Question

i) What is the difference between true stress and engineering stress? Why do engineers not consider a test specimen's true stress? ii) Explain how a plot of stress versus strain is produced from force versus extension data iii) Looking at the diagram shown below 400 3 2 S 300 200 100 Metal 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 Strain a) What is the name of the 0 to 1 region in Metal A? b) With reference to crystal structure, explain what is occurring in Metal A in the region from 2 to 3 and then from 3 to 4? Why does the metal carry more stress from 3 to 4? c) What is the significance of point 4 in metal A? d) What is the name of the process which is occurring in Metal A in the region from 4 to 5? e) What is the elastic modulus of Metal A? f) What is the 0.2% proof stress of Metal B? g) Of the two metals shown in the above graph, which would make a better crash barrier material and why?

Answer 1

Hol area mateviol, o the Lsod ne SHYK ,becowe fhe area Upto elette unit of lood/り2 CPointi), the change /n areals very smal p'oste cleformos), hence in most of the dfesljns of engineetrg ti is considere Engg. strcs (ii) (A) 0-1 mgien → Elastic region Cb) Between 2 to3, the mattriul hay alrirdy suvpased the elasthc paper!j anol heefre the bond bejwun the mitecutes of matenol star'ts brťoking therfore the makrel ts new £ #dse t'tsnsistance to the amore d Leod and huce the stress va ue decresc . And the stress at yhis pein /s Caged the ULHmaftswess,修tr this potnt..the ASl d.005