Research On Hydraulic Expansion Joint Principle And Process Parameter Optimization Of Bimetal Composite Pipe

The bimetal composite pipe is composed of two kinds of metals,and the inner liner layer is made of corrosion-resistant alloy as a dielectric isolation layer.The outer pressure-bearing layer is generally protected by carbon steel as abase layer,and the inner and outer layers are closely adhered by plastic forming technology.The advantages of fully utilizing the advantages of good rigidity,high strength and low price of carbon steel,combined with the excellent corrosion resistance of the corrosion resistant alloy layer,the cost performance advantage is obvious.Among them,the hydraulic expansion process has the characteristics of reducing the process,reducing the cost,improving the strength and rigidity of the parts,and has wide application,and the bimetal composite pipe formed by the hydraulic expansion joint has large bonding force,high fatigue strength and strong structure stability.In this paper;the hydraulic expansion joint principle and process parameter optimization of bimetallic composite pipe are studied by the combination of elastoplastic mechanics theory and ANSYS/Workbench finite element analysis.The main research contents are:(1)Based on the elastoplastic theory,the composite tube forming process is divided into loading stage,holding stage and unloading stage.The elastoplastic theory analysis of different stages is carried out,and the theoretical analytical formula between the instantaneous extrusion stress during the forming process of the composite tube,the residual extrusion stress after forming and the pressure of the expansion fluid is established,and get the selection range of the expansion fluid pressure.Finally,the theoretical analytical solution of the composite tube forming process was verified by ANSYS/Workbench finite element analysis software,and the variation of residual extrusion stress after plastic yielding of the base pipe,the axial shrinkage of the liner and the length of the composite pipe were The relationship between the two was numerically simulated.(2)Design five factors and two indicators orthogonal test plan.The test factors are selected from the thickness of the liner,the thickness of the base pipe,the initial gap,the initial pipe length,the dwell time,and three levels are selected for each factor.The residual extrusion stress and wall thickness distribution uniformity index after the forming of the bimetal composite pipe is used as an experimental index.Through less numerical simulation,the test results under various parameter combinations are obtained.Through the visual analysis and variance analysis of the test results,the process parameters are determined.The primary and secondary order and significance of the impact of the test indicators.Finally,using the integrated balance method to obtain the best combination of process parameters is of great significance for guiding actual production.(3)Designing a device for small-scale high-hydraulic expansion test at room temperature.Based on previous researchers,it has been improved from pressurized expansion head,exhaust plug,sealing system and data acquisition system Withstands an ultra-high liquid pressure of up to 60Mpa.The device structure is simple and easy to disassemble.The visual detection algorithm is introduced by industrial camera and image processing means,instead of the traditional strain gauge data acquisition method,non-contact measurement is realized,the field wiring is simple and the detection precision is high,and the measurement data can be used as a reference for the improvement of production process.Based on,improve product quality.