超声波机械振荡的弹性特点

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1、超声波机械振荡的弹性特点 超声波是一种在弹性介质中的机械振荡,有两种形式:横 向振荡( 横波) 及纵向振 荡( 纵波)。在工 业 中应用主要采用纵向 振荡。超声波可以在气体、液体及固体中传播,其传播速度不 同。另外,它也有折射和反射现象,并且在传播过程中有衰减。 超声波在媒质中的反射、折射、衍射、散射等 传播 规律 ,与可 听声波的规律并没有本质上的区别。与可听声波比较,超声波 具有许多奇异特性: 传播特性超声波的衍射本领很差,它在 均匀介质中能够定向直线传播,超声波的波长越短,这一特性 就越显著。功率特性当声音在空气中传播时,推动空气中 的微粒往复振动而对微粒做功。在相同强度下,声波的频率越

2、 高,它所具有的功率就越大。由于超声波频率很高,所以超声波 与一般声波相比,它的功率是非常大的。空化作用当超声 波在液体中传播时,由于液体微粒的剧烈振动,会在液体内部 产生小空洞。这些小空洞迅速胀大和闭合,会使液体微粒之间 发生猛烈的撞击作用,从而产生几千到上万个大气压的压强。 微粒间这种剧烈的相互作用,会使液体的温度骤然升高,从而 使两种不相溶的液体(如水和油)发生乳化,并且加速溶质的溶 解,加速化学反应。这种由超声波作用在液体中所引起的各种 效应称为超声波的空化作用。 Ultrasound is a mechanical oscillation in the elastic medium,

3、 there are two kinds of forms: horizontal oscillation (shear wave) and the longitudinal oscillation (longitudinal wave). In industrial applications mainly adopts longitudinal oscillations. Ultrasonic can spread in gas, liquid and solid, the transmission speed is different. In addition, it also has t

4、he phenomenon of refraction and reflection, and in the process of transmission attenuation. Ultrasonic in the medium such as reflection, refraction, diffraction, scattering and spread rule, and the rule of audible sound waves there is essentially no difference between. Compared with audible sound wa

5、ves, ultrasonic has many strange properties: propagation characteristics ultrasonic diffraction ability is very poor, it can directional rectilinear propagation in homogeneous medium, the ultrasound of the shorter the wavelength, this feature is more significant. Power features when sound in air, pu

6、shing the particles in the air reciprocating vibration particles for doing work. Under the same intensity, the higher the frequency of sound waves, it has the greater the power. Due to the ultrasonic frequency is very high, so ultrasound compared with general sound waves, its power is very big. Cavi

7、tation when the spread of ultrasound in liquid, due to the liquid particle vibration, can produce small hole inside the liquid. These small hole expands rapidly and closed, can http:/ http:/ http:/ http:/ make the liquid particles between violent impact effect, generating thousands to tens of thousa

8、nds of atmospheres of pressure. The intense interaction between particles, can make the liquid temperature rise sharply, so that the two dont mix liquid (water and oil) emulsification, and accelerates the dissolution of the solute, to speed up chemical reactions. This role by ultrasonic wave in the

9、liquid caused by all kinds of effect is called ultrasonic cavitation effect. 超声波的特点:(1)超声波在传播时,方向性强,能量易 于集中;(2)超声波能在各种不同媒 质中传播,且可传播足够远 的距离;(3)超声波与 传声媒质的相互作用适中,易于携带有关 传声媒质状态的信息(诊断或对传声媒质产生效应)。 Ultrasonic characteristics when: (1) ultrasonic propagation, directionality is strong, energy easy to concent

10、rate; (2) ultrasonic can spread in a variety of different media, and can be spread far enough; (3) ultrasonic and sound transmission medium interaction is moderate, easy to carry information about the state of sound transmission medium (diagnosis or effect on sound transmission medium). 2.超声波传感器 2.

11、The ultrasonic sensor 超声波传感器是利用超声波的特性研制而成的 传感 器。以超声波作为检测手段,必须产生超声波和接收超声波。 完成这种功能的装置就是超声波传感器,习惯上称为超声换能 器,或者超声探头。 Ultrasonic sensor is made using ultrasonic characteristics to the sensor. In ultrasonic testing means, must produce and receive ultrasonic. Complete the function of device is the ultrasoni

12、c sensor, traditionally known as ultrasonic transducer, or ultrasonic probe. 超声波探头主要由压电晶片组成,既可以 发射超声波, 也可以接收超声波。超声探头的核心是其塑料外套或者金属 外套中的一块压电晶片。构成晶片的材料可以有许多种。超 声波传感器主要材料有压电晶体(电致伸缩)及镍铁铝合金(磁 致伸缩) 两 类。电致伸缩的材料有锆钛酸铅(pzt)等。压电晶体 组成的超声波传感器是一种可逆传感器,它可以将电能转变成 机械振荡而产生超声波,同时它接收到超声波时,也能转变成http:/ http:/ http:/ http:

13、/ 电能,所以它可以分成发送器或接收器。有的超声波传感器既 作发送,也能作接收。 酿酒设备超声波传感器由发送传感器(或 称波发送器)、接收传感器(或称波接收器)、控制部分与电源 部分组成。发送器传感器由发送器与使用直径为 15mm 左右 的陶瓷振子换能器组成,换能器作用是将陶瓷振子的电振动能 量转换成超能量并向空中幅射;而接收传感器由陶瓷振子换能 器与放大电路组成,换能器接收波产生机械振动,将其变换成 电能量,作为传感器接收器的输出,从而对发送的超进行检测。 控制部分主要对发送器发出的脉冲链频率、占空比及稀疏调 制和计数及探测距离等进行控制。 Ultrasonic probe is mainl

14、y composed of piezoelectric chip, can emit ultrasonic already, also can receive the ultrasonic. The core of the ultrasonic probe is its plastic or metal jacket coat of a piezoelectric wafer. Constitutes a material can have many kinds of chips. Ultrasonic sensor main material have piezoelectric cryst

15、al (electrostrictive) and nickel iron aluminum alloy (magnetostriction) two kinds. Electrostrictive material with lead zirconate titanate (PZT), etc. Piezoelectric ultrasonic sensor is composed of a reversible sensor, it can transform electrical energy into mechanical oscillation produced by ultrasonic, it receives the ultrasound at the same time, also can change into electricity, so it can be divided into the sender or receiver. Some ultrasonic sensors for send already, also can be received. Ultrasonic sensors sent by sensor (or wave transmitter), receives the sensor (or wave receiver), con