| Researchers' eyes were captured due to the high energy and insensitivity of 1.3,5-Triamino-2,4,6-trinitrobenzene(TATB)based polymer-bonded explosive(PBX)for a long time.TATB granules that have various and diverse structures are crucial intermediate in the process of thermal-pressure treatment.TATB granules have different mechanical properties and morphological structures,which makes TATB granular system(PBX)more complex and research of PBX mechanical properties more complicated.It's of great scientific and engineering significance for studying macroscopic properties of PBX to pour attention into mechanical properties and morphological structures of single TATB granule.In this paper,based on the in-situ mechanical loading device combined with X-ray computed tomography system,deformation and failure behaviors of single TATB granule are studied,and the relationship between the structure and mechanical properties is explored from the obtained granule structure data and mechanical parameters.The mean idea of this paper as follows:An in-situ mechanical loading device suitable for X-ray computed tomography system is developed.which can,from micrometer scale.study the evolution process of the structure and mechanical behavior of the samples under the mechanical loading in non-destructive,real-time and three-dimensional scanning conditions;the structural evolution of TATB granules during loading is observed and mechanical properties of TATB granules are recorded;A program algorithm for defect-recognition in the high-resolution CT image of granules is applied,and the approach of quantitating characterization of granule morphology and structure is established;the gray correlation analysis method has been used to analyze the Grey relational coefficient and grey relational grade between the morphological and mechanical characteristics of TATB granules.Subjected to uniaxial compression,granules show 3 stages successively:elastic deformation,elastic-plastic deformation,and collapse.Micrometer scale dispersed small internal defects hardly transform until failure of granule,while scores of microns scale large internal defects shorten the stage of elastic-plastic deformation.The deformation rate at collapse points of different granules also varies greatly due to the stochasticity of collapse.TATB granule presents a layered structure.From the outside to the inside of granule,the structures are dense surface layer,the dense area with fewer pores whose thickness accounts for about half of the granule radius,central zone with large and dense pores.The deference of internal structures is greater than the deference of the shape of different granules.The mechanical characteristics such as collapse force,failure force and yield force are strongly related to the morphological characteristics of the granules and are susceptible to morphological characteristics,especially porosity,the ratio of the thickness of the dense surface layer to the thickness of the dense area,the thickness of the dense surface layer,the thickness of the dense area and other parameters.By the study of granule structures and mechanical characteristics,mechanical parameters such as Young's modulus,yield strength,contact stiffness,and failure load of the granules are obtained.The effects of structural characteristics such as the flatness index of the contact surface and the distribution of defects inside the granules on the deformation,elastic-plastic stage,and collapse of granule are explained.Information that can quantitatively describe the structural characteristics of granules such as outline dimension,pores,dense area,the orientation of granule is got,which enriches the dimension of granule characterization.The application of the grey correlation analysis method establishes the correlation between granule structures and mechanical properties and compares the correlation between different characteristics,which lays foundations for the discovery of granule structures and mechanical properties. |
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