Abstract
Using the caustics method and the experimental system of digital laser dynamic caustics, the model experiment of drop hammer impact loading was carried out, and the effect of the defect shape (circular and rectangular) and the filling material (air, epoxy, and silicone rubber) on the propagation behavior of the running crack was investigated. The experimental results show that, under the impact loading, the running crack initiates at the end of precrack and propagates toward the defect. After the running crack connects to the defect, it accumulates energy within a certain period before initiating again at the upper edge of the defect. Subsequently, only one running crack is formed at the upper edge of the circular defect, but two running cracks are formed at the upper edge of the rectangular defect. The defect shape and the filling material have a significant effect not only on the energy accumulation time of the running crack at the defect but also on the stress intensity factor when initiating at the defect. The effect degree of the defect shape on the running crack propagation behavior is in the following order: circular defect > rectangular defect, whereas the effect degree of the filling material on the running crack propagation behavior follows this order: air > silicone rubber > epoxy.
Highlights
Defects such as cracks and empty holes inevitably contained in the engineering structure seriously impact their strength and mechanical properties [1]. erefore, the fracture behavior of defective structures has always been a key topic in related disciplines and has been investigated in detail, leading to many important results.In terms of theoretical research, Wasiluk and Golos [2] established the Z criterion and considered that the crack propagation direction can be determined by the minimum Z factor
In this study, we investigated the effect of defect shape and filling material on the fracture characteristics and crack propagation behavior in the polymethyl methacrylate (PMMA) specimen under dynamic impact loading by the three-point bend test
The effect of defect shape and filling material on the propagation behavior of the running crack was successfully studied by model experiments. e experiments show that the process of interaction between the defect and running crack can be divided into three stages
Summary
Defects such as cracks and empty holes inevitably contained in the engineering structure seriously impact their strength and mechanical properties [1]. erefore, the fracture behavior of defective structures has always been a key topic in related disciplines and has been investigated in detail, leading to many important results. Wu and Wong [16] used the numerical manifold method to study the effect of microcracks on the mechanical properties of granite under different loading rates, revealing that the dynamic strength and deformation performance of granite increased with increasing loading rate. The three-point bend test is a commonly used method to study the fracture behavior of materials under both static loading and dynamic loading. Erefore, studying the effect of defect shape and filling material on the dynamic fracture behavior of structures is of great scientific and engineering significance. In this study, we investigated the effect of defect shape and filling material on the fracture characteristics and crack propagation behavior in the PMMA specimen under dynamic impact loading by the three-point bend test
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