Allowable Bending Stress on Cold Drawn Material

[SoCalME]

I am designing a beam that will be loaded in bending. I am considering a 1045 cold drawn material for improved strenght, however, I am not sure how the residual tensile stresses in the outer fibers of the beam will withstand the tensile stress. Will these fibers have the same tensile strength as a tensile test specimen?

Thanks for your help,

Chris

 

[metengr]

SoCalME;
What kind of beam geometry do you need? There are I beams and other kinds of beams. Second, you need to have a basic understanding of static’s . You need to develop a free body drawing to understand loads at critical locations along the beam. Once this is completed, you can evaluate bending stress in outer fibers of a beam using known locations and moments and beam size and compare with allowable stress values for material that you select.

 

[SoCalME]

metengr,

Thanks for the quick reply. I have done the statics and M*c/I calculations on a round bar beam. The maximum stress calculated is 34 ksi. I am looking for a factor of safety of 2.0 or greater.

I hope this helps,

Chris

 

[metengr]

SoCalME;
Ok, Can you increase the diameter of the bar to reduce the fiber bending stress to around 15 Ksi? If so, you could use ASTM A 36 structural bar with a specified minimum yield strength of 36 Ksi .

If not, you will need to go with a high strength low alloy steel structural steel bar ordered to an ASMT specification that provides a minimum specified yield strength of 75 Ksi.

 

[metengr]

Sorry for the typo, this should be ASTM not ASMT.

 

[racookpe1978]

You need to look at the availability and cost of the "exotic" beam - compared to the "routine, simple, heck anybody could do that" simple steels.

If nothing else, you have to be able to "sell" your final design to a customer, and if the exotic steels can't be readily bought, cut, welded, and fabricated safely and inexpensively, you've only added yet one more reason for a competitor to take your customer (and your boss to take your job!!!!!) away.

Sure, NASA and the DOD and airline flight engineers need to shave a few ounces of weight. Very few other people can afford 200 million dollar aircraft.