Nastran 2017 Manual
The Manual option within the Surface Contact dialog allows you to choose the Master and Slave entities and to define all basic and advanced contact options. When you select the Manual option, the following settings are available: • Type: There are two methods to define surface contacts: • Surface to Surface: • Edge to Surface: You must select a minimum of two faces (one Master Entity and one Slave entity) in order to properly define surface contact and for contact elements to be created. You can also select multiple Master and Slave faces.
The flip buttons (vertical arrows) are provided in order to easily move or swap faces between the Slave and Master Entities list boxes. • Master Entity: • This field allows you to select the master surface. • The selection is initially set to be active in the Master Entity field. To reactivate the master selection mode (after you've made slave selection active) click in the Master Entity box. • Only surface selections are allowed. • Blue colored faces indicates that they are selected as Master entities. • Slave Entity: • This field allows you to select the slave surface.
• Activate slave selection mode by clicking in the Slave Entity box. • Both surface and edge selections are allowed. However, limit your selections to those applicable for the specified contact Type—faces for Surface to Surface contact, and edges for Edge to Surface contact. • Pink colored faces indicate that they are selected as Slave entities.
• Add To Analysis: Surface contacts generated this way can be applied to an analysis by clicking the Add to Analysis checkbox. You can also drag and drop, or copy and paste, contact pairs from the Model branch to the Analysis branch of the tree. Additionally, you can right-click Analysis, and select Add/Remove Entities from the context menu. The following dialog appears: In the list under Surface Contacts, entries that were initially highlighted are already active in the current analysis. Entries that are not initially highlighted exist only in the Model branch of the tree. Click to toggle the selection state of the contact entries.
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When you click OK, the highlighted contact pairs will be added to the current analysis, and the non-highlighted entries will be removed from the Analysis (if they were in it). This tool will not delete contact pairs from the Model branch of the tree. In the following image, the two manual surface contact pairs that were selected in the preceding dialog have been added to the Analysis. Ecoflam Gas Burner Manual here. • Contact Data: • Contact Type: In this section, different types of contact can be generated. The Contact Type terminology now matches Inventor Stress Simulation terminology.
Moreover, when you hover over the Contact Type drop-down menu, tool tips are available to show the Nastran terminology, as you can see in the image below: • Separation (Nastran: General) • This type of contact is a true surface to surface contact. Both sliding and opening are allowed. • The example in the figure below shows 3 blocks, the bottom block is pushed up and free surface contact is used between the touching surfaces. • Bonded (Nastran: Welded) • This type of contact is used to bond the touching surfaces together. It moves together with loading.
• The advantage with this type of contact is that the mesh does not have to be the same. • It can be useful in cases where touching surfaces on different parts have dissimilar meshes and do not undergo relative displacement. In other words the surfaces are treated to be bonded together. • The welded contact response between the beams is shown in the figure below. It moves together as shown in the picture. • Sliding / No Separation (Nastran: Slide) • With this type of contact the element will act similar to a welded contact element in tension and compression, but will slide in-plane.
• Slide contact can be used in linear and nonlinear solutions. • Separation / No Sliding (Nastran: Rough) • With this type of contact the element will act similar to a general contact element in tension and compression, but will not permit sliding in-plane. • If the analysis types are not nonlinear, the contact type will default to welded. • Offset Bonded (Nastran: Offset Weld) • The offset weld setting is intended for welded connections with significant separation between contact surfaces. • Penetration Type: It is applicable only for Manual contact. In this section, the type of master slave penetration can be selected.
Two types are available: • Unsymmetric: • In this method, only the penetration of the slave nodes into the master surface segment would be checked and adjusted. • This may lead to master nodes penetrating into slave surface segment that can be reduced with a finer mesh. • When some penetration of the master surface is expected, this method can be a good way to speed up the analysis.
In reality there is always some degree of master slave penetration. • Symmetric: • In this method, the segments of the contact pair, master and slave are also made to be slave and master respectively and both penetrations are checked and adjusted. • More accurate results can be obtained with this method at a cost of increased computational time depending on the model size. • In case of Edge to Surface contact, it is not applicable. • Stiffness Factor: This value controls the stiffness scaling of the contact.
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