Crush Behavior of Multilayered Pipes: Study of Pipe Integrity and Kinematic Assumptions

The crush of multilayer pipes is an important problem in mechanics. Many types of devices may be used to apply radial forces to keep a pipe fixed when it is loaded in the axial direction. To address this problem, one could use analytical or numerical approaches, dealing with the local bending of each cross section of the pipe. For taking into account the material and geometric nonlinearities, a finite element model can be also used. This work applies a numerical 2D model to address the crush problem caused by shoes applying radial loads in three-layered pipes. The inner and the outer layers are metallic, and the intermediate one polymeric. All the materials are considered to be nonlinear, being the metallic materials elastic-plastic. The polymeric material is assumed to have a nonlinear behavior. The main objective of the work is to study the pipe integrity and discuss the kinematics of the pipe layers when crushed. Two distinct conditions are considered: (i) slippage and gaps formations are allowed between the layers or (ii) the three layers are ideally adhered to each other. The effect of parametric variations of friction between layers is analyzed. This kinematics discussion is addressed by increasing the number of crushing loads applied to the pipe, from two to sixteen loads, from which a limit is inferred. The results and conclusions may be employed as a basis for improving simpler analytical models to face the same problem.