vetteboy
NAXJA Forum User
- Location
- morganville, nj
I've got some downtime while I'm on vacation in South Carolina, so I dusted off my copy of ANSYS and remembered how to use it again.
Basically, what I did was to create a program in ANSYS (a structural modeling software package, for those non-nerds out there) that allowed me to put in the coordinates of the A, B, C, and D pillars in the vehicle, generate a cage from these points, and analyze it from a variety of loadings. I did this because I don't have an XJ here to measure, so I created variables for each node in the cage (A-pillar base, A-pillar height, vehicle width, etc) that I plugged in arbitrarily for now and can later go back and edit to make them accurate.
Once the cage geometry is generated, there are 6 points that can be easily loaded (theoretically EVERY point can be loaded, but I only made variables for the top 6 nodes: a, b, c pillar on both sides). Each node can be loaded in any combination of X, Y, and Z direction, to whatever value I want.
The connections of the cage to the vehicle are fixed in all degrees of freedom, which means that I'm assuming the floor of the vehicle is rigid and won't deform, and also that the connections themselves are rigid. This is not completely accurate, but for the purposes of this program (and design exercise), it'll be close enough I think.
All tube connections are also assumed to be rigid, and all connected nodes share the same DOF constraints. This way I can be sure that all members in the cage are 'interacting' the way they would when welded.
I've also left variables for tube size and modulus of elasticity; the program then takes care of calculating moment of inertia (XX and YY) and cross-sectional area. I can also determine useful things like overall length of tubing used, and overall cage weight.
If anyone is really interested (you gotta be REALLY nerdy to appreciate this), here's a link to the program batch file.
http://www.phatserver.net/users/chris/cage/rollcage.txt
So enough chit chat, here's some pics of the first-generation of my XJ cage, scaled to an XJ from measurements that I approximated from memory. Yes, the tubing appears square, but that's because the program just generates a generic cross-section with the equivalent section modulus of whatever round tube I'm using.
Side view:
Front view:
Top view:
Isometric:
Keep in mind that I pretty much only have to input 10 or so coordinates, and it'll automatically scale and generate all the triangulation and stuff. Pretty neat.
Part II coming up: first-generation testing
Basically, what I did was to create a program in ANSYS (a structural modeling software package, for those non-nerds out there) that allowed me to put in the coordinates of the A, B, C, and D pillars in the vehicle, generate a cage from these points, and analyze it from a variety of loadings. I did this because I don't have an XJ here to measure, so I created variables for each node in the cage (A-pillar base, A-pillar height, vehicle width, etc) that I plugged in arbitrarily for now and can later go back and edit to make them accurate.
Once the cage geometry is generated, there are 6 points that can be easily loaded (theoretically EVERY point can be loaded, but I only made variables for the top 6 nodes: a, b, c pillar on both sides). Each node can be loaded in any combination of X, Y, and Z direction, to whatever value I want.
The connections of the cage to the vehicle are fixed in all degrees of freedom, which means that I'm assuming the floor of the vehicle is rigid and won't deform, and also that the connections themselves are rigid. This is not completely accurate, but for the purposes of this program (and design exercise), it'll be close enough I think.
All tube connections are also assumed to be rigid, and all connected nodes share the same DOF constraints. This way I can be sure that all members in the cage are 'interacting' the way they would when welded.
I've also left variables for tube size and modulus of elasticity; the program then takes care of calculating moment of inertia (XX and YY) and cross-sectional area. I can also determine useful things like overall length of tubing used, and overall cage weight.
If anyone is really interested (you gotta be REALLY nerdy to appreciate this), here's a link to the program batch file.
http://www.phatserver.net/users/chris/cage/rollcage.txt
So enough chit chat, here's some pics of the first-generation of my XJ cage, scaled to an XJ from measurements that I approximated from memory. Yes, the tubing appears square, but that's because the program just generates a generic cross-section with the equivalent section modulus of whatever round tube I'm using.
Side view:
Front view:
Top view:
Isometric:
Keep in mind that I pretty much only have to input 10 or so coordinates, and it'll automatically scale and generate all the triangulation and stuff. Pretty neat.
Part II coming up: first-generation testing