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Rebound is the main problem in the landing process of the combined airbag. To solve the problem, the design method of the combined lunar landing airbag without rebound was proposed in this paper. First, a new combined airbag structure was designed to avoid dust generated by venting during landing, and the analytical dynamics model of the combined lunar airbag was established on the basis of the deformation assumptions and gas exchange relationship of the main and secondary airbags, which is validated by simulation and experiment. Then, based on the analytical model, the combined airbag was optimized under the constraint of no rebound to realize the design of the airbag without rebound. Finally, the multiobjective optimization design of the combined airbag was carried out using this method. The optimized airbag with no bouncing back and no hard landing was also obtained, of which the maximum impact acceleration was smaller than the nonoptimized one. The analytical results of the optimized airbag are in good agreement with the simulation results, indicating that the proposed no-rebound design method is effective and feasible.

Transportation of a large amount of goods and materials to the lunar surface will be an urgent need with the increasing intensive exploration of the moon. The airbag cushioning system is the most prospective one due to its low cost, simple structure, adjustable performance, and well stability, when compared to other types like the soft-landing mechanism and sky crane. The special lunar environment of the thin atmosphere and low gravity calls for new types of the combined airbag. Thus, a new combined airbag structure that can avoid generating a lot of dust during venting was proposed to fit the lunar environment. By proposing an improved deformation assumption of the airbag based on large deformation, as well as considering gas exchange between main and secondary airbags, a novel combined airbag analytical model was put forward. The inflation and cushioning process were calculated and validated through simulation analysis and ground test. The analytical, numerical, and experimental results were in good agreement. Using the analytical model, the lunar landing cushioning process of the combined airbag with different layouts was analyzed, and the optimal layout was determined. Furthermore, parameter effects on the cushioning performance were studied. The results show that: main airbag initial pressure, venting threshold pressure, vent orifice diameter, and secondary airbag volume have a great impact on cushioning performance, while inflation gas temperature has little impact. Notably, the influence law of these parameters is not monotonous.

The optimal design of laminates of interlayer hybrid lamination with multicouplings is significantly beneficial to enhance the mechanical properties and reduce the cost of composite structures. The...

The optimized design of composite adaptive structures puts forward higher requirements and challenges to the actual configuration of the structural section. In this paper, a trapezoidal laminate model of composite materials is established. Based on the classical laminates theory, the bending problem of trapezoidal laminates is solved by using the Kantorovich method and the principle of minimum potential energy. The analytic form of the solution is found to satisfy the Euler equation and displacement boundary conditions. Taking the wing of a jet transport aircraft as an example, the accuracy of the analytical solution is verified by the finite element method. The Differential Evolution algorithm is used to realize the multi-objective optimal design of the bending–twisting coupled trapezoidal laminates, and the hygrothermal stability of laminates is verified by the finite element method. Finally, based on the Monte Carlo method, the robustness analysis of the bending–twisting coupling effect of laminate is realized; meanwhile the feasibility and reliability of the design scheme are verified. The stress and strain functions at each point of the trapezoidal laminate can be further obtained by the analytical solution, making it more convenient to analyze the stresses and calculate the static forces of the trapezoidal laminate and its composite structures, which is of great significance to effectively improve the comprehensive mechanical properties of the cross-section structure of composite materials.

To improve the mechanical properties of bending-twisting coupled structures, the necessary and sufficient conditions for composite laminates with extension-shear coupling effect which contribute to the bending-twisting coupled structures are deduced. Then the analytical expressions for torsional distortion of bending-twisting coupled structures are deduced. The Differential Evolution algorithm is used to optimize the bending-twisting coupled structures for the purpose of maximizing torsional distortion, the stacking sequences of two extension-shear coupled laminates are obtained through calculation. Lastly, the applicability of simplified model is verified. The hygro-thermal stability, bending-twisting coupling effect and buckling load of bending-twisting coupled structures are verified via simulation. The yield strength is analyzed based on Tsai-Wu criterion .

The influence of magnetic matrices, magnetic field intensity, secondary and three section superconducting magnetic separation on the separation was studied in this paper. The magnetic field and flo...

Interlayer hybrid laminated structures have the potential to solve the high cost issue of large-scale application of composite structures. Compared with single coupled laminate, multi-coupled laminates can avoid the limitations of low mechanical properties. At first, the interlayer hybrid multi-coupled laminates were studied, and research showed that there were 12 types of interlayer hybrid laminates with extension-twisting coupling, of which 8 types could meet the conditions of hygro-thermal stability. Then, 3 types of hygro-thermally stable interlayer hybrid multi-coupled laminates with the dominant coupled type were selected for the optimal ply design based on the Differential Evolution algorithm, including the Extension-Twisting / Bending-Twisting coupled laminate, the Extension-Twisting / Extension-Bending / Shearing-Twisting coupled laminate and the Extension-Twisting / Extension-Bending / Shearing-Twisting / Bending-Twisting coupled laminate. The total extension-twisting coupling could raise up to 7–8 times, when compared to classical laminates. Through reasonable ply design, the failure load and buckling load could be improved as much as possible in addition to enhancing its stiffness performance. The numerical simulation results verified the coupling and hygro-thermal stability; and the robustness analysis results proved the validity and feasibility of the ply accuracy.

Novel pavement design and size design are important factors to improve the mechanical properties and applicability of composite structures. Based on the multi-coupling of laminates, the universal analytical conditions for multi-coupled laminates are derived. Then four types of laminates with extension-shear coupling capable of forming bending-twisting coupled structure are designed, including three types of multi-coupled laminates. The shape of laminate is no longer limited to rectangular laminate, which is considered as a variable in the design process. Through the combination of theoretical calculation and numerical simulation, the optimal design of trapezoidal laminates with multiple coupling is achieved. The effect of the multi-coupling effect on the stiffness performance has been explored for free-layer laminates, and it has been found that the introduction of the multi-coupling can greatly improve the stiffness performance of laminates. Finally, the hygro-thermal stability performance is verified by numerical simulation and the robust analysis is obtained for stiffness performance.

Extension–Bending coupling behaviour is believed to arise uniquely in anti-symmetric Cross-ply laminates. The results in this article serve to dispel this misconception by presenting solutions for both Cross-ply laminates and Standard laminates, defined as containing combinations of angle plies and cross plies, for a range of different sub-sequence symmetries. Details of the algorithm used to develop the definitive list of laminate stacking sequences with up to 21 plies are presented. Finally, natural frequency factor envelopes are developed, which identify significant differences in the bounds, across a range of aspect-ratios, between Standard laminate configurations and the previously assumed Cross-ply designs.

Anti-symmetric angle-ply laminates are widely believed to uniquely possess Extension-Twisting (together with Shearing–Bending ) coupling behavior. The results in this article serve to dispel this misconception by presenting solutions for both standard laminates, containing combinations of angle plies (±45°) and cross plies (90° and/or 0°), and angle-ply laminates, containing only ± 45° ply orientations; chosen to reflect current industrial design practice, and also because they serve to produce hygro-thermally curvature-stable properties in some standard laminate configurations, i.e., with immunity to the thermal distortions that generally arise in this class of mechanically coupled laminate as a result of the high temperature curing process. Details of the algorithm used to develop the definitive list of laminate stacking sequences, with up to 21 plies, are given first. Closed form natural frequency solutions for each of these sub-groups are then presented, identifying significant differences in the frequency spectrum bounds across a range of aspect ratios, with respect to the ubiquitous anti-symmetric angle-ply designs.

Material-independent necessary and sufficient conditions are derived for extension-shear coupled laminate with immunity to hygro-thermal shearing distortion (HTSD) using classical lamination theory. It is proven that no standard form of extension-shear coupled laminate with immunity to HTSD exists. A survey is performed to identify free form of extension-shear coupled laminate with immunity to HTSD that produce maximum extension-shear coupling. This is achieved through a constrained optimization routine, where the constraints are the material-independent necessary and sufficient conditions for laminates with immunity to HTSD. Results are presented for the symmetric laminates that consist of 8–14 plies. Comparisons are made on hygrothermal behavior and buckling strength of extension-shear coupled laminates with and with immunity to HTSD. The robustness of the extension-shear coupled laminates with immunity to HTSD is verified by using Monte Carlo simulation for laminates with fiber orientation that slightly deviates from the theoretically designed direction.

Scale model test is an effective means to verify the design of stiffened cylindrical shells. However, there are problems of similarity distortion when traditional dimensional analysis is adopted to design scale models. In this study, an equivalent similarity method has been proposed to solve the problem. The method is applied to study the similarity of global bending mode of stiffened cylindrical shells. The equivalent criterion and scaling laws are derived and verified by numerical examples. The result of similar deviations shows that the scaling laws are highly accurate. The problem of similarity distortion can be resolved, and the parameters of scale model can be designed more freely with the proposed equivalent similarity method.

Physicochemical Problems of Mineral Processing; ISSN 2084-4735

Chinese GDP per capita fluctuated at a high level during the Northern Song and Ming dynasties before trending downwards during the Qing dynasty. China led the world in living standards during the Northern Song dynasty, but had fallen behind Italy by 1300. At this stage, it is possible that parts of China were still on a par with the richest parts of Europe, but by 1750 the gap was too large to be bridged by regional variation within China and the Great Divergence had already begun before the Industrial Revolution.

In order to ensure the safety of the missile-canister system in silo during the earthquake, a modified transfer matrix method is provided to study the dynamic characteristics of the system. Firstly, a discrete viscoelastic connected double-beam model is developed taking account of the structural nonuniformity and the discrete distribution of the adapters. Secondly, the transfer matrix method of a single beam is modified to solve the problem of discrete connection between the two beams of the double-beam model. Then the natural circular frequencies and mode shapes are calculated by the proposed method, comparing with the finite element method (FEM). Finally, the influence of the stiffness of radial vibration isolators and adapters on the dynamic characteristics of the system is analysed. The comparison shows that the results of the proposed method are well consistent with the FEM calculations and the proposed method is validated. The variations of the first six natural circular frequencies with radial vibration isolator stiffness and adapter stiffness are obtained, which provides a basis for the seismic-relieving design.

To explore the effect of particle size distributions of supports on thermal performances of phase change materials (PCMs), shape-stabilized composites were prepared by using stearic acid (SA) to hybridize size-different kaolinite (Kaol). The samples were characterized using SEM, XRD, FTIR, BET and DSC techniques. The results indicated that superior thermal capacity was ascribed to higher loading capacity and crystallinity of SA, which was closely related to the layout state of Kaol within the composites. Enhanced thermal conductivity could be achieved with the increasing crystallinity, the descending interfacial thermal resistance and efficient heat conductive network. The establishment of heat transfer network depended largely on the mutual proportion between small-sized and large-sized particles in supports. The tiny particles were inferred to act as junctions to bridge the separately dispersed plates, which was contributed to the continuous heat conducting pathways. The results suggested that particle size distributions of Kaol could exert a great influence on thermal performances of composites. Furthermore, Kaol could obviously uplift the thermal stability of composites, and the thermal cycling test has validated its excellent thermal reliability. We believe that this study will play an enlightening role in the design and fabrication of highly-efficient shape-stabilized PCMs for solar energy storage.

A new motion planning method is proposed for enlarging the solvable space of zero-disturbance motion planning for the space free-floating manipulator system. First, a class of translational zero-disturbance curves is put forward for the first time. The equation of translational zero-disturbance curve is deduced using the nonholonomic constraint of the manipulator system, and its characteristics are also discussed. Second, the zero-disturbance curve of the whole operating process is divided into two segments. The first one is a translational zero-disturbance curve which passes through the target point. Another one is a common zero-disturbance curve which passes through the original point and intersects with the translational zero-disturbance curve. Finally, the common zero-disturbance curve is obtained by a hybrid programming strategy based on Gauss pseudo-spectral method(GPM) and direct shooting method(DSM). The numerical simulation results indicate that the proposed method is effective, and that the solvable space of this method almost covers the whole work space of the manipulator system.