Seam-Rigid LTB

The Seam-Rigid LTB realization serves and realizes t-welds, lap-welds and butt-welds at the same time.

The weld type is identified automatically based on the orientation of the links to each other.

The dimensions and property for all heat affected zones (HAZ) can be defined separately. An edge treatment can be defined for t-welds and butt-welds to move the edge a precise distance from the opposite link.
Restriction: Available in the OptiStruct, Nastran, Abaqus, LS-DYNA, and Radioss solver interfaces, and can only be selected and defined in the Connector Entity Editor.


Figure 1. Seam-Rigid LTB

General Info

Weld Type
Defines weather to setup a configuration exclusively for a T, L, or B connection, or automatically setup a configuration for each connection based on the angle.
In any case, the connection type is dependent on the:
  • B/L classification angle
  • L/T classification angle
Both types of angles are defined in the Behavior section.


Figure 2. T Connection


Figure 3. L Connection


Figure 4. B Connection
 
Tolerance
Defines the distance from the connector location.
Only entities within this tolerance can be taken into account for the final realization. The tolerance is used to verify whether adequate link candidates are available to be connected with respect to the number of layers.

Weld Shape

T Weld Shape
Defines how the T weld is created.
The image below shows where the master and slave nodes of the rigid elements will be placed.


Figure 5. Vertical T Weld


Figure 6. Angled T Weld, Connected to Edge


Figure 7. Vertical and Horizontal T Weld


Figure 8. Angled T Weld, Connected at a Defined Vertical Height LTV
L Weld Shape
Defines how the L weld is created.
The image below shows where the master and slave nodes of the rigid elements will be placed.


Figure 9. Vertical L Weld


Figure 10. Angled L Weld


Figure 11. Vertical and Angled L Weld
 
B Weld Shape
B welds are always created in a straight manner.
The image below shows where the master and slave nodes of the rigid elements will be placed. The nodes can also be placed the opposite direction, but their position will always be consistent throughout each seam.


Figure 12. Straight B Weld

Realization Details

The Realization Details settings position the yellow marked nodes in Figure 13, Figure 14, and Figure 15.


Figure 13. T Dimensions


Figure 14. L Dimensions


Figure 15. B Dimensions
 
The dimension of the welds are dependent on the Weld Shape settings.
Dimensioning Scheme
Defines the dimensioning scheme for the dimensions of the T weld, L weld, and B weld connections.
input
Manually define discrete values for the weld dimensions, shown in black in Figure 13, Figure 14, and Figure 15, with the exception of thickness. The horizontal dimensions can be defined using a length or an angle.
thickness dependent
Choose a formula to define the weld dimensions, shown in black in Figure 13, Figure 14, and Figure 15, with the exception of thickness. The provided formulas are all dependent on the thicknesses t1 and t2. A formula can be chosen individually for each verticalV and horizontalH distance, or the same formula can be used for T, L and B.
weldsize dependent
Manually define discrete values for the weld dimensions, shown in red in Figure 13, Figure 14, and Figure 15. The verticalV and horizontalH distances are defined with formulas reflecting the weld sizes and the t1 and t2 thicknesses.
DIM T (Dimensioning T)
  Input Thickness dependent Weldsize dependent
Horizontal Lengths LTH
  • by angle
  • by length
  • (t1+t2)/2
  • 3*(t1+t2)/2
  • t1+t2
t1/2+wh/2 (fix)
Vertical Length LTV
  • by length
  • by edge
  • (t1+t2)/2
  • 3*(t1+t2)/2
  • t1+t2
  • by edge
  • t2/2+wv/2
  • by edge
DIM L (Dimensioning L)
  Input Thickness dependent Weldsize dependent
Horizontal Lengths LTH
  • by length
  • by angle
  • (t1+t2)/2
  • 3*(t1+t2)/2
  • t1+t2
wh/2 (fix)
DIM B (Dimensioning B)
  Input Thickness dependent Weldsize dependent
Lengths LB
  • by length
  • by angle
  • (t1+t2)/2
  • 3*(t1+t2)/2
  • t1+t2
  • by edge
  • wb
  • by edges
Edge Treatment (T/B)
When discrete lengths are requested for T and B connections, it is sometimes necessary to move the edges.
Edge treatment is not needed when the different length dimension settings are set to by edge.
When enabled, edges are allowed to move. See Edge Treatment Options for more information.
Max Length Value
Defines the maximum length value.
This setting is useful when lengths are calculated based on thicknesses. If a length is greater than the Max Length Value, then the Max Length Value will be used instead.

Element Details

The DOF parameter controls the setting for the Degrees of Freedom for the RBE2 elements, which are created during the realization.

Connectivity Info

imprint (default)
Creates quad weld elements, and stitches them to both links by adjusting their mesh. All required HAZ are performed.
skip imprint
Creates quad weld elements, but does not change the meshes of the links. Instead, additional elements are created to represent the requested HAZ. These elements are organized in the ^conn_imprint component, and can later be used for a manual imprint after they have been manipulated to your needs. This option can be helpful when working with more complex areas, where the standard imprint functionality fails, for example, conflicting connectors.
imprint/no HAZ
Creates quad weld elements, and stitches them to both links by adjusting their mesh. Mesh modifications are as minimal as possible, and no HAZ are performed.
none
Creates quad weld elements only. Quad weld elements will not be attached to the links. The connection will need further attention.

HAZ Info

The HAZ Info settings define the lengths of the different heat affected zones (HAZ), which are dependent on the HAZ lengths for T, L and B, defined in the Realization Details parameters. The HAZ length settings vary depending on the defined weld shapes (vertical, angled, vertical and angled, caps).
HAZ Scheme
Choose a dimensioning scheme for the HAZ lengths of T, L, and B.
input
Enables you to decide if the HAZ lengths should be defined individually, or if all HAZ lengths are determined using the same approach (same as all).
weldsize dependent
Only available if weldsize dependent has been chosen for the Dimensioning Scheme, as well.
HAZ Lengths
same as all
Assigns the same length to all HAZ lengths.
individual
Assign HAZ lengths individually.
Assign HAZ lengths individually
The following options are available in the various HAZ length settings.
input
Requires a discrete value be specified for the length.
average meshsize
Length is dependent on the average mesh size in the local area where the imprint is performed.
by thickness
Sets the length to the same value as the thickness of the link getting the HAZ.
LTH
Horizontal length for T connections, which is the length between the foot points of the vertical and angled part of a seam.
LLH
Horizontal length for L connections, which is the length between the foot points of the vertical and angled part of a seam.
LB
Butt weld length.
skip HAZ
Skips individual HAZ that are not required.
same as positive side
Assigns the same length as the positive side to the negative side.
wh or wh/2
Length is dependent on the horizontal weld size. Only available when HAZ Scheme is set to weldsize dependent.
wv or wv/2
Length is dependent on the vertical weld size. Only available when HAZ Scheme is set to weldsize dependent.
wb or wb/2
Length is dependent on the butt weld size. Only available when HAZ Scheme is set to weldsize dependent.
LTVedge

Choose between skip HAZ and LTVedge. Only available for the HAZTvedge length.

HAZ Length Factor (Avg. Meshsize/Thickness)
Factor that increases or decreases the HAZ lengths, which have been defined using the average meshsize or by thickness length options.
Max HAZ Length
Maximum length for all HAZ lengths. If the HAZ length is greater than this value, then the Max HAZ Length is used.
Dimensioning and Heat Affected Zones (HAZ):
Dimensioning T


Figure 16. Dimensioning T


Figure 17. Vertical T Weld HAZ


Figure 18. Angled T Weld HAZ


Figure 19. Vertical and Angled T Weld HAZ
Dimensioning L


Figure 20. Dimensioning L


Figure 21. Vertical L Weld HAZ


Figure 22. Angled L Weld HAZ


Figure 23. Vertical and Angled L Weld HAZ
Dimensioning B


Figure 24. Dimensioning B


Figure 25. Straight B Weld HAZ

Property and Material Info

The Property and Material Info settings define the properties and materials of the welds and the heat affected zones (HAZ).
HAZ Organize Scheme
Choose a HAZ organize scheme:
inherit property
Inherits the elements of the HAZ from the links in which the HAZ elements are imprinted.
general property
Assigns the same HAZ property throughout one link, or throughout all links.
Use the subsequent options to define how the properties are determined.
individual property
Assigns individual properties to each HAZ.
HAZ Component Option
stay in original
Keeps HAZ elements in the component they were imprinted into. No additional properties get created.
new component per original one
Creates a new component for each component that gets a HAZ imprinted. The direct property assignment setting is ignored when this option is selected.
HAZ Property Option
The options available are dependent on the HAZ Organize Scheme selected.
assign original property
Assigns the same property that was assigned to the original components to new components.
assign duplicated property
Duplicates the original properties and assigns them to new components.
select
Select a property from the current model via the Select Property For HAZ option. Unless direct property assignment is activated, a component named ltb_rigid_quad_haz_ with the property ID as a postfix is created.
same as original
Assigns HAZ elements the same property as the original. No further properties are created. HAZ elements are organized into components named ltb_rigid_quad_haz_ with the property ID as postfix.
scaled original thickness
Creates a new property and component for each link that has a HAZ imprinted.
The property is a copy of the original. Properties are named as ltb_rigid_quad_haz_<linkname>_<scaled thickness>, and components are named the same as the properties.
In addition, you can define the following:
HAZ thickness factor
Enables you to enter a factor to scale the thickness.
HAZ Property Grouping
Groups properties in order to reduce the amount of properties created.
do not group
Prevents grouping.
group same thickness
Groups HAZ elements with the same thickness into one property and component. HAZ elements of T, L, and B welds are also grouped together if they have the same thickness.
Properties are named ltb_rigid_quad_haz_<scaled thickness> or ltb_rigid_quad_haz_<property ID>, and components use the same name as properties.
group same thickness within T, L, and B
Groups all HAZ elements with the same thickness into one property and component, as long as they have the same weld type of T, L, B.
Properties are named ltb_rigid_quad_<t or l or b>_<thickness>, and components use the same name as properties.
input thickness
Creates a new property and component for each link that has a HAZ imprinted.
The property is a copy of the original. Properties are named ltb_rigid_quad_haz_<linkname>_<scaled thickness>, and components are named the same as the properties.
In addition, you can define the following:
HAZ thickness
Enables you to enter a factor for thickness.
HAZ Property Grouping
Groups properties in order to reduce the amount of properties created.
do not group
Prevents grouping.
group same thickness
groups all HAZ elements with the same thickness into one property and component. HAZ elements of T, L, and B welds are also grouped together if they have the same thickness.
Properties are named as ltb_rigid_quad_haz_<scaled thickness> or ltb_rigid_quad_haz_<property ID>, and components use the same name as properties.
group same thickness
Within T, L, and B groups all HAZ elements with the same thickness into one property and component as long as they have the same weld type of T, L, B.
Properties are named as ltb_rigid_quad_<t or l or b>_<thickness>, and components use the same name as properties.
same as positive side
Guarantees the HAZ on the positive and negative side of the T or L weld are assigned the same property.
same as the other size
Guarantees the HAZ on both sides of the B weld are assigned the same property.
Direct Property Assignment
When activated, additional components will not be created, and created or selected properties will be directly assigned to individual weld or HAZ elements.
Used for HAZ and weld property assignment.

Behavior

B/L classification angle
Angle that is automatically determined for each individual seam connector, whether it is to be considered a butt weld or a lap weld. Default is set to 10.0°.
If the angle of the two links is smaller than the B/L classification angle, then it will be considered a butt weld and a lap weld; a further check determines whether the links overlap. If the links do not overlap, a butt-weld is performed.
L/T classification angle
Angle that is automatically determined for each individual seam connector, whether it is to be considered a lap weld or a t-weld. Default is set to 10.0°.
Angle Direction
Defines which side the angled weld elements are created.
connector side
Angled weld elements are created on the side where the connector is located, as long as the connector is not perfectly on the free edge.
If the connector is on the free edge, the edge quad normal option will be automatically used.
positive side/negative side
The positive and negative side can be determined as long as the links are not perfectly perpendicular to each other.


Figure 26. . Overview of how the positive and negative side is determined. When links are perfectly perpendicular, the edge quad normal option is automatically used.
edge quad normal
Figure 27. . Overview of how the side for the angled weld is determined. If the normal directions are reversed, the side of the angled weld changes.


Snapping To Edge
Automatic edge snapping can be used to precisely position connectors. First, the connector snaps to, for example, the closest free edge, then the projection and FE creation starts.
The snapping distance can be defined separately for T, L and B connections.
You can choose whether to snap to:
  • maximum 1 element row
  • maximum 2 element rows
  • no (connector does not snap)


Figure 28. Original Model before Realization. Initial situation with one element row marked for the lap weld and two element rows for the t weld.


Figure 29. Edge Snapping Enabled


Figure 30. Edge Snapping Disabled
 
Edge Treatment (T/B)
The Edge Treatment(T/B) setting attempts to create specific vertical lengths for T connections LTV, and specific lengths for B connections LB.


Figure 31. Original Model before Realization


Figure 32. Realization using Edge Treatment. Free edges were contracted or extended.
Edge Treatment Options
Choose whether to:
  • extension and contraction
  • extension
  • contraction
Edge Treatment Limit
Edge treatment is a pure node movement; therefore, the maximum movement needs to be limited to prevent the elements at the edge from being destroyed. Movement is limited to a maximum of 0.5 times the element size at the edge. 0.5 is the maximum allowed value and default value.
Preserve Washer
Controls how washers are preserved during the seam imprint realization.


Figure 33. Original Mode with Perfectly Meshed Washers


Figure 34. No Washer Preservation Enabled. Washers have been opened.


Figure 35. Washer Preservation and Remesh Enabled. Washers are still intact, but the mesh seeding has been modified.


Figure 36. Washer Preservation and No Remesh Enabled. The washers have been fully preserved.
Don't Share Zone Elements
Seam imprint allows heat affected zones (HAZ) to be merged in close areas. In this situation, one element might touch the weld elements from two different connectors. Don't share zone elements prevents zone elements from being shared.
Quad in Corner
Controls whether a single or double element is created in corners of quad seam connectors with a certain vertex.
A angle must be defined for a single quad corner. If the corner angle is greater than the defined angle, a double quad corner is created.


Figure 37. Quad in Corner. A double quad corner is shown on the right, and a single quad corner is shown on the left.
Quad Control
Controls the maximum deviation from the perfect quad element for the heat affected zone (HAZ). It can be controlled, if the element size or the element skew is more important to retain.
Max Quadsize Reduction In % / Max Quad Skew In Degrees


Figure 38. Max Quad Size Reduction: 80.0 / Max Quad Skew: 5.0


Figure 39. Max Quad Size Reduction: 5.0 / Max Quad Skew: 45.0
Sliver Elements
Sliver elements are small elements that you may not want in your model. In the images below, a perfect perpendicular projection resulted in sliver elements. The Sliver Elements setting can be used to manage sliver elements in your model. In the images below, the red elements represent the HAZ elements.


Figure 40. Allow


Figure 41. Prevent by Moving Projection Points


Figure 42. Prevent by Moving Edge


Figure 43. Delete Sliver Elements
Element length<
This length controls which elements to treat as sliver elements.
Feature Angle
Determines important features to retain during the imprint. Features that cross the HAZ, as well as near by features cannot be retained.
Seam Test Point Alignment
A global option. If the seam connectors are close by activating “Seam test Points Alignment” option in connector entity editor, the test point alignment is based on the proximity of other connectors to get better mesh flow. It also ensures the cross-over connector should have a common test point, so that unique nodes will be created.
Seam Loose Ends
A local option set on individual connectors. Enabling “Seam Test Points Alignment” will also enable this option, which allows for the alignment of start and end points of seam connectors along with alignment of other test points.
Seam Fixed
A local option set on individual connectors. Enabling the “Seam Fixed” option considers all the test points of seam connectors as fixed and will not be disturbed.
Seam Consider Feature and Boundaries
A local option set on individual connectors. Enabling the "Seam Consider Feature and Boundaries" option will adjust test points so the projections fall on features/boundaries wherever possible. Overhanging test points will be trimmed.