Stress Analysis in Damaged Pipeline with Composite Coating

This paper studied the distribution of stresses near damage in the form of axial surface cracks in a pipeline reinforced with a spiral-wound composite coating. The authors applied the homogenization method to determine the effective elastic characteristics of a structurally anisotropic layered package. By means of the classical momentless theory of shells, it was established that the stress state of the coated intact pipe under the pressure of the pumped product depends on the parameters of the geometry of the capacity strip, as well as on the component composition of the heterogeneous coating. The finite element method was applied to solve the problem of plane deformation of a piecewise homogeneous ring with an internal crack perpendicular to the interface. This problem assumes the linearity of the materials and the ideal mechanical contact with the layers. The effect of the composite coating and the size of the damage on the magnitudes of the energy flow into the crack tip, and on the stress intensity factor, was studied in detail. Various variants of the coating were considered, namely, winding of the coating on an unloaded pipe and reinforcement of the pipe under repair pressure.

Optimal design and experimental investigation of teeth connection joint on a filament wound composite transmission shaft

For limited weight reduction and avoidance of composite damage caused by the press mounting of the traditional metal teeth press-fit joint, a novel teeth connection joint technique of the fiber wound composite transmission shaft was investigated by theoretical analysis, finite element simulation, and experiment verification. Based on the mechanics of composite materials, the expressions of equilibrium torsional stiffness and static torsional strength were derived. According to the three-dimensional Chang-Chang failure criterion, its finite element model of progressive damage analysis was established through the user material subroutine. Applying the fast curing resin system, a typical sample of the structure was prepared through co-curing for the static torsional strength test, and its failure details of the fracture surface were observed by using a scanning electron microscope, which confirmed the validity of theoretical and numerical results. Based on this, the influence of the ply method and geometric characteristics on the failure strength was studied, and the optimal design of the joint was realized by the genetic algorithm. Compared with the press-fit joint, this structure reduces weight by 70 % under the same joint strength, which provides a new way for the connection of the composite transmission shaft.