Experimental Research On Impact Splitting Tensile Mechanics Of Concrete With Ellipsoid Defect

Concrete materials are widely used in infrastructure construction such as housing construction,transportation and water conservancy.During the pouring process,due to the uneven vibration of the artificial material and the concrete material itself,there must be a certain amount of initial defects inside the concrete.In actual life,the concrete structure with initial defects will not only bear static load,but also be threatened by impact dynamic loads such as huge wheel impact piers and passenger aircraft impacting buildings;Under impact loading,serious consequences will occur because concrete materials not only produce compressive stress,but also tensile stress,and the tensile stren gth of concrete is far less than that of compressive strength.Therefore,it is of great significance to study the tensile mechanics of concrete with initial defects under impact load.This paper mainly carries out research work from the following aspects:(1)Characterizing initial defects in concrete with ellipsoidal.The ellipsoidal shell was fabricated by 3D printing technology to replace the initial defects in concrete;The ellipsoid defect is prefabricated at the center of concrete specimen by step casting method.(2)The static splitting tension test of concrete with ellipsoidal defects with loading rate of 0.5kN/s was carried out by universal testing machine.The initiation of cracks was judged by extensometer;the damage process was photographed by high-speed camera.The experimental results show that the existence of ellipsoidal defects can reduce the splitting tensile properties of concrete.(3)The impact splitting test of concrete with ellipsoidal defect was carried out on Split Hopkinson Pressure Bar(SHPB).The loading rates of concrete with ellipsoidal defects were 1.1×10~6 kN/s,2.1×10~6 kN/s and 3.5×10~6 kN/s,respectively.At the same time,the damage process was photographed with a high-speed camera.Using digital image correlation technique and stress wave theory,the determination methods for calculating impact splitting strength load were obtained respectively.The experimental results show that the splitting tensile strength of concrete specimens with ellipsoidal defect or without defect has obvious force loading rate effect,that is,the splitting tensile strength increases with the increase of force loading rate;the splitting tensile strength of concrete with loading angle of 0 is less than that with loading angle of 90;the existence of el lipsoidal defects will reduce the splitting tensile strength of concrete.The reason of loading rate effect in splitting tensile strength of concrete is explained from the fracture rate of gravel aggregate.