Design Consideration of Contact/Near-Contact Sliders Based on a Rough Surface Contact Model

Abstract

We numerically investigated contact characteristics of a contact pad with a rough disk surface and the possibility of contact/near-contact sliders, using a single-degree-of-freedom (1-DOF) slider and a random wavy surface model with random roughness. Contact characteristics of a contact pad are numerically calculated based on a modified Greenwood-Williamson model, considering the bulk deformation of the surface due to all other asperity contact forces. It was found that contact stiffness and other characteristics are mainly determined by asperity contact, to the extent that the contact pad penetrates into the upper standard deviation of asperity peak height. However, the contact stiffness tends to approach a constant value as the pad penetrates into the average asperity height because the bulk deformation becomes predominant. From the numerical simulations of a 1-DOF air bearing slider model in contact and near-contact regimes over a random wavy surface with random roughness, a typical example of design condition of disk surface waviness in terms of the tracking ability and wear durability are shown, and the possibility and difficulty of a contact/near-contact slider is discussed. Finally, we analyzed meniscus effects on the contact characteristics and found a hysteresis process of the touch down and take off of a slider due to the meniscus force.

Contact recording review

“…An elastic-plastic model was developed to extend the GW model for elastic-plastic contact using volume conservation assumption of plastic deformation (Chang et al 1987). Iida and Ono (2003) modified the GW model by assuming that the asperities are influencing each other during the contact process and the bulk deformation is considered. Shi and Polycarpou (2005) also employed an elastic-plastic hybrid adhesion model for calculating the contact force and the interfacial adhesion force.…”

Improved Elastic Contact Model Accounting for Asperity and Bulk Substrate Deformation

“…[22] they assumed a uniform contact pressure on a square area, where multiple asperities are acting. As seen in Fig.…”

“…2.3. Iida and Ono [22] used a simplified contact stiffness model to describe bulk substrate behavior given by…”

“…However, if a hard coating or surface film is applied to a softer substrate material, surface asperities are mainly made of harder film material on a softer substrate. For the contact of such harder film surfaces, the softer bulk deformation may have considerable effects on the surface deformation [22], thus a conventional GWbased contact may not fully describe its contact behavior. For example, in the case of magnetic recording disks, an amorphous carbon film of a few nanometers thick is deposited on top of the softer magnetic layers, where the surface evolution of the carbon film forms mound-like structures (asperities) on the softer substrate surface.…”

Slider surface control for ultra-high density recording

“…One such technique already being implemented in today's hard disk drives is the thermally actuated slider where spacing adjustment is achieved through the localized protrusion of the pole-tip area through heat (Meyer et al 1999). However, when the head-media spacing is reduced to less than 5 nm, the slider ABS roughness becomes one of the key limiting factors (Liu et al 2007;Iida and Ono 2003;Hua et al 2008;Gupta and Bogy 2008). Thus, it is important to control slider ABS roughness in ultra-low head-media spacing.…”