【作者】 张玉姣；

【导师】 刘庆锁；

【作者基本信息】 天津理工大学 ， 材料学， 2011， 硕士

【摘要】 本文利用模板,采用磁控溅射法在PZT基体上溅射沉积局限面积的NiTi SMA薄膜,运用SEM、显微硬度测试与阻抗分析等研究了所制备材料的显微组织结构、力学性能及电学性能。实验发现,当模板型腔间距固定为L=1mm、型腔宽度M≤2.0mm时,非连续NiTi SMA薄膜组织具有良好的等轴晶组织结构。在固定薄膜间距1mm条件下,随M的增加, NiTi SMA薄膜的组织从等轴晶结构向柱状晶结构变化。制备材料的力学性能测试表明,随型腔宽度M递增,膜基结合强度依次减小;等轴晶NiTi SMA薄膜试样的断裂韧性较柱状晶试样提高2倍以上;沉积有等轴晶NiTi SMA薄膜试样的阻尼材料的阻尼值较PZT材料略有下降。制备材料的介电性能测试显示,沉积有等轴晶结构的NiTi SMA薄膜的PZT材料与纯PZT相比,两者的介电损耗水平接近,介电常数较纯PZT升高17.7%,NiTi SMA薄膜的沉积对于PZT材料的介电性能并无损害。构建起了基于所制备的NiTi SMA/PZT材料传感的适于建筑工程结构健康状态监测的“监测系统”:该系统中传感器由所制备的NiTi SMA/PZT材料构成,传感器以粘贴方式与建筑结构集成;通过由采集卡、电荷放大器及滤波器等构成的电路系统进行数据的采集与处理;采用Visual B 6.0自主编制的软件系统进行测试系统的监控。监测结果表明,此监测系统的响应范围处于半径800mm的范围,反应速度在毫秒级,响应频率在0-1000赫兹,适于监测建筑工程结构的裂纹损伤状态。本论文采用激励试验进行建筑梁结构裂纹损伤状态测试;采用频谱分析方法探讨所构建的“监测系统”的裂纹状态评价机制。固定频率激励状态下,响应特征峰的位置状态变化直接反映结构裂纹状态变化;偏心激励产生的响应特征峰随裂纹远离结构中心峰强降低。荷载车辆运动激励响应测试发现,载车监测车速与实际车速基本接近;信号能量密度随载车配重的增加呈现出非线性的增加,出现裂纹时,能量密度下降,随着裂纹的逐步扩展,能量总值递减。更多还原

【Abstract】 The composite deposited confining NiTi SMA thin films on the PZT substrate was prepared by magnetron sputtering method with the specially designed mask. The microstructure, mechanical and electric properties of the prepared composite was studied with SEM, XRD, microhardness tester and impedance analyzer.It is found that the NiTiSMA thin films with the width of no more than 2mm and the mutual distance of 1mm exhibit the best equiaxed crystal structure after crystallization. With the increasing of the width of the NiTiSMA thin film, the microstructure of the NiTiSMA thin films gradually changes to columnar crystal structure under mutual distance of 1mm between the NiTiSMA thin films.The results of mechanical testing show that the binding force between the NiTiSMA thin film and PZT substrate decreases with increasing of the cavity width, and the fracture toughness of the prepared composite is greater twice than that of the composite deposited continuous NiTi SMA thin film on the PZT substrate. Compared with the pure PZT, the damping values of the prepared composite decrease slightly.The results of the dielectric measurement show that the prepared composite has similar dielectric loss to the pure PZT, but its dielectric coefficient is higher than pure PZT. So the deposited NiTi SMA thin films have no damage to electrical properties of the PZT.The structural health monitoring system based on the prepared NiTiSMA/PZT composite was constructed as following: the sensors of the system were made of the prepared composite; the sensors were stick on the building structure; the dates were collected and disposed through the electrical system composed of acquisition card, charge amplifier and filter; the system software was finished using VB language, and finally the function of the system was realized. The monitoring results indicate that response radius of the system is 800mm, reaction speed of the system is in millisecond, and response frequency of the system is in range of 0-1000 Hz. So the system is suitable for monitoring architectural engineering structure crack damage status.In the paper, the crack damage statuses of the construction were tested by the exciting means, and the evaluation mechanism of the crack damage statuses for the constructed structural health monitoring system was discussed by the spectral analysis method. The experiment results show that,in the fixed exciting frequency, the location state’s changes of the responses peaks directly reflect the changes of the crack state in the structure, and the peak height at the frequency of 9.5Hz reduces with the increasing of the distance between the exciting position and the geometrical center of the structure. Under the excitation of the vehicle load, it is found that the monitoring speed is close to the actual speed, and the values of the signal energy density is advanced nonlinearly in nonexistence of crack with the increasing the loaded weight, but that is opposite in existence of crack.更多还原