Pattern Formation Phenomena Generated in Steel Making Machines and Automobiles and Its Countermeasures

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1. According to the shape measurement of abandoned rolls, the polygonal number varies by roll position in the circumferential direction. It is confirmed that 37-polygon associated with the first mode (rotation mode, 47.5Hz), and 49-polygon associated with the second mode (linear mode, 63Hz), occur on the rolls.2. According to the vibration measurement of the hot leveler in operation, it was confirmed that a specific frequency component appeared selectively as the polygonal wear grew, and the only component of second natural frequency of the hot leveler appeared at the measuring time. This means the only 49-polygon associated with the second mode grew on all upper rolls.3.A two degree-of-freedom analytical model was presented in which a rigid body (the upper unit) vibrates in contact with a plate through the rolls, and was analyzed the polygonal wear taking the retardation effect of the wear into account. As the result, a good agreement between the phenomena in the actual machine and the numerical analytical results was confirmed.4. It is impossible to essentially prevent a polygonal wear, even if we change the rotating speed of the rolls and the natural frequency of the leveler.5. The modal analysis was applied to the system with time retardation by wear in order to obtain the equations of motion for each mode and some important parameters were derived. The characteristic roots of this system were treated analytically and approximately and the influence of the parameters for pattern formation phenomena was investigated, compared with the exact solutions.6. The countermeasures by changing the operating speed in a small way were studied by applying numerical simulation. As the results, it was confirmed that the growth speed of the pattern could be delayed by changing two operating speeds alternately. The optimum changing method of the operation speeds was also studied.