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Issue 17, July 2002

 Hot Topics Reliability Basics Tool Tips Latest Software Updates Hot News From the Edge Contribute to HotWire

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Hot Topics
Let the Data Speak About Activation Energy

There are many factors to consider when conducting an analysis of accelerated test data. One factor that is often overlooked or misrepresented is the activation energy. When considering accelerated life tests, the activation energy represents the magnitude of effect that the applied stress will have on the product under test. A large activation energy indicates that the applied stress will have a large effect on the life of the product. Understanding activation energy is one thing, but obtaining an accurate value is another. Currently, the published values of activation energy relate to a particular material, technology, or failure mode, but how this value relates to a product, which may be composed of many different materials, is unknown.

One possible method to alleviate the problem of selecting the most representative activation energy is to estimate the value based on collected data. Utilizing maximum likelihood theory, the parameters of the Arrhenius model are solved while using the Weibull distribution as the underlying life distribution. Once the parameters have been estimated, the activation energy and acceleration factor can be easily calculated.

Reliability Basics
The purpose of this section is to offer background and advice to the novice reliability engineer.

Differences Between Type I (Time) and Type II (Reliability) Confidence Bounds
When displaying confidence bounds on a plot there are many decisions to be made, such as whether to use one-sided or two-sided confidence bounds, what confidence level should be used and which confidence interval method is to be implemented. But when creating a probability plot you must also decide whether to display confidence bounds on time (Type I) or on reliability (Type II). A probability plot contains both an axis for time (x-axis) and an axis for reliability (y-axis), although the y-axis is usually displayed in terms of probability of failure. Both types of confidence bounds can be shown on a probability plot, so which one should you use? This article will explain the differences between the two types of confidence bounds and offer suggestions to help you decide which type to use.

Tool Tips

• How do I view a plot of Life vs. Stress, AF vs. Stress or Std vs. Stress for multiple stresses at the same time in ALTA 6?

• In ALTA 6 PRO, what do the Time Varying Stress Calculation options on the Calculations tab of the User Setup mean?

Service Pack 3b (CRV 6.0.9) is now available for ALTA 6. To download the latest service pack and to get information regarding the modifications that were made, go to http://www.reliasoft.com/altaupdates.htm.

 Application Date Created Version ALTA ALTA 6 6/20/02 6.0.9 ALTA 6 Service Pack 6/20/02 SP3b CRV 9
Hot News
Reliability Training Seminars - Next seminar in August in San Diego! The next ReliaSoft "Master the Subject, Master the Tools" seminar will be held in San Diego, California from August 19 - 23, 2002 at the Holiday Inn by the Bay. For more information on course content and how to register, see http://www.ReliaSoft.com/seminars/master.htm

11th Annual Applied Reliability Engineering and Product Assurance Institute for Engineers and Managers - Along with Boeing, Dade Behring, General Electric and Whirlpool, ReliaSoft will once again be co-sponsoring the Annual Applied Reliability Engineering and Product Assurance Institute for Engineers and Managers. The institute will be held July 22-25, 2002 in San Diego, California. If you will be participating in the institute, be sure to attend the overview of ReliaSoft's reliability engineering software tools, given by ReliaSoft's President and CEO Pantelis Vassiliou on Thursday, July 25th.
Delphi joins the ranks of customers with ReliaSoft Corporate Wide Licensing - Delphi Automotive Systems is the most recent company to obtain Corporate Wide Licensing of ReliaSoft's Weibull++ software. Welcome aboard Delphi!
Ford Motor Company R&M Standardization Initiative - The Weibull++ MT software, which was specifically designed to address the needs of the Ford Failure Reporting, Evaluation & Display program (aka "FRED"), has been released for a year now. ReliaSoft would like to thank Ford Motor Company and all Ford suppliers participating in this initiative for their support of the Weibull++ MT and BlockSim software.
Summer Time Special - For the months of July and August only, ReliaSoft is offering a US\$575 discount for customers purchasing ALTA 6 PRO and Weibull++ 6 at the same time. This limited time offer can be used in addition to the standard discounts for bundled purchases of software and training. For more information on bundled pricing options, see http://www.ReliaSoft.com/bundles.htm.

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:
 - August 5 - 7, 2002 - Life Data Analysis - August 8, 2002 - Accelerated Life Testing - October 14 - 16, 2002 - Life Data Analysis - October 17, 2002 - System Reliability
From The Edge
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:
• Analyzing Data from Equipment Downtime Logs - For product manufacturers who rely on repairable manufacturing equipment, downtime logs can be a valuable source of life data for reliability, maintainability and availability analyses. In order to prepare the data for reliability analysis, the analyst must convert the information in the equipment downtime logs into times-to-failure and times-to-repair. This can be a time-consuming and error-prone process when performed manually. This article describes the process for converting equipment downtime logs to usable reliability data and introduces Weibull++ MT, a special version of ReliaSoft's Weibull++ life data analysis software package that provides utilities to automate the process. See http://www.ReliaSoft.com/newsletter/1q2002/downtime.htm.
Contribute to HotWire
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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.