| Due to their excellent mechanical properties such as high strength,hardness,and good plasticity,metal materials are widely used in weapons,aerospace,transportation and other fields,and are an irreplaceable component of many industrial products.With the development of science and technology,the service environment of metal materials has become more severe,often facing a variety of extreme conditions such as high temperature,high pressure and high impact load.For example,the turbine blades of aero engines often bear impact loads when working in high temperature and high pressure environments.The armor is subjected to both high temperature and high pressure when it is attacked.The failure of metal materials usually occurs in these environments,and is accompanied by huge economic losses.The failure and destruction of metal materials under high temperature and high pressure environment must be closely related to their performance.Therefore,it is necessary to study the performance of metal materials under high temperature and high pressure environment and describe the change law of its performance,which requires the use of the equation of state.The equation of state is usually used to describe the state of matter under extreme conditions,under these conditions,the properties of matter will change.As the most widely used state equation,the Grüneisen equation of state can be combined with finite element software to predict the failure and destruction behavior of substances under extreme conditions.Therefore,it is of great engineering significance to study how to identify the parameters of the Grüneisen equation of state.And economic significance.The parameters of the Grüneisen equation of state of each metal material are different.The traditional Grüneisen equation of state parameter identification method requires multiple experiments under extreme conditions and combined with theoretical calculations.Such a parameter identification method is time-consuming and laborious;however,it has emerged in recent years.The combination of the numerical simulation methods(including MD and first principles of molecular dynamics)combined with the experiment not only saves time and effort,but also accurately obtains the parameters of the Grüneisen equation of state.However,only some metal materials with relatively simple composition and structure can be used to identify the parameters of the Grüneisen equation of state using a combination of numerical simulation and experiment.For multi-element alloys with more complex composition and structure,due to the lack of corresponding multi-element potential Function,the numerical simulation method is difficult to identify the parameters of the Grüneisen equation of state.Because of its excellent performance,multi-element alloys are often more widely used than binary and ternary alloys.Therefore,it is of great engineering and economic significance to study how to identify the parameters of the Grüneisen equation of state for multi-element alloy materials based on MD and first principles.In this paper,in order to explore the method of using numerical simulation to identify the parameters of the Grüneisen equation of state for multi-element alloys,the GH4169 alloy is used as the research object,using MD and first-principles methods to study the method of identifying the parameters of the Grüneisen equation of state for alloy materials.Main research content:1 The basic theory of the Grüneisen equation of state is studied,and based on the research of Ji et al.and Millett et al.,a method for calculating the parameters of the Grüneisen equation of state for multi-element alloys based on molecular dynamics and first-principles methods is proposed,which provides for subsequent calculations Theoretical basis.Taking the GH4169 superalloy as an example,the calculation was carried out.The molecular dynamics method was used to carry out the numerical simulation of the impact of each component in GH4169 under high pressure at the micro scale.The us-up curve was extracted,and the parameters C,S1,S2 and S3 were calculated.;Using first principles,calculate the Grüneisen coefficient ? of each component in GH4169,and finally get the Grüneisen coefficient ? of GH4169.In addition,the Hugoniot curve and its internal energy,0K isotherm and its internal energy are calculated,and compared with the results of the existing literature,the accuracy of the calculation method of the Grüneisen equation of state parameters of the multi-element alloy is preliminarily proved.2 In order to prove the accuracy and necessity of the calculation method of the Grüneisen equation of state parameters for the multi-element alloy proposed in this paper,the Grüneisen equation of state parameters of the GH4169 approximate replacement model are calculated based on molecular dynamics.The approximate replacement model uses Ni as the matrix and Ni3 Al as the strengthening phase.In order to avoid the misorientation affecting the accuracy of the calculation results,by studying the influence of the misorientation on the mechanical properties and deformation mechanism of the alternative model,five misorientations that affect the performance of the model are determined.In order to eliminate the influence of misorientation,the average value of all model parameters was used as the Grüneisen state equation parameter of the alternative model.Hugoniot curve and its internal energy,0K isotherm and its internal energy were also calculated,and compared with the previous work and existing The results of the literature are compared.The results show that the approximate replacement model cannot replace GH4169 alloy for Grüneisen equation of state parameter identification.At the same time,this result also proves the importance and necessity of the parameter calculation method of the Grüneisen equation of state for the multi-element alloy proposed in this paper.3 In order to verify the accuracy of the calculation method of the Grüneisen equation of state parameters for the multi-element alloy proposed in this paper,a plate impact experiment was carried out on the GH4169 superalloy,and the free surface particle velocity of the target was measured by DISAR.The parameters calculated in this paper are input into AUTODYN,the plate impact experiment is simulated,and the free surface particle velocity is extracted and compared with the actual experimental results.The experimental and simulation results are in good agreement,indicating that the parameters of the Grüneisen equation of state for GH4169 alloy calculated in this paper are correct. |
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