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Search Publications by: Jon R. Pratt (Fed)

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Displaying 101 - 115 of 115

Towards a Traceable Nanoscale Force Standard

May 1, 2001
Author(s)
Jon R. Pratt, David B. Newell, Edwin R. Williams, Douglas T. Smith, John A. Kramar
The National Institute of Standards and Technology has launched a five-year project to traceably link the International System of Units (SI) to forces between 10 -8N and 10 -2N. In this paper, we give a background and overview of this project, discuss the

Regenerative Stablity Analysis of Highly Interrupted Machining

January 1, 2001
Author(s)
Matthew A. Davies, Jon R. Pratt, Brian S. Dutterer, Timothy J. Burns
We discuss theoretical and experimental work that supports the use of very low radia immersion in the high-speed milling of difficult-to-machine materials, such as titanium alloys. Our theory is based upon modeling the cutting process by a kicked harmonic

SI Traceability of Force at the Nanonewton Level

January 1, 2001
Author(s)
David B. Newell, Jon R. Pratt, John A. Kramar, Douglas T. Smith, L Feeney, Edwin R. Williams
Although nanonewton force measurements are commonplace in industry, no National Measurement Institute supports a link to the International System of Units (SI) below one newton. The National Institute of Standards and Technology has launched a five-year

Stability Analysis of Interrupted Cutting With Finite Time in the Cut

January 1, 2001
Author(s)
P V. Bayly, J E. Halley, Matthew A. Davies, Jon R. Pratt
The stability of interrupted cutting is examined for the case in which the tool is in contact with the work piece for a small, but finite, fraction of the tooth-passing period. A model of a single degree-of-freedom tool excited by intermittent

Broadband Ac-dc Difference Calibrations of Current Shunts up to 100 A at NIST

July 1, 2000
Author(s)
Joseph R. Kinard Jr., Thomas E. Lipe Jr., Clifton B. Childers, Owen B. Laug, Jon R. Pratt
NIST is now offering broadband, ac-dc difference calibrations of current shunts from 3 A to 100 A, and at frequencies up to 30 kHz, as special tests. We present an overview of this new service including the design and construction of the NIST standard

The Stability of Low Radial Immersion Milling

January 1, 2000
Author(s)
Matthew A. Davies, Jon R. Pratt, Brian S. Dutterer, Timothy J. Burns
Traditional regenerative stability theory predicts a set of spindle speeds with locally optimum stability at integer fractions of the natural frequency of the most flexible mode of the system. The assumptions of this theory become invalid for highly

Dynamic Interrogation of a Basic Cutting Process

July 1, 1999
Author(s)
Matthew A. Davies, Michael Kennedy, Jon R. Pratt, Christopher J. Evans
A dynamic cutting fixture based on the test rig pioneered by Peters et al. has been developed to aid investigations of cutting process dynamics. This active fixture consists of a flexure-based tool holder with a single dominant modal direction, two voice

A Wide Bandwidth Printed Wiring Board Transmission Line Probe

March 1, 1999
Author(s)
Nicholas Paulter, Jon R. Pratt
An inexpensive, wide bandwidth, high cycle 50 ω probe is described for making electrical contact to printed wiring board planar transmission lines. The electrical transfer function of the probe and its contact repeatability are presented.

Frequency Domain Modal Estimation Techniques, Experimental Techniques

January 1, 1998
Author(s)
S Fahey, Jon R. Pratt
In this brief, we discuss the estimation of modal parame-ters using single-degree-of-freedom approximations. Then, we proceed to review two multi-degree-of- freedom techniques for modal parameter estimations-the first based on dynamic matrices and the

On the dynamics of high-speed milling with long slender endmills

January 1, 1998
Author(s)
Matthew A. Davies, A Schaut, Jon R. Pratt, Brian S. Dutterer
Tool deflections of high length-to-diameter ratio endmills are measured with capacitance probes during high-speed milling and compared with the predictions of regenerative chatter theory. Poincar? sectioning (once per revolution sampling) techniques are

Time Domain Modal Estimation

January 1, 1998
Author(s)
S Fahey, Jon R. Pratt
In a previous technical feature,2 we described some motives for performing structural dynamic tests and subsequently reviewed some frequency domain techniques for uncovering modal parameters. This time, we take up some applicable time domain algorithms by