关键词： Delta机械手   Simulink   Simmechanics   计算力矩控制   模糊解耦控制  

摘要： 以三自由度Delta并联机械手作为研究对象,在Simulink环境下建立基于虚功原理法得到的并联机构系统动力学求解模型,并在Simmechanics中建立系统物理模型。在系统动力学方程的基础上设计了基于动力学的模糊解耦控制器,综合考虑了机构的运动学和动力学特性。给出平台运动的期望轨迹,分别在Simulink和Simmechanics中进行逆动力学仿真分析,验证逆动力学方程的准确性,之后进行模糊解耦控制Simulink/Simmechanics联合仿真分析。运行结果表明,Delta机械手的响应符合预期期望,精度高于计算力矩控制,跟踪效果较好。

关键词： Boron nitride-carbon nanotube   Nanocomposite   Interfacial shear strength   Molecular dynamics  

摘要： The newly discovered hybrid boron nitride-carbon nanotubes (BN-CNTs) are very promising for the innovative design of next-generation nanocomposites. In this work, molecular dynamics simulation based pull-out studies have been performed to characterise the interfacial properties of BN-CNT reinforced polyethylene (PE) composites. Our results show that the interfacial shear strength (ISS) of BNCNT/PE nanocomposites strongly depends on the BN composition and the connecting pattern of the C/BN fragment in the embedded BN-CNTs. Specifically, an ISS about 90% greater than that of the PE composite reinforced by the conventional carbon nanotube (CNT) is detected in the composite reinforced by the BN-CNT with certain connecting pattern and BN concentration. Such a superior ISS in the BN-CNT/PE composites is found to mainly originate from the unique rough van der Waals surface of the BN-CNT and the greater binding interaction between the embedded BN-CNT and the PE matrix, both of which contribute to enhancing the interface load transfer of nanocomposites. The enhanced ISS detected in the composite reinforced by BN-CNTs suggests that, compared with the most commonly used CNT, the novel BN-CNT can be a better reinforcement candidate in the design of nanocomposites. (C) 2017 Elsevier B.V. All rights reserved.

关键词： 中机联   陈斌   利润总额   经济运行   机械企业   工程机械   田淑   统计工作   智能制造   主要产品产量  

摘要： 8月8日,2017年上半年机械工业运行情况发布会在中国机械工业联合会（简称＂中机联＂）举行。中机联执行副会长陈斌、中国汽车工业协会常务副会长董扬、中机联统计工作部副主任田淑坤出席,会议由中机联执行副会长兼秘书长赵驰主持。陈斌指出,考虑到去年下半年基数较高的因素,预计全年机械工业增加值增长8%左右,主营业务收入和利润总额增长8%左右,

关键词： 液压机械无级变速器   非线性动力学   换挡过程   换挡控制策略  

摘要： 建立液压机械无级变速器换挡非线性动力学模型,根据连续换挡过程仿真曲线,对决定变速器换挡品质的一类工况进行基于物理参数和换挡时序的换挡控制策略研究。研究表明通过优化变速器物理参数和换挡时序可大大提高换挡品质。基于物理参数的换挡控制策略为在发动机小转速,外负载小转矩,较小的主油压以及较大的调速阀流量时,可获得较好的换挡品质。基于换挡时序的换挡控制策略为首先切换换挡机构离合器,再切换行星齿轮机构待分离离合器,最后切换行星齿轮机构待接合离合器。

关键词： 动力机械强度学   教学内容   教学改革  

摘要： 《动力机械强度学》课程是能源类专业的主干专业学位课程之一,存在课程教材内容相对落后,教学模式以"满堂灌"的纯理论讲述为主,难以充分激发学生兴趣等突出问题。基于此,本文在紧扣高校自身特点以及能动学院背景的基础上优化整合具有能源特色的《动力机械强度学》课程内容,建立系统的《动力机械强度学》课程教学内容,旨在培养学生综合运用理论知识分析以及解决实际工程问题的方法与能力,提高高校本科生创新能力与科研能力。

关键词： Liquid alloy Ni64Zr36   Pressure effect   Microstructural evolution   Molecular dynamics simulation   Cluster-type index method  

摘要： To deeply understand the effects of pressure on microstructural evolutions and mechanical properties, a molecular dynamics simulation study has been performed under pressures of 0-50 GPa for liquid Ni64Zr36 alloy during solidification process. Adopting several microstructural analyzing methods, especially the cluster-type index method (CTIM-3) to analyze the local microstructures in the system, it is found that the icosahedral cluster (12012000000) and the defect icosahedral cluster (1208000220), (1228200000) play a key role during the microstructural transitions. All the solidified structures are of amorphous structures consisted of various basic clusters and their combinations with different sizes. It is worth noting that all the glass transition temperature T-g, main bond-types, main basic clusters and elastic constants are almost increased linearly with the increase of pressure. Especially, the amorphous structure formed under 50 GPa would possess the admirable microstructural configuration and excellent mechanical properties of materials. (C) 2017 Elsevier B.V. All rights reserved.

关键词： MOLECULAR simulation methods   LIQUID ammonia   RESIDENCE time (Biogeochemistry)   SOLVATION   COORDINATION number (Chemistry)  

摘要： Structure and dynamics of solvated Ca2+ in liquid ammonia have been investigated using the quantum mechanical charge field molecular dynamics simulation approach, including the ion and its entire first plus second solvation shells in the QM zone. The Ca2+-ammonia interactions were calculated using ab initio HF calculations with Def2-SVP and DZP for Ca2+ and ammonia, respectively. A labile first shell structure at 2.63 A was observed with the dominant coordination numbers being 7 and 8. A number of exchange processes of ammonia ligands occurred throughout the simulation with a first shell mean ligand residence time of 12.9 ps. (C) 2017 Elsevier B.V. All rights reserved.

关键词： POLYMERIC nanocomposites   GUMS & resins   CROSSLINKING (Polymerization)   MOLECULAR dynamics   MECHANICAL behavior of materials   YOUNG'S modulus   DENSITY  

摘要： Finite-element method and micromechanical formulations have been used to predict mechanical properties of epoxy-based nanocomposites in recent years. The results of these investigations, however, show large scatters and do not agree well with experimental measurements. The differences in the results may be due to the fact that these approaches do not take some important material parameters into account, such as resin crosslinking ratio, nanotube/matrix interface, and nanotube agglomeration. The main objective of this article is to investigate the effects of resin crosslinking ratio on mechanical properties of epoxy-based nanocomposites using molecular dynamics (MD). First, models of partially cured epoxy resin were created in Materials Studio software to determine resin properties at different crosslinking ratios. Next, one sample of neat epoxy and four samples of nanocomposite with different resin crosslinking ratios were modeled using MD. These models were analyzed using constant strain method to determine mechanical properties of the five samples. Also, the effects of crosslinking ratio on nanocomposite density were investigated. The simulation results show that nanocomposite Young's modulus increases with resin crosslinking ratio. Resin crosslinking ratio, however, did not have a significant effect on nanocomposite density. Further, molecular simulation results were compared with rule of mixtures and Mori-Tanaka predictions. In addition, the results were compared with those found in the literature and good agreement was observed between the results. (C) 2016 Society of Plastics Engineers

关键词： Mechanical systems with impact and friction   Contact detection algorithm   Mechanical toys   Rolling bearing mechanism  

摘要： In this work, some new results are presented on the dynamics of a class of multibody mechanical systems, involving contact and friction. The main contribution refers to the development of a systematic, accurate and efficient method for detecting contact among the components of a system of solid bodies. For some simple geometries, this task is achieved by employing analytical means. For systems possessing components with complex geometric shapes a more involved numerical methodology is developed. In both cases, once a potential contact point is detected, the common tangent plane and normal vector are located and the penetration depth is calculated, leading to determination of the force arising between the contacting bodies. This information is then passed to a solver, providing the full dynamic response of the system. The validity and numerical efficiency of the methodology developed is first demonstrated by considering a number of examples with relatively small geometric complexity but large traditional value and interesting dynamic response. Some new results are obtained and presented on the dynamics of these systems. Finally, the same methodology is also tested in a more complicated and demanding mechanical application. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： Carbon nanotube   mechanical properties   molecular dynamics   graphene   thermal conductivity  

摘要： Single layer graphene sheets and carbon nanotubes have resulted in the development of new materials for a variety of applications. Though there are a large number of experimental and numerical studies related to these nanofillers, still there is a lack of understanding of the effect of geometrical characteristics of these nanofillers on their mechanical properties. In this study, molecular dynamics simulation has been used to assess this issue. Two different computational models, single layer graphene sheets-copper and carbon nanotube-copper composites have been examined to study the effect of nanofiller geometry on Young's modulus and thermal conductivity of these nanocomposites. Effect of increase in temperature on Young's modulus has also been predicted using molecular dynamics. The effect of nanofiller volume fraction (V-f) on Young's modulus and thermal conductivity has also been studied. Results of thermal conductivity obtained using molecular dynamics have been compared with theoretical models. Results show that with increase in V-f the Young's modulus as well as thermal conductivity of single layer graphene sheets-Cu composites increases at a faster rate than that for carbon nanotube-Cu composite. For the same V-f, the Young's modulus of single layer graphene sheets-Cu composite is higher than carbon nanotube-Cu composite.