461 Matching Results

Search Results

Advanced search parameters have been applied.

Failure analysis: Status and future trends

Description: Failure analysis is a critical element in the integrated circuit manufacturing industry. This paper reviews the changing role of failure analysis and describes major techniques employed in the industry today. Several advanced failure analysis techniques that meet the challenges imposed by advancements in integrated circuit technology are described and their applications are discussed. Future trends in failure analysis needed to keep pace with the continuing advancements in integrated circuit technology are anticipated.
Date: February 1, 1995
Creator: Anderson, R. E.; Soden, J. M. & Henderson, C. L.
Partner: UNT Libraries Government Documents Department

Less than severe worst case accidents

Description: Many systems can provide tremendous benefit if operating correctly, produce only an inconvenience if they fail to operate, but have extreme consequences if they are only partially disabled such that they operate erratically or prematurely. In order to assure safety, systems are often tested against the most severe environments and accidents that are considered possible to ensure either safe operation or safe failure. However, it is often the less severe environments which result in the ``worst case accident`` since these are the conditions in which part of the system may be exposed or rendered unpredictable prior to total system failure. Some examples of less severe mechanical, thermal, and electrical environments which may actually be worst case are described as cautions for others in industries with high consequence operations or products.
Date: August 1, 1996
Creator: Sanders, G.A.
Partner: UNT Libraries Government Documents Department

Damage measurements on the NWTC direct-drive, variable-speed test bed

Description: The NWTC (National Wind Technology Center) Variable-Speed Test Bed turbine is a three-bladed, 10-meter, downwind machine that can be run in either fixed-speed or variable-speed mode. In the variable-speed mode, the generator torque is regulated, using a discrete-stepped load bank to maximize the turbine`s power coefficient. At rated power, a second control loop that uses blade pitch to maintain rotor speed essentially as before, i.e., using the load bank to maintain either generator power or (optionally) generator torque. In this paper, the authors will use this turbine to study the effect of variable-speed operation on blade damage. Using time-series data obtained from blade flap and edge strain gauges, the load spectrum for the turbine is developed using rainflow counting techniques. Miner`s rule is then used to determine the damage rates for variable-speed and fixed-speed operation. The results illustrate that the controller algorithm used with this turbine introduces relatively large load cycles into the blade that significantly reduce its service lifetime, while power production is only marginally increased.
Date: December 31, 1998
Creator: Sutherland, H.J. & Carlin, P.W.
Partner: UNT Libraries Government Documents Department

Application of measured loads to wind turbine fatigue and reliability analysis

Description: Cyclic loadings produce progressive damage that can ultimately result in wind turbine structural failure. There are many issues that must be dealt with in turning load measurements into estimates of component fatigue life. This paper deals with how the measured loads can be analyzed and processed to meet the needs of both fatigue life calculations and reliability estimates. It is recommended that moments of the distribution of rainflow-range load amplitudes be calculated and used to characterize the fatigue loading. These moments reflect successively more detailed physical characteristics of the loading (mean, spread, tail behavior). Moments can be calculated from data samples and functional forms can be fitted to wind conditions, such as wind speed and turbulence intensity, with standard recession techniques. Distributions of load amplitudes that accurately reflect the damaging potential of the loadings can be estimated from the moments at any, wind condition of interest. Fatigue life can then be calculated from the estimated load distributions, and the overall, long-term, or design spectrum can be generated for any particular wind-speed distribution. Characterizing the uncertainty in the distribution of cyclic loads is facilitated by using a small set of descriptive statistics for which uncertainties can be estimated. The effects of loading parameter uncertainty can then be transferred to the fatigue life estimate and compared with other uncertainties, such as material durability.
Date: January 1, 1997
Creator: Veers, P.S. & Winterstein, S.R.
Partner: UNT Libraries Government Documents Department

Evaluation of Demo 1C composite flywheel rotor burst test and containment design

Description: Laboratory-Directed funds were provided in FY 1995 for research to develop flywheel containment specifications and to consider concepts that could satisfy these specifications and produce a prototype small, lightweight, inexpensive, mobile flywheel containment. Research activities have included an analytical and pictorial review of the Demo 1C flywheel failure test, which provided significant insight about radial and axial failure modes; calculations of the thickness of ultra-conservative pressure vessel containment; entertainment of advanced containment concepts using lightweight materials and armor literature; consideration of fabrication assembly procedures; and participation in a Flywheel Energy Storage Workshop during which additional flywheel failure experiences were discussed. Based on these activities, calculations, and results, a list of conclusions concerning flywheel containment and its relation to the flywheel are presented followed by recommendations for further research.
Date: July 1, 1998
Creator: Kass, M.D.; McKeever, J.W.; Akerman, M.A.; Goranson, P.L.; Litherland, P.S. & O`Kain, D.U.
Partner: UNT Libraries Government Documents Department

System safety assessments combining first principles and model based safety assessment methodologies

Description: In performing assessments of low probability, high consequence systems, it is often preferable to use more than one methodology in order to assure that such systems undergo a thorough assessment. Hence, employing two methodologies in a complementary manner allows the analyst to bring the strongest features of each approach to bear upon the problem. The results of one methodology can be used to crosscheck or better characterize the results of another methodology, with the results being synergized in providing a comprehensive assessment of the system. This paper will briefly describe both the first principles and model based safety assessment methodologies, and will illustrate how both methods are used in a complementary manner in order to perform overall safety assessments of low probability, high consequence engineered systems at Sandia National Laboratories.
Date: January 1, 1998
Creator: Dvorack, M.A.; Jones, T.R.; Carlson, D.D.; Wolcott, J.F. & Sanders, G.A.
Partner: UNT Libraries Government Documents Department

SSC 17-meter dipole magnet DD000Z test results and investigation of coil failure: The report of the {open_quotes}Z{close_quotes} Committee

Description: Following the failure of the lower inner coil of magnet DD000Z on November 3, 1987, a committee was formed on November 11 and given the following charges: `To review the events leading up to and including the failure of the coils of magnet DD000Z. The intent of the review will be to determine the cause of the failure and to make recommendations to reduce the likelihood of such failures in the future. Given the fact that this is the first long magnet to be disassembled, the committee may uncover leads which point to other opportunities for improvement. The committee should follow up on these leads. The committee should prepare a plan to serve as an initial guide for the disassembly and provide guidance as the disassembly progresses.` The committee held its first meeting at FNAL on 17 and 18 Nov to review the record of events leading up to the failure and to establish an initial disassembly procedure. This was followed by further meetings at FNAL, BNL, and CDG, leading to this final report. Committee activities included interviewing personnel who had been involved in the design, assembly and testing of DD000Z, reviewing all documents relating to the magnet and its failure, and participating in and providing guidance during the disassembly. The intention of the committee was to report factual findings, to consider well founded hypotheses, not to consider conjecture and to avoid speculation.
Date: March 1988
Creator: Coombes, R.; Mirk, K.; Tompkins, J.; Zbasnik, J.; Lundy, R.; Schneider, W. et al.
Partner: UNT Libraries Government Documents Department

Historical review of plutonium storage container failures at Lawrence Livermore National Laboratory

Description: As part of the DOE Plutonium Vulnerability Assessment, an investigation was made to characterize the can failures at LLNL. Since the LLNL Plutonium Facility was opened for plutonium operations in 1961, there have only been three can failures that could be remembered by plutonium handlers, vault workers, chemical analysts, and material managers. Only one of these can failures was discovered during the processing of more than 606 packages containing plutonium as part of the LLNL Plutonium Inventory Reduction Program. A very low failure rate, especially since some of the 606 cans had been in storage for two to three decades. Two of the three containers that failed were made of aluminum and were packaged with 1.25 inch diameter plutonium metal spheres. The cans were split down their entire length and the plutonium metal was heavily oxidized. The secondary gallon container of the third package failure was found to be imploded in the storage vault. Upon closer examination, the plastic bags around the inner pint can were badly melted and the lid on the can was loose. Like the other two failures, the metal was heavily oxidized. In all three of the can failures, it is theorized that air entered the inner can through incomplete sealing and the oxygen in the air then reacted with the plutonium metal to produce plutonium oxide. Air was supplied to the inner can by permeation through the surrounding plastic bag. The air could have either diffused through the bag or could have been pumped through the twisted and taped ends of the inner most bag. The inner bags and cans were packaged into second bags and cans in an air atmosphere; therefore, trapping air inside the packaging configuration that could have passed through the bags. A failure of the inner can integrity would be necessary ...
Date: May 1994
Creator: Dodson, K. E.
Partner: UNT Libraries Government Documents Department

Check valve failure experience in the nuclear industry

Description: Check valves are critical components in the operation of current generation nuclear power plants and may serve an increasingly critical role in the designs of future advanced passive light water reactors. Recognizing that check valve failures can result in significant operating transients, increased maintenance costs, and/or decreased system availability, the nuclear industry has taken a proactive approach to failure detection and prevention. As part of the Nuclear Regulatory Commission`s (NRC`s) program to evaluate the effects of age and wear on nuclear systems components, Oak Ridge National Laboratory (ORNL) has analyzed hundreds of check valve failures in safety-related applications. This research, combined with efforts by industry, regulatory, and codes and standards organizations, has provided insight into check valve performance history and may be used to provide a basis for evaluation of changes to utilities inservice test and inspection practices.
Date: December 1995
Creator: McElhaney, K. L.
Partner: UNT Libraries Government Documents Department

Aging assessment of Westinghouse PWR and General Electric BWR containment isolation functions

Description: A study was performed to assess the effects of aging on the Containment Isolation (CI) functions of Westinghouse Pressurized Water Reactors and General Electric Boiling Water Reactors. This study is part of the Nuclear Plant Aging Research (NPAR) program, sponsored by the U.S. Nuclear Regulatory Commission. The objectives of this program are to provide an understanding of the aging process and how it affects plant safety so that it can be properly managed. This is one of a number of studies performed under the NPAR program which provide a technical basis for the identification and evaluation of degradation caused by age. Failure data from two national databases, Nuclear Plant Reliability Data System (NPRDS) and Licensee Event Reports (LERs), as well as plant specific data were reviewed and analyzed to understand the effects of aging on the CI functions. This study provided information on the effects of aging on component failure frequency, failure modes, and failure causes. Current inspection, surveillance, and monitoring practices were also reviewed.
Date: March 1996
Creator: Lee, B. S.; Travis, R.; Grove, E. & DiBiasio, A.
Partner: UNT Libraries Government Documents Department


Description: Recent reports have shown that, despite efforts to the contrary, chemical accidents continue to occur at an unacceptable rate and there is no evidence that this rate is decreasing. Based on this observation, one can conclude that previous analyses have not accurately identified and implemented appropriate fixes to eliminate identified root causes for chemical events. Based on this, it is time to reevaluate chemical accident data with a fresh eye and determine (a) what corrective actions have already been identified but have not been implemented, (b) what other root causes may be involved, and (c) what new corrective actions should be taken to eliminate these newly identified root causes.
Date: August 5, 2008
Creator: Simmons, F
Partner: UNT Libraries Government Documents Department

Licensee contractor and vendor inspection status report: Quarterly report, October--September, 1994. Volume 18, Number 4

Description: This periodical covers the results of inspections performed by the NRC`s Special Inspection Branch, Vendor Inspection Section, that have been distributed to the inspected organizations during the period from October 1994 through December 1994. The Vendor Inspection Section (VIS) of the Special Inspection Branch reviews and inspects nuclear steam system suppliers (NSSSs), architect engineering (AE) firms, suppliers of products and services, independent testing laboratories performing equipment qualification tests, and holders of NRC licenses (construction permit holders and operating licenses) in vendor-related areas. These inspections are performed to assure that the root causes of reported vendor-related problems are determined and appropriate corrective actions are developed. The inspections also review the vendors` conformance with applicable NRC and industry quality requirements, the adequacy of licensees` oversight of their vendors, and that adequate interfaces exist between licensees and vendors.
Date: February 1, 1995
Partner: UNT Libraries Government Documents Department

Detection of damage in axial (membrane) systems

Description: In a recent paper, two methods of damage identification (Modified Damage Index and Change-in-Flexibility) were applied to detection of damage in an 8-DOF vibrating system. The goal of the work was to detect damage (reduction in stiffness of one or more of the elements) as well as to locate the particular damaged elements (S). However, the investigation was limited to numerical simulations only. In this paper, a physical, spring-mass model of a similar, degenerate 8-DOF system (7 normal modes plus a rigid-body mode) was constructed. Experiments were then performed and the modal properties of the system were determined in undamaged and damaged states. Excitation was provided either by an impact hammer or by an electromechanical shaker. Damage was induced by replacing one of the springs with a spring of lower stiffness. The Modified Damage Index method clearly isolated the location of damage for a variety of damage locations and levels of damage. The Change-in-Flexibility method, however, was found to be less reliable. The ability of the method to locate damage depended strongly on location and the level of damage as well as the number of modes included.
Date: December 31, 1998
Creator: Duffey, T.A.; Baker, W.E.; Farrar, C.R. & Rhee, W.H.
Partner: UNT Libraries Government Documents Department

Relating aviation service difficulty reports to accident data for safety trend prediction

Description: A synthetic model of scheduled-commercial U.S. aviation fatalities was constructed from linear combinations of the time-spectra of critical systems reporting using 5.5 years of Service Difficulty Reports (SDR){sup 2} and Accident Incident Data System (AIDS) records{sup 3}. This model, used to predict near-future trends in aviation accidents, was tested by using the first 36 months of data to construct the synthetic model which was used to predict fatalities during the following eight months. These predictions were tested by comparison with the fatality data. A reliability block diagram (RBD) and third-order extrapolations also were used as predictive models and compared with actuality. The synthetic model was the best predictor because of its use of systems data. Other results of the study are a database of service difficulties for major aviation systems, and a rank ordering of systems according to their contribution to the synthesis. 4 refs., 8 figs., 3 tabs.
Date: October 1, 1996
Creator: Fullwood, R.R.; Hall, R.E.; Martinez-Guridi, G.; Uryasev, S. & Sampath, S.G.
Partner: UNT Libraries Government Documents Department

A method for critical software event execution reliability in high assurance systems

Description: This paper presents a method for Critical Software Event Execution Reliability (Critical SEER). The Critical SEER method is intended for high assurance software that operates in an environment where transient upsets could occur, causing a disturbance of the critical software event execution order, which could cause safety or security hazards. The method has a finite automata based module that watches (hence SEER) and tracks the critical events and ensures they occur in the proper order or else a fail safe state is forced. This method is applied during the analysis, design and implementation phases of software engineering.
Date: March 1, 1997
Creator: Kidd, M.E.C.
Partner: UNT Libraries Government Documents Department

Analysis and testing of the DIII-D ohmic heating coil lead repair clamp

Description: DIII-D has been operating for the last year with limited volt-second capabilities due to structural failure of a conductor lead to one of the ohmic heating (OH) solenoids. The conductor failure was due to poor epoxy impregnation of the overwrap of the lead pack, resulting in copper fatigue and a water leak. A number of structural analyses were performed to assist in determining the failure scenario and to evaluate various repair options. A fatigue stress analysis of the leads with a failed epoxy overwrap indicated crack initiation after 1,000 cycles at the maximum operating conditions. The failure occurred in a very inaccessible area which restricted design repair options to concepts which could be implemented remotely. Several design options were considered for repairing the lead so that it can sustain the loads for 7.5 Vs conditions at full toroidal field. A clamp, along with preloaded banding straps and shim bags, provides a system that guarantees that the stress at the crack location is always compressive and prevents further crack growth in the conductor. Due to the limited space available for the repair, it was necessary to design the clamp system to operate at the material yield stress. The primary components of the clamp system were verified by load tests prior to installation. The main body of the clamp contains a load cell and potentiometer for monitoring the load-deflection characteristics of the clamp and conductors during plasma operation. Strain gages provides redundant instrumentation. If required, the preload on the conductors can be increased remotely by a special wrench attached to the clamp assembly.
Date: November 1, 1997
Creator: Reis, E.E.; Anderson, P.M.; Chin, E. & Robinson, J.I.
Partner: UNT Libraries Government Documents Department

Flow excursion time scales in the advanced neutron source reactor

Description: Flow excursion transients give rise to a key thermal limit for the proposed Advanced Neutron Source (ANS) reactor because its core involves many parallel flow channels with a common pressure drop. Since one can envision certain accident scenarios in which the thermal limits set by flow excursion correlations might be exceeded for brief intervals, a key objective is to determine how long a flow excursion would take to bring about a system failure that could lead to fuel damage. The anticipated time scale for flow excursions has been examined by subdividing the process into its component phenomena: bubble nucleation and growth, deceleration of the resulting two-phase flow, and finally overcoming thermal inertia to heat up the reactor fuel plates. Models were developed to estimate the time required for each individual stage. Accident scenarios involving sudden reduction in core flow or core exit pressure have been examined, and the models compared with RELAP5 output for the ANS geometry. For a high-performance reactor like the ANS, flow excursion time scales were predicted to be in the millisecond range, so that even very brief transients might lead to fuel damage. These results should prove useful whenever one must determine the time involved in any portion of a flow excursion transient.
Date: April 1995
Creator: Sulfredge, C. D.
Partner: UNT Libraries Government Documents Department

First reliability test of a surface micromachined microengine using SHiMMeR

Description: The first-ever reliability stress test on surface micromachined microengines developed at Sandia National Laboratories (SNL) has been completed. We stressed 41 microengines at 36,000 RPM and inspected the functionality at 60 RPM. We have observed an infant mortality region, a region of low failure rate (useful life), and no signs of wearout in the data. The reliability data are presented and interpreted using standard reliability methods. Failure analysis results on the stressed microengines are presented. In our effort to study the reliability of MEMS, we need to observe the failures of large numbers of parts to determine the failure modes. To facilitate testing of large numbers of micromachines. The Sandia High Volume Measurement of Micromachine Reliability (SHiMMeR) system has computer controlled positioning and the capability to inspect moving parts. The development of this parallel testing system is discussed in detail.
Date: August 1, 1997
Creator: Tanner, D.M.; Smith, N.F. & Bowman, D.J.
Partner: UNT Libraries Government Documents Department

Preliminary studies on the impact of smoke on digital equipment

Description: Last year the USNRC initiated a program at Sandia National Laboratories to determine the potential impact of smoke on advanced safety-related digitial instrumentation. In recognition of the fact that the reliability of safety-related equipment during or shortly after a fire in a nuclear power plant is more risk significant than long-term effects, we are concentrating on short-term failures. We exposed a multiplexer module board to three different types of smoke to determine whether the smoke would affect its operation. The operation of the multiplexer board was halted by one out of the three smoke exposures. In coordination with Oak Ridge National Laboratory, an experimental digital safety system was also smoke tested. The series of tests showed that smoke can cause potentially serious failures of a safety system. Most of these failures were intermittent and showed that smoke can temporarily interrupt communication between digital systems.
Date: December 1, 1995
Creator: Tanaka, T.J.; Korsah, K. & Antonescu, C.
Partner: UNT Libraries Government Documents Department

Computer aided failure analysis. Final report

Description: A computer aided failure analysis (CAFA) system was developed to troubleshoot defects in electronic assemblies. Through a question and answer procedure, the system provides step-by-step corrections to guide a troubleshooter to the fault location. A diagnostic logic routine has been established for one product and the software necessary to store and implement the routine has been developed. The TSO terminal has been installed and the completed system is functional. A visual aid catalog has been developed for the current CAFA routine.
Date: December 1, 1978
Creator: Smith, R.S.
Partner: UNT Libraries Government Documents Department

Independent criticality safety evaluation of deposits in cooler equipment in Building K-31 at the Oak Ridge K-25 Site, Oak Ridge, Tennessee

Description: This report provides an independent assessment of nuclear criticality issues associated with uranium deposits in the West and East Coolers for the 6A Booster Station in Building K-31 at the Oak Ridge K-25 Site. This assessment investigates the applicability of the initial assumptions used by Lockheed Martin Energy Systems (Energy Systems) and evaluates criticality calculations previously completed by Energy Systems. The calculations were independently verified. Each component was evaluated for its ability to satisfy requirements for subcriticality and meet the double contingency principle. Facility walk downs, detailed neutronics analysis, and fault tree analysis (FTA) were performed. The facility walk downs provided a better understanding of the building condition and status, equipment configuration, and uranium deposit locations. The detailed neutronics analysis focused on system geometry and moderation levels applicable to the individual components. The FTA considered the annual rate of occurrence for the events identified as potential causes of criticality issues. This report also examines the advantages of using this type of evaluation to assess the removal process for additional components and equipment.
Date: October 1, 1996
Partner: UNT Libraries Government Documents Department

Gamma prior distribution selection for Bayesian analysis of failure rate and reliability

Description: It is assumed that the phenomenon under study is such that the time-to-failure may be modeled by an exponential distribution with failure rate lambda. For Bayesian analyses of the assumed model, the family of gamma distributions provides conjugate prior models for lambda. Thus, an experimenter needs to select a particular gamma model to conduct a Bayesian reliability analysis. The purpose of this report is to present a methodology that can be used to translate engineering information, experience, and judgment into a choice of a gamma prior distribution. The proposed methodology assumes that the practicing engineer can provide percentile data relating to either the failure rate or the reliability of the phenomenon being investigated. For example, the methodology will select the gamma prior distribution which conveys an engineer's belief that the failure rate lambda simultaneously satisfies the probability statements, P(lambda less than 1.0 x 10/sup -3/) equals 0.50 and P(lambda less than 1.0 x 10/sup -5/) equals 0.05. That is, two percentiles provided by an engineer are used to determine a gamma prior model which agrees with the specified percentiles. For those engineers who prefer to specify reliability percentiles rather than the failure rate percentiles illustrated above, it is possible to use the induced negative-log gamma prior distribution which satisfies the probability statements, P(R(t/sub 0/) less than 0.99) equals 0.50 and P(R(t/sub 0/) less than 0.99999) equals 0.95, for some operating time t/sub 0/. The report also includes graphs for selected percentiles which assist an engineer in applying the procedure. 28 figures, 16 tables.
Date: July 1, 1976
Creator: Waller, R. A.; Johnson, M. M.; Waterman, M. S. & Martz, H. F. Jr.
Partner: UNT Libraries Government Documents Department

Computer aided approach to qualitative and quantitative common cause failure analysis for complex systems

Description: Common cause failure analysis, also called common mode failure analysis, is an integral part of a complete system reliability analysis. Existing methods of computer aided common cause failure analysis are extended by allowing analysis of the complex systems often encountered in practice. The methods aid in identifying potential common cause failures and also address quantitative common cause failure analysis.
Date: January 1, 1977
Creator: Cate, C. L.; Wagner, D. P. & Fussell, J. B.
Partner: UNT Libraries Government Documents Department