Escapement The independent watchmaker, De Bethune, has developed a concept where a magnet makes a resonator vibrate at high frequency, replacing the traditional balance spring. In the late 19th century, electromechanical escapements were developed for pendulum clocks. In these, a switch or phototube energised an electromagnet for a brief section of the pendulum's swing. On some clocks the pulse of electricity that drove the pendulum also drove a plunger to move the gear train. In 1843 Matthäus Hipp first mentioned a purely mechanical clock being driven by a switch called "echappement à palette". A varied version of that escapement has been
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