38CrMoAl钢机筒棒料镗孔切削性能比对分析

通过比对镗孔切削性能有差异的38CrMoAl钢机筒棒料的化学成分、显微组织、硬度、残余应力等参数,确定了造成镗孔性能存在差异的主要原因是：①复合型硫化物和氮化物夹杂;②残余元素总含量高;③残余钛元素含量、氮元素含量高;④铁素体含量低。由此确定了38CrMoAl钢机筒棒料生产工艺中4项质量控制点。     

Development of a virtual machining system, part 1: approximation of the size effect for cutting force prediction

In this three-part paper, components of a virtual machining system for evaluating and optimizing cutting performance in -axis NC machining are presented. Part 1 describes a new method of calculating cutting-condition-independent coefficient and its application to the prediction of cutting forces over a wide range of cutting conditions. The prediction of the surface form error and transient cutting simulations, described in Parts 2 and 3, respectively, can be effectively performed based on the cutting force model with the improved size effect model that is presented in Part 1.

The relationship between the instantaneous uncut chip thickness and the cutting coefficients is calculated by following the movement of the center position of the cutter, which varies with nominal feed, cutter deflection and runout. The salient feature of the presented method is that it determines the cutting-condition-independent coefficients using experimental data processed for one cutting condition. The direct application of instantaneous cutting coefficient with size effects provides more accurate predictions of the cutting forces. A systematic comparison of the predicted and measured cutting forces over a wide range of cutting conditions confirms the validity of the proposed mechanistic cutting force and size effect models.     

带筋拉深曲面零件压边力的临界计算

分析了带筋拉深曲面零件时板料的受力状况,对确保板料外缘一直压靠拉深筋所需的最小压边力以及防止内皱发生的最大压边力进行了临界计算,获得了曲面零件带筋拉深最大和最小压边力的取值范围。     

Three-dimensional cutting force analysis based on the lower boundary of the shear zone. Part 1: Single edge oblique cutting

Traditional models of cutting based on Merchant's shear plane idealization are incapable of predicting any of the cutting force components without a priori knowledge of chip-tool friction. However, Rubenstein's work on orthogonal cutting has shown that this limitation can be avoided by utilizing the stress distributions on the lower boundary of the shear zone. The present work aims to extend this approach to oblique cutting with. single and two edged tools. This paper focuses on single edge oblique cutting whereas Part 2 analyses two edge cutting. It is assumed that the progressive deformation of the work material into chip material occurs within the effective plane. The resulting stress distributions on the lower boundary are integrated to yield expressions for estimating cutting forces from given tool and chip geometries. This provides a mechanism for predicting the power and lateral components of the cutting force in single edge oblique cutting. The predictions are verified against new and previously published experimental data.     

Development of a reference cutting force model for rough milling feedrate scheduling using FEM analysis

Recently developed feedrate scheduling systems regulate cutting forces at the desired level by changing the feedrate to reduce the machining time and to avoid undesirable situations. For effective scheduling, an optimized criterion is required to adjust the feedrate. In this study, a method to obtain the most appropriate reference cutting force for rough milling was developed. The reference cutting force was determined by considering the transverse rupture strength of the tool material and the area of the rupture surface. A finite element method analysis was performed to accurately calculate the area of the rupture surface. Using the analyzed results, the effect of various cutting parameters on the chipping phenomenon was determined. The calculation method for the reference cutting force considered the area of the rupture surface, the effect of the rake angle, and the axial depth of the cut. The reference cutting force calculated using the developed model was applied to feedrate scheduling for pocket machining. The experimental results clearly show that the reference cutting force obtained from the proposed method met the desired constraints that guarantee higher productivity without tool failure.     

An in-depth analysis of the synchronization between the measured and predicted cutting forces for developing instantaneous milling force model

This paper proposes an analytical approach to synchronize the measured and predicted cutting forces for calibrating instantaneous cutting force coefficients that vary with the instantaneous uncut chip thickness in general end milling. Essential issues such as the synchronization criterion, phase determination of measured cutting forces, specification of calibration experiments and related cutting parameters are highlighted both theoretically and numerically to ensure the calibration accuracy. A closed-form criterion is established to select cutting parameters ensuring the single tooth engagement. Numerical cutting simulations and experimental test results are compared to validate the proposed approach.     

Evaluation of the total cutting force in drilling of CFRP: a novel experimental method for the analysis of the cutting mechanism

The CFRP drilling process has not yet been fully mastered, which is due to the fact that it is not possible to measure all the cutting force components. In order to gain new insights into the drilling process, a novel experimental setup is being developed in order to record all cutting force components (cutting force, feed force, passive force). The results show that the force components are strongly dependent on the fiber cutting angle θ and the wear condition. Thereby, it will be possible to draw conclusions about the cutting mechanics in the drilling of unidirectional CFRP based on the transformation of the forces perpendicular and parallel to the fiber.     

An analytical model for the optimized design of micro-textured cutting tools

Proper design of micro-textured cutting tools is an effective strategy to improve the machining performance by reducing the tool-chip contact length and the resultant friction and thus improving tool life and workpiece surface integrity. In this paper, an Oxely-based analytical model is developed to optimize micro-textured cutting tool design(s) which eliminate the occurrence of derivative cutting. The model accommodates any workpiece material, tool geometry, and machining parameter. The model was validated by orthogonal cutting of AISI 1045 steel tubes. The results show that the optimum micro-texture design eliminates derivative cutting and lowers forces compared to the non-textured cutting tool.     

冷轧不锈钢连续退火炉加热工艺分析及系统设计

基于冷轧不锈钢连续退火工艺及制度分析,对其连续退火炉加热系统进行了设计,通过表面能量平衡方程和能量守恒方程可计算出炉长配置及燃烧功率配置。通过实际算例与实际运行情况对比分析,得到该设计方法是有效的,能够完成从产品大纲、工艺分析基础到机组加热系统集成、布置、设备总体布置的设计过程,为后续冷轧不锈钢连续退火炉加热系统二级模型提供了理论基础。     

Upper bound analysis of oblique cutting: improved method of calculating the friction area

This paper describes further development of the upper bound analysis of oblique cutting with nose radius tools described previously by Adibi-Sedeh et al. [[1]] by incorporation of an improved method for calculating the friction area at the chip-tool interface. Previously, the friction area was obtained from the shear surface area assuming that the ratio of these areas is the same as in orthogonal machining. Our results showed that this led to overestimation of the effect of friction on the chip flow angle, thereby resulting in smaller changes in the chip flow angle with inclination angle as compared to experimental data. In the new approach, the chip-tool contact length is obtained from the length of the shear surface assuming that the ratio of the lengths is the same as in orthogonal machining and the friction area is calculated using this length. The chip flow angle predicted using the new approach shows much better agreement with experimental data. In particular, the dependence of the chip flow angle on the inclination angle is accurately reproduced. Upper bound analysis of oblique cutting using this new model for the friction area provides an elegant explanation for the relative influence of the normal and equivalent rake angles on the cutting force.     

Three-dimensional cutting force analysis based on the lower boundary of the shear zone. Part 2: Two edge oblique cutting

The problem of partitioning the overall cutting force between the two active cutting edges in two edge oblique cutting, although of crucial importance in modelling the temperature and wear rates prevailing in form cutting, has so far eluded solution. This paper presents two solutions to the problem: one utilizing the Merchant shear plane (MSP) approach and the other utilizing the solution developed in Part 1 for single edge oblique cutting based on the lower boundary (LB) of the shear zone. Both approaches avoid the anomalies encountered in previous attempts at solving the partitioning problem. This was done through the simultaneous application of the principles of chip equilibrium, force-velocity collinearity and chip interaction. Arguments are presented to indicate that the LB approach is more reliable than that of the MSP approach. Further, the LB approach is able to predict the power component of the overall cutting force in two edge cutting just as in the case of single edge cutting.     

伺服压力机传动系统动态特性分析与研究

为了提高伺服压力机传动系统的动态特性,建立了曲柄肘杆传动系统的结构简图,运用矢量方程法建立了该机构的几何参数数学模型,然后根据等效转动惯量的转换条件建立了该系统的等效转动惯量数学方程,最后通过MATLAB软件建立了该系统的数学模型,分析得出该机构在主滑块不同行程长度时所对应的等效转动惯量幅值曲线,并分析了在伺服电机恒扭矩输出时曲柄的加减速性能。分析结果表明,通过减小该机构的主滑块行程长度,可以明显减小转动惯量,提高曲柄的角加速度,从而提高该系统的动态性能。     

Grey relational analysis coupled with principal component analysis for optimization design of the cutting parameters in high-speed end milling

This paper investigates optimization design of the cutting parameters for rough cutting processes in high-speed end milling on SKD61 tool steel. The major characteristics indexes for performance selected to evaluate the processes are tool life and metal removal rate, and the corresponding cutting parameters are milling type, spindle speed, feed per tooth, radial depth of cut, and axial depth of cut. In this study, the process is intrinsically with multiple performance indexes so that grey relational analysis that uses grey relational grade as performance index is specially adopted to determine the optimal combination of cutting parameters. Moreover, the principal component analysis is applied to evaluate the weighting values corresponding to various performance characteristics so that their relative importance can be properly and objectively described. The results of confirmation experiments reveal that grey relational analysis coupled with principal component analysis can effectively acquire the optimal combination of cutting parameters. Hence, this confirms that the proposed approach in this study can be an useful tool to improve the cutting performance of rough cutting processes in high-speed end milling process.     

The prediction of dimensional error for sculptured surface productions using the ball-end milling process. Part 1: Chip geometry analysis and cutting force prediction

The study of machining errors caused by tool deflection in the balkend milling process involves four issues, namely the chip geometry, the cutting force, the tool deflection and the deflection sensitivity of the surface geometry. In this paper, chip geometry and cutting force are investigated. The study on chip geometry includes the undeformed radial chip thickness, the chip engagement surface and the relationship between feed boundary and feed angle. For cutting force prediction, a rigid force model and a flexible force model are developed. Instantaneous cutting forces of a machining experiment for two 2D sculptured surfaces produced by the ball-end milling process are simulated using these force models and are verified by force measurements. This information is used in Part 2 of this paper, together with a tool deflection model and the deflection sensitivity of the surface geometry, to predict the machining errors of the machined sculptured surfaces.     

The mechanics of continuous chip formation in oblique cutting with single-edged tool—part II. Experimental verification of the theory

Experimental results obtained during oblique cutting of annealed steel Ck 45 (SAE-AISI 1045) with a single-edged tool are presented. Extensive measurements of forces, cutting ratio, chip flow angle etc. have been carried out under a wide range of cutting conditions. The measured data obtained from these cutting tests are used to test assumptions proposed in the first part of this work. In relation to previous works dealing with oblique cutting problems the present one extends to tools with angles of tool obliquity ranging from 30° to 70° and having a large negative rake angle.     

压铸成形减震器支撑件浇注系统的改进设计分析

采用数值模拟软件ProCAST,对减震器支撑件压铸模浇注系统改进前、后的成形过程进行分析,综合分析零件充型过程、温度场、凝固场以及缺陷分布云图,结合实物试验准确预测铸件的缺陷位置和形式。数值模拟结果具有较高的可信度。改进浇注系统后成形的零件缺陷倾向明显减小,数值模拟技术有效降低试模风险和成本,缩短模具改进设计周期和提高产品的质量。     

An analytical evaluation of the cutting forces in self-piloting drilling using the model of shear zone with parallel boundaries. Part 1: Theory

The performance of a self-piloting tool is affected by its design and geometry parameters. These parameters constitute the tool-force system which directly defines quality of the machined holes, tool life and required power. This paper presents an analytical approach to describe the cutting forces in self-piloting drilling. The approach is useful at the level of tool and process design. The subject has been covered in two parts. Part one deals with the analysis of the cutting mechanics employing the shear-zone model with parallel boundaries. The analysis of the continuity condition results in better understanding of the traditional cutting model's characteristics, such as the chip compression ratio and velocity diagram. Based on this analysis and using the thermomechanical model of the work-material resistance to cutting, a cutting-force model is proposed and has been verified experimentally.     

Quantitative analysis of observations on diffusion induced grain boundary migration for random boundaries in the Cu(Zn) system using a driving force model

Diffusion induced grain boundary migration (DIGM) in the Cu(Zn) system was experimentally studied by Li and Hillert using polycrystalline Cu specimens zincified with binary Cu–Zn alloys containing 3.9–30.5 wt% of Zn at temperatures between 573 and 773 K. Their experimental results have been quantitatively analyzed using the energy balance model proposed by Kajihara and Gust. The effective driving force Δ^efG for DIGM has been evaluated from the migration rate v of the moving boundary and the composition in the region alloyed with Zn behind the moving boundary, and then the mobility M of the moving boundary has been calculated using the relationship M=v/Δ^efG. According to the analysis, the grain boundary migration obeys the chemical driving force model proposed by Hillert and Purdy for the largest experimental values of v at 573 and 623 K. However, the chemical driving force is partially consumed by the volume diffusion of Zn in the Cu matrix ahead of the moving boundary for the other experimental values of v at 623–773 K. In such a case, the migration rate dependence of the effective driving force should be taken into consideration. The temperature dependence of the mobility gives a value of Q_M=177 kJ/mol as the activation enthalpy for the grain boundary migration. This value is close to the activation enthalpy for volume diffusion of Zn in Cu, 191 kJ/mol. Consequently, the grain boundary migration is considered to be controlled by the solute drag effect due to the volume diffusion of Zn in the Cu matrix in the neighborhood of the moving boundary.     

带嵌件的电容器壳体成型工艺分析与模具设计

运用有限元分析方法分析了电容器壳体塑件成型熔体充填过程、冷却过程中塑料的收缩规律,结果表明:塑件厚壁对收缩率有较大影响,其中最大壁厚处的收缩率达14.86%。根据塑件的成型特点,设计了三板式模具结构;为减小收缩率对塑件质量的影响,根据注射压缩成型原理,采用液压缸驱动的双弹簧压缩成型机构实现压缩模塑过程,同时为提高生产效率,设计了嵌件快装机构,减少了嵌件的安装时间。