Investigation of squeeze-film dampers

Squeeze film dampers are a means of curing instabilities in rotating shaft assemblies. Their efficiency depends very much on the condition of the oil, which in turn depends on inlet and outlet arrangements, on damper geometry and on the flexibility of the rotor and surrounding structure. Rig investigations in which structural flexibility is included experimentally are discussed. Comparisons are made between measured and predicted results

A structure for maturing intelligent tutoring system student models

A special structure is examined for evolving a detached model of the user of an intelligent tutoring system. Tutoring is used in the context of education and training devices. A detached approach to populating the student model data structure is examined in the context of the need for time dependent reasoning about what the student knows about a particular concept in the domain of interest. This approach, to generating a data structure for the student model, allows an inference engine separate from the tutoring strategy determination to be used. This methodology has advantages in environments requiring real-time operation

Tribo-corrosion of steel in artificial saliva

Stainless steel is widely used as dental implant. However, there has been little work on the micro-abrasion of such materials in laboratory simulated oral environments, where abrasion, sliding wear can interact simultaneously. In this study, the effects of applied load, and exposure time were evaluated for a 316 stainless steel in a laboratory simulated artificial saliva. Polarization curves showed an enhancement of corrosion current density with increases in applied load. Wear maps were produced showing low wear safety regimes at intermediate loads and exposure times. Possible reasons for such trends are interpreted in terms of the ability of the passive film in providing resistance against third body particle impact and the concentration of particles in the contact at higher loads

Fearless: Christine Serwan and Sam Holmes

This week, we’re recognising the fearless work that Christine Serwan ’13 and Sam Holmes ’13 will be doing over the next two years during with the Peace Corps. [excerpt

Non-linear performance of a three-bearing rotor incorporating a squeeze-film damper

This paper is concerned with the non-linear vibration performance of a rigid rotor supported on three bearings, one being surrounded by a squeeze-film damper. This damper relies on the pressure built up in the squeeze film to help counter-act external forces arising from unbalance and other effects. As a result a vibration orbit of a certain magnetude results. Such vibration orbits illustrate features found in other non-linear systems, in particular sub-harmonic resonances and jump phenomena. Comparisons between theoretical prediction and experimental observations of these phenomena are made