Peter L. Schmidt

Thermal measurements using ultrasonic acoustical pyrometry

Reflections from geometric discontinuities can be used with ultrasonic energy to predict the temperature of an interface where classical temperature measurement techniques are impractical because of physical access limitations or harsh environmental conditions. Additionally, these same ultrasonic measurements can be used with inversion methods commonly applied to ill-posed heat transfer problems to increase the accuracy of the measurement of surface temperature or heat flux at the surface of interest. Both methods for determining surface temperature are presented, along with a comparison of results both from a verification example and using data gathered in a field test of the methods. The results obtained with these two methods are shown to be in good agreement with an empirical relationship used in the design of large caliber guns.

Effect of In-Plane Forces on Sound Radiation From Convected, Fluid Loaded Plates

It is well established that fluid flow can have significant effects on structural acoustic behavior, along with the fact that induced coupling between discrete modes of vibration becomes significant as flow velocity increases. Work in this area has been confined to flows in air, over unloaded structures, with the effects on sound radiation efficiency, kinetic energy, and sound power radiation quantified and compared for various flow speeds. The purpose of this work is to study the effects that plane stress has on these structural acoustic phenomena. Theoretical development of the equations governing the vibration of a simply supported plate subjected to in-plane forces in an infinite baffle and an aerodynamic system that models a semi-infinite flowing medium along with the method for coupling these systems is included. Computational results are presented illustrating the behavior of the uncoupled coupled effects on the sound power radiation from the plate in both subsonic and supersonic flows, for a variety of loading cases.

Residual surface stress: comparing traditional and modulated tool path machining processes

Traditional machining processes, where material is removed by a cutting tool from a workpiece, can introduce residual stresses at the surface of machined pieces. This paper provides an examination of an alternative machining methodology called modulated tool path machining. The ultimate objective of this research is to determine the effects of modulated tooling path machining processes, as applied to control chip geometry, on the surface stress of selected materials. Residual stresses in machined samples were characterised through the use of X-ray diffraction by comparing the modulated path method with a more traditional material removal technique (i.e. constant surface speed and constant contact). This paper is part of a Themed Issue on Measurement, modelling and mitigation of residual stress.

Chip formation and similarity in the plano-grinding of explosive surrogates

The processing of polymer-bonded explosives is not widely reported in the literature, especially the machining of explosive surrogates in the combined planing and grinding operation known as plano-grinding. The process of machining long pieces of an inert substitute using a wax binder to hold sugar particles together and then subjecting the surrogate material to a linear cutting motion to generate chip fragments is described. The aim and purpose of this work is to analyze the machining of explosive surrogates in terms of chip formation models (oscillating and stress ratio models) and similarity models (chip compression ratio, Poletica, and Peclet numbers). The analysis of machining is compared to standard engineering materials so that the explosives engineer can benchmark machining performance of explosive surrogates to standard materials. The article concludes with statements on how to improve the understanding of machining of explosive surrogates with specifically engineered abrasive cutting tools.

The effect of in‐plane forces on sound radiation from convected fluid‐loaded plates

It is well established that fluid flow can have significant effects on structural acoustic behavior, along with the fact that induced coupling between discrete modes of vibration becomes significant as flow velocity increases. Work in this area has been confined to flows in air, over unloaded structures, with the effects on sound radiation efficiency, kinetic energy, and sound power radiation quantified and compared for various flow speeds. The purpose of this work is to study the effects that plane stress has on these structural acoustic phenomena. Theoretical development of the equations governing the vibration of a simply supported plate subjected to in‐plane forces in an infinite baffle and an aerodynamic system that models a semi‐infinite flowing medium along with the method for coupling these systems is included. Computational results are presented illustrating the behavior of the uncoupled coupled effects on the sound power radiation from the plate in both subsonic and supersonic flows, for a varie...

Acoustic self‐localization of a wireless sensor network

One of the biggest challenges to the field of wireless sensor networks is self‐localization: that is the determination of the relative and absolute coordinates of each sensor node in the network. Previous work has been done to locate hydrophone arrays. However sensor networks have some unique constraints that make this more challenging. A typical application would involve the distribution of hundreds or thousands of sensor nodes over an area either by hand, airdrop or other means. One of the primary constraints on such a system is that centralized processing of self‐localization data may be prohibitively complex. Furthermore, the data may be incomplete, contain reflected path events, and may be subject to other mission specific constraints. Therefore, a distributed computational scheme has been developed to solve acoustic time‐of‐arrival equations. A priori information about some sensor locations and user triggered source localization events are used along with a regularized inversion solution. Results of...

A decentralized algorithm for acoustic localization using a distributed sensor network

An acoustic source localization algorithm has been developed for use with large‐scale sensor networks using a decentralized computing approach. This algorithm, based on a time delay of arrival (TDOA) method, uses information from the minimum number of sensors necessary for an exactly determined solution. Since the algorithm is designed to run on computational devices with limited memory and speed, the complexity of the computations has been intentionally limited. The sensor network consists of an array of battery‐operated COTS Ethernet‐ready embedded systems with an integrated microphone as a sensor. All solutions are calculated as distinct values, and the same TDOA method used for solution is applied for ranking the accuracy of an individual solution. Repeated for all combinations of sensor nodes, solutions with accuracy equivalent to complex array calculations are obtainable. Effects of sensor placement uncertainty and multipath propagation are quantified and analyzed, and a comparison to results obtain...