Measure of the hydride breathing while cyclically absorbing and desorbing hydrogen

When a hydride material absorbs hydrogen, the phase change occurring is accompanied by a volume change of the material. Very often, the material is of granular nature, and the problem boils down to the study of a powder material swelling and shrinking - which is referred to as the hydride breathing - in a close container. Due to this breathing, and depending on the material apparent density and granulometry, severe mechanical stresses can appear and threaten the mechanical integrity of the container. In the present work, an original method for measuring the stresses is presented. It combines the measure of a force transducer and a deformation field by image correlation. Some experiments have been conducted on a metallic hydride type. They show that some configuration can lead to quite strong stresses. Particularly, the influence of the first absorption, namely the activation, is shown to be playing an important role concerning the maximum level of stress created. The initial filling ratio of the container by the hydride powder is also of first importance. (C) 2015 Elsevier B.V. All rights reserved.