Numerical Simulation Of Interfacial Bonding And Strengthening Of Bimetal Clad Pipe

Bimetal clad pipe is a new kind of pipe with rapid development.It has both the excellent mechanical properties of base pipe and the anti-corrosion and wear-resisting properties of liner.It is a kind of pipe with extensive development prospects.According to the interface-bonding mode,it can be divided into metallurgical bonding and mechanical bonding bimetal clad pipes.Among them,the mechanical bimetal clad pipe by virtue of the advantages of its process and the controllability of pipe properties,have been widely concerned.Hydroforming is an important technology to realize the mechanical combination of the bimetal clad pipe and it has broad application prospects.However,for the large-diameter bimetal clad pipe,the hydroforming process still has problems such as low bonding strength and difficulty in optimizing process parameters.In this paper,the method of finite element analysis(FEA)and elastoplastic theory were used to study the interfacial bonding strength and optimization of bimetal clad pipe from the aspects of hydroforming pressure,pipes'mechanical properties and section size.(1)The bimetal clad pipe is regarded as a two-dimensional plane stress model,and the theory of elastic-plastic analysis was used to solve the theoretical formula of the hydroforming process.According to the theoretical results,the main factors affecting the interface bonding strength were confirmed as the hydroforming pressure,pipes'mechanical properties and cross section size.(2)The hydroforming pressure range of the common used large diameter bimetal clad pipe specifications for?219×(6+1)mm was determined,which provides a suitable reference hydroforming pressure for the subsequent researches.(3)The effect of base and lined pipe materials'elastic modules and poisson's ratios on the interfacial bonding strength was analyzed,and the two groups of different material combination of pipe was chosen as instance simulation.The results show that the higher the difference of elastic modulus between lined and base pipe material(E_i-E_o),the higher the interfacial bonding strength of the bimetal clad pipe.Compared with the elastic modulus,poisson's ratio has little influence on the interfacial bonding strength of the pipe.When the poisson's ratio of base pipe larger than the liner one,the interfacial bonding is higher.The materials properties have great influence on the pipes'interfacial bonding strength under the same specifications.For the L360QS lined Inconel825 bimetal clad pipe,the range of hydroforming pressure is 19.6~26.8MPa and the maximal bonding strength between the pipes is 1.04MPa.However,for the P110lined TA2 bimetal clad pipe,the range of hydroforming pressure is 44.5~54.7MPa,it needs larger hydroforming pressure compared with the former one,but the maximal interfacial bonding strength is only up to 0.89 MPa.(4)The transverse dimensions of the base and lined pipe were studied on the influence of the interfacial bonding strength.The results showed that the interface bonding strength is higher with the smaller the initial clearance between the pipes.With the increase of the lined pipe wall thickness,the bonding strength firstly increases and then decreases.The increase of wall thickness of base pipe will result in the decrease of interfacial bonding strength.The hydroforming process of series of specifications of large diameter bimetal clad pipe for?508×(10~14+1.5~4)mm was simulated.The results show that the smaller hydroforming pressure is needed for the pipe with larger diameter and the interfacial bonding strength is lower.For the actual production preparation of large diameter bimetal clad pipe,the subsequent processing should be applied to enhance the bonding strength.The researches can provide a theoretical guidance for the actual production of the bimetal clad pipe as respect to the pipes'materials selection,the size matching and hydroforming pressure setting.That would enhance the bonding strength between the base and lined pipe within the appropriate range of hydroforming pressure,and at the same time,prolong the service life,reducing material consumption,thus reduce production cost,make the enterprise benefit maximization.