The Influence of Temperature and High-Speed Heating on Tensile Strength of Granite and the Application of Digital Image Correlation on Tensile Failure Processes

Thermal induced cracks and the tensile strength variation of Eibenstock granite subjected to high-speed heating have been studied through lab testing. The Digital Image Correlation (DIC) technique was used for analysing the tensile behaviour of granite at high-speed heating rate and different temperatures. For samples heated to 800 degrees C with heating rates of 200 degrees C/min and 300 degrees C/min, thermal-induced macrocracks become visible to the naked eyes, while no obvious macrocracks are observed on samples heated according to ISO 834 curve. Compared to the influence of temperature, the selected heating rates only have a negligible impact on tensile strength and axial displacement. The DIC analysis shows the crack initiation and progressive crack propagation before the main crack is formed at failure. Compared to the samples heated up to 400 degrees C, the samples heated up to 800 degrees C show less brittle fracture behaviour, and the tensile strength is greatly reduced. The final failure patterns prove that different heating scenarios lead to different microcrack structures and consequently influence the failure mode at the macroscopic scale.