Jens E. Jorgensen

Measurement of fluid turbulence based on pulsed ultrasound techniques. Part 1. Analysis

The pulsed ultrasonic Doppler velocimeter has been used extensively in transcutaneous measurement of the velocity of blood in the human body. It would be useful to evaluate turbulent flow with this device in both medical and non-medical applications. However, the complex behaviour and limitations of the pulsed Doppler velocimeter when applied to random flow have not yet been fully investigated. In this study a three-dimensional stochastic model of the pulsed ultrasonic Doppler velocimeter for the case of a highly focused and damped transducer and isotropic turbulence is presented. The analysis predicts the correlation and spectral functions of the Doppler signal and the detected velocity signal. The analysis addresses specifically the considerations and limitations of measuring turbulent intensities and one-dimensional velocity spectra. Results show that the turbulent intensity can be deduced from the broadening of the spectrum of the Doppler signal and a mathematical description of the effective sample-volume directivity. In the measurement of one-dimensional velocity spectra at least two major complicacations are identified and quantified. First, the presence of a time-varying, broad-band random process (the Doppler ambiguity process) obscures the spectrum of the random velocity. This phenomenon is similar to that occurring in laser anemometry, but the ratio of the level of the ambiguity spectrum to the largest detected velocity spectral component can be typically two to three orders of magnitude greater for ultrasonic technique owing to the much greater wavelength. Secondly, the spatial averaging of the velocity field in the sample volume causes attenuation in the measured velocity spectrum. For the ultrasonic velocimeter, this effect is very significant. The influence of the Doppler ambiguity process can be reduced by the use of two sample volumes on the same acoustic beam. The signals from the two sample volumes are cross-correlated, removing the Doppler ambiguity process, while retaining the random velocity. The effects of this technique on the detected velocity spectrum are quantified explicitly in the analysis for the case of a three-dimensional Gaussianshaped sample-volume directivity.

Measurement of fluid turbulence based on pulsed ultrasound techniques. Part 2. Experimental investigation

An extensive experimental programme in both laminar and turbulent flow was undertaken to examine the validity of all of the major implications of the model of the pulsed ultrasonic Doppler velocimeter for turbulent flow developed in part 1 of this investigation. The turbulence measurements were made in fully developed flow at the centre of a 6·28 cm diameter pipe. The Reynolds number of the flow ranged from 6000 to 40000. The carrier frequency of the ultrasonic velocimeter was 4·7 MHz. Measurements of the turbulence intensity and of the one-dimensional velocity spectra made with the ultrasonic velocimeter are compared with the analysis and with the actual quantities as measured by a hot-film anemometer. The experimental results are in agreement with theoretical predictions. Measurements of one-dimensional turbulence spectra with reduced ambiguity spectra made by the two sample volume methods described in part 1 are presented. The results verify the analysis and indicate that an improvement in the useful dynamic range of the velocity power spectrum of nearly three orders of magnitude can realistically be achieved.

Surface Profile Measurement During Turning Using Fringe-Field Capacitive Profilometry

The use of fringe-field capacitive sensing for surface profile measurement during the turning process is described. Measurements of the local surface height are inferred from variations in a fringe electric field induced between the sensing element and the workpiece. The surface profile is determined from high-speed scanning of the sensing element across the surface. The technique is particularly well-suited to the relatively harsh environment of in-process measurement. We have implemented a system in which profile measurements are made continuously, in real-time, and immediately adjacent to the cutting tool

A bidirectional load applicator for the investigation of skin response to mechanical stress

Instrumentation was developed to apply controlled biaxial (normal and shear) forces to the skin of a human or animal subject. The instrument mimicked any reference waveform within the constraints of a bandwidth of 15 Hz, a maximum force of 20 N, and displacement ranges of 15 mm for the normal direction and 18 mm for the shear direction. Two shaker motors, positioned with their axes parallel, were used with a low effective mass linkage and small-angle rotational joints to deliver the force. A digital feedback controller independently controlled the instantaneous normal and shear forces and recorded the resultant displacements. Evaluations on human and animal (pig) subjects demonstrated mean absolute errors between the applied and reference waveforms of less than 1.2% full-scale output for both the normal and shear directions. No degradation in performance was apparent over the course of a 1-h loading session. The instrument is to be used for the investigation of skin adaptation to mechanical stress, information that could be used to design new therapeutic methods to encourage skin load-tolerance.

Interactive simulation for studying the design of feller-bunchers for forest thinning

ABSTRACT AN interactive numerical simulation method employing a stand map, thinning prescription, and a model harvest vehicle is described. Geometric parameters and an operating strategy are used to generate a feasible cutting path for a feller-buncher. The path, along with appropriate time related parameters, determines operating time for the harvesting vehicle. Animated graphics provide a tool for verification and evaluation of the simulations. Thinning with a feller-buncher is examined as a base case for evaluation of design concepts. The results indicate that the technique is suitable for evaluating design and operational parameters, and their effects on thinning system performance.

Manufacturing Systems Delphi Study

Abstract This paper presents the results of a Delphi inquiry carried out to determine the short and long range technology needs and plans of small and medium sized manufacturers in the Pacific Northwest. Policy directions which cooperative research centers might adopt to aid these enterprises are also examined. Delphi results demonstrated a strong consensus that many types of advanced manufacturing technologies will be used widely by the year 2000 and that their adoption is correlated with company size, net income, and gross sales volume. Functions and types of industrial robots forecasted for use are discussed as well as are timetables for the first use of various technologies. Industry-University cooperative research centers may best serve the needs of manufacturing firms by providing improved educational skills, improved information flow on assessment of technologies, and research in technologies likely to be implemented.

A summative assessment strategy for a multi-institutional, multi-task project: the case of the manufacturing engineering education partnership

In 1994, a unique partnership of universities Penn State, University of Washington and University of Puerto Rico at Mayaguez-in collaboration with Sandia National Laboratories, received funding from the ARPA Technology Reinvestment Program (TRP) to develop a new, practice-based curriculum and physical facilities for product realization and manufacturing. This initiative is named the Manufacturing Engineering Education Partnership and its overall outcome is the development at each participating institution of what we call The Learning Factory. This paper describes the projects summative assessment strategy being implemented project-wide that will allow interested parties to evaluate the projects performance and achievement of goals and objectives. It describes the projects four major tasks and deliverables, the assessment plan and its principal elements. It also presents the assessment schedule and the tools used for qualitative evaluation. The assessment scheme depicted in this paper could be used as a model for similar multi-institutional, multi-task projects.

An educational Program in Product Realization

As part of the Manufacturing Engineering Educational Partnership (MEEP) design and manufacturing courses have been restructured into a sequence leading to a Program in Products Realization (PPR) in our undergraduate engineering curriculum. The purpose is to provide a broad based, interdisciplinary program for undergraduate students interested in the design and manufacturing of industrial products. Although each school has taken a slightly different approach to the implementation, the students at the three schools experience design and manufacturing activities each semester (or quarter) in residence. The program bridges the gap between engineering science and practice, and allows students to work in teams on real industrial problems. The implementation of the program has required restructuring of existing courses, the addition of new resources, and the creation of Learning Factories at each of the institutions. The Learning Factories provide modern facilities for design, manufacturing, fabrication, and testing of products. In addition, the program has attracted the support of over 100 industrial sponsors, who have helped promote hands-on experience and provided projects and class room support. This paper describes the new program at each of the institutions, the resources required, and operational experiences to date. This project was supported by the ARPA Technology Reinvestment Program and the National Science Foundation.