4_Torsional analysis(spot weld flange)

Torsional analysis is a very important aspect of structural and mechanical engineering.

The main purpose of this analysis is to understand and predict how a structure or mechanical part will 

respond to a torsional force or torque.

 

In this example, compare the torsional stiffness and rotation angle of a shell element with node sharing versus spot welding.

 

Boundary condition

 

E = 207GPa,

v = 0.327

T = 250 kNmm

If closed section beam.

where $T$ is the torsional moment, $G$ is the shear modulus, ${J_{EFF}}$ is the polar moment of inertia, $\tau $ is the shear stress.

 

and if p=80mm (weld pitch)

 

 

Run HyperMesh and drow lines

 

Create - Materials

E : 207000

NU : 0.327

Materials

 

Create - Properties

Card Image : PSHELL

Material : (1) material1

T : 1

Properties

 

Assigning a property to a component.

 

Geom - Surfaces - Drag along Vector

direction : x-axis

distance : 500

Drag + 

 

2D - automesh - surfs

Select all planes

element size : 4

mesh type : quads

 

When done creating the mesh, specify the nodes want to share.

Tool - edges

Change from comps to elems.

tolorance : 0.1

Select 4 elements 40mm from the right, then select elements 80mm apart.

Select the same for the back for symmetry.

 

Click preview equiv

Pressing equivalenced will share the node.

 

Create - Load Collector

name : spc

BCs - create - constraints

Check all dof and select left node

spc

 

Create - Load Collector

name : moment

1D - rigids

Set calculate node

elem types : RBE2

Select all nodes on the right

 

BCs - Create - Moments

Select the created RBE2 element.

magnitude : -250000

direction : x-axis

 

 

Create - Load Steps

Analysis type : Linear Static

SPC : (1) spc

LOAD : (2) moment

Load Step

Check the displacement of the OUTPUT

FORMAT : H3D

ROTATIONS : ROTA(Output the rotational displacement result)

 

Analysis - OptiStruct

 

node sharing

 

The maximum rotational displacement in the x direction is -5.891e-3 rad.

The error from the theoretical value was about 5.0%, which was larger than I expected.

 

To do a spot weld, set the same except for node sharing.

Create - component

name : upper

tool - organize - collectors

 

select elemtns

dest component : upper

copy and return

 

Create - component

name : lower

tool - organize - collectors

select elemtnes

dest component : lower

copy and return

 

Sharing nodes with existing components and components created using equivalence.

 

upper

lower

 

Create - three Properties

name : upper, lower and pweld

upper and lower

 

pweld

 

Create - Component

name : spot_weld

Assigning a property to a component.

 

1D - spotweld

using elems

select upper and lower element

element config : rod

property : pweld

weld location : select upper and lower node

search tolerance : 0.1

Create - return

 

Analysis - Optistruct

 

spotweld

 

The maximum rotational displacement in the x direction is -6.639e-3 rad.

The error from the theoretical value was about 7.0%

	ground truth	node sharing	spot weld
Rotation(x)	-6.205	-5.891 (5%)	-6.639 (7%)