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CES EduPack Bulletin, Sep 2009

Hints and Tips

In this edition:

1. Support for FE/CAD packages
   
   
2. Some tips for advanced graphs
   
   
3. Using material indices

Tip 1 - Support for FE/CAD packages

You can export data from CES EduPack records for use in selected CAD / FE / CAE packages. Simply browse to the record of interest, for example using the tree view in the EduPack browse mode. Then either right-click on the record of interest and select "Export" (right) or select "Export Record..." from the File menu.

The Export Record dialog (below) will appear. This shows the supported software systems.

Before exporting the data in the required format, you may want to specify how the export process will work. To do this, click the "Settings" button. This opens the following dialog.

You can output the data to the clipboard, for pasting into the appropriate application, or save it to file. Confirm your choice and select "OK" in the Export Record dialog to complete the process.

Tip 2 - Some tips for advanced graphs

You may wish to create graphs which combine properties on the axes - for example, in order to plot material indices (see next tip) or to plot a property such as specific stiffness (Young's modulus / Density). Here's how...

Open CES EduPack. Choose your database - for example, CES EduPack Level 2.

Choose "Select" on the toolbar.

To create a graph, we work down the Selection Project wizard.

In "1. Selection Data" ensure "Select From:" is set to: "Edu Level 2: Materials".

In "2. Selection Stages" click "Graph". The New Graph Stage dialog appears.

Click on the "Advanced..." button. The Set Axis dialog appears.

You can construct your advanced propertry by selecting attributes from the list at the bottom of the dialog, clicking "Insert" to add an attribute to your formula, and using the operator buttons (+, -, / etc.) to complete the formula. Above, we have specified specific stiffness. Click "OK" and this will be defined as the Y axis of your graph.

For the X axis, we illustrate another advanced plotting feature. Select the "X-Axis" tab on the New Graph Stage dialog. Choose the "Trees" tab on the Set Axis dialog.

This allows you to plot specific records, or groups of records, along the specified axis. For example, by double-clicking on each of the top-level folders above, we add them to the list at the top of the dialog. This will group the data on the X-axis of the graph according to these materials families. Click "OK" on this dialog and on the New Graph Stage wizard and the following graph appears - specific stiffness for all of the materials in the database, grouped by material type..

Tip 3 - Using material indices

Performance indices are a powerful tool in systematically studying materials choice for a particular design application. The performance index is a mathematical formula showing the combination of properties that must be maximized or minimized in order to optimize performance against the desired objective for a given function and constraint - for example, to optimize cost (objective) for a beam in bending (function) of specified stiffness (constraint).

In CES EduPack

In CES EduPack, the goal is to teach students the fundamentals of performance indices. The software encourages students to understand the theory behind indices - helped by the text in the CES In-Depth system. To access this, click the "CES Help" button on the CES EduPack toolbar, and choose "materials selection methodology" under "CES InDepth" in the contents. Here you will find extensive background information and links to the formulae for many common engineering circumstances.

More information is also available in the book: Ashby MF, "Materials Selection in Mechanical Design", 3rd edition, Elsevier Butterworth Heinemann, Oxford, UK, 2005.

The student can then enter the performance index formula and plot indices exactly as we showed in tip 2 above.

In CES Selector

The CES Selector software, however, is designed for use in practical industrial problems, rather than as a teaching tool. Here the goal is to get the user the appropriate performance index as quickly as possible - so the system offers a powerful Performance Index Finder tool.

To access it, we click the "Graph/Index" option under step 2, "Selection Stages", of the Selection Project wizard. Choosing "Performance Index Finder" at the top of the resulting window presents us with the option of selecting a design application from a drop-down menu, below.

The simple-to-use graphical menu allows us to quickly find the situation closest to our application - scrolling down the list presents further mechanical, thermal, electrical, and barrier property scenarios. Choosing one of these scenarios then allows us to quickly select options that specify our design objective and constraint. In the picture below, we have chosen a Beam in bending as our function, stiffness as the limiting constraint, and decided that we want to optimize cost.

The performance index for this objective is automatically computed.

In the graph below, this index has been plotted (Y axis) against an index to optimize volume for the same function and constraint. This allows the user to consider which materials offer the best trade off between these objectives (optimal choices are towards the bottom left of the graph)..