## General Mechanical

#### Compression test using force…DOF…Why?

• Catacaldos
Subscriber

Hi everyone

I´m trying to do a compression test using Static Structural. I want to make it as real as possible, so I´m using two rectangular elements that carry out the compression and between them I have placed the piece to be compressed. This piece is oval.

When I simulate the test, applying the desired force, I get the error that I put in the attached image. It refers to the upper piece. I have done this same test with four guides and including frictionless, but the oval shape of the center piece balances the top piece and energy is lost in the guides, which does not directly affect the oval piece. The lower part is fixed support.

I have also tried to include a Displacement, where I indicate that it only moves in the direction of compression (in this case X = Free, Y = 0; Z = 0), but it gives me the same error. And if I indicate it to move a distance in X, it "forgets" the force and only moves the distance that I indicated.

I just want the upper part to lower the desired force on the X axis without any friction or deflection on other axes, and that the central oval piece is crushed as the upper part falls. What can I be failing? Should I use some different support?

Thank you very much in advance.

• peteroznewman
Subscriber

ANSYS Staff are not permitted to open attachments, so please Insert images directly into your post. I have done that below for you.

The model will converge more easily using displacement of the top plate.  You can delete the cylinder and just apply displacement to the square face. Make the displacement 0 in Y and Z so the plate does not go sideways.

To know the force squeezing the oval object, add a Probe under the Solution branch for the Reaction Force of the Displacement (or Fixed Support). You will get a chart of Force vs Time. You can also plot the Displacement of the top part and you will get a chart of Displacement vs Time. You can use those two tables to make a chart of Force vs Displacement.

Under Analysis Settings, you have to turn on Auto Time Stepping and set the Initial Substeps to 100 and Maximum Substeps to 100. You must turn on Large Deflection.

Under the Connections folder, insert a Contact Tool. Generate the Initial Contact Status. Are all the frictional contacts closed?  That is required to start the analysis.

• Catacaldos
Subscriber

Thank you!