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The lubricant bridge connecting the slider and the disk will significantly deteriorate the read–write stability of the hard disk drive. This paper builds a model of disk-lubricant-slider system. The coarse-grained bead-spring model is used to represent perfluoropolyethers molecules. And the molecular dynamic method is used to study the formation time and the molecule number of the lubricant bridge under different disk rotation speeds and slider flying heights. Furthermore, the influence of lubricant bridge on the pressure acting on the slider pad is also studied. [ABSTRACT FROM AUTHOR]

Previous works investigated particle trajectories in hard disk drives (HDDs) with the actuator arm and the head gimbals assembly at a fixed position. Actually, internal fluid field characteristics of HDDs can be greatly changed by the arm swing during track-seeking operations, which can affect particle trajectories and trapping status. In this paper, using the dynamic mesh method in a 2.5 in HDD for the first time considers the arm swing in the computational fluid dynamics (CFD) simulation. Al2O3 particle trajectories in this HDD are studied by the CFD solver FLUENT with user-defined functions. The trapping criterion for Al2O3 particles is used as a boundary condition for colliding surfaces. Simulation results reveal that the particle undergoes a larger number of collisions with the disk surface for the average seek time of 12 ms than for the average seek time of 6 ms. In addition, the faster the arm swings, the larger the number of particles that gather near the arm, and the shorter time it will take for particles to be trapped. Moreover, particle-surface collisions can successively take place many times in the helium flow. Furthermore, the particles are trapped slower in the helium-filled drive than in the air-filled drive. [ABSTRACT FROM AUTHOR]

A numerical method is presented to study the air-flow pattern and particle trajectory in the head–disk interface (HDI) in this paper. It first solves the generalized steady-state Reynolds equation with slip boundary conditions to get the slider attitude. Then, it solves the reduced Navier–Stokes equation to get the air flow velocity distribution in the HDI. The motion equations of particles are solved to obtain the particle trajectory in the HDI by using the fourth-order Runge–Kutta method. Air flow characteristics and particle behaviors are investigated to illustrate the relationship between the air flow and particle trajectory. The effect of the particle release height is also studied. The simulation results show that particle trajectories basically overlap air flow streamlines in the horizontal plane. The particle moves a longer horizontal distance at a lower particle release height. The difference between the horizontal velocity of the particle and the air flow indicates that the Saffman force points to the disk in the transition region close to the leading edges of leading pads. Moreover, the peak values of the air flow vertical velocity in the previously mention location increase with the reduction of the particle release height. And the air flow vertical velocity along the particle trajectory is almost two times larger than that of the particle at the leading edges of leading pads. The results also show that the drag force of the air flow mainly drives particles up toward the air bearing surface at the leading edges of leading pads, but not the Saffman force. [ABSTRACT FROM PUBLISHER]

The presence of particles, which can intrude into the air bearing, is one of the most common factors in the failure of hard disk drives (HDDs). Previous studies have investigated particles trajectories with the assumption of ideal trapping or reflecting boundary conditions in air-filled drives. However, only the colliding particle with insufficient energy to escape the potential well will be trapped by the surface. In this paper, considering the particle-surface energy during the collision, the trapping criterion of the incident normal critical velocity ( V\text {ni}^{\mathrm {\ast }}) for Al2O3 particles is developed as the boundary conditions for different colliding surfaces inside a 2.5 in drive. Then, trapping status for Al2O3 particles and particles trajectories inside the drive are simulated by using the commercial computational fluid dynamics solver FLUENT with user-defined functions. The results reveal that the particles will travel longer distances until trapped by HDD components when considering the trapping criterion. In addition, smaller particles will more likely degrade the head–disk interface reliability, since they easily stick on the disk surface. [ABSTRACT FROM PUBLISHER]

Nowadays, hard disk drive filling with helium has emerged to achieve highly stable magnetic recording. The bearing force in helium is different from that in air. This paper uses the 3-D direct simulation Monte Carlo method to investigate the bearing force over bit-patterned media in the filling gases of air and helium under different conditions, including groove depth, ambient temperature, slider surface temperature, rotation speed of the disk, and different velocity losses during the collision process between the gas molecules and the slider. [ABSTRACT FROM AUTHOR]

This paper presents a numerical method to simulate the particle trajectory in the head–disk interface (HDI). The simulator solves the reduced Navier–Stokes equation with the second-slip boundary conditions to get the air velocity distribution, then solves the motion equations of particles and obtains the trajectories of the particles in the HDI using the binary Lagrange interpolation and the fourth-order Runge–Kutta method. The calculated trajectories of particles follow well with the air streamlines in the recessed regions. The particle density, diameter, and initial entering velocity have different effects on particle movement. Furthermore, particle velocity behaviors in the recessed regions are investigated for the first time. The particle is accelerated or decelerated by the action of the drag force and becomes close to the velocity of local air flow. Such effects are more obvious for small particles than large particles. The particle velocity becomes very small when it is close to the leading edge of the trailing pad. The numerical results also show that the particle goes up when it crosses the transition regions, and the particle moves upward more sharply with higher initial entrance height due to the larger vertical velocity of the local air flow. [ABSTRACT FROM AUTHOR]