Analysis of the vibration characteristics of pin-connected hammer rotor of straw rubbing filament machine

The finite element method and the 3D laser Doppler measurement technology were used to simulate and test the vibration characteristics of the pin-connected hammer rotor. This was done to determine the critical speeds of the pin-connected hammer rotor of the straw rubbing filament machine and avoid the resonance of the straw rubbing filament machine during operation. The frequencies and mode shapes of the rotor’s first six free modes were determined. The accuracy of the pin-connected hammer rotor finite element model is validated by comparing calculation and test values. On this basis, the prestressed modes of the pin-connected hammer rotor under actual working conditions are calculated. The effect of the hammer swing angles rotating around the pin shaft is investigated, and the critical speeds of the pin-connected hammer rotor are calculated. The results indicate that the rotor has the same mode shapes at 11 kinds of joint swing angles, and the maximum relative error for each order frequency is 0.88%. It can be seen that the hammer-pin swing angles have little effect on the vibrational frequencies and mode shapes of the hammer-pin articulated rotor. Compared to the free modes, the prestressed modes all have an additional torsional mode and consist of two-mode shapes of global and local; the global mode shapes are similar to the free ones except for an additional torsional mode shape, with increased amplitudes and modal frequencies; the local mode shapes mainly occur in cutting knives and hammers. The critical speed range of the rotor of the 9ZR-2.2 straw rubbing filament machine must be 2076.99–2348.32 r/min which is based on ensuring the processing quality of straw. The study provides a reference method for investigating the vibration characteristics of pin-connected hammer rotors. It is also of great practical importance to scientifically predict the critical speed of a pin-connected hammer rotor in order to reduce failure and safety accidents.