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SOFTWARE DESCRIPTIONS:
WinSMITH (TM) Weibull, WinSMITH (TM) Visual, SuperSMITH (TM), YBath (TM)
PUBLICATION DESCRIPTIONS:
The New Weibull Handbook(c), PlayTIME(TM) with SuperSMITH(TM), New Weibull Methods + Video
Accelerated
testing generally consists of increasing some or all of the stresses that
control the length of product life. This is done to produce the same or similar
results as the lower stresses that normally occur, but with shorter overall
test times and lower cost. It often is very difficult to increase the stresses
without also changing the physics of failure. Even after a successful
accelerated test (no significant failure mechanism change) the life data from
higher loading still must be correlated to life at normal load. Dr. Wayne Nelson, a
leading authority on accelerated testing, refers to many such techniques in his
Accelerated Testing book. One source for accelerated testing analysis
is WinSMITH TM Weibull software. Weibull life curves for the product,
at different stress levels, can be easily estimated based upon test results.
Then the shorter characteristic lifetime, found at higher stress in the
laboratory, is lengthened to actual service lifetime using this model. No more
fudge factors!
SuperSMITH (TM)
is the leading Weibull analysis software. Ours is the accepted metric analysis
standard for the automotive industry, the medical industry, the power
generation industry, the hydrocarbon processing industry, the railroad
industry, the aerospace industry, the computer industry, the communications
industry and many other industries and organizations including the U.S.
military and the Federal Aviation Administration. Classic case studies out of
standard textbooks provide ideal benchmarks for our software calibration. Our
thousands of customers demand this high standard. Such case studies might
typically include analysis of aircraft components after in-flight shutdowns,
comparison of new and old medical remedies, and performance of electrical
insulation in power transmission. SuperSMITH
(TM) Weibull software includes several
benchmarks ready to use for comparison and validation. The supplied data values
are easily copied for use in other software. Full instructions are given for
interpretation. Find out if you are using the best software. Can the software
you use measure up? Try the benchmark data and see.
The latest
edition of The New Weibull Handbook by Dr. Robert Abernethy contains standard
procedures for performing Weibull analyses. Best-practice methods are specified
for different data analysis situations. Does your reliability effort produce
the most cost-efficient results and the most accurate results? Maybe you should
be using standard procedures to minimize the work required for the maximum
output. Join the thousands of companies that have chosen The New Weibull Handbook as the standard metric analysis method for their reliability
programs.
Does your
software give you the most for your time and effort? Is it performing at the
highest industry expectations? A conscientious analyst can be selective with
all of the analytical methods available for the computer. There are many
complex equations thrown into software (copied directly from a textbook) that
are practically unusable, or worse … misleading. This technical clutter can be
confusing or maybe even misleading. We recommend picking out a few good tools
to keep handy that have proven worthwhile. The
New Weibull Handbook written by Dr. Bob Abernethy
is the world standard reference for Weibull analysis and provides the select
few best-practice methods. This handbook cuts through the clutter with a
handful of solid techniques. SuperSMITH (TM) is the only software that is 100% capable of
these best-practice techniques. It is the only Weibull software widely
recognized as the world standard.
Yes/no, on/off,
good/bad, pass/fail all can be binomial situations. The simple classic formula
for the binomial distribution was discovered in 1663 by John Newton (Is he any
relation to Sir Isaac?). If you know the proportion of the time that each of
the two outcomes are expected and you know how many samplings are to be
made, you are home free. This most basic of all distributions is used
extensively in quality control applications and in gambling. Another basic
distribution is the Poisson distribution for rare events in a continuum. The
Poisson is often used as an approximation for binomial when the values are
within appropriate limits. Read more about these related methods in The New Weibull Handbook by Dr. Bob Abernethy.
B-value is the
shorthand for percentile in the world of Weibull. The bearing industry
uses it as a barometer for rated length of service. For example, B-10 life
represents the length of service time allowable with approximately 10 percent
expected to fail. B-5 life for the same part would be some reduced service time
with only 5 percent expected to fail. These values are provided in WinSMITH TM
Weibull, by entering the data and looking at the graph. It's easy to get
precise readings with the predict button in the software.
NOTE: See the contents page for
schedules and locations of public sessions.
Dr. Robert Abernethy (Dr. Bob) developed the Weibull/LogNormal
Analysis course over ten years ago, teaching the applications and
techniques of Weibull analysis. Dr. Bob has taught this course hundreds of
times for engineering/trade society conventions and on-site for business and
government with continuous improvements for new research. Wes Fulton is the
instructor approximately half of the time now. On rare occasions both
instructors participate in the same seminar. It can be the best introduction to
Weibull for the novice as well as a solid refresher course for the experienced.
It comes in 2-day, 3-day and 4-day formats. Sample topics are:
Day 1: Overview, 23-minute Video, First Weibull, Good
Weibulls, Bad Weibulls, Predicting Failures with/without Renewals, Case
Studies, Customer Usage, Maintenance Planning, Goodness of Fit with Critical
Correlation Coefficients, Weibull Experiments, Classwork Problems and
Solutions.
Day 2: WeiBayes, Improving Accuracy, Smaller Samples,
Substantiation Tests, Problem Resolution, Zero-failure Testing,
Zero-one-failure Testing, Sudden Death Testing, Warranty Analysis, Maximum
Likelihood, Rank Regression vs. Maximum Likelihood, Extremely Small Samples,
Inspection Data, Suspensions/Sample-size Effects on Uncertainty, Experiment
Analysis, Least-cost Replacement, Hands-on Computer Use, Analysis of
Student-supplied Data.
Day 3: Confidence Intervals, Design Comparison, Monte
Carlo Solutions, Binomial, Poisson, Exponential, Duane-AMSAA Reliability
Growth, Kaplan-Meier Survivability, System Analysis, More Hands-on Computer
Use.
Day 4: History of Monte Carlo, Examples, Random
Numbers, System Simulation with Renewal, Case Studies, Hands-on Computer
Simulation, Reliability and Maintainability with Raptor and Monten, Free Copies
of Simulation Software.
Note: A
separate two day refresher course includes review of risk analysis
through to the latest Weibull technology recently implemented in software.
Lecturers:
Either Dr. Bob Abernethy or Wes Fulton will lead the seminar. On occasion, both
will participate.
Please contact Dr.
Bob or Wes Fulton as indicated in the E-mail Addresses, Sites and Telephone #'s section.
Confidence - Useful confidence methods include:
- Johnson's Beta-Binomial
- Nelson's Fisher Matrix
- Lawless's Likelihood Ratio
- Greenwood's Variance for Kaplan-Meier
- Binomial for Probit
- Abernethy/Fulton Likelihood Ratio Contours
- Monte Carlo Simulation
Before putting
your faith in published analysis results, be sure to find out how confidence is
calculated. According to The New Weibull
Handbook by Dr. Bob Abernethy
the best practice for small samples (around 10 or less) is MONTE CARLO SIMULATION
based upon a pivotal statistic (pv method) as it is automated in WinSMITH TM
Weibull. The best practice for larger samples using the maximum likelihood fit
method especially with a quantity of suspensions is LIKELIHOOD RATIO
confidence. Likelihood ratio was first made available for PC's in WinSMITH TM
Weibull. Best practice for larger samples using the least squares fit method
and few suspensions is Fisher matrix. Fisher matrix was first made available
for PC's in WinSMITH. Binomial bounds
are best for probit analysis. Greenwood's bounds are best for Kaplan-Meier
(also available first in WinSMITH). Many of these techniques are not available
elsewhere as of this writing.
Dr. Bob Abernethy and Wes Fulton are
available as schedule allows for consulting on life data, reliability and
maintenance concerns. Dr. Abernethy, the principle author of the original U.S.
Air Force Weibull Handbook, has over 40 years of experience as one of the
leading Weibull experts in the world. Wes Fulton, who released the first useful
PC Weibull plotting software over 10 years ago, is a pioneer in the development
of user-friendly technical software and he is the CEO of Fulton Findings TM.
Both are degreed engineers with many years of experience in actual application
of these techniques, and both now teach Dr. Abernethy's three-day course on
Weibull. They can be reached at the numbers given in E-mail Addresses, Sites and Telephone #'s. NOTE: Dr. Bob prefers that Wes consult for
northern clients in winter, except whenever the client is in Sweden. See a
pattern?
Are you talking
only the language of engineers and statisticians? Or can you speak the
universal language of business, so the people holding the checkbook understand?
When it comes time to renew the annual budget or buy capital equipment for
manufacture, then it helps to speak as clearly as possible. You can benefit by
thinking and communicating in terms of money. If you do, you will be noticed
and your priorities might go directly to the top of the agenda. How? Ask
Paul Barringer of
Barringer and Associates. From what we have seen, he communicates pretty well
for an engineer. One of the techniques promoted by Dr. Bob Abernethy
and Mr. Barringer is determination of the lowest-cost planned replacement
interval. The optimum replacement interval, or best allowed time of service
before equipment is retired and new equipment is substituted, is the one with
the smallest cost per unit time. Another way to reduce cost is by using sudden
death WeiBayes
testing as described in The New Weibull
Handbook. These techniques are automated
in WinSMITH TM Weibull software and provide an excellent icebreaker
for an executive boardroom discussion. But whatever you do in a boardroom, do
not confess any technical ability. We do not want anybody getting hurt.
Critical Correlation
Coefficient (CCC) and Distribution Analysis
Dr. Bob Abernethy has developed critical values of the correlation
coefficient for the Weibull distribution based upon simulations performed by Carl Tarum using MonteCarloSMITH TM software from Fulton FindingsTM. Goodness
of fit tests have been greatly simplified and have become easier to understand.
Use of the CCC is best practice for determining the most appropriate
distribution for a set of data from statistics. Certainly CCC must also be used
in conjunction with results from investigation into root cause of failure to
complete the analysis. These values are automatically included in WinSMITH TM
Weibull distribution analysis and in the reporting.
Comparing
designs is easy with WinSMITH TM Weibull. It automates the use of
likelihood ratio and provides the amount of difference between different sets
of data. Comparison is not limited to two sets. This technique is useful for
comparing new design to old design, supplier A against supplier B, and
application C vs. application D vs. application E, etc. You can also use
techniques such as likelihood contour comparison and graphical comparison as
requirements dictate. Let The New Weibull
Handbook be your guide to selecting the
appropriate design comparison method.
Dr. Robert Abernethy is known worldwide for his Weibull workshops
presented in Australia, China, Japan, Sweden, Israel, Great Britain, Canada and
the USA. Retired from Pratt & Whitney Aircraft, he has numerous awards from
SAE, ASME, AIAA, and ISA for his development of advanced Weibull technology
during the last thirty years including the Weibayes method, failure forecasting
and the Weibull substantiation test designs. He is a fellow of ASQ, SAE and the
Royal Statistical Society, and an associate fellow of AIAA. He received the
ASME 1988 Gold Medal the SAE 2001 McFarland award for contributions to Weibull
education. He founded and chaired SAE's G11 Committee on Reliability and
Maintainability. The patent on the J58 engine that powers the world's fastest
airplane, the SR-71 Blackbird, is in his name, as well as the patent on the
afterburner control on the F100 engine in the F15 and F16 fighters. He was a
Navy Scholar as well as a Fulbright Scholar to Great Britain. He is the
principal author of the original USAF Weibull Analysis Handbook and the
sole author of The New Weibull Handbook. He has presented his course, the
Weibull/Lognormal Analysis Workshop, all over the world and continues to teach
and provide consultation on Weibull related methods.
Wes Fulton is founder/CEO of Fulton Findings(TM) and the
creator of all of the Fulton Findings 'SMITH software
including WeibullSMITH, Visual*SMITH, MonteCarloSMITH, BiWeibullSMITH, WinSMITH
Weibull, WinSMITH Visual and the SuperSMITH package. He has 16 years of
experience as program engineer for Garrett AiResearch (product line ownership
changed several times … first to AlliedSignal and later to Moog). He supervised
development and production engineering of aircraft flight control projects,
especially maneuvering fly-by-wire actuation systems. He supervised the
successful Indigenous Defensive Fighter (IDF) wing leading edge flap actuation
system from development through completion of production and also developed the
IDF turbine engine flow-compensated fuel bypass. He was program engineer for
the F-16 leading edge flap production program and the X-31A leading edge flap
program. He co-patented the multi-fuseable shaft (a high-performance drive
train device) and is a member of ASME, IEEE, and SAE. He originated the Fulton
Factor used in set comparison, invented the concept of equivalent probability
and confidence known as assurance, and developed probabilistic S/N curve
analysis. He teaches seminars in Weibull analysis for organizations such as SAE
and ASME.
E. J. Gumbel in the
1920's was the first to seriously investigate extreme values, such as the
100-year flood level. He found that there were only six separate extreme value
distributions (proven by Gnedenko) and went on to complete a book, Statistics of Extremes, published in 1958. It is now the standard reference. The
Type-III-smallest extreme value distribution is the Weibull distribution.
Waloddi Weibull independently invented and used this distribution, and later
acknowledged E. J. Gumbel's contributions to extreme value research by using
his plotting paper.
Waloddi Weibull was a Swedish engineer and mathematician. He invented the
distribution that now carries his name in 1937 and delivered his first American
paper on the subject in 1951. He also wrote a treatise on fatigue testing, Fatigue Testing and Analysis of Results, which centered on the uses of this distribution.
History has shown that his techniques are extremely useful. They have become
the leading methods in the world for analyzing lifetime data. Click here to see a very
detailed biography of Waloddi Weibull.
* Abernethy,
Robert B., The New Weibull Handbook (NWH), self-published, 1997. This is
the world standard reference for Weibull analysis techniques. The NWH replaces
the original Air Force Weibull Handbook also written by Dr. Bob Abernethy, one
of the leading authorities on Weibull analysis. It contains step by step
instructions for performing a Weibull analysis and related techniques such as
forecasting failure quantity expected, WeiBayes comparison, substantiation test
planning, least cost replacement interval, and related techniques, with several
case studies for each method included. You can order this from Dr. Bob
Abernethy or Wes Fulton or Paul Barringer as indicated in E-mail Addresses, Sites and Telephone #'s. Price and availability is given on the Main Page.
* Abernethy,
Robert B., New Weibull Methods + Video, self-published, 2003. Seven case
studies in a Powerpoint presentation, explained in detail with an included Word
document, plus a 22 minute video showing 3 more case studies. You can order
this from Dr. Bob Abernethy or Wes Fulton or Paul Barringer as indicated in E-mail Addresses, Sites and Telephone #'s. Price and availability is given on the Main Page.
* Fulton, Wes, PlayTIME(TM)
with SuperSMITH(TM), self-published, 2003. This is the computer tutorial
for the Fulton Findings(TM) software. You can order this from Dr. Bob Abernethy
or Wes Fulton or Paul Barringer as indicated in E-mail
Addresses, Sites and Telephone #'s.
Price and availability is given on the Main Page.
* Gumbel, E.
J., Statistics of Extremes, Columbia University Press, New York, 1958.
* Liu,
Chi-Chao, A Comparison Between the Weibull and Lognormal Models Used to
Analyse Reliability Data, University of Nottingham Doctoral Thesis, 1997.
* Nelson,
Wayne, Accelerated Testing, John Wiley & Sons, New York, 1990. The
world standard reference on accelerated testing. This is an excellent
sourcebook for life data analysis. There are many new techniques in this volume
to complement his other standard references on life data analysis. Contact Dr.
Wayne Nelson as indicated in E-mail Addresses,
Sites and Telephone #'s if you are
interested.
* Weibull,
Waloddi, Fatigue Testing and Analysis of Results, Pergammon, New York,
1961.
Languages
and International Use
Version 2.0 and
above of all Fulton FindingsTM Windows software includes simple
language translation capability. Please contact Wes Fulton as indicated in E-mail
Addresses, Sites and Telephone #'s, if
you want to have the program translated into another language. New language
files will be added to the distributed software, as they become available. A
character or a brief character combination can be selected to specify currency.
Also, Version 2.0 and above recognizes the selection of decimal symbol (either
period or comma) made in the Control Panel setup in Windows. These new features
were added by request from our customers overseas. Version 4.0D and above of
the software allows for input of a new additional language file that has the
name SMITHLNG.LNG. If languages are not already provided, then a translated
version of the English text file can be renamed to SMITHLNG.LNG and then input
as an Additional Language as described below. Italian is new for version 4.0D
and must be downloaded (however after download it should appear as the Italiano
selection in the menu).
GET A LANGUAGE
FILE HERE. THE FOLLOWING FILES ARE TEXT FILES AND CAN BE EASILY COPIED AND
SAVED TO A TEXT (WITH LINE BREAKS) FILE IN THE SAME SUBDIRECTORY WITH THE
PROGRAM FILES.
French - Francais
German - Deutsch
Swedish - Svenska
Spanish - Espanol
Dutch - Nederlands
Portuguese (Brazilian) - Portugues
Italian - Italiano
After you
download or copy the language text file, make sure it is in the same
subdirectory with the other program files such as SMITH.INI, SMITHWSW.HLP, etc.
Then run the software program and select the Setup icon (showing a computer)
from the main screen. Select the Language / Currency / Decimal / Time / Date
icon (showing two people talking) and then select L…Language from that menu to
get the language menu. You should see the language file just downloaded listed
in the menu, unless it is a new additional language file. For additional
language files, the file name must be copied to a file named SMITHLNG.LNG first
and then selected from the language menu as Z...Additional Language.
The likelihood
ratio method for confidence was made accessible by Fulton Findings TM
in 1990 and is still not available elsewhere for easy use on a PC as of
this writing. Since that time, the likelihood ratio technique has been expanded
in Fulton Findings software to compare designs for significant difference based
upon exclusive research conducted by Wes Fulton and Dr. Bob Abernethy. WinSMITH TM
Weibull appears to be the only easily accessible and widely used personal
computer software using it for confidence. Many other uses of this technique
are projected. With proper compensation for small sample bias, it is the best
practice available for comparison of groups of data.
Several data
formats and associated methods of analysis are available. They include rank
regression, maximum likelihood, probit, Kaplan-Meier, etc. Each technique has
benefits for certain data formats. For example, inspections produce data
different than tests where precise failure times are known. This is similar to
coarse readout data from imprecise instrumentation. Grouped data can be handled
effectively with either probit or Kaplan-Meier. Rank regression has benefits
for smaller sample size and maximum likelihood is suggested for data with many
suspended values. There are other issues associated with plotting methods and
interval data. The New Weibull Handbook is the best source of information regarding these
different methods and their application. WinSMITH TM
Weibull provides all of these techniques that are best practice based upon the
particular data format.
Sometimes the
data collection is less than perfect. Different failure mechanisms can be mixed
together. The mixed distribution model is covered in The New Weibull Handbook TM (NWH). One technique is to analyze for competing risk.
WinSMITH ™ Weibull (WSW) searches for a competing risk solution from two
possible mechanisms (two Weibulls or two Normals or two Lognormals, etc.) by
evaluating ordered combinations. P-value technology is found to indicate the
power of the mixed distribution model. If the power is very low, WSW indicates
a small probability of mixture. Otherwise the p-value is given along with the
four parameter solution. This level of competing risk mixture analysis is not
available elsewhere. YBath TM software originally programmed by Carl Tarum and now
owned by Fulton Findings™ provides additional analysis of more complex
situations including partial populations and competing risk.
Beware of
amateur software from other sources with unsubstantiated mixture analysis
methods. Bad software provides solutions even without reasonable supporting
evidence. You must always take care with mixture analysis, since false
indication of mixture for non-mixed data is common. This can be easily tested.
Feed the suspect software several random samples from a single distribution and
determine the frequency you obtain mixture solutions. If a high proportion of
mixture solutions (high p-values if given) are provided for the single
distribution samples, then the software is not very good. The best procedure is
to perform careful analysis of mechanism root cause to avoid mixing altogether.
Refer to NWH for more details.
Monte Carlo
Simulation and Confidence
Monte Carlo
(mc) is a special technique for simulation made possible with fast computers.
It is used as a prediction tool and can provide a reference for analytical
techniques. The pivotal (pv) confidence method is based upon generating and
processing large quantities of random variates. WinSMITH
TM Weibull software uses the
power of Monte Carlo to generate correlation P-Value and confidence limits for
B-lives and parameters such as Beta and Eta. Distribution of the correlation
coefficient and t0 (third parameter in Weibull) for research purposes can be
investigated with MonteCarloSMITH TM. WinSMITH Weibull pv confidence
should be used for small samples (around 10 or less) instead of analytical
techniques. The 4th day in Dr. Abernethy's 4-day Weibull/LogNormal Analysis Seminar is devoted to mc simulation. For more
information, please contact Dr. Bob Abernethy or Wes Fulton as indicated in
E-mail Addresses, Sites and Telephone #'s.
Probabilistic
analysis is just what the doctor ordered for new designs. The previous method
of using safety margins and safety factors is not good enough any more.
Reducing the chance of failure is the real challenge. That means you need to
measure the probability of the applied stress being larger than the strength
for each load application. If you can estimate the distribution of stress and
the distribution of load, then WinSMITH TM Weibull can estimate the
probability of failure within your needed accuracy. This very flexible and
powerful technique can also be applied to life distribution vs. usage
distribution with similar results.
For software
questions contact Wes Fulton at Fulton Findings and for Weibull analysis
questions contact Dr. Bob Abernethy as indicated in E-mail Addresses, Sites and Telephone #'s section. All software and handbooks are
guaranteed for customer satisfaction. Most questions are resolved with one
call. Any suggestions for software or handbook enhancement are welcome.
Probability of
success is the definition of reliability. A reliable product intelligently
maintained will provide adequate service life and garner high marks for
customer satisfaction. An unreliable product without proper maintenance is a
disaster. Scheduled maintenance can be costly and should only be considered for
wearout failure mechanisms when older parts are more likely to fail
(increasing instantaneous failure rate). Weibull analysis can indicate whether
older parts or newer parts are more likely to fail. For electronics, generally
newer parts are more likely to fail at least during normal usage (decreasing
instantaneous failure rate). This type of failure mechanism common in
electronics is called infant mortality due to the higher probability of
failure at the start of service life. Constant failure rate indicates the exponential
distribution. Maintenance for infant mortality and exponential failure
mechanisms is wasteful. A better approach is to apply some sort of screening
just before actual usage. Certainly, this is why we feel better after the
computer store has burned-in our new computer for a few hours before we take
delivery. WinSMITH TM Weibull software provides useful
estimates of failure mechanism type, the predicted number of failures to
expect, the lowest-cost replacement strategy, spares requirements, and
assessments of corrective action effectiveness. Also, reliability/maintainability/availability software from Paul
Barringer of Barringer & Associates can help to solve complex problems in this area.
Reliability
Growth (Crow/AMSAA based upon J.T. Duane's postulate)
A technique
related to Weibull analysis for evaluating failure occurrence is called
reliability growth modeling. It requires less information than Weibull
requires, but it still can indicate instantaneous failure rate changes. Of 27
different competing reliability growth models, Crow/AMSAA has been found to be
best practice. Dr. Larry Crow took J. T. Duane's postulate for learning curve
modeling and extended the analysis with powerful statistical capabilities. It
is included as a part of WinSMITH TM Visual software. There is no need
for a separate program, since this technique simply consists of plotting a
straight line on a log-log plot. Predicting the quantity of failures to expect
for spares ordering and maintainability planning is very easy. The New Weibull Handbook has a complete section devoted to Crow/AMSAA.
Risk Analysis (Expected Quantity Forecast)
Estimating the expected quantity of occurrences or failures in the coming months is called risk analysis. Chapter 4 in The New Weibull Handbook covers this type of estimating. It is extremely useful for identifying a batch problem or for determining spares purchase policy. It was developed and used effectively by Dr. Abernethy years ago in response to customer information requirements. Risk analysis is automated in WinSMITH TM Weibull software and is not available elsewhere as of this writing for easy use on a PC.
Be careful. We
recommend checking all potential software out with a set of benchmarks from
standard textbooks. Our software meets the benchmarks and often betters them.
We have copied the benchmarks for you and they are easily accessible from our
Windows software. Please contact us if you want to use the benchmarks for
comparison. If possible, try the benchmarks on software you might buy before
actual purchase to see if the software measures up. You may be surprised to
find out how disappointing some software can be. You will not be disappointed
with our software. It is the world standard for performing Weibull analysis.
General
descriptions follow. Click here for the latest software version numbers and
revision information.
SuperSMITH (TM)
is a bundled package of programs from Fulton FindingsTM for
reliability and variability solutions on a personal computer at a discount
price. It is a complete self-study package with WinSMITH
(TM) Weibull and WinSMITH
(TM) Visual from Fulton Findings
(TM), the PlayTIME With SuperSMITH (TM) tutorial and The New Weibull Handbook (NWH) copyrighted 1997 by Dr. Bob
Abernethy. These friendly stand-alone
programs are also available separately to minimize cost. SuperSMITH performs
all of the techniques covered in The New Weibull Handbook. It is the standard
for performing Weibull life data analysis, and is used by thousands of
companies worldwide. Recently published benchmarks indicate SuperSMITH as the
only trustworthy source for best practice solutions to these kind of problems.
You can order this from Dr. Bob Abernethy or Wes Fulton or Paul Barringer as
indicated in E-mail Addresses, Sites and
Telephone #'s. Price and availability is
given on the Main Page.
WinSMITHTM
Weibull (WSW) software for Windows performs all of the Weibull techniques in
Dr. Abernethy's New Weibull Handbook. WSW contains results of independent
research with several methods developed by Dr. Abernethy in cooperation with
Fulton Findings. Many of these techniques are not available elsewhere,
such as likelihood ratio confidence, simplified design (set) comparison,
Kaplan-Meier simulation and solution, critical correlation coefficient,
sudden-death WeiBayes, parameter as a function of engineering variable, etc.
WinSMITH Weibull for Windows uses Weibull, Normal or LogNormal equations. It
replaces the DOS program WeibullSMITHTM , previously the leading
Weibull analysis software. You can order this from Dr. Bob Abernethy or Wes
Fulton or Paul Barringer as indicated in E-mail
Addresses, Sites and Telephone #'s.
Price and availability is given on the Main Page.
WinSMITHTM
Visual (WSV) software for Windows provides general scientific plotting. It
includes Duane/AMSAA modeling for reliability growth analysis and it plots
probability density functions, cumulative distribution functions (regular
scaling), likelihood contours, least-cost replacement intervals, failure
forecasts, and histograms all from WinSMITHTM Weibull files. The
likelihood contour comparison capability is not available elsewhere. The
program also includes function plots, data transforms (global edit), and curve
fitting as well as XY plots, bar charts and pie graphs. You can order this from
Dr. Bob Abernethy or Wes Fulton or Paul Barringer as indicated in E-mail Addresses, Sites and Telephone #'s. Price and availability is given on the Main Page.
WeibullSMITH ™
(WS) for DOS (available only from archives) was the first commercial PC
implementation of Weibull analysis including plotting and failure forecasting.
It was replaced by WinSMITH Weibull (WSW) for Windows. All previous capability
plus a lot more is now in WSW.
VisualSMITH ™
(VS) for DOS (available only from archives) is the precursor to WinSMITH Visual
(WSV). All capability plus a lot more is now in WSV.
MonteCarloSMITHTM
(MC) for DOS (available only from archives) is a research tool available for
general use. Regular Monte Carlo simulation and Monte Carlo confidence is
available in WinSMITH Weibull. What makes MC special is its ability to create,
analyze and store the data from up to 1000 simulations (up to 1000000 for
certain comparisons). This process provides Monte Carlo estimates of confidence
for probability model parameters such as the mean, standard deviation and 95th
percentile of a normal distribution for example. Weibull, Normal and LogNormal
equations are provided. These techniques, absolutely necessary to remove bias
for small samples, are not available elsewhere. The current MC software
is already easy to run in Windows, since graphics are not involved. Please
contact Wes Fulton as indicated in EmailTeleponeE-mail Addresses, Sites and Telephone #'s for more information on Monte Carlo software.
BiWeibullSMITH TM
(BW) for DOS (available only from archives) solves two fit lines for one set of
data without partitioning. This is useful for warranty analysis with both
infant mortality and wearout failure mechanisms. The late Alan Townsend of
Allison Engines pioneered this BiWeibull solution technique. This competing
risk analysis capability is not available elsewhere and has now been
moved to WinSMITH Weibull. Other software available for mixed population
analyis is Ybath TM from Fulton Findings. Contact us as designated in E-mail Addresses, Sites and Telephone #'s section.
YBath TM
for Windows - Contact Wes Fulton as indicated in E-mail
Addresses, Sites and Telephone #'s for
additional information on YBath bathtub curve modeling for multiple and mixed
failure mechanisms. Both rank regression and maximum likelihood techniques are
now available.
Reliability,
Maintainability, Availability - Please contact Paul Barringer indicated in E-mail Addresses, Sites and Telephone #'s for information on
reliability/maintainability/availability modeling tools. These tools are
especially needed for complex facility or system management to minimize costs
and maximize product integrity. MonteCarloSimulationS and
Reliability/Maintainability Modeler are software packages summarized below:
1)
MonteCarloSimulationS TM is a collection of Excel spreadsheets for
use in simulations. Details are available at http://www.barringer1.com/simul.htm.
MonteCarloSimulationS contains a series of simulation models written in Excel
which combines the use of spreadsheets, Weibull statistical failure data, and
random numbers to solve diffiult problems in reliability, availability, and
cost. A sampler of these tools can be downloaded at no cost from http://www.barringer1.com/mc.htm.
2)
Reliability/Availability Modeler TM is a software modeling package
using process flow diagrams of unit operations, subassemblies of plants, or a
complete plant for building a reliability/availability Monte Carlo simulation
model. The simulation model joins equipment with logic, costs, and Monte Carlo
calculations. Outputs from the simulation model give ages-to-failure for
finding the overall reliability, availability, and costs for unreliability for
a plant or process. The simulation model and its pallet of tools are under
development with first applications expected beginning of second quarter '97.
The software package will use Gensym's G2 knowledge-based intelligent modeling
engine running simulations on a PC in a Windows NT environment. Details are
available at http://www.barringer1.com/modeler.htm.
Units that have
not failed by the failure mechanism under investigation are called suspensions,
or censored units. Suspension times represent values that are less than
the actual life with respect to the failure mechanism of interest. In other
words, the actual length of life is greater than the length of service
recorded. Such data can make the study more accurate and should always be
included to complete the analysis. Methods are available for treating suspended
data as detailed in The New Weibull
Handbook.
When is it
better to make something more difficult? Answer: When planning a test, of
course. Test design is based on setting up a tough obstacle course and then
navigating through it. The harder the obstacle course, the better you feel when
you walk (or crawl) across the finish line. Completing a difficult course gives
you more confidence that you could do it again if needed. Using this impeccable
logic and the binomial distribution you can plan your test, but be prepared for
lots of testing! The binomial (pass or fail) distribution requires lots of test
samples. You don't get much life information from pass/fail tests. However,
combining this with the Weibull distribution to model useful life can
drastically lower the amount of testing needed (and reduce the cost). Good
software should include comprehensive test planning. You may have to make it
difficult for your products when planning a test. So make it easy on yourself
and use WinSMITH TM Weibull, the most comprehensive
software for test planning.
PlayTIME (TM) with SuperSMITH is a tutorial for learning how to perform Weibull analysis. It is a complete self-study course when combined with SuperSMITH software and The New Weibull Handbook(c). This combination is called the SuperSMITH package. Case studies are presented in the tutorial representing 40 years of actual problem-solving in the industry. It is written in an easy-to-follow style with actual computer excercises. This tutorial comes as part of the Weibull/Lognormal seminar presented by either Wes Fulton or Dr. Bob Abernethy, or it is available separately.
The third
parameter for Weibull analysis is called t-zero. It is a time shift
causing curvature on the Weibull graph for time scaling as originally recorded.
The t-zero can also be used for other distributions. The value of t-zero is
subtracted from each data value before analyzing. A positive t-zero solution
indicates a failure-free period where the probability of failure is negligible.
A negative t-zero indicates loss of some reliability before service officially
begins. The critical correlation coefficient (CCC) accounts for the bias in correlation associated
with an additional parameter. WinSMITH TM Weibull solves for the optimum
t-zero for a given data set and distribution.
Warranty data
naturally forms a triangular matrix. The data is collected by batches produced
on a regular basis. If production is by months, then reports for the last batch
produced cannot have age greater than one month. Underneath the production
quantity number for the last month there is only one age interval (one month).
The batch produced just before the last one can have ages of either one month
or two months, so there are two age intervals underneath the production
quantity number for that batch. This trend continues with each month further
back into the past having additional age intervals possible. The first row in
the table below represents production quantity by month, in this case 1000 each
month. Underneath the production quantity are report quantity grouped by age in
months after shipment.
WARRANTY DATA FORMAT
|
1000 |
1000 |
1000 |
1000 |
1000 |
1000 |
|
1 |
0 |
0 |
3 |
1 |
4 |
|
4 |
1 |
1 |
3 |
1 |
|
|
2 |
0 |
1 |
1 |
|
|
|
1 |
1 |
2 |
|
|
|
|
1 |
4 |
|
|
|
|
|
0 |
|
|
|
|
|
WinSMITH (TM) can convert warranty data into Weibull
inspect option #1 (with or without renewal), Weibull Kaplan-Meier option #4
(with or without renewal) and Duane/AMSAA reiliability growth (with or without
renewal). The analysis can be truncated before the last month of production or
can be extended past the end of production by selection of less or additional
columns respectively as described in the software. The data above is from The New Weibull Handbook.
WeiBayes is a term coined by Dr.
Bob Abernethy for Weibull analysis when
the slope parameter is selected beforehand, relating to Bayesian assumption.
Dr. Abernethy refers to this technique alternately as the one-parameter
Weibull, since one of the two standard Weibull parameters is already
selected. Other sources now also refer to this technique pioneered by Dr.
Abernethy and independently by Lois Jackson (Gates Rubber Co.) using the same
terminology. This powerful method based upon maximum likelihood provides
answers to difficult questions concerning product improvement and design
comparison. Use is possible without the requirement of testing to failure,
which can be long and costly. The no-failure situation produces a lower
confidence bound for characteristic life. The presence of failures reduces the characteristic
life value to a point estimate. Dr. Wayne Nelson has extended the technique producing confidence
limits even when failures exist. Case studies and technique details can be
found in The New Weibull Handbook, Chapter 5.
Weibull
Analysis for Variability Control (including Normal, Lognormal, Exponential,
Gumbel lower and Gumbel higher)
Graphical
analysis using several probability distributions is now called Weibull
analysis. The most commonly used is the Weibull 2-parameter distribution,
but the Weibull 3-parameter, the normal distribution, the lognormal
distribution, the exponential distribution, the Gumbel lower (or "Extreme
Value") distribution and the Gumbel higher distribution can also be used
effectively. The Normal and Gumbel distributions can predict negative life for
high reliability requirements, an impossibility. Car must be used when modeling
product life with these distributions. Weibull and Lognormal never predict
negative life when used properly. In addition, Weibull has the special
capability to diagnose failure types such as infant mortality (particulary for
electronics), age-independent (accidents and natural occurrences), or wear-out
type mechanisms (bearings, filters, etc.). Dr. Abernethy's course on Weibull and Lognormal Analysis has become the standard introduction to this
method with hands-on use of related software. Engineers, technicians, quality
assurance personnel, management and others responsible for variability control
can begin to apply Weibull techniques in the workplace afterward. Many societies and professional organizations host these seminars during organizational
meetings. Please contact Dr. Bob Abernethy or one of the organizations, if you are
interested in attending.
Get closer to
reality by investigating the source of your data. There is no substitute for
some old fashioned detective work to find the root cause of reported
difficulties or measured phenomena. Data analysis methods cannot improve bad
data. When there is an indication of mixed root-cause mechanisms, the first
thing you should do is to group the data according to mechanism. Weibull
analysis is best when analyzing each mechanism separately. You can also zoom
into your statistical analysis by using the Zoom button (showing magnifying
glass) in WinSMITH (TM) Weibull. There are many features for graphical data
editing, hiding or highlighting, changing X-axis and Y-axis ranges and so on in
the Zoom portion of the software.