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This paper presents an experimental program of reinforced concrete beam without stirrups tested by impact three-point-bending under different initial velocity (drop height). As the results shown, for the static events, the failure mode is bending firstly, and then translates to shearing. the longitudinal reinforcements play an important role for the increasing of loading during bending stage. For the impact events, reinforced concrete beams failed in a flexural failure model at slow rates of loading and in shear failure model at high impact loading rate relatively. Moreover, the shear failure and bending failure have developed during the peak stage of Force-deflection curves. That is different with the emergence sequence of cracks under static tests. So the mechanical parameters of peak stage should be considered for the resistance of concrete beam under impact loading.

Expanding ring experiment is an important method for dynamic fragmentation of solid under 1D tensile loading. Based on the split Hokinson pressure bar (SHPB), a liquid-driving experimental technology was developed for conducting expanding ring tests. The loading fixture includes a hydraulic cylinder filled with water, which is pushed by a piston connected to the input bar. As the water is driven, it expands the metallic ring specimen in the radial direction. The approximately incompressible property of the water makes it possible to drive the specimen in very high radial velocity by low velocity movement of piston, according to the large sectional area ratio of the cylinder to specimen. Using liquid-driving expanding ring device, 1060 aluminum rings (ductile materials)/PMMA rings (brittle materials) were fragmented and the fragments were recovered. Impact deformation of free-flying fragments was avoided through the use of “sample soft-capture” technology. The fragmentation process was observable by high speed camera through modifying the driving direction of the water. From the observations of the fracture morphology and the residual internal cracks of the recovered fragments, it is concluded that the fracture of the rings is caused by the circumferential tensile stress.

In relation to the dynamic tests of materials, the approach to solve the viscoelastic wave propagations in a one dimensional viscoelastic rod was summarized. By conducting Laplace transform, the governing partial differential equations were transformed to ordinary differential equations for the image functions, which were solved analytically with suitable boundary equations. Inversely transforming these image functions gives the results of the stress, velocity, and strain in the bar. Two wave problems occurred in split Hopkinson pressure bar (SHPB) tests are analyzed: 1) the problem of evaluating the internal stress distributions in a viscoelastic specimen; and 2) the problem of stress wave propagations in a viscoelastic bar. Both problems were solved numerically by way of numerical inverse Laplace transform. For the first problem, the special case when the specimen is pure elastic was solved analytically, giving the exact solution to the problem of elastic wave propagation in a sandwich elastic media.

Quasistatic compression tests for alumina (Al2O3) cylinders were conducted for the investigations of the compressive strengths and the dynamic fragmentation properties of the material. We focused on the post-failure dynamic fragmentation phenomenon. Most of the fragments were collected after tests, the shapes and sizes of these fragments were measured and statistically analyzed. The fragments were divided into three types on basis of their shapes and sizes, namely: the flaky medium sized fragments, the tiny debris, and the remaining large blocks, each type of the fragments were formed at different stages of the compressive failure-fragmentation process. The tiny debris were mainly generated from the ”explosion” of the cylindrical specimen, in this stage the stored elastic energy within the specimen was released rapidly. The tiny fragments accounted the most part of the fragments in numbers. The average fragment size calculated by the proposed formula agree well with the experimental data.

The adiabatic shear bands (ASB) of the tubular metal specimens expanded explosively have been studied by many researchers in the recent years. The onset and evolutions of the multiple shear failure of metal cylinder under explosive loadings are affected by many factors such as the characteristics of the impulsive loadings, the dynamic behavior of the materials, etc. In this work, we investigate the failure and fragmentation of 45# steel cylinder shell driven by the JOB9003 explosive. Experimental and FEM numerical simulation investigations are made for cylinder modeled shell. The results show that for the perfect homogeneous FEM model, the failure mechanism of cylinder shell is differs from that of the experiments, in which the spalling originates is oriented by high intensity of rarefaction wave. Through numerical experiments, it was found that distributed geometrical defects of cylinder shell affect the fragmentation process and mechanism, in which the strain localization controlled by the defects and shear bands initiate on the inter-surface of the cylinder shell.

Online reviews may influence unsafe acts and are significant in the context of big data. This study acquired online reviews related to air traffic control from social media websites. The word frequency statistics and coding of negative comments were taken to mine risk factors. Combined with the human factors analysis and classification system (HFACS), a conceptual model of the risk factors associated with the unsafe acts of air traffic controllers (ATCers) was constructed. The results indicate that the frequency of risk factors in online reviews, ranked from high to low, is organizational influences, ATCers' adverse states, environmental factors and unsafe supervision. Organizational influences, environmental factors and unsafe supervision indirectly affect the unsafe acts through the ATCers' adverse states. It is demonstrated that the combination of HFACS and online reviews to identify risk factors enables the identification of problems in the air traffic control industry and demands of ATCers. [ABSTRACT FROM AUTHOR]