August 2005 Issue

  2005 Online
Journal of the IEST

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The following peer-reviewed technical papers and Tech Talk articles are available in the 2005 online Journal of the IEST:

Four Tech Talk articles are accessible free of charge (access Journal of the IEST). Tech Talk provides a medium for industry professionals to share ideas about trends, new methods, and cost-saving techniques. Tech Talk articles are not peer-reviewed, but are selected for general interest and timeliness.

Advancements in Nanotechnology Open Opportunities for Environmental Sciences
Clifford (Bud) Frith

Nanotechnology are the new buzzwords for the next generation of research, development, engineering, operations, marketing, and distribution. How will this new frontier affect the environmental sciences? This article explores the potential challenges and opportunities.

Treatise Helps Users Interpret and Apply MIL-STD-810—A Test Method Standard
A Journal of the IEST interview with Herb Egbert, TRI-S Inc., author of The History and Rationale of MIL-STD-810

Touted for its visionary treatment of environmental tailoring in test procedures, MIL-STD-810F, Test Method Standard for Environmental Engineering Considerations and Laboratory Tests, is undergoing revision for the next issue. This article discusses how this standard evolved from a 66-page booklet with a single sentence on using realistic test limits to a 540-page document containing an entire section on tailoring.

How Low Can You Go?
David C. Gibbons, Agilent Technologies

The target was a very low random vibration level of 0.001 gRMS. This article describes how the challenge was met by developing a simple, "back of the envelope" test system based on commonly available vibration control technology.

Converting Semiconductor Fabs: The Vibration Design Perspective
Ahmad Bayat and Jon Byron Davis, Vibro-Acoustic Consultants

As silicon chip manufacturing technologies advance to submicrometer and nanometer scales, many high-tech facilities must retool their processes. This article discusses the vibration upgrade aspect of converting an old fab to a new fab.

The 2005 issue of the Journal of the IEST also contains peer-reviewed technical papers related to the fields of contamination control; design, test, and evaluation; and product reliability. IEST members and Journal of the IEST subscribers have full access to technical papers in the current issue as well as an archive of papers and articles. Others may obtain full-text abstracts of peer-reviewed technical papers and have the option to purchase individual papers (access Journal of the IEST).

Prediction of Vibration in Bandtrack Driven Military Vehicles
Michael K. McCullough and Darren Simoni, United Defense, LP, Inc.

Analytical methods for predicting the vibration levels in bandtrack-driven military tracked vehicles are described, contrasted, and compared. These methods range from parametric models superimposed upon existing dynamic simulation models to first principle models developed from direct measurement of suspension and bandtrack geometric physical properties. The first principle models are implemented in a multibody dynamics computer code for mechanical system simulation and used for predicting vibration, track retention, and rolling resistance.

A Novel Approach to the Dynamic Balancing of Spun/De-Spun Spacecraft
John A. Montgomery and Robert W. Haynes,, US Naval Research Laboratory, Naval Center for Space Technology

This paper is a peer-reviewed, technically edited, and updated revision of a paper originally presented in the Proceedings of the 21st Aerospace Testing Seminar. In response to challenges encountered in the dynamic balancing of the Windsat instrument, a novel approach to dynamic balancing of dual-spin spacecraft was developed. The Windsat instrument is a 675-lb microwave radiometer consisting of a small, 200-lb stationary module topped by a large rotating truss structure approximately 9 feet in height. A 72-in.-diameter reflector atop the truss, designed to direct microwave energy into the Windsat radiometer, was a significant source of aerodynamic lift and drag during spin balance testing. The approach developed in this study allows the spacecraft integrator to balance the vehicle while spinning under its own power and about its own spin axis. This balancing system is also capable of operating in a vacuum environment, thus eliminating aerodynamic forces that result in test-induced errors. The balancing system consists of a two degree of freedom (DOF) suspension system similar to that found in conventional balancing machines. Unbalance forces and moments are reacted through two piezo-electric force transducers, the outputs of which are recorded using a vibration lab data acquisition system. To prove viability, a prototype of this system has been developed and integrated into existing Naval Research Laboratory (NRL) spacecraft vibration test facilities. Using existing instrumentation and data acquisition systems, extensive experimentation with this system prototype has demonstrated this concept to be viable, yielding results that agree closely with analytical predictions.

Surface Deposition of Diethyl Phthalate on SiO2 and Si3N4 Wafers in Simulated Cleanroom Environment
Yuhao Kang, National Chiao-Tung University, Republic of China; Walter Den, Tunghai University, Republic of China; Hsunling Bai, National Chiao-Tung University, Republic of China; Fu-Hsiang Ko, National Nano Device Laboratory, Republic of China

The surface deposition kinetics of airborne diethyl phthalate (DEP), a representative compound for high-boiling-point organic contaminants in cleanroom environments, were investigated in this study. Between the two types of wafer surfaces evaluated, wafer surfaces with oxide (SiO2) and wafer surfaces with nitride (Si3N4), DEP exhibited a stronger propensity to adsorb on the SiO2 wafers, presumably due to the greater dipole moment between DEP and SiO2 surfaces. Under well-controlled exposure conditions, the rate parameters of a theoretical surface kinetic model were determined by employing a heuristic algorithm for numerical optimization to match the experimental profile. Subsequently, a series of time-dependent surface DEP concentrations were simulated and validated with the experimental data under various ambient concentrations. Estimation of the allowable wafer exposure durations and the maximum ambient concentrations were exemplified based on the guideline recommended by the International Technology Roadmap for Semiconductors (ITRS).

A Process for Estimating Component Life in Support of Reliability Predictions for Present and Future Military Combat Vehicles
William E. De Porter, United Defense L.P.

The manufacture of future military combat vehicles faces a number of challenges. One of those challenges is to balance producibility, reliability, and weight. An additional challenge is the military's frequent need to extend the life of its current combat vehicles. Imperfections resulting from the manufacturing process may contribute to both of these challenges by shortening the fatigue life of the vehicle structure or components. Use of an assessment fatigue process can help meet these manufacturing challenges. Established technologies can extract past life events and anticipated extended life events. These combined life events can then be compared to the vehicle life boundaries. The results can be used to extend combat vehicle life or to pursue new challenges such as improved weight balance.

Response of Large Membrane Optical Surfaces to Acoustic Environment
Gordon L. Maahs, HYTEC, Inc.; Jason A. Tolomeo, Lockheed Martin Advanced Technology Center

Acoustic launch vibration is often the critical source of vibration for space telescopes. The large surfaces of membrane optics act as receivers of acoustic energy and can experience significant stresses on launch and significant displacements during laboratory testing. Using the finite element software MSC.NASTRAN, several membrane reflector geometries were analyzed under applied axial tension to the membrane surfaces. The pressure field was applied with a sin (kx)/(kx) spatial correlation. Stress and displacements were found at selected points on the membrane surface. Recommendations regarding membrane launch and laboratory testing states are presented in this paper.

Autonomous Environmental Definition of C-130 Flap Well Skin Panel
David Banaszak, Dansen L. Brown, and David J. Laird, Air Force Research Laboratory (AFRL)

Air Force C-130 aircraft require numerous aluminum doubler repairs on the wing flap skin aft of the right-hand outboard engine. These repairs are costly and require riveting. Rivets often provide new areas of stress concentration, which causes new cracks to develop elsewhere. Boeing and the Air Force Research Laboratory (AFRL) are measuring the thermal and strain environment behind the right-hand outboard engine of a North Carolina Air National Guard (NCANG) operational C-130 aircraft (TN 93-1456) for use in design of a damped repair patch to prevent the growth of cracks in skin under the wing flap panel. During June 2003, AFRL engineers and technicians acquired data using an autonomous damage dosimeter during five operational C-130 flights. The damage dosimeter measures structural strains and temperatures on in-service aircraft to diagnose structural conditions that are difficult to analyze, such as acoustics and high cycle fatigue (HCF). The first flight was from Charlotte, North Carolina to Warner Robins Air Force Base (AFB), Georgia and returned to Charlotte. The last four flights were assault flights where the C-130 simulated cargo drops. Pilots logged the altitude and indicated airspeed, engine speed, and flap positions for the first four flights. Flap position settings were compared with dosimeter temperature and root mean square (rms) strain measurements. This paper presents typical third octave plots showing engine speed vibratory frequencies, rms time histories (TH), and correlation data for a flight. This paper also presents typical limited data in TH, probability density function (PDF), power spectral density (PSD), and rain flow formats.

Practical Assessment of Electronic Circuit Cards Under Mechanical Shock Loading
Thomas J. Stadterman, US Army Materiel Systems Analysis Activity; and Donald B. Barker, University of Maryland

This paper presents a practical approach for assessing electronic circuit cards for mechanical shock loading. The approach is comprised of three areas: determining board response, assessing damage to the printed wiring boards, and assessing damage to the components. Determining the board response to the shock loading provides the basis for the damage assessments. To determine board response, the approach recommends specific structures to model and finite element analysis (FEA) methods to use. Failure models for circuit board and component failures are provided in terms of failure risk. To demonstrate this practical assessment approach, an example of a US Army circuit card from a computer assembly mounted on a tracked vehicle is provided. This practical assessment approach will allow electronic circuit card designers to quickly evaluate circuit cards with minimal testing and FEA. It also provides information necessary for circuit card redesign to improve failure risk for shock loading.

A Design for Combining Biological and Semiconductor Cleanrooms for Nanotechnology Research
John R. Weaver, Birck Nanotechnology Center at Purdue University (courtesy of Delphi Corporation)

Nanotechnology brings together various functional areas for interdisciplinary research, making it necessary for them to reside in a single facility. The conjoining of biology, biomedical engineering, and bio-nano-micro-electro-mechanical systems (MEMS) with semiconductor and MEMS processing requires that these technologies coexist in ultraclean facilities, while the facility designs and operating practices are incompatible. This case study describes a design concept in a collaborative research environment that meets biocleanliness goals and International Organization for Standardization (ISO) Class 4 particle concentrations (as defined in ISO 14644-1, Cleanrooms and associated controlled environments – Part 1: Classification of air cleanliness).

Maturation of the Vibration Environment in Advanced Technology Facilities
Michael Gendreau and Hal Amick, Colin Gordon & Associates

Semiconductor production and other advanced technology facilities are often designed in two states, the "base-build" state and the "hook-up" state. The base-build state, which after completion is termed "as-built" by the International Organization for Standardization (ISO) 14644-1, includes the design and construction of the shell structure and all architectural, mechanical, electrical, and process systems needed for building operation. The hook-up state includes the installation of the production tools and their local support equipment (dry pumps, piping attachments, etc.). During the project design, cleanroom environment vibration and noise requirements are often assigned for compliance in the as-built state only (before tool hook up), since often a different design team or construction team or both is involved in the hook-up state and the base-build design team has little control of operational vibration and noise levels. This paper discusses typical changes, or maturation, in the production vibration environment after the as-built state. In these mature states, identified by ISO as "at rest" and "operational," there is usually an increase in environmental vibration and noise levels with the addition of tools and tool support equipment. This paper also discusses the role of maturation in building mechanical equipment as well as the means of controlling the increase in vibration.

Modal Testing and Finite Element Analysis of a Battery Rack for Seismic Applications
Elzbieta G. Berak, Marconi Communications

One of the most challenging aspects of reliability testing in the telecommunication industry is earthquake resistance testing. Cabinet systems, battery racks, equipment racks, and distribution frames are considered compliant with Network Equipment-Building System (NEBS) criteria for surviving earthquake conditions if test results indicate (1) the maximum deflection of the top of the structure does not exceed 7.6 cm (3 in.), (2) there are no permanent deformations or structural damage, and (3) the equipment or batteries remain functional (as defined in NEBS Requirements: Physical Protection, Specification GR-73 Issue 2). Based on seismic test results of a large population of telecom enclosures, it is accepted that a system always passes the seismic test if its fundamental natural frequency is at least 6 Hz. It is costly to produce and configure enclosures and conduct seismic qualification testing. To minimize the risk of telecom system failure, a modal finite element analysis (FEA) of the system should first be performed. Numerical results of the FEA should then be verified with experimental resonance search data generated by modal testing or sine sweep testing, combined with static pull testing where applicable. The resonance search results will determine the need for seismic testing (seismic analysis) prior to seismic qualification testing. This paper elaborates on key aspects of the static pull test method supported by the test results for a cabinet framework and a configured cabinet relative to the seismic test results. The paper also discusses sine sweep testing of a battery cabinet and results of two modal test methods used on the corresponding battery rack. Finally, this paper describes modal FEA of the same battery rack anchored to a concrete pad supported by a polystyrene plastic foam sheet and explains the correlation of the numerical results with the experimental modal analysis results. The correlated model serves as the baseline model for analyzing other battery racks and equipment cabinets configured with batteries.

Standard Accelerated Life Testing Model Applied to Mechanical Components
O. Tebbi, F. Guérin, and B. Dumon, LASQUO: Laboratoire en Sûreté de fonctionnement, Qualité et Organisation, Institut des Sciences et Techniques de l‘Ingénieur d'Angers

This paper is a peer-reviewed, technically edited, and updated revision of a paper originally presented in the Annual Reliability and Maintainability Symposium 2003 Proceedings. This paper provides an overview of the application of accelerated life testing (ALT) models to mechanical components. Estimates are based upon a classical test plan using a sample system tested under accelerated conditions (not under operating conditions). The time transfer regression model is considered log-linear. The parametric model, proportional hazards (PH) model, and semiparametric model are studied. This paper illustrates an experimental example on a paper clip.

Mars Exploration Rover (MER) Airbag Retraction Actuator (ARA) Pyroshock Test Results
Kurng Y. Chang, Jet Propulsion Laboratory, California Institute of Technology

This paper presents the shock test results achieved in the Mars Exploration Rover (MER) airbag retraction actuator (ARA)/brush motor pyroshock qualification. The results of MER flight system pyrofiring tests are compared with ARA shock test requirements. Alternate test methods were developed in an effort to qualify critical MER equipment for adequate performance under actual flight pyroshock conditions. Simulated pyroshock qualification tests were conducted using shakers, mechanical impacts, and explosive charges for excitation. Comparisons of excitation and responses of an ARA subjected to different shock tests are presented.

Application of a Real-time Process Simulator to PLC Programming for a Satellite Thermal Vacuum Chamber
Younggy Shin, Sejong University, Korea; Seok-Weon Choi, Guee-Won Moon, Hee-Jun Seo, Sang-Hoon Lee, and Hyokjin Cho, Korea Aerospace Research Institute

A thermal vacuum chamber is used to simulate thermal environments of a test satellite in orbits where daily temperature variations range from 80 K to above 400 K. The test facility is complex and consists of expensive parts. Modification of control software is discouraged as the modification may cause unexpected system failure. This paper describes a study that develops a real-time dynamics model of the thermal vacuum chamber that can be used to create control algorithms and simulate electrical inputs and outputs for interface with a programmable logic controller (PLC). The dynamics model is represented by simulation software and exported to a target PC in the Microsoft® Disk Operating System (DOS) mode to exploit the real-time kernel of the DOS software. The model is executed in real-time and communicates with a microprocessor-based input/output (I/O) board via a serial port to emulate electrical inputs and outputs.

The target process to model is the gaseous nitrogen (GN2) mode in which GN2 circulates in a closed loop through thermal shrouds encompassing a test object. A blower boosts the GN2. Injected liquid nitrogen (LN2) and an electric heater control the set temperature of the GN2. The realized simulator dynamics are quite similar to those of the thermal vacuum chamber and serve as an appropriate system to verify the control performance of a programmed PLC.

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