Some attempts at engineering problems with Prepromax!

[xupeiwust]

I got a message that it is said that Pardiso MKL after 2019 cannot be used. It was available before. When was your solver compiled?

[xupeiwust]

@SergioP1975

I try yesterday to mesh your part using shell elements, and the same as you, lot of error with the negative Jacobian element´s. I look at the bellows, and it doesn´t seems to be modeled with constant thikness, if you look in the interior side, you’ll see some radius are omitted. Also, in the exterior side, some radius are too small, they must be higher than thikness of the part. Another point is that there are some surfaces not well generated, even in the straight zones of the tube.
I would improve the CAD modeling before meshing (lot of human time), and as free mesh will lead to
lot of element, swithc to some structured mesh in Salome. Or as you did, use the best tet mesh with the actual part (lot of cpu time).

Indeed, but I think the bellows should be a constant thickness, it may be caused by an incorrect cad model, thank you for your attempt.

[FEAnalyst]

@xupeiwust

Also is there a value for logarithmic strain in prepomax?

Good question. PrePoMax uses the default strain measure available as output in CalculiX. Here’s a quote from CalculiX’s documentation:

As basic measure of strain in CalculiX the Lagrangian strain tensor E is used for elastic media, the Eulerian strain tensor e is used for deformation plasticity and the deviatoric elastic left Cauchy-Green tensor is used for incremental plasticity.

In PrePoMax, apart from the standard E strain output, you can also request the output of plastic strain PE.

[ANYS]

Hi xupeiwust,

As a fast check I have request the first 4 vibrating modes and:

-Tri6 elements and Pardiso out of core ccx_MKL.exe Solved ok. Total CalculiX Time: 1013.850340s

-TRI3 elements and ccx_dynamic.exe v2.19 Pastix (Mixed precision =1) Solved ok.

-Tri6 gives me a memory error, but I only have 16Gb (and I have been working on other things while running the analysis).

The issue with your model is the thickness of the bellows. Many elements had negative Jacobian due to crossing nodes and bad shapes in the plies.

In pipping industry , bellows are normally thinner than the pipe and made of higher strength material to allow smaller thicknesses.

I don’t think your bellow could even be fabricated or be flexible enough to do its job. I have considered 0.3mm thickness for them as a first try and the system solved straight forward.

I would simplify the clamps by a simple BC. They represent a lot of elements without too much contribution to the system analysis.

By other hand , if you are mainly interested in stresses, As I comment, I would not start my model shape with the bellows already stretched. That means you remove any preexisting Stress.

[xupeiwust]

@ANYS

As a fast check I have request the first 4 vibrating modes and:

-Tri6 elements and Pardiso out of core ccx_MKL.exe Solved ok. Total CalculiX Time: 1013.850340s

-TRI3 elements and ccx_dynamic.exe v2.19 Pastix (Mixed precision =1) Solved ok.

-Tri6 gives me a memory error, but I only have 16Gb (and I have been working on other things while running the analysis).

The issue with your model is the thickness of the bellows. Many elements had negative Jacobian due to crossing nodes and bad shapes in the plies.

In pipping industry , bellows are normally thinner than the pipe and made of higher strength material to allow smaller thicknesses.

I don’t think your bellow could even be fabricated or be flexible enough to do its job. I have considered 0.3mm thickness for them as a first try and the system solved straight forward.

I would simplify the clamps by a simple BC. They represent a lot of elements without too much contribution to the system analysis.

By other hand , if you are mainly interested in stresses, As I comment, I would not start my model shape with the bellows already stretched. That means you remove any preexisting Stress.

Thank you for your attempt. In fact, the CAD model sent by the designer has so many problems. I deal with model processing for a long time. Your results are very beautiful

[xupeiwust]

abaqus.zip (3.4 MB)
Unsupported s3r cell caused problems with importing inp files, it should be easy to fix
Also does calculix support pyramid cells?
Or the import of tetrahedral and hexahedral hybrid models?

[FdoLorenzo]

You need to copy the entire set into the Solver folder in your system, and then either rename the cxx_dynamic.exe to cxx_static.exe, or point to the pardiso solver in settings:

[Matej]

@xupeiwust

Also does calculix support pyramid cells?
Or the import of tetrahedral and hexahedral hybrid models?

Calculix only support triangular pyramids - tetrahedrons. Then it supports triangular prisms - wedges and quadrilateral prisms - hexahedrons. And mixed meshes are also supported.

[Matej]

@xupeiwust

Unsupported s3r cell caused problems with importing inp files, it should be easy to fix

According to the Abaqus documentation: Abaqus

Both S3 and S3R refer to the same 3-node triangular shell element.

So I will add support for reading S3R elements but in the meantime you can change the S3R name in the .inp file to the S3 name and PrePoMax should normally import the mesh.

[xupeiwust]

strong text
good job