Shear force of steel and bolts
Here follows a short example of how to work out the shear force of a piece of steel. The factor of 0.6 used to change from tensile to shear force could vary from 0.58 - 0.62 and will depend on application.
Steel called EN8 bright has a tensile strength of 800 MPa and Mild steel has a tensile strength of 400 MPa.
To work out the force to shear a 25 mm diameter round steel EN8 bright;
- Area of the 25 mm round steel in mm2 = 12.52*π = 490.8 mm2
- 0.8 kN/mm2 x 490.8 mm2 = 392.64 kN = 40 ton X 0.6 (to change force from tensile to shear) = 24 ton
When working with a bolted joint, the strength comes from friction between the materials bolted together. Bolts are correctly torqued to maintain the friction. The shear force only becomes relevant when the bolts are not torqued.
A bolt with property class 12.9 has a tensile strength of 1200 MPa (1 MPa = 1 N/mm2) or 1.2 kN/mm2 and the Proof Load is 900 MPa = 0.9 kN/mm2
A bolt with property class 4.6 has a tensile strength of 400 MPa (1 MPa = 1 N/mm2) or 0.4 kN/mm2 and the Proof Load is 600 MPa = 0.6 kN/mm2 shear force = the force applied tangentially to a body is known as shear force.