An Application Study On Ultrasonic Imaging Software Design Which Is Based On Virtual Instrument That Apply To Spring Flat Steel Inspection

Spring steel with good elasticity in the state of quenching and tempering is adopted in making elastic component. Spring steel is one kind of important industrial steel, which is widely applied to transportation facility such as aviation, railway vehicles, automobiles, motorcycles and other industrial products. The defects include inclusions, cracks, decarburization, uneven organization structure can be produced by the production course and service period. These defects influence the fatigue performance of spring flat steel seriously. However, it is still not mature for the nondestructive testing method of spring steel at present. Destructive testing such as fatigue test, metallographic test and electrolysis method can only be used in sampling inspection of spring steel,and which need long testing time, high cost. Moreover, the destructive method can not be used to reflect the distribution of the whole internal defect and structure organization, and these methods are only applied to a part or a plane of a small number of products.The characteristics of ultrasonic propagation contains amplitude, velocity and attenuation coefficient. In the thesis, ultrasonic C-scan method based on ultrasonic propagation characteristic is used to analysis the characteristics of the imaging detection of spring steel. Ultrasonic nondestructive testing has the advantages of short testing time, low cost, general using, and it can achieve 100% detection for product. Ultrasonic imaging results directly reflect the whole internal defect and distribution situation of organization structure of spring steel which provides an important means for a comprehensive evaluation of the quality of spring flat steel. However, a general commercial ultrasonic non-destructive testing equipment generally possess the function of B-scan and C-scan imaging, and most of them are using waveform amplitude as character value of imaging, which limit the expression ability of ultrasonic imaging. In order to achieve a variety of propagation characteristics of ultrasonic imaging and the comprehensive imaging detection of spring flat, in this study progress, a modular construction method of virtual instrument technology is adopted. The design of nondestructive testing of imaging analysis software is suitable for testing the internal defects of spring steel, to carry out the research on the nondestructive testing methods of spring flat steel by using this software. The main research contents include:(1) Design of imaging software based on ultrasonic propagation characteristic parametersIn the research, a set of ultrasonic feature imaging software was designed for testing internal defects and microstructure of spring flat steel, the software uses ultrasonic wave propagation characteristics, such as amplitude, velocity and attenuation coefficient, which can realize B/C scanning imaging, ultrasonic velocity imaging and attenuation coefficient imaging. Using C-scan to analyze the distribution of internal defects of spring flat steel and measure the size of defect, the distribution of internal defects and microstructure uniformity of spring flat steel can be obtained through the imaging of velocity and attenuation coefficient.(2) Study on ultrasonic feature imaging method of spring steelIn the experiment of C-scan imaging, the defect boundary of the C-scanning image is confirmed by analyzing the influence of the diameter of the acoustic beam on the detection result. The defect size can be measured accurately by 0.73 times of the amplitude of the defect diameter to the maximum extent. Testing the spring steel by C-scan, the test results show that the amplitude of imaging software can directly display the distribution of defects in spring steel, and the "red-blue" boundary of the measurement method can accurately measure the size of the defect. The velocity and attenuation coefficient of imaging are used to test spring steel, test results show that the velocity and attenuation coefficient imaging software can display the organization structure visually non-uniform distribution of spring steel.(3) The design of 3D imaging software and the research of detection methodIn the research, a 3D imaging software was designed for testing the defects of spring steel, the software is able to reconstruct the multi layer C-scanning data, and obtain the 3D internal structure of the object. Studying on test method for 3D imaging of the spring flat steel and determining the amplitude of the acoustic wave decreased to the maximum amplitude of the 90% measured focal column height(5.9mm)as the scanning interval of the stratified C-scan through the analysis of the influence of acoustic beam column height on the test results. The scanning interval was used to test the sample with a thickness of 16 mm by C-scan detection of three different depth of focus, which can achieve the purpose of full thickness detection, and the three-dimensional imaging software was used to reconstruct the multi layer C scanning data. The test results show that the detection method of hierarchical C-scanning can achieve full thickness detection of spring flat steel, three dimensional internal structure of 3D imaging software can display the 3D spatial distribution of defects directly.