Research On Creep Damage Constitutive Relation Of Titanium Alloy With Double Modulus

Deep submersible vehicle plays an important role in the exploitation of resources,scientific exploration,and maintenance of marine rights and interests.Manned pressure cabin is the key components of the deep submersible vehicle,which is subjected to extreme deep sea pressure during the operation so that titanium alloy material with high specific strength and high specific rigidity is usually used in engineering,but the creep of titanium alloy material under high-pressure environment for a long time cannot be ignored.At present,most of the creep studies are focused on the structure under tensile load at high temperature,which can not be directly applied to the creep behavior of titanium alloy at room temperature and high pressure.The damage mechanism of titanium alloy material under tension and compression is different,resulting in different mechanical responses of the structure during creep.If the traditional tensile method is used to study the compressive structure,it will inevitably cause larger errors.Therefore,it is necessary to establish a room temperature creep constitutive relationship that can consider different damage mechanisms of tensile and compression.Based on the theory of continuous damage mechanics and the theory of double modulus and creep damage mechanics,this paper first proposed a double modulus creep damage constitutive relationship model,and according to the creep characteristics of titanium alloy at room temperature,the constitutive relationship of double modulus creep damage was studied.Firstly,this paper adopts the method of theoretical analysis,connected the effective elastic modulus of isotropic damage material and the elastic theory of different modulus of tension and compression.The material with different creep behaviors of tension and compression is regarded as a special double modulus material,a double modulus creep damage constitutive model is proposed.Secondly,this paper uses Fortran language to carry out secondary development of ABAQUS,compiles UMAT and USDFLD subroutines,realizes the numerical simulation method considering the different tension and compression in each main direction of the material point according to the stress state of a point,and compares it with the classical physical model,preliminarily verifies the correctness of the program.Finally,according to the creep behavior of titanium alloy at room temperature,the creep damage constitutive equation is derived from the microscopic point of view.According to the existing test data,the relevant parameters in the model are obtained,and the creep analysis oftitanium alloy at room temperature under tension and compression is carried out.it is necessary to consider different damage mechanisms of tension and compression in creep analysis of titanium alloy structure under compression load.In this paper,through theoretical analysis and numerical simulation,the double modulus creep damage constitutive relation of titanium alloy is studied deeply,and a method which can consider different damage in each main direction is proposed.The damage parameters of titanium alloy in tension and compression are determined,which can be used to evaluate the creep life of the pressure structure of titanium alloy for theoretical basis and technical support.