球头刀铣削淬硬钢倾斜表面切削力试验研究

采用正交试验方法,使用PCBN涂层硬质合金球头铣刀,对不同铣削参数下的52HRC淬硬钢Cr12MoV倾斜表面进行了铣削试验。研究了各工艺参数对切削力的影响规律。试验结果表明:三向力中,Fz远大于Fx和Fy的切削分力,Fz为主铣削力;切削深度对主铣削力的影响大于进给速度、工件倾角和主轴转速对其的影响;工件倾角16.7°,主轴转速6000r/min,进给速度800mm/min,切削深度0.1mm为优选工艺条件。同时,对比试验表明,采用顺铣方式能有效减小切削力,改善铣削稳定性。本文研究结果对淬硬钢Cr12MoV铣削工艺参数的优化具有一定的参考价值。     

不等距立铣刀切削力模型的建立及试验分析

在特定铣削条件下,建立了多齿不等距铣刀的切削力模型,并通过正交试验验证所建的切削力模型;通过分析不同的切削参数对切削力系数的影响,综合确定了在小切削宽度铣削过程中合理选用切削参数的基本原则。     

高速铣削超高强度钢的切削力及表面粗糙度研究

选用涂层硬质合金刀具对300M超高强度钢进行高速铣削试验,通过单因素试验和多因素正交试验法,得出铣削参数(主轴转速、每齿进给量、铣削深度)对切削力及表面粗糙度的影响规律及主次关系。对正交试验结果做最小二乘法分析,建立切削力及表面粗糙度与铣削参数之间的经验模型;对经验模型的回归方程及系数做显著性检验,并对其进行参数优化,得出铣削参数的最优组合。结果表明:主轴转速和铣削深度对切削力的作用较大,而每齿进给量对其影响相对较弱;每齿进给量对表面粗糙度作用最强,铣削深度次之,主轴转速对其作用最弱。     

面铣刀铣削钛合金时切削参数对切削力影响规律的仿真

为了研究面铣刀铣削钛合金时背吃刀量、铣削速度和进给量对刀齿所受切削力的影响,建立面铣刀铣削钛合金的模型。采用单因素实验法,基于ABAQUS有限元仿真软件对所建模型进行铣削仿真,在不同背吃刀量、铣削速度和进给量的条件下,分别对刀齿切削力的变化规律进行分析。研究表明：面铣刀铣削钛合金时,背吃刀量的改变对切削力影响程度最大。在中高速铣削条件下,使用小背吃刀量和大进给量,可以降低切削力,提高刀具寿命。     

PCBN可转位面铣刀铣削灰铸铁HT200的试验研究

采用多因素正交试验方法进行PCBN可转位面铣刀铣削灰铸铁HT200的试验,通过最小二乘法和回归分析建立了铣削力经验公式模型.回归方程及回归系数的显著性检验表明所建立的模型可信度较高.试验结果表明3个方向的铣削力中,切向铣削力Fz最大,其次是轴向铣削力Fx和径向切削力Fy.通过对试验结果的分析,总结出了各铣削参数对于铣削力的影响变化规律,给出了切削参数的推荐取值范围.     

端铣刀铣削加工铝合金铣削力试验及切屑分析

采用正交试验设计方法对铝合金进行铣削试验,测得了不同切削用量情况下硬质合金铣刀的铣削力。运用方差分析法确定了主轴转速、轴向切深、径向切深、进给速度等切削参数对切削力的影响程度,并对切屑进行了金相分析。这为设计刀具和选择切削用量提供了借鉴。     

高速铣削加工铝合金表面残余应力研究

基于Doelle—Hauk方法测量了铣削加工铝合金工件表面的残余应力状态,结果表明,应力主平面与试样表面基本平行,说明铣削加工铝合金表面的残余应力近似处于二维平面应力状态。在分析了织构对残余应力测试影响的基础上,采用X射线衍射法中的回摆法测量了铣削加工工件表面不同切削几何位置、不同转速下残余应力的分布规律。为了对残余应力的分布作出解释,采用Kisterler测试仪测试了不同主轴转速下切削力的变化规律;建立了双刃斜角切削有限元模型,得到了单个切屑形成时已加工工件表面的切削温度场。最后,从热力耦合的角度对残余应力的形成机理进行了研究。     

300M超高强度钢高速铣削切削力建模研究

通过建立300M超高强度钢(低合金超高强度钢40CrNi2Si2MoVA)高速铣削切削力经验模型,分析切削参数对切削力的影响,为高速铣削切削参数的合理选择提供可靠依据.采用多因素正交试验方法进行300M超高强度钢高速铣削实验,使用最小二乘法等概率统计方法和回归分析原理建立切削力与轴向切深、主轴转速、进给量、径向切深之间的经验模型,对回归方程及回归系数进行显著性检验,通过切削参数优化验证切削力模型的有效性.通过正交试验直观分析考察切削参数对于铣削力的影响规律.     

超声振动铣削陶瓷基复合材料切削力模拟研究

针对陶瓷基复合材料在加工过程中易出现毛刺、分层、崩边等加工问题,提出超声振动切削方法加工陶瓷基复合材料并进行了铣削过程的有限元模拟分析。给出了主轴转速、进给速度对铣削过程中各向切削力的影响,对比分析了超声振动铣削加工与普通铣削加工的切削力波形曲线。结果表明,两种加工方法各向切削力均随主轴转速的增大而减小,进给速度的增大而增大,但当主轴转速达到4000r/min时,超声作用消失,超声振动切削力与普通铣削切削力相当;同时,超声振动铣削加工条件下各向切削力峰值都明显低于普通铣削切削力,平均切削力更是有大幅度降低,超声振动切削方法更适合加工陶瓷基复合材料。     

内螺纹铣削力预测模型及试验研究

通过分析内螺纹铣刀的铣削机理和切屑厚度,确定内螺纹加工的主轴转速、进给率、刀具几何参数,提出了一种通用的内螺纹铣削力数学预测模型,研究内螺纹铣削力的变化规律。结合具体的铝合金7075内螺纹加工试验来验证本数学预测模型。试验研究表明,切削力在X方向,其分量力最大,对铣刀旋转角度的变化也最为敏感,力分量最小为Y方向分量,对铣刀旋转角度的变化最不敏感。试验结果与所建立切削力预测模型在力变化趋势上以及分力数值上都很好的匹配。数学模型所预测切削力与试验所测数据平均误差控制在10%以内,从而验证了所建数学模型的精确性。     

基于断裂力学的Nomex蜂窝复合材料超声切割机理研究

Nomex蜂窝复合材料的超声切割技术克服了传统高速铣削中存在的工件固持困难、加工粉尘大等问题。基于断裂力学研究Nomex蜂窝复合材料的超声切割机理,为超声切割工艺参数优化以及超声波声学主轴的优化设计提供理论依据。根据直刃刀超声切割Nomex蜂窝复合材料加工工艺,建立直刃刀的运动学方程,分析得到超声切割断续加工过程中直刃刀与材料相互作用时间关系;应用断裂力学理论,引入动态应力强度因子建立蜂窝复合材料的断裂韧性模型,研究超声切割作用下蜂窝复合材料的微观断裂过程,根据直刃刀位移和裂纹扩展的关系模型,分析切削力的影响因素,并进行仿真研究。研制了超声切割工艺试验台,对蜂窝复合材料进行了有超声和无超声切割加工的对比试验,试验结果显示超声切割显著地减小了切削力,也证实了冲击产生的微裂纹扩展是蜂窝复合材料在直刃刀超声切割作用下,切割力减小的主要原因。理论分析和试验研究表明基于断裂力学的Nomex蜂窝复合材料超声切割机理研究具有有效性和合理性。     

石英玻璃微铣削加工的离散元模拟与试验分析

针对石英玻璃的微铣削过程,采用离散元模拟软件PFC3D建立真实的离散元模型,模拟裂纹的生成与扩展情况,得到铣削力曲线图以及铣削过程的较优加工工艺参数,并通过铣削力试验验证了石英玻璃三维离散元模型有效性及离散元法模拟石英玻璃切削过程的合理性。基于模型和试验一致,得出不同铣削参数下铣削力的变化规律。结果表明:铣削力随主轴转速的增加则先减小后增加再减小,随切削深度和进给速度的增加而增加,随刀具倾角的增加则先增加后减小。     

球头铣刀加工倾角对切削力的影响

对球头铣刀刀具轴线和工件加工表面之间的加工倾角进行了理论研究,建立了加工曲面时刀具倾角的数学模型,并通过试验研究了高速铣削铝合金时刀具倾角对切削力的影响规律。随着刀具轴线相对于进给方向倾斜角度β的增大,切削力变化的趋势是减小;编制多轴数控加工程序时可以通过设置合理的刀具倾角来改善切削条件。     

A novel 5-DOFs dynamic model of aerostatic spindle considering the effect of process damping in ultra-precision machining

The existing aerostatic spindle dynamic model only analyses the effects of mass imbalance and external load, ignoring the influence of cutting system on the spindle dynamic characteristics under cutting conditions. In this paper, a 5-DOFs aerostatic spindle dynamic model is established considering the influence of the micro-scale non-linear dynamic performance of the aerostatic spindle and cutting process damping. First, an analytical identification model of process damping with blunt circular cutter is established. Then, the micro-scale dynamic characteristics of the aerostatic spindle are analyzed and a 5-DOFs aerostatic spindle dynamic model is established considering the influence of process damping. Finally, the model is simulated and the influence of process damping on the dynamic characteristics of aerostatic spindle is analyzed. The simulation results show that the process damping of the cutting system has a significant influence on the dynamic characteristics of the aerostatic spindle. This study can provide theoretical guidance for coupling research of cutting system and spindle system.

     

Optimization of cutting conditions for minimum residual stress,cutting force and surface roughness in end milling of S50C medium carbon steel

Residual stresses are usually imposed on a machined component due to thermal and mechanical loading. Tensile residual stresses are detrimental as it could shorten the fatigue life of the component; meanwhile, compressive residual stresses are beneficial as it could prolong the fatigue life. Thermal and mechanical loading significantly affect the behavior of residual stress. Therefore, this research focused on the effects of lubricant and milling mode during end milling of S50C medium carbon steel. Numerical factors, namely, spindle speed, feed rate and depth of cut and categorical factors, namely, lubrication and milling mode is optimized using D-optimal experimentation. Mathematical model is developed for the prediction of residual stress, cutting force and surface roughness based on response surface methodology (RSM). Results show that minimum residual stress and cutting force can be achieved during up milling, by adopting the MQL-SiO₂ nanolubrication system. Meanwhile, during down milling minimum residual stress and cutting force can be achieved with flood cutting. Moreover, minimum surface roughness can be attained during flood cutting in both up and down milling. The response surface plots indicate that the effect of spindle speed and feed rate is less significant at low depth of cut but this effect significantly increases the residual stress, cutting force and surface roughness as the depth of cut increases.     

Analysis of cutting force coefficients in high-speed ball end milling at varying rotational speeds

In high-speed ball end milling, cutting forces influence machinability, dimensional accuracy, tool failure, tool deflection, machine tool chatter, vibration, etc. Thus, an accurate prediction of cutting forces before actual machining is essential for a good insight into the process to produce good quality machined parts. In this article, an attempt has been made to determine specific cutting force coefficients in ball end milling based on a linear mechanistic model at a higher range of rotational speeds. The force coefficients have been determined based on average cutting force. Cutting force in one revolution of the cutter was recorded to avoid the cutter run-out condition (radial). Milling experiments have been conducted on aluminum alloy of grade Al2014-T6 at different spindle speeds and feeds. Thus, the dependence of specific cutting force coefficients on cutting speeds has been studied and analyzed. It is found that specific cutting force coefficients change with change in rotational speed while keeping other cutting parameters unchanged. Hence, simulated cutting forces at higher range of rotational speed might have considerable errors if specific cutting force coefficients evaluated at lower rotational speed are used. The specific cutting force coefficients obtained analytically have been validated through experiments.     

大悬伸状态加工水室封头重型铣削振动分析

针对大悬伸状态下加工水室封头产生的重型铣削振动,以重型铣削水室封头现场加工实验为基础,分析重型铣削振动产生的原因,并根据现场实验对工件已加工表面形貌进行对比分析。建立重型铣削刀具偏心跳动模型、刀具与主轴系统的轻微变形模型和进给系统刚度的模型,分析其对重型铣削瞬时切削厚度的影响,同时建立重型铣削力数学模型和铣削轨迹模型。分析重型铣削系统振动影响因素及规律,振动模型预测结果与实验结果吻合较好。该工作为进一步研究重型铣削振动特性提供依据。     

端铣刀切入过程应力场有限元分析

断续切削中脆性刀具易在切入工件的初始阶段发生破损.文中采用有限元软件DEFORM,对端铣刀在不同切削参数条件下切削碳素钢的切入过程进行仿真,以确定铣刀切入过程所受的载荷;然后分析切削参数对刀具应力的影响,确定切入过程刀具的应力变化及分布,为建立合理的铣刀切入破损预测模型提供参考.     

Radial grip rigidity of the matching of lengthened shrink-fit holder and cutter in high-speed milling

Though the lengthened shrink-fit holder (LSFH) is widely applied in high speed milling of the parts characterized by deep cavities at present,its design and selection mainly depends on the experience and lacks a correct theoretical guidance.In this paper,attention is focus on the radial grip rigidity of the matching of LSFH and cutter in high speed milling.Based on the experiment modal analysis (EMA) technique,an accurate finite element model of the matching of LSFH and cutter is established firstly.Subsequently,the influence of different interference,grip length and spindle speed on the grip rigidity of LSFH are analyzed.The analysis results show that there is a reasonable interference and grip length between the LSFH and cutter so that to have a steepless grip and have a good radial grip rigidity and at the same time to avoid the strength of LSFH to exceed it’s yield limit which will reduce the precision and service life of LSFH,besides when spindle speed reach a extension the weakening influence of the centrifugal force on the radial grip rigidity of the matching of LSFH and cutter should been taken into account.Finally,the finite element analysis results are verified based on the construction of measurement method of the grip rigidity and the results fit very well.The studies provide a theoretical basis for the design,selection and the serialization and standardization of the matching of LSFH and cutter.     

高速主轴系统切削稳定性预测及影响因素分析

高速主轴系统切削稳定性直接影响产品的表面加工精度和切削系统的使用寿命,是评价高速主轴系统性能优劣的重要因素,而研究影响切削稳定性的因素并制定提高稳定性的合理途径同样也受到关注。提出从稳定性评价准则及系统频响函数的不同求解方法入手,分析无条件稳定区和有条件稳定区的影响因素,总结出系统所受激励、主轴转速及系统结构是影响切削稳定性的重要因素。以德国GMN高速主轴系统为例,在采用5自由度轴承受力与变形关系模型模拟角接触球轴承和分布式弹簧模型模拟主轴-刀柄-刀具结合部的基础上,建立完整高速主轴系统通用有限元模型;利用三维稳定性叶瓣图、极限切削深度和叶瓣交点随参数的变化曲线表征切削力幅值、转速及阻尼比等参数对切削稳定性的影响规律,为优化加工工艺、提高系统切削稳定性提供理论依据。