【作者】 高远飞；

【导师】 黄朝晖； Richard Todd；

【作者基本信息】 中国地质大学（北京） ， 岩石矿物材料学， 2014， 博士

【摘要】 为充分揭示陶瓷装甲材料的抗弹机理及探索优化陶瓷材料的高应变率形变性能测试的技术方法，针对目前陶瓷材料在进行真实子弹速度的抗弹性能测试后靶材破坏严重无法进行后续材料结构分析与动态载荷响应表征的突出问题，本论文利用压缩空气高速气枪在可控子弹质量与速度的前提下进行了100m/s子弹击打实验研究，并使用分离式霍普金森压杆（SHPB）实验对陶瓷材料的高应变率载荷下压缩强度性能进行分析，取得一些重要研究成果。论文分析了晶粒尺寸与第二相纳米颗粒对陶瓷材料力学性能的影响，细晶1.7μm的氧化铝材料具有较高的硬度18.3GPa，5wt%纳米碳化硅颗粒加入时Al2O3/SiC复相材料的强度和韧性明显提高，相比1550℃烧结的氧化铝陶瓷分别增加60%与45%，晶粒成分均匀的碳化硅陶瓷性能较好。研究了陶瓷试样弹坑表面形貌与弹坑下方裂纹类型，并结合Cr3+荧光/SiC拉曼光谱技术对试样的应力应变分布情况进行分析。结果表明高硬度的陶瓷材料中，弹坑逐渐减小且剖面裂纹类型从尖锐型压痕裂纹向锥形裂纹转变，高硬度23.8GPa的碳化硅试样中的锥形裂纹与表面角度小于45°；由于碳化硅与B4C/Al8B4C7材料脆性较大造成试样表面出现碎裂；氧化铝试样表面最大残余压应力为3.25GPa，双轴应力引起弹痕区域出现大量微裂纹，其中Al2O3/SiC材料弹坑中心区域微裂纹密度较大，更多地消耗了子弹侵彻的能量。借助Yoffe’s模型计算出了尖锐型压痕裂纹的出现位置与发展方向。根据子弹形变模型计算出子弹高速冲击瞬间产生1000℃以上高温，造成子弹与陶瓷靶材击打点局部材料的弹性模量降低，子弹与试样变形程度相对于准静态子弹压痕较大；氧化铝材料准静态子弹压痕区域最大残余压应力为5.19GPa，压痕下应力应变程度与子弹高速冲击后相似，塑性变形区域深度较浅。通过改变分离式霍普金森压杆实验的测试条件，研究了碳化钨垫块种类、陶瓷试样形状尺寸、入射波整形技术、接触端面摩擦效应等因素与测试过程中的陶瓷试样应力平衡状态及一维性、均匀性前提条件的关系。在1200-1800/s的高应变率压缩载荷下评价了陶瓷材料的压缩强度，发现随着氧化铝陶瓷晶粒尺寸减小其SHPB强度逐渐增加，最大为3.63GPa，含有5wt%碳化硅纳米颗粒的Al2O3/SiC复相陶瓷的SHPB压缩强度略有提高。由于裂纹尖端惯性效应的原因，所研究的陶瓷材料表现出高应变率敏感的力学性能特征。陶瓷材料高应变率形变过程中氧化铝陶瓷呈现较小的形变量，Al2O3/SiC陶瓷的弹坑区域残余应力较小且分布较均匀，较高硬度的陶瓷材料出现的锥形裂纹对装甲破坏程度最小。本研究为进一步丰富陶瓷装甲抗弹机理和新型陶瓷装甲材料设计提供重要的理论依据。更多还原

【Abstract】 In order to fully understand the bullet-proof mechanism of ceramic armour and furtheroptimize the testing technique of high strain rate deformation properties of ceramic materials,and aim at the continual problem: ceramic targets for bullet-proof properties testing, which areusually carried out at ballistic velocities, are seriously damaged after impact and cannot be usedfor the post-characterization of microstructure and dynamic response. The projectiles with thecontrolled speed and tip quality were fired by gas gun to impact the ceramic specimens at100m/sto mimic the bullet-proof properties testing, the microstructure, residual stress and plasticdeformation on both the target surface and cross-section were analysed in the project. The SplitHopkinson Pressure Bar (SHPB) method was also used to test the compression strength ofceramics under high strain rate.In this thesis, the effects of grain sied and nano particles as the second phase on themechanical properties of ceramics were studied. The alumina ceramic with fine grain size1.7μmhad higher Vickers hardness of18.3GPa. Compared with the alumina sintered at1550°C, thestrength and toughness of Al2O3/SiC nanocomposites increased by60%and45%respectively,when5wt%nano silicon carbide particle was added.The influence of different material mechanical properties on the bullet-proof efficiency wasanalysed in the project, the vital property for ceramic armour appeared to be hardness. Thecomparisons of the imparct region microstructure and crack categories beneath the impact ofdifferent materials were made, and the residual stress and material plastic deformation wereexamined by Cr3+fluorescence or SiC Raman spectroscopic technique. The results show that:with the increase of material hardness, the dimension of impact crater reduced and the conicalcracks appeared. The cracks in SiC sample with23.8GPa hardness were almost conical and hadless than45°angle to the surface. The surface materials of SiC and B4C/Al8B4C7Ceramics werepartly fractured due to the low toughness. The alumina sample had the highest compressionresidual stress level at3.25GPa, the microcracks in the impact region were induced by sufficientbiaxial stress. The highest microcrack density was observed in the centre area of Al2O3/SiCcrater and more energy of the penetrating projectile can be consumed. It is feasible to use theYoffe’s model to predict the crack patterns and positions under sharp impact. Because of the high temperature above1000°C was reached when the high speed impactoccurred, the Young’s Modulus of both projectiles and ceramic materials in the small impactregion reduced. Hence the projectiles and targets deformed significantly, and the bigger impactarea with lower level compression residual stress was found when compared to the quasi-staticspecimens. The highest compression stress for quasi-static samples was also existed in aluminaat5.19GPa. However compared to the dynamic tests, the residual stress and material plasticdeformation level beneath the quasi-static indentation were nearly the same but with moreshallow material deformation region.According to the effect studies of the tungsten carb anvils’ shape, ceramic specimen shapeand dimension designing, incident pulse shaping and interfacial frictions on the Split HopkinsonPressure Bar technique, the testing equipment and condition were modified and to assure thespecimens were in stress equilibrium during dynamic compression, so the preconception ofone-dimensional and uniform planar elastic wave propagation can be achieved. In this project theSHPB compression strength of different ceramics at1200-1800/s high strain rate obtained, thestrength increased with the reduction of grain size in alumina and the maximum result was3.63GPa. Compared with alumina ceramics, the5wt%addition of nano SiC particles had littleimprovement of the SHPB strength for Al2O3/SiC nanocomposites. Due to the inertia associatedwith the crack tip, ceramic materials exhibit rate-sensitive failure strength under the high strainrate load.The high strain rate deformation level of alumina was smaller than other materials; howeverAl2O3/SiC nanocomposites showed uniform and low residual stress in the crater region, the conecracks in high hardness materials was less harmful to ceramic armour. This study is a supplementto the bullet-proof mechanism of ceramics, and it can provide theoretical basis for designing andpreparing ceramic armours.更多还原