Improving the stability of cutting by a tool with a nanocoating

The influence of the composition and structure of a wire-resistant coating on the stability of cutting is investigated.     

Three dimensional cutting force analysis in end milling

The analysis of cutting forces plays an important part in the design of machine tool systems as well as in the planning, optimization, and control of machining processes. This paper presents a three-dimensional model of cutting forces in peripheral end milling in terms of material properties, cutting parameters, machining configuration, and tool/work geometry. Based on the relationship of the local cutting force and the chip load, the total cutting force model is established via the angle domain convolution integration of the local forces in the feed, cross feed, and axial directions. The integration is taken along the cutter axis and summarized across the cutting flutes. The convolution integral leads to a periodic function of cutting forces in the angle domain and an explicit expression of the dynamic cutting force components in the frequency domain. The closed-form nature of the expressions allows the prediction and optimization of cutting forces to be performed without the need of numerical iterations. To assess the fidelity of the analytical model, experimental data from end milling tests are presented in the context of three dimensional time waveforms, power spectra, and phase angles, in comparison to the values predicted by the model.     

A new wavelet filtering for analysis of fractal engineering surfaces

Recently B-spline wavelets (ISO 16610-29) have been accepted in precision engineering as an official Technical Specification for analyzing engineering surfaces. However, in some applications where fractal signals are involved it is better that the wavelet behaves like a fractional differentiator. The purpose of this paper is to introduce a fractional spline wavelet-based framework for analyzing fractal engineering surfaces. We will use the orthonormal fractional spline wavelet filter and develop an algorithm for the implementation of the associated wavelet transform. We illustrate our method by considering PTB roughness standards.     

基于二维连续小波变换的三维轮廓测量技术比较研究

为解决在物体高度梯度变化较大的情况下三维轮廓测量技术的测量精度问题,将连续小波变换应用到三维轮廓测量技术中.开展了基于2d-paul和2d-morlet连续小波变换轮廓术研究,进行了三维轮廓测量术比较分析,建立了小波“脊”相位与高度之间的关系,提出了在物体高度梯度变化较大的情况下基于2d-paul算法优于2d-morlet算法.在对比分析的基础上对两种连续小波变换轮廓测量技术的测量精度进行了评价,进行了Matlab和实测试验.研究结果表明：物体高度梯度变化较大的情况下适合采用2d-paul算法,其能更有效地提高三维轮廓测量技术的测量精度.     

Analysis of cutting on the basis of plasticity theory

The problem of how to cut the ideal rigid-plastic material has been examined on the base of theory of plasticity. The segments where (from theoretical standpoint) the intensive cold hardening should take place and the cracks can form are pointed. The correlation between the contact friction and cracks formation has been explained. The formulas describing the cutter forces are presented.     

The effect of cutting conditions on dimensional accuracy

The effects of speed, feed and depth of cut on the dimensional accuracy of aluminium bars turned on a lathe were studied. The optimum values of the dimensional accuracy with respect to speed, feed and depth of cut were determined.     

Evaluation of the wavelet transform method for machined surface topography 2: fractal characteristic analysis

In this paper, a new method based on wavelet transform is proposed as a means for studying the fractal characteristics of rough surfaces. Through estimation of normal mathematical curves with known fractal dimensions, generated by the Weierstrass-Mandelbrot function, Majumdar-Bhushan function, Fractal Brownian motion (including three methods: the Midpoint FBm, the Additions FBm, the Interpolated FBm) and Interposed method (Kiesswetter curve), it is validated that the wavelet transform method can accurately calculate the fractal dimension. These fractal functions have been used to simulate some surface profiles. The results indicate that the Wavelet transform method is the most precise in its calculation of the fractal dimensions of the curves. It obtains more accurate results than seven other methods, named the Box counting method, the Yardstick method, the Co-variation method, the Structure function method, the Variation method, the Power Spectrum method and the Rescaled range analysis method. Precisely calculating the fractal dimensions of the curves is the first step in characterising machined surface topography. In addition, this paper aims to further develop the evaluation procedure for the fractal characteristics of machined surface topography.     

基于价值分析的装配尺寸链公差可靠性优化分配

讨论了公差与制造成本之间的关系,同时从概率设计的角度提出了装配尺寸链可靠度的概念及设计方法。建立了以总制造成本为目标函数,装配尺寸可靠度为约束条件的装配尺寸链优化 设计数学模型,实例设计结果表明这里提出的公差分配方法较传统方法更科学,准确。     

小波及分形理论在互有位移图像序列重构中的应用

提出一种基于小波及分形理论的插值算法,用于互有位移序列图像的重构,它既考虑了各幅图像的细节特征又考虑了图像的全局特征,使得到的重构图像更接近原图。阐述了超分辨力复原技术的理论基础及复原算法,指出了基于序列图像的高分辨力成像技术的合理性,并利用小波及分形相结合的方法对互有位移的双幅图像进行了重构,实验和仿真的复原图像表明,这种方法是可行和有效的。与传统方法相比,此种方法的PSNR提高了约5dB。     

基于小波分形技术提取发动机曲轴轴承故障特征

利用小波技术对发动机曲轴轴承振动信号进行分解,对特定层的信号进行重构,并计算重构信号的分形维数,来实现发动机曲轴不同技术状态下特征提取。实验结果表明,特定频率带振动信号的分形维数更能敏感反应发动机曲轴轴承技术状态,它可以作为诊断发动机曲轴轴承故障的一个重要特征量。     

断裂韧性的两端截尾分布概率法设计

利用两端截尾分布理论及应力－ 强度干涉模型建立了断裂韧性的概率设计方法,消除了目前使用的、利用理论分布进行断裂韧性计算时可靠度永远小于１ 的情况,使可靠度计算更符合实际情况。通过大量实例计算表明该方法具有重要的现实应用意义。     

Effect of fixture compliance and cutting conditions on workpiece stability

This paper computes and investigates the effect of fixture compliance and cutting conditions on workpiece stability and uses it as a basis for selecting a suitable fixture among several alternatives. We use two criteria, the minimum eigenvalue of the fixture stiffness matrix and the largest displacement of the workpiece due to the cutting forces to assess the stability of the workpiece. First, the minimum eigenvalues of the fixture stiffness matrices, for the fixtures being considered, are computed. Second, since the eigenvalues are not dependant on the cutting forces, a displacement measure, the largest displacement of the workpiece due to the cutting force, is computed for each fixture. This displacement is a function of the cutting force and the fixture compliance. The choice of fixture is often a compromise between the two criteria. We also consider the combined influence of fixture compliance and cutting conditions on workpiece stability. The results from the simple study used for illustration show that the eigenvalues remain constant under different cutting conditions whilst the largest displacement reduces by 68%, a significant reduction.     

改善不锈钢切削加工性的试验研究

这里推导出阶梯法耐用度试验的数据处理公式，并利用此方法对普通奥氏体不锈钢和加硒不锈钢材料进行了切削加工对比试验，证明了加硒不锈钢的切削加工性比普通奥氏体不锈钢提高了1．5倍。     

小波系数表征机械加工表面分形特征的计算方法

针对表征机械加工表面轮廓形貌分形特性,提出应用小波变换系数计算分形维数的算法。基于Majumdar-Bhushan分形函数构造典型曲线,采用工程常用的三种小波基函数,通过小波分解提取小波系数,并将在不同分解尺度和阶数下计算出的分形维数进行对比分析和验证,选择出计算分形维数精度较高的小波基函数和分解尺度。用该方法对车削和铣削加工的结合面实验试件表面形貌的分形维数进行计算,评价了表面形貌的分形特征。     

Improving the cutting mechanism of a disk-type wood chipper

Methods of waste-free woodchip production are verified. This permits improvement in the cutting mechanism of a disk-type wood chipper.