Question:

(a) Explain why metals are mostly ductile and ceramics brittle at room temperature.

(b) Describe what you understand by the following terms. Use appropriate illustrations.

(i) Elasticity
(ii) Ductility
(iii) Resilience
(iv) True stress and strain of a material

(c) From the tensile stress-strain behaviour for the brass specimen shown in Figure 1 on following page, determine:

(i) The modulus of elasticity (the stress/strain axes have been expanded in the inset)

(ii) The yield strength at a strain offset of 0.002.

(iii) The maximum load that can be sustained by a cylindrical specimen having an original diameter of 12.8 mm.

(iv) The change in length of a specimen originally 250 mm long that is subjected to a tensile stress of 345 MPa.