Fracture Surface And Experimental Investigation Of Structural Steel

As an important problem in many industries,crack play a vital role in bearing capacity and operational life span of structural members,and the filed of steel structure is not exception too.In the 1994 Northridge earthquake in America and 1995 Hyogoken-Nanbu earthquake in Japan,there were great many brittle failures of beam-to-column connections,which indicated that cognitions of people on the stress behavior and damage mechanism of structural steel were rather inadequate.In order to avoid the personnel casualty and the property damage,the United States and Japan set up specialized research institutions and proposed a lot of modified programs.But these programs whether with enough effectiveness only after another large earthquake we can know the result.At present,many researches are concentrated on beam-to-column connections, they want to solve the problems through improve the modes of beam-to-column connection.But there are only a few researches about structural steel fracture mechanism on mechanics.So,we will seek the crack criterion of structural steel from this way.This article proposed a new fracture criterion on the basis of metal strength theory,fracture mechanics,damage mechanics,materials science and so on,which had rotary paraboloid in the scope ofσ_m＞0.At the same time,in order to examine the fracture criterion this article did fracture tests of structural steel,and then did the numerical simulation about these experiments.Through the simulated results of structural steel specimens we know that the fracture criterion has suitable mode and enough precision.Because in the past there were many experiments supported Mises' criterion, this article will still use it in the scope ofσ_m＜0.On the pure shear plane the new fracture criterion of this article and Mises' criterion integrated together.In three-dimensional stress space,spatial model of this new fracture criterion like a bullet which has smooth appearance and mathematical tractability.In order to use this new fracture criterion in the theory research and projects, this article detailed described the fracture design of it.Research contents of this article are very new,and the research way entirely disengage itself from the restraint of existing research results and theory,and open new research method,the proposed results and suggestions for projects design and theory research have values of definite magnitude.