Fracture Analysis For Torsion Problem Of Composite Cylinder With Cracks

As modern engineering develops, the composite cylinder has been used much more widely in recent years. Meanwhile, for the need of production and life,irregular buildings become much more common then before, and the torsional response of them in an earthquake can not be ignored. Therefore, the study of torsion problems of a composite cylinder with cracks is not only the improving and deepening of the torsion theory of cracked cylinder,but also full of a practical value. In this paper ,the Saint-Venant torsion problems of a composite cylinder with curvilinear cracks were investigated .Combining with the situation of Concrete-filled steel tube column, a corresponding model is built and some numerical results are obtained. On the basis of the existing boundary integral equation for the torsion problem of a composite cylinder with internal cracks , the singularity of order at the cross point(intersection) between the interface and the crack is deduced, using the boundary element method to solve the torsion problem of a composite bar consisting two materials.When the cracks and the interface of two materials are in touch with each other, the crack's singularity of order changes, is not being 1/2 anymore. the paper obtained the relationship between the shear modulus ratio of the two materials and the singularity through derivation ,in order to solve the improperly posed problem of the equations, new supplement equation are proposed ,and a compatible boundary numerical method is established. The torsion rigidity ,stress field and the stress intensity factors can be easily calculated through the equations, which has important reference value in the aspect of calculating the bearing capacity and analyzing the fatigue property . The FORTRAN general-purpose calculation procedure is composed, and the practical torsion problem of the widely used concrete-filled steel tube in engineering is worked out. Some typical numerical results are given ,and the results demonstrate that the boundary element method in this article is correct and effective.