解析深沟球轴承装配自动线
来源：南京博克纳自动化系统有限公司 日期：2017-09-25 关键词：涡流探伤，涡流探伤仪
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1. Ultrasonic testing
Ultrasonic testing is one of the nondestructive testing methods. Nondestructive testing is the general name of all kinds of technical methods to check the macro defect of workpiece or to measure the characteristics of workpiece without damaging the premise. Conventional nondestructive testing methods are: ultrasonic detection of Ultrasonic Testing (UT); ray detection (RT); Radiographic Testing Magnetic particle Testing magnetic particle testing (MT); Penetrant Testing penetration test (PT); Testing Eddy current eddy current testing (ET);
2 、 ultrasonic flaw detector
By using the method of ultrasonic detection instrument to detect the called ultrasonic flaw detector. It is the principle of ultrasonic detection in materials dissemination, influence propagation change material acoustic properties and the internal organization of the ultrasonic, understanding the properties and structure of materials by detecting the change degree and status influence on the ultrasonic technology called ultrasonic detection. Ultrasonic detection methods usually have penetration method, pulse reflection method, tandem method etc.
Ultrasonic flaw detection is able to penetrate deep metal material by ultrasonic, and into another section by section, inspection method for defects in parts to the characteristics of the interface edge reflection occurs, when the ultrasonic beam from the part surface by the probe through the internal metal, encountered defects and parts of the bottom surface respectively reflected waves and the formation of pulse waveform on the screen, to judge the defect position and size according to the pulse waveform.
Nondestructive testing of internal defects of materials using the influence of acoustic properties difference between materials and their defects on ultrasonic propagation. Now widely used is the observation of acoustic pulse reflected in the material of the ultrasonic pulse reflection method, in addition to observation through the material after the incident wave amplitude change penetration method, etc.. The commonly used frequency ranges from 0.5 to 5MHz.
The commonly used test instrument displays the pulse reflection type ultrasonic flaw detector for A. According to the presence or absence of the reflected signal on the oscilloscope screen, the time interval between the reflected signal and the incident signal and the height of the reflected signal, the presence, location and relative size of the reflecting surface can be determined. The basic structure and principle of the instrument are shown in figure 1.
There are many kinds of waves in ultrasonic wave propagation in media. The most commonly used methods are longitudinal wave, transverse wave, surface wave and plate wave. With the existence of compressional wave can be detected metal ingot, billet, plate, large forging shape and relatively simple parts of inclusions, cracks, shrinkage, flaking, defects such as delamination; transverse wave can be detected in the pipe circumferential and axial cracks, scratches, weld porosity, slag, crack, weld penetration defects; surface defects of surface wave detection of simple shape parts; plate wave detecting defects in thin plates.
The B type and C type flaw detectors developed on the basis of A type flaw detector can be used to obtain the signals in different directions, and B type and C type display combinations can also be used to obtain the three-dimensional display of the internal reflection surface of the material.
All the above detectors use impulse electrical signals to stimulate the piezoelectric transducer to emit ultrasonic waves, but the eddy current transducer can also be used to test the conductive materials. Can be in the process of surface inspection for the transducer, without contact with the material, don't need coupling, you can test the surface roughness and the high temperature of 500 DEG C to metal material, widely used in metallurgical industry.
Ultrasonic wave propagation in the material, due to the absorption and scattering intensity, attenuation, so the measurement of attenuation of consumable furnace smelting alloy in vacuum in the possible nondestructive material uniformity of the organization to understand the situation.
Compared with other nondestructive inspection method of ultrasonic pulse reflection method
The main advantage is that:
The strong penetrating ability, probing depth up to several meters;
The high sensitivity, can be found in the air gap reflection ability and a diameter of about a few tenths of a millimeter reflector;
The more accurate in determining the internal reflector orientation, size, shape and properties etc.;
The only side close to the tested object from;
Providing defect inspection results immediately;
The operation is safe, portable equipment.
The main drawback is that:
Careful operation by experienced personnel;
The rough, irregular shape, small, thin or heterogeneous materials difficult to check;
There are still difficulties in qualitative and quantitative characterization of the defects found very accurate.
