冲击破岩掘进机耙装过程铰点力仿真分析

为了探究冲击破岩掘进机在耙装过程中两种不利工况下工作臂各铰点的受力情况,利用SolidWorks建立冲击破岩掘进机工作机构的3维实体模型,根据威尔分布的随机过程结合确定型分析方法建立了法向阻力模型,用双参数法建立了侧向阻力模型,用联合分布随机信号法建立了切向阻力模型,确定耙装阻力变化。用ADAMS建立其虚拟样机模型,通过仿真得到各铰点受力变化规律。结果表明:两种工况下各铰点力随耙装阻力变化波动明显,且在耙装工况下耙斗处于耙装最低点时摇臂与装载臂铰点受到载荷最大,易使工作机构支臂产生疲劳裂纹。其仿真结果为工作机构的力学分析提供理论依据。     

耙吸船消能箱对装舱影响的数值计算

利用Fluent软件对耙吸挖泥船装舱过程进行了模拟仿真。重点分析了消能箱不同布置对装载过程和流场分布等的影响。结果表明,在装舱后期,消能箱远离溢流筒布置时更利于泥沙的沉积,沉淀效果和装舱效果更好。     

按照给定运动轨迹曲线设计铰链四杆机构(续)

二、蟹耙式装载机工作机构的没计最近几年来。蟹耙式装载机在运输和矿山等部门得到广泛地应用。它是一种适用于装卸散粒物料的连续装载机。1.耙取工作机构的基本型式及其结构变换在蟹耙式装载机中,耙取机构的最基本型式是如图1所示的两个对称布置的曲柄摇杆机构M_AABM_B。将连杆的伸出端做呈“蟹爪”形,当曲柄M_AA作连续转动时,“蟹爪”的端     

AP1000装卸料样机提升机构的国产化设计

对比了AP1000装卸料机主提升机构与秦山二扩装卸料机及宁德装卸料机主提升机构的布置形式和机构特点。对样机的主提升机构重新进行优化设计,使其具有维护便利、经济性好的特点。     

2F-5000型链耙刮板式大肥量有机肥撒施机设计

介绍了2F-5000型链耙刮板式大肥量有机肥撒施机的技术特点及结构设计,见图1。该机主要由半挂式挂车牵引底盘、装肥车厢、厢底输送链耙和旋转刮料辊等组成,其动力由拖拉机后输出轴提供,通过减速换向,再通过链传动机构传递给棘轮减速装置,驱动链耙刮板带动有机肥料移动,实现有机肥的大肥量撒施作业。     

大口径透镜姿态调整机构的支承分布设计

为了设计大口径透镜姿态调整机构,研究了三顶三拉调平结构布置方式的调节性能及其对受力变形和光束质量的影响。采用几何方法,得出了三顶三拉结构在任意三角形布置下升高量与调整角度变化的关系,定义了角度调整的相关系数;利用有限元分析软件分析了3类支承点布置情况下调节平板的变形情况。分析结果表明,三顶三拉调整机构具有调整量可计算的特点,当调节平板的尺寸为580 mm×570 mm×20 mm,采用等腰三角形支承点布置方式时,重力引起的最大变形为12.51μm。对采用了等腰三角形三顶三拉结构的透镜姿态调整机构进行了装校调试及打靶实验,结果证实了该布点方式对姿态调整的有效性和调整完成后精度的稳定性。     

敞车散料耙平机研制

矿石敞车中的矿石等散料运输必须耙平,若偏载将带来安全等系列问题。目前,敞车散料一般采用人工耙平,工人劳动强度大,工作效率低。为解决该问题,研制了一种矿石敞车散料耙平机,该设备包括动力机车、底座、立柱、主横梁、行走小车横梁、立柱转动机构、旋转机构、刮板器、耙板、液压站总成和控制系统。底座通过立柱转动机构与立柱形成可转动连接。立柱转动机构包括立柱、液压马达、驱动齿和齿圈。齿圈装在底座上端外周上。立柱的中部设有大臂孔,大臂通过大臂孔和铰链连接与立柱配合。大臂的端面装有两根行走小车横梁。两根行走小车横梁上装有行走小车。在行走小车的面上设有齿轮齿条摆动油缸。耙板轴轴向依次穿过行走小车耙轴孔、齿轮齿条摆油缸中键槽孔和法兰缸筒,耙板轴的轴端与升降油缸活塞杆连接。齿轮齿条摆动油缸工作时,齿条往复移动,驱动齿轮顺时针或逆时钟转动,从而带去动耙把轴及其耙板顺时针或逆时钟转动,从而快捷、有效耙平列车车箱散装物料,达到运输要求。试验研究表明,该耙平机能实现自动、安全、可靠、高效的矿石敞车散料耙平作业,敞车不偏载,减轻了工人劳动强度,提高了工作效率。     

比例技术在耙料驱动机构中的应用分析

分析耙料驱动机构的工况,通过仿真技术分析模拟了料耙的运动状况,确定在耙料机构中应用比例控制技术,改善料耙的运动曲线,使整个料耙机构的运动工况得到了改进.     

核电厂燃料抓取机桥架驱动机构自主化设计

以核电厂燃料抓取机为例,介绍了其桥架驱动机构的设计要求、结构布置,给出了设计计算过程。该部件的自主化设计方法能够推广用于核电厂其他设备的驱动机构设计,有益于提升我国核电厂装换料设备的自主化研发能力。     

推耙机散热系统研究与开发

针对农作物类工况推耙机散热系统常被堵塞引起系统高温的问题，研发出一种电子风扇中冷器和大片距铜质水散热器，并通过在整机上的合理布置，有效解决了该工况下散热器堵塞及高温问题，研究成果可为类似农作物类工况推耙机、推土机等散热系统设计提供借鉴。     

Development of a novel variable rake angle mechanism for noncircular turning and its control

A prototype tool stage with a variable rake angle mechanism has been developed and controlled. The objective of the variable rake angle mechanism is to provide two-degrees-of-freedom to the conventional noncircular turning process, so that the rotational tool mechanism can compensate for the rake angle change caused by the noncircular cam profile itself while the translational tool motion generates the cam profile. Inverse kinematics, kinematic sensitivity and stiffness, and design of the variable rake angle mechanism are discussed. Robust repetitive controllers are designed for two actuators in the variable rake angle mechanism. Two actuators operate together to change the tool position as well as the tool angle. Experimental results on the variable rake angle mechanism support the design concept and control approach.     

Wear mechanism of the loose layer on the rake face of a new cemented carbide micro groove turning tool

The loose layer can appear on the rake face of a turning tool under certain cutting conditions and have an important influence on the rake face wear. In this paper, wear morphology and wear mechanism of loose layer on the rake face of the original turning tool and the new cemented carbide micro groove turning tool developed independently during the cutting process are studied, by the combination of theoretical analysis and cutting test. And the relationships between the diffusion wear and the adhesive wear of the loose layer on the rake face of the new micro groove turning tool are further analyzed and revealed. The research results show that the loose layer on the rake face of two turning tools is caused by the diffusion wear, which is formed by the brittleness-weakening of tool material in the region resulting from elements diffusion. Meanwhile, the wear degree of the rake face of tools is aggravated by the mutual promotion of diffusion wear and adhesive wear. In the normal wear stage, the degree of looseness and brittleness of the rake face of the original turning tool is greater than the one of the micro groove turning tool. In the severe wear stage, cobalt elements in the rake face of the two turning tools are dissolved and diffused in varying degrees, which further aggravates the brittle-weakening of materials in the region. But the degree of loose brittleness of the rake face of the original turning tool is still greater than the one of the micro groove turning tool. It can be concluded that the micro groove on the rake face of the new turning tool can improve the rake face wear to a certain extent.     

MOLECULAR DYNAMICS SIMULATION OF NANOMETRIC CUTTING

Molecular Dynamics (MD) simulations of nanometric cutting of single-crystal copper were conducted to predict cutting forces and investigate the mechanism of chip formation at the nano-level. The MD simulations were conducted at a conventional cutting speed of 5 m/s and different depths of cut (0.724–2.172 nm), and cutting forces and shear angle were predicted. The effect of tool rake angles and depths of cut on the mechanism of chip formation was investigated. Tools with different rake angles, namely 0°, 5°, 10°, 15°, 30°, and 45°, were used. It was found that the cutting force, thrust force, and the ratio of the thrust force to cutting force decrease with increasing rake angle. However, the ratio of the thrust force to the cutting force is found to be independent of the depth of cut. In addition, the chip thickness was found to decrease with an increase in rake angle. As a consequence, the cutting ratio and the shear angle increase as the rake angle increases. The dislocation and subsurface deformation in the workpiece material were observed in the cutting region near the tool rake face. The adhesion of copper atoms to the diamond tool was clearly seen. The same approach can be used to simulate micromachining by significantly increasing the number of atoms in the MD model to represent cutting depths in the order of microns.     

钛合金铣削过程刀具前刀面磨损解析建模

钛合金Ti6Al4V作为典型的航空航天难加工材料,在其铣削过程中硬质合金刀具的磨损会降低加工过程稳定性,进而影响加工效率和已加工表面表面质量。刀具前刀面磨损会导致刀具刃口强度降低,并影响切屑的流向和折断情况。针对前刀面磨损机理进行分析并构建了月牙洼磨损深度预测模型。首先运用解析方法构建了前刀面应力场模型,得到切屑在前刀面滑动过程中的刀具前刀面应力分布情况及磨损位置。基于刀-屑接触关系的基础上建立了前刀面温度场模型。然后,基于所得刀具前刀面应力与温度分布,构建综合考虑磨粒磨损、粘结磨损与扩散磨损的铣刀月牙洼磨损深度预测模型,获得月牙洼磨损预测曲线;结合铣刀月牙洼磨损带沿切削刃方向分布的特点,建立了随时间变化的铣刀前刀面磨损体积预测模型。最后通过试验验证了切削宽度对前刀面磨损的影响规律,预测结果与试验测量值具有较好的吻合性。结果表明随着切削宽度的增加,月牙洼磨损深度及前刀面磨损体积都随之增加。研究结果为钛合金铣削用刀具的设计和切削参数的合理选择提供了理论基础。     

Experimental Study on Wear Characteristics of PCBN Tool with Variable Chamfered Edge

Owing to heavy dynamic and thermal loads, PCBN tools are seriously worn during hard cutting, which largely constrains the improvement of their machining performance. Therein, the chamfered structure of a cutting edge has a notable influence on the tool wear. Thus, a comparative study was carried out on the wear morphology and wear mechanism of PCBN tools with either a variable chamfered edge or an invariable chamfered edge. The results indicate that, for a PCBN tool with a variable chamfered edge, the rake wear area is far from the cutting edge and slowly extends toward it. A shallow large-area crater wear occurs on the rake face, and the flank wear area has a long triangular shape with a smaller wear area and width, and the cutting edge remains in a good state during the cutting process. In contrast, for a PCBN tool with an invariable chamfered edge, a deep small-area crater appears on the rake face,and the wear area is close to the cutting edge and quickly extends toward it. Thus, it is easy for chips to accumulate in the crater, resulting in large-area and high-speed wear on the flank face. In addition, the tool shows a weak wear resistance. In the initial wear stage, the rake wear mechanism of the two cutting tools is a mixture of abrasive, oxidation, and other types of wear, whereas their flank wear mechanism is dominated by abrasive wear. With an aggravation of the tool wear, the oxidation and di usion wear mechanism are both increasingly strengthened. The rake wear of the cutter with a variable chamfered edge showed an obvious increase in the oxidation and di usion wear, as did the flank wear of the cutter with an invariable chamfered edge. This study revealed the wear mechanism of the PCBN tool with a variable chamfered edge and provided theoretical and technological support for its popularization and application in the machining of high-hardness materials.     

多齿刀具加工金属长纤维的机理

研究了多齿刀具加工金属纤维的机理．研究发现．多齿刀具各细齿切削属双刃斜角切削．建立了双刃斜角切削模型并用实验验证，从理论上预测各细齿切削时的流屑角．根据流屑角计算各细齿的实际切削前角。结果表明．多齿刀具备细齿切削时具有很大的实际切削前角．这正是多齿刀具能够加工金属长纤维的机理。     

Single-point diamond turning of CaF2 for nanometric surface

Single-crystal CaF₂ is an important optical material. In this work, single-point diamond turning experiments were performed to investigate the nanometric machining characteristics of CaF₂. The effects of tool feed, tool rake angle, workpiece crystal orientation and cutting fluid were examined. It was found that two major types of microfracturing differing in mechanism limited the possibility of ductile regime machining. The critical conditions for microfracturing depend strongly on the tool rake angle and the type of cutting fluid. The results also indicate that one type of the microfractures is caused by thermal effect, and can be completely eliminated by using a sufficiently small undeformed chip thickness and an appropriate negative rake angle under dry cutting conditions. Continuous chips and ductile-cut surfaces with nanometric roughness were generated.     

某型大尺寸进气道测量耙振动与应力相关性试验研究

为了解决应变计测量法在试飞中对测量耙应力难以监控的问题,对自行设计的某型大尺寸进气道测量耙进行振动试验,建立测量耙振动与应力的相关性,实现利用测量耙振动信息监视分析测量耙应力的目的。通过扫频和定频试验,得到了相应的振动和应变试验数据。通过试验数据分析,得到了耙的固有频率,并根据各测点应变与振动的相关性初步建立了耙的振动与应力之间的关系方程,为后续试飞中测量耙安全监控提供一定试验基础和依据。     

多齿刀具切削机理及其在金属纤维制造中的应用

研究了一种新型刀具——多齿刀具的切削特点和机理 :该刀具切削时多个细齿同时参与切削 ,具有分屑作用 ;各细齿具有较大的实际切削前角。并从理论上分析了实际切削前角与各参数的关系。通过实验研究了该刀具在金属长纤维制造中的应用及如何选择刀具参数和切削用量。实验表明 ,该刀具能同时制造多根当量直径在 5 0μm以下的长纤维     

大型刮板取料机新型结构料耙设计

料耙设计采用双层钢桁立体结构,料耙各梁采用不同规格的异形钢管制成,料耙耙齿采用栓接结构。这种结构的料耙重量轻,强度好,刚性好,变形小,运行平稳,耙齿更换方便,利于设备的使用维护。