energy needed to cut a hole 1

[pardal]

Hi all.

I have to cut sae 1070 Harden and tempered to 55 HRC, blue spring strip, 0.5mm thick 6 mm diameter hole.
It is done by hiting a 6 mm punch , made from HSS, to the such strip. I did it by a hammer about 1000 grams by my arm force.
It Works.
But I want to do it by a free fall weigth, or potential energy.
So my question is : how much energy is need to cut such hole.
For a 55 HRC the ultimate yield is about 212 Kg/mm2, so for a 6 mm diameter there is 6 mm * pi* 0.5 mm = 9.42 mm2 area
and for this ultimete yield 9.42 mm2 * 212 Kg/mm2 = 1997.04 Kg
But this is weigth , not energy.
As the work to do is seldom used I want to make the free fall hammer . The allowed heigth will be 2.00 meter , what will be the hammer weigth.
It seem to be a lazy student home work , but not .
Furthermore that all we are allways student I'm 55 old mechanics and want to know the theory on this fact.








Pardal

 

[desertfox]

Hi pardal

The formula I have is for the punching force and is :-

F=1.5 x s x L x t

where s= ultimate shear stress of the material

L= perimeter

t=material thickness

ultimate shear stress for a material = 0.7 x ultimate
tensile strength


so to calculate the energy required then:-

energy = force x (the distance the force it acts over)

so using your figures 212kg/mm^2 x 0.7=148.4kg/mm^2


blanking force =148.4 x 1.5 x 6 x 3.142 x 0.5=2098.2276kg


energy req= 2098.2276kg x 9.81 (to convert kg to newtons)x
0.0005m

energy req = 10.29J

mass req at a 2m height

energy = mass x 9.81 x 2


10.29j/(9.81 x2)=mass=2.098kg

please note these formula are approximations only.

hope this helps

regards

desertfox

 

[Lcubed]

desertfox,
0.6 is closer to the shear strength / tension strength ratio for most materials. Was that a typo?

 

[desertfox]

Hi Lcubed

It was no typo according to my machinery's hand book
all steels listed which include steels from the sae range and structural,stainless are given a maximum shear stress
of 0.75 x u.t.s.
I am aware though that this figure for shear can vary some use 50%, some 60% and others 70 to 75% depends what your doing and what safety factor you use.

regards

desertfox