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Repetitive Impact Response Of A Beam Structure Subjected To Harmonic Base Excitation, Elizabeth K. Ervin, Jonathan A. Wickert Oct 2007

Repetitive Impact Response Of A Beam Structure Subjected To Harmonic Base Excitation, Elizabeth K. Ervin, Jonathan A. Wickert

Jonathan A. Wickert

This paper investigates the forced response dynamics of a clamped–clamped beam to which a rigid body is attached, and in the presence of periodic or non-periodic impacts between the body and a comparatively compliant base structure. The assembly is subjected to base excitation at specified frequency and acceleration, and the potentially complex responses that occur are examined analytically. The two sets of natural frequencies and vibration modes of the beam-rigid body structure (in its in-contact state, and in its not-in-contact state), are used to treat the forced response problem through a series of algebraic mappings among those states. A ...


Surface Friction Guiding For Reduced High-Frequency Lateral Vibration Of Moving Media, V. Kartik, Jonathan A. Wickert Jun 2007

Surface Friction Guiding For Reduced High-Frequency Lateral Vibration Of Moving Media, V. Kartik, Jonathan A. Wickert

Jonathan A. Wickert

The free and forced vibration of a moving medium is examined in an application where distributed friction guiding is used to control lateral position passively. Subambient pressure features formed in the guides intentionally modify the naturally occurring self-pressurized air bearing and increase the contact force between the medium and the guide's surface. These features increase friction to a level beyond that achievable based on the nominal wrap pressure. The moving medium is modeled as a beam that is transported over frictional regions and subjected to prescribed boundary disturbances arising from runout of a supply or take-up roll. For axial ...


Corrugation And Buckling Defects In Wound Rolls, Jonathan A. Wickert, P.M. Lin Feb 2006

Corrugation And Buckling Defects In Wound Rolls, Jonathan A. Wickert, P.M. Lin

Jonathan A. Wickert

Sheet metal, paper, and polymer webs are often stored and processed as large rolls comprising thousands of layers. Depending on the elastic properties of the web material, the roll's dimensions, the type of core, and the winding tension, the stresses that develop within the roll can be sufficiently high to cause local or gross buckling defects to form. For instance, the cylindrical core onto which the web is wound can collapse, a failure mode that is termed "v-buckling." In other cases, while the core might remain intact, a group of layers interior to the roll can wrinkle into a ...


Optimizing Vibration Isolation Of Flex Circuits In Hard Disk Drives, M. R. Brake, Jonathan A. Wickert Apr 2005

Optimizing Vibration Isolation Of Flex Circuits In Hard Disk Drives, M. R. Brake, Jonathan A. Wickert

Jonathan A. Wickert

A "flex circuit" is a laminate of polyimide substrate, adhesive, and copper conductors that is used to connect the stationary electronic components in a computer hard disk drive to the rotating arm that positions read/write heads above the disks. The flex circuit's transverse and longitudinal vibrations couple with the arm, and those motions, although seemingly small, degrade performance during seek operations from one data track to another. The flex circuit and arm mechanism is defined by a number of geometric parameters, and some latitude is available at the design stage for choosing dimensions and angles so as to ...


Contribution Of Support Means To Stresses Developed In Sheet Metal Coils, Jonathan A. Wickert, Y.M. Lee Aug 2004

Contribution Of Support Means To Stresses Developed In Sheet Metal Coils, Jonathan A. Wickert, Y.M. Lee

Jonathan A. Wickert

Sheet metal is often stored in large wound coils and processed through such manufacturing stages as cleaning, coating, and slitting in a finishing plant or thickness reduction in a rolling mill. During winding and unwinding operations, as well as during storage and transportation, a coil can be supported in a variety of methods. The coil can be formed on a relatively compliant fiber core, or it can be mounted with the core onto a drive shaft or a pair of core chucks. The stresses within the coil develop in response to the sheet metal's material properties, the process tension ...


Analysis Of Core Buckling Defects In Sheet Metal Coil Processing, P.M. Lin, Jonathan A. Wickert Nov 2003

Analysis Of Core Buckling Defects In Sheet Metal Coil Processing, P.M. Lin, Jonathan A. Wickert

Jonathan A. Wickert

The elastic stability of a wound coil comprising a central core and many layers of sheet metal is modeled and analyzed. A common failure mode resulting from unfavorable internal stresses—called v-buckling—is characterized by a section of the core buckling inward, possibly with several nearby sheet metal layers. In the present study, the core is modeled as a thin cylinder that is subjected to (i) the uniform external pressure generated by the coil's wound-in stresses and (ii) a nonuniform elastic foundation around its circumference that represents core-coil contact or loss thereof. The model and an iterative numerical technique ...


Vibration Of Flex Circuits In Hard Disk Drives, Jonathan A. Wickert Jul 2003

Vibration Of Flex Circuits In Hard Disk Drives, Jonathan A. Wickert

Jonathan A. Wickert

A flex circuit connects the stationary electronic components in a hard disk drive to the rotating arm that carries the read/write heads and positions them above data tracks on the disk. Flex circuits are conventionally formed as a laminate of polyimide substrate, adhesive, and copper conductors. Deformation of a flex circuit is discussed in the context of the following stages: the initial unstressed shape, configurations in which stresses set and relax in response to elevated temperature, equilibrium, and small amplitude vibration. The model involves displacements of the flex circuit in the directions tangent and normal to the local equilibrium ...


Width-Wise Variation Of Magnetic Tape Pack Stresses, Jonathan A. Wickert, Y.M. Lee May 2002

Width-Wise Variation Of Magnetic Tape Pack Stresses, Jonathan A. Wickert, Y.M. Lee

Jonathan A. Wickert

A model is developed for predicting the stress and displacement fields within a magnetic tape pack, where those quantities are allowed to vary in both the pack's radial and transverse (cross-tape) directions. As has been the case in previous analyses based upon one-dimensional wound roll models, the present approach accounts for the anisotropic and nonlinear constitutive properties of the layered tape, and the incremental manner in which the pack is wound. Further, such widthwise variation effects as differential hub compliance and nonuniform winding tension, which can be significant in data cartridge design, are also treated in the model. The ...


Stress Field In Finite Width Axisymmetric Wound Rolls, Jonathan A. Wickert, Y.M. Lee Mar 2002

Stress Field In Finite Width Axisymmetric Wound Rolls, Jonathan A. Wickert, Y.M. Lee

Jonathan A. Wickert

A model is developed for predicting the stress field within a wound roll of web material, in which the radial, circumferential, transverse, and shear stresses can vary in both the roll's radial and cross-web (transverse) directions. As has been the case in previous wound roll stress analyses based on one-dimensional models, the present approach accounts for the anisotropic and nonlinear material properties of the layered web material, and the incremental manner in which the roll is wound. In addition, the present development accounts for arbitrary cross-sectional geometry and material of the core, and the presence of nonuniform tension across ...


Damper For Brake Noise Reduction (Brake Drums), Jonathan A. Wickert, Adnan Akay Sep 2000

Damper For Brake Noise Reduction (Brake Drums), Jonathan A. Wickert, Adnan Akay

Jonathan A. Wickert

An apparatus of reducing unwanted brake noise has a ring damper affixed around a periphery of brake drum in a drum brake system in a manner that permits relative motion and slippage between the ring damper and the brake drum when the brake drum vibrates during braking. In a preferred embodiment, the ring damper is an almost circular ring that is inserted in a groove formed in the periphery of the brake drum. The ring damper is held in place by the groove itself and by the interference pre-load or pre-tension between the ring damper and the brake drum.


Spatial Modulation Of Repeated Vibration Modes In Rotationally Periodic Structures, M. Kim, J. Moon, Jonathan A. Wickert Jan 2000

Spatial Modulation Of Repeated Vibration Modes In Rotationally Periodic Structures, M. Kim, J. Moon, Jonathan A. Wickert

Jonathan A. Wickert

When a structure deviates from axisymmetry because of circumferentially varying model features, significant changes can occur to its natural frequencies and modes, particularly for the doublet modes that have non-zero nodal diameters and repeated natural frequencies in the limit of axisymmetry. Of technical interest are configurations in which inertia, dissipation, stiffness, or domain features are evenly distributed around the structure. Aside from the well-studied phenomenon of eigenvalue splitting, whereby the natural frequencies of certain doublets split into distinct values, modes of the axisymmetric structure that are precisely harmonic become contaminated with certain additional wavenumbers. From analytical, numerical, and experimental perspectives ...


Damper For Brake Noise Reduction, Jonathan A. Wickert, Adnan Akay Jan 1999

Damper For Brake Noise Reduction, Jonathan A. Wickert, Adnan Akay

Jonathan A. Wickert

An apparatus for reducing unwanted brake noise has a ring damper affixed around a periphery of a brake rotor in a disk brake system in a manner that permits relative motion and slippage between the ring damper and the rotor when the rotor vibrates during braking. In a preferred embodiment, the ring damper is disposed in a groove formed in the periphery of the disk and is pre-loaded against the rotor both radially and transversely. The ring damper is held in place by the groove itself and by the interference pre-load or pretension between the ring damper and the disk ...