Highlights from the Manufacturing
Engineering Laboratory, October 2004

Impact of NIST Research and Services

NIST Force Calibrations Help Ensure Safety of Nuclear Power Containment Vessels

The NIST Force Metrology Laboratory recently calibrated a secondary standard load cell to 13.345 MN (3 Mlbf) for Precision Surveillance Corporation — a key player in the U.S. nuclear power industry. This NIST customer requires traceable measurements over a range far exceeding even that available in the largest NIST deadweight machine that is capable of generating 4.45 MN (1 Mlbf). U.S. federal codes require that all calibrations for equipment used in the nuclear power industry be performed by approved laboratories that meet special industry standards. Due to the NIST metrology capabilities, staff expertise, and international recognition of measurement performance, NIST force calibrations meet all traceability and competence requirements.

The load cell will be used to calibrate the working field-based hydraulic systems that apply and measure post-tension forces on large steel cable tendons embedded in the concrete shells comprising nuclear reactor containment vessels. The tendons experience creep and relaxation over time. The resultant slack cables may contribute to a dangerous degradation of the ability of the containment structure itself to withstand and protect against the results of possible overpressure situations within the vessel. Periodic re-tensioning of the up to several hundred tendons in each containment vessel is the only solution to this scenario. U.S. vessel codes require the post-tension forces to be known within 1.5% of nominal target forces. NIST enabled the customer to meet that requirement by providing standard forces to 13.345 MN with an uncertainty of less than 0.01%.

Large forces are calibrated at NIST by first calibrating three NIST-owned 4.45 MN secondary standard load cells directly in the NIST 4.45 MN deadweight machine. This method provides the best possible initial uncertainty as a basis for all subsequent uncertainties that are to be derived from the measurements. These three calibrated devices are arranged in parallel and then stacked collectively in series with the transducer to be calibrated. The NIST 53 MN (12 Mlbf) hydraulic universal testing machine (UTM) applies the nominal desired forces to the entire stack. All applied forces pass simultaneously through the NIST standard load cells and the transducer under test thus enabling a direct transfer of measurements from the NIST standards to the other transducer. Uncertainty propagation is managed in compliance with ISO guidelines as outlined in the NIST Division 822 Quality Manual for Mechanical Measurement Services.

U.S. federal regulations require that nuclear power plants are to be periodically shut down and inspected for a wide variety of conditions, typically on a five-year inspection cycle. Inspection and post-tensioning of the containment vessel tendons is a critical, necessary step. For this customer, the quality and timeliness of the measurements were crucial. Without the ability to deliver NIST-traceable measurements to the field site via a calibrated system within extremely tight deadlines, this company was facing extended and costly downtime (i.e., no electrical power generation capability) for a group of power plants that are currently undergoing inspection. NIST force calibrations met the full requirements of the industry demand by providing accredited calibration service at high force capacity coupled with the prescribed uncertainty.

Contact: Rick Seifarth, 301 975 6652

Programmatic/Technical Accomplishments

ISO Standard on Axes of Rotation Passes Final Technical Hurdle

Alkan Donmez, a MEL researcher, served as technical expert and member of the three-person U.S. delegation to the meeting of the ISO Technical Committee 39 (TC39, Machine Tools) and as Secretariat of the corresponding Subcommittee 2 (TC39/SC2, Test Conditions for Metal Cutting Machine Tools) during the week of October 18, 2004. The meeting included a thorough review of the ballot comments for the draft ISO/DIS 230-7.2 standard on "Geometric accuracy of axes of rotation." Alkan prepared and presented proposed modifications to the standard in response to ballot comments. After extensive review of this revised document, the committee reached consensus to approve the standard to proceed to Final Draft International Standard (FDIS) stage. This decision cleared all technical hurdles to the first-ever performance-based ISO standard on geometric accuracy of axes of rotation. This achievement is significant in that U.S. industry needs and methods are now accommodated and the international standard is now in alignment with the U.S. national standard. NIST has a long-term record of scientific contributions and standards development in this area through the ANSI committees B89 (Inspection Equipment) and B5 (Machine Tools). The U.S. standards community has long advocated a science-based approach to machine performance evaluation through recognition of appropriate error sources and analysis of how these errors impact machine performance and the quality of the resulting measurement or workpiece. Based on the U.S. national standards and relevant research and technical papers from the International Institution for Production Engineering Research (CIRP), Alkan developed and brought forward to ISO TC39/SC2 the initial working draft of ISO/WD 230-7 in 2001. Since then he has actively promoted the acceptance of the draft by providing technical arguments and necessary modifications to satisfy international concerns. The publication of the International Standard ISO 230-7 is expected within the next six months.

Contact: Alkan Donmez, 301 975 6618

ISO Standard Published on Time Domain Windows for Fourier Transform Analysis of Mechanical Vibration and Shock Measurements

ISO 18431-2 "Mechanical vibration and shock–Signal processing–Part 2: Time domain windows for Fourier Transform analysis" was published by ISO. This document was produced by ISO Technical Committee (TC) 108 Working Group 26, which is convened by MEL researcher Dave Evans. The standard specifies the algebraic functions that describe a selected set of time domain windows commonly used for preprocessing digitally sampled vibration and shock data as a precursor to Discrete Fourier Transform (usually Fast Fourier Transform or FFT) spectral analysis. Vibration and shock data can consist of displacement, velocity, or acceleration measurements, which can be either stationary or non-stationary with respect to time. For both classes of signals, spectral decomposition by Discrete Fourier Transform is one of the analysis tools used in structural testing and modal analysis in the aerospace and automotive industries, in the prognosis and diagnostics of the condition of machinery, and in the calibration of transducers. The standard is a first step toward ensuring the equivalence of measurement results obtained using different FFT analyzers by uniquely defining the algebraic functions, and therefore the figures of merit, associated with a particular set of time domain windows.

Contact: Dave Evans, 301 975 6637

Competence Project Funded for Joint Research in High Resolution Optics

A NIST competence project championed by MEL to advance optical microscopy to unprecedented levels of performance through theoretical and experimental development of a new technique called "scatterfield optical imaging" was selected for funding. This new optical methodology promises to make possible optical measurements of nanometer-sized features using high-throughput, low cost optical methods with the potential for an enormous impact on innovation and quality control in semiconductor manufacturing and nanotechnology as well as providing the measurement basis for new calibration standards well beyond the state-of-the-art. The feasibility of the basic approach, which uses structured illumination, high-resolution Charge-Coupled Device (CCD)-array processing, engineered target designs, detailed theoretical modeling of electromagnetic scattering, and phase-sensitive data analysis, has been demonstrated. Significant interest in the proposed technique by elements of the semiconductor industry and evolving nanomanufacturing industry suggests applications of this new measurement science and technology could have a major impact on manufacturing quality, process control, and throughput.

Contact: Richard Silver, 301 975 5609

Interactions

Explosive Ordnance Disposal (EOD) Robots are Tested at the NIST Arenas

The NIST test arenas at the NIKE site are being upgraded to support several explosive ordnance (EOD) specific tasks. On October 21 — 22, 2004, MEL staff supported ITL's human-robot interaction (HRI) testing efforts of EOD robots at the NIKE site grounds and within the NIST Arenas. Two robot operators of the Naval Surface Warfare Center's Indianhead-based EOD group brought two iRobot Packbot EOD models for two days of tests designed by MEL and ITL personnel. The NIST Arenas, using the new highly modular and flexible "stacking racks", were extended to accommodate the initial EOD tasks, which included grasping/lifting common objects, opening doors with various knobs/latches, navigating/turning around in tight spaces, ascending ramps of varying angles, climbing stairs, traveling over logs of various diameters, and searching for a package around a vehicle. The operators and robot interfaces were timed, videotaped, and interviewed while they performed tasks so that successes and shortcomings may be quantified and analyzed to improve real EOD operations. This initial round of testing was very productive, well-received, and will pave the way for future EOD robot testing.

Contact: Brian A. Weiss, 301 975 4373

Recognition

Silver Medal Awarded for Two-dimensional Grid calibration and collaboration

A DOC Silver medal was awarded for two-dimensional grid calibration artifacts and the collaborations that resulted from the fabrication and certification. A new photomask standard, calibrated in a unique industry/NIST collaboration, was delivered to Standards Reference Materials (SRM) Office. The new SRM 5001, a two-dimensional grid photomask standard was delivered to the SRM office with complete uncertainty analysis with world class leading uncertainty. This represents the first time this new standard 6 inch photomask has been delivered to the SRM office and has been available for registration metrology. This SRM will provide a traceable standard for the calibration of photomask positioning metrology tools as well as tools which require accurate placement of a wafer within the field of view. Lithography stepper tools will also benefit from this new standard which has been needed for quite some time. A key aspect of this calibration process was the collaboration of NIST and Photoronics (a photomask manufacturer) using a leading edge industry metrology tool that was effectively calibrated through a sampling strategy with the NIST Linescale Interferometer. This very important aspect of the calibrations process allowed NIST researchers to apply their advanced algorithms to data taken on a several million dollar leading edge measurement tool whose capability is well beyond any large scale two-dimensional measurement apparatus at NIST. The patterns were designed in a NIST collaboration with the SEMI 2-dimensional grids task force comprised of several leading semiconductor manufacturers. The statistical methods were developed jointly between MEL researchers and the ITL Statistical Engineering Division.

Contact: Richard Silver, 301 975 5609