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WO2000070105A1 - Lunettes et parties de lunettes fabriquees a partir d'alliages a memoire de forme - Google Patents

Lunettes et parties de lunettes fabriquees a partir d'alliages a memoire de forme Download PDF

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Publication number
WO2000070105A1
WO2000070105A1 PCT/US2000/013151 US0013151W WO0070105A1 WO 2000070105 A1 WO2000070105 A1 WO 2000070105A1 US 0013151 W US0013151 W US 0013151W WO 0070105 A1 WO0070105 A1 WO 0070105A1
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WIPO (PCT)
Prior art keywords
alloy
eyeglass frame
shape memory
temperature
pseudoelastic
Prior art date
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Ceased
Application number
PCT/US2000/013151
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English (en)
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Memory Corp PLC
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Memory Corp PLC
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Filing date
Publication date
Application filed by Memory Corp PLC filed Critical Memory Corp PLC
Publication of WO2000070105A1 publication Critical patent/WO2000070105A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/006—Resulting in heat recoverable alloys with a memory effect
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C19/00—Alloys based on nickel or cobalt
    • C22C19/03—Alloys based on nickel or cobalt based on nickel

Definitions

  • the present invention relates generally to the fabrication of eyeglasses, and, more particularly, to the making of eyeglass frames and parts thereof from a specially processed Nickel-Titanium shape memory alloy.
  • Alloys used in conventional eyeglass frames include stainless steel, copper based alloys and nickel-silver, which all can be given quite high yield strength through work hardening, but in use can be fairly easily permanently deformed. Normal metals, even with very high yield strength, cannot sustain strains much greater than 0.2% without suffering a permanent set. Once a bend or kink has been sustained in a metal eyeglass frame fabricated from one of the above conventional alloys it is virtually impossible to remove.
  • the concept of using shape memory alloys for eyeglass components has been suggested in numerous articles and patents. Y. Suzuki, at that time head of shape memory alloy research at Furukawa Electric in Japan, published in Kinzoku Journal, vol. 31, No.
  • Shape memory alloys belong to a class which exhibit what is termed thermoelastic martensite transformation.
  • martensite refers to the crystalline phase which is produced in steels when quenched from a high temperature.
  • the phase which exists at the elevated temperature is referred to as austenite; these terms have been carried over to describe the transformations which occur in shape memory alloys.
  • austenite When a steel has been quenched from the austenitic temperature to martensite, to again form austenite requires heating the structure to quite high temperatures, usually in excess of 1400° F.
  • the thermoelastic shape memory alloys can change from martensite to austenite and back again on heating and cooling over a very small temperature range, typically from 18 to 55° F.
  • the transformation of a shape memory alloy is usually described by its hysteresis curve. See FIG. 1 for an example of one.
  • the Young's Modulus of austenite is about 12xl0 6 psi while that for martensite is about 4x10 6 psi and the yield strength, which depends on the amount of cold work the alloy is given, ranges from 28 to 100 ksi for austenite and from 10 to 20 ksi for martensite.
  • An object of the present invention is to provide a nickel-titanium alloy which is particularly useful for eyeglass frames and parts thereof. Another object of the present invention is to provide an alloy having pseudo- elastic properties and which is useful for eyeglass frames and parts thereof.
  • a further object of the present invention is to provide a material for making eyeglass frames and parts thereof which is formable with the creation of cracks.
  • shape memory alloys are their ability to recover deformation.
  • SMA shape memory alloy specimen
  • the strain is accommodated by the growth and shrinkage of individual martensite variants rather than by the mechanisms which prevail in conventional alloys: slip, grain boundary sliding and dislocation motion.
  • deformed martensite is heated to the austenite finish temperature A f the part reverts to its original undeformed state. This process is illustrated in FIG. 2.
  • Dy shape memory alloys such as Au-Cd, Cu-Zn-Al, Ni-Ti and many others makes possible the complete “elastic" recovery of strains as great as 8%. Due to its high recoverable strain and its excellent resistance to corrosion, the shape memory alloy of preference for eyeglass frames and components has been within the Ni-Ti family of alloys.
  • the treatment and the alloy selection provided by the present invention is a modification of those commonly proposed. Prior studies have not provided detailed information on the temperature range over which the pseudoelastic behaviour is observed in alloys subjected to solution treatment and aging. With the treatment described, the present invention provides a method of producing a pseudoelastic nickel-titanium alloy which exhibits properties ideal for easy fabrication of eyeglass frames combined with those properties desired for an eyeglass frame which features wearer comfort and high resistance to accidental damage.
  • a process to obtain pseudoelastic behaviour is by a solution heat treatment of a high nickel SMA at about 850° C followed by water quenching and then precipitation hardening at a lower temperature.
  • High nickel alloy means alloys with a nickel content in excess of 50.5 atomic %.
  • the present invention provides using an alloy with higher than the equiatomic
  • Ni/Ti ratio subjecting it to a high temperature solution treatment, followed by water quenching, and a subsequent aging treatment, that a pseudoelastic behaviour is obtained combined with excellent forming characteristics and a strain recovery of at least 3% over a temperature range from -20 to +40° C.
  • the treated alloy yield strength ranges from 42 to 72 Ksi.
  • the present invention seeks to provide a shape memory alloy and process which reduces the complexity of producing components for eyeglass frames by using a precipitation hardening treatment of a high nickel allo"" rather than the presently used cold working and heat treating.
  • the resulting components are characterised by pseudoelastic properties which dramatically reduce the chance for accidental deformation or kinking.
  • the precipitation process combined with the particular nickel-titanium alloy composition employed feature.- a relative low upper plateau stress which renders the components flexible which, in turn, make eyeglasses fabricated in the described manner comfortable to wear.
  • FIG. 1 is a hysteresis curve showing the transformation of a shape memory alloy.
  • FIG. 2 is a schematic view of the process of the present invention.
  • FIG. 3 is a curve showing the behaviour of SIM.
  • FIG. 4 is a curve showing the stress required to produce SIM and the temperature dependence of stress-induced martensite.
  • FIG. 5 is a stress-strain diagram for cold worked martensite yielding linear superelastic behaviour.
  • FIG. 6 is a stress-strain curve for the alloy with the treatment.
  • FIG. 7 is a stress-strain curve for the alloy of FIG. 6 tested at -10° C.
  • FIG. 8 is the stress-strain curve of the alloy of FIG. 6 tested at 0° C.
  • FIG. 9 is the stress-strain curve of the alloy of FIG. 6 tested at +10° C.
  • FIG. 10 is the stress-strain curve of the alloy of FIG. 6 tested at 30° C.
  • FIG. 11 is the stress-strain curve of the alloy of FIG. 6 tested at 40° C.
  • FIG. 12 is the stress-strain curve of the alloy with a different treatment from that of FIG. 6.
  • FIG. 13 is the stress-strain curve of the alloy of FIG. 12 tested at 0° C.
  • FIG. 14 is the stress-strain curve of the alloy of FIG. 12 tested at 25° C.
  • FIG. 15 is the stress-strain curve of the alloy of FIG. 12 tested at 30° C.
  • FIG. 16 is the stress-strain curve of the alloy of FIG. 12 tested at 40° C.
  • FIG. 17 is a stress-strain curve for the alloy with a modified treatment.
  • FIG. 18 is a stress-strain curve showing that performance is maintained over many cycles at 5% strain.
  • FIG. 19 is a stress-strain curve showing that performance is maintained over many cycles at 8% strain.
  • FIG. 20 is an isometric view of a eyeglass frame showing the various parts thereof.
  • Martensite forms when a SMA is cooled from the austenitic region to below the M s temperature; it can also form when the austenite is stressed to above some critical level.
  • the martensite so formed is called stress-induced-martensite (SIM). Since the martensite formed under stress is at a temperature where it is not stable, when the stress is removed the alloy spontaneously reverts to its prior unstressed shape. This behaviour is illustrated in FIG. 3. It can be observed that the reversion stress is lower than the stress at which martensite from. These stresses are referred to as the upper and lower plateau stresses and their magnitude is dependent on the thermal and mechanical treatment which the SMA has received.
  • the 50/50 At% alloy is by weight % 55 Ni-45 Ti.
  • the alloy which has proven optimum for this application is one with a 56.1 wt% Ni and 43.9 wt% Ti. It should be understood that other high nickel NiTi binary compositions can also be used, and that these alloys may have additions of Mo, Ta, Nb, Zr, Cu, Co, Fe, Cr, Mn or V as partial substitution for the nickel with similar results.
  • a NiTi alloy with a composition of 56.1 wt% Ni-43.5 wt% Ti is cold worked 29% and then solution treated at 850° C for 30 minutes followed by water quenching. The specimen is then aged at 350° C for 30 minutes and water quenched.
  • the stress- strain curves for the alloy with this treatment are shown in FIGS. 6 through 11 for test temperatures from -20° C to +40° C. After the first cycle there is a residual strain which ranges from 1.7% at 40° C to 0.35% at 0° C. Subsequent cycles show a residual strain of approximately 0.15%. In all cases the recoverable strain is greater than 3%.
  • a NiTi alloy with the same composition as shown in FIGS. 6-11 is cold worked
  • FIG. 20 shows an eyeglass frame, part(s) or all of which may be made of the material provided by the present invention.
  • the eyeglass frame includes the lens frames 2, the bridge 1, the hinges 3, the ear pieces 4 and the nose pieces 5.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Eyeglasses (AREA)

Abstract

L'invention concerne une monture de lunettes ou un composant (1, 2, 3, 4, 5) afférent fabriqué dans un alliage à mémoire de forme à base de Ni-Ti, l'alliage se composant de nickel atomique à au moins 50,5 %. L'alliage est traité dans une solution à une température comprise entre 650 et 1100 °C pendant 10 à 60 minutes. Après refroidissement, l'alliage subit un vieillissement par chauffage à une température de 350 °C environ pendant 10 à 60 minutes. L'alliage se caractérise par le fait qu'il possède des propriétés pseudo-élastiques sans formage à froid, ces propriétés étant supérieures à une élasticité de 2,5 % dans une plage de températures allant de 20 à +40 °C, et qu'il permet de produire une grande déformation plastique lors de la fabrication du composant avant l'obtention des propriétés pseudo-élastiques voulues. Les procédés de fabrication de l'alliage et du composant offrent une plus grande flexibilité dans la conception et éliminent la nécessité d'un formage à froid sensible de l'alliage. Les nouveaux procédé et produit permettent d'obtenir un alliage ductile facile à former et le traitement à chaud unique dote d'une grande élasticité les composants de lunettes fabriqués, ce qui augmente le confort du porteur et améliore la résistance des lunettes aux dommages causés par des accidents.
PCT/US2000/013151 1999-05-15 2000-05-12 Lunettes et parties de lunettes fabriquees a partir d'alliages a memoire de forme Ceased WO2000070105A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US31208999A 1999-05-15 1999-05-15
US09/312,089 1999-05-15

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002077311A1 (fr) * 2001-03-22 2002-10-03 Revel International Limited Composants de lunettes et leurs procedes de fabrication
CN111575534A (zh) * 2020-06-10 2020-08-25 中国石油大学(北京) 一种高Ni纳米晶NiTi形状记忆合金型材及其制备方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4758285A (en) * 1986-10-14 1988-07-19 Cvi/Beta Ventures, Inc. Shape-memory alloy resetting method
US4865663A (en) * 1987-03-20 1989-09-12 Armada Corporation High temperature shape memory alloys
JPH0860276A (ja) * 1994-08-19 1996-03-05 Kanto Special Steel Works Ltd ＮｉＴｉ基合金眼鏡部材とその製法

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4758285A (en) * 1986-10-14 1988-07-19 Cvi/Beta Ventures, Inc. Shape-memory alloy resetting method
US4865663A (en) * 1987-03-20 1989-09-12 Armada Corporation High temperature shape memory alloys
JPH0860276A (ja) * 1994-08-19 1996-03-05 Kanto Special Steel Works Ltd ＮｉＴｉ基合金眼鏡部材とその製法

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002077311A1 (fr) * 2001-03-22 2002-10-03 Revel International Limited Composants de lunettes et leurs procedes de fabrication
CN111575534A (zh) * 2020-06-10 2020-08-25 中国石油大学(北京) 一种高Ni纳米晶NiTi形状记忆合金型材及其制备方法

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