yield strength

[hill.josh]

Ok I can't find this anywhere.. probably cause its common knowledge, but how thick is a piece of metal is being used when testing for yield strengths? all i can figure out is its in PSI but can't figure out how thick something is or if different thicknesses are used. Any help would be appreciated.

[Jose Gomez]

Yield strength is measured in PSI, which is pounds per square inch. So all yield strengths listed relate to a 1 square inch sample.

[Quenchcrack]

The sample can be any size but there are usually standardized specimen dimensions. The size of the sample can affect the reading somewhat. Since the units in Yield strength are "Pounds / Square Inch" the pounds will be directly proportional to the square inches for a given strength. For example, 50000 pounds / .5 square inches = 100,000 psi. 100,000 pounds / 1 square inch = 100,000 psi., 10,000 pounds / .1 square inches = 100,000 psi. A typical round tensile specimen will be 1/2" diameter.

[ThomasPowers]

Sample size is directly correlated to the test machine---does no good to test a 2" square sample on a machine that will only handle 1/2" square material!

Instructions on preparing samples should be with the machine to be used.

[hill.josh]

ok well when it says 100'000psi is that meaning that the piece tested is 1x1x1/4 or or 1x1x1 or something in between? I think that would affect the strength greatly.. wouldn't that latter be four times as strong?
and Thomas i don't have a machine to test with I'm just taking this off the internet to get basic ideas of steel strength because what's being built has to be strong but also as lightweight as possible

[racer3j]

Certificate tests usually use what is called a "coupon." This is a piece of material at a specified alloy,heat-treat(aluminum) and thickness that is calibrated with the tester.
I learned by myself in a garage with my O/A a big vise and a similarly sized hammer and a 14" adjustable wrench( wrench is excellent for bending). Just kept doing it and re-reading and doing it again until I got it right. The real test is- would you let a friend or someone other than yourself depend upon it?mt

[ThomasPowers]

100,000 PSI means that a piece 1" square will take 100,000 pounds now the piece it may be tested on might be 1/2" square but the *VALUE* for yield strength is normailzed to a 1 sq inch value.

So a 4 square inch piece would take 400,000 pounds to reach yield strength and a 1/2 square inch piece would take 50,000 pounds to reach yield strength

It has *nothing* to do with the size that was tested to produce the yield strength value.

[maddog]

my understanding of the yield strength is that its tensile strengh. the test would be to weld two rods together and grind the weld flush and smooth. Then to pull them apart. If the weld gives at, lets say, 50,000lbs of tension on the rod then the yield strength would be 50,000 lb divided by the x section area of the weld. If the weld had a x section of 0.5 sq ins then the yield strength would be 100,000 psi