Creep-fatigue Damage Mechanism And Lifetime Prediction Of Large Extrusion Container Under Complicated Service Conditions

Extrusion products have been widely used in the field of transportation, aerospace, electronics and electric power etc., due to less material consumption, high production efficiency and environmental concept of green and Low-carbon development. Specifically, the large panel extrusion products receive more and more concern in recent years.Large extrusion container is the key part of large extrusion machine, its durability and service lifetime is of great influence to extrusion cost. Serving in the extreme working conditions with thermo-mechanical loadings would result deterioration in their mechanical properties and make it prone to failure due to existence of inside container from mediate one or extrusion deformation even fracture unpredictably. Therefore, it is important to investigate the lifetime prediction of container.Most foreign studies aimed at combining the experimental results to reflect the constitutive properties of materials and numerical simulations to predict the extrusion container lifetime, this method is very complicated and difficult. However, the domestic studies on this field is extremely few. This paper takes a large size extrusion container as the research object, and puts most concern on lifetime calculation method under fatigue damage, creep damage and fatigue-creep interaction in order to improve the service lifetime of extrusion container.①The developed designation of extrusion container is based on the Lame formula, combining DDM method, it can realize the analysis of the stress of multilayer interference extrusion container, including assembly interference and extrusion process. Compared with the traditional superposition method, this method is simple and suitable for the analysis of multilayer extrusion container.②To more accurately simulating the changes of extrusion container stress in the extrusion process, based on the previous finite element analysis, the paper simplified the complex condition of extrusion process. Only considering the influence of internal ramp load and temperature on physical properties of material, the stress distribution and variation on container in the whole extrusion process are derived based on the DDM method.③The fatigue creep properties of container material H13 under high temperature can be determined through fatigue test and creep test. Fitting the experimental results, the S-N curve and creep rate function are achieved, which provide a good foundation for subsequent life analysis of extrusion container.④A new definition of the fatigue-creep interaction is proposed, i.e. creep deformation lead to interference changes which influences stress distribution and results in fatigue damage, while stress distribution change in turn affects the creep rate and creep deformation, so that the creep-fatigue interaction lifetime is defined as the time when fatigue failure or creep failure happened. Based on this definition, the creepfatigue interaction lifetime is analyzed.In summary, this paper mainly adopts the combination of experimental and theoretical analysis to study the extrusion container lifetime, which can provide reference for the design of extrusion container for considering fatigue-creep interaction.