Study On Bond Mechanical Properties Of NiTi Shape Memory Alloy Fiber And High Ductility Cement-based Composites

In this paper,the bonding properties and main influencing factors of shape memory alloy fibers and high ductility cement-based composites are studied by experiments.at the same time,combined with the existing research,the bond-slip constitutive model of shape memory alloy and high ductility cement-based composites is proposed.The main contents are as follows:(1)With reference to the existing mix ratio of high ductility cement-based composites,the ultimate tensile strain is more than 3%.Through the direct tensile test of dog-bone-shaped specimens,the properties of the test materials and the ultimate tensile strain are verified.(2)Through the direct tensile test and cyclic tensile test of the SMA wire used in the test,the basic mechanical properties of SMA wire were obtained,including initial elastic modulus,yield plateau stress,ultimate tensile strength,residual deformation in the cycle and its corresponding recovery rate.(3)In the experiment,four experimental groups were set up according to the three factors of fiber diameter,fiber end and embedded depth.Through the direct drawing and cyclic drawing tests,the stress-strain curves and bond stress-slip curves of each group of specimens were obtained.At the same time,the maximum fiber stress,maximum bond stress and fiber utilization ratio were used to evaluate each group of specimens.The results show that the knotted end can effectively improve the bonding properties and give full play to the superelastic properties of the fiber.Through comprehensive evaluation,too long embedding depth and too large diameter will reduce the utilization rate of fiber.(4)The bond-slip constitutive relations of shape memory alloy-high ductility cement-based composites are divided into two types: insufficient anchoring and sufficient anchoring.Two formulas are proposed to describe the two kinds of constitutive relations.At the same time,the proposed constitutive model is fitted and compared with the curve obtained by experimental analysis by origin,and it is found that in most cases,the constitutive model proposed in this paper is in good agreement with the experimental curve.