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Issue 3, May 2001

 Hot Topics Reliability Basics Tool Tips Hot News From The Edge Contribute to Hotwire

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Hot Topics
Determining the Reliability of Complex Systems
Part 2 - Simulation

A complex system is one that cannot be broken down into groups of series and parallel components. Due to this, it can sometimes be difficult to determine the reliability of the system as a function of the component reliabilities. There are two general strategies when solving for system reliability: analytical techniques and simulation.

In last month's article, we looked at some of the analytical techniques that can be employed to determine system reliability. While these techniques can provide useful information that is unattainable elsewhere, determining the analytical solution can be time-consuming. Furthermore, if you want to incorporate maintainability and availability into the analysis, an analytic solution may be mathematically impossible. In cases such as these, we can use simulation techniques to estimate the reliability of the complex system. This article discusses the simulation techniques employed by ReliaSoft's BlockSim to simulate the behavior of complex systems.

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

Developing Good Reliability Specifications
While most organizations are concerned with the reliability of their products, many will not develop good reliability specifications. This is a serious flaw that can result in unreliable products reaching the field. Even the most vigorous reliability testing program will be of little use if the product being tested has a poorly-defined reliability requirement. Sometimes, reliability requirements will be developed by a marketing organization or other groups with little or no experience in life data analysis. This can result in vague or unrealistic requirements that do little to aid in the development of the product. This article discusses ways to improve your product's reliability by improving reliability specifications.

Tool Tips

• How do I obtain component failure and repair information for RBD blocks in BlockSim?

• How can I change the default plot settings for multi-plots in Weibull++?

• I have a data set with two stresses in ALTA. How can I insure that both stresses will be taken into account in the analysis and plotting?

Hot News
From The Edge

Every quarter, 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 - Accurate predictions about the quantity of products that will be returned under warranty can provide huge benefits to manufacturing organizations. These include the ability to predict and allocate resources, anticipate customer support needs, and estimate warranty costs. This article discusses a way to predict warranty returns based on currently available shipping and return data. See http://www.reliasoft.com/newsletter/1q2001/warranty.htm.
• A Simple Demonstration of Accelerated Life Testing Analysis - Accelerated life testing consists of tests designed to quantify the life characteristics of a product under normal use conditions by testing the units at higher stress levels. Performed correctly, these tests can provide valuable information about a product’s performance under use conditions that can empower a manufacturer to bring its products to market more quickly and economically than would be possible using standard life testing methods. See http://www.reliasoft.com/newsletter/1q2001/accelerated.htm.
Contribute to Hotwire
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.