一种流体驱动式模块化软体仿生象鼻关节变刚度结构设计及仿真分析

在兼顾软体抓持装置顺应性的前提下,为进一步提升其承载能力,提出一种采用磁流变液变刚度控制的流体驱动式模块化软体仿生象鼻机构。建立了仿生象鼻关节变形量和刚度理论数学模型;利用有限元分析方法基于Yeoh模型对不同结构参数的仿生象鼻关节进行了变形仿真分析,在相同压力下优选出了变形量最大的模型结构和确定了最佳输入气体压力值;对关节变形后两端电磁铁的叠加磁场分布进行了有限元仿真,通过分析磁场分布均匀性初步确定了两端电磁铁形成磁场的最佳距离即关节长度;最后对不同长度关节进行了变形仿真分析,综合考虑磁场分布均匀性和变形量,通过两者的最优组合确定最终关节长度,验证了仿生象鼻的多自由度变形和可变刚度特性。     

Biotribology: Friction,wear, and lubrication of natural synovial joints

Studies have been carried out over the past several years to explore possible interconnections between tribology — the study of friction, wear, and lubrication — and arthrology, more specifically, mechanisms of synovial joint lubrication and degeneration. The focus of this paper is on the tribological behaviour of natural and so-called ‘normal’ synovial joints. A separate paper deals with possible connections between tribology and degenerative joint disease (e.g., osteoarthritis). The purpose of this paper is fourfold: (1) to present a summary of salient work on mechanisms of synovial joint lubrication; (2) to review the key findings of our in vitro wear studies made with bovine articular cartilage; (3) to discuss the significance of the cartilage wear studies in relation to existing joint lubrication theories; and (4) to describe a new device being used for studies of cartilage-on-cartilage deformation, friction, wear and damage under in vitro conditions.     

飞机结构强度试验局部约束装置设计

采用加载夹具对中央翼接头加载过程中,由于中央翼发生航向变形,垂向和侧向载荷在航向产生载荷分量,容易对接头造成损伤。因此设计一种局部约束装置,通过卡板把该装置安装在中央翼上,限制夹具与接头之间的相对变形,使航向载荷分量通过约束装置传递至中央翼盒段,以保证接头的安全。     

Pseudo-rigid-body model for corrugated cantilever beam used in compliant mechanisms

Common compliant joints generally have limited range of motion, reduced fatigue life and high stress concentration. To overcome these shortcomings, periodically corrugated cantilever beam is applied to design compliant joints. Basic corrugated beam unit is modeled by using pseudo-rigid-body method. The trajectory and deformation behavior of periodically corrugated cantilever beam are estimated by the transformation of coordinate and superposition of the deformation of corrugated beam units. Finite element analysis（FEA） is carried out on corrugated cantilever beam to estimate the accuracy of the pseudo-rigid-body model. Results show that the kinetostatic behaviors obtained by this method, which has a relative error less than 6%, has good applicability and corrugated cantilever beam has the characteristics of a large range of motion and high mechanical strength. The corrugated cantilever beam is then applied to design a flexible rotational joint to obtain a larger angle output. The paper proposes a pseudo-rigid-body model for corrugated cantilever beam and designed a flexible rotational joint with large angle output.     

柔性机器人动力学分析与振动控制研究综述

综述了柔性机器人动力学分析与振动控制的研究现状，对变形的描述、变形场的离散化、建模方法、近似分析减振结构设计及关节作动系统控制律设计等关键问题进行了详细阐述。     

复杂锻件成形中塑性应变的测试新方法及应用

为解决复杂锻件成形过程中应变难以测定的问题,采用了一种利用螺纹进行测量的新方法。以压气机叶轮件为例,设计了一套组合式模具,凹模由4块镶块组合而成。采用等温模锻方法成形了该叶轮件。利用螺纹法对成形过程中不同截面上4条流线及其轴向、径向应变分别进行了测量分析,并定量给出了该叶轮件成形过程中变形及应变的分布规律。结果表明,该方法是测试模锻成形过程中金属塑性变形流动较为有效的实验手段,利用该方法可对一般塑性体积成形中金属流动和应变分布进行研究。     

尺度相关的分形结合面法向接触刚度模型

基于分形理论,利用双变量Weierstrass-Mandelbrot函数模拟三维分形结合面,建立尺度相关的三维分形结合面法向接触刚度模型。推导出各等级微凸体发生弹性、弹塑性以及完全塑性变形的存在条件。确定结合面上各等级微凸体的面积分布密度函数,推导出法向接触刚度和法向接触载荷的解析表达式。计算结果表明：当结合面上的微凸体只能发生弹性变形,即自身等级小于弹性临界等级的微凸体,该部分微凸体引起的法向接触刚度和对应法向载荷关系呈非线性。当微凸体的等级大于弹性临界等级,在结合面接触过程中,微凸体弹性变形引起的法向接触刚度与对应的法向载荷关系为线性,非弹性变形引起的法向接触刚度与法向载荷关系为非线性。微凸体的等级范围对结合面的刚度影响较大,在相同的法向载荷作用下,高等级微凸体的结合面产生较高的法向接触刚度,即结合面越平整,结合面的法向刚度越高。     

25 Cr2 Ni2 MoV 钢焊接接头低周疲劳性能研究

对新型汽轮机焊接转子材料25Cr2Ni2MoV焊接接头及其母材进行应变控制的低周疲劳试验,并进行了相应的断裂位置统计和循环变形特征分析。试验结果表明,焊接削弱了焊接接头的疲劳强度,受到结构非均匀性和各部分力学性能的相对不匹配等因素的影响,焊接接头的断裂位置体现出明显的应变水平依赖性;焊接接头和母材在循环变形过程中均表现出循环软化特性,且存在明显的拉压不对称性,拉压不对称程度随应变水平的增加而增加;与母材相比,焊接接头表现出更加明显的平均应力松弛现象,且平均应力绝对值随着循环周次不断减小最后趋于常值。     

自驱动关节臂测量机结构设计与仿真分析

为了使自驱动关节臂测量机的结构满足测量和定位精度要求,通过分析自驱动关节臂测量机的工作原理,建立了测量机的运动传递模型,完成了测量和定位误差源分析,在此基础上对关键部件进行设计和选型。对测量机进行了整体结构设计和关节结构设计,得到最优设计方案,在此基础上推算出各个关节的重力矩及惯性矩,完成了各关节模组的选型。建立了测量机的三维虚拟样机,对虚拟样机的几种典型测量姿态进行了静力学和结构变形分析,根据仿真结果进行优化设计,使测量机在典型和极限测量姿态下的静态变形均符合设计要求。针对测量机测量过程的触测段进行动态变形仿真,仿真结果表明竖直(Y)方向动态变形误差较大,需要建立动静态误差补偿模型进行修正。进一步对测量机进行模态分析,分析结果表明测量机的最高运行频率低于最低阶固有频率,不会产生结构共振以致影响测量和定位精度。     

滚滑复合被动关节的研究与开发

研究开发了滚滑复合的新型被动关节,它兼有滚动运动副和贴塑滑动运动副的特点,可以提高并联机构被动关节的抗力矩能力和运动精度的稳定性。建立了滚滑复合被动关节结合部的变形解析求解方法,为其设计提供了依据,并对所研制的一种滚滑复合被动关节进行了解析计算和试验验证。同时给出了滚滑复合被动关节的应用方法,并在所研究开发的六轴混联数控机床6PM2上进行了应用。     

考虑硬度变化的结合面法向接触刚度分形模型*

基于分形几何理论,考虑微凸体因应变硬化而造成弹塑性变形阶段硬度随变形量变化而变化,建立结合面第一、第二弹塑性变形阶段单次加载刚度分形模型。推导出在计入硬度变化的情况下,单个微凸体在弹塑性变形阶段法向接触刚度与接触面积之间的关系式,进而得出结合面在弹塑性变形阶段法向接触刚度与接触面积、接触载荷之间量纲为一的关系式,并通过仿真分析得出相关参数对结合面法向接触刚度的影响。仿真结果显示:考虑硬度变化时,结合面量纲一法向接触刚度的值与法向实际接触载荷、实际接触面积之间存在关系;结合面法向接触刚度随着分形维数D的增大而增大;分形维数一定时,结合面法向接触刚度随表面长度尺度参数G值增大而增大。     

关于逆向车削加工细长轴误差的力学分析

针对细长轴车削加工，分别在两种不同装夹条件下(一端卡盘夹紧、一端顶尖支承和两端顶尖支承)进行正向切削和逆向切削时的工件变形进行了力学分析，建立了正逆向切削工件在切削力作用下产生弯曲变形的解析模型。具体算例表明：逆向切削时工件的弯曲变形以及由此引起的加工误差远小于同等条件下正向切削的变形和误差。该模型及分析结果可用于细长轴加工的工艺设计。     

梳棉机锡林的结构分析与优化

锡林是梳棉机主要的梳理部件,利用ANSYS Workbench对锡林机构进行静力学分析,得到在针布张力等效载荷下的总变形云图、径向变形图、轴向变形图、与周向变形图以及等效应力图。由于在高速运转下的变形将直接影响梳棉机的纤维梳理质量,而锡林的关键尺寸参数对其抵抗变形的能力起着决定性的作用。因此,基于Pro/E与ANSYS Workbench的联合仿真功能对锡林机构的关键参数进行优化设计,得到最优的设计参数。     

依据各向异性分形几何理论的固定结合部法向接触力学模型

基于各向异性分形几何理论,考虑微凸体变形特点、表面微凸体承受法向载荷的连续性和光滑性原理,以及区分微凸体分别处于弹性、塑性变形时的一个微凸体实际微接触面积,建立固定结合部法向接触力学模型。采用二变量Weierstrass-Mandelbrot函数模拟各向异性三维分形轮廓表面。推导出划分弹塑性区域的临界弹性变形微接触截面积、结合部量纲一法向载荷、结合部量纲一法向接触刚度的数学表达式。数值仿真结果表明：当表面形貌的分形维数、分形粗糙度一定时,真实接触面积随着结合部法向载荷的增大而增大;结合部法向接触刚度随着真实接触面积、结合部法向载荷、相关因子或材料特性参数的增大而变大;当分形维数由1变大时,结合部法向接触刚度随着分形维数的变大而增大;当分形维数增加到趋近于2时,结合部法向接触刚度有时却会随着分形维数的增加而降低。结合部法向接触力学模型的构建,有助于分析固定接触表面间的真实接触情况。     

球笼式等速万向节结构轻量化设计

为了实现球笼式等速万向节的结构轻量化设计,以球笼式等速万向节最大接触应力、接触总变形和塑性变形为依据,分别对钢球数量为6和8的两种结构的球笼式等速万向节进行了初步研究.对球笼式等速万向节的主要结构尺寸即钢球中心圆直径与钢球直径之比、万向节外径与内套花键分度圆直径之比,以及球笼式等速万向节的偏心距与钢珠中心圆半径之比进行了优化选择和比较.研究结果初步表明,对于球笼式等速万向节,当钢球数量由6增加为8时,由于钢球直径的减小,不但其外形尺寸可以减小12%、质量可以减少近20%,而且万向节的承载能力反而可以得到少许提高.因此,增加球笼式等速万向节的钢球数量是实现其结构轻量化设计的一种有效方法.     

Comparative study by computed radiography,histology, and scanning electron microscopy of the articular cartilage of normal goats and in chronic infection with caprine arthritis‐encephalitis virus

In the northeast of Brazil, caprine arthritis‐encephalitis (CAE) is one of the key reasons for herd productivity decreasing that result in considerable economic losses. A comparative study was carried out using computed radiography (CR), histological analysis (HA), and scanning electronic microscopy (SEM) of the joints of CAE infected and normal goats. Humerus head surface of positive animals presented reduced joint space, increased bone density, and signs of degenerative joint disease (DJD). The carpal joint presented no morphological alterations in CR in any of the animals studied. Tarsus joint was the most affected, characterized by severe DJD, absence of joint space, increased periarticular soft tissue density, edema, and bone sclerosis. Histological analysis showed chronic tissue lesions, complete loss of the surface zone, absence of proteoglycans in the transition and radial zones and destruction of the cartilage surface in the CAE positive animals. Analysis by SEM showed ulcerated lesions with irregular and folded patterns on the joint surface that distinguished the limits between areas of normal and affected cartilage. The morphological study of the joints of normal and CAE positive goats deepened understanding of the alteration in the tissue bioarchitecture of the most affected joints. The SEM finding sustained previous histological reports, similar to those found for rheumatoid arthritis, suggesting that the goat infected with CAE can be considered as a potential model for research in this area. Microsc. Res. Tech. 77:11–16, 2014. © 2013 Wiley Periodicals, Inc.     

管内可控铰接柔性结构双层接触非线性力学分析

管内可控万向铰接柔性细长结构是超短半径侧钻水平井的特有结构。考虑可控万向铰结构中的机构问题、结构不连续和开槽不完整结构的三体两层接触问题,将空间梁单元、万向铰单元、刚性梁单元和梁梁接触单元相结合,建立了管内可控万向铰接柔性结构双重接触非线性有限元模型及数值计算方法。与有解析解的算例进行比对,计算结果吻合较好。通过对超短半径水平井造斜钻进时的柔性钻具进行力学分析,得到了柔性钻具受力变形状态、载荷传递规律及其与井壁之间的接触力分布规律。     

细长轴车削加工误差的分析

针对细长轴的车削加工。分别对在一端卡盘夹紧、一端顶尖支承及两端顶尖支承的装夹条件下车削加工时的变形进行力学分析。建立在切削力作用下产生弯曲变形的解析模型。算侧表明：逆向车削时轴的弯曲变形以及加工误差远小于同等条件下正向车削的变形和误差。     

Joining process for copper and aluminum tubes by rotary swaging method

Connection technique of copper and aluminum is a key challenge in refrigeration industry. In this paper, rotary swaging connection process is proposed to connect cooper tube and aluminum tube in physical way. We find the length of overlapped area has a great effect on the joint reliability, and it should exceed the deformation region length. The joint strength is approximately determined by necking. With the reduction of the diameter at the necking area, joint strength first increases and then decreases. Some experiments are carried out to test the joining strength. It is shown that the joints are reliable enough, and joining by rotary swaging method is effective to combine copper and aluminum tubes.