Considering the effect of raceway waviness, a dynamic nonlinear contact force model for work roll failure bearings is established based on Hertz elastic contact theory. On this basis, the three-degree-of-freedom nonlinear vertical vibration model of the strip mill under the fault of raceway waviness of work roll bearing is established considering the influence of structural vibration of the mill roll system. The effects of parameters such as ripple degree wave number, amplitude, bearing clearance and rotational speed on the nonlinear vibration characteristics of mill rolls are analyzed with numerical simulation. It is found that under the excitation of the nonlinear contact force of the faulty bearing, the vibration spectrum of different ripple numbers shows different fault characteristic frequencies, multiplier frequencies and combined frequencies with the roll rotation frequency; when the ripple number is equal to the number of rolling bodies, the roll will produce violent vibration. With the increase of roll bearing ripple degree amplitude, the characteristic frequency of fault and its triplet frequency amplitude increase significantly, which can be effectively suppressed with reasonably changing the bearing clearance, but the excessive bearing clearance will reduce the system stability. In the medium speed range, the bearing ripple fault will lead to a variety of nonlinear vibration behaviors in the mill such as superharmonic resonance and main resonance. In addition, the rolling mill system is more sensitive to the performance of the inner ring corrugation failure of the work roll bearing compared to the outer ring failure.
Key words
raceway waviness /
bearing /
nonlinear /
strip mill /
vertical vibration
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