The basic principle of ultrasonic transducer
Piezoelectric transducer: piezoelectric transducer utilizes the electrostrictive effect single crystal piezoelectric effect of certain materials and some of the polycrystalline material.
Ultrasonic piezoelectric effect
Some single crystal material structure has an asymmetric characteristic, when the material is subjected to applied stress and strain occurs, change its internal lattice structure (deformation) would destroy the original macro performance electrically neutral state, the polarization electric field (polarization), an electric field (polarization intensity) generated proportional to the size of strain. This phenomenon is called piezoelectric effect, it was discovered by the Curie brothers in 1880. Subsequently, in 1881 has further found that such a single crystal material with inverse piezoelectric effect, i.e., a material having a piezoelectric effect when subjected to applied electric field, will generate stress and strain, the strain and the size of the external electric field into proportional. The piezoelectric effect is a characteristic crystal structure, it asymmetric crystal structure, whereas the stress or electric field magnitude and nature of the piezoelectric effect is applied to the crystal axis of the crystal relative to the direction of the relevant. Single crystal material having a piezoelectric effect of the type of many of the most commonly used such as natural quartz (SiO2) crystals, as well as artificial materials such as single crystal lithium sulfate (Li2SO4), lithium niobate (LiNbO3) and the like.
2 electrostrictive effect
There are some polycrystalline material formed spontaneously molecular group, the so-called 'electric domain', it has a certain polarization, and is often different from the longitudinal direction along the length of the other polarization direction. When there are external electric field, electric domains will rotate happen to the polarization direction of the applied electric field direction consistent, so that the material along the length of the applied electric field direction will change, the performance of elastic strain. This phenomenon is called electrostrictive effect.
3. magnetostrictive transducers
Magnetostrictive transducer utilizes magnetostrictive effect, then the physical characteristics of the particular alloy crystal structure, i.e., some ferromagnetic and alloys thereof, as well as some of the magnetic domains in the ferrite, in which the direction of spontaneous magnetization length may be different from other directions. When a magnetic field is applied, the magnetic domain will occur due to this rotation, so that the magnetization direction as the direction of the external magnetic field with the convergence, so that the material along the length direction of the external magnetic field will change, expressed as elastic strain (of course, This strain deformation is very small, between about 10-5 to 10-6). This phenomenon that is the magnetostrictive effect. On the contrary, the material has been subjected magnetostrictive effect applied stress or strain, its magnetization will change, that is, for the inverse magnetostrictive effect. Thus, in the magnetostrictive material when subjected to an alternating magnetic field, the magnetostrictive material deformation occurs along the direction of magnetic field lines, which can stimulate the mechanical vibration waves in close contact with its surface MEDIUM - [1]. Similarly, the use of inverse magnetostrictive effect can achieve the purpose of receiving ultrasonic: applied to the strain (elastic stress - ultrasonic force) will cause the magnetostrictive material in an external magnetic field in the magnetic flux density of the material of its occurrence change (namely the so-called magneto-elastic effect), so that the coil will be located on the surface of the material to detect the magnetic flux density due to changes arising from EMF, can be used as a signal magnetic elastic effect, to achieve the effect of receiving ultrasound (note the direction of the magnetic field should and stress direction - particle ultrasonic vibration generated in the same direction). According to state change of magnetostriction can be divided into:
[1] a linear magnetostriction: in the event of strain, the same volume of the material, but the degree of stretching in the longitudinal direction of the change of the large, which is the type magnetostrictive transducer main application. However, it can only happen below the Curie temperature, if the temperature exceeds the Curie point will only exist volumetric magnetostriction.
[2] Volume magnetostrictive type: in the event of strain, the volume of the material will change. Magnetostrictive transducer is mainly used for low-power situations, which with its frequency is limited and restricted by factors related to the magnetic material parameters, it is widely used in particular in the field of power ultrasound application, which is characterized mainly mechanical high strength, stability, watertight require low (not hydrolysis). However, it is a large eddy current and hysteresis losses, electro-acoustic conversion efficiency of as good as piezoelectric transducers, and usually require a larger excitation energy for high power applications. It should be noted that, when subjected to an alternating magnetic field, due to the skin effect
The penetration depth of the impact will be limited, so this magnetostrictive effect only to the extent of the spread of the material surface. When generating ultrasonic waves, ultrasonic waves depends on the material strength of the alternating magnetic field strength of the surface layer, in addition, the acoustic medium and the degree of close contact with the surface material (acoustic coupling) is also very important. Commonly used in magnetostrictive transducer materials are nicke
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The basic principle of ultrasonic transducer
Piezoelectric transducer: piezoelectric transducer utilizes the electrostrictive effect single crystal piezoelectric effect of certain materials and some of the polycrystalline material.
Ultrasonic piezoelectric effect
Some single crystal material structure has an asymmetric characteristic, when the material is subjected to applied stress and strain occurs, change its internal lattice structure (deformation) would destroy the original macro performance electrically neutral state, the polarization electric field (polarization), an electric field (polarization intensity) generated proportional to the size of strain. This phenomenon is called piezoelectric effect, it was discovered by the Curie brothers in 1880. Subsequently, in 1881 has further found that such a single crystal material with inverse piezoelectric effect, i.e., a material having a piezoelectric effect when subjected to applied electric field, will generate stress and strain, the strain and the size of the external electric field into proportional. The piezoelectric effect is a characteristic crystal structure, it asymmetric crystal structure, whereas the stress or electric field magnitude and nature of the piezoelectric effect is applied to the crystal axis of the crystal relative to the direction of the relevant. Single crystal material having a piezoelectric effect of the type of many of the most commonly used such as natural quartz (SiO2) crystals, as well as artificial materials such as single crystal lithium sulfate (Li2SO4), lithium niobate (LiNbO3) and the like.
2 electrostrictive effect
There are some polycrystalline material formed spontaneously molecular group, the so-called 'electric domain', it has a certain polarization, and is often different from the longitudinal direction along the length of the other polarization direction. When there are external electric field, electric domains will rotate happen to the polarization direction of the applied electric field direction consistent, so that the material along the length of the applied electric field direction will change, the performance of elastic strain. This phenomenon is called electrostrictive effect.
3. magnetostrictive transducers
Magnetostrictive transducer utilizes magnetostrictive effect, then the physical characteristics of the particular alloy crystal structure, i.e., some ferromagnetic and alloys thereof, as well as some of the magnetic domains in the ferrite, in which the direction of spontaneous magnetization length may be different from other directions. When a magnetic field is applied, the magnetic domain will occur due to this rotation, so that the magnetization direction as the direction of the external magnetic field with the convergence, so that the material along the length direction of the external magnetic field will change, expressed as elastic strain (of course, This strain deformation is very small, between about 10-5 to 10-6). This phenomenon that is the magnetostrictive effect. On the contrary, the material has been subjected magnetostrictive effect applied stress or strain, its magnetization will change, that is, for the inverse magnetostrictive effect. Thus, in the magnetostrictive material when subjected to an alternating magnetic field, the magnetostrictive material deformation occurs along the direction of magnetic field lines, which can stimulate the mechanical vibration waves in close contact with its surface MEDIUM - [1]. Similarly, the use of inverse magnetostrictive effect can achieve the purpose of receiving ultrasonic: applied to the strain (elastic stress - ultrasonic force) will cause the magnetostrictive material in an external magnetic field in the magnetic flux density of the material of its occurrence change (namely the so-called magneto-elastic effect), so that the coil will be located on the surface of the material to detect the magnetic flux density due to changes arising from EMF, can be used as a signal magnetic elastic effect, to achieve the effect of receiving ultrasound (note the direction of the magnetic field should and stress direction - particle ultrasonic vibration generated in the same direction). According to state change of magnetostriction can be divided into:
[1] a linear magnetostriction: in the event of strain, the same volume of the material, but the degree of stretching in the longitudinal direction of the change of the large, which is the type magnetostrictive transducer main application. However, it can only happen below the Curie temperature, if the temperature exceeds the Curie point will only exist volumetric magnetostriction.
[2] Volume magnetostrictive type: in the event of strain, the volume of the material will change. Magnetostrictive transducer is mainly used for low-power situations, which with its frequency is limited and restricted by factors related to the magnetic material parameters, it is widely used in particular in the field of power ultrasound application, which is characterized mainly mechanical high strength, stability, watertight require low (not hydrolysis). However, it is a large eddy current and hysteresis losses, electro-acoustic conversion efficiency of as good as piezoelectric transducers, and usually require a larger excitation energy for high power applications. It should be noted that, when subjected to an alternating magnetic field, due to the skin effect
The penetration depth of the impact will be limited, so this magnetostrictive effect only to the extent of the spread of the material surface. When generating ultrasonic waves, ultrasonic waves depends on the material strength of the alternating magnetic field strength of the surface layer, in addition, the acoustic medium and the degree of close contact with the surface material (acoustic coupling) is also very important. Commonly used in magnetostrictive transducer materials are nicke
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