Question

3. In a stress–strain curve from a tension test, the specimen begins to neck and the elongation between the gage marks is no longer uniform once the load is beyond .

a) yield strength b) proportional limit c) ultimate tensile strength d) Fracture stress

4. The two parameters that can define ductility are _____ and _______.

a) elongation b) engineering strain c) reduction of area c) poisson’s ratio

Answer 1

DYM a) yield Strength :- The point after which the material begine to deform plastically i.e. the point after which nonlinear (elastic + plastic) deformation sets in.

6) proportional limiti in the stress-strain Curve the point upto which oat & Hooke's law is strictly valid upto this point only. Beyond this point which stress-strain relation becomes non-linear = c) Ultimate tensile strength - Highest point on stress-strain curve . Max stress the material can carry before fracture. Necking occurs in metals when the rate of work hardering is lower stress. This corresponds to point of highest load in load displacement curve, well before failure and any cracks have appeared In practical sense we can say additional strains or deformations demand decrease in load/stress because of neck formation after this point.

d) Fracture stress in the curve after which physically. last the point on stress-strain material separates

4) The - two two parameters paramet that define ductility are elongation and reduction in Area % elongation a change in length x100 original length Reduction in Area Decrease original in Area Area Engineering strain : Response of the material to the load applied assuring uniform cl throughout loading cycle. Material property constant for the given load applied. poissons ratio !- Material property