A constitutive model is critical for the prediction accuracy of a metal cutting simulation. The highest strain rate involved in the cutting process can be in the range of 104-106 s 1. Flow stresses at high strain rate...A constitutive model is critical for the prediction accuracy of a metal cutting simulation. The highest strain rate involved in the cutting process can be in the range of 104-106 s 1. Flow stresses at high strain rates are close to that of cutting are difficult to test via experiments. Split Hopkinson compression bar （SHPB） technology is used to study the deformation behavior of Ti-6Al-4V alloy at strain rates of 10 -4-10 4s- 1. The Johnson Cook （JC） model was applied to characterize the flow stresses of the SHPB tests at various conditions. The parameters of the JC model are optimized by using a genetic algorithm technology. The JC plastic model and the energy density-based ductile failure criteria are adopted in the proposed SHPB finite element simulation model. The simulated flow stresses and the failure characteristics, such as the cracks along the adiabatic shear bands agree well with the experimental results. Afterwards, the SHPB simulation is used to simulate higher strain rate（approximately 3 × 10 4 s -1） conditions by minimizing the size of the specimen. The JC model parameters covering higher strain rate conditions which are close to the deformation condition in cutting were calculated based on the flow stresses obtained by using the SHPB tests （10 -4 - 10 4 s- 1） and simulation （up to 3 × 10 4 s - 1）. The cutting simulation using the constitutive parameters is validated by the measured forces and chip morphology. The constitutive model and parameters for high strain rate conditions that are identical to those of cutting were obtained based on the SHPB tests and simulation.展开更多
The split Hopkinson pressure bar(SHPB)tests are often conducted to obtain the dynamic compressive strengths of concrete-like materials which need to be interpreted or analyzed correctly as these data are very importan...The split Hopkinson pressure bar(SHPB)tests are often conducted to obtain the dynamic compressive strengths of concrete-like materials which need to be interpreted or analyzed correctly as these data are very important for the construction of reliable constitutive equations used in numerical simulations.In the present work,a numerical study is performed on the influence of specimen size on concrete in SHPB tests using a rate-independent material model.A new empirical equation for the dynamic increase factor due to inertia(confinement)effect is also proposed which took account of specimen size effect through its volume.It is shown that the empirical formula agrees well with the numerical results for the SHPB tests on concrete with different specimen sizes,and the dynamic increase factor due to inertia(confinement)effect increases with the increase of specimen size.展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.51205284,51575384)
文摘A constitutive model is critical for the prediction accuracy of a metal cutting simulation. The highest strain rate involved in the cutting process can be in the range of 104-106 s 1. Flow stresses at high strain rates are close to that of cutting are difficult to test via experiments. Split Hopkinson compression bar （SHPB） technology is used to study the deformation behavior of Ti-6Al-4V alloy at strain rates of 10 -4-10 4s- 1. The Johnson Cook （JC） model was applied to characterize the flow stresses of the SHPB tests at various conditions. The parameters of the JC model are optimized by using a genetic algorithm technology. The JC plastic model and the energy density-based ductile failure criteria are adopted in the proposed SHPB finite element simulation model. The simulated flow stresses and the failure characteristics, such as the cracks along the adiabatic shear bands agree well with the experimental results. Afterwards, the SHPB simulation is used to simulate higher strain rate（approximately 3 × 10 4 s -1） conditions by minimizing the size of the specimen. The JC model parameters covering higher strain rate conditions which are close to the deformation condition in cutting were calculated based on the flow stresses obtained by using the SHPB tests （10 -4 - 10 4 s- 1） and simulation （up to 3 × 10 4 s - 1）. The cutting simulation using the constitutive parameters is validated by the measured forces and chip morphology. The constitutive model and parameters for high strain rate conditions that are identical to those of cutting were obtained based on the SHPB tests and simulation.
基金National Natural Science Foundation of China(11572317)
文摘The split Hopkinson pressure bar(SHPB)tests are often conducted to obtain the dynamic compressive strengths of concrete-like materials which need to be interpreted or analyzed correctly as these data are very important for the construction of reliable constitutive equations used in numerical simulations.In the present work,a numerical study is performed on the influence of specimen size on concrete in SHPB tests using a rate-independent material model.A new empirical equation for the dynamic increase factor due to inertia(confinement)effect is also proposed which took account of specimen size effect through its volume.It is shown that the empirical formula agrees well with the numerical results for the SHPB tests on concrete with different specimen sizes,and the dynamic increase factor due to inertia(confinement)effect increases with the increase of specimen size.
