AutoCAD在机械设计基础中的应用

本文结合机电专业机械设计基础课程的教学特点，将AutoCAD引入课程的设计教学中。这将有益于该课程教学质量的进一步提高。     

海水泵轴激光修复试验研究

轴类部件的损坏是工农业生产中常遇到的问题。大型轴件的损坏 (如发电机转轴、水泵泵轴以及卷扬机传动轴的损坏 )会造成重大经济损失与人身危害。同时 ,这些轴大都价格较高 ,生产周期长 ,具有较高的修复价值。传统工艺 (如手工电焊 )对轴类部件的修复存在着修复层结合强度低、工件易变形、操作难度高等问题。本文作者采用激光堆焊技术 ,进行了海水泵轴的激光修复实验。修复对象为一根已磨损的长 1.5m ,直径 30cm的海水泵轴。实验结果表明 :激光修复由于热量很快通过基体导走 ,不会造成大的热应力集中和变形 ;修复层与轴件基体是冶金结合 ,结合强度高 ,修复层更耐磨 ;数控编程等手段的运用大大提高了工作效率 ,也降低了现场操作的难度。     

高精度陀螺漂移伺服转台伺服精度的实验研究

在由交流力矩电机驱动带滑环伺服系统的气浮转台中 ,滑环伺服系统对气浮主轴的干扰力矩是主要的干扰力矩。提高滑环伺服系统跟踪精度、选用高柔性的两轴系之间输电导线、减小它们与轴心的距离是提高主轴伺服精度的有效措施     

HL-2M 装置的 300MVA 发电机组保护装置

为保证 HL-2M 装置的 300MVA 立式发电机组的安全运行，需要对其设置保护装置。针对机组自身 特性，保护装置为发电机的多分支绕组采用了完全裂相横差保护、完全纵差保护和零序电流型横差保护。基于机 组脉冲工作模式，保护装置采用了快速频率跟踪算法实现频率变化时对发电机组的电压电流快速跟踪测量。实验 证明该保护装置满足机组的安全运行要求。      

Driveline modeling and estimation of individual clutch torque during gear shifts for dual clutch transmission

The purpose of the proposed work centers on the unprecedented task of accurately estimating the torque transmitted through each clutch of the dual clutch transmission. This is to possibly improve the clutch control performance during vehicle launch and gearshifts and to elongate the clutch life. Such goal is attained by only using the measurements and data that are already available in current production vehicles. The suggested estimator requires the speed measurements of engine, input shafts, and wheels, and nominal engine torque information obtained as a function of driver input and engine speed. By synthesizing the estimations obtained by shaft model-based observer, unknown input observers, and adaptive output torque observer, the novel algorithm to estimate the torque of each clutch separately is developed. Stability of the entire combined observer system is analyzed as well. In the process of developing the transfer shaft model-based observer, an original approach for the driveline modeling is proposed. The driveline modeling procedures include compliance model of each transfer shafts with the convenient methods to express the clutch torque without having to use complex clutch friction models, and the developed model is compared with the actual experiment data to validate its accuracy. The effectiveness of the individual clutch torque estimator is demonstrated both through simulations using SimDriveline, and tests on an actual vehicle equipped with a dual clutch transmission.     

Random vibrations of a rotating shaft with non-linear damping

Bending vibrations of a rotating shaft due to external random excitation are considered for the case of potential instability of the shaft's linear model due to the presence of internal or “rotating” damping. A two-degree-of-freedom model is studied which accounts for non-linearity in external or “non-rotating” damping. An explicit expression is obtained for a stationary joint probability density of displacements and velocities as an exact analytical solution to the corresponding Fokker-Planck-Kolmogorov equation. The results are used to develop criterion for on-line detection of instability for the operating shaft from its measured response.     

Finite-Element Dynamic Analysis of a Rotating Shaft with or without Nonlinear Boundary Conditions Subject to a Moving Load

A C ⁰ continuity isoparametricfinite-element formulation is presented for the dynamic analysis of arotating or nonrotating beam with or without nonlinear boundaryconditions subject to a moving load. The nonlinear end conditions arisefrom nonlinear rolling bearings (both the nonlinear stiffness andclearance(s) are accounted for) supporting a rotating shaft. The shaftfinite-element model includes shear deformation, rotary inertia, elasticbending, and gyroscopic effect. Lagrange's equations are employed toderive system equations of motion which, in turn, are decoupled usingmodal analysis expressed in the normal coordinate representation. Theanalyses are implemented in the finite-element program DAMRO 1.Dynamic deflections under the moving load of rotating and nonrotatingsimply supported shafts are compared with those obtained using exactsolutions and other published methods and a typical coincidence isobtained. Samples of the results, in both the time and frequencydomains, of a rotating shaft incorporating ball bearings are presentedfor different values of the bearing clearance. And the results show thatsystems incorporating ball bearings with tight (zero) clearance have thesmallest amplitude-smoothest profile dynamic deflections. Moreover, fora system with bearing clearance, the vibration spectra of the shaftresponse under a moving load show modulation of the system naturalfrequencies by a combination of shaft rotational and bearing cagefrequencies. However, for a simply supported rotating shaft, the firstnatural frequency in bending dominates the response spectrum. The paperpresents the first finite-element formulation for the dynamic analysisof a rotating shaft with or without nonlinear boundary conditions underthe action of a moving load.     

深厚表土中煤矿立井非采动破裂的研究

本文介绍了近年来我国华东矿区深厚表土层中煤矿立井井壁非采动破裂的特点。分析了井壁破裂的工程地质条件，研究了井壁与土接触面上土─混凝土作用变形和强度参数，并将该接触面视为接触面单元，用弹塑性有限元法，模拟了深厚表土底部含水层失水时土与井壁的相互作用，得到了井壁附加应力随深度和含水层水头降的变化规律，分析了井壁稳定性，揭示了井壁破裂的内在机理。     

Cytochrome P450cam–monoterpene interactions

The use of the molecular mechanics AMBER force field (FF) to predict product profiles for the hydroxylation of the monoterpenes 1R-camphor, 1S-camphor, 1R-norcamphor, 1S-norcamphor and camphane by the enzyme cytochrome P450cam from the soil bacterium Pseudomonas putida was investigated. Predictions were carried out by applying multiple substrate (starting) orientations in the enzyme pocket in two procedures: a procedure based on molecular dynamics (MD) and a procedure based on short MD simulations followed by geometry optimisations. The latter (GO) procedure is faster and enabled the use of more monoterpene starting orientations. Monoterpene orientations were transformed into product profiles by applying both energetic and geometrical criteria appropriate for the (monoterpene) hydrogen abstraction reaction. Good predictions compared to experimental data were obtained for most compounds in both the MD and GO procedures. Prior to the product profile calculations, the FF was calibrated by reproducing the experimental data for the binding energy of 1R-camphor and 1S-camphor to P450cam and the energy of vaporisation of water. Focus of the calibration was on the value for the scaling factor for the electrostatic interactions.