A dynamic model and numerical study on the liquid balancer used in an automatic washing machine

The rotational system of an automatic washing machine has two major technical difficulties. One is the collision of the tub against the frame at the beginning of its early spinning stage. A factor that causes such instability of the rotational object can be attributed to the deflection of the liquid inside the liquid balancer due to the unbalance mass. This study proposes the installation of a middle plate to avoid the deflection of the liquid and a CFD method is used to verify its effectiveness. The other is the whirling vibration occurred during the high speed rotation of the basket and it shakes the center of its rotational axis. This is because the balancer cannot generate enough restoration forces during its high speed rotation. It is necessary to employ the multi-race in the balancer in order to increase restoration forces. The analysis for the configuration has been performed using a dynamic model.     

Automatic balancing of flexible vertical rotors using a guided ball

Automatic balancing of flexible vertical rotors using a ball guided to move freely in a circular groove housed in the rotor disk is studied. The dynamic interaction between the balancing ball and the rotor is investigated using an undamped three-degrees-of-freedom system model in a rotating reference frame. The centrifugal force on the balancing-ball moves it to a relative rest position in the groove and thereby modifies the effective rotor unbalance. The stability of balancing ball position during the rotor whirling motion is analyzed and the conditions under which the unbalanced rotor vibration can be neutralized by the automatic balancer are identified. The stability results are presented graphically to facilitate an effective automatic balancer design. The results show that the automatic balancer can neutralize the unbalance whirling motion of the rotor, when operated at speeds higher than its critical speed.     

Dynamic modeling and analysis of drum-type washing machine

In this study, dynamic analysis of a drum-type washing machine has been conducted using a simplified dynamic model considering gyroscopic effects. Its mathematical model has 6-degree of freedom in the complex coordinate space into which is transformed real coordinate space to understand the whirling motion easily. Dynamic analysis is performed using MATLAB. For the purpose of numerical verification, the results for unbalance response are presented and compared with the experimental vibration test. The mathematical model proves quite good accuracy in predicting dynamic characteristics which could be changed by the parameters of design variable and can reduce design cycle shortly. Dynamic characteristics of a washing machine are shown through shape and directivity index (SDI), whirling orbits, rigid and flexible mode of a drum type washing machine during drum run-up. In designing drum type of washing machine, it is efficient than finite element method to analyze behaviors of drum and tub.     

环状液体平衡器的平衡理论及其应用分析

建立了环状液体平衡器的动力学模型，在此基础上对平衡器的自平衡机理进行了分析，并着重对环状液体平衡器的平衡液的等效质量作了深入分析，提出并研究了在滚筒洗衣机上应用环状液体平衡器的效果。最后指出应注意科学设计平衡器尺寸及确定平衡液质量，选择恰当的应用场合，才能发挥其独特的减振效能。     

Stability analysis of a ball-rod-spring automatic balancer

The traditional ball-type automatic balancer, which consists of several balls moving along a fixed circular orbit, has been applied to different fields for rotational vibration reduction. Under proper working conditions, the balls will counter-balance the rotor by positing to appropriate locations. This particular equilibrium configuration is referred to as the perfect balancing configuration. The unbalance vibrations at steady state can be totally suppressed only if the perfect balancing configuration is stable. The stability of the perfect balancing configuration depends on the parameters of the system. To achieve perfect balancing, the system parameters must lie in the stable region of the perfect balancing configuration in the parameter space. An automatic balancer with a larger stable region of the perfect balancing configuration will be more robust. This paper provides a detailed analysis of a new design of auto-balancer, the ball-rod-spring balancer, which is aimed to increase the stable region of the perfect balancing configuration. A theoretical model of a rotor packed with a two-unit ball-rod-spring balancer is constructed. Closed form formulae of the equilibrium configurations are presented. The stability of each equilibrium configuration is investigated both analytically and numerically. Results of numerical analysis confirm that the stable region of the perfect balancing configuration of the new design is larger than that of the traditional fixed orbit balancer.     

新型智能砂轮半自动平衡仪

介绍新研制成功的精密磨床砂轮半自动平衡仪。该仪器利用数字相敏检波技术提取砂轮的不平衡振动信号及最小二乘技术识别砂轮不平衡量;设计出友善的人机界面,用于提示、指导识别与平衡过程;仪器的绝大部分功能均由软件完成,成本低,可靠性高。试验表明仪器原理正确,平衡精度高。     

基于ANSYS的旋转床转鼓系统动力学分析

旋转床转鼓系统的动力学性能影响旋转床的运行效果,是旋转床设计的重要技术指标。应用ANSYS软件建立旋转床转鼓系统的三维有限元模型,在转鼓系统静力学分析的基础上进行动力学分析。通过静态和动态两种状态下转鼓系统固有频率和振型的对比,研究转速对旋转床转鼓系统固有频率的影响。结果表明,转速使得转鼓系统的固有频率减小;在一定范围内,可能导致转鼓的强烈振动,需要提高转鼓系统的刚度。为旋转床转鼓系统动态设计提供依据。     

一种新型电磁平衡头的静态磁特性研究

传统机上动平衡和现场动平衡无法适应高速旋转机械智能化和精密化的发展趋势,因此具有不停机和高精度优势的在线主动动平衡成为当前旋转机械抑制失衡的重要手段.针对某高速磨削电主轴,设计了一款具有环形对称结构、依靠电磁和永磁原理实现驱动和自锁的在线主动平衡头.基于此,研究了它的磁路和磁场分布,采用有限元法获得了其静态自锁力、力矩和静态驱动力、力矩.研究结果可指导平衡头的优化,进而以获得最佳的平衡效果.     

带球体平衡环的滚筒洗衣机平面模型稳定性分析

应用平衡环技术抑制滚筒洗衣机脱水振动已成为发展趋势。但由于轴线水平,重力的作用使得球体相对脱水桶周期振荡,且模型本身难以转为合适的自治形式。为分析带有球体平衡环的滚筒洗衣机振动稳定性,建立了滚筒洗衣机平面振动模型,开发了适合周期解稳定性分析的伪弧长单参数延拓算法与分岔点的双参数追踪算法。应用该算法求解发现了系统周期解的倍周期、半周期、环面与叉形分岔现象,并指出了低速区的3个失稳区域。通过数值仿真验证了分岔结论的正确性。     

Stability analyses of a vertical axis automatic washing machine with a hydraulic balancer

This paper analyzes non-linear vibration characteristics associated with the spin drying process of a vertical axis automatic washing machine with a hydraulic balancer. A two-ball model is employed to describe the effect of the hydraulic balancer and a mathematical model is built for the washing machine. Based on a rotating coordinate transformation, this model is then converted to an autonomous form for stability analyses. The continuation package AUTO [1] is employed and two unstable regions of the spin drying process denoted by M and N are identified. The unstable region N is discussed in detail because it has an essential effect on the spin drying process. At last, the existence of the unstable region N is proved by both simulations and experiments.     

电磁滑环式在线动平衡系统特性分析与实验

为了测试一种电磁滑环式在线动平衡装置的平衡特性,搭建了实验平台,采用影响系数法进行在线动平衡实验研究。主要从实验平台本身的振动特性、主轴转速对平衡效果的影响以及试加配重的角度对平衡效果的影响3个方面进行了分析研究,得到了实验平台和主轴转速对在线动平衡系统的影响,以及试加配重位置的选择方式,为高速主轴双面动平衡和模态分析的研究打下基础。     

基于不平衡振动的旋转刀具动态特性分析

根据旋转刀具不平衡振动理论分析,得出旋转刀具不平衡量和工作转速是影响振动的主要因素。利用NX Nastran有限元软件对旋转刀具进行了模态分析,计算了刀具的固有模态。通过模拟旋转刀具在不平衡振动激励下的强迫响应,在给定不平衡量情况下,得出了转速越高刀具振动的幅值越大,但由于工作转速远离刀具临界转速,振动幅值是在较小的范围内变化。有限元分析结果为该刀具的设计和改进提供了理论依据。     

A method for vibration isolation of a vertical axis automatic washing machine with a hydraulic balancer

This paper discusses a method for vibration isolation of a vertical axis automatic washing machine with a hydraulic balancer. First, a way to isolate vibration through a small amplitude of the suspension rod’s axial force is proposed, and a base circle of a cone along which the lower joint of a suspension rod moves is discussed. Based on the circle, a geometric constraint involving the slant angle of the suspension rod, the deflection angle of the washing/spinning assembly, the suspension radius of the tub and the eccentricity of the system at the steady state is derived. Considering that the trace along which the suspension rod moves is also affected by the dynamics of the system, a governing equation satisfying the equilibrium conditions of the centrifugal forces and torques is obtained. Combing the geometric constraint and governing equation together achieves a general governing equation for vibration isolation of the system. Finally, the general governing equation is proven by simulations, and the relations between the optimal installing height and several parameters are discussed.     

卧螺离心机转鼓主要参数对其模态的影响

研究清楚离心机转鼓参数与转鼓应力、变形的关系，是保证其在安全的工作状态下，对转鼓进行参数优化的基础。在诸多参数中，对转鼓3个主要参数：转速、转鼓壁厚和液池深度进行分析研究。结果表明，各种载荷下转鼓的最大径向位移均与转速的二次方成比例，且随着转速的增加，会导致转鼓径向变形增大；正常工况（Fw＋Pc）下的应力SINT（SINT为第三强度理论的等效应力）最大值随着转鼓壁厚的减小而增大，但增大的幅度较小；转鼓的总径向位移最大值和物料离心压力引起的径向位移的最大值均随着液池深度的增加而增大，但增长速度缓慢；转鼓自身质量离心力产生的径向位移与转鼓的液池深度无关。这些数据将为己有的卧螺离心机的改造优化和工程实际应用提供设计依据。     

Relation between segregation patterns and granular flow modes in conical rotating drum

Generally, it is difficult to observe, without any disturbance, flow structures or velocities inside flows such as granular flows, particle-fluid flows and so on. It is effective to use a non-contact and non-destructive measurement method for such flows. In the present paper, an MRI (Magnetic Resonance Imaging) technique is employed to measure the motion and velocity inside the flows. MRI has been applied to granular flows since about 1990. Our group has studied the particle motion inside the rotating drum using MRI. The rotating drum is industrial equipment which is widely utilized in engineering processes. In the cylindrical rotating drum it is well-known that axial and/or radial segregation take place. In the present study, we use a conical rotating drum which is sometimes employed in the granulation process. The conical rotating drum is half-filled with a mixture of two different sizes of spherical particles. We varied the rotational speed. Then we investigated the effect of the rotational speed on the axial segregation pattern and observed the flow mode.     

螺旋滚筒的非线性动态特性分析

针对采煤机滚筒在生产中出现的振动现象,利用非线性振动理论,建立了滚筒在变刚度变阻尼下的两自由度非线性振动模型,分析了截割转速变化对滚筒振动的影响。结果表明,合理选择截割转速可以有效的减少滚筒的振动,保证采煤机良好的工作性能和稳定性。     

Effect of process parameters on tensile strength of friction stir welding A356/C355 aluminium alloys joint

In the present investigation, A356/C355 aluminium alloys are welded by friction stir welding by controlling various welding parameters. A356 and C355 aluminium alloys materials have a set of mechanical and physical properties that are ideally suited for application in aerospace and automobile industries and not widely used because of its poor weldebility. To overcome this barrier, weldebility analysis of A356 and C355 aluminium alloys with high speed steel (Wc-Co) tool has been investgated. An attempt has been made to investigate the influence of the rotational speed of the tools, the axial force and welding speed on tensile strength of A356/C355 aluminium alloys joint. The experiments were conducted on a milling machine. The main focus of investigation is to determine good tensile strength. Response surface methodology (box Behnken design) is chosen to design the optimum welding parameters leading to maximum tensile strength. The result shows that axial force increases, tensile strength decreases. Whereas tool rotational speed and welding speed increase, tensile strength increases. Optimum values of axial force (3 /KN), tool rotational speed (900 RPM) and welding speed (75 mm/min.) during welding of A356/C355 aluminium alloys joint to maximize the tensile strength (Predicted 223.2 MPa) have been find out.     

弱非平稳转速下转子动平衡方法

提出弱非平稳转速下转子动平衡方法,通过对动不平衡振动信号的时间频率联合分析处理获取各次动平衡试验振动信号的转速无关化幅值、相位和振幅转速无关化信号初相点等转速无关化振动信息。根据转速无关化振动信息给出了分别采用影响系数法、振型平衡法和全息谱平衡法计算不平衡量重径积和相位的方法。弱非平稳转速下转子动平衡方法免去了现有动平衡方法理论上对平衡转速必须处于恒定转速的严格要求,允许动平衡试验中平衡转速可以有一定的波动范围,消除现有动平衡方法中转速波动对动平衡精度的影响,实现超精密转子动平衡技术。     

数控机床HSK刀柄和主轴在高速旋转下的连接性能分析

刀柄与主轴连接性能对数控机床的加工精度以及工作安全性影响显著。针对HSK刀柄在高速旋转过程中发生刀柄和主轴连接失效这一主要失效形式,应用弹性力学理论建立了任一转速下刀柄与主轴连接锥面的接触应力模型,且有限元分析结果与该理论模型有较好的一致性。在此基础上,综合考虑夹紧力以及刀柄、主轴配合过盈量的影响,建立了基于HSK刀柄与主轴连接的临界转速计算模型以及连接可靠性模型。根据临界转速模型可以从理论上计算出一定过盈量和夹紧力下的临界转速,分析夹紧力和过盈量对临界转速的影响。根据连接可靠性模型可以求解任一转速下刀柄和主轴连接的可靠度,并得到可靠度随转速的变化规律。这两个模型的建立对防止HSK刀柄、主轴连接的失效,保证高速切削加工的精度以及工作的安全性有重要意义,同时也为正确使用HSK刀柄以及刀柄尺寸结构进一步优化和可靠性设计提供了理论基础。
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超重力机自动平衡系统的设计及模拟试验研究

为了解决某些旋转机械转子振动会发生随机突变的问题,以超重力机为例,根据其动力学特性和用户实际使用时的振动幅值、相位变化数据,计算其可承受的最大不平衡量,以此为依据,根据液体"自衡"原理设计连续注排液式平衡头,实现了超重力机转子振动模拟和在线消除。模拟试验研究结果证明,应用连续注排液式平衡头的自动平衡系统可以有效地降低转子的振动,提高设备的稳定性,延长其生产周期。这些数据为此系统应用到超重力机和其他旋转机械提供了参考和依据。