CAD-Modeling - Science method

Hello

See this link

José Luis Junquera, Saddle polyhedra are three-dimensional objects with curved faces. They are not polyhedra in the traditional sense, because polyhedra must have flat faces. However, saddle polyhedra do have some properties that are similar to those of polyhedra. For example, they have an Euler characteristic, which is a topological invariant that is defined for all three-dimensional objects. addle polyhedra are the only other three-dimensional objects known to have an Euler characteristic of 2. This is an interesting fact, because it suggests that saddle polyhedra have some topological similarities to spheres and flat-faced polyhedra. The two saddle polyhedra that are known to exist are the saddle tetrahedron and its tessellation. The saddle tetrahedron has four curved faces, six edges, and four vertices. Its tessellation is a three-dimensional tiling that fills all of space. Saddle polyhedra are a relatively new area of research, and there is still much to learn about their geometry and topology. However, the fact that they have an Euler characteristic of 2 is a significant discovery, and it suggests that these objects have some interesting properties.

sir Josnier Ramos Guardarrama , thank you so much. I tested this solution and it worked for me. Thank you so much

Ankush Pratap Singh, you can do this by using the following steps:

1. Generate random points within the geometry. Rhino is an efficient tool to perform this step.

2. Assign random pore size to each point.

3. Generate desired pore shape at each point with assigned pore size.

4. Subtract the pore shapes from the geometry.

To generate a geometry with a desired porosity, you have to play with the range of assigned pore sizes.

To change the unit system in OpenCascade using pythonocc, you can modify the system of units used by the TopoDS_Shape object Nils Wagner

Thanks, Dmitrii for the reply. I need a hollow model of this with 12 mm thickness. I tried in solid works but its difficult to convert a (.step file) into a hollow model of 12mm thickness.

We can convert a surface from MATLAB to STL file by using the codes below.

The STLWRITE codes are also attached.

____________________________

These are an example:

[x, y, z] = meshgrid (-pi:pi/16:pi); % 3D coordinates defined by x, y, z

v = sin(x).*cos(y)+sin(y).*cos(z)+sin(z).*cos(x); %gyroid formula

figure(1);

fv=isosurface (x, y, z, v, 0);

hold on;

figure(1);

stlwrite('test.stl',fv);

FreeCAD a very good tool to convert complex stl to CAD.

Both are good in what they are designed for, but I will lean towards Simpleware ScanIP due to ease of integration of its output with downstream finite element analysis tool.

Dear Prof. Osman Eroğlu,

It can be modeled with each ring. Also, the lattice of the rings can be 0-360.

I wish you good studies.

Best regards

Ross James Friel thank you, I will do that as well as explore further. I was using a 3D scanner previously to do the same but couldn't get the desired output

Just use cm or meters as your base unit instead of nm. Then just note your scale factor for your model.

Hey Naveshin,

Maybe using Fusion 360 may be the easiest, haven't tried my self but seems to be a lot of tutorials online: https://www.youtube.com/watch?v=KFQ4-1GH0wg

-Chris

google search

In AutoLISP or ObjectARX C#/C

- Disable all layers except envelopes, partitions, doors and space labels.

- With each space label: Zoom centre then zoom out to a common zoom factor: You'll be able to figure out a factor by zoom extents on the largest space's boundary.

- Use the space label's insertion point (assumption that label insertion points are within their space's boundary.

- Run boundary poly command "_bp" (I think)

- With each space boundary, get the selection set of intersecting envelopes.

- Finally, for each bpoly line segment, match the points from the segment to the adjacent envelope/partition/door.

Hello! We are engaged in modeling and creating materials with ordered porosity - https://www.scopus.com/record/display.uri?eid=2-s2.0-85013168155&origin=resultslist. To model an unordered porous structure, we created our own macro program.

On my research thesis, I used Ansys Workbench but at entry level only. Some researcher are discussing your issue too. Sometimes in Ansys you have to use some techniques to solve the issue. because it is not "straightforward software". It is like doing research, putting other people answer together and solving puzzles... then see if you can find your answer (Up)

By the way, maybe this link of website below is useful for you.

Hi, Hüseyin Emre Özgür

The answer of M.Sc Eoghan McNamara is very correct. He shared his aponion and recommended it.

Thanks, Victor. Could you please elaborate on when (which step) is least mean squares or Tikhonov regularization used?

So far I've found that due to the differences between the meshing of the loaded and load-free part, there is about 5-10% error in recovered shape (even after re-doing the meshing completely). If the part geometry gets more complex, the error gets bigger. Is there a way to reduce this error?

What an odd request. First, you might try some calories looking in the literature and contacting labs that might already have a CAD file to work with. However I would not hold my breath. Secondly, you might want to try making one. Have you ever heard of the "Visible Human Project?" Look it up. I was part of a group that did some similar type of work. Where the VHP took a man and literally sliced him up and took pictures to be able to make a reconstruction of the human body to make an incredible 3D module, I was part of some work where we looked at cellular and dendritic alloy micro-structure and we sliced up the alloy in a directional manor and made a 3D model of the alloy structure (see linked articles in my profile at Researchgate). Anway, you could try getting a model of a joint from https://www.sawbones.com. It looks like you can order models of bones and joints... all sorts of cool models. Then per some nice images I see on

https://musculoskeletalkey.com/acetabular-reconstruction-classification-of-bone-defects-and-treatment-options/ --> Figures 89.5 and 89 6 for 3A and 3B defects.

You could modify the model to create the type of defect you are after. Now for the fun part. You put this point into an epoxy in a nice flat edge mold container. Then say at approx. 0.1 mm at a time you grind/polish a layer off and take a digital images of the cross section each time. You do this for the entire joint creating a database of 2D layers of the 3D model. For the alloy samples we cut those with a Leica Ultamiller. The VHP used a big version of that in a freezer. I am sure you can find documentaries on Youtube about that, here is an overview (https://www.youtube.com/watch?v=7GPB1sjEhIQ ). Now maybe you could get your hands on this software and use it to generate your joint where you could also modify a model to introduce the 3A and 3B defects? Who knows maybe contacts with that VHP might be helpful?

Now depending on some coding ability or connections and collaboration you could create a 3D module of this. So, I don't know you if you are doing a MS or PhD, but I have a feeling if you want to do some FEA and or use something like Solidworks or some other cool software to analyze the joint and defects then you have an idea here where one could go to generate a model from scratch. Are you trying to correct the defect, replace the defect???

I mentioned the alloy work, well I also once supplied a turkey leg to my mentor at the time Dr. S.N. Tewari who as I recall used that turkey bone and the same general technique on the alloys (seem citations in my profile) to generate a model on the pore structure of a load bearing turkey bone. That went towards some other graduate students work. I was at this time an undergraduate in a cool and fun lab. Well, I just went and found you that link to the turkey bone project: https://link.springer.com/article/10.1023%2FB%3AJMSC.0000007746.00517.ba

So

You will be in a hunt for that CAD file that may or may not exist. Maybe the sawbones.com company might have some sort of file to share? Again, I had a hoot of a time working with Dr. S.N. Tewari. He is a top notch man and engineer/scientist. He likely has other papers beyond what I contributed to so if you like anything I am saying he is a source in the literature.

On the other hand if you can get an animal joint... (non-human) you could do the same thing where you put into a mold. Now with an animal source you could also grind/build the defects into those joints. After that is done you can put the Type 3A and Type 3B defect models into epoxy and make the 3D models slice by slice. I like that version. I used Sigma Scan Pro at the time to draw the layer by layer boundaries. A PhD student at that time (Lu Yu) who is in the articles was the one making the 3D models of the alloy structures. That was a while ago and computers and software have gotten better but the Sun Work Station type and any software used should be in the articles.

Now that was some rambled brain storming but I hope it might help. Good Luck no matter how your path goes.

I suggest you to use the OpenCv library is very powerful in detecting the object whit new algorithms and methods. I was use in my article in sector automotive , we can see you my article in profile , I applied in real-time.

I hope that be Clair for you. @Carina Mieth

Thank you, I'll check it out.

A nice library that helps to generate DXF files

https://qcad.org/en/90-dxflib

+1

Hello. You can do this to a large extent using: wizfds

Dear Sohaib Ahmad

1. http://www.ablesw.com/3d-doctor/dental.html

2. https://www.embodi3d.com/files/category/41-dental-orthodontic-maxillofacial-cts/

3. https://sketchfab.com/blogs/community/video-tutorial-converting-ct-scans-3d-models/

1. Wallner, J. et al. Computed tomography data collection of the complete human mandible and valid clinical ground truth models. Sci. Data. 6:190003 https://doi.org/10.1038/sdata.2019.3 (2019).

2. Aki Hasegawa, Akikazu Shinya, Yuji Nakasone, Lippo V. J. Lassila, Pekka K. Vallittu, and Akiyoshi Shinya, “Development of 3D CAD/FEM Analysis System for Natural Teeth and Jaw Bone Constructed from X-Ray CT Images,” International Journal of Biomaterials, vol. 2010, Article ID 659802, 7 pages, 2010. https://doi.org/10.1155/2010/659802.

Hello Riccardo Longo,

Is it possible to export geometry from Paraview to ANSYS or any meshing software for generating meshing.

Thanks,

vidyadhar

Saad Najeeb Shehab thankyou sir.

is there any reliable journal papers to refer regarding the geometry of the combustor.

Please help me.

Thank you for the offer, Poul, but I think I have resolved my problem for now.

For posterity sake, it seems my problem was that the space between my sliding mesh and the tip of my turbine blade was too small, and the mesher was not automatically making the mesh smaller to work in that space; specifically, I had set a 1 cm gap while using a 2.5 cm element maximum size. I had also defined my inflation layer such that 1 cm was not enough space to fill it out, which exacerbated the problem.

I fixed the problem by increasing the space between the blade tip and the rotating zone to 10 cm; I think there was probably a way to make the mesh much finer instead. That would have taken much longer to resolve, but I suspect it would have worked.

I think that copying may have gone wrong. I have already imported several STL files in catia in this way. There is also a rapid prototyping tool in catia. But currentl i use blender for such problems.

Blood flow is an non-Newtonian fluid so you can use a fluid that near to blood properties and make numerical simulation representing the actual case study.So the mechanism including the non-Newtonian fluid case can be used in validating the actual case study.

Ansys workbench will be the best option

ADAMS is a multibody dynamics simulation software equipped with Fortran and C++ numerical solvers. ADAMS was originally developed by Mechanical Dynamics Incorporation which then was acquired by MSC Software Corporation. So it is specifically designed to solve the problem.

Dear Javad,

Maybe you find a solution in this link: https://www.mathworks.com/matlabcentral/fileexchange/13253-iges-toolbox

Regards.

while building parts and products in 2D views is sufficient for some, many users need a 3D model for mass properties, interference-checking and visualization.

With SpaceClaim it is comfortable using 2D can now make an easy transition to 3D. As continue to work in 2D views while the system automatically provides the benefits of 3D modeling. The software lets engineers create and edit in “live” cross sections (both in a solid model and in the drawing space), taking advantage of SpaceClaim’s major modeling tools:

Pull

Move

Fill

Combine.

Dear Ivan,

You're right. I forgot that YADE only uses spherical particles. Best regards,

Nabeel Mahdi Al-janabi

Thank you very much.

Actually, the STEP AP242 was developed to support GD&T information; however, the CAD venders didn't use this facility yet. This is kind of a shortcoming in CAD systems since their inner translators don't extract GD&T information from the presentation level and add them as semantics via the STEP AP242 in the representation level.

If u are using solidworks..then...u can make configuration and set the level of burning fule and evluate moi from evaluation toolbar

not sure you should be looking at CAD apps then ... sounds like you're better off with CGI apps like Blender, Maya, & 3DSMax. Those apps have solid mesh implementations and rich APIs.

You can perform a transient Structural-thermal multiphysics simulation in ANSYS mechanical to see the effect of cryogenic temprature on your maerial. However you need to define temperature dependent material first (If there is published data available for this material of course). If this is somthing you want to do. Ask me to provide more info for performing a multiphysics simulation for you.

So I looked at the model and found the following problems:

Your units are probably wrong: You give density as 1600 (probably in kg/m^3), but your geometric unit seems to be millimeter so your units are not consistent.

You should specifiy NLGEOM=ON in a contact problem unless you do small sliding

The displacement bc on the top is strange: You apply it so some points (or a RP? or both?)and then do some kind of kinematic coupling to transfer it to other points. And then in step 3 you add a concentrated load to the RP?

The BC on the tibia is wrong - you should not specify a bc on a contact surface, but on the bottom surface, I suppose.

It is also very wasteful to start with such alarge gap between the parts.

Also note that you are dealing with a Hertzian contact (sphere with a plane), this requires a much finer mesh to be resolved correctly.

Since I could not really make sense of your three loading steps. I deactivated them and changed the model so that the first step runs (was fun, actually). Hope you can take it from there.

PS: Please also note that if you actually want to model a knee joint, you will have to account for synovial fluid, cartilage etc., which will be very difficult to model (and to get material parameters for...)

Hi Raghuram,

COMSOL Multiphysics is one software that involves equation based modeling. You can check those links if could help: https://goo.gl/YGJDN1 .

Also, a better and more time convenient method is to develop a Verilog-A model that characterize your whole system. Given that you already have one device described in differential equations you can model the other device also and write a complete model for the system and thus you can simulate them easily using any circuit simulation tools (e.g., Cadence Virtuoso).

Dear Jonah

To give reinforcements in Abaqus. you have to define the contact, try to do Face to face contact by layers with nonlinear-elastic behavior

Hakim

If you are doing research - I would suggest that you liaise with your local radiologist and ethics to use the CT unit database.

Dear Vishal Agrawal,

if you have a tool to visualize your initial CAD model, or geometry, than you could do the following: produce a new geometry by using the original B-Spline basis (or NURBS, or whatever kind of splines you are using) with the new control points. Those control points you get by adding displcament DoFs to the corresponding control points of the initial geometry. The resulting geometry you can visualize in the same way as your initial one.

That would be "the true IGA way". But of course you could also just sample your geometry and the displacement field and send it to Paraview to do the job.

What exactly you are interested in?

Thanks Alex! I searched earlier on Zygote but did not find any CAD with movable limbs.

Hi,

May be you should try this Helius Composite Case Study Demo from YouTube

Thank you all for your quick response.

One very relevant topic (and surprisingly not that well researched) is the issue of on boarding the augmented reality application in the first place. To pick up the phone from your pocket, turn it on, find and/or download the application, find the correct place to use the app, and to experience the augmented reality content is a long list of interactions for the user to take - prone to many break downs in the action cycle. This problem is more immediate in context like in un-faciliated private use cases, such as when using AR in private, at an exhibition ect. 

We touch a bit upon the issues in this paper http://vbn.aau.dk/en/publications/adopting-the-unknown-through-the-known(5ad7fa54-c683-4695-ae0a-847620598aed).html but there are definitely more work to be done in this arena for HCI research.

Hello,

I have some experience in 3D printing, but bioprinters are a bit different. I have knowledge about a few:

If you need to control the flow you will need a electronic controlled valve, but they are expensive

if it was just on/off you would be good with a solenoid valve.

You can make your own valve by hacking a manual flow valve and adding to it a servo or a stepper, but you would have to program the software on your printer board to actuate the servo on recieving the M code.

By the way you can cook up your own M-codes, there is a list of reserved M-codes you can use for your own implementations

Dear Sergey,

Please have in mind that if you are considering a parametric CAD environment, introducing suppression will impact on other features that rely on that very one you tend to suppress.  I'm not sure how to help you here, but I thought I had to point this out.

What you have identified potentially is a safe starting material - not knowing what you are manufacturing it is hard to answer the question. 

If this is a medical device or pharmaceutical product you would still have requirements for traceability on the design of the parts you are printing (i.e. drawings, manufacturing records of such, cleaning) to make final products.  Additionally, you may want to provide some justification or testing to demonstrate that the safe material you started with is still safe; thus locking in your printing parameters for future justifications of parts and purchase specification / release requirements for the Nylon filament. 

It is a tricky question without all the details, although it is certainly a lower bar to 3d print a production aid than say a component of an implant.  Documentation is key - remember to err on the side of caution and CYA; get your QA group involved, maybe they can help.

For single part without complex surfaces "Parasolid" kernel i sufficient. But when it comes to large assemblies or complex surface geometry and multiple branches, CATIA in my opinion is still a winner of competition due to independecy of surfacing and solid modelling but still in integrated environment.

How do i model a grid electrode in ANSYS Maxwell? I would like to place a curved grid electrode below a suspended tip electrode to simulate charge distribution on it.

Thanks Max!  That's a very awesome answer!

I also had other answers from Alberto Pretto about code implementing his paper "D2CO: Fast and Robust Registration of 3D Textureless Objects using the Directional Chamfer Distance".  Mister Pretto said that his group will release the refactored version of the code under BSD license!

There is also a paper named "Fast 6D pose estimation for texture-less objects

from a single RGB image" which works on the same kind of problem.

Again, thanks for having taken so much time to explain the work you did on the problem.  I hope you will find the following links interesting!

Bruno

Hi,

You must make a study of sensitivity to the mesh size and the elements type on your numerical model.

you take three types : fine mashed, Medium and coarse . and see who offers a good results.

The solution is to create a script file in python as shown here in page 3:

Generally, it is a very useful pacjage with many featyres. I have made many studies and the solaver is tested and the results reliable.

For turbulence, κ-ε model. Also check this link https://forum.solidworks.com/thread/82486

Jaider: You mean automatic manufacturing features extraction using rule-based? Not quite. I have employed rule-based techniques to extract parameters and geometric attributes from CAD models, 

Take  a look...

I am not sure if scaling the mesh will reduce the strain on your computer. The number of cells in your mesh will still be the same. You can reduce the mesh density, but this will likely effect your results. You could run a mesh independence study to determine what mesh density is needed for accurate results.

Hello sir,  welcome

Hi Alejandro,

There are two types of models you can use. One is Voxel model and other is normal CAD. Both of them have some resolution. Contrary to what you may believe that CAD models are smooth with infinite resolution, this is not the case. Also, resolution of CAD/Voxel model and meshing are two different things. Let me explain both these issues.  

These models whether Voxel or CAD, are generated from the MRI or CT scan images of the real people /dead bodies. These images themselves have the resolution limitation. For example, for an MRI scan with 1.5T machine may have the maximum resolution of 1mm (as a general case ). Naturally, any model which is generated from these images can have the maximum resolution of 1mm. What this means is that the positional /spatial accuracy of the model is 1mm. Any changes in the physical arrangement of various body parts can have the maximum deviation of 1mm. Now you can very well see that this resolution is practically sufficient for all the purposes. After all, from person to person, this 1mm deviation can easily occur. For example, one of my teeth can easily differ from yours by 1mm and you may have more muscle than an average person. So there is no point in having a higher accuracy of the model. So you see, the resolution of model means how closely the model represents actual human being. Thus, this has got nothing to do with meshing accuracy.

Now meshing for both CAD/Voxel model is done based on the frequency of operation. In meshing, what we are interested in knowing the E and H fields at different locations. For the implantable antenna, we are also interested in knowing SAR values. Now, if you are working at very low frequencies,.the number of mesh cells will be small and for the higher frequency, they will be large, just as with any other model. That being said, you may also like to know that meshing is always done such that you have mesh cells where the material boundary changes. Naturally, if you have more boundaries, which means more types of tissues in a small space, you will have more elements. I would conclude by saying that you do have the infinite resolution in terms of meshing. Theoretically, there is no limitation on this. The mesh for which your solution converges is the best value for you. 

Now answering your main question, What are advantages of Voxel over CAD. Immediately I can say that it is more compatible with time domain method used by CST. In the frequency domain , CAD model is good. Secondly, If you have the large number of meshcells for Voxel model, your simulation will take a very long time or you can also use GPU to reduce time. However, in CAD model, if the number of tetrahedrons increases beyond your RAM limitations, there is no way you can simulate your design without increasing RAM. 

That's All Folks. Have a good time simulating :)

STL file structure was developed many years ago, additive manufacturing is a recently new process. The multi color printing heads are just now becoming common. It's easier to write a slicing program that can incorporate multifunctional data. That, being based on a machine capable of reading the code.  G-code is still the language of the machine processor, I program multi-axis 3-D milling projects using 2-D data. The skin of an STL file is truly the only data necessary for both additive and subtractive processing.  My biggest interest would be in having an affordable application that can fully manipulate and repair an STL model, closing the manafold is tiresome. It's a legacie thing really, not many CADD programs can translate to STL 

Its all about interfacing the mind and the machine. We can imagine complex structures, but telling a machine how to create it in binary code is a completely new ball game. I see a big future in additive processing, when we can "print" using molecularly bonded (welded) metal within .0001" tolarance, the Art will have been perfected. Until then 

What you can do is get hold of some online CT data, import it into OsiriX or a similar DICOM reader. Then export the volume rendered scan as a STL file. That'll give you a very rough file, but it's a starting point. Another method is to import the CT DICOM files into Slicer, it's a free an open source app that let's you fine tune the part of the CT image series that you want to convert to a 3D STL file. You'll still need to refine and simplify the STL file in Solidworks before you can mesh it in Ansys.

Dear Sumit,

In the past I've done exactly this for micro-CT captured 3D reconstructions using both free software and academic licensed CAD software so very low cost. I imported the final geometry into COMSOL FEA software and ran models which were then successfully validated using data from acoustic tests and previous simulations of similar 3D geometry captured using optical methods.

To try and help answer your question I require some more information please, specifically, what software was used to reconstruct the SEM images, what format are the 3D files currently in and, finally, on average, what size are the 3D recon files?

Best,

David

For simple geometries such as circles, squares etc., the control points and weights can be found in any CAD books such as:

L.A. Piegl, W. Tiller, The NURBS Book, Springer, 1996. Or you can find them in the paper on Isogeometric Analysis: 

T.J.R. Hughes, J.A. Cottrell, Y. Bazilevs, Isogeometric analysis: CAD, nite elements, NURBS, exact geometry and mesh re nement, Comput. Methods Appl. Mech. Engrg. 194 (39–41) (2005) 4135–4195. 

For other geometries, you can use a software such Rhino.

Best regards,

Phu

You're welcome, Please provide feedback about your results ;-)

Regarding the library side, if you wanna do SfM or Multiple View Geometry computation => You can take a look to https://github.com/openMVG/openMVG

Note: I have 4 Generators, 3 of them supplies the load with appropriate generation but the smallest generator goes to the motor mode( the generation amount of power is negative p.u and is very small compare to others, 0.3 p.u for instance.)

I can't figure out the problem.

Dear Kazem:

Any powders of nanoparticles, microparticles compared parameters characterize a specific surface area in units of cm2 / cm3.

Regards

Clients are the most beneficent in BIM implementation process. While clients get benefits after completions that is much more valuable than the others in design and construction face. 

One example of application for extraction of mid-surfaces is the preparation of geometry data for finite-elements simulation of automotive body in white. Here, challenges can be found in complex curved surfaces (including holes, beads and seams), different sheet metal wall thicknesses, connection technology (overlapping weld spot flanges and bonding flanges). In addition, multi-material componentes and components with variable wall thickness (e.g. casted  junction plate) require more effort to extract the mid surfaces.

Kind regards,

Mario

This is a number of questions - some of them I can answer:

- If you want to compute the stiffness parameters of a bo