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排序方式: 共有331条查询结果,搜索用时 15 毫秒
141.
基于140 GHz兆瓦级回旋振荡器电子枪设计和研制,利用ANSYS热分析软件,建立相应的磁控注入电子枪模型,分析电子枪工作时阴极温度均匀性及热形变,尝试通过相关几何和电参数的调整,在改善阴极温度均匀性的基础上,尽可能消除热形变对电子轨迹质量的影响。通过对比相同加热功率下阴极发射带的实测温度及仿真温度,评价了仿真模型及结果的合理性,为阴极组件的实际设计提供了参考数据。 相似文献
142.
Mengxin Yang Jing Wu Wenjie Jiang Xiaorui Hu Mohammad Irfan Iqbal Fengxin Sun 《Advanced functional materials》2023,33(5):2210351
Soft pneumatic actuators possess the increasing potential for various healthcare applications, such as smart wearable devices, safe human-robot interaction, and flexible manipulators. However, it is difficult to translate the existing technologies to commercial applications due to their inefficient volumetric power, sophisticated control with high operation pressure, slow production, and high cost. To overcome these issues, herein, a caterpillar-inspired actuator using hierarchical textile architectures based on simple fabrication and low-cost strategy is designed. Unlike the existing textile-based pneumatic actuators, the designed actuators are constructed by combining boucle fancy yarns with a novel trilayer-knit architecture. The as-prepared actuators concurrently possess fast response (1100° s−1), large bending actuation strain (1080° m−1), high-power density (272 W m−3), mechanical robustness, easy-programmable motions, and human-tactile comfort, which outperforms currently reported textile-based pneumatic actuators. Furthermore, due to the geometrical transition of the engineered hierarchical structure, the developed actuators exhibit superior dual-stiffness effect with stress evolution, providing a facile approach to addressing the conflict of flexibility and force output in soft fluidic actuators. This concept as a paradigm provides new insights to develop soft actuators with outstanding design flexibility, adaptability, and multifunctionality using engineered textile-structure, which has great potential for real-world applications in medical rehabilitation, physiotherapy, and soft robotics. 相似文献
143.
基于惯性传感器输出匹配的舰船变形估计方法 总被引:3,自引:0,他引:3
大型舰船在海上航行过程中由于风浪作用、载荷变化、太阳照射以及载体机动等原因会产生一定的变形,该变形会极大地影响到舰载武器装备所需姿态信息的精度.针对这一问题,本文提出了在战位点安装惯性测量单元(IMU:陀螺+加速度计),直接根据IMU输出的速度增量和角速度信息,结合舰船主惯性导航系统的输出信息,利用卡尔曼滤波估计舰船变... 相似文献
144.
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146.
Finite deformations of an initially stressed cylindrical shell under internal pressure 总被引:1,自引:0,他引:1
P.B. Gonalves D. Pamplona S.R.X. Lopes 《International Journal of Mechanical Sciences》2008,50(1):92-103
This paper investigates the large deformations of an extended thick cylindrical tube under internal pressure, with emphasis on the static nonlinear behavior and instabilities of the shell. Thick elastic tubes that undergo large elastic deformations under internal pressure can exhibit novel instabilities. After some deformation, part of the tube becomes highly deformed taking the form of a bulge, while the remainder appears almost unchanged. This local instability phenomenon corresponds to a limit point along the nonlinear equilibrium path. After the onset of these highly nonuniform deformations, the local bulge initially grows with a marked decrease in internal pressure while the rest of the tube unloads. First, a detailed experimental analysis is carried out involving different geometries and initial axial forces and the influence of the axial force and of the internal pressure on the critical pressure is investigated. The shell used in the experiments is composed of an isotropic, homogeneous and hyperelastic rubber, which is modeled as a Mooney–Rivlin incompressible material, described by two elastic constants. These constants are obtained by comparing the experimental and numerical solutions for the shell under axial tension. The governing shell equations are solved numerically using the finite-element method, using the program ABAQUS. The experimental results are, as shown in the paper, in satisfactory agreement with the numerical analysis. 相似文献
147.
WANG Liping JIANG Yao LI Tiemin 《机械工程学报(英文版)》2014,(5):890-899
Parallel kinematic machines have drawn considerable attention and have been widely used in some special fields.However,high precision is still one of the challenges when they are used for advanced machine tools.One of the main reasons is that the kinematic chains of parallel kinematic machines are composed of elongated links that can easily suffer deformations,especially at high speeds and under heavy loads.A 3-RRR parallel kinematic machine is taken as a study object for investigating its accuracy with the consideration of the deformations of its links during the motion process.Based on the dynamic model constructed by the Newton-Euler method,all the inertia loads and constraint forces of the links are computed and their deformations are derived.Then the kinematic errors of the machine are derived with the consideration of the deformations of the links.Through further derivation,the accuracy of the machine is given in a simple explicit expression,which will be helpful to increase the calculating speed.The accuracy of this machine when following a selected circle path is simulated.The influences of magnitude of the maximum acceleration and external loads on the running accuracy of the machine are investigated.The results show that the external loads will deteriorate the accuracy of the machine tremendously when their direction coincides with the direction of the worst stiffness of the machine.The proposed method provides a solution for predicting the running accuracy of the parallel kinematic machines and can also be used in their design optimization as well as selection of suitable running parameters. 相似文献
148.
It is still a challenge to model swelling phenomena occurring in charged hydrated porous media. This is not only due to the
overall complexity of the model but also to the fact that boundary conditions occur, which depend on internal variables. In
the present contribution, a multi-component model based on the Theory of Porous Media (TPM) is presented. The advantage of
this model is that it is thermodynamically consistent and it consists of only three primary variables. As a result of the
boundary conditions depending on internal variables, the numerical treatment within the finite element method (FEM) by use
of the mixed finite element scheme reveals artificial oscillations in the numerical results. To overcome these oscillations,
we propose to fulfil boundary conditions weakly. 相似文献
149.
Guido Sala Ton van Vliet Martien Cohen Stuart Fred van de Velde George A. van Aken 《Food Hydrocolloids》2009,23(7):1853-1863
The effect of the ratio between the modulus of the oil droplets and that of the gel matrix (varied by changing gelling agent concentration and oil droplet size) on the large deformation properties of gelatine, κ-carrageenan and whey protein isolate (WPI) gels was studied at different compression speeds. The effect of gelling agent concentration and oil droplet size on strain-dependency of modulus and viscoelastic properties was also studied. An increase in the concentration of gelling agent resulted in denser gels with more bonds between structural elements. This induced an increase of both Young's modulus and fracture stress for all gels. With increasing gelling agent concentration, polymer gels (gelatine and κ-carrageenan) became less strain-hardening, and the particle gels (WPI) even became strain-softening. The effect of a decrease in the oil droplet size on the Young's modulus was generally according to the Van der Poel theory, unless when the oil droplets were aggregated. Moreover, a decrease in oil droplet size induced a decrease of the fracture strain in gels with non-aggregated bound droplets. The extent of these changes was shown to depend on the gelling agent concentration. The effect of a decrease of the oil droplet size on other fracture parameters and in other gel systems was minor. With decreasing oil droplet size gelatine gels with unbound droplets and WPI gels became more viscous and less elastic. 相似文献
150.
Three simple models for including the effect of beam-column joint deformation in the analysis of steel moment resisting frame and framed tube structures are presented. The first model, called the Fictitious Joint model, is based on two-dimensional frame analysis and is useful for preliminary analysis only. The second model, called the Krawinkler Joint model, and the third model, known as the Scissors Joint model, use an assembly of rigid links and rotational springs to represent the joint, and may be used in preliminary and final analysis of full structural systems. All derivations are provided in the form of “displacement participation factors”, which allow a detailed breakdown of the various components of subassemblage displacement.When applied to isolated beam-column subassemblages, it is shown that all three modeling approaches produce the same general expression for computing deflections arising from shear deformations in the panel zone region. However, the Krawinkler and Scissors models do not include the effects of flexural deformation within the beam-column joint, whereas the Fictitious Joint model does. While not the dominant source of deformation, it is shown in the paper that the effects of flexural deformations in the beam-column joint should not be ignored.It is also shown in this paper that the overall displacements predicted by the simplified models correlate very well with displacements computed from detailed three dimensional finite element analysis of the same subassemblage. However, the finite element analysis approach, taken alone, is not capable of providing a breakdown of the subassemblage displacements into components, such as panel zone shear, or column joint flexure. Part 2 of the paper presents a method for providing this information from the results of detailed finite element analysis. 相似文献