Rivets

About

The Rivets is a load feature where so called “Rivets” are created and placed in a group folder in the current structural (or thermal) analysis. The Rivet is constructed of BEAM188 solid circular beam element for the rivet shaft and a MPC CERIG or RBE3 remote points for the heads and intermediate sections. In thermal analysis LINK33 is used. This is the similar as the standard “Beam connection” except that rivet creates one beam element for each layer in the connected assembly. The additional features with the Rivets compared to “Beam connection” are that:

• Multiple rivets can be defined in one load object, i.e. all D12 rivets of the model.
• A point mass (MASS21 element) can be added to the rivet head to account for missing mass.
• All rivets are saved in one place, the “Rivets Group” folder.
• The rivets can have different orientation.
• Custom Behavior for the “Head” interaction can be defined in an APDL macro.
• Thermal loads on the bodies will be mapped to the rivets to account for correct thermal elongation.
• Post processing of the Rivets is done using the Rivets Result object.

Usage

Click on “Rivets” in the toolbar to insert the Rivets Group folder in the current static analysis as well as creating the first Rivets load object. To add additional rivets, right click on the Rivets Group folder and select “Add Rivets” or click on “Rivets” in the toolbar. You can also use “Duplicate” on an existing Rivets and modify the properties.
You can add multiple “Rivets Groups” using the context action “Insert>Rivets Group” on the the selected “Analysis”.

Inputs to define the rivets are:

(i) Scoping Method

The manual “Geometry Selection” can be converted to a “Named Selection” using the context action “Promote to Named Selection”.

(ii) Geometry

Vertices on shell bodies and edges on shell and solid bodies are supported. If selecting faces/bodies the range of Hole Diameter (min), and Hole Diameter (max), d0 is used to search for holes defined by at least one circular edge section.
The face/body selection can be converted to edge selection using the context action “Convert to Edge Selection”.

(iii) Material

The following material properties (and corresponding MAPDL MP Lab) are supported: Young’s Modulus (EX), Poisson’s Ratio (NUXY), Density (DENS), Coefficient of Thermal Expansion (ALPX), Thermal Conductivity, (KXX), Specific Heat (C), Isotropic Hardening (BISO & MISO), Kinematic Hardening (BKIN, KINH). If orthotropic properties are defined the X component is automatically used (EX, NUXY, ALPX & KXX).

Graphics

A graphic representation is created once valid inputs are given. At least two sets of hole edges are needed to make a valid selection. The Rivets load object connect holes fulfilling the following criteria:

• The normal distance is in the range of Min thickness to Maximum thickness.
• The angle between the face normals is less than Face angle tolerance.
• The planar offset between the hole centroids is less than 10% of the Shaft Diameter.

Hole centroids in the same plane with a distance offset less than 10% (Rivet coincident tolerance factor) of the Shaft Diameter are made coincident. The default values for “Rivet coincident tolerance factor” and “Face angle tolerance” can be edited in the Bolt Settings object.
The head diameter is plotted as a disc normal to the rivet shaft (if Head Diameter > Hole Diameter) and the rivet shaft as a cylinder. The active Rivet Holes or Rivet Source edges are plotted in thick red lines. The active Rivet Target edges are plotted in thick blue lines (for Body to Body rivets). Edges shared between two different rivet objects are plotted in thick orange lines.

Un connected hole edges are plotted in thin red lines. If the coincident edges don’t match the average centroid is used when creating the rivet so that the rivet shaft is straight.
The rivet section Id number is printed at the center of each connected edge and is used in the result tables. The colour, translucency and printing of “Id” numbers is defined in the Rivets Group object. The display of all rivets in the Rivets Group can be disabled by setting “Show Graphics = No”. The default values for the group can be defined in the Bolt Settings.

A property file is also written to the solver files directory that is used by the Bolt Report feature.

Custom behavior

The Rivets connection behavior is defined in the macro file “buildRivet.mac” found in the extension installation folder. (%AppData%\Ansys\v2XY\ACT\extensions\BoltToolkit_V2XY.Z)

Edit the file in the sections “*else ! ‘Custom’” to define any type of connections using the center node on the rivet shaft (_npilot) and the selected edge nodes.

Rivets Body to Body

The Rivets Body to Body is a variant of Rivets that uses two scoping groups (Rivet Source and Rivet Target) and will only create rivets connecting holes between the two groups.
This is useful for defining connections to assemble different components when using “Model assembly” on the project page to avoid creating new connections within the individual components.

Right click on the Rivets Group folder and select “Add Rivets Body to Body”.

Group Features

The Group object is used to collect and organize the individual types of joints (Rivets/Pretension/Simplified Bolts/Advanced Bolts). It is possible to insert more than one Group object using the context action “Insert>Rivets Group” on the selected “Analysis”.

Load Colour

The colour of the Rivet/Bolt geometry can be set for each group individual. This is useful if using several groups of Rivets/Bolts for different parts or sub-assemblies of the model.

Attribute File

An “Attribute file” property can be enabled for the Rivets/Bolts Group by using the context action “Reset Attribute File” to toggle the property visibility.
The attribute file is a csv file containing a list of rivet coordinates and optional properties to define the rivet, see example below.
When selecting an Attribute File a Rivet/Bolt object will be created for each “Attribute” in the file if unused in the group. If selecting an “attribute” name for the Rivet/Bolt object the holes will be filtered to match the coordinates in the file. The Hole Diameter multiplied by the Pinball factor is used as the search pinball radius when filtering the holes. The Show Attribute Centroids is used to select an Attribute to display the coordinate points and also the resulting pinball sphere if the attribute is used in any rivet object.
The properties, Caption, objectName, rivetHoles, rivetTarget, material, nonlinear, shaftDiameter, headDiameter, holeDiameter, addMass, maxThickness, behavior and pinBallFactor can also be defined. The coordinates, (X, Y, Z) may be left blank to avoid filtering the holes. The scoping properties (rivetHoles, rivetTarget) defines the Named Selection to use.

The template file below can be copied by clicking in the upper right corner of the code window.

// RivetAttributes.csv
attribute,Id,X [mm],Y [mm],Z [mm],Caption,objectName,rivetHoles,rivetTarget,material,nonlinear,shaftDiameter [mm],headDiameter [mm],holeDiameter [mm],addMass [kg],maxThickness [mm],behavior,pinBallFactor
solid.prt, 1,30.,30.,-75.,Rivets 3 plates solid,rivetConnections,solid bodies,,Steel bolt  5.8,No,12.0,24.0,13.0,,10.0,Rigid,1.0
solid.prt, 2,30.,10.,-75.,Rivets 3 plates solid,rivetConnections,solid bodies,,Steel bolt  5.8,No,12.0,24.0,13.0,,10.0,Rigid,1.0
solid.prt, 3,30.,20.,-75.,Rivets 3 plates solid,rivetConnections,solid bodies,,Steel bolt  5.8,No,12.0,24.0,13.0,,10.0,Rigid,1.0
solid.prt, 4,30.,0.0,75.,Rivets 3 plates solid,rivetConnections,solid bodies,,Steel bolt  5.8,No,12.0,24.0,13.0,,10.0,Rigid,1.0