固体中线性相控阵列的瞬态聚焦特性

The transient beam focusing characteristics of linear phased arrays in solid

针对线性相控阵列在固体介质中的声场聚焦特性及参数优化问题,该文给出了一个线性阵列的纵波瞬态聚焦声场模型。数值结果表明,当阵元被短时脉冲信号激励时,瞬态聚焦声场中不会形成栅瓣,突破了传统稳态理论模型中对阵元间距的限制;同时由于横纵波在聚焦区域内可完全分离,声束旁瓣的幅值也得到了抑制。其次,增大阵元间距能够显著提高聚焦性能,但会导致聚焦声场能量减弱,综合考虑后,最佳的阵元间距为一个波长左右。并且发现,阵元宽度对于聚焦性能几乎没有影响,但宽阵元能够提高聚焦能量。此外,受到纵波激发特性的影响,使得相控阵只能在低偏转角处获得理想的纵波聚焦性能。最后,采用不同阵元间距的相控阵探头对试块进行成像实验,观察到大阵元间距可以显著改善缺陷成像分辨率,从而验证了理论分析的结果。

Aiming at the beam focusing characteristics and parameter optimization of linear phased array in solid,the model of transient beam focusing of compressional waves for linear arrays is developed.The numerical results show that when the elements are excited by short pulses,it is hard to form the grating lobes in the field.And the short pulses also makes the compressional and shear waves completely separated at the focal point,which reduces the side lobe amplitude effectively.Besides,the enlargement of inter-element spacing can effectively improve beam focusing performance,which liberates the inter-element spacing limited in the tradi-tional study.But focusing energy tends to decrease as the inter-element spacing increases.With comprehensive consideration,the inter-element spacing approaching one wavelength is an optimal choice.Finally,the arrays with different inter-element spacing are employed to perform the imaging experiments for the standard test block.It can be observed that the larger inter-element spacing can improve the imaging resolution for defects,which verifies the results of theoretical analysis.