TC4钛合金高速车削温度与车削振动 特性的试验研究

对TC4标准试件进行单轴拉伸试验,得到了钛合金材料的基本力学性能参数。通过非接触式红外热像仪、三向振动加速度传感器以及振动信号采集仪同步采集了TC4钛合金试件的车削温度和车削振动信号,得到了试件在给定车削参数下刀尖附近的车削温度和车削振动的时域曲线,结合试验数据分析了车削参数对车削温度、三向振动加速度及切屑形貌的影响,基于灰色关联度理论分析了车削温度和车削三向振动加速度之间的关系。研究表明:1)钛合金材料高速车削时的温度明显高于普通材料,基于各次试验所得车削温度最高值及三向振动加速度最大值的统计分析,二者的变化趋势基本一致; 2)随着相关车削参数值的升高,试件车削温度的最高值也随之升高,对应三向振动加速度的最大值变化也更为剧烈; 3)相同车削条件下,随着进给速度的增大,试件切屑更为粗糙且颜色更深; 4)车削温度最高值与车削三向振动加速度最大值之间的相对灰色关联度均高于0.8。     

SiCp/Al复合材料薄壁件车削力的仿真研究

应用有限元分析软件ABAQUS对Si Cp/Al复合材料薄壁件车削力进行了仿真研究,得到了切削用量对切削力的影响规律,并结合文献的实验成果对相应规律进行了分析。仿真结果表明:在Si Cp/Al复合材料薄壁件车削过程中,随切削速度的增大,三向切削分力(轴向力Fx、径向力Fy、切向力Fz)均增大,但径向力Fy增幅很小;随进给量的增大,三向切削分力都有增大的趋势;随背吃刀量的增大,三向切削分力均显著增大;背吃刀量是影响切削力的主要因素。     

PCD刀具超声振动车削SiC_p/Al复合材料时的切削力特性研究

用PCD刀具对SiCp/Al复合材料进行了超声振动车削与普通车削的对比试验 ,探讨了切削速度、进给量和切深三种切削参数在两种切削状态下对切削力的影响规律 ,得出了超声振动车削SiCp/Al复合材料的主切削力经验公式。     

6061铝合金径向超声振动车削的表面完整性研究

为研究径向超声振动参数及切削参数对车削6061铝合金表面残余应力、表面粗糙度以及表面形貌的影响,采用与普通车削进行对比的方法对6061铝合金进行纵向超声振动切削试验。结果表明:与普通车削相比,径向超声振动辅助车削能显著提高零件加工表面的残余压应力;在两种切削方式下,表面残余压应力均随切削速度的增加而增大;在相同切削参数下,随着径向超声振幅的增加,6061铝合金加工表面的残余压应力变大;与普通车削相比,径向超声振动车削使工件表面的粗糙度变大,并且伴随振幅的增加,表面粗糙度呈上升趋势;通过对加工表面的三维形貌进行观测发现,超声振动辅助车削能有效抑制传统车削加工中的积屑瘤和鳞刺等表面缺陷,并显著提高加工表面质量。     

超声振动辅助磨削NdFeB永磁材料磨削力试验研究

磨削过程中,降低磨削力有利于提高硬脆材料的加工表面质量.对切向、径向和轴向超声振动辅助磨削NdFeB永磁材料的磨削力进行了试验研究,研究结果表明:超声振动的引入使磨削力随砂轮粒度和磨削用量变化的趋势减缓;与普通磨削相比较,三种超声振动方式均使磨削力降低,对于切向磨削力,轴向超声振动使之大幅度上升,切向超声振动次之,而径向超声振动使之下降;对于法向磨削力,三种超声振动方式均使之大幅降低,其中径向超声振动的影响最为明显,切向超声振动次之,轴向超声振动的影响最弱.     

精密车削Cr12模具钢的切削力研究

利用SB—CNC超精密车床精密车削Cr12钢的切削试验。研究了切削速度、进给量和切削深度对切削力的影响变化规律，并分析了产生这些变化的原因。结果表明提高切削速度能减小切削力，而进给量越大。切削力也越大；但刀尖圆弧对径向切削分力和轴向切削分力的影响很大。在小切深时。径向切削分力大于轴向切削分力。随着切深的增加，径向分力越来越小。轴向分力越来越大，当切深大于圆弧半径时。径向切削力保持不变。     

用双刀三刃法车削梯形螺纹丝杠

车削梯形螺纹是一项加工难度比较大的技术活，尤其车削长度较长的梯形丝杠。如果采用传统的切槽法切削，其径向切削力比较大，容易引起振动；而用左右切削法车削，其轴向切削力比较大，切削时工件易变形弯曲；若采用直进法，常常会扎刀，使工件表面拉伤。另外，还有工件刚性不足，对车削质量也有影响。所以，车削梯形螺纹要达到梯形螺纹的技术要求，加工难度较大。作者经多次实践，总结出双刀三刃车削梯形螺纹丝杠的方法，效果良好，简介如下。     

刀具角度对车铣加工SiC_p/Al复合材料动态特性的影响

通过SiCp/Al复合材料正交车铣加工试验研究了刀具角度对正交车铣加工过程中刀杆振动的影响。分别用不同前角、后角和刃倾角的铣刀对Si Cp/Al复合材料进行切削加工。结果表明:刀杆轴向的加速度比切向和径向大得多,且在入刀和稳定切削阶段,当前角和后角达到15°和2°时,加速度达到最小,随着刃倾角的增加,各个方向的加速度几乎不变。由此得出随着刀具角度变化刀杆加速度的变化规律,从而为车铣加工刀具参数选择提供指导。     

双刀三刃车削梯形丝杆

梯形螺纹的车削加工难度较大、技术性较强。采用传统的切槽法切削时,因径向切削力较大,容易引起振动;用左右切削法切削时,因轴向切削力比较大,工件易变形弯曲;若采用直进法,常常会轧刀,造成工件表面拉伤。此外在车削较长的梯形螺纹丝杆时,还存在工件刚性不足的影响因素。笔者经过反复实践总结出梯形丝杆双刀三刃车削方法,可以满足梯形螺纹精度和表面粗糙度的加工要求。     

单激励超声振动车削装置的结构及其切削方式优化

设计单激励超声振动车削装置通常采用车刀轴向与变幅杆轴向相垂直的结构,切削方式比较单一,主要采用主切削力方向振动的方式进行加工。本文分析了现有结构及切削方式的不足,提出车刀轴向与变幅杆轴向一致的结构,并采取新的复合振动。根据原理进行分析,通过AdvantEdge FEM进行仿真,论证新结构及切削方式的可行性,并指出脆硬材料和塑性材料在超声振动车削中的不同之处。     

In-process prediction of surface roughness in turning of Ti–6Al–4V alloy using cutting parameters and vibration signals

In this work, an attempt has been made to use vibration signals for in-process prediction of surface roughness during turning of Ti–6Al–4V alloy. The investigation was carried out in two stages. In the first stage, only acceleration amplitude of tool vibrations in axial, radial and tangential directions were used to develop multiple regression models for prediction of surface roughness. The first and second order regression models thus developed were not found accurate enough (maximum percentage error close to 24%). In the second stage, initially a correlation analysis was performed to determine the degree of association of cutting speed, feed rate, and depth of cut and the acceleration amplitude of vibrations in axial, radial, and tangential directions with surface roughness. Subsequently, based on this analysis, feed rate and depth of cut were included as input parameters aside from the acceleration amplitude of vibrations in radial and tangential directions to develop a refined first order multiple regression model for surface roughness prediction. This model provided good prediction accuracy (maximum percentage error 7.45%) of surface roughness. Finally, an artificial neural network model was developed as it can be readily integrated into a computer integrated manufacturing environment.     

面向行驶平顺性的轿车振动系统性能参数设计方法

给出一种轿车面向行驶平顺性分析的简化仿真模型 ,应用仿真模型对某国产轿车进行了随机不平路面输入下的汽车振动系统性能参数仿真试验研究 ,得出了振动系统性能参数对汽车行驶平顺性指标———车身振动加速度均方根值的影响规律 ,为确定该车振动系统性能参数优化设计的设计空间和优化值提供了依据     

Effect of lubricant viscosity grade on mechanical vibration of roller bearings

This work aims to characterize vibration behavior of roller bearings as a function of lubricant viscosity. Experimental tests were performed in NU205 roller bearings, lubricated with mineral oil of three different viscosity grades (ISO 10, 32 and 68). The mechanical vibration was determined through the processing and analysis of bearing radial vibration data, obtained from each of the lubrication conditions, during 2 h of test run for temperature stabilization and under several bearing shaft speeds. The applied radial load was 10% of the bearing nominal load. Through root mean square (RMS) analysis of the vibration signals, it was possible to identify specific frequency bands modulated by the change in lubricant viscosity, which was related to change in oil film thickness.     

基于垂向性能研究的新型悬架参数设计

设计了一种用于四轮独立转向独立驱动电动轿车的独立悬架,该悬架采用双横臂、螺旋弹簧结构,悬架连接带轮毂电机的大质量电动车轮。对悬架系统进行简化,建立了悬架二自由度振动模型,采用均方根值分析方法,计算出振动系统的频率响应函数及振动响应的均方根值(包括车身加速度均方根值、车轮相对动载荷均方根值及悬架动挠度均方根值),基于悬架参数对电动车辆垂向性能的研究,提出了新型悬架弹簧刚度和减振器阻尼系数的设计方法,结合仿真及实验验证了设计方法的合理性。     

卫星随机试验的振动响应分析

介绍基础激励下结构随机振动响应的分析方法,并对某配重卫星轴向和横向的窄带随机激励进行有限元计算。通过对此卫星结构加速度响应的均方根值、累积均方值和功率谱密度等统计量的分析,研究随机振动试验中卫星结构的随机响应,以此考察卫星承受此种动力学环境的能力,为卫星上仪器设备的减振方案设计和提高卫星发射的可靠性提供参考。     

Optimization of secondary suspension of piecewise linear vibration isolation systems

A comprehensive optimal design solution is presented for piecewise-linear vibration isolation systems. First, primary suspension optimum parameters are established, followed by an investigation of jump-avoidance conditions for the secondary suspension. Within the no-jump zones, an optimal design solution is then obtained for the secondary system and overall results are discussed.Averaging method is employed to obtain an implicit function for frequency response of a bilinear system under steady-state conditions. This function is examined for jump-avoidance and a condition is derived which when met ensures that the undesirable phenomenon of ‘jump’ does not occur and the system response is functional and unique. Optimal stiffness and damping parameters for the primary suspension are extracted from a recently established work for passive linear vibration systems. For each point of the primary suspension optimal curve, jump-free zones are identified. Iterating this process, a boundary surface between no-jump (unique response) and jump (multiple-response) areas is established. Keeping optimal parameters for the primary suspension system fixed, the secondary suspension stiffness and damping parameters are varied inside the no-jump zones to explore optimum solutions for the secondary.The root mean square (RMS) of the absolute acceleration is minimized against the RMS of the relative displacement (η). It is observed that there is a certain band of parameters defined by primary damping, within which a valid frequency response can be obtained. An optimum numerical solution is sought within this band of parameters. Optimal solution curves are achieved for the secondary suspension. These can be used in conjunction with the optimal curve for the primary suspension to select design parameter values for the best possible vibration isolation performance in a given application.     

Modelling the effect of flank wear on machining thrust stability

This paper discusses an analytical assessment of the effect of cutting tool flank wear on machining stability along the thrust direction in a turning operation based on an analysis of frequency band root-mean-square (RMS) level of the accelerometer signals. The energy content of machining at the tool-tip/workpiece interface along the flank is represented by the RMS signal level, in comparison to the random vibration of the cantilever portion of the tool holder. The RMS signals measured from a tool-post accelerometer in stable machining with tool wear effect are calculated using the frequency band RMS method at the first natural frequency of the cantilever portion of the tool holder. Increasing flank wear results in increasing stability and decreasing RMS in the thrust direction in machining. For model validation, a series of machining experiments were performed under the condition of various flank wear/land widths, while the RMS signals from a tool-post accelerometer were collected and studied. It was found that theoretical predictions were shown to be in agreement with experimental results.     

离心泵后泵腔内液体压力数值分析与验证

离心泵轴向力的大小与泵腔内压力分布密切相关,而试验测量轴向力成本较高,因此采用数值模拟展开泵腔内压力分布规律研究,并提出简便的试验测量轴向力方法显得格外必要。利用数值模拟计算,在0.6 Q_(sp)~1.2Q_(sp)工况下,研究离心泵后泵腔压力沿轴向、径向、切向分布规律,绘制后泵腔压力在0°、90°、180°、270°及压力均值沿径向分布曲线,得出后泵腔轴向力大小,推导两种近似计算泵腔轴向力公式,提出简便的试验测量泵腔轴向力方法,并将后泵腔压力模拟结果与试验结果对比,验证模拟结果的真实可靠性。结果表明:同一流量工况点,后泵腔压力沿轴向保持不变,沿径向随半径增大而增大。流量越大,后泵腔压力沿切向分布越具有轴对称性,沿径向增大越均匀。后泵腔轴向力两种公式计算结果与数值计算结果相对误差极小,后泵腔区域压力均值与其径向几何中心处压力均值大小相等。在试验测量离心泵泵腔轴向力时,只需要测量泵腔沿180°径向中心处压力值,便可近似求得泵腔区域轴向力大小。     

Multi-objective optimization modification of a tooth surface with minimum of flash temperature and vibration acceleration RMS

The minimum of tooth surface flash temperature and vibration acceleration RMS design is proposed and analyzed. The tooth contact analysis (TCA) and the load tooth contact analysis (LTCA) method and multi-objective optimization are also detailed. Satisfying design variables in multiple physical quantities leads to the minimum of multi-objective optimization. Considering the tooth surface loading conditions are uniform or not, the optimal modification of the tooth surface for improving gear comprehensive characteristics under various load bearing conditions is improved. The tooth surface flash temperature and vibration acceleration root mean square (RMS) values in different transmission modes of marine ship power rear gears drive system are derived. This research considers the multi-objective optimization modifications of tooth surface, and its main purpose is to propose an approach to help design tooth corrections to simultaneously optimize several objective physical quantities.     

高速列车二系垂向悬挂系统设计解析表达式*

根据1/4车体4自由度垂向振动模型,利用随机振动理论及留数定理,建立轨道高低不平顺激励下的车辆垂向振动响应均方根值解析表达式;通过数值计算对解析表达式的正确性进行了验证,结果表明在一定有效数字范围内解析计算值与数值计算值完全吻合,表明所建立的解析表达式是正确的;通过整车仿真对比对解析计算方法的可靠性进行了验证,可知车体垂向振动加速度均方根值和二系悬挂垂向行程均方根值的解析计算值与整车仿真验证值的最大相对偏差分别仅为12.50%和15.47%,表明所建立的解析计算方法是可靠的。在此基础上,利用黄金分割原理,建立了二系垂向悬挂系统阻尼比优化设计方法,并通过实例对其可行性进行了分析,为高速列车二系垂向悬挂系统参数的初始设计提供了参考。