Abstract
To study the process of brittle fracture, initiated by a microsecond range pulse action, we applied the magnetic pulse technique of controllable pressure pulse generation with pulse amplitude up to 2 GPa. The threshold energy level has been found, and related to a parameter specific of each material - energy accumulation time. With application of the thermodynamic approach, we develop and demonstrate the destruction criterion that allows us to define this material parameter. Following the results of experimental data and numerical simulation, we show how to describe the destruction process both for samples with crack-type macro defects, and defect-free samples. The study reveals the dependency of the surface energy from the load build-up and material properties when exposed to magnetic pulse action.
Highlights
The loss of strength properties and bearing capacity of samples is caused by de-homogenization of material structure and occurrence of structural integrity rupture zones
The aim of the present study is to demonstrate the possibility of the magnetic-pulse technique for investigation of the process of pulse material fracture and clarify some general details of the generation of new surfaces at material fracture under the high-rate loading
A generator Pulse current generator (PCG)-125, equipped with two pulse low-inductance KMK-50-6 type capacitors of 6 μF each, charging voltage up to 50 kV and acting as storage batteries, has been used to carry out the experiments. This generator allows getting a unidirectional pulse under pulse loading up to 20 nH, its amplitude is up to 600 kA of 4 microseconds, that corresponds to the pressure pulse of up to 2000 MPa
Summary
The loss of strength properties and bearing capacity of samples is caused by de-homogenization of material structure and occurrence of structural integrity rupture zones. Multiple papers examine the issues of fracturing and fracture propagation under various loading conditions. An adequate analysis of brittle fracture under conditions of pulse loading has not been definitely shaped yet. The destruction process analysis is a challenge due to the influence of multiple factors and singularities, related to material properties, exposure parameters, variety and structural difference of force fields during the experiments. The aim of the present study is to demonstrate the possibility of the magnetic-pulse technique for investigation of the process of pulse material fracture and clarify some general details of the generation of new surfaces at material fracture under the high-rate loading. Tests, carried out with various materials, exhibit the threshold nature of fracture and increase of failure amplitude in response to loading pulse contraction during destruction of both defect-free samples, and those having crack-type macro-defects [1,2,3]. Seen below are the results of experimental research and analysis of material destruction when exposed to magnetic pulse action
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