Design Concept of Clad Pipe Considering Effect of Clad Metal on Structural Integrity (Part 2)
Effect of Clad Metal on Buckling Strength of Clad Pipe in Bending
1993 Volume 31 Issue 5 Pages 264-269
Details
1993 Volume 31 Issue 5 Pages 264-269
The new design concept which treated clad metal as the equivalent base metal thickness of bi⋅(σTC/σTB) was proposed in the first paper. This paper describes applicability of the new design concept from the view point of bending properties. As the results of 4-point bending test of large-diameter clad pipe, the critical buckling strain of the clad pipe was smaller than that of a carbon steel “solid” pipe with the same mechanical properties and pipe dimensions as the clad pipe.
The reason could be thought to be due to an additional bending moment caused by inhomogeneous strength between clad metal and base metal. However, disbonding did not occur at the interface of buckled portion and there was no significant difference in shear strength obtained by shear test between before and after buckling. Furthermore, the local buckling did not affect the overall deformation behavior of the clad pipe.
As a clad pipe designed by the new concept is thinner than those by the conventional ones when strength of the clad thickness is higher than that of base metal, the critical buckling strain of clad pipe designed by the new concept is smaller than the conventional ones. However, applied stress is practically restrained to 72% of specified minimum yield strength or lower during laying of clad pipe. It was confirmed that the clad pipe designed by the new concept had sufficient safety factor for the practical level. Therefore, it was concluded that plastic buckling did not become a negative factor for practical level when the new design concept was applied.
