Macroscopic analysis of deformation characterization of a novel NPR bolt ductile material under tensile action

TAO Zhigang; SUI Qiru; FENG Yuxiang; MENG Zhigang; YAO Xulong; HE Manchao

Abstract：According to the research,geotechnical engineering is easy to produce large deformation disasters when subjec-ted to complex geological conditions,and the conventional support materials are unable to tolerate the large deformation and failure damage occurs.To cope with the large deformation disaster,the author's team developed a novel ductile mater-ial NPR(Negative Poisson's ratio)bolt.In this paper,in order to explore the macroscopic deformation characteristics of the novel ductile material NPR bolts,indoor tensile comparison experiments of NPR bolts were carried out.The experi-ment adopts a universal testing machine for NPR bolts,and utilizes a camera to record the deformation characteristic of the whole process.The experimental results found that:NPR bolts have better uniform deformation characteristics,and uni-form deformation begins to occur in the early stage of the whole process of tensile deformation failure;The failure frac-tures classification of different steel bars,which were mainly divided into"delamination-type fracture surfaces"and"frac-ture-type fracture surfaces"where the interface between the fibers and the matrix breaks down;Analyzing the uniform de-formation characteristics of the NPR anchors through the mechanical mechanisms and the reason for the insignificant necking phenomenon:it is found that the radius of curvature of NPR steel is larger at the necking place after tensile de-formation failure,so that the necking phenomenon is not obvious,which is due to the relatively small difference between the maximum uniform strain and the maximum strain;Numerical simulation of the effects of the threaded-rib structure and the light-circle structure on the deformation of the steel bars is carried out by the LS-DYNA algorithm:the analysis results show that the threaded-rib structure makes the steel bars better deformed during the tensile process,which is the result of the numerical simulation.The results show that the threaded rib structure makes the steel better deformed uniformly and absorbs the deformation energy in the tensile process.In summary,the macroscopic analysis of the deformation character-istics of the novel NPR bolt ductile material helps to better reveal its static tensile properties,which provides a valuable reference for quasi-static engineering practice.