Topic: Machine Design
A 50 mm diameter solid shaft is welded to a flat plate all around by fillet weld of 4mm leg size as shown in Fig. If the allowable shear strength of the weld material is 100 MPa, the maximum approximate torque in Nm that the welded joint can sustain under pure torsion is
- A. 500*pi / $\sqrt{2}$
- B. 1000*pi / $\sqrt{2}$
- C. 500*pi*$\sqrt{2}$
- D. 1000*pi*$\sqrt{2}$
Answer: A. 500*pi / $\sqrt{2}$
Explanation: Throat thickness t = 0.707 * s = 4 / $\sqrt{2}$ mm. Polar moment of inertia of a circular weld J = pi * t * D³ / 4. Torsional shear stress tau = (T * r) / J. Therefore, T = tau * J / r = tau * (pi * t * D²) / 2. T = 100 * pi * (4 / $\sqrt{2}$) * (50^2) / 2 = 500,000 * pi / $\sqrt{2}$ N-mm = 500 * pi / $\sqrt{2}$ N-m.