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

ANSWER: Tension
 

    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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