| Highlights from the Manufacturing |
Engineering Laboratory, May 2010
Effects of Friction on AFM Cantilever Calibration
It has long been recognized that the angular deflection of an atomic force microscope (AFM) cantilever under "normal" loading conditions can be profoundly influenced by the friction between the tip and the surface. In a paper appearing in a recent issue of the Journal of Applied Physics, MEL researchers Jon Pratt and Gordon Shaw teamed with colleagues from the University of Florida and Worcester Polytechnic Institute to accurately model and quantify this effect. The results will not only improve the quantitative testing of micro- and nanomechanical components by leading to more accurate calibration of forces measured using AFM, but also provide nanotribologists access to information about contact friction from normal force curves, yielding a simpler approach to obtaining this information. A key finding of the study was that a remarkably quantifiable hysteresis occurs in the slope of loading curves whenever the normal flexural stiffness of the AFM cantilever is greater than that of the sample. This situation arises naturally in cantilever-on-cantilever calibration, but also when trying to measure the stiffness of nanomechanical devices or test structures, or when probing any type of surface or structure that is much more compliant along the surface normal than in transverse directions. Expressions and techniques for evaluating the coefficient of sliding friction between the cantilever tip and sample from normal force curves, as well as relations for determining the stiffness of a mechanically compliant specimen were presented in the paper and are currently being considered for inclusion in a new ISO standard. The model is experimentally supported by the results of cantilever-on-cantilever spring constant calibrations. The cantilever spring constants determined here agree with the values determined using the NIST electrostatic force balance (EFB) within the limits of the largest uncertainty component, which had a relative value of less than 2.5%. A copy of the full paper Quantitative assessment of sample stiffness and sliding friction from force curves in atomic force microscopy ( J. Appl. Phys. 107, 044305 (2010); doi:10.1063/1.3284957 (6 pages))can be found at http://jap.aip.org/japiau/v107/i4/p044305_s1?view=fulltext
Contact: Jon Pratt, (301) 975-5470
Improved Stability of Magnetic Suspension Technique for Mass Comparisons
MEL researchers in the Mass and Force Group have improved the stability of the magnetic suspension technique that will be used to "connect" a mass artifact in air to a high precision mass balance that is in vacuum to provide a direct comparison between masses in two different pressure environments. This will be important for transferring an "electronic kilogram" realized in vacuum to real-world mass artifacts that are used in air. The stability for suspension (magnetic coupling) of a 1 kg artifact plus its carriage (total of 1.5 kg) has been improved to 1 mg or better in a proof-of-concept system that uses a mass balance that is limited to a resolution of 1 mg. Suspension in this system is sustained using a high quality magnetic flux sensor as a feedback element in a servo loop that measures the suspending magnetic field. To improve the stability of the magnetic suspension, recent experiments have focused on the influence of magnetic pole shape and the vertical position of the magnetic flux sensor in the suspension field. Promising results have been obtained with disk-shaped soft iron poles. Including a 1 kg test mass and its suspension hardware, we have successfully magnetically suspended nearly 3 kg of mass. Suspension stability is very sensitive to the vertical position of the magnetic flux sensor, and we have found that placing the sensor as close as possible to the suspended mass improves the ease of achieving magnetic suspension and the stability of the suspended position at equilibrium. These improvements will be incorporated when the suspension apparatus is interfaced to a high precision mass balance, and the entire experiment is transferred to a large vacuum chamber. The new balance has a resolution of 10 µg, which is sufficient to resolve the experiment's target stability of 20 µg.
Contact: Patrick Abbott, (301) 975-4218
Pashto Translation Systems Tested by NIST for the First Time
In April 2010, NIST held an evaluation to assess the performance of computer-based speech translation systems in support of the Defense Advanced Research Projects Agency (DARPA)-funded TRANSTAC (Spoken Language Communication and Translation System for Tactical Use) program. The goal of the TRANSTAC program is to demonstrate capabilities to rapidly develop and field two-way translation systems that enable speakers of different languages to spontaneously communicate with one another in real-world tactical situations. NIST, funded by DARPA, is the Independent Evaluation Team (IET) for this effort. Unlike previous evaluations, this one was unique in that it focused on a new language (Pashto) and the hardware platforms shifted from laptop-sized units to handheld phone units. NIST assessed the performance of three systems developed by BBN, IBM, and SRI by having Marines and native Pashto speakers use the systems to communicate with one another during mock military scenarios. Twenty-six interactions per system were recorded. Video of these interactions were captured for further analysis and the Marines and Pashto speakers filled out surveys after each scenario and participated in semi-structured interviews with the evaluation team.
Overall, the performance of the systems were quite impressive considering the limited amount of time the research teams had to train their systems and the limited amount of data they received. NIST, as the IET, defined the evaluation procedures in such a way to ensure that they will get a comprehensive view of the capabilities of the systems. A panel of bilingual judges will come to NIST in May 2010 to help the NIST (i.e., the IET team) quantitatively assess the systems' performance.
Contact: Craig Schlenoff 301-975-3456
NIST Represented at Consultative Committee Meetings and Workshop on Redefinition of Kilogram
The Consultative Committee on Mass and related quantities (CCM), its Working Groups on Mass Standards, and the Task Groups on Vacuum Mass Measurements and Uncertainty conducted meetings at the Bureau International des Poids et Mesures (BIPM) in France in March 2010. In addition, the CCM Working Group on the SI (the International System of Units) held a workshop on the redefinition of the kilogram. The discussions focused on the progress and status of the Watt balance experiments and Avogadro project to redefine the kilogram, activities of national metrology institutes on vacuum mass metrology, requirements for a redefinition of the kilogram, and a "mise-en-pratique" or practical realization of the new definition, including a presentation on NIST's air-to-vacuum magnetic levitation mass measurements project, stable mass standards, and practical realization and dissemination of a redefined kilogram. NIST was represented by Zeina Jabbour and Patrick Abbott from the MEL mass metrology technical area and by David Newell from the EEEL Watt balance project.
Contact: Zeina Jabbour, (301) 975-4468
MEL Hosts Digital Depot Technology Demonstration Workshop
MEL and the Department of Defense (DoD) hosted a technology demonstration workshop for DoD maintenance depots at NIST in April 2010. The focus of the workshop was on how government maintenance and production facilities might be able to take advantage of Model Based Enterprise (MBE) technologies in their manufacturing and facilities planning activities. Attendees included representatives from Army, Navy, Air Force, NASA, and the Defense Logistics Agency.
During the course of the technology demonstration, representatives from all three major Computer Aided Design/Product Lifecycle Management (CAD/PLM) software providers demonstrated their functions for manufacturing planning, using an engineering change request scenario developed by the DoD digital depot team. Demonstrators used the Bradley Fighting Vehicle cross drive transmission that was modeled by Red River Army Depot for their Digital Depot project. The demonstrations provided insight on leveraging technology to improve processes.
The test case scenario was intended to demonstrate a typical production scenario that could be planned and managed utilizing production planning software. A demonstration of the ease at which a Manufacturing Bill of Material (MBOM) is created utilizing geometry provided by Design Engineering. Once the MBOM is created, the planner defined processes operations and required resources. From these processes, routings and work instructions were created. Electronic notifications were directed to departments where Numerical Controller (NC) programs and tooling will be needed. Also, an MBOM spreadsheet was automatically outputted that could be transferred to Manufacturing Resource Planning (MRP) systems thus eliminating a manual re-entry process. Once the manufacturing process was demonstrated, demonstrators showed how revision changes are handled. All operations, routings and work instructions, were required to be updated according to the effectivity defined in the scenario.
Among the presentations given, MEL Guest Researcher Deo Kibira gave a presentation on the status of the Discrete-Event Simulation (DES) assessment support project. He introduced the nature and importance of using computer simulation; and explained various application domains, including manufacturing, where simulation modeling has played a major role in improving operations, and the criteria for selecting a particular simulation software. He presented the DES comparison table, which compares sixteen DES software applications, explaining the various elements and contents in the table that were collected and summarized from different sources including software manuals, home pages of the applications of developers, and direct communication with the vendors.
Contact: Simon Frechette, (301) 975-3335
MEL Visits Star Cryoelectronics
STAR Cryoelectronics, in Santa Fe, NM invited MEL researcher Michael T. Postek to visit. STAR Cryoelectronics is developing a microcalorimeter-type x-ray detecting system based upon the NIST invention. Dr. Postek discussed potential contacts within the microscopy community with whom STAR could collaborate to facilitate productization.
Contact: Michael T. Postek (301) 975-2299
MEL Gives Talk at Sandia National Laboratories
Sandia National Laboratories in Albuquerque, NM invited MEL researcher Michael T. Postek present a talk entitled "Three Keys to the Nanotech Kingdom: Instrumentation, Metrology and Standards." Dr. Postek was hosted by Dr. Eleni Kousvelari from The National Institutes of Health who is currently on assignment to Sandia National Laboratories. While there Dr. Postek met with Dr. Glen Kubiak, Director Biological & Material Sciences, Dr. Julia Phillips, Director 1200 Nuclear Weapons S&T Programs, toured the research and production fabs and met with several of the other technical staff.
Contact: Michael T. Postek (301) 975-2299
MEL Gives SME Keynote Presentation
Measurements are critical where all phases of manufacturing are concerned. Size matters, especially for nanomanufacturing. Knowing dimension with a known uncertainty is primary to understanding the function of nanomaterials. MEL researcher Michael T. Postek presented the Keynote talk for the nanomanufacturing section of the 2010 MicroManufacturing Conference & Exhibits held by the Society of Manufacturing Engineers (SME) at the Hilton Phoenix East/Mesa, Mesa AZ. The title of the talk was "Make it Small, Measure it Accurately." This presentation discussed the need for advanced instrumentation, metrology and standards – all of which are critical to the success of the future for micromanufacturing and nanomanufacturing. It also discussed some of the ongoing work in the NIST Manufacturing Engineering Laboratory to meet these needs. The 2010 NanoManufacturing Conference & Exhibits was co-located with the SME 2010 MicroManufacturing Conference & Exhibits. The conference highlighted the current, near-term, and future applications of nanotechnology and how they are transforming the way products are manufactured.
Contact: Michael T. Postek (301) 975-2299