Principal Stress Trajectories

Hello Everyone,

I've been looking into deriving lines of principal stress on curved surfaces and have come across some really interesting stuff but I'm hoping to spark a discussion that might create a clearer picture of the processes involved. So far I've come accross:

- Odysseas's Principal Stress Grid

- Jon Mirtschin's post on importing FEA data from GSA to Grasshopper

- and Christina Doumpioti's thesis on The Adaptive Growth of Fibre Composite Structures

From these sources I gather one must:??

- use a finite element analysis program to determine the magnitude and directions of the principal stresses at all the mesh vertices

- then bring that data into grasshopper

- write a script that generates a vector field from the FEA data and interpolates a series of evenly distributed curves that follows the principal stress vectors

Would this be the most sensible way to go about this? I just want to make sure I have decent course of action laid out as my scripting/solid mechanics knowledge is rather limited so it's going to be quite the undertaking...lol

Any comments or reference suggestions would be greatly appreciated. Thanks kindly in advance for any and all help.

All the best,

Matt

www.mattschmid.com

Replies to This Discussion

Permalink Reply by Jon Mirtschin on April 22, 2013 at 1:33pm

Hi Matteo,

I haven't tried yet but I've no reason to think it shouldn't work in v8.6

On the GSA filter of my blog (http://geometrygym.blogspot.com/search/label/GSA) you can find this

http://ssi.wikidot.com/local--files/2011-blog-posts/110403%20mesh%2...

I'm pretty sure I've tested similar with Robot Structural Analysis, I can't recall if I've done it with SAP2000.

Let me know if it works or you see problems.

Cheers,

Jon

Permalink Reply by matteo on April 23, 2013 at 9:12am

hi Jon,

I have solved, thanks!

matteo

Permalink Reply by Vadim Shapiro on August 12, 2010 at 4:43pm

Matt, I wonder if you have seen the Scan&Solve Plug-in for Rhino we just released. You can download (for free) and view it in action at www.scan-and-solve.com

It will compute the magnitudes of the principal stresses for you ... but we have not done anything about the directions (at least not yet). It just has not been high on our priority list. Now I am wondering how many people out there are actually interested in this...

Anyway, try out the plug in and tell us what you think!

-Vadim

Permalink Reply by Matt Schmid on August 12, 2010 at 10:54pm

Hi Vadim,

Thanks very much, scan-and-solve looks like a really interesting plugin. I really like the idea of doing these things right inside rhino and without meshes. It would be great if there was some way to access the direction of the principal stresses in the material. I look forward to watching it develop!

Cheers,

Matt

Permalink Reply by Vadim Shapiro on August 12, 2010 at 11:11pm

Matt, give it a try. Right now, we do not have a utility to display vector fields of Rhino boundaries, but it sounds very doable. The problem is time of course. This whole beta experiment for us is to find out what people can do with this kind of plug-in and what kind of features they would like to have. So we started "Wish list" and "Solved by S&S" categories in the forum. Please post your suggestions! We depend on your feedback. Thank you.

-V

Permalink Reply by Odysseas Georgiou on August 31, 2010 at 2:53am

Hello all,

this is a very interesting discussion.
i've been doing some work on principal stress trajectories for my masters thesis. I 've extracted stress data from Robot structural using Robots' api. The problem is that robot only exports principal data at the center of each element and you might need to average the data at the nodes (if thats what you need), which is not a very straightforward process.

Robot can output the stress magnitude and the angle between the major P. stress direction and the major local axis of the each corresponding element. Concequently, there's some additional work to be done in GH in order to align the vector field with the mesh topology to be visualised.

Attachments:

PrincipalStressVectorsPerspective.jpg, 729 KB

Permalink Reply by Jon Mirtschin on August 31, 2010 at 3:12am

Hi Odysseas,

The routines I've added into the SSI plug-in effectively do as per your post, acknowledge only the element centre results (if you need more refined data I'd expect refining the mesh would be acceptable). My routine could average the data at nodes if it was necessary (The mesh contour coloring for results routine already does this).

GSA also reports the angle relative to element local axis or "default" element axis so my routine uses this when calculating the lines representing the 3d vector field.

I've not done any programming of the post processing of this for topology creation, but if there's any references/papers or available research, I'm interested in seeing them.

Cheers,

Jon

Permalink Reply by Jon Mirtschin on October 4, 2010 at 5:17am

I'm managed to find a few hours to extend the functionality in StructDrawRhino to develop streamlines from vector fields. I've still some alterations and improvements to make (but at least I'm getting some credible results). If anyone is interested in being involved in testing and validation of this, please get in touch. It will be part of StructDrawRhino before too long.

Permalink Reply by sivam krish on October 4, 2010 at 8:21am

I would like to test it for teaching purposes.

Permalink Reply by Jon Mirtschin on October 4, 2010 at 8:56am

Sure, well download structdrawrhino from http://www.geometrygym.com/downloads, install and run the rhino command sdrZZLicenseRequest and I'll email back with instructions.

I've removed a lot of the wiggle shown in the image, still working on getting better continuity.

Permalink Reply by msgrom on November 4, 2010 at 1:35pm

Hello Jon,

Ive been reading the thread hoping it would lead to exactly this functionality.
Im trying to make a tool that would draw contour lines on a territory given values extracted from a vector field. Its basically the same functionality replacing the structural information with topographic information.
I have the vector field working but am having trouble creating the contour lines.
Any help would be enormously helpful.

Great work,

Mateo

Permalink Reply by Jon Mirtschin on November 4, 2010 at 1:47pm

Hi Mateo,

I just got your email, will reply there. I haven't progressed this much further than what was shown, but your welcome to put it to the test.

Cheers,

Jon