粘弹性材料声学参数脉冲法测试关键技术研究

The accurate characterization of the acoustic properties of viscoelastic materials at low frequency range has been a formidable problem when applied in practical underwater enviroment. In general, it can be summarized as follows: 1. the measurement accuracy of the acoustic parameters can not meet the requirement of prictical use when conducted by the traditional methods;2. little knowledge is available about the rules when acoustic parameters is regarded as a function of temperature and water depth; 3. the transformation relationship between the sample test results under labrotary enviroment and its counterpart used in practice is still not reliable.Based on above analysis, the measuring techniques of acoustic parameters for viscoelastic materials and its prediction approaches are presented in this program based on the short impulse signal. Firstly, the measuring system is implemented in underwater acoustic tube, anechoic tank as well as pressurized tank, respectively, through which, the measuring accuracy and the frequency limit can be improved at low frequencies. Secondly, when large sample insonified by incident waves with different incident angles and wavefronts, the internal relationship and its transformation formulas for the acoutic parameters will be explored, after which, the plane wave acoustic parameters will be deduced based on the internal relationship, meanwhile, through the measuring results, it can predict the acoustic performance of these materials when utilized in pratical enviromental.lastly, the acoustic model will be presented that incorporates the temperature and pressure factors depending on the stain-stress constitutive relationship, through the model analysis, the prediction problems of acoustic parameters which encounters the complex temperature and pressure circumferences may be solved to some extent .Through these work, the study on the sound propagation in viscoelastic materials will be deepened, and a kind of novel measuring technique may be provided for the low frequency performance measurement of practical underwater acoustic materials.

在实际水声环境下，粘弹性材料低频声学性能的精确测量是水声领域的一个难题。具体说，1.现有测量方法的低频限较高；2.对材料参数随温度、压力等环境因素变化的规律缺少研究；3.实验室样品测试与其在实际应用环境下的性能尚无可靠的转换关系。本项目提出基于短脉冲信号的粘弹性材料声学参数测试技术及性能预测方法。首先，建立可用于水声管、消声水池及压力罐的脉冲法声学测试系统,改善低频声学参数测试的频率限制和测量精度。其次，研究不同入射波波形和角度条件下声学参数的转换关系，提出由球面波声学参数反演相关平面波声学参数，并由实验测量结果预测实际应用条件下的声学性能。最后，基于粘弹性材料应力-应变本构关系及衰减系数幂函数定律，建立包括温度和压力因素的声学参数模型，通过模型分析，进一步解决声学参数在复杂水压和温度条件下的预测问题，深化粘弹性材料内部声传播规律的研究，并为实际水声材料低频性能测试提供一种新的技术路径。

在实际水声环境下，粘弹性材料低频声学性能的精确测量是水声领域的一个难题。具体说，1.现有测量方法的低频限较高；2.对材料参数随温度、压力等环境因素变化的规律缺少研究；3.实验室样品测试与其在实际应用环境下的性能尚无可靠的转换关系。本项目提出基于短脉冲信号的粘弹性材料声学参数测试技术及性能预测方法。通过研究，建立了可用于水声管、消声水池及压力罐的脉冲法声学测试系统，对水声橡胶材料力学和声学参数测试技术进行了深入的探讨，改善了低频声学参数测试的频率限制和测量精度，水声管测量低频限可低至200Hz，其次，探讨了力学参数的六参数宽带分数导数模型，初步考虑了温度对力学参数的影响，为进一步建立包含温度和压力等因素的力学参数模型奠定了基础，最后，基于可控脉冲生成技术，在激振器上产生了宽带短脉冲，并使用该脉冲对粘弹性细棒进行了激励。结果表明，利用共振法计算得到的的力学参数与粘弹仪数据吻合较好，二阶以上共振频率处的计算结果由于模态耦合的影响导致测量结果不准确。通过上述研究，进一步解决了声学参数在复杂水压和温度条件下的预测问题，深化了粘弹性材料内部声传播规律的研究，并为实际水声材料低频性能测试提供一种新的技术路径。