## Pro Mechanica Tutorial on Midsurface Shell

written by: Suvo • edited by: Lamar Stonecypher • updated: 10/20/2010

Midsurface shell option will allow you to create shell from the solid model for Pro Mechanica. We will discuss where we can use this option and where we can not.

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Shell increases the efficiency of your analysis in terms of memory consumption and time. So, wherever possible you should think of using shell. Normally, if the thickness of your model is substantially smaller that the width and length, then the shell model is ideal.

Types of shell

In pro mechanica you can create shell in two ways:

1. Standard shell
2. Midsurface shell

Standard shell

This type of shell is used when you need to create the shell as a layer on the solid or you want to add the laminates properties for the shell. You can even create shell which is having material properties different than the rest of the part.

Midsurface shell

Midsurface shell is constructed from a pair of opposing surfaces. The opposing surface can be selected mostly manually, some cases depending upon the model type the opposing surface pair can be auto detected. You cannot define laminate properties for midsurface shell. But you can solve most of the real life problems by using midsurface shell effectively.

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How to create midsurface shell

Create the model either in sheet metal or in solid, then go to insert>midsurface, the menu bar will appear. Click on the new, now you have to select any one of the following options:

1. constant
2. multi const

Constant: If you select this option, then all the surface pairs (for which you want to extract mid surface) need to be of exactly constant thickness. Most of the times you may like to go with this option only.

Multi constant: By using this option, pro mechanica will create midsurface even if all the surface pairs are not of constant thickness. Using this option will produce results which are comparatively less accurate in the multi constant thickness area.

Now, as you have done with the selection of any of the above option, pro mechanica will ask for the opposing surface pairs (for which you want to extract the mid surface).

Like the new option, you can use auto detect option as well for detecting the mid surfaces. But the auto detect option works only for the following features:

• shells
• ribs
• ears
• thin protrusions
• sheet metals

So, typically you can start with the auto detect, pro engineer will compress the part of the model, the remaining part needs to be compressed by the new option then.

After selecting the pair of surfaces (either by auto detect or by new) you click on the compress, the menu will expand further and will have to more options like below:

Shells only: This option will show how it looks if pro mechanica treat the model as shells only after compression.

Shells and solids: This option will show how it looks if pro mechanica treat the model as mixed model (shell and solid).

Further, there are three more options for visualization of the compressed midsurface shell, the showcompress will show only the compressed or the created mid surface, the showoriginal will display the original model, the show both will show both the midsurface as well as the original surfaces.