1. 1/10 prototype support tube
July 30, ’03
KEK H. Yamaoka
1/10 prototype support tube
Thin Tube
Prototype support tube
Shaker
This figure shows the drawing of the prototype support tube. The size of the support tube is 80mm diameter and 10mm thick. And this is assembled from four pieces. And these support tubes are connected by this thin tube. Size is 200mm length and 3mm thick.

2. Tube with taper flange Connection tube Tube with flat flange
Configuration of one piece is like this. Both ends of the tube have flanges to join another tube. And end configuration is taper. And I prepare another type of prototype support tube. This is with flat flanges. Purpose is comparison with the vibration properties between these two.

4. ○ Test items Joining bolts Cantilever ・Taper flange/Flat flange
- Measuring oscillation properties
- Compare to the ANSYS calculation
- Effects of joining strength
Both-ends supported
- Thickness of connection tube
connection tube
Test items are with the taper flange type and flat flange type, measuring oscillation properties and compare to the ANSYS calculation. At this item, by changing the number of joining bolts, effects of joining strength was measured.

5. ○ Tests(Hammering test)
FRF(Frequency Response Function)
Xi: Output Acc.
Fj: Input force
Input
FRF Table
Input
FFT
Output
Output
FRF
Prototype support tube is set-up like this. Tube is mounted on this support base like this.
In this test, shaker was not used. Test was done by hammering/impulse method. This test is, by using this hammer, impulse is given to the support tube and output signal is measured. This hammer is mounted the load cell, so I can know the input force.
Input and output signals are like this and output signal are like these. After FFT, force can be input this frequency range, so output signal is like this. These peaks indicates resonant frequencies.
By carrying out the same thing at each point, It can be made this table. And from amplitude and phase angle, mode shape can be made.
FFT

6. ○ Results (Taper flange, 12-M6) A: 77.5Hz B: 90Hz C: 258Hz D: 522Hz B
G-sensor 20 21 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 B D C A
Fixed
Fixed
A: 77.5Hz
B: 90Hz
C: 258Hz
This is the test result in case of taper flange type with joining 12 bolts. Data was taken at these points from 1 to 9. And these plots show the FRF results. Each peak shows the resonant frequency and each line show the measurement data..
First peak is A. This mode shape is like this. It’s only rotation. Tube is not bending/deformed. This is due to the stiffness of the connection. If this connection is stiffer, this mode will be disappeared.
Next mode is like this, 129Hz. This is the typical 1st mode of cantilever type. Second mode is 585Hz. This mode is also deformed the joining point. 3rd mode is like this at this frequency.
D: 522Hz

7. ○ FEM 76Hz 256Hz 489Hz t15x230x80(Al) 5(height)x170(width)x80
100(dia.)x94(inner)x200(length)
110(dia.)x60(inner)x20(length)
80(dia.)xt10:Al
76Hz
256Hz
I compare to the ANSYS calculation. ANSYS model is defined like this. These lines show the support tube. And input the stiffness such as moment of inertia and area of cross section. This purple lines show these flanges. Support base was modeled like this.
Result is, first mode is 117Hz like this mode shape, 2nd mode is 656Hz, and third mode, 4th mode.
489Hz

8. Effects of joining strength
Joining bolts
Taper Flange:
3-M6 6-M6 12-M6
1st:
1st’:
2nd:
3rd:
Flat Flange
In progress.
Next, I have studied the effects of joining strength. In this test, when changing the number of joining bolts, difference of vibration properties were measured. The number of joining bolts were changed 3, 6 and 12. Then each resonant frequencies was measured like these.
In this figure, horizontal line shows the axial force reacted to the bolt. If the support tube is connected by 12 of M6 bolts, axial force in the bolts is about 3300 kg. In case of 6 bolts, it’s about this and in case of 3, it’s about this. And solid line shows in case of the taper flange, and dotted line shows the flat flange.
Result is, difference between the number of joining bolts, at first mode is not so change, but at the higher mode, difference is larger. Resonant frequency become lower. This is the same meaning as the stiffness decreasing.
Difference between taper and flat flange, first mode is not so large, but according to increase the resonant frequency, difference is larger. So taper flange is effective to keep the stiffness.