Figure 2.21: Pretension Definition
The normal direction is specified via the PSMESH command and is part of the section data. This is in
contrast to the previous method (the PTSMESH command), which used real constants to specify the
normal direction.
The meshed pretension section does not need to be flat. The elements underlying the pretension section
can have almost any shape: line, triangle, quadrilateral, tetrahedron, wedge, or hexahedron. However,
there must be coincident nodes on the two sides (A and B) of the pretension section. Sides A and B on
the pretension section are connected by one or more pretension elements, one for each coincident
node pair.
A pretension node (K) is used to control and monitor the total tension loads. The pretension load direction
of the pretension section can be specified relative to side A when the section is created by the PSMESH
command. All pretension elements on a specific pretension section must use the same section, and
must have the same pretension node K. Node K is the third position for the pretension element definition.
2.8.2. Applying Pretension to a Fastener Meshed as Two Pieces
If the fastener has been meshed in two separat e pieces (such as in an existing, legacy model), the pre-
tension elements (PRETS179) can be inserted between the pieces using EINTF,TOLER,K (Main Menu>
Preprocessor> Modeling> Create> Elements> Auto Numbered> At Coincid Nd ...). If K is not defined,
the program creates it automatically. Before using the EINTF command, the element type ID and section
properties must be defined properly. (See the SECDATA command for more information on using the
PRETENSION section type.) The connecting surfaces (A and B) must have matching mesh patterns with
coincident nodes. If some node pairs between the two surfaces are not connected with pretension
elements, the resulting analysis can be inaccurate.
2.8.3. Example Pretension Analysis
The following example describes the typical procedure used to perform a pretension analysis using the
PSMESH command.
- Mesh the bolt joint, then cut the mesh and insert the pretension elements to form the pretension section.
For example, the following creates a pretension section called “example” by cutting the mesh and inserting
the section into volume 1. Note that a component is created as well (npts) that aids in plotting or selecting
the pretension elements.
psmesh,,example,,volu,1,0,z,0.5,,,,npts
Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential informationDefining Pretension in a Joint Fastener