Dynamic strength of sapphire crystal (3)

Dynamic strength of sapphire crystal (3)

Shock wave loading is accompanied by an increase in temperature, which is dependent on the amplitude of the shock wave. At amplitudes of tens of GPa, the temperature rise for uniform heating is hundreds of degrees. Local heating at the slip line may exceed the temperature for uniform heating. Non-uniform heating Causes a short-term loss of its own strength. Then the temperature is lowered by thermal diffusion in the intense heat area and the strength properties are recovered.

The behavior of elasto-plastic materials can be characterized by shock wave elasticity (predecessor of elastic Gugonio) and the splitting of the plastic part. Some experimental methods for studying shear strength are based on expansion wave elastoplastic structures and non-hydrodynamic shock wave damping. In modern experiments In this method, the spatiotemporal distribution of loading and unloading waves is recorded by means of fast piezoelectric, piezocapacitive and piezoresistive sensors.

In the proposed experimental method, it should be possible to distinguish the technique used to record the normal stress of the wavefront. In this case, an additional formula for the intermediate flow is not necessary, since the dynamic flow is limited to the stress difference.

Failure is induced by unloading wave interference. When passing through a material, the shock wave changes the microstructure of the material, hardening the material. The hardening and failure processes occur simultaneously. The damping of the shock wave in the material results in the destruction of the interface between the shocker and the material, preventing The entry of the impactor. The damping of the shock wave in the impactor, caused by the interaction with the unloading wave on one side, accelerates the flow of material by creating a new compression pulse. The failure of the sample begins with the formation of a channel-like cut along the axis of symmetry. The formation of such a crack is caused by the concentration of the unloading wave next to it. In the following loading, the crack itself becomes an unloading wave source, which leads to the formation of a circular coaxial cut-off crack. The material begins to segment, the impactor The contact area is implemented, and a hollow is formed under this area. The latent phase of surface failure ends when, based on the geometry, the shock wave reflected back from the bottom of the hollow starts to pass through the adjacent wall. The reflected pulse, this pulse reaches the contact area Near the front surface, causing a cross crack (front cut).

Over the past decade, the behavior of brittle materials has been thoroughly studied. In particular, complete deformation maps have been obtained and the different behaviors of ceramics under the influence of shock waves have been taken into account. The most meaningful results achieved in this field are comparable to those achieved in glass shock The discovery of failure waves during compression is linked. The formation of failure waves is one of the mechanisms of catastrophic strength loss in materials with high hardness and demonstrates non-local loading effects. In ceramics, interatomic bonds can be Interruption. Maximum resistance to failure is characteristic of materials with the highest dynamic compression and decomposition energies.

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