Hajim School of Engineering and Applied Sciences Department of Mechanical Engineering

Faculty

David Quesnel

David J. Quesnel

Professor of Mechanical Engineering
Professor of Materials Science

Office: 220 Hopeman Hall
Phone: (585) 275-5215
Fax: (585) 256-2509
david.quesnel@rochester.edu
Web Site

PhD, Northwestern University, 1977

Bio

Next Generation Piezoelectrics

Single Crystals with the perovskite structure are the next generation of piezoelectrics. They exhibit about 10 times the piezoelectric properties of ordinary polycrystalline ceramic piezoelectrics. My group studies them to improve the apparent mechanical properties through the use of well-characterized processing which reduces the number and sizes of surface flaws. We have succeeded in improving the properties by a factor of 5. We have also developed a relief polishing process which lets us examine the domain structures of these materials so that the principles of materials science can be applied to better control their properties. We are currently working on developing a criteria to predict the appearance of cracks and the growth of cracks under combined electrical and mechanical loading.

Computer Simulation of Corrosion

The behavior of materials during aqueous corrosion is extremely complex. Yet the fundamental behavior of reacting or dissociating species is relatively simple. The work of my group is to provide a computerized view of what is happening at the atomic scale by using a simulation method called Molecular Automation. Developed in our group over the last few years, Molecular Automation combines concepts from molecular dynamics and cellular automation to simulate the motions of species, their interactions with each other and with fields, and their tendency to chemically react and dissociate. Starting with a discrete set of probabilities that represent the possible outcomes of a thermally activated event that can occur when specific local environments are present, and including the response of charged species and dipoles to local electric fields, the simulation generates complex outcomes. That is, simple input algorithms, repetitively and probabilistically applied, create complex emergent behaviors that include: exchange currents, electric double layers, hydrogen evolution and hydrogen charging, surface film formation, surface roughening, vacancy injection, and even the enhanced metallic corrosion rates associated with the presence of chloride ions in aqueous solution. Validation efforts include diffusion calculations and ionic conductivity calculations for comparison with known experimental outcomes.

Stress Corrosion Cracking

The synergy between mechanical forces and chemical reactivity lead to a phenomena known as stress corrosion cracking (SCC). Here a metallic sample demonstrates the ability to fracture at stresses far lower than would be needed without the aggressive environment and further, without the stress, the aggressive environment does nothing. Our group works to better understand the physical, chemical, and electrical processes that give rise to stress corrosion cracking. We have developed methods of measuring crack growth in wet environments that include AC and DC potential drop, ultrasonic methods, and, of course, the standard compliance and optical methods. Our work at present is concentrated on examining the role of applied voltages that can modify the outcome of SCC experiments, on the role of microstructure as influenced by usage, storage, and processing, and on examining the effect of chemical species concentrations and their time histories. In short, we are studying the materials science of stress corrosion cracking.

Previous Reserach Activities

Professor Quesnel has worked on a wide range of topics including low cycle fatigue in steels, aluminums, and plastics, elevated temperature mechanical testing and the mechanical properties of solder joints, residual stress analysis, fracture of glasses and ceramics, adhesion, molecular dynamics, and contact mechanics. His interests are in the physics which controls materials science. He holds 7 patents and has authored two books.

For a complete list of Professor Quesnel’s publications, search the science citation index using author = Quesnel DJ.

 

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