Please help me to solve this. 5 stars guarantee You need to design a new mobile

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Please help me to solve this. 5 stars guarantee

You need to design a new mobile crane for a factory. Assume that the crane must carry 7000 lbs as shown in the vertical direction. The roller assembly is assumed rigid and much stronger than the bar and hook. Calculate the stress present in bar AB. Determine the factor of safety of the bar against yeild for the two proposed materials below: Aluminum Alloy 5456-H116: Yield Strength: 33ksi Structural Steel (A36): Yield Strength: 36ksi Based on your findings, would you reccomend this bar be built of either material? Or would you reccomend a design change? (remember to not blindly trust numbers, think: is there a way these factors could be further skewed in the real world?)

Explanation / Answer

Only normal stress is presented in AB.

=P/A = 7000/(*0.52/4) = 35650.7 psi = 35.65 ksi.

Safety Factors

nAL = 33/35.65 = 0.926

nsteel = 36/35.65 = 1.01

Would not recommend either of the two materials. FOr the aluminum, it is obviously seen that it will fail.

FOr the steel, the safety margin ( = safety factor - 1) is too small. In the real world, stress concentration will occur at the end of the bar. This will lead to failure. Also, possible misalignment of the load , curvature of the bar, load variation in application as well as material property variation will also lead to possible failure of the member. A minimum of safety of 1.5 is required in aerospace applications, and higher safety factors are required in other applications.

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