Experimental and numerical study of plastic shear instability under high-speed loading conditions

2014 ◽  
Author(s):  
Mikhail Sokovikov ◽  
Vasiliy Chudinov ◽  
Dmitry Bilalov ◽  
Vladimir Oborin ◽  
Sergey Uvarov ◽  
...  
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Shear Instability ◽  
Loading Conditions ◽  
Plastic Shear

An Experimental and Numerical Study of Hybrid III Dummy Response to Simulated Underbody Blast Impacts

2017 ◽  
Vol 139 (12) ◽  
Author(s):  
Karthik Somasundaram ◽  
Anil Kalra ◽  
Don Sherman ◽  
Paul Begeman ◽  
King H. Yang ◽  
...  
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
High Stress ◽  
Fe Model ◽  
Loading Conditions ◽  
Stress Concentrations ◽  
Vertical Loading ◽  
Laboratory Setup ◽  
Body Regions ◽  
Hybrid Iii

Anthropometric test devices (ATDs) such as the Hybrid III dummy have been widely used in automotive crash tests to evaluate the risks of injury at different body regions. In recent years, researchers have started using automotive ATDs to study the high-speed vertical loading response caused by underbody blast impacts. This study analyzed the Hybrid III dummy responses to short-duration, large magnitude vertical accelerations in a laboratory setup. Two unique test conditions were investigated using a horizontal sled system to simulate underbody blast loading conditions. The biomechanical responses in terms of pelvis acceleration, chest acceleration, lumbar spine force, head accelerations, and neck forces were measured. Subsequently, a series of finite element (FE) analyses were performed to simulate the physical tests. The correlation between the Hybrid III test and numerical model was evaluated using the correlation and analysis (cora) version 3.6.1. The score for the Wayne State University (WSU) FE model was 0.878 and 0.790 for loading conditions 1 and 2, respectively, in which 1.0 indicated a perfect correlation between the experiment and the simulated response. With repetitive vertical impacts, the Hybrid III dummy pelvis showed a significant increase in peak acceleration accompanied by a rupture of the pelvis foam and flesh. The revised WSU Hybrid III model indicated high stress concentrations at the same location, providing a possible explanation for the material failure in actual Hybrid III tests.

Mechanical and Microstructural Aspects of Localized Plastic Flow

2015 ◽  
Vol 243 ◽  
pp. 113-120
Author(s):  
Mikhail Sokovikov ◽  
Vasiliy Chudinov ◽  
Dmitry Bilalov ◽  
Vladimir Oborin ◽  
Sergey Uvarov ◽  
...  
Keyword(s):  
High Speed ◽  
Shear Instability ◽  
Plastic Shear ◽  
Optical Interferometer ◽  
Temperature Field Distribution ◽  
Infra Red ◽  
Split Hopkinson ◽  
Instability Regions ◽  
Plug Formation

The behavior of specimens dynamically loaded during the split Hopkinson (Kolsky) bar tests in a regime close to simple shear conditions was studied. The lateral surface of the specimens was investigated in-situ using a high-speed infra-red camera CEDIP Silver 450M. The temperature field distribution obtained at different time allowed one to trace the evolution of plastic strain localization. The process of target perforation involving plug formation and ejection was examined using a high-speed infra-red camera and a VISAR velocity measurement system. The microstructure of tested specimens was analyzed using an optical interferometer-profiler and a scanning electron microscope. The development of plastic shear instability regions has been simulated numerically.

Thermal comfort analysis of a high-speed train cabin considering the solar radiation effects

2019 ◽  
Vol 29 (8) ◽  
pp. 1101-1117
Author(s):  
Lin Yang ◽  
Xiangdong Li ◽  
Jiyuan Tu
Keyword(s):  
Solar Radiation ◽  
Thermal Comfort ◽  
High Speed ◽  
Radiation Effects ◽  
Numerical Study ◽  
Thermal Conditions ◽  
Long Distance ◽  
High Speed Rail ◽  
Hot Weather ◽  
Cabin Environment

Due to the fast development of high-speed rail (HSR) around the world, high-speed trains (HSTs) are becoming a strong competitor against airliners in terms of long-distance travel. Compared with airliner cabins, HST cabins have much larger window sizes. When the big windows provide better lighting and view of the scenery, they also have significant effects on the thermal conditions in the cabins due to the solar radiation through them. This study presents a numerical study on the solar radiation on the thermal comfort in a typical HST cabin. The effect of solar radiation was discussed in terms of airflow pattern, temperature distribution and thermal comfort indices. Parametric studies with seven different daytime hours were carried out. The effect of using the roller curtain was also studied. The overall cabin air temperature, especially near passengers, was found to have significantly increased by solar radiation. Passengers sitting next to windows were recorded to have an obvious thermal comfort variation at different hours of the day. To improve the passengers’ comfort and reduce energy consumption during hot weather, the use of a curtain could effectively reduce the solar radiation effect in the cabin environment.

Numerical study on the mechanism of drag reduction for interceptors on planning boats

2021 ◽  
Author(s):  
Lianzheng Cui ◽  
Zuogang Chen ◽  
Yukun Feng
Keyword(s):  
Drag Reduction ◽  
High Speed ◽  
Degrees Of Freedom ◽  
Numerical Study ◽  
Dynamic Pressure ◽  
Motion Model ◽  
Gauge Pressure ◽  
Reduction Effect ◽  
Pressure Resistance ◽  
Viscous Pressure

The drag reduction effect of interceptors on planning boats has been widely proven, but the mechanism of the effect has been rarely studied in terms of drag components, especially for spray resistance. The resistance was caused by the high gauge pressure under the boats transformed from the dynamic pressure, and it is the largest drag component in the high-speed planning mode. In this study, numerical simulations of viscous flow fields around a planning boat with and without interceptors were conducted. A two degrees of freedom motion model was employed to simulate the trim and sinkage. The numerical results were validated against the experimental data. The flow details with and without the interceptor were visualized and compared to reveal the underlying physics. A thinner and longer waterline could be achieved by the interceptor, which made the boat push the water away more gradually, and hence, the wave-making resistance could be decreased. The improved waterline also reduced the component of the freestream normal to the hull surface and led to the less transformed dynamic pressure, resulting in the lowAer spray resistance. Furthermore, the suppression of the flow separation could also be benefited from the interceptor; the viscous pressure resistance was therefore decreased.

A numerical study of snow accumulation on the bogies of high-speed trains based on coupling improved delayed detached eddy simulation and discrete phase model

2018 ◽  
Vol 233 (7) ◽  
pp. 715-730 ◽  
Author(s):  
Mingyang Liu ◽  
Jiabin Wang ◽  
Huifen Zhu ◽  
Sinisa Krajnovic ◽  
Guangjun Gao
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Snow Accumulation ◽  
Phase Model ◽  
Detached Eddy Simulation ◽  
Discrete Phase Model ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Flow Mechanisms ◽  
Discrete Phase

A numerical simulation method based on the improved delayed detached eddy simulation coupled with a discrete phase model is used to study the influence of the snow on the performance of bogies of a high-speed train running in snowy weather. The snow particle trajectories, mass of snow packing on the bogie, and thickness of snow accumulation have been analyzed to investigate the flow mechanisms of snow accumulation on different parts of the bogies. The results show that the snow accumulation on the first bogie of the head vehicle is almost the same as that of the second bogie, but the total accumulated snow on the top side of the second bogie is more than 74% higher than that of the first bogie. Among all the components of the bogies, the motors were found to be strongly influenced by the snow accumulation. The underlying flow mechanisms responsible for the snow accumulations are discussed.

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