Remanent Strength Analysis For Engineering Materials With Flaws

Based on the theory of fracture mechanics and damage mechanics, the fracture strength is analyzed for several engineering materials. The material fracture properties is researched by fracture experiment, the test data is compared with the calculation results. In this dissertation, the following contents are studied concretely:(1) For metal bar with circumferential notch, a series of test samples are loaded by tension equipment. From the data of experiment, several strength indexes are calculated and compared with each other. The stress distribution of metal bar is also calculated with finite element software.(2) Based on the fracture criterion and the analysis of crack cohesive force, the stress intensity factor of materials structure is calculated and the computation formula of loading capacity for the notch bar is deduced with the nonlinear fracture theory. Three-point bending beams, tensile bars and torsion samples are tested and the experiment results are compared with the numerical results.(3) After the samples of CFRP and GFRP sheets are prefabricated, material of FRP are tested with uniaxes tension and with the four-point bending beams, then the testing results of two methods are analyzed with each other.(4) The strain sheets are adhered on the surface of CFRP of four-point bending concrete beam or three-point bending beam of cast iron. With the electromotive method, the two kinds of samples are tested on equipment, and the fracture parameters of two kinds of materials are analyzed respectively.(5) A series of quasi-compact tensile specimens of concrete are tested. From the experiment data, the loading capability is calculated with the crack cohesive force and double-K model; then, the fracture parameters and size effects of concrete are discussed.Combined with the theory of fracture, the fracture properties of engineering materials for metal, FRP and concrete with flaws are analysized; and the results are valuable for engineering.