混杂纤维高强混凝土的抗冲击性能

Quasi-static and impact test of Hybrid Fibers Reinforced High Strength Concrete (HFRHSC) will be conducted using MTS material testing machine and SHPB , and the compressive strength, split tensile strength, and spall tensile strength, and the stress-strain curves of HFRHSC at strain ratio range from 0.0001/s to 100/s will be obtained from the test. An ecperiment method called "freezing in" damage test will be used to decouple the strain raito hardening effect and damage softening effect. The fractal dimension and relative stress at the initial damage and critical fracture state of concrete specimen will be deterimined by the realtion between fracture toughness and the fractal dimension. The damage variable will be expressed by fractal dimension, and the anisotropic damage and irreversible deformation Helmholtz free energy of concrete will be defined, and the anisotropic damage constitutive equation and elastic module equation of concrete will be obtained. In order obtain the spall tensile strength and study spall damage evolvement process of concrete specimen, the SHPB will be refitted to the eqipment which can conduct direct measure spalling test, and the refitting method are as follows, absorption rod will be made by polymeric material instead of steel, and based the one-demension characteristic line theory. Based on the above equations and mechanical property parameters obtained from test, the dynamic property of five kinds of concrete under intense impact loading will be analyzed numerically by the continuum mechanics finite element method and distinct element method in an attempt to confirm and analyse the main component materials and strain raito's influence on the dynamic behaviour of HFRHSC during the tests.

采用MTS试验机和SHPB装置，对混杂纤维高强混凝土(HFRHSC)进行准静态和冲击试验，测试其在应变率0.0001~100/s范围内的抗压和抗拉强度、应力应变曲线。通过损伤"冻结"试验，将HFRHSC应变率硬化效应与损伤软化效应解耦。根据混凝土断裂韧性与分形维数之间的关系确定混凝土初始损伤和临界断裂状态时的分形维数和相应的应力，由分形维数表示损伤变量，定义包含各向异性损伤和不可逆变形的Helmholtz自由能，推导考虑各向异性损伤的混凝土本构模型、弹性模量方程。将SHPB改装成可以直接测试层裂的装置：吸收杆采用高聚物材料取代钢材，按照一维特征线理论，由吸收杆上的应变波形得出混凝土的层裂强度和层裂损伤演化过程。基于上述方程与实测参数，采用连续介质力学的有限元法与离散元框架内的离散法，分别对HFRHSC的冲击试验过程进行仿真，验证并分析冲击过程中组分材料和应变率对HFRHSC动态性能之影响。

课题组采用了MTS材料试验机和SHPB装置，对混杂纤维高强混凝土（HFRHSC）进行了准静态和冲击试验，测试出其在应变率0.0001/s至100/s范围内的抗压强度、劈拉强度、层裂强度、应力应变全曲线。通过损伤“冻结”试验，将HFRHSC应变率硬化效应与损伤软化效应解耦。根据混凝土断裂韧性与分形维数之间的关系确定混凝土初始损伤和临界断裂状态时的分形维数和相应的应力，由分形维数表示损伤变量，定义了包含各向异性损伤和不可逆变形的Helmholtz自由能，推导了考虑各向异性损伤的混凝土本构模型，根据回归分析建立了HFRHSC弹性模量方程和劈裂拉伸方程。将SHPB改装成可以直接测试层裂的装置：吸收杆采用高聚物材料取代钢材，按照一维特征线理论，由吸收杆上的应变波形得出混凝土材料的层裂强度和层裂损伤演化过程。依据最大拉伸应力模型，采用复合材料力学理论，建立HFRHSC层裂本构方程。基于上述建立的方程与实测力学性能参数，采用离散元颗粒流软件EDEM对HFRHSC试块进行动态压缩的仿真，获得了试验过程的不同时刻HFRHSC试块的破坏形态，并分析了不同应变率下试块的破坏历程。利用有限元软件ANSYS/LS-DYNA数值仿真再现了瞬态冲击下试块的压缩、劈裂、层裂破坏过程。离散元软件、有限元软件数值仿真结果都与HFRHSC的冲击试验结果吻合良好。