SUPERELASTIC BALLS FOR BALL BEARINGS AND METHOD OF MANUFACTURE

Abstract

One aspect relates to a rolling element for a ball bearing wherein the rolling element has: (i) a Young modulus E in the range up to and including 100 GPa; and (ii) a yield strength Rp.sub.0.2 in the range up to and including 1800 MPa, or wherein the rolling element has at least an alloy of nickel (Ni) and titanium (Ti), wherein the weight ratio of Ni:Ti in the alloy is in the range of from 57:43 to 50:50. One aspect is a rolling bearing with: a. at least an outer ring; b. at least an inner ring, wherein a raceway is defined by the arrangement of the outer ring and the inner ring; and c. at least three rolling elements wherein the rolling elements are arranged in the raceway, wherein at least one rolling element comprises at least an alloy as mentioned above.

Claims

1. A ball bearing comprising: a raceway; a rolling element in the raceway, the rolling element comprising at least an alloy of Nickel and Titanium, wherein the weight ratio of Ni:Ti in the alloy is in the range of from 55:45 to 50:50; wherein the amount of alloy in the rolling element is from 85 wt. % to 100 wt. %, based on the total weight of the rolling element; wherein the ball bearing is configured within a medical handheld device, a pacemaker or a watch; and wherein the ball bearing comprises more than two points of contact with the rolling element

2. The ball bearing of claim 1, wherein the weight ratio of Ni:Ti in the alloy is 55:45.

3. The ball bearing of claim 1, wherein the raceway comprises and inner ring and an outer ring, the inner ring having an inner diameter in the range of 4 to 10 mm.

4. A ball bearing including a rolling element, wherein the rolling element comprises: (i) a Young modulus E in the range up to and including 100 GPa; (ii) yield strength Rp.sub.0.2 in the range up to and including 1800 MPa; and (iii) at least an alloy of Nickel and Titanium, wherein the weight ratio of Ni:Ti in the alloy is in the range of from 55:45 to 50:50 wherein the ball bearing is configured within a medical handheld device, a pacemaker or a watch.

5. The ball bearing of claim 4, wherein the rolling element is a ball.

6. The ball bearing of claim 4, wherein the rolling element comprises at least one alloy in an amount of from 85 wt.-% to 100 wt. %, based on the total weight of the rolling element.

7. The ball bearing of claim 6, wherein the weight ratio of Ni:Ti in the alloy of the rolling element is 55:45, based on the total weight of the rolling elements.

8. A method of manufacturing a ball bearing with balls and inner and outer rings, comprising: i) providing a precursor, wherein the precursor comprises at least an alloy of Nickel and Titanium, wherein the weight ratio of Ni:Ti in the alloy is in the range of from 55:45 to 50:50, wherein the amount of alloy in the precursor is from 85 wt. % to 100 wt. %, based on the total weight of precursor; ii) cutting off ball blanks from the precursor, wherein the ball blanks are cubical or cylindrical in shape; and iii) grinding the ball blanks in a ball grinder to a desired spherical shape and size, whereby balls for ball bearings are obtained; iv) proving the inner ring having an inner diameter in a range of 1 to 100 mm.

9. The method of claim 8, wherein the precursor has a.) a Young modulus E in the range up to and including 100 GPa; and b.) a yield strength Rp.sub.0.2 in the range up to and including 1800 MPa.

10. The method of claim 8, the inner ring has an inner diameter in a range of 4 to 10 mm.

11. The method of claim 8, wherein the weight ratio of Ni:Ti in the alloy of at least one rolling element is 55:45 ratio based on the total weight of the rolling elements.

12. A rolling bearing at least comprising a. at least an outer ring and b. at least an inner ring, wherein a raceway is defined by the arrangement of the at least one outer ring and at least one inner ring, and c. at least 3 rolling elements, wherein the rolling elements are arranged in the raceway, wherein at least one rolling element c.-1) comprises at least one alloy of Nickel and Titanium, wherein the weight ratio of Ni:Ti in the alloy is in the range of from 55:45 to 50:50, wherein the amount of alloy in the rolling element is from 85 wt. % to 100 wt. %, based on the total weight of the rolling element; or c.-2) has (i) a Young modulus E in the range up to and including 100 GPa; and (ii) a yield strength Rp0.2 in the range up to and including 1800 MPa; or c.-3) is characterized by the combined features of alternatives c.-1) and c.-2) above; or c.-4) is obtainable by i) providing a precursor, wherein the precursor comprises at least an alloy of Nickel and Titanium, wherein the weight ratio of Ni:Ti in the alloy is in the range of from 55:45 to 50:50, wherein the amount of alloy in the precursor is from 85 wt. % to 100 wt. %, based on the total weight of precursor; ii) cutting off ball blanks from the precursor, wherein the ball blanks are cubical or cylindrical in shape; and iii) grinding the ball blanks in a ball grinder to a desired spherical shape and size, whereby balls for ball bearings are obtained.

13. The rolling bearing of claim 12, wherein each rolling element of the rolling bearing is a ball.

14. The rolling bearing of claim 12, wherein at least one of the inner ring or the outer ring is made from stainless steel.

15. The rolling bearing of claim 12, wherein the inner diameter of the inner ring of the rolling bearing is in the range of from 1 mm to 100 mm.

16. The rolling bearing of claim 12, wherein at least one rolling element comprises at least one alloy of Nickel and Titanium, wherein the weight ratio of Ni:Ti in the alloy of the at least one rolling element is in the range of from 57:43 to 50:50, preferably in the range of from 56:44 to 54:46, the ratio based on the total weight of the rolling elements and has a Young modulus E in the range up to and including 100 GPa and a yield strength Rp0.2 in the range up to and including 1800 MPa.

17. The rolling bearing of claim 12, wherein the load improvement ratio LIR of the rolling bearing is 1.5 or more, the load improvement ratio LIR being determined according to the method described herein.

18. The rolling bearing of claim 12, wherein no lubricant is present in the raceway.

19. The rolling bearing of claim 12, wherein the rolling bearing has a rotating axis in an article, wherein the rotating axis of the rolling bearing is operated at in the range of 1 to 150 revolutions per minute.

20. A method of manufacturing a rolling bearing comprising: (I) providing at least these items: a. an outer ring, b. at least an inner ring and c. at least 3 rolling elements; wherein at least one of the rolling elements c.-1) is composed of at least one alloy of Nickel and Titanium, wherein the weight ratio of Ni:Ti in the alloy is in the range of from 55:43 to 50:50, based on the total weight of the alloy, wherein the amount of alloy in the rolling element is from 85 wt. % to 100 wt. %, based on the total weight of the rolling element; or c.-2) wherein at least one of the rolling elements has a Young modulus E in the range up to and including 100 GPa and a yield strength Rp0.2 in the range up to and including 1800 MPa; or c.-3) wherein at least one of the rolling elements has the combined features of c-1) and c-2) above; c.-4) is obtainable by i) providing a precursor, wherein the precursor comprises at least an alloy of Nickel and Titanium, wherein the weight ratio of Ni:Ti in the alloy is in the range of from 55:43 to 50:50, wherein the amount of alloy in the precursor is from 85 wt. % to 100 wt. %, based on the total weight of precursor; ii) cutting off ball blanks from the precursor, wherein the ball blanks are cubical or cylindrical in shape; and iii) grinding the ball blanks in a ball grinder to a desired spherical shape and size, whereby balls for ball bearings are obtained; and (II) Assembling the rolling elements provided in step i), wherein a rolling bearing is obtained, which has a raceway which is defined by the arrangement of the at least one outer ring and at least one inner ring, wherein the rolling elements are arranged in the raceway.

21. The method of claim 20, wherein the weight ratio of Ni:Ti in the alloy is 55:45 ratio based on the weight of the rolling elements.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0207] FIG. 1 shows schematically a side view of a bearing according to one embodiment.

[0208] FIG. 2 schematically shows a partially sectioned perspective view of a bearing according to one embodiment.

[0209] FIG. 3 shows how a partially sectioned perspective view of a variant of the bearing according to one embodiment.

[0210] FIG. 4 shows schematically a sectional view of a second embodiment of the bearing according to one embodiment.

[0211] FIG. 5 shows the experimental setup used for performing the static indentation test.

[0212] FIG. 6 is a perspective view of an ingot of material to be made into balls.

[0213] FIG. 7 is a perspective view of a plate of material to be made into balls.

[0214] FIG. 8 a perspective view of an industrial laser cutting cubes from th plate shown in FIG. 7.

[0215] FIG. 9 is a schematic representation of an abrasive tumbling machine in which the cubes cut from the sheet as shown in FIG. 14 are tumbled to produce rounded cubes shown in FIG. 10.

[0216] FIG. 10 is a perspective view of a rounded cube produced in the tumbler of FIG. 9.

[0217] FIG. 11 is a schematic block representing a conventional ball grinder.

[0218] FIG. 12 is a spherical ball ground in the ball grinder of FIG. 11.

[0219] FIGS. 13-16 are plan views showing a laser cutting pattern for cutting cubical ball blanks from the sheet shown in FIGS. 7 and 8.

[0220] FIGS. 17-20 are plan views showing a laser cutting pattern for cutting cylindrical ball blanks from the sheet shown in FIGS. 7 and 8.

[0221] FIGS. 21-25 show a process for making roller elements, in flow diagram form, starting from a rod which had been purchased.

[0222] FIG. 26 shows a standard Chapuis device.

[0223] FIGS. 27 and 28 show results from static indentation tests obtained by the test method described herein.

[0224] FIGS. 1 and 2 show a bearing 1 which comprises an outer ring 2, an inner ring 3, a number of rolling elements (balls) 5 and a cage 6 to keep the rolling elements spaced from each other. In a variant visible in FIGS. 3 and 4, the bearing comprises more than two points of contact, e.g. three or four points of contact. Then the inner ring 3 is composed of two parts 3a and 3b. The outer ring 2 has an outer face 21 and an inner face 22. The inner face 22 is used as the path for the rolling bodies 5. Preferably, the inner side 22 is curved so as to ease the movement of the rolling elements 5. Indeed, an inner curved face 22 allows for less friction while naturally preventing the rolling bodies 5 out of the way. The outer ring 2 is fitted with an inner ring 3. The inner ring 3 includes an outer face 31 and an inner face 32. The outer face 31 is also used as a path for the rolling elements 5. In the case of an inner ring 3 consists of two parts 3a and 3b, the parts 3a and 3b are assembled before being inserted into the outer ring 2. The path formed by the outer face 31 of the inner ring 3 and the inner face 22 of the outer ring 2 is designed to allow the movement of rolling bodies 5, wherein said path is adapted to the shape of the rolling body 5.

[0225] When the inner ring 3 is inserted into the outer ring 2, a space 4 arises between the inner ring 3 and the outer ring. In this space 4 are placed rolling body 5. The rolling bodies are in the form of balls or cylindrical pieces or tapered cylinder.

[0226] The rolling elements 5 are disposed regularly in the said space 4 so that the space between each rolling body 5 is identical. For this, the rolling elements 5 are placed in a cage 6. The cage 6 is in the form of multiple strapping elements 6a interconnected by fastening sections 6b. Indeed, each rolling body 5 is inserted into an element belting 6a. This strapping member 6b is designed so as to maintain the rolling element 5 while allowing it to turn on itself. The attachment sections 6b are used to secure all the rolling elements 5 together. The fastening sections 6b have all the same length in order to leave the roller body 5. Of course, it may be provided that the cage 6 comprises two elements secured together.

[0227] The cage 6 with the rolling elements 5 is inserted into the space 4 so that the outer ring 2 and inner ring 3 can rotate independently of each other. The cage 6 must be manufactured precisely to enable both, good maintenance of the rolling elements 5 but also allow them to have a good freedom of movement. The rolling elements 5 are to be inserted by force into the cage 6 is it comprises several assembled parts around the rolling bodies 5.

[0228] A process for making rolling elements according to one embodiment is shown in FIGS. 12-27, wherein a billet or ingot 60 of the material, shown in FIG. 6, is rolled, cast, or otherwise formed into a plate or sheet 62, as shown in FIG. 7. As shown in FIG. 8, the sheet 62 is cut into cubical ball blanks 64 and the ball blanks 64 are reduced to rounded cubes 66, illustrated in FIG. 10, by abrasive tumbling in a conventional abrasive tumbling apparatus 68 schematically shown in FIG. 9. The rounded cubes 66 are reduced to spherical balls 70, shown in FIG. 12, by grinding in the conventional ball grinder 44, illustrated schematically in FIG. 11.

[0229] The cubes 64 can be cut from the sheet or plate 62 of the precursor, e.g. Nitinol 50, by laser, following a pattern shown in FIGS. 13-16. As the cubes are cut out of the sheet, they fall through the support grid on which the sheet lies and fall into a pan below. The cubes 64 tend to bounce when they hit the bottom of the pan and the compressed gas from the laser head blows the small cubes 64 out of the pan, so the bottom of the pan can be lined with a material such as felt impregnated with high temperature grease or a mesh material to reduce the tendency of the cubes 64 to bounce and facilitates their capture and easy removal from the pan.

[0230] Another ball blank form from which balls can be ground is cylinders. A scalloped laser-cutting pattern, shown in FIGS. 17-20, uses matching semicircular cuts instead of squares to produce cylindrical ball blanks 75 instead of cubes 64. The diameter of the cylinders is equal to the thickness of the plate (not shown) so the three orthogonal dimensions through the center of the cylindrical ball blank 75 are equal, as is the case with the cubical ball blanks 64. The cylindrical ball blanks 75 have smaller corner and edge protrusions and would not require as much time in the tumbler 68 to round off their edges to make them ready for the ball grinder. Indeed, the cylinders 75 may not require any tumbling time at all. However, the laser time to cut cylinders 75 is considerably longer than to cut cubes, and the yield of ball blanks from a sheet or plate of a given size would be less.

[0231] A preferred pattern of laser-cutting leaves the cylindrical ball blanks 75 connected at the cusp 77 to produce a string of cylinders 75 connected by a small rib 78 at adjacent edges. The laser travel mechanism is accurate enough to leave a rib that is only a few thousandths of an inch thick allowing the cylinders 75 in the string of cylinders to be easily broken apart after cutting.

[0232] FIG. 26 is a schematic representation of a standard Chapuis device. Basically, the standard Chapuis device transforms a rotational movement into an oscillating movement. It consists of at least wheels A and C are shown, further may exist, e.g. wheel B or others (not shown). The wheels are in a motional relationship determined by a connecting rod mounted to and connecting wheel A and wheel B, and further by the teeth of toothed wheels B and C. More specifically, wheel A is driven by a motor (not shown). The rotating motion of wheel A is transformed into an oscillating motion at wheel B by a connecting rod D. The angle at the rotating axis in the center of wheel B and the two points I.sub.1 and I.sub.2 is about 150, where the rotational direction of wheel B is inverted. The oscillating motion of toothed wheel B is transferred to a further toothed wheel C, eventually using one or more further intermediate wheels (not shown). A sample holder capable of holding up to ten roller bearings, or devices with roller bearings, e.g. a wrist watch, is mounted on wheel C. The speed ratio between wheel B and wheel C is adjusted so that wheel C performs one full revolution around its axis when wheel B is rotated from the first point of inversion I.sub.1 to the second point of inversion I.sub.2. The watch mounted on the sample holder performs 34 oscillations back and forth per minute during the test.

Roller Bearing Elements

[0233] Turning now to FIGS. 21-25, a process for making roller elements (e.g. from Nitinol 50) for roller bearings, shown in flow diagram form, starts rod which had been purchased. The rod 90 is polished using a rod polishing machine 100 to a smooth surface finish on the order of 1 microinch. It is then removed to a cutting operation as shown in FIG. 22, preferably an automated roto-ase cutting machine having a rod support that rotates the polished rod 90 under the laser 102 to cut it cleanly into properly sized roller bearing element blanks 105 without significant waste of material. The cut roller bearing element blanks 105 may be edge trimmed to chamfer and polish the ends of the blanks 105 to produce finished roller elements 110.

[0234] Embodiments are further exemplified by examples. These examples serve for exemplary elucidation of one embodiment and are not intended to limit the scope of the embodiments or the claims in any way.

Test Methods

1. Static Indentation Test

[0235] A polished plate of the race material with dimension 10 mm is placed on the testing device. The ball to be tested having a diameter of 0.4 mm is carefully placed on the plate, which has a thickness of 5 mm. The plate is made from the material used for the raceway. Then a calibrated weight of 2 kg (4 kg) is carefully applied to the ball in a smoothly way without any shock during for 5 s. Then, the weight is removed and indentation depth and diameter on the plate are measured by mean of a White Light Interferometer Microscope (Zygo White Ligth Interferometer). The deformation of the ball is measured with a mechanical micrometre (Meseltron). Reference is made to FIG. 5 which shows a sketch of the testing set-up, result are shown in FIG. 27 for 2 kg load and 28 for 4 kg load. The top plate is an aluminium plate with thickness=2 mm. The sole purpose of the top plate is to stabilize the position of the calibrated weight on the ball.

2. Ageing Test

[0236] Ageing tests are performed on a standard Chapuis device. The test consists in rotating the mass of an automatic watch during 90 days. It corresponds to a real life cycle of 10 years. No tribo-corrosion should occur in the ball bearing and the winding performance should be still acceptable.

[0237] The bearing is mounted on an oscillating mass which is then assembled in a real watch movement. The watch is wound up so that the mechanism can start. The watch is placed on the Chapuis device. The Chapuis device rotates the watch back and forth at a rate of 34 rpm.

[0238] The working principle of a Chapuis device is further detailed in FIG. 23. Several wheels A, B and C are shown, further may exist (not shown). The wheels are in a rotational relationship determined by a mounted connecting rod and further by the teeth of toothed wheels. More specifically, wheel A is driven by a motor (not shown). The rotating motion of wheel A is transformed into an oscillating motion at wheel B by a connecting rod D. The angle at the rotating axis in the center of wheel B and the two points I.sub.1 and I.sub.2 where the rotational direction of wheel B is inverted is about 150. The oscillating motion of toothed wheel B is transferred to a further toothed wheel C, eventually using one or more further intermediate wheels (not shown). A sample holder capable of holding up to ten roller bearings, or devices with roller bearings, e.g. a wrist watch, is mounted on wheel C. The speed ratio between wheel B and wheel C is adjusted so that wheel C performs one full revolution around its axis when wheel B is rotated from the first point of inversion I.sub.1 to the second point of inversion I.sub.2. The watch mounted on the sample holder performs 34 oscillations back and forth per minute during the test.

3. Young's Modulus & Tensile Strength of Metallic Materials

[0239] Testing of a sample wire is carried out using a Zwick Roell machine Z005. The sample is fixed at its ends between two sets of grips Type 8206 (maximum testing force 2.5 kN) of the machine. The first end of the sample is secured within the first set of grips, and the second end of the sample is secured within the second set of grips. The diameter and length of the sample between the two sets of grips is entered into the software of the Zwick Z005 machine. Then, the upper set of grips is pulled in the Zwick machine at a constant speed rate of 25 mm/min until rupture of the sample whilst recording the force required for the constant pull rate. A test report comprising the values of R.sub.m (for a superelastic alloy such as Nitinol, the Yield Strength R.sub.p0.2 corresponds to the Upper Plateau) is retrieved from the machine. R.sub.p0.2 (=yield strength at 0.2% elongation) is determined graphically from the chart in the report.

[0240] Young's modulus is calculated for the region that shows a linear behavior. This is at the very beginning of the curve for Nitinol samples. For samples exhibiting superelastic properties, e.g. Nitinol samples, secant Young's modulus is calculated by measuring the slope of the line between origin and the end of the plateau (typically at 6 to 8% deformation) according to E=/.

Testing of the sample is further characterized by the following parameters:

TABLE-US-00001 Parameter Value Fixation of the wire grips 2.5 kN Sample length 300 mm Precursor diameter 0.6 mm Sensor head 5 kN Preload 10 N/mm.sup.2 Method of measurement of the elongation crosshead motion

5. Load Improvement Ratio LIR

[0241] The load improvement ratio LIR is calculated using the yield strength Rp.sub.0.2, Young Modulus E and the Poisson coefficient V. The value of LIR indicates how much higher an impact (applied force) of a ball of a material could be with reference to a system of ZrO.sub.2 balls and flat race of 4C27A stainless steel without plastically deforming (indenting) the race, each testing setup having the same geometry. Poisson coefficient of metals and alloys is in general between 0.2 and 0.4. The influence on the result of calculation is little. Poisson coefficient was assumed to be constant, i.e. to equal 0.3 in all cases (metals and alloys) for the purpose of the present calculation. The calculation is performed in the following way:

Material of the races (reference=4C27A): E.sub.0, Y.sub.0, V.sub.0
Material of the balls (reference=ZrO2): E.sub.1, Y.sub.1, V.sub.1
Material of the new balls: E.sub.2, Y.sub.2, V.sub.2
Wherein E.sub.n is the Young modulus, Y.sub.n is the yield strength Rp.sub.0.2 and Y.sub.n is Poissons ratio. (with: n=0, 1, 2 and Vn=0.3). Pn (n=1, 2) stands for the load of the ball and the race. The Load Improvement Ratio LIR is defined as:

LIR=P.sub.2/P.sub.1=(Min[Y.sub.2;Y.sub.0].sup.3/Min[Y.sub.1;Y.sub.0].sup.3)*(E.sub.1.sup.2/E.sub.2.sup.2)

with

1/E.sub.1=(1V.sub.0.sup.2)/E.sub.0+(1V.sub.1.sup.2)/E.sub.1

1/E.sub.2=(1V.sub.0.sup.2)/E.sub.0+(1V.sub.2.sup.2)/E.sub.2.

EXAMPLES

1. Manufacture of Nitinol 50 Balls

[0242] Straight Nitinol wires of 0.5 m in length were cut to pieces of a length of about 50 mm. Then a bundle of several hundreds of wire was placed in a support. The bundle was then cut into slices with a thickness equal to the wire diameter. Thereby, small cylinders were obtained. The cylinders were placed in a vibratory tumbler in order to smooth all the edges through the treatment in the tumbler. The rounded cylinders were then placed in a lapping machine in order to get accurate, perfectly round and shiny balls. The whole smoothing process takes about 4-10 weeks.

2. Manufacture and Tests of Roller Bearings

[0243] Ball bearings were assembled which have a 4 contact points raceway made from stainless steel, quenched of hardness 700HV1, as shown in FIG. 4, suited to bear balls of size of 0.4 mm. Each time seven balls of 0.4 mm were integrated into the bearing. The raceway had a diameter of 4.7 mm. The following examples were produced:

Experimental dataRaceways made from stainless steel, quenched, hardness 700HV1

TABLE-US-00002 Material Static Static of the balls indentation Ball indentation Ageing, non in the ball on raceway deformation on raceway lubricated bearing 2 Kg load 2 Kg load 4 Kg load (+works; fail) Nivaflex + 45/5 Stainless steel 440C Ceramic + + (ZrO2) Nitinol 60 + + Nitinol 50 + + + + (Inventive) Meaning of symbols for static indentation tests and ball deformation test: + = no indentation/deformation (very little) = little indentation/deformation = much indentation/deformation
Measurements on static indentation was performed using a white Light Interferometer (3D Optical Surface Profiler from ZYGO. The ball deformation was measured with a mechanical micrometer.

Description of Materials of Balls and Raceways:

[0244]

TABLE-US-00003 Composition (numbers in brackets are wt-%, based Material on total composition) Supplier Nivaflex Mulpi-phase alloy: Co Vacuumschmelze 45/5 (45), Ni (21), Cr (18), GmbH&Co. KG, (Nivaflex) Fe (5), W (4), Mo (4), 63450 Hanau, Ti (1), Be (0.2) Germany Stainless Alloy: Fe (79.15), Cr Carpenter Technology steel 440C (17), C (1.1), Mn (1), Corp., Reading, PA (440C) Si (1), Mb (0.75) 19612-4662, US Ceramic Zr (85), O (15) Kyocera Fineceramics (ZrO2) GmbH, 73730 Esslingen, Germany Nitinol 60 Alloy: Ni (60), Ti (40) Abbott Ball Company Inc., West Hartford, CT 06133-0100, US Nitinol 50* Alloy: Ni (55), Ti (45) Abbott Ball Company Inc., West Hartford, CT 06133-0100, US Stainless Stainless steel with: C Sandvik AB,81181 steel 4C27A (0.22), Si (0.6), Mn (1.6), Sandviken, Sweden P(0.03), S (0.18), Cr (13), Ni (0.8), Mo (1.2) Stainless X40CrMoVN16-2 Aubert Duval (Groupe steel 1.4123 Eramet) Beta-Ti c Ti3Al8V6Cr4Mo4Zr Dynamet (Carpenter) Gum metal Ti36Nb2Ta3Zr0.3O Toyota, Toyotsu, Nissey BMG Mg65Cu25Al10 Furukawa Techno Material Co., Kanagawa, Japan CuBe CuBe2 Le Bronze Industriel Phynox Co CrNi MoMnC Si Fe Aperam Alloys, 58160 (39-41 19-21 15-18 Imphy, France 6.5-7.5 1.5-2.5 < 0.15 < 1.2 bal.) *50 in Nitinol 50 refers to atomic ratio, wherein 60 in Nitinol 60 refers to weight ratio. This difference in labelling both Nitinol materials is common in the market and known to the expert.

3. Young's Modulus, Yield Strengths Measurements and Load Improvement Calculation

[0245] Most of the Young's Modulus and Yield Strengths listed below have been found in tables or on Internet and confirmed by using the above described test methods. As an estimation, the Poisson coefficient has been set to 0.3 for all the materials

TABLE-US-00004 E Rp.sub.0.2 or Secant E or Upper for Plateau for superelastic superelastic alloys alloys Poisson example body material [Gpa] [Mpa] V LIR 0 race 4C27A 215 1900 0.3 1 ball ZrO2 200 2500 0.3 1 race 4C27A 215 1900 0.3 0.9 ball 4C27A 215 1900 0.3 2 race ZrO2 200 2500 0.3 2.4 ball ZrO2 200 2500 0.3 3 race 1.4123 195 1825 0.3 1.0 ball ZrO2 200 2500 0.3 4 race 4C27A 215 1900 0.3 0.5 ball Beta-Ti 80 1000 0.3 5 race 4C27A 215 1900 0.3 1.5 ball Gummetal 45 1100 0.3 6 race 4C27A 215 1900 0.3 2.3 ball BMG 80 1700 0.3 7 race 4C27A 215 1900 0.3 0.9 ball Nivaflex 220 2475 0.3 8 race 4C27A 215 1900 0.3 0.8 ball CuBe 131 1500 0.3 9 race 4C27A 215 1900 0.3 1.0 ball Phynox 208 2400 0.3 10 race 4C27A 215 1900 0.3 2.5 ball NiTi 60 95 2500 0.3 11 race 4C27A 215 1900 0.3 5.7 ball NiTi 50 7 550 0.3 secant 12 race 1.4123 195 1825 0.3 1.0 ball ZrO2 200 2500 0.3 13 race 1.4123 195 1825 0.3 1.0 ball 1.4123 195 1825 0.3 14 race 1.4123 195 1825 0.3 1.6 ball Gummetal 45 1100 0.3 15 race 1.4123 195 1825 0.3 2.4 ball BMG 80 1700 0.3 16 race 1.4123 195 1825 0.3 5.7 ball NiTi 50 7 550 0.3 secant 17 race NiTi 60 95 2500 0.3 10.8 ball NiTi 60 95 2500 0.3 18 race ZrO2 200 2500 0.3 5.9 ball NiTi 60 95 2500 0.3 19 race NiTi 50 7 550 0.3 21.3 secant ball NiTi 50 7 550 0.3 secant 20 race Gummetal 45 1100 0.3 4.1 ball Gummetal 45 1100 0.3 21 race BMG 80 1700 0.3 4.8 ball BMG 80 1700 0.3 [0246] The rolling elements of example no. 4, 5, 6, 11, 14, 15, 16, 19, 20 and 21 have [0247] (i) a Young modulus E in the range up to and including 100 GPa; and [0248] (ii) a yield strength Rp.sub.0.2 in the range up to and including 1800 MPa. [0249] For Nitinol, the Rp0.2 is to the Upper Plateau that is found in the Tensile Test. [0250] The secant Young's Modulus is determined by measuring the slope of the line between the origin and the end of the plateau [0251] Ball bearings according to example no. 5, 6, 10, 11, 17, 18, 19, 20 and 21 have a LIR of 1.5 or more, examples no. 11, 16, 17, 18, 19, 20 and 21 have a LIR of 3.0 or more.