Experimental Analysis of Smart Structure with Damping Treatment and SMA
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Mat. Res. Soc. Symp. Proc. Vol. 459 01997 Materials Research Society
Computer with STAR System
Dual Channel Signal Analyzer
Figure 1 Experiment Scheme
then analyzed. Beam Structure The damping material used for the experiments is called DYAD 606 from THE SOUNDCOAT COMPANY, INC. DYAD 606 is Soundcoat's constrained layer damping material for vibration damping at low temperature. DYAD 601 provides maximum damping at about 100 0 F (38C), but the material has a useful damping range from 500 to 150°F (10C to 66C). The original uncovered structure is an aluminum beam with dimensions 533.00 mm x 25.4 mm x 3.175 mm. The dimensions for the DYAD 606 damping material are 25.4 mm x 0.6 mm with different lengths of coverage. The constraining layer is an aluminum sheet with dimensions 25.4 mm x 1 mm. The Nitin6l SMA material with thickness of 0.833 mm is used in the experiment. The austenite starting temperature As=61C and the finishing temperature Af=72C. RESULTS AND DISCUSSION The experiments were carried out for the above structure to obtain the frequency and loss factor of the system. The results for different coverage are shown in Figures 2 - 5. Coverane Length Effects The effects of coverage length on the natural frequency of the system are shown in Figure 2. We note from the figure that an increase in coverage length will increase the first and second natural frequencies. This tendency follows the numerical trends found for other types of constrained viscoelastic coverings [6,8]. Figure 3 shows the results of system loss factor versus coverage length ratio. From the figure, we note that an increase in the coverage length ratio will increase the system loss
164
100
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Second Mode
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First Mode
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0.000
j
i
0.200
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0.400 0.600 Coverage Ratio
0.800
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Figure 2 Coverage Ratio vs. Frequency
1.000
SMA Temperature = 60 C = 40 C 0 0
-4J
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0.01040.000
0
0.400
0.200
0 0.600
Coverage Ratio Figure 3 Coverage Ratio vs. Loss Factor
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0.800
factor because more damping material is used, again in consonance with results previously discussed in [6,8]. Temperature
Effects
Figure 4 show the results of system frequency versus the SMA layer temperature. When the temperature is less than the SMA As temperature, an increase in temperature will decrease the system frequency. Between the A. and Af temperatures, increase of temperature will increase system frequency because of austenite phase transformation effects on Young's modulus. But if the coverage is small (e.g., less than 20%), we can hardly see the increase in system frequency because the SMA austenite transformation effects-which increase the frequency--are balanced by the temperature effects which decrease the frequency. Figure 5 shows the results of system loss factor versus coverage ratio. It is noted that there exists a temperature which makes the system loss factor a maximum. This optimal temperature is close to the maximum damping material loss factor temperature as discussed in [15]. Also, an increase in the cov
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