Study On Dynamic Behavior Of A95 Alumina Ceramics Under Plane Shock Loading

Ceramics has been widely used in the key fields such as electronics, computer, laser, nuclear reactor, space navigation and weapon industry due to its excellent properties including heat-resistant, wearable, anticauterization, antioxidant, good insulation and high compressive strength. That the pores, defects and grain-interface in ceramics makes the mechanical behaviors and its application effects of ceramics complicated and numerous researchers in the field of material and mechanics are attracted to pay attention to the material behaviors. The research for dynamic response of ceramic materials under shock loadings has been becoming the most active subject in dynamical behaviors of materials in recent years.In this dissertation, the dynamic responses of alumina ceramic under plate shock loading were studied. The dynamic behaviors of ceramics under high-pressure and high strain-rates were reviewed. The plate impact experiments for alumina ceramics specimen were taken with one-stage light gas gun and VISAR measurement was performed. Hugioniot elastic limit was checked for different loading conditions. Effects ofσHEL with different thicknesses were analyzed and compared. Spallation in OFHC was observed and spallation mechanism was analyzed. The Drucker-Prager yield criterion was utilized to modify the dynamic strength formulation of brittle materials. The principal investigation and conclusions of the dissertation are as follows:①An insight was made into the failure mechanism, constitutive models, strain-rate effect and damage mechanisms of ceramic materials under plane shock loadings. The art-of-state and problems of dynamic behaviors of ceramics were clarified. Ceramic configuration was analyzed from material structure as well as microscopic structure. The fundamental elements affecting ceramic material behaviors were pointed out.②The physical and mechanical behaviors as well as the affecting factors were presented. The focus was placed on the deformation performance, fracture feature, elasto-plastic property and grain size in analysis, especially on the mechancal properties and failure behaviors of ceramics at high strain-rates. The shock wave experiment principle and methods, loading process and measurement methods were discussed in the dissertation.③The basic physical and mechanical parameters of alumina ceramics specimens were measured in ultrasonic experiments. The meso-scopic structure was observed by Scanning Electron Microscope (SEM). The remarkable meso-scopic heterogeneity of alumina ceramics was revealed with SEM.④Plate impact experiments of alumina specimens with one-stage light gas gun were designed and carried out. The surface particle velocity history of alumina specimens with different thicknesses was measured by VISAR. And theσHEL for alumina specimens was calculated and checked with the experimental results. Hugoniot Elastic Limit decreases as the specimen thickness increases. The recompression phenomenon was found in the particle velocity history of alumina specimens while as the impact pressure between 6GPa-8GPa. The recompression signals occurring in alumina under shock loaings are similar to those in glass where failure waves have been widely recognized.⑤The modified formulation for theσHEL was further investigated. Hugoniot Elastic Limit of A95 alumina ceramics was presented by use of the modified form of Drucker-Prager yield criterion. Comparisons were made between the calculational and experimental results.⑥Spallation phenomenon in flyer was observed when the target was impacted by different material flyer and the grain size in OFHC flyer was increased in the process. The spallation mechanism for the ductile metal when impacting ceramics was analyzed.⑦Numerical simulation for the dynamic behaviors of alumina ceramics under plate shock compressive loadings was made by ANSYS/LS-DYNA. In comparison of the experimental results with numerical simulating results the similarity and difference were analyzed. Projectile penetration into a metal target and a ceramic/metal composite target were numerical modeled and the anti-penetration capability of material was discussed.