Investigations On The Dynamic Fracture Characteristics Of ITO Glass Based On The X-ray Phase Contrast Imaging

The behavior of a material under dynamic shock is tremendously different from quasi-static.Dynamic damage and fracture of a conductive glass are investigated using a split Hopkinson pressure bar,implemented with in situ X-ray phase contrast imaging and optical imaging for comparison.In this paper,the basics of the stress wave theory of elastic wave control equation are introduced first,and then the principle of SHPB device are explained,and the development of SHPB device,existing problems and corresponding solutions are briefly introduced.In view of these two difficulties in the initial stress of specimen loading and the difficulty of constant strain rate loading in SHPB experiments,organic glass was selected as the experimental material to discuss the effect of the copper shaper and the impact bar speed on the incident pulse waveform.In the front end of the incident bar,different red copper pieces of different diameters are added.When the shaping deformation is used to prolong the rising edge of the incident pulse,the failure time of the sample is delayed,and the conditions of stress balance and uniform deformation during loading of the sample are satisfied.The experimental results and analysis indicate that the use of a pulse shaper can indeed improve the incident waveform and achieve an ideal consequence.Through the comparison of X-ray and optical imaging modes,X-ray imaging demonstrated the advantage of X-ray imaging in revealing the initiation of crack propagation during the dynamic failure of brittle materials,due to its strong penetration and high resolution.The predamage of the glass sample results in a greater dispersion of its breaking strength.A large number of grayscale statistical analysis of the damage evolution process of the sample.Compared with the theoretical prediction,the damage degree under the low strain rate loading does not increase but decreases.The imaging shows that this is due to some major cracks undergoing growth,closure,and re-expansion.This may be caused by the interaction of the stress wave and the crack tip.However,at higher loading strain rates,there is no stagnation period for the degree of damage.This is due to the simultaneous nucleation of cracks at the edges and body defects,which accelerates the damage process of thespecimen.The complete fragmentation of the sample shows a large number of wing cracks,supplementing the energy dissipation method.The scanning electron microscopy(SEM)analysis of the recovered debris can observe the river patterns and is a typical feature of brittle material loading and destruction.The backscattered mode showed no obvious heterogeneity of the cross section.At the same time,micropores and bulges can be observed in the fractured section.