Temperature Dependent Dynamic And Damage Model Of Typical Metal Structure Materials

Metal structural materials are widely used in construction machinery and equipment.In the service process of aerospace,pressure vessel and other major equipment,its structure is easy to be affected by dynamic load and high temperature environment,resulting in plastic deformation and fracture of metal structural materials.Therefore,the establishment of constitutive relationship and damage model which can accurately describe the high temperature dynamic coupling of metal structural materials is very important for structural safety design and evaluation.However,the existing classical mechanical models do not consider the coupling effect of loading speed and temperature,which makes it difficult to accurately describe the large plastic deformation and fracture failure behavior of materials under the combined action of dynamic load and high temperature.Therefore,aiming at the above problems,this paper selects two typical metal structural materials-1420 aluminum alloy for aerospace and X80 Pipeline Steel for high-pressure pipeline-to carry out systematic experimental and simulation research.The main research contents and conclusions are as follows:(1)A constitutive model for temperature and strain rate coupling of 1420 Al Li alloy.Firstly,the high temperature deformation of the material is described by Arrhenius constitutive model.The results show that the strain rate is insensitive at 293 ? 423 K;The improved Johnson cook model is used to describe the experimental phenomena.(2)The temperature dependent constitutive model of X80 pipeline steel is studied.Firstly,through mechanical test,the results show that the strength of X80 pipeline steel is different from 1420 Al Li alloy under different temperature and strain conditions;The difference between the shear and tensile test results of 1420 Al Li alloy and X80 pipeline steel was observed,and the Lode angle parameter was introduced to describe the mechanical behavior.(3)The fracture failure behavior of the two materials under stress triaxiality,temperature and strain rate was discussed.Firstly,tensile tests with different notch radius and compression tests with different diameter height ratio are carried out.It is found that with the increase of notch radius,the strength decreases and the overall trend of compression performance is similar.Secondly,Bao-wierzbicki damage model is used to describe the fracture failure behavior of two materials in high stress triaxial test and negative stress triaxial test.Finally,the change trend of fracture strain with temperature is analyzed by using the improved Johnson cook damage model.(4)The fracture morphology of the two materials at different temperatures was observed to understand the effect of temperature on the fracture mode of the materials.Firstly,the fracture analysis of 1420 Al Li alloy shows that intergranular fracture at low temperature,poor plasticity at macro level,and obvious dimple and Recrystallization at high temperature.In addition,the fracture surfaces of X80 pipeline steel all have accumulated plastic dimples,and the dimples are thicker and deeper,showing better plasticity.Finally,based on the classical constitutive model and failure damage model combined with the specific test phenomenon,the Johnson-Cook constitutive model and failure damage model are modified.Considering the coupling effect of temperature and strain rate,the influence of different stress states on the strain and the impact on fracture strain,the special mechanical behavior of the material is described accurately,To ensure the safety of metal structure.