130×130曲柄飞剪剪切力能参数计算

建立了起停式曲柄飞剪机剪切力能参数的计算模型,并利用所建模型对130×130飞剪机进行计算分析。在飞剪机力能参数计算分析过程中,主要考虑电机是否能够在允许的启动角内启动、在剪切过程中能够释放足够的动能以及剪刃水平分速度是否大于等于轧件速度。传动系统的速降所释放动能提供剪切轧件所需的剪切功,根据电机起动平均力矩来确定电机功率。曲柄转速变化规律和飞轮尺寸决定传动系统所释放的动能大小。分析结果表明：可将所确定的起停式曲柄飞剪机剪切力能参数计算模型用于飞剪机剪切力能检验及同类飞剪机的设计。     

起停式曲柄飞剪剪切机构运动学性能分析

起停式曲柄飞剪 ,设计思路新颖 ,是目前较先进的飞剪机之一。针对起停式曲柄飞剪剪切机构的运动学模型 ,采用MATLAB程序设计语言将其程序化 ,得出了飞剪剪刃运动轨迹和剪刃速度变化曲线 ,对于了解飞剪剪切过程、定量分析剪切机构的工作性能和设计同类飞剪具有参考价值。     

起停式曲柄飞剪剪切机构运动学性能分析

起停式曲柄飞剪，设计思路新颖，是目前较先进的飞剪机之一。针对起停式曲柄飞剪剪切机构的运动学模型，采用MATLAB程序设计语言将其程序化，得出了飞剪剪刃运动轨迹和剪刃速度变化曲线，对于了解飞剪剪切过程、定量分析剪切机构的工作性能和设计同类飞剪具有参考价值。     

应用Inventor Professional建立起停式曲柄飞剪运动仿真

飞剪机（见图1）主要任务是将运行着的轧件按照工艺要求定尺剪断。随着轧机轧制速度和生产能力的不断提高，提高飞剪的速度和性能已成为生产中有待解决的问题。较先进的机型为起停式曲柄飞剪，飞剪一般处于静止状态，剪切时，采用低惯量大扭矩直流电动机，直接完成起动、剪切、制动等工艺过程。     

棒材启停式冷飞剪的设计新方法

介绍了某钢厂棒材车间引进的启停式曲柄冷飞剪的结构特点,分析其工作原理,研究其 机械设计的新方法.将解析法与CAD几何法相结合建立了冷飞剪剪切力能参数的计算模型,阐述了系 统转动惯量的确定方法和主传动电机的选择方法,并进行了仿真分析.结果表明,设计方法具有新颖独特、简单实用的特点,不但对于进行同类冷飞剪的设计或改进以及设备工艺参数的制定是可行的,也为其它机械设备的研究提供了新的思路.     

偏心摆式飞剪机剪切过程及机械参数的优化设计

本文依据对飞剪机的剪切过程中机构位置角、水平速度、轨迹的要求，确定优化设计变量，建立目标函数和约来函数，完成了基于Powell内点惩罚函数法的剪切机构优化设计模型，通过该模型对实际偏心摆式飞剪机剪切机构进行优化设计，使飞剪机的机械参数满足了剪切过程要求，同时提高了飞剪机剪切性能和轧件的剪切质量。     

启停式飞剪工作转角的分析与计算

启停式飞剪是棒线材生产线上重要设备,其设计计算复杂,除了对飞剪剪切能力计算外,针对飞剪剪刃在一个工作周期内的转角分析计算,来更加准确的分析所选传动电机是否适合.从而迭到优化设计目的.     

冷连轧机组滚筒式飞剪力能参数计算分析

以某1420 mm 冷连轧机组飞剪为例，对电机功率、加速时间等力能参数确定原则及与带钢剪切速度、剪切半径、转动惯量、加速范围的关系进行分析，并对现有飞剪启动工作制进行优化。     

冲切式飞剪系统的运动分析和数学建模

根据起停式飞剪机的剪切工艺要求,对整个工作周期全过程进行运动分析和数学建模,并据此推导得到原动构件运转的同步速度控制曲线,为控制系统建模提供理论依据.     

曲柄摇杆式飞剪剪切机构的优化设计

利用约束优化设计的直接解法--随机方向搜索法,基于多刚体系统动力学原理,对宝钢热轧厂主轧线设备曲柄摇杆式飞剪机的曲柄连杆机构进行杆长优化.编制C 程序,计算出若干组杆长组合,从中筛选出一组最优解.优化后,在剪切区,剪刃剪切倾角和连杆水平速度均匀性两项指标均有所提高.     

基于最小能量法的高速切削锯齿状切屑变形分析

以高速切削典型变形特征为研究对象,建立了锯齿状切屑的几何模型。根据高速切削绝热剪切理论,通过对剪切面相对滑移失稳瞬间的切屑块受力平衡分析建立力学模型和运动学模型,获得切屑摩擦力和剪切力及剪切速度和切屑流动速度,并确定了切削能量方程。在考虑应变、应变率、切削温度和变形硬化因素条件下按最小能量原理求变形方程,结合变形曲线的分析和切削理论确定了高速切削变形方程及影响变形的因素。分析结果表明,切屑锯齿化是塑性变形超过临界失稳条件的结果。     

Nonlinear thermodynamic model of boundary friction

Melting of an ultrathin lubricant film confined between two atomically flat surfaces is studied. An excess volume parameter is introduced, the value of which is related to the presence of defects and inhomogeneities in the lubricant. Via minimization of the free energy, the Landau-Khalatnikov kinetic equation is obtained for this parameter. The kinetic equation is also used for relaxation of elastic strains, which in its explicit form contains the relative shear velocity of the rubbing surfaces. With the numerical solution of these equations, a phase diagram with domains corresponding to the sliding and dry stationary friction regimes is built at a fixed shear velocity. A simple tribological system is used to demonstrate that in the dynamic case, three friction regimes can occur, namely, dry, stick-slip, and sliding friction. It is shown that a lubricant can melt when the shear velocity exceeds a critical value and with elevation of its temperature. The dependence of the dynamic friction force on the pressure applied to the surfaces, the temperature of the lubricant, and the shear velocity is considered. It is shown that growth of pressure leads to the forced ordering and solidification of the lubricant.     

Squeeze fluid film of spherical hydrophobic surfaces with wall slip

Isothermal squeeze film flow of Newtonian fluid between spherical hydrophobic surfaces with wall slip is investigated using a limiting shear stress model and complementary algorithm. Wall slip velocity is controlled by the liquid–solid interface limiting shear stress. It is found that the wall slip dramatically decreases the hydrodynamic support force of the squeeze fluid film. In the case of large wall slip the hydrodynamic support force increases only slightly with the decrease in the film thickness. We find that wall slip decreases with increasing film thickness and limiting shear stress, but increases with increasing fluid viscosity and approaching velocity. An empirical equation is given for prediction of the fluid load support capacity. The possible effect of pressure on wall slip is also discussed. It is found that fluid pressure suppresses wall slip after the proportionality coefficient of limiting shear stress reaches a critical threshold. However, almost no effect is found when it is below this critical threshold. Good agreements exist between the present theoretical predictions and some existing experimental observations.     

6 km自容式湍流观测剖面仪设计与试验研究

目前大部分湍流观测剖面仪的观测范围在1 km以浅。为获取深海湍流数据,探究深海动力过程演变机制与能量耗散过程,研制6 km自容式湍流观测剖面仪。从湍流观测应用的翼型剪切流传感器测量原理出发,分析约束深海剖面仪设计的关键技术,开展了深海剖面仪稳定水动力布局设计、耐压6 km的轻量化结构设计、下潜速度分析与控制设计。观测传感器集成微结构的双PNS系列翼型剪切流传感器与FP07快速温度传感器,实现了深海湍流两个维度下湍动能耗散与热耗散的同步、高速观测,采用模块化的设计思想完成自容式湍流观测硬件系统的设计。通过性能检测试验,剖面仪可满足6 km应用,下潜速度线性可调范围0.4~0.9 m/s,验证了剖面仪结构设计的可行性;海上试验,并与MSS90进行比测,剖面仪测量湍流脉动剪切变化趋势与MSS90相同,计算的湍流剪切波数谱与Nasmyth理论谱在截止波数前非常吻合,相同深度的湍动能耗散率与MSS90为同一数量级,验证了深海6 km自容式湍流观测剖面仪湍流测量的准确性。     

What determines static friction and controls the transition to sliding?

We studied the shear response of a confined lubricant layer on approach of the transition to sliding with a surface force apparatus modified for oscillatory shear. In a given experiment, we found that the transition to sliding occurred always around the same deformation amplitude although the shear stress needed to initiate sliding varied up to a factor of two depending on sample history. This suggests the concept of deformation-controlled switching from rest to sliding. The elastic spring-constant, in the stick state, weakened with increasing deformation amplitude. This decrease can be described by a power law when plotted versus the distance to a critical deformation amplitude. The build-up of solid-like behavior after sliding stopped was also gradual and was consistent with a logarithmic time dependence. We suggest a model relating the gradual decrease of stiffness to weakening of the boundary layer, specifically to destruction of some elastic links between molecules or between molecules and the solid surfaces. Static friction (the force that must be overcome at the onset of kinetic motion) is proportional to the number of such links formed during the time of stick.     

基于SH导波的防腐层能量密度检测机理研究

涂敷防腐层是确保油气管道完整性非常重要的手段,但因环境或外力等因素使防腐层产生剥离、孔洞等缺陷。本文针对埋地管道外涂防腐层轴向剥离、孔洞缺陷,利用粘弹性动力学理论建立能量平衡单元体F的双层结构波动模型,对单元体F的频散特性、能量密度和导波衰减进行理论分析和数值计算,并设计SH-EMAT换能器进行了防腐层剥离缺陷实验研究。研究表明:防腐层剥离程度可引起单元体F中各模态频散特性变化,防腐层剥离厚度越大,SH导波模态对应相速度、群速度越大,且差异显著。在一定频率范围内,其相速度与防腐层剥离缺陷尺寸成正比。导波能量衰减依赖于能量密度因子QE且独立于导波模态,能量密度趋向于防腐层等效粘弹性介质的剪切速度倒数;单元体F中能量密度因子QE的特征参数可为管道防腐层剥离、孔洞缺陷内检测的量化研究提供理论依据。     

Velocity dependent friction laws in contact mode atomic force microscopy

Friction forces in the tip–sample contact govern the dynamics of contact mode atomic force microscopy. In ambient conditions typical contact radii between tip and sample are in the order of a few nanometers. In order to account for the large interaction area the dynamics of contact mode atomic force microscope (AFM) is investigated under the assumption of a multi-asperity contact interface between tip and sample. Thus, the kinetic friction force between tip and sample is the product of the real contact area between both solids and the interfacial shear strength. The velocity strengthening of the lateral force is modeled assuming a logarithmic relationship between shear-strength and velocity. Numerical simulations of the system dynamics with this empirical model show the existence of two different regimes in contact mode AFM: steady sliding and stick–slip where the tip undergoes periodically stiction and kinetic friction. The state of the system depends on the scan velocity as well as on the velocity dependence of the interfacial friction force between tip and sample. Already small viscous damping contributions in the tip–sample contact are sufficient to suppress stick–slip oscillations.     

基于斜角切削的曲线端铣切削力建模

切削力预测是制定与优化加工工艺的重要环节。针对曲线端铣加工过程,提出一种基于斜角切削的切削力建模方法。将刀具沿轴向微分,以曲线微分几何计算微元刃上的工作基面。在微元刃的工作法平面参考系中,应用最小能量原理,构建微元刃中力矢量、速度矢量、流屑角、法向摩擦角、法向剪切角及剪应力等切削参数之间的约束。以单齿直线铣削试验对切削参数进行标定,其中法向摩擦角、法向剪切角及剪应力等可表示为瞬时未变形切屑厚度的函数。选取高强度钢PCrNi3MoVA试件,分别进行圆弧和Bézier曲线端铣加工试验。试验结果表明,曲线端铣时切削力的变化与瞬时进给方向和曲线曲率相关。切削力预测值的幅值大小和变化趋势与试验值一致,验证了该切削力建模方法的有效性。     

对剪力引起梁弯曲变形的思考和探索

应用变形能法对矩形、圆形、工字形截面梁在剪力作用下的弯曲变形进行了定量分析比较。结果得出,剪力对梁弯曲变形的影响与梁的截面形状、跨度、截面高度等因素有关。认为在有些情况下,剪力对弯曲变形的影响相当大,不能略去,进而为合理设计梁的结构提供科学可靠的理论依据。