Study on Pattern Formation Phenomena Gernerated in Contact Rotating Systems

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1. Regarding the roll system as a multi-layred structure, taking flexural deformation of the roll axs into account, the rubber as a viscoelastic body and the contact roll system as a system with time lag accompanied by viscoelastic deformation, the polygonal deformation phenomena of roll-covering rubber in a paper making machine were analyzed. Then, their mechanisms were made clear and the countermeasures to prevent the pattern formation were discussed. As the results, (1) The polygonization of roll-covering rubber is caused by out-of-phase modes between rolls, (2) For the convex mode among out-of-phase modes in which the elastic bending mode and the rigid body transitional mode of the rolls are superimposed in the same phase, suppression of pattern formation by only bearing support damping can not be expected to be effective, and the installation of a non-rotating center shaft between bearings inside the rotating rolls prevents the pattern forming phenomenon because it is expected tha … More t the oil film between the center shaft and the cell contributes to the damping effect and the center shaft to the strengthening complementarily the roll stiffness. Hence, the operating rotational speed of the rolls is considerably increased in accordance with the optimum condition.2. The polygonal wear phenomenon of truck/bus and car tires was treated experimentally and analytically, and the generation mechanisms of the polygonal wear caused by the first natural vibration mode of the tire in the vertical direction were made clear. In the analysis, the phenomenon is modeled as time delay system accompanied by self-excited wear in which the wear amount of tire is fed back as forced displacement in the vertical direction after the time period of the rotation. The growth process of the polygonal wear of tire is very slow and is realized by the unstable vibration from steady-state wear process generated in the limited regions where the products of polygonal number and rotational speed of tire are less than the natural frequencies of the tire system. The tire is deformed in the shape of almost regular polygon when the polygonal wear is generated. The expression and the rigidity of tire wear are almost independent of the width of generation regions. On the other hand, the damping is directly related to the width of generation regions. A good agreement between experimental and analytical results concerning the occurrence of the polygonal wear of tire was confirmed. Less