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1
Content available Optimisation of double floating bodies for small unmanned marine devices based on a new hydraulic flexible wemp system
Cong Dongsheng, Ma Kai, Zhang Ruijun, Li Li, Zhang Xu
Polish Maritime Research
|
2024
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nr 2
99--108
EN
Low-power, small-size, unoccupied devices are often used in the ocean. However, the requirements for long-distance operation and long-term, high-power supplies have always been difficult technical problems to solve. Wave Energy can be effectively used to meet the requirements of a high power supply. Based on a comprehensive analysis of the shortcomings of existing wave energy converters, we present an innovative design for a novel hydraulic flexible wave energy mobile power system and its internal structure. The dynamic model is then simplified into a double-float system, with a spring force from a flexible liquid bag on the upper and lower floating bodies. Furthermore, a model is developed to assess the energy efficiency of the double floating body, and the energy supply strategy and the posture of the double-float system are investigated. The hydrodynamic parameters of three typical axisymmetric rotary floating bodies are analysed using AQWA software, and it is found that the hemispheric-bottomed cylinder (HBC) exhibits superior energy efficiency under the same conditions of space, mass, and drainage volume. Its energy efficiency is mainly reflected in its ability to capture the wave frequency and wave width. HBC floaters perform optimally in both respects. The stability of our design is analysed, and a mathematical relationship between the centroid G and the centre O of the HBC model is developed. The stability of the model is then studied. This study provides a theoretical basis for the provision of low-power, compact, unmanned maritime equipment.
2
Content available Study on stress characteristics of high-porosity coal gangue subgrade during filling process
Hui Bing, Hui Yingxin, Zhang Xu, Zhang Wenjun, Yan Sheng, Men Guangyu
Journal of Theoretical and Applied Mechanics
|
2023
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Vol. 61 nr 3
625--641
EN
By analyzing geological conditions of a coal gangue filling roadbed, stress characteristics and settlement changes during the filling process of the coal gangue roadbed are simulated. The following conclusions are drawn: (1) As height of the coal gangue filling increases, the stress and settlement of each part will also increase. (2) During the filling process, the vertical stress acts as the first principal stress, and the stress and strain at the centerline of the roadbed are 10 times that of the roadbed. (3) The final stable value of uneven settlement of the coal gangue roadbed is 18.85mm. (4) The monitoring results indicate that the settlement of the coal gangue roadbed is stable, and the settlement amount is small ensuring safety of the roadbed.
3
Content available Interception of a hypersonic vehicle by low-speed interceptors: novel perspectives and cost optimisation
Liu Shuangxi, Liu Shijun, Yan Binbin, Zhang Tong, Zhang Xu, Yan Jie
Bulletin of the Polish Academy of Sciences. Technical Sciences
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2022
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Vol. 70, nr 6
art. no. e143537
EN
The conditions for accurately intercepting hypersonic vehicles by low-speed interceptors in the terminal guidance process are examined, considering the general form of a guidance scheme. First, based on the concept of the engagement geometry, three interception scenarios are established considering different manoeuvring configurations of the interceptors and hypersonic vehicle. Second, the boundary conditions for intercepting hypersonic vehicles (with speeds higher than those of the interceptors) are specified for the three scenarios, considering several factors: the speed, path angle, line-of-sight angle, and available overload of the interceptor; path angle and manoeuvrability of the hypersonic vehicle; and relative distance between the interceptor and vehicle. A series of simulations are performed to clarify the influence of each factor on the interception performance in the three interception scenarios. The challenges associated with accurately intercepting hypersonic vehicles by low-speed interceptors are summarised, and several recommendations for designing guidance laws are presented.
4
Content available remote AA5052 failure prediction of electromagnetic flanging process using a combined fracture model
Deng Huakun, Mao Yunfei, Li Guangyao, Zhang Xu, Cui Junjia
Archives of Civil and Mechanical Engineering
|
2022
|
Vol. 22, no. 2
art. no. e84, 1--17
EN
Electromagnetic forming process could significantly increase the forming limit of aluminum alloy. However, high-speed fracture prediction of aluminum alloys is a major problem in the development of electromagnetic flanging process. In this study, notched specimen tensile tests with high-speed Digital Image Correlation system were conducted under the strain rate range from 0.001 to 100 s-1. A fracture model of AA5052 alloys which combined of an uncoupled fracture model, Gissmo damage evolution model and Johnson-Cook strain rate effect was established. Electromagnetic flanging experiments were conducted to verify the failure criteria effectiveness. Results showed that failure strain was significantly influenced by strain rate under various loading path. Compared with the experiments, the percentage error of established electromagnetic flanging process FEM model was less than 4%. The fracture model established could well predict notched specimen high-speed failure, and also accurately predict sheet failure model of electromagnetic flanging experiments and, thus, verified the effectiveness of the established dynamic failure criteria in electromagnetic flanging process.
5
Content available remote Adiabatic shearing mechanism on Al-4.2%Cu alloy bars subjected to electromagnetic loading
Zhang Xu, Huang Yunkai, Meng Shengfei, Zhu Congcong, Li Guangyao, Cui Junjia
Archives of Civil and Mechanical Engineering
|
2021
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Vol. 21, no. 1
393--405
EN
This paper proposed an electromagnetic loading process with the high-speed impact. Al-4.2% Cu alloy bars were used to employ electromagnetic impact (EI) experiments. Deformation mechanism and microstructure evolution of EI samples were revealed by theoretical model and microstructure characterizations. The EI process had impact force (peak value 40 kN) and impact velocity (peak value 6.7 m/s) during a short time period (1.25 ms). Adiabatic shearing mechanism dominated the whole deformation process, causing that significant microstructure characteristic was adiabatic shear bands (ASBs). The theoretical analysis implied that the formation of ASBs was accounted for the radial velocity gradient. Most plastic deformations concentrated in ASBs, and approximately pure shear deformations resulted in adiabatic temperature rise of 0.33–0.42 Tm inside ASBs. The width of ASBs was about 135 μm, in which original equiaxial grains were elongated into laminated sub-structures. TEM observations showed multi-slip systems were simultaneously actuated due to severe shear deformations. High dislocation density and dislocation tangles distributed with the ASBs. Adiabatic temperature rise and distorted energies drove sub-grains rotate into recrystallization grains (70–280 nm) with large angle grain boundaries. The needed maximum time (45 μs) for rotational dynamic recrystallization was far less than that of plastic deformation, indicating that rotational dynamic recrystallization mechanism contributed to the formation of recrystallization grains.
6
Content available Fluka simulation of PGNAA system for determining heavy metal pollution in the soil sample
Zhang Can, Yang Jianbo, Li Rui, Qiao Yujie, Zhang Xu, Xu Jie
Nukleonika
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2020
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Vol. 65, No. 1
13--17
EN
This study presented a self-designed prompt gamma neutron activation analysis (PGNAA) model and used Fluka simulation to simulate the heavy metals (Mn, Cu, Hg, Ni, Cr, Pb) in soil samples. The relationship between the prompt gamma-ray yield of each heavy metal and soil thickness, content of heavy metals in the soil, and source distance was obtained. Simulation results show that the prompt gamma-ray yield of each heavy metal increases with the increase in soil thickness and reaches saturation at 18 cm. The greater the proportion of heavy metals in the soil, the greater the prompt gamma-ray yield. The highest content is approximately 3%, and the change in distance between the neutron source and soil sample does not affect the prompt gamma-ray yield of heavy metals.
7
Content available remote Investigations on microstructure evolution of TA1 titanium alloy subjected to electromagnetic impact loading
Zhang Xu, Zhu Congcong, Hu Lin, Wu Hequan, Li Chunfeng
Archives of Civil and Mechanical Engineering
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2019
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Vol. 19, no. 3
639--647
EN
In this work, the adiabatic shear band of TA1 titanium alloy subjected to electromagnetic impact loading was investigated. The formation of adiabatic shear band and microstructure evolution within it were revealed by microstructure characterizations. Deformation results showed an adiabatic shear band with the width of 10 mm located in shear deformation zone, and most deformations mainly concentrated in the narrow band. The compressive insta-bility and the hardness difference contributed to the formation of adiabatic shear band. Severe shear deformations led to high location density within the adiabatic shear band. A large amount of dislocations distributed in the form of dislocation cells and random dislocations. The rotational dynamic recrystallization mechanism caused that many dy-namic recrystallization grains with the size of 100–200 nm were found inside the adiabatic shear band. Adiabatic temperature rise and distortion energies stored by high dislocation densities provided sub-grain rotations with the driving forces.
8
Content available remote Investigations on mechanical properties and microtopography of electromagnetic self-piercing riveted joints with carbon fiber reinforced plastics/aluminum alloy 5052
Liang Jusong, Jiang Hao, Zhang Jinsheng, Wu Xianhe, Zhang Xu, Li Guangyao, Cui Junjia
Archives of Civil and Mechanical Engineering
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2019
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Vol. 19, no. 1
240--250
EN
In this paper, the mechanical properties of electromagnetic self-piercing riveted (E-SPR) joints with carbon fiber reinforced plastics (CFRP)/aluminum alloy (Al) 5052 were comprehensively investigated. Microtopography observations, hardness measurements and tensile-shear strength tests were performed by comparing with regular pressure self-piercing riveted (P-SPR) joints. Results showed that the undercut value of E-SPR joints was higher than that of P-SPR joints. The hardness values on rivet legs of E-SPR joints were larger and almost no difference on rivet heads between the E-SPR and P-SPR. In addition, it was found that mechanical properties of E-SPR joints were higher than that of P-SPR joints. The shear fracture appearance indicated that E-SPR joints with higher undercut were more difficult to rupture in the bottom of Al sheet.
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