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I have been assigned by my tutor to design a hydraulic guillotine (rubber bale cutter).

After designing its features of the hydraulic, cutting blade etc.

I tried to calculate the force needed of cutting a piece of Rubber bale (Natural as reference) having an ultimate tensile strength of 30 MPa (Shear strength assumed to be equal to tensile).

The maximum thickness of the rubber bale is fixed to 120 mm and width of the bale is 350 mm.

This set up would cater for the maximum cutting action since rubber material is spread all over the blades.

The equation I used was: F = A x Ss

where F is the cutting force, A is the shear area (120 x 350) mm² , and Ss is the Shear strength 30 MPa.

Using this equation the cutting force would be ridiculously large, 1260 kN or 128 Tonne.

But a normal rubber bale cutter has maximum 12 - 15 Tonne.

Can someone please point me in the right direction or correction ?

Books, examples and explanations are appreciated.

Thanks

After designing its features of the hydraulic, cutting blade etc.

I tried to calculate the force needed of cutting a piece of Rubber bale (Natural as reference) having an ultimate tensile strength of 30 MPa (Shear strength assumed to be equal to tensile).

The maximum thickness of the rubber bale is fixed to 120 mm and width of the bale is 350 mm.

This set up would cater for the maximum cutting action since rubber material is spread all over the blades.

The equation I used was: F = A x Ss

where F is the cutting force, A is the shear area (120 x 350) mm² , and Ss is the Shear strength 30 MPa.

Using this equation the cutting force would be ridiculously large, 1260 kN or 128 Tonne.

But a normal rubber bale cutter has maximum 12 - 15 Tonne.

Can someone please point me in the right direction or correction ?

Books, examples and explanations are appreciated.

Thanks

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