新型钢板滚切剪剪切机构运动学分析

通过对新型滚切剪空间剪切机构的原理分析,建立以关键点坐标为变量的剪切机构显式三维非线性轨迹方程,并对确定导向杆与机架铰接点位置的求解理论给予修正。以某大型钢厂2 800 mm单轴双偏心滚切剪的研发项目为依托,对剪切机构的运动轨迹进行模拟仿真。上下剪刃重叠量、刀弧水平偏移量的计算结果表明,应用显式轨迹方程组及修正的导向杆约束理论,是提高轨迹求解精度、优化杆件尺寸、降低刀弧水平位移量、提高剪刃重叠量均匀度的重要手段。现场剪机重叠量、刀弧水平综合位移量的实际值及高质量的钢板剪切断面也证实了上述剪切机构运动学理论及导向点约束修正理论的正确性。     

基于ADAMS的IHI摆式飞剪剪切机构特性分析与优化

为探究IHI摆式飞剪剪切机构特性及优化方法,分析了IHI摆式飞剪剪切机构的结构组成和工作原理, 通过数值方法推导了剪切机构几何位置的解析法公式,计算出剪切机构初始位置.基于ADAMS动力学分析软件,建立飞剪剪切机构的机构杆件模型.仿真分析再现了飞剪的运动过程,得到剪切机构上、下剪刃的运动轨迹,速度变化曲线,剪刃开口度变化曲线和剪切过程中详细数据值.针对分析结果,利用ADAMS进行结构优化设计.优化结果改进了飞剪剪切过程中的速度超前和滞后问题,有利于剪切过程以及轧制工艺.基于ADAMS的分析方法与优化结果对IHI飞剪剪切机构的结构设计与改造具有实际运用价值.     

滚切式双边剪的修配改

滚切式双边剪是70年代初发展起来的一种新型中厚板剪切设备,因其弧形上刀刃在平直下刀刃上作滚动剪切．在剪切范围内刀片重叠量和剪切角几乎不变,被剪钢板两纵边的平行度好、接口错边量小、切口断面光滑、便于实现自动化,剪切效率高等优点,近年来国外新建或改建的现代化中厚板生产线广泛应用滚切式双边剪。     

滚切式双边剪剪切相关问题分析

随着社会经济和科学技术的发展,市场对于宽厚板的外观和质量要求也日益提高,而滚切式双边剪是确保宽厚板剪切平直、光滑和高精度生产的重要设备。本文主要概述了厚板厂滚切式双边剪,并分析了滚切式双边剪剪切的常见问题,并提出了提高双边剪剪切效率的对策。     

中厚板切边圆盘剪的设计与结构分析

本文利用计算机辅助系统,借鉴国外的先进技术,自主设计了国产化的中厚板切边圆盘剪,主要阐述了其结构特征及工作原理,并对主要结构件进行了参数制定分析,剪刃重叠量及侧隙对剪切质量的影响。     

基于 ADAMS 的模切机双肘杆机构优化设计研究

利用MSC.ADAMS对模切机双肘杆机构进行了参数化建模,通过建立双肘杆机构优化目标函数,实现了双肘杆机构的结构尺寸参数化优化分析,并进行了相关的运动学、动力学仿真。优化结果表明,减小动平台与水平方向的震动偏角和在水平方向的位移,将大大提高模切速度、精度和整机的稳定性。     

圆盘剪剪切中板间隙值浅析

圆盘剪剪切钢板过程中,如果能采用合理适合的方法来调整剪切时的间隙,可以保证切过质量,又能使剪刃承受适合的剪切力避免崩刀的风险和减小磨损。因此对剪切中板的间隙值进行攻关优化,确定调整间隙值的规律。     

10 kV真空断路器弹簧操动机构合闸传动优化设计

真空断路器弹簧操动机构中四杆机构杆件结构与合闸弹簧参数对动触头合闸速度和位移特性具有直接影响,包括冲程弹跳与机构磨损量等。以10kV断路器用弹簧操动机构为对象,采用SolidWorks软件建立运动系统三维模型;引入动力学仿真软件ADAMS对三维模型进行运动特性分析。在保证分闸储能位分闸弹簧压缩量不变的条件下,以连架杆与连杆尺寸、合闸弹簧预紧拉力为优化变量,以动触头最高瞬时速度最低和相对杆长之和最小为目标,采用DOE参数化分析方法对机构进行多参数多目标优化设计,以调控机构输出特性。     

位移约束桁架尺寸优化设计的改进齿形法

该文提出一种改进齿形法应用于具有应力与位移约束的桁架尺寸优化问题。对于应力约束所需的杆件截面积由杆件各工况荷载下的最大内力来确定。对于位移约束所需的杆件截面积,按当前迭代位移比最大的位移约束、采用桁架满位移设计准则确定。分别计算应力约束和位移约束的杆件截面积比,取二者较大者并施加松弛系数作为准则步时杆件截面积更新的参数。对三杆及十杆平面桁架的算例进行了优化设计研究,结果表明该文提出的方法稳定性好、收敛速度快、优化效果好、应用简单。     

复合材料层板冲击剪切实验技术研究

基于HOPKINSON杆冲击剪切试验技术、复合材料层板的材料性能及应用特点的分析,对“杆-管”冲击剪切动态力学性能实验技术进行了改进优化,解决了输入杆跳动、同轴调节困难、结果分散大等实验技术问题。根据输入杆、输出管和复合材料试样的匹配分析,确立了输入杆、试样和输出管针对动态冲击剪切实验的约束尺寸条件。通过有限元数值分析,研究了预置剪切间隙对冲击剪切的影响,研究认为0.2mm～0.3mm间隙设计对Ф14.5mm输入杆冲击 2mm～4mm层板试样的冲剪试验是合适的。冲击剪切实验数据表明,加载率对玻纤增强复合材料层板的动态剪切力学性能影响明显。     

振动剪切流场的等效稳态剪切速率

根据瞬态网络结构理论,建立了振动剪切流场中聚合物熔体缠结密度的动态速率微分方程。计算结果表明,当振动剪切达到动态平衡时,缠结密度在平衡位置处周期性地波动,其时均值等于稳态剪切速率下的缠结密度。因此,在时均意义上,振动剪切流的时均网络结构状态可等效为稳态剪切流的缠结平衡状态。通过计算发现:当应变振幅小于1.7时,等效稳态剪切速率可取振动剪切速率的周期平均值,由此产生的均方根误差随着应变振幅增加而增大,但小于0.017;而当应变振幅大于1.7时,则取峰-峰均值作为等效剪切速率,其均方根误差随着应变振幅增加而减小。     

盒形件拉深时法兰变形区的剪应力与剪切变形

针对盒形件拉深成形时法兰变形区的变形进行了材料塑性流动的理论分析,提出了位移速度差诱发剪应力的观点。通过试验证明了剪切变形是盒形件拉深成形时法兰变形区的主要变形方式之一,剪应力与剪切变形的分布规律构成了盒形件成形的自身特点。     

Localization of Plastic Shear under Impact Loading

Experimental results on shear localization in disk (HAT-type) specimens under impact loading conditions are presented. The results of metallographic analysis of the plastic flow region were used to obtain the characteristic strain distribution across the shear band.     

对冷冲模具冲裁间隙的商讨

通过冲裁间隙对冲裁断面、冲裁力的影响,提出合理冲裁间隙。     

Compression Shear Test (CST) – A Convenient Apparatus for the Estimation of Apparent Shear Strength of Composite Materials

A convenient apparatus for the determination of apparent shear strength of flat as well as curved composite materials and adhesive joints, the compression shear device (CSD), is described in detail. Compared with other commonly used tests the sample preparation is very easy, inexpensive, and consumes less material. The obtained values of apparent shear strength for different classes of materials are comparable with values determined by established tests. Using an additional extensometer, the estimation of shear strain and shear modulus is also possible with the proposed equipment.     

巨型水轮发电机剪断销研发与质量控制

为获得设计需要的巨型水轮发电机剪断销的剪切力,得到剪切力波动受控的批量剪断销,通过拉伸试验、冲击试验、硬度试验和剪断销剪切试验等讨论了全尺寸剪断销剪切试验的可行性,分析了剪切试验时正常剪断和非正常剪断的剪断销材料性能差异,探究了剪断销的剪切力质量稳定性控制方法。结果表明:控制剪断销料坯的布氏硬度波动,可实现间接控制剪断销剪切强度的波动;通过试验总结的六步法可达到控制批量剪断销质量和剪切力波动的目的。     

Visualization of Shear Motions of Cohesive Powders in the True Biaxial Shear Tester

Steady-state flow of powders is defined as a continuous deformation of the material without volume change while the stresses at the specimen's boundaries remain constant. Recent investigations have shown that this state, especially for cohesive powders, is not always as steady as it should be by definition. In this article a recent extension of the true biaxial shear tester is introduced that allows a view of the shear motion of the brick-shaped powder specimen inside the tester. By applying a dark-colored powder pattern onto a light powder sample, the movement of the powder can be captured using a CCD camera. Development of shear bands and inhomogeneities of the sample can be visualized. Experiments with a cohesive powder with purely strain-controlled, volume-preserving shear cycles, as well as mixed stress-strain controlled experiments, are presented. The recorded images as well as stress-strain data from discrete elements simulations are compared to the experimental results.     

The Effect of Friction on Wide Shear Bands

Frictional and frictionless granular materials in a split-bottom ring shear cell geometry show wide shear bands under slow, quasi-static deformation. Here, the differences between frictional and frictionless materials are elaborated using discrete element simulations (DEM). Several continuum fields like the density, the velocity field, the deformation gradient, and the stress are used here for comparison.

Interestingly, the shear stress intensity, i.e., the shear stress divided by the pressure, is approximately constant throughout the wide shear band, as long as the strain rate is large enough—indicating a Mohr-Coulomb type yield stress fluid. The “viscosity,” i.e., the shear stress divided by the strain rate, is proportional to the pressure, which is increasing with the contact number density. Furthermore, the viscosity is inversely proportional to the nondimensional strain rate, indicating shear softening behavior inside the wide shear bands.     

Visualization of Shear Motions of Cohesive Powders in the True Biaxial Shear Tester

Steady-state flow of powders is defined as a continuous deformation of the material without volume change while the stresses at the specimen's boundaries remain constant. Recent investigations have shown that this state, especially for cohesive powders, is not always as steady as it should be by definition. In this article a recent extension of the true biaxial shear tester is introduced that allows a view of the shear motion of the brick-shaped powder specimen inside the tester. By applying a dark-colored powder pattern onto a light powder sample, the movement of the powder can be captured using a CCD camera. Development of shear bands and inhomogeneities of the sample can be visualized. Experiments with a cohesive powder with purely strain-controlled, volume-preserving shear cycles, as well as mixed stress-strain controlled experiments, are presented. The recorded images as well as stress-strain data from discrete elements simulations are compared to the experimental results.     

Shear strength of plain concrete

Concrete shear strength is one of important parameters in structural design and analysis. Brittle failure of concrete under shear has substantial impact on performance of structure. Concrete shear strength as stipulated in standard codes of different nations is based on RC beam elements. Majority of research also focused on reinforced elements or on indirect shearing. There have been few studies performed on plain concrete subjected to pure shear. Hence, pure shear strength of plain concrete is not established. In light of foregoing, the present work attempts to build loading method that is efficient and capable of creating uniform shear force in standard specimen. The study investigates fracture behaviour of plain concrete when subjected to pure shear force. The pure shear state of specimen is verified using Mohr's circle method. FEA is performed to validate experimental data. The proposed test set-up is effective in determining pure shear strength of plain concrete.