Fracture structures subjected to rock blasts and military

Fracture is a failure mechanism of brittle materials that has great importance to the performance of structures.

Failure from fracture can occur for many reasons, including uncertainties in the loading or environment, defects in the materials, inadequacies in design and deficiencies in construction or maintenance to name a few. Failure of load-bearing components can be catastrophic, so fracture is a very important consideration for engineers in designing structures such as automobiles, airplanes, power plants, bridges, etc. Rapid and violent failures of large-scale geotechnical, mining or civil engineering structures cause significant safety hazards, material damage, and interruption to or even cessation of mining or building activities. The need to understand the dynamic behavior of ductile metals at high strain rates of loading is of critical importance in applications such as aerospace industry, accidental automobile impact structures subjected to rock blasts and military installations required to withstand from missile or projectile. Under such dynamic conditions, the strain rate dependency of the metals leads to a significantly different material behavior from what is observed under quasi-static condition. At high loading rates, tiny fluctuations in the plastic flow field induce important acceleration of material particles.

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Thus, significant inertia effects are taking place at the macroscopic level and sometimes also at the level of microscopic deformation mechanisms. Naturally, when subjected to dynamic loading the behavior of metallic materials is quite distinct from that observed under quasi-static conditions. The flow stress has higher rate dependence. The load-bearing capacity is altered by thermal softening due to adiabatic heating resulting from plastic work. So the integrity of mechanical and structural components subjected to dynamic loading requires the knowledge of the fracture behavior of the material at high strain rates.