Crumple Zone

[Lash]

Hey Guys,

I'm looking for some ideas for a design of a crush zone. Let me know if you have any good ideas. Even formulas would be nice.

Thanks.

[Agent4573]

f=kx

[Cement Legs]

∆M = ½ m(v2 – v1)^2

[Lyn Labahn UW-Madison]

Look at pictures of other cars for ideas. Read your mechanics of materials book for some formulas. Make one and crush it in a compression test machine to get an idea of its capability.

[Denny Trimble]

James Waltman wrote a book or two about crush zone analysis here on the forum, but it seems to have disappeared. Anybody have any luck finding it?

Aluminum honeycomb is probably the best performer in terms of energy absorption per unit weight, unless you're at WWU and you have carbon honeycomb up the ying-yang.

[James Waltman]

Book number one is here. (http://fsae.com/eve/forums/a/tpc/f/125607348/m/85510167411/r/85510167411#85510167411)

I've been having trouble searching the forum lately too. Something is messed up. As I write this it shows that Denny has 0 posts.

[Lyn Labahn UW-Madison]

Ah, Denny jogged my memory on something. If you find a material that you would like, say aluminum honeycomb, check out a manufacturers website for it. Often they will have whitepapers on the material that will tell you all sorts of critical information. If it is a safety oriented material, it may even have a section on how to design using it, with equations and examples.

Also, take the time to enter all of the equations into a program. It will allow you to quickly iterate the design. Doing the calcs by hand once isn't too bad, but it gets really old after three or four "tweaks" that you will inevetibly have. It will also give you some intuition on how the parameters affect the energy absorbtion.

[Travis Garrison]

Here are some misc links to honeycomb data...

Automotive barriers:
http://www.hexcelcomposites.com/markets/markets/automotive/barriers.htm

This page has a refrence to their crush structure design guide / sales brochure half way down the page:

http://www.hexcelcomposites.com/markets/products/honeycomb/hexweb_attrib/hw_p10.htm


Towards the end of the aluminum honeycomb section, look for the tube-core download (#2800), it will give you the sales pitch on hexcel's ready made crush structures...also, most of the other data sheets located around the site will give you some kind of crush value for a given type of honeycomb:

http://www.hexcelcomposites.com/markets/downloads/default.asp?root=hon



-Travis Garrison

[Cement Legs]

I didnt find a required minimum energy absorption forthe crush zone in the rules. Did I miss it somewhere, and if so what is the stated value?

[Denny Trimble]

That's because it's not there. No rules on deceleration rates either.

[Lash]

The only thing I saw was a minimum area and length protruding out of the frame. I've heard of teams using pop cans!!

Anyways the rules say to stop the car within a "reasonable" range. I wanted to know if any teams came up with some reasonable numbers.

I was thinking 50 km/hr and about 25 G's max deceleration. The surviable range is quite broad depending on where it is applied to the body and for how long. Let me know what you guys think.

P.S. Thanks Travis for the links!!

[CMURacing - Prometheus]

i believe the "death zone" for humans is between 25 and 40g's, depending on length of exposure...

[Travis Garrison]

http://www.pbs.org/wgbh/nova/escape/pioplane.html

http://www.vnh.org/FSManual/24/03HumanTolerance.html

http://www.vnh.org/FSManual/02/03ImpactAcceleration.html

Survivable limit should be closer to 60G's depending on conditions...

Lapbelts bring it WAY down according to the virtual naval hospital pages...so...I guess don't use a 2 point harness http://fsae.com/groupee_common/emoticons/icon_smile.gif

But keeping it under 40G's would be the kind thing to do for your drivers...


-Travis

[Travis Garrison]

Sooo at the risk of beating a very dead horse (homework break) check out how mercedes / mclaren does it...



http://www.germancarfans.com/photos/3030603.001/1087.jpg

http://www.germancarfans.com/photos/3030603.001/1089.jpg

[BryanH]

The decel. rate is obviously very dependant on the object being run into. The organizers have made the assumption that fsae cars only crash head-on! The nosecone rule is a very good thing but is a massive cop out on their part, they have a duty of care to provide a safe racetrack in regard to probable impact with roadside furniture. Adequate track safety barriers is what's required
Bryan Hester

[MikeWaggoner at UW]

There was a critiscism of the safety rules in a magazine article, and a response. Basically they (SAE) said they left the rules loose, but made it clear to teams that any team hoping to get into design finals had better have a decent crush structure. Something to keep in mind before putting on that 6 pack.

[Lash]

Does any one have pictures of their crush zones or other teams Designs?

[Lyn Labahn UW-Madison]

Originally posted by Lash:
Does any one have pictures of their crush zones or other teams Designs?

Is your friend (http://www.google.com)

[Lash]

Does anyone know what kind of speed is reasonable for a crash for FSAE ??