Measurement of the speed of crack propagation in a PE pipe

A well mapped crack propagation mechanism is the basis for accurate lifetime prediction of various components. While crack propagation rate measurement techniques are relatively well developed for metallic materials and the mechanisms are well described, this is not the case for polymeric materials. This work focuses on the measurement of crack propagation rate in various types of High Density Polyethylene (HDPE) specimens, which are mainly used in the manufacture of pressure pipes. In this material, failure occurs by a slow crack growth mechanism in which creep combined with cyclic loading plays an important role. The experimental programme, in which the student should actively participate, will focus on the debugging of the measurement procedure, the methods of monitoring crack growth and the peculiarities of propagation in different types of specimens – cylindrical with circumferential crack, conventional CT solids and CT solids modified for constant stress intensity factor. The student will primarily be expected to evaluate the tests, but will also be expected to assist with the actual tests and will be trained in the use of the Instron E3000 fatigue machine and its accessories.