Finite element analysis of a sandwich pipe joint

Sandwich pipes in which the core material performs both thermal insulation and structural function are viewed as a lightweight alternative to conventional pipe-in-pipe systems in which insulation material carries no loading. Developing a suitable method that permits the joining of sandwich pipes in an efficient manner is essential for their successful application. In this paper, the mechanical response of a swaged field joint between sandwich pipes subjected to bending is investigated using a series of finite element models. In order to gain a thorough understanding of the response of the joint components to installation based loadings, parametric studies are carried out to establish the effect of the inner pipe thickness, cutback length, and stiffness of the field joint filler on the strain concentration at the joint, with particular focus on the swaged weld region and the girth weld region. The influence of interface adhesion properties and weld metal yield strength on the variation of strain intensity is also evaluated. Numerical studies show that increasing filler stiffness and maintaining a cutback length less than 2.5 times the radius of the inner pipe could produce lower
strain intensity at the two regions of interest.