# US 8,782,902 B2 · Method of making bearing using ultrasonic nano crystal surface modification technology

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- Number: US 8,782,902 B2
- Document ID: US8782902B2
- Status: Granted
- Kind: B2
- Application number: 12/578,517
- Filed: 2009-10-13
- Published: 2010-02-04
- Granted: 2014-07-22
- Earliest claimed: 2008-05-14
- Assignees: Designmecha Co., Ltd.
- Applicants: Young Sik Pyun; Jeong Hyeon Park; Chang Sik Kim; In Ho Cho
- Inventors: Young Sik Pyun; Jeong Hyeon Park; Chang Sik Kim; In Ho Cho
- Web page: https://patentgrep.com/patent/US8782902B2

## CPC

- B24B 35/00: Machines or devices designed for superfinishing surfaces on work, i.e. by means of abrading blocks reciprocating with high frequency
- B24B 39/006: {Peening and tools therefor}
- F16C 33/64: Special methods of manufacture
- Y10T 29/49707: Bearing surface treatment
- Y10T 29/49709: Specific metallic composition
- B24B: MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING (grinding of gear teeth B23F, of screw-threads B23G1/36; by electro-erosion B23H; abrasive or related blasting B24C; tools for grinding, buffing or sharpening B24D; polishing compositions C09G1/00; abrasives C09K3/14; electrolytic etching or polishing C25F3/00; grinding arrangements for use on assembled railway tracks E01B31/17); DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- F16C: SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A method of making a bearing includes providing a bearing intermediate, which is unfinished while having an overall shape of a finished bearing product; and repeatedly impacting a surface of the bearing intermediate at one or more ultrasonic frequencies to modify characteristics of the bearing intermediate. The resulting bearing intermediate or finished bearing product includes nano-size grains at or underneath the surface.

## Claims

### Claim 1

A method of making a bearing, comprising:
providing a bearing intermediate, which is unfinished while having an overall shape of a finished bearing product;
providing a machine comprising a vibration generator, a vibration amplifier and an impacting tip, which form an integrated body, wherein the impacting tip is fixed to the vibration amplifier, which is attached to the vibration generator; and
simultaneously applying dynamic load and static load onto a surface of the bearing intermediate with the integrated body to cause plastic deformation of the surface without grinding of the surface, wherein applying the dynamic and static loads repeatedly impacts the surface of the bearing intermediate at one or more ultrasonic frequencies to modify characteristics of the bearing intermediate, wherein the resulting bearing intermediate or finished bearing product comprises a substantial amount of nano-size grains at or underneath the surface, wherein the resulting bearing intermediate or finished bearing product has the following properties:
a roughness value smaller than about Ra 0.19 μm,
a hardness value greater than about HRc 60 at the surface, and
a compressive residual stress value between about −300 and about −2500 MPa at the surface.

### Claim 2 (depends on 1)

The method of claim 1, wherein the nano-size grains are substantially distributed from the surface to the depth of about 100 μm.

### Claim 3 (depends on 1)

The method of claim 1, wherein the compressive residual stress value between about −400 MPa and about −700 MPa is found in the depth up to about 200 μm.

### Claim 4 (depends on 1)

The method of claim 1, wherein the method does not comprise grinding the surface before or after repeatedly impacting.

### Claim 5 (depends on 1)

The method of claim 1, wherein the bearing intermediate is not subject to an additional treatment that causes a significant change in one of roughness, hardness and compressive residual stress thereof.

### Claim 6 (depends on 1)

The method of claim 1, wherein providing the bearing intermediate comprises turning a bearing blank and thereafter grinding to make the overall shape of the finished bearing product, wherein the bearing intermediate is not subject to an additional treatment that causes a significant change in one of roughness, hardness and compressive residual stress thereof between grinding and repeatedly impacting.

### Claim 7 (depends on 1)

The method of claim 1, wherein the bearing intermediate prior to the repeated impacting is substantially free of nano-size grains.

### Claim 8 (depends on 1)

The method of claim 1, wherein prior to repeatedly impacting the surface and a portion underneath the surface has the following properties:
a roughness value greater than about Ra 0.2 μm,
a hardness value smaller than HRc 60, and
a compressive residual stress value between about +500 and about −300 MPa at the surface.

### Claim 9 (depends on 1)

The method of claim 1, wherein the bearing intermediate prior to repeatedly impacting comprises a substantial amount of micro-hair cracks at or underneath the surface.

### Claim 10 (depends on 1)

The method of claim 1, wherein the resulting bearing intermediate or finished bearing product is substantially free of micro-hair cracks at or underneath the surface.

### Claim 11 (depends on 1)

The method of claim 1, wherein the surface is applied a static load from about 1 N to about 500 N.

### Claim 12 (depends on 1)

The method of claim 1, wherein repeatedly impacting further comprises:
vibrating the impacting tip at a dynamic load from about 2 N to about 1000 N, while contacting with the surface.

### Claim 13 (depends on 1)

The method of claim 1, wherein the impacting tip is repeatedly impacted with a force applied in a direction having an angle with reference to the surface from about 30° to 90°.

### Claim 14 (depends on 1)

The method of claim 1, wherein repeated impacting further comprises:
moving the impacting tip relative to the surface while vibrating.

### Claim 15 (depends on 14)

The method of claim 14, wherein the impacting tip moves relative to the surface in a direction tangential to the surface.

### Claim 16 (depends on 14)

The method of claim 14, wherein the impacting tip moves at a linear speed of from about 0.1 to about 100 m/min.

### Claim 17 (depends on 1)

The method of claim 1, wherein the resulting bearing intermediate or finished bearing product comprises a pattern of dimples formed on the surface, wherein the pattern has a substantially constant pitch between two immediately neighboring dimples.

### Claim 18 (depends on 1)

The method of claim 1, wherein the finished bearing product is a piece of a bearing selected from a group consisting of a journal bearing, a rolling bearing, a ball bearing, a roller bearing, a needle bearing, a radial bearing and a thrust bearing.

### Claim 19 (depends on 1)

The method of claim 1, wherein repeatedly impacting the surface does not change the overall shape while changing a contour of the surface.

### Claim 20 (depends on 1)

The method of claim 1, further comprising, prior to simultaneously applying, adjusting the static load and the dynamic load.