Abstract
Rock-like brittle materials under dynamic load will show more complex dynamic mechanical properties than those under static load. The relationship between pulse waveform characteristics and strain rate effect and inertia effect is rarely discussed in the split-Hopkinson pressure bar (SHPB) numerical simulation research. In response to this problem, this paper discusses the effects of different pulse types and pulse waveforms on the incident waveform and dynamic response characteristics of specimens based on particle flow code (PFC). The research identifies a critical interval of rock dynamic strength, where the dynamic strength of the specimen is independent of the strain rate but increases with the amplitude of the incident stress wave. When the critical interval is exceeded, the dynamic strength is determined by the strain rate and strain rate gradient. The strain rate of the specimen is only related to the slope of the incident stress wave and is independent of its amplitude. It is also determined that the inertia effect cannot be eliminated in the SHPB. The slope of the velocity pulse waveform determines the strain rate of the specimen, the slope of the force pulse waveform determines the strain rate gradient of the specimen, and the upper bottom time determines the strain rate of the specimen. It provides a reference for SHPB numerical simulation. A dynamic strength prediction model of rock-like materials is then proposed, which considers the effects of strain rate and strain rate gradient.
Highlights
Publisher’s Note: MDPI stays neutralThe split-Hopkinson pressure bar (SHPB) is an important piece of testing equipment for analyzing the dynamic mechanical properties of materials and is widely used in dynamic mechanical response analysis of rock-like brittle materials [1,2]
The different strain rate gradients εc can be obtained by changing the rise time while keeping the amplitude Af and the rise time tr of the force pulse waveform unchanged
The different strain rate gradients ε c can be obtained by changing the rise time μs while keeping the amplitude Af and the rise time tr of the force pulse waveform unchanged.200However, when the rise time is too large, the rising slope of the incident waveform decreases, and the strain rate will decrease
Summary
The split-Hopkinson pressure bar (SHPB) is an important piece of testing equipment for analyzing the dynamic mechanical properties of materials and is widely used in dynamic mechanical response analysis of rock-like brittle materials [1,2]. In order to study the dynamic characteristics of rock-like brittle materials, many scholars first analyzed whether the incident wave waveform met the constant strain rate deformation of the specimen [7,8]. Bagher et al [16] studied the effects of striker bar velocity, diameter, and thickness of the pulse shaper on shaping pulses by SHPB tests experimentally and numerically. On the basis of previous theoretical analysis and numerical calculation results, a dynamic strength prediction model of rock-like brittle material is proposed. This model comprehensively considers the effects of strain rate and strain rate gradient on macro dynamic strength
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