For each of the applications below, please suggest which strengthening mechanism

Question

For each of the applications below, please suggest which strengthening mechanisms would be helpful and which would not. Explain your reasoning. Make sure to include performance and cost in your analysis. a.) Springs for shock absorbers in a pick up truck-suggested material, carbon steel. b.) High pressure (2MPa) steam tube for heat transfer in nuclear reactor-max temperature 600 degree C-suggested material nickel alloy. c) Aircraft wing-suggested material-aluminum alloy. d.) Cast engine block for sedan automobile-suggested material aluminum alloy.

Explanation / Answer

a). Spring for shock absorber has precipitation hardened steel which provide high fatigue resistance at safe strength, provide dampening due to fine grain size and also it is economical. Further these are high strength steel and so will have higher spring constant. It has good stability of phases and have low strain hardening and thus provide long life.

b).High pressure steam tube with max temperature at 600oC uses Ni as it provide high temperature oxidation resistance, good high temperature creep behaviour. These steel are usualy dual phase steel fine grained steel and has grain boundary precipitation which provides excellent high temperature creep resistance. These are again ultra low hydrogen steel to protect against Hydrogen embittlement and Stress Corrosion Cracking (SCC).

c).Aircraft wing are made of Aluminium alloy as it is lighter and have excellent strength to weight ratio. Further it has excellent low temperature thermal fatigue properties. It will have excellent surface finish which provide good aerodynamics and low drag. Further it is resistant against corrosion and has natural anti-fouling properties which prevents against any microbial growth.

d).Cast engine block for sedan automobile suggested material is alluminium alloy as it is lighter and thus saves the vehicle weight and improve the fuel efficiency. Moreover, it has good dampening behaviour which reduces the engine vibration and related noise. It is better heat conducter and so engine heat can be better managed and will have improved response time of the engine vis-a-vis to cast steel engine block.Al-alloy engine are almost corrosion free and so no chance of corrosion build-up due to fuel additives or due to coolants and thus low maintenance and high reliability. Only shortcoming is it is costlier than cast steel engine but in order to consider the improved fuel efficiency in the life cycle of the vehicle, it is steel turn out to be a cheaper and beter option.

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