电液自由锻锤锤头开裂失效分析

应用金相显微镜、扫描电镜、拉力试验机、冲击试验机、硬度计、光谱测试仪等通过宏观检查、尺寸检查、断口形貌分析、化学成分分析、机械性能试验、非金属夹杂物评级、金相组织分析等方法对某电液自由锻锤锤头开裂现象进行分析。分析结果表明锤头发生开裂的裂纹起始于燕尾槽槽底的R角处,开裂初始部位断口形貌显示有应力集中现象存在,锤头的开裂主要呈脆性断裂特征,裂纹扩展存在休止迹象。     

碳纤维机载电磁屏蔽机箱制造工艺研究

某机载电磁屏蔽机箱对重量的控制要求严苛,因此采用碳纤维复合材料制造该机箱。文中论述了该碳纤维机载电磁屏蔽机箱的制造工艺过程,即对该整体成型机箱的制造工艺流程进行了介绍,并对模具设计、铺层设计、金属预埋件精确定位、表面金属化等关键技术进行了详细讨论。与相同结构的铝制机箱相比,该碳纤维机箱的质量减轻了约30%,并通过了电磁屏蔽性能测试以及振动、盐雾、湿热、温度冲击等环境适应性试验验证,完全满足设计和使用要求。     

基于某舰船高压空压机模块抗冲击分析的研究

依据舰船用高压空压机模块的抗冲击使用要求,基于舰船设备抗冲击理论,通过仿真计算和试验分析,建立了模块(双机双层隔振)及单机系统(单机双层隔振)的抗冲击动力学模型,采用Adams软件模拟了空压机、浮筏的冲击加速度及隔振器的变形等动态特性.结合单机系统的双波冲击试验和裸机(单台空压机)的落锤冲击试验,综合评价了该高压空压机...     

水锤效应对高、低位罐加油机的破坏差异分析

水锤现象普遍客观存在。它对低位罐加油机和高位罐加油机的影响及破坏力是不一样的,此差异主要的是由于这两种加油机泵的不同结构造成的。低位罐加油机的泵,其油气分离室可以充当压力冲击的"缓冲囊",破坏力有限。高位罐加油机的泵,其内部没有吸收冲击的缓冲地带,因此破坏力比前者大,并可能损坏元器件、破坏液压件的密封、造成泄漏等。把单向阀从高位罐加油机的泵进油口处取消后,其液压系统与储油罐连通一体,可以吸收压力冲击,排除了故障隐患。在液压系统中合理设置类似气囊的压力缓冲件,可以有效削减水锤效应的压力峰值,减少液压元件损坏和系统泄漏。     

某机载电子设备系统中央接收机结构设计

本文就某机载电子设备系统中央接收机的模块化设计、热设计、电磁兼容性设计、防冲击、振动、噪声设计、“三防”设计等结构设计作了详细的论述。     

A mini desktop impact test system using multistage electromagnetic launch

A miniaturized Split Hopkinson Bar (SHB) system has been developed based on electromagnetic launch. The novel and simple multistage electromagnetic launch technique has been investigated for being against the drawback of traditional pneumatic loading system, such as the need for very-high air pressures, lack of test repeatability, high operation noise, large size, and large overall weight of the apparatus. The easy and practicable multistage electromagnetic launch device and its working principle are described in details. A simple launch speed calibration technique, methods of eliminating the electromagnetic signal effect and erasing magnetism in bars are also described. With the same multistage electromagnetic launch device and main components, the system could be switched between impact compression and tension modes for mini specimen testing easily. Successful validation tests on aluminum alloy for impact compression and polyimide/SiO₂ film for impact tension were carried out for verifying the feasibility and reliability of the system.     

An accurate probe pre-travel error compensation model for five-axis on-machine inspection system

On a five-axis CNC machine tool, the pretravel errors of touch-trigger probes are severely affected by gravity and must be compensated to ensure the required measurement accuracy. The situation is more complex than that of the three-axis on-machine inspection system. This paper proposes a simple and accurate modeling and compensation method for the probe pretravel error of a five-axis on-machine inspection system. First, the pretravel error for the 5-axis CNC tool is decoupled into three parts, which are analyzed based on the probe's mechanical structure. Then, a new calibration point selection strategy is proposed to obtain the accurate reference sphere center. Finally, we carry out calibration tests to validate the proposed method. The compensation results show that the proposed compensation method for the probe pretravel error under the influence of gravity (PPEUG) can improve the accuracy considerably.     

Impact wear of MgO single crystals I. Wear characteristics

The impact wear characteristics of MgO single crystals have been investigated using an impact testing machine provided with a sintered alumina hammer having a tip radius of 2 mm. There is a fixed zero wear duration time for each selected impact load. Plastic deformation caused by slip of the {110} planes and cracking by impact occur during zero wear, but wear fragment are not produced. The zero wear period corresponds to a process of impact fatigue. Measurable wear, which is obtained by repeated impact over the zero wear limit, depends on the impact load and the action of wear fragments. When the test is performed in water wear is accelerated by abrasive erosion caused by impulsive flow of water containing wear fragments between the hammer and the scar wall.     

The 250 kN primary shock force calibration device at PTB

A new facility for primary shock force calibrations up to a force amplitude of 250 kN is presented. Shock forces are generated by the impact of two airborne cylindrical mass bodies. Two laser-Doppler interferometers simultaneously measure the bodies’ dynamic motions on their common axis of motion. Traceability of force is realised by the determination of mass and acceleration. This paper is an extended version of the original contribution to the IMEKO 2010 conference in Pattaya, Thailand.     

Estimation of the saw-tooth shock wave using a lead shock programmer

Structure durability under shock load is evaluated by performing a shock resistance test. Saw-tooth shock wave is generated in a specific environment and transmitted to the structure. The saw-tooth shock wave is generated using a specific impact test system. In general, the impact test system is generally composed of three types: Drop, lateral and rotational. Each type of impact test system has different detail parts. This study applies the drop-type impact test system. A test table, a fixed table, and a shock programmer compose comprise the drop-type impact test system. The drop-type impact test system uses the initial height of the test table, where the specimen is mounted on. The impact velocity in the drop-type impact test is determined by the initial height of the test table. The shock programmer generates the shock wave transmitted to the specimen mounted on the test table, which is then. The shock wave transmitted to the specimen is then generated by the shock programmer material. Parameter research of the parameter testing on the shock programmer has to be performed using the drop-type impact test system to generate the saw-tooth shock wave with non-linear characteristics. This study generates the saw-tooth shock wave by designing and simulating the lead shock programmer. Lead is considered as the shock programmer material. The accuracy of the simulation program (i.e., LS-Dyna) is verified by performing the drop shock test of theon the three types of lead shock programmer with three types. The results of the time history on the test table acceleration between the simulation and the test are compared with those of the shock test and the simulation. The shock test and simulation results are plotted using the tolerance range of the saw-tooth shock wave presented in MIL-STD-810G. The saw-tooth shock wave generated using the lead shock programmer with conical and truncated conical shape is estimated using the verified simulation program. The aspect ratio of the conical and truncated conical lead shock programmer is presented to generate the saw-tooth shock wave is also presented.

     

Development of computer aided calibration module for CMMs and machine tools using a compensated step gauge

This paper shows a micro computer aided error calibration system for CMMs and machine tools, which is a fast and efficient error calibration system: A micro computer stores the error calibration data of a step gauge which were precalibrated with more precise equipments such as laser interferometer, then the step gauge is probed with the specific CMMs or machine tools. The probing data are compared with the stored precalibration data, in order to give the linear displacement accuracy of the machines. High degree of computer integration has been performed in the measurement path planning, measurement operation, and error evaluation. Thus a rigorous computer aided error calibration system has been implemented with full potential of practical application to most of commercial CMMs and machine tools of CNC type.     

基于机器视觉的阀芯自动装配系统

针对球阀阀芯自动装配过程中存在装配柔性低、时常无法精确定位的问题,基于机器视觉技术,构建了一套在线机器视觉系统。采用NI Vision Assistant模块对系统及图像进行快速、准确的标定,并在其中对零件图像进行预处理、模式匹配以及边缘检测等修正处理。在LabVIEW中调用Vision Assistant节点,得出零件的位置和角度信息,经以太网与下位机实现通信,动态改变机器人装配动作,并在所搭建的硬件实验台上进行了在线验证。实验表明,该系统采用的方法可行且稳定,能够满足阀芯装配快速、准确的要求。     

动态测量数控机床的几何误差

数控机床的检测与修正是机床行业中的一个关键组成部分,每个国家都有相应的测量数控机床几何位置精度,特别是静态几何精度的标准。由于工件是在动态的过程中进行加工,数控机床的静态精度并不能完全代表其几何位置精度,对于某些精密加工和高速加工场合,必须对数控机床进行动态测量补偿,本文介绍了一种动态测量数控机床位置精度的系统,并给出了一些动态误差的实验结果。     

Comparison of electrostatic fins with piezoelectric impact hammer techniques to extend impulse calibration range of a torsional thrust stand

With the progression of high-power electric propulsion and high thrust-to-power propulsions system, thrust stand diagnostics require high-fidelity calibration systems that are accurate over a large-range of thrust levels. Multi-mode and variable I(sp) propulsion devices also require that a single stand be capable of measuring thrust from 10's of uNs to 100's of mNs. While the torsional thrust stand mechanic and diagnostics are capable of operating over such a large range, current pulsed calibration schemes are typically limited to a few orders of magnitude of dynamic range. In order to develop a stand with enough dynamic range, two separate calibration methods have been examined and compared to create a combined system. Electrostatic fin (ESF) and piezoelectric impact hammer (PIH) calibration systems were simultaneously tested on a large scale torsional thrust stand system. The use of the these two methods allowed the stand to be calibrated over four orders of magnitude, from 0.01 mNs to 750 mNs. The ESF system produced linear results within 0.52% from 0.01 mNs to 20 mNs, while the PIH system extended this calibration range from 10 mNs to 750 mNs with an error of 0.99%. The two calibration methods agreed within 4.51% over their overlapping range of 10-20 mNs.     

液压软管脉冲试验机电液伺服系统的设计与研究

随着我国飞机、汽车、工程机械的快速发展,对液压系统的管路及附件的耐压性、抗冲击性及其可靠性提出了更高的要求。根据对液压软管的液压脉冲实验要求设计了液压软管压力脉冲试验机电液伺服系统,并针对正弦波、水锤波的不同类型输入信号对系统进行了仿真研究,根据试验机周期性测试任务以及电液伺服系统非线性的特点,采用了重复控制和PID控制的复合控制策略,仿真结果表明此控制方法可以提高压力跟踪精度、动态特性和系统的鲁棒性。通过设计基于LabVIEW虚拟仪器和PLC的测控系统,对系统进行实验研究。仿真结果和实验结果研究相比表明,所设计的液压伺服系统可以满足用户提出的严格测试要求。     

液压破碎锤破碎混凝土的动力学分析

液压破碎锤工作环境十分恶劣,其中活塞杆、钎杆、活塞缸体是其最易失效的零件.针对YYC300型行程反馈式液压破碎锤,利用SOLIDWORKS进行实体建模,在LS-DYNA中对活塞杆撞击钎杆、钎杆受力侵彻混凝土的过程进行了刚柔体运动、非线性接触碰撞动力学仿真,获得了液压破碎锤主要零部件—冲击缸体、钎杆、活塞杆的应力云图以及液压破碎锤的应力集中点在撞击过程中的应力变化曲线及混凝土破碎情况.依据对混凝土破碎结果的分析,可为选择液压锤型提供依据,通过对液压锤关键部位应力变化的试验研究,验证了仿真结论的正确性.     

Robot calibration using an automatic theodolite

The Vision Based Automatic Theodolite (VBAT) is an automatic partial pose measurement system for robot calibration. It uses low resolution rotation stages and resolution enhancement from a vision system to determine the line-of-sight to a spherical illuminated target. Automatic tracking, focusing, and centring provide the calibration system with speed, reliability, and repeatability. A kinematic model of the VBAT is described which includes both the mechanical parts of the system and the optics, using a modified Denavit-Hartenberg approach. All parameters in the VBAT model are identified and embedded into the system controller producing an instrument of 2 arc second accuracy. The system is then used in a conventional manner to calibrate a six degree of freedom PUMA robot, and the results compared to another calibration of the same arm by a coordinate measuring machine with repeatability and accuracy of 0.02 mm. The calibration using the VBAT enhances the accuracy of the PUMA to within 0.2 mm of that produced by the CMM calibration, compared to an accuracy of 14 mm prior to calibration.     

基于刚柔耦合模型的强夯机动力学分析

履带式强夯机工作级别高,工作环境恶劣,在突然释放夯锤时,整机受到强大冲击.在ADAMS动力学仿真环境下联合Pro/E和ANSYS软件建立400 t·m强夯机整机的刚柔耦合模型,对其突然卸载工况进行仿真分析,研究卸载过程中结构件的振动响应、整机的稳定性,对柔性体的动态应力及整机动态响应参数进行分析,为整机的疲劳寿命分析及部件的设计改进与优化提供载荷谱数据.     

Design and static performance of high speed machining centre with “direct drive”

“Direct drive” is an ideal method for speeding machine tools. In the structure of a CNC machining centre with “direct drive”, the linear motor’s primary and secondary parts are assembled into the worktable and machine bed respectively to directly drive the worktable. The built-in rotary motor is assembled in the spindle to realize the main transmission system of the machine tool “direct drive”. All mechanical transmission elements in machine tools are eliminated. High speed, efficiency, and accuracy are easily obtained. However, in this type of “direct drive” machining centre, the magnetic attraction force between the primary and the secondary linear motors and the dynamic impact at acceleration and deceleration are directly imposed on the machine tool, and influence the performance of the machining centre. This paper analyzes the special demands of “direct drive” on the machine centre, and introduces a new structure of the machining tool. The worktable and machine bed are optimized to meet the special demands of “direct drive”. Static performance simulation on the machining centre is done to reveal an ideal result.     

FUZZY NEURAL NETWORK FOR MACHINE PARTS RECOGNITION SYSTEM

The primary purpose is to develop a robust adaptive machine parts recognition system. A fuzzy neural network classifier is proposed for machine parts classifier. It is an efficient modeling method. Through learning, it can approach a random nonlinear function. A fuzzy neural network classifier is presented based on fuzzy mapping model. It is used for machine parts classification. The experimental system of machine parts classification is introduced. A robust least square back-propagation (RLSBP) training algorithm which combines robust least square (RLS) with back-propagation (BP) algorithm is put forward. Simulation and experimental results show that the learning property of RLSBP is superior to BP.