3DEC Modelling Exploration of Residual Stress Mechanisms

Residual stress exists as a natural phenomenon found in situ and as a by-product of creation for certain man-made materials. An early implication for residual stresses was illustrated with Prince Rupert's drops where, due to induced compressive residual stress magnitudes the material strength is effectively increased. Residual stress exists in a state of equilibrium with their own internal forces, and as a result are often omitted from stress considerations for design but we believe that these stresses may impact the mechanical behaviour. The purpose of this study was to include residual stresses in modelled specimens of rock to investigate the potential for damage to be present as a result of their redistribution. Residual stresses were formed under load, and once present the specimen was unloaded and damage was quantified through the number of broken subcontacts within the model. Compression tests were then performed on the damaged specimens to investigate the presence of crack closure strains as a result of the produced damage. It was shown that residual stresses can produce damage, and such damage also can produce crack closure strains. 1. INTRODUCTION Residual stresses exist as a natural phenomenon found in situ and as a byproduct of formation for certain man-made materials. The state of residual stress contains both compressive and tensile stress magnitudes which allows for the residual stress field to reach a state of equilibrium independently from external pressures. As a result of this self-equilibrating nature, residual stresses are often overlooked as they exist separately from both in situ stress and excavation-induced stresses. However, if a residual stress field is disturbed (e.g., fracture formation), the stresses will mobilize in an attempt to reach a new state of equilibrium and will accompany a measurable strain. Although these stresses exist separately from other common stresses, it is important to understand their existence as they may have consequential impacts if not properly understood. An example of this in steel is the case of the split I-beam (Nau, 2015) where due to casting, residual stresses were created within the beam. Once fully hardened the beam was cut at an angle on both ends which disturbed the state of equilibrium and caused a redistribution of the residual stresses. As a result of their redistribution, the I-beam fully split through the web which then destroyed the beam.