yield point of auto sheet metal at low heat graph. 1

[mendadent]

can anyone point me to a graph (source unknown) of yield point vs. temperature for automotive sheet metal?

i'm curious to see the effects below 400 degrees fahrenheit.

 

[mendadent]

i have to laugh at myself.... if nothing else comes of these inquiries from me, at least you and cory are being forced to recollect what you learned in all your college courses.

i asked above
"is the coefficient of thermal expansion a fancy name for what we're discussing above?"


cory answered
"No, that is an elastic property that characterizes the dimensional changes due to temperature changes. We are discussing the elastic and plastic mechanical properties due to temperature changes.
Regards,"

if the cooefficient of thermal expansion is characterizing dimensional changes, would this not apply in my profession since i am dealing with a dimensional dent as well as stamped body panel? albeit we know the heats effect is minimal at my proposed temperatures?

 

[NickE]

actually corypad might have confused you....

We are discussing changes to mechanical properties with respect to temperature differences.

The coeefficient (9year of college and I cnat speel eiter) of thermal expansion is the "growth" of dimensions due to heating.

IE: Aluminium 99.996% will grow .0000236" per inch * C
Pure iron will grow .0000117" per inch * C

So that means that if a cube of aluminium is 1"x1"x1" at 20 C then at 100C the cube will now measure 1.0001888 on all three sides. ( I hope I did that right)

anyway the thermal expansion is completely reversible though. So when my cube when returned to 20C returns to being 1x1x1

Now the reduction of strenght due to heating is also reversible but is completely different than thermal expansion.

(I hope I didn't confuse you more.)

 

[CoryPad]

mendadent,

It is possible that thermal expansion coefficient applies to your profession.

My earlier post was answering directly your questions "can anyone point me to a graph (source unknown) of yield point vs. temperature for automotive sheet metal?" and "is the coefficient of thermal expansion a fancy name for what we're discussing above?"

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[mendadent]

i asked:"here's the delimma; is their enough heat at 240 degrees or lower, say 160 degrees, to effect a change in the molecular structure of a stamped and painted automobile exterior painted to make the metal more malleable even slighly if being manipulated with a very sharp tool?now i mean heated all the way through, placing a thermo thermometer for accuracy."

nick replied:"no there will be no effect of heating automotive body steels to 160-240F. Heck thats barely above water boiling.. What do you think the skin temp is for a black car w/ neglected paint in the summer sun in arizona?"

now it is hear that we determined my heating would not get hot enough to help with yield stress in the elastic or plastic mechanical properties.

i switched gears to thermal expansion coefficient and asked:

"if the cooefficient of thermal expansion is characterizing dimensional changes, would this not apply in my profession since i am dealing with a dimensional dent as well as stamped body panel? albeit we know the heats effect is minimal at my proposed temperatures?"



cory said "It is possible that thermal expansion coefficient applies to your profession."


cory,nick: is this then the reason my heat is working?
i mean if we're getting expansion at 160 degrees fahrenheit to 240 degrees fahrenheit then here's my answer i've been pressing for all along eh?


if the above is possible,i have another dilemma with this revelation, i'll hit you both with after you both contemplate the above.
thanks, i'm heading home now. will check back in the am.
mendadent

 

[mendadent]

i'm not sure what the reply to the above question will be, but here's my next. up till now we in my field are heating the center of the dent. well in my mind if coefficient of expansion does in fact relate to our work, then wouldn't i be better of keeping the dent cool, and heating the outside parameter f dent with a conical type attachment to my heat gun? to simplify: if dent is even remotely in the plastic deformation stage, and i'm trying to shrink it with a very sharp tool, the last thing i would want would be expanding metal in the very dent,eh?

heat the outer area hoping to expand outward towards end of panel would seem more logical to me, would any of you care to help me with this line of thinking?
thanks
mendadent.

 

[mendadent]

does this software allow pictures?

 

[CoryPad]

Yes. Click on the Process TGML link that is part of the Step 2 Options at the bottom of the new post box (it is just above the Submit Post button).

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[mendadent]

if this works, it'll show you what i'm up against. as we expand our craft, you can maybe get a glimpse of why i'm so inquisitive. i do wish someone couls please give me input on my last question, it's for the betterment of many, thanks to you all.
mendadent

 

[metman]

menadent.. You need to look more closely a NickE's last post.

For Nick's example of Aluminum if it were Steel, it would be approximately 1.0000629" from 20C to 100C. That is an extremely small number to have any effect in your applicaion.

I can readily believe you have sufficient experience to feel 7% difference in yield strength while working the metal but no way you can feel 0.00629% difference and clearly it, the coefficient of linear expansion, will have negligible effect on the process.

I believe it was suggested in the other thread that an ASM course is available titled "Metallurgy for the Non-Metallurgist." Your interest level and depth of questions suggest to me that you would enjoy and benefit from such a course.

 

[mendadent]

i want to thank all of you that have set me on the right path. metman thanks for that last reply.i came to you gentlemen for guidance and you steered me in the right direction.
so it appears unequivically that i can now in confidence reveal to my peers that electricity and time is being wasted in believing the myth that heating a panel has any noticeable effect on our craft.
this is going to be tough, because a group of about 50 people swear by it. we all in the craft know it helps for tough dents to loosen up the paint, but again, others swear by the heat for malleability.
thankyou all again. and yes i should get the book.i am intrigued. i hope you all and your families had a great christmas.