Page 24 - Mechanical Engineer's Data Handbook

STRENGTHS OF MATERIALS 13

Butt weld

The strength of the weld is assumed equal to that of the
plates themselves.

Fillet weld

Parallel loading: Maximum shear stress due to moment 7bs M/Z
(an assumption)
Shear stress 7 = F/tL where: M= bending moment.
Weld throat t =0.7w
where w = weld leg size. Direct shear stress T~ = F/A
where: A = total area of weld at throat, F =load.
Resultant stress 7r = J‘m

from which t is found.

Welded bracket subject to torsion

Maximum shear stress due to torque (T) z,= Tr/J (T=Fa)
Polar second moment of area J = I, + I,
where: r = distance from centroid of weld group to any
point on weld.
Direct shear stress sd = F/A
is
r
Resultant stress (T~) the vector sum of T~ and T~; is
Transverse loading: chosen to give highest value of T~. From T, the value oft
Shear stress 7 = F/tL is found, and hence w.
Throat t = 0.77~

I

,n\\\’m

1

Symbols used :
I=second moment of area of weld group (treated as
lines) = constant x t
Z = l/ymax = bending modulus