Creating Contact surface on glass

[Krishnakumar Sankar]

Hi
Could anyone suggest me how to create a contact surface for glass since Im working on evaluating forces on holding a glass.For ball I created contact sphere in the shape of the ball.But for glass,the contact surface is sphere shaped.Any solution for this?

Thank you

[Thomas Uchida]

You could use an ElasticFoundationForce (https://simtk.org/api_docs/opensim/api_ ... Force.html) if you have a mesh of the object—though you might also want to carefully consider how you would validate such a simulation.

[Krishnakumar Sankar]

Thank you sir..
Also I had an idea of Creating multiple contact spheres on the glass where the finger segments will come in contact with . through Hunt Crossley forcewill it work ?.

[Thomas Uchida]

Also I had an idea of Creating multiple contact spheres on the glass where the finger segments will come in contact with . through Hunt Crossley forcewill it work ?

Yes, that may work as well, depending on how precisely you need to model the shape of the object.

[Krishnakumar Sankar]

Ok Sir.Thank you

[Krishnakumar Sankar]

depending on how precisely you need to model the shape of the object

.

Img 1.JPG (27.58 KiB) Viewed 2610 times

This is how I created contact spheres sir. on the glass surface sir. Could you provide feedbacks on this

[Thomas Uchida]

Could you provide feedbacks on this

It looks like your simulation results might be sensitive to the arbitrary positioning of the contact spheres. The parameters you use for the contact model may be another source of uncertainty, so the results you get may not be realistic. You might want to look at the following paper for some ideas on designing and validating your model:

Hicks, J.L., Uchida, T.K., Seth, A., Rajagopal, A., Delp, S.L. Is my model good enough? Best practices for verification and validation of musculoskeletal models and simulations of movement. ASME Journal of Biomechanical Engineering 137(2):020905, 2015. http://nmbl.stanford.edu/publications/pdf/Hicks2015.pdf

[Krishnakumar Sankar]

arbitrary positioning of the contact spheres

The spheres in the glass come exactly in contact with the spheres of the finger segments

Image.tiff (440.65 KiB) Viewed 2589 times

The parameters you use for the contact model may be another source of uncertainty

Previously for working on grip activity of a ball, I had used Hunt crosseley methodology.In order to maintain uniformity in determining joint moments of fingers when dealing with objects of different shapes, I used the same methodology for glass (the material property was same as that of ball) thereby concentrating only the shape of the objects.

[jimmy d]

The spheres in the glass come exactly in contact with the spheres of the finger segments

They are arbitrary. Doesn't matter that they come into contact exactly. You have chosen an arbitrary number of points and arbitrarily placed them. If you add or reduce the number of points, or change their position, you will generate different forces and moments.

Previously for working on grip activity of a ball, I had used Hunt Crossley methodology.To maintain uniformity in determining joint moments of fingers when dealing with objects of different shapes, I used the same methodology for glass (the material property was same as that of ball) thereby concentrating only the shape of the objects.

It is great that you are consistent across the models, but that doesn't address if the parameters for your contact elements have uncertainty or not.

Please read the paper Tom suggested. You will need to figure out how to validate your model and simulations.