Could someone kindly provide me with the figures for the loading at which a 6mm ordinary mild steel rod will begin to stretch and one at which it will break please, assuming room temperature? An answer in kilogrammes would be good, just to settle an argument.
Stretching strain + breaking strain 6mm rod
Sep 29, 2011
11 Replies
It will start stretching under *any* load, linear(ish) up to about 15% at about four tons, and it will snap at just over 5 tons. A lot depends on the end fastenings, though, as welding it to something will have an unpredictable result on the strength of the bit affected by heat, and the same goes for ultimate srength. Cutting a thread so you can tighten it up with a nut will reduce the strength by a lot, depending on the thread form. Strongest is hot rolled Whitworth, as it shouldn't have the sharp, stress raising, corners of a cut thread.
Brilliant, thanks exactly what I needed.
Fallen out with SWMBO:-)?
Not his time :-)
Your typo, or maybe HWMBO? ;-)
Richard explained on 29/09/2011 :
My wireless keyboard sometimes misses a typed character.
What I typed was 'Not this time :-)'
The figure I have for S235 mild steel is a yield strength of 460N/mm2.
6mm rod has an area of 28.3mm2 x 460/1000 = 13kN, or 1.33 tonnes.
Finds missing divide by four under flap of envelope.
That seems very weak for 6mm rod.
68,300 psi breaking srain for mild steel, divide by four squared, then by pi, then by 4. 1.398 imperial tons. Then knock half off for the thread weakening it, or the heat affecting the metal near the welds. If I use a reasonably long spanner, I can easily snap a quarter inch diameter bolt. It's how I normally get the exhaust off the Land Rover.
yebbut that's shear strength, not tensile strength and in torsion which is odd in that the center plays little part.
Pretty sure i've lifted (most of) a car on a single 1/4" rod in part of a pulley block. Mind you it did deform a bit..
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