# Hyperelastic Material Not Deforming Much

Member Posts: 2
edited October 2020

Hi everyone,

I am currently trying to model a single flexible robot arm. The arm deforms as pressure is being applied but even if more pressure is applied, the bending is the same. Below attach are my settings as well as my geometry as well as the end product I want to achieve.

P/S: I am using ANSYS Academic Student 2020 R2

I have been trying for a week and still couldnt get the result. I would be really grateful if you could help me out.

Sorry for the wrong end product. Below is the end result I want to achieve.

• Posts: 11,546Member

@hariprakash

The images you showed in your first post didn't disclose that you were using joints. Your model is supposed to simulate what you have in the real world. There is no joint in the real world. Delete the joints from your model.

I understand the goal is more pressure induces more bending. That is easily done with a different geometry shape such as this:

You have photographs of something that is bending, but the photo does not look like the geometry. I have circled what looks like a square cross-section, but your geometry shows a circle. I don't believe your geometry matches the physical prototype. Better photographs might convince me that you have accurate geometry in your model. Maybe you can take an X-ray or CT scan of your device and see what shape is on the inside.

• Posts: 11,546Member

A Google search of "unable to converge" on this site has 192 results.

• Posts: 11,546Member
• Posts: 11,546Member

If you want control over the labels on the axis, for example a zero label instead of 1e-6, then copy the Tabular Data out of Mechanical and paste into Excel where you have that kind of control.

• Posts: 11,546Member

@hariprakash When you pick a vertex, they are all equal.

When you pick an edge/curve, face/surface or body, then it computes those statistics for all the nodes on the scoped geometry.

• Posts: 11,546Member

@hariprakash The flexible rotation probe creates a pilot dependent node that follows the average motion of all the independent nodes. That means it adds no stiffness to the structure.

The proper way to use it is to select all the nodes on an end face.

The first time you tried it, you only picked a single node on a solid element, and a single node on a solid element has no rotational DOF so the angle output is always zero.

You can pick several faces, but then you are averaging the rotation of all those faces and the faces that don't rotate much will pull down the average from the faces that rotate a lot.

«1

• Posts: 11,546Member

You included a zip file with the image of the Final Result.

But you have a structure that doesn't have these side pockets that create the structure.

How do you expect to get the final result when the geometry doesn't have the features needed to create the final result?

• Posts: 18Member

I am sorry for including the wrong image. The post is updated with a new photo. What am trying to achieve is to bend my arm the way the image is shown. For now its bending but even if I increase the pressure, its not bending more

• Posts: 11,546Member
edited October 2020

@hariprakash You can't update the post with a new photo. In this new Forum, you can only edit for 1 hour, then the post is frozen. Attach the new photos in a new comment below.

• Posts: 18Member

here is the photo as requested. The problem i'm facing is that is bending the directing im applying pressure to. But the angle of curvature remains the same even more pressure is applied.

• Posts: 11,546Member

The cross-section geometry doesn't look like the photo. Next time you take a photo, try using a dark background. White on white is not easy to see.

• Posts: 18Member

I am sorry for the late reply Peter. I redid my simulation and almost got my answer but I would like to know if I can bridge pressure and joint rotation together. Below are the settings ive made. Properties i am using are

• Density - 1190kg/m^3
• Hyperelastic - Yeoh model

a. Contacts

b. Joints

c. Pressure

d. Joint rotation

e. Analysis settings

f. Result 1

g. Result 2

As you can see there are 3 chambers within the main chamber. My goal is to inflate one of the internal chamber with pressure and where size of inflation should be proportional to the amount of pressure fed and the arm should bend accordingly. As you can see from Result 1, there is bending but no inflation but when I suppress Joint in analysis settings, I get my inflation as in Result 2. How do i combine both where the bending is affected by the pressure applied in of the internal chambers.

• Posts: 18Member

Thank you Peter. I understand now. Guess ill check the real model and then try out.

• Posts: 18Member

Hi Peter @peteroznewman ,

Hope you are doing well. I am doing another new geometry using hyper elastic material. Single chamber, 2 chambers and 3 chambers. The bending of the 1 and 2 chambers are what i expected but for the 3 chambers, the model isnt solving. I just added extra one chamber for the 2 chamber model. The settings are the same just but still i couldnt get ANSYS to solve. As you can see, the bending isnt what im getting from 3 chambers. After all, i just added one more chamber from the 2 chamber model

1 chamber

2 chambers

3 chambers

• Posts: 18Member

Hope you are doing well. i tried again but still fail to solve in ANSYS.

Below are the images.

The difference between the two images are that the first one has no pressure in the last chamber (Chamber 3) and the second image has pressure in the last chamber (chamber 3). When there is no pressure, ANSYS able to solve it but when i include pressure in the 3rd chamber, ANSYS couldn't solve it. The error displayed was.

"The solver engine was unable to converge on a solution for the nonlinear problem as constrained"

The ANSYS i am using is ANSYS 2020R2 student version.

Hari Prakash Thanabalan

• Posts: 18Member

is it possible to get the bending angle in ansys for my structure?

• Posts: 18Member

Hi Peter. Hope you are fine. I am having a slight problem with my data.

Im just wondering, why is the position of my node in either X, Y or Z axis is extremely small. it starts with like e-06 m. How do i start my point from 0 and then displays the coordinates from there.

Thank you Peter

• Posts: 18Member
• Posts: 18Member

Hope you're doing ok. Just want to ask you. What is the min, max and average column in total deformation? where can detailed information about it?