Study Of Principle And Process On Multi-Layercl Adpipe Formed By Hydraulic Expansion

Cald tube is a new type tube, which is made of more than two different meta lmateria ls. It is complex utilized the advantages of the inner and outer tubes materia l,so it has a widely foreground applica tion. For the marine pipeline,good tesistance isrequired in the inside and outside of the pipe. the requirements can not meet by thecurrent double layer cald pipe.In this disser tation ,t he hydraulic forming theory and technology for multi-layertube had been researched. Based on the elast ic-plast ic theory ,the feasibility ofsimultaneous forming was discussed and proved for multi-layer tube. The theoret ica lcalculation formulas relating the expanding pressure to the resid ual contact pressurehave been derived. The results of the formulas are consistent which have beencompared with the results of Marc.Based on the theory of expansion of cald pipe, consider ing the effects of themateria l mechanical properties on the plast ic forming technology for clad tube, thestudy discovered that the core factors in hydraulic forming are Yong's modulus andflow stress of joined pairs because of their crucia l effects on elast ics recovery ofjoi ned pairs, so this paper has presented the theoret ica l gist(?) which satisfiesthe inner and outer tubes to be hydraulic forming composited. Through compared theresults of exper iments with theoret ica l and the Marc, the reasonable calculatingformulas and process parameters of hydraulic expansion have been derived.The appropriate device for the clad pipe formed by hydraulic expansion wasdesigned and manufactured.The exper iment of the double and triple layers clad pipewere completed. The theoret ica l results and numer ica l simulations were consistent bythe expriments.