Numerical Research To Mechanical Property And Thermal Stress Of SHS Composite Pipes

Oil is an important strategic material, and special commodity, oil resources affect a country's economic development and national security. With the amount of recoverable oil reduced gradually,it's more difficult to exploit oil because of increasing depth and more complex work environment of oil wells. Because of working in corrosive liquid, and bearing the plume force, friction and cyclic loading, tubing are easy to abraded and be corrosion.In order to enhance the anti-wear and corrosion resistance of pipeline,ceramic-lined composite pipes were produced to replace the steel tubing. Ceramic-lined pipes which produced by Self-Propagating High-temperature Synthesis (SHS) have excellent corrosion resistance, wear resistance, heat resistance, thermal shock and mechanical impact resistance. Process of SHS is simple, high productivity and low cost, so ceramic-lined pipes have great potential and prospects. By now, a few works were done to study mechanical properties and residual stress of ceramic-lined pipes, and residual stress can not be measured by experimental methods.Finite element analysis (FEA) method is a mature and perfect numerical calculation, with the finite element method combined with the computer, many large numerical software emerged, and has been applied to the industrial production and engineering calculations. It has also been applied in the petroleum machinery area.The main purpose of this paper is to establish accurate and efficient finite element models to study mechanical properties of tubing. it Includes the following three aspects: (1) The establishment of three-dimensional finite element solid model to study Maximum stress and residual strength of the disabled tubing, Provide failure criterion for the N80, P110 steel line. (2) Established plane finite element model which composed by ceramic layer, pure iron layer and steel layer, calculated the value of temperature during the cooling process and the thermal stress of ceramic-lined composite pipe to analysis the cause of ceramics cracks. (3) Established plane models of steel pipe and ceramic lined pipe, then simulate the crushing strength of steel pipe and ceramic lined pipe .At last, crushed the two kinds of pipes, Contrast the Simulation and experimental value of the crushing strength .Obtains the following conclusions:Simulation and theory value of the maximum stress in pipes with defects are about the same .And verify the reliability of the FEA. The outer diameter of the standard pipe is 73 mm and thickness of pipe wall is 5.5 mm .When it works in the well which with 2000m depth, take a safety factor of 2, for the N80 steel pipeline, defect depth which to be sentenced as invalided is 1.5 mm; for the P110 steel pipeline, the depth is 2.9 mm.The value of temperature during the cooling process calculated by FEA is accurate; it cooled to room temperature in about 1.5h. Thermal stress of composite steel is the main reason which leads to crack of ceramic. Plastic deformation of iron and carbon steel layers can mitigate the thermal stress. After cooling to room temperature, composite pipe, there is large internal residual stress in ceramic layer, ceramic and Fe layers bear compressive stress, and the steel layer bears tensile stress.Simulation value of the crushing strength is very close to experimental value, it verifies the accuracy of the simulation process. Deviation of the two values is about 1%.And mechanical properties of ceramic-lined pipes are significantly better than steel pipes.