1. Percussive Riveting Analysis
University of Washington, Seattle
Department of Mechanical Engineering
Computational Techniques in Engineering – ME 535
Presented to: Professor Ashley Emery
Presented by: Wadih Zaklit

2. Outline Introduction Tools tested Methods Least square fit
Fast Fourier transform
Parameter estimation
Computational techniques
Conclusion

3. Introduction
Riveting: forging process that may be used to join parts together by way of a metal part called a rivet.
In an airplane there is about 5 million rivets from which 20% is done manually.
Mechanics are experiencing shoulder problems as well as Vibration White Finger.

4. Tools Tested 3 rivet guns Atlas Copco 12P (AC12P)
Ingersoll-Rand AVC-27 (AVC27)
Modified Ingersoll-Rand AVC-27 (MERG)
3 bucking bars
3kg Steel bar (SBBG)
7kg Steel bar (SBBM)
7kg Tungsten bar (TBB)

5. Methods Data was acquired collected using many sensors
Shock accelerometers to measure shock and vibrations
Lasers to measure distance
Least squares fit was used on the laser data
To predict rivet formation rate
Fast Fourier Transform was conducted on the acceleration of the bucking bar
To calculate the weighted accelerations
A simulation with parameter estimation is being built

6. Least Square Fit
Least squares is a standard approach in regression analysis to approximate the solution of overdetermined systems
The objective consists of adjusting the parameters of a model function to best fit a data set.
During the test bench testing
Laser data was collected
Rivet formation rate was found
Manual testing
Used the fit from test bench
Predicted formation rate

7. Least Square Fit Results
Manual testing takes longer than the automated testing to get the rivets’ tails height into specification
The TBB and SBBM reduce cycle time relative to the SBBG
Slight decrease in cycle time in the TBB compared to the SBBM

8. Fast Fourier Transform
A fast Fourier transform is an algorithm that samples a signal over a period of time (or space) and divides it into its frequency components
These components are single sinusoidal oscillations at distinct frequencies each with their own amplitude and phase

9. Fast Fourier Transform
Raw shock accelerometer data from bucking bar
Power spectral density of the signal using FFT
ISO Standard (Measurement and evaluation of human exposure to hand- transmitted vibration) use for frequency weighting

10. Fast Fourier Transform Results
The AC12P reduces the vibration emissions the most
Tungsten is superior to steel for bucking bars as it reduces vibration emissions

11. Simulation and Parameter Estimation
To predict the results without having to physically test different combinations a model of the gun and bucking bar is being simulated via Simulink
Using the parameter estimation toolbox, the system’s characteristics are estimated
Friction
Damping
stiffness

12. Conclusion
It is recommended that the standard gun used in the riveting process would be the AC12P.
The tungsten bar allows mechanics to work more efficiently than an equivalent mass of steel.
Further research is being conducted with a recoilless bucking bar.

13. Questions ?