The tension and compression of face-centered-cubic high-entropy alloy(HEA) nanowires are significantly asymmetric, but the tension–compression asymmetry in nanoscale body-centered-cubic(BCC) HEAs is still unclear. In...The tension and compression of face-centered-cubic high-entropy alloy(HEA) nanowires are significantly asymmetric, but the tension–compression asymmetry in nanoscale body-centered-cubic(BCC) HEAs is still unclear. In this study,the tension–compression asymmetry of the BCC Al Cr Fe Co Ni HEA nanowire is investigated using molecular dynamics simulations. The results show a significant asymmetry in both the yield and flow stresses, with BCC HEA nanowire stronger under compression than under tension. The strength asymmetry originates from the completely different deformation mechanisms in tension and compression. In compression, atomic amorphization dominates plastic deformation and contributes to the strengthening, while in tension, deformation twinning prevails and weakens the HEA nanowire.The tension–compression asymmetry exhibits a clear trend of increasing with the increasing nanowire cross-sectional edge length and decreasing temperature. In particular, the compressive strengths along the [001] and [111] crystallographic orientations are stronger than the tensile counterparts, while the [110] crystallographic orientation shows the exactly opposite trend. The dependences of tension–compression asymmetry on the cross-sectional edge length, crystallographic orientation,and temperature are explained in terms of the deformation behavior of HEA nanowire as well as its variations caused by the change in these influential factors. These findings may deepen our understanding of the tension–compression asymmetry of the BCC HEA nanowires.展开更多
The vibration characteristics of composite vertical stabilizer skin structures play a critical role in damping effects designed for overcoming the air disturbances experienced by aircraft structural components during ...The vibration characteristics of composite vertical stabilizer skin structures play a critical role in damping effects designed for overcoming the air disturbances experienced by aircraft structural components during flight.The first-order fundamental frequencies and their corresponding damping characteristics of the vertical stabilizer skin structure tow-steered by automatic fiber placement technique were optimized with the parameterized trajectories and plies as design variables.Firstly,the vibration and damping numerical models were derived based on Kirchhoff laminate theory,the Rayleigh-Ritz method,and the Strain Energy Method.Then the optimization model was developed by adopting the self-adaptive Differential Evolution Multi-objective optimization algorithm and incorporating the solution method of Pareto Front.The constraints of this optimization model considered the experimentally obtained minimum turning radius of prepregs tow-steered in automatic fiber placement process obtained from experimental tests.Finally,the comparison of numerical simulation results was conducted for the optimized trajectories and the conventional straight trajectories under various boundary conditions,and the numerical results were partially validated through damping and frequency tests.The results indicate the vibration characteristics of the composite vertical stabilizer skin structure can be enhanced to a large extent by optimizing fiber trajectories,and the enhancement percentage is affected by the boundary conditions of the actual structure.展开更多
This paper tested the viscosity of prepreg in the automatic placement process, and conducted the probe and placement-90° peel tests through the test systems. The law of variation of prepreg viscosity during the l...This paper tested the viscosity of prepreg in the automatic placement process, and conducted the probe and placement-90° peel tests through the test systems. The law of variation of prepreg viscosity during the laying process was studied through these tests under different conditions by taking the peel force to intuitively and quantitatively characterise the viscosity of the prepreg.The results show that this viscosity is inversely proportional to the laying rate, proportional to the laying pressure, and quadratic to the laying temperature. Then, peel tests were simulated to validate both the correctness of the peel test and that of the probe test data fitting the two-line cohesion model. On this basis, a response surface test for laying and peeling was designed. Taking viscous peel force as the response target, the laying process parameters were optimised and the significance of their influence was further studied. The error between the test value and the predicted value of the maximum viscous peel force is 3.03%.展开更多
A multi-objective optimization method was proposed for different dome reinforcement methods of a filament-wound solid rocket motor composite case based on a Radial Basis Function(RBF)model.Progressive damage of the co...A multi-objective optimization method was proposed for different dome reinforcement methods of a filament-wound solid rocket motor composite case based on a Radial Basis Function(RBF)model.Progressive damage of the composite case was considered in a simulation based on Hashin failure criteria,and simulation results were validated by hydraulic burst tests to precisely predict the failure mode,failure position,and burst pressure.An RBF surrogate model was estab-lished and evaluated by Relative Average Absolute Error(RAAE),Relative Maximum Absolute Error(RMAE),Root Mean Squared Error(RMSE),and R^(2)methods to improve the optimization efficient of dome reinforcement.In addition,the Non-dominated Sorting Genetic Algorithm(NSGA-II)was employed to establish multi-objective optimization models of variable-angle and variable-polar-radius dome reinforcements to investigate the coupling effect of the reinforcement angle,reinforcement layers,and reinforcement range on the case performance.Optimal reinforce-ment parameters were obtained and used to establish a progressive damage model of the composite case with dome reinforcement.In accordance with progressive damage analysis,the burst pressure and performance factor were obtained.Results illustrated that variable-angle dome reinforcement was the optimal reinforcement method compared with variable-polar-radius dome reinforcement as it could not only ensure the reinforcement angle’s continuous changing but also decrease the mass of composite materials.Compared with the unreinforced case,the reinforced case exhibited an increase in the burst pressure and performance factor of 36.1%and 23.5%,respectively.展开更多
A ring-shaped focus, such as a focused vortex beam, has played an important role in microfabrication and optical tweezers.The shape and diameter of the ring-shaped focus can be easily adjusted by the topological charg...A ring-shaped focus, such as a focused vortex beam, has played an important role in microfabrication and optical tweezers.The shape and diameter of the ring-shaped focus can be easily adjusted by the topological charge of the vortex. However,the flow energy is also related to the topological charge, making the individual control of diameter and flow energy of the vortex beam impossible. Meanwhile, the shape of the focus of the vortex beam remains in the hollow ring. Expanding the shape of focus of structural light broadens the applications of the vortex beam in the field of microfabrication. Here, we proposed a ring-shaped focus with controllable gaps by multiplexing the vortex beam and annular beam. The multiplexed beam has several advantages, such as the diameter and flow energy of the focal point can be individually controlled and are not affected by the zero-order beam, and the gap size and position are controllable.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No.12272118)the National Key Research and Development Program of China (Grant No.2022YFE03030003)。
文摘The tension and compression of face-centered-cubic high-entropy alloy(HEA) nanowires are significantly asymmetric, but the tension–compression asymmetry in nanoscale body-centered-cubic(BCC) HEAs is still unclear. In this study,the tension–compression asymmetry of the BCC Al Cr Fe Co Ni HEA nanowire is investigated using molecular dynamics simulations. The results show a significant asymmetry in both the yield and flow stresses, with BCC HEA nanowire stronger under compression than under tension. The strength asymmetry originates from the completely different deformation mechanisms in tension and compression. In compression, atomic amorphization dominates plastic deformation and contributes to the strengthening, while in tension, deformation twinning prevails and weakens the HEA nanowire.The tension–compression asymmetry exhibits a clear trend of increasing with the increasing nanowire cross-sectional edge length and decreasing temperature. In particular, the compressive strengths along the [001] and [111] crystallographic orientations are stronger than the tensile counterparts, while the [110] crystallographic orientation shows the exactly opposite trend. The dependences of tension–compression asymmetry on the cross-sectional edge length, crystallographic orientation,and temperature are explained in terms of the deformation behavior of HEA nanowire as well as its variations caused by the change in these influential factors. These findings may deepen our understanding of the tension–compression asymmetry of the BCC HEA nanowires.
基金co-supported by the National Natural Science Foundation of China(Nos.51875159,52175311,52175133,12102115,52005446)the Fok Ying Tung Education Foundation,China(No.171046)the Fundamental Research Funds for the Central Universities,China(Nos.JZ2021HGTA0178,JZ2020HGQA0197)。
文摘The vibration characteristics of composite vertical stabilizer skin structures play a critical role in damping effects designed for overcoming the air disturbances experienced by aircraft structural components during flight.The first-order fundamental frequencies and their corresponding damping characteristics of the vertical stabilizer skin structure tow-steered by automatic fiber placement technique were optimized with the parameterized trajectories and plies as design variables.Firstly,the vibration and damping numerical models were derived based on Kirchhoff laminate theory,the Rayleigh-Ritz method,and the Strain Energy Method.Then the optimization model was developed by adopting the self-adaptive Differential Evolution Multi-objective optimization algorithm and incorporating the solution method of Pareto Front.The constraints of this optimization model considered the experimentally obtained minimum turning radius of prepregs tow-steered in automatic fiber placement process obtained from experimental tests.Finally,the comparison of numerical simulation results was conducted for the optimized trajectories and the conventional straight trajectories under various boundary conditions,and the numerical results were partially validated through damping and frequency tests.The results indicate the vibration characteristics of the composite vertical stabilizer skin structure can be enhanced to a large extent by optimizing fiber trajectories,and the enhancement percentage is affected by the boundary conditions of the actual structure.
基金supported by the National Natural Science Foundation of China(No.51875159)the Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratory,China(No.XHT 2020-002)+5 种基金Fok Ying Tung Education Foundation,China(No.171046)the Key Research and Development Program of Anhui Province,China(No.201904d07020013)the Fundamental Research Funds for the Central Universities,China(Nos.PA2020GDJQ0029 and PA2020GDSK0075)the National Key Research and Development Project,China(No.2019YFB1504800)the Beijing Natural Science Foundation,China(No.2192044)2020 and 2021 Open Project of State Key Laboratory of Organic-Inorganic Composites,China(Nos.Oic-202001008 and Oic-202101008)。
文摘This paper tested the viscosity of prepreg in the automatic placement process, and conducted the probe and placement-90° peel tests through the test systems. The law of variation of prepreg viscosity during the laying process was studied through these tests under different conditions by taking the peel force to intuitively and quantitatively characterise the viscosity of the prepreg.The results show that this viscosity is inversely proportional to the laying rate, proportional to the laying pressure, and quadratic to the laying temperature. Then, peel tests were simulated to validate both the correctness of the peel test and that of the probe test data fitting the two-line cohesion model. On this basis, a response surface test for laying and peeling was designed. Taking viscous peel force as the response target, the laying process parameters were optimised and the significance of their influence was further studied. The error between the test value and the predicted value of the maximum viscous peel force is 3.03%.
基金co-supported by the National Natural Science Foundation of China(52175311,52175133,12102115,52005446)the Fundamental Research Funds for Central Universities in China(JZ2021HGTA0178,JZ2022HGQA0150).
文摘A multi-objective optimization method was proposed for different dome reinforcement methods of a filament-wound solid rocket motor composite case based on a Radial Basis Function(RBF)model.Progressive damage of the composite case was considered in a simulation based on Hashin failure criteria,and simulation results were validated by hydraulic burst tests to precisely predict the failure mode,failure position,and burst pressure.An RBF surrogate model was estab-lished and evaluated by Relative Average Absolute Error(RAAE),Relative Maximum Absolute Error(RMAE),Root Mean Squared Error(RMSE),and R^(2)methods to improve the optimization efficient of dome reinforcement.In addition,the Non-dominated Sorting Genetic Algorithm(NSGA-II)was employed to establish multi-objective optimization models of variable-angle and variable-polar-radius dome reinforcements to investigate the coupling effect of the reinforcement angle,reinforcement layers,and reinforcement range on the case performance.Optimal reinforce-ment parameters were obtained and used to establish a progressive damage model of the composite case with dome reinforcement.In accordance with progressive damage analysis,the burst pressure and performance factor were obtained.Results illustrated that variable-angle dome reinforcement was the optimal reinforcement method compared with variable-polar-radius dome reinforcement as it could not only ensure the reinforcement angle’s continuous changing but also decrease the mass of composite materials.Compared with the unreinforced case,the reinforced case exhibited an increase in the burst pressure and performance factor of 36.1%and 23.5%,respectively.
基金This work was supported by the National Natural Science Foundation of China(Nos.62005262 and 51875160)Fundamental Research Funds for the Central Universities(Nos.PA2020GDSK0077 and PA2020GDKC0010)。
文摘A ring-shaped focus, such as a focused vortex beam, has played an important role in microfabrication and optical tweezers.The shape and diameter of the ring-shaped focus can be easily adjusted by the topological charge of the vortex. However,the flow energy is also related to the topological charge, making the individual control of diameter and flow energy of the vortex beam impossible. Meanwhile, the shape of the focus of the vortex beam remains in the hollow ring. Expanding the shape of focus of structural light broadens the applications of the vortex beam in the field of microfabrication. Here, we proposed a ring-shaped focus with controllable gaps by multiplexing the vortex beam and annular beam. The multiplexed beam has several advantages, such as the diameter and flow energy of the focal point can be individually controlled and are not affected by the zero-order beam, and the gap size and position are controllable.