A new beam suspension model for load/unload simulations of magnetic hard disk drive sliders is presented. The model is applicable to the load/unload process as well as to the dynamic flying behavior of the slider on the disk. Suspension and gimbal are modeled with C 1 continuous beam elements. The roll degree of freedom of the slider is decoupled from spacing and pitch. The numerical implementation of the model is described. Loading and unloading of a typical subambient pressure type slider is presented.

A finite element model of a hard disk drive (HDD) is developed for simulating shock testing and head slap. Individual components of the disk drive are modeled using Hypermesh, a commercially available mesh generator. The following components are modeled: the base plate, the impact surface, the actuator arm, the suspension arm, the head gimbal assembly (HGA) and the disk. The boundary conditions and contact surfaces are defined in Hypermesh [1] prior to importing them to the solver, LS-Dyna [2], for the transient finite element solution. The solution calculates displacement, velocity, acceleration and stress at every time step.

Diamond-like carbon (DLC) films are excellent candidates to improve tribological properties of silicon nitride (Si 3 N 4 ) ceramic elements. Particular attentions have been paid to the preparation and analysis of DLC films on rings and discs. However, few researches on fabrication of DLC films on ball surfaces were carried out, especially on ceramic ball surfaces, because it is hard to achieve uniform coatings on ball surfaces. In this paper, DLC films on ceramic ball surfaces were studied with both experiment and FEA method. DLC films were deposited on Si 3 N 4 ceramic ball and disc surfaces with plasma immersion ion implantation and deposition techniques (PIII-D). Surface topography of ceramic balls before and after coated with DLC films showed that DLC films on ceramic ball surfaces were uniform. Tribological tests under dry friction were conducted with a ceramic ball sliding against ceramic disc and, alternatively, one of the two surfaces was coated with DLC films. The tests demonstrated that DLC films on disc surfaces were worn, while ball surface films were partly flaked. 3-D FEA models of ceramic ball sliding against ceramic disc were built and the ceramic ball/disc was coated with DLC films alternatively. DLC films were supposed to be bonded with ceramic substrates. The FEA stress fields in DLC films and on film/substrate interface showed that DLC films had great effects on stress distribution due to the low frictional coefficient and material difference from substrates. The friction force caused an increment of the stress near surfaces during sliding process, and the material difference leaded to discontinuous stress distribution on film/substrate interface. The shear stress on film/substrate interface was very slightly different between DLC films coated on ceramic balls and discs. Under almost the same shear stress, the flakes and wear of DLC films were mainly determined on the adherence of DLC films to ceramic substrates.

A three dimensional finite element model of a rigid sphere lightly sliding over an elastic-perfectly plastic multilayered medium under thermo-mechanical surface loading is developed in order to investigate the mechanical and thermal responses during the light sliding contact of a spherical corner or thermal protrusion of a slider with a rotating disk. In this simulation, the effects of the magnetic recording layer thickness t and sliding contact parameters such as normal load F and friction coefficient μ on maximum temperature T max of head-disk interface (HDI) and maximum scratch depth h on the multilayered disk media are analyzed for both glass and aluminum disks. The results show that the magnetic recording layer thickness t has a negligible effect on the maximum temperature T max of the HDI and scratch depth h on the disk for both types of substrates, but the sliding contact parameters strongly affect the temperature variation and mechanical deformation of the HDI. In addition, the effect of the disk material is also very pronounced.

The key points of method derivation and a numerical example for bearing with three dimensional air flow are presented.

Transient thermo-mechanical contact between a rigid sphere sliding over an elastic-plastic sphere with a larger radius is studied using finite element analysis. Plastic deformation and temperature rise in the contact zone between the two spheres are investigated.

This paper presents a hybrid mobility solution approach to the analysis of dynamically loaded misaligned journal bearings. Mobility data obtained for misaligned bearings (calculated from a finite element representation of the Reynolds equation) are compared with existing curve-fitted mobility maps representative of a perfectly aligned bearing. A relative error analysis of mobility magnitude and direction provides a set of misaligned journal bearing configurations (midplane eccentricity ratio and normalized misalignment angle) where existing curve-fitted mobility map components based on aligned bearings can be used to calculate the resulting journal motion. For bearing configurations where these mobility maps are not applicable, the numerical simulation process proceeds using a complete finite element solution of the Reynolds equation. A set of numerical examples representing misaligned main and connecting rod bearings in a four-stroke automotive engine illustrate the hybrid solution method. Substantial savings in computational time are obtained using the hybrid approach over the complete finite element solution method without loss of computational accuracy.

Great flexibility in prosthetic sockets, with long range of spring like action is needed while designing a socket. A finite element analysis is conducted to investigate the stress and displacement distribution for different socket cases where relief is needed. The relieved socket after optimization of the pressure distribution areas showed less wear and more comfort for amputees than the non-relieved socket. A Design of Experiment using 2 level factorial design is used to optimize the relief areas with respect to pressure distribution. Stresses and displacements were included in the model desirability. Higher deformation of the pressure relief areas is sought while preserving the socket structural integrity. A compromise with the structural integrity of the socket and the optimized values with high desirability of the Design of Experiment Model imply that Duraform socket A with 1.69mm relief area could be the best design scenario between several cases. Wear and skin analysis indicated that the relieved socket is significantly better than the unrelieved one.

Most of elasto-aerodynamic approaches under dynamic conditions proposed in the technical literature include only the static pressure induced deformation of foils. This paper presents a theoretical investigation on the effects of both static and dynamic deformations of the foils on the dynamic performance characteristics and stability of a self-acting air foil journal bearing operating under small harmonic vibrations. To take into account the dynamic deformations of foils, the perturbation method is used for determining the gas-film stiffness and damping coefficients for given values of excitation frequency, compressibility number, and compliance factor of the bump foil. The nonlinear stationary Reynolds’ equation is solved by means of the Galerkin’s finite element formulation while the finite differences method are used to solve the first order complex dynamic equations resulting from the perturbation of the transient compressible Reynolds’ equation. It was found that the dynamic properties and stability of the compliant finite length journal bearing are significantly affected by the compliance of foils especially when the dynamic deformation of foils is considered in addition to the static one by applying the principle of superposition.

Yield inception of a coated substrate indented by a rigid sphere is analyzed using finite element analysis. The critical interference is studied as a function of film thickness and material properties of both the film and the substrate. The results show that critical interference, corresponding to yield inception of the coated substrate, is a strong function of the film thickness, the Young’s modulus, and the yield strength of both the film and the substrate.

A bump-type foil bearing consists of a compliant corrugated sheet metal supporting structure that is covered by a thin top foil surface. Bumps serve as stiffener and damping elements to increase the stability of the system while top foil creates necessary wedge surface for aerodynamic film formation. Foil bearings are hard to analyze as flexible foil surface deforms and changes shape while aerodynamic film pressure forms. Fully coupled finite element approach is presented. To increase the accuracy, the geometry is discretized with quadratic hexagonal elements. The gas film is modeled by compressible Reynolds equation. The effect of velocity on load capacity will be investigated to reveal the performance of the code.

The effect of contact conditions on yield inception of a spherical shell compressed by a rigid flat is studied using finite element analysis. A wide range of material properties and shell thickness values, corresponding to the dimensionless shell parameter, were studied. This work provides the critical load ratio as a function of the shell parameter for different values of the Poisson’s ratio under both slip and stick contact condition. At small values of the Poisson’s ratio the behavior in stick is very different from that in slip. At high values of the Poisson’s ratio the yield inception in stick and slip is similar.

A finite element contact model of a layered hemisphere with a rigid flat, which includes the effect of adhesion, is developed. This configuration has been suggested as a design for a microswitch contact because it has the potential to achieve low adhesion, low contact resistance, and high durability. Elastic-plastic material properties were used for each of the materials comprising the layered hemisphere. Adhesion was modeled based on the Lennard-Jones potential. The effect of the layer thickness on the adhesive contact was investigated. In particular the influence of layer thickness on the pull-off force and maximum contact radius was studied. The results are presented as load vs. interference and contact radius vs. interference for loading and unloading from different values of the maximum interference.

Tribological properties during rock cutting under extremely high pressure and high temperature (HPHT) conditions are important in deep mining and drilling operations. In the present investigation, a rock fragmentation process is simulated during mechanical cutting of rock using an explicit finite element code, LS-DYNA. In the simulations, a rigid steel cutting tool of different rake angles was moved at different velocities against a stationary rock material. Rock material properties have been incorporated using an advanced damage constitute material model. In addition, the friction factors at the cutting tool–rock interface were varied in the contact model. The variation of cutting forces, stresses and rock fragment morphology have been investigated. Overall, the results indicate that the explicit finite element model is a powerful tool for simulating rock cutting and the fragmentation process. More specifically, the separation of rock fragments from the rock slab was accurately predicted using the numerical model. The rake angle was found to have significant influence on the fragment morphology during rock cutting. Moreover, the cutting forces and the discontinuous fragmentation process were strongly influenced by the friction and cutting velocity.

Milling hardened steels has emerged as a key technology in mold and die manufacturing industries. In cutting, a portion of work material is pushed upward by the tool rake face to form the chip while the other portion below this layer is ploughed under the cutting edge to become the machined surface. Although the ploughed material is a very small fraction of the uncut chip thickness, it determines surface integrity after machining. In this study, a 3D finite element simulation model of milling hardened AISI H13 tool steel (HRC 50) has been developed to study material deformation under the cutting edge of a milling insert. The ploughed depth in the range of 0.6 μm to 3.0 μm is used to study the material flow under the cutting edge. Friction between the cutting edge and workpiece surface has a significant influence on the ploughed depth. Different coefficients of friction are used to study their effects on stresses/strains and temperature during ploughing. The Johnson-Cook model is used to model the plastic behavior of workpiece material. The 3D finite element analysis gives an insight into some key issues in a milling process. The FEA model illustrates the effects of micro cutting edge geometry on pile-up in front of the cutting edge, transient stresses and temperatures, and a transition from ploughing to cutting in a milling process.

The present work proposes a methodology study of Carbon/Carbon composites under dynamical stress and conditions of rubbing contact. It is based on the use of finite elements method (FEM), and homogenization technique is applied an elementary cell of composite under contact condition. The comparison of random equivalent representative volume element underlines the importance to take into account the contact interface in such process.

Particle based modeling approaches, such as the discrete element method (DEM) approach, require the definition of accurate contact (collision) models. An essential parameter within these models is the coefficient of restitution ( e ), which defines the ratio of post-collision to pre-collision relative velocity during the collision of two materials. In this study, e of various steel-material combinations is predicted through both physical experiments and explicit finite element modeling of a falling sphere colliding with a stationary plate, and examined against a theoretical formulation of e . Experiments are performed on various sphere materials including steel, brass, chrome steel, tungsten carbide, aluminum, polybutadiene, and nitinol 60, Experimental results for metals colliding with steel, match what is predicted by theory, as they show a decreasing trend in e with increasing impact velocities. Additional experimental results for polybutadiene rubber show no velocity dependence, remaining constant across the impact velocities examined; this matches with theory. Modeling results, obtained via the explicit finite element method (FEM) approach, are compared against experimental results for verification. Current explicit FEM results show very good quantitative agreement with experimental results for various materials (brass, steel, tungsten carbide, and chrome steel) impacting steel, but do not display the proper decreasing trend in e for increasing impact velocity, over the range of impact velocities examined (∼2 m/s–3.2 m/s). However, for simulations at impact velocities above this range, a decrease in e is witnessed. Current and future work focuses on refining the models to correctly display this qualitative trend within the current range of experimental impact velocities, as well as performing experiments on a wider range of impact velocities.

Dynamic indentation of an elastic-plastic half-space by a rigid sphere was studied with the finite element method. A parametric analysis was performed to examine the effects of indentation velocity and yield strength of the half-space material on dynamic contact deformation. Velocity effects are discussed in the context of simulation results of global and local contact parameters, such as mean contact pressure, contact area, and equivalent plastic strain. The evolution of deformation as the material response transitions from elastic to fully-plastic deformation during dynamic contact is interpreted in light of numerical results. This study elucidates the effect of dynamic contact loading on the deformation behavior of elastic-plastic materials for a wide range of length scales where a continuum mechanics description holds.

Transient contact between a sphere and a moving flat is investigated using finite element analysis. The sphere is assumed to be rigid while the flat is treated as an elastic-plastic body with isotropic hardening. Temperature and strain distributions of the sphere and the flat are obtained as a function of the vertical initial velocity of the sphere, the coefficient of friction between the sphere and the flat, and the tangential velocity of the flat. In addition, dimensionless solutions are presented for the maximum temperature rise and the maximum residual penetration as a function of the dimensionless vertical initial velocity of the sphere. The numerical solutions are independent of material properties and sphere radius, and can be applied to minimize data loss of the slider disk interface during slider-disk contacts.

Skin is the largest organ of the human body. Its main role is to ensure cohesion and protection of the internal body structures, acting as a physical and social interface to the external environment. The geometry and biophysics of this multi-layered biological structure are key elements in determining the nature and characteristics of these interactions [1]. Skin wrinkles [2], of particular relevance for skin care and shaving products, are the result of a complex interplay between material and structural properties, boundary and loading conditions the exact nature of which remains to be elucidated [3]. The variability of these properties/conditions according to the anatomical site, gender, race, from individuals to individuals or from experimental measurement techniques call for stochastic computational models [4]. The objective of this study was therefore to quantify the relative dependence of the wrinkling behavior of skin on these mechanical and geometrical factors by performing a stochastic finite element study accounting for 14 random variables. An integrated methodology combining design of experiment, solid modeling, finite element analysis and Bayesian meta-modeling was developed for this purpose. A three-layer finite element skin model including epidermis, dermis and hypodermis was designed. The sensitivity of the eigenvalues of the skin structure, number of wrinkles, amplitude of wrinkles, average roughness of the skin surface to the 14 probabilistic variables were calculated. It was found that the first four eigenvalues of the three-layer skin structure are mostly sensitive to the stiffness of the epidermis whilst this is no longer the case from the fifth eigenvalue. The thickness of the epidermis has the most significant effect on the number of wrinkles whilst the sensitivity of the average roughness to the length of the skin sample is maximum.