Reliability HotWire: eMagazine for the Reliability Professional
Reliability HotWire

Issue 50, April 2005

Tool Tips

* What is the purpose of the Algorithm Setup window in BlockSim?

Multiple numerical integrations are used by the Analytical QCP when performing analytical calculations on an RBD that includes load sharing and standby container blocks. The Algorithm Setup window allows you to further define the parameters of the numerical integration, as well as to enable self-checking algorithms for standby and load sharing container blocks.

The Algorithm Setup window can be accessed by clicking the Integration Parameters button on the standby container block Item page or the load sharing container block Item page of the Container Properties window. The appearance of this window will vary depending on the type of container block (i.e. standby or load sharing) and whether or not the Check Accuracy option is selected.

If you select the Check Accuracy option, the Algorithm Setup window will look like the one shown next.

standby Algorithm Setup

If Check Accuracy is selected, the Analytical QCP will repeat the integration until the desired accuracy is achieved. You can enter the maximum number of integrations that should be performed to achieve the desired accuracy in the Maximum Number of Iterations input box. Next, enter the number of quadrature points that are used in the first integration in the Baseline Quadratures input box. Finally, enter the desired accuracy in the Accuracy input box. The second integration will multiply the baseline number by the value you enter in the Points Multiplier input box and check the result against the desired accuracy. This is repeated up to the maximum number of iterations or until the desired accuracy is achieved. 

When you perform calculations in the Analytical QCP, if the acceptable accuracy is not reached within the number of defined iterations, you will get a message indicating this.

If you do not select the Check Accuracy option in the Algorithm Setup window, the window will look like the one shown next.

Standby Algorithm Setup

If Check Accuracy is not selected, the Analytical QCP will not repeat the integration until the desired accuracy is achieved. The number of iterations will be displayed in the Iterations input box; enter the number of quadrature points that are used in the integration in the Baseline Quadratures input box.

* How can two times-to-failure data sets be compared in ALTA?

In ALTA, two times-to-failure data sets can be compared by using the Test of Comparison tool. Select Tests of Comparison from the Tools menu or click its icon on the Data Analysis toolbar.

General Wizard

Once two data sets have been selected, click Compare to get the results of the comparison.

When performing a test of comparison, the comparison is based on P(T2J>=T1J). In other words, the utility determines whether the first population is better, the same, or worse than the second. This is based on whether the returned reliability is greater, the same, or less than 50%.

The panel at the top of the window displays the probability that the first data set is better than the second data set. The panel at the bottom of the window displays comments on the comparison, such as a summary of the results. In the above example, the second data set was found to be better than the first with a 90% probability, as shown next.

 Comparison Wizard
 

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