arXiv subjects

Randall D. Peters

Publications and source records attributed to Randall D. Peters.

44 records · Page 3Linked to original sources

arXiv2002

Model of Internal Friction Damping in Solids

A model for harmonic oscillator damping due to the internal friction of solids has been developed, based on considerations of a long period pendulum. The assumption of a complex elastic modulus to describe stress-strain hysteresis in the support structure of the pendulum yields an expression for the figure of merit Q that agrees with many experiments involving material damping. As such, the approximations of this linear model stand in contrast with common theory.

physics.class-ph↗

arXiv2002

Toward a Universal Model of Damping--Modified Coulomb Friction

A modification of Coulomb's law of friction uses a variable coefficient of friction that depends on a power law in the energy of mechanical oscillation. Through the use of three different exponents: 0, 1/2 and 1; all commonly encountered non-viscous forms of damping are accommodated. The nonlinear model appears to yield good agreement with experiment in cases of surface, internal, and amplitude dependent damping.

physics.class-ph↗

arXiv2002

A Novel Magnetometer

A magnetometer has been developed by a simple modification of the TEL-Atomic Cavendish balance designed by the author. The usual tungsten wire fiber has been replaced with a silk thread, and a rare earth magnet has been attached to the boom near where the fiber connects. Because of the mechanical common mode rejection feature of the instrument, pendulous noise is largely removed from this compass-like magnetometer that is quite sensitive to direction changes in the Earth's field.

physics.ins-det↗

arXiv2002

Bistability of a Torsion Magnetometer

Low-level bistability has been observed in the output from a recently developed novel magnetometer. It is not known whether this behavior is associated with the torsion fiber of the instrument or with the Earth's magnetic field. Whatever its cause, this form of complexity is not widely known.

physics.gen-ph↗

arXiv2002

The Pendulum in the 21st Century--Relic or Trendsetter

When identifying instruments that have had great influence on the history of physics, none comes to mind more quickly than the pendulum. Though 'birthed' by Galileo in the 16th century, and in some respects nearly 'dead' by the middle of the 20th century; the pendulum experienced 'rebirth' by becoming an archetype of chaos. With the resulting acclaim for its surprising behavior at large amplitudes, one might expect that there would already be widespread interest in another of its significant nonlinearities. Such is not the case, however, and the complex motions of small amplitude physical pendula are barely known. The present paper shows that a simply-constructed metallic rod pendulum is capable of demonstrating rich physics in a largely unstudied area.

physics.class-ph↗

arXiv2002

The Study of Complex Mechanical Oscillators using an Inexpensive Computer Acquisition and Processing System

An inexpensive analog-to-digital converter has been built around the game port of the IBM personal computer. Using a single field effect transistor (FET) and three carbon resistors, it allows the game card to measure voltage, instead of its usual measurement of resistance. Since power for the FET is drawn from the game port, the total cost of components, external to the computer, is very low at about one U.S. dollar. The converter is linear enough for many applications, and is presently used to study the complex free decay of a long period physical pendulum. Software support is via QuickBasic, and the hardware/software package design was influenced by a consideration of amateur seismology needs.

physics.class-ph↗

arXiv2001

The Stirling Engine-Refrigerator: Rich Pedagogy from Applied Physics

A Stirling engine of the type used for demonstration purposes has been outfitted with a pair of sensors that measure pressure and piston displacement when the engine is operating with a small temperature difference between the hot and cold reservoirs. Measured variables are compared against computer generated output based on a simple theory that involves nonlinear equations of motion. Theory and experiment are found to be in reasonable agreement. Temperature dependence of the graph of pressure versus piston displacement, for different directions of flywheel rotation, permits a better understanding of the physics of heat engines and refrigerators in general.

physics.class-ph↗

arXiv2001

Creep and Mechanical Oscillator Damping

Although "friction" is included in many models of oscillator damping, including viscous ones applied to the pendulum; they "miss the mark" with regard to a conceptual understanding of the mechanisms responsible for energy loss. The theory of the present paper corrects some of these misunderstandings by considering the influence of internal friction which derives from the structural members of the oscillator through secondary rather than primary creep. The simple model properly describes the variation of Q with frequency.

physics.class-ph↗