A synchronous thermal-mechanical in-situ device for dynamic fracture initiation

As a typical failure behavior, the dynamic fracture is critical for material safety assessment and design, whose rapid evolution in the crack tip over a short time causes tremendous challenges in characterizing the evolution of the local temperature field. Although researchers have pointed out that temperature significantly affects fracture toughness, the temperature rise and the role of thermal softening in the crack tip region during the dynamic crack initiation need to be clarified. This work aims to evaluate the temperature rise effect at crack initiation in TC4 (Ti-6Al-4V) alloy under impact loading. We developed a thermal-mechanical coupled in-situ measurement system to obtain synchronized COD (crack-tip opening displacement) and temperature field evolution for the dynamic mode I fracture with high temporal and spatial resolution. The evolution of synchronous COD and temperature field during crack initiation under dynamic loading was investigated. The corresponding simulation was conducted to analyze the thermal softening effect at dynamic crack initiation. In TC4 alloy, the maximum temperature detected at crack initiation is about 130 °C, and the thermal effect on the material property is minor. The results of this work fulfill data support for investigating the coupled thermal-mechanical fracture behavior of metal.