# Numerical - Reason for failure, given principal stress & elastic limit stress

Q.  Principal stress of 30 Mpa and -70 Mpa acts on a material which has elastic limit stress in simple tension and compression as 60 Mpa and 200 Mpa respectively. Specify the reason for failure of the material assuming maximum principle stress theory.
- Published on 23 Sep 15

a. Compression
b. Tension
c. Unpredictable

#### Discussion

• Sravanthi   -Posted on 25 Nov 15
Given: Principal stress in tension (30 Mpa and 60 elastic limit stress), principal stress in compression (-70 Mpa and 200 elastic limit stress )

1) Tensile test

Maximum stress ≤ elastic limit stress

FOS = 60 / 30 = 2 ---------- (1)

2) Compression test

Minimum stress ≤ elastic limit stress

FOS = 200 / 70 = 2.8 --------- (2)

From (1) and (2) , it is observed at factor of safety for the material, which fails due to tension is less and that due to compression is more. Hence, the material fails due to tension.

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