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| Reliability HotWire | |
| Tool Tips | |
 Can
I display the locations of suspensions on my probability plots?
Yes, relative locations of suspensions can be displayed as triangles along the x-axis of plots in Weibull++ 6 or ALTA 6. This option is set by selecting User Setup from the File menu, and clicking the Plot tab in the User Setup window. At the bottom of the page, select the "Show Suspensions" option.
With this option selected, the suspensions will appear as triangular symbols on the x-axis of probability, reliability vs. time, and unreliability vs. time in Weibull++ 6 and ALTA 6.
You can't. The sad fact of the matter is that you get out of a reliability test what you put into it. If you do not put in enough test units or time in a test, you cannot expect to get good results from the analysis. (See this month's Reliability Basics article for more information of reliability test design.) However, if you have some information about the life distribution of the product (i.e. type of distribution and shape parameter), you can use the Design of Reliability Testing (DRT) tool in Weibull++ 6 to help design acceptance tests. Acceptance tests do not provide detailed information about the reliability characteristics of your product, but they can indicate whether or not the product has a minimum reliability value at a given confidence level. The DRT tool can be accessed via the Tools menu, or by clicking the DRT icon in the toolbar.
Under the Parametric Binomial tab, you can enter the assumed distribution, assumed shape parameter, and the reliability to be demonstrated. The tool returns the number of units to test for a given time or the amount of time needed for a given number of test units in order to demonstrate the required goal. A Tables/Plots function gives you the ability to conduct trade-off studies between units and test time to determine the optimum test design.
The Non-Parametric Binomial tab allows you to perform limited demonstration design calculations without having to make assumptions about the life distribution. The only drawback to this is that the test time has to equal the demonstration time. For example, if you were attempting to design a test that would demonstrate a reliability of 90% at 1,000 hours with 95% confidence, the test would also have to be 1,000 hours in duration. The Exponential Chi-Squared tab allows you to perform acceptance test design calculations for products with constant failure rates. The results of these calculations are in accumulated test time, which allows you to break out the test into specific units and test time. For example, if the calculated accumulated test time were 120 hours, the test could be performed on 12 units for 10 hours, 6 units for 20 hours, etc. How
can I copy a reliability block diagram (RBD) into the same diagram sheet in
BlockSim?
Entire RBDs or sections of RBDs can be copied and pasted into the same diagram sheet in BlockSim merely by clicking outside the blocks and dragging an outline around the section of interest. This will highlight a group of blocks that can be copied by selecting Copy from the Edit menu, or by pressing Ctrl+C. By selecting Paste from the Edit menu, or pressing Ctrl+V, the entire section of blocks (with connections) will be pasted back into the same diagram sheet and additional blocks and connections can be inserted to link this portion of the diagram with the original section of blocks.
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