A simplified approach for negative skin friction calculation of special-shaped pile considering pile-soil interaction under surcharge

A simplified approach was proposed to analyze the negative skin friction calculation of special-shaped pile considering pile-soil interaction under surcharge. Based on the concentric cylinder shearing theory, considering the changes of pile shape(such as, taper angle and diameters of pile base, etc.), the load-transfer of special-shaped pile was built. The accuracy of the developed simplified approach was verified by numerical simulation model with the same condition. Then, the influence factors, such as, taper angles, the diameter of pile base, surcharge, and pile-soil interface parameters were analyzed and discussed. The results show that the developed simplified approach can calculate NSF of special-shaped pile under surcharge effectively. A limited parametric study indicates that in many practical situations special-shaped piles(such as belled wedge pile shown in this work) offer a design option that is more economical than traditional uniform cross-section piles.

Experimental Study on Seismic Behavior of Exterior Joints of Special-shaped Columns with Different Lengths of Limbs

Four exterior joints with special-shaped columns which have different lengths of limbs are tested under low cyclic loading. Speeial-shaped columns adopted are L- and T-shaped in section. It can be concluded that crack pattern, failure mode and shear strength of joints are affected by the length of limb, and that shear strength and ductility increase with the length of limb; the joints with the flexural failure of the beam have better seismic behavior than those with the shear failure of the joint core.

Design of Special-shaped Interchange between Expressway and Urban Road in Mountainous Cities

Driven by the rapid economic development,the development of transportation in China has begun to move towards mountainous areas.The climate environment,topography and landform of mountainous cities are different from those of plain areas.In mountainous cities,the area of opposite interchanges between expressways and urban roads is generally large,which has a certain contradiction with the topographic conditions of mountainous cities.Therefore,it is necessary to reasonably design the opposite interchanges between expressways and urban roads in mountainous cities.The author explores and analyzes the factors restricting the special-shaped interchange between expressway and urban road in mountainous cities and the main fbnns of special-shaped interchange,and puts forward a reasonable design scheme,hoping to make a smooth development of the special-shaped interchange in mountainous cities.

Optimizing Multi-Row Cam Roller Bearing for Long Fatigue Life of Hydraulic Motors

Cam-lobe radial-piston hydraulic motors are widely used as rotation driving units for various marine machinery owing to their ultrahigh output torque(more than 100 kN m).A multi-row cam roller bearing(MCRB)is the key component that directly determines the fatigue life of a cam-lobe radial-piston hydraulic motor.However,compact geometry and complex loads render MCRB susceptible to fatigue failure,highlighting the need for an optimized MCRB to achieve longer fatigue life and higher reliability.Therefore,this study proposes an innovative geometry optimization method for an MCRB to improve its fatigue life.In this method,a quasi-static model was developed to calculate the load distribution,with the fatigue life of the MCRB calculated using both basic dynamic loading and load distribution.Subsequently,a genetic algorithm was used to obtain the optimized geometry parameters,which significantly improved the fatigue life of the MCRB.Finally,a loading test was conducted on a hydraulic motor installed with both the initial and optimized MCRB to validate the effectiveness of the proposed optimization method.This study provides a theoretical guideline for optimizing the design of MCRB,thereby increasing the fatigue life of hydraulic motors.

Roller Screw and Threaded Chain Speed Reducer: An Experimental Evaluation

We are developing a speed reducer that can be considered a transformation of a worm gear reducer: the worm is replaced by an inverted roller screw, and the gear is replaced by a threaded chain drive. This configuration lessens wear, increases load capacity, and improves efficiency. The threaded chain consists of nut-shaped links. This paper presents the results of tests carried out on a prototype with a reduction ratio of 46.

高铁路基振动压实机-土耦合系统动力学分析

压路机连续压实系统根据振动压实过程中振动轮响应评价压实质量,并根据土体压实质量反馈调节压路机工作参数。基于集中参数模型引入塑性弹簧,将压实过程分为弹性、弹塑性、分离三阶段;分别建立三阶段动力学控制方程,依据轮-土相对位移与作用力确定各阶段切换条件;采用现场实测数据验证模型可靠性;揭示激振力特性(激振力幅值、激振频率)和土体参数的振动响应规律。结果表明:激振力幅值不变时,振动轮振幅和分离周期随激振频率的增大而减小。激振频率不变时,振动轮振幅和分离周期随着激振频率的增大而增大。当激振力幅值与激振频率不变,振动轮振幅随着土体动剪切模量的提升而降低,土体动剪切模量较小时,土体以塑性变形为主。土体动剪切模量较大时,土体以弹性变形为主,振幅缓慢下降,直至趋于平缓。

Nonlinear Dynamics Behaviors of a Rotor Roller Bearing System with Radial Clearances and Waviness Considered

A rotor system supported by roller beatings displays very complicated nonlinear behaviors due to nonlinear Hertzian contact forces, radial clearances and bearing waviness. This paper presents nonlinear bearing forces of a roller bearing under four-dimensional loads and establishes 4-DOF dynamics equations of a rotor roller bearing system. The methods of Newmark-β and of Newton-Laphson are used to solve the nonlinear equations. The dynamics behaviors of a rigid rotor system are studied through the bifurcation, the Poincar è maps, the spectrum diagrams and the axis orbit of responses of the system. The results show that the system is liable to undergo instability caused by the quasi-periodic bifurcation, the periodic-doubling bifurcation and chaos routes as the rotational speed increases. Clearances, outer race waviness, inner race waviness, roller waviness, damping, radial forces and unbalanced forces-all these bring a significant influence to bear on the system stability. As the clearance increases, the dynamics behaviors become complicated with the number and the scale of instable regions becoming larger. The vibration frequencies induced by the roller bearing waviness and the orders of the waviness might cause severe vibrations. The system is able to eliminate non-periodic vibration by reasonable choice and optimization of the parameters.

Roller转子密炼机聚合物流体的混沌混合特性

建立了Roller转子密炼机二维有限元模型,利用网格重叠技术,对密炼机流体的流动过程进行了数值模拟。利用粒子示踪技术,采用4阶Runge-Kutta法计算了不同转数和不同流体粒子释放位置的密炼机Poincaré截面、平均对数线拉伸及Lyapunov指数等混沌混合参数。从非线性混沌理论的视角研究了Roller转子密炼机的混沌混合机理。结果表明,在双转子周期性扰动的作用下,聚合物流体在密炼机内被反复地拉伸、折叠,且啮合区的Poincaré截面出现了典型的"马蹄形"混沌结构。随着混合周期的增加,平均线拉伸以指数形式增长,且Lyapunov指数大于零。Roller转子密炼机流体具有混沌对流的特征。

基于FluidSIM的装配机器人气动回路设计及分析

以某一装配机器人为例,根据其实际工作中气缸的动作顺序要求,利用Fluid SIM软件对其气动回路进行设计、仿真,根据仿真结果分析气缸异常动作原因,并采用单向滚轮杠杆阀、延时阀消除障碍信号,最终得到了符合要求的气动回路。

Occurrence of Rice Leaf Roller in China and Its Identification and Prevention

Rice leaf roller （Cnaphalocrocis medinalis Guenée） is a migratory pest, which mainly causes damage on rice. The morphology characteristic of rice leaf roller is introduced, which is also compared with the morphology characteristic of the other insects such as Susumia exigua Butler and Tryporyza incertulas （walker）. The occurrence law, living habit and selection of prevention pesticides against rice leaf roller in China are summarized, which will provide the intergrated situation of rice leaf roller in China for worldwide further research on the insect.

EQUATION OF MOTION FOR NOVEL FRICTION PENDULUM SYSTEM WITH DUAL ROLLERS

A novel friction pendulum system （FPS） with dual rollers is studied based on the multibody dynamics theory. By analyzing kinematic characteristics of the system, it is reduced to a one degree-of-freedom system. Then the equation of motion for the system is analytically derived by applying the theorem of the relative kinetic energy for a system of particles in differential form in the non-inertial reference system described as a nonlinear differential equation. In the case of the small angular displacement, the natural frequency of the corresponding undamped linear system is obtained, which is consistent with the experimental observation. The derived equation is useful for the study of dynamic characteristics of novel FPS, and its solution directly expedites the simulation of the system in a control loop, and further facilitates the semi-active control process including novel FPS.

炒烘结合工艺对烘青绿茶品质的影响

以湖北宣恩县伍家台栽培茶一芽二、三叶鲜叶为实验原料,通过正交试验探究烘青绿茶加工过程中滚炒环节的温度、投叶量及茶叶水分含量对烘青产品品质的影响,采用主成分分析优化滚炒环节工艺参数,确定最优工艺。结果表明:综合32项指标提取的5个主成分累计贡献率为90.06%,以构建评价函数作为评判指标,结合主效应分析得到最佳工艺参数为:滚炒环节温度(150±5)℃、投叶量2 kg、炒制后水分质量分数25%;烘青绿茶经滚炒后,感官评价结果发现其外形、香气、滋味、叶底得分较未经滚炒处理的样品均有所提高,涩味降低;茶叶条索匀整度、紧细度更好。研究显示,对于烘青绿茶产品,在加工过程中增加滚炒工艺环节对提升烘青绿茶品质具有较好效果。

圆柱滚子轴承内圈挡边与滚子球基面的优化设计

考虑离心力、陀螺力矩、滚子偏斜以及套圈挡边与滚子球基面之间的润滑,建立联合载荷作用下圆柱滚子轴承力学分析模型,基于该模型分析了滚子球基面半径对轴承接触特性及发热量的影响,结果表明:随滚子球基面半径增大,接触点距离滚道表面越近,最大接触应力越小,发热量越少。基于轴承寿命理论对不同偏差的内、外圈挡边倾角和滚子球基面半径进行匹配优化,轴承寿命可提升约34%。

RV减速器滚针轴承动态磨损特性分析

RV(rotary vector)减速器中滚针轴承径向尺寸小,所受动态接触载荷变化复杂,在实际使用中容易出现磨损失效,导致RV减速器的工作性能急剧下降,失去原有的传动精度,甚至出现故障损坏.为揭示RV减速器滚针轴承动态磨损特性,基于接触多体动力学和Archard磨损理论,提出摆线针轮-滚针轴承传动机构的动力学与磨损耦合模型.该方法通过接触多体动力学求解滚针轴承动态接触载荷,分别得到滚动体与内外滚道之间的瞬时法向接触力,借助Archard磨损模型依次计算出内外滚道的瞬时磨损量,再进行累积以表达轴承内外滚道磨损形状.以RV20E-121减速器为对象,基于摆线针轮-滚针轴承传动机构的动力学与磨损耦合模型,分析滚针轴承内外滚道的动态磨损特性,获得内外滚道的累积磨损量大小和分布情况,并绘制磨损后内外滚道形状.研究结果表明:轴承内外滚道磨损量不均匀,且内滚道磨损比外滚道严重;轴承内滚道在垂直偏心距方向上的累积接触磨损量较大,轴承外滚道在摆线轮圆周方向上累积接触磨损量较大;基于RV20E-121减速器耐久疲劳试验,通过轴承滚道磨损形状检测发现,内外滚道磨损不均匀,滚针轴承内滚道的磨损情况比外滚道严峻,内滚道的磨损主要集中在垂直偏心距方向上,外滚道的磨损集中在摆线轮圆周方向上,累积磨损规律与仿真计算结果具有一致性.

Cement Grinding System Status of Roller Press

The working principle of cement roller press and current development of wear resistance on the cement grinding system status at home and abroad was described. The main improvement of previous research on the wear resistance of roller press was proposed from three aspects of wear-resistant material, roller press roller structure, and surface morphology.

摩托过山车乘客加速度分析与评价

游乐设施乘客加速度是影响乘客生理指标的最重要的技术参数,科学评价乘客加速度是保证游乐设施乘客安全性和乘客束缚装置有效性的重要技术手段。针对摩托过山车乘客加速度分析方法尚不完善的问题,分析并得到了用于评价乘客加速度阈值范围和乘客束缚装置技术参数的测试坐标系及其解析方法并进行了乘客加速度测试。基于5Hz的4阶巴特沃斯低通滤波数据进行了乘客加速度阈值范围评价,结果表明摩托过山车的单向加速度和组合加速度符合标准要求,但YZ组合加速度有超出允许值边界的数据,能够以此为指导对设备进行优化。基于1Hz的4阶巴特沃斯低通滤波数据进行了乘客束缚装置技术参数评价,结果表明摩托过山车乘客束缚装置的技术参数满足加速度区域3所对应的技术要求。通过乘客加速度分析与评价,保证了摩托过山车的乘客安全性和乘客束缚装置有效性。

外圈故障状态下动车组轴箱轴承振动响应影响因素分析

针对轴箱轴承故障下的动力学响应问题,将滚子设为刚性体,其他部件设为柔性体,构建了带外滚道剥落故障的双列圆锥滚子轴承的刚柔耦合有限元模型,研究了故障尺寸、故障位置以及载荷变化对轴承动态响应的影响。结果表明:刚柔耦合模型既改善了全刚性体振动响应偏大的问题,又避免了全柔性体计算时间过长的缺点;轴承的故障尺寸越大,故障位置越接近承载区,轴承载荷越大,振动信号显示出的故障特征越明显,故障尺寸达到一定程度时故障特征将由单冲击变为双冲击;径向载荷对轴承故障响应的影响远大于轴向载荷。

Banbury和Roller转子密炼机局部和全局混合特性

采用有限元法,利用Polyflow软件计算了Banbury和Roller两种转子密炼机检测线的速度、剪切速率和混合指数分布,对比分析了两种转子的局部混合特性。通过计算停留时间分布、对数拉伸率、平均混合效率和粒子束分布指数等混合参数,对比分析了两种转子密炼机的全局混合特性。在此基础上,研究了具有典型运动规律流体粒子的动力学特性,分析了密炼机流体的位移和速度突变产生的受力和混合突变特征,为深入理解密炼机流体的复杂混合机理提供了一定的理论参考。

弹齿式辣椒采摘滚筒的分析与试验

随着我国经济的不断发展,辣椒种植规模不断扩大,对于辣椒收获机械的需求日益增加。采摘滚筒是滚筒式辣椒收获机采摘台的主要工作总成之一,可通过对辣椒植株的高速梳刷完成采摘。为改善辣椒采摘装置的收获性能,对辣椒采摘过程进行受力分析,并借助Adams软件对采摘滚筒进行运动学分析,旨在为今后辣椒采摘装置的设计制造提供参考。同时,确定了采摘弹齿结构、转速等关键参数,对弹齿运动过程进行分析,通过理论分析确定滚筒转速的范围,并设计Box-Behnken试验。结果表明:在较优参数组合下,即前进速度6.4 km/h、预设弹齿间隙89 mm、滚筒转速180 r/min时,辣椒破损率优化值为2.4%,符合行业要求。

船用发动机喷油器重载工况下的滚轮−滚轮销混合热弹流润滑分析

喷油器中的摩擦损失以滚轮−滚轮销副为主,并且容易发生磨损、卡滞等问题。因此,针对滚轮−滚轮销副摩擦学性能,建立重载工况下的考虑喷油器压力的混合热弹流润滑模型,获得该摩擦副在一个工作循环内的摩擦学结果。经分析表明,来自喷油器的极高压力会显著降低滚轮−滚轮销摩擦副之间的油膜厚度,并且产生明显的弹性变形以及较高的微凸体接触和油膜温升现象。研究滚轮−滚轮销配合间隙对减摩和降磨的影响,结果表明,当配合间隙为20μm时可以降低约30.7%的摩擦损失以及25.0%的磨损负载,合适的配合间隙可以有效改善滚轮−滚轮销副的润滑状态,降低摩擦和磨损。