基于ESPI技术的混凝土单轴拉伸断裂特性研究

为了研究混凝土的拉伸断裂特性,对带有预制切口的C80高强混凝土棱柱体进行单轴拉伸试验,采用电子散斑干涉(ESPI)技术测量棱柱体表面的场位移等信息,分析加载过程得到混凝土的断裂参数以及断裂特性等。为进行对比分析,本次试验还采用线性位移计和夹式位移计测量试件的变形程度。对比结果表明ESPI技术的测量结果与夹式位移计结果吻合较好,证实了ESPI技术用于测量混凝土表面位移场的精确性和可行性。分析得到:初裂点应力约为峰值应力的82%;峰值下裂缝口张开位移(CMOD)为11 μm,结合公式得到混凝土在单轴拉伸下的断裂韧度约为0.41 MPa·m^1/2,断裂能约为24.71 N/m;利用两种拟合公式对试验应力-应变关系进行拟合,得到了较好的拟合结果。最后,通过不同加载步骤下ESPI技术测得的位移云图分析裂缝口张开位移随试件宽度的变化规律,得到了单轴拉伸下的裂纹扩展规律。

Uniaxial Tensile Fracture Characteristics of Concrete Based on ESPI Technology

In order to study the tensile fracture characteristics of concrete, the uniaxial tensile test of C80 high-strength concrete prism with precast cuts was carried out, the field displacement of the prism surface was measured by electronic speckle pattern interferometry (ESPI) technology, and the fracture parameters and fracture characteristics of concrete were analyzed during the loading process. For comparative analysis, the deformation of specimen was also measured using a linear displacement meter and a clip-on displacement meter. The comparison results show that the ESPI technology measurement results are in good agreement with the clip-on displacement meter results, which confirms the accuracy and feasibility of ESPI technology to measure the displacement field of concrete surface. The analysis shows that the initial crack point stress is about 82% of the peak stress. The crack mouth opening displacement (CMOD) of the peak load is 11 μm, and the fracture toughness of concrete under uniaxial tension is obtained by combining the formula to obtain a fracture toughness of about 0.41 MPa·m^1/2, and the fracture energy is about 24.71 N/m. The experimental stress-strain relationship is fitted by using two fitting formulas, and the fitting results are good. Finally, the crack propagation law under uniaxial tension was obtained by analyzing the crack mouth opening displacement varied with the width of specimen in the displacement cloud map measured by ESPI technology at different loading steps.