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  1. A bar is subjected to a combination of a steady load of 60 kN and a load fluctuating between - 10 kN and 90 kN. The corrected endurance limit of the bar is 150 MPa. the yield strength of the material is 480 MPa and the ultimate strength of the material is 600 MPa. The bar cross-section is square with side a. If the factor of safety is 2, the value of a (in mm), according to the modified Goodman's criterion, is _________ (correct to two decimal places).
    1. 31.62
    2. 31.6
    3. 31.52
    4. 31
Correct Option: A

Pm =
Pmax + Pmin
2

Pa =
Pmax - Pmin
2

Pm = 100 kN; Pa = 50 kN
σm =
100 × 103
MPa
a2

σa =
50 × 103
MPa
a2

By Goodman’s equation,

a = 31.62 mm
By yield line equation,

a = 25 mm
Final answer is 31.62 mm



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