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| In this
issue: |
Issue
16, June 2002 |
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| Hot Topics |
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Verifying the
Assumption of a Constant Shape Parameter in Accelerated Life Testing Data
It is a generally
accepted practice to assume a constant shape parameter across the
different stress levels (independent of stress) when analyzing data from
an accelerated life test. For the Weibull distribution, the shape parameter
is Beta and for the lognormal
distribution, the shape parameter is the log-std. This implies that the unit/component will fail in the same manner across
different stress levels. But how can you validate this assumption? Does
the unit/component actually behave in this manner? There are multiple ways
that you could test the validity of this assumption, such as a likelihood
ratio test or a maximum ratio test. However, this article will employ a
graphical method utilizing ReliaSoft's ALTA
6 and Weibull++ 6
software.
To
read more, see http://www.weibull.com/hotwire/issue16/hottopics16.htm
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| Reliability
Basics |
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| The
purpose of this section is to offer background and advice to the novice
reliability engineer.
Comparison of MLE and Rank Regression Analysis When the Data Set Contains
Suspensions
In previous issues of the HotWire, we have discussed the maximum
likelihood estimation (MLE) and rank regression methods for parameter
estimation. We have also mentioned
that when your data set contains a large number of suspensions, it is suggested
that you use MLE for parameter estimation. But why? In this month's
Reliability Basics, we will take a closer look at this "rule of
thumb" and illustrate how rank
regression does not take into account the characteristics of the entered
data when there are a large number of suspensions.
To read more, see http://www.weibull.com/hotwire/issue16/relbasics16.htm
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| Tool
Tips |
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The
Tool Tips section addresses helpful hints and frequently asked questions
about ReliaSoft software products.
To read more, see http://www.weibull.com/hotwire/issue16/tooltips16.htm
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Latest
Software Updates |
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This section will present the latest software update information
for ReliaSoft software products. To determine the compile revision of the
application on your computer, from the Help menu, click About.
In the About window, click the Details button.
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| Hot
News |
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Reliability
Training Seminars - Upcoming ReliaSoft public reliability
training seminars include:
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QALT
Boot Camp intensive three day course on advanced
topics, concepts and applications of quantitative accelerated
life testing (QALT), such as time-varying stress, multiple
stress testing and ReliaSoft's ALTA PRO software: June
26-28, 2002 in Tucson, Arizona. For more information, see http://www.ReliaSoft.com/seminars/qalt.htm. |
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Master
the Subject, Master the Tools training seminar for
life data analysis, accelerated life data analysis and system
reliability: August 19 - 23, 2002 in San Diego,
California.
For more information, see http://www.ReliaSoft.com/seminars/master.htm. |
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New
Resources on weibull.com
- Recent additions to the weibull.com reliability resource Web site include
iTools and Rank Tables for
Probability Plotting. The new iTools section provides a collection
of quick Web-based reliability analysis tools, including a simple
Weibull analysis, a rank calculator and more. The weibull.com site's popular
probability plotting papers reference has been expanded to include
rank tables for probability plotting. Whenever you have reliability
related questions, be sure to turn to http://www.weibull.com for the
answers!
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ReliaSoft
at AQC - ReliaSoft
would like to thank those of you who stopped by the ReliaSoft booth in
the vendors area during the recent Annual Quality Congress in Denver,
Colorado. We hope that we helped to make this a productive and
interesting conference for you.
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Reliability
Training at GM Knowledge Center - We
are pleased to announce that once again ReliaSoft will be providing
training classes for GM employees at the General Motors Knowledge
Center in Warren, Michigan. The courses offered will cover three
diverse disciplines of reliability engineering and include life data
analysis, accelerated life testing analysis and system reliability,
maintainability and availability analysis. For more information,
visit the GMU Knowledge Center Web site at http://www.gmulearning.com
or contact ReliaSoft at +1.520.886.0410. Class size is limited. GM
suppliers should check with GM for class availability. The remaining
2002 class schedule is as follows:
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August 5 - 7, 2002 - Life Data Analysis
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August 8, 2002 - Accelerated Life Testing
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October 14 - 16, 2002 - Life Data Analysis
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October 17, 2002 - System Reliability
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| From
The Edge |
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In addition to the
monthly Reliability HotWire, ReliaSoft publishes Reliability
Edge, a printed journal that includes articles and information
related to the field of reliability engineering. Articles of interest in
the current edition:
- Predicting
Warranty Returns Based on Customer Usage Data
-
In recent years,
there has been a lot of research in understanding how the customer
is using the product.
Despite the significant investment into these efforts, much of this
customer usage information is being underutilized, or is not being
used at all, because the proper analysis method is unknown. This
article presents a methodology for utilizing customer usage data in
order to perform reliability predictions. The approach presented
here is based on a combination of quantitative accelerated life
testing (QALT) data analysis methodologies and stress-strength
interference analysis, a method used in probabilistic design. See
http://www.ReliaSoft.com/newsletter/1q2002/usage.htm.
- Implementing
an Automated Reliability/Quality System: What You Can Expect
- The
benefits of automated analysis and reporting systems for reliability
and quality data are abundant and well-understood within the product
manufacturing community. The rewards to companies that invest in
automated reliability analysis systems range from improved product
design to increased customer satisfaction. When deciding to make
the commitment to implementing such a system, the company must also
carefully consider the investment of time and money as well as the
risks of undertaking a project of this nature.
This article is intended to provide some insight into what can be
expected when an organization undertakes the implementation of an
automated analysis system for reliability and quality data.
See http://www.ReliaSoft.com/newsletter/1q2002/systems.htm.
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Contribute
to HotWire
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Contributions
Welcomed
As always, your
feedback and contributions are appreciated. ReliaSoft is able to provide the most
user-friendly reliability software packages and support because we
listen to our customers. This applies to our newsletters and
publications as well. We welcome any suggestions or contributions you may
have for Reliability HotWire.
If you have a topic or
article that you think would be useful to the readers of Reliability
HotWire, feel free to contact us. We can be reached by
e-mail at HotWire@ReliaSoft.com,
or by standard mail at 1450 S. Eastside Loop, Tucson, AZ 85710-6703, USA.
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Copyright © 2002 ReliaSoft
Corporation, ALL RIGHTS RESERVED
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