IL41599A - Hollow articles made from a memory metal and their manufacture - Google Patents

Description

Hollow articles mads a memory metal their manufacture 39802 invention relates to hollow for example especially couplings and similar and to processes for their manufacture and Considerable effort has been expended over many years to provide simple and reliable means for joining the abutting ends of pipes and method used should not interfere stantially with the material in the no should flow be restricted to any significant The joint between the two pipes should be capable of withstanding any mechanical or chemical that the pipes themselves can without being too expensive or difficult to repair or With the great use of pipes in aerospace for example in aircraft hydraulic additional requirements of light weight in some small size have to be as aircraft are frequently taken apart for the connections to hydraulic equipment in various components have to be broken and remade in the often in confined These requirements militate against the use of welded or brazed which would otherwise appear to be an obvious method of overcoming the because welding and brazing require bulky equipment which must completely surround the pipes to be the resulting joints cannot readily be taken apart and Quite recently there have been discovered certain classes of metallic materials which can be made to exhibit useful sional changes during phase Such metallic materials will hereinafter be referred to as As used herein the term means a metallic material from which a article can be that an article which can be deformed from an original heat stable to a di configuration in which it will remain until raised a certain temperature the present the temperature of the memory when it will or attempt to towards its original con It will be understood that the heat recoverable article is of returning its original configuration without the further application of outside It will further be understood that by the term of expanding there is meant that the hollow article will expand of it is forcibly restrained from doing so out the further application of an external transition temperature of the memory metal may be a temperature range as hysteresis usually the precise temperature at a transition takes place on whether the temperature of the article is being raised or Furthermore the transition temperature is a function of the stress applied to the the temperature rising with increasing Typical memory are described for Patents and and Belgian Patent the disclosures of which incorporated herein by this As is it is necessary mechanically to deform articles made from memory metals i order to realise useful results from the phase changes or similar phenomena which occur at the transition to heating and cooling a memory t its transition temperature withoutprior defomation will not give useful dimensional The present invention is based on our surprising and unexpected observation that it is preferable to deform the article so that it cannot completely recover its original that is advantageous to introduce a amount of secondary deformation the By secondary mation there herein meant that deformation which cannot be recovered the recovery of the The present invention accordingly provides a method of a article by mechanicall deforming a hollow article from a memory as hereinbefore below the transition temperature of the which also comprises the step of imparting secondary ae to the The present invention also provides hollow article made from a memory as hereinbefore which contains some secondary as hereinbefore Without in any way intending to restrict the scope of the present invention it is believed that the email amount of secondary deformation introduces stresses into the article which stresses can b relieved the article is passed downwardly through its transitio It further believed that release of the internal in some way actuates the changes which occur at the transition temperature and thus spontaneous and more it is believed that it is the internal stresses that cause surprising of the articles of the present invention in tha they are eapabl of expansion after contraction and vice present invention accordingly further provides a hollow article which after contracting or expanding on passing through the transition temperature of metal is sequently capable of expanding or o g repassed through transition Secondary deformation ca be introduced in a number of by expanding article below the transition temperature and then heating it causing it to recover and contract about an object having a greater than the corresponding of the original high temperature of the articl Other methods may be used include imposing a force on the article which exceeds that to impart the maximum and working article above the transition temperature of the metal so that only secondary deformation ie in intentional deformation not be necessary because the metal may have been internally in the right direction during the manufacture of the This may be the for if the manufactured article not In annealing since thie removes random residual stresses and ensures satisfactory results from subsequent Amongst the metallic materiale which can be used in the present invention for the alloys disclosed in Patents and and Belgian Patent to is made clear in those such alloys undergo a transition at a certain which in the case of the and alloys described in Patent ie simply referred to as a phase other patents describe the transition which takes place in the disclosed alloys as one bet een and martensitic forms of the It to be understood that the alloys disclosed in the references cited above only exemplary of memory metals which may used in and it is be understood that scope of the invention is in no way limited to theee nor to the materials specifically set forth as examples in Bach of materials tested has been found capable of being subjected to a secondary mation sufficient to give useful spontaneous expansion to an article constructed in accordance with the Preferably the hollow article the word as used herein not being limited to right cylindrical hollow but also including members of irregular varying well as and similar One the important applications of the articles of the present invention XB in the coupling of objects as tubes and especially in hydraulic and it has been found that the ability of the couplings to withstand very high pressure without pulling apart can greatly be enhanced by the location of teeth within the A tubular coupling member made from a memor metal and provided with at least one inner projecting tooth claimed in our copending Application from which this application has been It preferred that the hollow article should be provided with one o projecting teeth on its inner Especially in the of a tubular coupling member it la preferable that the article ehould be provided with a continuous ferential Preferably the teeth are formed from a plurality of tapered sections and the distance between adjacent teeth and the angle of tapering are that expansion of objects to be connected caused by the biting of the teeth into the object on shrinkage can be aecoiamodated in the space between the biting angle of each tooth a end one edge of the biting angle advantageously lies approximately in a radial plane of the tubular coupling Tubular coupling according to the present invention are preferably provided with a recess of increased internal diameter about along their length that the abutting ends of the objects to be connected to not come into with the internal surface of coupling the tubular coupling have of reduced thickness at their ends and are preferably tapered or doubly tapered at these so that in these regions only a positive pressure is exerted on the being Especially when the tubular coupling members of the preeent invention are to be used i hydraulic systems it ie pre that the minimum wall ie such that radial expansion of the coupling under a given internal a hydraulic slightly less than the radial expansion under the internal pressure of the hydraulic pipes being that the connection remains tight under high hydraulic A preferred article constructed in accordance with the present invention a especially a for use in especially in Present require hydraulic equipment to be capable of operating at within the range of from about to but i desirable to have equipment capable of operating between about with some special e example in engine capable of withstanding over For reasons which will he a metallic material for in hydraulic line fittings therefore have a transition temperature below Liquid boiling at offers a convenient means of reducing temperatures of articles to its boiling Temperatures lower than of be obtained by other liquefied but nitrogen offers the advantages of ready availability and comparative metals for use in this aspect of the present invention those which have a transition perature within of about and In addition to satisfying the environment the use of such a metal at normal temperatures that it is in its a form where greater Among metals for the present invention there may be by way of the following i which the percentages are atomic percentages and are 1 50 Nickel 47 Iron 5 2 Titanium to 50 Aluminium Titanium 4 Titanium 48 Manganese 2 These alloys each have transition temperature within the desired It will be appreciated that the alloys may contain incidental impurities provided that the impurities do not adversely affect the mechanical and physical properties of the nor alter the transition temperature to each an estent that the article is rendered unsuitable for its intended Theee alloys for a hydraulic coupling or for any other application of the be manufactured and formed by any of the usual methods Of titanium either from their constituent elements or from alloys or compounds of the constituents in other Among such methods there may be mentioned by way of example consumable and arc inductio melting in graphite electron beam powder metallurgical methods and floating zone The resulting alloy can readily be formed into suitable blanks for final manufacture of the articles for hot hot hot or hot to a lesser by cold Whatever method of is the alloys are desirably annealed to ensure reproducibility of properties in the resulting Aircraft hydraulic systems contain many lengths of pipe haw to be joined and the like and which terminate in a variety of meters and operational At each such junction or a fitting of some type will be For simplicity of a coupling fo a simple butt joint between two pipes of the identical material and diameter will now described in more but it will be understood that the present invention provides fittings of configurations other than such a A tube of a metallic material of the type referred to is expanded is distorted at a temperature below the transition temperature of the for by forcing through the tube a mandrel having a diameter greater than the original diameter of the The degree of expansion is great enough so that both thermally recoverable and secondary deformation hereinbefore take tube is then raised above the transition temperature while being maintained in the expanded position by the mandrel or a keeper of approximately similar will fit tightly on the mandrel or keeper because it will to recover and contract radially toward its original conf At appropriate the tube ia again cooled to below its transition When tube reaches the transition tube expands in response to the elastic stress existing between the tube and thus lowering the spontaneous expansion increasing the internal diameter of tube and resulting in the tube being removable from the mandrel or As long as the temperature of the tube kept below transition it will retain this new internal enabling the coupling to placed in position over the pipes or other objects to be of must have an outside diameter than the expanded diameter1 of the and slightly larger than the original internal diameter of the After the coupling has been installed on the to be the joint is heated to above the transition perature of the metal of the Phe coupling being it shrinks towards its original configuration until it engages objects and is restrained further Because the recovery forces are the coupling makes an extremely tight fit on the objects so long as the joint is maintained above the transition restraining action of the objects on the which prevents complete recovery of the further deformation stresses explained into the coupling material and when the coupling is again cooled to the transition temperature it will undergo spontaneous expansion allowing the objects to be The introduction of secondary for tubular coupling is caused to contract over a a mandrel o pipes which to be prevents plete recovery the coupling That is to say if the total deformation is 9 of which are the coupling can only recover 7 units if the secondary deformation is completely This means that the new heat stable configuration is effectively 2 units greater than original configuration and therefore that the objects which to be coupled be greater at 2 than the original In order to make the articles of the present invention as versatile for example to the range of diameter of the pipes which can be it is obviously preferable that as great a possible percentage of the total deformation consistent with the need for at least some permanent We have found that the elasticity of most of the metals in the present invention results in the of able deformation being than might have been Thus when a coupling caused to contract about a mandrel so that secondary deformation let it has been found that generall the new configuration lies where between that defined by the mandrel and the original In other before permanent deformation an elastic deformation oecurs which an elastic to the article which will be released when the restraining force is the alloys discussed the elasticity is about so that the objects to be connected can have diameters that much smaller than the of the mandrel or By properly selecting the material of the mandrel or keeper is or its the total elastic plus of the coupling can be made to approach that which was originally built into it upon The distance through which the coupling can be recovered can be for by constructing the mandrel or keepe of a material having substantial In such a the elastic limit of the coupling must be exceeded before permanent deformation takes place in the For this the keeper could be constructed of the same material as is the or of another material having substantial for beryllium the keeper may be constructed of a material exhibiting a negative coefficient of In this the diameter would contrac as it was raised in allowing the coupling to recover to a greater degree than if the diameter of the keeper remained To the same result the keeper could be constructed in the form of a cylindrical spring such as a conventional roll pin that could be collapsed by recovery of the coupling on Other alternative methods of providing the keeper with sufficient elasticity for the purposes described will be apparent to those skilled in the art and are intended to be included within the scope the Prom the foregoing description it can be seen that the resent invention ro ides m ta lic article useful for man temperatures and are quick and easy to install or yet can withstand extreme temperature Various forms of the present invention will now he described in more by way of example with reference to the accompanying in which Figure 1 is a view of one form of coupling according to the present Figure 2 is an end view of the coupling of Figure is a view of the coupling of 1 positioned over a pair of Figure is a view of the coupling of 1 after installation on the Figure a view of a second form of coupling according to the present Figure 6 is a view of the coupling of positioned over a pair of Figure i a view of the coupling of after installation on the and Figure 8 is a view of a length of pipe with a band of metal shrunk about its Referring to the drawings and particularly Figure a coupling indicated generally by the reference numeral was formed as described The outside surface of the coupling 10 comprises a central portion 12 of constant section and two end portions and 16 each tapering toward their respective ends 20 of the The inner formed by the bore comprises a central portion of constant and flared end portions 26 and Between each end portion and the central between the end portion 28 and the central portion The teeth are each generally of saw tooth the radial portion of each saw tooth facing the centre of the It has been discovered that the strength of such a coupling is substantially increased by proper spacing of the teeth along the interior wall of the The strength of the coupling is further enhanced when the tubing material to be joined is itself deformed by the Figures 5 through 8 illustrate such a In Figure a coupling fabricated from a metal has an outer wall having a cylindrical portion and tapering portions 2 and at each The interior wall has a series of spaced teeth 5 and and a recess Figure 6 shows the coupling 5 in an expanded condition with tubes 61 and 62 inserted The space between tubes 61 and 62 is centrally positioned in the recess Figure 7 shows the coupling after recovery on tubes 61 and As can be the tubes 61 and 62 are partially deformed by the teeth of the It should be understood that the illustrated deformation is exaggerated for purposes of in normal situations the deformation is ably less than that Typical deformation sufficient to significantly increase the strength of the The optimum spacing and minimum depth of the teeth depend on the properties of tubes 61 and One method the dimensions and is shown in Figure A ring of the memory metal from which the coupling is and having the same recovered is shrunk movement of some of its the maximum outward deformation being indicated by in Figure The axial extent of the radial deformation is indicated by in Figure 8 which thus is the distance from the point where radial deformation begins to the point where it This distance is then used as the spacing between adjacent teeth as shown in Figure The depth of the teeth in Figure 6 is preferably selected to be equal to or greater than the dimension of Figure The minimum coupling wall thickness along the cylindrical portion 5 that the thickness or the wall in the area of the recess is determined by the maximum expected pressure in the hydraulic line and by the relative elasticity of the material of tubings 61 and 62 and that of the The thickness is preferably sufficient to withstand the maximum hydraulic pressure and to resist bulging of the and to withstand metal fatigue under operating the thickness is preferably such that the coupling will tend to expand elastically under pressure less than tubing 61 and when the joint is subjected to high the greater expansion of the coupling would cause By so designing the minimum wall coupling weight may be The inside diameter of recess 57 preferably sufficiently so that the tubing ends do not touch the coupling at any particularly when subjected to vibration as fretting corrosion of the coupling by the tubing might occur resulting in a weakening of the coupling and ultimately its The tapered end portions and of the coupling comprise another important feature of the The purpose of providing the taper to the inner surface 65 is to reduce the radial force exerted on the tubing at the ends of the coupling upon its A high radial force on the tubing at the ends of the coupling would tend to weaken the tubing at those particularly if the tubing was subjected to bending or A zero radial force would be theoretically it has been found that if the coupling ends are not tight around the tubing a rubbing can occur with vibration and this can lead to fretting corrosion and the inside diameter at the coupling ends advantageously be such that when the coupling shrinks about the tubing there will be a slight positive pressure on the tubing but the pressure be as low as The provision of the taper to the oute surfaces 66 further helps keep the pressure as low as possible because a thinner metal will exert less force than a thicker The tapered outer surface imparts flexibility to the coupling which to protect the tubing from the effects of bending or This is ularly true in the case of titanium this reduction in outside diameter should be a substantial It has been found that an edge thickness on the order of or of the minimum wall thickness of the coupling at the recess 57 particularly It has been found that the teeth are most effective when their biting edges approximate a right preferably as close to radial as These tial teeth need not be formed by tapered and could be formed merely by forming a series of or shaped ridges or the like in the interior of the A coupling as shown in was constructed as of nickel titanium Corporation and iron The strips were cleaned to remove any dirt or weighed and assembled in bundles such that the elements were in the ratio of alloy 1 above at each through the longitudinal axis of the The bundle was then hung in the chamber a Lepel floating zone The chamber was then with high purity argon to a pressure of 1 this procedure was repeated after the third filling a pressure of gauge was established and maintained during the melting to minimize air The lower end of the was heated by a induction coil attached to the secondary winding of a loac matching step down the primary being powered by a Lepel high frequency induction heating unit operating in the kilohertz Rapid melting resulted from the combination of induction heating and the heat of formation of the intermetallic compound The falling droplets of alloy were collected in a cold copper the bundle being fed into the induction coil until i had all been melted and collected in the After the copper mould and ingot were removed from the and the mould was The dripped which was a was returned to the chamber and an argon atmosphere established as A molten zone was passed along the ingot from bottom to top at a rate of about using the floating zone technique to avoid possible nation by a The product was a free bar of alloy about 2 12 An axial hole was drilled in the end of the bar of the of the central portion and the blank cut off the end of the The tapered end portion 26 was then formed on a using a lathe taper The attachment was then reset and a radial cut to form the outer tooth A second taper then and a second radial cut to form the inner tooth The cut was then continued parallel to the axis to form half the central portion The coupling was then turned and the tapered portion teeth and and the remaining half of the central portion bored to The tapered portions 14 and 16 on the outer surface were then the surfaces polished and The machined coupling was then heated in an inert atmosphere at for cooled rapidly to to and maintained at that temperature for 2 still in an inert The coupling could alternatively be treated initially for a longer period at a somewhat lower 2 hours at and the second heating period can be at any temperature between and This treatment anneals the coupling and removes the internal stresses The coupling was then in liquid nitrogen and a tapered previously cooled to liquid nitrogen forced through the bore 22 of the coupling to expand it radially by enough to provide both thermally recoverable and secondary deformation of the The mandrel and a previously cooled rod or keeper having a diameter slightly less than the maximum diameter of the mandrel inserted in the The coupling and its keeper were then allowed to return to room the The ends of two stainless steel hydraulic pipes were and prepared for a on each pipe indicating the correct extent of insertion into the The ling was then removed from the liquid the keeper being readily removed from its As in Figure the ends of the pipes 40 and 42 were then inserted into the coupling up to the indicated and the assembly was left to warm up to room As shown in Figure a firm junction between the pipe ends was the teeth of the coupling biting into the pipes and and being deformed in the The extent of the deformation depends on the relative hardness of the coupling compared to that of the pipes to be is to be understood that the of Figure is for the purpose of clarity and is not necessarily intended to be to By a procedure similar to that described above a coupling of Alloy 3 above was manufactured and applied to form a butt joint between two stainless steel hydraulic pipes of outside diameter inch The pipes were filled with petroleum base hydraulic fluid to and subjected to the following The pressure in the system was maintained at x 108 for 5 then at 8 2 x 10 for No leak was observed at the end of either The coupling was then subjected to the rotating beam test to with the hydraulic o p fluid at x 10 being cycles at approximately for x 10 No leaks were nor was any damage to the coupling The system was tested in a mass with helium at atmospheric pressure outside the the inside of the system being helium was observed inside the the sensitivity of the spectrometer was 11 Couplings of Alloy were applied to pairs of hydraulic pipes as described The following tests were carried One system was filled with hydraulic fluid at a pressure of x 108 The temperature of the system was cycled between and 29 each cycle occupying about 2 Ho leak was The other systems were tested to destruction by increasing the internal pressure of hydraulic In each the stainless steel tubing burst before any leak took place at the the pressures varying between 000 and 000 x and x All the tests described above show that the invention provides a reliable leakproof hydraulic coupling which can be stored and transported at normal temperatures and can be quickly and easily installed at conveniently obtainable low temperatures without the use of bulky and complex equipment and by people of relatively little The strength of the coupling can be further increased by suitable selection of the materials and by the incorporation of advantageous design Although the couplings will in general be stored on as described it is also possible to store them without relying on their expansion on cooling to obtain sufficient clearance to install them on the articles insufficientOCRQuality

Claims (1)

1. A of a hollow article mechanically deforming a hollow article made from a as hereinbefore below the transition temperature of the which also comprises th step of imparting secondary as hereinbefore to the A method ae claimed in claim wherein the secondary deformation is imparted by deforming the hollow article below the transition temperature of the metal a force greater than that necessary to impart maximum A method claimed in claim wherein secondary deformation is imparted by working the article above transition A method claimed in claim wherein the secondary deformation imparted by the article to recover and come with an object which prevents total A method as claimed in claim wherein the object A method claimed in claim wherein the object is made from a metal having an elasticity substantially the same that of the metal of hollow A method in claim wherein the ob made from beryllium A method as claimed in claim wherein the object is a mechanically resilient for as cylindrical A method as claimed in claim wherein the object is made from a material having a negative coefficient of A method as claimed in any of claims 1 to wherein the hollow article is deformed by A hollow article made by a method as claimed in any one of claims 1 to A hollow article made from a memory hereinbefore which contains some secondary as before A hollow article as claimed in claim or claim wherein the transition temperature of the memory metal lies in the range of from to A hollow article ae claimed in any one of to wherein the memory metal ie an alloy of about 50 atom percent about 47 atom percent Ni and about 3 atom percent A hollow article ae claimed in any one of claims to wherein the memory metal is an alloy of about 50 atom percent about to about atom percent Al and correspondingly about to about 49 atom percent A hollow article claimed in any one of claims 11 to wherein the memory metal ie an alloy of about atom peroent Ni and about atom percent A hollow article ae claimed i any one of claims 11 to wherein the memory metal is an alloy of about 2 atom percent about 48 atom percent Ni and about atom percent A hollow article as claimed any one of claims to 1 wherein article provided with one or more inwardly ting on inner A hollow article as claimed in claim wherein the article is provided with a series of axially separated continuous ferential A hollow article claimed any one of claims to wherein the article is 2 A hollow article as claimed in any one of claims to which is capable of spontaneous expansion or contraction on passing through the transition temperature of the memory A hollow article as claimed in any one of claims 1 to which after contracting or on passing through transition temperature of the metal ie subsequently capable of expanding or on being repassed through the transition A hollow article as claimed in any one of claims to which is being maintained in its low temperature form by immersion in liquid A hollow article as claimed in any one of claims to which is being maintained in a relatively expanded heat unstable form by being over a A hollow article claimed in claim wherein the keeper A hollow article as claimed in wherein the keeper is made from a laetal having an elasticity substantially the as that of metal of the hollow A article as claimed in claim wherein the keeper is made from beryllium A hollow article as claimed in claim wherein the keeper is from a material having a negative coefficient of thermal hollow article as claimed in claim wherein the keeper comprises a mechanicall resilient member for example as a cylindrical method of a connection between one or more objects which comprises positioning the object or objects to be connected within a hollow article as claimed in any of to and causing the hollow to contract and grip the by heating it to above the transition temperature of the connection between one or objects when made by a ae claimed in claim For the Applicanfs REINHOLD COHN AND PARTNERS insufficientOCRQuality