基于ABAQUS的金属切削过程模拟

基于ABAQUS系统强大的大变形分析功能,对A6061铝合金材料的正交切削过程进行了有限元模拟分析.讨论了切削过程中切削层内部应变场和工件中残余应力的分布,分析了不同参数对切削力、残余应力的影响.模拟结果与切削试验数据相互吻合.     

金属切削加工过程的数值模拟

运用商业非线性有限元软件MSC.MARC,对金属切削加工过程进行了弹塑性热力耦合模拟,分析了不同刀具几何参数及切削用量在切削加工过程中对切削力、应力分布、工件残余应力及残余变形的影响.     

金属切削过程热力耦合的三维数值仿真

以金属块体为研究对象,利用动态显式积分有限元程序对金属的切削过程进行三维热力耦合分析,讨论切削过程数值模拟关键技术,展现切屑的形成、工件与刀具的接触、分离和摩擦,给出切削过程中工件和切屑中的温度、应力和应变分布的变化情况,分析切削速度对不同形貌的切屑形成的影响.文中的计算方法可为更复杂的切削过程的数值模拟提供技术支撑.     

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.     

基于ABAQUS的TC4合金切削变形区有限元仿真

在不同的切削速度和平面应力应变厚度下,对工件切削变形区的温度和切削力进行了研究。基于弹塑性有限元理论建立TC4合金的二维有限元模型,运用ABAQUS有限元分析软件对TC4合金进行了弹塑性仿真分析。通过分析工件切削变形区的温度变化云图和切削力变化曲线可知:切削速度的变化对工件切削变形区的温度影响较大,平面应力应变厚度影响较小,切削力随着平面应力应变厚度的增加而变大。     

基于热力耦合模型的切削加工残余应力的模拟及试验研究

航空精密薄壁零件具有复杂的型腔结构,切削加工残余应力是薄壁零件精度稳定性的重要影响因素,因此必须对切削加工残余应力进行研究。根据热—弹塑性有限元理论,建立切削加工三维有限元模型,对航空铝合金材料Al2A12进行切削加工非线性弹塑性有限元模拟分析,对切削加工表面残余应力进行预测和计算。通过有限元分析,得到不同切削参数、刀具参数条件下的已加工表面残余应力的模拟结果,并对结果进行比较分析,得到各个因素对工件已加工表面残余应力的基本影响规律;进行不同加工工序条件下的切削加工残余应力的有限元模拟,在加工表面已有一次切削加工残余应力分布的情况下,进行二次切削加工有限元模拟,得到二次切削加工对工件已加工表面残余应力的影响规律;并且进行不同切削参数对残余应力影响的试验研究,验证有限元模型的正确性。     

微切削已加工表面残余应力预测

准确预测残余应力对提高微小工件的可靠性非常重要.建立微切削残余应力的理论分析预测模型,应用有限元仿真方法,探求了不同切削速度和进给量下微切削45钢已加工表面残余应力分布规律,分析了切削速度和进给量对已加工表面残余应力的影响,为优化微切削过程和防止微小零件疲劳破坏提供可靠的依据.     

带有残余应力的关节轴承外圈硬切削有限元仿真研究

针对关节轴承冷挤压装配后,其轴承外圈存在较大的残余应力的问题,对多次硬切削关节轴承外圈对残余应力的影响和轴承内外圈间隙的分布规律进行了研究,对自润滑关节轴承挤压装配过程和冷却回弹过程进行了仿真分析,开展了多次硬切削带残余应力的GCr15轴承钢关节轴承外圈有限元仿真分析,建立了材料本构模型、损伤初始准则及损伤演化准则之间的关系,提出了热力耦合有限元仿真分析的方法。在Abaqus软件上对多次硬切削对应力分布情况和轴承外圈回弹量等进行了评价分析。研究结果表明,有限元仿真分析能够预测硬切削对自润滑关节轴承外圈残余应力大小的影响和轴承内外圈间隙的变化规律,这对于通过硬切削释放残余应力,控制和提高工件质量具有重要的理论指导意义。     

基于Deform的枞树型轮槽铣刀加工仿真研究

利用三维建模软件PRO/Engineer,建立枞树型轮槽铣刀模型。运用专业的塑性成形非线性有限元分析软件DEFORM-3D软件,对轮槽铣刀铣削加工汽轮机转子材料的过程进行了动态模拟仿真,并且获得了切削力、切削温度和工件残余应力等数据。分析了轮槽铣削加工仿真过程中切削力、切削温度、工件残余应力等影响因素。     

基于有限元法的振动刨削仿真分析

由于有限元数值模拟技术具有试验方法和理论解析方法相结合的特点,文中采用有限元分析软件对振动刨削时工件的受力过程进行仿真。为了揭示振动切削的应力波对切削过程的影响差异,进行了直角自由刨削仿真分析,得出振动切削微观机理的有效解释。     

FEM-based prediction of heat partition in dry metal cutting of AISI 1045

Thermal effects often limit the performance of cutting processes. The energy spent in cutting is almost completely converted into heat which partly flows to workpiece, chip, and tool during the process. Therefore, knowledge about this partition is valuable for the process, tool, and coolant system design or for the compensation of thermal deformations of the workpiece and machine tool. For this reason, a simulation model based on the finite element method was developed to analyze the heat partition in dry metal cutting. The model utilizes the coupled Eulerian-Lagrangian method to simulate the chip formation in orthogonal cutting and to calculate the temperature distribution within workpiece, chip, and tool. This distribution was used to compute the heat partition between workpiece, chip, and tool in dependence of relevant process parameters. Furthermore, the results were validated by orthogonal cutting experiments and summarized in a formula to calculate the rate of heat flow into the workpiece as a function of those parameters.     

Fundamental modeling for oblique cutting by thermo-elastic-plastic FEM

In this paper, the finite deformation theory and updated Lagrangian formulation were used to describe the oblique cutting process. Either the tool geometrical location condition or the strain energy density constant was combined with the twin node processing method to act as the chip separation criterion. An equation of three-dimensional tool face geometrical limitation was first established to inspect and correct the relation between the chip node and the tool face. And, a three-dimensional finite-difference heat transfer equation was derived. Based on this approach, tool advancement was achieved in displacement increment step by step from the initial tool contact with the workpiece till the formation of steady cutting force. In this case, a large deformation thermo-elastic–plastic finite element model for oblique cutting was established. The mild steel was used as the workpiece, the tool was P20 and the cutting speed was 274.8 mm/s in this article. The chip deformation process and temperature effect on the strain energy density, chip flow angle, cutting force and specific cutting energy were studied first. Finally, the integrity on machined workpiece surface was explored from the variation of residual stresses and temperature distribution on it after cutting. During the chip deformation process, the chip flow angle obtained by this simulation result was approximately equal to the tool inclination angle, which confirmed with the geometrical requirement of Stabler’s criterion. Besides, the simulated specific cutting energy was compared with the experimental specific cutting energy value, the result of which was within acceptable range. It is obvious from the above findings that the model presented in this paper is consistent with the geometrical and mechanical requirements, which verifies the proposed model is acceptable.     

An explicit finite element model to study the influence of rake angle and friction during orthogonal metal cutting

A fundamental understanding of the tribology aspects of machining processes is essential for increasing the dimensional accuracy and surface integrity of finished products. To this end, the present investigation simulates an orthogonal metal cutting using an explicit finite element code, LS-DYNA. In the simulations, a rigid cutting tool of variable rake angle was moved at different velocities against an aluminum workpiece. A damage material model was utilized for the workpiece to capture the chip separation behavior and the simultaneous breakage of the chip into multiple fragments. The friction factor at the cutting tool–workpiece interface was varied through a contact model to predict cutting forces and dynamic chip formation. Overall, the results showed that the explicit finite element is a powerful tool for simulating metal cutting and discontinuous chip formation. The separation of the chip from the workpiece was accurately predicted. Numerical results found that rake angle and friction factor have a significantly influence on the discontinuous chip formation process, chip morphology, chip size, and cutting forces when compared to the cutting velocity during metal cutting. The model was validated against the experimental and numerical results obtained in the literature, and a good agreement with the current numerical results was found.     

成形铣齿加工过程中的切削热模型

为了获得铣齿切削时切削区域的温升分布,在分别对铣削热产生和传出的机理,以及刀具和工件之间几何关系分析的基础上,得出包含对应虚拟镜像热源的热源模型。考虑到剪切面热源和刀屑接触面摩擦热源对工件、切屑和刀具的温升作用效果的不同,根据傅里叶导热定律推导出顶刃切削时相应热源的温升计算公式,分别对3者的温升分布进行计算可以获得整个切削区域的温升分布。结果表明,铣削过程中温度随切削的深入而升高,在不改变工件和刀具材料的情况下,进给速度是影响切削温度的主要因素,改变刀盘转速对温升的影响不大。     

车削中三维复杂断屑槽刀具断屑仿真研究

为有效缩短现有断屑槽刀具的设计周期、降低设计成本,采用有限元方法模拟了切削过程中切屑折断过程。利用Solid Works软件建立了三种刀具的三维模型,并在Deform 3D软件中对车削45钢工件过程进行了三维切削仿真。其中,工件材料采用了Johnson-Cook模型和Cockroft-Latham韧性断裂准则,仿真模型采用了有效参数设置以保证数值计算精度与效率。通过仿真研究了不同切削参数下的切屑形态、断屑过程及主切削力等。研究结果表明,仿真结果与试验结果吻合良好,该仿真模型及方法能有效应用于断屑槽刀具断屑性能研究,是三维复杂断屑槽刀具设计和切削参数优化的一种新方法。     

A stability analysis of regenerative chatter in turning process without using tailstock

A new approach to analyze the stability of cutting processes when considering the deformation of the workpiece is proposed in this article. In past studies, the workpiece was assumed to be rigid and no deformation was considered. In those studies, the stability of the cutting process was analyzed by merely the dynamic equation of tools. However, the workpiece does have deformation when there is external force exerting on it. Such deformation will change the chip thickness and have an effect on the critical chip thickness of stability. To describe the cutting in turning process, partial differential equations are used and a set of dynamic equations will be considered based on the interaction between the tool and the workpiece. After performing the Laplace transformation, stability can be analyzed based on the length, radius, natural frequency, deflection, aspect ratio and material stiffness of the workpieces. The effect of the critical chip width under different spindle speed will also be discussed in this article. By considering the deformation of the workpiece under different conditions, the results show that the critical chip width of the deformed case is always larger than the rigid body case.     

A model of the cutting mechanism in grinding

In order to achieve optimum working results during grinding, information regarding both the kinematic relations and the structure of the multiple cutting-edge tool is necessary. In addition, the physical and metallurgical properties of the workpiece material and the specific influence of the interfacial frictional effects must be taken into account.This paper presents a contribution to the understanding of the cutting mechanisms in grinding. An analysis of the grinding mechanism is made on the basis of the cutting-edge geometry and the kinetics involved. One physical model has been developed to explain all the phenomena from friction to ploughing and cutting under plane strain conditions.Starting from the velocity relation at an averaged penetrating cutting edge and characterizing frictional conditions at the interface between the cutting edge and the workpiece material, it is possible to calculate a slip-line field which satisfies all the existing boundary conditions. The flow pattern of the material can be drawn taking the corresponding hodograph into account. This results in a distortion of the square grid characterizing the material on passing through the region of plastic deformation. Agreement with cross sections of actual chip formation zones during grinding is observed. The significance of this analysis lies in the fact that it establishes a relation between chip formation and the resultant surface integrity.     

Force prediction and stability analysis of plunge milling of systems with rigid and flexible workpiece

Time domain simulation model is developed to study the dynamics of plunge milling process for system with rigid and flexible workpiece. The model predicts the cutting forces, system vibration as a function of workpiece and tool dynamics, tool setting errors, and tool kinematics and geometry. A horizontal approach is used to compute the chip area to consider the contribution of the main and side edge in the cutting zone and to deal with any geometric shape of the insert. The dynamic chip area is evaluated based on the interaction of the insert main and side cutting edges with the workpiece geometry determined by the pilot hole and surface left by the previous insert. For the case of system with a flexible workpiece, the workpiece dynamics, as well as its variation in the axial direction with respect to hole location, is considered in the simulation. Cutting tests with single and double inserts were carried out to validate the simulation model and predicted stability lobe for both systems with rigid and flexible workpiece and to check the correctness of the cutting coefficient model. Good agreement was found between the measured and the predicted cutting forces and vibration signals and power spectra. This indicates the ability of the model to accurately predict cutting forces, system vibration, and process stability for process planning prior to machining. The results show dominance of workpiece dynamics in the axial direction for systems with flexible workpiece due to its flexibility as compared to the tool axial rigidity. On the other hand, chatter behavior was found to occur due to tool lateral modes for case of rigid workpiece.     

Investigation of the direction of chip motion in diamond turning

Management of the chips generated in diamond turning is often critical since contact between chips and the workpiece can result in superficial damage to the finished surface. Controlling chip motion is not a trivial process as the proper positioning of an oil or an air stream requires an understanding of the dynamics of a diamond turned chip and the machining parameters that affect it. Previous work [1] introduced the chip curvature parameter, χ, which is useful in predicting chip radius of curvature over a wide range of cutting speeds, depths of cut, tool geometries and workpiece material properties. To control chip motion, however, an understanding of the direction chips leave the tool/workpiece interface must also be obtained. Cutting experiments were performed investigating the influence of cutting speed, depth of cut, feed rate, tool path angle, tool geometry and tool orientation on the directional characteristics of the motion of diamond turned chips. Flow angle measurements obtained during cutting were found to remain within ± 10° of predictions from a simple geometrical model originally proposed for conventional machining.     

The investigation of mechanism of serrated chip formation under different cutting speeds

Chip type is determined by the coupled effects of workpiece material property, cutting speed, uncut chip thickness, feed rate, and tool edge geometry. The understanding of chip formation plays a critical role in studying surface integrity and optimization of machining process variables. Serrated chip, one of the major important chip type, is usually formed in hard cutting at high speed. In this study, a new analytical model has been proposed to better understand the formation of serrated chip, and the simulations have been acquired using ABAQUS/Explicit in machining AISI 1045 during different speeds (from 60 to 6000 m/min). The workpiece material property is modeled with the Johnson-Cook model, and the experiments have been conducted with AISI 1045 during speeds from 60 to 1200 m/min. It has been shown that flow stress is influenced simultaneously by the strain rate hardening and temperature softening. When the speed reaches very high, the temperature softening will fail, and the strain rate hardening will play a more important role. Also, it can be found that the hardening ratio increases when the cutting speed rises. The results of the simulations and experiments correlated well. The cutting force and thrust force both decrease as the cutting speed increases, and the difference between them will shrink when the machining speed reaches a high level.