Balance Relations of Thermodynamics

Abstract

The work of a system of forces changes a material body’s kinetic energy content according to the balance of mechanical power: only a certain fraction of the power of external forces is transformed into kinetic energy; the remainder is stress power. Stress power makes two contributions to the energy budget of a material body as a general rule: part of the work done by the stresses on the strain rates is stored in the material body. Experience has shown that another part is transformed into non-mechanical energy. This part is closely related to a phenomenon which is known as dissipation. Dissipation either increases the non-mechanical energy contents or is released into the environment in the form of heat.