New insights into the effects of low temperatures on the stress-optical properties of printable photopolymers: An experimental investigation

Abstract

The application of 3D printing technology for replicating natural rock models and achieving the visualization and quantification of hidden structural changes and stress evolution in underground rocks holds significant importance for engineering disaster prevention as well as the development of oil and gas resources. The key to achieving this lies in developing model materials suitable for 3D printing that accurately depict the physical and mechanical properties of rocks. In this paper, the impact of temperature cycle treatment on the mechanical properties of printing material VeroClear was tested and the effect of temperature on the stress-optical properties of VeroClear was analyzed. By using 3D printing models with pre-existing cracks, the crack initiation conditions, propagation laws and stress field distribution characteristics of stress-sensitive materials at different temperatures were obtained. The results show that the mechanical properties of the freshly printed VeroClear model exhibit instability due to incomplete curing. Heat treatment can facilitate complete curing and enhance their mechanical characteristics, whereas cold treatment fails to yield similar improvements. Lower ambient temperatures reduce photoelastic fringe susceptibility to stress, yet allow accurate quantification of full-field stress within models by VeroClear. Lowering the temperature significantly enhances the brittleness of VeroClear, enabling printed models to demonstrate crack evolution characteristics similar to those observed in actual rocks. By analyzing the evolution of photoelastic fringe, it is found that the wing crack propagates along the direction of the local minimum principal stress difference near the crack tip. These findings provide a foundation for utilizing stress-sensitive materials with enhanced brittleness in low-temperature environments for simulating rocks and quantitatively analyzing their fracture behavior and the role of stress field control.