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来降低飞行高度，实验阐明了目前使用的两种飞头滑块在近接触状态下接触弹跳振动的细节。结果发现，增加静态俯仰角可以降低临界飞行高度(起跳高度)。这是因为粘附力可以通过减少形成半月板的接触面积来降低。不稳定的反弹振动是以这样的方式诱导的，即后缘首先被吸引到磁盘上，从而作用在滑块上的摩擦力激发反弹振动。失稳振型很可能是低节距振型，但理论上接近滑块-空气轴承系统的反谐振型。不稳定振动模式是平移和俯仰运动之间的耦合振动，相移很小，不包含…2)考虑气浮支承刚度非线性的二自由度滑块模型弹跳振动的理论研究首次研究了滑块与小凹凸体高度圆盘的接触特性，包括弯月面作用力和整体变形。然后我们发现，对于用于高密度记录的光滑盘，接触特性可以由整体变形中的接触刚度、半月面粘附力以及拉入和拉出分离来模拟。其次，利用这些接触特性，我们分析了一个两自由度滑块模型的弹跳振动，该模型除了考虑普通的干摩擦力外，还考虑了润滑剂的剪切摩擦力。我们发现，用该理论可以很好地估计弹跳振动的迟滞现象、弹跳振动的模式及其失稳过程。通过参数研究发现，通过减小润滑剂的粘附力、摩擦力和剪切摩擦力，增加空气轴承刚度，可以降低临界飞行高度(起飞高度)。3)通过球面滑块在静止磁盘上的碰撞运动识别接触力、粘附力和阻尼力。以半径为1 mm和2 mm的玻璃半球滑块和0、1、2、3 nm润滑剂厚度为0、1、2、3 nm的磁盘为例，利用数字激光多普勒测振仪对滑块运动的位移、速度和加速度进行了实验测量。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。结果发现，接触反作用力可以用赫兹接触理论很好地预测，并且动态粘附力几乎等于静态弯月面作用力。随着接触半径的增大、分离速度的增大、紫外光辐照处理后粘结率的增加，粘附力比理论的半月面力有减小的趋势。这表明在这种条件下很难形成半月板桥。这些结果可以证明，磁头滑块与磁盘之间的粘附力不是由范德尔华力引起的，而是由弯月面力引起的。较少

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