Modeling and Optimal Design of Planar Linkage Mechanism of Coupled Joint Clearances for Manufacturing

The uncertainty of the mechanism motion error is mostly caused by the manufacturing process,so the motion error cannot be effectively predicted at the design phase.The problems of manufacturing complexity and the relationship between design and manufacturing are analyzed,and the influence of dimensional tolerance and fit tolerance on the motion accuracy of the system is considered in the design process.Then based on the Monte Carlo simulation,an optimal design model of planar linkage mechanism is set up.A typical offset slider-crank mechanism is used as an illustrative example to carry out the optimal design.Compared with the result of typical robustness design,the similar variation characteristics of the mean value and the standard deviation can be found,so the proposed method is effective.The method is furthermore applied in the optimization of the schemes with different fit tolerances and the prediction of motion errors in the design phase is achieved.A set of quantitative evaluation system for mechanism optimal design is provided.Finally,a basic strategy is presented to balance the motion precision and manufacturing cost.

CALCULATION OF ELASTIC ERROR OF PLANAR MECHANISM—AN EQUIVALENT METHOD

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Analytical expression of non steady-state concentration profiles at planar electrode for the CE mechanism

The analytical solutions of the non-steady-state concentrations of species at a planar microelectrode are presented. These simple new approximate expressions of concentrations are valid for all values of time and possible values of rate constants. Analytical equations are given to describe the current when the homogeneous equilibrium position lies heavily in favour of the electroinactive species. Working surfaces are presented for the variation of limiting current with a homogeneous kinetic parameter and equilibrium constant. Moreover, in this work we employ the Homotopy perturbation method to solve the boundary value problem.

Mechanism of amorphous Ge_2Sb_2Te_5 removal during chemical mechanical planarization in acidic H_2O_2 slurry

In this paper, chemical mechanical planarization （CMP） of amorphous Ge2Sb2Te5 （a-GST） in acidic H2O2 slurry is investigated. It was found that the removal rate of a-GST is strongly dependent on H2O2 concentration and gradually increases with the increase in H2O2 concentration, but the static etch rate first increases and then slowly decreases with the increase in H2O2 concentration. To understand the chemical reaction behavior of H2O2 on the a-GST surface, the potentiodynamic polarization curve, surface morphology and cross-section of a-GST immersed in acidic slurry are measured and the results reveal that a-GST exhibits a from active to passive behavior for from low to high concentration of H2O2. Finally, a possible removal mechanism of a-GST in different concentrations of H2O2 in the acidic slurry is described.

Dynamics Response and Non⁃linear Characteristics Analysis of Complex Planar 2⁃DOF Mechanism with Revolute Clearances

There are clearances in mechanism because of manufacture and assembly error,which reduces operation life and working accuracy of mechanism and has a great impact on dynamical responses.At the moment,research in this area mainly focuses on single degree⁃of⁃freedom mechanism considering one clearance,while research of multi⁃DOF mechanism considering multi⁃clearance is less.With the purpose of studying the dynamical characteristics of complex multi⁃DOF mechanism with multi⁃clearances,a dynamic model was developed.The dynamic responses of 2⁃DOF mechanism with two clearances under different positions,values,and numbers of clearance were analyzed.The displacement,velocity,acceleration,collision force,and the axis trajectory at clearance were then given.In addition,there is a limited amount of literature on chaotic phenomena,which mainly focuses on the chaotic phenomena of end⁃effector of mechanism.But in this paper,the non⁃linear characteristics were analyzed by chaotic phenomenon of clearance joint,then chaotic phenomenon was identified by Poincarémappings and phase diagrams.Bifurcation diagrams were given.The results will offer a reliable technical support for the study of dynamical responses of planar mechanisms and the analysis of chaotic phenomena.

A Method for Automatically Establishing a Mathematical Model of Kinematic Analysis to a Planar Mechanism with a Multiple Joint and Prismatic Pair

A method for automatically establishing a mathematical model of kinematic analysis to a planar mechanism with multiple joint and prismatic pair is presented. The breadth （ or depth ） first search spanning tree can be obtained based on an adjacency matrix of the mechanism. Then the kinematic chain （or mechanism）＇s basic loops can be obtained. On the basis of these basic loops, a mathematical model of kinematic analysis can be established and solved automatically. In the sense of a calculative mechanism, structural analysis of the kinematic chain relates to the kinematic analysis of a mechanism. Thus, an effective way is supplied to the given mechanism＇s kinematic analysis for automatic modeling and solving, and a method is supplied to the structural type to optimize kinematic synthesis.

A New Design Method for Realizing Accurate Track of Hybrid-driven Five-bar Mechanism

The concept of virtual slider crank mechanism is proposed and decoupled to obtain parameters of controllable five bar mechanism without any principle error for any given trajectory. The model is simple and easy to solve. This method has no convergence,flexible workspace and singularity of the mechanism problem. Through this method,we don’ t need any curve to fit the trajectory point. Using MATLAB program to calculate,the computation time can be reduced to less than 3% of the original. Finally,an example is given to illustrate the method which is meanwhile compared with the traditional five bar design method.

VELOCITY ANALYSIS OF A PLANAR MECHANISM USING A METHOD FROM STATICS

A new method for solving the velocity analysis of a mechanism is presented. Central to the method is how to convert the probem of velocity analysis of a mechanism to one of static analysis. Application of the method to certain practical problems has advantages compared to conventional methods for both graphical and analytical solutions. For brevity an example of a planar mechanism only is presented.

用Pro/Mechanism实现复杂凸轮机构的设计及运动分析

针对复杂平面运动从动件盘形凸轮机构设计的困难,介绍1种利用Pro/Mechanism的强大功能实现复杂凸轮机构的创新设计、运动仿真及运动分析。这种创新方法可以使复杂凸轮机构设计变的快捷、便利。

TWO STEPS CHEMICAL-MECHANICAL POLISHING OF RIGID DISK SUBSTRATE TO GET ATOM-SCALE PLANARIZATION SURFACE

In order to get atomic smooth rigid disk substrate surface, ultra-fined alumina slurry and nanometer silica slurry are prepared, and two steps chemical-mechanical polishing （CMP） of rigid disk substrate in the two slurries are studied. The results show that, during the first step CMP in the alumina slurry, a high material removal rate is reached, and the average roughness （Ra） and the average waviness （Wa） of the polished surfaces can be decreased from previous 1.4 nm and 1.6 nm to about 0.6 nm and 0.7 nm, respectively. By using the nanometer silica slurry and optimized polishing process parameters in the second step CMP, the Ra and the Wa of the polished surfaces can be further reduced to 0.038 nm and 0.06 am, respectively. Atom force microscopy （AFM） analysis shows that the final polished surfaces are ultra-smooth without micro-defects.

凸棱非平面聚晶金刚石齿的破岩机理及在含砾地层中的应用

为提高聚晶金刚石复合片(PDC)钻头在含砾、软硬交错等不均质地层中的抗冲击性能,开展了凸棱非平面PDC齿的研究。通过仿真和室内实验对比分析了凸棱非平面齿与常规平面齿的破岩机理。与平面齿相比,凸棱非平面齿与岩石的接触应力分布更均匀,切削破岩过程中的载荷波动幅度明显更小,切削稳定性更高。凸棱齿特殊的非平面结构改变了切削齿与岩石的互作用方式,在不均质地层得到成功应用。

大跨度底轴驱动式翻板闸门结构计算分析

以某工程翻板闸门为例,分别采用空间体系法和平面体系法,对大跨度、低水头的底轴驱动式翻板闸结构进行计算。结果表明,空间体系法能更好地反映闸门的受力和变形特性,研究成果为该类型的闸门在实际工程中的设计与运用提供了参考和借鉴。

pH调节剂在CMP工艺中的应用研究进展

pH调节剂在化学机械抛光(CMP)工艺中有重要应用,可以调节抛光液的pH值以确保抛光过程的化学反应在理想的pH值下进行,同时保持抛光化学环境的稳定等。对无机酸、有机酸、无机碱和有机碱四大类pH调节剂在合金、金属和金属化合物等材料的CMP中的应用及其作用机理进行综述。无机酸pH调节剂的主要作用机理是快速腐蚀材料表面,但其主要缺点是会将多余的金属离子引入抛光液中污染金属表面。有机酸pH调节剂的主要作用机理是螯合金属离子形成大分子络合物,但其主要缺点是稳定性差,难以保存。无机碱pH调节剂的主要作用机理是在基底表面生成一层软化层,使其在机械作用下更容易被去除,但其主要缺点是仍会引入金属离子污染材料表面。有机碱pH调节剂的主要作用机理是加速钝化膜的形成,但其主要缺点是制备困难、成本高。最后对pH调节剂在CMP中的应用前景进行了展望。

机械原理虚拟仿真实验教学系统的设计与实现

针对“机械原理”课程实践性强的特点,设计开发了一款虚拟仿真实验教学系统,该系统包括平面机构认知、平面连杆机构、凸轮机构、齿轮传动、动平衡原理5个模块。该系统实现了机械零部件的三维动画展示、各类机构的运动仿真模拟、实验设备的虚拟拆卸安装、实验装置各参数的虚拟测试等功能,该系统交互性、趣味性强,有助于提高学生的学习积极性和主动性。

基于SimMechanics和iSIGHT的平面四杆机构的运动仿真和优化

以平面四杆机构为典型算例,应用MATLAB/SIMULINK中的SimMechanics模块建立机构运动模型,并进行仿真分析。应用iSIGHT对模型进行预订轨迹的尺度优化设计,为机构仿真和优化提供了一种高效、直观的仿真手段,为其他机构的仿真和优化提供了借鉴。

Reconfigurable parallel mechanisms with planar five-bar metamorphic linkages

This paper presents the idea of constructing reconfigurable limbs by integrating metamorphic linkages as subchains.The planar five-bar metamorphic linkages that have three phases resulting from locking of motors are considered.Under the assumption that the constraint exerted by the reconfigurable limb can switch between no constraint,a constraint force,and a constraint couple,the output motions of the metamorphic linkage in its two planar four-bar linkage phases are identified.By adding an appropriate joint to planar four-bar linkages with translational output,four planar five-bar linkages that can be employed in the construction of reconfigurable limbs are enumerated.Serial chains that can provide a constraint couple and a constraint force are synthesized based on screw theory.Reconfigurable limbs that have three configurations associated with the three distinct phases of the metamorphic linkages are assembled with planar five-bar metamorphic linkages and serial chains with four degrees of freedom.A class of reconfigurable parallel mechanisms are constructed by connecting a moving platform and a base with three identical reconfigurable limbs.The degrees of freedom of the reconfigurable parallel mechanism in different configurations with the metamorphic linkages in different phases are given.Finally,the actuation scheme for this kind of mechanisms is addressed.

Effects of high order deformations on the strength of planar lattice materials

Lattice materials have been attractive over the last decade for use as load-carrying structures, energy absorbing elements and heat exchanging structures because of their excellent mechanical properties and multifunctional characters. However, the quantitative analysis accounting for high order deformations upon the collapse of lattice materials, which is important for their applications, has not been reported. An analytical investigation of yield surfaces with respect to the high order deformations was carried out for two typical planar lattice materials： triangular and Kagome lattices separately. The analytical results were validated by the finite element method （FEM） simulations. It was found that the effect of high order deformation on the yield strength increases with the relative density. The bending effect of the Kagome lattice is more obvious than that of the triangular one with the same relative density and stress state. The yield strength of the Kagome lattice calculated by neglecting the bending effect overestimates the result by more than 10% when the relative density is higher than about 11.1%, which may not be ignored in engineering applications. The yielding surfaces of the two lattice materials demonstrated in the paper also confirm the analytical results.

FURTHER RESEARCH ON THE SPLINE MODEL METHOD OF KED ANALYSIS IN A PLANAR FLEXIBLE LINKAGE

This paper relates to the deep research on the Splinc Model Method of KED analysis. With the use of cubic B-splinc function as a link’s transverse deflection interpolation function, the principle of virtual displacement is presented as a basic theory for the general formulation of the equations of motion, and thus abandoned the kinematic assumption and the instantaneous structure assumption which arc used in the Spline Model Method. In thc same time, the nonlinear terms sue as coupling terms between thc rigid body motion and elastic deformation arc included. New member’s spline models are established. Mass matrix, Coriolis mass matrix, normal and tangential mass matrix, linear stiffness matrix, nonlinear stiffness matrix and rotation matrix arc derived. The kinematic differential equations of a member and system are deduced in the end. The Newmark direct integration method is used as the solution scheme of the kinematic differential equations to get the periodic response.