# 3 point bending test on a beam

Member Posts: 1

Hello,

I am trying to simulate a 3 point bending test on a Beam with the following dimensions: L= 125 mm, W= 12.7 mm and T=3.2 mm.

the span length is 51.2 mm ( the distance between the 2 supports).

I took the advantage of symmetry and draw my geometry in space claim as following:

Here the length of the beam is 62.5mm.

Here I split the face for the support which is far 36.9 mm from the origin.

I am using the printed ABS orthotropic material properties as shown in the pictures, which is found in the literature.

I assigned the material to my geometry and created the mesh with element size of 2mm.

I applied the boundary conditions as remoted displacement at the top end of the beam where all components are zero except in y direction it is -15mm

also remote displacement at the support where all components are free except Y is zero. However, I applied frictionless support at each face to get solution for full model not only the symmetry part.

Here are the results I obtained. but these results are not the desired. Could you please assist me in finding out what is the mistake here?

is it a mesh problem or Boundary conditions? Also, I would like to confirm if solid rods are modeled as rollers instead of splitting the face, they will not affect the results right?

Thank you in advance.

Best Regards,

## Answers

• Posts: 11,378Member

I see the orthotropic material has lower stiffness in the Z direction, which I assume is the build direction. What direction was your beam built in? I expect it is the Y direction. That means the material orientation doesn't match the part orientation. A simple fix would be to swap the Y and Z values in Engineering Data.

Two elements through the thickness is not sufficient for a good resolution of stress values. Change the mesh method to sweep so that you can use large element edge lengths along the length and width, but set the number of sweep elements to 8.

Try replacing the Remote Displacements with Displacement BCs on the two edges.

What results are desired and why don't the results you obtained satisfy the desired results?

• Posts: 2Member

Hi Peter,

Thank you for your response.

Well I didn't print my beam yet, however I have the previous orthotropic material properties. My friend did the simulation using ansys APDL where he used 3 solid rods, 2 as supports and one as pusher and the support is far 20mm from the origin. he got the following results

Deformation in Y

Stress in X

Von misses Stress

I draw the geometry again and split the face 20 mm from origin and made a sweep mesh as u suggested. I applied Displacement as Boundary conditions. I want to match my results on workbench with Mechanical APDL. But unfortunately, I couldn't got the same results.

Here is the sweep method, however the generate the mesh with default element size

Here are the 2 Boundary conditions:

Here are the results I obtained which are different and there is a warning ( the deformation is large compared....)

Thank you in advance.

• Posts: 5Member

Hi,

In the model with solid rods used for bearing and pusher, how was the contact defined between the rod and the beam?

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