Template in NLFE Belt - Pulley Subsystem

Davide_21943

Hi,

I have some problems to understand how the template works in the subsystem Belt - Pulley, available in MotionView. 

Reference: https://2021.help.altair.com/2021/hwdesktop/mv/topics/motionview/subsystems_belt_pulley_create_t.htm

First of all, why all ID are equal to 0? 

In the template there are entities that are not defined in the model, for example it's written

  <LINE2  id="4"  pid="5"  g1="43"  g2="{b_Belt.pt0.idstring}" />

There is not "b_Belt" body because the variable name for the belt is "ldb_belt". Check the screenshot uploaded. 

I need to understand how the template is written because I'd like to create nodes at the periphery of a NLFE body, since the beam element has just nodes at the center line and it's very limiting. 

Praful

Hello Davide

For the NLFE Belt Pulley system, the interaction between the belt and the pulley is defined through the Template

as additional cards that go into the NLFE xml solver deck.

On any model, the ids will appear as 0 before a Check Model is done, as the id assignment happens through the Check Model. Once a Check Model is performed, non-zero ids should appear.

Regarding variable name "b_belt" in the template:  A template in MotionView works similar to a System, where an entity external to the system can be passed as an attachment. It is similar to the programming concept of how functions/procedure works where a local variable is defined within the function and arguments are passed while calling the function. the local variables then take the value of the argument being passed.

In case of this Template, ldb_belt (with label NLFEBelt) is being passed as an attachment to the template definition and the attachment variable name is b_belt.

 

Regarding your need to create peripheral nodes, could you please elaborate more on what exactly you are trying to accomplish ? The beam elements take only 2 nodes. You may add nodes on the peripher, but they will not be associated with the beam element unless connected via other elements.

though it is highly recommended not to edit this template, as there is risk of breaking the working of this system, you may add GRID cards or any other NLFE statements in this template such that it does not conflict with the rest of the NLFE model.

Regards

Praful

 

 

Davide_21943

Hello Praful, thank you for the reply.

I got it for the belt but what about the other elements? It seems that in the template there are different entities. For example the line:

  <LINE2  id="4"  pid="5"  g1="43"  g2="{b_Belt.pt0.idstring}" />

It's creating a spring-damper element between grid1 and grid2. Grid2 is referred to a point called pt0 but in the model there is no such point.

 

Regarding my objective, I'd like to simulate a pieace of paper (banknote) that is dragged by a roller. Since the non linearity nature of the problem, I thought to model the banknote with a BEAM NLFE element. The problem is that I have nodes just on the center line and it is very limiting. 
For example I can't apply a Force in other points and It's very hard to model the contact with the roller. So I was thinking to create nodes all over the surface of the banknote with a Template, but I don't know if it is possible, if it makes sense or what strategies I can use. 

I would really appreciate your help. 

Praful

Davide_21943 said:

Hello Praful, thank you for the reply.

I got it for the belt but what about the other elements? It seems that in the template there are different entities. For example the line:

  <LINE2  id="4"  pid="5"  g1="43"  g2="{b_Belt.pt0.idstring}" />

It's creating a spring-damper element between grid1 and grid2. Grid2 is referred to a point called pt0 but in the model there is no such point.

 

Regarding my objective, I'd like to simulate a pieace of paper (banknote) that is dragged by a roller. Since the non linearity nature of the problem, I thought to model the banknote with a BEAM NLFE element. The problem is that I have nodes just on the center line and it is very limiting. 
For example I can't apply a Force in other points and It's very hard to model the contact with the roller. So I was thinking to create nodes all over the surface of the banknote with a Template, but I don't know if it is possible, if it makes sense or what strategies I can use. 

I would really appreciate your help. 

Hi Davide

Grid2 is referred to a point called pt0 but in the model there is no such point.

As you can see, pt0 is part of the expression b_Belt.pt0.idstring.  the pt0 here is an attribute of b_Belt. The points that are used to define the NLFE Body can be accessed through these attributes such as pt0, pt1 etc.. So pt0 in the expression refers to the first point used in the NLFE body connectivity.

Modeling the paper behavior is quite challenging. the beam element would not suffice to model its flexibilty completely. A Beam element is a good start initially, you should be able to model bending in the longitudinal direction.

An increased model fidility would be required by representing the paper as quad elements, which at the moment is not directly supported by MotionView interface. With a bit of efforts it would be possible though to create these quad elements in a Template through some form of programming.

Regards

Praful

Davide_21943

Praful Prabhu_20784 said:

Hi Davide

Grid2 is referred to a point called pt0 but in the model there is no such point.

As you can see, pt0 is part of the expression b_Belt.pt0.idstring.  the pt0 here is an attribute of b_Belt. The points that are used to define the NLFE Body can be accessed through these attributes such as pt0, pt1 etc.. So pt0 in the expression refers to the first point used in the NLFE body connectivity.

Modeling the paper behavior is quite challenging. the beam element would not suffice to model its flexibilty completely. A Beam element is a good start initially, you should be able to model bending in the longitudinal direction.

An increased model fidility would be required by representing the paper as quad elements, which at the moment is not directly supported by MotionView interface. With a bit of efforts it would be possible though to create these quad elements in a Template through some form of programming.

Regards

Praful

Hi ppraf,

can you tell me where I can find information about the template syntax?

For example, you explained me that body.pt0 is referred to the first point of the body. Where can I find such information?

I need to understand how a template is built.

Thanks in advance

Praful

Davide_21943 said:

Hi ppraf,

can you tell me where I can find information about the template syntax?

For example, you explained me that body.pt0 is referred to the first point of the body. Where can I find such information?

I need to understand how a template is built.

Thanks in advance

Hi Davide -

There are some sparse information related to Templates. You can find them at

Templates panel, *Template and *DefineTemplate

In general, Template is a text processing entity. Underneath, it uses a math and text processor called Templex, which is part of Hyperworks.

I have put in some slides with more information on how templates can be used. (see attached pdf)

Regarding you explained me that body.pt0 is referred to the first point of the body. Where can I find such information?

Each entity has properties. The information of each of the properties available for an entity can be seen in an expression builder. You may invoke the expression builder from any panel (make sure you don't change the expression if not intended to) to review the properties.

e.g.

In case of NLFE body, the points used to define the NLFE appear as attributes pt0, pt1 and so on. The numbers depend on number of points used to define the NLFE body. If the points in the connectivity is changed, then references of pt0, pt1 etc.. automatically change as they are parametric reference.

Hope this clarifies. If you have further doubts, please reach me at ppraf@altair.com

Regards

praful