Relaxation of non-crystalline solids under mechanical stress

Non-crystalline solids submitted to a thermomechanical stimulus have similar properties in materials as different as amorphous polymers, molecular, metallic or oxide glasses. The purpose of the present paper is to give some insights into the mechanical response of glassy or liquid media, in relation to their state of disorder. To describe thermomechanical response of non-crystalline solids, a molecular theory has been developed. We show how the concept of quasi-point defects (QPD) introduced in the theory is consistent with small angle X-ray scattering results. The calculations based on the QPD model are also compared to experimental data for various glass-forming systems. The magnitudes of the parameters, introduced in the model for these different systems, are discussed.