said cavity, transmitting sonic waves through the pressurized powdered metal in the cavity in such manner as to produce first an individual random bodily vibratory action and migato'ry travel of the individual metal particles of the material to cause a settling and consolidation thereof and a filling of the material into exisfing corners, undercuts or crevices of the mold cavity, and then, as the material consolidates, an elastic deformation wave vibradon thereof, and sustaining said sonic wave transmission until the metal particles of the material are worked and keyed thereby into intimate mechanical juncture with one another at a multiplicity or points of surface contact within the material such that a dense and highly compact self body isproduced.
8. The subject ensues of claim ya have a,
said sonic vibration frequency of the consolidated unitary body, whereby to set up in said body a resonant acoustic standing wave having spacially separate localized pressure and velocity anti-node regions, such that the body is subjected to a maximized pressure variation cycle at, and most greatly compacted in, the localized pressure anti-node regions.
9. The process of forming powdered metal material into a compact self-sustaining consolidated body that comprises: introducing the powdered metal into a closed mold cavity, exerting and sustaining a compressive force on said powdered metal material in said cavity, establishing a resonant sonic standing wave in a sonic wave transmitting medium including as at least a part thereof the pressurized powdered metal in said cavity in such manner as to produce first an individual random bodily vibratory action and migratory travel of the individual metal particles of the material to cause a settling and consolidation thereof and a filling of the material into existing corners, undercuts, or crevices of the mold cavity, and then, as the material consolidates an elastic deformation wave vibration thereof, establishing the frequency of said sonic standing wave at a value such as to locate a pressure antlnode thereof within at least a portion of the consolidated elastic body of material, and sustaining said sonic standing wave, until the metal particles of the material are worked and keyed thereby into intimate mechanical juncture with one another at a multiplicity of points of surface contact within the material such that a dense and highly compact, self-sustaining body is produced.
10. The process of claim 5, which includes placing an elastic rod with one end portion in firm end engagement with the powdered metal material in the cavity, and with its other end portion free for longitudinal vibration, and setting up a longitudinal oscillating force in said rod at a frequency in the general region of a natural longitudinal resonant frequency of the rod while molding pressure on the body is gradually increased, whereby the rod tends to vibrate as a half wavelength rod while the body is in early stages of compression, and gradually undergoes a transition toward quarter wavelength vibration as the body is compacted, so as to set up a pressure antinode condition in the body during the later stages of compression.
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