| The cracks in high-end equipment of engineering machinery lead to accidents frequently,so the nondestructive testing of high-end equipment is very important to ensure its safety service and reduce the incidence of accidents and property loss.Crack quantitative detection is very important for the analysis of crack state of equipment components.Therefore,it is very necessary to establish the corresponding relationship between the crack and signal for the evaluation of equipment damage.In this paper,the simulation and experimental study of acoustic propagation characteristics under different factors such as crack length,crack shape,crack width and crack angle are carried out.The main work is as follows:Firstly,Two-dimensional linear crack model was established and verified.A two-dimensional spring proton model was established by Hooke’s law.With the combination of the propagation condition and stability condition of the acoustic wave,the acoustic field of the cracked model was simulated,and the validity of the crack model was discussed.Secondly,we obtained the significant factors which influencing the signal of the crack using the orthogonal experiment design method.The orthogonal test table was designed according to the parameters and levels,and the energy and amplitude parameters of acoustic signal were selected as the index.The influence of different crack length,crack shape,crack width and crack angle on the propagation characteristics of acoustic signals were simulated.The numerical simulation results were verified by experiments,it was found that,compared with the significant level a of 0.05,the crack length and crack angle were the most significant factor.Finally,the influence of crack length,crack angle on acoustic signal characteristic parameters were obtained.Take 45#steel for example,according to the impact order in previous chapter,the influence of the crack length and the crack angle on the propagation characteristics of the acoustic signal were studied.The change of the characteristic parameters such as the energy,amplitude and peak frequency of the acoustic signal under the single crack factor were studied.The numerical simulation results were verified by experiments.Results show that the relative attenuation of acoustic signal energy and amplitude change linearly with crack length.The attenuation of acoustic signal is not obvious when the crack length is less than 6 mm;Whereas,the relative attenuation is obvious.In this paper,Two-dimensional linear crack model is established and verified.The impact of the acoustic signals parameters is studied by crack parameters.The impact trend of crack length and crack angle were obtained for acoustic signal characteristic parameters.The results provide a theoretical basis for quantitative detection of crack of high-end equipment. |
