A double U-shaped butt weld is to connect two plates 200 mm (d) × 20 mm (b), as shown in the figure. What is the stress developed in the weld if it is subjected to a moment of 10000 kN-mm?

A double U-shaped butt weld is to connect two plates 200 mm (d) × 20 mm (b), as shown in the figure. What is the stress developed in the weld if it is subjected to a moment of 10000 kN-mm?

Right Answer is:

75 N/mm2

SOLUTION

Assuming full penetration of groove butt weld. Using the bending equation the bending stress is given by

σmax = M.Ymax/I ——- (1)

Where

σmax = Max bending stress
Ymax= Vertical distance away from the neutral axis
M = Bending moment = 10 × 106
I = Moment of inertia

The Moment of inertia of a rectangular section about an axis through the Neutral axis is given by

I = BD3/12

where

B = Rectangular section width

D = Depth

I = (20 × 2003)/12 

And Distance of outermost layer from N.A. is given by,

ymax = d/2 = 200/2

Putting the value of M, I, and Ymax in equation 1 we get

= 75 N/mm2

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