Consider the tensile stress-strain diagrams in Fig. 5 labelled 1 and 2 and answe
ID: 1765820 • Letter: C
Question
Consider the tensile stress-strain diagrams in Fig. 5 labelled 1 and 2 and answer the following questions. These diagrams are typical of metals. Consider each question as an independent question that has no relationship with the other questions. 500 400 300 100 0.05 0.1 0.15 0.2 Figure 5: stress-strain curves for two materials 1) Do the stress-strain curves given on Figure 2 represent the true-stress-strain or the engineering stress-strain curves? Explain. 2) Which of materials 1 and 2 has the largest ductility? Explain. 3) Materials 1 and 2 are identical except for the grain size. Which material has the smaller grains? Explain. 4) Materials 1 and 2 are identical except that they were tested at different temperatures. Which material was tested at the lower temperature? Explain. 5) Materials 1 and 2 are identical except that one of them is a pure metal while the other has a small percentage of alloying elements. Which material has beern alloyed? Explain 6) Materials 1 and 2 are steels and the following table gives their Which material will be the easiest to weld? Explain your reasoning Material | %C | % Si | % Mn | % Ni | %Cu | %V | % Cr | % Mo 0.13 0.35 0.60 2 0.33 0.35 0.70 1.20 0.25Explanation / Answer
1) fig 2 represents true stress strain curve.
Explanation - Stress is linearly varing with strain up to proportionality limit . Then it has upper and lower yielding points.
Again in between ( strain value) 0.1 to 0.15 yielding zone is present. Strain hardening zone after 0.15 value of strain.
2) Material 2 is more ductile as it can sustain more strain than material 1. Material 1 have more tensile strength than material 2 but material 1 can sustain lesser value of strain than material 2.
3) Material 2 has fine grain size . Again because of more strain , it is more ductile. Material which is more ductile have fine grain size.
4) Material 2 is tested at lower temperature , as it is more ductile. Material which are more ductile (i.e. having more strain) are tested at lower temperature and material containing high carbaon (therefore more strngth ) are tested at higher temperature.
5) Material 1 has more brittelity as having less strain. Mmaterial which is more brittle may have more alloyes. If alloyes get added, material ductility changes to brittelity.
6) Material 1 is easy to weld as less percentage of carbon i.e. 0.13 %, more % of carbon more difficulties in welding.
Still there is formula to work out combined effect of carbon and alloying elements on weldability, it is given by carbon equivalent value (Ceq),
Ceq = %C + %Mn/6 + (%Cr + %Mo +% V ) / 5 + (%Ni + %Cu) / 15 .......( Ceq Should be less than 0.42 %)
Ceq ( Material 1) = 0.23 %
Ceq ( Material 2) = 0.73%