APPARATUS AND A METHOD OF DETERMINING THE QUALITY OF A FRICTION WELD

• US 20120012644A1
• Filed: 02/04/2011
• Published: 01/19/2012
• Est. Priority Date: 02/18/2010
• Status: Active Grant

• Current Assignee: Rolls-Royce PLC (Rolls-Royce Holdings Plc)
• Original Assignee: Rolls-Royce PLC (Rolls-Royce Holdings Plc)
• Inventors: BAXTER, Gavin J., BRAY, Simon E., HORWELL, Mark G.
• Granted Patent: US 8,342,382 B2
• Time in Patent Office: Days
• US Class Current: 228/104
• CPC Class Codes: B23K 20/121 Control circuits therefor

Abstract

A method of determining the quality of a friction weld between two components, the method comprising joining two components together using a friction welding process, measuring the loss of length of the components as a function of time during the friction welding process, determining the double differential with respect to time of the loss in length of the components as a function of time, determining the quality of the friction weld by calculating the R² value of the linear fit to the loss in length of the components as a function of time over a defined time period, determining the end of the defined time period by identifying the start of the final positive peak of the double differential with respect to time of the loss of length of the components as a function of time, calculating R² from the least square difference of the linear fit over the defined time period of the loss of length of the components as a function of time and comparing the calculated value of R² with acceptable values of R² to determine if the quality of the friction weld is acceptable.

Claims

1. A method of determining the quality of a friction weld between two components, the method comprising joining two components together using a friction welding process, measuring the loss of length of the components as a function of time during the friction welding process, determining the quality of the friction weld by fitting a curve to the measured loss of length of the components as a function of time over a defined time period, determining the accuracy of fit of the curve to the measured loss of length of the components as a function of time, comparing the accuracy of the fit of the curve to the measured loss of length of the components as a function of time with acceptable values of accuracy to determine if the quality of the friction weld is acceptable.

2. A method as claimed in claim 1 comprising determining the quality of the friction weld by calculating the R² value of the linear fit to the loss in length of the components as a function of time over the defined time period, calculating R² from the least square difference of the linear fit over the defined time period of the loss of length of the components as a function of time and comparing the calculated value of R² with acceptable values of R² to determine if the quality of the friction weld is acceptable.

3. A method as claimed in claim 1 comprising determining the quality of the friction weld by calculating the R² value of the non-linear fit to the loss in length of the components as a function of time over the defined time period, calculating R² from the least square difference of the non-linear fit over the defined time period of the loss of length of the components as a function of time and comparing the calculated value of R² with acceptable values of R² to determine if the quality of the friction weld is acceptable.

4. A method as claimed in claim 1 wherein the friction welding process is selected from the group consisting of linear friction welding, rotary friction welding, orbital friction welding and friction stir welding.

5. A method as claimed in claim 4 wherein the rotary friction welding is selected from the group consisting of inertia friction welding, direct drive rotary friction welding and hybrid rotary friction welding.

6. A method as claimed in claim 4 wherein the linear friction welding process comprises welding a blade to a rotor.

7. A method as claimed in claim 6 wherein the linear friction welding process is selected from the group consisting of welding a fan blade to a fan rotor, welding a compressor blade to a compressor rotor and welding a turbine blade to a turbine rotor.

8. A method as claimed in claim 4 wherein the rotary friction welding process is selected from the group consisting of welding a first shaft to a second shaft, welding a first disc to a second disc and welding a shaft to a disc.

9. A method as claimed in claim 1 wherein the friction welding process is selected from the group consisting of welding titanium alloy components, welding nickel superalloy components, welding steel components and welding any other suitable combination of metals.

10. A method as claimed in claim 1 comprising determining the double differential with respect to time of the loss in length of the components as a function of time.

11. A method as claimed in claim 10 comprising determining the end of the defined time period by identifying the start of the final positive peak of the double differential with respect to time of the loss of length of the components as a function of time.

12. A method as claimed in claim 10 comprising monitoring the double differential with respect to time of the loss in length of the components to ensure it is within predefined limits for the friction weld.

13. A method as claimed in claim 12 comprising determining that the double differential with respect to time of the loss of length of the components falls below a predefined lower limit for the friction weld and increasing the pressure and/or speed to bring the double differential with respect to time of the loss of length of the components back within the predefined limits for the friction weld.

14. A method as claimed in claim 12 comprising determining that the double differential with respect to time of the loss of length of the components rises above a predefined upper limit for the friction weld and decreasing the pressure and/or speed to bring the double differential with respect to time of the loss of length of the components back within the predefined limits for the friction weld.

15. An apparatus for determining the quality of a friction weld between two components, comprising an apparatus for friction welding two components together, a sensor to measure the loss of length of the components as a function of time during the friction welding process, a device to determine the quality of the friction weld by fitting a curve to the measured loss of length of the components as a function of time over a defined time period, a device to determine the accuracy of fit of the curve to the measured loss of length of the components as a function of time, a device to compare the accuracy of the fit of the curve to the measured loss of length of the components as a function of time with acceptable values of accuracy to determine if the quality of the friction weld is acceptable.

16. An apparatus as claimed in claim 15 wherein the apparatus for friction welding two components together comprises a first device to rotate the first component and a second device to hold the second component rigidly.

17. An apparatus as claimed in claim 15 wherein the apparatus for friction welding two components together comprises a first device to oscillate the first component and a second device to hold the second component rigidly.