Influence of a Lubricant on Nonisothermal Motion of an Elastoviscoplastic Material in a Pipe under Variable Pressure

Using a model of large strains, a solution of a nonisothermal boundary-value problem on deformation of a material in a rigid circular pipe under the influence of a variable pressure drop is obtained. Between the material and the pipe is a lubricant layer that can slide along the pipe wall. When the lubricant rubs against the pipe, it heats up and the heat is then transferred to the base material. The temperature of the materials also changes due to irreversible deformation. The base material and the lubricant have different elastic moduli, yield strengths and viscosity coefficients. The entire deformation process is considered, from reversible deformation and the occurrence of viscoplastic flow to flow deceleration, unloading and cooling.