what is the best modeling & stress analysis software???

[.::Jonesy:]

hi,
I have little experiance in CAD but have started looking to buy a decent programe, or share with others for a projects im working on. everone just said use autocad, i tried and died, im told auto cad realy isnt that good and its just because so many people have it that its popular.
Anyways, maybe you can help me with somthing, I have seen aviation engineers use CAD like software to put stress on certain parts designed to see how they hold up.
Well is there a programe that you can create 3D objects?? but then you can say test them for strength. im told solidworks pro is good???

What i need in a programe is one thats relativly easy to use or learn and has plenty of help along the way such as tutorials (once again im told use soliworks)
I need to be able to make 3d objects, and then stress analyse them, It would also be great if i could animate these objects such as the action of a bolt action rifle.
With that said is this possible with one set of software or would i use two, eg one for 3d design and another for testing.
If so what is the best money not and issue and whats the compromise when money is, names and websites if possible.
thanks
jonesy

[RotarySMP]

Hi Jonesy,

This will sound harsh, but have you taken any courses in FEM- Finite Element Method (that is what this stress analysis is called)?

The problem with FEM is that you always get a result, but the result is only as good as the assumptions and limitations of the model, and the expertise of the designer in supplying the mesh and boundary conditions. SISO!

If you don't have to engineering background to understand the assumptions made in the software and limations of it, and to set boundary conditions and mesh, you will end up with, at best, pretty colored pictures of distorted parts, and at worst dangerous parts waiting to fail in service.

I would suggest you best bang for your buck would be to enroll in some FEM class at a local engineering university.

Once you have the knowledge to use the various packages on the market, you will also know what you need.

For modelling parts, Rhino is very popular and has a reputation for being easy to learn.

There is some info on FEM here:
http://femur.wpi.edu/
http://dattaraj_rao.tripod.com/FEM/index.html

[.::Jonesy:]

hi,
thanks for the info and sites lots of reading for me Unfortunatly i have not completed a FEM course, i had hoped that i could grasp the basics and do some testing befor passing my stuff onto those in the no, to get them to look it over prior to any prototype production began.
Have you herd anything about solidworks??
My main analysis points is concerned with locking mechanisms on rifles/pistlos. Its hard to explain if you dont know but, a cartrigle is chambered in the barrel then behind it sits the bolt which is held there by locking lugs. I need to find out if my locking lugs are large, thick, enough of them, etc to suport the cartrige when fired. Basicaly i need to know how much rearward force can be applied to the bolt befor the bolt locking lugs (or the receiver cam which holds the lugs) hits a unsafe level, i was hoping it was i could grasps the basics of it enough to make a few tests.
A silly question im sure espaily because ive used CAD, but what is the differance between CAD, CAM and so foth??
Anyone else got thoughts on best CAD??

thanks
jonesy

[RotarySMP]

For your specific requirement, you would be really far better off to get some graduate engineering student to do this for you for a few crates of beer

Those web sites just give you an overview of what FEM is.

If you get an FEM package and play with it, you will probably work out how to get a mesh applied to the part, apply some pressure to the face of the bolt to represent the pressure in the chamber, and get the software to deliver a pretty colored picture of a distorted bolt showing that you maximum stress occurs somewhere in the radius of the lug or on the point of contact. You tweak the lug radius and get all the colored zones down to an acceptable stress.

The scary part is that this picture has a strong reassuring effect on people, even though it is nearly completely worthless information.

I've had a Prof at Cranfield introduce CFD as Color For Directors

A good example is a Turbine disk burst which happened in commerical aviation because the designer (who would have really known his stuff) had a slighty too coarse mesh on a radius.

He would have had a pretty picture showing that all areas of his disk had safe stress margin. Once they analysed the fractured disk and identified where the crack initiated, they tweaked the model and the mesh size locally till it explain why it happened. In the future they have a better model and better set of assumptions.

You would be better off to copy the lug design from a proven rifle using the best steel and controlled heat treatment.

I have never used Solid Works.

My experience had been with AutoCAD and then Catia.

CAD is used to design and size a part (with the modern packages adding features like building assembles and simulating motion etc).

CAM software is used to create a tool path from that part.

A post is needed to translate the tool path to a G-code file for your machine tool. The post is normal a customize plug-in to the CAM software.

G-Code is the generic name for the ASCII tool path file which will be feed to the machine. The original standard RS-274D is not strickly adhered too, beyond the basic moves. Most machine controllers have a specific flavour of G-code.

There are integrated CAD/CAM/POST systems for sale, some of which are even affordable. Dophin and Vector have good reviews but I have never used either.