前端开横向矩形通孔的新型大振幅纵向振动系统及其多变量优化设计

Enlargement of amplitude amplification factor for ultrasonic horns and amplitudes and frequency bandwidth for longitudinal transducers by means of optimization design of the geometrical sizes and the position of a transverse rectangle hole at front end. Combining the finite element method with the genetic optimization algorithm, taking the amplitude of the front end and frequency bandwidth of longitudinal vibration transducer respectively,, and amplitude magnification coefficients of uniform horn and of variable cross-section horns as the target functions, and taking operating frequency and the radius of the large and small end faces (for transducers being the radius of the large end face) as the state variables, and taking the distance of the hole from the front end surface and the length and width of the hole as the design variables, make the objective function achieve maximum by the method of multi-variable optimization design, and then, the optimized position and the geometrical sizes of the hole will be got. In the same way, the large amplitude amplification factor of ultrasonic horns with larger face output end will be studied by optimization design of the geometrical sizes and the position of a transverse rectangle hole at its front end. Furthermore, the influence of the hole on the whole amplitude distributions at the front end and on stress distributions of the transducer and the horn along their axial direction will be investigated by using the finite element method. All of above calculated and optimized results will be validated by experimental tests, including test of the amplitude magnification coefficients and vibration mode shapes of the ultrasonic solid uniform horns with no or with a hole, of variable cross-section ultrasonic horns with no or with a hole, and test of whole amplitude distributions at the front end, of voltage transmitting response, and of -3dB frequency bandwidth of a longitudinal transducer with no or with a hole. It will provide better performances and more applicable transducers and ultrasonic horns for power ultrasound and underwater acoustic technology through investigation of this kind of vibration system.

本申请项目提出距振动前端面一定位置处开一横向方向的矩形通孔，优化设计孔位置及几何参数以达到增大变幅杆的振幅放大系数和纵振换能器的振幅并展宽频带的目的。结合有限元方法和遗传优化算法，分别以纵振换能器前端面的振幅、频带宽度，以及等截面变幅杆和系列变截面变幅杆的振幅放大系数为目标函数，以工作频率、大小端面的半径（若对换能器则为其前盖板的大端面的半径）为状态变量，以孔距离前端面的位置、孔的长度和宽度为设计变量，进行多变量优化设计，优化开孔位置及开孔尺寸，使目标函数达到最大。同理，优化设计大端面变幅杆输出端上的孔以增大振幅放大系数。计算矩形通孔对前辐射端面整体振幅分布、应力分布及位移节点的影响。设计并加工实心、开横向通孔及优化后的换能器及系列变幅杆，测试换能器的电压发射响应和-3dB频带宽度，测试换能器和变幅杆的振型、放大系数，验证理论计算结果，为功率超声和水声技术提性能更佳的换能器和变幅杆。

功率超声和水声技术需要相对于传统纵振动系统工作频带更宽、放大系数更大的实用振动器件及其设计方法。本项目提出研究结构为前盖板开横向内通孔的纵向振动压电换能器。换能器器前端开孔后，因孔的存在导致换能器无论在空气还是在水中将增加两个弯曲振动模态，与纵振模态耦合后会拓宽换能器的频带宽度。耦合效应也使得开孔后的换能器振幅大于实心结构同频率的换能器。对21.69kHz的未开孔换能器，其发射电压响应为146dB，-3dB带宽为3kH。前端开孔后，在15-30kHz范围内，在空气中有三个谐振频率分别为 18.71kHz, 25.98kHz和31.40 kHz，在水中的三个谐振频率分别为17.50kHz, 25.50kHz, and 30.38 kHz，其中30.38kHz处的发射电压响应变为141dB，-3dB带宽覆盖22-32.50kHz，明显拓宽了工作频带；提出并研究了前端开横向内通孔的系列变截面（包括等截面）大振幅变幅杆。如对频率为20kHz左右的均匀等截面传振杆，原本振幅放大系数为1，但开孔后，均匀等截面的传振杆的放大系数竟能达到3.39；对同频率的输入端面面积相同的阶梯型、悬链线型、指数型和圆锥形的变幅杆，原本它们的放大系数分别为1.82、1.35、1.34和1.33，开孔后的变幅杆各相应的放大系数也增为未开孔的2-3倍。.特别地，对输出端面大于输入端面的倒锥形变幅杆，原本其振幅放大系数只有0.57，在其前端开孔后其放大系数能达到2.38.项目的研制为水声技术及功率超声技术提供了性能更佳的换能器和变幅杆及（优化）设计方法。在振动式机械天线的应用中，为避免金属导体被驻极体极化而产生反向点偶极矩，需选择高强度的非金属材料作为换能器组件。因此，利用基金的资助，本项目中研究了聚苯硫醚型换能器。研制的前盖板为聚苯硫醚、后盖板为钢(1#)和前后盖板均为聚苯硫醚(2#)的两个换能器进行了测试. 结果表明, 当两个换能器尺寸一定时，1#换能器具有较大的电压-振幅比；两种换能器在应变较大处耗散功率较高, 分析表明耗散功率与外加电压平方成正比，与理论计算相吻合。另外，前后为PPS材料的带宽较宽，有利于宽频带工作。.研究了一般较复杂声场的计算方法，对任意形状的辐射体声源，计算出其表面位移振幅分布后，将表面分割的各小单元视为点源组合，编制程序就能计算其声场分布。