Patent ID: 8342382

Claim:
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 over the defined time period, comparing the accuracy of the fit of the curve to the measured loss of length of the components as a function of time over the defined time period with acceptable values of accuracy to determine if the quality of the friction weld is acceptable, determining a double differential with respect to time of the loss of length of the components as a function of time, determining the end of the defined time period by identifying the start of a final positive peak of the double differential with respect to time of the loss of length of the components as a function of time.