Question

QUESTION 2 The 3 curves in the graph below belong to 3 materials i.e. concrete, coarse aggregate and cement. a) What is the graph representing of? [1 mark] b) How to measure it? [2 marks] c) Why is this property important? [1 mark] d) What are the factors that impact this property? Forks! [2 marks] e) Name one related structure for this case. [1 mark] f) Name J, K and L. Which is concrete, coarse aggregate and cement? [3 marks) Stress Strain

Answer 1

a)

The graph represents the stress-strain curve for the given three materials from which Young's Modulus of elasticity is determined.

b)

The initial linear part of the graph of each curve upto proportional limit obeys hooks law and their slope gives

Young's Modulus of Elasticity.

c)

Young's modulus is a measure of the ability of a material to withstand changes in length when under lengthwise tension or compression. It describes stiffness and is therefore one of the most important properties of solid materials. It is defined as ratio of longitudinal stress to longitudinal strain within the limit of proportionality.

d)

So by definition itself, it can be concluded that young’s modulus depends on following factors:

1. stress
2. strain
3. change of length, i.e , ∆l , as strain is the ratio of change of length to initial length of wire
4. elongation: it is inversely proportional to Young’s modulus.
5. Effect of temperature : In general as the temperature increases the elastic property of a material decreases.
6. Effect of impurities : Addition of impurity to metal may increase or decrease the elasticity. If the impurity has more elasticity than the material to which it is added, it increases the elasticity. If the impurity is less elastic than the material it decreases the elasticity.

f)

J - Coarse Aggregate

K - Concrete

L - Cement