Influence of Filler Crystal Sizes on Acoustic Emission Parameters during Tensile Testing of Parts Made of Plasticized HMX

We study changes in the parameters of acoustic emission that develops during quasistatic deformation of parts made of plasticized coarse- and fine-grained HMX under tension. Characteristic changes in acoustic emission dependences and absolute values of acoustic emission parameters have been determined during transition from a coarse- to a fine-grained material structure. In accordance with the results of the experiments, we analyze possible scenarios of the development of the process of damage accumulation and failure of parts with a change in the size of crystals that form their internal structure. As a confirmation of the corresponding changes in the parameters of acoustic emission, we have investigated the structure of the surface of parts in the zones of their failure using an electron microscope. Under tension, the failure of parts based on finely dispersed HMX occurs instantly, when a critical level of damage is reached in any part of the volume and conditions are created for microcracks to combine into macrocracks. For parts containing coarse HMX, failure typically occurs according to the principle of a “weak” link, ie., localization of microcracks in one or several zones over the volume of the deformed material as early as at the initial stage of loading. These zones become the spots where cracks merge and the focus of their further development up to failure at a new scale level. The results obtained expand the existing understanding of the process of damage accumulation and failure of energy-yielding materials and can be used in the development and improvement of relevant mathematical models.