Simulation and testing for the residual stress-strain of lined steel pipe after plastic forming

Internal corrosion of oil tubular goods is becoming increasingly serious in the gas & oil exploitation. Lined steel pipe is a new anti-corrosion material in preventing gas & oil material internal corrosion. The mechanical property after forming is one of the key factors affecting the service characteristics of lined steel pipe. A parametric finite element analysis (FEA) numerical model is established in this paper to simulate the plastic forming process of lined steel pipe. Furthermore, FEA numerical simulation has been made for the residual stress-strain of carbon steel tubing Φ70×3.5 mm and stainless steel tubing Φ63×1.16 mm. Studies show that the inner pipe produces residual compressive stress and the outer pipe produces residual tensile stress after forming. The bonding force between inner and outer pipes increases linear to the forming force. The deformation law of outer pipe in the loading & unloading process is analyzed by resistance-strain test method. Experimental results point out that the plastic deformation of lined steel pipe is nonlinear in the loading process, but rebounds linearly in the unloading process. FEA numerical simulating results are close to the experimental data, of which the accuracy can meet the engineering requirements. Studies in the paper can provide theoretical reference for the manufacturing and application of lined steel pipe.