Showing papers by "Walter F. O'Brien published in 1994"

Artificial neural networks for predicting nonlinear dynamic helicopter loads

Abstract: This paper proposes using an artificial neural network (ANN) to predict the loads in critical components based on flight variable information that can be easily measured. The artificial neural network learns the relationship between flight variables and component loads through exposure to a database of flight variable records and corresponding load histories taken from an instrumented military helicopter undergoing standard maneuvers. Eight standard flight variables are used as inputs for predicting the time varying mean and oscillatory components of the tailboom bending load and the pitch link load for seven flight maneuvers

Dynamic Turbine Blade Temperature Measurements

Abstract: Turbine blade surface temperatures were studied during transient operation in a turbofan engine test rig. A single fiber radiation pyrometer was used to view the suction side of the blades from approximately 60% axial chord to the trailing edge at an average radial location of 70% blade height. A single ceramic-coated blade produced a once-per-revolution signal that allowed for the tracking of individual blades during the transients. The investigation concentrated on the light-off starting transient and the transients obtained during accelerating and decelerating between power settings. During starting and acceleration transients, the blade surface temperature gradient was observed to reverse. This phenomenon was most apparent during starting when the trailing edge was initially much hotter than the 60% chord location, resulting in large temperature gradients. In steady operation, the trailing-edge temperature was lower than the 60% chord location, and the gradients were less severe. During deceleration transients, the trailing edge cooled more rapidly than the 60% chord location. This resulted in larger temperature gradients than were seen in steady operation, but no profile inversion was observed. These temperature gradients and profile inversions represent a cycling of thermally induced stresses which may contribute to low-cycle fatigue damage. A simple one-dimensional heat transfer model is presented as a means of explaining the different heating rates observed during the transients.

Relative Cost of Owning and Using Traditional and Innovative Cooking Appliances

Abstract: A matrix was developed to provide a framework to organize information and compare the relative cost in monetary and human resources of owning and using traditional and innovative residential major cooking appliances. Laboratory data collected by the first author and by other university researchers with the same five types of cook tops and a microwave oven were analyzed with ANOVA, Student-Newman-Keuls, and Tukey's HDS procedures. Data were then used to complete the matrix comprising monetary and human resource dimensions thought to contribute to the total cost of ownership and use. Each dimension was assigned a weight to represent its level of importance to consumers. Based on the data, appliances were ranked high, medium, or low on each dimension of the matrix, and a total score was developed for each appliance. The microwave oven received the highest score, followed in order by cooktops with conventional gas burners, conventional electric coils, solid elements, and induction elements. Additional work is needed to refine data collection techniques, to expand the data set to include all types of major appliances currently available for surface cooking, and to validate the content and weights of the matrix.