tensile strength
tensile strength
(OP)
I am trying to calculate the tensile strength of a screw by taking the wire tensile strength and drawing it down thru a wire drawer and then cold heaing it. Example .224 302 wire 72ksi drawn down to .214 diameter and headed to .2150 dia. Is there a formula to determine how much tensile will increase per .001 that the wire is drawn?





RE: tensile strength
RE: tensile strength
I would not expect hte strength of drawn wire to correlate with strengths for roll formed parts anyway. Very different working methods.
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Corrosion never sleeps, but it can be managed.
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RE: tensile strength
RE: tensile strength
One thing that has a large bearing on the strength after drawing is the draw die geometry. The entry angle and land width have a surpisingly large impact on the after drawing results.
The earlier comment about the effects of chemistry is very true; you cannot extrapoplate between alloys what any reliability.
RE: tensile strength
What you have described is a common practice in the forming and forging industry. Usually this analysis is performed in order to know what the forming loads will be at various stages of deformation, which aids in determination of appropriate tools and presses. The following equation is used to describe the stress vs. strain behavior of isotropic metals during plastic deformation:
σ = Kεn
where σ = the flow stress
ε = the true strain
n = strain hardening exponent
K = strength coefficient
For annealed austenitic stainless steels like Type 302 & Type 304, the value for K = 1300 MPa (N/mm2) and n = 0.45. Values for annealed Type 316 are K = 1100 MPa and n = 0.40. This data was obtained from the International Cold Forging Group document ICFG Document No. 11/01 Steels for Cold Forging - their behavior and selection. If you know the amount of true strain (a 20% change in diameter is a strain of 0.20), then you should be able to calculate the increase in strength during forming.
As the others have already noted, variations in alloying, wire drawing practice, etc. will affect the deformation behavior. Strain rate also has a significant effect. You should discuss this issue further with your stainless steel supplier, as they should have a technical contact who can provide more specific data. Also, you can find some graphs of increase in tensile strength vs. % cold work by using the following links:
Carpenter
http://cartech.ides.com/ImageDisplay.aspx?E=313&am...
Nickel Institute
http://www.nickelinstitute.org/index.cfm/ci_id/114...
RE: tensile strength
A 20% change in LENGTH is an engineering strain of 0.20. For TRUE strain and DIAMETER change, the relationship is:
ε = ln (d02/df2)
where
ε is the true strain
d0 is the original diameter
df is the final diameter
Regards,
Cory
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RE: tensile strength
= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.
http://www.trenttube.com/Trent/tech_form.htm