Based On Energy Dissipation Theory Of Fatigue Trial Study

With the study of the fatigue behaviors of materials, it is found that the existing energy dissipation-based fatigue theory has many deficiencies, especially an integrated study is lacked. The former researchers only studied the energy dissipation during fatigue from their most interested subjects. Actually, with the appearance of advanced experiment apparatus, it is conceivable to achieve the integrated research. On the basis of this, the author hopes to solve the integrated problem and perfect energy dissipation-based fatigue theory by the temperature response and the micrograph change of pure copper during low cycle fatigue.Through analyzing the energy dissipation process during fatigue, the author find that the mechanical energy is dissipated in various forms of energy, which are mainly the heat energy, which dissipates into the environment, and the stored energy, which is consumed by the deformation of the microstructures. Through analyzing the thermal dissipation and the stored energy during fatigue, it is found that the thermal dissipation elevates the temperature of the specimen above that of the environment. Thermal conduction takes place between the material volume units and thermal exchange between the specimen and the environment. The energy stored in materials during fatigue changes the energy state of the materials, and the energy state reflects the change of the surface microstructures, which is directly related to the damage state.Many studies show: Temperature change, which can reflect the dissimilar course of the fatigue behaviors of materials during low cycle fatigue, is self-similar with the change of thermal dissipation. The change of surface micrograph, which can reflect the dissimilar state of the fatigue behavior of materials, is coincident with the change of the stored energy. Consequently, in order to study the energy dissipation-based fatigue theory. the author think it integrated and scientific to measure synchronously temperature response and the micrograph change of pure copper during low cycle fatigue.In this paper, the test method and test result of the mechanical energy dissipation during fatigue are introduced. It is found that pure copper is a Masing martial whose cyclic creep can take place during fatigue, and the cycle stress\strain curves is divided into three segments. The cyclic hysteretic energy rises quickly at its earlier cycle, and gradually it rises steadily at the steady cycle, but it decreases quickly before ruptures. The cumulative plastic strain energy increases with the increase of the loading frequency and stress level, which is linear with fatigue life on semilog coordinate.The temperature response and the micrograph change of pure copper under low cycle fatigue are studied by use of infrared photography instrument and remote high power objective microscopy. The results showed: there exits obvious relationships between the measured temperature and the microscopic shape. Furthermore, temperature and the microscopic occur to dissimilar change with the differentia of loading mode and specimen shape. According to the Fourier's Law of the thermal conduction, the governing equation of the energy dissipation, and the finite elementmethod, the author find that temperature has one relation on the basis of energy with the surface, but the determinate relation isn't obtained due to the limits of the experiment instruments and time. Therefore, the author hopes to solve this problem and perfect the energy dissipation-based fatigue theory through farther studies.