| Summary: | 碩士 === 國立臺灣大學 === 材料科學與工程學研究所 === 92 === Damping properties of cold-rolled and heat-treated , and (in at%) shape memory alloys are investigated using Dynamic Mechanical Aanlyzer (DMA). The damping values, , at transient peaks of and are both over 0.1 while their storage modulus is still above 30GPa under temperature sweep mode at cooling rate of 3℃/min with frequency and amplitude and respectively. Under constant temperature mode, after keeping the peak temperature for hour, the value at the transient peak of descends 92% while that at the relaxation peak only descends 24%. For the latter case, the value is which is comparable to that of at transformation, so both of them have highly potential engineering applications. The of alloys in their single phase decreases with increasing the frequency in the low frequency range of (uniform amplitude in ) under multi-frequency mode. When the amplitude ranged from to (uniform frequency in ) under multi-strain mode, the of each phase increases with increasing the strain. Therefore, the damping value of alloys in martensite phase can achieve high damping capacity provided that the strain is high enough. For example, of alloy at ℃( transformation peak) is when the amplitude exceeds .
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