NiTi-Al金属基复合材料梁固有频率调节特性理论与实验研究

根据Timoshenko梁理论考虑NiTi回复应力作用,建立了NiTi-Al金属基复合材料梁(简称复合梁)的自由振动微分方程,研究了复合梁的固有频率调节特性.对于悬臂梁,NiTi回复应力使复合梁呈压应力状态,造成固有频率降低,在梁长度80mm、NiTi体积分数8%、预应变3%时,温度由20℃升至80℃,固有频率的减小量可达52.1%.对于固支梁,其内部应力状态取决于NiTi回复应力和热膨胀共同作用,使固支梁固有频率增加的最小NiTi体积分数约为20%.最后,利用超声波焊接技术制造了复合梁,通过热模态实验测试了NiTi-Al悬臂梁固有频率随温度变化规律.结果表明,埋入NiTi能有效调节复合梁固有频率,且实验结果与理论计算结果规律一致.

Theoretical and Experimental Research of Frequency Tuning Characteristics of NiTi-Al MMCs Beam

Abstract： A Timoshenko beam vibration model was built by considering the recovering stress of NiTi to predict the frequency tuning characteristics of NiTi Al beam. The recovering stress of NiTi resulted in the compressive stress in Clamped-Free (CF) beam which caused the frequency to decrease. For a 80 mm length CF beam with 8% of NiTi (prestrain 3%) embedded, the base frequency decreased by 52.1% when heated to 80 ℃, while the stress status of Clamped-Clamped (CC) beam depended on the combined effect of thermal expansion and NiTi recovering stress. At least 20% of NiTi should be embedded to increase the frequency of CC beam. Finally, theh NiTi Al MMCs beam was manufactured by ultrasonic welding process. A thermal modal experiment was conducted to study the frequency tuning characteristics of NiTi-Al CF beam. The results show that by embedding NiTi the frequency of the beam could be effectively tuned. The experimental data conforms to the theoretical data.