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Dynamic Fault Tree Method (Part 2 of 3)

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Dynamic Gates
The DFT is based on the developing of new gates, including Priority-AND (PAND) gate, Functional Dependency (FDEP) gate, Spare gate and Sequence Enforcing (SEQ) gate.
DFTs were developed based on SFTs with new types of gates, which are called dynamic gates.
The use of these new dynamic gates makes it feasible to involve time and cross dependencies in the calculations.

As mentioned, the DFT brings four new dynamic gates; including PAND gate (Fig. 2-a), which fails if all of its inputs fail in a pre-defined order (left-to-right in the visual presentation of the gate), FDEP gate (Fig. 2-b), which compels its secondary (dependent) inputs to fail when the primary input (trigger) occurs, along with the first event, SPARE gate (Fig. 2-c), which has one primary input and a number of spare inputs, and SEQ gate (Fig. 2-d), which compels its inputs to occur in a pre-defined order (left-to-right in the visual presentation of the gate).
ASQ-RD-Sept2015-Newsletter-jIMbEDITSwithupdates - Google Chrome

DFT Solution Methods
Several researches have been conducted on altering old approaches for solving DFTs.
Existing methods for solving DFTs are generally based on the mapping the DFT into a different model [5].
In general, solution approaches to solve a DFT, are classified to four different methods; including analytical, simulation based, diagram representation
and hybrid methods.
There are three classes of quantitative analytical models, which are used to solve a DFT [6]:

combinatorial approaches, which are unable to handle dynamic dependencies among the system components [13];

state-space approaches, which improve static models for modeling complex systems; but the statespace model of a system can be too large and it may require too much computation time [12], and

modular approaches, which are combination of previous approaches and mostly used for DFT analysis [1,8].

Most of these methods are particular for a special case and it is difficult to extend that solution method for other cases.
In addition, the complexity of the real systems requires the modeling of their reliability with realistic considerations, which suggests the use of analytical methods very grinding and effortful [7].

Simulation based methods, especially Monte Carlo simulation based techniques, can solve these problems.
According to the researches, complex systems which may be difficult to solve with analytical methods are simply solved with Monte Carlo simulation approach [3,4,7,12].
The reliability methods, which are based on Monte Carlo simulation approach, because of their ability in modeling the real conditions and stochastic behavior of the system,

By: Mohammad Pourgol-Mohammad, Ph.D, P.E, CRE, mpourgol@gmail.com

Previously published in the September 2015 Volume 6, Issue 3 ASQ Reliability Division Newsletter

Picture © B. Poncelet https://bennyponcelet.wordpress.com

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Dynamic Fault Tree Method (Part 1 of 3)

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Introduction
One of the most important goals for the reliability analysis is “Predicting the reliability of the system for a specified mission time” [1].
There are plenty of techniques accessible to be used to reach this goal.
In order to predict the reliability of a system, a proper reliability model must be selected.
Fault Tree Analysis (FTA) is one of the most developed and dominant techniques in reliability studies.
First in 1962, FTA techniques have been created at Bell Telephone Laboratories [2].
Nowadays, FTA is widely used for quantitative reliability analysis and safety assessment of complex and critical engineering systems [3].
In fact, FTA is a logical tree demonstrating the ways in which a system fails.
The tree starts with an unpleasant event (top event), and all conceivable paths for top event to occur are shown.
For this logic tree, the leaves are basic events (BEs), which model component failures [4] and generally linked to the failure of components [5].
The BEs demonstrate root causes for the unpleasant event.
Each BE has a proper failure distribution (mostly Weibull and exponential distributions), its suitability is verified by goodness of fit techniques [4].
Nowadays, FTA method is the most used quantitative technique for accident scenario assessment in the industry [6]; however, this method is often used in the static form not proper for analyzing the complex systems.

Static Fault Tree (SFT)
The main assumptions for the use of the SFTs are [6,7]:
i) binary BEs;
ii) statistically independent BEs;
iii) instantaneous transition between the working and the failed state;
iv) restoration of components as good as new by maintenance; if the failure of a component influences other events on superior levels, its repair restores these events to the normal operative condition.
The way that events are connected to produce system failure, is represented by means of logical Boolean gates (AND; OR; Voting).
ASQ-RD-June2015-Newsletter.pdf - Google Chrome
AND gate (Fig. 1-a) has failed output when all inputs fail, OR gate (Fig. 1-b) fails if at least one of inputs fails and Voting gate (Fig. 1-c) fails if at least k out of n inputs fails [4].
SFTs with AND, OR, and Voting (k of n) gates cannot encompass the dynamic behavior of system failure mechanisms [8].
To overcome this problem, Dynamic Fault Tree (DFT) analysis is suggested in recent research.

Dynamic Fault Tree
Most of reliability modeling techniques are based on statistical methods.
Their typical examples are reliability block diagram (RBD), FTA, and Markov chains [9].
These methods are not able to encompass the dynamic behavior of complex systems.
Dynamic reliability assessment methods were developed on common basic of static reliability analysis, in order to encompass the dynamic behavior of sequence, spare or time dependency actions or failures in the complex systems.
The key parameter to separate dynamic behavior from static behavior is the time.
Dynamic reliability approaches are powerful formalisms and invent a more realistic modeling of complex systems [10].
Among these new formalisms (DFT analysis, Dynamic RBDs, Boolean logic Driven Markov Process and etc.), which proposed to reliability calculation studies, DFT analysis has been the most used and practical one As compared with the SFT, DFT is a graphical model for the reliability studies that combines the ways how an undesired event (top event) can occur.
However, in a DFT, top event is a time dependent event.
DFT represents a better estimation of the traditional FT by including the time dependency [11].
Like a SFT, the DFT is a tree in which the leaves are BEs; however, in this approach, BEs are more realistic and detailed than SFT technique.
The main assumptions for the use of the DFTs are [12]:
i) binary BEs;
ii) Non-repairable components (recently, some efforts have been made to consider repair in DFT [5]).

By: Mohammad Pourgol-Mohammad, Ph.D, P.E, CRE, mpourgol@gmail.com

Previously published in the June 2015 Volume 6, Issue 2 ASQ Reliability Division Newsletter

Picture © B. Poncelet https://bennyponcelet.wordpress.com

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RAMS BEST PAPER AWARD 2016

We congratulate Vladimir Babishin, Sharareh Taghipour with the 2016 RAMS BEST PAPER AWARD for the paper “Joint Maintenance and Inspection Optimization of a k-out-of-n System”

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RAMS 2017 – Visit ASQ Reliability Division

As currently RAMS is ongoing in Orlando.
Please visit the ASQ Reliability Division booth, and talk to the Reliability experts and see what the Reliability Division has to offer.

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2015-2016 Quality Engineering Best Reliability Paper Award

On behalf of the ASQ Reliability Division (ASQ RD) and the QE Best Reliability Paper Award committee, we congratulate Michael Scott Hamada being selected as the winner for the 2015-2016 QE Best Reliability Paper Award.

For the paper “Bayesian Analysis of Step-Stress Accelerated Life Tests and Its Use in Planning,” this award includes a plaque, presented at the annual ASQ RD dinner banquet in Orlando, FL on Tuesday, January 24, 2017.

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Rabia Muammar spoke at the 2016 Industrial Engineering Forum at Hashemite University

In September Mr. Rabia Muammar spoke about ASQ Division on the 2016 Industrial Engineering Forum at Hashemite University.

It was a useful conference, and I he received an excellent feedback from the participants.

Included the presentation.

 

Audience

Mr. Rabia Muammar

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Interested in volunteer opportunities in reliability engineering?

Interested in volunteer opportunities in reliability engineering?

Our ASQ division is very active in engineering education, conferences and publications both in the US and abroad.

If you are interested in learning more about our group and how to get involved, I invite you to join our yearly planning meeting via WebEx.

Our meeting will be held on 1 October and you can volunteer from any geographic region.

Please email me (marc@asqrd.org) if you are interested!

Please also have a look on our website to learn more.

www.asqrd.org

asqrd-at-rams

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Keynote Speakers on ASTR 2016

This year on ASTR:  Dr. William Meeker Dr. Andre Kleyner and Dr. Elisabetta Jerome are the key speakers.

They are know for many thinks, but certainly as co-authors of “Statistical Methods for Reliability Data”, “Statistical Intervals” and “Practical Reliability Engineering”

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Afbeeldingsresultaat voor Statistical Intervals with Gerald Hahn

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ARS North America 2016 Award Winners

TUCSON, AZ (July 20, 2016) – ReliaSoft announced the winners of the Excellent Presentation Awards of the International Applied Reliability Symposium (ARS) North America 2016. The peer-selected winners were revealed at a hosted awards dinner that closed out the 3-day event in San Diego, California, which ran June 21 – 23. Winners were recognized with certificates and cash prizes.

Congratulations to the Excellent Presentation Award Winners at ARS North America 2016:

  • Gold – Vishal Mhaske of Tesla Motors
    Tailoring the DFMEA Process to Fit a Fast Paced Company Culture
  • Silver – Rachel Stanford of Schlumberger
    Reliability Centered Maintenance: Applying an Aviation Philosophy to Oil & Gas
  • Bronze – Ray Gibson of Philips – Respironics Sleep Therapy Product Group
    Combining Reliability Tools in the Pursuit of Root Cause from Field Data

More than 160 reliability and maintainability professionals from over 100 cities attended this year’s event. Both new and experienced presenters contributed to the diverse range of topics discussed, from FMEA and safety & risk analysis to maintenance strategy and design for reliability.

ReliaSoft VP of Business Development Adamantios Mettas said, “On behalf of ReliaSoft, I want to thank all the presenters who led the conversations at ARS by sharing their experiences, challenges and solutions to the reliability and maintainability engineering community. We invite past presenters to continue enriching the community, as well as new presenters to bring their unique voice to the forum. We look forward to next year’s event.”

For more details about the about ARS North America 2016 event, visit http://www.arsymposium.org/2016/index.htm

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About ReliaSoft Corporation

ReliaSoft Corporation is the industry leader in reliability engineering software, training and services that combine the latest theoretical advances with essential tools for the practitioner in the field. Founded in 1992, ReliaSoft has evolved into a total reliability solutions company, offering software and expertise focused primarily on the reliability engineering and quality needs of product manufacturers and maintenance organizations. For more information, visit www.reliasoft.com.

For More Information

To view event details on ARS North America 2016, visit http://www.arsymposium.org/2016/index.htm. To purchase digital copies of the ARS proceedings, visit the ReliaSoft Online Store at https://store.reliasoft.com/store/home.php?cat=29. To view pictures from the event, visit http://www.arsymposium.org/2016/pictures/.

For questions, please contact Nikki Helms, Marketing Specialist at nikki.helms@hbmprenscia.com.

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ASTR Conference 2016, 28-30 September,

“Finding the Balance between Testing, Modeling and Analysis to ensure Product Reliability and Safety”

Panelists:

  • Dr. William Meeker – Distinguished Professor, Iowa State University
  • Dr. Andre Kleyner – Global Reliability Engineering Leader, Delphi
  • Dr. Elisabetta Jerome – Technical Advisor, Armament & Weapons Test and Evaluation, United States Air Force (USAF)

Exceeding customer expectations and designing highly reliable products and systems is a complex task that should balance modeling and testing. Failure modes must be identified, modeled and mitigated in order to reduce risk while growing reliability.

  • However, what type of testing should be conducted?
  • When should modeling be used instead or in conjunction with testing?
  • How much testing should be performed?
  • What type of evidence should vendors provide in order to ensure reliability requirements?

These are tough questions engineers, analysts and managers face during the design and manufacturing process.

The ASTR 2016 panelists will discuss these important questions.

http://www.ieee-astr.org/

Have a question for the panel? Submit it today to marc@asqrd.org!

Keynote Speaker

Dr. William Meeker Dr. William Meeker | Professor of Liberal Arts and Sciences, Iowa University
Dr. William Meeker is Professor of Statistics and Distinguished Professor of Liberal Arts and Sciences at Iowa State University. He is a Fellow of the American Statistical Association (ASA) the American Society for Quality (ASQ), and the American Association for the Advancement of Science, and a past Editor of Technometrics. He is co-author of the books Statistical Methods for Reliability Data with Luis Escobar (1998), and Statistical Intervals with Gerald Hahn (1991), 14 book chapters, and of numerous publications in the engineering and statistical literature. He has won the ASQ Youden prize five times and the ASQ Wilcoxon Prize three times. He was recognized by the ASA with their Best Practical Application Award in 2001 and by the ASQ Statistics Division’s with their W.G. Hunter Award in 2003. In 2007 he was awarded the ASQ Shewhart medal. He won the 2012 Jerome Sacks Award for Cross-Disciplinary Research and the 2014 ASQ Brumbaugh Award. He has done research and consulted extensively on problems in reliability data analysis, warranty analysis, accelerated testing, nondestructive evaluation, and statistical computing.

Featured Speakers

Dr. Elisabetta Jerome Dr. Elisabetta Jerome | Technical Advisor, Armament and Weapons Test and Evaluation, Eglin Air Force, Florida
Dr. Elisabetta L. “Betta” Jerome, a member of the Senior Executive Service, is Technical Advisor, Armament and Weapons Test and Evaluation, Eglin Air Force, Florida. She is the senior technical advisor to the Air Force Test Center Commander and serves as the senior Air Force technical advisor and national/international authority in armament and weapons test and evaluation. Dr Jerome also has responsibility for providing technical advice and guidance to the highest levels of the Air Force, the DoD, as well as nationally-important conventional weapon system development efforts with regard to test infrastructure, test capabilities and best practices, modeling and simulation, and interpretation of test results. Dr. Jerome holds a Doctor of Philosophy in Aerospace Engineering from the University of Florida, Master of Science degree in Mechanical Engineering and Bachelor of Science degree in Mechanical Engineering from Ohio State University.
Dr. Elisabetta Jerome Dr. Andre Kleyner | Global Reliability Engineering Leader, Delphi Electronics & Safety
Andre Kleyner has 30 years of engineering, research, consulting, and managerial experience specializing in reliability of electronic and mechanical systems designed to operate in severe environments. He received the doctorate in Mechanical Engineering from University of Maryland, and Master of Business Administration from Ball State University. Dr. Kleyner is a Global Reliability Engineering Leader with Delphi Electronics & Safety and an adjunct professor at Purdue University. He is a Fellow of the American Society for Quality (ASQ), a Certified Reliability Engineer, Certified Quality Engineer, and a Six Sigma Black Belt. He also holds several US and foreign patents and authored multiple professional publications including three books on the topics of reliability, statistics, warranty management, and lifecycle cost analysis. Andre Kleyner is also the editor of the Wiley Series in Quality and Reliability Engineering (John Wiley & Sons). For more information please visit www.andre-kleyner.com.

 

 

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