Simulation And Experimental Study On Vibration Characteristics Of Gear Crack In Gear System

As the basic components of gear transmission system,the fixed shaft gearbox and the planetary gearbox have vibration and noise,which directly affect the reliability of the equipment operation.The complex and changeable operation condition of gearbox makes the fault characteristic signal often submerged in vibration response and difficult to identify.Hence,it is of great significance and application value for the health condition monitoring and fault diagnosis of different gear system to study the modulation mechanism of the vibration response of each fault condition.?1?Based on LMS Virtual.lab dynamic simulation software,a rigid and flexible coupling model of gearbox is established.The fault model of gear root crack is set up,and gear meshing pair is simulated by CAD Contact Force.The contour recognition function is adopted to generate the corresponding internal excitation with gear crack.The modulation mechanism of vibration signal of gear crack fault is studied,which is acquired from the measuring point fixed on the box.?2?A rigid and flexible coupling model of the fixed shaft gearbox with gear crack fault is established.When the size of crack is small,whose frequency component of vibration response including meshing frequency harmonics is almost similar to that caused by the normal gear.However,when the crack size increases to a certain extent,a new resonant modulation sideband appears in natural frequency.The modulation frequency is the rotational frequency of fault gear.The amplitude and width of the modulation sideband are proportional to the crack depth and the load of the gear train.?3?The rigid-flexible coupling model of the single-stage planetary gearbox of the sun gear and the planetary gear with tooth root crack is established respectively.When the crack depth is small,the order component of the vibration response signal order spectrum is not significantly different from that of normal gearbox.The vibration response contains dominant meshing orders that could be divisible by passing frequency of planet,and weak orders of rotational frequency of carrier and the sideband orders around peaks.When the crack depth of sun gear increases to a certain extent,twice of absolute rotation frequency of sun gear and its harmonics appear around existing peaks in vibration signal.There are two groups of modulation sideband(with interval of NJ_sc,where N is the number of planet,J_sc is the rotational frequency order of sun gear relative to carrier)inside the resonance band,leading to characteristic order interval(the interval is the difference between J_sc and NJ_c,J_c is the rotational frequency order of carrier).When planet gear has crack,two sets of modulation sidebands are also present in the resonant band?the interval is the rotational order of planetary relative to carrier?,an specific feature order interval is formed?the interval is the difference between absolute rotational order of planet and J_c?.In the order spectrum,due to the mutual modulation of the fault characteristic orders,there are many order components with weak amplitudes.The amplitude and width of the modulation sideband are proportional to the crack depth and the load of the gear train.The correctness of simulation analysis is verified by experiment test.