Ultrasound is used to obtain several pieces of information for communication applications, called ultrasonic testing. Ultrasonic thickness gauges use a pulsed reflection of ultrasonic waves in a medium to test the thickness of an object. Ultrasonic thickness gauge can measure the thickness of metal or non-metal materials, and can also measure the sound velocity of materials, in order to judge the properties of materials, and also to check the defects near and parallel to the surface. The measurement accuracy of general wall thickness below 10mm can reach 0.01. Mm. The accuracy of osenon's ultrasonic sensors is very high and is good for high-precision measuring instruments. Ultrasonic thickness gauges are divided according to the working principle: resonance method, interference method and pulse reflection method.
Due to the convenience of ultrasonic treatment and good directivity, ultrasonic technology measures the thickness of metal and non-metal materials, which is fast, accurate and non-polluting. Especially when only one side can be touched, it can show its superiority. It is widely used in various plate, pipe wall thickness, boiler vessel wall thickness and local corrosion and rust. Therefore, it is responsible for product inspection of metallurgy, shipbuilding, machinery, chemical, electric power, atomic energy and other industrial sectors. And modern management plays a major role.
The ultrasonic thickness gauge works as follows: its pulse generator excites a dedicated high-damping piezoelectric transducer with a narrow electric pulse. This pulse is the initial pulse, and a part of the ultrasonic signal generated by the initial pulse excitation is reflected at the material interface. The signal is called the beginning wave. The rest penetrates into the material and reflects back from the opposite side. This return signal is called the back echo. The time interval between the start wave and the back echo represents the sound path time of the ultrasonic signal passing through the device under test. If the sound path time is measured, the thickness of the test piece can be determined by the following formula, and the sound speed is determined when the thickness is measured.
Where d is the thickness of the device under test, C is the propagation velocity of the ultrasonic wave in the device under test (ie, the speed of sound), and t is the duration of the sound path.
On the contrary, it can be known from the above formula that the sound velocity in the workpiece to be tested can be obtained by measuring the thickness of the workpiece and the sound path time. The sound velocity is the basic physical quantity describing the propagation characteristics of the ultrasonic wave in the medium, and its size is determined by the propagation medium, that is, the material. The modulus of elasticity, density, ultrasonic wave pattern and Poisson's ratio are related. Although the elastic modulus of a metal material is insensitive to the structure of the structure, it is also affected by the structure of the structure because it is related to the interatomic force and the interatomic distance, and the atomic spacing is related to the crystal structure. In addition, the density of the metal material is microscopically related to the structure of the structure, and the volume of the unit cell is related to the structure of the structure, so the speed of sound is inextricably linked with the internal structure of the metal material, so that the measured thickness is measured using an ultrasonic thickness gauge. The change in the speed of sound in the piece can determine the abnormality of the internal structure in the device under test.