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LLNL/Lion Precision LVDT amplifier

Description: A high-precision, low-noise, LVDT amplifier has been developed which is a significant advancement on the current state of the art in contact displacement measurement. This amplifier offers the dynamic range of a typical LVDT probe but with a resolution that rivals that of non contact displacement measuring systems such as capacitance gauges and laser interferometers. Resolution of 0.1 {mu} in with 100 Hz bandwidth is possible. This level of resolution is over an order of magnitude greater than … more
Date: April 1, 1994
Creator: Hopkins, D. J.
Partner: UNT Libraries Government Documents Department
open access

Methods and Results of Reducing Following Error in the LLNL Large Optics Diamond Turning Machine

Description: The USAF Integrated Flight Experiment (IFX) Project is part of the development of the Space Based Laser (SBL) Program. The LLNL Large Optics Diamond Turning Machine (LODTM) is responsible for diamond turning the aspheric laser cavity mirrors. These large optics must be manufactured to micro-inch tolerances. The optics are made of silicon to minimize cooling requirements and weight in the SBL. Diamond turning silicon presents many challenges to the LODTM; one of which is silicon's anisotropic pr… more
Date: April 10, 2001
Creator: Hopkins, D J
Partner: UNT Libraries Government Documents Department
open access

Defining and Testing the Influence of Servo System Response on Machine Tool Compliance

Description: Compliance can be defined as the measurement of displacement per unit of force applied e.g. nano-meters per Newton (m/N). Compliance is the reciprocal of stiffness. High stiffness means low compliance and visa versa. It is an important factor in machine tool characteristics because it reflects the ability of the machine axis to maintain a desired position as it encounters a force or torque. Static compliance is a measurement made with a constant force applied e.g. the average depth of cut. Dyna… more
Date: March 24, 2004
Creator: Hopkins, D J
Partner: UNT Libraries Government Documents Department
open access

Active Vibration Isolation of an Unbalanced Machine Spindle

Description: Proper configurations of controls, sensors, and metrology technologies have enabled precision turning machines to achieve nanometer positioning. However, at this level of positioning resolution, vibration sources can become a limiting factor. One of the largest sources of vibration in a turning machine may be an unbalanced rotating spindle. In this paper, a system is implemented to actively cancel spindle unbalance forces. Specifically, to attenuate the spindle housing vibration using an active… more
Date: August 13, 2004
Creator: Hopkins, D J & Geraghty, P
Partner: UNT Libraries Government Documents Department
open access

Lawrence Livermore National Laboratory ULTRA-350 Test Bed

Description: LLNL has many in-house designed high precision machine tools. Some of these tools include the Large Optics Diamond Turning Machine (LODTM) [1], Diamond Turning Machine No.3 (DTM-3) and two Precision Engineering Research Lathes (PERL-I and PERL-II). These machines have accuracy in the sub-micron range and in most cases position resolution in the couple of nanometers range. All of these machines are built with similar underlying technologies. The machines use capstan drive technology, laser inter… more
Date: April 10, 2001
Creator: Hopkins, D J; Wulff, T A & Carlisle, K
Partner: UNT Libraries Government Documents Department
open access

Lawrence Livermore National Laboratory ULTRA-350 Test Bed

Description: LLNL has many in-house designed high precision machine tools. Some of these tools include the Large Optics Diamond Turning Machine (LODTM) [1], Diamond Turning Machine No.3 (DTM-3) and two Precision Engineering Research Lathes (PERL-1 and PERL-11). These machines have accuracy in the sub-micron range and in most cases position resolution in the couple of nanometers range. All of these machines are built with similar underlying technologies. The machines use capstan drive technology, laser inter… more
Date: April 10, 2001
Creator: Hopkins, D J; Wulff, T A & Carlisle, K
Partner: UNT Libraries Government Documents Department
open access

A Machine Tool Controller using Cascaded Servo Loops and Multiple Feedback Sensors per Axis

Description: In the past, several of LLNL precision machine tools have been built with custom in-house designed machine tool controllers (CNC). In addition, many of these controllers have reached the end of their maintainable lifetime, limit future machine application enhancements, have poor operator interfaces and are a potential single point of failure for the machine tool. There have been attempts to replace some of these custom controllers with commercial controller products, unfortunately, this has occ… more
Date: March 19, 2004
Creator: Weinert, G F; Hopkins, D J & Wulff, T A
Partner: UNT Libraries Government Documents Department
open access

DEVELOPMENT OF A HYDROSTATIC JOURNAL BEARING WITH SLIT-STEP COMPENSATION

Description: This paper describes the mathematical modeling and initial testing of an oil-hydrostatic bearing that derives compensation from both a central radial slit where fluid enters and stepped clearances near each end. Bearings using either a radial slit or stepped clearances for compensation were well studied over forty years ago by Donaldson. These bearings have smooth bores uninterrupted with multiple recesses around the circumference. The present slit-step bearing achieves the best of both types w… more
Date: July 28, 2006
Creator: Hale, L C; Donaldson, R R; Castro, C; Chung, C A & Hopkins, D J
Partner: UNT Libraries Government Documents Department
open access

Density Changes in Plutonium Observed from Accelerated Aging Using Pu-238 Enrichment

Description: In support of Stockpile Stewardship activities, accelerated aging tests on a plutonium alloy enriched with 7.3 atomic percentage of {sup 238}Pu is underway using dilatometry at 35, 50, and 65 C and immersion density measurements of material stored at 50 C. Changes in density are expected from radiation damage in the lattice and helium in-growth. After twenty-five equivalent years of aging, the dilatometry data shows that the alloys at 35 C have expanded in volume by 0.11% to 0.12% and have star… more
Date: October 19, 2005
Creator: Chung, B. W.; Thompson, S. R.; Woods, C. H.; Hopkins, D. J.; Gourdin, W. H. & Ebbinghaus, B. B.
Partner: UNT Libraries Government Documents Department
open access

Density Changes in Plutonium Observed from Accelerated Aging using Pu-238 Enrichment

Description: Plutonium, because of its radioactive nature, ages from the ''inside out'' by means of self-irradiation damage and thus produces Frankel-type defects (vacancies and self-interstitial atoms) and defect clusters. The self-irradiation damage in Plutonium-239 occurs mainly by {alpha}-particle decay, where most of the damage comes from the U-235 recoil nucleus. The defects resulting from the residual lattice damage and helium in-growth could result in microstructural and physical property changes. B… more
Date: December 19, 2003
Creator: Chung, B. W.; Thompson, S. R.; Woods, C. H.; Hopkins, D. J.; Gourdin, W. H. & Ebbinghaus, B. B.
Partner: UNT Libraries Government Documents Department
open access

Density and Tensile Properties Changed by Aging Plutonium

Description: We present volume, density, and tensile property change observed from both naturally and accelerated aged plutonium alloys. Accelerated alloys are plutonium alloys with a fraction of Pu-238 to accelerate the aging process by approximately 18 times the rate of unaged weapons-grade plutonium. After thirty-five equivalent years of aging on accelerated alloys, the dilatometry shows the samples at 35 C have swelled in volume by 0.12 to 0.14% and now exhibit a near linear volume increase due to heliu… more
Date: March 14, 2005
Creator: Chung, B. W.; Choi, B. W.; Thompson, S. R.; Woods, C. H.; Hopkins, D. J. & Ebbinghaus, B. B.
Partner: UNT Libraries Government Documents Department
open access

Physical Property Changes in Plutonium from Accelerated Aging using Pu-238 Enrichment

Description: We present changes in volume, immersion density, and tensile properties observed from accelerated aged plutonium alloys. Accelerated alloys (or spiked alloys) are plutonium alloys enriched with approximately 7.5 weight percent of the faster-decaying {sup 238}Pu to accelerate the aging process by approximately 17 times the rate of unaged weapons-grade plutonium. After sixty equivalent years of aging on spiked alloys, the dilatometry shows the samples at 35 C have swelled in volume by 0.15 to 0.1… more
Date: December 20, 2006
Creator: Chung, B. W.; Choi, B. W.; Saw, C. K.; Thompson, S. R.; Woods, C. H.; Hopkins, D. J. et al.
Partner: UNT Libraries Government Documents Department
open access

Analysis of Density Changes in Plutonium Observed from Accelerated Aging Using Pu-238 Enrichment

Description: We present dimensional and density changes in an aging plutonium alloy enriched with 7.3 at.% of {sup 238}Pu and reference alloys of various ages. After 45 equivalent years of aging, the enriched alloys at 35 C have swelled in volume by 0.14 to 0.16% and now exhibit a near linear volume increase, without void swelling. Based on X-ray diffraction measurements, the lattice expansion by self-irradiation appears to be the primary cause for dimensional changes during the initial 2-3 years of aging. … more
Date: July 11, 2006
Creator: Chung, B. W.; Saw, C. K.; Thompson, S. R.; Quick, T. M.; Woods, C. H.; Hopkins, D. J. et al.
Partner: UNT Libraries Government Documents Department
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