【作者】 赵洋；

【导师】 杨日福；

【作者基本信息】 华南理工大学 ， 无线电物理， 2019， 硕士

【摘要】 超声波是一种频率高于人类听觉的可听限度上限的声波,其频率为20 kHz至几千兆赫兹。超声波有三个明显的特点。超声波具有高频率,因此超声波传播的指向性很强,而且可以穿透几乎所有材料;介质中的质点在超声波传播过程中会产生一个很大的加速度;超声波在液体传播时,如果声强达到某个阈值,会产生空化现象。超声空化指的是超声在液体内传播时,致使液体中的气泡从出现到破碎消失的过程。超声空化存在一个阈值。超声波被应用于许多领域。超声波设备用于在水中测量距离。工业上,超声波用于清洁,还有混合和加速化学过程。在产品和结构的无损检测中,超声波用于检测其中不可见的缺陷。超声成像和超声治疗通常在医学中被广泛使用。超声换能器是一种声学传感器,分为三大类:发射器,接收器和收发器。发射器将电信号转换为超声波,接收器将超声波转换为电信号,收发器可以发送和接收超声波。超声换能器能够产生超声波,但是单个超声换能器通常不能满足实际应用中的多方面要求,通常这时候就需要利用超声换能器阵列来满足这些要求。目前国内外研究的主要是单一超声换能器作为阵元的超声换能器阵列,关于多种超声换能器共同作为阵元的超声换能器阵列的研究较少。因此,本文采用圆型活塞换能器和矩形活塞换能器共同作为超声换能器阵列的基本阵元。本论文首先介绍了换能器的声场特性和指向性的定义。接下来,介绍了圆形活塞换能器和方形活塞换能器在远场的声场特性和指向性,并进行了模拟仿真。最后介绍了换能器阵的声场特性和指向性,并对乘法定理和加法定理进行了阐述。本文的研究内容分为两个部分。第一部分是通过改变换能器阵列的排列计算它们变化引发的换能器阵列指向性的变化。首先举例说明了采用单一阵元组成的3×3换能器阵列的几种排列和采用两种阵元组成的3×3换能器阵列的几种排列,并计算并仿真了其的指向性。研究结果表明:采用两种阵元组成的超声换能器阵列的最大旁瓣在几种排列中最小。因此采用两种阵元组成的3×3换能器阵列在指向性上可以比采用单一阵元组成的3×3换能器阵列好。然后研究了采用单一阵元组成的4×4换能器阵列的几种排列和采用两种阵元组成的4×4换能器阵列。最后研究了采用单一阵元组成的5×5换能器阵列的几种排列和采用两种阵元组成的5×5换能器阵列。也得出了类似的结论。因此,采用两种阵元的换能器阵列在指向性上可以比采用单一阵元的换能器阵列好。第二部分是改变两种阵元组成的换能器阵列的参数计算它们变化引发的阵列指向性的变化。通过计算不同阵元间距的两种阵元组成的换能器阵列的指向性。研究结果表明:阵元间距越小,两种阵元的换能器阵列的指向性越好。通过计算不同阵元尺寸的两种阵元的换能器阵列的指向性。研究结果表明:阵元尺寸越大,两种阵元的换能器阵列的指向性越好。通过计算不同阵元频率的两种阵元的换能器阵列的指向性。研究结果表明:超声频率越大,两种阵元的换能器阵列的指向性越好。通过计算不同介质的两种阵元的换能器阵列的指向性。研究结果表明:介质中声音速度越小,两种阵元的换能器阵列的指向性越好。更多还原

【Abstract】 Ultrasound is a sound wave with a frequency higher than the upper limit of the audible limit of human hearing,with a frequency of 20 kHz to several gigahertz.Ultrasound has three distinct features.Ultrasonic waves have a high frequency,so the directivity of ultrasonic propagation is very strong and can penetrate almost all materials;The particles in the medium produce a large acceleration during ultrasonic propagation;When the ultrasonic wave propagates in the liquid,if the sound intensity reaches a certain threshold,cavitation will occur.Ultrasonic cavitation refers to the process from the appearance of bubbles in the liquid to the process of breaking when the ultrasound propagates through the liquid.There is a threshold for ultrasonic cavitation.Ultrasound is used in many fields.Ultrasonic equipment is used to measure distance in water.Industrially,ultrasonics are used for cleaning,as well as mixing and accelerating chemical processes.In the non-destructive testing of products and structures,ultrasonic waves are used to detect defects that are not visible therein.Ultrasound imaging and ultrasound therapy are commonly used in medicine.Ultrasonic transducers are acoustic sensors that fall into three broad categories: transmitters,receivers,and transceivers.The transmitter converts the electrical signal into ultrasonic waves,the receiver converts the ultrasonic waves into electrical signals,and the transceiver can transmit and receive ultrasonic waves.Ultrasonic transducers are capable of generating ultrasound,but a single ultrasound transducer typically does not meet the multifaceted requirements of practical applications,and it is often necessary to utilize an array of ultrasound transducers to meet these requirements.At present,domestic and foreign research is mainly focused on a single type of ultrasonic transducer array as an array element,and there is little research on a variety of ultrasonic transducers as an array element.Therefore,the circular piston transducer and the rectangular piston transducer are used together as the basic elements of the ultrasonic transducer array.This paper first introduces the definition of the sound field characteristics and directivity of the transducer.Next,the sound field characteristics and directivity of the circular piston transducer and the square piston transducer in the far field are introduced and simulated.Finally,the sound field characteristics and directivity of the transducer array are introduced,and the multiplication theorem and addition theorem are expounded.The research content of this paper is divided into two parts.The first part is to calculate the change in the directivity of the transducer array caused by their change by changing the arrangement of the transducer arrays.Firstly,several arrangements of a 3×3 transducer array composed of a single array element and several arrangements of a 3×3 transducer array composed of two array elements are illustrated,and the directivity of the array is calculated and simulated.The results show that the largest side lobes of an ultrasound transducer array consisting of two array elements are the smallest of several arrangements.Therefore,a 3×3 transducer array composed of two array elements can be better in directivity than a 3×3 transducer array composed of a single array element.Several arrangements of a 4x4 transducer array consisting of a single array element and a 4x4 transducer array consisting of two array elements were then investigated.Finally,several arrangements of a 5×5 transducer array composed of a single array element and a 5×5 transducer array composed of two array elements were studied.A similar conclusion was reached.Therefore,a transducer array employing two array elements can be better in directivity than a transducer array using a single array element.The second part is to change the parameters of the transducer array composed of two array elements to calculate the change of the directivity of the array caused by their change.The directivity of the transducer array composed of two elements with different spacing is calculated.The research results show that the smaller the array element spacing,the better the directivity of the transducer array of the two array elements.By calculating the directivity of transducer arrays of two elements with different element sizes.The results show that the larger the element size,the better the directivity of the transducer arrays of the two elements.The directivity of transducer arrays of two elements with different element frequencies is calculated.The results show that the higher the ultrasonic frequency is,the better the directivity of the transducer arrays of the two elements is.The directivity of transducer arrays with two elements in different media is calculated.The results show that the smaller the sound velocity in the medium,the better the directivity of the transducer arrays of the two arrays.更多还原