关键词： SiC-graphene composite   Molecular dynamics   Reuss-Voigt-Hill approximation   Compressive strength   Tensile strength   Mechanical properties  

摘要： In this article, using molecular dynamics (MD) simulation, several mechanical properties of graphene were calculated for pristine single layer graphene sheet (SLGS), defective SLGS, multilayer graphene sheets (MLGS) without defects and for composites of SiC and graphene. Firstly, the room temperature elastic moduli (Young's, shear and bulk), constants and Poison's ratios were simulated for the above structures and then their properties such as stress vs strain under tensile and compressive loading were simulated within the temperature range of 300K-2000K. The simulations were performed in both zigzag and armchair directions of graphene surface and differences were observed in the mechanical properties. Simulations revealed that the location of defects as well as their type influence the elastic moduli and constants at room temperature and that their tensile and compressive properties vary with temperature. For both MLGS, and SiC-graphene composites, the properties improved with increase in number of continuous graphene layers.

关键词： 涡流   超声降解率   声场   温度  

摘要： 涡流场影响着声场分布,进而影响着声空化特性,以机械搅拌产生的涡流场为研究对象,使用COMSOL软件数值模拟了不同搅拌速度下的声场分布情况.结果显示,机械搅拌增加了声场分布的均匀性和声压幅值.接下来将仿真得到的瞬时声压值用Origin软件拟合,然后将拟合得到的声压函数代入Keller-Miksis气泡动力学方程中,得到了不同搅拌速度下空化泡的半径随时间的变化情况,从计算结果中发现,未加机械搅拌的条件下,只有z=7.3 cm截面上有空化效应产生.最后根据所得到的空化泡半径,计算了空化泡内部的温度.结果显示,空化泡在有搅拌存在的条件下,内部温度得到了大幅增加,当搅拌速度达到1000 r/min后,空化泡内部温度会随着搅拌速度的增加而降低.最后设计实验验证了仿真结果.仿真得到的结果不仅从理论上解释了机械搅拌提高有机溶液超声降解率的原因,还发现了过高的搅拌速度会降低声空化强度,从而降低声化学反应速率,这为通过机械搅拌来进一步提高超声降解率提供了新思路.

关键词： Smart electronic textiles   Self-powered haptic sensing   Superhydrophobicity   Triboelectric nanogenerators   Wearable human-machine interfaces  

摘要： Textile-based triboelectric nanogenerators (t-TENGs) have attracted extensive attention in wearable power source and movement monitoring. However, the electrical output performance and environmental adaptability of t-TENGs in single-electrode mode are still unsatisfactory, which significantly limits their applications. This limitation is especially more pronounced in humid environments. In the present study, a humidity-resistant and stretchable single-electrode t-TENG (abbreviated as PFL@WFCF-TENG) consisting of the porous flexible layer (PFL) and waterproof flexible conductive fabric (WFCF) has been designed to improve the output performance. Considering the three-dimensional structure and excellent superhydrophobicity of PFL and superior conductivity of WFCF, the resultant PFL@WFCF-TENG (2 x 4 cm(2) area) has high outputs (similar to 135 V, similar to 7.5 mu A, 26 mu C/m(2) , 631.5 mW/m(2)) and favorable humidity-resistant (80% RH). Based on these excellent features, the proposed PFL@WFCF-TENG is expected to be applied for intelligent alarming, haptic sensing, and energy harvesting. Moreover, combined with the microelectronic module, a portable and wearable self-powered haptic controller based on the PFL@WFCF-TENG has been designed for various human-machine interface (HMI) scenarios, such as controlling of the lamp, electronic badge, computer application, and humidifier. The PFL@WFCF-TENG proposed in this study not only provides a feasible solution for developing wearable electronic devices with high electrical output even in high-humidity environments but also shows promising applications in a variety of areas, including wearable power supply, portable computer peripherals, intelligent robots and security systems.

关键词： 工程船舶   动力机械   状态监测   故障诊断  

摘要： 本文深入分析工程船舶动力机械的运行特征,明确工程船舶动力机械状态监测及故障诊断的作用和意义,同时,确定动力机械状态监测和故障诊断中最合理的方法,结合监测及故障诊断现状明确技术发展的未来趋势,以期推动工程船舶动力机械领域的持久发展。

关键词： Molecular dynamics   Structure   Intermixing   Deformation   Zr content   Scratching depth  

摘要： The molecular dynamics simulations method is applied to survey the deposition and annealing processes of ZrxCu100-x film on a Cu(001) surface. The influences of ZrxCu100-x compositions and depths on the force, deformation behavior, pile-up, and hardness are investigated using nano scratching and nanoindentation processes. We find out that the structure of ZrxCu100-x alloy has stability increases when decreasing the Zr content. The surface roughness of Zr-Cu film increases when improving the Zr content. After annealing, the morphology surface of the Zr-Cu amorphous alloy becomes smoother. The scratching forces and average friction coefficient of the Zr20Cu80 film surge as the scratching depth rises. While the pile-up height, normal force, and friction force decrease as increasing the Zr ratio. Under the plastic and elastic deformations, shear transformation zones are formed in the Zr-Cu amorphous film. While in the nanoindentation process, the hardness of ZrxCu100-x film amorphous film tends to decrease when increasing the Zr content.

关键词： 机械传动系统   机械动力   红石   模组   传动杆   机器间   传送带   蒸汽朋克  

摘要： 当齿轮与传动杆取代了红石电路,我们将看到一个怎样的世界呢?今天,小约将给大家介绍一个以建筑、装饰和机械为主题的模组(Mod):"机械动力"(Create)。不同于传统的红石工业,"机械动力"中的机器不由红石供能,而是需要玩家搭建机械传动系统来进行驱动。在"机械动力"中,我们看到的不是显示屏上单调的数字变化,而是一个个齿轮缓缓转动(图1),一块块铁锭借助传送带在机器间穿梭(图2)——能够实现这种效果的模组可谓少之又少。

关键词： 多关节机器臂   动力学参数   最小参数集   随机数  

摘要： 文章以多关节机械臂为例分析动力学参数的简化关系,基于动力学参数辨识的需求,提出利用随机数确定机械臂最小动力学参数集的方法,并采用MDH(modified Denavit-Hartenberg)方法,建立多关节机械臂的运动学模型;基于递归牛顿欧拉法,建立考虑关节摩擦和电机转动惯量影响的动力学模型;利用随机数模拟运动学参数,设计了变换矩阵,对动力学参数的回归矩阵进行列变换,借助符号和数值计算确定多关节机械臂的最小动力学参数集合,为进一步提升多关节机械臂动力学性能奠定了基础。

关键词： 选矸机械臂   瞬态动力学   ANSYS   静力学分析  

摘要： 通过对选矸机械臂有限元分析,校验其部件在工作中的结构可靠性;对六自由度选矸机械臂进行运动规划,并对其进行瞬态动力学分析,模拟真实工况下机械臂设计的合理性。通过CAD软件SolidWorks对机械臂三维建模,应用Adams动力学仿真软件对机械臂进行运动规划,将相关数据导入ANSYS Workbench中,根据实际受力状况对大臂进行静力学分析以及机械臂瞬态动力学分析。在机械臂极限位置受力分析时,大臂最大变形量0.041446 mm,最大受压1.0761 MPa;在实际运动规划后的瞬态动力学分析中,机械臂最大变形量0.14455 mm,最大受压处在基座与腰部连接处。校验结果更加真实,具有一定的可靠性,验证了结构设计的合理性。

关键词： High-entropy alloy   Molecular dynamics study   Mechanical response   Plastic deformation mechanism  

摘要： Mechanical properties of high-entropy alloys(HEAs)with the face-centered cubic(fcc)structure strongly depend on their initial grain ***,the orientation-dependent mechanical responses and the underlying plastic fl ow mechanisms of such alloys are not yet well ***,deformation of the equiatomic FeMnCoCrNi HEA with various initial orientations under uniaxial tensile testing has been studied by using atomistic simulations,showing the results consistent with the recent experiments on fcc *** quantitative analysis of the activated deformation modes shows that the initiation of stacking faults is the main plastic deformation mechanism for the crystals initially oriented with[001],[111],and[112],and the total dislocation densities in these crystals are higher than that with the[110]and[123]*** faults,twinning,and hcp-martensitic transformation jointly promote the plastic deformation of the[110]orientation,and twinning in this crystal is more significant than that with other *** in the crystal oriented with[123]is dominated by the hcp-martensite *** of the mechanical behaviors in the FeMnCoCrNi alloy and the conventional materials,*** and Fe50Ni50,has shown that dislocation slip tends to be activated more readily in the *** is attributed to the larger lattice distortion in the HEA than the low-entropy materials,leading to the lower critical stress for dislocation nucleation and elastic–plastic transition in the *** addition,the FeMnCoCrNi HEA with the larger lattice distortion leads to an enhanced capacity of storing ***,for the[001]-oriented HEA in which dislocation slip and stacking fault are the dominant deformation mechanisms,the limited deformation modes activated are insu fficient to improve the work hardening ability of the material.

关键词： 机械结构   结构设计   动力学分析  

摘要： 本文主要探讨了机械结构设计中的动力学分析与仿真技术。首先介绍了机械结构设计的动力学基本理论和分析方法,以及目前常用的动力学仿真技术。接着通过多个案例研究,详细讨论了动力学分析与仿真在机械结构设计中的应用,包括基于仿真技术的动力学分析、机械结构设计中的振动分析以及基于动力学仿真的故障诊断与优化设计。最后总结了机械结构设计中的动力学分析与仿真技术的应用现状和发展趋势,为相关领域的研究提供了一定的参考和启示。