Science.gov

Sample records for failure modes analysis

  1. Failure mode analysis to predict product reliability.

    NASA Technical Reports Server (NTRS)

    Zemanick, P. P.

    1972-01-01

    The failure mode analysis (FMA) is described as a design tool to predict and improve product reliability. The objectives of the failure mode analysis are presented as they influence component design, configuration selection, the product test program, the quality assurance plan, and engineering analysis priorities. The detailed mechanics of performing a failure mode analysis are discussed, including one suggested format. Some practical difficulties of implementation are indicated, drawn from experience with preparing FMAs on the nuclear rocket engine program.

  2. Failure Mode Identification Through Clustering Analysis

    NASA Technical Reports Server (NTRS)

    Arunajadai, Srikesh G.; Stone, Robert B.; Tumer, Irem Y.; Clancy, Daniel (Technical Monitor)

    2002-01-01

    Research has shown that nearly 80% of the costs and problems are created in product development and that cost and quality are essentially designed into products in the conceptual stage. Currently, failure identification procedures (such as FMEA (Failure Modes and Effects Analysis), FMECA (Failure Modes, Effects and Criticality Analysis) and FTA (Fault Tree Analysis)) and design of experiments are being used for quality control and for the detection of potential failure modes during the detail design stage or post-product launch. Though all of these methods have their own advantages, they do not give information as to what are the predominant failures that a designer should focus on while designing a product. This work uses a functional approach to identify failure modes, which hypothesizes that similarities exist between different failure modes based on the functionality of the product/component. In this paper, a statistical clustering procedure is proposed to retrieve information on the set of predominant failures that a function experiences. The various stages of the methodology are illustrated using a hypothetical design example.

  3. Failure modes and effects analysis automation

    NASA Technical Reports Server (NTRS)

    Kamhieh, Cynthia H.; Cutts, Dannie E.; Purves, R. Byron

    1988-01-01

    A failure modes and effects analysis (FMEA) assistant was implemented as a knowledge based system and will be used during design of the Space Station to aid engineers in performing the complex task of tracking failures throughout the entire design effort. The three major directions in which automation was pursued were the clerical components of the FMEA process, the knowledge acquisition aspects of FMEA, and the failure propagation/analysis portions of the FMEA task. The system is accessible to design, safety, and reliability engineers at single user workstations and, although not designed to replace conventional FMEA, it is expected to decrease by many man years the time required to perform the analysis.

  4. A streamlined failure mode and effects analysis

    SciTech Connect

    Ford, Eric C. Smith, Koren; Terezakis, Stephanie; Croog, Victoria; Gollamudi, Smitha; Gage, Irene; Keck, Jordie; DeWeese, Theodore; Sibley, Greg

    2014-06-15

    Purpose: Explore the feasibility and impact of a streamlined failure mode and effects analysis (FMEA) using a structured process that is designed to minimize staff effort. Methods: FMEA for the external beam process was conducted at an affiliate radiation oncology center that treats approximately 60 patients per day. A structured FMEA process was developed which included clearly defined roles and goals for each phase. A core group of seven people was identified and a facilitator was chosen to lead the effort. Failure modes were identified and scored according to the FMEA formalism. A risk priority number,RPN, was calculated and used to rank failure modes. Failure modes with RPN > 150 received safety improvement interventions. Staff effort was carefully tracked throughout the project. Results: Fifty-two failure modes were identified, 22 collected during meetings, and 30 from take-home worksheets. The four top-ranked failure modes were: delay in film check, missing pacemaker protocol/consent, critical structures not contoured, and pregnant patient simulated without the team's knowledge of the pregnancy. These four failure modes hadRPN > 150 and received safety interventions. The FMEA was completed in one month in four 1-h meetings. A total of 55 staff hours were required and, additionally, 20 h by the facilitator. Conclusions: Streamlined FMEA provides a means of accomplishing a relatively large-scale analysis with modest effort. One potential value of FMEA is that it potentially provides a means of measuring the impact of quality improvement efforts through a reduction in risk scores. Future study of this possibility is needed.

  5. Mod 1 wind turbine generator failure modes and effects analysis

    NASA Technical Reports Server (NTRS)

    1979-01-01

    A failure modes and effects analysis (FMEA) was directed primarily at identifying those critical failure modes that would be hazardous to life or would result in major damage to the system. Each subsystem was approached from the top down, and broken down to successive lower levels where it appeared that the criticality of the failure mode warranted more detail analysis. The results were reviewed by specialists from outside the Mod 1 program, and corrective action taken wherever recommended.

  6. Failure Modes and Effects Analysis (FMEA) Assistant Tool Feasibility Study

    NASA Technical Reports Server (NTRS)

    Flores, Melissa; Malin, Jane T.

    2013-01-01

    An effort to determine the feasibility of a software tool to assist in Failure Modes and Effects Analysis (FMEA) has been completed. This new and unique approach to FMEA uses model based systems engineering concepts to recommend failure modes, causes, and effects to the user after they have made several selections from pick lists about a component s functions and inputs/outputs. Recommendations are made based on a library using common failure modes identified over the course of several major human spaceflight programs. However, the tool could be adapted for use in a wide range of applications from NASA to the energy industry.

  7. Failure Modes and Effects Analysis (FMEA) Assistant Tool Feasibility Study

    NASA Astrophysics Data System (ADS)

    Flores, Melissa D.; Malin, Jane T.; Fleming, Land D.

    2013-09-01

    An effort to determine the feasibility of a software tool to assist in Failure Modes and Effects Analysis (FMEA) has been completed. This new and unique approach to FMEA uses model based systems engineering concepts to recommend failure modes, causes, and effects to the user after they have made several selections from pick lists about a component's functions and inputs/outputs. Recommendations are made based on a library using common failure modes identified over the course of several major human spaceflight programs. However, the tool could be adapted for use in a wide range of applications from NASA to the energy industry.

  8. Failure Modes and Effects Analysis (FMEA): A Bibliography

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Failure modes and effects analysis (FMEA) is a bottom-up analytical process that identifies process hazards, which helps managers understand vulnerabilities of systems, as well as assess and mitigate risk. It is one of several engineering tools and techniques available to program and project managers aimed at increasing the likelihood of safe and successful NASA programs and missions. This bibliography references 465 documents in the NASA STI Database that contain the major concepts, failure modes or failure analysis, in either the basic index of the major subject terms.

  9. Failure mode analysis of a spacecraft power system

    SciTech Connect

    Lee, J.R.

    1995-12-31

    For the spacecraft power system`s dynamic analyses, dc/dc converters are usually modeled with a linearized model using the state space averaging technique. The linearized model can be used for small-signal ac and transient analyses. However, since the linearized model has limitations in its accuracies, certain types of transient analyses including a failure mode must be performed by using a more accurate cycle-by-cycle model. In this paper, a failure mode analysis is presented with a small-signal analysis and corresponding transient simulations.

  10. Cycles till failure of silver-zinc cells with competing failure modes - Preliminary data analysis

    NASA Technical Reports Server (NTRS)

    Sidik, S. M.; Leibecki, H. F.; Bozek, J. M.

    1980-01-01

    The data analysis of cycles to failure of silver-zinc electrochemical cells with competing failure modes is presented. The test ran 129 cells through charge-discharge cycles until failure; preliminary data analysis consisted of response surface estimate of life. Batteries fail through low voltage condition and an internal shorting condition; a competing failure modes analysis was made using maximum likelihood estimation for the extreme value life distribution. Extensive residual plotting and probability plotting were used to verify data quality and selection of model.

  11. Failure Mode Effects Analysis for an Accelerator Control System

    SciTech Connect

    Hartman, Steven M

    2009-01-01

    Failure mode effects analysis (FMEA) has been used in industry for design, manufacturing and assembly process quality control. It describes a formal approach for categorizing how a process may fail and for prioritizing failures based on their severity, frequency and likelihood of detection. Experience conducting a partial FMEA of an accelerator subsystem and its related control system will be reviewed. The applicability of the FMEA process to an operational accelerator control system will be discussed.

  12. Failure modes and effects analysis (RADL Item 2-23)

    SciTech Connect

    1980-04-01

    The Pilot Plant is a central receiver design concept. It is comprised of five major subsystems as shown schematically, plus a set of equipment (Plant Support Subsystem) used to support total plant operation. The failure modes and effects analysis (FMEA) is a bottom-up analysis used to identify the failure characteristics of the system (total equipment used to produce electrical power), that is, the failure of a single component is assumed and the effect of that failure upon the system is determined. The FMEA is concerned with the plant from an operational standpoint (i.e., the production of electrical power). This analysis was performed to the component level. This was interpreted as a valve, computer, measurement sensor and its associated signal conditioning, an electronic black box, etc.

  13. Failure modes and effects analysis of fusion magnet systems

    SciTech Connect

    Zimmermann, M; Kazimi, M S; Siu, N O; Thome, R J

    1988-12-01

    A failure modes and consequence analysis of fusion magnet system is an important contributor towards enhancing the design by improving the reliability and reducing the risk associated with the operation of magnet systems. In the first part of this study, a failure mode analysis of a superconducting magnet system is performed. Building on the functional breakdown and the fault tree analysis of the Toroidal Field (TF) coils of the Next European Torus (NET), several subsystem levels are added and an overview of potential sources of failures in a magnet system is provided. The failure analysis is extended to the Poloidal Field (PF) magnet system. Furthermore, an extensive analysis of interactions within the fusion device caused by the operation of the PF magnets is presented in the form of an Interaction Matrix. A number of these interactions may have significant consequences for the TF magnet system particularly interactions triggered by electrical failures in the PF magnet system. In the second part of this study, two basic categories of electrical failures in the PF magnet system are examined: short circuits between the terminals of external PF coils, and faults with a constant voltage applied at external PF coil terminals. An electromagnetic model of the Compact Ignition Tokamak (CIT) is used to examine the mechanical load conditions for the PF and the TF coils resulting from these fault scenarios. It is found that shorts do not pose large threats to the PF coils. Also, the type of plasma disruption has little impact on the net forces on the PF and the TF coils. 39 refs., 30 figs., 12 tabs.

  14. TU-AB-BRD-02: Failure Modes and Effects Analysis

    SciTech Connect

    Huq, M.

    2015-06-15

    Current quality assurance and quality management guidelines provided by various professional organizations are prescriptive in nature, focusing principally on performance characteristics of planning and delivery devices. However, published analyses of events in radiation therapy show that most events are often caused by flaws in clinical processes rather than by device failures. This suggests the need for the development of a quality management program that is based on integrated approaches to process and equipment quality assurance. Industrial engineers have developed various risk assessment tools that are used to identify and eliminate potential failures from a system or a process before a failure impacts a customer. These tools include, but are not limited to, process mapping, failure modes and effects analysis, fault tree analysis. Task Group 100 of the American Association of Physicists in Medicine has developed these tools and used them to formulate an example risk-based quality management program for intensity-modulated radiotherapy. This is a prospective risk assessment approach that analyzes potential error pathways inherent in a clinical process and then ranks them according to relative risk, typically before implementation, followed by the design of a new process or modification of the existing process. Appropriate controls are then put in place to ensure that failures are less likely to occur and, if they do, they will more likely be detected before they propagate through the process, compromising treatment outcome and causing harm to the patient. Such a prospective approach forms the basis of the work of Task Group 100 that has recently been approved by the AAPM. This session will be devoted to a discussion of these tools and practical examples of how these tools can be used in a given radiotherapy clinic to develop a risk based quality management program. Learning Objectives: Learn how to design a process map for a radiotherapy process Learn how to

  15. [Failure mode and effect analysis: application in chemotherapy].

    PubMed

    Chuang, Ching-Hui; Chuang, Sheu-Wen

    2009-08-01

    Medical institutions are increasingly concerned about ensuring the safety of patients under their care. Failure mode and effect analysis (FMEA) is a qualitative approach based on a proactive process. Strongly promoted by the Joint Commission Accredited of Health Organization (JCAHO) since 2002, FMEA has since been adopted and widely practiced in healthcare organizations to assess and analyze clinical error events. FMEA has proven to be an effective method of minimizing errors in both manufacturing and healthcare industries. It predicts failure points in systems and allows an organization to address proactively the causes of problems and prioritize improvement strategies. The application of FMEA in chemotherapy at our department identified three main failure points: (1) inappropriate chemotherapy standard operating procedures (SOPs), (2) communication barriers, and (3) insufficient training of nurses. The application of FMEA in chemotherapy is expected to enhance the sensitivity and proactive abilities of healthcare practitioners during potentially risky situations as well as to improve levels of patient care safety.

  16. Cycles till failure of silver-zinc cells with completing failures modes: Preliminary data analysis

    NASA Technical Reports Server (NTRS)

    Sidik, S. M.; Leibecki, H. F.; Bozek, J. M.

    1980-01-01

    One hundred and twenty nine cells were run through charge-discharge cycles until failure. The experiment design was a variant of a central composite factorial in five factors. Preliminary data analysis consisted of response surface estimation of life. Batteries fail under two basic modes; a low voltage condition and an internal shorting condition. A competing failure modes analysis using maximum likelihood estimation for the extreme value life distribution was performed. Extensive diagnostics such as residual plotting and probability plotting were employed to verify data quality and choice of model.

  17. Letter report seismic shutdown system failure mode and effect analysis

    SciTech Connect

    KECK, R.D.

    1999-09-01

    The Supply Ventilation System Seismic Shutdown ensures that the 234-52 building supply fans, the dry air process fans and vertical development calciner are shutdown following a seismic event. This evaluates the failure modes and determines the effects of the failure modes.

  18. Failure mode and effects analysis: too little for too much?

    PubMed

    Dean Franklin, Bryony; Shebl, Nada Atef; Barber, Nick

    2012-07-01

    Failure mode and effects analysis (FMEA) is a structured prospective risk assessment method that is widely used within healthcare. FMEA involves a multidisciplinary team mapping out a high-risk process of care, identifying the failures that can occur, and then characterising each of these in terms of probability of occurrence, severity of effects and detectability, to give a risk priority number used to identify failures most in need of attention. One might assume that such a widely used tool would have an established evidence base. This paper considers whether or not this is the case, examining the evidence for the reliability and validity of its outputs, the mathematical principles behind the calculation of a risk prioirty number, and variation in how it is used in practice. We also consider the likely advantages of this approach, together with the disadvantages in terms of the healthcare professionals' time involved. We conclude that although FMEA is popular and many published studies have reported its use within healthcare, there is little evidence to support its use for the quantitative prioritisation of process failures. It lacks both reliability and validity, and is very time consuming. We would not recommend its use as a quantitative technique to prioritise, promote or study patient safety interventions. However, the stage of FMEA involving multidisciplinary mapping process seems valuable and work is now needed to identify the best way of converting this into plans for action.

  19. The Worker Exposure Failure Modes and Effects Analysis

    SciTech Connect

    Cadwallader, L.C.

    2005-05-15

    The Worker Exposure Failure Modes and Effects Analysis (WE-FMEA) is a new approach to quantitatively evaluate worker risks from possible failures of co-located equipment in the complex environment of a magnetic or inertial fusion experiment. For next-step experiments such as the International Thermonuclear Experimental Reactor (ITER) or the National Ignition Facility (NIF), the systems and equipment will be larger, handle more throughput or power, and will, in general, be more robust than past experiments. These systems and equipment are necessary to operate the machine, but the rooms are congested with equipment, piping, and cables, which poses a new level of hazard for workers who will perform hands-on maintenance. The WE-FMEA systematically analyzes the nearby equipment and the work environment for equipment failure or inherent hazards, and then develops exposure scenarios. Once identified, the exposure scenarios are evaluated for the worker hazards and quantitative worker risk is calculated. Then risk scenarios are quantitatively compared to existing statistical data on worker injuries; high-risk scenarios can be identified and addressed in more detail to determine the proper means to reduce, mitigate, or protect against the hazard. The WE-FMEA approach is described and a cooling system maintenance example is given.

  20. Failure mode and effects analysis outputs: are they valid?

    PubMed Central

    2012-01-01

    Background Failure Mode and Effects Analysis (FMEA) is a prospective risk assessment tool that has been widely used within the aerospace and automotive industries and has been utilised within healthcare since the early 1990s. The aim of this study was to explore the validity of FMEA outputs within a hospital setting in the United Kingdom. Methods Two multidisciplinary teams each conducted an FMEA for the use of vancomycin and gentamicin. Four different validity tests were conducted: · Face validity: by comparing the FMEA participants’ mapped processes with observational work. · Content validity: by presenting the FMEA findings to other healthcare professionals. · Criterion validity: by comparing the FMEA findings with data reported on the trust’s incident report database. · Construct validity: by exploring the relevant mathematical theories involved in calculating the FMEA risk priority number. Results Face validity was positive as the researcher documented the same processes of care as mapped by the FMEA participants. However, other healthcare professionals identified potential failures missed by the FMEA teams. Furthermore, the FMEA groups failed to include failures related to omitted doses; yet these were the failures most commonly reported in the trust’s incident database. Calculating the RPN by multiplying severity, probability and detectability scores was deemed invalid because it is based on calculations that breach the mathematical properties of the scales used. Conclusion There are significant methodological challenges in validating FMEA. It is a useful tool to aid multidisciplinary groups in mapping and understanding a process of care; however, the results of our study cast doubt on its validity. FMEA teams are likely to need different sources of information, besides their personal experience and knowledge, to identify potential failures. As for FMEA’s methodology for scoring failures, there were discrepancies between the teams’ estimates

  1. Use of failure mode and effects analysis for proactive identification of communication and handoff failures from organ procurement to transplantation.

    PubMed

    Steinberger, Dina M; Douglas, Stephen V; Kirschbaum, Mark S

    2009-09-01

    A multidisciplinary team from the University of Wisconsin Hospital and Clinics transplant program used failure mode and effects analysis to proactively examine opportunities for communication and handoff failures across the continuum of care from organ procurement to transplantation. The team performed a modified failure mode and effects analysis that isolated the multiple linked, serial, and complex information exchanges occurring during the transplantation of one solid organ. Failure mode and effects analysis proved effective for engaging a diverse group of persons who had an investment in the outcome in analysis and discussion of opportunities to improve the system's resilience for avoiding errors during a time-pressured and complex process.

  2. FMEA, the alternative process hazard method. [Failure Mode Effects Analysis

    SciTech Connect

    Goyal, R.K. )

    1993-05-01

    Failure mode effects analysis (FMEA) is an old reliability/assurance tool finding its way into the HPI. Not popular yet, this hazard technique has some viable applications that can improve hazard assessment data. Notably, FMEA studies can identify possible areas for improvement that may have not been discovered using other methods. Also, FMEA is not as labor intensive and costly as other process hazard analysis (PHA) methods. PSHA 1910.119 set in place an informational structure whose main purpose is the reduction of potential accidents and minimizing risks in the event of an accident. Consequently, HPI operators must evaluate their process systems and identify potential major hazards, such as fires, explosions and accidental release of toxic/hazardous chemicals, and protect their facilities, employees, the public and the environment. But, which PHA method(s) apply to a particular plant or process still remains a difficult question. This paper describes what FMEA is; types of FMEA; how to conduct a FMEA study; comparison with HAZOP (hazard and operability study); computer software; applicability of FMEA; and examples of its use.

  3. Analysis of the shearout failure mode in composite bolted joints

    NASA Technical Reports Server (NTRS)

    Wilson, D. W.; Pipes, R. B.

    1981-01-01

    A semi-empirical shearout strength model has been formulated for the analysis of composite bolted joints with allowance for the effects of joint geometry. The model employs a polynomial stress function in conjunction with a point stress failure criterion to predict strength as a function of fastener size, edge distance, and half spacing. The stress function is obtained by two-dimensional plane-stress finite element analysis using quadrilateral elements with orthotropic material properties. Comparison of experimentally determined shearout strength data with model predicted failures has substantiated the accuracy of the model.

  4. Failure Mode Analysis of V-Shaped Pyrotechnically Actuated Valves

    NASA Technical Reports Server (NTRS)

    Sachdev, Jai S.; Hosangadi, A.; Chenoweth, James D.; Saulsberry, Regor L.; McDougle, Stephen H.

    2012-01-01

    Current V-shaped stainless steel pyrovalve initiators have rectified many of the deficiencies of the heritage Y-shaped aluminum design. However, a credible failure mode still exists for dual simultaneous initiator (NSI) firings in which low temperatures were detected at the booster cap and less consistent ignition was observed than when a single initiator was fired. In order to asses this issue, a numerical framework has been developed for predicting the flow through pyrotechnically actuated valves. This framework includes a fully coupled solution of the gas-phase equation with a non-equilibrium dispersed phase for solid particles as well as the capability to model conjugate gradient heat transfer to the booster cap. Through a hierarchy of increasingly complex simulations, a hypothesis for the failure mode of the nearly simultaneous dual NSI firings has been proven. The simulations indicate that the failure mode for simultaneous dual NSI firings may be caused by flow interactions between the flame channels. The shock waves from each initiator interact in the booster cavity resulting in a high pressure that prevents the gas and particulate velocity from rising in the booster cap region. This impedes the bulk of the particulate phase from impacting the booster cap and reduces the heat transfer to the booster cap since the particles do not impact it. Heat transfer calculations to the solid metal indicate that gas-phase convective heat transfer may not be adequate by itself and that energy transfer from the particulate phase may be crucial for the booster cap burn through.

  5. The Application of Failure Modes and Effects Analysis Methodology to Intrathecal Drug Delivery for Pain Management

    PubMed Central

    Patel, Teresa; Fisher, Stanley P.

    2016-01-01

    Objective This study aimed to utilize failure modes and effects analysis (FMEA) to transform clinical insights into a risk mitigation plan for intrathecal (IT) drug delivery in pain management. Methods The FMEA methodology, which has been used for quality improvement, was adapted to assess risks (i.e., failure modes) associated with IT therapy. Ten experienced pain physicians scored 37 failure modes in the following categories: patient selection for therapy initiation (efficacy and safety concerns), patient safety during IT therapy, and product selection for IT therapy. Participants assigned severity, probability, and detection scores for each failure mode, from which a risk priority number (RPN) was calculated. Failure modes with the highest RPNs (i.e., most problematic) were discussed, and strategies were proposed to mitigate risks. Results Strategic discussions focused on 17 failure modes with the most severe outcomes, the highest probabilities of occurrence, and the most challenging detection. The topic of the highest‐ranked failure mode (RPN = 144) was manufactured monotherapy versus compounded combination products. Addressing failure modes associated with appropriate patient and product selection was predicted to be clinically important for the success of IT therapy. Conclusions The methodology of FMEA offers a systematic approach to prioritizing risks in a complex environment such as IT therapy. Unmet needs and information gaps are highlighted through the process. Risk mitigation and strategic planning to prevent and manage critical failure modes can contribute to therapeutic success. PMID:27477689

  6. The use of failure mode effect and criticality analysis in a medication error subcommittee.

    PubMed

    Williams, E; Talley, R

    1994-04-01

    Failure Mode Effect and Criticality Analysis (FMECA) is the systematic assessment of a process or product that enables one to determine the location and mechanism of potential failures. It has been used by engineers, particularly in the aerospace industry, to identify and prioritize potential failures during product development when there is a lack of data but an abundance of expertise. The Institute for Safe Medication Practices has recommended its use in analyzing the medication administration process in hospitals and in drug product development in the pharamceutical industry. A medication error subcommittee adopted and modified FMECA to identify and prioritize significant failure modes in its specific medication administration process. Based on this analysis, the subcommittee implemented solutions to four of the five highest ranked failure modes. FMECA provided a method for a multidisciplinary group to address the most important medication error concerns based upon the expertise of the group members. It also facilitated consensus building in a group with varied perceptions.

  7. WE-G-BRA-08: Failure Modes and Effects Analysis (FMEA) for Gamma Knife Radiosurgery

    SciTech Connect

    Xu, Y; Bhatnagar, J; Bednarz, G; Flickinger, J; Arai, Y; Huq, M Saiful; Vacsulka, J; Monaco, E; Niranjan, A; Lunsford, L Dade; Feng, W

    2015-06-15

    Purpose: To perform a failure modes and effects analysis (FMEA) study for Gamma Knife (GK) radiosurgery processes at our institution based on our experience with the treatment of more than 13,000 patients. Methods: A team consisting of medical physicists, nurses, radiation oncologists, neurosurgeons at the University of Pittsburgh Medical Center and an external physicist expert was formed for the FMEA study. A process tree and a failure mode table were created for the GK procedures using the Leksell GK Perfexion and 4C units. Three scores for the probability of occurrence (O), the severity (S), and the probability of no detection (D) for failure modes were assigned to each failure mode by each professional on a scale from 1 to 10. The risk priority number (RPN) for each failure mode was then calculated (RPN = OxSxD) as the average scores from all data sets collected. Results: The established process tree for GK radiosurgery consists of 10 sub-processes and 53 steps, including a sub-process for frame placement and 11 steps that are directly related to the frame-based nature of the GK radiosurgery. Out of the 86 failure modes identified, 40 failure modes are GK specific, caused by the potential for inappropriate use of the radiosurgery head frame, the imaging fiducial boxes, the GK helmets and plugs, and the GammaPlan treatment planning system. The other 46 failure modes are associated with the registration, imaging, image transfer, contouring processes that are common for all radiation therapy techniques. The failure modes with the highest hazard scores are related to imperfect frame adaptor attachment, bad fiducial box assembly, overlooked target areas, inaccurate previous treatment information and excessive patient movement during MRI scan. Conclusion: The implementation of the FMEA approach for Gamma Knife radiosurgery enabled deeper understanding of the overall process among all professionals involved in the care of the patient and helped identify potential

  8. Preliminary Failure Modes and Effects Analysis of the US Massive Gas Injection Disruption Mitigation System Design

    SciTech Connect

    Lee C. Cadwallader

    2013-10-01

    This report presents the results of a preliminary failure modes and effects analysis (FMEA) of a candidate design for the ITER Disruption Mitigation System. This candidate is the Massive Gas Injection System that provides machine protection in a plasma disruption event. The FMEA was quantified with “generic” component failure rate data as well as some data calculated from operating facilities, and the failure events were ranked for their criticality to system operation.

  9. Preliminary Failure Modes and Effects Analysis of the US DCLL Test Blanket Module

    SciTech Connect

    Lee C. Cadwallader

    2007-08-01

    This report presents the results of a preliminary failure modes and effects analysis (FMEA) of a small tritium-breeding test blanket module design for the International Thermonuclear Experimental Reactor. The FMEA was quantified with “generic” component failure rate data, and the failure events are binned into postulated initiating event families and frequency categories for safety assessment. An appendix to this report contains repair time data to support an occupational radiation exposure assessment for test blanket module maintenance.

  10. Preliminary Failure Modes and Effects Analysis of the US DCLL Test Blanket Module

    SciTech Connect

    Lee C. Cadwallader

    2010-06-01

    This report presents the results of a preliminary failure modes and effects analysis (FMEA) of a small tritium-breeding test blanket module design for the International Thermonuclear Experimental Reactor. The FMEA was quantified with “generic” component failure rate data, and the failure events are binned into postulated initiating event families and frequency categories for safety assessment. An appendix to this report contains repair time data to support an occupational radiation exposure assessment for test blanket module maintenance.

  11. A Tool To Support Failure Mode And Effects Analysis Based On Causal Modelling And Reasoning

    NASA Astrophysics Data System (ADS)

    Underwood, W. E.; Laib, S. L.

    1987-05-01

    A prototype knowledge-based system has been developed that supports Failure Mode & Effects Analysis (FMEA). The knowledge base consists of causal models of components and a representation for coupling these components into assemblies and systems. The causal models are qualitative models. They allow reasoning as to whether variables are increasing, decreasing or steady. The analysis strategies used by the prototype allow it to determine the effects of failure modes on the function of the part, the failure effect on the assembly the part is contained in, and the effect on the subsystem containing the assembly.

  12. Failure modes and effects criticality analysis and accelerated life testing of LEDs for medical applications

    NASA Astrophysics Data System (ADS)

    Sawant, M.; Christou, A.

    2012-12-01

    While use of LEDs in Fiber Optics and lighting applications is common, their use in medical diagnostic applications is not very extensive. Since the precise value of light intensity will be used to interpret patient results, understanding failure modes [1-4] is very important. We used the Failure Modes and Effects Criticality Analysis (FMECA) tool to identify the critical failure modes of the LEDs. FMECA involves identification of various failure modes, their effects on the system (LED optical output in this context), their frequency of occurrence, severity and the criticality of the failure modes. The competing failure modes/mechanisms were degradation of: active layer (where electron-hole recombination occurs to emit light), electrodes (provides electrical contact to the semiconductor chip), Indium Tin Oxide (ITO) surface layer (used to improve current spreading and light extraction), plastic encapsulation (protective polymer layer) and packaging failures (bond wires, heat sink separation). A FMECA table is constructed and the criticality is calculated by estimating the failure effect probability (β), failure mode ratio (α), failure rate (λ) and the operating time. Once the critical failure modes were identified, the next steps were generation of prior time to failure distribution and comparing with our accelerated life test data. To generate the prior distributions, data and results from previous investigations were utilized [5-33] where reliability test results of similar LEDs were reported. From the graphs or tabular data, we extracted the time required for the optical power output to reach 80% of its initial value. This is our failure criterion for the medical diagnostic application. Analysis of published data for different LED materials (AlGaInP, GaN, AlGaAs), the Semiconductor Structures (DH, MQW) and the mode of testing (DC, Pulsed) was carried out. The data was categorized according to the materials system and LED structure such as AlGaInP-DH-DC, Al

  13. EVALUATION OF SAFETY IN A RADIATION ONCOLOGY SETTING USING FAILURE MODE AND EFFECTS ANALYSIS

    PubMed Central

    Ford, Eric C.; Gaudette, Ray; Myers, Lee; Vanderver, Bruce; Engineer, Lilly; Zellars, Richard; Song, Danny Y.; Wong, John; DeWeese, Theodore L.

    2013-01-01

    Purpose Failure mode and effects analysis (FMEA) is a widely used tool for prospectively evaluating safety and reliability. We report our experiences in applying FMEA in the setting of radiation oncology. Methods and Materials We performed an FMEA analysis for our external beam radiation therapy service, which consisted of the following tasks: (1) create a visual map of the process, (2) identify possible failure modes; assign risk probability numbers (RPN) to each failure mode based on tabulated scores for the severity, frequency of occurrence, and detectability, each on a scale of 1 to 10; and (3) identify improvements that are both feasible and effective. The RPN scores can span a range of 1 to 1000, with higher scores indicating the relative importance of a given failure mode. Results Our process map consisted of 269 different nodes. We identified 127 possible failure modes with RPN scores ranging from 2 to 160. Fifteen of the top-ranked failure modes were considered for process improvements, representing RPN scores of 75 and more. These specific improvement suggestions were incorporated into our practice with a review and implementation by each department team responsible for the process. Conclusions The FMEA technique provides a systematic method for finding vulnerabilities in a process before they result in an error. The FMEA framework can naturally incorporate further quantification and monitoring. A general-use system for incident and near miss reporting would be useful in this regard. PMID:19409731

  14. Evaluation of Safety in a Radiation Oncology Setting Using Failure Mode and Effects Analysis

    SciTech Connect

    Ford, Eric C. Gaudette, Ray; Myers, Lee; Vanderver, Bruce; Engineer, Lilly; Zellars, Richard; Song, Danny Y.; Wong, John; DeWeese, Theodore L.

    2009-07-01

    Purpose: Failure mode and effects analysis (FMEA) is a widely used tool for prospectively evaluating safety and reliability. We report our experiences in applying FMEA in the setting of radiation oncology. Methods and Materials: We performed an FMEA analysis for our external beam radiation therapy service, which consisted of the following tasks: (1) create a visual map of the process, (2) identify possible failure modes; assign risk probability numbers (RPN) to each failure mode based on tabulated scores for the severity, frequency of occurrence, and detectability, each on a scale of 1 to 10; and (3) identify improvements that are both feasible and effective. The RPN scores can span a range of 1 to 1000, with higher scores indicating the relative importance of a given failure mode. Results: Our process map consisted of 269 different nodes. We identified 127 possible failure modes with RPN scores ranging from 2 to 160. Fifteen of the top-ranked failure modes were considered for process improvements, representing RPN scores of 75 and more. These specific improvement suggestions were incorporated into our practice with a review and implementation by each department team responsible for the process. Conclusions: The FMEA technique provides a systematic method for finding vulnerabilities in a process before they result in an error. The FMEA framework can naturally incorporate further quantification and monitoring. A general-use system for incident and near miss reporting would be useful in this regard.

  15. Application of failure mode and effect analysis in an assisted reproduction technology laboratory.

    PubMed

    Intra, Giulia; Alteri, Alessandra; Corti, Laura; Rabellotti, Elisa; Papaleo, Enrico; Restelli, Liliana; Biondo, Stefania; Garancini, Maria Paola; Candiani, Massimo; Viganò, Paola

    2016-08-01

    Assisted reproduction technology laboratories have a very high degree of complexity. Mismatches of gametes or embryos can occur, with catastrophic consequences for patients. To minimize the risk of error, a multi-institutional working group applied failure mode and effects analysis (FMEA) to each critical activity/step as a method of risk assessment. This analysis led to the identification of the potential failure modes, together with their causes and effects, using the risk priority number (RPN) scoring system. In total, 11 individual steps and 68 different potential failure modes were identified. The highest ranked failure modes, with an RPN score of 25, encompassed 17 failures and pertained to "patient mismatch" and "biological sample mismatch". The maximum reduction in risk, with RPN reduced from 25 to 5, was mostly related to the introduction of witnessing. The critical failure modes in sample processing were improved by 50% in the RPN by focusing on staff training. Three indicators of FMEA success, based on technical skill, competence and traceability, have been evaluated after FMEA implementation. Witnessing by a second human operator should be introduced in the laboratory to avoid sample mix-ups. These findings confirm that FMEA can effectively reduce errors in assisted reproduction technology laboratories.

  16. Failure Mode and Effects Analysis (FMEA) Introductory Overview

    DTIC Science & Technology

    2012-06-14

    effects based on how severe they are, how often they might occur, and how easily we can find them. 3. Effects: the consequences of failure. The...Actions ! 0 l!1 .. requirE-ments ~ l=ailure 1-’rP.vP.ntion .., llP.tP.c::tion Completion Dato Action• Taken P. il "’ ; · .. "’ = 0 i;r= ~ ~ " S pnrg

  17. Failure mode analysis of a post-tension anchored dam using linear finite element analysis

    NASA Astrophysics Data System (ADS)

    Corn, Aimee

    There are currently over 84,000 dams in the United States, and the average age of those dams is 52 years. Concrete gravity dams are the second most common dam type, with more than 3,000 in the United States. Current engineering technology and technical understanding of hydrologic and seismic events has resulted in significant increases to the required design loads for most dams; therefore, many older dams do not have adequate safety for extreme loading events. Concrete gravity dams designed and constructed in the early 20th century did not consider uplift pressures beneath the dam, which reduces the effective weight of the structure. One method that has been used to enhance the stability of older concrete gravity dams includes the post-tension anchor (PTA) system. Post-tensioning infers modifying cured concrete and using self-equilibrating elements to increase the weight of the section, which provides added stability. There is a lack of historical evidence regarding the potential failure mechanisms for PTA concrete gravity dams. Of particular interest, is how these systems behave during large seismic events. The objective of this thesis is to develop a method by which the potential failure modes during a seismic event for a PTA dam can be evaluated using the linear elastic finite element method of analysis. The most likely potential failure modes (PFM) for PTA designs are due to tensile failure and shear failure. A numerical model of a hypothetical project was developed to simulate PTAs in the dam. The model was subjected to acceleration time-history motions that simulated the seismic loads. The results were used to evaluate the likelihood of tendon failure due to both tension and shear. The results from the analysis indicated that the PTA load increased during the seismic event; however, the peak load in the tendons was less than the gross ultimate tensile strength (GUTS) and would not be expected to result in tensile failure at the assumed project. The analysis

  18. Model-OA wind turbine generator - Failure modes and effects analysis

    NASA Technical Reports Server (NTRS)

    Klein, William E.; Lali, Vincent R.

    1990-01-01

    The results failure modes and effects analysis (FMEA) conducted for wind-turbine generators are presented. The FMEA was performed for the functional modes of each system, subsystem, or component. The single-point failures were eliminated for most of the systems. The blade system was the only exception. The qualitative probability of a blade separating was estimated at level D-remote. Many changes were made to the hardware as a result of this analysis. The most significant change was the addition of the safety system. Operational experience and need to improve machine availability have resulted in subsequent changes to the various systems, which are also reflected in this FMEA.

  19. An improved method for risk evaluation in failure modes and effects analysis of CNC lathe

    NASA Astrophysics Data System (ADS)

    Rachieru, N.; Belu, N.; Anghel, D. C.

    2015-11-01

    Failure mode and effects analysis (FMEA) is one of the most popular reliability analysis tools for identifying, assessing and eliminating potential failure modes in a wide range of industries. In general, failure modes in FMEA are evaluated and ranked through the risk priority number (RPN), which is obtained by the multiplication of crisp values of the risk factors, such as the occurrence (O), severity (S), and detection (D) of each failure mode. However, the crisp RPN method has been criticized to have several deficiencies. In this paper, linguistic variables, expressed in Gaussian, trapezoidal or triangular fuzzy numbers, are used to assess the ratings and weights for the risk factors S, O and D. A new risk assessment system based on the fuzzy set theory and fuzzy rule base theory is to be applied to assess and rank risks associated to failure modes that could appear in the functioning of Turn 55 Lathe CNC. Two case studies have been shown to demonstrate the methodology thus developed. It is illustrated a parallel between the results obtained by the traditional method and fuzzy logic for determining the RPNs. The results show that the proposed approach can reduce duplicated RPN numbers and get a more accurate, reasonable risk assessment. As a result, the stability of product and process can be assured.

  20. Damage mechanics - failure modes

    SciTech Connect

    Krajcinovic, D.; Vujosevic, M.

    1996-12-31

    The present study summarizes the results of the DOE sponsored research program focused on the brittle failure of solids with disordered microstructure. The failure is related to the stochastic processes on the microstructural scale; namely, the nucleation and growth of microcracks. The intrinsic failure modes, such as the percolation, localization and creep rupture, are studied by emphasizing the effect of the micro-structural disorder. A rich spectrum of physical phenomena and new concepts that emerges from this research demonstrates the reasons behind the limitations of traditional, deterministic, and local continuum models.

  1. Failure mode and effect analysis-based quality assurance for dynamic MLC tracking systems

    SciTech Connect

    Sawant, Amit; Dieterich, Sonja; Svatos, Michelle; Keall, Paul

    2010-12-15

    Purpose: To develop and implement a failure mode and effect analysis (FMEA)-based commissioning and quality assurance framework for dynamic multileaf collimator (DMLC) tumor tracking systems. Methods: A systematic failure mode and effect analysis was performed for a prototype real-time tumor tracking system that uses implanted electromagnetic transponders for tumor position monitoring and a DMLC for real-time beam adaptation. A detailed process tree of DMLC tracking delivery was created and potential tracking-specific failure modes were identified. For each failure mode, a risk probability number (RPN) was calculated from the product of the probability of occurrence, the severity of effect, and the detectibility of the failure. Based on the insights obtained from the FMEA, commissioning and QA procedures were developed to check (i) the accuracy of coordinate system transformation, (ii) system latency, (iii) spatial and dosimetric delivery accuracy, (iv) delivery efficiency, and (v) accuracy and consistency of system response to error conditions. The frequency of testing for each failure mode was determined from the RPN value. Results: Failures modes with RPN{>=}125 were recommended to be tested monthly. Failure modes with RPN<125 were assigned to be tested during comprehensive evaluations, e.g., during commissioning, annual quality assurance, and after major software/hardware upgrades. System latency was determined to be {approx}193 ms. The system showed consistent and accurate response to erroneous conditions. Tracking accuracy was within 3%-3 mm gamma (100% pass rate) for sinusoidal as well as a wide variety of patient-derived respiratory motions. The total time taken for monthly QA was {approx}35 min, while that taken for comprehensive testing was {approx}3.5 h. Conclusions: FMEA proved to be a powerful and flexible tool to develop and implement a quality management (QM) framework for DMLC tracking. The authors conclude that the use of FMEA-based QM ensures

  2. Failure mode and effect analysis-based quality assurance for dynamic MLC tracking systems

    PubMed Central

    Sawant, Amit; Dieterich, Sonja; Svatos, Michelle; Keall, Paul

    2010-01-01

    Purpose: To develop and implement a failure mode and effect analysis (FMEA)-based commissioning and quality assurance framework for dynamic multileaf collimator (DMLC) tumor tracking systems. Methods: A systematic failure mode and effect analysis was performed for a prototype real-time tumor tracking system that uses implanted electromagnetic transponders for tumor position monitoring and a DMLC for real-time beam adaptation. A detailed process tree of DMLC tracking delivery was created and potential tracking-specific failure modes were identified. For each failure mode, a risk probability number (RPN) was calculated from the product of the probability of occurrence, the severity of effect, and the detectibility of the failure. Based on the insights obtained from the FMEA, commissioning and QA procedures were developed to check (i) the accuracy of coordinate system transformation, (ii) system latency, (iii) spatial and dosimetric delivery accuracy, (iv) delivery efficiency, and (v) accuracy and consistency of system response to error conditions. The frequency of testing for each failure mode was determined from the RPN value. Results: Failures modes with RPN≥125 were recommended to be tested monthly. Failure modes with RPN<125 were assigned to be tested during comprehensive evaluations, e.g., during commissioning, annual quality assurance, and after major software∕hardware upgrades. System latency was determined to be ∼193 ms. The system showed consistent and accurate response to erroneous conditions. Tracking accuracy was within 3%–3 mm gamma (100% pass rate) for sinusoidal as well as a wide variety of patient-derived respiratory motions. The total time taken for monthly QA was ∼35 min, while that taken for comprehensive testing was ∼3.5 h. Conclusions: FMEA proved to be a powerful and flexible tool to develop and implement a quality management (QM) framework for DMLC tracking. The authors conclude that the use of FMEA-based QM ensures efficient

  3. Performance improvement through proactive risk assessment: Using failure modes and effects analysis

    PubMed Central

    Yarmohammadian, Mohammad Hossein; Abadi, Tahereh Naseri Boori; Tofighi, Shahram; Esfahani, Sekine Saghaeiannejad

    2014-01-01

    Introduction: Cognizance of any error-prone professional activities has a great impact on the continuity of professional organizations in the competitive atmosphere, particularly in health care industry where every second has critical value in patients’ life saving. Considering invaluable functions of medical record department — as legal document and continuity of health care — “failure mode and effects analysis (FMEA)” utilized to identify the ways a process can fail, and how it can be made safer. Materials and Methods: The structured approach involved assembling a team of experts, employing a trained facilitator, introducing the rating scales and process during team orientation and collectively scoring failure modes. The probability of the failure-effect combination was related to the frequency of occurrence, potential severity, and likelihood of detection before causing any harm to the staff or patients. Frequency, severity and detectability were each given a score from 1 to 10. Risk priority numbers were calculated. Results: In total 56 failure modes were identified and in subsets of Medical Record Department including admission unit dividing emergency, outpatient and inpatient classes, statististic, health data organizing and data processing and Medical Coding units. Although most failure modes were classified as a high risk group, limited resources were, as an impediment to implement recommended actions at the same time. Conclusion: Proactive risk assessment methods, such as FMEA enable health care administrators to identify where and what safeguards are needed to protect against a bad outcome even when an error does occur. PMID:25013821

  4. Using the failure mode and effects analysis model to improve parathyroid hormone and adrenocorticotropic hormone testing

    PubMed Central

    Magnezi, Racheli; Hemi, Asaf; Hemi, Rina

    2016-01-01

    Background Risk management in health care systems applies to all hospital employees and directors as they deal with human life and emergency routines. There is a constant need to decrease risk and increase patient safety in the hospital environment. The purpose of this article is to review the laboratory testing procedures for parathyroid hormone and adrenocorticotropic hormone (which are characterized by short half-lives) and to track failure modes and risks, and offer solutions to prevent them. During a routine quality improvement review at the Endocrine Laboratory in Tel Hashomer Hospital, we discovered these tests are frequently repeated unnecessarily due to multiple failures. The repetition of the tests inconveniences patients and leads to extra work for the laboratory and logistics personnel as well as the nurses and doctors who have to perform many tasks with limited resources. Methods A team of eight staff members accompanied by the Head of the Endocrine Laboratory formed the team for analysis. The failure mode and effects analysis model (FMEA) was used to analyze the laboratory testing procedure and was designed to simplify the process steps and indicate and rank possible failures. Results A total of 23 failure modes were found within the process, 19 of which were ranked by level of severity. The FMEA model prioritizes failures by their risk priority number (RPN). For example, the most serious failure was the delay after the samples were collected from the department (RPN =226.1). Conclusion This model helped us to visualize the process in a simple way. After analyzing the information, solutions were proposed to prevent failures, and a method to completely avoid the top four problems was also developed. PMID:27980440

  5. Failure mode and effects analysis of witnessing protocols for ensuring traceability during IVF.

    PubMed

    Rienzi, Laura; Bariani, Fiorenza; Dalla Zorza, Michela; Romano, Stefania; Scarica, Catello; Maggiulli, Roberta; Nanni Costa, Alessandro; Ubaldi, Filippo Maria

    2015-10-01

    Traceability of cells during IVF is a fundamental aspect of treatment, and involves witnessing protocols. Failure mode and effects analysis (FMEA) is a method of identifying real or potential breakdowns in processes, and allows strategies to mitigate risks to be developed. To examine the risks associated with witnessing protocols, an FMEA was carried out in a busy IVF centre, before and after implementation of an electronic witnessing system (EWS). A multidisciplinary team was formed and moderated by human factors specialists. Possible causes of failures, and their potential effects, were identified and risk priority number (RPN) for each failure calculated. A second FMEA analysis was carried out after implementation of an EWS. The IVF team identified seven main process phases, 19 associated process steps and 32 possible failure modes. The highest RPN was 30, confirming the relatively low risk that mismatches may occur in IVF when a manual witnessing system is used. The introduction of the EWS allowed a reduction in the moderate-risk failure mode by two-thirds (highest RPN = 10). In our experience, FMEA is effective in supporting multidisciplinary IVF groups to understand the witnessing process, identifying critical steps and planning changes in practice to enable safety to be enhanced.

  6. Failure modes and effects analysis of a coal-slurry preheater

    SciTech Connect

    Mitchell, H.A.; Parsly, L.F.; Smith, A.N.

    1981-09-01

    The Fossil Energy performance assurance program is concerned with the application of reliability, safety, and quality assurance techniques in the design and operation of the pilot plants and demonstration plants that exist or are being planned as part of the US Department of Energy fossil energy conversion programs. This report involves the application of one technique, failure modes and effects analysis (FMEA), on the safety and reliability analysis of the coal slurry preheater, a critical component in a typical coal direct liquefaction plant. The analysis identifies 55 potential failure modes. Fourteen of these events, if they should occur, would result in losses of sufficient magnitude to require special consideration in the design or operating phase to assure control of risk at an acceptable level. The report concludes that the FMEA could be a valuable tool in the identification of critical components for coal conversion systems. For maximum effect, FMEA needs to be used during the initial design phase. Its principal value is to determine high-risk failure modes, which could have unacceptable impacts on system safety and reliability/availability. The usefulness of FMEA will be improved if it is supplemented by the development of a failure data base; this data base could also be of value in selected cases as input to a more detaled technique such as fault-tree analysis.

  7. Application of failure mode and effect analysis in a radiology department.

    PubMed

    Thornton, Eavan; Brook, Olga R; Mendiratta-Lala, Mishal; Hallett, Donna T; Kruskal, Jonathan B

    2011-01-01

    With increasing deployment, complexity, and sophistication of equipment and related processes within the clinical imaging environment, system failures are more likely to occur. These failures may have varying effects on the patient, ranging from no harm to devastating harm. Failure mode and effect analysis (FMEA) is a tool that permits the proactive identification of possible failures in complex processes and provides a basis for continuous improvement. This overview of the basic principles and methodology of FMEA provides an explanation of how FMEA can be applied to clinical operations in a radiology department to reduce, predict, or prevent errors. The six sequential steps in the FMEA process are explained, and clinical magnetic resonance imaging services are used as an example for which FMEA is particularly applicable. A modified version of traditional FMEA called Healthcare Failure Mode and Effect Analysis, which was introduced by the U.S. Department of Veterans Affairs National Center for Patient Safety, is briefly reviewed. In conclusion, FMEA is an effective and reliable method to proactively examine complex processes in the radiology department. FMEA can be used to highlight the high-risk subprocesses and allows these to be targeted to minimize the future occurrence of failures, thus improving patient safety and streamlining the efficiency of the radiology department.

  8. Failure mode analysis of silicon-based intracortical microelectrode arrays in non-human primates

    NASA Astrophysics Data System (ADS)

    Barrese, James C.; Rao, Naveen; Paroo, Kaivon; Triebwasser, Corey; Vargas-Irwin, Carlos; Franquemont, Lachlan; Donoghue, John P.

    2013-12-01

    Objective. Brain-computer interfaces (BCIs) using chronically implanted intracortical microelectrode arrays (MEAs) have the potential to restore lost function to people with disabilities if they work reliably for years. Current sensors fail to provide reliably useful signals over extended periods of time for reasons that are not clear. This study reports a comprehensive retrospective analysis from a large set of implants of a single type of intracortical MEA in a single species, with a common set of measures in order to evaluate failure modes. Approach. Since 1996, 78 silicon MEAs were implanted in 27 monkeys (Macaca mulatta). We used two approaches to find reasons for sensor failure. First, we classified the time course leading up to complete recording failure as acute (abrupt) or chronic (progressive). Second, we evaluated the quality of electrode recordings over time based on signal features and electrode impedance. Failure modes were divided into four categories: biological, material, mechanical, and unknown. Main results. Recording duration ranged from 0 to 2104 days (5.75 years), with a mean of 387 days and a median of 182 days (n = 78). Sixty-two arrays failed completely with a mean time to failure of 332 days (median = 133 days) while nine array experiments were electively terminated for experimental reasons (mean = 486 days). Seven remained active at the close of this study (mean = 753 days). Most failures (56%) occurred within a year of implantation, with acute mechanical failures the most common class (48%), largely because of connector issues (83%). Among grossly observable biological failures (24%), a progressive meningeal reaction that separated the array from the parenchyma was most prevalent (14.5%). In the absence of acute interruptions, electrode recordings showed a slow progressive decline in spike amplitude, noise amplitude, and number of viable channels that predicts complete signal loss by about eight years. Impedance measurements showed

  9. Application of Failure Mode and Effects Analysis to Intraoperative Radiation Therapy Using Mobile Electron Linear Accelerators

    SciTech Connect

    Ciocca, Mario; Cantone, Marie-Claire; Veronese, Ivan; Cattani, Federica; Pedroli, Guido; Molinelli, Silvia; Vitolo, Viviana; Orecchia, Roberto

    2012-02-01

    Purpose: Failure mode and effects analysis (FMEA) represents a prospective approach for risk assessment. A multidisciplinary working group of the Italian Association for Medical Physics applied FMEA to electron beam intraoperative radiation therapy (IORT) delivered using mobile linear accelerators, aiming at preventing accidental exposures to the patient. Methods and Materials: FMEA was applied to the IORT process, for the stages of the treatment delivery and verification, and consisted of three steps: 1) identification of the involved subprocesses; 2) identification and ranking of the potential failure modes, together with their causes and effects, using the risk probability number (RPN) scoring system, based on the product of three parameters (severity, frequency of occurrence and detectability, each ranging from 1 to 10); 3) identification of additional safety measures to be proposed for process quality and safety improvement. RPN upper threshold for little concern of risk was set at 125. Results: Twenty-four subprocesses were identified. Ten potential failure modes were found and scored, in terms of RPN, in the range of 42-216. The most critical failure modes consisted of internal shield misalignment, wrong Monitor Unit calculation and incorrect data entry at treatment console. Potential causes of failure included shield displacement, human errors, such as underestimation of CTV extension, mainly because of lack of adequate training and time pressures, failure in the communication between operators, and machine malfunctioning. The main effects of failure were represented by CTV underdose, wrong dose distribution and/or delivery, unintended normal tissue irradiation. As additional safety measures, the utilization of a dedicated staff for IORT, double-checking of MU calculation and data entry and finally implementation of in vivo dosimetry were suggested. Conclusions: FMEA appeared as a useful tool for prospective evaluation of patient safety in radiotherapy. The

  10. Risk assessment of the emergency processes: Healthcare failure mode and effect analysis

    PubMed Central

    Taleghani, Yasamin Molavi; Rezaei, Fatemeh; Sheikhbardsiri, Hojat

    2016-01-01

    BACKGROUND: Ensuring about the patient’s safety is the first vital step in improving the quality of care and the emergency ward is known as a high-risk area in treatment health care. The present study was conducted to evaluate the selected risk processes of emergency surgery department of a treatment-educational Qaem center in Mashhad by using analysis method of the conditions and failure effects in health care. METHODS: In this study, in combination (qualitative action research and quantitative cross-sectional), failure modes and effects of 5 high-risk procedures of the emergency surgery department were identified and analyzed according to Healthcare Failure Mode and Effects Analysis (HFMEA). To classify the failure modes from the “nursing errors in clinical management model (NECM)”, the classification of the effective causes of error from “Eindhoven model” and determination of the strategies to improve from the “theory of solving problem by an inventive method” were used. To analyze the quantitative data of descriptive statistics (total points) and to analyze the qualitative data, content analysis and agreement of comments of the members were used. RESULTS: In 5 selected processes by “voting method using rating”, 23 steps, 61 sub-processes and 217 potential failure modes were identified by HFMEA. 25 (11.5%) failure modes as the high risk errors were detected and transferred to the decision tree. The most and the least failure modes were placed in the categories of care errors (54.7%) and knowledge and skill (9.5%), respectively. Also, 29.4% of preventive measures were in the category of human resource management strategy. CONCLUSION: “Revision and re-engineering of processes”, “continuous monitoring of the works”, “preparation and revision of operating procedures and policies”, “developing the criteria for evaluating the performance of the personnel”, “designing a suitable educational content for needs of employee”,

  11. Failure mode and effects analysis using intuitionistic fuzzy hybrid weighted Euclidean distance operator

    NASA Astrophysics Data System (ADS)

    Liu, Hu-Chen; Liu, Long; Li, Ping

    2014-10-01

    Failure mode and effects analysis (FMEA) has shown its effectiveness in examining potential failures in products, process, designs or services and has been extensively used for safety and reliability analysis in a wide range of industries. However, its approach to prioritise failure modes through a crisp risk priority number (RPN) has been criticised as having several shortcomings. The aim of this paper is to develop an efficient and comprehensive risk assessment methodology using intuitionistic fuzzy hybrid weighted Euclidean distance (IFHWED) operator to overcome the limitations and improve the effectiveness of the traditional FMEA. The diversified and uncertain assessments given by FMEA team members are treated as linguistic terms expressed in intuitionistic fuzzy numbers (IFNs). Intuitionistic fuzzy weighted averaging (IFWA) operator is used to aggregate the FMEA team members' individual assessments into a group assessment. IFHWED operator is applied thereafter to the prioritisation and selection of failure modes. Particularly, both subjective and objective weights of risk factors are considered during the risk evaluation process. A numerical example for risk assessment is given to illustrate the proposed method finally.

  12. Model OA Wind Turbine Generator FEMA (Failure Modes and Effects Analysis)

    SciTech Connect

    Klein, W.E. . Plum Brook Station); Lalli, V.R. . Lewis Research Center)

    1989-10-01

    This report presents the results of Failure Modes and Effects Analysis (FMEA) conducted for the Wind Turbine Generators. The FMEA was performed for the functional modes of each system, subsystem, or component. The single-point failures were eliminated for most of the systems. The blade system was the only exception. The qualitative probability of a blade separating was estimated at Level D-remote. Many changes were made to the hardware as a result of this analysis. The most significant change was the addition of the safety system. Operational experience and need to improve machine availability have resulted in subsequent changes to the various systems which are also reflected in this FMEA. 2 refs., 3 figs.

  13. Using causal reasoning for automated failure modes and effects analysis (FMEA)

    NASA Astrophysics Data System (ADS)

    Bell, Daniel; Cox, Lisa; Jackson, Steve; Schaefer, Phil

    The authors have developed a tool that automates the reasoning portion of a failure modes and effects analysis (FMEA). It is built around a flexible causal reasoning module that has been adapted to the FMEA procedure. The approach and software architecture have been proven. A prototype tool has been created and successfully passed a test and evaluation program. The authors are expanding the operational capability and adapting the tool to various CAD/CAE (computer-aided design and engineering) platforms.

  14. Common Cause Failure Modes

    NASA Technical Reports Server (NTRS)

    Wetherholt, Jon; Heimann, Timothy J.; Anderson, Brenda

    2011-01-01

    High technology industries with high failure costs commonly use redundancy as a means to reduce risk. Redundant systems, whether similar or dissimilar, are susceptible to Common Cause Failures (CCF). CCF is not always considered in the design effort and, therefore, can be a major threat to success. There are several aspects to CCF which must be understood to perform an analysis which will find hidden issues that may negate redundancy. This paper will provide definition, types, a list of possible causes and some examples of CCF. Requirements and designs from NASA projects will be used in the paper as examples.

  15. Using Failure Mode and Effects Analysis to design a comfortable automotive driver seat.

    PubMed

    Kolich, Mike

    2014-07-01

    Given enough time and use, all designs will fail. There are no fail-free designs. This is especially true when it comes to automotive seating comfort where the characteristics and preferences of individual customers are many and varied. To address this problem, individuals charged with automotive seating comfort development have, traditionally, relied on iterative and, as a result, expensive build-test cycles. Cost pressures being placed on today's vehicle manufacturers have necessitated the search for more efficient alternatives. This contribution aims to fill this need by proposing the application of an analytical technique common to engineering circles (but new to seating comfort development), namely Design Failure Mode and Effects Analysis (DFMEA). An example is offered to describe how development teams can use this systematic and disciplined approach to highlight potential seating comfort failure modes, reduce their risk, and bring capable designs to life.

  16. SU-E-T-420: Failure Effects Mode Analysis for Trigeminal Neuralgia Frameless Radiosurgery

    SciTech Connect

    Howe, J

    2015-06-15

    Purpose: Functional radiosurgery has been used successfully in the treatment of trigeminal neuralgia but presents significant challenges to ensuring the high prescription dose is delivered accurately. A review of existing practice should help direct the focus of quality improvement for this treatment regime. Method: Failure modes and effects analysis was used to identify the processes in preparing radiosurgery treatment for TN. The map was developed by a multidisciplinary team including: neurosurgeon, radiation oncology, physicist and therapist. Potential failure modes were identified for each step in the process map as well as potential causes and end effect. A risk priority number was assigned to each cause. Results: The process map identified 66 individual steps (see attached supporting document). Corrective actions were developed for areas of high risk priority number. Wrong site treatment is at higher risk for trigeminal neuralgia treatment due to the lack of site specific pathologic imaging on MR and CT – additional site specific checks were implemented to minimize the risk of wrong site treatment. Failed collision checks resulted from an insufficient collision model in the treatment planning system and a plan template was developed to address this problem. Conclusion: Failure modes and effects analysis is an effective tool for developing quality improvement in high risk radiotherapy procedures such as functional radiosurgery.

  17. Material wear and failure mode analysis of breakfast cereal extruder barrels and screw elements

    NASA Astrophysics Data System (ADS)

    Mastio, Michael Joseph, Jr.

    2005-11-01

    Nearly seventy-five years ago, the single screw extruder was introduced as a means to produce metal products. Shortly after that, the extruder found its way into the plastics industry. Today much of the world's polymer industry utilizes extruders to produce items such as soda bottles, PVC piping, and toy figurines. Given the significant economical advantages of extruders over conventional batch flow systems, extruders have also migrated into the food industry. Food applications include the meat, pet food, and cereal industries to name just a few. Cereal manufacturers utilize extruders to produce various forms of Ready-to-Eat (RTE) cereals. These cereals are made from grains such as rice, oats, wheat, and corn. The food industry has been incorrectly viewed as an extruder application requiring only minimal energy control and performance capability. This misconception has resulted in very little research in the area of material wear and failure mode analysis of breakfast cereal extruders. Breakfast cereal extruder barrels and individual screw elements are subjected to the extreme pressures and temperatures required to shear and cook the cereal ingredients, resulting in excessive material wear and catastrophic failure of these components. Therefore, this project focuses on the material wear and failure mode analysis of breakfast cereal extruder barrels and screw elements, modeled as a Discrete Time Markov Chain (DTMC) process in which historical data is used to predict future failures. Such predictive analysis will yield cost savings opportunities by providing insight into extruder maintenance scheduling and interchangeability of screw elements. In this DTMC wear analysis, four states of wear are defined and a probability transition matrix is determined based upon 24,041 hours of operational data. This probability transition matrix is used to predict when an extruder component will move to the next state of wear and/or failure. This information can be used to determine

  18. Anticipating risk for human subjects participating in clinical research: application of Failure Mode and Effects Analysis.

    PubMed

    Cody, Robert J

    2006-03-01

    Failure Mode and Effects Analysis (FMEA) is a method applied in various industries to anticipate and mitigate risk. This methodology can be more systematically applied to the protection of human subjects in research. The purpose of FMEA is simple: prevent problems before they occur. By applying FMEA process analysis to the elements of a specific research protocol, the failure severity, occurrence, and detection rates can be estimated for calculation of a "risk priority number" (RPN). Methods can then be identified to reduce the RPN to levels where the risk/benefit ratio favors human subject benefit, to a greater magnitude than existed in the pre-analysis risk profile. At the very least, the approach provides a checklist of issues that can be individualized for specific research protocols or human subject populations.

  19. Failure Mode and Effect Analysis for Delivery of Lung Stereotactic Body Radiation Therapy

    SciTech Connect

    Perks, Julian R.; Stanic, Sinisa; Stern, Robin L.; Henk, Barbara; Nelson, Marsha S.; Harse, Rick D.; Mathai, Mathew; Purdy, James A.; Valicenti, Richard K.; Siefkin, Allan D.; Chen, Allen M.

    2012-07-15

    Purpose: To improve the quality and safety of our practice of stereotactic body radiation therapy (SBRT), we analyzed the process following the failure mode and effects analysis (FMEA) method. Methods: The FMEA was performed by a multidisciplinary team. For each step in the SBRT delivery process, a potential failure occurrence was derived and three factors were assessed: the probability of each occurrence, the severity if the event occurs, and the probability of detection by the treatment team. A rank of 1 to 10 was assigned to each factor, and then the multiplied ranks yielded the relative risks (risk priority numbers). The failure modes with the highest risk priority numbers were then considered to implement process improvement measures. Results: A total of 28 occurrences were derived, of which nine events scored with significantly high risk priority numbers. The risk priority numbers of the highest ranked events ranged from 20 to 80. These included transcription errors of the stereotactic coordinates and machine failures. Conclusion: Several areas of our SBRT delivery were reconsidered in terms of process improvement, and safety measures, including treatment checklists and a surgical time-out, were added for our practice of gantry-based image-guided SBRT. This study serves as a guide for other users of SBRT to perform FMEA of their own practice.

  20. Application of failure mode and effects analysis (FMEA) to pretreatment phases in tomotherapy.

    PubMed

    Broggi, Sara; Cantone, Marie Claire; Chiara, Anna; Di Muzio, Nadia; Longobardi, Barbara; Mangili, Paola; Veronese, Ivan

    2013-09-06

    The aim of this paper was the application of the failure mode and effects analysis (FMEA) approach to assess the risks for patients undergoing radiotherapy treatments performed by means of a helical tomotherapy unit. FMEA was applied to the preplanning imaging, volume determination, and treatment planning stages of the tomotherapy process and consisted of three steps: 1) identification of the involved subprocesses; 2) identification and ranking of the potential failure modes, together with their causes and effects, using the risk probability number (RPN) scoring system; and 3) identification of additional safety measures to be proposed for process quality and safety improvement. RPN upper threshold for little concern of risk was set at 125. A total of 74 failure modes were identified: 38 in the stage of preplanning imaging and volume determination, and 36 in the stage of planning. The threshold of 125 for RPN was exceeded in four cases: one case only in the phase of preplanning imaging and volume determination, and three cases in the stage of planning. The most critical failures appeared related to (i) the wrong or missing definition and contouring of the overlapping regions, (ii) the wrong assignment of the overlap priority to each anatomical structure, (iii) the wrong choice of the computed tomography calibration curve for dose calculation, and (iv) the wrong (or not performed) choice of the number of fractions in the planning station. On the basis of these findings, in addition to the safety strategies already adopted in the clinical practice, novel solutions have been proposed for mitigating the risk of these failures and to increase patient safety.

  1. Failure mode analysis of silicon-based intracortical microelectrode arrays in non-human primates

    PubMed Central

    Barrese, James C; Rao, Naveen; Paroo, Kaivon; Triebwasser, Corey; Vargas-Irwin, Carlos; Franquemont, Lachlan; Donoghue, John P

    2016-01-01

    Objective Brain–computer interfaces (BCIs) using chronically implanted intracortical microelectrode arrays (MEAs) have the potential to restore lost function to people with disabilities if they work reliably for years. Current sensors fail to provide reliably useful signals over extended periods of time for reasons that are not clear. This study reports a comprehensive retrospective analysis from a large set of implants of a single type of intracortical MEA in a single species, with a common set of measures in order to evaluate failure modes. Approach Since 1996, 78 silicon MEAs were implanted in 27 monkeys (Macaca mulatta). We used two approaches to find reasons for sensor failure. First, we classified the time course leading up to complete recording failure as acute (abrupt) or chronic (progressive). Second, we evaluated the quality of electrode recordings over time based on signal features and electrode impedance. Failure modes were divided into four categories: biological, material, mechanical, and unknown. Main results Recording duration ranged from 0 to 2104 days (5.75 years), with a mean of 387 days and a median of 182 days (n = 78). Sixty-two arrays failed completely with a mean time to failure of 332 days (median = 133 days) while nine array experiments were electively terminated for experimental reasons (mean = 486 days). Seven remained active at the close of this study (mean = 753 days). Most failures (56%) occurred within a year of implantation, with acute mechanical failures the most common class (48%), largely because of connector issues (83%). Among grossly observable biological failures (24%), a progressive meningeal reaction that separated the array from the parenchyma was most prevalent (14.5%). In the absence of acute interruptions, electrode recordings showed a slow progressive decline in spike amplitude, noise amplitude, and number of viable channels that predicts complete signal loss by about eight years. Impedance measurements showed

  2. SU-E-T-627: Failure Modes and Effect Analysis for Monthly Quality Assurance of Linear Accelerator

    SciTech Connect

    Xie, J; Xiao, Y; Wang, J; Peng, J; Lu, S; Hu, W

    2014-06-15

    Purpose: To develop and implement a failure mode and effect analysis (FMEA) on routine monthly Quality Assurance (QA) tests (physical tests part) of linear accelerator. Methods: A systematic failure mode and effect analysis method was performed for monthly QA procedures. A detailed process tree of monthly QA was created and potential failure modes were defined. Each failure mode may have many influencing factors. For each factor, a risk probability number (RPN) was calculated from the product of probability of occurrence (O), the severity of effect (S), and detectability of the failure (D). The RPN scores are in a range of 1 to 1000, with higher scores indicating stronger correlation to a given influencing factor of a failure mode. Five medical physicists in our institution were responsible to discuss and to define the O, S, D values. Results: 15 possible failure modes were identified and all RPN scores of all influencing factors of these 15 failue modes were from 8 to 150, and the checklist of FMEA in monthly QA was drawn. The system showed consistent and accurate response to erroneous conditions. Conclusion: The influencing factors of RPN greater than 50 were considered as highly-correlated factors of a certain out-oftolerance monthly QA test. FMEA is a fast and flexible tool to develop an implement a quality management (QM) frame work of monthly QA, which improved the QA efficiency of our QA team. The FMEA work may incorporate more quantification and monitoring fuctions in future.

  3. Failure mode and effects analysis of skin electronic brachytherapy using Esteya® unit

    PubMed Central

    Bautista-Ballesteros, Juan Antonio; Bonaque, Jorge; Celada, Francisco; Lliso, Françoise; Carmona, Vicente; Gimeno-Olmos, Jose; Ouhib, Zoubir; Rosello, Joan; Perez-Calatayud, Jose

    2016-01-01

    Purpose Esteya® (Nucletron, an Elekta company, Elekta AB, Stockholm, Sweden) is an electronic brachytherapy device used for skin cancer lesion treatment. In order to establish an adequate level of quality of treatment, a risk analysis of the Esteya treatment process has been done, following the methodology proposed by the TG-100 guidelines of the American Association of Physicists in Medicine (AAPM). Material and methods A multidisciplinary team familiar with the treatment process was formed. This team developed a process map (PM) outlining the stages, through which a patient passed when subjected to the Esteya treatment. They identified potential failure modes (FM) and each individual FM was assessed for the severity (S), frequency of occurrence (O), and lack of detection (D). A list of existing quality management tools was developed and the FMs were consensually reevaluated. Finally, the FMs were ranked according to their risk priority number (RPN) and their S. Results 146 FMs were identified, 106 of which had RPN ≥ 50 and 30 had S ≥ 7. After introducing the quality management tools, only 21 FMs had RPN ≥ 50. The importance of ensuring contact between the applicator and the surface of the patient’s skin was emphasized, so the setup was reviewed by a second individual before each treatment session with periodic quality control to ensure stability of the applicator pressure. Some of the essential quality management tools are already being implemented in the installation are the simple templates for reproducible positioning of skin applicators, that help marking the treatment area and positioning of X-ray tube. Conclusions New quality management tools have been established as a result of the application of the failure modes and effects analysis (FMEA) treatment. However, periodic update of the FMEA process is necessary, since clinical experience has suggested occurring of further new possible potential failure modes. PMID:28115958

  4. Use of failure mode effect analysis (FMEA) to improve medication management process.

    PubMed

    Jain, Khushboo

    2017-03-13

    Purpose Medication management is a complex process, at high risk of error with life threatening consequences. The focus should be on devising strategies to avoid errors and make the process self-reliable by ensuring prevention of errors and/or error detection at subsequent stages. The purpose of this paper is to use failure mode effect analysis (FMEA), a systematic proactive tool, to identify the likelihood and the causes for the process to fail at various steps and prioritise them to devise risk reduction strategies to improve patient safety. Design/methodology/approach The study was designed as an observational analytical study of medication management process in the inpatient area of a multi-speciality hospital in Gurgaon, Haryana, India. A team was made to study the complex process of medication management in the hospital. FMEA tool was used. Corrective actions were developed based on the prioritised failure modes which were implemented and monitored. Findings The percentage distribution of medication errors as per the observation made by the team was found to be maximum of transcription errors (37 per cent) followed by administration errors (29 per cent) indicating the need to identify the causes and effects of their occurrence. In all, 11 failure modes were identified out of which major five were prioritised based on the risk priority number (RPN). The process was repeated after corrective actions were taken which resulted in about 40 per cent (average) and around 60 per cent reduction in the RPN of prioritised failure modes. Research limitations/implications FMEA is a time consuming process and requires a multidisciplinary team which has good understanding of the process being analysed. FMEA only helps in identifying the possibilities of a process to fail, it does not eliminate them, additional efforts are required to develop action plans and implement them. Frank discussion and agreement among the team members is required not only for successfully conducing

  5. Cost Based Failure Modes and Effects Analysis (FMEA) for Systems of Accelerator Magnets.

    SciTech Connect

    Spencer, Cherrill M

    2003-06-02

    The proposed Next Linear Collider (NLC) has a proposed 85% overall availability goal, the availability specifications for all its 7200 magnets and their 6167 power supplies are 97.5% each. Thus all of the electromagnets and their power supplies must be highly reliable or quickly repairable. Improved reliability or repairability comes at a higher cost. We have developed a set of analysis procedures for magnet designers to use as they decide how much effort to exert, i.e. how much money to spend, to improve the reliability of a particular style of magnet. We show these procedures being applied to a standard SLAC electromagnet design in order to make it reliable enough to meet the NLC availability specs. First, empirical data from SLAC's accelerator failure database plus design experience are used to calculate MTBF for failure modes identified through a FMEA. Availability for one particular magnet can be calculated. Next, labor and material costs to repair magnet failures are used in a Monte Carlo simulation to calculate the total cost of all failures over a 30-year lifetime. Opportunity costs are included. Engineers choose from amongst various designs by comparing lifecycle costs.

  6. Practical Implementation of Failure Mode and Effects Analysis for Safety and Efficiency in Stereotactic Radiosurgery

    SciTech Connect

    Younge, Kelly Cooper; Wang, Yizhen; Thompson, John; Giovinazzo, Julia; Finlay, Marisa

    2015-04-01

    Purpose: To improve the safety and efficiency of a new stereotactic radiosurgery program with the application of failure mode and effects analysis (FMEA) performed by a multidisciplinary team of health care professionals. Methods and Materials: Representatives included physicists, therapists, dosimetrists, oncologists, and administrators. A detailed process tree was created from an initial high-level process tree to facilitate the identification of possible failure modes. Group members were asked to determine failure modes that they considered to be the highest risk before scoring failure modes. Risk priority numbers (RPNs) were determined by each group member individually and then averaged. Results: A total of 99 failure modes were identified. The 5 failure modes with an RPN above 150 were further analyzed to attempt to reduce these RPNs. Only 1 of the initial items that the group presumed to be high-risk (magnetic resonance imaging laterality reversed) was ranked in these top 5 items. New process controls were put in place to reduce the severity, occurrence, and detectability scores for all of the top 5 failure modes. Conclusions: FMEA is a valuable team activity that can assist in the creation or restructuring of a quality assurance program with the aim of improved safety, quality, and efficiency. Performing the FMEA helped group members to see how they fit into the bigger picture of the program, and it served to reduce biases and preconceived notions about which elements of the program were the riskiest.

  7. Failure mode and effects analysis (FMEA) for the Space Shuttle solid rocket motor

    NASA Technical Reports Server (NTRS)

    Russell, D. L.; Blacklock, K.; Langhenry, M. T.

    1988-01-01

    The recertification of the Space Shuttle Solid Rocket Booster (SRB) and Solid Rocket Motor (SRM) has included an extensive rewriting of the Failure Mode and Effects Analysis (FMEA) and Critical Items List (CIL). The evolution of the groundrules and methodology used in the analysis is discussed and compared to standard FMEA techniques. Especially highlighted are aspects of the FMEA/CIL which are unique to the analysis of an SRM. The criticality category definitions are presented and the rationale for assigning criticality is presented. The various data required by the CIL and contribution of this data to the retention rationale is also presented. As an example, the FMEA and CIL for the SRM nozzle assembly is discussed in detail. This highlights some of the difficulties associated with the analysis of a system with the unique mission requirements of the Space Shuttle.

  8. Risk management for outsourcing biomedical waste disposal – Using the failure mode and effects analysis

    SciTech Connect

    Liao, Ching-Jong; Ho, Chao Chung

    2014-07-15

    Highlights: • This study is based on a real case in hospital in Taiwan. • We use Failure Mode and Effects Analysis (FMEA) as the evaluation method. • We successfully identify the evaluation factors of bio-medical waste disposal risk. - Abstract: Using the failure mode and effects analysis, this study examined biomedical waste companies through risk assessment. Moreover, it evaluated the supervisors of biomedical waste units in hospitals, and factors relating to the outsourcing risk assessment of biomedical waste in hospitals by referring to waste disposal acts. An expert questionnaire survey was conducted on the personnel involved in waste disposal units in hospitals, in order to identify important factors relating to the outsourcing risk of biomedical waste in hospitals. This study calculated the risk priority number (RPN) and selected items with an RPN value higher than 80 for improvement. These items included “availability of freezing devices”, “availability of containers for sharp items”, “disposal frequency”, “disposal volume”, “disposal method”, “vehicles meeting the regulations”, and “declaration of three lists”. This study also aimed to identify important selection factors of biomedical waste disposal companies by hospitals in terms of risk. These findings can serve as references for hospitals in the selection of outsourcing companies for biomedical waste disposal.

  9. Outcomes of a Failure Mode and Effects Analysis for medication errors in pediatric anesthesia.

    PubMed

    Martin, Lizabeth D; Grigg, Eliot B; Verma, Shilpa; Latham, Gregory J; Rampersad, Sally E; Martin, Lynn D

    2017-03-28

    The Institute of Medicine has called for development of strategies to prevent medication errors, which are one important cause of preventable harm. Although the field of anesthesiology is considered a leader in patient safety, recent data suggest high medication error rates in anesthesia practice. Unfortunately, few error prevention strategies for anesthesia providers have been implemented. Using Toyota Production System quality improvement methodology, a multidisciplinary team observed 133 h of medication practice in the operating room at a tertiary care freestanding children's hospital. A failure mode and effects analysis was conducted to systematically deconstruct and evaluate each medication handling process step and score possible failure modes to quantify areas of risk. A bundle of five targeted countermeasures were identified and implemented over 12 months. Improvements in syringe labeling (73 to 96%), standardization of medication organization in the anesthesia workspace (0 to 100%), and two-provider infusion checks (23 to 59%) were observed. Medication error reporting improved during the project and was subsequently maintained. After intervention, the median medication error rate decreased from 1.56 to 0.95 per 1000 anesthetics. The frequency of medication error harm events reaching the patient also decreased. Systematic evaluation and standardization of medication handling processes by anesthesia providers in the operating room can decrease medication errors and improve patient safety.

  10. Failure mode and effects analysis of witnessing protocols for ensuring traceability during PGD/PGS cycles.

    PubMed

    Cimadomo, Danilo; Ubaldi, Filippo Maria; Capalbo, Antonio; Maggiulli, Roberta; Scarica, Catello; Romano, Stefania; Poggiana, Cristina; Zuccarello, Daniela; Giancani, Adriano; Vaiarelli, Alberto; Rienzi, Laura

    2016-09-01

    Preimplantation genetic diagnosis and aneuploidy testing (PGD/PGS) use is constantly growing in IVF, and embryo/biopsy traceability during the additional laboratory procedures needed is pivotal. An electronic witnessing system (EWS), which showed a significant value in decreasing mismatch occurrence and increasing detection possibilities during standard care IVF, still does not guarantee the same level of efficiency during PGD/PGS cycles. Specifically, EWS cannot follow single embryos throughout the procedure. This is however critical when an unambiguous diagnosis corresponds to each embryo. Failure Mode and Effects Analysis (FMEA) is a proactive method generally adopted to define tools ensuring safety along a procedure. Due to the implementation of a large quantitative PCR (qPCR)-based blastocyst stage PGD/PGS programme in our centre, and to evaluate the potential procedural risks, a FMEA was performed in September 2014. Forty-four failure modes were identified, among which six were given a moderate risk priority number (>15) (RPN; product of estimated occurrence, severity and detection). Specific corrective measures were then introduced and implemented, and a second evaluation performed six months later. The meticulous and careful application of such measures allowed the risks to be decreased along the whole protocol, by reducing their estimated occurrence and/or increasing detection possibilities.

  11. Human factors process failure modes and effects analysis (HF PFMEA) software tool

    NASA Technical Reports Server (NTRS)

    Chandler, Faith T. (Inventor); Valentino, William D. (Inventor); Philippart, Monica F. (Inventor); Relvini, Kristine M. (Inventor); Bessette, Colette I. (Inventor); Shedd, Nathaneal P. (Inventor)

    2011-01-01

    Methods, computer-readable media, and systems for automatically performing Human Factors Process Failure Modes and Effects Analysis for a process are provided. At least one task involved in a process is identified, where the task includes at least one human activity. The human activity is described using at least one verb. A human error potentially resulting from the human activity is automatically identified, the human error is related to the verb used in describing the task. A likelihood of occurrence, detection, and correction of the human error is identified. The severity of the effect of the human error is identified. The likelihood of occurrence, and the severity of the risk of potential harm is identified. The risk of potential harm is compared with a risk threshold to identify the appropriateness of corrective measures.

  12. Optimisation of shock absorber process parameters using failure mode and effect analysis and genetic algorithm

    NASA Astrophysics Data System (ADS)

    Mariajayaprakash, Arokiasamy; Senthilvelan, Thiyagarajan; Vivekananthan, Krishnapillai Ponnambal

    2013-07-01

    The various process parameters affecting the quality characteristics of the shock absorber during the process were identified using the Ishikawa diagram and by failure mode and effect analysis. The identified process parameters are welding process parameters (squeeze, heat control, wheel speed, and air pressure), damper sealing process parameters (load, hydraulic pressure, air pressure, and fixture height), washing process parameters (total alkalinity, temperature, pH value of rinsing water, and timing), and painting process parameters (flowability, coating thickness, pointage, and temperature). In this paper, the process parameters, namely, painting and washing process parameters, are optimized by Taguchi method. Though the defects are reasonably minimized by Taguchi method, in order to achieve zero defects during the processes, genetic algorithm technique is applied on the optimized parameters obtained by Taguchi method.

  13. A blackboard model of an expert system for failure mode and effects analysis

    NASA Astrophysics Data System (ADS)

    Russomanno, David J.; Bonnell, Ronald D.; Bowles, John B.

    The design of an expert system to assist in performing a failure mode and effects analysis (FMEA) is approached from a knowledge-use-level perspective to provide a thorough understanding of the problem and insight into the knowledge and expertise needed to automate the FMEA process. A blackboard model is a conceptual model that provides the organizational principles required for the design of an expert system without actually specifying its realization. In the blackboard model of an intelligent FMEA, the system is functionally decomposed into a set of knowledge sources, each containing the knowledge associated with a subfunction of the FMEA process. The conceptual model derived can be used to evaluate attempts to automate the FMEA process, and it can serve as the foundation for further research into automating the FMEA process. An example is presented illustrating the interaction among the knowledge sources in the blackboard model to construct a FMEA for a domestic hot water heater.

  14. Incident Learning and Failure-Mode-and-Effects-Analysis Guided Safety Initiatives in Radiation Medicine

    PubMed Central

    Kapur, Ajay; Goode, Gina; Riehl, Catherine; Zuvic, Petrina; Joseph, Sherin; Adair, Nilda; Interrante, Michael; Bloom, Beatrice; Lee, Lucille; Sharma, Rajiv; Sharma, Anurag; Antone, Jeffrey; Riegel, Adam; Vijeh, Lili; Zhang, Honglai; Cao, Yijian; Morgenstern, Carol; Montchal, Elaine; Cox, Brett; Potters, Louis

    2013-01-01

    By combining incident learning and process failure-mode-and-effects-analysis (FMEA) in a structure-process-outcome framework we have created a risk profile for our radiation medicine practice and implemented evidence-based risk-mitigation initiatives focused on patient safety. Based on reactive reviews of incidents reported in our departmental incident-reporting system and proactive FMEA, high safety-risk procedures in our paperless radiation medicine process and latent risk factors were identified. Six initiatives aimed at the mitigation of associated severity, likelihood-of-occurrence, and detectability risks were implemented. These were the standardization of care pathways and toxicity grading, pre-treatment-planning peer review, a policy to thwart delay-rushed processes, an electronic whiteboard to enhance coordination, and the use of six sigma metrics to monitor operational efficiencies. The effectiveness of these initiatives over a 3-years period was assessed using process and outcome specific metrics within the framework of the department structure. There has been a 47% increase in incident-reporting, with no increase in adverse events. Care pathways have been used with greater than 97% clinical compliance rate. The implementation of peer review prior to treatment-planning and use of the whiteboard have provided opportunities for proactive detection and correction of errors. There has been a twofold drop in the occurrence of high-risk procedural delays. Patient treatment start delays are routinely enforced on cases that would have historically been rushed. Z-scores for high-risk procedures have steadily improved from 1.78 to 2.35. The initiatives resulted in sustained reductions of failure-mode risks as measured by a set of evidence-based metrics over a 3-years period. These augment or incorporate many of the published recommendations for patient safety in radiation medicine by translating them to clinical practice. PMID:24380074

  15. Comparison Study of Electromagnet and Permanent Magnet Systems for an Accelerator Using Cost-Based Failure Modes and Effects Analysis.

    SciTech Connect

    Spencer, C

    2004-02-19

    The next generation of particle accelerators will be one-of-a-kind facilities, and to meet their luminosity goals they must have guaranteed availability over their several decade lifetimes. The Next Linear Collider (NLC) is one viable option for a 1 TeV electron-positron linear collider, it has an 85% overall availability goal. We previously showed how a traditional Failure Modes and Effects Analysis (FMEA) of a SLAC electromagnet leads to reliability-enhancing design changes. Traditional FMEA identifies failure modes with high risk but does not consider the consequences in terms of cost, which could lead to unnecessarily expensive components. We have used a new methodology, ''Life Cost-Based FMEA'', which measures risk of failure in terms of cost, in order to evaluate and compare two different technologies that might be used for the 8653 NLC magnets: electromagnets or permanent magnets. The availabilities for the two different types of magnet systems have been estimated using empirical data from SLAC's accelerator failure database plus expert opinion on permanent magnet failure modes and industry standard failure data. Labor and material costs to repair magnet failures are predicted using a Monte Carlo simulation of all possible magnet failures over a 30-year lifetime. Our goal is to maximize up-time of the NLC through magnet design improvements and the optimal combination of electromagnets and permanent magnets, while reducing magnet system lifecycle costs.

  16. Failure Modes Effects and Criticality Analysis, an Underutilized Safety, Reliability, Project Management and Systems Engineering Tool

    NASA Astrophysics Data System (ADS)

    Mullin, Daniel Richard

    2013-09-01

    The majority of space programs whether manned or unmanned for science or exploration require that a Failure Modes Effects and Criticality Analysis (FMECA) be performed as part of their safety and reliability activities. This comes as no surprise given that FMECAs have been an integral part of the reliability engineer's toolkit since the 1950s. The reasons for performing a FMECA are well known including fleshing out system single point failures, system hazards and critical components and functions. However, in the author's ten years' experience as a space systems safety and reliability engineer, findings demonstrate that the FMECA is often performed as an afterthought, simply to meet contract deliverable requirements and is often started long after the system requirements allocation and preliminary design have been completed. There are also important qualitative and quantitative components often missing which can provide useful data to all of project stakeholders. These include; probability of occurrence, probability of detection, time to effect and time to detect and, finally, the Risk Priority Number. This is unfortunate as the FMECA is a powerful system design tool that when used effectively, can help optimize system function while minimizing the risk of failure. When performed as early as possible in conjunction with writing the top level system requirements, the FMECA can provide instant feedback on the viability of the requirements while providing a valuable sanity check early in the design process. It can indicate which areas of the system will require redundancy and which areas are inherently the most risky from the onset. Based on historical and practical examples, it is this author's contention that FMECAs are an immense source of important information for all involved stakeholders in a given project and can provide several benefits including, efficient project management with respect to cost and schedule, system engineering and requirements management

  17. Evaluating the application of failure mode and effects analysis technique in hospital wards: a systematic review

    PubMed Central

    Asgari Dastjerdi, Hoori; Khorasani, Elahe; Yarmohammadian, Mohammad Hossein; Ahmadzade, Mahdiye Sadat

    2017-01-01

    Abstract: Background: Medical errors are one of the greatest problems in any healthcare systems. The best way to prevent such problems is errors identification and their roots. Failure Mode and Effects Analysis (FMEA) technique is a prospective risk analysis method. This study is a review of risk analysis using FMEA technique in different hospital wards and departments. Methods: This paper has systematically investigated the available databases. After selecting inclusion and exclusion criteria, the related studies were found. This selection was made in two steps. First, the abstracts and titles were investigated by the researchers and, after omitting papers which did not meet the inclusion criteria, 22 papers were finally selected and the text was thoroughly examined. At the end, the results were obtained. Results: The examined papers had focused mostly on the process and had been conducted in the pediatric wards and radiology departments, and most participants were nursing staffs. Many of these papers attempted to express almost all the steps of model implementation; and after implementing the strategies and interventions, the Risk Priority Number (RPN) was calculated to determine the degree of the technique’s effect. However, these papers have paid less attention to the identification of risk effects. Conclusions: The study revealed that a small number of studies had failed to show the FMEA technique effects. In general, however, most of the studies recommended this technique and had considered it a useful and efficient method in reducing the number of risks and improving service quality. PMID:28039688

  18. Failure mode and effects analysis based risk profile assessment for stereotactic radiosurgery programs at three cancer centers in Brazil

    SciTech Connect

    Teixeira, Flavia C.

    2016-01-15

    Purpose: The goal of this study was to evaluate the safety and quality management program for stereotactic radiosurgery (SRS) treatment processes at three radiotherapy centers in Brazil by using three industrial engineering tools (1) process mapping, (2) failure modes and effects analysis (FMEA), and (3) fault tree analysis. Methods: The recommendations of Task Group 100 of American Association of Physicists in Medicine were followed to apply the three tools described above to create a process tree for SRS procedure for each radiotherapy center and then FMEA was performed. Failure modes were identified for all process steps and values of risk priority number (RPN) were calculated from O, S, and D (RPN = O × S × D) values assigned by a professional team responsible for patient care. Results: The subprocess treatment planning was presented with the highest number of failure modes for all centers. The total number of failure modes were 135, 104, and 131 for centers I, II, and III, respectively. The highest RPN value for each center is as follows: center I (204), center II (372), and center III (370). Failure modes with RPN ≥ 100: center I (22), center II (115), and center III (110). Failure modes characterized by S ≥ 7, represented 68% of the failure modes for center III, 62% for center II, and 45% for center I. Failure modes with RPNs values ≥100 and S ≥ 7, D ≥ 5, and O ≥ 5 were considered as high priority in this study. Conclusions: The results of the present study show that the safety risk profiles for the same stereotactic radiotherapy process are different at three radiotherapy centers in Brazil. Although this is the same treatment process, this present study showed that the risk priority is different and it will lead to implementation of different safety interventions among the centers. Therefore, the current practice of applying universal device-centric QA is not adequate to address all possible failures in clinical processes at different

  19. Risk Management in Magnetic Resonance: Failure Mode, Effects, and Criticality Analysis

    PubMed Central

    Granata, Vincenza; Filice, Salvatore; Raiano, Nicola; Amato, Daniela Maria; Zirpoli, Maria; di Finizio, Alessandro; Sansone, Mario; Russo, Anna; Covelli, Eugenio Maria; Pedicini, Tonino; Triassi, Maria

    2013-01-01

    The aim of the study was to perform a risk management procedure in “Magnetic Resonance Examination” process in order to identify the critical phases and sources of radiological errors and to identify potential improvement projects including procedures, tests, and checks to reduce the error occurrence risk. In this study we used the proactive analysisFailure Mode Effects Criticality Analysis,” a qualitative and quantitative risk management procedure; has calculated Priority Risk Index (PRI) for each activity of the process; have identified, on the PRI basis, the most critical activities and, for them, have defined improvement projects; and have recalculated the PRI after implementation of improvement projects for each activity. Time stop and audits are performed in order to control the new procedures. The results showed that the most critical tasks of “Magnetic Resonance Examination” process were the reception of the patient, the patient schedule drafting, the closing examination, and the organization of activities. Four improvement projects have been defined and executed. PRI evaluation after improvement projects implementation has shown that the risk decreased significantly following the implementation of procedures and controls defined in improvement projects, resulting in a reduction of the PRI between 43% and 100%. PMID:24171173

  20. A Case Study on Improving Intensive Care Unit (ICU) Services Reliability: By Using Process Failure Mode and Effects Analysis (PFMEA)

    PubMed Central

    Yousefinezhadi, Taraneh; Jannesar Nobari, Farnaz Attar; Goodari, Faranak Behzadi; Arab, Mohammad

    2016-01-01

    Introduction: In any complex human system, human error is inevitable and shows that can’t be eliminated by blaming wrong doers. So with the aim of improving Intensive Care Units (ICU) reliability in hospitals, this research tries to identify and analyze ICU’s process failure modes at the point of systematic approach to errors. Methods: In this descriptive research, data was gathered qualitatively by observations, document reviews, and Focus Group Discussions (FGDs) with the process owners in two selected ICUs in Tehran in 2014. But, data analysis was quantitative, based on failures’ Risk Priority Number (RPN) at the base of Failure Modes and Effects Analysis (FMEA) method used. Besides, some causes of failures were analyzed by qualitative Eindhoven Classification Model (ECM). Results: Through FMEA methodology, 378 potential failure modes from 180 ICU activities in hospital A and 184 potential failures from 99 ICU activities in hospital B were identified and evaluated. Then with 90% reliability (RPN≥100), totally 18 failures in hospital A and 42 ones in hospital B were identified as non-acceptable risks and then their causes were analyzed by ECM. Conclusions: Applying of modified PFMEA for improving two selected ICUs’ processes reliability in two different kinds of hospitals shows that this method empowers staff to identify, evaluate, prioritize and analyze all potential failure modes and also make them eager to identify their causes, recommend corrective actions and even participate in improving process without feeling blamed by top management. Moreover, by combining FMEA and ECM, team members can easily identify failure causes at the point of health care perspectives. PMID:27157162

  1. Failure Mode/Mechanism Distributions

    DTIC Science & Technology

    1991-09-01

    Boards: Flashover (24996-000,NR) Broken NR Terminal Boards: Mechanical Breakage (24996-000,NR) Cortact Failure MR Terminals: (Intermittent contact... mechanism data on of various discrete semiconductor device types. The data has been compiled from reports of reliability demonstration tests conducted in...Room 3C0, Fnrbes Bu ilinn. Order No. FMD-91 Failure Mode/ Mechanism Distributions DTiC QUALIi INSPECTED 5 1991 Ace 94taa Yor SNTTS ai Prepared by: ,= t

  2. Using Failure Mode Effects and Criticality Analysis for High-Risk Processes at Three Community Hospitals

    SciTech Connect

    Coles, Garill A.; Fuller, Becky; Nordquist, Kathleen; Kongslie, Anita

    2005-03-01

    The staff at three Washington State hospitals and Battelle Pacific Northwest Division have been collaborating to apply Failure Mode Effects and Criticality Analysis (FMECA) to assess several hospital processes. The staff from Kadlec Medical Center (KMC), located in Richland, Washington; Kennewick General Hospital (KGH), located in Kennewick, Washington; and Lourdes Medical Center (LMC), located in Pasco, Washington, along with staff from Battelle, which is located in Richland, Washington have been working together successfully for two and a half years. Tri-Cities Shared Services, a local organization which implements shared hospital services, has provided the forum for joint activity. This effort was initiated in response to the new JCAHO patient safety standards implemented in July 2001, and the hospitals’ desire to be more proactive in improving patient safety. As a result of performing FMECAs the weaknesses of six medical processes have been characterized and corresponding system improvements implemented. Based on this collective experience, insights about the benefits of applying FMECAs to healthcare processes have been identified.

  3. Effectiveness and cost of failure mode and effects analysis methodology to reduce neurosurgical site infections.

    PubMed

    Hover, Alexander R; Sistrunk, William W; Cavagnol, Robert M; Scarrow, Alan; Finley, Phillip J; Kroencke, Audrey D; Walker, Judith L

    2014-01-01

    Mercy Hospital Springfield is a tertiary care facility with 32 000 discharges and 15 000 inpatient surgeries in 2011. From June 2009 through January 2011, a stable inpatient elective neurosurgery infection rate of 2.15% was observed. The failure mode and effects analysis (FMEA) methodology to reduce inpatient neurosurgery infections was utilized. Following FMEA implementation, overall elective neurosurgery infection rates were reduced to 1.51% and sustained through May 2012. Compared with baseline, the post-FMEA deep-space and organ infection rate was reduced by 41% (P = .052). Overall hospital inpatient clean surgery infection rates for the same time frame did not decrease to the same extent, suggesting a specific effect of the FMEA. The study team believes that the FMEA interventions resulted in 14 fewer expected infections, $270 270 in savings, a 168-day reduction in expected length of stay, and 22 fewer readmissions. Given the serious morbidity and cost of health care-associated infections, the study team concludes that FMEA implementation was clinically cost-effective.

  4. Risk management for outsourcing biomedical waste disposal - using the failure mode and effects analysis.

    PubMed

    Liao, Ching-Jong; Ho, Chao Chung

    2014-07-01

    Using the failure mode and effects analysis, this study examined biomedical waste companies through risk assessment. Moreover, it evaluated the supervisors of biomedical waste units in hospitals, and factors relating to the outsourcing risk assessment of biomedical waste in hospitals by referring to waste disposal acts. An expert questionnaire survey was conducted on the personnel involved in waste disposal units in hospitals, in order to identify important factors relating to the outsourcing risk of biomedical waste in hospitals. This study calculated the risk priority number (RPN) and selected items with an RPN value higher than 80 for improvement. These items included "availability of freezing devices", "availability of containers for sharp items", "disposal frequency", "disposal volume", "disposal method", "vehicles meeting the regulations", and "declaration of three lists". This study also aimed to identify important selection factors of biomedical waste disposal companies by hospitals in terms of risk. These findings can serve as references for hospitals in the selection of outsourcing companies for biomedical waste disposal.

  5. Application of ISO22000 and Failure Mode and Effect Analysis (fmea) for Industrial Processing of Poultry Products

    NASA Astrophysics Data System (ADS)

    Varzakas, Theodoros H.; Arvanitoyannis, Ioannis S.

    Failure Mode and Effect Analysis (FMEA) model has been applied for the risk assessment of poultry slaughtering and manufacturing. In this work comparison of ISO22000 analysis with HACCP is carried out over poultry slaughtering, processing and packaging. Critical Control points and Prerequisite programs (PrPs) have been identified and implemented in the cause and effect diagram (also known as Ishikawa, tree diagram and fishbone diagram).

  6. Proactive Risk Assessment of Blood Transfusion Process, in Pediatric Emergency, Using the Health Care Failure Mode and Effects Analysis (HFMEA)

    PubMed Central

    Dehnavieh, Reza; Ebrahimipour, Hossein; Molavi-Taleghani, Yasamin; Vafaee-Najar, Ali; Hekmat, Somayeh Noori; Esmailzdeh, Hamid

    2015-01-01

    Introduction: Pediatric emergency has been considered as a high risk area, and blood transfusion is known as a unique clinical measure, therefore this study was conducted with the purpose of assessing the proactive risk assessment of blood transfusion process in Pediatric Emergency of Qaem education- treatment center in Mashhad, by the Healthcare Failure Mode and Effects Analysis (HFMEA) methodology. Methodology: This cross-sectional study analyzed the failure mode and effects of blood transfusion process by a mixture of quantitative-qualitative method. The proactive HFMEA was used to identify and analyze the potential failures of the process. The information of the items in HFMEA forms was collected after obtaining a consensus of experts’ panel views via the interview and focus group discussion sessions. Results: The Number of 77 failure modes were identified for 24 sub-processes enlisted in 8 processes of blood transfusion. Totally 13 failure modes were identified as non-acceptable risk (a hazard score above 8) in the blood transfusion process and were transferred to the decision tree. Root causes of high risk modes were discussed in cause-effect meetings and were classified based on the UK national health system (NHS) approved classifications model. Action types were classified in the form of acceptance (11.6%), control (74.2%) and elimination (14.2%). Recommendations were placed in 7 categories using TRIZ (“Theory of Inventive Problem Solving.”) Conclusion: The re-engineering process for the required changes, standardizing and updating the blood transfusion procedure, root cause analysis of blood transfusion catastrophic events, patient identification bracelet, training classes and educational pamphlets for raising awareness of personnel, and monthly gathering of transfusion medicine committee have all been considered as executive strategies in work agenda in pediatric emergency. PMID:25560332

  7. Root-cause analysis and health failure mode and effect analysis: two leading techniques in health care quality assessment.

    PubMed

    Shaqdan, Khalid; Aran, Shima; Daftari Besheli, Laleh; Abujudeh, Hani

    2014-06-01

    In this review article, the authors provide a detailed series of guidelines for effectively performing root-cause analysis (RCA) and health failure mode and effect analysis (HFMEA). RCA is a retrospective approach used to ascertain the "root cause" of a problem that has already occurred, whereas HFMEA is a prospective risk assessment tool whose aim is to recognize risks to patient safety. RCA and HFMEA are used for the prevention of errors or recurring errors to create a safer workplace, maintain high standards in health care quality, and incorporate time-saving and cost-saving modifications to favorably affect the patient care environment. The principles and techniques provided here should allow reviewers to better understand the features of RCA and HFMEA and how to apply these processes appropriately. These principles include how to organize a team, identify root causes, seed out proximate causes, graphically describe the process, conduct a hazard analysis, and develop and implement potential action plans.

  8. Matrix Failure Modes and Effects Analysis as a Knowledge Base for a Real Time Automated Diagnosis Expert System

    NASA Technical Reports Server (NTRS)

    Herrin, Stephanie; Iverson, David; Spukovska, Lilly; Souza, Kenneth A. (Technical Monitor)

    1994-01-01

    Failure Modes and Effects Analysis contain a wealth of information that can be used to create the knowledge base required for building automated diagnostic Expert systems. A real time monitoring and diagnosis expert system based on an actual NASA project's matrix failure modes and effects analysis was developed. This Expert system Was developed at NASA Ames Research Center. This system was first used as a case study to monitor the Research Animal Holding Facility (RAHF), a Space Shuttle payload that is used to house and monitor animals in orbit so the effects of space flight and microgravity can be studied. The techniques developed for the RAHF monitoring and diagnosis Expert system are general enough to be used for monitoring and diagnosis of a variety of other systems that undergo a Matrix FMEA. This automated diagnosis system was successfully used on-line and validated on the Space Shuttle flight STS-58, mission SLS-2 in October 1993.

  9. Failure modes of electrospun nanofibers

    NASA Astrophysics Data System (ADS)

    Zussman, E.; Rittel, D.; Yarin, A. L.

    2003-06-01

    Failure modes of electrospun polymer nanofibers are reported. The nanofibers have diameters in the range of 80-400 nm and lengths greater then several centimeters. The nanofibers fail by a multiple necking mechanism, sometimes followed by the development of a fibriliar structure. This phenomenon is attributed to a strong stretching of solidified nanofibers by the tapered accumulating wheel (electrostatic lens), if its rotation speed becomes too high. Necking has not been observed in the nanofibers collected on a grounded plate.

  10. Degradation analysis of anode-supported intermediate temperature-solid oxide fuel cells under various failure modes

    NASA Astrophysics Data System (ADS)

    Lee, Tae-Hee; Park, Ka-Young; Kim, Ji-Tae; Seo, Yongho; Kim, Ki Buem; Song, Sun-Ju; Park, Byoungnam; Park, Jun-Young

    2015-02-01

    This study focuses on mechanisms and symptoms of several simulated failure modes, which may have significant influences on the long-term durability and operational stability of intermediate temperature-solid oxide fuel cells (IT-SOFCs), including fuel/oxidation starvation by breakdown of fuel/air supply components and wet and dry cycling atmospheres. Anode-supported IT-SOFCs consisting of a Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF)-Nd0.1Ce0.9O2-δ (NDC) composite cathode with an NDC electrolyte on a Ni-NDC anode substrate are fabricated via dry-pressings followed by the co-firing method. Comprehensive and systematic research based on the failure mode and effect analysis (FMEA) of anode-supported IT-SOFCs is conducted using various electrochemical and physiochemical analysis techniques to extend our understanding of the major mechanisms of performance deterioration under SOFC operating conditions. The fuel-starvation condition in the fuel-pump failure mode causes irreversible mechanical degradation of the electrolyte and cathode interface by the dimensional expansion of the anode support due to the oxidation of Ni metal to NiO. In contrast, the BSCF cathode shows poor stability under wet and dry cycling modes of cathode air due to the strong electroactivity of SrO with H2O. On the other hand, the air-depletion phenomena under air-pump failure mode results in the recovery of cell performance during the long-term operation without the visible microstructural transformation through the reduction of anode overvoltage.

  11. Risk Assessment of Using Entonox for the Relief of Labor Pain: A Healthcare Failure Modes and Effects Analysis Approach

    PubMed Central

    Najafi, Tahereh Fathi; Bahri, Narjes; Ebrahimipour, Hosein; Najar, Ali Vafaee; Taleghani, Yasamin Molavi

    2016-01-01

    Introduction In order to prevent medical errors, it is important to know why they occur and to identify their causes. Healthcare failure modes and effects analysis (HFMEA) is a type of qualitative descriptive that is used to evaluate the risk. The aim of this study was to assess the risks of using Entonox for labor pain by HFMEA. Methods A mixed-methods design (qualitative action research and quantitative cross-sectional research) was used. The modes and effects of failures in the process of using Entonox were detected and analyzed during 2013–2014 at Hefdahe Shahrivar Hospital, Mashhad, Iran. Overall, 52 failure modes were identified, with 25 being recognized as high-risk modes. Results The results revealed that 48.5% of these errors fall into the care process type, 22.05% belong to the communicative type, 19.1% fall into the administrative type, and 10.2% are of the knowledge and skills type. Strategies were presented in the forms of acceptance (3.2%), control (90.3%), and elimination (6.4%). Conclusion The following actions are suggested for improving the process of using Entonox: Close supervision by the midwife, precise recording of all the stages of the process in the woman’s medical record, the necessity of the presence of the anesthesiologist at the woman’s bedside during labor, confirming the indications for use of Entonox, and close monitoring to ensure the safety of the gas cylinder guards. PMID:27123224

  12. Failure mode analysis of degraded InGaAs-AlGaAs strained quantum well multi-mode vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Sin, Yongkun; Lingley, Zachary; Brodie, Miles; Huang, Michael; Bushmaker, Adam; Theiss, Jesse; Presser, Nathan; Foran, Brendan; Moss, Steven C.

    2016-03-01

    Remarkable progress made in vertical cavity surface emitting lasers (VCSELs) emitting at 850 and 980 nm has led them to find an increasing number of applications in high speed data communications as well as in potential space satellite systems. However, little has been reported on reliability and failure modes of InGaAs VCSELs emitting at ~980 nm although it is crucial to understand failure modes and underlying degradation mechanisms in developing these VCSELs that exceed lifetime requirements for space missions. The active layer of commercial VCSELs that we studied consisted of two or three InGaAs quantum wells. The laser structures were fabricated into deep mesas followed by a steam oxidation process to form oxide-apertures for current and optical confinements. Our multi- mode VCSELs showed a laser threshold of ~ 0.5 mA at RT. Failures were generated via accelerated life-testing of VCSELs. For the present study, we report on failure mode analysis of degraded oxide-VCSELs using various techniques. We employed nondestructive techniques including electroluminescence (EL), optical beam induced current (OBIC), and electron beam induced current (EBIC) techniques as well as destructive techniques including focused ion beam (FIB) and high-resolution TEM techniques to study VCSELs that showed different degradation behaviors. Especially, we employed FIB systems to locally remove a portion of top-DBR mirrors of degraded VCSELs, which made it possible for our subsequent EBIC and OBIC techniques to locate damaged areas that were generated as a result of degradation processes and also for our HR-TEM technique to prepare TEM cross sections from damaged areas. Our nondestructive and destructive physical analysis results are reported including defect and structural analysis results from pre-aged VCSELs as well as from degraded VCSELs life-tested under different test conditions.

  13. Design of a safer approach to intravenous drug infusions: failure mode effects analysis

    PubMed Central

    Apkon, M; Leonard, J; Probst, L; DeLizio, L; Vitale, R

    2004-01-01

    Objectives: A set of standard processes was developed for delivering continuous drug infusions in order to improve (1) patient safety; (2) efficiency in staff workflow; (3) hemodynamic stability during infusion changes, and (4) efficient use of resources. Failure modes effects analysis (FMEA) was used to examine the impact of process changes on the reliability of delivering drug infusions. Setting: An 11 bed multidisciplinary pediatric ICU in the children's hospital of an academic medical center staffed by board certified pediatric intensivists. The hospital uses computerized physician order entry for all medication orders. Methods: A multidisciplinary team characterized key elements of the drug infusion process. The process was enhanced to increase overall reliability and the original and revised processes were compared using FMEA. Resource consumption was estimated by reviewing purchasing and pharmacy records for the calendar year after full implementation of the revised process. Staff satisfaction was evaluated using an anonymous questionnaire administered to staff nurses in the ICU and pediatric residents who had rotated through the ICU. Results: The original process was characterized by six elements: selecting the drug; selecting a dose; selecting an infusion rate; calculating and ordering the infusion; preparing the infusion; programming the infusion pump and delivering the infusion. The following practice changes were introduced: standardizing formulations for all infusions; developing database driven calculators; extending infusion hang times from 24 to 72 hours; changing from bedside preparation by nurses to pharmacy prepared or premanufactured solutions. FMEA showed that the last three elements of the original process had high risk priority numbers (RPNs) of >225 whereas the revised process had no elements with RPNs >100. The combined effect of prolonging infusion hang times, preparation in the pharmacy, and purchasing premanufactured solutions resulted

  14. Fracture - An Unforgiving Failure Mode

    NASA Technical Reports Server (NTRS)

    Goodin, James Ronald

    2006-01-01

    During the 2005 Conference for the Advancement for Space Safety, after a typical presentation of safety tools, a Russian in the audience simply asked, "How does that affect the hardware?" Having participated in several International System Safety Conferences, I recalled that most attention is dedicated to safety tools and little, if any, to hardware. The intent of this paper on the hazard of fracture and failure modes associated with fracture is my attempt to draw attention to the grass roots of system safety - improving hardware robustness and resilience.

  15. Comprehensive reliability allocation method for CNC lathes based on cubic transformed functions of failure mode and effects analysis

    NASA Astrophysics Data System (ADS)

    Yang, Zhou; Zhu, Yunpeng; Ren, Hongrui; Zhang, Yimin

    2015-03-01

    Reliability allocation of computerized numerical controlled(CNC) lathes is very important in industry. Traditional allocation methods only focus on high-failure rate components rather than moderate failure rate components, which is not applicable in some conditions. Aiming at solving the problem of CNC lathes reliability allocating, a comprehensive reliability allocation method based on cubic transformed functions of failure modes and effects analysis(FMEA) is presented. Firstly, conventional reliability allocation methods are introduced. Then the limitations of direct combination of comprehensive allocation method with the exponential transformed FMEA method are investigated. Subsequently, a cubic transformed function is established in order to overcome these limitations. Properties of the new transformed functions are discussed by considering the failure severity and the failure occurrence. Designers can choose appropriate transform amplitudes according to their requirements. Finally, a CNC lathe and a spindle system are used as an example to verify the new allocation method. Seven criteria are considered to compare the results of the new method with traditional methods. The allocation results indicate that the new method is more flexible than traditional methods. By employing the new cubic transformed function, the method covers a wider range of problems in CNC reliability allocation without losing the advantages of traditional methods.

  16. Defense against common mode failures in protection system design

    SciTech Connect

    Wyman, R.H.; Johnson, G.L.

    1997-08-27

    The introduction of digital instrumentation and control into reactor safety systems creates a heightened concern about common-mode failure. This paper discusses the concern and methods to cope with the concern. Common-mode failures have been a ``fact-of-life`` in existing systems. The informal introduction of defense-in-depth and diversity (D-in-D&D)-coupled with the fact that hardware common-mode failures are often distributed in time-has allowed systems to deal with past common-mode failures. However, identical software operating in identical redundant systems presents the potential for simultaneous failure. Consequently, the use of digital systems raises the concern about common-mode failure to a new level. A more methodical approach to mitigating common-mode failure is needed to address these concerns. Purposeful introduction of D-in-D&D has been used as a defense against common-mode failure in reactor protection systems. At least two diverse systems are provided to mitigate any potential initiating event. Additionally, diverse displays and controls are provided to allow the operator to monitor plant status and manually initiate engineered safety features. A special form of conimon-mode failure analysis called ``defense-in-depth and diversity analysis`` has been developed to identify possible conimon-mode failure vulnerabilities in digital systems. An overview of this analysis technique is provided.

  17. The use of failure mode and effects analysis to construct an effective disposal and prevention mechanism for infectious hospital waste

    SciTech Connect

    Ho, Chao Chung; Liao, Ching-Jong

    2011-12-15

    Highlights: > This study is based on a real case in a regional teaching hospital in Taiwan. > We use Failure mode and effects analysis (FMEA) as the evaluation method. > We successfully identify the risk factors of infectious waste disposal. > We propose plans for the detection of exceptional cases of infectious waste. - Abstract: In recent times, the quality of medical care has been continuously improving in medical institutions wherein patient-centred care has been emphasized. Failure mode and effects analysis (FMEA) has also been promoted as a method of basic risk management and as part of total quality management (TQM) for improving the quality of medical care and preventing mistakes. Therefore, a study was conducted using FMEA to evaluate the potential risk causes in the process of infectious medical waste disposal, devise standard procedures concerning the waste, and propose feasible plans for facilitating the detection of exceptional cases of infectious waste. The analysis revealed the following results regarding medical institutions: (a) FMEA can be used to identify the risk factors of infectious waste disposal. (b) During the infectious waste disposal process, six items were scored over 100 in the assessment of uncontrolled risks: erroneous discarding of infectious waste by patients and their families, erroneous discarding by nursing staff, erroneous discarding by medical staff, cleaning drivers pierced by sharp articles, cleaning staff pierced by sharp articles, and unmarked output units. Therefore, the study concluded that it was necessary to (1) provide education and training about waste classification to the medical staff, patients and their families, nursing staff, and cleaning staff; (2) clarify the signs of caution; and (3) evaluate the failure mode and strengthen the effects.

  18. Meteorological Satellites (METSAT) and Earth Observing System (EOS) Advanced Microwave Sounding Unit-A (AMSU-A) Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL)

    NASA Technical Reports Server (NTRS)

    1996-01-01

    This Failure Modes and Effects Analysis (FMEA) is for the Advanced Microwave Sounding Unit-A (AMSU-A) instruments that are being designed and manufactured for the Meteorological Satellites Project (METSAT) and the Earth Observing System (EOS) integrated programs. The FMEA analyzes the design of the METSAT and EOS instruments as they currently exist. This FMEA is intended to identify METSAT and EOS failure modes and their effect on spacecraft-instrument and instrument-component interfaces. The prime objective of this FMEA is to identify potential catastrophic and critical failures so that susceptibility to the failures and their effects can be eliminated from the METSAT/EOS instruments.

  19. SU-E-T-421: Failure Mode and Effects Analysis (FMEA) of Xoft Electronic Brachytherapy for the Treatment of Superficial Skin Cancers

    SciTech Connect

    Hoisak, J; Manger, R; Dragojevic, I

    2015-06-15

    Purpose: To perform a failure mode and effects analysis (FMEA) of the process for treating superficial skin cancers with the Xoft Axxent electronic brachytherapy (eBx) system, given the recent introduction of expanded quality control (QC) initiatives at our institution. Methods: A process map was developed listing all steps in superficial treatments with Xoft eBx, from the initial patient consult to the completion of the treatment course. The process map guided the FMEA to identify the failure modes for each step in the treatment workflow and assign Risk Priority Numbers (RPN), calculated as the product of the failure mode’s probability of occurrence (O), severity (S) and lack of detectability (D). FMEA was done with and without the inclusion of recent QC initiatives such as increased staffing, physics oversight, standardized source calibration, treatment planning and documentation. The failure modes with the highest RPNs were identified and contrasted before and after introduction of the QC initiatives. Results: Based on the FMEA, the failure modes with the highest RPN were related to source calibration, treatment planning, and patient setup/treatment delivery (Fig. 1). The introduction of additional physics oversight, standardized planning and safety initiatives such as checklists and time-outs reduced the RPNs of these failure modes. High-risk failure modes that could be mitigated with improved hardware and software interlocks were identified. Conclusion: The FMEA analysis identified the steps in the treatment process presenting the highest risk. The introduction of enhanced QC initiatives mitigated the risk of some of these failure modes by decreasing their probability of occurrence and increasing their detectability. This analysis demonstrates the importance of well-designed QC policies, procedures and oversight in a Xoft eBx programme for treatment of superficial skin cancers. Unresolved high risk failure modes highlight the need for non-procedural quality

  20. Failure mode and effects analysis of the universal anaesthesia machine in two tertiary care hospitals in Sierra Leone

    PubMed Central

    Rosen, M. A.; Sampson, J. B.; Jackson, E. V.; Koka, R.; Chima, A. M.; Ogbuagu, O. U.; Marx, M. K.; Koroma, M.; Lee, B. H.

    2014-01-01

    Background Anaesthesia care in developed countries involves sophisticated technology and experienced providers. However, advanced machines may be inoperable or fail frequently when placed into the austere medical environment of a developing country. Failure mode and effects analysis (FMEA) is a method for engaging local staff in identifying real or potential breakdowns in processes or work systems and to develop strategies to mitigate risks. Methods Nurse anaesthetists from the two tertiary care hospitals in Freetown, Sierra Leone, participated in three sessions moderated by a human factors specialist and an anaesthesiologist. Sessions were audio recorded, and group discussion graphically mapped by the session facilitator for analysis and commentary. These sessions sought to identify potential barriers to implementing an anaesthesia machine designed for austere medical environments—the universal anaesthesia machine (UAM)—and also engaging local nurse anaesthetists in identifying potential solutions to these barriers. Results Participating Sierra Leonean clinicians identified five main categories of failure modes (resource availability, environmental issues, staff knowledge and attitudes, and workload and staffing issues) and four categories of mitigation strategies (resource management plans, engaging and educating stakeholders, peer support for new machine use, and collectively advocating for needed resources). Conclusions We identified factors that may limit the impact of a UAM and devised likely effective strategies for mitigating those risks. PMID:24833727

  1. Analysis of functional failure mode of commercial deep sub-micron SRAM induced by total dose irradiation

    NASA Astrophysics Data System (ADS)

    Zheng, Qi-Wen; Cui, Jiang-Wei; Zhou, Hang; Yu, De-Zhao; Yu, Xue-Feng; Lu, Wu; Guo, Qi; Ren, Di-Yuan

    2015-10-01

    Functional failure mode of commercial deep sub-micron static random access memory (SRAM) induced by total dose irradiation is experimentally analyzed and verified by circuit simulation. We extensively characterize the functional failure mode of the device by testing its electrical parameters and function with test patterns covering different functional failure modes. Experimental results reveal that the functional failure mode of the device is a temporary function interruption caused by peripheral circuits being sensitive to the standby current rising. By including radiation-induced threshold shift and off-state leakage current in memory cell transistors, we simulate the influence of radiation on the functionality of the memory cell. Simulation results reveal that the memory cell is tolerant to irradiation due to its high stability, which agrees with our experimental result.

  2. MO-D-213-02: Quality Improvement Through a Failure Mode and Effects Analysis of Pediatric External Beam Radiotherapy

    SciTech Connect

    Gray, J; Lukose, R; Bronson, J; Chandler, B; Merchant, T; Farr, J

    2015-06-15

    Purpose: To conduct a failure mode and effects analysis (FMEA) as per AAPM Task Group 100 on clinical processes associated with teletherapy, and the development of mitigations for processes with identified high risk. Methods: A FMEA was conducted on clinical processes relating to teletherapy treatment plan development and delivery. Nine major processes were identified for analysis. These steps included CT simulation, data transfer, image registration and segmentation, treatment planning, plan approval and preparation, and initial and subsequent treatments. Process tree mapping was utilized to identify the steps contained within each process. Failure modes (FM) were identified and evaluated with a scale of 1–10 based upon three metrics: the severity of the effect, the probability of occurrence, and the detectability of the cause. The analyzed metrics were scored as follows: severity – no harm = 1, lethal = 10; probability – not likely = 1, certainty = 10; detectability – always detected = 1, undetectable = 10. The three metrics were combined multiplicatively to determine the risk priority number (RPN) which defined the overall score for each FM and the order in which process modifications should be deployed. Results: Eighty-nine procedural steps were identified with 186 FM accompanied by 193 failure effects with 213 potential causes. Eighty-one of the FM were scored with a RPN > 10, and mitigations were developed for FM with RPN values exceeding ten. The initial treatment had the most FM (16) requiring mitigation development followed closely by treatment planning, segmentation, and plan preparation with fourteen each. The maximum RPN was 400 and involved target delineation. Conclusion: The FMEA process proved extremely useful in identifying previously unforeseen risks. New methods were developed and implemented for risk mitigation and error prevention. Similar to findings reported for adult patients, the process leading to the initial treatment has an

  3. Quality risk analysis in a cGMP environment: multiple models for comprehensive failure mode identification during the computer system lifecycle.

    PubMed

    Gervais, Brian; D'Arcy, Deirdre M

    2014-01-01

    Pharmaceutical quality systems use various inputs to ensure product quality and prevent failures that might have patient consequences. These inputs are generally data from failures that have already occurred, for example process deviations or customer complaints. Risk analysis techniques are well-established in certain other industries and have become of interest to pharmaceutical manufacturers because they allow potential quality failures to be predicted and mitigating action taken in advance of their occurring. Failure mode and effects analysis (FMEA) is one such technique, and in this study it was applied to implement a computerized manufacturing execution system in a pharmaceutical manufacturing environment. After introduction, the system was monitored to detect failures that did occur and these were analyzed to determine why the risk analysis method failed to predict them. Application of FMEA in other industries has identified weaknesses in predicting certain error types, specifically its dependence on other techniques to model risk situations and its poor analysis of non-hardware risks, such as human error, and this was confirmed in this study. Hierarchical holographic modeling (HHM), a technique for identifying risk scenarios in wide-scope analyses, was applied subsequently and identified additional potential failure modes. The technique for human error rate prediction (THERP) has previously been used for the quantitative analysis of human error risk and the event tree from this technique was adapted and identified further human error scenarios. These were input to the FMEA for prioritization and mitigation, thereby strengthening the risk analysis in terms of failure modes considered.

  4. Application of ISO 22000 and Failure Mode and Effect Analysis (FMEA) for industrial processing of salmon: a case study.

    PubMed

    Arvanitoyannis, Ioannis S; Varzakas, Theodoros H

    2008-05-01

    The Failure Mode and Effect Analysis (FMEA) model was applied for risk assessment of salmon manufacturing. A tentative approach of FMEA application to the salmon industry was attempted in conjunction with ISO 22000. Preliminary Hazard Analysis was used to analyze and predict the occurring failure modes in a food chain system (salmon processing plant), based on the functions, characteristics, and/or interactions of the ingredients or the processes, upon which the system depends. Critical Control points were identified and implemented in the cause and effect diagram (also known as Ishikawa, tree diagram and fishbone diagram). In this work, a comparison of ISO 22000 analysis with HACCP is carried out over salmon processing and packaging. However, the main emphasis was put on the quantification of risk assessment by determining the RPN per identified processing hazard. Fish receiving, casing/marking, blood removal, evisceration, filet-making cooling/freezing, and distribution were the processes identified as the ones with the highest RPN (252, 240, 210, 210, 210, 210, 200 respectively) and corrective actions were undertaken. After the application of corrective actions, a second calculation of RPN values was carried out resulting in substantially lower values (below the upper acceptable limit of 130). It is noteworthy that the application of Ishikawa (Cause and Effect or Tree diagram) led to converging results thus corroborating the validity of conclusions derived from risk assessment and FMEA. Therefore, the incorporation of FMEA analysis within the ISO 22000 system of a salmon processing industry is anticipated to prove advantageous to industrialists, state food inspectors, and consumers.

  5. The use of failure mode and effect analysis in a radiation oncology setting: the Cancer Treatment Centers of America experience.

    PubMed

    Denny, Diane S; Allen, Debra K; Worthington, Nicole; Gupta, Digant

    2014-01-01

    Delivering radiation therapy in an oncology setting is a high-risk process where system failures are more likely to occur because of increasing utilization, complexity, and sophistication of the equipment and related processes. Healthcare failure mode and effect analysis (FMEA) is a method used to proactively detect risks to the patient in a particular healthcare process and correct potential errors before adverse events occur. FMEA is a systematic, multidisciplinary team-based approach to error prevention and enhancing patient safety. We describe our experience of using FMEA as a prospective risk-management technique in radiation oncology at a national network of oncology hospitals in the United States, capitalizing not only on the use of a team-based tool but also creating momentum across a network of collaborative facilities seeking to learn from and share best practices with each other. The major steps of our analysis across 4 sites and collectively were: choosing the process and subprocesses to be studied, assembling a multidisciplinary team at each site responsible for conducting the hazard analysis, and developing and implementing actions related to our findings. We identified 5 areas of performance improvement for which risk-reducing actions were successfully implemented across our enterprise.

  6. Key Performance Outcomes of Patient Safety Curricula: Root Cause Analysis, Failure Mode and Effects Analysis, and Structured Communications Skills

    PubMed Central

    2011-01-01

    As colleges and schools of pharmacy develop core courses related to patient safety, course-level outcomes will need to include both knowledge and performance measures. Three key performance outcomes for patient safety coursework, measured at the course level, are the ability to perform root cause analyses and healthcare failure mode effects analyses, and the ability to generate effective safety communications using structured formats such as the Situation-Background-Assessment-Recommendation (SBAR) situational briefing model. Each of these skills is widely used in patient safety work and competence in their use is essential for a pharmacist's ability to contribute as a member of a patient safety team. PMID:22102754

  7. Failure modes in surface micromachined microelectromechanical actuators

    SciTech Connect

    Miller, S.L.; Rodgers, M.S.; LaVigne, G.; Sniegowski, J.J.; Clews, P.; Tanner, D.M.; Peterson, K.A.

    1998-03-01

    In order for the rapidly emerging field of MicroElectroMechanical Systems (MEMS) to meet its extraordinary expectations regarding commercial impact, issues pertaining to how they fail must be understood. The authors identify failure modes common to a broad range of MEMS actuators, including adhesion (stiction) and friction induced failures caused by improper operational methods, mechanical instabilities, and electrical instabilities. Demonstrated methods to mitigate these failure modes include implementing optimized designs, model based operational methods, and chemical surface treatments.

  8. Application of Failure Mode and Effect Analysis (FMEA), cause and effect analysis, and Pareto diagram in conjunction with HACCP to a corn curl manufacturing plant.

    PubMed

    Varzakas, Theodoros H; Arvanitoyannis, Ioannis S

    2007-01-01

    The Failure Mode and Effect Analysis (FMEA) model has been applied for the risk assessment of corn curl manufacturing. A tentative approach of FMEA application to the snacks industry was attempted in an effort to exclude the presence of GMOs in the final product. This is of crucial importance both from the ethics and the legislation (Regulations EC 1829/2003; EC 1830/2003; Directive EC 18/2001) point of view. The Preliminary Hazard Analysis and the Fault Tree Analysis were used to analyze and predict the occurring failure modes in a food chain system (corn curls processing plant), based on the functions, characteristics, and/or interactions of the ingredients or the processes, upon which the system depends. Critical Control points have been identified and implemented in the cause and effect diagram (also known as Ishikawa, tree diagram, and the fishbone diagram). Finally, Pareto diagrams were employed towards the optimization of GMOs detection potential of FMEA.

  9. Risk assessment of component failure modes and human errors using a new FMECA approach: application in the safety analysis of HDR brachytherapy.

    PubMed

    Giardina, M; Castiglia, F; Tomarchio, E

    2014-12-01

    Failure mode, effects and criticality analysis (FMECA) is a safety technique extensively used in many different industrial fields to identify and prevent potential failures. In the application of traditional FMECA, the risk priority number (RPN) is determined to rank the failure modes; however, the method has been criticised for having several weaknesses. Moreover, it is unable to adequately deal with human errors or negligence. In this paper, a new versatile fuzzy rule-based assessment model is proposed to evaluate the RPN index to rank both component failure and human error. The proposed methodology is applied to potential radiological over-exposure of patients during high-dose-rate brachytherapy treatments. The critical analysis of the results can provide recommendations and suggestions regarding safety provisions for the equipment and procedures required to reduce the occurrence of accidental events.

  10. Use of failure modes and effects analysis in design of the tracker system for the HET wide-field upgrade

    NASA Astrophysics Data System (ADS)

    Hayes, Richard; Beets, Tim; Beno, Joseph; Booth, John; Cornell, Mark; Good, John; Heisler, James; Hill, Gary; Kriel, Herman; Penney, Charles; Rafal, Marc; Savage, Richard; Soukup, Ian; Worthington, Michael; Zierer, Joseph

    2012-09-01

    In support of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX), the Center for Electromechanics at The University of Texas at Austin was tasked with developing the new Tracker and control system to support the HETDEX Wide-Field Upgrade. The tracker carries the 3,100 kg Prime Focus Instrument Package and Wide Field Corrector approximately 13 m above the 10 m diameter primary mirror. Its safe and reliable operation by a sophisticated control system, over a 20 year life time is a paramount requirement for the project. To account for all potential failures and potential hazards, to both the equipment and personnel involved, an extensive Failure Modes and Effects Analysis (FMEA) was completed early in the project. This task required participation of all the stakeholders over a multi-day meeting with numerous follow up exchanges. The event drove a number of significant design decisions and requirements that might not have been identified this early in the project without this process. The result is a system that has multiple layers of active and passive safety systems to protect the tens of millions of dollars of hardware involved and the people who operate it. This paper will describe the background of the FMEA process, how it was utilized on HETDEX, the critical outcomes, how the required safety systems were implemented, and how they have worked in operation. It should be of interest to engineers, designers, and managers engaging in complex multi-disciplinary and parallel engineering projects that involve automated hardware and control systems with potentially hazardous operating scenarios.

  11. Structural system reliability under multiple failure modes

    NASA Technical Reports Server (NTRS)

    Mahadevan, S.; Chamis, C. C.

    1993-01-01

    This paper describes a computational method for system reliability estimation of propulsion structures. The failure domain of the entire structural system is computed through the union of failure regions for various critical system failure modes. The effect of non-critical progressive damage is incorporated through structural reanalysis, resulting in the construction of several linear segments to approximately cover the system failure domain. An adaptive damage imposition scheme is outlined for the sake of computational efficiency. The proposed method is used to construct the system survival cdf (cumulative distribution function) of a two-rotor system.

  12. Finite Element Analysis and Failure Mode Characterization of Pyramidal Fin Arrays Produced by Masked Cold Gas Dynamic Spray

    NASA Astrophysics Data System (ADS)

    Cormier, Yannick; Dupuis, Philippe; Jodoin, Bertrand; Ghaei, Abbas

    2015-12-01

    This work evaluates the shear strength of pyramidal fin arrays made from various feedstock materials (cylindrical aluminum, spherical nickel, and cylindrical stainless steel 304 powders) deposited on an Al6061-T6 substrate. Higher shear strength was measured for the nickel fin array followed by the stainless steel 304 and the aluminum arrays. Different failure modes were observed by inspecting the fracture surfaces under Scanning Electron Microscope. Deposition between the cold sprayed nickel and stainless fins was detected whereas dimples were noticed on the substrate between the fins when aluminum is used as the feedstock material. A numerical simulation of normal and angled impacts using the high strain rate Preston-Tonks-Wallace model was carried out in order to have a better understanding of the experimental results. The equivalent plastic strain (PEEQ) obtained from the finite element analysis at normal impact correlates with the different shear strengths measured experimentally. Furthermore, even if a higher PEEQ was observed for angled impacts compared to its normal collision counterpart, it is suggested that the particles may not bond because of the rotational restitution momentum caused by the tangential friction generated during angled impacts. This rotational restitution momentum was not detected for particle impacts normal to the substrate surface.

  13. A Framework for Creating a Function-based Design Tool for Failure Mode Identification

    NASA Technical Reports Server (NTRS)

    Arunajadai, Srikesh G.; Stone, Robert B.; Tumer, Irem Y.; Clancy, Daniel (Technical Monitor)

    2002-01-01

    Knowledge of potential failure modes during design is critical for prevention of failures. Currently industries use procedures such as Failure Modes and Effects Analysis (FMEA), Fault Tree analysis, or Failure Modes, Effects and Criticality analysis (FMECA), as well as knowledge and experience, to determine potential failure modes. When new products are being developed there is often a lack of sufficient knowledge of potential failure mode and/or a lack of sufficient experience to identify all failure modes. This gives rise to a situation in which engineers are unable to extract maximum benefits from the above procedures. This work describes a function-based failure identification methodology, which would act as a storehouse of information and experience, providing useful information about the potential failure modes for the design under consideration, as well as enhancing the usefulness of procedures like FMEA. As an example, the method is applied to fifteen products and the benefits are illustrated.

  14. Application of Failure Mode and Effect Analysis (FMEA) and cause and effect analysis in conjunction with ISO 22000 to a snails (Helix aspersa) processing plant; A case study.

    PubMed

    Arvanitoyannis, Ioannis S; Varzakas, Theodoros H

    2009-08-01

    Failure Mode and Effect Analysis (FMEA) has been applied for the risk assessment of snails manufacturing. A tentative approach of FMEA application to the snails industry was attempted in conjunction with ISO 22000. Preliminary Hazard Analysis was used to analyze and predict the occurring failure modes in a food chain system (snails processing plant), based on the functions, characteristics, and/or interactions of the ingredients or the processes, upon which the system depends. Critical Control points have been identified and implemented in the cause and effect diagram (also known as Ishikawa, tree diagram, and fishbone diagram). In this work a comparison of ISO22000 analysis with HACCP is carried out over snails processing and packaging. However, the main emphasis was put on the quantification of risk assessment by determining the RPN per identified processing hazard. Sterilization of tins, bioaccumulation of heavy metals, packaging of shells and poisonous mushrooms, were the processes identified as the ones with the highest RPN (280, 240, 147, 144, respectively) and corrective actions were undertaken. Following the application of corrective actions, a second calculation of RPN values was carried out leading to considerably lower values (below the upper acceptable limit of 130). It is noteworthy that the application of Ishikawa (Cause and Effect or Tree diagram) led to converging results thus corroborating the validity of conclusions derived from risk assessment and FMEA. Therefore, the incorporation of FMEA analysis within the ISO22000 system of a snails processing industry is considered imperative.

  15. Administrative risk quantification of subcutaneous and intravenous therapies in Italian centers utilizing the Failure Mode and Effects Analysis approach

    PubMed Central

    Ponzetti, Clemente; Canciani, Monica; Farina, Massimo; Era, Sara; Walzer, Stefan

    2016-01-01

    Background In oncology, an important parameter of safety is the potential treatment error in hospitals. The analyzed hypothesis is that of subcutaneous therapies would provide a superior safety benefit over intravenous therapies through fixed-dose administrations, when analyzed with trastuzumab and rituximab. Methods For the calculation of risk levels, the Failure Mode and Effect Analysis approach was applied. Within this approach, the critical treatment path is followed and risk classification for each individual step is estimated. For oncology and hematology administration, 35 different risk steps were assessed. The study was executed in 17 hematology and 16 breast cancer centers in Italy. As intravenous and subcutaneous were the only injection routes in medical available for trastuzumab and rituximab in oncology at the time of the study, these two therapies were chosen. Results When the risk classes were calculated, eight high-risk areas were identified for the administration of an intravenous therapy in hematology or oncology; 13 areas would be defined as having a median-risk classification and 14 areas as having a low-risk classification (total risk areas: n=35). When the new subcutaneous formulation would be applied, 23 different risk levels could be completely eliminated (65% reduction). Important high-risk classes such as dose calculation, preparation and package labeling, preparation of the access to the vein, pump infusion preparation, and infusion monitoring were included in the eliminations. The overall risk level for the intravenous administration was estimated to be 756 (ex-ante) and could be reduced by 70% (ex-post). The potential harm compensation for errors related to pharmacy would be decreased from eight risk classes to only three risk classes. Conclusion The subcutaneous administration of trastuzumab (breast cancer) and rituximab (hematology) might lower the risk of administration and treatment errors for patients and could hence indirectly have

  16. Fracture Analysis of Competing Failure Modes of Aluminum-CFRP Joints Using Three-Layer Titanium Laminates as Transition

    NASA Astrophysics Data System (ADS)

    Woizeschke, P.; Vollertsen, F.

    2015-09-01

    The structural properties of lightweight constructions can be adapted to specific local requirements using multi-material designs. Aluminum alloys and carbon fiber-reinforced plastics (CFRP) are materials of great interest requiring suitable joining techniques in order to transfer the advantages of combining the materials to structural benefits. Thus, the research group "Schwarz-Silber" investigates novel concepts to enable frontal aluminum-CFRP joints using transition structures. In the foil concept titanium foils are used as transition elements. Specimens have been produced using three-layer titanium laminates. In tensile tests, three failure locations have been observed: (1) Al-Ti seam, (2) Ti-CFRP hybrid laminate, and (3) CFRP laminate. In this paper, the fracture mechanisms of these failure modes are investigated by analyzing metallographic micrographs and fracture surfaces as well as by correlating load-displacement curves to video imaging of tensile tests. The results show that the cracking of the CFRP layers can be traced back to an assembly error. The laminate character of the titanium part tends to reduce the Al-Ti seam strength. However, two sub-joint tests demonstrate that the Al-Ti seam can endure loads up to 9.5 kN. The ductile failure behavior of the Ti-CFRP hybrid laminates is caused by plastic deformations of the titanium laminate liners.

  17. Utilization of Failure Mode and Effects Analysis (FMEA) Method in Increasing the Revenue of Emergency Department; a Prospective Cohort Study

    PubMed Central

    Shahrami, Ali; Rahmati, Farhad; Kariman, Hamid; Hashemi, Behrooz; Rahmati, Majid; Baratloo, Alireza; Forouzanfar, Mohammad Mehdi; Safari, Saeed

    2013-01-01

    Introduction: The balance between revenue and cost of an organization/system is essential to maintain its survival and quality of services. Emergency departments (ED) are one of the most important parts of health care delivery system. Financial discipline of EDs, by increasing the efficiency and profitability, can directly affect the quality of care and subsequently patient satisfaction. Accordingly, the present study attempts to investigate failure mode and effects analysis (FMEA) method in identifying the problems leading to the loss of ED revenue and offer solutions to help fix these problems. Methods: This prospective cohort study investigated the financial records of ED patients and evaluated the effective errors in reducing the revenue in ED of Imam Hossein hospital, Tehran, Iran, from October 2007 to November 2009. The whole department was divided into one main system and six subsystems, based on FMEA. The study was divided into two phases. In the first phase, the problems leading to the loss of revenue in each subsystem were identified and weighted into four groups using risk priority number (RPN), and the solutions for fixing them were planned. Then, in the second phase, discovered defects in the first phase were fixed according to their priority. Finally, the impact of each solution was compared before and after intervention using the repeated measure ANOVA test. Results: 100 financial records of ED patients were evaluated during the first phase of the study. The average of ED revenue in the six months of the first phase was 73.1±3.65 thousand US dollars/month. 12 types of errors were detected in the predefined subsystems. ED revenue rose from 73.1 to 153.1, 207.06, 240, and 320 thousand US dollars/month after solving first, second, third, and fourth priority problems, respectively (337.75% increase in two years) (p<0.001). 111.0% increase in the ED revenue after solving of first priority problems revealed that they were extremely indispensable in

  18. Recognising and referring children exposed to domestic abuse: a multi-professional, proactive systems-based evaluation using a modified Failure Mode and Effects Analysis (FMEA).

    PubMed

    Ashley, Laura; Armitage, Gerry; Taylor, Julie

    2017-03-01

    Failure Modes and Effects Analysis (FMEA) is a prospective quality assurance methodology increasingly used in healthcare, which identifies potential vulnerabilities in complex, high-risk processes and generates remedial actions. We aimed, for the first time, to apply FMEA in a social care context to evaluate the process for recognising and referring children exposed to domestic abuse within one Midlands city safeguarding area in England. A multidisciplinary, multi-agency team of 10 front-line professionals undertook the FMEA, using a modified methodology, over seven group meetings. The FMEA included mapping out the process under evaluation to identify its component steps, identifying failure modes (potential errors) and possible causes for each step and generating corrective actions. In this article, we report the output from the FMEA, including illustrative examples of the failure modes and corrective actions generated. We also present an analysis of feedback from the FMEA team and provide future recommendations for the use of FMEA in appraising social care processes and practice. Although challenging, the FMEA was unequivocally valuable for team members and generated a significant number of corrective actions locally for the safeguarding board to consider in its response to children exposed to domestic abuse.

  19. Metal matrix composites: Testing, analysis, and failure modes; Proceedings of the Symposium, Sparks, NV, Apr. 25, 26, 1988

    NASA Technical Reports Server (NTRS)

    Johnson, W. S. (Editor)

    1989-01-01

    The present conference discusses the tension and compression testing of MMCs, the measurement of advanced composites' thermal expansion, plasticity theory for fiber-reinforced composites, a deformation analysis of boron/aluminum specimens by moire interferometry, strength prediction methods for MMCs, and the analysis of notched MMCs under tensile loading. Also discussed are techniques for the mechanical and thermal testing of Ti3Al/SCS-6 MMCs, damage initiation and growth in fiber-reinforced MMCs, the shear testing of MMCs, the crack growth and fracture of continuous fiber-reinforced MMCs in view of analytical and experimental results, and MMC fiber-matrix interface failures.

  20. Analysis of possibilities for carbon removal from porous anode of solid oxide fuel cells after different failure modes

    NASA Astrophysics Data System (ADS)

    Subotić, Vanja; Schluckner, Christoph; Schroettner, Hartmuth; Hochenauer, Christoph

    2016-01-01

    This study focuses on the investigation of possibilities for carbon removal from the fuel electrode of anode supported solid oxide fuel cells (ASC-SOFCs) after different degradation modes. To design the conditions which generally lead the cell in the range of carbon depositions the performed thermodynamic calculations show that the SOFC operating temperature range seems to be appropriate for formation of elemental carbon in various types. Concerning this the loaded large planar single SOFCs are fed with synthetic diesel reformate thus simulating realistic operating conditions and enabling the formation and deposition of carbon on the anode side. A mixture of hydrogen/water vapor/nitrogen is used to remove the detected carbon depositions in a cell-protecting manner. For the purpose of this investigation several failure modes are induced after which determination the already defined regeneration strategy is applied. The cathode degradation is first induced and secondly the fuel supply is interrupted to induce re-oxidation of nickel (Ni) on the anode side. The undertaken investigations determine that carbon can be fully removed from the anode surface after nickel oxidation, while cathode degradation disables the complete cell regeneration.

  1. Life Cost Based FMEA Manual: A Step by Step Guide to Carrying Out a Cost-based Failure Modes and Effects Analysis

    SciTech Connect

    Rhee, Seung; Spencer, Cherrill; /Stanford U. /SLAC

    2009-01-23

    Failure occurs when one or more of the intended functions of a product are no longer fulfilled to the customer's satisfaction. The most critical product failures are those that escape design reviews and in-house quality inspection and are found by the customer. The product may work for a while until its performance degrades to an unacceptable level or it may have not worked even before customer took possession of the product. The end results of failures which may lead to unsafe conditions or major losses of the main function are rated high in severity. Failure Modes and Effects Analysis (FMEA) is a tool widely used in the automotive, aerospace, and electronics industries to identify, prioritize, and eliminate known potential failures, problems, and errors from systems under design, before the product is released (Stamatis, 1997). Several industrial FMEA standards such as those published by the Society of Automotive Engineers, US Department of Defense, and the Automotive Industry Action Group employ the Risk Priority Number (RPN) to measure risk and severity of failures. The Risk Priority Number (RPN) is a product of 3 indices: Occurrence (O), Severity (S), and Detection (D). In a traditional FMEA process design engineers typically analyze the 'root cause' and 'end-effects' of potential failures in a sub-system or component and assign penalty points through the O, S, D values to each failure. The analysis is organized around categories called failure modes, which link the causes and effects of failures. A few actions are taken upon completing the FMEA worksheet. The RPN column generally will identify the high-risk areas. The idea of performing FMEA is to eliminate or reduce known and potential failures before they reach the customers. Thus, a plan of action must be in place for the next task. Not all failures can be resolved during the product development cycle, thus prioritization of actions must be made within the design group. One definition of detection

  2. Failure modes and conditions of Itokawa

    NASA Astrophysics Data System (ADS)

    Hirabayashi, Masatoshi; Scheeres, Daniel J.

    2015-11-01

    The YORP effect has been found to play a crucial role in the rotational evolution of small bodies. Recent studies have argued that the YORP effect is very sensitive to the shape of an asteroid (Statler, 2015, Icarus 202, 502) and, as the shape deforms, can possibly change (McMahon, 2015, DDA meeting #301.04). Such sensitivity has been considered to affect the orbital evolution of an asteroid (Bottke et al., 2015, Icarus 247, 191). As a result, this mysterious effect could make fast and slow rotators (personal communication with Bill Bottke, 2015). In addition, possible candidates of rotational disruption have also been discovered in the last decades (e.g., Jewitt et al., 2014, ApJ 784, L8). These studies gave rise to the following question: how does the shape of an asteroid change when subject to rotational variations from the YORP effect? Better understandings of asteroid deformation and failure at different spin periods will help us find clues of it. To do this we are surveying the failure modes and conditions of available shape models with detailed mass information. The main technique used is a plastic finite element model by Hirabayashi and Scheeres (2015, ApJ 798, L8). We have analyzed asteroid Itokawa, which is currently spinning at a spin period of 12.1 hours. Itokawa’s failure conditions at different spin periods can be described by using the minimum cohesive strength that ensures stability of the structure. The results show that this minimum cohesive strength increases as the spin period becomes shorter. If the spin period is longer than 4.5 hours, a failure mode caused by a combination of compression and tension occurs at cohesive strength less than 6 Pa. At shorter spin periods, however, tension spreads out across the neck, causing the body to fail even at cohesive strength higher than it. Since Hill’s stability condition is 5.2 hours, once the body fails at spin periods shorter than 4.5 hours, it breaks into two components that eventually escape

  3. Application of ISO22000, failure mode, and effect analysis (FMEA) cause and effect diagrams and pareto in conjunction with HACCP and risk assessment for processing of pastry products.

    PubMed

    Varzakas, Theodoros H

    2011-09-01

    The Failure Mode and Effect Analysis (FMEA) model has been applied for the risk assessment of pastry processing. A tentative approach of FMEA application to the pastry industry was attempted in conjunction with ISO22000. Preliminary Hazard Analysis was used to analyze and predict the occurring failure modes in a food chain system (pastry processing plant), based on the functions, characteristics, and/or interactions of the ingredients or the processes, upon which the system depends. Critical Control points have been identified and implemented in the cause and effect diagram (also known as Ishikawa, tree diagram, and fishbone diagram). In this work a comparison of ISO22000 analysis with HACCP is carried out over pastry processing and packaging. However, the main emphasis was put on the quantification of risk assessment by determining the Risk Priority Number (RPN) per identified processing hazard. Storage of raw materials and storage of final products at -18°C followed by freezing were the processes identified as the ones with the highest RPN (225, 225, and 144 respectively) and corrective actions were undertaken. Following the application of corrective actions, a second calculation of RPN values was carried out leading to considerably lower values (below the upper acceptable limit of 130). It is noteworthy that the application of Ishikawa (Cause and Effect or Tree diagram) led to converging results thus corroborating the validity of conclusions derived from risk assessment and FMEA. Therefore, the incorporation of FMEA analysis within the ISO22000 system of a pastry processing industry is considered imperative.

  4. Modelling the failure modes in geobag revetments.

    PubMed

    Akter, A; Crapper, M; Pender, G; Wright, G; Wong, W S

    2012-01-01

    In recent years, sand filled geotextile bags (geobags) have been used as a means of long-term riverbank revetment stabilization. However, despite their deployment in a significant number of locations, the failure modes of such structures are not well understood. Three interactions influence the geobag performance, i.e. geobag-geobag, geobag-water flow and geobag-water flow-river bank. The aim of the research reported here is to develop a detailed understanding of the failure mechanisms in a geobag revetment using a discrete element model (DEM) validated by laboratory data. The laboratory measured velocity data were used for preparing a mapped velocity field for a coupled DEM simulation of geobag revetment failure. The validated DEM model could identify well the critical bag location in varying water depths. Toe scour, one of the major instability factors in revetments, and its influence on the bottom-most layer of the bags were also reasonably represented in this DEM model. It is envisaged that the use of a DEM model will provide more details on geobag revetment performance in riverbanks.

  5. Study Of The Risks Arising From Natural Disasters And Hazards On Urban And Intercity Motorways By Using Failure Mode Effect Analysis (FMEA) Methods

    NASA Astrophysics Data System (ADS)

    DELİCE, Yavuz

    2015-04-01

    Highways, Located in the city and intercity locations are generally prone to many kind of natural disaster risks. Natural hazards and disasters that may occur firstly from highway project making to construction and operation stages and later during the implementation of highway maintenance and repair stages have to be taken into consideration. And assessment of risks that may occur against adverse situations is very important in terms of project design, construction, operation maintenance and repair costs. Making hazard and natural disaster risk analysis is largely depending on the definition of the likelihood of the probable hazards on the highways. However, assets at risk , and the impacts of the events must be examined and to be rated in their own. With the realization of these activities, intended improvements against natural hazards and disasters will be made with the utilization of Failure Mode Effects Analysis (FMEA) method and their effects will be analyzed with further works. FMEA, is a useful method to identify the failure mode and effects depending on the type of failure rate effects priorities and finding the most optimum economic and effective solution. Although relevant measures being taken for the identified risks by this analysis method , it may also provide some information for some public institutions about the nature of these risks when required. Thus, the necessary measures will have been taken in advance in the city and intercity highways. Many hazards and natural disasters are taken into account in risk assessments. The most important of these dangers can be listed as follows; • Natural disasters 1. Meteorological based natural disasters (floods, severe storms, tropical storms, winter storms, avalanches, etc.). 2. Geological based natural disasters (earthquakes, tsunamis, landslides, subsidence, sinkholes, etc) • Human originated disasters 1. Transport accidents (traffic accidents), originating from the road surface defects (icing

  6. Tools for developing a quality management program: proactive tools (process mapping, value stream mapping, fault tree analysis, and failure mode and effects analysis).

    PubMed

    Rath, Frank

    2008-01-01

    This article examines the concepts of quality management (QM) and quality assurance (QA), as well as the current state of QM and QA practices in radiotherapy. A systematic approach incorporating a series of industrial engineering-based tools is proposed, which can be applied in health care organizations proactively to improve process outcomes, reduce risk and/or improve patient safety, improve through-put, and reduce cost. This tool set includes process mapping and process flowcharting, failure modes and effects analysis (FMEA), value stream mapping, and fault tree analysis (FTA). Many health care organizations do not have experience in applying these tools and therefore do not understand how and when to use them. As a result there are many misconceptions about how to use these tools, and they are often incorrectly applied. This article describes these industrial engineering-based tools and also how to use them, when they should be used (and not used), and the intended purposes for their use. In addition the strengths and weaknesses of each of these tools are described, and examples are given to demonstrate the application of these tools in health care settings.

  7. Tools for Developing a Quality Management Program: Proactive Tools (Process Mapping, Value Stream Mapping, Fault Tree Analysis, and Failure Mode and Effects Analysis)

    SciTech Connect

    Rath, Frank

    2008-05-01

    This article examines the concepts of quality management (QM) and quality assurance (QA), as well as the current state of QM and QA practices in radiotherapy. A systematic approach incorporating a series of industrial engineering-based tools is proposed, which can be applied in health care organizations proactively to improve process outcomes, reduce risk and/or improve patient safety, improve through-put, and reduce cost. This tool set includes process mapping and process flowcharting, failure modes and effects analysis (FMEA), value stream mapping, and fault tree analysis (FTA). Many health care organizations do not have experience in applying these tools and therefore do not understand how and when to use them. As a result there are many misconceptions about how to use these tools, and they are often incorrectly applied. This article describes these industrial engineering-based tools and also how to use them, when they should be used (and not used), and the intended purposes for their use. In addition the strengths and weaknesses of each of these tools are described, and examples are given to demonstrate the application of these tools in health care settings.

  8. An evaluation of mixed-mode delamination failure criteria

    NASA Technical Reports Server (NTRS)

    Reeder, J. R.

    1992-01-01

    Many different failure criteria have been suggested for mixed mode delamination toughness, but few sets of mixed mode data exist that are consistent over the full mode I opening to mode II shear load range. The mixed mode bending (MMB) test was used to measure the delamination toughness of a brittle epoxy composite, a state of the art toughened epoxy composite, and a tough thermoplastic composite over the full mixed mode range. To gain insight into the different failure responses of the different materials, the delamination fracture surfaces were also examined. An evaluation of several failure criteria which have been reported in the literature was performed, and the range of responses modeled by each criterion was analyzed. A new bilinear failure criterion was analyzed. A new bilinear failure criterion was developed based on a change in the failure mechanism observed from the delamination surfaces. The different criteria were compared to the failure criterion. The failure response of the tough thermoplastic composite could be modeled well with the bilinear criterion but could also be modeled with the more simple linear failure criterion. Since the materials differed in their mixed mode failure response, mixed mode delamination testing will be needed to characterize a composite material. A critical evaluation is provided of the mixed mode failure criteria and should provide general guidance for selecting an appropriate criterion for other materials.

  9. Failure modes of lead/acid batteries

    NASA Astrophysics Data System (ADS)

    Culpin, B.; Rand, D. A. J.

    , have been afforded little discussion. Progressive life-limiting factors encountered with flooded-electrolyte batteries are discussed in detail. These are mainly associated with degradation of the positive plate, the negative plate and the separator. The technology of valve-regulated (i.e., immobilized-electrolyte) batteries is still at an early stage compared with that of flooded designs and, consequently, published information on failure modes is very limited. Nevertheless, based on the reports that are available and the authors' own knowledge, it is possible to make estimates of the major and minor causes of failure (note, these will also occur in flooded systems, but with shifted emphasis). Grid corrosion and growth are generally considered to be of major importance. Both negative-plate sulphation and water loss are also of concern, particularly in cycling applications. By contrast, the traditional problems associated mossing and dendritic growth of the active material should be reduced in valve-regulated batteries.

  10. Global Failure Modes in Composite Structures

    NASA Technical Reports Server (NTRS)

    Knauss, W. G.; Gonzalez, Luis

    2001-01-01

    Composite materials provide well-known advantages for space and aeronautical applications in terms of strength and rigidity to weight ratios and other mechanical properties. As a consequence, their use has experienced a constant increase in the past decades and it is anticipated that this trend will be maintained in the near future. At the same time, being these materials relatively new compared to metals, and having failure characteristics completely different from them, their damage growth and their failure mechanisms are not as well understood in a predictive sense. For example, while in metals fracture produces "clean" cracks with their well defined analytically stress fields at the crack tip, composite fracture is a more complex phenomenon. Instead of a crack, we confront a "damage zone" that may include fiber breakage, fiber microbuckling, fiber pullout, matrix cracking, delamination, debonding or any combination of all these different mechanisms. These phenomena are prevalent in any failure process through an aircraft structure, whether one addresses a global failure such as the ripping of a fuselage or wing section, or whether one is concerned with the failure initiation near a thickness change at stringers or other reinforcement. Thus the topic that has been under consideration has wide application in any real structure and is considered an essential contribution to the predictive failure analysis capability for aircraft containing composite components. The heterogeneity and the anisotropy of composites are not only advantageous but essential characteristics, yet these same features provide complex stress fields, especially in the presence of geometrical discontinuities such as notches, holes or cutouts or structural elements such as stiffeners, stringers, etc. To properly address the interaction between a damage/crack front and a hole with a stringer it is imperative that the stress and deformation fields of the former be (sufficiently well) characterized

  11. Gearbox Typical Failure Modes, Detection, and Mitigation Methods (Presentation)

    SciTech Connect

    Sheng, S.

    2014-01-01

    This presentation was given at the AWEA Operations & Maintenance and Safety Seminar and focused on what the typical gearbox failure modes are, how to detect them using detection techniques, and strategies that help mitigate these failures.

  12. Failure mode interaction in fiber reinforced laminated composites

    NASA Astrophysics Data System (ADS)

    Prabhakar, Pavana

    A novel computational modeling framework to predict the compressive strength of fiber reinforced polymer matrix composite (FRPC) laminates has been presented. The model development has been motivated by a set of experimental results on the compression response of two different FRPCs. The model accounts for failure mode interaction between kink-banding and interface fracture (or delamination), which are observed in the experimental results. To reduce the size of the computational model, those interfaces that are most susceptible to delamination are first determined through a free-edge stress analysis. Furthermore, 0-axis layers, which are passive in the failure process are represented through an equivalent homogenized model, but the microstructural features of the on-axis layers (zero plies) are retained in the computational model. The predictions of the model matched well with the experimental observations, and they were found to accurately account for failure mechanism interactions. Therefore, this model has the potential to replace the need to carry out large numbers of tests to obtain the compressive strength allowable for FRPC laminates, the latter allowable being an essential element in the design of lightweight FRPC aerostructures. Furthermore, the thesis presents a new computational model to predict fiber/matrix splitting failure, a failure mode that is frequently observed in in-plane tensile failure of FRPC's. By considering a single lamina, this failure mechanism was seamlessly modeled through the development of a continuum-decohesive nite element (CDFE). The CDFE was motivated by the variational multiscale cohesive method (VMCM) presented earlier by Rudraraju et al. (2010) at the University of Michigan. In the CDFE, the transition from a continuum to a non-continuum is modeled directly (physically) without resorting to enrichment of the shape functions of the element. Thus, the CDFE is a natural merger between cohesive elements and continuum elements. The

  13. Applicability of NASA contract quality management and failure mode effect analysis procedures to the USGS Outer Continental Shelf oil and gas lease management program

    NASA Technical Reports Server (NTRS)

    Dyer, M. K.; Little, D. G.; Hoard, E. G.; Taylor, A. C.; Campbell, R.

    1972-01-01

    An approach that might be used for determining the applicability of NASA management techniques to benefit almost any type of down-to-earth enterprise is presented. A study was made to determine the following: (1) the practicality of adopting NASA contractual quality management techniques to the U.S. Geological Survey Outer Continental Shelf lease management function; (2) the applicability of failure mode effects analysis to the drilling, production, and delivery systems in use offshore; (3) the impact on industrial offshore operations and onshore management operations required to apply recommended NASA techniques; and (4) the probable changes required in laws or regulations in order to implement recommendations. Several management activities that have been applied to space programs are identified, and their institution for improved management of offshore and onshore oil and gas operations is recommended.

  14. Integration of Value Stream Map and Healthcare Failure Mode and Effect Analysis into Six Sigma Methodology to Improve Process of Surgical Specimen Handling.

    PubMed

    Hung, Sheng-Hui; Wang, Pa-Chun; Lin, Hung-Chun; Chen, Hung-Ying; Su, Chao-Ton

    2015-01-01

    Specimen handling is a critical patient safety issue. Problematic handling process, such as misidentification (of patients, surgical site, and specimen counts), specimen loss, or improper specimen preparation can lead to serious patient harms and lawsuits. Value stream map (VSM) is a tool used to find out non-value-added works, enhance the quality, and reduce the cost of the studied process. On the other hand, healthcare failure mode and effect analysis (HFMEA) is now frequently employed to avoid possible medication errors in healthcare process. Both of them have a goal similar to Six Sigma methodology for process improvement. This study proposes a model that integrates VSM and HFMEA into the framework, which mainly consists of define, measure, analyze, improve, and control (DMAIC), of Six Sigma. A Six Sigma project for improving the process of surgical specimen handling in a hospital was conducted to demonstrate the effectiveness of the proposed model.

  15. Decomposition-Based Failure Mode Identification Method for Risk-Free Design of Large Systems

    NASA Technical Reports Server (NTRS)

    Tumer, Irem Y.; Stone, Robert B.; Roberts, Rory A.; Clancy, Daniel (Technical Monitor)

    2002-01-01

    When designing products, it is crucial to assure failure and risk-free operation in the intended operating environment. Failures are typically studied and eliminated as much as possible during the early stages of design. The few failures that go undetected result in unacceptable damage and losses in high-risk applications where public safety is of concern. Published NASA and NTSB accident reports point to a variety of components identified as sources of failures in the reported cases. In previous work, data from these reports were processed and placed in matrix form for all the system components and failure modes encountered, and then manipulated using matrix methods to determine similarities between the different components and failure modes. In this paper, these matrices are represented in the form of a linear combination of failures modes, mathematically formed using Principal Components Analysis (PCA) decomposition. The PCA decomposition results in a low-dimensionality representation of all failure modes and components of interest, represented in a transformed coordinate system. Such a representation opens the way for efficient pattern analysis and prediction of failure modes with highest potential risks on the final product, rather than making decisions based on the large space of component and failure mode data. The mathematics of the proposed method are explained first using a simple example problem. The method is then applied to component failure data gathered from helicopter, accident reports to demonstrate its potential.

  16. CSM RCS Design Considerations and Failure Modes

    NASA Technical Reports Server (NTRS)

    Interbartolo, Michael

    2009-01-01

    Objectives include: a) Define major Command and Service Module (CSM) design considerations; b) List Command Module (CM) RCS failures and lessons learned; and c) List Service Module (SM) RCS failures and lessons learned.

  17. A bilinear failure criterion for mixed-mode delamination

    NASA Technical Reports Server (NTRS)

    Reeder, James R.

    1993-01-01

    Many different failure criteria have been suggested for mixed-mode delamination toughness, but few sets of mixed-mode data exist that are consistent over the full range of Mode 1 opening load to Mode 2 shear load range. The mixed-mode bending (MMB) test was used to measure the delamination toughness of a brittle epoxy composite, a state-of-the-art toughened epoxy composite, and a tough thermoplastic composite over the full mixed-mode range. To gain insight into the different failure responses of the different materials, the delamination fracture surfaces were also examined. An evaluation of several failure criteria that have been reported in the literature was performed, and the range of responses modeled by each criterion was analyzed. A bilinear failure criterion was introduced based on a change in the failure mechanism observed from the delamination surfaces. The different criteria were compared to the failure response of the three materials tested. The responses of the two epoxies were best modeled with the new bilinear failure criterion. The failure response of the tough thermoplastic composite could be modeled well with the bilinear criterion but could also be modeled with the more simple linear failure criterion. Since the materials differed in their mixed-mode failure response, mixed-mode delamination testing will be needed to characterize a composite material. This paper presents consistent sets of mixed-mode data, provides a critical evaluation of the mixed-mode failure criteria, and should provide general guidance for selecting an appropriate criterion for other materials.

  18. Light water reactor lower head failure analysis

    SciTech Connect

    Rempe, J.L.; Chavez, S.A.; Thinnes, G.L.

    1993-10-01

    This document presents the results from a US Nuclear Regulatory Commission-sponsored research program to investigate the mode and timing of vessel lower head failure. Major objectives of the analysis were to identify plausible failure mechanisms and to develop a method for determining which failure mode would occur first in different light water reactor designs and accident conditions. Failure mechanisms, such as tube ejection, tube rupture, global vessel failure, and localized vessel creep rupture, were studied. Newly developed models and existing models were applied to predict which failure mechanism would occur first in various severe accident scenarios. So that a broader range of conditions could be considered simultaneously, calculations relied heavily on models with closed-form or simplified numerical solution techniques. Finite element techniques-were employed for analytical model verification and examining more detailed phenomena. High-temperature creep and tensile data were obtained for predicting vessel and penetration structural response.

  19. SU-C-BRD-02: A Team Focused Clinical Implementation and Failure Mode and Effects Analysis of HDR Skin Brachytherapy Using Valencia and Leipzig Surface Applicators

    SciTech Connect

    Sayler, E; Harrison, A; Eldredge-Hindy, H; Dinome, J; Munro, S; Anne, R; Comber, E; Lockamy, V

    2014-06-15

    Purpose: and Leipzig applicators (VLAs) are single-channel brachytherapy surface applicators used to treat skin lesions up to 2cm diameter. Source dwell times can be calculated and entered manually after clinical set-up or ultrasound. This procedure differs dramatically from CT-based planning; the novelty and unfamiliarity could lead to severe errors. To build layers of safety and ensure quality, a multidisciplinary team created a protocol and applied Failure Modes and Effects Analysis (FMEA) to the clinical procedure for HDR VLA skin treatments. Methods: team including physicists, physicians, nurses, therapists, residents, and administration developed a clinical procedure for VLA treatment. The procedure was evaluated using FMEA. Failure modes were identified and scored by severity, occurrence, and detection. The clinical procedure was revised to address high-scoring process nodes. Results: Several key components were added to the clinical procedure to minimize risk probability numbers (RPN): -Treatments are reviewed at weekly QA rounds, where physicians discuss diagnosis, prescription, applicator selection, and set-up. Peer review reduces the likelihood of an inappropriate treatment regime. -A template for HDR skin treatments was established in the clinical EMR system to standardize treatment instructions. This reduces the chances of miscommunication between the physician and planning physicist, and increases the detectability of an error during the physics second check. -A screen check was implemented during the second check to increase detectability of an error. -To reduce error probability, the treatment plan worksheet was designed to display plan parameters in a format visually similar to the treatment console display. This facilitates data entry and verification. -VLAs are color-coded and labeled to match the EMR prescriptions, which simplifies in-room selection and verification. Conclusion: Multidisciplinary planning and FMEA increased delectability and

  20. Failure mode analysis and a mechanism for hot-ductility improvement in the Nb-microalloyed steel

    NASA Astrophysics Data System (ADS)

    Zarandi, Faramarz; Yue, Steven

    2004-12-01

    Loss of hot ductility at the straightening stage of the continuous casting of high-strength low-alloy steel is attributed to different microalloying elements, in particular, Nb. However, such elements are essential for the desired mechanical characteristics of the final product. Since the chemistry cannot be altered to alleviate the problem, thermomechanical processing was studied in order to improve the hot ductility. Two Nb-microalloyed steels, one also containing B, were examined. The thermal history occurring in the continuous casting process was taken into account as well. First, it was noticed that the steel with B has a higher hot ductility than the other after being subjected to in-situ melting followed by the thermal schedule. Grain boundary sliding was recognized as the failure mechanism. Then, the effect of deformation applied in the vicinity of the δ→ γ transformation, while the thermal schedule was being executed, was investigated. Such deformation appeared to improve the hot ductility remarkably. Finally, the mechanism of such improvement in the hot ductility was elaborated.

  1. Wind Turbine Gearbox Failure Modes - A Brief (Presentation)

    SciTech Connect

    Sheng, S.; McDade, M.; Errichello, R.

    2011-10-01

    Wind turbine gearboxes are not always meeting 20-year design life. Premature failure of gearboxes increases cost of energy, turbine downtime, unplanned maintenance, gearbox replacement and rebuild, and increased warranty reserves. The problem is widespread, affects most Original Equipment Manufacturers, and is not caused by manufacturing practices. There is a need to improve gearbox reliability and reduce turbine downtime. The topics of this presentation are: GRC (Gearbox Reliability Collaborative) technical approach; Gearbox failure database; Recorded incidents summary; Top failure modes for bearings; Top failure modes for gears; GRC test gearbox; Bearing nomenclature; Test history; Real damage; Gear sets; Bearings; Observations; and Summary. 5 refs.

  2. Investigation of successive failure modes in graphite/epoxy laminated composite beams

    NASA Astrophysics Data System (ADS)

    Greif, R.; Chapon, E.

    1993-05-01

    A theoretical and experimental investigation is conducted for the successive failure modes of graphite-epoxy laminated beams, on the basis of the Tsai-Wu and maximum stress failure theories, giving attention to behavior beyond the first failure. It is assumed that, once a ply fails in a laminate, it can carry no further load and its elastic properties are set to zero. The failure analysis is then repeated with the modified laminae on updated matrices, until the next failure point is reached. Theoretical results are compared with experimental ones, and it is found that theory-based failures occur at substantially lower loads than those of actual fracture.

  3. Failure Modes Experienced on Spacecraft Nicd Batteries

    NASA Technical Reports Server (NTRS)

    Gross, S.

    1985-01-01

    A review was made of failures and irregularities experienced on nickel cadmium batteries for 31 spacecraft. Only rarely did batteries fail completely. In many cases, poorly performing batteries were compensated for by a reduction in loads or by continuing to operate in spite of out-of-voltage conditions. Low discharge voltage was the most common problem observed in flight spacecraft (42%). Spacecraft batteries are often designed to protect against cell shorts, but cell shorts accounted for only 16% of the failures. Other causes of problems were high charge voltage (16%), battery problems caused by other elements of the spacecraft (10%), and open circuit failures (6%). Problems of miscellaneous or unknown causes occurred in 10% of the cases.

  4. Safety Management of a Clinical Process Using Failure Mode and Effect Analysis: Continuous Renal Replacement Therapies in Intensive Care Unit Patients.

    PubMed

    Sanchez-Izquierdo-Riera, Jose Angel; Molano-Alvarez, Esteban; Saez-de la Fuente, Ignacio; Maynar-Moliner, Javier; Marín-Mateos, Helena; Chacón-Alves, Silvia

    2016-01-01

    The failure mode and effect analysis (FMEA) may improve the safety of the continuous renal replacement therapies (CRRT) in the intensive care unit. We use this tool in three phases: 1) Retrospective observational study. 2) A process FMEA, with implementation of the improvement measures identified. 3) Cohort study after FMEA. We included 54 patients in the pre-FMEA group and 72 patients in the post-FMEA group. Comparing the risks frequencies per patient in both groups, we got less cases of under 24 hours of filter survival time in the post-FMEA group (31 patients 57.4% vs. 21 patients 29.6%; p < 0.05); less patients suffered circuit coagulation with inability to return the blood to the patient (25 patients [46.3%] vs. 16 patients [22.2%]; p < 0.05); 54 patients (100%) versus 5 (6.94%) did not get phosphorus levels monitoring (p < 0.05); in 14 patients (25.9%) versus 0 (0%), the CRRT prescription did not appear on medical orders. As a measure of improvement, we adopt a dynamic dosage management. After the process FMEA, there were several improvements in the management of intensive care unit patients receiving CRRT, and we consider it a useful tool for improving the safety of critically ill patients.

  5. Failure analysis of surface-micromachined microengines

    SciTech Connect

    Peterson, K.A.; Tangyunyong, P.; Pimentel, A.A.

    1998-11-01

    Microelectronic failure analysis (FA) has been an integral part of the development of state-of-the-art integrated circuits. FA of MicroElectroMechanical Systems (MEMS) is moving from its infancy stage to assume an important role in the successful design, fabrication, performance and reliability analysis for this new technology. In previous work, the authors focused on the application of several techniques developed for integrated circuit analysis to an earlier version of a surface micromachined microengine fabricated at Sandia. Recently, they have identified important new failure modes in binary counters that incorporate a newer design of the microengine, using a subset of integrated circuit failure analysis techniques including optical microscopy, focused ion beam (FIB) techniques, atomic force microscopy (AFM), and scanning electron microscopy (SEM). The primary failure mode they have identified is directly related to visible wear on bearing surfaces. In this paper, they describe in detail the characteristics of the failure modes in binary counters. They also compare the failure characteristics with those of an earlier version of the microengine.

  6. Predicting Modes and Displacements of Seismic Rock Slope Failures

    NASA Astrophysics Data System (ADS)

    Gibson, M. D.; Wartman, J.; Keefer, D. K.; Maclaughlin, M.; Arnold, L.; Applegate, K. N.; Smith, S.; Adams, S.

    2013-12-01

    Seismically induced rock slope failures have resulted in billions of dollars of economic damage and enormous loss of life throughout the world. Accurate prediction of the triggering and run out of these failures is elusive for a variety of reasons, including knowledge of the physical modes of failure. Our research explores the potential failure modes of an idealized rigid rock block and expands the modes typically considered to include not only sliding but also toppling (pure forward rotation) and slumping (combined backward rotation and translation). The yield acceleration (or minimum inertial acceleration to cause block movement) for slumping, similar to toppling, is found to be lower than for pure translational sliding. These yield accelerations indicate the initial modes of rock block failure; however, they do not always predict the ultimate failure mode. To predict the final failure modes, the results of discrete element numerical analyses were compared to pseudo static yield acceleration to develop a seismic failure mode decision-making chart based on block geometry and interface friction. With regard to seismic displacement predictions, current simplified models predicting ultimate displacement of a mass under seismic conditions are limited to purely translating, sliding blocks (i.e. Newmark's sliding block method). Our modeling introduces additional simplified analyses to predict ultimate displacement in toppling and slumping modes as well. Important findings from these new methods are that the magnitude of seismically-induced displacement is dependent on the size of the block (or failure mass) and that as the yield acceleration decreases the seismically induced displacements increase. We plan to map these tools into analyses that evaluate rock slope systems with complex geology and geotechnical characteristics. It is envisioned that the decision chart, which predicts the initial and ultimate modes of failure based on block geometry and interface friction

  7. Failure modes for pipelines in landslide areas

    SciTech Connect

    Bruschi, R.; Spinazze, M.; Tomassini, D.; Cuscuna, S.; Venzi, S.

    1995-12-31

    In recent years a number of incidences of pipelines affected by slow soil movements have been reported in the relevant literature. Further related issues such as soil-pipe interaction have been studied both theoretically and through experimental surveys, along with the environmental conditions which are responsible for hazard to the pipeline integrity. A suitable design criteria under these circumstances has been discussed by several authors, in particular in relation to a limit state approach and hence a strain based criteria. The scope of this paper is to describe the failure mechanisms which may affect the pipeline in the presence of slow soil movements impacting on the pipeline, both in the longitudinal and transverse direction. Particular attention is paid to environmental, geometric and structural parameters which steer the process towards one or other failure mechanism. Criteria for deciding upon remedial measures required to guarantee the structural integrity of the pipeline, both in the short and in the long term, are discussed.

  8. SU-E-T-119: Analysis the Efficacy of Different Radiotherapy Methods and Failure Mode in No-Metastasis Esophageal Squamous Cell Carcinoma

    SciTech Connect

    Yankun, C; Zhihui, T; Runxiao, L; Shen, W

    2015-06-15

    Purpose: To evaluate the curative effect of radio (chemo) therapy and mode of treatment failure in no-metastasis and lesion length ≤ 5.0cm esophageal squamous cell carcinoma (ESCC). Methods: There were 158 eligible patients were retrospectively analyzed, to analysis the curative effect of radio (chemo) therapy, prognosis factors, toxicity and prognostic index model. Results: To all patients the 1, 3, 5 overall survival rate were 83.54%, 52.53%, 32.58%, the local recurrence rate were 15.08%, 33.60% and 38.14%; distant metastasis rate were 10.64%, 25.21% and 36.06%; tumor specific survival rate were 76.64%, 54.07% and 44.51%. Multivariate analysis showed that patients with ECOG grade (χ2=13.945, P=0.000), short-term effect (χ2=19.360, P=0.000) and different radiotherapy methods (χ2=9.866, P=0.002) as the independent prognostic factors. Prognostic index model showed that the survival rate was significantly higher in the lower value of PI group than in the larger value of PI group (χ2=49.19, P=0.0000). In our whole group, there were simple locoregional recurrence (LR) 40 cases (25.3%), simple Distant metastasis (DM) 31 cases (19.6%), LR and DM in 14 cases (8.9%) after treatment. The chi-square test showed that there were no significant difference in the incidence of Elective Nodal Irradiation (ENI )and Involved Field Irradiation (IFI) patients with LR and DM ( χ2=2.363, 2.950, P=0.124, 0.085). Conclusion: Radio (chemo) therapy has a good curative effect in no-metastasis and lesion length ≤ 5.0cm ESCC patients.

  9. Failure modes and materials design for biomechanical layer structures

    NASA Astrophysics Data System (ADS)

    Deng, Yan

    Ceramic materials are finding increasing usage in the area of biomechanical replacements---dental crowns, hip and bone implants, etc.---where strength, wear resistance, biocompatibility, chemical durability and even aesthetics are critical issues. Aesthetic ceramic crowns have been widely used in dentistry to replace damaged or missing teeth. However, the failure rates of ceramic crowns, especially all-ceramic crowns, can be 1%˜6% per year, which is not satisfactory to patients. The materials limitations and underlying fracture mechanisms of these prostheses are not well understood. In this thesis, fundamental fracture and damage mechanisms in model dental bilayer and trilayer structures are studied. Principle failure modes are identified from in situ experimentation and confirmed by fracture mechanics analysis. In bilayer structures of ceramic/polycarbonate (representative of ceramic crown/dentin structure), three major damage sources are identified: (i) top-surface cone cracks or (ii) quasiplasticity, dominating in thick ceramic bilayers; (iii) bottom-surface radial cracks, dominating in thin ceramic bilayers. Critical load P for each damage mode are measured in six dental ceramics: Y-TZP zirconia, glass-infiltrated zirconia and alumina (InCeram), glass-ceramic (Empress II), Porcelain (Mark II and Empress) bonded to polymer substrates, as a function of ceramic thickness d in the range of 100 mum to 10 mm. P is found independent of d for mode (i) and (ii), but has a d 2 relations for mode (iii)---bottom surface radial cracking. In trilayer structures of glass/core-ceramic/polycarbonate (representing veneer porcelain/core/dentin structures), three inner fracture origins are identified: radial cracks from the bottom surface in the (i) first and (ii) second layers; and (iii) quasiplasticity in core-ceramic layer. The role of relative veneer/core thickness, d1/d 2 and materials properties is investigated for three core materials with different modulus (114--270GPa

  10. Failure modes at room and elevated temperatures. Technical report

    SciTech Connect

    Braun, L.M.

    1995-04-01

    Successful development of reliable ceramic composites will depend on an understanding of matrix cracking and damage mechanisms in these materials. Therefore, the objective of the Failure Models subtask is to investigate failure and damage mechanisms in fiber reinforced ceramic composites. Issues such as how fiber coatings, the fiber/matrix interface, residual stresses, and fiber volume fraction affect frictional stresses, fiber debonding, fiber pull-out and failure modes will be examined. The effect of these microstructural parameters on matrix crack initiation, propagation and damage will also be determined. The resulting observations and measurements data will be used to develop theoretical models for damage mechanisms in fiber reinforced composites. This report presents results concerning the effect of temperature on the failure modes of continuous fiber ceramic composites performed during the last quarter of FY 1993 and FY 1994. The Raman stress measurements and calculations were performed during the last quarter of FY 1994 and the first quarter of FY 1995.

  11. Recent performance, lifetime, and failure modes of the 5045 klystron population at SLAC

    SciTech Connect

    Koontz, R.F.; Lee, T.G.; Pearson, C.; Vlieks, A.E.

    1992-08-01

    The 65 MW S-Band klystrons (5045) used to power SLC have been in service for over seven years. Currently, 244 of these tubes are in place on the accelerator, operating full power at 120 pulses per second. Enough tubes have now reached end of life, or experienced other failures to allow a good analysis of failure modes, and to project average lifetime for this type of tube. This paper describes the various modes of failure seen in klystrons rammed from SLC service, and provides data on expected lifetime from current production based on accumulated SLC operating experience.

  12. Risk assessment of failure modes of gas diffuser liner of V94.2 siemens gas turbine by FMEA method

    NASA Astrophysics Data System (ADS)

    Mirzaei Rafsanjani, H.; Rezaei Nasab, A.

    2012-05-01

    Failure of welding connection of gas diffuser liner and exhaust casing is one of the failure modes of V94.2 gas turbines which are happened in some power plants. This defect is one of the uncertainties of customers when they want to accept the final commissioning of this product. According to this, the risk priority of this failure evaluated by failure modes and effect analysis (FMEA) method to find out whether this failure is catastrophic for turbine performance and is harmful for humans. By using history of 110 gas turbines of this model which are used in some power plants, the severity number, occurrence number and detection number of failure determined and consequently the Risk Priority Number (RPN) of failure determined. Finally, critically matrix of potential failures is created and illustrated that failure modes are located in safe zone.

  13. Failure analysis of high performance ballistic fibers

    NASA Astrophysics Data System (ADS)

    Spatola, Jennifer S.

    High performance fibers have a high tensile strength and modulus, good wear resistance, and a low density, making them ideal for applications in ballistic impact resistance, such as body armor. However, the observed ballistic performance of these fibers is much lower than the predicted values. Since the predictions assume only tensile stress failure, it is safe to assume that the stress state is affecting fiber performance. The purpose of this research was to determine if there are failure mode changes in the fiber fracture when transversely loaded by indenters of different shapes. An experimental design mimicking transverse impact was used to determine any such effects. Three different indenters were used: round, FSP, and razor blade. The indenter height was changed to change the angle of failure tested. Five high performance fibers were examined: KevlarRTM KM2, SpectraRTM 130d, DyneemaRTM SK-62 and SK-76, and ZylonRTM 555. Failed fibers were analyzed using an SEM to determine failure mechanisms. The results show that the round and razor blade indenters produced a constant failure strain, as well as failure mechanisms independent of testing angle. The FSP indenter produced a decrease in failure strain as the angle increased. Fibrillation was the dominant failure mechanism at all angles for the round indenter, while through thickness shearing was the failure mechanism for the razor blade. The FSP indenter showed a transition from fibrillation at low angles to through thickness shearing at high angles, indicating that the round and razor blade indenters are extreme cases of the FSP indenter. The failure mechanisms observed with the FSP indenter at various angles correlated with the experimental strain data obtained during fiber testing. This indicates that geometry of the indenter tip in compression is a contributing factor in lowering the failure strain of the high performance fibers. TEM analysis of the fiber failure mechanisms was also attempted, though without

  14. BIOASSAY VESSEL FAILURE ANALYSIS

    SciTech Connect

    Vormelker, P

    2008-09-22

    Two high-pressure bioassay vessels failed at the Savannah River Site during a microwave heating process for biosample testing. Improper installation of the thermal shield in the first failure caused the vessel to burst during microwave heating. The second vessel failure is attributed to overpressurization during a test run. Vessel failure appeared to initiate in the mold parting line, the thinnest cross-section of the octagonal vessel. No material flaws were found in the vessel that would impair its structural performance. Content weight should be minimized to reduce operating temperature and pressure. Outer vessel life is dependent on actual temperature exposure. Since thermal aging of the vessels can be detrimental to their performance, it was recommended that the vessels be used for a limited number of cycles to be determined by additional testing.

  15. Transition among failure modes of the bending system with a stiff film on a soft substrate

    SciTech Connect

    Dai, Longchao; Huang, Yin; Chen, Hang; Feng, Xue; Fang, Daining

    2015-01-12

    Growing interest is being attracted by stretchable and flexible electronics recently due to their attractive characteristics, commercial potentials, and engineering challenges. In comparison with the system on a macroscopic scale, different failure modes are observed in a system with a thin film bonded on an elastomeric substrate. Furthermore, the experimental observations reveal that failure modes occur in turn with the increasing of thickness ratio of the film to substrate. In this paper, theoretical analysis is performed on the failure mechanism in this system with the focus on transitions among these failure modes based on the theory of fracture mechanics. The present theoretical predictions are coincident with related experiment results and can be used to guide the related structural design.

  16. Tensile and compressive failure modes of laminated composites loaded by fatigue with different mean stress

    NASA Technical Reports Server (NTRS)

    Rotem, Assa

    1990-01-01

    Laminated composite materials tend to fail differently under tensile or compressive load. Under tension, the material accumulates cracks and fiber fractures, while under compression, the material delaminates and buckles. Tensile-compressive fatigue may cause either of these failure modes depending on the specific damage occurring in the laminate. This damage depends on the stress ratio of the fatigue loading. Analysis of the fatigue behavior of the composite laminate under tension-tension, compression-compression, and tension-compression had led to the development of a fatigue envelope presentation of the failure behavior. This envelope indicates the specific failure mode for any stress ratio and number of loading cycles. The construction of the fatigue envelope is based on the applied stress-cycles to failure (S-N) curves of both tensile-tensile and compressive-compressive fatigue. Test results are presented to verify the theoretical analysis.

  17. Failure environment analysis tool applications

    NASA Technical Reports Server (NTRS)

    Pack, Ginger L.; Wadsworth, David B.

    1994-01-01

    Understanding risks and avoiding failure are daily concerns for the women and men of NASA. Although NASA's mission propels us to push the limits of technology, and though the risks are considerable, the NASA community has instilled within it, the determination to preserve the integrity of the systems upon which our mission and, our employees lives and well-being depend. One of the ways this is being done is by expanding and improving the tools used to perform risk assessment. The Failure Environment Analysis Tool (FEAT) was developed to help engineers and analysts more thoroughly and reliably conduct risk assessment and failure analysis. FEAT accomplishes this by providing answers to questions regarding what might have caused a particular failure; or, conversely, what effect the occurrence of a failure might have on an entire system. Additionally, FEAT can determine what common causes could have resulted in other combinations of failures. FEAT will even help determine the vulnerability of a system to failures, in light of reduced capability. FEAT also is useful in training personnel who must develop an understanding of particular systems. FEAT facilitates training on system behavior, by providing an automated environment in which to conduct 'what-if' evaluation. These types of analyses make FEAT a valuable tool for engineers and operations personnel in the design, analysis, and operation of NASA space systems.

  18. Failure environment analysis tool applications

    NASA Technical Reports Server (NTRS)

    Pack, Ginger L.; Wadsworth, David B.

    1993-01-01

    Understanding risks and avoiding failure are daily concerns for the women and men of NASA. Although NASA's mission propels us to push the limits of technology, and though the risks are considerable, the NASA community has instilled within, the determination to preserve the integrity of the systems upon which our mission and, our employees lives and well-being depend. One of the ways this is being done is by expanding and improving the tools used to perform risk assessment. The Failure Environment Analysis Tool (FEAT) was developed to help engineers and analysts more thoroughly and reliably conduct risk assessment and failure analysis. FEAT accomplishes this by providing answers to questions regarding what might have caused a particular failure; or, conversely, what effect the occurrence of a failure might have on an entire system. Additionally, FEAT can determine what common causes could have resulted in other combinations of failures. FEAT will even help determine the vulnerability of a system to failures, in light of reduced capability. FEAT also is useful in training personnel who must develop an understanding of particular systems. FEAT facilitates training on system behavior, by providing an automated environment in which to conduct 'what-if' evaluation. These types of analyses make FEAT a valuable tool for engineers and operations personnel in the design, analysis, and operation of NASA space systems.

  19. Mud pump failure analysis

    SciTech Connect

    Lewis, E.C. II

    1981-10-01

    Extrusion, the primary cause of piston failure, is the degradation of a seal caused by the seal material moving into the interface between the two parts being sealed. It is shown that operational dynamics of the mud piston lead to an aggravated extrusion condition. As both the liner wall and the piston OD lose material, the clearance gap between liner and piston increases. This gap provides the piston seal a space to move into when pressurized. This movement, called extrusion, is undesirable because the piston rubber is then subjected to abnormal stresses which it cannot tolerate. As the piston moves forward, this extruded material is gradually nibbled away. Extrusion and nibble action continue on each stroke of the pump as additional rubber moves away from the high-pressure side of the piston toward the low-pressure side. A discussion is presented of extrusion rates and seal leakage.

  20. System Reliability Assessment for a Rock Tunnel with Multiple Failure Modes

    NASA Astrophysics Data System (ADS)

    Lü, Qing; Chan, Chin Loong; Low, Bak Kong

    2013-07-01

    This paper presents a practical procedure for assessing the system reliability of a rock tunnel. Three failure modes, namely, inadequate support capacity, excessive tunnel convergence, and insufficient rockbolt length, are considered and investigated using a deterministic model of ground-support interaction analysis based on the convergence-confinement method (CCM). The failure probability of each failure mode is evaluated from the first-order reliability method (FORM) and the response surface method (RSM) via an iterative procedure. The system failure probability bounds are estimated using the bimodal bounds approach suggested by Ditlevsen (1979), based on the reliability index and design point inferred from the FORM. The proposed approach is illustrated with an example of a circular rock tunnel. The computed system failure probability bounds compare favorably with those generated from Monte Carlo simulations. The results show that the relative importance of different failure modes to the system reliability of the tunnel mainly depends on the timing of support installation relative to the advancing tunnel face. It is also shown that reliability indices based on the second-order reliability method (SORM) can be used to achieve more accurate bounds on the system failure probability for nonlinear limit state surfaces. The system reliability-based design for shotcrete thickness is also demonstrated.

  1. New understandings of failure modes in SSL luminaires

    SciTech Connect

    Shepherd, Sarah D; Mills, Karmann C; Yaga, Robert; Johnson, Cortina; Davis, J Lynn

    2014-09-18

    As SSL products are being rapidly introduced into the market, there is a need to develop standard screening and testing protocols that can be performed quickly and provide data surrounding product lifetime and performance. These protocols, derived from standard industry tests, are known as ALTs (accelerated life tests) and can be performed in a timeframe of weeks to months instead of years. Accelerated testing utilizes a combination of elevated temperature and humidity conditions as well as electrical power cycling to control aging of the luminaires. In this study, we report on the findings of failure modes for two different luminaire products exposed to temperature-humidity ALTs. LEDs are typically considered the determining component for the rate of lumen depreciation. However, this study has shown that each luminaire component can independently or jointly influence system performance and reliability. Material choices, luminaire designs, and driver designs all have significant impacts on the system reliability of a product. From recent data, it is evident that the most common failure modes are not within the LED, but instead occur within resistors, capacitors, and other electrical components of the driver. Insights into failure modes and rates as a result of ALTs are reported with emphasis on component influence on overall system reliability.

  2. New understandings of failure modes in SSL luminaires

    NASA Astrophysics Data System (ADS)

    Shepherd, Sarah D.; Mills, Karmann C.; Yaga, Robert; Johnson, Cortina; Davis, J. Lynn

    2014-09-01

    As SSL products are being rapidly introduced into the market, there is a need to develop standard screening and testing protocols that can be performed quickly and provide data surrounding product lifetime and performance. These protocols, derived from standard industry tests, are known as ALTs (accelerated life tests) and can be performed in a timeframe of weeks to months instead of years. Accelerated testing utilizes a combination of elevated temperature and humidity conditions as well as electrical power cycling to control aging of the luminaires. In this study, we report on the findings of failure modes for two different luminaire products exposed to temperature-humidity ALTs. LEDs are typically considered the determining component for the rate of lumen depreciation. However, this study has shown that each luminaire component can independently or jointly influence system performance and reliability. Material choices, luminaire designs, and driver designs all have significant impacts on the system reliability of a product. From recent data, it is evident that the most common failure modes are not within the LED, but instead occur within resistors, capacitors, and other electrical components of the driver. Insights into failure modes and rates as a result of ALTs are reported with emphasis on component influence on overall system reliability.

  3. First passage failure: Analysis alternatives

    SciTech Connect

    PAEZ,THOMAS L.; NGUYEN,H.P.; WIRSCHING,PAUL H.

    2000-04-17

    Most mechanical and structural failures can be formulated as first passage problems. The traditional approach to first passage analysis models barrier crossings as Poisson events. The crossing rate is established and used in the Poisson framework to approximate the no-crossing probability. While this approach is accurate in a number of situations, it is desirable to develop analysis alternatives for those situations where traditional analysis is less accurate and situations where it is difficult to estimate parameters of the traditional approach. This paper develops an efficient simulation approach to first passage failure analysis. It is based on simulation of segments of complex random processes with the Karhunen-Loeve expansion, use of these simulations to estimate the parameters of a Markov chain, and use of the Markov chain to estimate the probability of first passage failure. Some numerical examples are presented.

  4. Study of electrical breakdown and secondary pull-in failure modes for NEM relays

    NASA Astrophysics Data System (ADS)

    Ramezani, M.; Severi, S.; Tilmans, H. A. C.; De Meyer, K.

    2017-01-01

    In this work, two common failure modes of nano-electro-mechanical (NEM) relays: (1) electrical breakdown and (2) stiction due to secondary pull-in were analyzed. These effects are dominant when dimensions of the device are scaled to the sub-micrometer scale. Like MEMS devices, design adjustments, such as introduction of dimples, cannot provide a solution. The geometrical parameters and working environment drive directly the occurrence of these failure modes. The beam length is the key parameter in driving the electrical breakdown while the distance of the gate to the drain, the beam thickness, and the actuation gap set the limits for secondary pull-in voltage. The analysis shows that these failure modes could be mitigated and a physical parameters design space could be identified to achieve NEM devices for high speed operation.

  5. Structural integrity and potential failure modes of hanford high-level waste tanks

    SciTech Connect

    Han, F.C.

    1996-09-30

    Structural Integrity of the Hanford High-Level Waste Tanks were evaluated based on the existing Design and Analysis Documents. All tank structures were found adequate for the normal operating and seismic loads. Potential failure modes of the tanks were assessed by engineering interpretation and extrapolation of the existing engineering documents.

  6. SU-E-T-128: Applying Failure Modes and Effects Analysis to a Risk-Based Quality Management for Stereotactic Radiosurgery in Brazil

    SciTech Connect

    Teixeira, F; Almeida, C de; Huq, M

    2015-06-15

    Purpose: The goal of the present work was to evaluate the process maps for stereotactic radiosurgery (SRS) treatment at three radiotherapy centers in Brazil and apply the FMEA technique to evaluate similarities and differences, if any, of the hazards and risks associated with these processes. Methods: A team, consisting of professionals from different disciplines and involved in the SRS treatment, was formed at each center. Each team was responsible for the development of the process map, and performance of FMEA and FTA. A facilitator knowledgeable in these techniques led the work at each center. The TG100 recommended scales were used for the evaluation of hazard and severity for each step for the major process “treatment planning”. Results: Hazard index given by the Risk Priority Number (RPN) is found to range from 4–270 for various processes and the severity (S) index is found to range from 1–10. The RPN values > 100 and severity value ≥ 7 were chosen to flag safety improvement interventions. Number of steps with RPN ≥100 were found to be 6, 59 and 45 for the three centers. The corresponding values for S ≥ 7 are 24, 21 and 25 respectively. The range of RPN and S values for each center belong to different process steps and failure modes. Conclusion: These results show that interventions to improve safety is different for each center and it is associated with the skill level of the professional team as well as the technology used to provide radiosurgery treatment. The present study will very likely be a model for implementation of risk-based prospective quality management program for SRS treatment in Brazil where currently there are 28 radiotherapy centers performing SRS. A complete FMEA for SRS for these three radiotherapy centers is currently under development.

  7. MEMS Reliability: Infrastructure, Test Structures, Experiments, and Failure Modes

    SciTech Connect

    TANNER,DANELLE M.; SMITH,NORMAN F.; IRWIN,LLOYD W.; EATON,WILLIAM P.; HELGESEN,KAREN SUE; CLEMENT,J. JOSEPH; MILLER,WILLIAM M.; MILLER,SAMUEL L.; DUGGER,MICHAEL T.; WALRAVEN,JEREMY A.; PETERSON,KENNETH A.

    2000-01-01

    The burgeoning new technology of Micro-Electro-Mechanical Systems (MEMS) shows great promise in the weapons arena. We can now conceive of micro-gyros, micro-surety systems, and micro-navigators that are extremely small and inexpensive. Do we want to use this new technology in critical applications such as nuclear weapons? This question drove us to understand the reliability and failure mechanisms of silicon surface-micromachined MEMS. Development of a testing infrastructure was a crucial step to perform reliability experiments on MEMS devices and will be reported here. In addition, reliability test structures have been designed and characterized. Many experiments were performed to investigate failure modes and specifically those in different environments (humidity, temperature, shock, vibration, and storage). A predictive reliability model for wear of rubbing surfaces in microengines was developed. The root causes of failure for operating and non-operating MEMS are discussed. The major failure mechanism for operating MEMS was wear of the polysilicon rubbing surfaces. Reliability design rules for future MEMS devices are established.

  8. Aligning Demand for Spare Parts with their Underlying Failure Mode.

    DTIC Science & Technology

    1995-09-01

    5095 11 3 55.6 44 3091.36 1936 2446.4 5096 11 0 328.5 91 107912.3 8281 29893.5 5097 11 0 514 129 264196 16641 66306 5098 11 2 151.6 128 22982.56...Special I »X\\! 0 h\\ 1 < ,i ^ 3 ALIGNING DEMAND FOR SPARE PARTS WITH THEIR UNDERLYING FAILURE MODES THESIS Steven D. Kephart, B.S. Captain...of Tables viii List of Acronyms ix Abstract x I. Introduction 1-1 Background 1-2 Indentured Component Structure 1- 3 Consumables and Reparables

  9. Maximum likelihood estimation for life distributions with competing failure modes

    NASA Technical Reports Server (NTRS)

    Sidik, S. M.

    1979-01-01

    Systems which are placed on test at time zero, function for a period and die at some random time were studied. Failure may be due to one of several causes or modes. The parameters of the life distribution may depend upon the levels of various stress variables the item is subject to. Maximum likelihood estimation methods are discussed. Specific methods are reported for the smallest extreme-value distributions of life. Monte-Carlo results indicate the methods to be promising. Under appropriate conditions, the location parameters are nearly unbiased, the scale parameter is slight biased, and the asymptotic covariances are rapidly approached.

  10. Damage mechanisms and failure modes of cortical bone under components of physiological loading.

    PubMed

    George, W T; Vashishth, D

    2005-09-01

    Fatigue damage development in cortical bone was investigated in vitro under different mechanical components of physiological loading including tension, compression, and torsion. During each test, stress and strain data were collected continuously to monitor and statistically determine the occurrence of the primary, secondary, and tertiary stages associated with fatigue and/or creep failure of bone. The resultant microdamage and failure modes were identified by histological and fractographic analysis, respectively. The tensile group demonstrated Mode I cracking and the three classic stages of fatigue and creep suggesting a low crack initiation threshold, steady crack propagation and final failure by coalescence of microcracks. In contrast, the compressive group displayed Mode II cracking and a two-stage fatigue behavior with limited creep suggesting a high crack initiation threshold followed by a sudden fracture. The torsion group also displayed a two-stage fatigue profile but demonstrated extensive damage from mixed mode (Modes II and III) microcracking and predominant time-dependent damage. Thus, fatigue behavior of bone was found to be uniquely related to the individual mechanical components of physiological loading and the latter determined the specific damage mechanisms associated with fatigue fracture.

  11. Integrated Circuit Failure Analysis Hypertext Help System

    SciTech Connect

    Henderson, Christopher L.; Barton, Daniel L.; Campbell, Ann N.; Cole, Edward I; Mikawa, Russell E.; Peterson, Kenneth A.; Rife, James L.; Soden, Jerry M.

    1995-02-23

    This software assists a failure analyst performing failure analysis on integrated circuits. The software can also be used to train inexperienced failure analysts. The software also provides a method for storing information and making it easily available to experienced failure analysts.

  12. Failure analysis: Status and future trends

    SciTech Connect

    Anderson, R.E.; Soden, J.M.; Henderson, C.L.

    1995-02-01

    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.

  13. ATM CMG bearing failure analysis

    NASA Technical Reports Server (NTRS)

    1975-01-01

    The cause or causes for the failure of ATM CMG S/N 5 (Skylab 1) and the anomalies associated with ATM CMG S/N 6 (Skylab 2) were investigated. Skylab telemetry data were reviewed and presented in the form of parameter distributions. The theory that the problems were caused by marginal bearing lubrication was studied along with the effects of orbital conditions on lubricants. Bearing tests were performed to investigate the effect of lubricant or lack of lubricant in the ATM CMG bearings and the dispersion and migration of the lubricant. The vacuum and weightless conditions of space were simulated in the bearing tests. Analysis of the results of the tests conducted points to inadequate lubrication as the predominant factor causing the failure of ATM CMG S/N 5 (Skylab 1) and the anomalies associated with ATM CMG S/N 6 (Skylab 2).

  14. Failure of the ERBE scanner instrument aboard NOAA 10 spacecraft and results of failure analysis

    NASA Technical Reports Server (NTRS)

    Miller, J. B.; Weaver, W. L.; Kopia, L. P.; Howerton, C. E.; Payton, M. G.; Harris, C. J.

    1990-01-01

    The Earth Radiation Budget Experiment (ERBE) scanner instrument on the NOAA 10 spacecraft malfunctioned on May 22, 1989, after more than 4 years of in-flight operation. After the failure, all instrument operational mode commands were tested and the resulting data analyzed. Details of the tests and analysis of output data are discussed therein. The radiometric and housekeeping data appear to be valid. However, the instrument will not correctly execute operational scan mode commands or the preprogrammed calibration sequences. The data indicate the problem is the result of a failure in the internal address decoding circuity in one of the ROM (read only memory) chips of the instrument computer.

  15. Failure Analysis and Mechanisms of Failure of Fibrous Composite Structures

    NASA Technical Reports Server (NTRS)

    Noor, A. K. (Compiler); Shuart, M. J. (Compiler); Starnes, J. H., Jr. (Compiler); Williams, J. G. (Compiler)

    1983-01-01

    The state of the art of failure analysis and current design practices, especially as applied to the use of fibrous composite materials in aircraft structures is discussed. Deficiencies in these technologies are identified, as are directions for future research.

  16. Graphical Displays Assist In Analysis Of Failures

    NASA Technical Reports Server (NTRS)

    Pack, Ginger; Wadsworth, David; Razavipour, Reza

    1995-01-01

    Failure Environment Analysis Tool (FEAT) computer program enables people to see and better understand effects of failures in system. Uses digraph models to determine what will happen to system if set of failure events occurs and to identify possible causes of selected set of failures. Digraphs or engineering schematics used. Also used in operations to help identify causes of failures after they occur. Written in C language.

  17. Reliability, failure modes, and degradation mechanisms in high power single- and multi-mode InGaAs-AlGaAs strained quantum well lasers

    NASA Astrophysics Data System (ADS)

    Sin, Yongkun; Presser, Nathan; Lingley, Zachary; Brodie, Miles; Foran, Brendan; Moss, Steven C.

    2016-03-01

    High power single-mode (SM) and multi-mode (MM) InGaAs-AlGaAs strained quantum well (QW) lasers are critical components for both telecommunications and potential space satellite communications systems. However, little has been reported on failure modes of state-of-the-art SM InGaAs-AlGaAs strained QW lasers although it is crucial to understand failure modes and underlying degradation mechanisms in developing these lasers that meet lifetime requirements for space satellite systems, where extremely high reliability of these lasers is required. Our present study addresses the aforementioned issues by performing long-term life tests under different test conditions followed by failure mode analysis (FMA) and physics of failure investigation. We performed long-term accelerated life-tests on state-of-the-art SM and MM InGaAs-AlGaAs strained QW lasers under ACC (automatic current control) mode. Our life-tests have accumulated over 25,000 test hours for SM lasers and over 35,000 test hours for MM lasers. FMA was performed on failed SM lasers using electron beam induced current (EBIC). This technique allowed us to identify failure types by observing dark line defects. All the SM failures we studied showed catastrophic and sudden degradation and all of these failures were bulk failures. Our group previously reported that bulk failure or COBD (catastrophic optical bulk damage) is the dominant failure mode of MM InGaAs-AlGaAs strained QW lasers. To the best of our knowledge, this is the first report demonstrating that the dominant failure mode of both SM and MM InGaAs-AlGaAs strained QW lasers is the bulk failure. Since degradation mechanisms responsible for COBD are still not well understood, we also employed other techniques including focused ion beam (FIB) processing and high-resolution TEM to further study dark line defects and dislocations in post-aged SM and MM lasers. Our long-term life test results and FMA results are reported.

  18. Common-Cause Failure Analysis in Event Assessment

    SciTech Connect

    Dana L. Kelly; Dale M. Rasmuson

    2008-09-01

    This paper describes the approach taken by the U. S. Nuclear Regulatory Commission to the treatment of common-cause failure in probabilistic risk assessment of operational events. The approach is based upon the Basic Parameter Model for common-cause failure, and examples are illustrated using the alpha-factor parameterization, the approach adopted by the NRC in their Standardized Plant Analysis Risk (SPAR) models. The cases of a failed component (with and without shared common-cause failure potential) and a component being unavailable due to preventive maintenance or testing are addressed. The treatment of two related failure modes (e.g., failure to start and failure to run) is a new feature of this paper. These methods are being applied by the NRC in assessing the risk significance of operational events for the Significance Determination Process (SDP) and the Accident Sequence Precursor (ASP) program.

  19. Manufacturing quality from electronic failure analysis results

    NASA Astrophysics Data System (ADS)

    Dobbs, B.

    The Electronic Failure Analysis Group of the AFWAL/Materials Laboratory Systems Support Division has investigated numerous electronic device failures that resulted from manufacturing process defects. The electronic failure analysis program that verifies the device failure, locates the failure site, establishes the cause of failure and recommends corrective actions is discussed in relation to improving the quality of electronic devices; performing electronic failure analysis is a high-payoff activity. Corrective actions usually involve very small costs to the manufacturer and provide the user with a large return on investment. Brief case histories are presented in regard to packaging, die attachment, solder flux removal, package moisture content, IC metallization processes, potted modules, and handling procedures affecting device cleanliness. Situations are identified where better quality control could eliminate many device defects that lead to premature part failure.

  20. A novel approach for evaluating the risk of health care failure modes.

    PubMed

    Chang, Dong Shang; Chung, Jenq Hann; Sun, Kuo Lung; Yang, Fu Chiang

    2012-12-01

    Failure mode and effects analysis (FMEA) can be employed to reduce medical errors by identifying the risk ranking of the health care failure modes and taking priority action for safety improvement. The purpose of this paper is to propose a novel approach of data analysis. The approach is to integrate FMEA and a mathematical tool-Data envelopment analysis (DEA) with "slack-based measure" (SBM), in the field of data analysis. The risk indexes (severity, occurrence, and detection) of FMEA are viewed as multiple inputs of DEA. The practicality and usefulness of the proposed approach is illustrated by one case of health care. Being a systematic approach for improving the service quality of health care, the approach can offer quantitative corrective information of risk indexes that thereafter reduce failure possibility. For safety improvement, these new targets of the risk indexes could be used for management by objectives. But FMEA cannot provide quantitative corrective information of risk indexes. The novel approach can surely overcome this chief shortcoming of FMEA. After combining DEA SBM model with FMEA, the two goals-increase of patient safety, medical cost reduction-can be together achieved.

  1. Failure Analysis of Sapphire Refractive Secondary Concentrators

    NASA Technical Reports Server (NTRS)

    Salem, Jonathan A.; Quinn, George D.

    2009-01-01

    Failure analysis was performed on two sapphire, refractive secondary concentrators (RSC) that failed during elevated temperature testing. Both concentrators failed from machining/handling damage on the lens face. The first concentrator, which failed during testing to 1300 C, exhibited a large r-plane twin extending from the lens through much of the cone. The second concentrator, which was an attempt to reduce temperature gradients and failed during testing to 649 C, exhibited a few small twins on the lens face. The twins were not located at the origin, but represent another mode of failure that needs to be considered in the design of sapphire components. In order to estimate the fracture stress from fractographic evidence, branching constants were measured on sapphire strength specimens. The fractographic analysis indicated radial tensile stresses of 44 to 65 MPa on the lens faces near the origins. Finite element analysis indicated similar stresses for the first RSC, but lower stresses for the second RSC. Better machining and handling might have prevented the fractures, however, temperature gradients and resultant thermal stresses need to be reduced to prevent twinning.

  2. Distinct failure modes in bio-inspired 3D-printed staggered composites under non-aligned loadings

    NASA Astrophysics Data System (ADS)

    Slesarenko, Viacheslav; Kazarinov, Nikita; Rudykh, Stephan

    2017-03-01

    The superior mechanical properties of biological materials originate in their complex hierarchical microstructures, combining stiff and soft constituents at different length scales. In this work, we employ a three-dimensional multi-materials printing to fabricate the bio-inspired staggered composites, and study their mechanical properties and failure mechanisms. We observe that bio-inspired staggered composites with inclined stiff tablets are able to undergo two different failure modes, depending on the inclination angle. We find that such artificial structure demonstrates high toughness only under loading applied at relatively small angle to the tablets stacking direction, while for higher angles the composites fail catastrophically. This aspect of the failure behavior was captured experimentally as well as by means of the finite element analysis. We show that even a relatively simple failure model with a strain energy limiter, can be utilized to qualitatively distinguish these two different modes of failure, occurring in the artificial bio-inspired composites.

  3. Failure Analysis at the Kennedy Space Center

    NASA Technical Reports Server (NTRS)

    Salazar, Victoria L.; Wright, Clara

    2010-01-01

    History has shown that failures occur in every engineering endeavor, and what we learn from those failures contributes to the knowledge base to safely complete future missions. The necessity of failure analysis is at its apex at the end of one aged program (i.e. Shuttle) and at the beginning of a new and untested program (i.e. Constellation). The information that we gain through failure analysis corrects the deficiencies in the current vehicle to make the next generation of vehicles more efficient and safe. The Failure Analysis and Materials Evaluation section in the Materials Science Division at the Kennedy Space Center performs metallurgical, mechanical, electrical, and non-metallic failure analysis and accident investigations on both flight hardware and ground support equipment (GSE) for the Shuttle, International Space Station, Constellation, and Launch Services Programs. This presentation will explore a variety of failure case studies at KSC and the lessons learned that can be applied in future programs.

  4. Fabric Controls on the Failure Mode of Strongly Deformed Metamorphic Rocks with Multiple Anisotropies

    NASA Astrophysics Data System (ADS)

    Agliardi, F.; Zanchetta, S.; Crosta, G. B.; Barberini, V.; Fusi, N.; De Ponti, E.

    2012-12-01

    resolutions (MicroCT: 40-60 μm; medical CT: 625 μm) and micro-structural analysis of thin sections. Investigation results suggest that the failure of strongly deformed metamorphic rocks is controlled by the occurrence of multiple anisotropies related to micro-fabric, not always characterised by clear meso-scale expression, including crenulation folding, shape preferred orientation, intracrystalline deformation microstructure. Different failure modes dominate depending on the geometrical arrangement of both foliation and fold axial surfaces, in turn affecting the values of rock strength and deformability. The results of this study point to the need of accounting for the effects of multiple, geometrically complex anisotropies in setting up realistic models of rock fracturing at different scale and for different geological and engineering applications.

  5. European Extremely Large Telescope (E-ELT) availability stochastic model: integrating failure mode and effect analysis (FMEA), influence diagram, and Bayesian network together

    NASA Astrophysics Data System (ADS)

    Verzichelli, Gianluca

    2016-08-01

    An Availability Stochastic Model for the E-ELT has been developed in GeNIE. The latter is a Graphical User Interface (GUI) for the Structural Modeling, Inference, and Learning Engine (SMILE), originally distributed by the Decision Systems Laboratory from the University of Pittsburgh, and now being a product of Bayes Fusion, LLC. The E-ELT will be the largest optical/near-infrared telescope in the world. Its design comprises an Alt-Azimuth mount reflecting telescope with a 39-metre-diameter segmented primary mirror, a 4-metre-diameter secondary mirror, a 3.75-metre-diameter tertiary mirror, adaptive optics and multiple instruments. This paper highlights how a Model has been developed for an earlier on assessment of the Telescope Avail- ability. It also describes the modular structure and the underlying assumptions that have been adopted for developing the model and demonstrates the integration of FMEA, Influence Diagram and Bayesian Network elements. These have been considered for a better characterization of the Model inputs and outputs and for taking into account Degraded-based Reliability (DBR). Lastly, it provides an overview of how the information and knowledge captured in the model may be used for an earlier on definition of the Failure, Detection, Isolation and Recovery (FDIR) Control Strategy and the Telescope Minimum Master Equipment List (T-MMEL).

  6. Wind Turbine Failures - Tackling current Problems in Failure Data Analysis

    NASA Astrophysics Data System (ADS)

    Reder, M. D.; Gonzalez, E.; Melero, J. J.

    2016-09-01

    The wind industry has been growing significantly over the past decades, resulting in a remarkable increase in installed wind power capacity. Turbine technologies are rapidly evolving in terms of complexity and size, and there is an urgent need for cost effective operation and maintenance (O&M) strategies. Especially unplanned downtime represents one of the main cost drivers of a modern wind farm. Here, reliability and failure prediction models can enable operators to apply preventive O&M strategies rather than corrective actions. In order to develop these models, the failure rates and downtimes of wind turbine (WT) components have to be understood profoundly. This paper is focused on tackling three of the main issues related to WT failure analyses. These are, the non-uniform data treatment, the scarcity of available failure analyses, and the lack of investigation on alternative data sources. For this, a modernised form of an existing WT taxonomy is introduced. Additionally, an extensive analysis of historical failure and downtime data of more than 4300 turbines is presented. Finally, the possibilities to encounter the lack of available failure data by complementing historical databases with Supervisory Control and Data Acquisition (SCADA) alarms are evaluated.

  7. Failure Analysis at the Kennedy Space Center

    NASA Technical Reports Server (NTRS)

    Salazar, Victoria L.; Wright, M. Clara

    2010-01-01

    History has shown that failures occur in every engineering endeavor, and what we learn from those failures contributes to the knowledge base to safely complete future missions. The necessity of failure analysis is at its apex at the end of one aged program and at the beginning of a new and untested program. The information that we gain through failure analysis corrects the deficiencies in the current vehicle to make the next generation of vehicles more efficient and safe. The Failure Analysis and Materials Evaluation Branch in the Materials Science Division at the Kennedy Space Center performs metallurgical, mechanical, electrical, and non-metallic materials failure analyses and accident investigations on both flight hardware and ground support equipment for the Space Shuttle, International Space Station, Constellation, and Launch Services Programs. This paper will explore a variety of failure case studies at the Kennedy Space Center and the lessons learned that can be applied in future programs.

  8. Future technology challenges for failure analysis

    SciTech Connect

    Anderson, R.E.; Soden, J.M.; Henderson, C.L.

    1995-08-01

    Failure analysis is a critical element in the integrated circuit manufacturing industry. This paper explores the challenges for IC failure analysis in the environment of present and future silicon IC technology trends, using the 1994 National Technology Roadmap for Semiconductors as a technology guide. Advanced failure analysis techniques that meet the challenges of state-of-the-art IC technology are described and their applications are discussed. New paradigms will be required for failure analysis to keep pace with future advancements in IC technology.

  9. Failure analysis of PB-1 (EBTS Be/Cu mockup)

    SciTech Connect

    Odegard, B.C. Jr.; Cadden, C.H.

    1996-11-01

    Failure analysis was done on PB-1 (series of Be tiles joined to Cu alloy) following a tile failure during a high heat flux experiment in EBTS (electron beam test system). This heat flux load simulated ambient conditions inside ITER; the Be tiles were bonded to the Cu alloy using low-temperature diffusion bonding, which is being considered for fabricating plasma facing components in ITER. Results showed differences between the EBTS failure and a failure during a room temperature tensile test. The latter occurred at the Cu-Be interface in an intermetallic phase formed by reaction of the two metals at the bonding temperature. Fracture strengths measured by these tests were over 300 MPa. The high heat flux specimens failed at the Cu-Cu diffusion bond. Fracture morphology in both cases was a mixed mode of dimple rupture and transgranular cleavage. Several explanations for this difference in failure mechanism are suggested.

  10. Predicting Ductility and Failure Modes of TRIP Steels under Different Loading Conditions

    SciTech Connect

    Choi, Kyoo Sil; Liu, Wenning N.; Sun, Xin; Khaleel, Mohammad A.

    2010-06-12

    We study the ultimate ductility and failure modes of a TRIP (TRansformation-Induced Plasticity) 800 steel under different loading conditions with an advanced micromechanics-based finite element analysis. The representative volume element (RVE) for the TRIP800 under examination is developed based on an actual microstructure obtained from scanning electron microscopy (SEM). The evolution of retained austenite during deformation process and the mechanical properties of the constituent phases of the TRIP800 steel are obtained from the synchrotron-based in-situ high-energy X-ray diffraction (HEXRD) experiments and a self-consistent (SC) model. The ductile failure of the TRIP800 under different loading conditions is predicted in the form of plastic strain localization without any prescribed failure criteria for the individual phases. Comparisons of the computational results with experimental measurements suggest that the microstructure-based finite element analysis can well capture the overall macroscopic behavior of the TRIP800 steel under different loading conditions. The methodology described in this study may be extended for studying the ultimate ductile failure mechanisms of TRIP steels as well as the effects of the various processing parameters on the macroscopic behaviors of TRIP steels.

  11. SNS STRIPPER FOIL FAILURE MODES AND THEIR CURES

    SciTech Connect

    Galambos, John D; Luck, Chris; Plum, Michael A; Shaw, Robert W; Ladd, Peter; Raparia, Deepak; Macek, Robert James; Kim, Sang-Ho; Peters, Charles C; Polsky, Yarom

    2010-01-01

    The diamond stripper foils in use at the Spallation Neutron Source worked successfully with no failures until May 3, 2009, when we started experiencing a rash of foil system failures after increasing the beam power to ~840 kW. The main contributors to the failures are thought to be 1) convoy electrons, stripped from the incoming H beam, that strike the foil bracket and may also reflect back from the electron catcher, and 2) vacuum breakdown from the charge developed on the foil by secondary electron emission. In this paper we will detail these and other failure mechanisms, and describe the improvements we have made to mitigate them.

  12. The assessment of low probability containment failure modes using dynamic PRA

    NASA Astrophysics Data System (ADS)

    Brunett, Acacia Joann

    Although low probability containment failure modes in nuclear power plants may lead to large releases of radioactive material, these modes are typically crudely modeled in system level codes and have large associated uncertainties. Conventional risk assessment techniques (i.e. the fault-tree/event-tree methodology) are capable of accounting for these failure modes to some degree, however, they require the analyst to pre-specify the ordering of events, which can vary within the range of uncertainty of the phenomena. More recently, dynamic probabilistic risk assessment (DPRA) techniques have been developed which remove the dependency on the analyst. Through DPRA, it is now possible to perform a mechanistic and consistent analysis of low probability phenomena, with the timing of the possible events determined by the computational model simulating the reactor behavior. The purpose of this work is to utilize DPRA tools to assess low probability containment failure modes and the driving mechanisms. Particular focus is given to the risk-dominant containment failure modes considered in NUREG-1150, which has long been the standard for PRA techniques. More specifically, this work focuses on the low probability phenomena occurring during a station blackout (SBO) with late power recovery in the Zion Nuclear Power Plant, a Westinghouse pressurized water reactor (PWR). Subsequent to the major risk study performed in NUREG-1150, significant experimentation and modeling regarding the mechanisms driving containment failure modes have been performed. In light of this improved understanding, NUREG-1150 containment failure modes are reviewed in this work using the current state of knowledge. For some unresolved mechanisms, such as containment loading from high pressure melt ejection and combustion events, additional analyses are performed using the accident simulation tool MELCOR to explore the bounding containment loads for realistic scenarios. A dynamic treatment in the

  13. Space Shuttle Stiffener Ring Foam Failure Analysis, a Non-Conventional Approach

    NASA Technical Reports Server (NTRS)

    Howard, Philip M.

    2015-01-01

    The Space Shuttle Program made use of the excellent properties of rigid polyurethane foam for cryogenic tank insulation and as structural protection on the solid rocket boosters. When foam applications de-bond, classical methods of failure analysis did not provide root cause of the failure of the foam. Realizing that foam is the ideal media to document and preserve its own mode of failure, thin sectioning was seen as a logical approach for foam failure analysis to observe the three dimensional morphology of the foam cells. The cell foam morphology provided a much greater understanding of the failure modes than previously achieved.

  14. Lunar Module Electrical Power System Design Considerations and Failure Modes

    NASA Technical Reports Server (NTRS)

    Interbartolo, Michael

    2009-01-01

    This slide presentation reviews the design and redesign considerations of the Apollo lunar module electrical power system. Included in the work are graphics showing the lunar module power system. It describes the in-flight failures, and the lessons learned from these failures.

  15. The Failure Analysis in Traction Power System

    NASA Astrophysics Data System (ADS)

    Kim, Hyungchul; Heo, Guk-bum; Lee, Hyungwoo; Kim, Dong Jin; Kim, Jin O.

    2008-10-01

    This paper presents a failure analysis of traction power systems. The electric railway consists of traction power systems, various vehicles, operating equipment, track, overhead line and electric equipment. It is a fundamental function of traction power systems that they supply customers with acceptable reliability and high quality power. Perhaps the most commonly used reliability assessment for railway systems has been the failure analysis of the traction signal system. The reliability assessment of traction power systems has also been an indispensable issue for reliability assessment. This paper deals with the classification of railway accidents caused by electrification problems, the estimation of failure rate in power equipments and failure analysis using fault trees. In study cases, the fault tree method for failure analysis is applied to railway substations in South Korea.

  16. Failure Mode, Effects, and Criticality Analysis (FMECA)

    DTIC Science & Technology

    1993-04-01

    5 2.2 M IL-STD -1629 Tasks, ................................................................................................ 7 3.0 FMEA ...93 10.0 ADDITIONAL SOURCES/METHODS ................................................................ 95 10.1 Process FMEA ...CRTA-FMECA vii LIST OF FIGURES Page Figure 1: FMEA Worksheet (Task 101) .................................................................... 10 Figure 2

  17. Global Failure Modes in Composite Structures for High Altitudes

    NASA Technical Reports Server (NTRS)

    Knauss, W. G.

    2004-01-01

    This report summarizes the accomplishments under the referenced grant. The work described was started under the guidance and supervision of the late Dr. James Stames as the technical contact. It was aimed at investigating the development of analysis tools to deal with the problem of rupture in reinforced structural skin of future composites-based aircraft. It was of particular interest to assess methods by which failure features reminiscent of cracks in metallic structures would develop and propagate in fiber reinforced structures in interaction with the reinforcing frame. To eventually achieve that goal it was necessary to first understand the stress or strain distribution at the front of such features so that interactions between such features and reinforcing agents could be assessed computationally. Thus the major emphasis here was on the assessment of damage front and methods on how to assess or characterize it. During the conduct of this research program Dr. Stames changed to a different NASA- internal assignment, which divorced him of the direct supervision of this grant. A student who was approximately % into the completion of his Ph.D. research needed to finish this work, and NASA funds were made available under Dr. Damodar Ambur, the successor Branch Manager for Dr. James Starnes, for the completion of this work. The current grant was the thus a new and fmal support increment for completion of the started research. Final reports for previous funding have been completed and submitted. Because of the interconnection of this last phase of the investigation with previous work it is deemed useful to make the Ph.D. thesis by Luis Gonzales the body of this report.

  18. Life Prediction and Classification of Failure Modes in Solid State Luminaires Using Bayesian Probabilistic Models

    SciTech Connect

    Lall, Pradeep; Wei, Junchao; Sakalaukus, Peter

    2014-05-27

    A new method has been developed for assessment of the onset of degradation in solid state luminaires to classify failure mechanisms by using metrics beyond lumen degradation that are currently used for identification of failure. Luminous Flux output, Correlated Color Temperature Data on Philips LED Lamps has been gathered under 85°C/85%RH till lamp failure. The acquired data has been used in conjunction with Bayesian Probabilistic Models to identify luminaires with onset of degradation much prior to failure through identification of decision boundaries between lamps with accrued damage and lamps beyond the failure threshold in the feature space. In addition luminaires with different failure modes have been classified separately from healthy pristine luminaires. It is expected that, the new test technique will allow the development of failure distributions without testing till L70 life for the manifestation of failure.

  19. Failure modes of a concrete nuclear-containment building subjected to hydrogen detonation

    SciTech Connect

    Fugelso, L.E.; Butler, T.A.

    1983-01-01

    Calculated response for the Indian Point reactor containment building to static internal pressure and one case of a dynamic pressure representing hydrogen combustion and detonation are presented. Comparison of the potential failure modes is made. 9 figures.

  20. Effects of Fusion Zone Size on Failure Modes and Performance of Advanced High Strength Steel Spot Welds

    SciTech Connect

    Sun, Xin; Stephens, Elizabeth V.; Khaleel, Mohammad A.

    2006-04-28

    This paper examines the effects of fusion zone size on failure modes, static strength and energy absorption of resistance spot welds (RSW) of advanced high strength steels (AHSS). DP800 and TRIP800 spot welds are considered. The main failure modes for spot welds are nugget pullout and interfacial fracture. Partial interfacial fracture is also observed. The critical fusion zone sizes to ensure nugget pull-out failure mode are developed for both DP800 and TRIP800 using the limit load based analytical model and the micro-hardness measurements of the weld cross sections. Static weld strength tests using cross tension samples were performed on the joint populations with controlled fusion zone sizes. The resulted peak load and energy absorption levels associated with each failure mode were studied using statistical data analysis tools. The results in this study show that the conventional weld size of 4 t can not produce nugget pullout mode for both the DP800 and TRIP800 materials. The results also suggest that performance based spot weld acceptance criteria should be developed for different AHSS spot welds.

  1. Progressive Failure Analysis of Composite Stiffened Panels

    NASA Technical Reports Server (NTRS)

    Bednarcyk, Brett A.; Yarrington, Phillip W.; Collier, Craig S.; Arnold, Steven M.

    2006-01-01

    A new progressive failure analysis capability for stiffened composite panels has been developed based on the combination of the HyperSizer stiffened panel design/analysis/optimization software with the Micromechanics Analysis Code with Generalized Method of Cells (MAC/GMC). MAC/GMC discretizes a composite material s microstructure into a number of subvolumes and solves for the stress and strain state in each while providing the homogenized composite properties as well. As a result, local failure criteria may be employed to predict local subvolume failure and the effects of these local failures on the overall composite response. When combined with HyperSizer, MAC/GMC is employed to represent the ply level composite material response within the laminates that constitute a stiffened panel. The effects of local subvolume failures can then be tracked as loading on the stiffened panel progresses. Sample progressive failure results are presented at both the composite laminate and the composite stiffened panel levels. Deformation and failure model predictions are compared with experimental data from the World Wide Failure Exercise for AS4/3501-6 graphite/epoxy laminates.

  2. Failure modes and durability of Kevlar/epoxy composites

    SciTech Connect

    Morgan, R.J.; Mones, E.T.; Steele, W.J.; Deutscher, S.B.

    1980-06-04

    The fracture topographies of Kevlar 49/epoxy composite strands and multilayer composites in the form of pressure vessels are discussed in terms of the microscopic deformation and failure processes of the composites. The effect of resin ductility and fiber-matrix interfacial bond strength on mechanisms of fiber damage are considered. The failure of the Kevlar 49 fibers by a splitting process and the parameters, such as fiber fibrillation and macromolecular chain scission, that control such a process, are discussed in relation to fiber and composite performance.

  3. Failure modes and durability of kevlar/epoxy composites

    SciTech Connect

    Morgan, R.J.; Mones, E.T.; Steele, W.J.; Deutscher, S.B.

    1981-04-01

    The fracture topographies of Kevlar 49/epoxy composite strands and multilayer composites in the form of pressure vessels are discussed in terms of the microscopic deformation and failure processes of the composites. The effect of resin ductility and fiber-matrix interfacial bond strength on mechanisms of fiber damage are considered. The failure of the Kevlar 49 fibers by a splitting process and the parameters, such as fiber fibrillation and macromolecular chain scission, that control such a process are discussed in relation to fiber and composite performance.

  4. Ambulatory heart rate range predicts mode-specific mortality and hospitalisation in chronic heart failure

    PubMed Central

    Cubbon, Richard M; Ruff, Naomi; Groves, David; Eleuteri, Antonio; Denby, Christine; Kearney, Lorraine; Ali, Noman; Walker, Andrew M N; Jamil, Haqeel; Gierula, John; Gale, Chris P; Batin, Phillip D; Nolan, James; Shah, Ajay M; Fox, Keith A A; Sapsford, Robert J; Witte, Klaus K; Kearney, Mark T

    2016-01-01

    Objective We aimed to define the prognostic value of the heart rate range during a 24 h period in patients with chronic heart failure (CHF). Methods Prospective observational cohort study of 791 patients with CHF associated with left ventricular systolic dysfunction. Mode-specific mortality and hospitalisation were linked with ambulatory heart rate range (AHRR; calculated as maximum minus minimum heart rate using 24 h Holter monitor data, including paced and non-sinus complexes) in univariate and multivariate analyses. Findings were then corroborated in a validation cohort of 408 patients with CHF with preserved or reduced left ventricular ejection fraction. Results After a mean 4.1 years of follow-up, increasing AHRR was associated with reduced risk of all-cause, sudden, non-cardiovascular and progressive heart failure death in univariate analyses. After accounting for characteristics that differed between groups above and below median AHRR using multivariate analysis, AHRR remained strongly associated with all-cause mortality (HR 0.991/bpm increase in AHRR (95% CI 0.999 to 0.982); p=0.046). AHRR was not associated with the risk of any non-elective hospitalisation, but was associated with heart-failure-related hospitalisation. AHRR was modestly associated with the SD of normal-to-normal beats (R2=0.2; p<0.001) and with peak exercise-test heart rate (R2=0.33; p<0.001). Analysis of the validation cohort revealed AHRR to be associated with all-cause and mode-specific death as described in the derivation cohort. Conclusions AHRR is a novel and readily available prognosticator in patients with CHF, which may reflect autonomic tone and exercise capacity. PMID:26674986

  5. An assessment of BWR (boiling water reactor) Mark III containment challenges, failure modes, and potential improvements in performance

    SciTech Connect

    Schroeder, J.A.; Pafford, D.J.; Kelly, D.L.; Jones, K.R.; Dallman, F.J. )

    1991-01-01

    This report describes risk-significant challenges posed to Mark III containment systems by severe accidents as identified for Grand Gulf. Design similarities and differences between the Mark III plants that are important to containment performance are summarized. The accident sequences responsible for the challenges and the postulated containment failure modes associated with each challenge are identified and described. Improvements are discussed that have the potential either to prevent or delay containment failure, or to mitigate the offsite consequences of a fission product release. For each of these potential improvements, a qualitative analysis is provided. A limited quantitative risk analysis is provided for selected potential improvements. 21 refs., 5 figs., 46 tabs.

  6. Effect of Different Groundwater Levels on Seismic Dynamic Response and Failure Mode of Sandy Slope.

    PubMed

    Huang, Shuai; Lv, Yuejun; Peng, Yanju; Zhang, Lifang; Xiu, Liwei

    2015-01-01

    Heavy seismic damage tends to occur in slopes when groundwater is present. The main objectives of this paper are to determine the dynamic response and failure mode of sandy slope subjected simultaneously to seismic forces and variable groundwater conditions. This paper applies the finite element method, which is a fast and efficient design tool in modern engineering analysis, to evaluate dynamic response of the slope subjected simultaneously to seismic forces and variable groundwater conditions. Shaking table test is conducted to analyze the failure mode and verify the accuracy of the finite element method results. The research results show that dynamic response values of the slope have different variation rules under near and far field earthquakes. And the damage location and pattern of the slope are different in varying groundwater conditions. The destruction starts at the top of the slope when the slope is in no groundwater, which shows that the slope appears obvious whipping effect under the earthquake. The destruction starts at the toe of the slope when the slope is in the high groundwater levels. Meanwhile, the top of the slope shows obvious seismic subsidence phenomenon after earthquake. Furthermore, the existence of the groundwater has a certain effect of damping.

  7. Effect of Different Groundwater Levels on Seismic Dynamic Response and Failure Mode of Sandy Slope

    PubMed Central

    Huang, Shuai; Lv, Yuejun; Peng, Yanju; Zhang, Lifang; Xiu, Liwei

    2015-01-01

    Heavy seismic damage tends to occur in slopes when groundwater is present. The main objectives of this paper are to determine the dynamic response and failure mode of sandy slope subjected simultaneously to seismic forces and variable groundwater conditions. This paper applies the finite element method, which is a fast and efficient design tool in modern engineering analysis, to evaluate dynamic response of the slope subjected simultaneously to seismic forces and variable groundwater conditions. Shaking table test is conducted to analyze the failure mode and verify the accuracy of the finite element method results. The research results show that dynamic response values of the slope have different variation rules under near and far field earthquakes. And the damage location and pattern of the slope are different in varying groundwater conditions. The destruction starts at the top of the slope when the slope is in no groundwater, which shows that the slope appears obvious whipping effect under the earthquake. The destruction starts at the toe of the slope when the slope is in the high groundwater levels. Meanwhile, the top of the slope shows obvious seismic subsidence phenomenon after earthquake. Furthermore, the existence of the groundwater has a certain effect of damping. PMID:26560103

  8. Survey of failure modes from 122 residential solar water heaters

    SciTech Connect

    Not Available

    1984-10-01

    This report describes the results of a survey on the operation of active solar heating and cooling systems and their components. Questionnaires were sent to homeowners and installers, covering 122 systems. Results were categorized according to problem severity, location, system type, length of system operation, and time of the year. Approximately 47% of the systems had at least one reliability problem over a two-year period. Flat-plate collector and storage systems were highly reliable. Improper operation of these components was attributed to installation problems. Drainback designs also had the greatest reliability; draindown systems were the least reliable, largely because of the failure of draindown valves. Differential controllers caused the largest number of failures that resulted in a repair cost in excess of $50 to the homeowner.

  9. Global Failure Modes in High Temperature Composite Structures

    NASA Technical Reports Server (NTRS)

    Knauss, W. G.

    1998-01-01

    Composite materials have been considered for many years as the major advance in the construction of energy efficient aerospace structures. Notable advances have been made in understanding the special design considerations that set composites apart from the usual "isotropic" engineering materials such as the metals. As a result, a number of significant engineering designs have been accomplished. However, one shortcoming of the currently favored composites is their relatively unforgiving behavior with respect to failure (brittleness) under seemingly mild impact conditions and large efforts are underway to rectify that situation, much along the lines of introducing thermoplastic matrix materials. Because of their relatively more pronounced (thermo) viscoelastic behavior these materials respond with "toughness" in fracture situations. From the point of view of applications requiring material strength, this property is highly desirable. This feature impacts several important and distinct engineering problems which have been' considered under this grant and cover the 1) effect of impact damage on structural (buckling) stability of composite panels, the 2) effect of time dependence on the progression of buckling instabilities, and the 3) evolution of damage and fracture at generic thickness discontinuities in structures. The latter topic has serious implications for structural stability problems (buckling failure in reinforced shell structures) as well as failure progression in stringer-reinforced shell structures. This grant has dealt with these issues. Polymer "toughness" is usually associated with uncrosslinked or thermo-plastic polymers. But, by comparison with their thermoset counterparts they tend to exhibit more pronounced time dependent material behavior; also, that time dependence can occur at lower temperatures which places restriction in the high temperature use of these "newer and tougher" materials that are not quite so serious with the thermoset matrix

  10. Launch Vehicle Failure Dynamics and Abort Triggering Analysis

    NASA Technical Reports Server (NTRS)

    Hanson, John M.; Hill, Ashely D.; Beard, Bernard B.

    2011-01-01

    Launch vehicle ascent is a time of high risk for an on-board crew. There are many types of failures that can kill the crew if the crew is still on-board when the failure becomes catastrophic. For some failure scenarios, there is plenty of time for the crew to be warned and to depart, whereas in some there is insufficient time for the crew to escape. There is a large fraction of possible failures for which time is of the essence and a successful abort is possible if the detection and action happens quickly enough. This paper focuses on abort determination based primarily on data already available from the GN&C system. This work is the result of failure analysis efforts performed during the Ares I launch vehicle development program. Derivation of attitude and attitude rate abort triggers to ensure that abort occurs as quickly as possible when needed, but that false positives are avoided, forms a major portion of the paper. Some of the potential failure modes requiring use of these triggers are described, along with analysis used to determine the success rate of getting the crew off prior to vehicle demise.

  11. Failure analysis of thick composite cylinders under external pressure

    NASA Technical Reports Server (NTRS)

    Caiazzo, A.; Rosen, B. W.

    1992-01-01

    Failure of thick section composites due to local compression strength and overall structural instability is treated. Effects of material nonlinearity, imperfect fiber architecture, and structural imperfections upon anticipated failure stresses are determined. Comparisons with experimental data for a series of test cylinders are described. Predicting the failure strength of composite structures requires consideration of stability and material strength modes of failure using linear and nonlinear analysis techniques. Material strength prediction requires the accurate definition of the local multiaxial stress state in the material. An elasticity solution for the linear static analysis of thick anisotropic cylinders and rings is used herein to predict the axisymmetric stress state in the cylinders. Asymmetric nonlinear behavior due to initial cylinder out of roundness and the effects of end closure structure are treated using finite element methods. It is assumed that local fiber or ply waviness is an important factor in the initiation of material failure. An analytical model for the prediction of compression failure of fiber composites, which includes the effects of fiber misalignments, matrix inelasticity, and multiaxial applied stresses is used for material strength calculations. Analytical results are compared to experimental data for a series of glass and carbon fiber reinforced epoxy cylinders subjected to external pressure. Recommendations for pretest characterization and other experimental issues are presented. Implications for material and structural design are discussed.

  12. Achieving Resiliency by Eliminating Common Mode Failures in the Smart Grid

    SciTech Connect

    Dagle, Jeffery E.

    2012-01-19

    Abstract—This panel presentation will provide perspectives of resiliency as it relates to smart grids. As smart grid technologies are deployed, the interconnected nature of these systems is becoming more prevalent and more complex, and while resilience is expected to be enhanced, the presence of common mode failures will thwart the ability of the smart grid to achieve full levels of resilience. Studying system behavior in the face of failures (e.g., cyber attacks) allows a characterization of the systems’ response to failure scenarios, loss of communications, and other changes in system environment (such as the need for emergent updates and rapid reconfiguration). The impact of such failures on the availability of the system can be assessed and mitigation strategies considered. This panel will consider measures to identify and eliminate common mode failure mechanisms that might be present in the deployment of smart grid systems.

  13. Failure modes of current total ankle replacement systems.

    PubMed

    Pappas, Michael J; Buechel, Frederick F

    2013-04-01

    Methodology for evaluation of total ankle replacements is described. Fusion and its problems are discussed as are those of total ankle joint replacement. Fusion is an imperfect solution because it reduces ankle functionality and has significant complications. Early fixed-bearing total ankles were long-term failures and abandoned. Currently available fixed-bearing ankles have proved inferior to fusion or are equivalent to earlier devices. Only mobile-bearing devices have been shown reasonably safe and effective. One such device, the STAR, has been approved by the Food and Drug Administration after a rigorous controlled clinical trial and is available for use in the United States.

  14. Failure mode and ageing of steel/epoxy joints

    NASA Astrophysics Data System (ADS)

    De'Nève, B.; Delamar, M.; Nguyen, T. T.; Shanahan, M. E. R.

    1998-09-01

    Torsional adhesive joints were made using a filled DGEBA based epoxy resin cured with dicyandiamide (DDA). Ageing, both of the joints and the bulk adhesive, was effected at 40, 55 and 70°C at ca. 98% relative humidity. Joint strength was monitored after various ageing periods. Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) were used to analyze the adhesive and joint fracture surfaces. It was found that the adhesive composition near the adherent (zinc-electrocoated and bare steel) was modified compared with the bulk material. Before ageing there appeared to be an enrichment in hardener (DDA) near the adherent/adhesive interface and apparently adhesive failures were indeed interfacial. During ageing, the formation of ester groups subsequently transformed into carboxylates was observed. After ageing for up to 11 000 h, joints using a zinc electrocoated steel adherent showed fracture near the interface brought about by the modification of the adhesive. For longer ageing periods, failure occurred in a corrosion layer mixed with adhesive. A slightly better performance observed with the zinc electrocoated adherents has been attributed to the migration of Zn or Zn species into the adhesive during ageing.

  15. Plastic and Failure Analysis of Composites

    NASA Technical Reports Server (NTRS)

    Bigelow, C. A.; Johnson, W. S.

    1985-01-01

    Three-dimensional finite-element computer program called PAFAC (Plastic and Failure Analysis of Composites) developed for elastic/plastic analysis of fiber-reinforced composite materials and structures. PAFAC written in FORTRAN IV for batch execution. Particularly suited for analyzing laminated metal-matrix composites.

  16. Temperature effect on the performance of a dissipative dielectric elastomer generator with failure modes

    NASA Astrophysics Data System (ADS)

    Chen, S. E.; Deng, L.; He, Z. C.; Li, Eric; Li, G. Y.

    2016-05-01

    Research on dielectric elastomer generators (DEGs) which can be utilized to convert mechanical energy to electrical energy has gained wide attention lately. However, very few works account for the operating temperature, viscoelasticity and current leakage in the analysis of DEGs simultaneously. In this study, under several compound four-stroke conversion cycles, the electromechanical performance and energy conversion of a dissipative DEG made of a very-high-bond (VHB) elastomer are investigated at different operating temperatures. The performance parameters such as energy density and conversion efficiency are calculated under different temperatures. Moreover, the common failure modes of the generator are considered: material rupture, loss of tension, electrical breakdown and electromechanical instability. The numerical results have distinctly shown that the operating temperature plays an important role in the performance of DEGs, which could possibly make a larger conversion efficiency for the DEG.

  17. Specific Energy as an Index to Identify the Critical Failure Mode Transition Depth in Rock Cutting

    NASA Astrophysics Data System (ADS)

    He, Xianqun; Xu, Chaoshui

    2016-04-01

    Rock cutting typically involves driving a rigid cutter across the rock surface at certain depth of cut and is used to remove rock material in various engineering applications. It has been established that there exist two distinct failure modes in rock cutting, i.e. ductile mode and brittle mode. The ductile mode takes precedence when the cut is shallow and the increase in the depth of cut leads to rock failure gradually shifted to brittle-dominant mode. The threshold depth or the critical transition depth, at which rock failure under cutting changes from the ductile to the brittle mode, is associated with not only the rock properties but also the cutting operational parameters and the understanding of this threshold is important to optimise the tool design and operational parameters. In this study, a new method termed the specific cutting energy transition model is proposed from an energy perspective which is demonstrated to be much more effective in identifying the critical transition depth compared with existing approaches. In the ductile failure cutting mode, the specific cutting energy is found to be independent of the depth of cut; but in the brittle failure cutting mode, the specific cutting energy is found to be dependent on the depth of cut following a power-law relationship. The critical transition depth is identified as the intersection point between these two relationships. Experimental tests on two types of rocks with different combinations of cutting velocity, depth of cut and back rake angle are conducted and the application of the proposed model on these cutting datasets has demonstrated that the model can provide a very effective tool to analyse the cutting mechanism and to identify the critical transition depth.

  18. Automatic tools for microprocessor failure analysis

    NASA Astrophysics Data System (ADS)

    Conard, Didier; Laurent, J.; Velazco, Raoul; Ziade, Haissam; Cabestany, J.; Sala, F.

    A new approach for fault location when testing microprocessors is presented. The startpoint for the backtracing analysis converging to the failure is constituted by the automatic localization of a reduced area. Automatic image comparison based on pattern recognition is performed by means of an electron beam tester. The developed hardware and software tools allow large circuit areas to be covered offering powerful diagnosis capabilities to the user. The validation of this technique was performed on faulty 68000 microprocessors. It shows the feasibility of the automation of the first and most important step of failure analysis: fault location at the chip surface.

  19. General Monte Carlo reliability simulation code including common mode failures and HARP fault/error-handling

    NASA Technical Reports Server (NTRS)

    Platt, M. E.; Lewis, E. E.; Boehm, F.

    1991-01-01

    A Monte Carlo Fortran computer program was developed that uses two variance reduction techniques for computing system reliability applicable to solving very large highly reliable fault-tolerant systems. The program is consistent with the hybrid automated reliability predictor (HARP) code which employs behavioral decomposition and complex fault-error handling models. This new capability is called MC-HARP which efficiently solves reliability models with non-constant failures rates (Weibull). Common mode failure modeling is also a specialty.

  20. DELPHI expert panel evaluation of Hanford high level waste tank failure modes and release quantities

    SciTech Connect

    Dunford, G.L.; Han, F.C.

    1996-09-30

    The Failure Modes and Release Quantities of the Hanford High Level Waste Tanks due to postulated accident loads were established by a DELPHI Expert Panel consisting of both on-site and off-site experts in the field of Structure and Release. The Report presents the evaluation process, accident loads, tank structural failure conclusion reached by the panel during the two-day meeting.

  1. Effects of soil-engineering properties on the failure mode of shallow landslides

    USGS Publications Warehouse

    McKenna, Jonathan Peter; Santi, Paul Michael; Amblard, Xavier; Negri, Jacquelyn

    2012-01-01

    Some landslides mobilize into flows, while others slide and deposit material immediately down slope. An index based on initial dry density and fine-grained content of soil predicted failure mode of 96 landslide initiation sites in Oregon and Colorado with 79% accuracy. These material properties can be used to identify potential sources for debris flows and for slides. Field data suggest that loose soils can evolve from dense soils that dilate upon shearing. The method presented herein to predict failure mode is most applicable for shallow (depth 8), with few to moderate fines (fine-grained content <18%), and with liquid limits <40.

  2. Failure Analysis of Ceramic Components

    SciTech Connect

    B.W. Morris

    2000-06-29

    Ceramics are being considered for a wide range of structural applications due to their low density and their ability to retain strength at high temperatures. The inherent brittleness of monolithic ceramics requires a departure from the deterministic design philosophy utilized to analyze metallic structural components. The design program ''Ceramic Analysis and Reliability Evaluation of Structures Life'' (CARES/LIFE) developed by NASA Lewis Research Center uses a probabilistic approach to predict the reliability of monolithic components under operational loading. The objective of this study was to develop an understanding of the theories used by CARES/LIFE to predict the reliability of ceramic components and to assess the ability of CARES/LIFE to accurately predict the fast fracture behavior of monolithic ceramic components. A finite element analysis was performed to determine the temperature and stress distribution of a silicon carbide O-ring under diametral compression. The results of the finite element analysis were supplied as input into CARES/LIFE to determine the fast fracture reliability of the O-ring. Statistical material strength parameters were calculated from four-point flexure bar test data. The predicted reliability showed excellent correlation with O-ring compression test data indicating that the CARES/LIFE program can be used to predict the reliability of ceramic components subjected to complicated stress states using material properties determined from simple uniaxial tensile tests.

  3. Interface failure modes explain non-monotonic size-dependent mechanical properties in bioinspired nanolaminates

    PubMed Central

    Song, Z. Q.; Ni, Y.; Peng, L. M.; Liang, H. Y.; He, L. H.

    2016-01-01

    Bioinspired discontinuous nanolaminate design becomes an efficient way to mitigate the strength-ductility tradeoff in brittle materials via arresting the crack at the interface followed by controllable interface failure. The analytical solution and numerical simulation based on the nonlinear shear-lag model indicates that propagation of the interface failure can be unstable or stable when the interfacial shear stress between laminae is uniform or highly localized, respectively. A dimensionless key parameter defined by the ratio of two characteristic lengths governs the transition between the two interface-failure modes, which can explain the non-monotonic size-dependent mechanical properties observed in various laminate composites. PMID:27029955

  4. Common failure modes for composite aircraft structures due to secondary loads

    NASA Astrophysics Data System (ADS)

    Rubin, A. M.

    The most common examples of composite laminate failure in typical aircraft structures are discussed, with particular consideration given to the effects of out-of-plane loads (and the resulting interlaminar shear/interlaminar tension) and bolted joint failure modes on the composite substructure and skins. It is noted that design allowables and environmental strength reduction factors for these types of failure model can be easily developed by performing simple element tests under RT/Dry and worst-case environmental conditions. The strength/stiffness factors identified during these tests may then be used to modify data obtained during full-scale RT/Dry tests.

  5. Molecular dynamics study on the failure modes of aluminium under decaying shock loading

    NASA Astrophysics Data System (ADS)

    Shao, Jian-Li; Wang, Pei; He, An-Min; Duan, Su-Qing; Qin, Cheng-Sen

    2013-04-01

    We have investigated the failure modes of single crystal aluminium under decaying shock loading by using molecular dynamics simulations. The microstructure evolution during the failure is presented in terms of the central symmetry parameter, and the corresponding pressure and temperature profiles are calculated and discussed. These results explain the failure morphology and mechanical properties under dynamic tension and especially the difference between solid and melted states. In addition, the fracture strength of aluminium is analyzed from surface velocity within acoustic approximation and virial theorem.

  6. Finite element modelling of woven composite failure modes at the mesoscopic scale: deterministic versus stochastic approaches

    NASA Astrophysics Data System (ADS)

    Roirand, Q.; Missoum-Benziane, D.; Thionnet, A.; Laiarinandrasana, L.

    2017-01-01

    Textile composites are composed of 3D complex architecture. To assess the durability of such engineering structures, the failure mechanisms must be highlighted. Examinations of the degradation have been carried out thanks to tomography. The present work addresses a numerical damage model dedicated to the simulation of the crack initiation and propagation at the scale of the warp yarns. For the 3D woven composites under study, loadings in tension and combined tension and bending were considered. Based on an erosion procedure of broken elements, the failure mechanisms have been modelled on 3D periodic cells by finite element calculations. The breakage of one element was determined using a failure criterion at the mesoscopic scale based on the yarn stress at failure. The results were found to be in good agreement with the experimental data for the two kinds of macroscopic loadings. The deterministic approach assumed a homogeneously distributed stress at failure all over the integration points in the meshes of woven composites. A stochastic approach was applied to a simple representative elementary periodic cell. The distribution of the Weibull stress at failure was assigned to the integration points using a Monte Carlo simulation. It was shown that this stochastic approach allowed more realistic failure simulations avoiding the idealised symmetry due to the deterministic modelling. In particular, the stochastic simulations performed have shown several variations of the stress as well as strain at failure and the failure modes of the yarn.

  7. Beam and shell modes of buckling of buried pipes induced by compressive ground failure

    SciTech Connect

    Chiou, Y.J.; Chi, S.Y.

    1995-12-31

    The buckling of buried pipeline induced by compressive ground failure was investigated. Both the beam mode of buckling and local shell mode of buckling, and their interactions were studied. The pipeline response was analyzed numerically. The results agree qualitatively with past researches and possess satisfactory comparisons with actual case histories. The relations of critical buried depth versus ratio of pipe diameter to thickness for buried pipe with different imperfections and various soil foundations were established.

  8. FAILURE ANALYSIS: WASTEWATER DRUM BULGING

    SciTech Connect

    Vormelker, P

    2008-09-15

    A 55 gallon wastewater drum lid was found to be bulged during storage in a remote area. Drum samples were obtained for analysis. The interior surface of these samples revealed blistering and holes in the epoxy phenolic drum liner and corrosion of the carbon steel drum. It is suspected that osmotic pressure drove permeation of the water through the epoxy phenolic coating which was weakened from exposure to low pH water. The coating failed at locations throughout the drum interior. Subsequent corrosion of the carbon steel released hydrogen which pressurized the drum causing deformation of the drum lid. Additional samples from other wastewater drums on the same pallet were also evaluated and limited corrosion was visible on the interior surfaces. It is suspected that, with time, the corrosion would have advanced to cause pressurization of these sealed drums.

  9. Failure analysis of fuze power supply

    SciTech Connect

    Menke, J.T.

    1996-10-01

    Batteries in storage which were used in electronic fuzes were found to be leaking after 5 years. The leaking battery ampules were made of copper and contained mixture of fluoboric acid and methylene bromide. The corrosion mechanism is described along with the testing/analysis required to simulate the field failures.

  10. A Summary of Taxonomies of Digital System Failure Modes Provided by the DigRel Task Group

    SciTech Connect

    Chu T. L.; Yue M.; Postma, W.

    2012-06-25

    Recently, the CSNI directed WGRisk to set up a task group called DIGREL to initiate a new task on developing a taxonomy of failure modes of digital components for the purposes of PSA. It is an important step towards standardized digital I&C reliability assessment techniques for PSA. The objective of this paper is to provide a comparison of the failure mode taxonomies provided by the participants. The failure modes are classified in terms of their levels of detail. Software and hardware failure modes are discussed separately.

  11. Nonlinear Temperature Dependent Failure Analysis of Finite Width Composite Laminates.

    DTIC Science & Technology

    1979-12-01

    tangent modulii obtained by Ramberg-Osgood parameters. It is shown that a’ring stresses and stresses due to tensile loading are significant as edge ... effect in all types of laminate studies. The tensor polynomial failure criterion is used to predict the initiation of failure. The mode of failure is

  12. Failure analysis for micro-electrical-mechanical systems (MEMS)

    SciTech Connect

    Peterson, K.A.; Tangyunyong, P.; Barton, D.L.

    1997-10-01

    Micro-Electrical Mechanical Systems (MEMS) is an emerging technology with demonstrated potential for a wide range of applications including sensors and actuators for medical, industrial, consumer, military, automotive and instrumentation products. Failure analysis (FA) of MEMS is critically needed for the successful design, fabrication, performance analysis and reliability assurance of this new technology. Many devices have been examined using techniques developed for integrated circuit analysis, including optical inspection, scanning laser microscopy (SLM), scanning electron microscopy (SEM), focused ion beam (FIB) techniques, atomic force microscopy (AFM), infrared (IR) microscopy, light emission (LE) microscopy, acoustic microscopy and acoustic emission analysis. For example, the FIB was used to microsection microengines that developed poor performance characteristics. Subsequent SEM analysis clearly demonstrated the absence of wear on gear, hub, and pin joint bearing surfaces, contrary to expectations. Another example involved the use of infrared microscopy for thermal analysis of operating microengines. Hot spots were located, which did not involve the gear or hub, but indicated contact between comb structures which drive microengines. Voltage contrast imaging proved useful on static and operating MEMS in both the SEM and the FIB and identified electrostatic clamping as a potentially significant contributor to failure mechanisms in microengines. This work describes MEMS devices, FA techniques, failure modes, and examples of FA of MEMS.

  13. Failure Analysis of Composite Structure Materials.

    DTIC Science & Technology

    1986-05-01

    listed in order of preference, based on applicability, reliability, cost , and sample requirements. Figure 5-4. Failure Analysis Technique...development of a methodology in which optical analysis is used to increase the time and cost effectiveness of analyzing failed composite material struc...regarding the integrity of the bond. Accurate bondline defect information was achieved in such structures utilizing a transportable californium -252 (2 5 2

  14. Analysis of cascading failure in gene networks.

    PubMed

    Sun, Longxiao; Wang, Shudong; Li, Kaikai; Meng, Dazhi

    2012-01-01

    It is an important subject to research the functional mechanism of cancer-related genes make in formation and development of cancers. The modern methodology of data analysis plays a very important role for deducing the relationship between cancers and cancer-related genes and analyzing functional mechanism of genome. In this research, we construct mutual information networks using gene expression profiles of glioblast and renal in normal condition and cancer conditions. We investigate the relationship between structure and robustness in gene networks of the two tissues using a cascading failure model based on betweenness centrality. Define some important parameters such as the percentage of failure nodes of the network, the average size-ratio of cascading failure, and the cumulative probability of size-ratio of cascading failure to measure the robustness of the networks. By comparing control group and experiment groups, we find that the networks of experiment groups are more robust than that of control group. The gene that can cause large scale failure is called structural key gene. Some of them have been confirmed to be closely related to the formation and development of glioma and renal cancer respectively. Most of them are predicted to play important roles during the formation of glioma and renal cancer, maybe the oncogenes, suppressor genes, and other cancer candidate genes in the glioma and renal cancer cells. However, these studies provide little information about the detailed roles of identified cancer genes.

  15. Dynamic Failure Mode Transitions in 7075Al Expanding rings driven by Electromagnetic loading

    NASA Astrophysics Data System (ADS)

    Liu, Mingtao; Tang, Tiegang; Guo, Zhaoliang; Fan, Cheng

    Dynamic failure mode transitions are observed in 7075Al electromagnetic expanding rings with a typical size of 3mm in thickness and 0.5mm in height. The rings are driven to maximum expanding velocities ranged from 60m/s to 180m/s, corresponding to strain rates of about 3000 to 9000 per second. At lower strain rates, the fractures of the rings are dominated by the hoop tensile stress, and the cracks are along the radial direction. At higher strain rates, the fractures of the rings are dominated by the maximum shear stress, and the cracks are lie along with an angle of about 45 degree with the radial direction. While the rings deform at medium strain rates, a mixed failure mode is observed, which simultaneously consists of tensile fracture and shear fracture. The failure strains of the specimen and the numbers of the fragmentations were measured after testing. The failure strains show a maximum value as the strain rate increasing, but the numbers of the fragmentations increase firstly, then decrease and then increase again. These phenomena were found to have a close relationship with the dynamic failure mode transitions.

  16. Failure Modes and Diagnostic Signatures Working Group - Ignition Diagnostics Requirements Update

    SciTech Connect

    Cerjan, C; Haan, S; Hatchett, S; Koch, J

    2007-03-26

    We have performed an initial assessment of the sensitivity of various expected ignition diagnostic signatures to ignition failure modes using one and two-dimensional hydrodynamics simulations and post-processed simulated diagnostic output. As a result of this assessment, we recommend several changes to the current requirements for the ignition diagnostic suite. These recommendations are summarized in Table 1.

  17. A Study of Energy Management Systems and its Failure Modes in Smart Grid Power Distribution

    NASA Astrophysics Data System (ADS)

    Musani, Aatif

    The subject of this thesis is distribution level load management using a pricing signal in a smart grid infrastructure. The project relates to energy management in a spe-cialized distribution system known as the Future Renewable Electric Energy Delivery and Management (FREEDM) system. Energy management through demand response is one of the key applications of smart grid. Demand response today is envisioned as a method in which the price could be communicated to the consumers and they may shift their loads from high price periods to the low price periods. The development and deployment of the FREEDM system necessitates controls of energy and power at the point of end use. In this thesis, the main objective is to develop the control model of the Energy Management System (EMS). The energy and power management in the FREEDM system is digitally controlled therefore all signals containing system states are discrete. The EMS is modeled as a discrete closed loop transfer function in the z-domain. A breakdown of power and energy control devices such as EMS components may result in energy con-sumption error. This leads to one of the main focuses of the thesis which is to identify and study component failures of the designed control system. Moreover, H-infinity ro-bust control method is applied to ensure effectiveness of the control architecture. A focus of the study is cyber security attack, specifically bad data detection in price. Test cases are used to illustrate the performance of the EMS control design, the effect of failure modes and the application of robust control technique. The EMS was represented by a linear z-domain model. The transfer function be-tween the pricing signal and the demand response was designed and used as a test bed. EMS potential failure modes were identified and studied. Three bad data detection meth-odologies were implemented and a voting policy was used to declare bad data. The run-ning mean and standard deviation analysis method proves to be

  18. Progressive Failure Analysis Methodology for Laminated Composite Structures

    NASA Technical Reports Server (NTRS)

    Sleight, David W.

    1999-01-01

    A progressive failure analysis method has been developed for predicting the failure of laminated composite structures under geometrically nonlinear deformations. The progressive failure analysis uses C(exp 1) shell elements based on classical lamination theory to calculate the in-plane stresses. Several failure criteria, including the maximum strain criterion, Hashin's criterion, and Christensen's criterion, are used to predict the failure mechanisms and several options are available to degrade the material properties after failures. The progressive failure analysis method is implemented in the COMET finite element analysis code and can predict the damage and response of laminated composite structures from initial loading to final failure. The different failure criteria and material degradation methods are compared and assessed by performing analyses of several laminated composite structures. Results from the progressive failure method indicate good correlation with the existing test data except in structural applications where interlaminar stresses are important which may cause failure mechanisms such as debonding or delaminations.

  19. Post Buckling Progressive Failure Analysis of Composite Laminated Stiffened Panels

    NASA Astrophysics Data System (ADS)

    Anyfantis, Konstantinos N.; Tsouvalis, Nicholas G.

    2012-06-01

    The present work deals with the numerical prediction of the post buckling progressive and final failure response of stiffened composite panels based on structural nonlinear finite element methods. For this purpose, a progressive failure model (PFM) is developed and applied to predict the behaviour of an experimentally tested blade-stiffened panel found in the literature. Failure initiation and propagation is calculated, owing to the accumulation of the intralaminar failure modes induced in fibre reinforced composite materials. Hashin failure criteria have been employed in order to address the fiber and matrix failure modes in compression and tension. On the other hand, the Tsai-Wu failure criterion has been utilized for addressing shear failure. Failure detection is followed with the introduction of corresponding material degradation rules depending on the individual failure mechanisms. Failure initiation and failure propagation as well as the post buckling ultimate attained load have been numerically evaluated. Final failure behaviour of the simulated stiffened panel is due to sudden global failure, as concluded from comparisons between numerical and experimental results being in good agreement.

  20. Reliability and failure modes of implant-supported zirconium-oxide fixed dental prostheses related to veneering techniques

    PubMed Central

    Baldassarri, Marta; Zhang, Yu; Thompson, Van P.; Rekow, Elizabeth D.; Stappert, Christian F. J.

    2011-01-01

    Summary Objectives To compare fatigue failure modes and reliability of hand-veneered and over-pressed implant-supported three-unit zirconium-oxide fixed-dental-prostheses(FDPs). Methods Sixty-four custom-made zirconium-oxide abutments (n=32/group) and thirty-two zirconium-oxide FDP-frameworks were CAD/CAM manufactured. Frameworks were veneered with hand-built up or over-pressed porcelain (n=16/group). Step-stress-accelerated-life-testing (SSALT) was performed in water applying a distributed contact load at the buccal cusp-pontic-area. Post failure examinations were carried out using optical (polarized-reflected-light) and scanning electron microscopy (SEM) to visualize crack propagation and failure modes. Reliability was compared using cumulative-damage step-stress analysis (Alta-7-Pro, Reliasoft). Results Crack propagation was observed in the veneering porcelain during fatigue. The majority of zirconium-oxide FDPs demonstrated porcelain chipping as the dominant failure mode. Nevertheless, fracture of the zirconium-oxide frameworks was also observed. Over-pressed FDPs failed earlier at a mean failure load of 696 ± 149 N relative to hand-veneered at 882 ± 61 N (profile I). Weibull-stress-number of cycles-unreliability-curves were generated. The reliability (2-sided at 90% confidence bounds) for a 400N load at 100K cycles indicated values of 0.84 (0.98-0.24) for the hand-veneered FDPs and 0.50 (0.82-0.09) for their over-pressed counterparts. Conclusions Both zirconium-oxide FDP systems were resistant under accelerated-life-time-testing. Over-pressed specimens were more susceptible to fatigue loading with earlier veneer chipping. PMID:21557985

  1. Comprehensive characterization and failure modes of tungsten microwire arrays in chronic neural implants

    NASA Astrophysics Data System (ADS)

    Prasad, Abhishek; Xue, Qing-Shan; Sankar, Viswanath; Nishida, Toshikazu; Shaw, Gerry; Streit, Wolfgang J.; Sanchez, Justin C.

    2012-10-01

    activated microglia were present near the electrode tracks in all non-acute animals studied, thus indicating presence of a neuroinflammatory response regardless of post-implantation survival times and electrode performance. Conversely, dystrophic microglia detectable as fragmented cells were found almost exclusively in acute animals surviving only few hours after implantation. While there was no consistent relationship between microglial cell responses and electrode performance, we noticed co-occurrence of high ferritin expression, intraparenchymal bleeding, and microglial degeneration suggesting presence of excessive oxidative stress via Fenton chemistry. Biochemical analysis indicated that these electrodes always caused a persistent release of axonal injury biomarkers even several months after implantation suggesting persistent tissue damage. Our study suggests that mechanisms of electrode failure are multi-factorial involving both abiotic and biotic parameters. Since these failure modes occur concurrently and cannot be isolated from one another, the lack of consistent relationship between electrode performance and microglial responses in our results suggest that one or more of the abiotic factors were equally responsible for degradation in electrode performance over long periods of time.

  2. Factors Influencing Progressive Failure Analysis Predictions for Laminated Composite Structure

    NASA Technical Reports Server (NTRS)

    Knight, Norman F., Jr.

    2008-01-01

    Progressive failure material modeling methods used for structural analysis including failure initiation and material degradation are presented. Different failure initiation criteria and material degradation models are described that define progressive failure formulations. These progressive failure formulations are implemented in a user-defined material model for use with a nonlinear finite element analysis tool. The failure initiation criteria include the maximum stress criteria, maximum strain criteria, the Tsai-Wu failure polynomial, and the Hashin criteria. The material degradation model is based on the ply-discounting approach where the local material constitutive coefficients are degraded. Applications and extensions of the progressive failure analysis material model address two-dimensional plate and shell finite elements and three-dimensional solid finite elements. Implementation details are described in the present paper. Parametric studies for laminated composite structures are discussed to illustrate the features of the progressive failure modeling methods that have been implemented and to demonstrate their influence on progressive failure analysis predictions.

  3. Shift in failure modes in foam core sandwich composites subject to repeated slamming on water

    NASA Astrophysics Data System (ADS)

    Figueroa, Evaristo; Shafiq, Basir

    2013-06-01

    A test program designed and carried out to mimic the repeated impact of the bow section of fast-moving small boats on the ocean surface provided some unique observations in terms of failure mode transition. Damage progression and modes of failure were evaluated for two types of sandwich composites with comparable global strength and stiffness but different foam density and facesheet strength. Testing was performed on flat rectangular specimens that contained symmetric semi-elliptical edge flaws produced near the end of the specimen held by the rotating cam. Type 1 specimens (softer core/stronger facesheet) consistently failed by interface and through-the-thickness core shear, independent of the flaw size. In contrast, a gradual decrease in flaw size in Type 2 specimens (denser core/weaker facesheet) produced a striking transition in the mode of failure from local buckling in the vicinity of the flaw site along with exponentially increasing lifetime, to interface shear failure at the free end accompanied by a dramatic drop in lifetime. The lifetime of Type 2 specimens was more than two orders of magnitude greater than that of Type 1 specimens.

  4. Failure modes and conditions of a cohesive, spherical body due to YORP spin-up

    NASA Astrophysics Data System (ADS)

    Hirabayashi, Masatoshi

    2015-12-01

    This paper presents transition of the failure mode of a cohesive, spherical body due to The Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) spin-up. On the assumption that the distribution of materials in the body is homogeneous, failed regions first appearing in the body at different spin rates are predicted by comparing the yield condition of an elastic stress in the body. It is found that as the spin rate increases, the locations of the failed regions move from the equatorial surface to the central region. To avoid such failure modes, the body should have higher cohesive strength. The results by this model are consistent with those by a plastic finite element model. Then, this model and a two-layered-cohesive model first proposed by Hirabayashi et al. are used to classify possible evolution and disruption of a spherical body. There are three possible pathways to disruption. First, because of a strong structure, failure of the central region is dominant and eventually leads to a breakup into multiple components. Secondly, a weak surface and a weak interior make the body oblate. Thirdly, a strong internal core prevents the body from failing and only allows surface shedding. This implies that observed failure modes may highly depend on the internal structure of an asteroid, which could provide crucial information for giving constraints on the physical properties.

  5. Rapid repair of severely earthquake-damaged bridge piers with flexural-shear failure mode

    NASA Astrophysics Data System (ADS)

    Sun, Zhiguo; Wang, Dongsheng; Du, Xiuli; Si, Bingjun

    2011-12-01

    An experimental study was conducted to investigate the feasibility of a proposed rapid repair technique for severely earthquake-damaged bridge piers with flexural-shear failure mode. Six circular pier specimens were first tested to severe damage in flexural-shear mode and repaired using early-strength concrete with high-fluidity and carbon fiber reinforced polymers (CFRP). After about four days, the repaired specimens were tested to failure again. The seismic behavior of the repaired specimens was evaluated and compared to the original specimens. Test results indicate that the proposed repair technique is highly effective. Both shear strength and lateral displacement of the repaired piers increased when compared to the original specimens, and the failure mechanism of the piers shifted from flexural-shear failure to ductile flexural failure. Finally, a simple design model based on the Seible formulation for post-earthquake repair design was compared to the experimental results. It is concluded that the design equation for bridge pier strengthening before an earthquake could be applicable to seismic repairs after an earthquake if the shear strength contribution of the spiral bars in the repaired piers is disregarded and 1.5 times more FRP sheets is provided.

  6. Data Collection Plan to Populate the Light Water Reactor Sustainability Failure Mode Degradation Library

    SciTech Connect

    Magdy S. Tawfik; Binh T. Pham; Vivek Agarwal; Nancy J. Lybeck

    2011-09-01

    Interest in implementing advanced Prognostic Health Management (PHM) systems in commercial nuclear power plants (NPPs) has increased rapidly in recent years, with an overarching goal of implementing of improving the safety, reliability, and economics/profitability of the aging nuclear fleet and extending their service life in the most cost-effective manner. The PHM system utilizes prognostic tools to estimate the remaining useful life (RUL) of a component or system of components based on current and predicted operating conditions. An effective implementation of the PHM system will anticipate and identify unique age-dependent degradation modes to provide early warning of emerging problems. Selection of the components and structures to be monitored is a crucial step for successful PHM implementation in NPPs. A selection framework is recommended for risk significant components (both safety-related and non-safety related) based on the Fussell-Vesely (F-V) Importance Measure and the Risk Achievement Worth (RAW) measure. For the selected components, a failure mode degradation library will be developed consisting of data corresponding to different failure/degradation modes. In lieu of constructing an expensive scaled test facility, several data sources are identified for populating the failure mode degradation library, including various national laboratories, universities, agencies, and industries.

  7. Failure Analysis of Worn Surface Micromachined Microengines

    SciTech Connect

    Walraven, Jeremy A.; Headley, Thomas J.; Campbell, Ann N.; Tanner, Danelle M.

    1999-07-21

    Failure analysis (FA) tools have been applied to analyze failing polysilicon microengines. These devices were stressed to failure under accelerated conditions in both oxidizing and non-oxidizing environments. The dominant failure mechanism of these microengines was identified as wear of rubbing surfaces. This often results in either seized microengines or microengines with broken pin joints. Analysis of these failed polysilicon devices found that wear debris was produced in both oxidizing and non-oxidizing environments. By varying the relative percent humidity (%RH), they observed an increase in the amount of wear debris with decreasing humidity. Plan view imaging using scanning electron microscopy revealed build-up of wear debris on the surface of microengines. Focused ion beam (FIB) cross sections revealed the location and build-up of wear debris on the surface of microengines. Focused ion beam (FIB) cross sections revealed the location and build-up of wear debris within the microengine. Seized regions were also observed in the pin joint area using FIB processing. By using transmission electron microscopy in conjunction with energy dispersive x-ray spectroscopy (EDX) and electron energy loss spectroscopy (EELS), they were able to identify wear debris produced in low (1.8% RH), medium and high (39% RH) humidities.

  8. FASTHELP. Integrated Circuit Failure Analysis Hypertext Help System

    SciTech Connect

    Henderson, C; Barton, D; Campbell, A; Cole, E; Mikawa, R E; Peterson, K A; Rife, J L; Soden, J M

    1994-09-30

    This software assists a failure analyst performing failure analysis on integrated circuits. The software can also be used to train inexperienced failure analysts. The software also provides a method for storing information and making it easily available to experienced failure analysts.

  9. Water Ingress Failure Analysis of Whistler II Unit

    DTIC Science & Technology

    2014-08-01

    Water Ingress Failure Analysis of Whistler II Unit by Andrew J Bayba ARL-TN-0623 August 2014...Failure Analysis of Whistler II Unit Andrew J Bayba Sensors and Electron Devices Directorate, ARL...Ingress Failure Analysis of Whistler II Unit 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Andrew J Bayba

  10. Sliding Mode Control of the X-33 with an Engine Failure

    NASA Technical Reports Server (NTRS)

    Shtessel, Yuri B.; Hall, Charles E.

    2000-01-01

    Ascent flight control of the X-3 is performed using two XRS-2200 linear aerospike engines. in addition to aerosurfaces. The baseline control algorithms are PID with gain scheduling. Flight control using an innovative method. Sliding Mode Control. is presented for nominal and engine failed modes of flight. An easy to implement, robust controller. requiring no reconfiguration or gain scheduling is demonstrated through high fidelity flight simulations. The proposed sliding mode controller utilizes a two-loop structure and provides robust. de-coupled tracking of both orientation angle command profiles and angular rate command profiles in the presence of engine failure, bounded external disturbances (wind gusts) and uncertain matrix of inertia. Sliding mode control causes the angular rate and orientation angle tracking error dynamics to be constrained to linear, de-coupled, homogeneous, and vector valued differential equations with desired eigenvalues. Conditions that restrict engine failures to robustness domain of the sliding mode controller are derived. Overall stability of a two-loop flight control system is assessed. Simulation results show that the designed controller provides robust, accurate, de-coupled tracking of the orientation angle command profiles in the presence of external disturbances and vehicle inertia uncertainties, as well as the single engine failed case. The designed robust controller will significantly reduce the time and cost associated with flying new trajectory profiles or orbits, with new payloads, and with modified vehicles

  11. Evaluation of a fracture failure mode in the Space Shuttle hydrogen pressurization system flow control valves

    NASA Astrophysics Data System (ADS)

    Hauver, S. E.; Sueme, D. R.

    1992-07-01

    During acceptance testing of the Space Shuttle Endeavor hydrogen flow control valves, which are used in the Orbiter's fuel tank pressurization system, two of the valves experienced fracture of the poppet flange. The poppets are made of 440 C, a high strength, wear-resistant, low ductility, martensitic stainless steel. The investigation which was initiated to determine the cause of these failures is traced. All aspects of the poppet processing that may have introduced a defect were assessed. This included machining, heat treating, passivation, assembly, and test. In addition, several potential failure modes were investigated. The extensive investigation revealed no obvious cause of the failures, but did result in a recommendation for a different material application.

  12. Different failure modes for V-containing and V-free AB2 metal hydride alloys

    NASA Astrophysics Data System (ADS)

    Young, K.; Wong, D. F.; Yasuoka, S.; Ishida, J.; Nei, J.; Koch, J.

    2014-04-01

    Failure modes of a V-containing and a V-free AB2 Laves phase-based metal hydride alloy were studied by the combination of X-ray diffractometer, scanning electron microscope, X-ray energy dispersive spectroscopy, inductively coupled plasma, Soxhlet extraction, and magnetic susceptibility measurement. Cells with the V-containing alloy exhibited less capacity degradation up until venting occurred in the cells, after which the capacity rapidly degraded. Cells with the V-free alloy remained linear in capacity degradation throughout the cycle life test. The failure mechanism for the V-containing alloy is related to the formation of an oxide layer that penetrates deeper into the alloy particles due to high V leaching and impedes gas recombination, while the failure mechanism for the V-free alloy is related to the continuous pulverization of the main AB2 phase.

  13. Memories and NASA Spacecraft: A Description of Memories, Radiation Failure Modes, and System Design Considerations

    NASA Technical Reports Server (NTRS)

    LaBel, Kenneth A.; Ladbury, Ray; Oldhamm, Timothy

    2010-01-01

    As NASA has evolved it's usage of spaceflight computing, memory applications have followed as well. In this slide presentation, the history of NASA's memories from magnetic core and tape recorders to current semiconductor approaches is discussed. There is a brief description of current functional memory usage in NASA space systems followed by a description of potential radiation-induced failure modes along with considerations for reliable system design.

  14. Lunar Module ECS (Environmental Control System) - Design Considerations and Failure Modes. Part 1

    NASA Technical Reports Server (NTRS)

    Interbartolo, Michael

    2009-01-01

    Design considerations and failure modes for the Lunar Module (LM) Environmental Control System (ECS) are described. An overview of the the oxygen supply and cabin pressurization, atmosphere revitalization, water management and heat transport systems are provided. Design considerations including reliability, flight instrumentation, modularization and the change to the use of batteries instead of fuel cells are discussed. A summary is provided for the LM ECS general testing regime.

  15. Long-term lumen depreciation behavior and failure modes of multi-die array LEDs

    NASA Astrophysics Data System (ADS)

    Jayawardena, Asiri; Marcus, Daniel; Prugue, Ximena; Narendran, Nadarajah

    2013-09-01

    One of the main advantages of multi-die array light-emitting diodes (LEDs) is their high flux density. However, a challenge for using such a product in lighting fixture applications is the heat density and the need for thermal management to keep the junction temperatures of all the dies low for long-term reliable performance. Ten multi-die LED array samples for each product from four different manufacturers were subjected to lumen maintenance testing (as described in IES-LM-80-08), and their resulting lumen depreciation and failure modes were studied. The products were tested at the maximum case (or pin) temperature reported by the respective manufacturer by appropriately powering the LEDs. In addition, three samples for each product from two different manufacturers were subjected to rapid thermal cycling, and the resulting lumen depreciation and failure modes were studied. The results showed that the exponential lumen decay model using long-term lumen maintenance data as recommended in IES TM-21 does not fit for all package types. The failure of a string of dies and single die failure in a string were observed in some of the packages.

  16. Recent Advances In Structural Vibration And Failure Mode Control In Mainland China: Theory, Experiments And Applications

    SciTech Connect

    Li Hui; Ou Jinping

    2008-07-08

    A number of researchers have been focused on structural vibration control in the past three decades over the world and fruit achievements have been made. This paper introduces the recent advances in structural vibration control including passive, active and semiactive control in mainland China. Additionally, the co-author extends the structural vibration control to failure mode control. The research on the failure mode control is also involved in this paper. For passive control, this paper introduces full scale tests of buckling-restrained braces conducted to investigate the performance of the dampers and the second-editor of the Code of Seismic Design for Buildings. For active control, this paper introduces the HMD system for wind-induced vibration control of the Guangzhou TV tower. For semiactive control, the smart damping devices, algorithms for semi-active control, design methods and applications of semi-active control for structures are introduced in this paper. The failure mode control for bridges is also introduced.

  17. Precursory changes in seismic velocity for the spectrum of earthquake failure modes

    NASA Astrophysics Data System (ADS)

    Scuderi, M. M.; Marone, C.; Tinti, E.; di Stefano, G.; Collettini, C.

    2016-09-01

    Temporal changes in seismic velocity during the earthquake cycle have the potential to illuminate physical processes associated with fault weakening and connections between the range of fault slip behaviours including slow earthquakes, tremor and low-frequency earthquakes. Laboratory and theoretical studies predict changes in seismic velocity before earthquake failure; however, tectonic faults fail in a spectrum of modes and little is known about precursors for those modes. Here we show that precursory changes of wave speed occur in laboratory faults for the complete spectrum of failure modes observed for tectonic faults. We systematically altered the stiffness of the loading system to reproduce the transition from slow to fast stick-slip and monitored ultrasonic wave speed during frictional sliding. We find systematic variations of elastic properties during the seismic cycle for both slow and fast earthquakes indicating similar physical mechanisms during rupture nucleation. Our data show that accelerated fault creep causes reduction of seismic velocity and elastic moduli during the preparatory phase preceding failure, which suggests that real-time monitoring of active faults may be a means to detect earthquake precursors.

  18. A molecular dynamics study of the failure modes of a glassy polymer confined between rigid walls

    NASA Astrophysics Data System (ADS)

    Kulmi, Udit; Basu, Sumit

    2006-09-01

    Adhesion is a complex and multifaceted phenomenon which is controlled by various factors such as the loading rate, interface toughness, temperature and geometric and molecular properties. The mode of failure of adhesive joints (adhesive or cohesive) is decided through a complex interplay between these factors. In this work, we study the failure under tensile loading of a thin layer of a polymeric material confined between two rigid walls using molecular dynamics simulations. The strength of the interface is controlled by the interaction potential between the polymer and wall atoms. The polymer modelled is a simple linear chain of 'united atoms' having a fixed bond length but contributions to the energy arise from bending and torsion of bonds as well as from non-bonded interactions between the 'united atoms'. The results indicate that even when the adhesion between the wall and the polymer is weak, a short chained polymer is more likely to fail by a mixed adhesive cohesive mode. A long chained polymer, with the same interface strength, fails in a pure adhesive manner. However, when the interface is sufficiently strengthened, the long chained polymer fails cohesively and it can bear a much higher load. The failure mode is somewhat modulated by the rate at which deformation occurs. Moreover, when the polymer is confined such that the spacing between the walls is comparable to the end-to-end distance of the polymer chain, strength of the joint increases significantly. In such a situation, even polymers with weak interfacial adhesion might fail cohesively.

  19. Precursory changes in seismic velocity for the spectrum of earthquake failure modes.

    PubMed

    Scuderi, M M; Marone, C; Tinti, E; Di Stefano, G; Collettini, C

    2016-09-01

    Temporal changes in seismic velocity during the earthquake cycle have the potential to illuminate physical processes associated with fault weakening and connections between the range of fault slip behaviors including slow earthquakes, tremor and low frequency earthquakes1. Laboratory and theoretical studies predict changes in seismic velocity prior to earthquake failure2, however tectonic faults fail in a spectrum of modes and little is known about precursors for those modes3. Here we show that precursory changes of wave speed occur in laboratory faults for the complete spectrum of failure modes observed for tectonic faults. We systematically altered the stiffness of the loading system to reproduce the transition from slow to fast stick-slip and monitored ultrasonic wave speed during frictional sliding. We find systematic variations of elastic properties during the seismic cycle for both slow and fast earthquakes indicating similar physical mechanisms during rupture nucleation. Our data show that accelerated fault creep causes reduction of seismic velocity and elastic moduli during the preparatory phase preceding failure, which suggests that real time monitoring of active faults may be a means to detect earthquake precursors.

  20. Precursory changes in seismic velocity for the spectrum of earthquake failure modes

    PubMed Central

    Scuderi, M.M.; Marone, C.; Tinti, E.; Di Stefano, G.; Collettini, C.

    2016-01-01

    Temporal changes in seismic velocity during the earthquake cycle have the potential to illuminate physical processes associated with fault weakening and connections between the range of fault slip behaviors including slow earthquakes, tremor and low frequency earthquakes1. Laboratory and theoretical studies predict changes in seismic velocity prior to earthquake failure2, however tectonic faults fail in a spectrum of modes and little is known about precursors for those modes3. Here we show that precursory changes of wave speed occur in laboratory faults for the complete spectrum of failure modes observed for tectonic faults. We systematically altered the stiffness of the loading system to reproduce the transition from slow to fast stick-slip and monitored ultrasonic wave speed during frictional sliding. We find systematic variations of elastic properties during the seismic cycle for both slow and fast earthquakes indicating similar physical mechanisms during rupture nucleation. Our data show that accelerated fault creep causes reduction of seismic velocity and elastic moduli during the preparatory phase preceding failure, which suggests that real time monitoring of active faults may be a means to detect earthquake precursors. PMID:27597879

  1. Timing analysis of PWR fuel pin failures

    SciTech Connect

    Jones, K.R.; Wade, N.L.; Katsma, K.R.; Siefken, L.J. ); Straka, M. )

    1992-09-01

    Research has been conducted to develop and demonstrate a methodology for calculation of the time interval between receipt of the containment isolation signals and the first fuel pin failure for loss-of-coolant accidents (LOCAs). Demonstration calculations were performed for a Babcock and Wilcox (B W) design (Oconee) and a Westinghouse (W) four-loop design (Seabrook). Sensitivity studies were performed to assess the impacts of fuel pin bumup, axial peaking factor, break size, emergency core cooling system availability, and main coolant pump trip on these times. The analysis was performed using the following codes: FRAPCON-2, for the calculation of steady-state fuel behavior; SCDAP/RELAP5/MOD3 and TRACPF1/MOD1, for the calculation of the transient thermal-hydraulic conditions in the reactor system; and FRAP-T6, for the calculation of transient fuel behavior. In addition to the calculation of fuel pin failure timing, this analysis provides a comparison of the predicted results of SCDAP/RELAP5/MOD3 and TRAC-PFL/MOD1 for large-break LOCA analysis. Using SCDAP/RELAP5/MOD3 thermal-hydraulic data, the shortest time intervals calculated between initiation of containment isolation and fuel pin failure are 10.4 seconds and 19.1 seconds for the B W and W plants, respectively. Using data generated by TRAC-PF1/MOD1, the shortest intervals are 10.3 seconds and 29.1 seconds for the B W and W plants, respectively. These intervals are for a double-ended, offset-shear, cold leg break, using the technical specification maximum peaking factor and applied to fuel with maximum design bumup. Using peaking factors commensurate widi actual bumups would result in longer intervals for both reactor designs. This document also contains appendices A through J of this report.

  2. Effects of Fusion Zone Size and Failure Mode on Peak Load and Energy Absorption of Advanced High Strength Steel Spot Welds under Lap Shear Loading Conditions

    SciTech Connect

    Sun, Xin; Stephens, Elizabeth V.; Khaleel, Mohammad A.

    2008-06-01

    This paper examines the effects of fusion zone size on failure modes, static strength and energy absorption of resistance spot welds (RSW) of advanced high strength steels (AHSS) under lap shear loading condition. DP800 and TRIP800 spot welds are considered. The main failure modes for spot welds are nugget pullout and interfacial fracture. Partial interfacial fracture is also observed. Static weld strength tests using lap shear samples were performed on the joint populations with various fusion zone sizes. The resulted peak load and energy absorption levels associated with each failure mode were studied for all the weld populations using statistical data analysis tools. The results in this study show that AHSS spot welds with conventionally required fusion zone size of can not produce nugget pullout mode for both the DP800 and TRIP800 welds under lap shear loading. Moreover, failure mode has strong influence on weld peak load and energy absorption for all the DP800 welds and the TRIP800 small welds: welds failed in pullout mode have statistically higher strength and energy absorption than those failed in interfacial fracture mode. For TRIP800 welds above the critical fusion zone level, the influence of weld failure modes on peak load and energy absorption diminishes. Scatter plots of peak load and energy absorption versus weld fusion zone size were then constructed, and the results indicate that fusion zone size is the most critical factor in weld quality in terms of peak load and energy absorption for both DP800 and TRIP800 spot welds.

  3. PAFAC- PLASTIC AND FAILURE ANALYSIS OF COMPOSITES

    NASA Technical Reports Server (NTRS)

    Bigelow, C. A.

    1994-01-01

    The increasing number of applications of fiber-reinforced composites in industry demands a detailed understanding of their material properties and behavior. A three-dimensional finite-element computer program called PAFAC (Plastic and Failure Analysis of Composites) has been developed for the elastic-plastic analysis of fiber-reinforced composite materials and structures. The evaluation of stresses and deformations at edges, cut-outs, and joints is essential in understanding the strength and failure for metal-matrix composites since the onset of plastic yielding starts very early in the loading process as compared to the composite's ultimate strength. Such comprehensive analysis can only be achieved by a finite-element program like PAFAC. PAFAC is particularly suited for the analysis of laminated metal-matrix composites. It can model the elastic-plastic behavior of the matrix phase while the fibers remain elastic. Since the PAFAC program uses a three-dimensional element, the program can also model the individual layers of the laminate to account for thickness effects. In PAFAC, the composite is modeled as a continuum reinforced by cylindrical fibers of vanishingly small diameter which occupy a finite volume fraction of the composite. In this way, the essential axial constraint of the phases is retained. Furthermore, the local stress and strain fields are uniform. The PAFAC finite-element solution is obtained using the displacement method. Solution of the nonlinear equilibrium equations is obtained with a Newton-Raphson iteration technique. The elastic-plastic behavior of composites consisting of aligned, continuous elastic filaments and an elastic-plastic matrix is described in terms of the constituent properties, their volume fractions, and mutual constraints between phases indicated by the geometry of the microstructure. The program uses an iterative procedure to determine the overall response of the laminate, then from the overall response determines the stress

  4. Notch strengthening or weakening governed by transition of shear failure to normal mode fracture

    PubMed Central

    Lei, Xianqi; Li, Congling; Shi, Xinghua; Xu, Xianghong; Wei, Yujie

    2015-01-01

    It is generally observed that the existence of geometrical discontinuity like notches in materials will lead to strength weakening, as a resultant of local stress concentration. By comparing the influence of notches to the strength of three typical materials, aluminum alloys with intermediate tensile ductility, metallic glasses with no tensile ductility, and brittle ceramics, we observed strengthening in aluminum alloys and metallic glasses: Tensile strength of the net section in circumferentially notched cylinders increases with the constraint quantified by the ratio of notch depth over notch root radius; in contrast, the ceramic exhibit notch weakening. The strengthening in the former two is due to resultant deformation transition: Shear failure occurs in intact samples while samples with deep notches break in normal mode fracture. No such deformation transition was observed in the ceramic, and stress concentration leads to its notch weakening. The experimental results are confirmed by theoretical analyses and numerical simulation. The results reported here suggest that the conventional criterion to use brittleness and/or ductility to differentiate notch strengthening or weakening is not physically sound. Notch strengthening or weakening relies on the existence of failure mode transition and materials exhibiting shear failure while subjected to tension will notch strengthen. PMID:26022892

  5. Notch strengthening or weakening governed by transition of shear failure to normal mode fracture.

    PubMed

    Lei, Xianqi; Li, Congling; Shi, Xinghua; Xu, Xianghong; Wei, Yujie

    2015-05-29

    It is generally observed that the existence of geometrical discontinuity like notches in materials will lead to strength weakening, as a resultant of local stress concentration. By comparing the influence of notches to the strength of three typical materials, aluminum alloys with intermediate tensile ductility, metallic glasses with no tensile ductility, and brittle ceramics, we observed strengthening in aluminum alloys and metallic glasses: Tensile strength of the net section in circumferentially notched cylinders increases with the constraint quantified by the ratio of notch depth over notch root radius; in contrast, the ceramic exhibit notch weakening. The strengthening in the former two is due to resultant deformation transition: Shear failure occurs in intact samples while samples with deep notches break in normal mode fracture. No such deformation transition was observed in the ceramic, and stress concentration leads to its notch weakening. The experimental results are confirmed by theoretical analyses and numerical simulation. The results reported here suggest that the conventional criterion to use brittleness and/or ductility to differentiate notch strengthening or weakening is not physically sound. Notch strengthening or weakening relies on the existence of failure mode transition and materials exhibiting shear failure while subjected to tension will notch strengthen.

  6. Fatigue Failure Modes of the Grain Size Transition Zone in a Dual Microstructure Disk

    NASA Technical Reports Server (NTRS)

    Gabb, Timothy P.; Kantzos, Pete T.; Palsa, Bonnie; Telesman, Jack; Gayda, John; Sudbrack, Chantal K.

    2012-01-01

    Mechanical property requirements vary with location in nickel-based superalloy disks. In order to maximize the associated mechanical properties, heat treatment methods have been developed for producing tailored grain microstructures. In this study, fatigue failure modes of a grain size transition zone in a dual microstructure disk were evaluated. A specialized heat treatment method was applied to produce varying grain microstructure in the bore to rim portions of a powder metallurgy processed nickel-based superalloy disk. The transition in grain size was concentrated in a zone of the disk web, between the bore and rim. Specimens were extracted parallel and transversely across this transition zone, and multiple fatigue tests were performed at 427 C and 704 C. Grain size distributions were characterized in the specimens, and related to operative failure initiation modes. Mean fatigue life decreased with increasing maximum grain size, going out through the transition zone. The scatter in limited tests of replicates was comparable for failures of uniform gage specimens in all transition zone locations examined.

  7. Failure analysis of laminated composites by using iterative three-dimensional finite element method

    NASA Astrophysics Data System (ADS)

    Hwang, W. C.; Sun, C. T.

    1989-05-01

    A failure analysis of laminated composites is accomplished by using an iterative three-dimensional finite element method. Based on Tsai-Wu failure theory, three different modes of failure are proposed: fiber breakage, matrix cracking, and delamination. The first ply failure load is then evaluated. As the applied load exceeds the first ply failure load, localized structural failure occurs and the global structural stiffness should change. The global stiffness matrix is modified by taking nonlinearity due to partial failures within a laminate into consideration. The first ply failure load is analyzed by using a iterative mixed field method in solving the linear part of the finite element equations. The progressive failure problem is solved numerically by using Newton-Raphson iterative schemes for the solution of nonlinear finite element equations. Numerical examples include angle-ply symmetric Thornel 300 graphite/934 resin epoxy laminates under uniaxial tension. First ply failure loads as well as the final failure loads are evaluated. Good correlation between analytical results and experimental data are observed. Numerical results also include the investigation of composite specimens with a centered hole, under uniaxial tension. Excellent correlation with the experimental data is observed.

  8. Common-Cause Failure Analysis in Event Assessment

    SciTech Connect

    D. M. Rasmuson; D. L. Kelly

    2008-06-01

    This paper reviews the basic concepts of modelling common-cause failures (CCFs) in reliability and risk studies and then applies these concepts to the treatment of CCF in event assessment. The cases of a failed component (with and without shared CCF potential) and a component being unavailable due to preventive maintenance or testing are addressed. The treatment of two related failure modes (e.g. failure to start and failure to run) is a new feature of this paper, as is the treatment of asymmetry within a common-cause component group.

  9. Effects of Fusion Zone Size on Failure Modes and Performance of Advanced High Strength Steel Spot Welds (2006-01-0531)

    SciTech Connect

    Sun, Xin; Stephens, Elizabeth V.; Khaleel, Mohammad A.

    2007-03-01

    This paper examines the effects of fusion zone size on failure modes, static strength and energy absorption of resistance spot welds (RSW) of advanced high strength steels (AHSS). DP800 and TRIP800 spot welds are considered. The main failure modes for spot welds are nugget pullout and interfacial fracture. Partial interfacial fracture is also observed. The critical fusion zone sizes to ensure nugget pull-out failure mode are developed for both DP800 and TRIP800 using the limit load based analytical model and the micro-hardness measurements of the weld cross sections. Static weld strength tests using cross tension samples were performed on the joint populations with controlled fusion zone sizes. The resulted peak load and energy absorption levels associated with each failure mode were studied using statistical data analysis tools. The results in this study show that the conventional weld size of 4 t1/2 can not produce nugget pullout mode for both the DP800 and TRIP800 materials. The results also suggest that performance based spot weld acceptance criteria should be developed for different AHSS spot welds.

  10. Effects of Fusion Zone Size and Failure Mode on Peak Load and Energy Absorption of Advanced High Strength Steel Spot Welds

    SciTech Connect

    Sun, Xin; Stephens, Elizabeth V.; Khaleel, Mohammad A.

    2007-01-01

    This paper examines the effects of fusion zone size on failure modes, static strength and energy absorption of resistance spot welds (RSW) of advanced high strength steels (AHSS). DP800 and TRIP800 spot welds are considered. The main failure modes for spot welds are nugget pullout and interfacial fracture. Partial interfacial fracture is also observed. The critical fusion zone sizes to ensure nugget pull-out failure mode are developed for both DP800 and TRIP800 using limit load based analytical model and micro-hardness measurements of the weld cross sections. Static weld strength tests using cross tension samples were performed on the joint populations with controlled fusion zone sizes. The resulted peak load and energy absorption levels associated with each failure mode were studied for all the weld populations using statistical data analysis tools. The results in this study show that AHSS spot welds with fusion zone size of can not produce nugget pullout mode for both the DP800 and TRIP800 materials examined. The critical fusion zone size for nugget pullout shall be derived for individual materials based on different base metal properties as well as different heat affected zone (HAZ) and weld properties resulted from different welding parameters.

  11. Mechanical failure modes of chronically implanted planar silicon-based neural probes for laminar recording.

    PubMed

    Kozai, Takashi D Y; Catt, Kasey; Li, Xia; Gugel, Zhannetta V; Olafsson, Valur T; Vazquez, Alberto L; Cui, X Tracy

    2015-01-01

    Penetrating intracortical electrode arrays that record brain activity longitudinally are powerful tools for basic neuroscience research and emerging clinical applications. However, regardless of the technology used, signals recorded by these electrodes degrade over time. The failure mechanisms of these electrodes are understood to be a complex combination of the biological reactive tissue response and material failure of the device over time. While mechanical mismatch between the brain tissue and implanted neural electrodes have been studied as a source of chronic inflammation and performance degradation, the electrode failure caused by mechanical mismatch between different material properties and different structural components within a device have remained poorly characterized. Using Finite Element Model (FEM) we simulate the mechanical strain on a planar silicon electrode. The results presented here demonstrate that mechanical mismatch between iridium and silicon leads to concentrated strain along the border of the two materials. This strain is further focused on small protrusions such as the electrical traces in planar silicon electrodes. These findings are confirmed with chronic in vivo data (133-189 days) in mice by correlating a combination of single-unit electrophysiology, evoked multi-unit recordings, electrochemical impedance spectroscopy, and scanning electron microscopy from traces and electrode sites with our modeling data. Several modes of mechanical failure of chronically implanted planar silicon electrodes are found that result in degradation and/or loss of recording. These findings highlight the importance of strains and material properties of various subcomponents within an electrode array.

  12. Mechanical failure modes of chronically implanted planar silicon-based neural probes for laminar recording

    PubMed Central

    Kozai, Takashi D. Y.; Catt, Kasey; Li, Xia; Gugel, Zhannetta V.; Olafsson, Valur T.; Vazquez, Alberto L.; Cui, X. Tracy

    2014-01-01

    Penetrating intracortical electrode arrays that record brain activity longitudinally are powerful tools for basic neuroscience research and emerging clinical applications. However, regardless of the technology used, signals recorded by these electrodes degrade over time. The failure mechanisms of these electrodes are understood to be a complex combination of the biological reactive tissue response and material failure of the device over time. While mechanical mismatch between the brain tissue and implanted neural electrodes have been studied as a source of chronic inflammation and performance degradation, the electrode failure caused by mechanical mismatch between different material properties and different structural components within a device have remained poorly characterized. Using Finite Element Model (FEM) we simulate the mechanical strain on a planar silicon electrode. The results presented here demonstrate that mechanical mismatch between iridium and silicon leads to concentrated strain along the border of the two materials. This strain is further focused on small protrusions such as the electrical traces in planar silicon electrodes. These findings are confirmed with chronic in vivo data (133–189 days) in mice by correlating a combination of single-unit electrophysiology, evoked multi-unit recordings, electrochemical impedance spectroscopy, and scanning electron microscopy from traces and electrode sites with our modeling data. Several modes of mechanical failure of chronically implanted planar silicon electrodes are found that result in degradation and/or loss of recording. These findings highlight the importance of strains and material properties of various subcomponents within an electrode array. PMID:25453935

  13. Modes of deformation and failure of Kevlar 49 fibers and composites

    SciTech Connect

    Pruneda, C.O.; Morgan, R.J.; Kong, F.M.; Hodson, J.A.; Kershaw, R.P.; Casey, A.W.

    1983-12-05

    Fracture-topography and stress-optical-microscopy are utilized to study the deformation and failure modes of Kevlar 49 fibers and their epoxy composites. Fracture topographies of bare yarns, composite strands, and pressure vessels reveal Kevlar 49 fibers fail in tension by axially splitting 20 to 50 times their diameter D (20 to 50D) along their lengths. This type of fiber failure involves shear-induced microvoid growth throughout the fiber which occurs principally along the fiber axis, followed by macroscopic crack propagation through such microscopic crack propagation through such microvoids. Fiber splitting in the fracture of single filaments is < 5D because of the absence of external shear stresses. The topographies observed in fractured single filaments are described in terms of longitudinal and transverse fiber crack propagation paths in the fiber skin and core. Hydrolytically-degraded Kevlar 49 fibers exhibit lower fiber split lengths in composites. There is a correlation between the percentage of fibers that exhibit transverse failure without splitting and the composite strength. Stress-optical-microscopy studies of the deformation and failure processes of simple composite laminates are reported as a function of laminate geometry, temperature, and fiber surface treatment.

  14. Analysis of the STS-126 Flow Control Valve Structural-Acoustic Coupling Failure

    NASA Technical Reports Server (NTRS)

    Jones, Trevor M.; Larko, Jeffrey M.; McNelis, Mark E.

    2010-01-01

    During the Space Transportation System mission STS-126, one of the main engine's flow control valves incurred an unexpected failure. A section of the valve broke off during liftoff. It is theorized that an acoustic mode of the flowing fuel, coupled with a structural mode of the valve, causing a high cycle fatigue failure. This report documents the analysis efforts conducted in an attempt to verify this theory. Hand calculations, computational fluid dynamics, and finite element methods are all implemented and analyses are performed using steady-state methods in addition to transient analysis methods. The conclusion of the analyses is that there is a critical acoustic mode that aligns with a structural mode of the valve

  15. Predicting the occurrence of mixed mode failure associated with hydraulic fracturing, part 2 water saturated tests

    SciTech Connect

    Bauer, Stephen J.; Broome, Scott Thomas; Choens, Charles; Barrow, Perry Carl

    2015-09-14

    Seven water-saturated triaxial extension experiments were conducted on four sedimentary rocks. This experimental condition was hypothesized more representative of that existing for downhole hydrofracture and thus it may improve our understanding of the phenomena. In all tests the pore pressure was 10 MPa and confirming pressure was adjusted to achieve tensile and transitional failure mode conditions. Using previous work in this LDRD for comparison, the law of effective stress is demonstrated in extension using this sample geometry. In three of the four lithologies, no apparent chemo-mechanical effect of water is apparent, and in the fourth lithology test results indicate some chemo-mechanical effect of water.

  16. Failure Analysis of a Complex Learning Framework Incorporating Multi-Modal and Semi-Supervised Learning

    SciTech Connect

    Pullum, Laura L; Symons, Christopher T

    2011-01-01

    Machine learning is used in many applications, from machine vision to speech recognition to decision support systems, and is used to test applications. However, though much has been done to evaluate the performance of machine learning algorithms, little has been done to verify the algorithms or examine their failure modes. Moreover, complex learning frameworks often require stepping beyond black box evaluation to distinguish between errors based on natural limits on learning and errors that arise from mistakes in implementation. We present a conceptual architecture, failure model and taxonomy, and failure modes and effects analysis (FMEA) of a semi-supervised, multi-modal learning system, and provide specific examples from its use in a radiological analysis assistant system. The goal of the research described in this paper is to provide a foundation from which dependability analysis of systems using semi-supervised, multi-modal learning can be conducted. The methods presented provide a first step towards that overall goal.

  17. X-Ray Computed Tomography for Failure Analysis Investigations

    DTIC Science & Technology

    1993-05-01

    AD-A268 086 WL-TR-93-4047 X - RAY COMPUTED TOMOGRAPHY FOR FAILURE ANALYSIS INVESTIGATIONS Richard H. Bossi William Shepherd Boeing Defense & Space... X - Ray Computed Tomography for Failure Analysis Investigations PE: 63112F PR: 3153 6. AUTilOR(S) TA: 00 Richard H. Bossi and William Shepherd WU: 06 7...feature detection and three-dimensional positioning capability of X - ray computed tomography are valuable and cost saving assets to a failure analysis

  18. 14 CFR 417.224 - Probability of failure analysis.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 4 2010-01-01 2010-01-01 false Probability of failure analysis. 417.224..., DEPARTMENT OF TRANSPORTATION LICENSING LAUNCH SAFETY Flight Safety Analysis § 417.224 Probability of failure analysis. (a) General. All flight safety analyses for a launch, regardless of hazard or phase of...

  19. Failure modes and fracture origins of porcelain veneers on bilayer dental crowns.

    PubMed

    Liu, Yihong; Liu, Guanghua; Wang, Yong; Shen, James Zhijian; Feng, Hailan

    2014-01-01

    The aims of this study were to determine the fracture origins and crack paths in the porcelain of clinically failed bilayer ceramic restorations and to reveal the correlation between the porcelain failures and material properties. Three clinically failed crowns of each material (bilayer zirconia crowns, galvano-ceramic crowns, and porcelain-fused-to-metal crowns) were collected and underwent failure analysis. The fractures found in porcelain veneers showed several characteristics including wear, Hertzian cone crack, chipping off, and delamination. The results indicated that the fracture origins and features of the porcelain in bilayer ceramic restorations might be affected by the rigidity of core materials and thickness of copings.

  20. Interactive multi-mode blade impact analysis

    NASA Technical Reports Server (NTRS)

    Alexander, A.; Cornell, R. W.

    1978-01-01

    The theoretical methodology used in developing an analysis for the response of turbine engine fan blades subjected to soft-body (bird) impacts is reported, and the computer program developed using this methodology as its basis is described. This computer program is an outgrowth of two programs that were previously developed for the purpose of studying problems of a similar nature (a 3-mode beam impact analysis and a multi-mode beam impact analysis). The present program utilizes an improved missile model that is interactively coupled with blade motion which is more consistent with actual observations. It takes into account local deformation at the impact area, blade camber effects, and the spreading of the impacted missile mass on the blade surface. In addition, it accommodates plate-type mode shapes. The analysis capability in this computer program represents a significant improvement in the development of the methodology for evaluating potential fan blade materials and designs with regard to foreign object impact resistance.

  1. Dynamic Response and Dynamic Failure Mode of a Weak Intercalated Rock Slope Using a Shaking Table

    NASA Astrophysics Data System (ADS)

    Fan, Gang; Zhang, Jianjing; Wu, Jinbiao; Yan, Kongming

    2016-08-01

    A large-scale shaking table test was performed to study the dynamic response of slopes parallel to geological bedding (bedding slopes) and slopes that cross-cut geological bedding (counter-bedding slopes). The test results show that the acceleration amplification coefficients increase with increasing elevation and, when the input earthquake amplitude is greater than 0.3 g, both bedding and counter-bedding slopes begin to show nonlinear dynamic response characteristics. With increasing elevation, the displacement of the bedding slope surface increases greatly. Conversely, the displacement of the counter-bedding slope surface increases first and then decreases; the slope develops a bulge at the relative elevation of 0.85. The displacement of the bedding slope surface is greater than that of the counter-bedding slope. The counter-bedding slope is more seismically stable compared with the bedding slope. Based on the Hilbert-Huang transform and marginal spectrum theories, the processes that develop dynamic damage of the bedding and counter-bedding slopes are identified. It is shown that the dynamic failure mode of the bedding slope is mainly represented by vertical tensile cracks at the rear of the slope, bedding slide of the strata along the weak intercalation, and rock collapse from the slope crest. However, the dynamic failure mode of the counter-bedding slope is mainly represented by staggered horizontal and vertical fissures, extrusion of the weak intercalation, and breakage at the slope crest.

  2. Factors influencing survival and mode of death in severe chronic ischaemic cardiac failure.

    PubMed Central

    Glover, D R; Littler, W A

    1987-01-01

    An evaluation of factors which may influence survival and mode of death was conducted over a three year period in a consecutive series of 50 patients with severe chronic ischaemic cardiac failure for more than three months. At the initial assessment all patients were already receiving intensive medical treatment. During follow up four patients successfully underwent cardiac surgery and medical treatment was modified in most patients, with four patients receiving antiarrhythmic drugs. Twenty six patients died: 17 suddenly within one hour of onset of symptoms and nine of progressive cardiac failure. The mortality by one year was 26% and by two years it was 62%. Comparison of those who survived with those who died within one year of follow up showed that a very low left ventricular ejection fraction, severe ventricular arrhythmias, the presence of gallop rhythm, and New York Heart Association class IV were the variables that predicted mortality. By two years left ventricular ejection fraction, ventricular arrhythmias, and pulmonary capillary wedge pressure were the variables that were significantly different in survivors and patients who died. No differences were found in any of the recorded variables between those who died suddenly and those who did not. Thus in patients with chronic ischaemic cardiac failure determination of the left ventricular ejection fraction and the severity of ventricular arrhythmia on the ambulatory electrocardiogram are the best ways to predict prognosis. The presence of gallop rhythm and New York Heart Association class IV status predict early death. PMID:3814447

  3. Analysis for the Progressive Failure Response of Textile Composite Fuselage Frames

    NASA Technical Reports Server (NTRS)

    Johnson, Eric R.; Boitnott, Richard L. (Technical Monitor)

    2002-01-01

    A part of aviation accident mitigation is a crash worthy airframe structure, and an important measure of merit for a crash worthy structure is the amount of kinetic energy that can be absorbed in the crush of the structure. Prediction of the energy absorbed from finite element analyses requires modeling the progressive failure sequence. Progressive failure modes may include material degradation, fracture and crack growth, and buckling and collapse. The design of crash worthy airframe components will benefit from progressive failure analyses that have been validated by tests. The subject of this research is the development of a progressive failure analysis for textile composite. circumferential fuselage frames subjected to a quasi-static, crash-type load. The test data for these frames are reported, and these data, along with stub column test data, are to be used to develop and to validate methods for the progressive failure response.

  4. Analysis for the Progressive Failure Response of Textile Composite Fuselage Frames

    NASA Technical Reports Server (NTRS)

    Johnson, Eric R.; Boitnott, Richard L. (Technical Monitor)

    2002-01-01

    A part of aviation accident mitigation is a crashworthy airframe structure, and an important measure of merit for a crashworthy structure is the amount of kinetic energy that can be absorbed in the crush of the structure. Prediction of the energy absorbed from finite element analyses requires modeling the progressive failure sequence. Progressive failure modes may include material degradation, fracture and crack growth, and buckling and collapse. The design of crashworthy airframe components will benefit from progressive failure analyses that have been validated by tests. The subject of this research is the development of a progressive failure analysis for a textile composite, circumferential fuselage frame subjected to a quasi-static, crash-type load. The test data for the frame are reported, and these data are used to develop and to validate methods for the progressive failure response.

  5. SU-E-T-179: Clinical Impact of IMRT Failure Modes at Or Near TG-142 Tolerance Criteria Levels

    SciTech Connect

    Faught, J Tonigan; Balter, P; Johnson, J; Kry, S; Court, L; Stingo, F; Followill, D

    2015-06-15

    Purpose: Quantitatively assess the clinical impact of 11 critical IMRT dose delivery failure modes. Methods: Eleven step-and-shoot IMRT failure modes (FMs) were introduced into twelve Pinnacle v9.8 treatment plans. One standard and one highly modulated plan on the IROC IMRT phantom and ten previous H&N patient treatment plans were used. FMs included physics components covered by basic QA near tolerance criteria levels (TG-142) such as beam energy, MLC positioning, and MLC modeling. Resultant DVHs were compared to those of failure-free plans and the severity of plan degradation was assessed considering PTV coverage and OAR and normal tissue tolerances and used for FMEA severity scoring. Six of these FMs were physically simulated and phantom irradiations performed. TLD and radiochromic film results are used for comparison to treatment planning studies. Results: Based on treatment planning studies, the largest clinical impact from the phantom cases was induced by 2 mm systematic MLC shift in one bank with the combination of a D95% target under dose near 16% and OAR overdose near 8%. Cord overdoses of 5%–11% occurred with gantry angle, collimator angle, couch angle, MLC leaf end modeling, and MLC transmission and leakage modeling FMs. PTV coverage and/or OAR sparing was compromised in all FMs introduced in phantom plans with the exception of CT number to electron density tables, MU linearity, and MLC tongue-and-groove modeling. Physical measurements did not entirely agree with treatment planning results. For example, symmetry errors resulted in the largest physically measured discrepancies of up to 3% in the PTVs while a maximum of 0.5% deviation was seen in the treatment planning studies. Patient treatment plan study results are under analysis. Conclusion: Even in the simplistic anatomy of the IROC phantom, some basic physics FMs, just outside of TG-142 tolerance criteria, appear to have the potential for large clinical implications.

  6. Extensive risk analysis of mechanical failure for an epiphyseal hip prothesis: a combined numerical-experimental approach.

    PubMed

    Martelli, S; Taddei, F; Cristofolini, L; Gill, H S; Viceconti, M

    2011-02-01

    There has been recent renewed interest in proximal femur epiphyseal replacement as an alternative to conventional total hip replacement. In many branches of engineering, risk analysis has proved to be an efficient tool for avoiding premature failures of innovative devices. An extensive risk analysis procedure has been developed for epiphyseal hip prostheses and the predictions of this method have been compared to the known clinical outcomes of a well-established contemporary design, namely hip resurfacing devices. Clinical scenarios leading to revision (i.e. loosening, neck fracture and failure of the prosthetic component) were associated with potential failure modes (i.e. overload, fatigue, wear, fibrotic tissue differentiation and bone remodelling). Driving parameters of the corresponding failure mode were identified together with their safe thresholds. For each failure mode, a failure criterion was identified and studied under the most relevant physiological loading conditions. All failure modes were investigated with the most suitable investigation tool, either numerical or experimental. Results showed a low risk for each failure scenario either in the immediate postoperative period or in the long term. These findings are in agreement with those reported by the majority of clinical studies for correctly implanted devices. Although further work is needed to confirm the predictions of this method, it was concluded that the proposed risk analysis procedure has the potential to increase the efficacy of preclinical validation protocols for new epiphyseal replacement devices.

  7. An assessment of BWR (boiling water reactor) Mark-II containment challenges, failure modes, and potential improvements in performance

    SciTech Connect

    Kelly, D.L.; Jones, K.R.; Dallman, R.J. ); Wagner, K.C. )

    1990-07-01

    This report assesses challenges to BWR Mark II containment integrity that could potentially arise from severe accidents. Also assessed are some potential improvements that could prevent core damage or containment failure, or could mitigate the consequences of such failure by reducing the release of fission products to the environment. These challenges and improvements are analyzed via a limited quantitative risk/benefit analysis of a generic BWR/4 reactor with Mark II containment. Point estimate frequencies of the dominant core damage sequences are obtained and simple containment event trees are constructed to evaluate the response of the containment to these severe accident sequences. The resulting containment release modes are then binned into source term release categories, which provide inputs to the consequence analysis. The output of the consequences analysis is used to construct an overall base case risk profile. Potential improvements and sensitivities are evaluated by modifying the event tree spilt fractions, thus generating a revised risk profile. Several important sensitivity cases are examined to evaluate the impact of phenomenological uncertainties on the final results. 75 refs., 25 figs., 65 tabs.

  8. Evaluation of shear bond strength of porcelain bonded to laser welded titanium surface and determination of mode of bond failure.

    PubMed

    Patil, Narendra P; Dandekar, Minal; Nadiger, Ramesh K; Guttal, Satyabodh S

    2010-09-01

    The aim of this study was to evaluate the shear bond strength of porcelain to laser welded titanium surface and to determine the mode of bond failure through scanning electron microscopy (SEM) and energy dispersive spectrophotometry (EDS). Forty five cast rectangular titanium specimens with the dimension of 10 mm x 8 mm x 1 mm were tested. Thirty specimens had a perforation of 2 mm diameter in the centre. These were randomly divided into Group A and B. The perforations in the Group B specimens were repaired by laser welding using Cp Grade II titanium wire. The remaining 15 specimens were taken as control group. All the test specimens were layered with low fusing porcelain and tested for shear bond strength. The debonded specimens were subjected to SEM and EDS. Data were analysed with 1-way analysis of variance and Student's t-test for comparison among the different groups. One-way analysis of variance (ANOVA) showed no statistically significant difference in shear bond strength values at a 5% level of confidence. The mean shear bond strength values for control group, Group A and B was 8.4 +/- 0.5 Mpa, 8.1 +/- 0.4 Mpa and 8.3 +/- 0.3 Mpa respectively. SEM/EDS analysis of the specimens showed mixed and cohesive type of bond failure. Within the limitations of the study laser welding did not have any effect on the shear bond strength of porcelain bonded to titanium.

  9. Ply-level failure analysis of a graphite/epoxy laminate under bearing-bypass loading

    NASA Technical Reports Server (NTRS)

    Naik, R. A.; Crews, J. H., Jr.

    1988-01-01

    A combined experimental and analytical study was conducted to investigate and predict the failure modes of a graphite/epoxy laminate subjected to combined bearing and bypass loading. Tests were conducted in a test machine that allowed the bearing-bypass load ratio to be controlled while a single-fastener coupon was loaded to failure in either tension or compression. Onset and ultimate failure modes and strengths were determined for each test case. The damage-onset modes were studied in detail by sectioning and micrographing the damaged specimens. A two-dimensional, finite-element analysis was conducted to determine lamina strains around the bolt hole. Damage onset consisted of matrix cracks, delamination, and fiber failures. Stiffness loss appeared to be caused by fiber failures rather than by matrix cracking and delamination. An unusual offset-compression mode was observed for compressive bearing-bypass laoding in which the specimen failed across its width along a line offset from the hole. The computed lamina strains in the fiber direction were used in a combined analytical and experimental approach to predict bearing-bypass diagrams for damage onset from a few simple tests.

  10. Ply-level failure analysis of a graphite/epoxy laminate under bearing-bypass loading

    NASA Technical Reports Server (NTRS)

    Naik, R. A.; Crews, J. H., Jr.

    1990-01-01

    A combined experimental and analytical study was conducted to investigate and predict the failure modes of a graphite/epoxy laminate subjected to combined bearing and bypass loading. Tests were conducted in a test machine that allowed the bearing-bypass load ratio to be controlled while a single-fastener coupon was loaded to failure in either tension or compression. Onset and ultimate failure modes and strengths were determined for each test case. The damage-onset modes were studied in detail by sectioning and micrographing the damaged specimens. A two-dimensional, finite-element analysis was conducted to determine lamina strains around the bolt hole. Damage onset consisted of matrix cracks, delamination, and fiber failures. Stiffness loss appeared to be caused by fiber failures rather than by matrix cracking and delamination. An unusual offset-compression mode was observed for compressive bearing-bypass loading in which the specimen failed across its width along a line offset from the hole. The computed lamina strains in the fiber direction were used in a combined analytical and experimental approach to predict bearing-bypass diagrams for damage onset from a few simple tests.

  11. Reliability Analysis of Systems Subject to First-Passage Failure

    NASA Technical Reports Server (NTRS)

    Lutes, Loren D.; Sarkani, Shahram

    2009-01-01

    An obvious goal of reliability analysis is the avoidance of system failure. However, it is generally recognized that it is often not feasible to design a practical or useful system for which failure is impossible. Thus it is necessary to use techniques that estimate the likelihood of failure based on modeling the uncertainty about such items as the demands on and capacities of various elements in the system. This usually involves the use of probability theory, and a design is considered acceptable if it has a sufficiently small probability of failure. This report contains findings of analyses of systems subject to first-passage failure.

  12. Analysis of failure and maintenance experiences of motor operated valves in a Finnish nuclear power plant

    NASA Astrophysics Data System (ADS)

    Simola, Kaisa; Laakso, Kari

    1992-01-01

    Eight years of operating experiences of 104 motor operated closing valves in different safety systems in nuclear power units were analyzed in a systematic way. The qualitative methods used were Failure Mode and Effect Analysis (FMEA) and Maintenance Effects and Criticality Analysis (MECA). These reliability engineering methods are commonly used in the design stage of equipment. The successful application of these methods for analysis and utilization of operating experiences was demonstrated.

  13. Reliability Measurement for Mixed Mode Failures of 33/11 Kilovolt Electric Power Distribution Stations

    PubMed Central

    Alwan, Faris M.; Baharum, Adam; Hassan, Geehan S.

    2013-01-01

    The reliability of the electrical distribution system is a contemporary research field due to diverse applications of electricity in everyday life and diverse industries. However a few research papers exist in literature. This paper proposes a methodology for assessing the reliability of 33/11 Kilovolt high-power stations based on average time between failures. The objective of this paper is to find the optimal fit for the failure data via time between failures. We determine the parameter estimation for all components of the station. We also estimate the reliability value of each component and the reliability value of the system as a whole. The best fitting distribution for the time between failures is a three parameter Dagum distribution with a scale parameter and shape parameters and . Our analysis reveals that the reliability value decreased by 38.2% in each 30 days. We believe that the current paper is the first to address this issue and its analysis. Thus, the results obtained in this research reflect its originality. We also suggest the practicality of using these results for power systems for both the maintenance of power systems models and preventive maintenance models. PMID:23936346

  14. Reliability measurement for mixed mode failures of 33/11 kilovolt electric power distribution stations.

    PubMed

    Alwan, Faris M; Baharum, Adam; Hassan, Geehan S

    2013-01-01

    The reliability of the electrical distribution system is a contemporary research field due to diverse applications of electricity in everyday life and diverse industries. However a few research papers exist in literature. This paper proposes a methodology for assessing the reliability of 33/11 Kilovolt high-power stations based on average time between failures. The objective of this paper is to find the optimal fit for the failure data via time between failures. We determine the parameter estimation for all components of the station. We also estimate the reliability value of each component and the reliability value of the system as a whole. The best fitting distribution for the time between failures is a three parameter Dagum distribution with a scale parameter [Formula: see text] and shape parameters [Formula: see text] and [Formula: see text]. Our analysis reveals that the reliability value decreased by 38.2% in each 30 days. We believe that the current paper is the first to address this issue and its analysis. Thus, the results obtained in this research reflect its originality. We also suggest the practicality of using these results for power systems for both the maintenance of power systems models and preventive maintenance models.

  15. Physicochemical characterization and failure analysis of military coating systems

    NASA Astrophysics Data System (ADS)

    Keene, Lionel Thomas

    Modern military coating systems, as fielded by all branches of the U.S. military, generally consist of a diverse array of organic and inorganic components that can complicate their physicochemical analysis. These coating systems consist of VOC-solvent/waterborne automotive grade polyurethane matrix containing a variety of inorganic pigments and flattening agents. The research presented here was designed to overcome the practical difficulties regarding the study of such systems through the combined application of several cross-disciplinary techniques, including vibrational spectroscopy, electron microscopy, microtomy, ultra-fast laser ablation and optical interferometry. The goal of this research has been to determine the degree and spatial progression of weathering-induced alteration of military coating systems as a whole, as well as to determine the failure modes involved, and characterizing the impact of these failures on the physical barrier performance of the coatings. Transmission-mode Fourier Transform Infrared (FTIR) spectroscopy has been applied to cross-sections of both baseline and artificially weathered samples to elucidate weathering-induced spatial gradients to the baseline chemistry of the coatings. A large discrepancy in physical durability (as indicated by the spatial progression of these gradients) has been found between older and newer generation coatings. Data will be shown implicating silica fillers (previously considered inert) as the probable cause for this behavioral divergence. A case study is presented wherein the application of the aforementioned FTIR technique fails to predict the durability of the coating system as a whole. The exploitation of the ultra-fast optical phenomenon of femtosecond (10-15S) laser ablation is studied as a potential tool to facilitate spectroscopic depth profiling of composite materials. Finally, the interferometric technique of Phase Shifting was evaluated as a potential high-sensitivity technique applied to the

  16. Dynamic mode decomposition analysis of detonation waves

    NASA Astrophysics Data System (ADS)

    Massa, L.; Kumar, R.; Ravindran, P.

    2012-06-01

    Dynamic mode decomposition is applied to study the self-excited fluctuations supported by transversely unstable detonations. The focus of this study is on the stability of the limit cycle solutions and their response to forcing. Floquet analysis of the unforced conditions reveals that the least stable perturbations are almost subharmonic with ratio between global mode and fundamental frequency λi/ωf = 0.47. This suggests the emergence of period doubling modes as the route to chaos observed in larger systems. The response to forcing is analyzed in terms of the coherency of the four fundamental energy modes: acoustic, entropic, kinetic, and chemical. Results of the modal decomposition suggest that the self-excited oscillations are quite insensitive to vortical forcing, and maintain their coherency up to a forcing turbulent Mach number of 0.3.

  17. Mechanical behavior and localized failure modes in a porous basalt from the Azores

    NASA Astrophysics Data System (ADS)

    Loaiza, S.; Fortin, J.; Schubnel, A.; Guéguen, Y.; Moreira, M.; Vinciguerra, S.

    2012-04-01

    Basaltic rocks are the main component of the oceanic upper crust. This is of potential interest for water and geothermal resources, or for storage of CO2. The aim of our work is to investigate experimentally the mechanical behavior and the failure modes of porous basalt as well as the permeability evolution during deformation. Cylindrical basalt samples, from the Azores, of 30 mm in diameter and 60 mm in length were deformed the triaxial cell of the Laboratoire de Geologie at the Ecole Normale Supérieure (Paris) at room temperature and at a constant axial strain rate of 10-5 s-1. The initial porosity of the sample was 18%. The Geodesign triaxial cell can reach 300MPa confining pressure; axial load is performed through a piston and can reach 900 MPa (for a 30mm diameter sample); maximum pore pressure is 100MPa (applied using two precision volumetric pumps). In our study, a set of experiments were performed at confining pressure in the range of 25-290 MPa. The samples were deformed under saturated conditions at a constant pore pressure of 5MPa. Two volumetric pumps kept the pore pressure constant, and the pore volume variations were recorded. The evolution of the porosity was calculated from the total volume variation inside the volumetric pumps. Permeability measurements were performed using the steady-state technique. Our result shows that two modes of deformation can be highlighted in this basalt. At low confining pressure (Pc < 50 MPa), the differential stress attains a peak before the sample undergoes strain softening; the failure of sample occurs by shear localization. Yet, the brittle regime is commonly observed in this low Pc range, the experiments performed at confining pressure higher than 50 MPa, show a totally different mode of deformation. In this second mode of deformation, an appreciable inelastic porosity reduction is observed. Comparing to the hydrostatic loading, the rock sample started to compact beyond a critical stress state; and from then

  18. Applying Systems Analysis to Program Failure in Organizations.

    ERIC Educational Resources Information Center

    Holt, Margaret E.; And Others

    1986-01-01

    Certain systems analysis techniques can be applied to examinations of program failure in continuing education to locate weaknesses in planning and implementing stages. Questions to guide an analysis and various procedures are recommended. Twelve issues that contribute to failures or discontinuations are identified. (Author/MLW)

  19. Micromechanics-Based Progressive Failure Analysis of Composite Laminates Using Different Constituent Failure Theories

    NASA Technical Reports Server (NTRS)

    Moncada, Albert M.; Chattopadhyay, Aditi; Bednarcyk, Brett A.; Arnold, Steven M.

    2008-01-01

    Predicting failure in a composite can be done with ply level mechanisms and/or micro level mechanisms. This paper uses the Generalized Method of Cells and High-Fidelity Generalized Method of Cells micromechanics theories, coupled with classical lamination theory, as implemented within NASA's Micromechanics Analysis Code with Generalized Method of Cells. The code is able to implement different failure theories on the level of both the fiber and the matrix constituents within a laminate. A comparison is made among maximum stress, maximum strain, Tsai-Hill, and Tsai-Wu failure theories. To verify the failure theories the Worldwide Failure Exercise (WWFE) experiments have been used. The WWFE is a comprehensive study that covers a wide range of polymer matrix composite laminates. The numerical results indicate good correlation with the experimental results for most of the composite layups, but also point to the need for more accurate resin damage progression models.

  20. Dilatancy, compaction, and failure mode in andesite: the transition from brittle faulting to shear-enhanced compaction in volcanic edifices

    NASA Astrophysics Data System (ADS)

    Heap, M. J.; Lavallee, Y.; David, E. C.; Petrakova, L.; Baud, P.; Dingwell, D. B.; Reuschle, T.

    2011-12-01

    Andesite is an extrusive volcanic rock of intermediate composition (i.e., SiO2 varies between 52-63%). Andesitic volcanoes, typical of convergent plate margin settings, represent about 25% of volcanoes worldwide. However, our understanding of the physical and mechanical properties of andesites, important for volcanic hazard mitigation, remains sparse. We have therefore embarked on a systematic study on the mechanical properties of a suite of andesites collected from Volcán de Colima, one of the most active volcanoes on the Trans-Mexican volcanic belt, Mexico. Our andesite samples (ranging from 8 to 18% porosity) had high initial crack densities (as inferred from both a newly-devised sliding crack model and from more traditional stereological techniques), corroborated by low ultrasonic wave velocities (P-wave velocities were about 2.5 km/s for all samples). Bulk geochemical analysis showed that all samples were compositionally identical. Compressive strength experiments, performed at room temperature and under a constant strain rate of 10-5 s-1, were performed under a range of effective confining pressures (representative of those within a volcanic edifice). When rock is exposed to an applied differential stress, it can react in two different ways. The void space (a combination of cracks and pores) within the rock can either demonstrate net dilatation or net compaction. The resultant behaviour of the rock is governed by the competition between micromechanical processes, namely dilatational microcracking versus grain crushing and pore collapse. The potency of these competing processes is dependent on both the initial physical properties of the rock, such as porosity and grain size, and the conditions under which the rock deforms. In our experiments, all of the andesites displayed dilatancy and/or dilatant modes of failure, either axial splitting (restricted to the uniaxial experiments) or shear faulting at low effective confining pressures. Under uniaxial conditions

  1. Failure Analysis of a Pilot Scale Melter

    SciTech Connect

    Imrich, K J

    2001-09-14

    Failure of the pilot-scale test melter resulted from severe overheating of the Inconel 690 jacketed molybdenum electrode. Extreme temperatures were required to melt the glass during this campaign because the feed material contained a very high waste loading.

  2. Failure Behavior Characterization of Mo-Modified Ti Surface by Impact Test and Finite Element Analysis

    NASA Astrophysics Data System (ADS)

    Ma, Yong; Qin, Jianfeng; Zhang, Xiangyu; Lin, Naiming; Huang, Xiaobo; Tang, Bin

    2015-07-01

    Using the impact test and finite element simulation, the failure behavior of the Mo-modified layer on pure Ti was investigated. In the impact test, four loads of 100, 300, 500, and 700 N and 104 impacts were adopted. The three-dimensional residual impact dents were examined using an optical microscope (Olympus-DSX500i), indicating that the impact resistance of the Ti surface was improved. Two failure modes cohesive and wearing were elucidated by electron backscatter diffraction and energy-dispersive spectrometer performed in a field-emission scanning electron microscope. Through finite element forward analysis performed at a typical impact load of 300 N, stress-strain distributions in the Mo-modified Ti were quantitatively determined. In addition, the failure behavior of the Mo-modified layer was determined and an ideal failure model was proposed for high-load impact, based on the experimental and finite element forward analysis results.

  3. Reliability Estimation and Failure Analysis of Multilayer Ceramic Chip Capacitors

    NASA Astrophysics Data System (ADS)

    Yang, Seok Jun; Kim, Jin Woo; Ryu, Dong Su; Kim, Myung Soo; Jang, Joong Soon

    This paper presents the failure analysis and the reliability estimation of a multilayer ceramic chip capacitor. For the failed samples used in an automobile engine control unit, failure analysis was made to identify the root cause of failure and it was shown that the migration and the avalanche breakdown were the dominant failure mechanisms. Next, an accelerated life testing was designed to estimate the life of the MLCC. It is assumed that Weibull lifetime distribution and the life-stress relationship proposed Prokopowicz and Vaskas. The life-stress relationship and the acceleration factor are estimated by analyzing the accelerated life test data.

  4. Analysis of the causes of pump failure and differences of failure characteristics.

    PubMed

    Korving, H; Ottenhoff, E C; Korving, H

    2008-01-01

    It is generally accepted that sewage pumping stations are directly responsible for affecting sewer system performance in terms of combined sewer overflows and flooding. However, the specific causes of pump failure are unknown. This paper presents the analysis of pump failure data provided by four sewer management authorities in The Netherlands. Pump failures have been studied accounting for the nature of failures, operation and maintenance procedures of the management authority, ageing of the pumps and changes in the environment of pumps. Pumps have been clustered on the basis of specific characteristics of their 'environment', including pump age, operating time, pump capacity and degree of pollution of the sewage. The analysis shows that the well known 'bathtub' type failure rate curve can describe failures of sewage pumps. The impact of the degree of pollution of the sewage, however, is less clear. Operating time and total pumping capacity show no correlation with failure rate. Consequently, further research using data mining techniques is needed to separate the impact of the different aspects of the environment of a pump.

  5. Failure Mode Classification for Life Prediction Modeling of Solid-State Lighting

    SciTech Connect

    Sakalaukus, Peter Joseph

    2015-08-01

    Since the passing of the Energy Independence and Security Act of 2007, the U.S. government has mandated greater energy independence which has acted as a catalyst for accelerating and facilitating research efforts toward the development and deployment of market-driven solutions for energy-saving homes, buildings and manufacturing, as well as sustainable transportation and renewable electricity generation. As part of this effort, an emphasis toward advancing solid-state lighting technology through research, development, demonstration, and commercial applications is assisting in the phase out of the common incandescent light bulb, as well as developing a more economical lighting source that is less toxic than compact fluorescent lighting. This has led lighting manufacturers to pursue SSL technologies for a wide range of consumer lighting applications. An SSL luminaire’s lifetime can be characterized in terms of lumen maintenance life. Lumen maintenance or lumen depreciation is the percentage decrease in the relative luminous flux from that of the original, pristine luminous flux value. Lumen maintenance life is the estimated operating time, in hours, when the desired failure threshold is projected to be reached at normal operating conditions. One accepted failure threshold of SSL luminaires is lumen maintenance of 70% -- a 30% reduction in the light output of the luminaire. Currently, the only approved lighting standard that puts forth a recommendation for long-term luminous flux maintenance projections towards a specified failure threshold of an SSL luminaire is the IES TM-28-14 (TM28) standard. iii TM28 was derived as a means to compare luminaires that have been tested at different facilities, research labs or companies. TM28 recommends the use of the Arrhenius equation to determine SSL device specific reaction rates from thermally driven failure mechanisms used to characterize a single failure mode – the relative change in the luminous flux output or

  6. The characterization of Mode I delamination failure in non-woven, multidirectional laminates

    NASA Technical Reports Server (NTRS)

    Chai, H.

    1984-01-01

    The uniform double cantilever beam test and SEM are presently used for the characterization of Mode I delamination behavior in fiber-reinforced epoxy laminates. Delamination failure assumes forms that depend on ply orientation, test specimen geometry, and matrix toughness, but the calculated fracture energy is noted to be heavily dependent on fracture surface morphology. A material property concept that is independent of both test specimen geometry and the orientation of the plies constituting the delaminating interface is elucidated, through the definition of interlaminar fracture solely in terms of an interlaminar separation that includes no fiber breakage or pull-out. This value, which dissipates the lowest possible amount of energy during crack growth, is the controlling factor for laminate toughness.

  7. Comparison of Failure Modes in 2-D and 3-D Woven Carbon Phenolic Systems

    NASA Technical Reports Server (NTRS)

    Rossman, Grant A.; Stackpoole, Mairead; Feldman, Jay; Venkatapathy, Ethiraj; Braun, Robert D.

    2013-01-01

    NASA Ames Research Center is developing Woven Thermal Protection System (WTPS) materials as a new class of heatshields for entry vehicles (Stackpoole). Currently, there are few options for ablative entry heatshield materials, none of which is ideally suited to the planetary probe missions currently of interest to NASA. While carbon phenolic was successfully used for the missions Pioneer Venus and Galileo (to Jupiter), the heritage constituents are no longer available. An alternate carbon phenolic would need to be qualified for probe missions, which is most efficient at heat fluxes greater than those currently of interest. Additional TPS materials such as Avcoat and PICA are not sufficiently robust for the heat fluxes required. As a result, there is a large TPS gap between the materials efficient at very high conditions (carbon phenolic) and those that are effective at low-moderate conditions (all others). Development of 3D Woven TPS is intended to fill this gap, targeting mid-density weaves that could with withstand mid-range heat fluxes between 1100 W/sq cm and 8000 W/sq cm (Venkatapathy (2012). Preliminary experimental studies have been performed to show the feasibility of WTPS as a future mid-range TPS material. One study performed in the mARC Jet Facility at NASA Ames Research Center characterized the performance of a 3D Woven TPS sample and compared it to 2D carbon phenolic samples at ply angles of 0deg, 23.5deg, and 90deg. Each sample contained similar compositions of phenolic and carbon fiber volume fractions for experimental consistency. The goal of this study was to compare the performance of the TPS materials by evaluating resulting recession and failure modes. After exposing both samples to similar heat flux and pressure conditions, the 2D carbon phenolic laminate was shown to experience significant delamination between layers and further pocketing underneath separated layers. The 3D Woven TPS sample did not experience the delamination or pocketing

  8. Failure analysis of explanted sternal wires.

    PubMed

    Shih, Chun-Ming; Su, Yea-Yang; Lin, Shing-Jong; Shih, Chun-Che

    2005-05-01

    To classify and understand the mechanisms of surface damages and fracture mechanisms of sternal wires, explanted stainless steel sternal wires were collected from patients with sternal dehiscence following open-heart surgery. Surface alterations and fractured ends of sternal wires were examined and analyzed. Eighty fractured wires extracted from 25 patients from January 1999 to December 2003, with mean implantation interval of 55+/-149 days (range 5-729 days) after cardiac surgery, were studied by various techniques. The extracted wires were cleaned and the fibrotic tissues were removed. Irregularities and fractured ends were assayed by a scanning electron microscopy. After stereomicroscopy and documentation, the explants were cleaned with 1% sodium hypochlorite to remove the blood and tissues and was followed by cleaned with deionized water and alcohol. The explants were examined by stereomicroscopy, and irregularities on surface and fracture surfaces of sternal wires were assayed by scanning electron microscopy, energy dispersive X-ray analysis (EDAX) and X-ray mapping. The explants with surrounding fibrotic tissue were stained and examined with stereomicroscopy and transmission electronic microscopy. Corrosion pits were found on the surface of explanted sternal wires. EDAX and X-ray mapping examinations revealed diminution of nickel concentration in the severely corroded pits on sternal wires. A feature of transgranular cracking was observed for stress corrosion cracking and striation character for typical corrosion fatigue was also identified. TEM examination of tissue showed the metallic particles in phagolysosomes of macrophages inside the surrounding sternal tissue. The synergic effect of hostile environment and the stress could be the precursors of failures for sternal wires.

  9. [Failure mechanisms in the transfusion process. Importance of anticipatory operational safety analysis].

    PubMed

    Hergon, E; Crespeau, H; Rouger, P

    1994-01-01

    The methods used for the safety previsional analysis of operations represent an interesting set of tools to follow the so-called transfusion process, defined as all the steps from donors sensitization to recipients follow-up. FMECA (Failure Mode Effects and Criticality Analysis) can be used as a prevention tool, independently of any dysfunction in the process. Of course, it can also be used following a failure, in order to analyse its causes and to apply specific corrections. Operation safety, quality insurance, epidemiologic surveillance and safety monitoring act in synergy. These three aspects of transfusion safety constitute a dynamic system.

  10. Predictions and Experimental Microstructural Characterization of High Strain Rate Failure Modes in Layered Aluminum Composites

    NASA Astrophysics Data System (ADS)

    Khanikar, Prasenjit

    Different aluminum alloys can be combined, as composites, for tailored dynamic applications. Most investigations pertaining to metallic alloy layered composites, however, have been based on quasi-static approaches. The dynamic failure of layered metallic composites, therefore, needs to be characterized in terms of strength, toughness, and fracture response. A dislocation-density based crystalline plasticity formulation, finite-element techniques, rational crystallographic orientation relations and a new fracture methodology were used to predict the failure modes associated with the high strain rate behavior of aluminum layered composites. Two alloy layers, a high strength alloy, aluminum 2195, and an aluminum alloy 2139, with high toughness, were modeled with representative microstructures that included precipitates, dispersed particles, and different grain boundary (GB) distributions. The new fracture methodology, based on an overlap method and phantom nodes, is used with a fracture criteria specialized for fracture on different cleavage planes. One of the objectives of this investigation, therefore, was to determine the optimal arrangements of the 2139 and 2195 aluminum alloys for a metallic layered composite that would combine strength, toughness and fracture resistance for high strain-rate applications. Different layer arrangements were investigated for high strain-rate applications, and the optimal arrangement was with the high toughness 2139 layer on the bottom, which provided extensive shear strain localization, and the high strength 2195 layer on the top for high strength resistance. The layer thickness of the bottom high toughness layer also affected the bending behavior of the roll-boned interface and the potential delamination of the layers. Shear strain localization, dynamic cracking and delamination were the mutually competing failure mechanisms for the layered metallic composite, and control of these failure modes can be optimized for high strain

  11. User-Defined Material Model for Progressive Failure Analysis

    NASA Technical Reports Server (NTRS)

    Knight, Norman F. Jr.; Reeder, James R. (Technical Monitor)

    2006-01-01

    An overview of different types of composite material system architectures and a brief review of progressive failure material modeling methods used for structural analysis including failure initiation and material degradation are presented. Different failure initiation criteria and material degradation models are described that define progressive failure formulations. These progressive failure formulations are implemented in a user-defined material model (or UMAT) for use with the ABAQUS/Standard1 nonlinear finite element analysis tool. The failure initiation criteria include the maximum stress criteria, maximum strain criteria, the Tsai-Wu failure polynomial, and the Hashin criteria. The material degradation model is based on the ply-discounting approach where the local material constitutive coefficients are degraded. Applications and extensions of the progressive failure analysis material model address two-dimensional plate and shell finite elements and three-dimensional solid finite elements. Implementation details and use of the UMAT subroutine are described in the present paper. Parametric studies for composite structures are discussed to illustrate the features of the progressive failure modeling methods that have been implemented.

  12. SDO Delta H Mode Design and Analysis

    NASA Technical Reports Server (NTRS)

    Mason, Paul A.; Starin, Scott R.

    2007-01-01

    While on orbit, disturbance torques on a three axis stabilized spacecraft tend to increase the system momentum, which is stored in the reaction wheels. Upon reaching the predefined momentum capacity (or maximum wheel speed) of the reaction wheel, an external torque must be used to unload the momentum. The purpose of the Delta H mode is to manage the system momentum. This is accomplished by driving the reaction wheels to a target momentum state while the attitude thrusters, which provide an external torque, are used to maintain the attitude. The Delta H mode is designed to meet the mission requirements and implement the momentum management plan. Changes in the requirements or the momentum management plan can lead to design changes in the mode. The momentum management plan defines the expected momentum buildup trend, the desired momentum state and how often the system is driven to the desired momentum state (unloaded). The desired momentum state is chosen based on wheel capacity, wheel configuration, thruster layout and thruster sizing. For the Solar Dynamics Observatory mission, the predefined wheel momentum capacity is a function of the jitter requirements, power, and maximum momentum capacity. Changes in jitter requirements or power limits can lead to changes in the desired momentum state. These changes propagate into the changes in the momentum management plan and therefore the Delta H mode design. This paper presents the analysis and design performed for the Solar Dynamics Observatory Delta H mode. In particular, the mode logic and processing needed to meet requirements is described along with the momentum distribution formulation. The Delta H mode design is validated using the Solar Dynamics Observatory High Fidelity simulator. Finally, a summary of the design is provided along with concluding remarks.

  13. X-framework: Space system failure analysis framework

    NASA Astrophysics Data System (ADS)

    Newman, John Steven

    Space program and space systems failures result in financial losses in the multi-hundred million dollar range every year. In addition to financial loss, space system failures may also represent the loss of opportunity, loss of critical scientific, commercial and/or national defense capabilities, as well as loss of public confidence. The need exists to improve learning and expand the scope of lessons documented and offered to the space industry project team. One of the barriers to incorporating lessons learned include the way in which space system failures are documented. Multiple classes of space system failure information are identified, ranging from "sound bite" summaries in space insurance compendia, to articles in journals, lengthy data-oriented (what happened) reports, and in some rare cases, reports that treat not only the what, but also the why. In addition there are periodically published "corporate crisis" reports, typically issued after multiple or highly visible failures that explore management roles in the failure, often within a politically oriented context. Given the general lack of consistency, it is clear that a good multi-level space system/program failure framework with analytical and predictive capability is needed. This research effort set out to develop such a model. The X-Framework (x-fw) is proposed as an innovative forensic failure analysis approach, providing a multi-level understanding of the space system failure event beginning with the proximate cause, extending to the directly related work or operational processes and upward through successive management layers. The x-fw focus is on capability and control at the process level and examines: (1) management accountability and control, (2) resource and requirement allocation, and (3) planning, analysis, and risk management at each level of management. The x-fw model provides an innovative failure analysis approach for acquiring a multi-level perspective, direct and indirect causation of

  14. Failure Analysis of Electrical Pin Connectors

    NASA Technical Reports Server (NTRS)

    Newman, John A.; Baughman, James M.; Smith, Stephen W.; Herath, Jeffrey A.

    2008-01-01

    A study was initiated to determine the root cause of failure for circuit board electrical connection pins that failed during vibRatory testing. The circuit board is part of an unmanned space probe, and the vibratory testing was performed to ensure component survival of launch loading conditions. The results of this study show that the pins failed as a result of fatigue loading.

  15. A Modeling Technique and Representation of Failure in the Analysis of Triaxial Braided Carbon Fiber Composites

    NASA Technical Reports Server (NTRS)

    Littell, Justin D.; Binienda, Wieslaw K.; Goldberg, Robert K.; Roberts, Gary D.

    2008-01-01

    Quasi-static tests have been performed on triaxially braided carbon fiber composite materials with large unit cell sizes. The effects of different fibers and matrix materials on the failure mode were investigated. Simulations of the tests have been performed using the transient dynamic finite element code, LS-DYNA. However, the wide range of failure modes observed for the triaxial braided carbon fiber composites during tests could not be simulated using composite material models currently available within LS-DYNA. A macroscopic approach has been developed that provides better simulation of the material response in these materials. This approach uses full-field optical measurement techniques to measure local failures during quasi-static testing. Information from these experiments is then used along with the current material models available in LS-DYNA to simulate the influence of the braided architecture on the failure process. This method uses two-dimensional shell elements with integration points through the thickness of the elements to represent the different layers of braid along with a new analytical method for the import of material stiffness and failure data directly. The present method is being used to examine the effect of material properties on the failure process. The experimental approaches used to obtain the required data will be described, and preliminary results of the numerical analysis will be presented.

  16. Performance and sensitivity analysis of the generalized likelihood ratio method for failure detection. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Bueno, R. A.

    1977-01-01

    Results of the generalized likelihood ratio (GLR) technique for the detection of failures in aircraft application are presented, and its relationship to the properties of the Kalman-Bucy filter is examined. Under the assumption that the system is perfectly modeled, the detectability and distinguishability of four failure types are investigated by means of analysis and simulations. Detection of failures is found satisfactory, but problems in identifying correctly the mode of a failure may arise. These issues are closely examined as well as the sensitivity of GLR to modeling errors. The advantages and disadvantages of this technique are discussed, and various modifications are suggested to reduce its limitations in performance and computational complexity.

  17. OH-58 helicopter transmission failure analysis

    NASA Technical Reports Server (NTRS)

    Townsend, D. P.; Coy, J. J.; Hatvani, B. R.

    1976-01-01

    The OH-58 main transmission gearbox was run at varying output torques, speeds, and oil cooling rates. The gearbox was subsequently run to destruction by draining the oil from the gearbox while operating at a speed of 6200 revs per minute and 36,000 inch-pounds output torque. Primary cause of gearbox failure was overheating and melting of the planet bearing aluminum cages. Complete failure of the gearbox occurred in 28 1/2 minutes after the oil pressure dropped to zero. The alternating and maximum stresses in the gearbox top case were approximately 10 percent of the endurance limit for the material. Deflection of the bevel gear at 67000 inch-pounds output torque indicate a marginal stiffness for the bevel gear supporting system.

  18. Safety Core Insulator Failures Reliability Analysis

    DTIC Science & Technology

    2006-10-01

    given below: 1. Improper installation a. Installed upside down. Air bubble exposes belt in high field area ( Haiku ) b. Installed with inadequate...ground. Cause – improperly installed spelter socket. New Safety Core Haiku , HI 1 EM-1 Down lead dogleg counterweight insulator exploded. Cause...insulators failed when they hit the ground following the failure of an improperly installed spelter socket. 4. Haiku , HI. Valley span antenna (Dec 1996

  19. Metallurgy, thermal stability, and failure mode of the commercial Bi-Te-based thermoelectric modules.

    SciTech Connect

    Yang, Nancy Y. C.; Morales, Alfredo Martin

    2009-02-01

    Bi-Te-based thermoelectric (TE) alloys are excellent candidates for power generation modules. We are interested in reliable TE modules for long-term use at or below 200 C. It is known that the metallurgical characteristics of TE materials and of interconnect components affect the performance of TE modules. Thus, we have conducted an extensive scientific investigation of several commercial TE modules to determine whether they meet our technical requirements. Our main focus is on the metallurgy and thermal stability of (Bi,Sb){sup 2}(Te,Se){sup 3} TE compounds and of other materials used in TE modules in the temperature range between 25 C and 200 C. Our study confirms the material suite used in the construction of TE modules. The module consists of three major components: AlN cover plates; electrical interconnects; and the TE legs, P-doped (Bi{sub 8}Sb{sub 32})(Te{sub 60}) and N-doped (Bi{sub 37}Sb{sub 3})(Te{sub 56}Se{sub 4}). The interconnect assembly contains Sn (Sb {approx} 1wt%) solder, sandwiched between Cu conductor with Ni diffusion barriers on the outside. Potential failure modes of the TE modules in this temperature range were discovered and analyzed. The results show that the metallurgical characteristics of the alloys used in the P and N legs are stable up to 200 C. However, whole TE modules are thermally unstable at temperatures above 160 C, lower than the nominal melting point of the solder suggested by the manufacture. Two failure modes were observed when they were heated above 160 C: solder melting and flowing out of the interconnect assembly; and solder reacting with the TE leg, causing dimensional swelling of the TE legs. The reaction of the solder with the TE leg occurs as the lack of a nickel diffusion barrier on the side of the TE leg where the displaced solder and/or the preexisting solder beads is directly contact the TE material. This study concludes that the present TE modules are not suitable for long-term use at temperatures above 160 C due

  20. Progressive Failure Analysis of Advanced Composites

    DTIC Science & Technology

    2008-07-25

    subroutine SUBROUTINE UVARM(UVAR,DIRECT,T,TIME,DTIME,CMNAME,ORNAME, 1 NUVARM,NOEL,NPT,LAYER,KSPT,KSTEP,KINC,NDI,NSHR,COORD, 2 JMAC ,JMATYP,MATLAYO,LACCFLA...CHARACTER dmkname*255, FNAMEX*80 DIMENSION UVAR(*),DIRECT(3,3),T(3,3),TIME(2) DIMENSION ARRAY(15),JARRAY(15), JMAC (*),JMATYP(*),COORD(*) C DIMENSION stress(6...CALL GETVRM(’S’,ARRAY,JARRAY,FLGRAY,JRCD, JMAC ,JMATYP,MATLAYO, 1 LACCFLA) C 48 if(klarc.eq.3) then ! LaRC03 failure criteria stress(1) = array(1

  1. Failure analysis of composite laminates including biaxial compression

    NASA Technical Reports Server (NTRS)

    Tennyson, R. C.; Elliott, W. G.

    1983-01-01

    This report describes a continued effort on the development and application of the tensor polynomial failure criterion for composite laminate analysis. In particular, emphasis is given to the design, construction and testing of a cross-beam laminate configuration to obtain "pure' biaxial compression failure. The purpose of this test case was to provide to permit "closure' of the cubic form of the failure surface in the 1-2 compression-compression quadrant. This resulted in a revised set of interaction strength parameters and the construction of a failure surface which can be used with confidence for strength predictions, assuming a plane stress state exists. Furthermore, the problem of complex conjugate roots which can occur in some failure regions is addressed and an "engineering' interpretation is provided. Results are presented illustrating this behavior and the methodology for overcoming this problem is discussed.

  2. Resistance Spot Weld Failure Mode and Weld Performance for Aluminium Alloys

    SciTech Connect

    Sun, Xin

    2010-01-30

    In this chapter, we present the strength and failure modes of reactive NanoFoil® bonded joints for similar and dissimilar lightweight materials. NanoFoil® is a multi-layer foil fabricated through the growth of thousands of nanoscale layers of aluminum and nickel by vapor deposition. Initiated by an energy impulse, the like-like bonds of the atoms of each layer in the foil are exchanged for more stable unlike bonds between atoms from neighboring layers. As the atoms of each layer mix, heat is generated, creating a self-sustaining reaction traveling along the length of the foil. The instantaneous release of heat energy by this reaction is controlled by the nanolayer thickness and lay-up, such that accurate control of a highly localized heat source can be realized, allowing bonding without compromising the properties/integrities of the base materials. First, solder and braze joints for similar and dissimilar material combinations of steel, aluminum and magnesium are fabricated. Static bond strength tests under tensile shear loading condition are then performed to quantify the bond strength for different material combinations. The through-thickness microstructure changes and modifications by the bonding process are quantified using SEM. Depending on the base material combinations, it is shown that the nanofoil bond strength is comparable to those of the conventional structural adhesive bonds.

  3. Independent Review of the Failure Modes of F-1 Engine and Propellants System

    NASA Technical Reports Server (NTRS)

    Ray, Paul

    2003-01-01

    The F-1 is the powerful engine, that hurdled the Saturn V launch vehicle from the Earth to the moon on July 16,1969. The force that lifted the rocket overcoming the gravitational force during the first stage of the flight was provided by a cluster of five F-1 rocket engines, each of them developing over 1.5 million pounds of thrust (MSFC-MAN-507). The F-1 Rocket engine used RP-1 (Rocket Propellant-1, commercially known as Kerosene), as fuel with lox (liquid Oxygen) as oxidizer. NASA terminated Saturn V activity and has focused on Space Shuttle since 1972. The interest in rocket system has been revived to meet the National Launch System (NLS) program and a directive from the President to return to the Moon and exploration of the space including Mars. The new program Space Launch Initiative (SLI) is directed to drastically reduce the cost of flight for payloads, and adopt a reusable launch vehicle (RLV). To achieve this goal it is essential to have the ability of lifting huge payloads into low earth orbit. Probably requiring powerful boosters as strap-ons to a core vehicle, as was done for the Saturn launch vehicle. The logic in favor of adopting Saturn system, a proven technology, to meet the SLI challenge is very strong. The F-1 engine was the largest and most powerful liquid rocket engine ever built, and had exceptional performance. This study reviews the failure modes of the F-1 engine and propellant system.

  4. Failure analysis of a graphite/epoxy laminate subjected to bolt bearing loads

    NASA Technical Reports Server (NTRS)

    Crews, J. H., Jr.; Naik, R. V. A.

    1984-01-01

    Quasi-isotropic graphite/epoxy laminates (T300/5208) were tested under bolt bearing loads to study failure modes, strengths, and failure energy. Specimens had a range of configurations to produce failures by the three nominal failure modes: tension, shearout, and bearing. Radiographs were made after damage onset and after ultimate load to examine the failure modes. Also, the laminate stresses near the bolt hole calculated for each test specimen configuration, and then used with a failure criterion to analyze the test data. Failures involving extensive bearing damage were found to dissipate significantly more energy than tension dominated failures. The specimen configuration influenced the failure modes and therefore also influenced the failure energy. In the width-to-diameter ratio range of 4 to 5, which is typical of structural joints, a transition from the tension mode to the bearing mode was shown to cause a large increase in failure energy. The failure modes associated with ultimate strength were usually different from those associated with the damage onset. Typical damage sequences involved bearing damage onset at the hole boundary followed by tension damage progressing from the hole boundary.

  5. Failure analysis of a graphite/epoxy laminate subjected to bolt-bearing loads

    NASA Technical Reports Server (NTRS)

    Crews, J. H., Jr.; Naik, R. V. A.

    1986-01-01

    Quasi-isotropic graphite-epoxy laminates (T300/5208) were tested under bolt bearing loads to study failure modes, strengths, and failure energy. Specimens had a range of configurations to produce failures by the three nominal failure modes: tension, shearout, and bearing. Radiographs were made after damage onset and after ultimate load to examine the failure modes. Also, the laminate stresses near the bolt hole calculated for each test specimen configuration, and then used with a failure criterion to analyze the test data. Failures involving extensive bearing damage were found to dissipate significantly more energy than tension dominated failures. The specimen configuration influenced the failure modes and therefore also influenced the failure energy. In the width-to-diameter ratio range of 4 to 5, which is typical of structural joints, a transition from the tension mode to the bearing mode was shown to cause a large increase in failure energy. The failure modes associated with ultimate strength were usually different from those associated with the damage onset. Typical damage sequences involved bearing damage onset at the hole boundary followed by tension damage progressing from the hole boundary.

  6. Quality by design I: Application of failure mode effect analysis (FMEA) and Plackett-Burman design of experiments in the identification of "main factors" in the formulation and process design space for roller-compacted ciprofloxacin hydrochloride immediate-release tablets.

    PubMed

    Fahmy, Raafat; Kona, Ravikanth; Dandu, Ramesh; Xie, Walter; Claycamp, Gregg; Hoag, Stephen W

    2012-12-01

    As outlined in the ICH Q8(R2) guidance, identifying the critical quality attributes (CQA) is a crucial part of dosage form development; however, the number of possible formulation and processing factors that could influence the manufacturing of a pharmaceutical dosage form is enormous obviating formal study of all possible parameters and their interactions. Thus, the objective of this study is to examine how quality risk management can be used to prioritize the number of experiments needed to identify the CQA, while still maintaining an acceptable product risk profile. To conduct the study, immediate-release ciprofloxacin tablets manufactured via roller compaction were used as a prototype system. Granules were manufactured using an Alexanderwerk WP120 roller compactor and tablets were compressed on a Stokes B2 tablet press. In the early stages of development, prior knowledge was systematically incorporated into the risk assessment using failure mode and effect analysis (FMEA). The factors identified using FMEA were then followed by a quantitative assessed using a Plackett-Burman screening design. Results show that by using prior experience, literature data, and preformulation data the number of experiments could be reduced to an acceptable level, and the use of FMEA and screening designs such as the Plackett Burman can rationally guide the process of reducing the number experiments to a manageable level.

  7. Computational Methods for Failure Analysis and Life Prediction

    NASA Technical Reports Server (NTRS)

    Noor, Ahmed K. (Compiler); Harris, Charles E. (Compiler); Housner, Jerrold M. (Compiler); Hopkins, Dale A. (Compiler)

    1993-01-01

    This conference publication contains the presentations and discussions from the joint UVA/NASA Workshop on Computational Methods for Failure Analysis and Life Prediction held at NASA Langley Research Center 14-15 Oct. 1992. The presentations focused on damage failure and life predictions of polymer-matrix composite structures. They covered some of the research activities at NASA Langley, NASA Lewis, Southwest Research Institute, industry, and universities. Both airframes and propulsion systems were considered.

  8. Failure analysis of a Stirling engine heat pipe

    NASA Technical Reports Server (NTRS)

    Moore, Thomas J.; Cairelli, James E.; Khalili, Kaveh

    1989-01-01

    Failure analysis was conducted on a heat pipe from a Stirling Engine test rig which was designed to operate at 1073 K. Premature failure had occurred due to localized overheating at the leading edge of the evaporator fin. It was found that a crack had allowed air to enter the fin and react with the sodium coolant. The origin of the crack was found to be located at the inner surface of the Inconel 600 fin where severe intergranular corrosion had taken place.

  9. Analysis of the progressive failure of brittle matrix composites

    NASA Technical Reports Server (NTRS)

    Thomas, David J.

    1995-01-01

    This report investigates two of the most common modes of localized failures, namely, periodic fiber-bridged matrix cracks and transverse matrix cracks. A modification of Daniels' bundle theory is combined with Weibull's weakest link theory to model the statistical distribution of the periodic matrix cracking strength for an individual layer. Results of the model predictions are compared with experimental data from the open literature. Extensions to the model are made to account for possible imperfections within the layer (i.e., nonuniform fiber lengths, irregular crack spacing, and degraded in-situ fiber properties), and the results of these studies are presented. A generalized shear-lag analysis is derived which is capable of modeling the development of transverse matrix cracks in material systems having a general multilayer configuration and under states of full in-plane load. A method for computing the effective elastic properties for the damaged layer at the global level is detailed based upon the solution for the effects of the damage at the local level. This methodology is general in nature and is therefore also applicable to (0(sub m)/90(sub n))(sub s) systems. The characteristic stress-strain response for more general cases is shown to be qualitatively correct (experimental data is not available for a quantitative evaluation), and the damage evolution is recorded in terms of the matrix crack density as a function of the applied strain. Probabilistic effects are introduced to account for the statistical nature of the material strengths, thus allowing cumulative distribution curves for the probability of failure to be generated for each of the example laminates. Additionally, Oh and Finney's classic work on fracture location in brittle materials is extended and combined with the shear-lag analysis. The result is an analytical form for predicting the probability density function for the location of the next transverse crack occurrence within a crack bounded

  10. Transient analysis mode participation for modal survey target mode selection using MSC/NASTRAN DMAP

    NASA Technical Reports Server (NTRS)

    Barnett, Alan R.; Ibrahim, Omar M.; Sullivan, Timothy L.; Goodnight, Thomas W.

    1994-01-01

    Many methods have been developed to aid analysts in identifying component modes which contribute significantly to component responses. These modes, typically targeted for dynamic model correlation via a modal survey, are known as target modes. Most methods used to identify target modes are based on component global dynamic behavior. It is sometimes unclear if these methods identify all modes contributing to responses important to the analyst. These responses are usually those in areas of hardware design concerns. One method used to check the completeness of target mode sets and identify modes contributing significantly to important component responses is mode participation. With this method, the participation of component modes in dynamic responses is quantified. Those modes which have high participation are likely modal survey target modes. Mode participation is most beneficial when it is used with responses from analyses simulating actual flight events. For spacecraft, these responses are generated via a structural dynamic coupled loads analysis. Using MSC/NASTRAN DMAP, a method has been developed for calculating mode participation based on transient coupled loads analysis results. The algorithm has been implemented to be compatible with an existing coupled loads methodology and has been used successfully to develop a set of modal survey target modes.

  11. The Worker Exposure Failure Modes and Effects Analysis

    SciTech Connect

    Lee C. Cadwallader

    2004-09-01

    This paper documents the activities of the US-Japan exchange in the area of personnel safety at magnetic and laser fusion experiments. A near-miss event with a visiting scientist to the US in 1992 was the impetus for forming the Joint Working Group on Fusion Safety. This exchange has been under way for over ten years and has provided many safety insights for both US and Japanese facility personnel at national institutes and at universities. The background and activities of the Joint Working Group are described, including the facilities that have been visited for safety walkthroughs, the participants from both countries, and the main safety issues examined during visits. Based on these visits, some operational safety ideas to enhance experiment safety are given. The near-term future plans of the Safety Monitor Joint Working Group are also discussed.

  12. SOLERAS: Photovoltaic power systems project. Module failure analysis

    NASA Astrophysics Data System (ADS)

    Huraib, F. S.; Imamura, M. S.; Salim, A. A.; Rao, N.

    1984-10-01

    The SOLERAS Photovoltaic Power System (PVPS) became operational in September 1981. The system has operated satisfactorily and has experienced very little downtime. Early in 1983 some degradation in the photovoltaic (PV) field performance was detected. A series of current voltage (I-V) tests and other analyses eventually uncovered a number of PV modules that have resulted in open circuit type failure in the four cell group, or a half module. As of August 1984, the estimated number of these defective modules in the PV field was 152. In addition, there are a total of 188 defective modules in the storage warehouse, resulting in a total of 340 modules that need repairs. At the current rate of failures (seven half modules per month), an additional 112 modules would be defective by the end of January 1986, resulting in 412 defective modules. This report presents the results of the failure analysis performed during the past several months on the open circuit modules. Background information as related to the module failures and the effects of such failures on the overall PV field power output are provided. In addition, a plan to continue the monitoring of the rate of failure and analyzing the failure mechanisms is presented.

  13. Using Failure Information Analysis to Detect Enterprise Zombies

    NASA Astrophysics Data System (ADS)

    Zhu, Zhaosheng; Yegneswaran, Vinod; Chen, Yan

    We propose failure information analysis as a novel strategy for uncovering malware activity and other anomalies in enterprise network traffic. A focus of our study is detecting self-propagating malware such as worms and botnets. We begin by conducting an empirical study of transport- and application-layer failure activity using a collection of long-lived malware traces. We dissect the failure activity observed in this traffic in several dimensions, finding that their failure patterns differ significantly from those of real-world applications. Based on these observations, we describe the design of a prototype system called Netfuse to automatically detect and isolate malware-like failure patterns. The system uses an SVM-based classification engine to identify suspicious systems and clustering to aggregate failure activity of related enterprise hosts. Our evaluation using several malware traces demonstrates that the Netfuse system provides an effective means to discover suspicious application failures and infected enterprise hosts. We believe it would be a useful complement to existing defenses.

  14. [Analysis of anti-reflux surgery failure].

    PubMed

    Cano Novillo, I; Benavent Gordo, M I; Portela Casalod, E; Delgado Muñoz, M D; Aguado Roncero, P; Vilariño Mosquera, A; Berchi García, F J

    2000-01-01

    Recurrent gastroesophageal reflux following fundoplication is a challenging problem, because it is usually refractory to medical treatment and a second, technically difficult, antireflux operation is required. Different factors that may contribute to surgery failure have been identified in children. We present 8 cases who underwent redofundoplication after failed procedures, from a total number of 96 patients operated on due to gastroesophageal reflux. Four patient's had their initial fundoplication performed at our institution. Six patients were neurologically impaired, six had chronic pulmonary disease, and two had esophageal atresia. The main presenting symptoms were recurrent vomiting (n = 8) and aspiration (n = 4). Gastroesophageal reflux was confirmed by barium swallow and endoscopy. Operative findings showed wrap breakdown in two cases, warp breakdown associated with hiatal hernia in five, wrap breakdown associated with paraesophageal hernia in two cases, and paraesophageal hernia with normal wrap in one. A second Nissen procedure were performed in five cases, whereas a Collis-Nissen gastroplasty was realized in three with a short esophagus. Six patients had a successful outcome remaining symptom free, one has severe disphagia, and one has recurrent vomiting. In our experience, patients with recurrent gastroesophageal reflux disease should undergo an antireflux procedure tailored to specific anatomic or functional abnormalities.

  15. A Failure Mode in Dense Infrared Detector Arrays Resulting in Increased Dark Current

    NASA Astrophysics Data System (ADS)

    Pinkie, Benjamin; Bellotti, Enrico

    2016-09-01

    In this paper, we investigate a failure mode that arises in dense infrared focal plane detector arrays as a consequence of the interactions of neighboring pixels through the minority carrier profiles in the common absorber layer. We consider the situation in which one pixel in a hexagonal array becomes de-biased relative to its neighbors and show that the dark current in the six neighboring pixels increases exponentially as a function of the difference between the nominal and anomalous biases. Moreover, we show that the current increase in the six nearest-neighbor pixels is in total larger than that by which the current in the affected pixel decreases, causing a net increase in the dark current. The physical origins of this effect are explained as being due to increased lateral diffusion currents that arise as a consequence of breaking the symmetry of the minority carrier profiles. We then perform a parametric study to quantify the magnitude of this effect for a number of detector geometric parameters, operating temperatures, and spectral bands. Particularly, numerical simulations are carried out for short-, mid-, and long-wavelength HgCdTe infrared detectors operating between 77 K and 210 K. We show that this effect is most prevalent in architectures for which the lateral diffusion current is the largest component of the total dark current—high operating temperature devices with narrow epitaxial absorber thicknesses and pitches small compared to the diffusion length of minority carriers. These results could prove significant particularly for short- and mid-wave infrared detectors, which are typically designed to fit these conditions.

  16. Probability of loss of assured safety in systems with multiple time-dependent failure modes.

    SciTech Connect

    Helton, Jon Craig; Pilch, Martin.; Sallaberry, Cedric Jean-Marie.

    2012-09-01

    Weak link (WL)/strong link (SL) systems are important parts of the overall operational design of high-consequence systems. In such designs, the SL system is very robust and is intended to permit operation of the entire system under, and only under, intended conditions. In contrast, the WL system is intended to fail in a predictable and irreversible manner under accident conditions and render the entire system inoperable before an accidental operation of the SL system. The likelihood that the WL system will fail to deactivate the entire system before the SL system fails (i.e., degrades into a configuration that could allow an accidental operation of the entire system) is referred to as probability of loss of assured safety (PLOAS). Representations for PLOAS for situations in which both link physical properties and link failure properties are time-dependent are derived and numerically evaluated for a variety of WL/SL configurations, including PLOAS defined by (i) failure of all SLs before failure of any WL, (ii) failure of any SL before failure of any WL, (iii) failure of all SLs before failure of all WLs, and (iv) failure of any SL before failure of all WLs. The effects of aleatory uncertainty and epistemic uncertainty in the definition and numerical evaluation of PLOAS are considered.

  17. Decentralized Sliding Mode Observer Based Dual Closed-Loop Fault Tolerant Control for Reconfigurable Manipulator against Actuator Failure

    PubMed Central

    Zhao, Bo; Li, Yuanchun

    2015-01-01

    This paper considers a decentralized fault tolerant control (DFTC) scheme for reconfigurable manipulators. With the appearance of norm-bounded failure, a dual closed-loop trajectory tracking control algorithm is proposed on the basis of the Lyapunov stability theory. Characterized by the modularization property, the actuator failure is estimated by the proposed decentralized sliding mode observer (DSMO). Moreover, the actuator failure can be treated in view of the local joint information, so its control performance degradation is independent of other normal joints. In addition, the presented DFTC scheme is significantly simplified in terms of the structure of the controller due to its dual closed-loop architecture, and its feasibility is highly reflected in the control of reconfigurable manipulators. Finally, the effectiveness of the proposed DFTC scheme is demonstrated using simulations. PMID:26181826

  18. Sensitivity Analysis for Dynamic Failure and Damage in Metallic Structures

    DTIC Science & Technology

    2005-03-01

    respect to the nominal alloy composition at the center of weld surface (Point 6 of Figure 7) -21 - U CO 2000 - * cE axc -2000 o" "....". . -401.11𔃺 1󈧄...Final Report Sensitivity Analysis for Dynamic Failure and Damage in Metallic Structures Office of Naval Research 800 North Quincy Street Arlington...3/31/05 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Sensitivity Analysis for Dynamic Failure and Damage in Metallic Structures Sb. GRANT NUMBER N000

  19. Failure Analysis of Space Shuttle Orbiter Valve Poppet

    NASA Technical Reports Server (NTRS)

    Russell, Rick

    2010-01-01

    The poppet failed during STS-126 due to fatigue cracking that most likely was initiated during MDC ground-testing. This failure ultimately led to the discovery that the cracking problem was a generic issue effecting numerous poppets throughout the Shuttle program's history. This presentation has focused on the laboratory analysis of the failed hardware, but this analysis was only one aspect of a comprehensive failure investigation. One critical aspect of the overall investigation was modeling of the fluid flow through this valve to determine the possible sources of cyclic loading. This work has led to the conclusion that the poppets are failing due to flow-induced vibration.

  20. Reliability and Failure Modes of Solid-State Lighting Electrical Drivers Subjected to Accelerated Aging

    SciTech Connect

    Lall, Pradeep; Sakalaukus, Peter; Davis, Lynn

    2015-02-19

    An investigation of an off-the-shelf solid-state lighting device with the primary focus on the accompanied light-emitting diode (LED) electrical driver (ED) has been conducted. A set of 10 EDs were exposed to temperature humidity life testing of 85% RH and 85 C (85/85) without an electrical bias per the JEDEC standard JESD22-A101C in order to accelerate the ingress of moisture into the aluminum electrolytic capacitor (AEC) and the EDs in order to assess the reliability of the LED drivers for harsh environment applications. The capacitance and equivalent series resistance for each AEC inside the ED were measured using a handheld LCR meter as possible leading indications of failure. The photometric quantities of a single pristine light engine were monitored in order to investigate the interaction between the light engine and the EDs. These parameters were used in assessing the overall reliability of the EDs. In addition, a comparative analysis has been conducted between the 85/85 accelerated test data and a previously published high-temperature storage life accelerated test of 135°C. The results of the 85/85 acceleration test and the comparative analysis are presented in this paper.

  1. Reliability and Failure Modes of Solid-State Lighting Electrical Drivers Subjected to Accelerated Aging

    DOE PAGES

    Lall, Pradeep; Sakalaukus, Peter; Davis, Lynn

    2015-02-19

    An investigation of an off-the-shelf solid-state lighting device with the primary focus on the accompanied light-emitting diode (LED) electrical driver (ED) has been conducted. A set of 10 EDs were exposed to temperature humidity life testing of 85% RH and 85 C (85/85) without an electrical bias per the JEDEC standard JESD22-A101C in order to accelerate the ingress of moisture into the aluminum electrolytic capacitor (AEC) and the EDs in order to assess the reliability of the LED drivers for harsh environment applications. The capacitance and equivalent series resistance for each AEC inside the ED were measured using a handheldmore » LCR meter as possible leading indications of failure. The photometric quantities of a single pristine light engine were monitored in order to investigate the interaction between the light engine and the EDs. These parameters were used in assessing the overall reliability of the EDs. In addition, a comparative analysis has been conducted between the 85/85 accelerated test data and a previously published high-temperature storage life accelerated test of 135°C. The results of the 85/85 acceleration test and the comparative analysis are presented in this paper.« less

  2. The quantitative failure of human reliability analysis

    SciTech Connect

    Bennett, C.T.

    1995-07-01

    This philosophical treatise argues the merits of Human Reliability Analysis (HRA) in the context of the nuclear power industry. Actually, the author attacks historic and current HRA as having failed in informing policy makers who make decisions based on risk that humans contribute to systems performance. He argues for an HRA based on Bayesian (fact-based) inferential statistics, which advocates a systems analysis process that employs cogent heuristics when using opinion, and tempers itself with a rational debate over the weight given subjective and empirical probabilities.

  3. Longitudinal compressive failure modes in fiber composites End attachment effects on IITRI type test specimens

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Sinclair, J. H.

    1985-01-01

    The end-attachment effects on longitudinal compressive strength of IITRI type specimen unidirectional fiber composites are formally assessed using finite-element analysis (FEA) in conjunction with composite mechanics. Sixteen different cases were analyzed to evaluate end-attachment effects (such as degree of misalignment, type of misalignment, progressive end-tab debonding, and specimen thickness) on stress distribution, peak stresses, buckling loads, and buckling mode shapes. The results obtained from the FEA and comparisons with fractured specimens show that eccentricities induce bending-type stresses which peak near the end-tabs and cause flexural type fracture. Also, guidelines are included for placing back-to-back strain gages to measure the presence/absence of possible end-attachment and eccentricity effects.

  4. Failure analysis of a tool-steel torque shaft

    SciTech Connect

    Reagan, J.R.

    1981-01-01

    A low design load drive shaft from an experimental diesel truck engine failed unexpectedly during highway testing. The shaft was driven by a turbine used to deliver power from an experimental exhaust heat recovery system to the engine's crankshaft. During design, fatigue was not considered a major problem because of the low operating cyclic stresses. An independent testing laboratory analyzed the failure by routine metallography. The structure of the hardened S-7 tool steel shaft was banded and the laboratory attributed the failure to fatigue induced by a banded microstructure. NASA was asked to confirm this analysis. Visual examination of the failed shaft plus the knowledge of the torsional load that it carried pointed to a 100% ductile failure with no evidence of fatigue. Scanning electron microscopy confirmed this. Torsional test specimens were produced from pieces of the failed shaft and torsional overload testing produced identical failures to that which had occurred in the truck engine. This pointed to a failure caused by a high overload and although the microstructure was defective it was not the cause of the failure.

  5. The effect of incomplete crown ferrules on fracture resistance and failure modes of endodontically treated maxillary incisors restored with quartz fiber post, composite core, and crowns

    PubMed Central

    Muangamphan, Panorjit; Sattapan, Boonrat; Kukiattrakoon, Boonlert; Thammasitboon, Kewalin

    2015-01-01

    Aim: To investigate the fracture resistance of restored endodontically treated teeth (RETT) with fiber posts, cores, and crowns with limited ferrules. Materials and Methods: Sixty maxillary anterior teeth were endodontically treated and decoronated 2 mm above the cemento-enamel junction, and then divided into 6 groups of 10 teeth each; Group circumferential ferrule (2FR), Group ferrule in the labial, mesial, and palatal region (2FR-LaMPa), Group ferrule in the labial, and palatal region (2FR-LaPa), Group 2FR-Pa and 2FR-La respectively, and Group 0FR (no ferrule). All 60 prepared teeth were then restored with quartz fiber posts, resin composite cores, and metal crowns. The specimens were subjected to load until failure occurred. Data were analyzed using one-way analysis of variance and Tukey's tests (α = 0.05). The mode of failure was determined under a stereoscope. Results: A statistical significant difference was found among groups 2FR-LaMPa, 2FR-Pa, 2FR-LaPa, and 2FR from the group 2FR-La, and from the group 0FR (P < 0.01). The predominant mode of failure was an oblique palatal to labial root fracture for the groups with remaining ferrules. Conclusion: For RETT that have incomplete crown ferrules, the location of the ferrules may affect their fracture resistance. PMID:26069401

  6. Statistical analysis of cascading failures in power grids

    SciTech Connect

    Chertkov, Michael; Pfitzner, Rene; Turitsyn, Konstantin

    2010-12-01

    We introduce a new microscopic model of cascading failures in transmission power grids. This model accounts for automatic response of the grid to load fluctuations that take place on the scale of minutes, when optimum power flow adjustments and load shedding controls are unavailable. We describe extreme events, caused by load fluctuations, which cause cascading failures of loads, generators and lines. Our model is quasi-static in the causal, discrete time and sequential resolution of individual failures. The model, in its simplest realization based on the Directed Current description of the power flow problem, is tested on three standard IEEE systems consisting of 30, 39 and 118 buses. Our statistical analysis suggests a straightforward classification of cascading and islanding phases in terms of the ratios between average number of removed loads, generators and links. The analysis also demonstrates sensitivity to variations in line capacities. Future research challenges in modeling and control of cascading outages over real-world power networks are discussed.

  7. Reliability-based failure analysis of brittle materials

    NASA Technical Reports Server (NTRS)

    Powers, Lynn M.; Ghosn, Louis J.

    1989-01-01

    The reliability of brittle materials under a generalized state of stress is analyzed using the Batdorf model. The model is modified to include the reduction in shear due to the effect of the compressive stress on the microscopic crack faces. The combined effect of both surface and volume flaws is included. Due to the nature of fracture of brittle materials under compressive loading, the component is modeled as a series system in order to establish bounds on the probability of failure. A computer program was written to determine the probability of failure employing data from a finite element analysis. The analysis showed that for tensile loading a single crack will be the cause of total failure but under compressive loading a series of microscopic cracks must join together to form a dominant crack.

  8. Equipment qualification research: test program and failure analysis of Class 1E solenoid valves

    SciTech Connect

    Paulson, D.V.; Shook, T.A.; Bacanskas, V.P.; Carfagno, S.P.

    1983-11-01

    This report documents the results of an equipment qualification research test program performed on ASCO solenoid valves. The valves were subjected to accelerated aging which included 50 Mrd of gamma radiation aging and accelerated thermal aging at 268/sup 0/F (131/sup 0/C). All valves performed satisfactorily during the seismic test. Of the seven valves exposed to the LOCA/MSLB simulation, only a metal-seated valve functioned properly throughout without leakage. At the conclusion of the post-LOCA functional testing, a failure analysis was undertaken to determine the failure mode(s) for each valve. The failure analysis included electrical testing of solenoid coils, controlled disassembly of valves, macro- and microscopic examination of internal parts, Shore A durometer testing of elastomeric components, and mass spectrometer analysis of several components. It was concluded that (1) the use of nitrogen to pressurize the valves during thermal aging severely inhibited the aging process since the majority of EPDM components were blanketed in nitrogen, and (2) operational cycling at the elevated thermal aging temperature may have produced stresses not representative of in-service use.

  9. Impact of Implantable Cardioverter-Defibrillator, Amiodarone, and Placebo on the Mode of Death in Stable Patients With Heart Failure

    PubMed Central

    Packer, Douglas L.; Prutkin, Jordan M.; Hellkamp, Anne S.; Mitchell, L. Brent; Bernstein, Robert C.; Wood, Freda; Boehmer, John P.; Carlson, Mark D.; Frantz, Robert P.; McNulty, Steve E.; Rogers, Joseph G.; Anderson, Jill; Johnson, George W.; Walsh, Mary Norine; Poole, Jeanne E.; Mark, Daniel B.; Lee, Kerry L.; Bardy, Gust H.

    2010-01-01

    Background The Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT) demonstrated that implantable cardioverterdefibrillator (ICD) therapy reduces all-cause mortality in patients with New York Heart Association class II/III heart failure and a left ventricular ejection fraction ≤35% on optimal medical therapy. Whether ICD therapy reduced sudden death caused by ventricular tachyarrhythmias without affecting heart failure deaths in this population is unknown. Methods and Results SCD-HeFT randomized 2521 subjects to placebo, amiodarone, or shock-only, single-lead ICD therapy. Over a median follow-up of 45.5 months, a total of 666 deaths occurred, which were reviewed by an Events Committee and initially categorized as cardiac or noncardiac. Cardiac deaths were further adjudicated as resulting from sudden death presumed to be ventricular tachyarrhythmic, bradyarrhythmia, heart failure, or other cardiac causes. ICD therapy significantly reduced cardiac mortality compared with placebo (adjusted hazard ratio, 0.76; 95% confidence interval, 0.60 to 0.95) and tachyarrhythmia mortality (adjusted hazard ratio, 0.40; 95% confidence interval, 0.27 to 0.59) and had no impact on mortality resulting from heart failure or noncardiac causes. The cardiac and tachyarrhythmia mortality reductions were evident in subjects with New York Heart Association class II but not in subjects with class III heart failure. The reduction in tachyarrhythmia mortality with ICD therapy was similar in subjects with ischemic and nonischemic disease. Compared with placebo, amiodarone had no significant effect on any mode of death. Conclusions ICD therapy reduced cardiac mortality and sudden death presumed to be ventricular tachyarrhythmic in SCD-HeFT and had no effect on heart failure mortality. Amiodarone had no effect on all-cause mortality or its cause-specific components, except an increase in non-cardiac mortality in class III patients. PMID:19917887

  10. Analysis of Mechanical Failure of Polymer Microneedles by Axial Force.

    PubMed

    Park, Jung-Hwan; Prausnitz, Mark R

    2010-04-01

    A polymeric microneedle has been developed for drug delivery applications. The ultimate goal of the polymeric microneedle is insertion into the specified region without failure for effective transdermal drug delivery. Mechanical failure of various geometries of microneedles by axial load was modeled using the Euler formula and the Johnson formula to predict the failure force of tapered-column microneedles. These formulas were compared with measured data to identify the mechanical behavior of microneedles by determining the critical factors including the actual length and end-fixed factor. The comparison of the two formulas with the data showed good agreement at the end-fixity (K) of 0.7. This value means that a microneedle column has one fixed end and one pinned end, and that part of the microneedle was overloaded by axial load. When the aspect ratio of length to equivalent diameter is 12:1 at 3 GPa of Young's modulus, there is a transition from the Euler region to the Johnson region by the decreased length and increased base diameter of the microneedle. A polymer having less than 3 GPa of stiffness would follow the Euler formula. A 12:1 aspect ratio of length to equivalent diameter of the microneedle was the mechanical indicator determining the failure mode between elastic buckling and inelastic buckling at less than 3 GPa of Young's modulus of polymer. Microneedles with below a 12:1 aspect ratio of length-to-equivalent diameter and more than 3 GPa of Young's were recommended for reducing sudden failure by buckling and for successfully inserting the microneedle into the skin.

  11. Failure analysis of solid rocket apogee motors

    NASA Technical Reports Server (NTRS)

    Martin, P. J.

    1972-01-01

    The analysis followed five selected motors through initial design, development, test, qualification, manufacture, and final flight reports. An audit was conducted at the manufacturing plants to complement the literature search with firsthand observations of the current philosophies and practices that affect reliability of the motors. A second literature search emphasized acquisition of spacecraft and satellite data bearing on solid motor reliability. It was concluded that present practices at the plants yield highly reliable flight hardware. Reliability can be further improved by new developments of aft-end bonding and initiator/igniter nondestructive test methods, a safe/arm device, and an insulation formulation. Minimum diagnostic instrumentation is recommended for all motor flights. Surplus motors should be used in margin testing. Criteria should be established for pressure and zone curing. The motor contractor should be represented at launch. New design analyses should be made of stretched motors and spacecraft/motor pairs.

  12. Space Shuttle Columbia Aging Wiring Failure Analysis

    NASA Technical Reports Server (NTRS)

    McDaniels, Steven J.

    2005-01-01

    A Space Shuttle Columbia main engine controller 14 AWG wire short circuited during the launch of STS-93. Post-flight examination divulged that the wire had electrically arced against the head of a nearby bolt. More extensive inspection revealed additional damage to the subject wire, and to other wires as well from the mid-body of Columbia. The shorted wire was to have been constructed from nickel-plated copper conductors surrounded by the polyimide insulation Kapton, top-coated with an aromatic polyimide resin. The wires were analyzed via scanning electron microscope (SEM), energy dispersive X-Ray spectroscopy (EDX), and electron spectroscopy for chemical analysis (ESCA); differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) were performed on the polyimide. Exemplar testing under laboratory conditions was performed to replicate the mechanical damage characteristics evident on the failed wires. The exemplar testing included a step test, where, as the name implies, a person stepped on a simulated wire bundle that rested upon a bolt head. Likewise, a shear test that forced a bolt head and a torque tip against a wire was performed to attempt to damage the insulation and conductor. Additionally, a vibration test was performed to determine if a wire bundle would abrade when vibrated against the head of a bolt. Also, an abrasion test was undertaken to determine if the polyimide of the wire could be damaged by rubbing against convolex helical tubing. Finally, an impact test was performed to ascertain if the use of the tubing would protect the wire from the strike of a foreign object.

  13. Bank stability analysis for fluvial erosion and mass failure

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The central objective of this study was to highlight the differences in magnitude between mechanical and fluvial streambank erosional strength with the purpose of developing a more comprehensive bank stability analysis. Mechanical erosion and ultimately failure signifies the general movement or coll...

  14. Analysis of Search Failures in Document Retrieval Systems: A Review.

    ERIC Educational Resources Information Center

    Tonta, Yasar

    1992-01-01

    Discusses the concept of search failure in document retrieval systems and three effectiveness measures, precision, recall, and "fallout." Four research methods--retrieval effectiveness measures, user satisfaction measures, transaction log analysis, and critical incident technique--are examined, and findings of major studies using each of the…

  15. Hope in elderly adults with chronic heart failure. Concept analysis.

    PubMed

    Caboral, Meriam F; Evangelista, Lorraine S; Whetsell, Martha V

    2012-01-01

    This topic review employed Walker and Avant's method of concept analysis to explore the construct of hope in elderly adults with chronic heart failure. The articles analyzed revealed that hope, as the belief of the occurrence of a positive result without any guarantee that it will be produced, is necessary for the survival and wellbeing of the elderly adults enduring this disease.

  16. Apollo CSM Power Generation System Design Considerations, Failure Modes and Lessons Learned

    NASA Technical Reports Server (NTRS)

    Interbartolo, Michael

    2009-01-01

    The objectives of this slide presentation are to: review the basic design criteria for fuel cells (FC's), review design considerations during developmental phase that affected Block I and Block II vehicles, summarize the conditions that led to the failure of components in the FC's, and state the solution implemented for each failure. It reviews the location of the fuel cells, the fuel cell theory the design criteria going into development phase and coming from the development phase, failures and solutions of Block I and II, and the lessons learned.

  17. Analysis of nuclear power plant component failures

    SciTech Connect

    Not Available

    1984-01-01

    Items are shown that have caused 90% of the nuclear unit outages and/or deratings between 1971 and 1980 and the magnitude of the problem indicated by an estimate of power replacement cost when the units are out of service or derated. The funding EPRI has provided on these specific items for R and D and technology transfer in the past and the funding planned in the future (1982 to 1986) are shown. EPRI's R and D may help the utilities on only a small part of their nuclear unit outage problems. For example, refueling is the major cause for nuclear unit outages or deratings and the steam turbine is the second major cause for nuclear unit outages; however, these two items have been ranked fairly low on the EPRI priority list for R and D funding. Other items such as nuclear safety (NRC requirements), reactor general, reactor and safety valves and piping, and reactor fuel appear to be receiving more priority than is necessary as determined by analysis of nuclear unit outage causes.

  18. Empirical mode decomposition analysis for visual stylometry.

    PubMed

    Hughes, James M; Mao, Dong; Rockmore, Daniel N; Wang, Yang; Wu, Qiang

    2012-11-01

    In this paper, we show how the tools of empirical mode decomposition (EMD) analysis can be applied to the problem of “visual stylometry,” generally defined as the development of quantitative tools for the measurement and comparisons of individual style in the visual arts. In particular, we introduce a new form of EMD analysis for images and show that it is possible to use its output as the basis for the construction of effective support vector machine (SVM)-based stylometric classifiers. We present the methodology and then test it on collections of two sets of digital captures of drawings: a set of authentic and well-known imitations of works attributed to the great Flemish artist Pieter Bruegel the Elder (1525-1569) and a set of works attributed to Dutch master Rembrandt van Rijn (1606-1669) and his pupils. Our positive results indicate that EMD-based methods may hold promise generally as a technique for visual stylometry.

  19. Stress analysis during slope failure from DEM simulations

    NASA Astrophysics Data System (ADS)

    Katz, O.; Morgan, J. K.

    2012-04-01

    We used Discrete Element Method (DEM) simulations to study the initiation and evolution of landsliding, with a focus on the development and propagation of the sliding plane, and on the effects of material strength on the behavior of the slope material during landsliding. Our simulated slopes were constructed of homogeneous materials, settled under gravity, bonded, and excavated to produce 70 deg slopes of 1050 m in height. Nine simulations were carried out, each using a different value of cohesions, ranging from 0.7 to 4.2 MPa (quantified through DEM direct shear simulations on representative materials). In each of our simulations, failure initiated at the foot of the slope, accompanied by disintegration of the slope material. Failure then propagated upward to the slope crest with further material disintegration. A discrete detachment surface formed below the disintegrated material. Downslope movement of the failed material (i.e. landsliding) occurred only after the failure plane intersected the upper slope face. By the end of landsliding, the disintegrated slope material formed a talus like deposit at the foot of the slope. The value of initial material cohesion influenced the nature of the landslide deposit and its dimension. Higher material strengths produced smaller landslides, as well as the occurrence of discrete landslide blocks, which originated from the shallow slopes, and became entrained within the finer talus. Stress analysis of the slope failure process clarifies how failure initiates and landsliding evolves, and further constrains the limiting failure criteria that define each simulated material. The local proximity to failure throughout the slope can be tracked during the simulation, revealing that high failure potential (high shear stress relative to mean stress) exists at the toe of the slope immediately following excavation. As material disintegrates near the toe of the slope, high tensile stresses develop in the overlying mass, causing the break

  20. Analysis of Noise Failure Characteristics for Superluminescent Diode Fiber-Optic Gyroscopes in Space Applications

    NASA Astrophysics Data System (ADS)

    Li, Min; Huang, Xiaokai; Jin, Jing; Chen, Yunxia; Kang, Rui

    Noise failure, particularly due to random walk error (RWE) degradation behavior, is one of the critical failure modes for fiber-optic gyroscopes (FOGs) in space applications. In this paper, firstly, the analytical model of RWE is presented and the affected parameters are listed according to the gamma irradiation damage mechanism. In addition, the influence of temperature is also included. The deterioration of affected parameters is determined through a 60Co radiation experiment on optic and optoelectronic components. Based on the parameters’ deterioration range and assumed distribution properties, their importance to the noise failure is calculated through the Sobol method, a global sensitivity analysis method. In the computation steps, the Latin Hyper Sampling (LHS) based Monte-Carlo numerical simulation technique is adopted. It is determined from calculation results that the detected light power (DLP) is the noise failure characteristic which is the most sensitive parameter in the space environment. Finally, another 60Co radiation experiment with the same conditions is performed on a superluminescent diode (SLD) FOG. The original noise degradation behavior is compared to the simulated RWE, calculated according to DLP, and the result shows that they follow trend almost identical. This supports the conclusion that DLP is the most sensitive noise failure characteristic for SLD-based FOGs.

  1. 3D statistical failure analysis of monolithic dental ceramic crowns.

    PubMed

    Nasrin, Sadia; Katsube, Noriko; Seghi, Robert R; Rokhlin, Stanislav I

    2016-07-05

    For adhesively retained ceramic crown of various types, it has been clinically observed that the most catastrophic failures initiate from the cement interface as a result of radial crack formation as opposed to Hertzian contact stresses originating on the occlusal surface. In this work, a 3D failure prognosis model is developed for interface initiated failures of monolithic ceramic crowns. The surface flaw distribution parameters determined by biaxial flexural tests on ceramic plates and point-to-point variations of multi-axial stress state at the intaglio surface are obtained by finite element stress analysis. They are combined on the basis of fracture mechanics based statistical failure probability model to predict failure probability of a monolithic crown subjected to single-cycle indentation load. The proposed method is verified by prior 2D axisymmetric model and experimental data. Under conditions where the crowns are completely bonded to the tooth substrate, both high flexural stress and high interfacial shear stress are shown to occur in the wall region where the crown thickness is relatively thin while high interfacial normal tensile stress distribution is observed at the margin region. Significant impact of reduced cement modulus on these stress states is shown. While the analyses are limited to single-cycle load-to-failure tests, high interfacial normal tensile stress or high interfacial shear stress may contribute to degradation of the cement bond between ceramic and dentin. In addition, the crown failure probability is shown to be controlled by high flexural stress concentrations over a small area, and the proposed method might be of some value to detect initial crown design errors.

  2. Lunar Module Environmental Control System Design Considerations and Failure Modes. Part 2

    NASA Technical Reports Server (NTRS)

    Interbartolo, Michael A.

    2009-01-01

    This viewgraph presentation seeks to describe the Lunar Module Environmental Control System (ECS) subsystem testing and redesign and seeks to summarize the in-flight failures of the Lunar Module (LM) Environmental Control System (ECS).

  3. Design, Fabrication and Failure Analysis of Stretchable Electrical Routings

    PubMed Central

    Hocheng, Hong; Chen, Chao-Ming

    2014-01-01

    Stretchable microelectromechanical systems (MEMS) possess higher mechanical deformability and adaptability than devices based on conventional solid and flexible substrates, hence they are particularly desirable for biomedical, optoelectronic, textile and other innovative applications. The stretchability performance can be evaluated by the failure strain of the embedded routing and the strain applied to the elastomeric substrate. The routings are divided into five forms according to their geometry: straight; wavy; wrinkly; island-bridge; and conductive-elastomeric. These designs are reviewed and their resistance-to-failure performance is investigated. The failure modeling, numerical analysis, and fabrication of routings are presented. The current review concludes with the essential factors of the stretchable electrical routing for achieving high performance, including routing angle, width and thickness. The future challenges of device integration and reliability assessment of the stretchable routings are addressed. PMID:24999718

  4. Analysis of valve failures from the NUCLARR data base

    SciTech Connect

    Moore, L.M.

    1997-11-01

    The Nuclear Computerized Library for Assessing Reactor Reliability (NUCLARR) contains data on component failures with categorical and qualifying information such as component design, normal operating state, system application and safety grade information which is important to the development of risk-based component surveillance testing requirements. This report presents descriptions and results of analyses of valve component failure data and covariate information available in the document Nuclear Computerized Library for Assessing Reactor Reliability Data Manual, Part 3: Hardware Component Failure Data (NUCLARR Data Manual). Although there are substantial records on valve performance, there are many categories of the corresponding descriptors and qualifying information for which specific values are missing. Consequently, this limits the data available for analysis of covariate effects. This report presents cross tabulations by different covariate categories and limited modeling of covariate effects for data subsets with substantive non-missing covariate information.

  5. Acoustic emission spectral analysis of fiber composite failure mechanisms

    NASA Technical Reports Server (NTRS)

    Egan, D. M.; Williams, J. H., Jr.

    1978-01-01

    The acoustic emission of graphite fiber polyimide composite failure mechanisms was investigated with emphasis on frequency spectrum analysis. Although visual examination of spectral densities could not distinguish among fracture sources, a paired-sample t statistical analysis of mean normalized spectral densities did provide quantitative discrimination among acoustic emissions from 10 deg, 90 deg, and plus or minus 45 deg, plus or minus 45 deg sub s specimens. Comparable discrimination was not obtained for 0 deg specimens.

  6. Statistical analysis of barrier isolator/glovebox glove failure.

    PubMed

    Park, Young H; Pines, E; Ofouku, M; Cournoyer, M E

    2007-01-01

    In response to new, stricter safety requirements set out by the federal government, compounding pharmacists are investigating applications and processes appropriate for their facilities. One application, cutrrently used by many industries, was developed by Los Alamos National Laboratories for defense work. A barrier isolator or "glovebox" is a containment device that allows work within a sealed space while providing protection for people and the environment. Though knowledge of glove box use and maintenance has grown, unplanned breaches (e.g., glove failures) remain a concern. Recognizing that effective maintenance procedures can minimize breaches, we analyzed data drawn from glove failure records of Los Alamos National Laboratory's Nuclear Materials Technology Division to evaluate current inventory strategy in light of actual performance of the various types of gloves. This report includes a description of the statistical methods employed. The results of our analysis pinpointed the most frequently occurring causes of glove failure and revealed a significant imbalance between the current glove replacement schedule and the rate of glove failures in a much shorter period. We concluded that, to minimize unplanned breaches, either the replacement period needs to be adjusted or causes of failure eliminated or reduced.

  7. Role of folded anisotropic fabric in the failure mode of gneiss: new insights from mechanical, microseismic and microstructural laboratory data

    NASA Astrophysics Data System (ADS)

    Agliardi, Federico; Vinciguerra, Sergio; Dobbs, Marcus R.; Zanchetta, Stefano

    2015-04-01

    Fabric anisotropy is a key control of the mechanical behaviour of rocks in a variety of geological settings and on different timescales. However, the effects of inherited, tectonically folded anisotropic fabrics on the brittle strength and failure mode of foliated metamorphic rocks is yet to be fully understood. Data from laboratory uniaxial compression tests on folded gneiss (Agliardi et al., 2014, Tectonophysics) recently showed that the brittle failure mode of this rock type depends on the arrangement of two distinct anisotropies (i.e. foliation and fold axial plane anisotropy), and that rock strength correlates with failure mode. Here we investigate the effects of confining pressure on this behaviour by performing triaxial compression experiments with acoustic emission (AE) monitoring, and analyse resulting fracture mechanisms and their microfabric controls using high resolution microanalysis techniques. We tested the Monte Canale Gneiss (Austroalpine Bernina nappe, Central Italian Alps), characterized by low phyllosilicate content, compositional layering folded at the cm-scale, and absence of a well-developed axial plane foliation. We used a servo-controlled hydraulic loading system to test 19 air-dry cylindrical specimens (diameter: 54 mm) that were characterized both in terms of fold geometry and orientation of foliation and fold axial planes to the axial load direction. We instrumented the specimens with direct contact axial and circumferential strain gauges. We performed tests at confining pressures of 40 MPa and constant axial strain rates of 5*10-6 s-1, measuring acoustic emissions and P- and S-wave velocities by three wideband (350-1000 kHz) piezoelectric transceivers with 40 dB preamps, mounted in the compression platens. We carried out post-failure microscale observation of fracture mechanisms, microcrack patterns and related fabric controls on resin-impregnated samples, using X-ray MicroCT (resolution: 9 μm), optical microscopy and SEM. Samples

  8. Fracture resistance and failure mode of posterior fixed dental prostheses fabricated with two zirconia CAD/CAM systems

    PubMed Central

    López-Suárez, Carlos; Gonzalo, Esther; Peláez, Jesús; Rodríguez, Verónica

    2015-01-01

    Background In recent years there has been an improvement of zirconia ceramic materials to replace posterior missing teeth. To date little in vitro studies has been carried out on the fracture resistance of zirconia veneered posterior fixed dental prostheses. This study investigated the fracture resistance and the failure mode of 3-unit zirconia-based posterior fixed dental prostheses fabricated with two CAD/CAM systems. Material and Methods Twenty posterior fixed dental prostheses were studied. Samples were randomly divided into two groups (n=10 each) according to the zirconia ceramic analyzed: Lava and Procera. Specimens were loaded until fracture under static load. Data were analyzed using Wilcoxon´s rank sum test and Wilcoxon´s signed-rank test (P<0.05). Results Partial fracture of the veneering porcelain occurred in 100% of the samples. Within each group, significant differences were shown between the veneering and the framework fracture resistance (P=0.002). The failure occurred in the connector cervical area in 80% of the cases. Conclusions All fracture load values of the zirconia frameworks could be considered clinically acceptable. The connector area is the weak point of the restorations. Key words:Fixed dental prostheses, zirconium-dioxide, zirconia, fracture resistance, failure mode. PMID:26155341

  9. User's manual for the coupled mode version of the normal modes rotor aeroelastic analysis computer program

    NASA Technical Reports Server (NTRS)

    Bergquist, R. R.; Carlson, R. G.; Landgrebe, A. J.; Egolf, T. A.

    1974-01-01

    This User's Manual was prepared to provide the engineer with the information required to run the coupled mode version of the Normal Modes Rotor Aeroelastic Analysis Computer Program. The manual provides a full set of instructions for running the program, including calculation of blade modes, calculations of variable induced velocity distribution and the calculation of the time history of the response for either a single blade or a complete rotor with an airframe (the latter with constant inflow).

  10. Analysis of Linear Conversion to Two Modes

    NASA Astrophysics Data System (ADS)

    Brizard, Alain J.; Jaun, Andre; Kaufman, Allan N.; Tracy, Eugene R.

    2003-10-01

    Recent experimental observations [1] and computer simulations [2] show that, in a tokamak plasma with multispecies ions, an incident magnetosonic wave converts either to an ion-hybrid Bernstein wave or to an ion-cyclotron wave, depending on the location of the conversion region in the poloidal cross section. We present a cold-plasma model of simultaneous conversion to these two modes, and obtain explicit expressions for transmission and conversion coefficients. Our approach is based on phase-space analysis of multiple conversion [3], in two or four phase-space dimensions (i.e., one or two spatial dimensions).Our ray-tracing algorithm [4], for detection of conversion and for treatment of ray-splitting due to conversion, will be applied to this process. 1.E Nelson-Melby, M Porkolab, P T Bonoli, Y Lin, A Mazurenko, S J Wukitch, Phys Rev Lett 90 (2003) 155004 2.E F Jaeger, L A Berry, J R Myra, D B Batchelor, E D'Azevedo, P T Bonoli, C K Phillips, D N Smithe, D A D'Ippolito, M D Carter, R J Dumont, J C Wright, R W Harvey, Phys Rev Lett 90 (2003) 195001 3. Y-M Liang, J J Morehead, D R Cook, T Fla, A N Kaufman, Physics Letters A193 (1994) 82 4. E R Tracy, A N Kaufman, A Jaun, Physics Letters A290 (2001) 309

  11. Changes in structural style of normal faults due to failure mode transition: First results from excavated scale models

    NASA Astrophysics Data System (ADS)

    Kettermann, Michael; Urai, Janos L.

    2015-05-01

    The effects of failure mode transition from tensile to shear on structural style and fault zone architecture have long been recognized but are not well studied in 3D, although the two modes are both common in the upper crust of Earth and terrestrial planets, and are associated with large differences in transport properties. We present a simple method to study this in physical scale models of normal faults, using a cohesive powder embedded in cohesionless sand. By varying the overburden thickness, the failure mode changes from tensile to hybrid and finally to shear. Hardening and excavating the cohesive layer allows post mortem investigation of 3D structures at high resolution. We recognize two end member structural domains that differ strongly in their attributes. In the tensile domain faults are strongly dilatant with steep open fissures and sharp changes in strike at segment boundaries and branch points. In the shear domain fault dips are shallower and fault planes develop striations; map-view fault traces undulate with smaller changes in strike at branches. These attributes may be recognized in subsurface fault maps and could provide a way to better predict fault zone structure in the subsurface.

  12. An analysis of molten-corium-induced failure of drain pipes in BWR Mark 2 containments

    SciTech Connect

    Taleyarkhan, R.P. ); Podowski, M.Z. )

    1991-01-01

    This study has focused on mechanistic simulation and analysis of potential failure modes for inpedestal drywell drain pipes in the Limerick boiling water reactor (BWR) Mark 2 containment. Physical phenomena related to surface tension breakdown, heatup, melting, ablation, crust formation and failure, and core material relocation into drain pipes with simultaneous melting of pipe walls were modeled and analyzed. The results of analysis have been used to assess the possibility of drain pipe failure and the resultant loss of pressure-suppression capability. Estimates have been made for the timing and amount of molten corium released to the wetwell. The study has revealed that significantly different melt progression sequences can result depending upon the failure characteristics of the frozen metallic crust which forms over the drain cover during the initial stages of debris pour. Another important result is that it can take several days for the molten fuel to ablate the frozen metallic debris layer -- if the frozen layer has cooled below 1100 K before fuel attack. 10 refs., 3 figs., 4 tabs.

  13. The effect of resin toughness and modulus on compressive failure modes of quasi-isotropic graphite/epoxy laminates

    NASA Technical Reports Server (NTRS)

    Sohi, M. M.; Hahn, H. T.; Williams, J. G.

    1986-01-01

    Compressive failure mechanisms in quasi-isotropic graphite/epoxy laminates were characterized for both unnotched and notched specimens and also following damage by impact. Two types of fibers (Thornel 300 and 700) and four resin systems (Narmco 5208, American Cyanamid BP907, and Union Carbide 4901/MDA and 4901/mPDA) were studied. For all material combinations, failure of unnotched specimens was initiated by kinking of fibers in the 0-degree plies. A major difference was observed, however, in the mode of failure propagation after the 0-degree ply failure. The strength of quasi-isotropic laminates in general increased with increasing resin tensile modulus. The laminates made with Thornel 700 fibers exhibited slightly lower compressive strengths than did the laminates made with Thornel 300 fibers. The notch sensitivity as measured by the hole strength was lowest for the BP907 resin and highest for the 5208 resin. For the materials studied, however, the type of fiber had no effect on the notch sensitivity.

  14. Failure modes of reduced-order orbit determination filters and their remedies

    NASA Technical Reports Server (NTRS)

    Scheeres, D. J.

    1993-01-01

    Ways in which failure can occur in reduced-order, orbit determination filter, error covariance calculations are discussed. In the context of this article, reduced-order filters denote nonoptimal filters which include fixed levels of uncertainty in some parameters of the measurement models or in the spacecraft dynamical model which are not explicitly estimated in the filter equations. Failure is defined as an increase in the orbit determination covariance with the addition of data or as an unreasonable growth in the covariance with time, i.e., nonasymptotic behavior of the covariance. Some simple, known cases of failure are discussed along with their traditional remedies. In addition, more modern remedies are discussed which are currently under development at the Jet Propulsion Laboratory. The article first describes the known problems of reduced-order filters when they are employed for orbit determination, and their traditional remedies. Then, having defined these, the relevancy and desirability of the more modern remedies are made apparent.

  15. STRESS AND FAILURE ANALYSIS OF RAPIDLY ROTATING ASTEROID (29075) 1950 DA

    SciTech Connect

    Hirabayashi, Masatoshi; Scheeres, Daniel J.

    2015-01-01

    Rozitis et al. recently reported that near-Earth asteroid (29075) 1950 DA, whose bulk density ranges from 1.0 g cm{sup –3} to 2.4 g cm{sup –3}, is a rubble pile and requires a cohesive strength of at least 44-76 Pa to keep from failing due to its fast spin period. Since their technique for giving failure conditions required the averaged stress over the whole volume, it discarded information about the asteroid's failure mode and internal stress condition. This paper develops a finite element model and revisits the stress and failure analysis of 1950 DA. For the modeling, we do not consider material hardening and softening. Under the assumption of an associated flow rule and uniform material distribution, we identify the deformation process of 1950 DA when its constant cohesion reaches the lowest value that keeps its current shape. The results show that to avoid structural failure the internal core requires a cohesive strength of at least 75-85 Pa. It suggests that for the failure mode of this body, the internal core first fails structurally, followed by the surface region. This implies that if cohesion is constant over the whole volume, the equatorial ridge of 1950 DA results from a material flow going outward along the equatorial plane in the internal core, but not from a landslide as has been hypothesized. This has additional implications for the likely density of the interior of the body.

  16. Beta blockers in heart failure haemodynamics, clinical effects and modes of action

    PubMed Central

    de Milliano, P.A.R.; Tijssen, J.G.P.; van Zwieten, P.A.; Lie, K.I.

    2001-01-01

    Treatment for heart failure may be directed at relieving symptoms and/or improving prognosis. One of the primary aims of research in heart failure is to alter the progressive decline in pump function and thereby improve prognosis. For many years, diuretics have been known as therapeutics in heart failure and they are very effective in symptom relief. Vasodilators and inotropes also have beneficial effects on symptom relief especially in the acute phase through changes in cardiac output, filling pressures and renal perfusion. However, although these treatments produce short-term relief, none have been shown to influence the disease process and thereby improve mortality. Indeed, many of these drugs may even lead to untoward long-term clinical outcomes as has been shown for example for milrinone and ibopamine. There is overwhelming evidence that drugs interfering with the neurohormonal activation in heart failure not only produce symptomatic relief but are also capable of attenuating disease progression with concomitant reductions in both morbidity and mortality. About a decade ago, convincing and large-scale evidence showed that ACE inhibitors produced favourable effects by antagonising the activated renin-angiotensin system. More recently, β-blockers, which antagonise the activated sympathetic system, were shown to be beneficial in the long term in moderate severe heart failure in terms of significant improvements in both morbidity and mortality. The RALES study further amplified the concept that drugs that interact in the neurohormonal system have beneficial effects. In this study, spironolactone, a weak, potassium-sparing diuretic counteracting aldosterone showed a reduction in mortality in more severe forms of heart failure. PMID:25696756

  17. Reliability analysis and prediction of mixed mode load using Markov Chain Model

    SciTech Connect

    Nikabdullah, N.; Singh, S. S. K.; Alebrahim, R.; Azizi, M. A.; K, Elwaleed A.; Noorani, M. S. M.

    2014-06-19

    The aim of this paper is to present the reliability analysis and prediction of mixed mode loading by using a simple two state Markov Chain Model for an automotive crankshaft. The reliability analysis and prediction for any automotive component or structure is important for analyzing and measuring the failure to increase the design life, eliminate or reduce the likelihood of failures and safety risk. The mechanical failures of the crankshaft are due of high bending and torsion stress concentration from high cycle and low rotating bending and torsional stress. The Markov Chain was used to model the two states based on the probability of failure due to bending and torsion stress. In most investigations it revealed that bending stress is much serve than torsional stress, therefore the probability criteria for the bending state would be higher compared to the torsion state. A statistical comparison between the developed Markov Chain Model and field data was done to observe the percentage of error. The reliability analysis and prediction was derived and illustrated from the Markov Chain Model were shown in the Weibull probability and cumulative distribution function, hazard rate and reliability curve and the bathtub curve. It can be concluded that Markov Chain Model has the ability to generate near similar data with minimal percentage of error and for a practical application; the proposed model provides a good accuracy in determining the reliability for the crankshaft under mixed mode loading.

  18. Evaluation of a Progressive Failure Analysis Methodology for Laminated Composite Structures

    NASA Technical Reports Server (NTRS)

    Sleight, David W.; Knight, Norman F., Jr.; Wang, John T.

    1997-01-01

    A progressive failure analysis methodology has been developed for predicting the nonlinear response and failure of laminated composite structures. The progressive failure analysis uses C plate and shell elements based on classical lamination theory to calculate the in-plane stresses. Several failure criteria, including the maximum strain criterion, Hashin's criterion, and Christensen's criterion, are used to predict the failure mechanisms. The progressive failure analysis model is implemented into a general purpose finite element code and can predict the damage and response of laminated composite structures from initial loading to final failure.

  19. Tearing mode analysis in tokamaks, revisited

    SciTech Connect

    Nishimura, Y.; Callen, J.D.; Hegna, C.C.

    1998-12-01

    A new {Delta}{sup {prime}} shooting code has been developed to investigate tokamak plasma tearing mode stability in a cylinder and large aspect ratio ({epsilon}{le}0.25) toroidal geometries, neglecting toroidal mode coupling. A different computational algorithm is used (shooting out from the singular surface instead of into it) to resolve the strong singularities at the mode rational surface, particularly in the presence of the finite pressure term. Numerical results compare favorably with Furth {ital et al.} [H. P. Furth {ital et al.}, Phys. Fluids {bold 16}, 1054 (1973)] results. The effects of finite pressure, which are shown to decrease {Delta}{sup {prime}}, are discussed. It is shown that the distortion of the flux surfaces by the Shafranov shift, which modifies the geometry metric elements, stabilizes the tearing mode significantly, even in a low-{beta} regime before the toroidal magnetic curvature effects come into play. {copyright} {ital 1998 American Institute of Physics.}

  20. Failure analysis of an Oregon coast reinforced concrete bridge

    SciTech Connect

    Holcomb, Gordon R.; Covino, Bernard S., Jr.; Cramer, Stephen D.; Bullard, Sophie J.; Russell, James H.; Soltesz, S.M.

    2001-01-01

    The coastal highway along the Oregon coast contains many reinforced concrete bridges constructed between 1925 and 1955. Chloride-induced corrosion resulted in the need for the rehabilitation or replacement of a number of these bridges. A failure analysis of the Rocky Point Viaduct (built in 1954, patched in 1969, replaced in 1994) is presented. Analysis included powder sampling and profiling of Cl concentration, determining the permeable void fraction in the concrete, and measuring rebar half cell potentials. Insufficient concrete cover over the shear stirrups was the major factor in the premature failure of the Viaduct. The time required for corrosion initiation and cracking was modeled by calculating diffusion parameters (surface Cl concentration (Co) and diffusion coefficient (D)) from Cl profiles. The model was used to examine the relative ineffectiveness of the patch repairs by showing increased Cl transport in the patch due to both higher Co and D values.

  1. Failure analysis of a half-micron CMOS IC technology

    SciTech Connect

    Liang, A.Y.; Tangyunyong, P.; Bennett, R.S.; Flores, R.S.

    1996-08-01

    We present the results of recent failure analysis of an advanced, 0.5 {mu}m, fully planarized, triple metallization CMOS technology. A variety of failure analysis (FA) tools and techniques were used to localize and identify defects generated by wafer processing. These include light (photon) emission microscopy (LE), fluorescent microthermal imaging (FMI), focused ion beam cross sectioning, SEM/voltage contrast imaging, resistive contrast imaging (RCI), and e-beam testing using an IDS-5000 with an HP 82000. The defects identified included inter- and intra-metal shorts, gate oxide shorts due to plasma processing damage, and high contact resistance due to the contact etch and deposition process. Root causes of these defects were determined and corrective action was taken to improve yield and reliability.

  2. Stripper foil failure modes and cures at the Oak Rdige Spallation Neutron Source

    SciTech Connect

    Plum, M.A.; Raparia, D.; Cousineau, S.M.; Galambos, J.; Kim, S.H.; Ladd, P.; Luck, C.F.; Peters, C.C.; Polsky, Y.; Shaw, R.W.; Macek, R.J.

    2011-03-28

    The Oak Ridge Spallation Neutron Source comprises a 1 GeV, 1.5 MW linear accelerator followed by an accumulator ring and a liquid mercury target. To manage the beam loss caused by the H{sup 0} excited states created during the H{sup -} charge-exchange injection into the accumulator ring, the stripper foil is located inside one of the chicane dipoles. This has some interesting consequences that were not fully appreciated until the beam power reached about 840 kW. One consequence was sudden failure of the stripper foil system due to convoy electrons stripped from the incoming H{sup -} beam, which circled around to strike the foil bracket and cause bracket failure. Another consequence is that convoy electrons can reflect back up from the electron catcher and strike the foil and bracket. An additional contributor to foil system failure is vacuum breakdown due to the charge developed on the foil by secondary electron emission. In this paper we detail these and other interesting failure mechanisms and describe the improvements we have made to mitigate them.

  3. Stripper foil failure modes and cures at the Spallation Neutron Source

    SciTech Connect

    Cousineau, Sarah M; Galambos, John D; Kim, Sang-Ho; Ladd, Peter; Luck, Chris; Peters, Charles C; Polsky, Yarom; Shaw, Robert W; Raparia, Deepak; Macek, Robert James; Plum, Michael A

    2011-01-01

    The Spallation Neutron Source comprises a 1 GeV, 1.4 MW linear accelerator followed by an accumulator ring and a liquid mercury target. To manage the beam loss caused by the $H^0$ excited states created during the $H^-$ charge exchange injection into the accumulator ring, the stripper foil is located inside one of the chicane dipoles. This has some interesting consequences that were not fully appreciated until the beam power reached about 840 kW. One consequence was sudden failure of the stripper foil system due to convoy electrons stripped from the incoming $H^-$ beam, which circled around to strike the foil bracket and cause bracket failure. Another consequence is that convoy electrons can reflect back up from the electron catcher and strike the foil and bracket. An additional contributor to foil system failure is vacuum breakdown due to the charge developed on the foil by secondary electron emission. In this paper we detail these and other interesting failure mechanisms and describe the improvements we have made to mitigate them.

  4. Fuzzy Failure Analysis: A New Approach to Service Quality Analysis in Higher Education Institutions (Case Study: Vali-e-asr University of Rafsanjan-Iran)

    ERIC Educational Resources Information Center

    Takalo, Salim Karimi; Abadi, Ali Reza Naser Sadr; Vesal, Seyed Mahdi; Mirzaei, Amir; Nawaser, Khaled

    2013-01-01

    In recent years, concurrent with steep increase in the growth of higher education institutions, improving of educational service quality with an emphasis on students' satisfaction has become an important issue. The present study is going to use the Failure Mode and Effect Analysis (FMEA) in order to evaluate the quality of educational services in…

  5. Shear Fracture of Dual Phase AHSS in the Process of Stamping: Macroscopic Failure Mode and Micro-level Metallographical Observation

    NASA Astrophysics Data System (ADS)

    Wang, Wurong; Wei, Xicheng; Yang, Jun; Shi, Gang

    2011-08-01

    Due to its excellent strength and formability combinations, dual phase (DP) steels offer the potential to improve the vehicle crashworthiness performance without increasing car body weight and have been increasingly used into new vehicles. However, a new type of crack mode termed as shear fracture is accompanied with the application of these high strength DP steel sheets. With the cup drawing experiment to identify the limit drawing ratio (LDR) of three DP AHSS with strength level from 600 MPa to 1000 MPa, the study compared and categorized the macroscopic failure mode of these three types of materials. The metallographical observation along the direction of crack was conducted for the DP steels to discover the micro-level propagation mechanism of the fracture.

  6. Failure Modes in Capacitors When Tested Under a Time-Varying Stress

    NASA Technical Reports Server (NTRS)

    Liu, David (Donhang)

    2011-01-01

    Power-on failure has been the prevalent failure mechanism for solid tantalum capacitors in decoupling applications. A surge step stress test (SSST) has been previously applied to identify the critical stress level of a capacitor batch to give some predictability to the power-on failure mechanism [1]. But SSST can also be viewed as an electrically destructive test under a time-varying stress (voltage). It consists of rapidly charging the capacitor with incremental voltage increases, through a low resistance in series, until the capacitor under test is electrically shorted. When the reliability of capacitors is evaluated, a highly accelerated life test (HALT) is usually adopted since it is a time-efficient method of determining the failure mechanism; however, a destructive test under a time-varying stress such as SSST is even more time efficient. It usually takes days or weeks to complete a HALT test, but it only takes minutes for a time-varying stress test to produce failures. The advantage of incorporating a specific time-varying stress profile into a statistical model is significant in providing an alternative life test method for quickly revealing the failure mechanism in capacitors. In this paper, a time-varying stress that mimics a typical SSST has been incorporated into the Weibull model to characterize the failure mechanism in different types of capacitors. The SSST circuit and transient conditions for correctly surge testing capacitors are discussed. Finally, the SSST was applied for testing Ta capacitors, polymer aluminum capacitors (PA capacitors), and multi-layer ceramic (MLC) capacitors with both precious metal electrodes (PME) and base metal electrodes (BME). The test results are found to be directly associated with the dielectric layer breakdown in Ta and PA capacitors and are independent of the capacitor values, the way the capacitors were built, and the capacitors manufacturers. The test results also show that MLC capacitors exhibit surge breakdown

  7. Tearing mode analysis in tokamaks, revisited

    SciTech Connect

    Nishimura, Y.; Callen, J.D.; Hegna, C.C.

    1997-12-01

    A new {Delta}{prime} shooting code has been developed to investigate tokamak plasma tearing mode stability in a cylinder and large aspect ratio ({epsilon} {le} 0.25) toroidal geometries, neglecting toroidal mode coupling. A different computational algorithm is used (shooting out from the singular surface instead of into it) to resolve the strong singularities at the mode rational surface, particularly in the presence of finite pressure term. Numerical results compare favorably with Furth et al. results. The effects of finite pressure, which are shown to decrease {Delta}{prime}, are discussed. It is shown that the distortion of the flux surfaces by the Shafranov shift, which modifies the geometry metric element stabilizes the tearing mode significantly, even in a low {beta} regime before the toroidal magnetic curvature effects come into play. Double tearing modes in toroidal geometries are examined as well. Furthermore, m {ge} 2 tearing mode stability criteria are compared with three dimensional initial value MHD simulation by the FAR code.

  8. Seismic analysis for translational failure of landfills with retaining walls.

    PubMed

    Feng, Shi-Jin; Gao, Li-Ya

    2010-11-01

    In the seismic impact zone, seismic force can be a major triggering mechanism for translational failures of landfills. The scope of this paper is to develop a three-part wedge method for seismic analysis of translational failures of landfills with retaining walls. The approximate solution of the factor of safety can be calculated. Unlike previous conventional limit equilibrium methods, the new method is capable of revealing the effects of both the solid waste shear strength and the retaining wall on the translational failures of landfills during earthquake. Parameter studies of the developed method show that the factor of safety decreases with the increase of the seismic coefficient, while it increases quickly with the increase of the minimum friction angle beneath waste mass for various horizontal seismic coefficients. Increasing the minimum friction angle beneath the waste mass appears to be more effective than any other parameters for increasing the factor of safety under the considered condition. Thus, selecting liner materials with higher friction angle will considerably reduce the potential for translational failures of landfills during earthquake. The factor of safety gradually increases with the increase of the height of retaining wall for various horizontal seismic coefficients. A higher retaining wall is beneficial to the seismic stability of the landfill. Simply ignoring the retaining wall will lead to serious underestimation of the factor of safety. Besides, the approximate solution of the yield acceleration coefficient of the landfill is also presented based on the calculated method.

  9. Measurement and Analysis of Failures in Computer Systems

    NASA Technical Reports Server (NTRS)

    Thakur, Anshuman

    1997-01-01

    This thesis presents a study of software failures spanning several different releases of Tandem's NonStop-UX operating system running on Tandem Integrity S2(TMR) systems. NonStop-UX is based on UNIX System V and is fully compliant with industry standards, such as the X/Open Portability Guide, the IEEE POSIX standards, and the System V Interface Definition (SVID) extensions. In addition to providing a general UNIX interface to the hardware, the operating system has built-in recovery mechanisms and audit routines that check the consistency of the kernel data structures. The analysis is based on data on software failures and repairs collected from Tandem's product report (TPR) logs for a period exceeding three years. A TPR log is created when a customer or an internal developer observes a failure in a Tandem Integrity system. This study concentrates primarily on those TPRs that report a UNIX panic that subsequently crashes the system. Approximately 200 of the TPRs fall into this category. Approximately 50% of the failures reported are from field systems, and the rest are from the testing and development sites. It has been observed by Tandem developers that fewer cases are encountered from the field than from the test centers. Thus, the data selection mechanism has introduced a slight skew.

  10. Fault tree analysis of most common rolling bearing tribological failures

    NASA Astrophysics Data System (ADS)

    Vencl, Aleksandar; Gašić, Vlada; Stojanović, Blaža

    2017-02-01

    Wear as a tribological process has a major influence on the reliability and life of rolling bearings. Field examinations of bearing failures due to wear indicate possible causes and point to the necessary measurements for wear reduction or elimination. Wear itself is a very complex process initiated by the action of different mechanisms, and can be manifested by different wear types which are often related. However, the dominant type of wear can be approximately determined. The paper presents the classification of most common bearing damages according to the dominant wear type, i.e. abrasive wear, adhesive wear, surface fatigue wear, erosive wear, fretting wear and corrosive wear. The wear types are correlated with the terms used in ISO 15243 standard. Each wear type is illustrated with an appropriate photograph, and for each wear type, appropriate description of causes and manifestations is presented. Possible causes of rolling bearing failure are used for the fault tree analysis (FTA). It was performed to determine the root causes for bearing failures. The constructed fault tree diagram for rolling bearing failure can be useful tool for maintenance engineers.

  11. Defining Human Failure Events for Petroleum Risk Analysis

    SciTech Connect

    Ronald L. Boring; Knut Øien

    2014-06-01

    In this paper, an identification and description of barriers and human failure events (HFEs) for human reliability analysis (HRA) is performed. The barriers, called target systems, are identified from risk significant accident scenarios represented as defined situations of hazard and accident (DSHAs). This report serves as the foundation for further work to develop petroleum HFEs compatible with the SPAR-H method and intended for reuse in future HRAs.

  12. Hope in elderly adults with chronic heart failure. Concept analysis

    PubMed Central

    Caboral, Meriam F.; Evangelista, Lorraine S.; Whetsell, Martha V.

    2015-01-01

    This topic review employed Walker and Avant’s method of concept analysis to explore the construct of hope in elderly adults with chronic heart failure. The articles analyzed revealed that hope, as the belief of the occurrence of a positive result without any guarantee that it will be produced, is necessary for the survival and wellbeing of the elderly adults enduring this disease. PMID:26321777

  13. Compressive failure modes and parameter optimization of the trabecular structure of biomimetic fully integrated honeycomb plates.

    PubMed

    Chen, Jinxiang; Tuo, Wanyong; Zhang, Xiaoming; He, Chenglin; Xie, Juan; Liu, Chang

    2016-12-01

    To develop lightweight biomimetic composite structures, the compressive failure and mechanical properties of fully integrated honeycomb plates were investigated experimentally and through the finite element method. The results indicated that: fracturing of the fully integrated honeycomb plates primarily occurred in the core layer, including the sealing edge structure. The morphological failures can be classified into two types, namely dislocations and compactions, and were caused primarily by the stress concentrations at the interfaces between the core layer and the upper and lower laminations and secondarily by the disordered short-fiber distribution in the material; although the fully integrated honeycomb plates manufactured in this experiment were imperfect, their mass-specific compressive strength was superior to that of similar biomimetic samples. Therefore, the proposed bio-inspired structure possesses good overall mechanical properties, and a range of parameters, such as the diameter of the transition arc, was defined for enhancing the design of fully integrated honeycomb plates and improving their compressive mechanical properties.

  14. Seismicity, shear failure and modes of deformation in deep subduction zones

    NASA Technical Reports Server (NTRS)

    Lundgren, Paul R.; Giardini, Domenico

    1992-01-01

    The joint hypocentral determination method is used to relocate deep seismicity reported in the International Seismological Center catalog for earthquakes deeper than 400 km in the Honshu, Bonin, Mariannas, Java, Banda, and South America subduction zones. Each deep seismic zone is found to display planar features of seismicity parallel to the Harvard centroid-moment tensor nodal planes, which are identified as planes of shear failure. The sense of displacement on these planes is one of resistance to deeper penetration.

  15. Fundamental aspects of and failure modes in high-temperature composites

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.; Ginty, Carol A.

    1990-01-01

    Fundamental aspects of and attendant failure mechanisms for high temperature composites are summarized. These include: (1) in-situ matrix behavior; (2) load transfer; (3) limits on matrix ductility to survive a given number of cyclic loadings; (4) fundamental parameters which govern thermal stresses; (5) vibration stresses; and (6) impact resistance. The resulting guidelines are presented in terms of simple equations which are suitable for the preliminary assessment of the merits of a particular high temperature composite in a specific application.

  16. Surface plasmon mode analysis of nanoscale metallic rectangular waveguide.

    PubMed

    Kong, Fanmin; Wu, Bae-Ian; Chen, Hongsheng; Kong, Jin Au

    2007-09-17

    A detailed study of guided modes in a nanoscale metallic rectangular waveguide is presented by using the effective dielectric constant approach. The guided modes, including both traditional waveguide mode and surface plasmon mode, are investigated for the silver rectangular waveguide. The mode evolution in narrow waveguide is also discussed with the emphasis on the dependence of mode dispersion with waveguide height. Finally, the red-shift of the cutoff wavelength of the fundamental mode is observed when the waveguide height decreases, contrary to the behavior of regular metallic waveguide with PEC boundary. The comprehensive analysis can provide some guideline in the design of subwavelength optical devices based on the dispersion characteristics of metallic rectangular bore.

  17. Further Development of Rotating Rake Mode Measurement Data Analysis

    NASA Technical Reports Server (NTRS)

    Dahl, Milo D.; Hixon, Ray; Sutliff, Daniel L.

    2013-01-01

    The Rotating Rake mode measurement system was designed to measure acoustic duct modes generated by a fan stage. After analysis of the measured data, the mode amplitudes and phases were quantified. For low-speed fans within axisymmetric ducts, mode power levels computed from rotating rake measured data would agree with the far-field power levels on a tone by tone basis. However, this agreement required that the sound from the noise sources within the duct propagated outward from the duct exit without reflection at the exit and previous studies suggested conditions could exist where significant reflections could occur. To directly measure the modes propagating in both directions within a duct, a second rake was mounted to the rotating system with an offset in both the axial and the azimuthal directions. The rotating rake data analysis technique was extended to include the data measured by the second rake. The analysis resulted in a set of circumferential mode levels at each of the two rake microphone locations. Radial basis functions were then least-squares fit to this data to obtain the radial mode amplitudes for the modes propagating in both directions within the duct. The fit equations were also modified to allow evanescent mode amplitudes to be computed. This extension of the rotating rake data analysis technique was tested using simulated data, numerical code produced data, and preliminary in-duct measured data.

  18. Failure Rate Data Analysis for High Technology Components

    SciTech Connect

    L. C. Cadwallader

    2007-07-01

    Understanding component reliability helps designers create more robust future designs and supports efficient and cost-effective operations of existing machines. The accelerator community can leverage the commonality of its high-vacuum and high-power systems with those of the magnetic fusion community to gain access to a larger database of reliability data. Reliability studies performed under the auspices of the International Energy Agency are the result of an international working group, which has generated a component failure rate database for fusion experiment components. The initial database work harvested published data and now analyzes operating experience data. This paper discusses the usefulness of reliability data, describes the failure rate data collection and analysis effort, discusses reliability for components with scarce data, and points out some of the intersections between magnetic fusion experiments and accelerators.

  19. Uncertainty Analysis via Failure Domain Characterization: Polynomial Requirement Functions

    NASA Technical Reports Server (NTRS)

    Crespo, Luis G.; Munoz, Cesar A.; Narkawicz, Anthony J.; Kenny, Sean P.; Giesy, Daniel P.

    2011-01-01

    This paper proposes an uncertainty analysis framework based on the characterization of the uncertain parameter space. This characterization enables the identification of worst-case uncertainty combinations and the approximation of the failure and safe domains with a high level of accuracy. Because these approximations are comprised of subsets of readily computable probability, they enable the calculation of arbitrarily tight upper and lower bounds to the failure probability. A Bernstein expansion approach is used to size hyper-rectangular subsets while a sum of squares programming approach is used to size quasi-ellipsoidal subsets. These methods are applicable to requirement functions whose functional dependency on the uncertainty is a known polynomial. Some of the most prominent features of the methodology are the substantial desensitization of the calculations from the uncertainty model assumed (i.e., the probability distribution describing the uncertainty) as well as the accommodation for changes in such a model with a practically insignificant amount of computational effort.

  20. Uncertainty Analysis via Failure Domain Characterization: Unrestricted Requirement Functions

    NASA Technical Reports Server (NTRS)

    Crespo, Luis G.; Kenny, Sean P.; Giesy, Daniel P.

    2011-01-01

    This paper proposes an uncertainty analysis framework based on the characterization of the uncertain parameter space. This characterization enables the identification of worst-case uncertainty combinations and the approximation of the failure and safe domains with a high level of accuracy. Because these approximations are comprised of subsets of readily computable probability, they enable the calculation of arbitrarily tight upper and lower bounds to the failure probability. The methods developed herein, which are based on nonlinear constrained optimization, are applicable to requirement functions whose functional dependency on the uncertainty is arbitrary and whose explicit form may even be unknown. Some of the most prominent features of the methodology are the substantial desensitization of the calculations from the assumed uncertainty model (i.e., the probability distribution describing the uncertainty) as well as the accommodation for changes in such a model with a practically insignificant amount of computational effort.

  1. SAS: a yield/failure analysis software tool

    NASA Astrophysics Data System (ADS)

    de Jong Perez, Susana

    1996-09-01

    As the device sizes decrease and the number of interconnect levels and wafer size increase, the device yield and failure analysis becomes more complex. Currently, software tools are being used to perform visual inspection techniques after many operations during which defects are detected on a sample of wafers. However, it has been observed that the correlation between the yield predicted on the basis of the defects found during such observations and the yield determined electrically at wafer final test is low. Of a greater interest to yield/failure analysis software tools is statistical analysis software. SASTM can perform extensive data analysis on kerf test structures' electrical parameters. In addition, the software can merge parametric and yield/fail bins data which reduces the data collection and data reduction activities involved in the correlation of device parameters to circuit functional operation. The data is saved in large databases which allow storage and later retrieval of historical data in order to evaluate process shifts and changes and their effect on yield. The merge of process parameters and on-line measurements with final electrical data, is also possible with the aid of process parameter extraction software. All of this data analysis provides excellent feedback about integrated circuit wafer processing.

  2. Simulation and Analysis of the Hybrid Operating Mode in ITER

    SciTech Connect

    Kessel, C.E.; Budny, R.V.; Indireshkumar, K.

    2005-09-22

    The hybrid operating mode in ITER is examined with 0D systems analysis, 1.5D discharge scenario simulations using TSC and TRANSP, and the ideal MHD stability is discussed. The hybrid mode has the potential to provide very long pulses and significant neutron fluence if the physics regime can be produced in ITER. This paper reports progress in establishing the physics basis and engineering limitation for the hybrid mode in ITER.

  3. Program to analyze the failure mode of lead-acid batteries

    SciTech Connect

    Zuckerbrod, D.

    1986-03-01

    The electrical characteristics of large lead-acid cells from nuclear power plants were studied. The overall goal was to develop nondestructive tests to predict cell failure using this easily obtained information. Cell capacitance, internal resistance, reaction resistance for hydrogen evolution and cell capacity were measured on a lead-calcium cell in good condition. A high float voltage and low internal resistance were found to correlate with good cell capacity in cells selected from a set of six lead-antimony cells in poor condition.

  4. Study on failure analysis of array chip components in IRFPA

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaonan; He, Yingjie; Li, Jinping

    2016-10-01

    Infrared focal plane array detector has advantages of strong anti-interference ability and high sensitivity. Its size, weight and power dissipation has been noticeably decreased compared to the conventional infrared imaging system. With the development of the detector manufacture technology and the cost reduction, IRFPA detector has been widely used in the military and commercial fields. Due to the restricting of array chip manufacturing process and material defects, the fault phenomenon such as cracking, bad pixel and abnormal output was showed during the test, which restricts the performance of the infrared detector imaging system, and these effects are gradually intensified with the expanding of the focal plane array size and the shrinking of the pixel size. Based on the analysis of the test results for the infrared detector array chip components, the fault phenomenon was classified. The main cause of the chip component failure is chip cracking, bad pixel and abnormal output. The reason of the failure has been analyzed deeply. According to analyze the mechanism of the failure, a series of measures which contain filtrating materials and optimizing the manufacturing process of array chip components were used to improve the performance of the chip components and the test pass rate, which is used to meet the needs of the detector performance.

  5. Canonical failure modes of real-time control systems: insights from cognitive theory

    NASA Astrophysics Data System (ADS)

    Wallace, Rodrick

    2016-04-01

    Newly developed necessary conditions statistical models from cognitive theory are applied to generalisation of the data-rate theorem for real-time control systems. Rather than graceful degradation under stress, automatons and man/machine cockpits appear prone to characteristic sudden failure under demanding fog-of-war conditions. Critical dysfunctions span a spectrum of phase transition analogues, ranging from a ground state of 'all targets are enemies' to more standard data-rate instabilities. Insidious pathologies also appear possible, akin to inattentional blindness consequent on overfocus on an expected pattern. Via no-free-lunch constraints, different equivalence classes of systems, having structure and function determined by 'market pressures', in a large sense, will be inherently unreliable under different but characteristic canonical stress landscapes, suggesting that deliberate induction of failure may often be relatively straightforward. Focusing on two recent military case histories, these results provide a caveat emptor against blind faith in the current path-dependent evolutionary trajectory of automation for critical real-time processes.

  6. Characterization of Deformation and Failure Modes of Ordinary and Auxetic Foams at Different Length Scales

    NASA Astrophysics Data System (ADS)

    Chiang, Fu-Pen

    Sandwich panels with foam core have gained substantial importance in marine structures for the past several decades. However, designers of ships still lack the confidence in composites when compared to traditional structural materials such as aluminum or steel. As a result, composite structures tend to be overdesigned to provide added safety. While there have been numerous studies, most investigators treat the foam cores as made of homogeneous and isotropic materials. But at the length scale of the order of millimeter or smaller, foam is neither homogeneous nor isotropic. In this paper, we present some results of the characteristics of deformation and failure mechanism of polymer foam composites at different length scales. Central to this investigation is a multiscale digital speckle photography technique whereby we can measure detailed full deformation with spatial resolution ranging from centimeters to micrometers. We first investigate the size effect on the mechanical properties of polyurethane foams with and without nanoparticles, crack tip deformation field at different length scales, and the crack propagation characteristics in a foam. Then we present results for a newly created auxetic PVC foam composite. Auxetic materials have a negative Poisson's ratio rendering them to be more resistant to shear failure, indentation, and impact damages. We describe the manufacturing process of this material and demonstrate its advantageous properties as compared to the original foam.

  7. Spaceflight-induced bone loss alters failure mode and reduces bending strength in murine spinal segments.

    PubMed

    Berg-Johansen, Britta; Liebenberg, Ellen C; Li, Alfred; Macias, Brandon R; Hargens, Alan R; Lotz, Jeffrey C

    2016-01-01

    Intervertebral disc herniation rates are quadrupled in astronauts following spaceflight. While bending motions are main contributors to herniation, the effects of microgravity on the bending properties of spinal discs are unknown. Consequently, the goal of this study was to quantify the bending properties of tail discs from mice with or without microgravity exposure. Caudal motion segments from six mice returned from a 30-day Bion M1 mission and eight vivarium controls were loaded to failure in four-point bending. After testing, specimens were processed using histology to determine the location of failure, and adjacent motion segments were scanned with micro-computed tomography (μCT) to quantify bone properties. We observed that spaceflight significantly shortened the nonlinear toe region of the force-displacement curve by 32% and reduced the bending strength by 17%. Flight mouse spinal segments tended to fail within the growth plate and epiphyseal bone, while controls tended to fail at the disc-vertebra junction. Spaceflight significantly reduced vertebral bone volume fraction, bone mineral density, and trabecular thickness, which may explain the tendency of flight specimens to fail within the epiphyseal bone. Together, these results indicate that vertebral bone loss during spaceflight may degrade spine bending properties and contribute to increased disc herniation risk in astronauts.

  8. Relaxation mode analysis and Markov state relaxation mode analysis for chignolin in aqueous solution near a transition temperature.

    PubMed

    Mitsutake, Ayori; Takano, Hiroshi

    2015-09-28

    It is important to extract reaction coordinates or order parameters from protein simulations in order to investigate the local minimum-energy states and the transitions between them. The most popular method to obtain such data is principal component analysis, which extracts modes of large conformational fluctuations around an average structure. We recently applied relaxation mode analysis for protein systems, which approximately estimates the slow relaxation modes and times from a simulation and enables investigations of the dynamic properties underlying the structural fluctuations of proteins. In this study, we apply this relaxation mode analysis to extract reaction coordinates for a system in which there are large conformational changes such as those commonly observed in protein folding/unfolding. We performed a 750-ns simulation of chignolin protein near its folding transition temperature and observed many transitions between the most stable, misfolded, intermediate, and unfolded states. We then applied principal component analysis and relaxation mode analysis to the system. In the relaxation mode analysis, we could automatically extract good reaction coordinates. The free-energy surfaces provide a clearer understanding of the transitions not only between local minimum-energy states but also between the folded and unfolded states, even though the simulation involved large conformational changes. Moreover, we propose a new analysis method called Markov state relaxation mode analysis. We applied the new method to states with slow relaxation, which are defined by the free-energy surface obtained in the relaxation mode analysis. Finally, the relaxation times of the states obtained with a simple Markov state model and the proposed Markov state relaxation mode analysis are compared and discussed.

  9. Failure Analysis of High Pressure Test Facility Control Valves

    DTIC Science & Technology

    2013-10-01

    larger than the axial load applied to the stem by the actuator in the closed valve position), so we decided that no further buckling analysis was...caused the stem to bend. There are only two modes by which the stem could have bent in the manner it did: buckling and/or a cantilever load...load; however, we have clearly demonstrated on other valves (much to our embarrassment) that it is entirely possible to buckle the stem by over

  10. Lithographic chip identification: meeting the failure analysis challenge

    NASA Astrophysics Data System (ADS)

    Perkins, Lynn; Riddell, Kevin G.; Flack, Warren W.

    1992-06-01

    This paper describes a novel method using stepper photolithography to uniquely identify individual chips for permanent traceability. A commercially available 1X stepper is used to mark chips with an identifier or `serial number' which can be encoded with relevant information for the integrated circuit manufacturer. The permanent identification of individual chips can improve current methods of quality control, failure analysis, and inventory control. The need for this technology is escalating as manufacturers seek to provide six sigma quality control for their products and trace fabrication problems to their source. This need is especially acute for parts that fail after packaging and are returned to the manufacturer for analysis. Using this novel approach, failure analysis data can be tied back to a particular batch, wafer, or even a position within a wafer. Process control can be enhanced by identifying the root cause of chip failures. Chip identification also addresses manufacturers concerns with increasing incidences of chip theft. Since chips currently carry no identification other than the manufacturer's name and part number, recovery efforts are hampered by the inability to determine the sales history of a specific packaged chip. A definitive identifier or serial number for each chip would address this concern. The results of chip identification (patent pending) are easily viewed through a low power microscope. Batch number, wafer number, exposure step, and chip location within the exposure step can be recorded, as can dates and other items of interest. An explanation of the chip identification procedure and processing requirements are described. Experimental testing and results are presented, and potential applications are discussed.

  11. Failure and Reliability Analysis for the Master Pump Shutdown System

    SciTech Connect

    BEVINS, R.R.

    2000-09-05

    The Master Pump Shutdown System (MPSS) will be installed in the 200 Areas of the Hanford Site to monitor and control the transfer of liquid waste between tank farms and between the 200 West and 200 East areas through the Cross-Site Transfer Line. The Safety Function provided by the MPSS is to shutdown any waste transfer process within or between tank farms if a waste leak should occur along the selected transfer route. The MPSS, which provides this Safety Class Function, is composed of Programmable Logic Controllers (PLCs), interconnecting wires, relays, Human to Machine Interfaces (HMI), and software. These components are defined as providing a Safety Class Function and will be designated in this report as MPSS/PLC. Input signals to the MPSS/PLC are provided by leak detection systems from each of the tank farm leak detector locations along the waste transfer route. The combination of the MPSS/PLC, leak detection system, and transfer pump controller system will be referred to as MPSS/SYS. The components addressed in this analysis are associated with the MPSS/SYS. The purpose of this failure and reliability analysis is to address the following design issues of the Project Development Specification (PDS) for the MPSS/SYS (HNF 2000a): (1) Single Component Failure Criterion, (2) System Status Upon Loss of Electrical Power, (3) Physical Separation of Safety Class cables, (4) Physical Isolation of Safety Class Wiring from General Service Wiring, and (5) Meeting the MPSS/PLC Option 1b (RPP 1999) Reliability estimate. The failure and reliability analysis examined the system on a component level basis and identified any hardware or software elements that could fail and/or prevent the system from performing its intended safety function.

  12. Characteristic fault zone architectures as result of different failure modes: first results from scale models of normal faulting

    NASA Astrophysics Data System (ADS)

    Kettermann, Michael; Urai, Janos L.

    2014-05-01

    It is known that fault zone architecture and structural style vary distinctly between tensile and shear failure modes, with strong effects on the associated fluid flow properties. A systematically comparative study in 3D has not been done so far, though. Inferring transport properties in sub-seismic scale from fault network geometries would have important applications in brittle lithologies such as carbonates or basalts. We present a method to investigate the structural properties of fault networks in 3D using cohesive hemihydrate powder (CaSO4 * 1/2H2O) embedded in two layers of dry fine grained sand. The material properties of the sand and powder are well known from previous studies. By increasing the overburden stress the failure mode of the powder can be changed from tensile to shear failure. Using hemihydrate powder allows us to harden and excavate the layer after the deformation by wetting the model slowly and brushing off the overburden sand. Visual investigation of the 3D structures is then possible in very high resolution. Analyses using photographs and 3D models from photogrammetry include qualitative observations as well as measurements of e.g. strike of fault segments, fault dip or graben width. We show a total of eight experiments that produce graben faults at four different overburden stresses (0, 1.5, 3, 6 cm overburden thickness) and at two increasing stages of strain (3 and 5 mm). In this set of models we describe two structural domains that show characteristic differences in their defining attributes. The tensile domain at small overburden stress (0 and 1.5 cm overburden) shows strongly dilatant faults with open fissures, vertical faults and large changes in strike at segment boundaries. The shear domain, formed by larger overburden stress (6 cm overburden), shows shallower fault dips around 65° with striations, numerous undulating fault branches and splays with low-angle fault intersections. Models with 3 cm overburden show a hybrid failure type

  13. Probability of Failure Analysis Standards and Guidelines for Expendable Launch Vehicles

    NASA Astrophysics Data System (ADS)

    Wilde, Paul D.; Morse, Elisabeth L.; Rosati, Paul; Cather, Corey

    2013-09-01

    Recognizing the central importance of probability of failure estimates to ensuring public safety for launches, the Federal Aviation Administration (FAA), Office of Commercial Space Transportation (AST), the National Aeronautics and Space Administration (NASA), and U.S. Air Force (USAF), through the Common Standards Working Group (CSWG), developed a guide for conducting valid probability of failure (POF) analyses for expendable launch vehicles (ELV), with an emphasis on POF analysis for new ELVs. A probability of failure analysis for an ELV produces estimates of the likelihood of occurrence of potentially hazardous events, which are critical inputs to launch risk analysis of debris, toxic, or explosive hazards. This guide is intended to document a framework for POF analyses commonly accepted in the US, and should be useful to anyone who performs or evaluates launch risk analyses for new ELVs. The CSWG guidelines provide performance standards and definitions of key terms, and are being revised to address allocation to flight times and vehicle response modes. The POF performance standard allows a launch operator to employ alternative, potentially innovative methodologies so long as the results satisfy the performance standard. Current POF analysis practice at US ranges includes multiple methodologies described in the guidelines as accepted methods, but not necessarily the only methods available to demonstrate compliance with the performance standard. The guidelines include illustrative examples for each POF analysis method, which are intended to illustrate an acceptable level of fidelity for ELV POF analyses used to ensure public safety. The focus is on providing guiding principles rather than "recipe lists." Independent reviews of these guidelines were performed to assess their logic, completeness, accuracy, self- consistency, consistency with risk analysis practices, use of available information, and ease of applicability. The independent reviews confirmed the

  14. Electromigration failure mode concerning negative resistance shift of Cu interconnects buried in porous low-k dielectric

    NASA Astrophysics Data System (ADS)

    Zheng, Hui; Yin, Binfeng; Yu, Hewei; Chen, Leigang; Gao, Lin; Zhou, Ke; Kuo, Chinte

    2017-02-01

    Electromigration failure mode concerning a negative resistance shift of 4%-11% and cathode burnout was reported for Cu interconnects buried in porous low-k in this paper. Evidence for oxidation and debonding of Ta/TaN liner at high temperature was revealed, which was demonstrated to have been enabled by the unsealed porous low-k due to moisture uptake. The cathode burnout was thus attributed to severe Joule heating induced in the insulated liner after oxidation. The resistance decay of Cu also exhibited to be mainly consistent with the calculation from specularity recovery of electron scattering at the Cu/Ta interface after oxidation and debonding of the liner, although other factors like strain relaxation may also have some contribution.

  15. Crack propagation studies to determine benign or catastrophic failure modes for aerospace thin-rim gears. Ph.D. Thesis

    SciTech Connect

    Lewicki, D.G.

    1996-05-01

    Analytical and experimental studies were performed to investigate the effect of rim thickness on gear tooth crack propagation. The goal was to determine whether cracks grew through gear teeth (benign failure mode) or through gear rims (catastrophic failure mode) for various rim thicknesses. Gear tooth crack propagation was simulated using a finite element based computer program. Principles of linear elastic fracture mechanics were used. Quarter-point, triangular elements were used at the crack tip to represent the stress singularity. Crack tip stress intensity factors were estimated and used to determine crack propagation direction and fatigue crack growth rate. The computer program used had an automated crack propagation option in which cracks were grown numerically using an automated re-meshing scheme. In addition, experimental studies were performed in the NASA Lewis Spur Gear Fatigue Rig. Gears with various backup ratios were tested to validate crack path predictions. Also, specialized crack propagation gages were installed on the test gears to measure gear tooth crack growth rate. From both predictions and tests, gears with backup ratios (film thickness divided by tooth height) of 3.3 and 1.0 produced tooth fractures while a backup ratio of 0.3 produced rim fractures. For a backup ratio of 0.5, the experiments produced rim fractures and the predictions produced both rim and tooth fractures, depending on the initial crack conditions. Good correlation between the predicted number of crack propagation cycles and measured number of cycles was achieved using both the Paris fatigue crack growth method and the Collipfiest crack growth equation when fatigue crack closure was considered.

  16. The Slip Behavior of Serpentinite and its Significance in Controlling the Mode of Fault Failure

    NASA Astrophysics Data System (ADS)

    Scuderi, M.; Carpenter, B. M.; Marone, C.; Saffer, D. M.

    2013-12-01

    Recent observations of deep tremor and low-frequency earthquakes (LFE) have raised fundamental questions about the physics and processes responsible for such slip behaviors. Current hypotheses propose that these events represent shear failure on a critically stressed fault, possibly in the presence of near-lithostatic pore fluid pressure. The presence of serpentinite at characteristic P-T conditions where most deep tremor and LFE are located is suggested by slow seismic velocities, high Poisson`s ratios, and studies of exhumed fault systems. Despite the inferred presence of serpentinite and its role in the generation of tremors and LFE, little is known about its physical and mechanical properties under conditions of extremely low effective stress. Here, we report on experiments designed to investigate the frictional behavior of intact serpentinite recovered from New Idria, California. These serpentinites were emplaced as diapirs associated with Cretaceous subduction predating the formation of the SAF. They currently outcrop along the SAF, and are believed to represent protolith for material present at depth along the fault zone. In this context, they serve as important natural analogs for serpentinites associated with both subduction megathrusts and the SAF. We cut samples parallel to the original foliation from intact blocks, and sheared them in a single direct shear configuration (SDS) using a true triaxial deformation apparatus. To simulate shear between oceanic and continental wall rocks, we sheared intact wafers of serpentine against intact Westerly granite. To simulate internal deformation within the serpentine body, we sheared two intact blocks of serpentinite against each other. Additional experiments were performed on pulverized serpentinite gouge in a double direct shear configuration and under similar boundary conditions for comparison. Effective normal stress (σ'n = σ n - Pp) was kept constant throughout our experiments at values of 2 MPa (with Pp = 1

  17. Modeling Freedom From Progression for Standard-Risk Medulloblastoma: A Mathematical Tumor Control Model With Multiple Modes of Failure

    SciTech Connect

    Brodin, N. Patrik; Vogelius, Ivan R.; Björk-Eriksson, Thomas; Munck af Rosenschöld, Per; Bentzen, Søren M.

    2013-10-01

    Purpose: As pediatric medulloblastoma (MB) is a relatively rare disease, it is important to extract the maximum information from trials and cohort studies. Here, a framework was developed for modeling tumor control with multiple modes of failure and time-to-progression for standard-risk MB, using published pattern of failure data. Methods and Materials: Outcome data for standard-risk MB published after 1990 with pattern of relapse information were used to fit a tumor control dose-response model addressing failures in both the high-dose boost volume and the elective craniospinal volume. Estimates of 5-year event-free survival from 2 large randomized MB trials were used to model the time-to-progression distribution. Uncertainty in freedom from progression (FFP) was estimated by Monte Carlo sampling over the statistical uncertainty in input data. Results: The estimated 5-year FFP (95% confidence intervals [CI]) for craniospinal doses of 15, 18, 24, and 36 Gy while maintaining 54 Gy to the posterior fossa was 77% (95% CI, 70%-81%), 78% (95% CI, 73%-81%), 79% (95% CI, 76%-82%), and 80% (95% CI, 77%-84%) respectively. The uncertainty in FFP was considerably larger for craniospinal doses below 18 Gy, reflecting the lack of data in the lower dose range. Conclusions: Estimates of tumor control and time-to-progression for standard-risk MB provides a data-driven setting for hypothesis generation or power calculations for prospective trials, taking the uncertainties into account. The presented methods can also be applied to incorporate further risk-stratification for example based on molecular biomarkers, when the necessary data become available.

  18. Analysis of a Turbine Blade Failure in a Military Turbojet Engine

    NASA Astrophysics Data System (ADS)

    Sahoo, Benudhar; Satpathy, R. K.; Panigrahi, S. K.

    2016-06-01

    This paper deals with failure analysis of a low-pressure turbine blade of a straight flow turbojet engine. The blade is made of a wrought precipitation hardened Nickel base superalloy with oxidation-resistant diffusion aluminizing coating. The failure mode is found to be fatigue with multiple cracks inside the blade having crack origin at metal carbides. In addition to the damage in the coating, carbide banding has been observed in few blades. Carbide banding may be defined as inclusions in the form of highly elongated along deformation direction. The size, shape and banding of carbides and their location critically affect the failure of blades. Carbon content needs to be optimized to reduce interdendritic segregation and thereby provide improved fatigue and stress rupture life. Hence, optimization of size, shape and distribution of carbides in the billet and forging parameters during manufacturing of blade play a vital role to eliminate/reduce extent of banding. Reference micrographs as acceptance criteria are essential for evaluation of raw material and blade. There is a need to define the acceptance criteria for carbide bandings and introduce more sensitive ultrasonic check during billet and on finished blade inspection.

  19. Perturbation analysis of electromagnetic geodesic acoustic modes

    SciTech Connect

    Ren, Haijun

    2014-06-15

    Lagrangian displacement and magnetic field perturbation response to the geodesic acoustic mode is analyzed by using the ideal magnetohydrodynamic equations in a large-aspect-ratio tokamak. δB{sub θ}, the poloidal component of magnetic field perturbation, has poloidal wave number m = 2 created by the poloidal displacement ξ{sub θ}. The parallel perturbation of magnetic field, δB{sub ∥}, has a poloidally asymmetric structure with m = 1 and is on the same order of magnitude with δB{sub θ} to the leading order. The radial displacement ξ{sub r} is of order O(βϵξ{sub θ}) but plays a significant role in determining δB{sub ∥}, where β is the plasma/magnetic pressure ratio and ϵ is the inverse aspect ratio.

  20. Failure Analysis of Nonvolatile Residue (NVR) Analyzer Model SP-1000

    NASA Technical Reports Server (NTRS)

    Potter, Joseph C.

    2011-01-01

    National Aeronautics and Space Administration (NASA) subcontractor Wiltech contacted the NASA Electrical Lab (NE-L) and requested a failure analysis of a Solvent Purity Meter; model SP-IOOO produced by the VerTis Instrument Company. The meter, used to measure the contaminate in a solvent to determine the relative contamination on spacecraft flight hardware and ground servicing equipment, had been inoperable and in storage for an unknown amount of time. NE-L was asked to troubleshoot the unit and make a determination on what may be required to make the unit operational. Through the use of general troubleshooting processes and the review of a unit in service at the time of analysis, the unit was found to be repairable but would need the replacement of multiple components.

  1. Structural failure analysis of reactor vessels due to molten core debris

    SciTech Connect

    Pfeiffer, P.A.

    1993-08-01

    Maintaining structural integrity of the reactor vessel during a postulated core melt accident is an important safety consideration in the design of the vessel. This paper addresses the failure predictions of the vessel due to thermal and pressure loadings from the molten core debris depositing on the lower head of the vessel. Different loading combinations were considered based on a wet or dry cavity and pressurization of the vessel based on operating pressure or atmospheric (pipe break). The analyses considered both short term (minutes) and long term (days) failure modes. Short term failure modes include creep at elevated temperatures and plastic instabilities of the structure. Long term failure modes are caused by creep rupture that lead to plastic instability of the structure. The analyses predict the reactor vessel will remain intact after the core melt has deposited on the lower vessel head.

  2. Deep Borehole Emplacement Mode Hazard Analysis Revision 0

    SciTech Connect

    Sevougian, S. David

    2015-08-07

    This letter report outlines a methodology and provides resource information for the Deep Borehole Emplacement Mode Hazard Analysis (DBEMHA). The main purpose is identify the accident hazards and accident event sequences associated with the two emplacement mode options (wireline or drillstring), to outline a methodology for computing accident probabilities and frequencies, and to point to available databases on the nature and frequency of accidents typically associated with standard borehole drilling and nuclear handling operations. Risk mitigation and prevention measures, which have been incorporated into the two emplacement designs (see Cochran and Hardin 2015), are also discussed. A key intent of this report is to provide background information to brief subject matter experts involved in the Emplacement Mode Design Study. [Note: Revision 0 of this report is concentrated more on the wireline emplacement mode. It is expected that Revision 1 will contain further development of the preliminary fault and event trees for the drill string emplacement mode.

  3. Influence of preparation design and ceramic thicknesses on fracture resistance and failure modes of premolar partial coverage restorations

    PubMed Central

    Guess, Petra C.; Schultheis, Stefan; Wolkewitz, Martin; Zhang; Strub, Joerg R.

    2015-01-01

    Statement of problem Preparation designs and ceramic thicknesses are key factors for the long-term success of minimally invasive premolar partial coverage restorations. However, only limited information is presently available on this topic. Purpose The aim of this in vitro study was to evaluate the fracture resistance and failure modes of ceramic premolar partial coverage restorations with different preparation designs and ceramic thicknesses. Material and methods Caries-free human premolars (n= 144) were divided into 9 groups. Palatal onlay preparation comprised reduction of the palatal cusp by 2 mm (Palatal-Onlay-Standard), 1 mm (Palatal-Onlay-Thin), or 0.5 mm (Palatal-Onlay-Ultra-Thin). Complete-coverage onlay preparation additionally included the buccal cusp (Occlusal-Onlay-Standard; Occlusal-Onlay-Thin; Occlusal-Onlay-Ultra-Thin). Labial surface preparations with chamfer reductions of 0.8 mm (Complete-Veneer-Standard), 0.6 mm (Complete-Veneer-Thin) and 0.4 mm (Complete-Veneer-Ultra-Thin) were implemented for complete veneer restorations. Restorations were fabricated from a pressable lithium-disilicate ceramic (IPS-e.max-Press) and cemented adhesively (Syntac-Classic/Variolink-II). All specimens were subjected to cyclic mechanical loading (F= 49 N, 1.2 million cycles) and simultaneous thermocycling (5°C to 55°C) in a mouth-motion simulator. After fatigue, restorations were exposed to single-load-to-failure. Two-way ANOVA was used to identify statistical differences. Pair-wise differences were calculated and P-values were adjusted by the Tukey–Kramer method (α= .05). Results All specimens survived fatigue. Mean (SD) load to failure values (N) were as follows: 837 (320/Palatal-Onlay-Standard), 1055 (369/Palatal-Onlay-Thin), 1192 (342/Palatal-Onlay-Ultra-Thin), 963 (405/Occlusal-Onlay-Standard), 1108 (340/Occlusal-Onlay-Thin), 997 (331/Occlusal-Onlay-Ultra-Thin), 1361 (333/Complete-Veneer-Standard), 1087 (251/Complete-Veneer-Thin), 883 (311/Complete

  4. ISTFA 1986 - International Symposium for Testing and Failure Analysis; Proceedings of the Symposium, Los Angeles, CA, Oct. 20-24, 1986

    SciTech Connect

    Not Available

    1986-01-01

    The conference presents papers on the analysis of electronic materials, problems with electronic materials, EOS/ESD, new techniques, failure analysis results, test methods, failure modes and mechanisms, and the effect of microstructure on properties. Topics include the analysis of on-line organic microcontaminants in semiconductor assembly plants, the role of surface chemistry in packaging failures, the testing and analysis of photovoltaic modules for electrochemical corrosion, the reliability improvement and evaluation of TWTs for communications satellites, and the analysis of adhesive bond joint fractures by scanning electron fractography and X-ray emission spectroscopy. Consideration is also given to observers for failure detection of actuation systems, mechanisms governing the high strain fracture behavior of Al-Li-X alloys, and the effect of nonmetallic inclusions and test temperature on the fatigue life of cast C355, 354, and A206 aluminum.

  5. Spatial Stratification of Order As Used in Failure Analysis

    NASA Astrophysics Data System (ADS)

    Leonard, Robert H.; Bachlechner, Martina E.

    2007-03-01

    Silicon nitride deposited on silicon substrates has application in dielectric layers for microelectronics as well as in photovoltaics. During production and operation of components involving silicon/silicon nitride interfaces, stresses and strains can build up at various temperatures resulting in component failure. Using molecular dynamics simulations the influence of temperature and rate of externally applied strain on silicon/silicon nitride interfaces has been analyzed. The primary purpose of this research is to understand the mechanisms leading to the failure of these films. Analyses involving bond lengths and angles have been developed to gain insight into these mechanisms. Methods for stratifying bond lengths and bond angles into unique sub-populations on the basis of spatial orientation have been developed, and have given much insight to how the material behaves, particularly with regards to the Poisson effect. Possible extensions of this stratification method to primitive rings will also be examined. In combination with experimental observations, this analysis will deepen our understanding of the structural properties of silicon/silicon nitride interfaces.

  6. Ayame/PAM-D apogee kick motor nozzle failure analysis

    NASA Technical Reports Server (NTRS)

    1981-01-01

    The failure of two communication satellites during firing sequence were examined. The correlation/comparison of the circumstances of the Ayame incidents and the failure of the STAR 48 (DM-2) motor are reviewed. The massive nozzle failure of the AKM to determine the impact on spacecraft performance is examined. It is recommended that a closer watch is kept on systems techniques,

  7. Analysis of the Intrinsic Mode Functions

    DTIC Science & Technology

    2004-01-01

    differential equations and vibration analysis was a major motivation in the development of the Sturm - Liouville theory. In the next section, we list some...relevant properties of the solutions of a self-adjoint ODE’s which will be useful for our analysis. 2.2 Self-adjoint ODE and Sturm - Liouville systems...0 and Q is continuous. More generally we can consider a Sturm - Liouville equation (λ real): d dt ( p(t) df dt ) + (λρ(t)− q(t))f = 0. (2.2) These

  8. Sharp boundary analysis of electrostatic flute modes

    SciTech Connect

    Lemons, D. S.

    1989-07-01

    A linear, electrostatic, stability analysis of a magnetized cross-fielddrifting plasma with a sharp boundary is presented. The analysis corrects anerror in a previously published sharp boundary theory (Phys. Fluids /bold 19/,882 (1976)) and extends another theory (Geophys. Res. Lett. /bold 14/, 60(1987)) to include finite electron mass and non-neutral perturbations. Theinstability's long wavelength structure is associated with the classical fluteinstability, while the peak of the growth rate curve, at much shorterwavelengths, is a Buneman-like instability.

  9. The Evolution and Practical Applications of Failure Modes and Effects Analyses

    DTIC Science & Technology

    1983-03-01

    originally intended for testability analysis can replace the need for FMEA in electronic systems. An electronic circuit simula- tor, such as LAZOR or...and Criticality Analy- sis" or any of several other Departmnt of Defense, Nuclear Regulatory Commission, and NASA Standards for specific types of

  10. Saturn component failure rate and failure rate modifiers

    NASA Technical Reports Server (NTRS)

    1971-01-01

    Failure mode frequency ratios, environmental adjustment factors, and failure rates for mechanical and electromechanical component families are presented. The failure rates and failure rate modifiers resulted from a series of studies whose purpose was to provide design, tests, reliability, and systems engineers with accurate, up-to-date failure rate information. The results of the studies were achieved through an extensive engineering analysis of the Saturn Program test data and Unsatisfactory Condition Reports (UCR's) and the application of mathematical techniques developed for the studies.

  11. Time-Frequency Analysis of the Dispersion of Lamb Modes

    NASA Technical Reports Server (NTRS)

    Prosser, W. H.; Seale, Michael D.; Smith, Barry T.

    1999-01-01

    Accurate knowledge of the velocity dispersion of Lamb modes is important for ultrasonic nondestructive evaluation methods used in detecting and locating flaws in thin plates and in determining their elastic stiffness coefficients. Lamb mode dispersion is also important in the acoustic emission technique for accurately triangulating the location of emissions in thin plates. In this research, the ability to characterize Lamb mode dispersion through a time-frequency analysis (the pseudo-Wigner-Ville distribution) was demonstrated. A major advantage of time-frequency methods is the ability to analyze acoustic signals containing multiple propagation modes, which overlap and superimpose in the time domain signal. By combining time-frequency analysis with a broadband acoustic excitation source, the dispersion of multiple Lamb modes over a wide frequency range can be determined from as little as a single measurement. In addition, the technique provides a direct measurement of the group velocity dispersion. The technique was first demonstrated in the analysis of a simulated waveform in an aluminum plate in which the Lamb mode dispersion was well known. Portions of the dispersion curves of the AO, A I , So, and S2 Lamb modes were obtained from this one waveform. The technique was also applied for the analysis of experimental waveforms from a unidirectional graphite/epoxy composite plate. Measurements were made both along and perpendicular to the fiber direction. In this case, the signals contained only the lowest order symmetric and antisymmetric modes. A least squares fit of the results from several source to detector distances was used. Theoretical dispersion curves were calculated and are shown to be in good agreement with experimental results.

  12. Time-Frequency Analysis of the Dispersion of Lamb Modes

    NASA Technical Reports Server (NTRS)

    Prosser, W. H.; Seale, Michael D.; Smith, Barry T.

    1999-01-01

    Accurate knowledge of the velocity dispersion of Lamb modes is important for ultrasonic nondestructive evaluation methods used in detecting and locating flaws in thin plates and in determining their elastic stiffness coefficients. Lamb mode dispersion is also important in the acoustic emission technique for accurately triangulating the location of emissions in thin plates. In this research, the ability to characterize Lamb mode dispersion through a time-frequency analysis (the pseudo Wigner-Ville distribution) was demonstrated. A major advantage of time-frequency methods is the ability to analyze acoustic signals containing multiple propagation modes, which overlap and superimpose in the time domain signal. By combining time-frequency analysis with a broadband acoustic excitation source, the dispersion of multiple Lamb modes over a wide frequency range can be determined from as little as a single measurement. In addition, the technique provides a direct measurement of the group velocity dispersion. The technique was first demonstrated in the analysis of a simulated waveform in an aluminum plate in which the Lamb mode dispersion was well known. Portions of the dispersion curves of the A(sub 0), A(sub 1), S(sub 0), and S(sub 2)Lamb modes were obtained from this one waveform. The technique was also applied for the analysis of experimental waveforms from a unidirectional graphite/epoxy composite plate. Measurements were made both along, and perpendicular to the fiber direction. In this case, the signals contained only the lowest order symmetric and antisymmetric modes. A least squares fit of the results from several source to detector distances was used. Theoretical dispersion curves were calculated and are shown to be in good agreement with experimental results.

  13. Mode Analysis with Autocorrelation Method (Single Time Series) in Tokamak

    NASA Astrophysics Data System (ADS)

    Saadat, Shervin; Salem, Mohammad K.; Goranneviss, Mahmoud; Khorshid, Pejman

    2010-08-01

    In this paper plasma mode analyzed with statistical method that designated Autocorrelation function. Auto correlation function used from one time series, so for this purpose we need one Minov coil. After autocorrelation analysis on mirnov coil data, spectral density diagram is plotted. Spectral density diagram from symmetries and trends can analyzed plasma mode. RHF fields effects with this method ate investigated in IR-T1 tokamak and results corresponded with multichannel methods such as SVD and FFT.

  14. Case history: Failure analysis of a 16K ROM with a polysilicon gate defect

    SciTech Connect

    Mikawa, R.E.; Campbell, A.N.

    1993-08-01

    This case history presents the analysis of a very unusual CMOS 2K {times} 8 read only memory (ROM) failure. The IC failure was discovered after a 1,000 hour, 150{degree}C static life test. Elevated quiescent power supply current was present that caused the IC to fail parametric testing, but the IC was fully functional at the specified operating power supply voltage of 10 V. Functional failures were ``forced`` by operating the IC at below nominal voltage. Electron beam probing and dynamic voltage contrast imaging performed while the IC was in the functional failing mode indicated the presence of an electrical open circuit in the polysilicon gate interconnect of a p-channel transistor. The IC was deprocessed down to the polysilicon and the defective gate was examined with a scanning electron microscope. An abrupt change in microstructure was observed at the location corresponding to the site of electrical discontinuity. Circuit simulations, performed using a series gate resistance to model the defective gate, showed that the gate signal to the p-channel transistor changed phase and high current was present if the gate resistance exceeded 1 {times} 10{sup 9} ohms. The change in microstructure and increased gate resistance are consistent with a localized reduction of dopant (phosphorus) concentration. During the life test, it is speculated that phosphorus segregated to the grain boundaries resulting in a net reduction of dopant atoms and a corresponding decrease in the conductivity of the polysilicon gate. This IC failure is apparently due to dopant segregation and carrier trapping at the grain boundaries in the polysilicon during the high temperature life test.

  15. Comprehensive failure analysis of leakage faults in bipolar transistors

    NASA Astrophysics Data System (ADS)

    Domengès, B.; Murray, H.; Schwindenhammer, P.; Imbert, G.

    2004-02-01

    The origin of a leakage current in several failed NPN bipolar transistors has been identified by complementary advanced failure analysis techniques. After precise localization of the failing area by photon emission microscopy and optical beam induced resistance change investigations, a focus ion beam technique was used to prepare thin lamellae adequate for transmission electron microscopy (TEM) study. Characterization of the related microstructure was performed by TEM and energy-dispersive spectrometry nanobeam analyses. It was identified as Ti-W containing trickle-like residue located at the surface of the spacers. Current-voltage measurements could be related to such structure defects and the involved conduction mechanism was identified as the Poole-Frenkel effect.

  16. Micromechanical analysis of the failure process in ceramic matrix composites

    NASA Technical Reports Server (NTRS)

    Rubinstein, Asher A.

    1991-01-01

    An analysis of the effectiveness of fiber reinforcement in brittle matrix composites is presented. The analytical method allows consideration of discrete fiber distribution and examination of the development of crack growth parameters on the microscale. The problem associated with bridging zone development is addressed here; therefore, the bridging zone is considered to be smaller than the main preexisting crack, and the small scale approach is used. The mechanics of the reinforcement is accurately accounted for in the process zone of a growing crack. Closed form solutions characterizing the initial failure process are presented for linear and nonlinear force-fiber pullout displacement relationships. The implicit exact solution for the extended bridging zone is presented as well.

  17. Magellan/Galileo solder joint failure analysis and recommendations

    NASA Technical Reports Server (NTRS)

    Ross, Ronald G., Jr.

    1989-01-01

    On or about November 10, 1988 an open circuit solder joint was discovered in the Magellan Radar digital unit (DFU) during integration testing at Kennedy Space Center (KSC). A detailed analysis of the cause of the failure was conducted at the Jet Propulsion Laboratory leading to the successful repair of many pieces of affected electronic hardware on both the Magellan and Galileo spacecraft. The problem was caused by the presence of high thermal coefficient of expansion heat sink and conformal coating materials located in the large (0.055 inch) gap between Dual Inline Packages (DIPS) and the printed wiring board. The details of the observed problems are described and recommendations are made for improved design and testing activities in the future.

  18. The Reconstruction and Failure Analysis of The Space Shuttle Columbia

    NASA Technical Reports Server (NTRS)

    Russell, Richard W.

    2010-01-01

    This viewgraph presentation describes a very detailed reconstruction plan and failure analysis of The Space Shuttle Columbia accident. The contents include: 1) STS-107 Timeline; 2) Foam Impact; 3) Recovery; 4) Reconstruction; 5) Reconstruction Plan; 6) Reconstruction Hanger; 7) Pathfinders; 8) Aluminum Pathfinder; 9) Early Analysis - Left MLG Door Area; 10) Emphasis Switched to Left Hand Wing Leading Edge; 11) Wing Leading Edge Subsystem (LESS); 12) 3D Reconstruction of Left WLE; 13) Left Wing Tile Table; 14) LESS Observations; 15) Left Hand Wing Debris Points to RCC 8/9 - Slumped Tile; 16) Reconstructed View of LC/P 9 tile with I/B Tile; 17) Reconstructed View of Lower C/P 9 Tile; 18) Carrier Panel 8 - Upper; 19) Left Hand Wing Debris Points to RCC 8/9 - Erosion and RCC with attach hole intact; 20) Erosion on Panel 8 Upper Outboard Rib; 21) RCC Panels 8 & 9 Erosion Features; 22) Slumping Source for Carrier Panel 9 Tile was Revealed; 23) Debris Indicated Highest Probability Initiation Site; 24) Left Hand Wing Debris Points to RCC 8/9- Metallic Deposits; 25) Relative Metallic Deposition on L/H Wing Materials; 26) Metallic Deposit Example, LH RCC 8; 27) High Level Questions; 28) Analysis Plan Challenges; 29) Analysis Techniques; 30) Analysis Approach; 31) RCC Panel 8 Erosion Features; 32) Radiographic Features; 33) Radiography WLE LH Panel 8; 34) LH RCC 8 Upper Apex; 35) LH RCC 8 - Deposit Feature: Thick Tear Shaped; 36) LH RCC 8 - Deposit Feature: Thick Globules; 37) LH RCC 8 - Deposit Feature: Spheroids; 38) LH RCC 8 - Deposit Feature: Uniform Deposit; 39) Significant Findings - Sampling All Other panels; 40) Proposed Breach Location and Plasma Flow; 41) Corroborating Information - RCC Panel Debris Locations; 42) Corroborating Information - LH OMS Pod Analysis; 43) Corroborating Information - Impact Testing; and 44) Overall Forensic Conclusions.

  19. Fundamental analysis of the failure of polymer-based fiber reinforced composites

    NASA Technical Reports Server (NTRS)

    Kanninen, M. F.; Rybicki, E. F.; Griffith, W. I.; Broek, D.

    1975-01-01

    A mathematical model predicting the strength of unidirectional fiber reinforced composites containing known flaws and with linear elastic-brittle material behavior was developed. The approach was to imbed a local heterogeneous region surrounding the crack tip into an anisotropic elastic continuum. This (1) permits an explicit analysis of the micromechanical processes involved in the fracture, and (2) remains simple enough to be useful in practical computations. Computations for arbitrary flaw size and orientation under arbitrary applied loads were performed. The mechanical properties were those of graphite epoxy. With the rupture properties arbitrarily varied to test the capabilities of the model to reflect real fracture modes, it was shown that fiber breakage, matrix crazing, crack bridging, matrix-fiber debonding, and axial splitting can all occur during a period of (gradually) increasing load prior to catastrophic failure. The calculations also reveal the sequential nature of the stable crack growth process proceding fracture.

  20. Failure Analysis in Space: International Space Station (ISS) Starboard Solar Alpha Rotary Joint (SARJ) Debris Analysis

    NASA Technical Reports Server (NTRS)

    Long, V. S.; Wright, M. C.; McDanels, S. J.; Lubas, D.; Tucker, B.; Marciniak, P. J.

    2010-01-01

    This slide presentation reviews the debris analysis of the Starboard Solar Alpha Rotary Joint (SARJ), a mechanism that is designed to keep the solar arrays facing the sun. The goal of this was to identify the failure mechanism based on surface morphology and to determine the source of debris through elemental and particle analysis.

  1. Visualization and classification of physiological failure modes in ensemble hemorrhage simulation

    NASA Astrophysics Data System (ADS)

    Zhang, Song; Pruett, William Andrew; Hester, Robert

    2015-01-01

    In an emergency situation such as hemorrhage, doctors need to predict which patients need immediate treatment and care. This task is difficult because of the diverse response to hemorrhage in human population. Ensemble physiological simulations provide a means to sample a diverse range of subjects and may have a better chance of containing the correct solution. However, to reveal the patterns and trends from the ensemble simulation is a challenging task. We have developed a visualization framework for ensemble physiological simulations. The visualization helps users identify trends among ensemble members, classify ensemble member into subpopulations for analysis, and provide prediction to future events by matching a new patient's data to existing ensembles. We demonstrated the effectiveness of the visualization on simulated physiological data. The lessons learned here can be applied to clinically-collected physiological data in the future.

  2. Failure analysis of a tool steel torque shaft

    NASA Technical Reports Server (NTRS)

    Reagan, J. R.

    1981-01-01

    A low design load drive shaft used to deliver power from an experimental exhaust heat recovery system to the crankshaft of an experimental diesel truck engine failed during highway testing. An independent testing laboratory analyzed the failure by routine metallography and attributed the failure to fatigue induced by a banded microstructure. Visual examination by NASA of the failed shaft plus the knowledge of the torsional load that it carried pointed to a 100 percent ductile failure with no evidence of fatigue. Scanning electron microscopy confirmed this. Torsional test specimens were produced from pieces of the failed shaft and torsional overload testing produced identical failures to that which had occurred in the truck engine. This pointed to a failure caused by a high overload and although the microstructure was defective it was not the cause of the failure.

  3. Incorporation of a progressive failure analysis method in the CSM testbed software system

    NASA Technical Reports Server (NTRS)

    Arenburg, Robert T.

    1989-01-01

    Analysis of the postbuckling behavior of composite shell structures pose many difficult and challenging problems in the field of structural mechanics. Current analysis methods perform well for most cases in predicting the postbuckling response of undamaged components. To predict component behavior accurately at higher load levels, the analysis must include the effects of local material failures. The CSM testbed software system is a highly modular structural analysis system currently under development at Langley Research Center. One of the primary goals of the CSM testbed is to provide a software environment for the development of advanced structural analysis methods and modern numerical methods which will exploit advanced computer architecture such as parallel-vector processors. Development of a progressive failure analysis method consists of the design and implementation of a processor which will perform the ply-level progressive failure analysis and the development of a geometrically nonlinear analysis procedure which incorporates the progressive failure processor. Regarding the development of the progressive failure processor, two components are required: failure criteria and a degradation model. For the initial implementation, the failure criteria of Hashin will be used. For a matrix failure which typically indicates the development of transverse matrix cracks, the ply properties will be degraded. Work to date includes the design of the progressive failure analysis processor and initial plans for the controlling geometrically nonlinear analysis procedure. The implementation of the progressive failure analysis has begun. Access to the model database and the Hashin failure criteria are completed. Work is in progress on the input/output operations for the processor related data and the finite element model updating procedures. In total the progressive failure processor is approximately one-third complete.

  4. Reliability Analysis of Large Commercial Vessel Engine Room Automation Systems. Volume 1. Results

    DTIC Science & Technology

    1982-11-01

    8217 parameters drifting or calibration problems, and only require adjustment. B. FAILURE MODES AND EFFECTS ANALYSIS. The FMEAs revealed conditions that...reliability analysis included relia- bility predictions, failure modes and effects analyses ( FMEA ), criticality analysis, and fault tree analyses. For...safety hazards. In order to better evaluate the effects of failures, Failure Modes and Effects Analysis ( FMEA ), Criticality Analysis and Fault Tree

  5. Probabilistic Failure Analysis for Wound Composite Ceramic Cladding Assembly

    SciTech Connect

    Hemrick, James Gordon; Lara-Curzio, Edgar

    2013-01-01

    Advanced ceramic matrix composites based on silicon carbide (SiC) are being considered as candidate material systems for nuclear fuel cladding in light water reactors. The SiC composite structure is considered due to its assumed exceptional performance under accident scenarios, where its excellent high-temperature strength and slow reaction kinetics with steam and associated mitigated hydrogen production are desirable. The specific structures of interest consist of a monolithic SiC cylinder surrounded by interphase-coated SiC woven fibers in a tubular form and infiltrated with SiC. Additional SiC coatings on the outermost surface of the assembly are also being considered to prevent hydrothermal corrosion of the fibrous structure. The inner monolithic cylinder is expected to provide a hermetic seal to contain fission products under normal conditions. While this approach offers the promise of higher burn-up rates and safer behavior in the case of LOCA events, the reliability of such structures must be demonstrated in advance. Therefore, a probability failure analysis study was performed of such monolithic-composite hybrid structures to determine the feasibility of these design concepts. This analysis will be used to predict the future performance of candidate systems in an effort to determine the feasibility of these design concepts and to make future recommendations regarding materials selection.

  6. Women's Experiences With Flap Failure After Autologous Breast Reconstruction: A Qualitative Analysis.

    PubMed

    Higgins, Kristen S; Gillis, Joshua; Williams, Jason G; LeBlanc, Martin; Bezuhly, Michael; Chorney, Jill M

    2016-10-06

    Clinical experience suggests that flap failure after autologous breast reconstruction can be a devastating experience for women. Previous research has examined women's experiences with autologous breast reconstruction with and without complications, and patients' experiences with suboptimal outcomes from other medical procedures. The authors aimed to examine the psychosocial experience of flap failure from the patient's perspective. Seven women who had experienced unilateral flap failure after deep inferior epigastric perforator flap surgery in the past 12 years completed semistructured interviews about their breast cancer treatments, their experiences with flap failure, the impact of flap failure on their lives, and the coping strategies they used. Interpretive phenomenological analysis, a type of qualitative analysis that provides an in-depth account of participant's experiences and their meanings, was used to analyze the interview data. From these data, patient-derived recommendations were developed for surgeons caring for women who have experienced flap failure. Three main themes (6 subthemes) emerged: coming to terms with flap failure (coping with emotions, body dissatisfaction); making meaning of flap failure experience (questioning, relationship with surgeon); and care providers acknowledging the emotional experience of flap failure (experience of being treated "mechanically," suggestions for improvement). In conclusion, flap failure in breast reconstruction is an emotionally difficult experience for women. Although there are similarities to other populations of patients experiencing suboptimal outcomes from medical procedures, there are also unique aspects of the flap failure experience. A better understanding of women's experiences with flap failure will assist in providing more appropriate supports.

  7. Failure analysis of the cement mantle in total hip arthroplasty with an efficient probabilistic method.

    PubMed

    Kaymaz, Irfan; Bayrak, Ozgu; Karsan, Orhan; Celik, Ayhan; Alsaran, Akgun

    2014-04-01

    Accurate prediction of long-term behaviour of cemented hip implants is very important not only for patient comfort but also for elimination of any revision operation due to failure of implants. Therefore, a more realistic computer model was generated and then used for both deterministic and probabilistic analyses of the hip implant in this study. The deterministic failure analysis was carried out for the most common failure states of the cement mantle. On the other hand, most of the design parameters of the cemented hip are inherently uncertain quantities. Therefore, the probabilistic failure analysis was also carried out considering the fatigue failure of the cement mantle since it is the most critical failure state. However, the probabilistic analysis generally requires large amount of time; thus, a response surface method proposed in this study was used to reduce the computation time for the analysis of the cemented hip implant. The results demonstrate that using an efficient probabilistic approach can significantly reduce the computation time for the failure probability of the cement from several hours to minutes. The results also show that even the deterministic failure analyses do not indicate any failure of the cement mantle with high safety factors, the probabilistic analysis predicts the failure probability of the cement mantle as 8%, which must be considered during the evaluation of the success of the cemented hip implants.

  8. Progressive failure analysis of fibrous composite materials and structures

    NASA Technical Reports Server (NTRS)

    Bahei-El-din, Yehia A.

    1990-01-01

    A brief description is given of the modifications implemented in the PAFAC finite element program for the simulation of progressive failure in fibrous composite materials and structures. Details of the memory allocation, input data, and the new subroutines are given. Also, built-in failure criteria for homogeneous and fibrous composite materials are described.

  9. Dam failure analysis for the Lago El Guineo Dam, Orocovis, Puerto Rico

    USGS Publications Warehouse

    Gómez-Fragoso, Julieta; Heriberto Torres-Sierra,

    2016-08-09

    considered within the model. The results of the hydrologic simulations indicated that for all hydrologic conditions scenarios, the Lago El Guineo Dam would not experience overtopping. For the dam breach hydraulic analysis, failure by piping was the selected hypothetical failure mode for the Lago El Guineo Dam.Results from the simulated dam failure of the Lago El Guineo Dam using the HEC–RAS model for the 6- and 24-hour probable maximum precipitation events indicated peak discharges below the dam of 1,342.43 and 1,434.69 cubic meters per second, respectively. Dam failure during the 24-hour, 100-year recurrence rainfall event resulted in a peak discharge directly downstream from Lago El Guineo Dam of 1,183.12 cubic meters per second. Dam failure during sunny-day conditions (no precipitation) produced a peak discharge at Lago El Guineo Dam of 1,015.31 cubic meters per second assuming the initial water-surface elevation was at the morning-glory spillway invert elevation.The results of the hydraulic analysis indicate that the flood would extend to many inhabited areas along the stream banks from the Lago El Guineo Dam to the mouth of the Río Grande as a result of the simulated failure of the Lago El Guineo Dam. Low-lying regions in the vicinity of Ciales, Manatí, and Barceloneta, Puerto Rico, are among the regions that would be most affected by failure of the Lago El Guineo Dam. Effects of the flood control (levee) structure constructed in 2000 to provide protection to the low-lying populated areas of Barceloneta, Puerto Rico, were considered in the hydraulic analysis of dam failure. The results indicate that overtopping can be expected in the aforementioned levee during 6- and 24-hour probable maximum precipitation events. The levee was not overtopped during dam failure scenarios under the 24-hour, 100-year recurrence rainfall event or sunny-day conditions.

  10. Cascading failure analysis and restoration strategy in an interdependent network

    NASA Astrophysics Data System (ADS)

    Hong, Sheng; Lv, Chuan; Zhao, Tingdi; Wang, Baoqing; Wang, Jianghui; Zhu, Juxing

    2016-05-01

    In modern society, many infrastructures are interdependent owing to functional and logical relations among components in different systems. These networked infrastructures can be modeled as interdependent networks. In the real world, different networks carry different traffic loads whose values are dynamic and stem from the load redistribution in the same network and disturbance from the interdependent network. Interdependency makes interdependent networks so fragile that even a slight initial disturbance may lead to a cascading failure of the entire systems. In this paper, interdependencies among networks are modeled and a failure cascade process is studied considering their effects on failure propagation. Meanwhile, an in-process restoration strategy after the initial failure is investigated. The restoration effects depend strongly on the trigger timing, restoration probability and priority of the restoration actions along with the additional disturbances. Our findings highlight the necessity to decrease the large-scale cascading failure by structuring and managing an interdependent network reasonably.

  11. Spatial correlation analysis of cascading failures: Congestions and Blackouts

    PubMed Central

    Daqing, Li; Yinan, Jiang; Rui, Kang; Havlin, Shlomo

    2014-01-01

    Cascading failures have become major threats to network robustness due to their potential catastrophic consequences, where local perturbations can induce global propagation of failures. Unlike failures spreading via direct contacts due to structural interdependencies, overload failures usually propagate through collective interactions among system components. Despite the critical need in developing protection or mitigation strategies in networks such as power grids and transportation, the propagation behavior of cascading failures is essentially unknown. Here we find by analyzing our collected data that jams in city traffic and faults in power grid are spatially long-range correlated with correlations decaying slowly with distance. Moreover, we find in the daily traffic, that the correlation length increases dramatically and reaches maximum, when morning or evening rush hour is approaching. Our study can impact all efforts towards improving actively system resilience ranging from evaluation of design schemes, development of protection strategies to implementation of mitigation programs. PMID:24946927

  12. Spatial correlation analysis of cascading failures: Congestions and Blackouts

    NASA Astrophysics Data System (ADS)

    Daqing, Li; Yinan, Jiang; Rui, Kang; Havlin, Shlomo

    2014-06-01

    Cascading failures have become major threats to network robustness due to their potential catastrophic consequences, where local perturbations can induce global propagation of failures. Unlike failures spreading via direct contacts due to structural interdependencies, overload failures usually propagate through collective interactions among system components. Despite the critical need in developing protection or mitigation strategies in networks such as power grids and transportation, the propagation behavior of cascading failures is essentially unknown. Here we find by analyzing our collected data that jams in city traffic and faults in power grid are spatially long-range correlated with correlations decaying slowly with distance. Moreover, we find in the daily traffic, that the correlation length increases dramatically and reaches maximum, when morning or evening rush hour is approaching. Our study can impact all efforts towards improving actively system resilience ranging from evaluation of design schemes, development of protection strategies to implementation of mitigation programs.

  13. Spatial correlation analysis of cascading failures: congestions and blackouts.

    PubMed

    Daqing, Li; Yinan, Jiang; Rui, Kang; Havlin, Shlomo

    2014-06-20

    Cascading failures have become major threats to network robustness due to their potential catastrophic consequences, where local perturbations can induce global propagation of failures. Unlike failures spreading via direct contacts due to structural interdependencies, overload failures usually propagate through collective interactions among system components. Despite the critical need in developing protection or mitigation strategies in networks such as power grids and transportation, the propagation behavior of cascading failures is essentially unknown. Here we find by analyzing our collected data that jams in city traffic and faults in power grid are spatially long-range correlated with correlations decaying slowly with distance. Moreover, we find in the daily traffic, that the correlation length increases dramatically and reaches maximum, when morning or evening rush hour is approaching. Our study can impact all efforts towards improving actively system resilience ranging from evaluation of design schemes, development of protection strategies to implementation of mitigation programs.

  14. Noninvasive ventilation practice patterns for acute respiratory failure in Canadian tertiary care centres: A descriptive analysis

    PubMed Central

    Digby, Geneviève C; Keenan, Sean P; Parker, Christopher M; Sinuff, Tasnim; Burns, Karen E; Mehta, Sangeeta; Ronco, Juan J; Kutsogiannis, Demetrios J; Rose, Louise; Ayas, Najib T; Berthiaume, Luc R; D’Arsigny, Christine L; Stollery, Daniel E; Muscedere, John

    2015-01-01

    BACKGROUND: The extent of noninvasive ventilation (NIV) use for patients with acute respiratory failure in Canadian hospitals, indications for use and associated outcomes are unknown. OBJECTIVE: To describe NIV practice variation in the acute setting. METHODS: A prospective observational study involving 11 Canadian tertiary care centres was performed. Data regarding NIV indication, mode and outcomes were collected for all adults (>16 years of age) treated with NIV for acute respiratory failure during a four-week period (between February and August 2011). Logistic regression with site as a random effect was used to examine the association between preselected predictors and mortality or intubation. RESULTS: A total of 330 patients (mean [± SD] 30±12 per centre) were included. The most common indications for NIV initiation were pulmonary edema (104 [31.5%]) and chronic obstructive pulmonary disease (99 [30.0%]). Significant differences in indications for NIV use across sites, specialty of ordering physician and location of NIV initiation were noted. Although intubation rates were not statistically different among sites (range 10.3% to 45.4%), mortality varied significantly (range 6.7% to 54.5%; P=0.006). In multivariate analysis, the most significant independent predictor of avoiding intubation was do-not-resuscitate status (OR 0.11 [95% CI 0.03 to 0.37]). CONCLUSION: Significant variability existed in NIV use and associated outcomes among Canadian tertiary care centres. Assignment of do-not-resuscitate status prevented intubation. PMID:26469155

  15. Mode Deactivation Therapy (MDT) Family Therapy: A Theoretical Case Analysis

    ERIC Educational Resources Information Center

    Apsche, J. A.; Ward Bailey, S. R.

    2004-01-01

    This case study presents a theoretical analysis of implementing mode deactivation therapy (MDT) (Apsche & Ward Bailey, 2003) family therapy with a 13 year old Caucasian male. MDT is a form of cognitive behavioral therapy (CBT) that combines the balance of dialectical behavior therapy (DBT) (Linehan, 1993), the importance of perception from…

  16. Malfunction and failure analysis investigations of C26000 (Cu-30% Zn) brass cartridge cases

    SciTech Connect

    Feng, C.; Clark, S. . Metallic Materials Branch of the Armaments Technology Div.)

    1994-01-01

    The C26000 alloy, containing 70% Cu and 30% Zn, is predominantly used for cartridge case production and has an outstanding record of service. A multiple-step manufacturing process is employed to produce different microstructure in different sections of the cartridge case. The constant demands to increase performance have resulted in frequent revisions to the manufacturing process, and more stringent controls have been implemented in an attempt to produce a better product. Not surprisingly, however, failures and malfunctions are encountered in the tryout'' experiments. Studies indicate that failures in the head section can usually be traced to factors associated with gun design and propellant materials. Failures in the wall section are primarily stress-induced. Descriptions are given of the distinctive modes of failure in various sections of the cartridge case. The causes of failure and the remedies to prevent their recurrence are discussed.

  17. Tensile failure criteria for fiber composite materials

    NASA Technical Reports Server (NTRS)

    Rosen, B. W.; Zweben, C. H.

    1972-01-01

    The analysis provides insight into the failure mechanics of these materials and defines criteria which serve as tools for preliminary design material selection and for material reliability assessment. The model incorporates both dispersed and propagation type failures and includes the influence of material heterogeneity. The important effects of localized matrix damage and post-failure matrix shear stress transfer are included in the treatment. The model is used to evaluate the influence of key parameters on the failure of several commonly used fiber-matrix systems. Analyses of three possible failure modes were developed. These modes are the fiber break propagation mode, the cumulative group fracture mode, and the weakest link mode. Application of the new model to composite material systems has indicated several results which require attention in the development of reliable structural composites. Prominent among these are the size effect and the influence of fiber strength variability.

  18. Going South: Analysis of an Historic Project Engineering Failure

    NASA Technical Reports Server (NTRS)

    Scott, John H.

    2009-01-01

    NASA's successful conduct of the Apollo Program greatly enhanced the prestige of the United States and remains broadly accepted as America's gift to all Mankind. NASA's accomplishments continue to amaze the world. With the Vision for Space Exploration (VSE) Americans once again tasked NASA to carry out a project that is expected to provide inspiration and economic stimulus to the United States and to the world. In preparation NASA has thoroughly examined space program precedents. There is, however, another precedent which has not been examined in this context but whose scope and environment in many ways parallel the VSE. This project was initiated by a team that had, ten years before, successfully completed an effort that, at a cost of $173 billion (in 2008 dollars), had pushed the envelope of technology, brought economic growth, established their country as the world leader in engineering, and been broadly accepted as that country's gift to all Mankind. The new project was again inspired by popular desire to enhance national prestige and make yet another major contribution to Humanity. This effort was predicted to require eight years and $156 billion (2008 dollars). However, after nine years and expenditures of 96% beyond the baseline, the project collapsed amid bankruptcy, political scandal, and criminal prosecution. This paper applies current project management metrics, such as earned value analysis, to review the strategic decisions in this historic failure and describe its ultimate collapse. Key mistakes are identified, and lessons are drawn which may prove useful in guiding the VSE.

  19. Urine monitoring system failure analysis and operational verification test report

    NASA Technical Reports Server (NTRS)

    Glanfield, E. J.

    1978-01-01

    Failure analysis and testing of a prototype urine monitoring system (UMS) are reported. System performance was characterized by a regression formula developed from volume measurement test data. When the volume measurement test data. When the volume measurement data was imputted to the formula, the standard error of the estimate calculated using the regression formula was found to be within 1.524% of the mean of the mass of the input. System repeatability was found to be somewhat dependent upon the residual volume of the system and the evaporation of fluid from the separator. The evaporation rate was determined to be approximately 1cc/minute. The residual volume in the UMS was determined by measuring the concentration of LiCl in the flush water. Observed results indicated residual levels in the range of 9-10ml, however, results obtained during the flushing efficiency test indicated a residual level of approximately 20ml. It is recommended that the phase separator pumpout time be extended or the design modified to minimize the residual level.

  20. Design and analysis of a mode B and mode JD satellite Earth station

    NASA Astrophysics Data System (ADS)

    Hance, Dennis J.

    1994-06-01

    This thesis focuses on the design, integration, and analysis of an amateur radio service mode B and mode JD satellite earth station. Preliminary designs were investigated to determine the optimum configuration for the earth station. Modern digital modems, cabling structures, an 80386-based computer system, satellite tracking software, transmission and reception antennas, preamplifiers, and sophisticated performance measurement technologies were integrated into a functioning earth station. Initially, component availability and station design dictated the selection and acquisition of the requisite station equipment, integration of the transmitter, receiver preamplifiers, antennas, and computer equipment followed. Preliminary testing of the various components in the integration station occupied a significant amount of time. Empirical test tracking of different amateur and commercial satellites verified proper operation of the earth station. Results are discussed throughout this thesis.

  1. Instantaneous normal mode analysis of melting of finite dust clusters.

    PubMed

    Melzer, André; Schella, André; Schablinski, Jan; Block, Dietmar; Piel, Alexander

    2012-06-01

    The experimental melting transition of finite two-dimensional dust clusters in a dusty plasma is analyzed using the method of instantaneous normal modes. In the experiment, dust clusters are heated in a thermodynamic equilibrium from a solid to a liquid state using a four-axis laser manipulation system. The fluid properties of the dust cluster, such as the diffusion constant, are measured from the instantaneous normal mode analysis. Thereby, the phase transition of these finite clusters is approached from the liquid phase. From the diffusion constants, unique melting temperatures have been assigned to dust clusters of various sizes that very well reflect their dynamical stability properties.

  2. Using Dynamic Master Logic Diagram for component partial failure analysis

    SciTech Connect

    Ni, T.; Modarres, M.

    1996-12-01

    A methodology using the Dynamic Master Logic Diagram (DMLD) for the evaluation of component partial failure is presented. Since past PRAs have not focused on partial failure effects, the reliability of components are only based on the binary state assumption, i.e. defining a component as fully failed or functioning. This paper is to develop an approach to predict and estimate the component partial failure on the basis of the fuzzy state assumption. One example of the application of this methodology with the reliability function diagram of a centrifugal pump is presented.

  3. Probabilistic analysis of cascade failure dynamics in complex network

    NASA Astrophysics Data System (ADS)

    Zhang, Ding-Xue; Zhao, Dan; Guan, Zhi-Hong; Wu, Yonghong; Chi, Ming; Zheng, Gui-Lin

    2016-11-01

    The impact of initial load and tolerance parameter distribution on cascade failure is investigated. By using mean field theory, a probabilistic cascade failure model is established. Based on the model, the damage caused by certain attack size can be predicted, and the critical attack size is derived by the condition of cascade failure end, which ensures no collapse. The critical attack size is larger than the case of constant tolerance parameter for network of random distribution. Comparing three typical distributions, simulation results indicate that the network whose initial load and tolerance parameter both follow Weibull distribution performs better than others.

  4. Mode shape analysis using a commercially available peak store video frame buffer

    NASA Technical Reports Server (NTRS)

    Snow, Walter L.; Childers, Brooks A.

    1994-01-01

    Time exposure photography, sometimes coupled with strobe illumination, is an accepted method for motion analysis that bypasses frame by frame analysis and resynthesis of data. Garden variety video cameras can now exploit this technique using a unique frame buffer that is a non-integrating memory that compares incoming data with that already stored. The device continuously outputs an analog video signal of the stored contents which can then be redigitized and analyzed using conventional equipment. Historically, photographic time exposures have been used to record the displacement envelope of harmonically oscillating structures to show mode shape. Mode shape analysis is crucial, for example, in aeroelastic testing of wind tunnel models. Aerodynamic, inertial, and elastic forces can couple together leading to catastrophic failure of a poorly designed aircraft. This paper will explore the usefulness of the peak store device as a videometric tool and in particular discuss methods for analyzing a targeted vibrating plate using the 'peak store' in conjunction with calibration methods familiar to the close-range videometry community. Results for the first three normal modes will be presented.

  5. Satellite time series analysis using Empirical Mode Decomposition

    NASA Astrophysics Data System (ADS)

    Pannimpullath, R. Renosh; Doolaeghe, Diane; Loisel, Hubert; Vantrepotte, Vincent; Schmitt, Francois G.

    2016-04-01

    Geophysical fields possess large fluctuations over many spatial and temporal scales. Satellite successive images provide interesting sampling of this spatio-temporal multiscale variability. Here we propose to consider such variability by performing satellite time series analysis, pixel by pixel, using Empirical Mode Decomposition (EMD). EMD is a time series analysis technique able to decompose an original time series into a sum of modes, each one having a different mean frequency. It can be used to smooth signals, to extract trends. It is built in a data-adaptative way, and is able to extract information from nonlinear signals. Here we use MERIS Suspended Particulate Matter (SPM) data, on a weekly basis, during 10 years. There are 458 successive time steps. We have selected 5 different regions of coastal waters for the present study. They are Vietnam coastal waters, Brahmaputra region, St. Lawrence, English Channel and McKenzie. These regions have high SPM concentrations due to large scale river run off. Trend and Hurst exponents are derived for each pixel in each region. The energy also extracted using Hilberts Spectral Analysis (HSA) along with EMD method. Normalised energy computed for each mode for each region with the total energy. The total energy computed using all the modes are extracted using EMD method.

  6. Failure Analysis of Discrete Damaged Tailored Extension-Shear-Coupled Stiffened Composite Panels

    NASA Technical Reports Server (NTRS)

    Baker, Donald J.

    2005-01-01

    The results of an analytical and experimental investigation of the failure of composite is tiffener panels with extension-shear coupling are presented. This tailored concept, when used in the cover skins of a tiltrotor aircraft wing has the potential for increasing the aeroelastic stability margins and improving the aircraft productivity. The extension-shear coupling is achieved by using unbalanced 45 plies in the skin. The failure analysis of two tailored panel configurations that have the center stringer and adjacent skin severed is presented. Finite element analysis of the damaged panels was conducted using STAGS (STructural Analysis of General Shells) general purpose finite element program that includes a progressive failure capability for laminated composite structures that is based on point-stress analysis, traditional failure criteria, and ply discounting for material degradation. The progressive failure predicted the path of the failure and maximum load capability. There is less than 12 percent difference between the predicted failure load and experimental failure load. There is a good match of the panel stiffness and strength between the progressive failure analysis and the experimental results. The results indicate that the tailored concept would be feasible to use in the wing skin of a tiltrotor aircraft.

  7. Earth recovery mode analysis for a Martian sample return mission

    NASA Technical Reports Server (NTRS)

    Green, J. P.

    1978-01-01

    The analysis has concerned itself with evaluating alternative methods of recovering a sample module from a trans-earth trajectory originating in the vicinity of Mars. The major modes evaluated are: (1) direct atmospheric entry from trans-earth trajectory; (2) earth orbit insertion by retropropulsion; and (3) atmospheric braking to a capture orbit. In addition, the question of guided vs. unguided entry vehicles was considered, as well as alternative methods of recovery after orbit insertion for modes (2) and (3). A summary of results and conclusions is presented. Analytical results for aerodynamic and propulsive maneuvering vehicles are discussed. System performance requirements and alternatives for inertial systems implementation are also discussed. Orbital recovery operations and further studies required to resolve the recovery mode issue are described.

  8. The Reconstruction and Failure Analysis of the Space Shuttle Columbia

    NASA Technical Reports Server (NTRS)

    Russell, Richard; Mayeaux, Brian; McDanels, Steven; Piascik, Robert; Sjaj. Samdee[; Jerman, Greg; Collins, Thomas; Woodworth, Warren

    2009-01-01

    (3200 F), which would severely degrade support structure, tiles, and RCC panel materials. The integrated failure analysis of wing leading edge debris and deposits strongly supported the hypothesis that a breach occurred at LH RCC Panel 8.

  9. Gyrokinetic linear stability analysis of NSTX L-mode plasmas

    NASA Astrophysics Data System (ADS)

    Han, Ke; Ren, Yang

    2016-10-01

    NSTX offered unique opportunities in studying transport and turbulence with low aspect ratio, strong plasma shaping and strong E ×B shear. NSTX L-mode plasmas have some favorable properties to facilitate the study of the relation between microturbulence and thermal transport: easier to obtain stationary profiles; easier to maintain MHD quiescence; no complications from edge transport barrier. Studies of NSTX RF/NBI-heated L-mode plasmas have provided new insight into the role of ion and electron-scale turbulence in driving anomalous transport. Here we present linear stability analysis of some NSTX L-mode plasmas with GS2 gyrokinetic code. GS2 is an initial value gyrokinetic code which, in its linear mode, finds the fastest growing mode for a given pair of poloidal and radial wavenumbers. The linear simulations used local Miller equilibria and plasma parameters derived from measured experimental profiles with electromagnetic effects, electron and ion collisions and carbon impurity. The work is supported by DOE, China Scholarship Council, the Natural Science Foundation of China (61402138) and the Natural Science Foundation of Heilongjiang Province (E201452).

  10. Failure analysis of plasma-sprayed thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Berndt, C. C.; Miller, R. A.

    1984-01-01

    Thermally induced failure processes of plasma-sprayed thermal barrier coatings are examined. Cracking processes give rise to noise which was monitored by acoustic emission (AE) techniques. The sequential failure of coatings was examined from samples which were thermally cycled. Coatings of yttria-stabilized zirconia with and without a NiCrAlZr bond coat were plasma-sprayed onto U700 alloy rod. In some cases the substrate was intentionally overheated during deposition of the thermal protection system to check how this process variable influenced the AE response of the specimen. In this way a qualitative appraisal of how process variables affect coating integrity could be discerned in terms of cracking behavior. Results from up to seven consecutive thermal cycles are reported here. Coating failure was observed in all cases. Failure of the thermal protection system is progressive, since cracking and crack growth were observed prior to ultimate failure. Thus castastrophic failure occurs at some stage when there is a transformation from the microcrack to a macrocrack network.

  11. Comparison Study of Fourier and SVD Method for Plasma Mode Analysis in Tokamaks

    NASA Astrophysics Data System (ADS)

    Saadat, Shervin; Salem, Mohammad K.; Goranneviss, Mahmoud; Khorshid, Pejman

    2011-02-01

    Fourier analysis and Singular Value Decomposition (SVD) are two familiar methods for mode detection in tokamaks. In this article this two methods, fourier and SVD, have compared. The results show fourier analysis in m ≥ 3 and when the energy is balanced between modes could not recognize the correct mode number. The SVD analysis is cited method for all modes.

  12. Experimental research and finite element analysis of bridge piers failed in flexure-shear modes

    NASA Astrophysics Data System (ADS)

    Sun, Zhiguo; Si, Bingjun; Wang, Dongsheng; Guo, Xun

    2008-12-01

    In recent earthquakes, a large number of reinforced concrete (RC) bridges were severely damaged due to mixed flexure-shear failure modes of the bridge piers. An integrated experimental and finite element (FE) analysis study is described in this paper to study the seismic performance of the bridge piers that failed in flexure-shear modes. In the first part, a nonlinear cyclic loading test on six RC bridge piers with circular cross sections is carried out experimentally. The damage states, ductility and energy dissipation parameters, stiffness degradation and shear strength of the piers are studied and compared with each other. The experimental results suggest that all the piers exhibit stable flexural response at displacement ductilities up to four before exhibiting brittle shear failure. The ultimate performance of the piers is dominated by shear capacity due to significant shear cracking, and in some cases, rupturing of spiral bars. In the second part, modeling approaches describing the hysteretic behavior of the piers are investigated by using ANSYS software. A set of models with different parameters is selected and evaluated through comparison with experimental results. The influences of the shear retention coefficients between concrete cracks, the Bauschinger effect in longitudinal reinforcement, the bond-slip relationship between the longitudinal reinforcement and the concrete and the concrete failure surface on the simulated hysteretic curves are discussed. Then, a modified analysis model is presented and its accuracy is verified by comparing the simulated results with experimental ones. This research uses models available in commercial FE codes and is intended for researchers and engineers interested in using ANSYS software to predict the hysteretic behavior of reinforced concrete structures.

  13. Fourier mode analysis of source iteration in spatially periodic media

    SciTech Connect

    Zika, M.R.; Larsen, E.W.

    1998-12-31

    The standard Fourier mode analysis is an indispensable tool when designing acceleration techniques for transport iterations; however, it requires the assumption of a homogeneous infinite medium. For problems of practical interest, material heterogeneities may significantly impact iterative performance. Recent work has applied a Fourier analysis to the discretized two-dimensional transport operator with heterogeneous material properties. The results of these analyses may be difficult to interpret because the heterogeneity effects are inherently coupled to the discretization effects. Here, the authors describe a Fourier analysis of source iteration (SI) that allows the calculation of the eigenvalue spectrum for the one-dimensional continuous transport operator with spatially periodic heterogeneous media.

  14. The distinct element analysis of toppling failure mechanisms

    NASA Astrophysics Data System (ADS)

    Özge Dinç, Şaziye; Sinan Işık, Nihat; Karaca, Zeki

    2016-04-01

    This project investigates the toppling failure mechanisms of rock masses having different rock materials and discontinuity properties in slopes that are designed in different heights. For this purpose, PFC2D as a distinct element code was used to anticipate the post failure behaviors of rock masses. After the simulation of laboratory tests on the samples in 2 (width) *4 (height) m, macro mechanical properties of rock masses were determined to be assigned the slopes. The properties of discontinuities were set up based on the smooth-joint method in PFC. The movements in the slopes -equipped with persistent and non-persistent discontinuities- were analyzed by using gravity increase method. The results show that the post failure behaviors of all rock samples have been controlled primarily by joint location and joint length. In addition to this, an increase on the slope height has an influence on the failure mechanism such that triggers the materials to transit from the toppling to circular yielding manner in some models. It has been also worth note that all models begin to fail as soon as the wing cracks develop by tension stresses, thus the tensile strength of the relevant rock material is the most critical mechanic parameter on the failure.

  15. Lubrication mode analysis of articular cartilage using Stribeck surfaces.

    PubMed

    Gleghorn, Jason P; Bonassar, Lawrence J

    2008-01-01

    Lubrication of articular cartilage occurs in distinct modes with various structural and biomolecular mechanisms contributing to the low-friction properties of natural joints. In order to elucidate relative contributions of these factors in normal and diseased tissues, determination and control of lubrication mode must occur. The objectives of these studies were (1) to develop an in vitro cartilage on glass test system to measure friction coefficient, mu; (2) to implement and extend a framework for the determination of cartilage lubrication modes; and (3) to determine the effects of synovial fluid on mu and lubrication mode transitions. Patellofemoral groove cartilage was linearly oscillated against glass under varying magnitudes of compressive strain utilizing phosphate buffered saline (PBS) and equine and bovine synovial fluid as lubricants. The time-dependent frictional properties were measured to determine the lubricant type and strain magnitude dependence for the initial friction coefficient (mu(0)=mu(t-->0)) and equilibrium friction coefficient (mu(eq)=mu(t-->infinity)). Parameters including tissue-glass co-planarity, normal strain, and surface speed were altered to determine the effect of the parameters on lubrication mode via a 'Stribeck surface'. Using this testing apparatus, cartilage exhibited biphasic lubrication with significant influence of strain magnitude on mu(0) and minimal influence on mu(eq), consistent with hydrostatic pressurization as reported by others. Lubrication analysis using 'Stribeck surfaces' demonstrated clear regions of boundary and mixed modes, but hydrodynamic or full film lubrication was not observed even at the highest speed (50mm/s) and lowest strain (5%).

  16. The failure analysis of composite material flight helmets as an aid in aircraft accident investigation.

    PubMed

    Caine, Y G; Bain-Ungerson, O; Schochat, I; Marom, G

    1991-06-01

    Understanding why a flying helmet fails to maintain its integrity during an accident can contribute to an understanding of the mechanism of injury and even of the accident itself. We performed a post-accident evaluation of failure modes in glass and aramid fibre-reinforced composite helmets. Optical and microscopic (SEM) techniques were employed to identify specific fracture mechanisms. They were correlated with the failure mode. Stress and energy levels were estimated from the damage extent. Damage could be resolved into distinct impact, flexure and compression components. Delamination was identified as a specific mode, dependent upon the matrix material and bonding between the layers. From the energy dissipated in specific fracture mechanisms we calculated the minimum total energy imparted to the helmet-head combination and the major injury vector (MIV) direction and magnitude. The level of protection provided by the helmet can also be estimated.

  17. Failure strength prediction for adhesively bonded single lap joints

    NASA Astrophysics Data System (ADS)

    Rahman, Niat Mahmud

    For adhesively bonded joint, failure strength depends on many factors such as material properties (both adhesive and adherend), specimen geometries, test environments, surface preparation procedures, etc. Failure occurs inside constitutive materials or along joint interfaces. Based on location, adhesively bonded failure mode can be classified as adhesive failure mode, cohesive failure mode and adherend failure mode. Failure mode directly affects the failure strength of joint. For last eight decades, researchers have developed analytical, empirical or semi-empirical methods capable of predicting failure strength for adhesively bonded joints generating either cohesive failure or adherend failure. Applicability of most of the methods is limited to particular cases. In this research, different failure modes for single lap joints (SLJs) were generated experimentally using epoxy based paste adhesive. Based on experimental data and analytical study, simplified failure prediction methods were developed for each failure mode. For adhesive failure mode, it is observed that peel stress distributions concur along interface near crack initiation points. All SLJs for this test endured consistent surface treatments. Geometric parameters of the joints were varied to study their effect on failure strength. Peel stress distributions were calculated using finite analysis (FEA). Based on peel stress distribution near crack initiation point, a failure model is proposed. Numerous analytical, empirical and semi-empirical models are available for predicting failure strengths of SLJs generating cohesive failures. However, most of the methods in the literature failed to capture failure behavior of SLJs having thickness of adhesive layer as variable. Cohesive failure mode was generated experimentally using aluminum as adherend and epoxy adhesive considering thickness of adhesive layers as variable within SLJs. Comparative study was performed among various methods. It was observed that

  18. Performance Analysis of Power Saving Mechanism Employing Both Sleep Mode and Idle Mode in IEEE 802.16e

    NASA Astrophysics Data System (ADS)

    Hwang, Eunju; Lee, Yong Hyun; Kim, Kyung Jae; Son, Jung Je; Choi, Bong Dae

    The IEEE 802.16e standard specifies the sleep mode and the idle mode of a mobile station (MS) for power saving. In this paper, to reduce the energy consumption of the MS, we employ the sleep mode while the MS is on-session, and the idle mode while it is off-session. Under the assumption that the time duration from the end of a session to the arrival of a new downlink session request follows an exponential distribution of the mean 1/ν and that arrivals of messages during an on-session follow a Poisson process with rate λ, we analyze the awake mode period and the sleep mode period by using the busy period analysis of the M/G/1 queue, and then we derive the total mean length of an on-session which consists of a geometric number of awake mode periods and sleep mode periods. Since the sum of an on-session and an off-session constitutes a cycle, we can express the average power consumption in terms of the mean lengths of an awake mode period, a sleep mode period and an idle mode period. The average power consumption indicates how much the MS can save energy by employing the sleep mode and the idle mode. We also derive the Laplace Stieltjes transform (and the mean) of the queueing delay of messages to examine a tradeoff between the power consumption and the delay of messages. Analytical results, which are shown to be well-matched by simulations, address that our employment of the sleep mode and the idle mode provides a considerable reduction in the energy consumption of the MS.

  19. Statistical failure analysis of adhesive resin cement bonded dental ceramics

    PubMed Central

    Wang, Yaou; Katsube, Noriko; Seghi, Robert R; Rokhlin, Stanislav I.

    2007-01-01

    The goal of this work is to quantitatively examine the effect of adhesive resin cement on the probability of crack initiation from the internal surface of ceramic dental restorations. The possible crack bridging mechanism and residual stress effect of the resin cement on the ceramic surface are examined. Based on the fracture-mechanics-based failure probability model, we predict the failure probability of glass-ceramic disks bonded to simulated dentin subjected to indentation loads. The theoretical predictions match experimental data suggesting that both resin bridging and shrinkage plays an important role and need to be considered for accurate prognostics to occur. PMID:18670583

  20. Investigation of TC-1 flight failure using power spectral analysis

    NASA Technical Reports Server (NTRS)

    Lorenzo, C. F.

    1976-01-01

    During the Titan Centaur 1 test flight a failure involving at least one of the Centaur propellant boost pumps occurred. Also, neither of the boost pump speed instruments indicated pump rotation. Accelerometer data from the Titan Centaur 1 flight failure were analyzed using power spectral density methods to determine boost pump speed during attempted starts of the Centaur. The technique was demonstrated on a reference flight. The hydrogen boost pump speed transient was determined for the TC-1 flight. Other trends are seen in the data. However, these are not believed to be the oxygen boost pump. Discussion of data enhancement techniques is also presented.

  1. Failure analysis of Chloride Silent Power, Ltd. PB cells

    NASA Astrophysics Data System (ADS)

    Beauchamp, E. K.

    1988-05-01

    Two beta double prime alumina electrolyte tubes from Chloride Silent Power, Ltd. PB cells which failed in testing at Sandia National Laboratories, showed extensive cracking. The cracks initiated at the interior surface under localized stress apparently resulting from nonuniform ionic currents. The nonuniform currents apparently were a result of nonuniform wetting of the interior surface of the electrolyte. Failure of the sodium electrode seal, which introduced contaminants to the electrolyte surface, may have been reponsible for the nonuniform wetting. In one of the electrolytes, large grains, produced by overfiring, contributed to the failure.

  2. Application of the cubic polynomial strength criterion to the failure analysis of composite materials

    NASA Technical Reports Server (NTRS)

    Tennyson, R. C.; Nanyaro, A. P.; Wharram, G. E.

    1980-01-01

    A comparative failure analysis is presented based on the application of quadratic and cubic forms of the tensor polynomial lamina strength criterion to various composite structural configurations in a plane stress state. Failure loads have been predicted for off-angle laminates under simple loading conditions and for symmetric-balanced laminates subject to varying degrees of biaxial tension, including configurations subject to multimode failures. Some experimental data are also provided to support these calculations. From these results, the necessity of employing a cubic strength criterion to accurately predict the failure of composite laminae is demonstrated.

  3. Failure analysis of fuel cell electrodes using three-dimensional multi-length scale X-ray computed tomography

    NASA Astrophysics Data System (ADS)

    Pokhrel, A.; El Hannach, M.; Orfino, F. P.; Dutta, M.; Kjeang, E.

    2016-10-01

    X-ray computed tomography (XCT), a non-destructive technique, is proposed for three-dimensional, multi-length scale characterization of complex failure modes in fuel cell electrodes. Comparative tomography data sets are acquired for a conditioned beginning of life (BOL) and a degraded end of life (EOL) membrane electrode assembly subjected to cathode degradation by voltage cycling. Micro length scale analysis shows a five-fold increase in crack size and 57% thickness reduction in the EOL cathode catalyst layer, indicating widespread action of carbon corrosion. Complementary nano length scale analysis shows a significant reduction in porosity, increased pore size, and dramatically reduced effective diffusivity within the remaining porous structure of the catalyst layer at EOL. Collapsing of the structure is evident from the combination of thinning and reduced porosity, as uniquely determined by the multi-length scale approach. Additionally, a novel image processing based technique developed for nano scale segregation of pore, ionomer, and Pt/C dominated voxels shows an increase in ionomer volume fraction, Pt/C agglomerates, and severe carbon corrosion at the catalyst layer/membrane interface at EOL. In summary, XCT based multi-length scale analysis enables detailed information needed for comprehensive understanding of the complex failure modes observed in fuel cell electrodes.

  4. Open-Mode Debonding Analysis of Curved Sandwich Panels Subjected to Heating and Cryogenic Cooling on Opposite Faces

    NASA Technical Reports Server (NTRS)

    Ko, William L.

    1999-01-01

    Increasing use of curved sandwich panels as aerospace structure components makes it vital to fully understand their thermostructural behavior and identify key factors affecting the open-mode debonding failure. Open-mode debonding analysis is performed on a family of curved honeycomb-core sandwich panels with different radii of curvature. The curved sandwich panels are either simply supported or clamped, and are subjected to uniform heating on the convex side and uniform cryogenic cooling on the concave side. The finite-element method was used to study the effects of panel curvature and boundary condition on the open-mode stress (radial tensile stress) and displacement fields in the curved sandwich panels. The critical stress point, where potential debonding failure could initiate, was found to be at the midspan (or outer span) of the inner bonding interface between the sandwich core and face sheet on the concave side, depending on the boundary condition and panel curvature. Open-mode stress increases with increasing panel curvature, reaching a maximum value at certain high curvature, and then decreases slightly as the panel curvature continues to increase and approach that of quarter circle. Changing the boundary condition from simply supported to clamped reduces the magnitudes of open-mode stresses and the associated sandwich core depth stretching.

  5. Ferrographic and spectrographic analysis of oil sampled before and after failure of a jet engine

    NASA Technical Reports Server (NTRS)

    Jones, W. R., Jr.

    1980-01-01

    An experimental gas turbine engine was destroyed as a result of the combustion of its titanium components. Several engine oil samples (before and after the failure) were analyzed with a Ferrograph as well as plasma, atomic absorption, and emission spectrometers. The analyses indicated that a lubrication system failure was not a causative factor in the engine failure. Neither an abnormal wear mechanism, nor a high level of wear debris was detected in the oil sample from the engine just prior to the test in which the failure occurred. However, low concentrations of titanium were evident in this sample and samples taken earlier. After the failure, higher titanium concentrations were detected in oil samples taken from different engine locations. Ferrographic analysis indicated that most of the titanium was contained in spherical metallic debris after the failure.

  6. Analysis of failures and poor results of lumbar spine surgery.

    PubMed

    Fager, C A; Freidberg, S R

    1980-01-01

    The failures and poor results of lumbar spine surgery are analyzed in a retrospectively study of 105 consecutive patients referred to the authors for evaluation during 1976. Those who had a history of industrial or vehicular accident outnumbered others by about two to one. Review of histories, physical findings, and myelograms in most of the patients failed to substantiate the diagnosis of ruptured disc or nerve root compression. Many of the failures occurred in thos patients in whom little if any evidence of nerve root compression was found. The indications for surgery were poor in this group. Other failures occurred in patients who had improper, incomplete, or inadequate operations, especially those with lumbar spondylosis, a retained fragment of disc, or surgery at the wrong level. In addition to failure, poor results were recorded in patients who had significant nerve root or cauda equina injury from surgery, associated "arachnoiditis" which is thought to result from surgical trauma in many instances, or multiple operations leading to a hopelessly disabled state.

  7. Structural mode significance using INCA. [Interactive Controls Analysis computer program

    NASA Technical Reports Server (NTRS)

    Bauer, Frank H.; Downing, John P.; Thorpe, Christopher J.

    1990-01-01

    Structural finite element models are often too large to be used in the design and analysis of control systems. Model reduction techniques must be applied to reduce the structural model to manageable size. In the past, engineers either performed the model order reduction by hand or used distinct computer programs to retrieve the data, to perform the significance analysis and to reduce the order of the model. To expedite this process, the latest version of INCA has been expanded to include an interactive graphical structural mode significance and model order reduction capability.

  8. Analysis and comparison of range — range positioning mode and hyperbolic positioning mode

    NASA Astrophysics Data System (ADS)

    Chen, Shi-Ru; Xu, Ding-Jie; Sun, Yao

    2002-06-01

    Three key factors are discussed, which affect positioning accuracy of range — range positioning mode and hyperbolic positioning mode. Based on the error elliptical theory, the expressions of positioning error and of positioning geometric factor of range — range positioning mode and hyperbolic positioning mode are derived, and the positioning error and the blind positioning area of two different positioning modes are analyzed. According to the requirement of navigation area, an optimum positional configuration among navigation stations of hyperbolic positioning mode is provided. Some considerable conclusions are obtained, and some graphs of distribution are presented, which are important to study and design a reasonable, precise radio navigation system.

  9. Failure analyses of composite bolted joints

    NASA Technical Reports Server (NTRS)

    Wilson, D. W.; Gillespie, J. W.; York, J. L.; Pipes, R. B.

    1980-01-01

    The complex failure behavior exhibited by bolted joints of graphite epoxy (Hercules AS/3501) was investigated for the net tension, bearing and shearout failure modes using combined analytical and experimental techniques. Plane stress, linear elastic, finite element methods were employed to determine the two dimensional state of stress resulting from a loaded hole in a finite width, semiinfinite strip. The stresses predicted by the finite element method were verified by experiment to lend credence to the analysis. The influence of joint geometric parameters on the state of stress and resultant strength of the joint was also studied. The resulting functional relationships found to exist between bolted joint strength and the geometric parameters, were applied in the formulation of semiempirical strength models for the basic failure modes. A point stress failure criterion was successfully applied as the failure criterion for the net tension and shearout failure modes.

  10. Slope stability analysis for Valles Marineris, Mars: a numerical analysis of controlling conditions and failure types

    NASA Astrophysics Data System (ADS)

    Crosta, G.; Castellanza, R.; De Blasio, F.; Utili, S.

    2012-04-01

    Valles Marineris (VM hereafter) in the equatorial area of Mars exhibits several gravitative failures often involving the whole 6-8 km thickness of the valley walls. The failures have resulted in a series of long-runout landslides up to several hundred cubic kilometres in volume (Quantin et al., 2004), and the formation of sub-circular alcoves perched on the top. Several questions arise as to forces at play in the stability of the walls of VM, the geometrical shape of the alcoves and the shape and long-runout of the landslides (see for example Lucas et al., 2011). In this work, we concentrate on the stability analysis of the walls of VM with two precise questions in mind starting from past studies (Bigot-Cormier and Montgomery, 2006; Neuffer and Schultz, 2006, Schultz, 2002). The first concerns the properties of the materials that give origin to instability. We performed several finite element and discrete element calculations tailored to slope stability analysis based on the genuine shape of the walls of VM taken from the MOLA topographic data. We considered stratified and differently altered/degraded materials to define the range of physical mechanical properties required for failure to occur and to explain the discrete distribution of failures along the VM valley flanks. A second question addressed in this work is the geometrical shape of the sub-circular alcoves. Normally, these shapes are commonplace for slopes made of uniform and isotropic properties, and are also observed in subaqueous environment. We performed calculations taking into consideration the progressive failure in the slope showing the final results in terms of surface failure geometry. Bigot-Cormier, F., Montgomery, D.R. (2007) Valles Marineris landslides: Evidence for a strength limit to Martian relief? Earth and Planetary Science Letters, 260, 1-2, 15, 179-186 Lucas, A., Mangeney, A., Mège, D., and Bouchut, F., 2011. Influence of the scar geometry on landslide dynamics and deposits

  11. Kelvin waves in ECMWF analysis: normal-mode diagnostics

    NASA Astrophysics Data System (ADS)

    Blaauw, Marten; Zagar, Nedjeljka

    2013-04-01

    Equatorial Kelvin waves show a large spread in spatial and temporal variability similar to their source of tropical convective forcing. Once decoupled from their source, Kelvin waves are modulated during their ascent by changes in the background wind and stability. In this presentation, we focus on the seasonal and interannual variability of Kelvin waves in relation with variability of (i) tropical convection and (ii) background zonal wind and static stability. Global data is extracted from ECMWF operational analysis from January 2007 till May 2011 on 91 model levels (top level at 0.01 hPa) and ~ 25 km horizontal resolution. Using three-dimensional orthogonal normal-mode expansions, we project input mass and wind data simultaneously onto balanced rotational modes and unbalanced inertia-gravity modes including Kelvin modes. Next, an inverse transformation of Kelvin modes to physical space is performed under the linearity assumption, allowing a study on the spatial and temporal variability of Kelvin wave zonal wind and temperature. Results show an annual cycle in KW zonal wind in agreement with other studies. Minima resp. maxima in zonal wind amplitudes are found in the Indian ocean resp. Western Pacific and are most pronounced in the tropical tropopause at 150 hPa in January and 100 hPa in July. The annual cycle is enhanced (reduced) through interaction with a descending westerly QBO phase and enhanced (reduced) convective forcing. We also note a gradual eastward shift of KW zonal wind maxima till January 2010 in correspondence with an eastward shift of tropical convection.

  12. Probabilistic low cycle fatigue failure analysis with application to liquid propellant rocket engines

    NASA Technical Reports Server (NTRS)

    Newlin, L.; Sutharshana, S.; Ebbeler, D.; Moore, N.; Fox, E.

    1990-01-01

    A probabilistic Low Cycle Fatigue (LCF) failure analysis of a candidate turbine disk for use in a turbopump of a rocket engine of the Space Shuttle Main Engine class is described. A state-of-the-art LCF failure prediction method was used in a Monte Carlo simulation to generate a distribution of failure lives. A stochastic Stress/Life (S/N) model was used for materials characterization. The LCF failure model expresses fatigue life as a function of stochastic parameters including environmental parameters, loads, material properties, structural parameters, and model specification errors. The rationale for the particular characterization of each stochastic input parameter is described. The results and interpretation of the failure analysis are given.

  13. NOLB : Non-linear rigid block normal mode analysis method.

    PubMed

    Hoffmann, Alexandre; Grudinin, Sergei

    2017-04-05

    We present a new conceptually simple and computationally efficient method for non-linear normal mode analysis called NOLB. It relies on the rotations-translations of blocks (RTB) theoretical basis developed by Y.-H. Sanejouand and colleagues. We demonstrate how to physically interpret the eigenvalues computed in the RTB basis in terms of angular and linear velocities applied to the rigid blocks and how to construct a non-linear extrapolation of motion out of these velocities. The key observation of our method is that the angular velocity of a rigid block can be interpreted as the result of an implicit force, such that the motion of the rigid block can be considered as a pure rotation about a certain center. We demonstrate the motions produced with the NOLB method on three different molecular systems and show that some of the lowest frequency normal modes correspond to the biologically relevant motions. For example, NOLB detects the spiral sliding motion of the TALE protein, which is capable of rapid diffusion along its target DNA. Overall, our method produces better structures compared to the standard approach, especially at large deformation amplitudes, as we demonstrate by visual inspection, energy and topology analyses, and also by the MolProbity service validation. Finally, our method is scalable and can be applied to very large molecular systems, such as ribosomes. Standalone executables of the NOLB normal mode analysis method are available at https://team.inria.fr/nano-d/software/nolb-normal-modes. A graphical user interfaces created for the SAMSON software platform will be made available at https: //www.samson-connect.net.

  14. Analysis of Emergency Diesel Generators Failure Incidents in Nuclear Power Plants

    NASA Astrophysics Data System (ADS)

    Hunt, Ronderio LaDavis

    In early years of operation, emergency diesel generators have had a minimal rate of demand failures. Emergency diesel generators are designed to operate as a backup when the main source of electricity has been disrupted. As of late, EDGs (emergency diesel generators) have been failing at NPPs (nuclear power plants) around the United States causing either station blackouts or loss of onsite and offsite power. These failures occurred from a specific type called demand failures. This thesis evaluated the current problem that raised concern in the nuclear industry which was averaging 1 EDG demand failure/year in 1997 to having an excessive event of 4 EDG demand failure year which occurred in 2011. To determine the next occurrence of the extreme event and possible cause to an event of such happening, two analyses were conducted, the statistical and root cause analysis. Considering the statistical analysis in which an extreme event probability approach was applied to determine the next occurrence year of an excessive event as well as, the probability of that excessive event occurring. Using the root cause analysis in which the potential causes of the excessive event occurred by evaluating, the EDG manufacturers, aging, policy changes/ maintenance practices and failure components. The root cause analysis investigated the correlation between demand failure data and historical data. Final results from the statistical analysis showed expectations of an excessive event occurring in a fixed range of probability and a wider range of probability from the extreme event probability approach. The root-cause analysis of the demand failure data followed historical statistics for the EDG manufacturer, aging and policy changes/ maintenance practices but, indicated a possible cause regarding the excessive event with the failure components. Conclusions showed the next excessive demand failure year, prediction of the probability and the next occurrence year of such failures, with an

  15. Case–Cohort Analysis with Accelerated Failure Time Model

    PubMed Central

    Kong, Lan; Cai, Jianwen

    2010-01-01

    Summary In a case–cohort design, covariates are assembled only for a subcohort that is randomly selected from the entire cohort and any additional cases outside the subcohort. This design is appealing for large cohort studies of rare disease, especially when the exposures of interest are expensive to ascertain for all the subjects. We propose statistical methods for analyzing the case–cohort data with a semiparametric accelerated failure time model that interprets the covariates effects as to accelerate or decelerate the time to failure. Asymptotic properties of the proposed estimators are developed. The finite sample properties of case–cohort estimator and its relative efficiency to full cohort estimator are assessed via simulation studies. A real example from a study of cardiovascular disease is provided to illustrate the estimating procedure. PMID:18537948

  16. Summary of failure analysis activities at Brookhaven National Laboratory

    SciTech Connect

    Cowgill, M.G.; Czajkowski, C.J.; Franz, E.M.

    1996-10-01

    Brookhaven National Laboratory has for many years conducted examinations related to the failures of nuclear materials and components. These examinations included the confirmation of root cause analyses, the determination of the causes of failure, identification of the species that accelerate corrosion, and comparison of the results of nondestructive examinations with those obtained by destructive examination. The results of those examinations, which had previously appeared in various formats (formal and informal reports, journal articles, etc.), have been collected together and summarized in the present report. The report is divided into sections according to the general subject matter (for example, corrosion, fatigue, etc.). Each section presents summaries of the information contained in specific reports and publications, all of which are fully identified as to title, authors, report number or journal reference, date of publication, and FIN number under which the work was performed.

  17. S Tank Farm SL-119 saltwell piping failure analysis report

    SciTech Connect

    Carlos, W.C.

    1994-08-05

    On January 24, 1992, while pressure testing saltwell line SL-119 in the 241-S Tank Farm, water was observed spraying out of heat trace enclosure. The SL-115, SL-116, SN-215, and SN-216 saltwell lines also recently failed pressure testing because of leaks. This study documents the pertinent facts about the SL-119 line and discusses the cause of the failures. The inspection of the SL-119 failure revealed two through-the-wall holes in the top center of the pipeline. The inspection also strongly suggests that the heat tracing system is directly responsible for causing the SL-119 failure. Poor design of the heat tracing system allowed water to enter, condense, and collect in the electric metallic tubing (EMT) carbon steel conduits. Water flowed to the bottom of the elbow of the conduit and corroded out the elbow. The design also allowed drifting desert sand to enter into the conduit and fall to the bottom (elbow) of the conduit. The sand became wet and aided in the corrosion of the elbow of the conduit. After the EMT conduits corroded though, the water dripped from the corroded ends of the EMT conduits onto the top of the saltwell pipe, corroding the two holes into the top of the line. If the heat tracing hot splice box had not allowed moisture to enter the EMT conduits, the saltwell piping would not have corroded and caused SL-119 to fail.

  18. Reciprocating compressor valve failure -- Digital modelling and analysis

    SciTech Connect

    Motriuk, R.W.

    1996-12-31

    Many problems in reciprocating compressors are caused by valve failures. Usually, valve failures are diagnosed early, and the worn out parts are replaced. This requires, however, unscheduled compressor shutdowns which increase the cost of operation and possibly breach gas delivery contracts. Thus, it is essential to design valves adequate for the particular compressors and flow conditions. In this paper, it is determined that the cause of an unusually large number of valve failures at one of the NOVA Gas Transmission Limited (NGTL) compressor stations was an inadequate valve design. It is shown that the type of valve presently used is unacceptable and should be replaced. Due to economic restrictions, however, the existing valves are modified rather than replaced. The method used to re-design the compressor valves includes two steps: field measurements and computer digital modelling. The modelling incorporates: (1) acoustic simulation of the system, (2) compressor valve dynamic simulation, and (3) simultaneous simulation of fluid solid interactions between the compressor valves, compressor cylinders and pipework. The results obtained by using models of (2) and (3) are compared.

  19. Failure Analysis of CCD Image Sensors Using SQUID and GMR Magnetic Current Imaging

    NASA Technical Reports Server (NTRS)

    Felt, Frederick S.

    2005-01-01

    During electrical testing of a Full Field CCD Image Senor, electrical shorts were detected on three of six devices. These failures occurred after the parts were soldered to the PCB. Failure analysis was performed to determine the cause and locations of these failures on the devices. After removing the fiber optic faceplate, optical inspection was performed on the CCDs to understand the design and package layout. Optical inspection revealed that the device had a light shield ringing the CCD array. This structure complicated the failure analysis. Alternate methods of analysis were considered, including liquid crystal, light and thermal emission, LT/A, TT/A SQUID, and MP. Of these, SQUID and MP techniques were pursued for further analysis. Also magnetoresistive current imaging technology is discussed and compared to SQUID.

  20. Coupled Mechanical-Electrochemical-Thermal Analysis of Failure Propagation in Lithium-ion Batteries

    SciTech Connect

    Zhang, Chao; Santhanagopalan, Shriram; Pesaran, Ahmad

    2016-07-28

    This is a presentation given at the 12th World Congress for Computational Mechanics on coupled mechanical-electrochemical-thermal analysis of failure propagation in lithium-ion batteries for electric vehicles.