Abstract：Inorganic glass has a lot of outstanding performances and is widely employed in various engineering applications. Apart from the quasi-static load, glass is usually subjected to the dynamic loading applied by different external objects, such as bird, stone and bullet. In addition, as a kind of brittle solid, glass features a much smaller tensile strength than the compressive strength. The fracture of glass in the service process also mostly occurs under the tensile type stress. As a result, the study on the tensile mechanical behavior and failure process of glass under various loading conditions is of great importance for the design of related engineering structures.
In this paper, the tensile properties of soda-lime silicate glass were tested by flattened circular ring (FCR) specimens. The quasi-static, dynamic unidirectional and uniaxial-bidirectional tests were separately conducted on the servo-hydraulic controlled universal testing machine and the electromagnetic split Hopkinson pressure bar (ESHPB). The crack initiation and propagation process in the loaded specimens was observed by a high-speed photograph system. The recorded images were related to the stress curve to reveal the dynamic failure mechanism of tensile specimen.
The testing results illustrated that the tensile strength of glass characterized a positive loading rate effect, namely it was apparently enhanced with the increase of loading rate. Different from the dynamic unidirectional loading, the uniaxial-bidirectional testing system is symmetric with respect to the middle section of specimen. Accordingly, the time from loading to achieving stress equilibrium is able to be greatly reduced. Contrary to the dynamic compressive strength, the dynamic tensile strength of glass material subjected to the above two stress wave loading modes was approximately the same. It was caused by the fact that the moment of crack generation in the specimens was synchronous with that of maximal stress. According to the finite element modelling results, a significant tensile stress gradient appears along the fracture route of flattened ring and semi-circular bend (SCB) specimens. It results in the tensile strength measured by these two specimens are not the same as that obtained by the flattened Brazilian disk (FBD) specimen. Specifically, the strength of FCR specimen is the highest, followed by SCB specimen and the strength of FBD specimen is the lowest.
The conclusions obtained from the present work are beneficial to the efficient use of glass materials and the prevention of glass breakage disasters. In addition, the dynamic testing method (ESHPB and FCR specimen) utilized in this work can also be applicable to other brittle solids, such as ceramics, rocks and concrete.
2023, Vol. 44 
