重型油缸侧缸BTA深孔套料加工刀具过度磨损崩刃的研究

深孔加工的BTA套料工艺方式,工艺系统是处于内、外切削液和切屑包容的环境中,系统的任何微小外扰,都会造成系统的失稳,引起钻杆振动和刀具非正常磨损与崩刃。通过分析高精度、重型油缸侧缸的BTA深孔套料工艺,提出工艺系统失稳的解决措施,通过实际生产验证了措施的有效性。通过工艺优选试切试验,找出适合重型油缸深孔套料的一些加工参数,对生产中类似工件深孔工艺参数的选取具有参考价值。     

Chatter suppression based on nonlinear vibration characteristic of electrorheological fluids

Self-excited chatter is a serious problem in machining shops and its frequency is always near the resonant frequency of the machining system. This paper proposes a novel design method for a tunable-stiffness boring bar containing an electrorheological (ER) fluid to suppress chatter in boring. The ER fluid undergoes a phase change when subjected to an external electrical field and serves as a complex spring behaving nonlinearly in the structure. The deformation modes of the ER fluid are dependent on the applied electric field and the strain amplitude. As a result, the global stiffness and energy dissipation properties of the boring bar under an electric field change drastically at different amplitudes of vibration. It is found that the amplitude of chatter can be prevented from increasing by using the nonlinear vibration characteristic of the ER fluid. It is shown experimentally that the chatter can be suppressed under a certain range of the electric field related to the cutting conditions.     

山地城市地铁制动/轨道结构参数对钢轨波磨的影响

目的 山地城市地铁相较于平原城市地铁具有爬坡大且曲线多的复杂线路特点,其钢轨波磨问题更加严重。探究山地城市地铁制动区间钢轨波磨的形成机理,提出相应钢轨波磨的控制方法。方法 首先,结合现场调研建立了轮对-轨道-制动系统的有限元模型。然后,采用复特征值分析法研究了轮对-轨道-制动系统的摩擦自激振动特性,进而对制动闸片的表面织构及扣件参数进行参数化分析。最后,基于最小二乘法,采用2种拟合方程对扣件参数进行多参数拟合,并采用遗传算法与粒子群算法确定抑制钢轨波磨扣件参数的最优解。结果 发现轮对-轨道-制动系统存在2个不稳定振动频率,分别为653.73 Hz与584.76 Hz,其中653.73 Hz的复特征值实部较大,为46.53。对比不同表面织构,采用正六边形织构表面闸片的轮对-轨道-制动系统复特征值实部最小,为19.46。对比扣件参数优化前后,采用优化后的扣件参数的轮对-轨道-制动系统复特征值实部较小,为0.49。结论 轮轨子系统与制动子系统的摩擦耦合作用导致轮对-轨道-制动系统摩擦自激振动,是诱导山地城市地铁制动区间钢轨波磨产生的重要因素。当采用正六边形表面织构闸片或设置扣件参数中垂向刚度为36.2 MN/m,垂向阻尼为2 800 N.s/m,横向刚度为25 MN/m,横向阻尼为2 000 N.s/m时能有效抑制钢轨波磨的产生。     

BTA深孔钻削过程中工件振动影响因素的研究

在BTA深孔钻削过程中,工件的振动是导致孔加工质量和精度降低的重要因素。通过实验和MATLAB拟合分析不同的切削参数(进给量f、切削速度v、主轴转速n)对工件振动的影响。分析结果表明,在深孔加工过程中,工件的中间位置振幅最大;随着进给量的和切削速度的增大,工件的振幅增大,振幅增大量先增大后减小;主轴转速的变化对工件的振动影响很小。合理的选择切削参数可以降低工件的振动。     

Simulation of the BTA deep-hole drilling process

The dynamic disturbances of the deep-hole drilling process pose a great challenge. Especially spiralling, which causes holes with several lobes, can damage the workpiece irreparably. The causes for spiralling are not well explored yet, and it is important to analyze which conditions and process parameters can cause the spiralling. This article presents a simulation system for the idealized BTA (Boring and Trepanning Association) deep-hole drilling process. Methods of computer graphics allow the realistic modeling of the cutting edge and the workpiece. The simulation is able to calculate the sweep volume, cutting forces, and regenerative tool vibrations. It is also possible to generate the resulting geometry of the workpiece depending on the eigenfrequencies of the boring bar and on the process parameters. Thus, the pre-conditions for the spiralling can be analyzed.     

A study of cutting process stability of a boring bar with active dynamic absorber

In this paper, the use of an active dynamic absorber to suppress machine tool chatter in a boring bar is studied. The vibrations of the system are reduced by moving an absorber mass using an active device such as an piezoelectric actuator, to generate an inertial force that counteracts the disturbance acting on the main system.An equivalent lumped mass model of a boring bar with active dynamic absorber is considered. A cutting process model that considers the dynamic variation of shear and friction angle, that causes self-excited chatter during the cutting process, is applied to the lumped mass model. The theory of regenerative chatter is also applied to the model. Stability boundaries have been calculated for maximum permissible width of cut as a function of cutting speed. A comparison of the boundaries for chatter-free cutting operation of a plain boring bar, a boring bar with passive tuned dynamic absorber and a boring bar with active dynamic absorber is provided in this paper. The comparison shows that a substantial increase in the maximum permissible width of cut for stable cutting operation, over a range of cutting speeds, is obtained for a boring bar equipped with an active dynamic absorber.     

Study on boring and drilling with vibration cutting

In this paper, vibration cutting (VC) has been applied to boring and drilling processes using a vibration device we developed. We analyzed the effect of vibration in boring by investigating the surface roughness of workpiece with the help of Taguchi method and analysis of variance (ANOVA). It has been shown that the utilization of VC in boring improves the surface roughness prominently. The shading-area method we proposed can be employed as a simple and feasible approach for the analysis of burrs in intersecting holes. High-frequency vibration boring can reduce the burr formation in intersecting holes effectively. The experimental results show that the utilization of VC reduces the burrs in intersecting holes noticeably.     

基于ANSYS的内置式双减振镗杆参数优化

内置式双减振镗杆通过动力学模型分析得出设计参数后,在Pro/engineer中建立镗杆的实体模型,导入Ansys Workbench中进行参数优化.由于双减振镗杆的两个减振块之间的距离及前后两减振橡胶的弹性模量这三个参数,在镗杆动力学模型分析中不能得出最优值,因此在Ansys中把这三个变量设为参数进行优化.得到这三个参数的最优值后,对减振镗杆进行谐响应分析,得出优化后的镗杆径向振幅和切向振幅均比优化前减小,证明优化后的镗杆具有更好的减振性能,为双减振镗杆制造提供了依据.     

A novel approach to machining condition monitoring of deep hole boring

In the optimization of deep hole boring processes, machining condition monitoring (MCM) plays an important role for efficient tool change policies, product quality control and lower tool costs. This paper proposes a novel approach to the MCM of deep hole boring on the basis of the pseudo non-dyadic second generation wavelet transform (PNSGWT). This approach is developed via constructing a valuable indicator, i.e., the wavelet energy ratio around the natural frequency of boring bar. Self-excited vibration occurs at the frequency of the most dominant mode of the machine tool structure. Via modeling dynamic cutting process and performing its simulation analysis during deep hole boring, it is found that the vibration amplitudes at the nature frequency of the machine tool rise with the tool wear. The PNSGWT that has relative adjustable dyadic time-frequency partition grids, good time-frequency localizability and exact shift-invariance is used to extract the wavelet energy in the specified frequency band. Accordingly, the MCM of deep hole boring can be implemented by means of normalizing the wavelet energy. Finally, a field experiment on deep hole boring machine tool is conducted, and the result shows that the proposed method is effective in the process of monitoring tool wear and surface finish quality for deep hole boring.     

Vibration suppression of boring bar by piezoelectric actuators and LR circuit

This paper presents the vibration suppression of a boring bar using piezoelectric actuators installed in the boring bar, and an inductor-resister (LR) circuit, which acts as a mechanical dynamic absorber. The frequency response function of the compliance was designed so that its real part is constrained to suppress regenerative chatter. The designed boring bar with an optimally tuned LR circuit was set on a lathe to evaluate its dynamic characteristic, and it was found that the chatter vibration was successfully suppressed in the cutting test.     

Dynamic simulation of boring process

This article presents a model to simulate the dynamics of boring process. In boring operations the boring bar should be long and slender; therefore it is easily subjected to vibrations. Tool vibrations result in reduced tool life, poor surface finish and may also introduce chatter. Hence, predicting the vibrational behavior of boring process for certain cutting conditions and tool work-piece properties is of great importance. The proposed method models the cutting tool geometry by B-spline parametric curves. By using B-spline curves it is possible to simulate different tool geometries with a single approach. B-spline curves also enable the modeling of the kinematics of chip formation for different tool work-piece engagement conditions with a single formulation. The boring bar has been modeled by the Euler–Bernoulli beam theory. The simulation process has been implemented with MATLAB. The algorithm consists of different computational modules that are interconnected by a main program. Experimental machining tests have been conducted to verify the validity of the proposed model. Proposed dynamic models have been able to predict the dynamic cutting force components and vibration frequencies with less than 15% deviation. The proposed model has been also able to predict the chatter onset correctly.     

Targeted suppression of vibration in deep hole drilling using magneto-rheological fluid damper

Under the concept of precision or targeted vibration suppression, a novel approach is developed to reduce the vibration of drilling tool system in deep-hole drilling process. The concept is to suppress the dominant vibration upon its emergence by variable damping or to force the harmful vibration morph into less harmful by different damper position. A magneto-rheological (MR) fluid damper is designed with adjustable damping capability to counteract emerging vibration. A series of experimental investigations are carried out on the BTA deep hole drilling process. The experimental results show that the adjustable MR damping brings down the vibration in all applications with different suppression effect. A relative optimal suppression can always be found. The suppressed vibration experiences a frequency shift which sheds light on the possible avoidance of matching of unwelcome frequency. Different damper locations have different but consistent suppression results which foresee a possibility of forcing the mode of vibration into less harmful one. A potential precision or targeted suppression of vibration upon its emergence is thus possible.     

On the Influence of Drilling Depth Dependent Modal Damping on Chatter Vibration in BTA Deep Hole Drilling

BTA (Boring and Trepanning Association) deep hole drilling is applied for machining bore holes with a high length to diameter ratio. The slender tools involved make BTA processes highly susceptible to chatter vibration. Chatter-free states and states with chatter vibration corresponding to one of the first three torsional eigenfrequencies can be observed to alternate during processes with constant cutting parameters. A detailed FEA model of the significant BTA tool components involved was developed. This takes into account the drilling depth variant boundary conditions. Using this model, the state transitions can be attributed to drilling depth dependent modal damping of the involved torsional vibration modes.     

内置式减振镗杆温升的分析与研究

深孔加工中镗杆的颤振严重影响孔的加工质量,而振动的抑制与镗杆的内部工作温度有很大关系.文章主要研究镗杆在工作中,温度升高以后对镗杆减振性能的影响.通过对镗杆的结构设计和三维模型的简化,根据热力学第一定律,对镗杆内置减振器振动产生的热量进行分析,运用有限元分析软件ANSYS Workbench,对镗杆进行稳态热分析和瞬态热分析,最后得出镗杆减振效果和阻尼液的温度变化情况.     

Generation mechanism of polygonal wear of work rolls in a hot leveler and a countermeasure by dynamic absorbers

This paper deals with the polygonal deformation phenomena of work rolls in a reversible hot plate leveler. According to the measurements of deformed rolls and the vibration measurement, a simple model regarding the polygonal deformation as unstable vibration caused by time retardation accompanied by wear on the surfaces of the rolls is proposed. Also, the modal analysis is applied to a general system with time retardation accompanied by wear in order to obtain the equations of motion for each mode and to derive some important parameters. Furthermore, a countermeasure for the polygonal deformation by using dynamic absorbers is considered. The optimal design of a dynamic absorber mounted on a single degree-of-freedom system where the polygonal wear is generated is discussed by applying the optimal design procedure of a dynamic absorber for forced vibration to this self-excited vibration system. As a result, a design in which the system is perfectly stabilized is obtained. This result is applied to a hot leveler as a two degree-of-freedom system through the modal analysis. By numerical analysis, it is confirmed that the hot leveler changes into a perfectly stable system by two dynamic absorbers, and the polygonal wear is not generated at all.     

超声波椭圆振动加工技术的研究进展

超声波椭圆振动加工是功率超声加工技术的重要分支之一,在硬脆性材料加工方面具有非常广阔的应用前景。综述了超声波椭圆振动加工系统的研究进展和超声波椭圆振动加工技术在车削、镗削、钻削、铣削、磨削、化学机械抛光、砂轮修整、表面滚压与焊接等方面的最新应用,最后对超声波椭圆振动加工技术的发展方向提出了一些建议。     

Magnetorheological fluid-controlled boring bar for chatter suppression

An innovative chatter suppression method based on a magnetorheological (MR) fluid-controlled boring bar for chatter suppression is developed. The MR fluid, which changes stiffness and undergoes a phase transformation when subjected to an external magnetic field, is applied to adjust the stiffness of the boring bar and suppress chatter. The stiffness and energy dissipation properties of the MR fluid-controlled boring bar can be adjusted by varying the strength of the applied magnetic field. A dynamic model of a MR fluid-controlled boring bar is established based on an Euler–Bernoulli beam model. The stability of the MR fluid-controlled boring system is analyzed, and the simulation results show that regenerative chatter can be suppressed effectively by adjusting the natural frequency of the system. Experiments in different spindle speeds utilizing a MR fluid-controlled boring bar are conducted. Under a 1 Hz square wave current, chatter can be suppressed, as evidenced by the elimination of chatter marks on the machined surfaces and the reduction in the vibration acceleration at the tip of the boring bar.     

40Cr表面微裂纹研究与应用

通过研究三钢1号小方坯连铸机振动参数,对比各种工艺对铸坯表面质量的影响,改善了铸坯的表面质量。振动参数优化如下：结晶器振动方式由采用正弦振动改为非正弦振动,偏斜率[ɑ]采用0.2,振动频率由152次/min提高至182 次/min,振动幅度由8.2 mm降低至7.2 mm,负滑脱时间由0.168 s降低至0.117s,铸坯表面质量得到有效改善。同时在保证铸坯表面质量的情况下,可以通过适当的提高连铸拉速,减少铸坯振痕深度。     

山地城市地铁牵引与制动工况下钢轨波磨成因对比研究

目的 探究山地城市地铁牵引与制动工况下的钢轨波磨成因。方法 基于摩擦自激振动理论,结合山地城市地铁长大坡道区段现场调研,分别构建上坡牵引和下坡制动工况下车辆−轨道系统的动力学模型,对比研究长大坡道区段牵引与制动工况下车辆−轨道系统的动力学特性。分别构建对应区段的轮对−钢轨−牵引系统和轮对−钢轨−制动系统的有限元模型,并采用复特征值法对比研究山地城市地铁牵引与制动工况下的钢轨波磨成因。采用最小二乘法和粒子群算法提出抑制长大坡道区段钢轨波磨的车辆−轨道参数的最优解。结果 在轮对−钢轨−牵引系统中存在不稳定振动频率369.93 Hz,其复特征值实部为19.36。在轮对−钢轨−制动系统中存在不稳定振动频率443.92 Hz,其复特征值实部为4.970 5。结论 在牵引摩擦副与轮轨摩擦副的共同作用下产生的摩擦自激振动,在制动摩擦副与轮轨摩擦副的共同作用下产生的摩擦自激振动,分别是长大坡道牵引与制动区段钢轨波磨的主要诱因,且牵引区段发生的可能性高于制动区段。在制动工况下设置制动压力为5 kN,在牵引工况下设置牵引运行速度为80 km/h,并结合优化后的扣件参数,能有效抑制长大坡道区段钢轨波磨。     

坡口机床进给丝杠副刚度计算

坡口机床进给系统中自激振动是制约加工效率的主要原因,有很大一部分振动来源于进给丝杠副。应用机床动力学理论建立进给系统自激振动力学模型并进行理论分析,计算不同支承方式下丝杠轴向刚度和螺母结构刚度,提出采用两端固定支承和双螺母的结构,可有效提高刚度、抑制振动现象发生。