STUDY ON PATTERN FORMATION PHENOMENA IN MECHANICAL ENGINEERING

1.为弄清汽车轮胎异常磨损之一的多边形磨损的产生机理，对其进行了建模和分析，实验结果与理论结果吻合较好。结果表明：(1)通过建立一个具有时滞的系统模型，明确了轮胎自身在垂直方向上的第一阶自振模态引起的花纹形成现象的产生机理，该系统在轮胎旋转一次后，在滚动接触面产生的磨损量作为垂直方向振动的强迫位移反馈到接触面上。(2)产生多边形磨损时，轮胎胎面在周向上形成几乎规则的多边形花纹。生成区域在满足（轮胎固有频率）*（轮胎多边形数）*（轮胎旋转…更多的轮胎频率）关系的有限区域。(3)轮胎磨损量和耐磨性的建模差异对多边形磨损产生区域的宽度几乎没有影响。然而，它对多边形磨损的产生速率（不稳定程度）有显著的影响。对工件在无心磨床上的花纹形成过程进行了动态分析，并将实验结果与理论结果进行了比较。图案的形成是指工件的多边形变形。在磨削过程中，工件表面变形成一定的凸多边形，这些工件因此变得无用。将该现象视为磨削过程中由于时间滞后而产生的不稳定振动，对系统进行了建模。结果表明：(1)不稳定振动往往发生在磨床系统和工件本身的固有频率附近；(2)工件主要振动的不稳定区域的位置在奇偶多边形之间周期性变化；(3)中心高度角对多边形变形的影响与实际机床的结果吻合良好。考虑到橡胶的粘弹性特性，分析了造纸机中包括轧辊覆盖橡胶的多级超级压延机产生的不稳定振动。10阶自然模态对滚覆橡胶多边形变形的实验结果与分析结果吻合较好。对直流电动机闪过现象进行了研究，建立了闪过现象的解析模型。将实验结果与分析结果进行比较。少

1.In order to make clear the generation mechanism of the polygonal wear which is one of the abnormal wears of automobile tire, the modeling and the analysis were performed, and a very good agreement between the experimental and the theoretical results were confirmed. The results obtained are summarized as follows :(1) The generation mechanism of the pattern formation phenomenon caused by the first natural vibration mode of tire itself in the vertical direction was made clear by modeling a system with time lag in which the wear quantity of the generated in the rolling contact surface is fed back to the contact surface after one rotation of tire as a forced displacement for the vibration in the vertical direction.(2) Almost regular polygonal pattern is formed on the tire tread in the circumferential direction when the polygonal wear is generated. The generation regions are in some limited ones satisfying the relation of (natural frequency of tire) * (polygonal number of tire) * (rotation … More al frequency of tire).(3) The difference in modeling of wear quantity of tire and wear resistance give almost no effect upon the width of generation regions of polygonal wear. However, it gives a significant influence upon the generation rate (the degree of instability) of the polygonal wear.2.The pettern formation of a work piece in centerless grinding machines was dynamically analyzed, and the experimental and the theoretical results were compared. The pattern formation means the polygonal deformation of the work piece. The surface of the work piece is deformed into a certain convex polygon during the grinding process, and these work pieces become consequently useless. The modeling of the system was described, regarding this phenomenon as an unstable vibration in grinding due to the time lag. As the results, it was made clear that (1) the unstable vibration tends to occur at nearly the natural frequencies of the grinder system and of the work piece itself, (2) the locations of the unstable regions in which mainy the work piece vibrates, vary periodically among even and odd polygonal numbers, and (3) the effect of the center height angle upon the polygonal deformation agrees well with the results of actual machines.3.The unstable vibration generated in multiple stage super calender including rolls covering rubber in the paper making machine was analyzed, taking the viscoelastic characteristics of rubber into account. The experimental results of the polygonal deformation of the roll-covering rubber due to the natural mode of order 10 agreed well with the analytical results.4.The flash over phenomenon of DC motor was researched, and the analytical model was constructes. The experimental and the analytical results will be compared. Less