Plastic Deformation Mechanism in Double-Roller Clamping Spinning of Flanged Thin-Walled Cylinder

Double?roller clamping spinning(DRCS) is a new process for forming a thin?walled cylinder with a complex surface flange. The process requires a small spinning force,and can visibly improve forming quality and production e ciency. However,the deformation mechanism of the process has not been completely understood. Therefore,both a finite element numerical simulation and experimental research on the DRCS process are carried out. The results show that both radial force and axial force dominate the forming process of DRCS. The deformation area elongates along the radial direction and bends along the axial direction under the action of the two forces. Both the outer edge and round corner of the flange show the tangential tensile stress and radial compressive stress. The middle region shows tensile tangential stress and radial stress,while the inner edge shows compressive tangential stress and radial stress. Tan?gential tensile strain causes a wall thickness reduction in the outer edge and middle regions of the flange. The large compressive thickness strain causes material accumulation and thus,an increase in the wall thickness of the round corner. Because of bending deformation,the round corner shows a large radial tensile strain in addition. The inner edge of the flange shows small radial compressive strain and tensile strain in thickness. Thus,the wall thickness on the inner edge of the flange continues to increase,although the increment is small. Furthermore,microstructure analysis and tensile test results show that the flanged thin?walled cylinder formed by DRCS has good mechanical properties. The results provide instructions for the application of the DRCS process.

Plastic Mechanism of Multi-pass Double-roller Clamping Spinning for Arc-shaped Surface Flange

Compared with the conventional single-roller spinning process, the double-roller clamping spinning（DRCS） process can effectively prevent the sheet metal surface wrinkling and improve the the production efficiency and the shape precision of final spun part. Based on ABAQUS/Explicit nonlinear finite element software, the finite element model of the multi-pass DRCS for the sheet metal is established, and the material model, the contact definition, the mesh generation, the loading trajectory and other key technical problems are solved. The simulations on the multi-pass DRCS of the ordinary Q235A steel cylindrical part with the arc-shaped surface flange are carried out. The effects of number of spinning passes on the production efficiency, the spinning moment, the shape error of the workpiece, and the wall thickness distribution of the final part are obtained. It is indicated definitely that with the increase of the number of spinning passes the geometrical precision of the spun part increases while the production efficiency reduces. Moreover, the variations of the spinning forces and the distributions of the stresses, strains, wall thickness during the multi-pass DRCS process are revealed. It is indicated that during the DRCS process the radical force is the largest, and the whole deformation area shows the tangential tensile strain and the radial compressive strain, while the thickness strain changes along the generatrix directions from the compressive strain on the outer edge of the flange to the tensile strain on the inner edge of the flange. Based on the G-CNC6135 NC lathe, the three-axis linkage computer-controlled experimental device for DRCS which is driven by the AC servo motor is developed. And then using the experimental device, the Q235A cylindrical parts with the arc-shape surface flange are formed by the DRCS. The simulation results of spun parts have good consistency with the experimental results, which verifies the feasibility of DRCS process and the reliability of the finite element model for DRCS.

Modeling and Analysis of a Random Excited Double-Clamped Piezoelectric Energy Harvester

A double-clamped piezoelectric energy harvester subjected to random excitation is presented,for which corresponding analytical model is established to predict its output characteristics.With the presented theoretical natural frequency and equivalent stiffness of vibrator,the closed-form expressions of mean power and voltage acquired from the double-clamped piezoelectric energy harvester under random excitation are derived.Finally theoretical analysis is conducted for the output performance of the doubleclamped energy harvester with the change of spectrum density（SD）of acceleration,load resistance,piezoelectric coefficient and natural frequency value,which is found to closely agree with Monte Carlo simulation and experimental results.

Numerical Simulation and Experimental Study of Heat-fluid-solid Coupling of Double Flapper-nozzle Servo Valve

The double flapper-nozzle servo valve is widely used to launch and guide the equipment. Due to the large instantaneous flow rate of servo valve working under specific operating conditions, the temperature of servo valve would reach 120℃ and the valve core and valve sleeve deform in a short amount of time. So the control precision of servo valve significantly decreases and the clamping stagnation phenomenon of valve core appears. In order to solve the problem of degraded control accuracy and clamping stagnation of servo valve under large temperature difference circumstance, the numerical simulation of heat-fluid-solid coupling by using finite element method is done. The simulation result shows that zero position leakage of servo valve is basically impacted by oil temperature and change of fit clearance. The clamping stagnation is caused by warpage-deformation and fit clearance reduction of the valve core and valve sleeve. The distribution roles of the temperature and thermal-deformation of shell, valve core and valve sleeve and the pressure, velocity and temperature field of flow channel are also analyzed. Zero position leakage and electromagnet＇s current when valve core moves in full-stroke are tested using Electro-hydraulic Servo-valve Characteristic Test-bed of an aerospace sciences and technology corporation. The experimental results show that the change law of experimental current at different oil temperatures is roughly identical to simulation current. The current curve of the electromagnet is smooth when oil temperature is below 80℃, but the amplitude of current significantly increases and the hairy appears when oil temperature is above 80℃. The current becomes smooth again after the warped valve core and valve sleeve are reground. It indicates that clamping stagnation is caused by warpage-deformation and fit clearance reduction of valve core and valve sleeve. This paper simulates and tests the heat-fluid-solid coupling of double flapper-nozzle servo valve, and the obtained results provide the reference value for the design of double flapper-nozzle force feedback servo valve.

二次装夹轴类零件同轴度精度控制方法研究

针对轴类零件在切削加工中需要二次装夹产生同轴度误差的现象,分别从测量误差和加工方法上对同轴度精度控制方法进行分析。以某典型轴类零件为例,分别从同轴度检测方法、原理上进行了误差探究,从加工方法上进行了三种方式的实践,得出采用定位误差补偿方法可以提高此类零件同轴度精度的结论。

SiC MOSFET串扰抑制驱动电路设计

SiC MOSFET相对于传统的Si MOSFET开关速度有明显的提升,但开关速度的提升引起电压/电流变化率的增大,器件寄生电感及布线电感等因素对电路的影响日益凸显。当器件自身的电压和电流变化时,会导致栅极-源极间产生预期以外的浪涌电压,从而导致开关管误导通。针对桥式电路上下管的串扰问题设计了一种外接无比较器米勒钳位的SiC MOSFET串扰抑制驱动电路。通过搭建双脉冲测试平台进行了实验验证,实验结果表明,所设计SiC MOSFET串扰抑制驱动电路能够有效抑制上下管之间的串扰,具有重要的工程应用价值。

基于液压变矩器的双环扣双向压紧钻孔装置设计与优化

在制造业的各个领域中,双环扣的应用非常普遍。在其生产过程中,准确的定位和加工方式对确保产品质量和提高生产效率十分重要。针对这一问题,提出并改进了一套基于液压变矩器的双向紧固钻孔装置。通过巧妙的工程布局和结构优化,使液压变矩器的双向固定结构得到了增强,同时双环形夹持构件经过优化设计,大大提高了整个工作装备的稳定性和可靠性。

碳化硅MOSFET驱动电路的研究与设计

随着碳化硅功率器件技术的不断发展,碳化硅功率器件发展优势明显,将逐步成为未来主流功率半导体器件。多家公司推出了多款碳化硅MOSFET,但是对于高压应用的碳化硅MOSFET驱动产品还处于半空白状态。文章针对A公司FF11MR12W1M1B11型碳化硅模块的驱动进行了研究与设计,在满足碳化硅驱动电流的基础上,增加了有源钳位保护、退饱和保护、故障信号反馈功能。有源钳位保护电路中具有动态有源钳位设计,在MOSFET关断时,降低嵌位电压来快速保护MOSFET,静态时抬高嵌位电压防止误动作。退饱和保护电路检测到故障后可迅速关闭驱动,并将故障信号进行反馈。通过双脉冲测试,验证了文中设计的驱动板功能,对FF11MR12W1M1B11型碳化硅模块在后续项目中的应用具有重要意义。

输电线路杆塔接地电阻测量装置设计

输电线路杆塔接地电阻测量对于电力运维人员是一项繁重的工作。为了实现在不解开接地引下线情况下即可测量杆塔的接地电阻,文章设计了一种新型输电线路杆塔接地电阻测量装置,该装置采用双钳法对接地电阻进行测量。首先,分析了新型输电线路接地电阻测量装置的原理;其次,采用模块化设计思路对接地电阻测量装置进行硬件设计;接着,对接地电阻测量装置进行软件设计,给出系统工作流程;最后,对所开发测量装置进行测试,所开发测量装置的测量值与精密电阻实际值误差在3%以内。

收获期油菜薹茎秆双层粘结离散元模型建立与优化

针对与油菜薹机械化收获中的切割、夹持输送、打捆等关键环节密切相关的油菜薹茎秆离散元仿真模型缺乏准确粘结参数的问题,以“油蔬两用”双低型油菜收获期油菜薹机械化夹持段茎秆为研究对象,利用EDEM仿真软件提出三轴空间坐标法构建油菜薹夹持中段茎秆双层粘结离散元仿真模型。采用Design-Expert软件依次设计了Plackett-Burman试验、最陡爬坡试验和Box-Behnken试验,完成油菜薹夹持中段茎秆仿真粘结参数标定。利用标定的参数优化解构建剪切和径向压缩模型进行相应仿真试验,通过与物理试验对比分析,对模型参数进一步优化。结果表明,内芯-内芯的法向/切向接触刚度、表皮-内芯法向/切向接触刚度,以及表皮-表皮法向接触刚度对茎秆力学性能影响显著,分别为1.94×107、9.56×108、6.28×109N/m;所有力学模型的仿真值与实测值相对误差不大于3%,且茎秆受力变化趋势基本一致,表明标定优化后的参数具有可行性和准确性。所构建的油菜薹茎秆双层粘结离散元模型能表征其内部结构的力学特性差异,可为油菜薹茎秆相关系统的数值模拟研究提供模型基础。

含双倍压DCM结构的高增益DC/DC变换器

为了增加直流变换器的电压增益,减少开关管的电压应力,将耦合电感倍压单元与二极管-电容(Diode capacitor multiplier,DCM)单元进行组合,提出一种双倍压DCM结构,将该结构引入含输出二极管的非隔离变换器中,不仅能提升该类变换器的电压增益,有效降低器件的电压应力,同时利用结构中的二极管-电容支路作为无源钳位支路吸收漏感能量,提高变换器的效率。并以含双倍压DCM结构的Sepic变换器为例进行了工作模态和工作性能的分析,推导了电感电流临界的工作状态,与同类型变换器进行了对比分析,充分证明了该类变换器具有高增益、低应力的优势。最后,搭建了一个60W的试验样机,验证了上述理论的正确性。

双U型地埋管换热器换热性能试验研究

双U型地埋管换热器(DUBTHE)在实际应用中易出现管路交叉,引起热短路,造成换热性能降低,直接影响浅层地源热泵系统的运行效率。以西安某浅层地源热泵项目为工程背景,基于无限长线热源理论和斜率法,通过现场岩土热响应试验、不同测温法测温试验,研究了岩土初始平均温度、导热系数和体积热容,及管卡间距对DUBTHE换热性能的影响。结果表明:多点式测温线缆测得的岩土初始平均温度为17.08℃,更接近实际地层温度。该地层的岩土综合导热系数和综合体积热容分别为1.65 W/(m·K)、2.81×10^(6 )J/(m^(3)·K)。DN25 DUBTHE的夏、冬季单位延米换热量随着管卡间距减小而增加,且增速随管卡间距的减小先增大后减小。当管卡间距分别为1、2、3、4 m时,DN25 DUBTHE的夏季单位延米换热量较无管卡分别提高了21.03%、19.48%、15.16%、3.92%;DN25 DUBTHE的冬季单位延米换热量较无管卡分别提高了20.83%、19.48%、14.94%、3.79%。工程中最优的管卡布置方式为2 m或3 m管卡间距的DN25 DUBTHE。研究结果可为关中地区浅层地源热泵系统的优化设计提供经验借鉴与数据支撑。

基于有限元法的导电滑环刷丝成型特性分析

导电滑环刷丝的工作性能对卫星的整体能源安全与在轨寿命有着至关重要的影响。为了保证信号和电流的实时传递,需要对刷丝角度进行控制。本研究通过有限元法的理论分析,建立了电刷板和刷丝的三维模型;结合显式动力学和隐式静力学的有限元模拟方法,确定了刷丝最佳的角度成型方式,完成了刷丝角度成型与回弹的有限元模拟;提出了一种基于有限元针对刷丝角度回弹过程的测量方法,并对刷丝回弹角的仿真值与理论值进行了对比分析。结果表明:与单侧偏转板和双侧短夹持板相比,双侧长夹持板对刷丝角度成型的作用方式最佳;刷丝的回弹角度与成型角度呈正相关,刷丝的成型角度越大,刷丝成型后的回弹变形值越大;刷丝成型角度在120°以上时,由于残余应力过大,所以刷丝材料很可能发生破坏。为了防止刷丝在发生弹塑性变形时其材料左侧根部发生破坏,应将夹持板左侧夹紧面尽量贴近刷丝左侧根部位置,对刷丝根部增加约束,以保证刷丝角度成型的质量;刷丝回弹角度的最大相对误差约为2°,但平均误差值在1°左右,总体回弹趋势基本一致,可以很好地表示出刷丝回弹角度的变化规律。

一种集成工程规则和卡箍调整的启发式布管算法

针对航空发动机外部管路布局规则多且效率低的问题,提出一种集成工程规则和卡箍调整的启发式布管算法。首先,在敷设层面内建立管路端口间的测地线方程,基于测地线建立路径的基准节点;其次,基于工程规则设计启发式搜索策略,快速求解符合工程规则的可行路径;在此基础上,为了使多管敷设方案满足双联卡箍约束,通过空间几何方法建立卡箍位姿变换方程,对多管敷设方案进行优化调整,实现基于双联卡箍约束的成束敷设。最后,通过多个敷设算例验证了该算法的可行性和高效性。

新型耦合电感高增益DC-DC变换器

为满足新能源并网母线所需的高增益直流电压输出,设计一种新型耦合电感高增益DC-DC变换器。拓扑引入耦合电路倍压单元进行变换器的增益调节,通过钳位回路吸收耦合电感的漏感能量,削减开关器件工作时的电压尖峰,提升变换器效率。对工作原理及模态进行分析,通过数学公式对器件应力、增益进行推演。与其他3种典型变换器进行性能比较,结合理论及实验,验证新型耦合电感高增益DC-DC变换器的可行性及有效性。

基于时域法的滑动式中间轴承抗冲击性能分析及结构优化

本文以某型舰用滑动式中间轴承为研究对象,建立基于时域法的中间轴承抗冲击数值模型,获得不同方向冲击载荷下的响应特性。进一步,针对冷却盘管在垂向冲击载荷作用下晃动幅度大并与轴承座发生剧烈碰撞的问题,采用双夹持机构的改进设计优化冷却盘管的支撑,分析优化后冷却盘管的响应特性以及夹持机构安装位置对冷却盘管响应特性的影响。研究结果表明:中间轴承主体部件在纵向冲击下响应最大,垂向最小;而冷却盘管响应规律则相反,其在垂向冲击下响应最大,并与轴承座发生剧烈碰撞,工作状况恶劣。优化后的冷却盘管在垂向冲击下最大应力下降了30.29%,并避免了剧烈碰撞现象的发生。轴承座、轴承盖在设计时应注意应力集中部位过渡圆角的控制,双夹持机构能有效改善冷却盘管的支撑,提高其抗冲击性能,且取安装系数为0.48~0.55的安装位置效果最佳。本文研究成果可为舰船滑动式中间轴承以及冷却盘管的结构设计与优化提供参考。

基于超声双波法的螺栓紧固力在线测量

为了保证螺栓处于稳定的连接状态,螺栓上需要施加一定大小的紧固力。现阶段,在役螺栓紧固力的测量仍是一个技术难题。提出了利用超声横波、纵波的双波声时比值法测量螺栓紧固力,并进行了测量验证,结果表明:双波法有较高的检测精度。研究了影响双波法测试精度的因素,提出了温度修正系数以补偿温度对螺栓紧固力测量的影响。该方法实现了在役螺栓紧固力的测量,具有较高的工程应用价值。

特高压输电线路新型接地线夹的研制与应用

针对目前现有特高压输电线路接地线夹挂设费时费力,效率低下问题,对接地线夹结构进行改进。采用内外双C型主体结构和辅助引导装置,并集成了啮合防脱的闭锁装置和基于“斜面原理”的操控装置,研制出特高压输电线路双C型接地线夹。经现场应用,发现新型接地线夹能够快速准确挂设,有效提高了工作效率、减轻了检修人员的劳动强度,提高了安全可靠性。

烟包纸箱折叠码垛机防脱防滑平衡双夹持拖箱装置的研究与应用

纸箱折叠码垛机是烟草制丝生产线上烟箱开包段的主要设备。FJ213型纸箱折叠码垛机拖箱装置,在夹箱和拖箱过程中常常因摩擦不平衡、夹具抓持力不足等产生纸箱拖偏卡箱或夹持脱落等现象,严重影响生产效率和质量。在原有拖箱装置夹紧机构的基础上,利用Workbench有限元仿真分析工具,应用新材料,创新设计夹具的结构和优化夹持方式,并在FJ213型纸箱折叠码垛机中成功应用,解决了该机型拖箱装置在夹箱和拖箱过程中出现的纸箱拉偏、卡箱以及夹持脱落等问题。

重型商用车前桥总成翻转平台设计

通过对重型商用车底盘装配线进行工艺分析,结合重型商用车前桥总成结构特点,研制了一种实现重型商用车前桥总成自动翻转的工作平台,该自动翻转平台能够消除人工翻转时存在的安全隐患,提高劳动生产率,将目前的前桥总成定位装配、翻转合为一个平台完成,工序节拍由6分钟缩短为5分钟,既提高装配线自动化程度又实现产能提升。