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1. The problem statement, all variables and given/known data

A 2.2m long steel towing bar of solid circular section diameter of 45mm is expected to carry a maximum load of 210 kN. The safety factor is 4; and for the steel the UTS is 540 MNm^{-2}and the modulus of elasticity is 200 GNm^{-2}

i) Calculate the actual towing capacity of the bar and state whether the proposed limit is acceptable

ii) Determine the extension of the bar under the maximum proposed load

2. Relevant equations

i) σ = Load / Area

Proposed limit acceptable= SF = UTS / σ

ii) Change in length = (σ / Modulus of elasticity) / Length

3. The attempt at a solution

Hi I have worked out what I think is right but I have trouble writing the correct units, I will put what i have worked out could someone check if I am right please, thank you very much:-

i) σ = Load / Area = 210kN / ((∏(45 x 10^{-3}) / 4)

=

840x10-3 / 6.362x10-3 = 132.04 (now I think this is MNm^{2})

Proposed limit acceptable = SF = 540 / 132.04 = 4.09

So the proposed limit in this case is acceptable as it is over the required Safety Factor of 4

ii) Change in length = (132.04 / 200) x 2.2

= 0.66 x 2.2 = 1.45mm (??)

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# Homework Help: Mechanical principles - Stess and modulus of elasticity

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