Study on Self-Induced Contact Bouncing Vibration and Stable Contact Sliding Conditions

1)不稳定弹跳振动的实验测量与分析通过降低环境压力降低飞头滑块的飞行高度，实验明确了两种目前使用的飞头滑块在近接触状态下的接触弹跳振动细节。结果表明，增大静俯仰角可以降低飞机的临界飞行高度（起飞高度）。这是因为粘附力可以通过减少可以形成半月板的接触面积而降低。不稳定的弹跳振动是通过这样一种方式引起的，即后缘首先被圆盘吸引，从而作用在滑块上的摩擦力激发了弹跳振动。不稳定振动模式可能是低螺距模式，但理论上接近滑块-空气轴承系统的抗共振模式。不稳定振动模式是平移和俯仰运动之间的耦合振动，具有较小的相移，不包含滚动运动。2)考虑气轴承刚度非线性的2自由度滑块模型的弹跳振动理论研究首先研究了滑块垫与小粗糙度盘的接触特性，包括半月板力和体变形。然后，我们发现接触特性可以通过接触刚度在整体变形，半月板附着力，以及拉入和拉出分离来建模，用于高密度记录。其次，利用这些接触特性，分析了考虑润滑油剪切摩擦力和普通干摩擦力的2自由度滑块模型的弹跳振动。结果表明，该理论可以很好地估计弹跳振动的滞回现象、弹跳振动的模态及其失稳过程。通过参数化研究发现，通过减小润滑油的粘附力、摩擦力和剪切摩擦力，增加气轴承刚度，特别是后置气轴承刚度，可以降低临界飞行高度（起飞高度）。3)利用球面滑块与静止磁盘的碰撞运动识别接触力、粘附力和阻尼力。采用半径分别为1和2 mm的半球形玻璃滑块，以及经过/未经过UV处理的0、1、2、3 nm润滑剂厚度的磁盘，利用数字激光多普勒测振仪实验测量了滑块运动的位移、速度和加速度，并确定了分离瞬间作用在滑块上的接触反作用力和粘附力。结果表明，接触反作用力可以用赫兹接触理论很好地预测，且动态粘附力几乎等于静态半月板力。随着接触半径的增大、分离速度的增大以及UV辐照处理导致粘接比的增大，黏附力从半月板力的理论值有减小的趋势。这表明在这些条件下，半月板桥很难形成。这些结果可以证明飞头滑块与磁盘之间的粘附力不是由范德尔华力引起的，而是由半月板力引起的。少

1)Experimental measurement and analysis of the unstable bouncing vibrationWe experimentally clarified the details of the contact bouncing vibration of two kinds of currently used flying head slider in near-contact regime by decreasing its flying height by reducing the ambient pressure. As a result, we found that the critical flying height (take-off height) can be decreased by increasing static pitch angle. This is because the adhesion force can be decreased by a decrease in contact area in which the meniscus can form. The unstable bouncing vibration is induced in such a way that the trailing edge is first attracted to the disk and thereby the friction force acting on the slider excites the bouncing vibration. The unstable vibration mode is likely to be the lower pitch mode, but theoretically is close to the anti-resonance mode of the slider-air bearing system. Unstable vibration mode is a coupled vibration between translation and pitch motion with a small phase shift and does not conta … More in the rolling motion.2)Theoretical study of the bouncing vibration of a 2-DOF slider model considering the nonlinearity of air bearing stiffnessContact characteristics between slider pad and disk with a small asperity height is first studied, including meniscus force and bulk deformation. Then we found that the contact characteristics can be modeled by the contact stiffness in bulk deformation, meniscus adhesion force, and pull-in and pull-off separations for smooth disks to be used for a high-density recording. Next, by using these contact characteristics, we analyzed the bouncing vibration of a 2-DOF slider model considering a shearing friction force of lubricant in addition to the ordinary dry friction force. The, we found that the hysteresis phenomena of the bouncing vibration, the mode of the bouncing vibration, its destabilizing process can well be estimated by this theory. From parametric study, we found that the critical flying height (take-off height) can be decreased by decreasing adhesion force, friction force, and shearing friction force of the lubricant, and increasing air bearing stiffness, particularly trailing air bearing stiffness.3)Identification of contact force, adhesion force and damping force by means of collision motion of a spherical slider on stationary magnetic disks.By using glass hemispherical sliders of 1 and 2 mm in radius, and magnetic disks of 0,1,2,3 nm lubricant thickness with/without UV treatment, we experimentally measured the displacement, velocity and acceleration of the slider motion by means of digital laser Doppler vibrometer, and identified the contact reacting force and adhesion force acting on the slider at the instant of separation. As a result, we found that the contact reacting force can well be predicted by Hertzian contact theory and that the dynamic adhesion force is almost equal to the static meniscus force. The adhesion force tends to decrease from the theoretical value of the meniscus force when the radius of contact increases, the separation velocity increase, and the bonded ratio increases due to UV irradiation treatment. This indicates that a meniscus bridge can hardly form in these conditions. These results can justify the fact that the adhesion force between a flying head slider and magnetic disk is caused not by Van del Waals force but by meniscus force. Less