| Connecting rod is an important part of engine.In order to strictly guarantee the quality of connecting rod,it is necessary to inspect all connecting rods.The forged connecting rod belongs to single metal mechanical parts.The most advanced detection method in the world is resonance acoustic non-destructive testing(RAM-NDT)for single metal mechanical parts on assembly line.In our country,resonance acoustic nondestructive testing(RAM-NDT)is still in the research and development stage.In this paper,based on the pipeline product quality inspection,combined with Hilbert-Huang transform(HHT),the resonance acoustic nondestructive testing method of connecting rod is studied,aiming at achieving fast and accurate nondestructive testing of connecting rod.Firstly,the principle of resonance acoustic nondestructive testing is deeply studied,and the key idea of resonance acoustic nondestructive testing is mastered.It is pointed out that using air as the medium and using high precision microphone and sound card equipment can realize the effective acquisition of vibration signals of parts.It is proved that the natural frequencies of parts series can be used as an important basis for the selection of parts defects.The idea,advantages and disadvantages of hammering method for modal parameters measurement are summarized,which accumulates experience for the test scheme of connecting rod resonance acoustic nondestructive testing proposed later.Secondly,in order to effectively analyze the vibration signal of the parts and realize the accurate identification of the Parts' state,the Hilbert-Huang transform(HHT)method,which has better effect on the non-stationary signal processing,is boldly proposed to analyze and process the vibration signal of the connecting rod.The basic principle and physical significance of important concepts of Hilbert-Huang transform(HHT)method are introducedin detail,and solutions to the shortcomings of HHT are proposed.The revised Hilbert-Huang transform(HHT)is validated by an example,which paves the way for the analysis of connecting rod vibration signal by using Hilbert-Huang transform(HHT)later.Then,based on the above theoretical analysis,a non-destructive testing platform for connecting rod resonance acoustics is built,which consists of elastic hammer,suspension wire,industrial sound card,high-precision microphone,bracket and computer.The acquisition,filtering,EMD decomposition and Hilbert transform of connecting rod vibration signal are realized by using MATLAB software programming.According to the input and output variables needed in the testing process,the computer control and display interface for resonance acoustic nondestructive testing is designed.Based on the above-mentioned experimental platform for resonant acoustic nondestructive testing,a connecting rod was tested,and the results were compared with the ANSYS simulation results to verify the reliability of the experimental platform for resonant acoustic nondestructive testing.Finally,the resonant acoustic non-destructive testing test platform is built to carry out repeated tests on qualified connecting rods,shrinkage connecting rods,surface cracked connecting rods and inclusion connecting rods under the same conditions.The differences and relations between qualified connecting rods and defective products are summarized by comparing and analyzing the mean,maximum and normalized frequency of the test data.Through the comparative analysis of similarity coefficients,the internal differences between qualified connecting rods and inferior products are revealed,and the standard database of qualified connecting rods is established based on similarity coefficients.A large number of repetitive tests were carried out to verify the standard database of qualified connecting rods,to achieve rapid and accurate non-destructive testing of connecting rods,and to verify the effectiveness of the proposed method based on HHT connecting rod resonance acoustic non-destructive testing. |
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