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Silence · 05-02-2008, 08:58 PM

I wasn't exactly thinking of Hooke's law, but you're right. Maybe rubber does follow the law for a certain amount of deflection, but beyond that, stretching is limited. That seems to be what happens with rubber bands (although I haven't measured) - the behavior changes as you reach the maximum deflection point. The rubber stops stretching and snaps when you pass the tensile strength.

Ben · 05-07-2008, 08:48 PM

Hooke's law describes a linear relationship between deflection and force (actually, stress and strain, but you'll see that in a statics class). Rubber apparently doesn't have a linear relationship for part of the curve, so it doesn't follow Hooke's law. That's the problem.

Since I'm in College Park (which is very close to Washington DC for those who don't know) I might head down to the Library of Congress and check out a book. If they really do have two copies of every book published in the United States, they should have something on the elastic properties of rubber.

Silence · 05-07-2008, 09:41 PM

I found a few links:
Rubber elasticity (PDF)
THe Physics of Rubber Elasticity
The only other books seem to be older versions of the one above. There are probably lots of papers on the subject too, but that probably going way too deep.

UVa has versions from 1949, 1967, 1975, and 2005 in various libraries. I'm not sure how well UMD's library compares, but your engineering department is large so I presume there's a copy floating around in there.

Anyway, pressure in rubber seems to work like a gas/compressible fluid, as I noticed an equation similar to the ideal gas law in the PDF. I didn't understand all the variables but I did catch n*R*T.

Ben · 05-07-2008, 10:09 PM

The Physics of Rubber Elasticity seems like the right book from what I've researched. The EPSL library here has a version from 1975. The problem with the EPSL library it is for reference only. Combine that with the date and I'm not sure if I want the book. I'll find it tomorrow though because I need a break and I don't have anything better to do (other than homework).

Silence · 05-07-2008, 10:50 PM

That's funny. Here they actually let employees and students check out books indefinitely, until they are called in by somebody else, which seldom happens. Fortunately the field can't have changed that much, although I dislike outdated books too (especially once updated editions appear).

05-02-2008, 08:58 PM	#16
Silence Administrator Join Date: Apr 2006 Location: Virginia Posts: 3,293 UserID: 576	Re: My new CPH I wasn't exactly thinking of Hooke's law, but you're right. Maybe rubber does follow the law for a certain amount of deflection, but beyond that, stretching is limited. That seems to be what happens with rubber bands (although I haven't measured) - the behavior changes as you reach the maximum deflection point. The rubber stops stretching and snaps when you pass the tensile strength. __________________ Forum rules

05-07-2008, 08:48 PM	#17
Ben Founder Join Date: Mar 2003 Location: College Park, Maryland Posts: 6,054 UserID: 1	Re: My new CPH Hooke's law describes a linear relationship between deflection and force (actually, stress and strain, but you'll see that in a statics class). Rubber apparently doesn't have a linear relationship for part of the curve, so it doesn't follow Hooke's law. That's the problem. Since I'm in College Park (which is very close to Washington DC for those who don't know) I might head down to the Library of Congress and check out a book. If they really do have two copies of every book published in the United States, they should have something on the elastic properties of rubber. __________________ email: / Forum rules / Read this page before emailing me. Do not send me a PM or email with a water gun question if someone else could answer the question. Post at the forums. You will get a response from me along with others' views or ideas.

05-07-2008, 09:41 PM	#18
Silence Administrator Join Date: Apr 2006 Location: Virginia Posts: 3,293 UserID: 576	Re: My new CPH I found a few links: Rubber elasticity (PDF) THe Physics of Rubber Elasticity The only other books seem to be older versions of the one above. There are probably lots of papers on the subject too, but that probably going way too deep. UVa has versions from 1949, 1967, 1975, and 2005 in various libraries. I'm not sure how well UMD's library compares, but your engineering department is large so I presume there's a copy floating around in there. Anyway, pressure in rubber seems to work like a gas/compressible fluid, as I noticed an equation similar to the ideal gas law in the PDF. I didn't understand all the variables but I did catch nRT. __________________ Forum rules

05-07-2008, 10:09 PM	#19
Ben Founder Join Date: Mar 2003 Location: College Park, Maryland Posts: 6,054 UserID: 1	Re: My new CPH The Physics of Rubber Elasticity seems like the right book from what I've researched. The EPSL library here has a version from 1975. The problem with the EPSL library it is for reference only. Combine that with the date and I'm not sure if I want the book. I'll find it tomorrow though because I need a break and I don't have anything better to do (other than homework). __________________ email: / Forum rules / Read this page before emailing me. Do not send me a PM or email with a water gun question if someone else could answer the question. Post at the forums. You will get a response from me along with others' views or ideas.

05-07-2008, 10:50 PM	#20
Silence Administrator Join Date: Apr 2006 Location: Virginia Posts: 3,293 UserID: 576	Re: My new CPH That's funny. Here they actually let employees and students check out books indefinitely, until they are called in by somebody else, which seldom happens. Fortunately the field can't have changed that much, although I dislike outdated books too (especially once updated editions appear). __________________ Forum rules

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