Controlling dynamic splitting of Brazilian disc specimens using Adelaide University Snapback Indirect Tensile test (AUSBIT)

Specimens of quasi-brittle materials under Brazilian disc testing usually fracture abruptly, with load carrying capacities dropping almost instantly from peak to zero. This abrupt failure in a split second is known due to the excess storage of strain energy at peak load that is released through the creation of new fracture surfaces and in the form of kinetic energy. This kind of dynamics and bursting is hard or impossible to control in laboratory testing using direct vertical displacement. We present our innovative technology, registered as an innovation patent in Australia, to control the dynamic splitting of Brazilian disc specimens so that the failure process is not abrupt, indicated by the snapback load-vertical displacement responses. Thanks to the use of lateral strain to control the loading, the time to complete the whole fracturing process increases significantly from a split second to a few hours, sufficient to enable advanced instrumentation using image-based techniques.  Acoustic Emission (AE) is used to monitor the fracturing process to make sure that the snapback response observed is not unloading. The proposed technology has been applied with largely success to a wide range of quasi-brittle materials, including sandstone, granite, and even 3D-printed rock-like materials with inherent weak discontinuities. This presentation reports the obtained results and challenges in controlling the dynamic splitting of Brazilian disc specimens using the proposed technology.