基于ANSYS的采煤机驱动轮塑性变形力学分析

针对采煤机驱动轮在工作过程中易发生塑性变形这一现象,基于驱动轮所受载荷的力学模型,采用有限元分析软件ANSYS对其进行静力学和动力学分析。通过分析,找出了驱动轮塑性变形的原因,并提出解决方案,为驱动轮的设计制造提供依据,从而减少设计和试验成本,提高实际生产效率。     

基于差动驱动的电子差速控制方法研究

针对目前采用转速或转矩控制模式实现电子差速所存在的问题,提出了一种基于差动驱动的电子差速控制方法,从整车动力学层面上设计了基于滑模控制理论的横摆运动控制模块;在充分考虑轮胎摩擦椭圆和执行机构物理限制的基础上,设计了差动驱动控制模块和滑转率控制模块.研究结果表明,该电子差速控制策略简单有效,不但能保证每个驱动轮都有很好的...     

断裂力学在超高压容器疲劳设计中的应用

阐述了断裂力学在富阳超高压容器疲劳设计中的应用。     

An Approach towards the Incorporation of Soft Aspects Such as Manufacturing Efforts into Structural Design Optimization

This paper introduces an efficient holistic approach to the design optimization of lightweight structures of braided fiber-reinforced plastic material. The approach aims to mitigate the paradox of making design decisions at early development phases, when necessary information is incomplete or lacking detail so as to properly make these decisions. However, expert knowledge is available and though it is imprecise in nature, it can compensate to create useful models. Manufacturing effort for the braiding process has been described by information accumulated via interviews with braiding experts. This information is then modelled using the soft-computing approach by fuzzy-rule-based systems. The resulting models can further be efficiently integrated into the structural design optimization process. A multidisciplinary design optimization is facilitated considering several aspects including manufacturing effort and structural mechanics, which can be used in early design phases leading to more holistic designing and, thereby, unlocking lightweight and cost-reducing potentials. Benefits of this method, including viability and ease of implementation, are proven by investigations on two academic test problems before advancing to the challenging automotive engineering design problem of the roadster A-pillar.     

自由锻造操作机冗余驱动系统的驱动力分配与协调

建立了自由锻造操作机提升系统冗余驱动机构的逆动力学模型,分析了运动协调、运动不协调、布置关节轴承协调运动3种工况下提升系统的驱动力分配情况.得到了3种工况驱动力分配与运动误差之间的关系,通过3种工况的对比分析了关节轴承的协调效果,并进一步分析了提升系统的自调特性.对现有操作机设计的合理性进行了分析,为今后新型操作机的设计打下了基础.     

步进电机驱动系统细分驱动波形修正

为了提高步进电机驱动系统运行的速度稳定性,通过对其影响因素的分析,根据步进电机细分驱动原理,给出了基于最小二乘法原理的细分驱动波形综合修正算法.该算法跳过了建立复杂驱动系统模型的过程,通过系统理想和实际的输入、输出误差,建立函数,得到实际空间角度的修正量,将其转化为相应的电角度后,获得修正波形.实验结果证明,电机驱动系统在修正波形的驱动下,速度稳定性得到了明显提高.     

Contact mechanics and the wear of metals

It is commonly observed that metallic wear debris takes the form of thin platelets, leading to the term ‘delamination wear’. Modelling this phenomenon has proved a stiff challenge in Contact Mechanics since the fractures which give rise to wear particles lie parallel, or nearly so, to the surface; i.e. on planes of maximum compressive stress. Sectioning the surface layer beneath a wear track has revealed it to have acquired severe plastic strains, which suggests that the cracks are ductile fractures, driven by plastic strain rather than elastic stress intensity. The paper reviews recent research into the progressive plastic deformation of surfaces in repeated sliding: the process known as ‘ratchetting’. Included is an analysis of ‘running-in’ of rough surfaces by repeated sliding and a discussion of the criterion of rupture under cyclic plastic strain.     

X-ray-based machine vision system for distal locking of intramedullary nails

In surgical procedures for femoral shaft fracture treatment, current techniques for locking the distal end of intramedullary nails, using two screws, rely heavily on the use of two-dimensional X-ray images to guide three-dimensional bone drilling processes. Therefore, a large number of X-ray images are required, as the surgeon uses his/her skills and experience to locate the distal hole axes on the intramedullary nail. The long-term effects of X-ray radiation and their relation to different types of cancer still remain uncertain. Therefore, there is a need to develop a surgical technique that can limit the use of X-rays during the distal locking procedure. A robotic-assisted orthopaedic surgery system has been developed at Loughborough University to assist orthopaedic surgeons by reducing the irradiation involved in such operations. The system simplifies the current approach as it uses only two near-orthogonal X-ray images to determine the drilling trajectory of the distal locking holes, thereby considerably reducing irradiation to both the surgeon and patient. Furthermore, the system uses robust machine vision features to reduce the surgeon's interaction with the system, thus reducing the overall operating time. Laboratory test results have shown that the proposed system is very robust in the presence of variable noise and contrast in the X-ray images.     

Theoretical aspects of technological mechanics: 1. Fundamentals of continuum mechanics

Fundamental principles of continuum mechanics are outlined and its basic subdisciplines are identified.     

CNG压缩机面面观

评说了高压CNG压缩机的运行特点,对其基本要求、结构型式的优选、气缸润滑方式等分别进行了阐述。     

Probing the effect of polymer molecular weight on penetration into the wood cell wall using polyethylenimine (PEI) as a model compound

Decking is one of the largest applications for the treated wood market. The most challenging property to obtain for treated wood is dimensional stability, which can be achieved, in part, by cell wall bulking, cell wall polymer crosslinking and removal of hygroscopic components in the cell wall. A commonly accepted key requirement is for the actives to infuse through the cell wall, which has a microporosity of ～5–13 nm. Equally as challenging is being able to measure and quantify the cell wall penetration. Branched polyethylenimine (PEI) was studied as a model polymer for penetration due to its water solubility, polarity, variable molecular weight ranges, and ability to form a chelation complex with preservative metals to treat lumbers. Two different molecular weight polyethylenimines (PEI), one with a weight average molecular weight (Mw) equal to 800 Da and the other 750 000 Da, were investigated for penetration by microscopy and spectroscopy techniques. Analytical methods were developed to both create smooth interfaces and for relative quantitation and visualisation of PEI penetration into the wood. The results showed both PEI with Mw of 800 Da and PEI with Mw of 750 000 Da coated the lumens in high density. However, only the PEI with Mw of 800 appeared to penetrate the cell walls in sufficient levels. Literature has shown the hydrodynamic radii of PEI 750 000 is near 29 nm, whereas a smaller PEI at 25 K showed 4.5 nm. Most importantly the results, based on methods developed, show how molecular weight and tertiary structure of the polymer can affect its penetration, with the microporosity of the wood being the main barrier.     

火驱产出水分析

火驱是一种提高原油采收率的技术。火驱产出物的组分含量能反映火驱燃烧程度。按照火驱产出物的形态和性质可以将火驱产出物划分为油、气、水。重点讨论了火驱产出水的分析。     

Aspects of paper abrasivity

The mechanism of wear by paper is reviewed, and it is established as being primarily abrasive. The severity of this type of wear is compared with other wear processes and shown to be relatively mild. In addition, new data regarding the effects of paper damage, paper debris and moisture on the abrasivity of paper are presented. In general, it is shown that the individual and combined effects of these factors reduce the abrasivity by as much as one to two orders of magnitude under certain conditions.     

Effect of various wood preservatives on limiting oxygen index levels of fir wood

Wood preservatives have been widely used to extend the service life of wood. The aim of this study is to evaluate the effects of various wood preservatives with different chemical loadings on fire performance of treated fir wood using by oxygen index test technique (ASTM D 2863-6). The limiting oxygen index (LOI) is the minimum percentage oxygen that is required to continue flaming combustion of a sample under laboratory conditions. For this purpose; wood preservatives commonly used in wood protection industry including amine–copper-quaternary, tanalith-E, wolmanit-CB, imersol aqua, vacsol aqua, timbercare aqua and protim-418 were studied as wood preservative chemicals. Mixture of boric acid + borax was also used as reference sample. The results indicated that LOI levels of all treated fir wood samples were higher than that of control samples except for timbercare aqua and protim-418 treated samples. The highest LOI level was obtained within 5% of wolmanit-CB and 2% of boric acid + borax treated wood samples. It appears that more than 3% concentration of wolmanit-CB treatment may have a potential fire retardant.     

High rate crushing of wood along the grain

The results of tests carried out to measure proximal end and distal end loads during dynamic crushing of oak along the grain over a velocity range of 20–260 m/s are presented. A stress enhancement factor of roughly 2 is seen in the distal end loads for impact velocities from 34 to 225 m/s. Further enhancements in stress measured at the proximal end are the result of inertia effects associated with the dynamic localisation of crushing. The crushing behaviour is analysed using shock wave theory together with rigid, softening, hardening and elastic, softening, hardening material models. The results of the analyses compare well with load histories recorded experimentally.     

油马达驱动主轴可行性分析

在液压传动中,液压马达作为执行元件对环境的保护有其特点;大扭矩液压马达以其低速稳定性、结构完善性、启动效率高、转动惯量小、使用时不需减速装置即可直接驱动、低速大扭矩负载等特点,得到广泛应用,因此油马达驱动主轴有其可行性.     

Aspects of tactile probing on the micro scale

This paper discusses the aspects that influence the interaction between a probe tip and a work piece during tactile probing in a coordinate measuring machine (CMM). Measurement instruments are sensitive to more than one physical quantity. When measuring the topography of a work piece, the measurement result will therefore always be influenced by the environment and (local) variations in the work piece itself. A mechanical probe will respond to both topography and changes in the mechanical properties of the surface, e.g. the Young's modulus and hardness. An optical probe is influenced by the reflectivity and optical constants of the work piece, a scanning tunneling microscope (STM) responds to the electrical properties of the work piece and so on (Franks, 1991 [1]).The trend of component miniaturization results in a need for 3-dimensional characterization of micrometer sized features to nanometer accuracy. As the scale of the measurement decreases, the problems associated with the surfaceprobe interactions become increasingly apparent (Leach et al., 2001 [2]). The aspects of the interaction that are discussed include the deformation of probe tip and work piece during contact, surface forces during single point probing and scanning, dynamic excitation of the probe, synchronization errors, microfriction, tip rotations, finite stiffness effects, mechanical filtering, anisotropic stiffness, thermal effects and probe repeatability.These aspects are investigated using the Gannen XP 3D tactile probing system developed by Xpress Precision Engineering using modeling and experimental verification of the effects. The Gannen XP suspension consists of three slender rods with integrated piezo resistive strain gauges. The deformation of the slender rods is measured using the strain gauges and is a measure for the deflection of the probe tip. It is shown that the standard deviation in repeatability is 2 nm in any direction and over the whole measurement range of the probe. Finally, this probe has an isotropic stiffness of 480 N/m and a moving mass below 25 mg.