Week 4-1D Element Creation Challenge

AIM: To study and create 1D element on the given component.

OBJECTIVE: To Mesh the Given component with the Size of 5 Units. Create 1D elements on the following component with given cross-section and DOF.

a. Rod element:- Translational DOF should be Constrained with RBE2 link

Cross-Section: BOX- Dimension a= 12 mm

dimension b=10 mm

Thickness t= 0.75 mm

b. Beam element:- All DOF should be constrained with RBE3 link

Cross-Section: I Section- Dimension a= 8 mm

Dimension b= 10 mm

Dimension c= 8.5 mm

Thickness t1= 0.75 mm

Thickness t2= .6 mm

Thickness t3= .6 mm

c. Bar element:- Constrain only x and y DOFs With RBE3 link

Cross-section: X section- Dimension DIM1= 5 mm

Thickness DIM2= 1.2 mm

Dimension DIM3= 10 mm

Thickness DIM4= 1.2mm

d. & e. Apply the mass of magnitude 10 with the RBE2 link

f. Join the two components with Spring elements

INTRODUCTION:

1D elements are used for modeling line-type members such as columns, piers, beams or poles. 2D elements are commonly used for plate-type members such as walls, slabs, shells, bridge abutments, tanks, domes. 3D elements are used for structure with complex geometry which cannot be simplified for analysis.

While working with 1D elements we come across the following element types:

• CROD
• CBAR
• CBEAM

CROD:

• CROD elements support (allow) tension and compression only. Also in certain softwares used for rotational as well but also limited.
• The nodes of a CROD element only have translation degrees of freedom (still this element has a torsional stiffness).

CBAR:

• CBARS elements support (allow) tension, compression and bending as well.
• A CBAR element is a kind of simplified CBEAM element and should be used whenever the cross-section of the structure and its properties is constant and symmetrical.
• The CBAR element requires that its shear center and the neutral axis coincide. Due to this requirement CBAR elements are not useful for modeling structures that may warp, such as open channel-sections.

CBEAM:

• CBEAMS elements support (allow) tension, compression and bending as well.
• CBEAM elements are used to model more “complicated” geometries with varying cross-sections.
• In CBEAM elements the neutral axis and shear center are non-coincident.

Apart from above 1D Elements, there are different types of 1D Elements used to connect the nodes, which are called Rigid Links.

• RBE2
• RBE3

RBE2:

• RBE2/Rigids are 1D elements has infinite stiffness and the nodes will not move at all.
• In RBE2 links the applied load will be distributed equally irrespective of their position and distance from the node to each and every element.

RBE3:

• RBE3 elements, on the other hand, serve to distribute loads without inducing unwanted stiffness. It is not an element to be used to model a connection, but rather an element to induce a motion in a node as a function of the weighted average of other nodes.
• RBE3 elements are similar to RBE2 with the only changes being the reversal of the Independent and Dependant nodes and the addition of a weight field.

PROCEDURE:

• Lets first import the model, and then need delete the unwanted lines and give autocleanup.

• Then, need to extract mid surface for that go to Geo>midsurface>auto midsurface>auto exctraction(surfs)>exctraction options and set it to offset+planes >go to auto exctraction and select the surface where the mid surface to be created and exctract.
• And rename the middle surface as Bracket_1 and create a new component as Bracket_2 and then create a mid surface for lower bracket.

• Then, go to delete(X) which is available on the menu or go to Tool>delete>set to solids >select solids from the model>delete entity.

• then, hide the components which are not required and then go to Geo> quick edit>washer split (set offset value as 5mm)>select the circles on the surface to create washer split which will helps in creating finer mesh.

• Go to Tool>Organize>collectors>surfs>dest component as Bracket_2>select the lower srface>Move.
• Then, delete the middle surface from the component which is not required.
• And also create the components and properties for Bracket_1, Bracket_2, Rod, Beam and Bar individually. And assign with proper image cards, material, and Beam sections.

• Go to 2D>AutoMesh>Surfs>element size as 5mm>mesh.

• Next, we are going to create links as given and for that go to 1D>Rigids (for Rbe2 links)>select multiple nodes and nodes by path option>click on the circle in a direction.
• for a. Rod element:- Translational DOF should be Constrained with RBE2 link.
• for b. Beam element:- All DOF should be constrained with RBE3 link.
• for c. Bar element:- Constrain only x and y DOFs With RBE3 link.
• for d & e Apply the mass of magnitude 10 with the RBE2 link.
• and for f Join the two components with Spring elements.

• After creating the Rbe2 and Rbe3 links we are going to create the cross sections of the beams, rod and bar, for that go to 1D>HyperBeam>standard section>standard section library (HYPERBEAM) and Standard section type(thinwalled box)>create.

• we can create different cross sections in the HyperBeam only as shown below.

• To create the links for rod, beam, and bar, go to 1D>rods>select the nodes between where the link to created and set the property and element types with respective ones.

• Now, for bar and beam go to 1D>bars>elect the nodes between where the link to created and set the property and element types with respective ones.
• for Beam.

• For Bar.

• For springs.

• Now for the cross sectional view, on the menu bar go to select from list in that select 1D traditional and detailed element representation.
• And at d and e to apply mass of magnitude10 with Rbe2 link.

CONCLUSION:

• Through this challenge I have learnt about how to exctract the midsurface and how to create rods, bars and beams.
• and also about RBE2 links, RBE3 links and springs and got an Idea about 1D element.
• And learnt to use some of the new commands in the HyperMesh tool like HyperBeam, Midsurface, Organize, RODs, BARS, rigids, Rbe3, springs, masses.

CONCLUSION:

• Through this challenge I have learnt about how to exctract the midsurface and how to create rods, bars and beams.
• and also about RBE2 links, RBE3 links and springs and got an Idea about 1D element.
• And learnt to use some of the new commands in the HyperMesh tool like HyperBeam, Midsurface, Organize, RODs, BARS, rigids, Rbe3, springs, masses.