【作者】 唐录成；

【导师】 刘占芳；

【作者基本信息】 重庆大学 ， 固体力学， 2009， 博士

【摘要】 陶瓷材料具备耐高温、耐磨、耐腐蚀、抗氧化、电绝缘性好、压缩强度大等优良性能,广泛应用于电子、计算机、激光、核反应堆、宇航、兵器等尖端技术领域,由于陶瓷材料中存在气孔、缺陷、晶界,使得对陶瓷性能及使用效能的研究较为复杂,引起了材料科学家、力学家的广泛关注。特别是对陶瓷材料动态力学响应研究,近几十年以来已成为国际冲击动力学领域十分活跃的研究课题。本文主要研究冲击压缩条件下氧化铝陶瓷的动态响应特性。在充分调研陶瓷材料在高压、高率条件下动力学响应特性等诸多关键问题研究现状的基础上,开展了一级轻气炮加载、VISAR测试的氧化铝陶瓷平板正撞实验。获得了A95陶瓷的Hugoniot弹性极限,分析了厚度对σHEL的影响;观察到无氧铜飞片层裂现象,并对其产生的机理进行了分析;修正了Drucker-Prager屈服准则,使之适用于分析陶瓷类脆性材料。本文的主要研究内容和结论如下:①对陶瓷材料的失效准则、本构模型、应变率效应、平面载荷作用下陶瓷材料的破坏机制等问题进行了调研,明确了陶瓷材料动态性能研究的进展和存在的问题。从陶瓷材料的物质结构及显微组织等方面对陶瓷材料的结构进行了分析,得出影响陶瓷材料性能的因素。②针对陶瓷材料的物理力学性能及其影响因素开展了分析,从陶瓷材料的变形、断裂特征及弹塑性性质、晶粒尺寸对陶瓷性能的影响关系,高应变率下陶瓷材料的力学性能和破坏行为等方面进行了重点论述。并对冲击波物理实验原理及方法、现有的加载手段和测试方法进行了讨论。③采用超声波测试获得了氧化铝陶瓷样品的基本物理力学参量,通过电镜扫描观察了氧化铝陶瓷的细观结构,电镜扫描结果显示氧化铝陶瓷具有强烈的细观非均匀性结构特征。④开展了氧化铝陶瓷一级轻气炮加载实验,采用VISAR测试了不同厚度的氧化铝陶瓷样品在一维应变冲击压缩条件下自由面质点速度历程,得到了氧化铝陶瓷样品Hugoniot弹性极限。实验结果表明:随着样品厚度的增加,氧化铝陶瓷的σHEL呈下降趋势;当冲击压力在6GPa-8GPa范围内,陶瓷样品自由面质点速度历程存在二次再压缩现象,判断是由于陶瓷内产生的破坏阵面(Failure front)所造成的,与玻璃中的破坏波现象具有可比性。⑤根据A95陶瓷的平板冲击实验结果,修正了Drucker-Prager屈服准则,提出适用于陶瓷材料Hugoniot弹性极限表征的修正公式,并计算了A95陶瓷的σHEL值,分析理论值与实验结果存在差异的原因。⑥实验观察到异质材料撞击时,在飞片中会产生层裂现象,且无氧铜飞片中晶粒长大,分析了延性金属与陶瓷材料撞击时的层裂机理。⑦开展了氧化铝陶瓷动态特性数值模拟,采用ANSYS/LS-DYNA有限元软件模拟了氧化铝陶瓷平板冲击压缩实验结果,对比实验结果与数值模拟结果,分析其中的异同。对弹丸侵彻钢靶和陶瓷/钢复合装甲过程进行了数值模拟,对比了不靶板的抗侵彻能力。更多还原

【Abstract】 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.更多还原