[Newbie] Migration from Adams

[Dummy ME]

Hello everyone,

I was working in R&D at an engineering firm and was mostly working with MSC-ADAMS. I picked up a hobby/research project which involves rigid/flex modelling and simulating a compound bow. Since MSC-ADAMS is not viable financially or otherwise, I looked up a few solutions online and I landed here on this forum. (the other package I found was FreeDyn, which was closer to ADAMS, but I couldn't find proper documentation, especially for modelling contact/collision). 

I aim to find the output of the system consisting of a compound bow and an arrow. By output, I mean, the ejecting velocity, range, stress (if we take up a flex part) etc. 

I would try to break my questions into pointers, so it's easy to reply :

1. Is it possible to model a compound bow and arrow using this project? 
2. If yes, how steep is the learning curve for someone with basic python experience? (I do have experience with C++ but it has been a while, python is my go-to language for day-to-day programming.)
   
3. Can contacts be modelled fairly easily? (In ADAMS it was particularly very easy)
   
4. If I have a CAD ready, will it be useful or do I need to manually define all the bodies?
   
5. As my project might involve deformation in some elements, can flex body be modelled with pychrono? (I saw it being listed in Brief Introduction)
   
   1. Do we need to find free/open-source FE software or it could be handled by the library?
   2. How difficult would it be?
      

I would be really thankful if anyone could answer all or even a few of the queries. This module seems to be promising for learning anyway (project or not). Hoping to start learning.

Thanks again.
DM

[alessand...@unipr.it]

Hi

On 03/08/2022 02:13, Dummy ME wrote:

Hello everyone,

I was working in R&D at an engineering firm and was mostly working with MSC-ADAMS. I picked up a hobby/research project which involves rigid/flex modelling and simulating a compound bow. Since MSC-ADAMS is not viable financially or otherwise, I looked up a few solutions online and I landed here on this forum. (the other package I found was FreeDyn, which was closer to ADAMS, but I couldn't find proper documentation, especially for modelling contact/collision). 

I aim to find the output of the system consisting of a compound bow and an arrow. By output, I mean, the ejecting velocity, range, stress (if we take up a flex part) etc. 

I would try to break my questions into pointers, so it's easy to reply :

1. Is it possible to model a compound bow and arrow using this project?
   

you can model the flexible arms using one of the ChElementBeamXXXYY FEA classes, then you need to enable the PARDISO MKL module & solver for best precision.
If you optionally want to simulate hard unilateral frictional contacts (ex the contact between the arrow and the rest) then you need the ChSystemSNC, but nonsmooth formulation + FEA do not go hand by hand, except if you use the (quite experimental) ADMM solver in Chrono.

We also have the ChElementCable ANCF FEA elelment that you can use for simulating the strings. The problem I see here is that there is no "cam-vs-wire" constraint in Chrono, unless you use a full 3D contact between the cable elements and a 3D cam, that might be computationally challenging. A custom "cam-vs-wire" constraint would make things much easier.

1. If yes, how steep is the learning curve for someone with basic python experience? (I do have experience with C++ but it has been a while, python is my go-to language for day-to-day programming.)
   
2. Can contacts be modelled fairly easily? (In ADAMS it was particularly very easy)
   
3. If I have a CAD ready, will it be useful or do I need to manually define all the bodies?
   

There is the solidworks Add-In, but you would need to define the FEA elements programmatically - currently this add in can only translate rigid bodies.

1. As my project might involve deformation in some elements, can flex body be modelled with pychrono? (I saw it being listed in Brief Introduction)
   

yes

best regards

Alessandro Tasora

1. 1. Do we need to find free/open-source FE software or it could be handled by the library?
   2. How difficult would it be?
      

I would be really thankful if anyone could answer all or even a few of the queries. This module seems to be promising for learning anyway (project or not). Hoping to start learning.

Thanks again.
DM

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[dummifiedme]

Hi Alessandro,

Thanks for the reply.

As for the beam, I understand it would be possible to use FE elements and the module you mentioned.
But, I am more concerned about modelling the cable over the cam, especially when the cam profile is not essentially circular. I am willing to model the contacts in full 3D if that's the only thing that could possibly help.
I don't think modelling the arrow is very critical, I would just be needing an eject velocity/force.

I am attaching a picture of what I need to simulate of sorts. If you have some time, maybe you can suggest how I can go on with it. This is just a representation and the cam is not circular for my case.



The wrapped portion of the cable over cam seem difficult to me. I haven't ever solved FE without a GUI but I am willing to try it out.

Thanks :)

Regards.