October 2006 Issue

  October 2006
Journal of the IEST

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The October issue of the Journal of the IEST offers technical papers as well as complimentary Tech Talk articles. Subjects include nanotechnology, investigating the rigidity of a military vehicle body, vibration concerns in the planning and design of a science and technology park, the use of ultrasonic cavitation in surface cleaning, aircraft passenger cabin ECS-generated ventilation velocity CFD simulation and velocity field validation, environmental chamber temperature calibration issues, and more.

The following three Tech Talk articles in the October 2006 issue of the Journal of the IEST are accessible free of charge (access Journal of the IEST).

ISO to Revise Two Cleanroom Standards
A Journal of the IEST article

The International Organization for Standardization (ISO) is reviewing airborne particulate classification factors, sampling requirements, and other clauses as it targets 2008 publication of new editions of ISO Standards 14644-1: Cleanrooms and associated controlled environments — Part 1: Classification of air cleanliness and 14644-2: Cleanrooms and associated controlled environments — Part 2: Specifications for testing and monitoring to prove continued compliance with ISO 14644-1.

IEST Focuses on Facilities in Nanotechnology Initiative
A Journal of the IEST interview with David Ensor

As interest grows in the design, construction, and operation of nanofacilities for R&D and manufacturing, a newly formed IEST Working Group addresses the question: What does it take to do nanotech work?

Environmental Chamber Temperature Calibration: Which Method to Use?
David C. Gibbons, Agilent Technologies, Santa Rosa, California

Calibration of environmental simulation temperature test chambers is anything but simple. This article explores factors that complicate attempts to calibrate these machines, and discusses strengths and weaknesses of various calibration approaches.

The October 2006 issue 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 a 21-year 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).

Investigating Rigidity of Military Vehicle Body Using Operating Deflection Shape (ODS) Analysis
Mark S. Bounds and George O. White, U.S. Army Materiel Systems Analysis Activity

The Army has many rigid-body dynamic models of various vehicle platforms. The adequacy of these rigid-body models has been questioned. In an effort to gain insight into the significance of flexibility in the development of dynamic vehicle models, operating deflection shape (ODS) techniques were applied to acceleration data gathered from the body of a wheeled military vehicle. The data were analyzed in an effort to determine a specific frequency range over which the assumption of rigidity would be valid. For the particular platform examined in this study, the assumption of rigidity would apply up to approximately 14 Hz. Future efforts include using operational modal analysis (OMA) to further examine the problem.

Vibration Case Study: Master Planning and Design of a Science and Technology Park
Christopher Papadimos, Consultant

Science and technology parks have become increasingly popular over the past few years in attracting research groups from diverse backgrounds, providing for opportunities for cross-pollination of various research disciplines, and acting as a favorable platform in limiting the risk and initial costs of start-up or incubator companies. During a recent engagement for site master planning and designing of a state-of-the-art research and technology park, the staff needed to overcome numerous challenges to provide for a vibration environment that would be acceptable for the range of anticipated research activities in the park and within each building while making provisions for future flexibility and phases of expansion.

This paper presents (1) some of the constraints of the selected site, such as existing soil conditions and vibration exposure due to existing transportation facilities, that were documented by extensive site testing; (2) how vibration exposure maps developed for the site were used to aid in the proper master planning of the park; (3) other site planning efforts that were required to ensure new transportation facilities serving the park and parking facilities within research buildings were appropriately placed, and the limitations for such facilities; and (4) how research space layouts were developed, vibration criteria were selected, and building designs were developed to address anticipated research uses while making provisions for future flexibility.

Use of Ultrasonic Cavitation in Surface Cleaning: A Mathematical Model to Relate Cleaning Efficiency and Surface Erosion Rate
Ramamurthy Nagarajan, PhD, Indian Institute of Technology Madras, Chennai, India

Ultrasonic cleaning, employing frequencies in the range of 40–200 kHz, is widely used in many industries requiring precision cleanliness in the micrometer to submicron particle size range—e.g., semiconductor wafer fabrication, hard disk drive manufacturing, and integrated circuit assembly. One overriding concern with the use of ultrasonic cleaning for delicate components and assemblies has been the specter of cavitation erosion—surface material loss and other functional degradation due to the impact of shock waves generated by collapsing bubbles and bubble clusters in an oscillating acoustic field. The simultaneous processes of surface cleaning and surface erosion in the presence of a high-frequency ultrasonic field (>/= 58 kHz) are described here mathematically, and the equations are coupled to allow conceptual optimization of parametric settings to maximize cleaning efficiency while minimizing the level of erosion damage. This theoretical analysis is presented for various ultrasonic field conditions (frequency, intensity, etc.), fluid medium properties (viscosity, density), and surface conditions (hardness, smoothness, etc.). The contribution of acoustic streaming to surface cleaning is incorporated in the model, and is shown to have minimal influence on the optimum cluster collapse pressure, but to have a significant effect on the net cleaning efficiency for the surface.

Aircraft Passenger Cabin ECS-Generated Ventilation Velocity and Mass Transport CFD Simulation: I. Velocity Field Validation
A. J. Baker, S. C. Ericson, J. A. Orzechowski, and K. L. Wong, University of Tennessee; R. P. Garner, Federal Aviation Administration

A collaborative research project, established between the University of Tennessee (UT) computational fluid dynamics (CFD) Lab and the Federal Aviation Administration (FAA) Civil Aerospace Medical Institute (CAMI), sought to validate CFD prediction of the environmental control system (ECS)-generated ventilation velocity vector flow field of a wide-body aircraft passenger cabin. Measurements generating the experimental database of the time-dependent, three-dimensional velocity vector field were conducted in the CAMI Aircraft Environmental Research Facility (AERF) and in an identical wide-body aircraft in cruise flight at altitude. The CFD simulations were conducted on the CFD Lab resident PC cluster using both commercial and proprietary CFD computer codes. The results of this velocity field validation study reported herein quantitatively assess CFD algorithm/code strengths and weaknesses, and fully confirm the dominance of unsteadiness in the aircraft ventilation velocity field. To be reported in a separate paper are the results of an add-on FAA Cooperative Research and Development Agreement (CRADA) project, which generated a mass transport validation component for a gaseous release into this ECS-generated velocity field.

Automated Sorting of Mixed Mode Environment’s Data
Nathan Roberts, Structural Dynamics Engineering; Jerry Cap, Structural Mechanics Engineering; Sandia National Laboratories

This paper is a peer-reviewed, technically edited, and updated revision of a paper originally presented in the 22nd Aerospace Testing Seminar Proceedings. Transportation of sensitive flight hardware requires information about the expected transportation environment as well as the actual transportation environment during the part’s movement—typically vibration with superimposed intermittent shocks. Each data type has different sampling, processing, and specification requirements. Analyzing shock data requires high sampling rates and leads to large file sizes.

A barrier to analyzing data has been the vast quantity of information acquired. Previous approaches have focused either on manually separating data or on selectively recording extreme data. The use of an automated approach allows for quickly verifying vibration and shock levels while retaining the robustness of the underlying data set. Further, the automated approach allows the environments engineer to select criteria for shock/vibration sorting, which removes the subjectivity associated with visual differentiation. This automated technique evaluated several vehicles over four different road conditions in the same time that one data set could have been processed using visual discrimination. Automated processing of satellite shipment vibration and shock data is made thoroughly and objectively vs. traditional shock and tilt indicators. The automated technique could also be useful in processing large amounts of on-orbit data for changes in vibration signature.

Design of a Zero-Failure Reliability Test Plan Based on Customer Usage and Bench Life Test Data
Jianxiong Chen, PhD, and Wenzhen Yan, Emerson Climate Technologies

This paper is a peer-reviewed, technically edited, and updated revision of a paper originally presented in the Annual Reliability and Maintainability Symposium 2005 Proceedings. Reliability tests are mandatory to evaluate new products prior to their release. The proper determination of a reliability test plan is crucial because an erroneous test plan can be very costly and misleading. This paper describes a probability-based method of designing a reliability demonstration test plan using both field customer usage and historical bench life test data. Statistical distribution analysis, Monte Carlo simulation (MCS) technique, and zero-failure test method are integrated into the probability-based method to create test plans that can more accurately evaluate product reliabilities for the required product service life using a small number of test samples.

Experimental Modal Analysis: Efficient Geometry Model Creation Using Optical Techniques
Steven Pauwels, Jan Debille, Jeff Komrower, and Jenny Lau, LMS International

This paper is a peer-reviewed, technically edited, and updated revision of a paper originally presented in the 2004 Proceedings of the 75th Shock & Vibration Symposium. Experimental modal analysis (EMA) is widely used to characterize the dynamic properties of structures. Recently EMA is being used on more complex structures often involving hundreds of measurement points. Modal analysis results are frequently used in combination with numerical models, imposing higher standards on the quality of the modal parameter estimation and the accuracy of the geometry models. These requirements are often contradictory to the availability of test cells and prototypes. In order to solve this challenge, innovative solutions using optical techniques have been developed that simplify and accelerate the creation of a geometrical model of a test object, while at the same time increase the accuracy of measured coordinates. Industrial applicability of these techniques is proven by a number of benchmarks on real-life structures.

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