Realizing Connectors In HyperMesh

What are Connectors?

A connector is a mechanism that specifies how an object (vertex, edge, or face) is connected to another object or the ground. By often simulating the desired behaviour without having to build the precise shape or specify contact circumstances, connectors make modelling simpler. Connections can be created as spot-weld, seam-weld, adhesive, bolts and masses. A realized connector will be considered as the successful representation of a CAD model in preprocessing and the connecting parts can be considered as connected.

 

States of Connectors

There are three different states in the connector's realization. They are:

 

• Realized Connector

• Unrealized connectors

• Failed connectors

 

State 1: Realized Connectors

Successfully created connectors (realized connectors) will be represented in Green colour as shown below:

 

 

State 2: Unrealized Connectors

The unrealized connector will be represented in Yellow colour as shown below:

 

 

State 3: Failed Connectors

Failed connectors will be represented in Red colour as shown below:

 

 

Now let’s create some connectors and look into the possible ways to realize the connections and detect the common errors.

 

Seam Weld

The process of joining the workpieces that are made of similar or dissimilar materials along a continuous seam is known as a Seam weld. In Hypermesh, seam panels under connectors will help to represent the Seam weld connection between the components.

A. Steps to be followed to create Seam - Quad (angled+Capped+L) Weld:

 

• Select 1D/2D → Connectors → Seam option.
• Now select the location, where the Weld has to be created, by clicking the “node list”.
• Tick the checkbox of “retain nodes” option, to retain the position of the nodes, while creating and realizing a connector.
• Specify the “spacing” value and select the “comps” option under “connect what”, in order to create the weld between those two components.
• Specify the “tolerance” value, based on the distance between the two components.
• Select the type as “seam-quad (angled+capped+L)”.
• Click on the “create” button, to create the seam weld (refer Fig1).

 

 

• After completion of the seam weld, the components will be connected as shown:

 

 

Note:

• Weld Angle: Angle between the normal projection of the nodes and slant length of the weld element. It is recommended to define weld angles between 0 and 90 degrees.

• Cap Angle: Angle between the normal of the first slant weld element (A) and its adjacent side element (B). To define seam weld for 0 to 45-degree cap angle, it is recommended to select ≤10 degree and for the 45 - 90 degree cap angle, it is recommended to select ≥75 degrees.

 

 

• Runoff Angle: The angle between the normal of the first slant weld element and its adjacent weld elements. It is recommended to define weld angles between 0 and 10 degrees.

 

 

Options to be changed to Realize the connectors:

 

• “Spacing” value (refer Fig1) defines the space between each node of the weld element, which should be equal to the Target element size, this will ease the weld element to be created between the components.
• Only entities within this tolerance can be taken into account for the link detection and the final realization. If the connection entities are away from the search tolerance, seam weld may not get realized.

 

 

• By switching the option from “quad transition” to “remesh”, we can realize the connector as shown below (ref Fig 2).

 

 

 

B. Steps to be followed to create Seam - Hexa Adhesive Weld:

 

• Select 1D/2D → Connectors → Seam option.
• Now select the location, where the Weld has to be created, by clicking the “node list”.
• Tick the checkbox of “retain nodes” option, to retain the position of the nodes, while creating and realizing a connector.
• Specify the “spacing” value and select the “comps” option under “connect what”, in order to create the weld between those two components.
• Specify the “tolerance” value, based on the distance between the two components.
• Select the type as “hexa (adhesive)”.
• Click on the “create” button, to create the seam weld (refer Fig 4).

 

 

• After completion of the seam- Hexa adhesive, the components will be connected as shown:

 

 

Options to be changed for Realizing the connectors:

• Spacing value and Tolerance value should be specified as per the “Target element length” and “Search distance” of the components to be connected.
• Changing the Strips value as per the connection data, will realize the connection.
• Strips: It defines the number of hexa elements required along the width as shown below:

 

 

• Changing the Coats value as per the connection data, will realize the connection.
• Coats : It defines the number of hexa elements required along the thickness(ref Fig 5)

 

 

 

• Changing the width value as per the connection data will realize the connection.
• Width: It defines the continuous hexa weld width in the direction perpendicular to the seam direction.

 

 

• The following changes can be obtained by changing the “hexa position to edge” option, this changes will also realize the connections:

 

A) Midpoint:This option will position the hexa element to the exact mid-location of the component's edge as shown below:

 

                                             

                                              B) Offset from edge: This option will position the hexa element upto to a certain distance from the edge of the components. Offset value can be specified in the location which is shown below as per connection data.

 

 

 

 

C) Positive edge: This option will position the hexa element away from the free edges (outside) of the component as shown below:

 

 

 

D) Negative edge: This option will position the hexa element, inside the free edges of the component as shown below:

 

 

•  Discontinuity: By default, the length and width of a hexa weld are defined by nodes of the current component along the edge. To ignore the predefined dimension of the weld elements and to define a specific element length, weld length, and break length, select the discontinuity checkbox. With this option, a hexa adhesive seam with alternating weld pieces and gaps is created. When a discontinuity is enabled, you must define the following inputs(refer Fig 6)

 

A) Elem length: It specifies the length of the Hexa element along the seam connector.

                     B) weld length/scale (elem): It specifies the number of the Hexa weld element, which is realized. 

                        C) break length/scale (elem): It specifies the amount of space to create in between the hexa welds.

 

 

 

Spot Weld

Spot welding is a resistance welding process that is used primarily for welding two or more metal sheets together by applying pressure and heat to the weld area. Heat for the welding process will be obtained from resistance to electric current. Realized spot weld in HyperMesh will represent the connection between the components.

 

A) Steps to be followed to create Spot Weld:

 

• Select 1D/2D → Connectors → Spot option.
• Now select the location, where the Weld has to be created, by clicking the “node list”.
• Tick the checkbox of “retain nodes” option, to retain the position of the nodes, while creating and realizing a connector.
• Specify the “spacing” value and select the “comps” option under “connect what”, in order to create the weld between those two components.
• Select the number of layers(Number of Components) to be welded, under “num layers” option.
• Specify the “tolerance” value, based on the distance between the two components.
• Select the type as “weld”.
• Click on the “create” button, to create the spot weld (refer Fig 7).

 

Note: Diameter value can be specified for Hexa element type.

 

• After completion of the spot weld, the components will be connected as shown:

 

 

Options to be changed to Realize the connectors:

 

• Spacing value and Tolerance value should be specified as per the “Target element length” and “Search distance” of the components to be connected.
• Changes made under “Mesh dependent” option in the spot weld panel (refer Fig 8)

 

Adjust realization: Adjust the realization itself, such as allowing non-normal realizations for the sake of locating nodes to create the realization.

 

 

A) Find nearest nodes: Connection can be established based on the closer nodes, which lies in the search tolerance value.

b) Project and find nodes: This option will project the connection and then it will search for the closer nodes.

C) Ensure  projection: This option will project the connection alone, it wont establish the connectivity with the nodes as shown below:

 

 

• Changes made under the “adjust mesh” option in the spot weld panel, consist of three different realization option listed as follow:
• Adjust mesh: It will adjust the mesh locally (such as creating transition elements or remeshing) to ensure proper realization.

                                    a). Smooth: Adjusts the mesh in such a way that the closest node to each layer is moved into the position of the projection point. The advantage of this option is that neither the element IDs nor the node IDs will be changed, and the element topology will remain the same.

 

 

                                   b). Remesh: This option will remesh the mesh of the entities after the connection has been established between the components to achieve better link connectivity.

 

 

c). Quad transition: This option will create quads to serve as a transition between the selected entities to get a spot weld connection.

 

 

Note: Quad size will determine the size of the quad elements created near the spot weld region as shown below:

 

• By selecting the “mesh independent” option, we can determine whether the realizations require a node connection or not (refer Fig 11)

 

Note: For a realization which does not need any node connection and the connection is primarily defined via a solver-specific card or the nodes which need to be connected are defined by just a cylinder.

 

Bolt Connection

Bolted joints are one of the most common elements in construction and machine design. A connection between structural members is made with plates and bolts, as opposed to a riveted or welded construction. In HyperMesh, we use the RBE2 elements to represent the Bolt connection, since it has more stiffness.

 

A) Steps to be followed to create Bolt connection:

 

• In order to create a Bolt connection, if we had a hole present in the components, we have to locate a centre node as shown below:

 

 

• Now click on the 1D/2D → Connectors → Bolt option.
• Under “location”, select the node, which we created already to establish the bolt connection.
• Then select the “comps” option under “connect what”, in order to create the weld between those two components.
• Select the number of layers to be welded, under “num layers” option.
• Specify the “tolerance” value, based on the distance between the two components.
• Select the type as “bolt (general)”.
• Click on the “create” button, to create the seam weld (refer Fig 12).

 

 

• After completion of the Bolt connection, the components will be connected as shown:

 

 

Options to be changed for Realize the connectors:

 

• The tolerance value should be specified as per the “Search distance” of the components to be connected.
• Defining a proper vector for the bolt connection will also realize the connection:

                             A) Use dynamic vector: It will be the default option, and it automatically determines the connector vector dependent on the projection directions during the link detection.

                             B)Use the existing vector: It will use the existing vector associated with the connector to define the bolt direction during realization. If no vector is associated so far, the dynamic vector option is used instead.

                             C) Define a new vector: It will define and associate a new vector with the connector by selecting the Nodes as N1, N2 and N3 in order to define the bolt direction during realization.

 

 

• By changing the option to “create hole, if none”, from the default option, we can realize the connection between the components (refer Fig 13).

Create hole, if none - After the realization, this option will create a hole in the mesh, if there is no pre-existing hole in the model. Here Model A shows the failed connectors Model B shows the Bolt connection created successfully.

Hint: Hole will be created in the FEA model alone, not on the surface of the component.

 

 

 

• By changing the option to “use hole, if available”, from the default option, we can realize the connection between the components (refer Fig 14).

 

 

Use hole, if available - This option will utilize the hole, which is present on the top surface of the component and it will realize the Bolt connection.

 

 

Note: For the last two above-mentioned options, we have two sub-options:

 

• Adjust Hole position: This option will adjust the hole in order to ease the creation of bolt connection between the two components as shown below.

 

 

• Adjust realization: This option will adjust the linking bolt connection according to the hole availability in the components as shown below.

 

 

By changing the option to “fill & remesh hole, if available”, from the default option, we can realize the connection between the components (refer Fig 15).

 

 

Fill & remesh hole, if available -  This option will fill the pre-existing hole present in the model and also remesh the model to realize the Bolt connection.

 

 

Hints: Re- realizing connectors can be done in the following two ways:

• By selecting the “realize” option under every type of connection panel.

 

 

• By using the “Connection browser” under “View” option in the Menu bar.