Problem

The resistance of a material to fracture is assessed via a fracture test. One such test is...

The resistance of a material to fracture is assessed via a fracture test. One such test is the Charpy impact test, in which the fracture toughness is assessed by measuring the energy required to break a specimen of a specified geometry. This is done by releasing a heavy pendulum from rest at an angle θi and by measuring the maximum swing angle θf reached by the pendulum after the specimen is broken. Suppose that in an experiment θi = 45°, θf = 23°, the weight of the pendulum’s bob is 3 lb, and the length of the pendulum is 3 ft. Neglecting the mass of any other component of the testing apparatus, assuming that the pendulum’s pivot is frictionless, and treating the pendulum’s bob as a particle, determine the fracture energy of the specimen tested. Assume that the fracture energy is the energy required to break the specimen.