同步辐射仪器中柔性铰链压弯机的研究

阐述了一种应用柔性铰链产生精密光学反射镜的弹性压弯机构的工作原理。应用经典力学方法对这种压弯机构进行了详细的力学分析 ,并将这种弹性压弯机构简化成平面钢架结构 ,用力法正则方程和梁的弯曲方程推导得出镜子的曲率与压弯机构参数及压弯驱动力之间的关系 ,即压弯机构驱动方程或镜子曲率方程。对影响镜子面形精度的弹性压弯机构参数进行分析 ,重点讨论了弹性压弯机构转动中心轴和镜子中性面不重合时对镜子面形精度的影响。分析了柔性铰链在这种弹性压弯机构中的作用及其对镜子面形精度的影响。并应用有限元数值计算方法对经典力学分析得出的压弯机构驱动方程进行验证 ,证实了经典力学分析的正确性。此压弯机构驱动方程可以作为这种弹性压弯机构设计的理论基础。

5MN压弯机油缸颤抖故障分析与排除

本文通过仔细分析压弯机的工作原理和在工作中出现的故障现象 ,利用故障分析方框图 ,找出故障点 ,顺利排除了故障。

压弯机自动定位控制系统改进探讨

目前所生产的压弯机的尺寸调整机构是用人工移动挡料板,用直尺等工具配合,实际测量挡料板的移动距离。这种调整机构与定位方式,不仅费时费工,而且也难保证一定的弯曲尺寸精度。针对以上问题,我们提出改进,在压弯机上采用单片微机自动定位装置,既定位实现了快速、准确、自动化,提高了折弯机的生产效率又提高了加工精度和操作性能。本系统主要由机械和电器两部分组成。机械部分主要由固定支架、丝杠、异形导轨等组成。电气部分主要由步进电机、PLC、触摸屏等主要部分组成。它的原理是通过触摸屏驱使PLC的程序控制步进电机的精确转动,再通过丝杠及异形导轨等组件,实现对要压弯的钢板精确定位。

轻便移动式液压钢板压弯机

介绍一种轻便移动式液压钢板压弯机 ,它比通用压弯机更适合于中、小规模施工现场操作使用 ,且维修方便。

装载机槽钢大梁3种制造方法的比较

自１９７２年我厂生产装载机以来，共采用过３种型式的槽钢大梁。（１）直接气割下料而成的槽钢大梁采用材质为Ａ３钢的热轧槽钢２５Ｃ直接气割下料而成。此法简单方便，下料规则，省时省力。但随着装载机吨位的增加其受力变得更加严重，加上槽钢２５Ｃ往往因锈蚀严重实际...

弯曲成形数值模拟与数控系统研究

弯曲在工业生产中是一种重要成形工艺。研究弯曲过程以减小回弹,有着十分重要的意义。本文简单介绍了弯曲成形工艺过程,建立了系统控制模型,并开发了弯曲成形过程计算机模拟与数控软件系统,实现了弯曲成形过程的计算机模拟和控制,提高了成形精度。

板料厚度误差对弯曲质量影响的分析

分析了板料厚度偏差对压弯机压制工件角度造成误差的原因，认为它是由于材料厚度偏差对压弯机行程调节的影响所造成的。据此提出了一种解决措施，并提供了有效的计算程序。

辐射测量与装置

O432.1 2003031631同步辐射仪器中柔性铰链压弯机的研究=Research on theflexural hinge-based bender in a synchrotron radiation instru- ment[刊,中]/曲艳峰(上海大学精密机械工程系.上海(200072)),吕丽军∥光学精密工程.—2002,10(2).—220-225阐述了一种应用柔性铰链产生精密光学反射镜的弹性压弯机构的工作原理。应用经典力学方法对这种压弯机构进行了详细的力学分析,并将这种弹性压弯机构简化成平面钢架结构。

大型角钢的弯制

在生产中经常会遇到角钢的平直或弯制。对于小型角钢来说,弯制比较容易,采用滚床或人工弯制都很简单。而对于大型角钢来说,弯制则比较困难。如果进行冷弯。一般的设备完成不了;而采用热弯,人工、燃料等消耗都较大,费时费力,效率低,而且一般弯制质量不太高。况且,有时工艺要求不允许热弯。 我们在丹东沙河口大桥施工中遇到大桥主拱肋的20/12.5-12角钢弯制成悬链线形弧状。按工艺要求,

Aerodynamic performance of high-turning curved compressor cascade with boundary layer suction

The impact of boundary layer suction on the aerodynamic performance of a high-turning compressor cascade was numerically simulated and discussed.The aerodynamic performance of a curved and a straight cascade with and without boundary layer suction were comparatively studied at several suction flow rates.The results showed that boundary layer suction dramatically improved the flow behavior within the flow passage.Moreover,higher loading over the whole blade height,lower total pressure loss,and higher passage throughflow were achieved with a relatively small amount of boundary layer removal.The integration of curved blade and boundary layer suction contributed to better aerodynamic performance than the cascades with only curved blade or boundary layer suction used,and the more favorable effect resulted from the weakening of the three dimensional effects of the boundary layer close to the endwalls.

Rate-Dependent Hysteresis Modeling and Compensation of Piezo-Driven Flexure-Based Mechanism

Updating parameters according to the driving rate of input, the rate-dependent Prandtl-Ishlinskii （PI） model is widely used in hysteresis modeling and compensation. In order to improve the modeling accuracy, two PI models identified at low and high driving rates separately are incorporated through a combination law. For the piezo- driven flexure-based mechanism, the very low damping ratio makes it easy to excite the structural vibration. As a re- suit, the measured hysteresis loop is greatly distorted and the modeling accuracy of the identified P1 model is signifi- cantly affected. In this paper, a novel time-efficient parameter identification method which utilizes the superimposed sinusoidal signals as the control input is proposed. This method effectively avoids the excitation of the structural vibra- tion. In addition, as the driving rate of the superimposed sinusoidal signals covers a wide range, all the coefficients required for modeling the rate-dependence can be identified through only one set of experimental data. Hysteresis modeling and trajectory tracking experiments were performed on a 2-DOF piezo-driven flexure-based mechanism. The experimental results show that the combined hysteresis model maintains the modeling accuracy over the entire work- ing range of the flexure-based mechanism. The mechanism＇s hysteresis is significantly suppressed by the use of the inverse PI model as the feedforward controller; and better result is achieved when a feedback loop is also incorporated. The tracking performance of the flexure-based mechanism is greatly improved.

Energy-Saving Design for Hydraulic Tube Bender

Generally speaking, hydraulic control systems can be divided into two different driving concepts. The first one is the well-known hydraulic valve-controlled system and the second one is the pump-controlled system. The former possesses the feature of fast dynamic response. However, the poor energy-saving performance is its major fault. On the contrary, the hydraulic pump-controlled system has the significant advantage of energy-saving which meets the current demand in modem machine design. In this paper, the simulation analysis using MatLab/SimuLink and DSHplus software for a newly developed energy-saving hydraulic tube bender is conducted. Instead of the conventional fixed displacement hydraulic pump, the new hydraulic tube bender utilizes an internal gear pump with AC servomotor as its driving power source. In the new energy-saving hydraulic circuit, the use of conventional pressure relief valve and unloading valve are no longer necessary since the demanded flow-rate and pressure output can be precisely obtained by continuously changing the speed of the AC servomotor. In addition, two closed-loop control schemes using fuzzy sliding-mode controller are adopted and compared. To compare the energy-saving control systems, such as load-sensing control system, constant supply pressure control scheme and conventional hydraulic control scheme. Furthermore, the simulation results also show that the newly developed hydraulic tube bender can save up to 43% of energy consumption in a working cycle as compared to the conventional hydraulic tube bender.

Improved model to solve influence coefficients of work roll deflection

According to the concept of virtual bending force,a rational explanation for SHOHET's model was presented. Considering the deformation characters of the work rolls in four-high mill,the deformation model of the work roll was regarded as a cantilever beam and new influence coefficients were deduced.The effect of the bending force was taken into account independently. Therefore,the contribution to work roll deflection caused by rolling load,rolling pressure between rolls and bending force can be got from the new formulas.To validate the accuracy of the formulas,the results obtained from the new formulas were compared with those from SHOHET's formulas.It is found that they highly coincide,which illustrates that the formulas are reliable.

Effects of blade bowing on the performance of a high pressure-ratio turbocharger centrifugal compressor with self-recirculation casing treatment

The effects of blade bowing on the performance of a high pressure-ratio turbocharger centrifugal compressor were studied by experiments and numerical simulation.The results showed that the negative bowing was capable of increasing the choke mass rate and the efficiency but decreased the surge mass flow rate,while the positive bowing had the opposite effects.When coupling with the self-recirculation casing treatment,the surge mass flow rate of the compressor with negative bowing blade was almost identical with that of the prototype,while the choke mass flow rate was still larger,and the total effect contributed to an increase of the stable flow range by 5.85%at design speed.Besides,the flow mechanism of the coupling effects of blade bowing and self-recirculation casing treatment was discussed.

Effect of a Curved Duct Upstream on Performance of Small Centrifugal Compressors for Automobile Turbochargers

Since the automobile turbochargers are installed in an engine compartment with limited space, the ducts upstream of the turbocharger compressor may be curved in a complex manner. In the present paper, the effect of a curved duct upstream on performance of small centrifugal compressors for automobile turbochargers is discussed. The computational fluid dynamics (CFD) analysis of a turbocharger compressor validated for the compressor model with the straight pipe applied to the compressor with the curved pipe are executed, and the deterioration of the performance for the curved pipe is confirmed. It is also found that the deterioration of compressor performance is caused by the interaction of the secondary flow and the impeller.

Upper bound solution of supporting pressure for a shallow square tunnel based on the Hoek-Brown failure criterion

To analyze the stability of a shallow square tunnel, a new curved failure mechanism, representing the mechanical characteristics and collapsing form of this type of tunnel, is constructed. Based on the upper bound theorem of limit analysis and the Hoek-Brown nonlinear failure criterion, the supporting pressure derived from the virtual work rate equation is regarded as an objective function to achieve optimal calculation. By employing variational calculation to optimize the objective function, an upper bound solution for the supporting pressure and the collapsing block shape of a shallow square tunnel are obtained. To evaluate the validity of the failure mechanism proposed in this paper, the solutions computed by the curved failure mechanism are compared with the results calculated by the linear multiple blocks failure mechanism when the Hoek-Brown nonlinear failure criterion is converted into the Mohr-Coulomb linear criterion. The influences of rock mass parameters on the supporting pressure and collapsing block shape are discussed.

Effects of Bending-torsional Duct-induced Swirl Distortion on Aerodynamic Performance of a Centrifugal Compressor

A turbocharger compressor working in commercial vehicles, especially in some passenger cars, often works together with some pipes with complicated geometry as an air intake system, due to limit of available space in internal combustion engine compartments. These pipes may generate various distortions of physical parameters of the air at the inlet of the compressor and therefore the compressor aerodynamic performance deteriorates. Sometimes, the turbocharging engine fails to work at some operation points. This paper investigates the effects of various swirl distortions induced by different bending-torsional intake ducts on the aerodynamic performance of a turbocharger compressor by both 3D numerical simulations and experimental measurements. It was found that at the outlet of the pipes the different inlet ducts can generate different swirl distortions, twin vortices and bulk-like vortices with different rotating directions. Among them, the bulk-like vortices not only affect seriously the pressure distribution in the impeller domain, but also significantly deteriorate the compressor performance, especially at high flow rate region. And the rotating direction of the bulk-like vortices is also closely associated with the efficiency penalty. Besides the efficiency, the transient flow rate through a single impeller channel, or the asymmetric mass flow crossing the whole impeller, can be influenced by two disturbances. One is from the upstream bending-torsional ducts; other one is from the downstream volute.