Page 14 - Mechanical Engineer's Data Handbook

STRENGTHS OF MATERIALS 3

M and torque T, the maximum direct and shear Stress due to a ‘suddenly applied’ load (h=O)
stresses, a, and 7,,, are equal to those produced by
‘equivalent’ moments Me and T, where urn = 2a,
5, = T,/Z, and a, = M,/Z
Stress due to a mass M moving at velocity v
where Z, = polar modulus
T, = ,/m Me = (M + T,)/2
and
nD3 K (D4-d4)
Z=- (solid shaft) or - (hollow shaft)
32 32 ~ D
nD3 I[ (D4-d4)
(hollow shaft)
Z,=- (solid shaft) or - -
16 16 D
See section 1.1.7.

M
b
I. I .3 Compound bar in tension
I. I .2 Impact stress
A compound bar is one composed of two or more bars
In many components the load may be suddenly of different materials rigidly joined. The stress when
applied to give stresses much higher than the steady loaded depends on the cross-sectional areas (A, and
stress. An example of stress due to a falling mass is Ab) areas and Young’s moduli (E, and Eb) of the
given. components .
Maximum tensile stress in bar
Stresses
a,=a,[l +J-
where :
a, = steady stress = mgiA
x, = steady extension = wL/AE
h = height fallen by mass m.