Research On Experimental Modal Parameter Based On Crankshaft Crack Identification

Shaft crack lead to the fact accident happen among the rotating machinery, so shaft measuring and it's studies is one important subject of the crack. After reading a large amount of domestic and international about shaft research materials, the thesis combines the concrete experimental condition of the laboratory , and the crankshaft crack modal parameter characteristic go on the theoretical research at different depth different position to smoothshaft, experimental study , test data processing , diagnose system developing work ect.At first, of thesis analyse a large amount of domestic and international to study about rotor crack characteristic testing modal research current situationing of analytical method synthetically, has understood existing problem, and studied the direction, the purpose and research contents clearly.Then the modal parameter of test of studying the cracked smoothshaft and cracked crankshaft discerns the principle, analysed and tests the modal analytical method to describe about the theory mode, is it build cracked smoothshaft and cracked crankshaft principle equation that parameter indentify to derive.Then it has carried on the theory that the modal parameter indentify and experimental study to the cracked smoothshaft and cracked crankshaft, draw the width 1 mm of crackle through the law of finite element, different positions are than (0.1, 0.2, 0.3, 0.4, 0.5) while comparing with depth (0.1, 0. 2, 0.3, 0.4, 0.5), the change relation of the natural frequency of the smoothshaft: (1) Compared with one position in crack, depth smoothshaft as crack in natural frequency than increase and reducing constantly. (2) Compared with one depth crack, with the first steps and the second steps natural frequency vibration, at 0.5 o'clock of position, the natural frequency is smaller; with the third steps and the fourth steps natural frequency vibration, comparing with the time of nearing 0.25 position, the natural frequency is smaller. Utilizing the principle of the smoothshaft to open 0.4 mm crankshaft to the width of crack: (1) When it compares with one position crack, crankshaft natural frequency as crack depth than increase and reducing constantly. (2) The crack compares with one depth with the first steps and the second steps natural frequency vibration, crack position near crank arm and main shaft transition round naturalfrequency little place under crankshaft; With the third steps and the fourth steps natural frequency vibration, the smaller close to the second crank arm of crankshaft and round place natural frequency of the main shaft transition the position is. And summarize theory data of the income, analyse, the strong guidance that offered for the thing that the ones that test go on; Under test according to theoretical research, using five smoothshafts and one EQB140-2 diesel engine crankshaft analyse through CRAS4.0 modal anlysis software is it proved the theory, and analyse to the result of the test, have made and analysed the compatible conclusion with the theory.Utilizing Matlab to carry on frequency spectrum, the analysis of the power spectrum in testing the signal of acceleration of income at the same time, reducing noise by wavelet, the signal reconstructed research ect, and make the satisfactory result.Data of a large amount of natural frequency obtained in the test according to the theory afterwards, use Delphi6.0 and SQLserver2000 to develop the crack and diagnosis system, realize information inquiry, revise, function of diagnosing etc.This subject is a sub subject of the project of fund " mechanical vibration and research of the source signal blind separation method of encouragement of the noise " of national natural science ( 50275109 ).