Department Faculty

Alan J. Markworth

Professor

Ph. D., The Ohio State University, 1969

Tel. (614) 688-3581

markworth.4@osu.edu

Dr. Markworth joined the OSU faculty in 1995 after a research career at Battelle Memorial Institute in Columbus that spanned nearly three decades. His primary interest has been in computational materials science, wherein he has contributed to a wide variety of subjects, ranging from the atomic to the macroscopic scale, and has received funding from both government and industrial agencies.

Results of his research have been reported in well over one hundred publications. For example, one study involved atomistic simulations of atomic arrangements around a crack tip in bcc iron, including effects of atomic hydrogen dissolved in the metal near the crack tip. Another involved modeling effects of gravity on the kinetics of phase segregation in liquid-phase miscibility-gap systems. The latter work also included participation in the planning of two sounding-rocket and two Space Shuttle experiments. Still another involved the formulation of continuum and stochastic models for simultaneously occurring oxidation of a metal surface and erosion of the oxide film.

A Poincaré section, illustrating the order that underlies the chaotic oscillations of a crack-tip atom in an atomististic model of brittle fracture. The 4,000 points shown here represent values of velocity and position of the atom measured each time its trajectory in phase space crosses a certain hyperplane moving in a specified direction.

For the past several years, Dr. Markworth has concentrated his efforts on the study of nonlinear systems, and in particular, on the extremely complex dynamical behavior that even very simple nonlinear systems can exhibit under certain conditions.

He has been dealing mainly with issues surrounding the occurrence of bifurcations, limit cycles, and chaos in nonlinear systems, including the development of strategies for the analysis, control, and prediction of chaotic oscillations. Materials-related subject areas, to which he has been applying these dynamical principles, include:

    • Brittle fracture,
    • Passivation of a metal surface
    • Pulse combustion,
    • Dissociative chemisorption of a diatomic gas on a metal surface,
    • Film growth by ballistic deposition and by condensation from a multicomponent vapor,
    • Plastic instabilities in metals (the Portevin-Le Châtelier effect),
    • Reproducibility considerations in the processing of complex oxide materials.
    • The evolution of fractal particles on surfaces,
    • Instabilities in a model electric power system.


Oscillations

Controlling chaotic oscillations in a model for the Portevin-LeChâtelier effect, sometimes called "serrated yielding". This phenomenon arises from coupled interactions between populations of different kinds of dislocations. The free (uncontrolled) chaotic oscillations of stress with time are shown in blue. A form of feedback control is applied between times 4,000 and 6,000, which serves to suppress the oscillations (red curve). The control is turned off at time 6,000 and the chaotic behavior resumes (green curve).

Selected Recent Publications