Question

33. ... .... treats fracture as a thermodynamically
process.
a) Drude's theory, irreversible
b) Drude's theory, reversible
c) Griffith's theory, irreversible
d) Griffith's theory, reversible​

Answer 1

Definition

The Griffith theory states that a crack will propagate when the reduction in potential energy that occurs due to crack growth is greater than or equal to the increase in surface energy due to the creation of new free surfaces. This theory is applicable to elastic materials that fracture in a brittle fashion.

Scientific Fundamentals

Through a series of experiments, stress analyses, and synthesis of prior work, in his remarkable paper Griffith (1921) developed the fundamental concept that underlies the modern theory of linear elastic fracture mechanics. His theory is based on balancing the reduction of potential energy that occurs during fracture with the increase in surface energy due to the creation of new free surfaces when a crack grows.

The energy release rate, G, is defined as the energy that flows to the crack tip per unit of new crack surface created. An energy balance shows that

$$ G = - \frac{{\partial \Pi...