Escapement of most pendulum clocks, and for the development of the grandfather clock, the first anchor clock to be sold commercially, which was invented around 1680 by William Clement, who disputed credit for the escapement with Hooke. The escapement increased the accuracy of pendulum clocks to such a degree that the minute hand was added to the clock face in the late 1600s (before this, clocks had only an hour hand). The anchor consists of an escape wheel with pointed, backward slanted teeth, and an "anchor"-shaped piece pivoted above it which rocks from side to side, linked to the pendulum. The
Strain energy release rate Strain energy release rate The strain energy release rate (or simply energy release rate) is the energy dissipated during fracture per unit of newly created fracture surface area. This quantity is central to fracture mechanics because the energy that must be supplied to a crack tip for it to grow must be balanced by the amount of energy dissipated due to the formation of new surfaces and other dissipative processes such as plasticity. For the purposes of calculation, the energy release rate is defined as where formula_2 is the potential energy available for crack growth, formula_3 is the work associated