# Numerical - Allowable shear stress, given tensile and yield strength

Q.  According to A.S.M.E code what is the allowable shear stress for a shaft without keyway effect, which has ultimate tensile strength and yield strength of 300 N/mm2 and 150 N/mm2 respectively.
- Published on 14 Sep 15

a. 45 N/mm2
b. 54 N/mm2
c. 40.5 N/mm2
d. None of the above

#### Discussion

• Sravanthi   -Posted on 03 Nov 15
A code was being established by A.S.M.E (American Society of Mechanical Engineers) for the design of transmission shafting.

Keyway: It is a square channel machined or slot cut into round steel bar/shaft.

Given: Yield strength (Syt) = 150 N/mm2 , ultimate tensile strength (Sut )= 300 N/mm2

Solution:

The allowable shear stress for a shaft without keyway effect can be calculated using the formula:

τall = 0.3 Syt or 0.18 Sut ----- (The minimum value obtained is considered as the allowable shear stress)

Therefore, substituting the given values we get,

τall = 0.3 x 150 = 45 N/mm2

τall = 0.18 x 300 = 54 N/mm2

τall = 45 N/mm2 is the minimum value obtained

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