Failure Mechanisms And Lifetime Assessment Of Extrusion Container Based On Unified Viscoplastic Constitutive-creep Model Coupled With Damage Rule

Extrusion technology has been extensively used in manufacturing industry due to its merits of less material consumption,high production efficiency and environmentfriendly concept of development.Extrusion container is the key component of large presses in the extrusion industry and its durability as well as lifetime has crucial influence on the extrusion cost.In order to investigate the evolution of extrusion container's serving properties and improve its capacity and lifetime,this study is designated to build a unified visco-plastic constitutive model coupled with damage rule to describe the response of the material AISI H11 and H13 under the condition of extrusion process.Parameters in the model are determined by a series of experiments at an elevated temperature and the numerical simulation is implemented to validate the constitutive model and the deterioration of extrusion container.This work is meaningful to prolong the lifetime of extrusion container,and it mainly includes 5 parts:(1)Lifetime analysis of creep-fatigue interaction based on the combination of DDM method,S-N curve and critical shrinkage,including the elastic/elastic-plastic design theory of compound layers and linear summation of creep/fatigue damage as well as its lifetime prediction,which offers the essential research direction to study extrusion containers' failure mechanisms furtherly and elaborately.(2)To build the unified visco-plastic constitutive model coupled with damage rule for materials H11/H13 employed in extrusion containers,including choosing the fundamental constitutive/damage frames and making some modifications,as well as interpreting and determining the parameters in the model.(3)Design of experiments for mechanical properties investigation,including axial tensile tests,axial stress/strain-controlled symmetrical/asymmetrical cyclic tests and axial creep tests at an elevated temperature.It's helpful to build a new or modified item in the constitutive model to indicate the specific mechanical properties of specific materials and make it more powerful and accurate.(4)ABAQUS simulation of extrusion container under cyclic extrusion loading at high temperature with the help of several user-defined subroutines UMAT,DLOAD,UTRACLOAD and UMESHMOTION,including the creep-fatigue damage accumulation,shrinkage loss between every two shrink-fitting layers and wear depth of the inner surface of the liner of the extrusion container.(5)Relatively full analysis of extrusion container's serving responses based on finite-element simulation results,including predicting the critical position of creepfatigue crack failure and its lifetime,revealing the evolution of the shrinkage loss between every two extrusion layers along with extrusion cycles and its influence on the lifetime of the extrusion container as well as investigating the wear condition of the extrusion liner.This work is promising and useful to guide the design and maintenance of the extrusion container in order to prolong its serving lifetime.