Experimental Investigation on Double-Layered Pipe During Hydro-Expanding

Hydro-expanding is one of main methods in manufacturing double-layered pipes. Experimental investigation of the hydro-expanding pressure on double-layered pipe is presented in this paper. The hoop strains at the external surface of the outer pipe were measured in seven experiments. The special experiment phenomenon, the strain values being nearly constant for about fifteen minutes when first pressurizing to 23.6MPa, was observed. The relationship between the hydro-expanding pressure and the hoop stress at the external surface of outer pipe was obtained. The results indicate that the range of the hydro-expanding pressure and the residual contact pressure in the experiment are both in good agreement with those in theory with a maximum relative error of 5.46%, and provide references for engineering application and further research in determining the range of the hydro-expanding pressure.