基于真实载荷的挖掘机工作装置瞬态动力学分析

用有限元法对挖掘机工作装置进行瞬态动力学分析,以6 t小型挖掘机工作装置为研究对象,针对斗杆液压缸驱动铲斗撞击地面工况,用压力传感器、位移传感器测试出撞击过程各液压缸工作腔压力和位移变化曲线,以所获各液压缸位移变化曲线和最大理论撞击力为驱动,用动力学仿真软件ADMAs对挖掘机撞击过程进行仿真,得出各铰销点在撞击过程中所承受载荷的变化曲线,采用测试所得各液压缸的驱动力验证仿真结果的准确程度.进一步将各铰销点受力的仿真结果作为工作装置的负载,对工作装置进行瞬态动力学分析,对比仿真计算与应力测试结果表明,对应测点的应力变化趋势基本一致,误差在10%以内,可为结构优化设计提供依据.     

实测载荷驱动下挖掘机动臂的疲劳寿命研究

针对挖掘机工作装置疲劳分析中由于复杂载荷难以模拟而导致结果误差大的问题,提出一种完全由真实载荷驱动的工作装置疲劳寿命研究方法,为工作装置结构设计提供了依据.以20t挖掘机为研究对象,采用D-H(Denavi-Hartenberg)法建立挖掘机工作装置动力学模型,并根据传感器记录的挖掘过程中各液压缸压力和位移的变化曲线结合力平衡方程得到动臂各铰点的真实工作载荷,再应用疲劳分析软件对动臂进行疲劳分析,获得寿命云图.研究结果为挖掘机工作装置的结构设计提供了参考依据.     

液压挖掘机斗杆的动态仿真和实验研究

针对液压挖掘机斗杆在工作过程中容易出现开裂、断裂等失效情况,利用Ansys与ADAMS模拟实际工况进行联合动态仿真,获得斗杆在挖掘作业过程中的动态应力变化曲线以及危险点的应力-时间历程,并通过应力测试实验进行验证。由仿真结果可知,斗杆最大应力出现在挖掘深度最大的时刻,危险点位于斗杆液压缸杆与斗杆铰接处的耳板与箱板焊接处。实验表明,仿真结果具有一定的可靠性。研究将为疲劳寿命、可靠性等问题的深入探讨提供数据基础,也可为工程机械关键构件的优化设计提供参考。     

挖掘机工作装置台架疲劳试验载荷等效方法研究

以挖掘机工作装置为研究对象,提出了一种考虑分段载荷均值特性的挖掘机工作装置台架疲劳试验方法,确定了疲劳试验姿态、试验等效载荷及试验载荷加载方式。首先,选取粘土、重粘土、密实硬土三类典型介质进行载荷采集试验,根据挖掘机实际载荷特性,分别对挖掘、提升回转、卸载、返回四个实际工况进行了平稳性检验。其次,选取挖掘阶段溢流阀打开时刻对应的实测油缸位移均值作为台架疲劳试验的加载姿态,通过调整斗尖当量载荷方向使各大应力点当量应力与实测应力误差最小的方法确定加载方向。最后,由力与应力之间的关系计算得斗尖等效载荷,并通过各测点等效应力与实测应力对比验证了该方法的合理性。这种台架试验载荷等效方法为挖掘机工作装置载荷谱疲劳可靠性试验及疲劳寿命预测提供参考。     

300t液压挖掘机虚拟样机动力学仿真研究

以300t大型反铲液压挖掘机为研究对象,通过ADAMS仿真分析了各液压缸以及4个主要铰接点在循环工况中的受力情况,为循环工况下铲斗、斗杆和动臂等的强度分析作准备。仿真结果表明:动臂液压缸、动臂与斗杆铰接点所受载荷的变化最为剧烈;各液压缸、铰接点所受载荷跟随挖掘阻力的变化而变化,其峰值与阻力的峰值几乎出现在同一时刻。     

电液谐振疲劳试验新方法

研究2D高频转阀控制液压缸实现谐振疲劳试验新方法。提出2D高频转阀控制单出杆液压缸谐振疲劳试验方案,2D高频转阀阀芯可以双自由度运动,阀芯旋转运动可以控制系统激振频率,阀芯轴向滑动可以控制系统输出载荷力幅值,液压缸无杆腔初始容积变化可以控制系统谐振频率。建立2D高频转阀、单出杆液压缸和阀控缸系统的数学模型,建立阀控缸系统的Simulink非线性仿真模型,仿真研究液压缸无杆腔定初始容积时阻尼对系统输出载荷力幅频特性、相频特性和系统流量的影响,及谐振工况时载荷力波形失真度和载荷力幅值控制方法。试验结果验证了电液谐振疲劳试验新方法的可行性。该方案能有效提高电液疲劳试验的谐振频率,拓展电液高频疲劳试验机在工程领域的应用范围。     

液压挖掘机关键部件疲劳寿命分析

论文在对某型号液压挖掘机进行典型工况作业试验获取挖掘机工作装置实际作业载荷历程的基础上,利用有限元ANSYS Workbench与疲劳分析软件nCode DesignLife相结合的方法得出挖掘机斗杆的疲劳分析结果。首先利用SolidWorks建模导入Workbench中施加载荷步进行斗杆静力学分析,然后根据斗杆材料的特性得到S-N曲线,并利用合理方法对S-N曲线进行修正,最后结合试验所得斗杆铰点载荷时间历程,选用S-N疲劳分析引擎分析得出斗杆寿命云图。确定疲劳失效易发生的部位,为挖掘机工作装置的疲劳设计提供依据。     

正铲液压挖掘机工作装置的动力学分析与仿真

对一种正铲液压挖掘机进行动力学分析,运用虚功原理对工作装置进行动力学建模。基于Matlab对动力学模型进行数值计算,在给定负载情况下得到了铲斗在挖掘过程中3组液压缸的驱动力变化曲线。利用ADAMS仿真软件对该挖掘机工作装置进行动力学仿真,将仿真得到的结果与计算值进行对比,得到3组液压缸的驱动力误差曲线,误差在合理范围内,证明了动力学建模方法的正确性。     

基于刚—柔耦合模型的液压挖掘机动力学仿真研究

用机械系统动力学仿真软件ADAMS和有限元分析软件ANSYS相结合的方法,建立液压挖掘机刚柔耦合虚拟样机,并对液压挖掘机刚柔耦合模型进行了运动仿真,通过动力学仿真分析研究了液压缸在复合挖掘过程中的受力情况及各铰接点处的受力变化。     

基于ADAMS的履带式挖掘机越障动力学建模与分析

履带式挖掘机作业时需跨越各类障碍物,在履带式挖掘机跨越障碍物时会受到来自地面的冲击载荷而产生疲劳破环,故研究履带式挖掘机的整机越障动力学特性十分必要。基于动力学仿真软件ADAMS,研究了履带式挖掘机的整机越障动力学特性。以某中型履带式挖掘机为例,在Pro/E中完成履带式挖掘机的三维建模,在ADAMS中建立其简化虚拟样机,完成该履带式挖掘机越障的动力学仿真。结果表明:越障过程中,挖掘机车体垂向最大位移与障碍物设置高度一致,整个越障过程较为平稳。此外,车体的转动角速度在车体越过障碍边缘到引导轮触地时刻存在较明显的变化过程。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.