Damage Assessment on Magnetic Hard Disks Due to Nanoasperity Impacts at Head-Disk Interface
Tze-Jer Chuang, Stephen M. Hsu
A 3D finite element model is constructed to simulate the local impact and its aftermath.For a given design of the disk structure with known elastic/plastic and damage properties as well as the slider s design with its surface texture, the model predicts maximum contact zone size, penetration depth and force, contact duration, damage characteristics (including damage forms, zone size, etc.), time-history of energy transfer and its partition and substrate stress field for a given impacting velocity (including impacting angle and magnitude). Special emphasis is placed on the damage assessment as a result of the impact because the damage could render the disk malfunction. In this regard, a damage map is constructed in the space of linear velocity versus friction coefficient for a given impact angle and disk properties. It was found that a threshold boundary line exists separating undamaged from damaged zone which favors higher values of velocity and friction coefficient. These results further showed that damage at threshold appears in the form of surface cracks or debris at second impact location. No subsurface damage was detected at threshold. The damage map should be useful as a design guide for the magnetic hard disk drive manufacturers.
computer hard disks, damage maps, dynamic analysis, energy transfe, finite element method, layered structure, nanomechanics modeling, residual stress, stress analysis