Study On Mechanical Behavior Of TC11 And DZ406 Materials At High Temperature And High Strain Rate

TC11 titanium alloy and DZ406 superalloy materials have excellent mechanical properties such as high temperature resistance,good plasticity and high strength,and have been used in engines.Because the engine works in high temperature and high pressure environment for a long time,the mechanical properties of the materials used will change under the impact load of high temperature and high strain rate.Accurately predicting the dynamic mechanical behavior of TC11 titanium alloy and DZ406 superalloy at high temperature and high strain rate is of great significance to the analysis and evaluation of engine structural performance.In this paper,a high-speed impact test was carried out on TC11 titanium alloy and DZ406 superalloy standard specimens by means of a split Hopkinson pressure bar(SHPB)device.The mechanical properties of these two materials at high temperature and high strain rate were studied.The Johnson-Cook(J-C)constitutive model parameters of the two materials were solved by reverse calculation based on the experimental data,and the obtained constitutive model parameters were verified by finite element analysis method.The main work is as follows:(1)A material performance test platform was built under high temperature and high strain rate conditions,and an experimental test scheme was designed.The testing principle and basic assumptions of SHPB test are introduced,including one-dimensional stress wave assumption and uniform stress distribution assumption.This paper introduces the processing methods of test data: three wave method and two wave method,and uses two wave method as the processing method of test data.A SHPB test platform that can meet the conditions of high temperature and high strain rate was built,and a set of test schemes for TC11 and DZ406 materials under high temperature and high strain rate tests were developed,including: high temperature loading scheme and high strain rate loading scheme,etc.Based on the test equipment and the test scheme,the axial impact tests of the two materials were carried out under the conditions of 10 and 5 × 10 strain rates in the temperature range of 25℃～400℃.The time-dependent strain data of the two materials at different temperatures and different strain rates are obtained.(2)The variation rule of typical mechanical properties of the two materials affected by temperature and strain rate was analyzed.By processing the basic test data,the real stress-strain curves and the maximum load-bearing stress of the two materials were obtained under the condition of high temperature and high strain rate,and the variation rules of the mechanical properties of the two materials affected by strain rate and temperature were analyzed.The results show that the strain rate and temperature have effects on the mechanical properties of TC11 material.Under the same temperature condition,the maximum bearing stress of TC11 material increases with the increase of strain rate,showing the phenomenon of strain rate enhancement.At the same strain rate,with the increase of temperature,the maximum bearing stress of the material decreases,showing the thermal softening phenomenon.For DZ406 material,the maximum bearing stress of the material increases with the increase of strain rate at the same temperature,showing the phenomenon of strain rate enhancement.When the strain rate is the same,in the temperature range of 200℃～300℃,the maximum bearing stress of the material decreases with the increase of temperature,showing the thermal softening phenomenon.In the temperature range of 25℃～200℃ and 300℃～400℃,the maximum bearing stress of the material increases with the increase of temperature.(3)The J-C constitutive model parameters of the two materials are solved.Based on the real stress-strain curve data of the two materials at different temperatures and different strain rates,the J-C constitutive model parameters of TC11 and DZ406 materials were inverse solved by using the stress data corresponding to the specified strain,including: under the condition of static yield strength,strain hardening parameter,strain hardening exponent,strain rate,temperature effect parameters,etc.,to solve the model prediction results compared with the test results,found the model predictive error,the use of different stress-strain curve under the conditions of all data points on the model parameters are fitted modifying,the prediction results of the optimized J-C constitutive model were compared with the experimental results,and the prediction accuracy was improved.Finally,the finite element simulation software LS-DYNA was used to verify the constitutive model,and the numerical simulation results are in good agreement with the experimental data results.