铲斗粘附土体现象的浅析和拨叉排土装置的设计

浅析了铲斗粘附土体的粘附力主要由机械粘附力和物理粘附力所构成,并设计了可跟随斗形、结构简单的拨叉排土装置.     

单斗液压挖掘机铲斗机构量纲一最优化设计方法

介绍了单斗液压挖掘机铲斗机构的量纲一分析方法,在此基础上,建立了铲斗机构量纲一优化设计的数学模型,并介绍了有量纲参数的反求方法.最后以某小型挖掘机的铲斗机构为例进行了量纲一优化设计,并得到最优结果.理论和实例表明了铲斗机构的量纲一最优化方法可得到较少的设计变量和约束,大大提高了优化设计的效率.     

矿用机械式挖掘机铲斗的原理设计

铲斗是矿用机械式挖掘机基本部件之一,铲斗性能、形状、几何参数合理与否直接影响挖掘阻力和满斗系数。根据挖掘性能要求,确定了铲斗形状、几何参数;通过分析铲斗的力学性能,将斗体简化成简支外伸梁,分别求得铲斗在宽度、长度方向的相关铰点距离,并与实例计算进行比较;运用冲击理论,提出合理冲击点,使铲斗轴套受力最小。     

基于工作装置主尺寸变化条件下的反铲挖掘机综合挖掘性能分析

为了实现对液压挖掘机综合挖掘性能的评价,提出一种基于工作装置尺寸变化因素的研究方法。以挖掘范围和挖掘力为研究对象,分别考虑挖掘作业中的斗杆挖掘和铲斗挖掘,选取机重相近的挖掘机的工作装置尺寸并进行动臂、斗杆和铲斗因素下的综合挖掘性能分析,应用仿真软件绘制包络图,并获得挖掘工作尺寸及各液压缸挖掘力。以相近吨位的某挖掘机为例,验证了工作装置各尺寸对于挖掘性能的影响规律。研究结果表明,运用坐标系变换法建立杆件坐标系并计算挖掘包络图,各组仿真的工作尺寸变化趋势与理论相符。建立挖掘力计算模型,对比各组挖掘力变化趋势,在斗杆挖掘中,随斗杆尺寸变化,斗杆最大挖掘力变化率达10.3%;铲斗挖掘中,随铲斗尺寸变化,铲斗最大挖掘力变化率达11.8%。综合挖掘性能分析方法针对工作装置的设计方面具有重要意义。     

斗轮堆取料机铲斗磨损分析

斗轮堆取料机日趋大型化,取料能力不断提高,铲斗磨损现象也越来越严重,铲斗磨损过程是一个非线性接触摩擦问题,挖取阻力受各种因素影响,极其复杂,分析起来相当困难。文中对铲斗磨损机理和挖掘过程所受阻力进行了分析,总结磨损影响因素并提出了耐磨防护措施。     

基于SolidWorks的挖掘机铲斗分析与优化设计

挖掘机铲斗是挖掘机工作装置中最为重要的部件之一,其在工作时,与石块、土壤等直接接触,工作条件极为恶劣。其结构设计的合理与否,直接影响到挖掘机铲斗的使用寿命。为解决这一问题,采用SolidWorks Simulation对挖掘机铲斗进行有限元分析,采用实体、壳体混合有限元网格模型,并进行相应的约束及载荷的加载,得到其在极端条件下的应力分布状态。并应用SolidWorks Simulation中结构参数优化功能,对挖掘机铲斗进行优化设计,以此改善挖掘机铲斗在极端工况下的受力,从而提高其使用寿命。     

基于HyperMesh-EDEM-Patran耦合的铲运机铲斗强度分析

传统铲斗强度分析是将铲斗受力简化为集中力或均布力,这样简化将导致铲斗强度分析结果不精确。以Sandvik 1400e铲运机为例,通过Hyper Mesh对铲斗进行前处理,应用EDEM仿真铲运机工作过程,得知铲斗在工作过程中受载具有复杂多变的特点。通过离散元与有限元耦合的方法,对铲斗进行了精确加载,完成铲斗在载荷工况下的强度分析与磨损量计算,为铲斗结构优化提供理论依据。     

液压挖掘机铲斗位置控制系统研究

为提高液压挖掘机铲斗位置控制性能,在建立铲斗位置控制系统开环传递函数基础上,分别采用蚁群算法和模糊算法进行铲斗位置PID控制器参数优化,并仿真比较了2种算法优化的系统响应性能和抗干扰性能。仿真结果表明:相比模糊算法,在加随机干扰力和不加随机干扰力2种情况下,基于蚁群算法的系统对于阶跃信号的超调量、调整时间、稳态误差等指标均降低;对于正弦信号的最大跟踪误差、平均跟踪误差均缩小5%以上。     

基于不同工作载荷的铲斗结构特性分析

针对挖掘机铲斗在未达到理论寿命之前,便发生严重磨损或断裂等破坏现象的问题,研究了复合挖掘方式对铲斗结构特性的影响。基于工作装置应力特性选择了4种挖掘机典型工况,并分别基于挖掘阻力经验公式、单独挖掘理论挖掘力模型和复合挖掘理论挖掘力模型,计算出了某21 T挖掘机铲斗的工作载荷,采用有限元法计算了铲斗在不同载荷作用下的应力变形情况。研究结果表明:在相同工况下,复合挖掘方式对应更大的铲斗外载荷,同时对应更大的应力和变形;该结果验证了复合挖掘是一种造成铲斗破坏的重要因素这一结论,为挖掘机铲斗结构强度分析和优化设计提供了理论依据。     

挖掘机铲斗结构优化

采用传统的方法对挖掘机反铲工作装置的铲斗进行结构优化存在工作量大、不精确和不直观等缺点.利用Pro/E三维软件建立WY100C液压挖掘机铲斗实体模型,并应用Pro/Mechanica模块对挖掘机铲斗的设计模型在受最大应力的危险工况下挖掘时进行强度分析和变形分析.在证明了WY100-C挖掘机铲斗的设计满足强度要求前提下,运用参数优化设计的方法对铲斗的结构进行优化,减轻铲斗的重量,改善了铲斗的结构,为挖掘机铲斗的设计改进提供了理论依据,对其它液压挖掘机铲斗的研制开发也有一定的借鉴意义.     

基于Pro/E的花键轴铲齿成形铣刀的三维造型设计

利用Pro/E软件的参数特征建模功能实现花键轴铲齿成形铣刀的三维造型设计。先根据花键轴铲齿成形铣刀的加工原理和结构特点完成刀具的切削部分基本形体的设计;再切出花键轴铲齿成形铣刀的容屑槽等特征。该产品的设计方法设计快捷、高效,故在工程设计中具有一定的借鉴价值。     

一种基于图理论的非刚体形状匹配算法

提出了一种基于图理论的非刚体形状匹配算法.该方法在每次迭代过程中,先利用形状上下文算法获得待匹配形状点集的初始匹配,然后利用图理论剔除误匹配点,并估算匹配点集之间的TPS(thin plate spline)变换参数,再利用这些参数使待匹配点集相互逼近,最终实现非刚体的形状匹配.实验结果表明该算法提高了匹配的精度.     

基于美学特征的参数化产品外形设计

随着个性化需求的发展,产品的工业美学设计愈加受到重视.产品的外形主要受一些关键形态要素,如尺寸、比率等影响.为此,文中运用形态控制参数表达产品的形态要素,给出一种基于形态要素的工业缝纫机参数化外形设计方法.通过对37种样本的美学形态要素进行分析,定义了描述工业缝纫机外形特征的12个形态要素,如机身长与机身高比率、中部主轴截面等形态要素.随后,建立了形态要素与工业缝纫机外形曲面的关键控制特征参数之间的映射关系,并运用这些特征参数构造了工业缝纫机的外形模型.修改特征参数,可以生成不同形态的工业缝纫机外形.     

A linear viscoelastic relaxation-contact model of a flat fractal surface: a Maxwell-type medium

In this paper a hybrid virtual prototype is developed for analyzing the stress applied on cable shovel components by integrating flexible bodies into rigid multi-body model. The general mechanical system of the cable shovel is modeled as a seven-bar linkage with four degrees of freedom. The relevant theories applied for the dynamic model are described in terms of Lagrangian dynamics equation. The flexible body stress related to the body deformation is obtained by the dynamic equilibrium equation for a structural component based on the finite element method. A P&H 4100A cable shovel is used to validate the hybrid virtual prototype by loading the motions and loads on the model. Von Mises stress distributions of the boom, handle, hoist rope and sheave are visualized during cable shovel operation 3 sec. The results show that a high stress field is around the hoist rope. The maximum stress of 313.31 MPa occurs at node 441. By comparing the simulation results with reliability analysis results, the former is found to match well with the latter. Attention of this study is devoted to the mechanisms of damage of the cable shovel and also the critical high stress areas.     

A novel iso-scallop tool-path generation for efficient five-axis machining of free-form surfaces

Weld cladding is a process of depositing a thick layer of a corrosion resistance material over carbon steel plate to improve the corrosion resistance properties. The main problem faced in stainless steel cladding is the selection of process parameters for achieving the required clad bead geometry and its shape relationships. This paper highlights an experimental study carried out to develop mathematical models to predict clad bead geometry and its shape relationships of austenitic stainless steel claddings deposited by gas metal arc welding process. The experiments were conducted based on four-factor, five-level central composite rotatable design with full replication technique. The mathematical models were developed using multiple regression method. The developed models have been checked for their adequacy and significance. The direct and interaction effects of process parameters on clad bead geometry and its shape relationships are presented in graphical form.     

Modeling,simulation and manufacturing of drill flutes

The designing of twist drill flutes (as well as that of end mills and of some combined tools) cannot be separated from the way they are manufactured. The aim of this paper is to present an intuitive direct method for modelling, simulation and manufacturing of the drill flutes with different shapes using conical grinding wheels with standardized shapes. The mathematical approach is described, which enables us to determine the flute profile in a section perpendicular to its axis as well as the manufacturing parameters. The grinding wheel has an initial position with respect to the cylindrical work piece, which is described using four parameters (Denavit Hartenberg parameters). We have presented algorithms in pseudocode that produce the flute shape and that compute the optimum parameters of the wheel position in the manufacturing process. Subsequently, a software application based on the aforementioned model is able to create visualizations of the flute shape. The analysis of the flute shape has enabled us to understand the influence of the geometrical parameters and the position of the grinding wheel on the resulting product in the grinding process. The order in which these parameters are to be set is also specified. We have built atlases of maps presenting the influence of the geometrical parameters and the position of the grinding wheel in the grinding process upon the shape of the flute. The validity of the method is proven by the agreement of the computed values with the input and output data produced by experiment. The proposed method allows helical flutes to be generated solely by using cylindrical and conical grinding wheels of standard shapes.     

基于PRO/E的挖掘机铲土装置的建模与运动仿真

利用PRO／E软件建立了反铲式挖掘机的实体模型；并利用PROE的机构运动Mechanism模块，对其进行动力学仿真分析，为进一步的设计、工程分析及制造奠定了基础。     

轮式装载机传动系载荷谱编制方法研究

为指导轮式装载机可靠性设计,提出一种轮式装载机传动系载荷谱编制方法。采用"五段法"测试了轮式装载机传动系载荷时间历程信号;通过频谱分析,确定载荷信号频率不超过1Hz的特征;按照"空载运行-铲掘装载-满载运行-卸载"四段的循环特征,对信号进行分割与合并,完成信号的平稳处理;通过雨流计数与工况合成法,获得载荷均值符合正态分布、幅值符合威布尔分布的特征,完成载荷幅值极值的统计推断;根据波动中心法,编制出了轮式装载机传动系各部件的八级载荷谱与程序加载谱。研究表明,轮式装载机传动系载荷信号可依特征分四段平稳处理,且具有显著的概率分布特征,编制的载荷谱符合装载机真实工况。     

地下铲运机铲装阻力分析

地下铲运机在铲装物料的过程中,铲装阻力的不确定性会使铲装过程受阻,需要调整铲斗姿态等,保证铲装顺利进行。针对地下铲运机铲装物料时铲装阻力不确定的问题,应用EDEM软件模拟地下铲运机铲装物料过程,通过仿真分析得出铲装阻力的变化趋势,进而为铲装过程中铲斗姿态的控制调整提供参考。     

Spatial kinematics and virtual prototype modeling of Bucyrus shovel

In this study, a 3D model of the shovel motion based multi-body system dynamics in the Automatic Dynamic Analysis of Mechanical Systems (ADAMS) environment was developed. The kinematics model of the shovel was modeled as a multi-body system, which comprises the lower, upper, and the attachment mechanisms. The Euler–Lagrangian equations were employed as the computational framework to describe the dynamic behavior of the model. A virtual prototype of the shovel was built in the ADAMS software environment. This environment allows the visualization of a 3D motion of the general mechanical system and the prediction of interference of the moving components of the shovel. The numerical analysis and animation of digging, swinging, and dumping motions for the shovel were performed. The superimposed display of the deployment for the shovel in three phases allows a detailed examination of the dynamic interference among assembly components. This research provides a solid foundation for further shovel dynamics performance studies.