Investigation of the effect of cutting tool edge radius on material separation due to ductile fracture in machining

This paper investigates the interaction between cutting tool edge radius and material separation due to ductile fracture based on Atkins’ model of machining. Atkins’ machining model considers the energy needed for material separation in addition to energies required for shearing at the primary shear zone and friction at the secondary shear zone. However, the effect of cutting tool edge radius, which becomes significant at microcutting conditions, was omitted. In this study, the effect of cutting tool edge radius is included in the model and its influence on material separation is investigated. A modification to the solution methodology of Atkins’ machining model is proposed and it is shown that the shear yield stress and the fracture toughness of the work material can be calculated as a function of uncut chip thickness.     

A study of the effect of tool cutting edge radius on ductile cutting of silicon wafers

Ductile mode cutting of silicon wafers can be achieved under certain cutting conditions and tool geometry. An experimental investigation of the critical undeformed chip thickness in relation to the tool cutting edge radius for the brittle-ductile transition of chip formation in cutting of silicon wafers is presented in this paper. Experimental tests for cutting of silicon wafers using diamond tools of different cutting edge radii for a range of undeformed chip thickness are conducted on an ultra-precision lathe. Both ductile and brittle mode of chip formation processes are observed in the cutting tests. The results indicate that ductile cutting of silicon can be achieved at certain values of the undeformed chip thickness, which depends on the tool cutting edge radius. It is found that in cutting of silicon wafers with a certain tool cutting edge radius there is a critical value of undeformed chip thickness beyond which the chip formation changes from ductile mode to brittle mode. The ductile-brittle transition of chip formation varies with the tool cutting edge radius. Within the range of cutting conditions in the present study, it has also been found that the larger the cutting edge radius, the larger the critical undeformed chip thickness for the ductile-brittle transition in the chip formation.     

金属切削刀具的工作角度及其影响因素的研究

从刀具标注角度与工作角度的概念出发,较系统地分析影响金属切削刀具实际几何角度的主要因素,提出合理选择刀具几何角度的方法。对合理地设计、制造刀具,保证零件加工质量,提高加工效率,延长刀具寿命,降低生产成本具有重要意义。     

The upper bound of tool edge radius for nanoscale ductile mode cutting of silicon wafer

For ductile mode cutting of brittle materials, such as silicon wafers, the undeformed chip thickness has to be smaller than the tool edge radius. In practical application, for high production rate, the undeformed chip thickness is expected to be as large as possible. Therefore, the tool edge radius is expected to be as large as possible. In this study, the upper bound of the tool edge radius is investigated through cutting experiments.     

基于圆锥直纹面刀具姿态控制的曲线插补算法

为提高参数曲线与圆锥直纹面相结合类复杂零件的加工精度,提出一种基于圆锥直纹面刀具姿态控制的曲线插补算法.在该算法中,根据给定圆锥直纹面信息确定圆锥直纹面刀具姿态曲线,实现对刀具姿态的控制;建立虚拟圆弧,将参数曲线与圆锥直纹面刀具姿态曲线间的重参数化问题转化为简单的求解向量夹角问题,从而避免产生多重拟合误差.此外,给出了适用于该插补算法的数控加工程序编程格式.实例验证及分析表明,所提算法能够控制加工中刀具姿态始终在所要求的圆锥直纹面上,并且可在缩短代码段数目的基础上,有效降低运算量和加工误差.     

Analysis of superplastic blow-forming in a conical closed die

A mathematical model using the finite-difference method has been proposed in this work to examine the plastic deformation behavior of the sheet during blow-forming in a conical closed die. In the formulation of this mathematical model, nonuniform thinning in the free bulged region and the contact condition including the sticking and sliding friction modes between the sheet and die are considered. Effects of various forming parameters such as the die entry radius, friction coefficient, inclined angle of the die, etc., upon the optimized pressurization profile, forming time and the thickness distribution of products were discussed systematically. Furthermore, experiments on superplastic blow-forming in a conical closed die were carried out using 8090 Al-Li sheets. It is found that the theoretical predictions agree with experimental results. The thickness distributions of the SPF-ed product obtained with different friction coefficients along the die entry, sidewall and bottom are closer to the experimental data than those obtained with a constant friction coefficient.     

低频水平位移锥摆测量仪的研制

针对地质灾害预报中的大地振动测量要求,通过考查国内外现有的各种大地振动测量仪器,提出一种大地水平振动测量的新装置--锥摆系统,并对其结构和原理进行了介绍,结合实际的建造,给出了初步的实验结果.这种测量系统具有二维水平振动位移响应,在大地测量和灾害监控方面具有广泛的应用前景.     

Finite element analysis of limit strains in biaxial stretching of sheet metals allowing for ductile fracture

To predict limit strains in biaxial stretching of sheet metals, a criterion for ductile fracture is combined with the finite element simulation. The limit strains are determined by substituting the values of stress and strain obtained from the finite element simulation into the ductile fracture criterion. Material constants in the criterion are obtained from the fracture strains measured in the biaxial stretching tests. Calculations are carried out for various strain paths from balanced biaxial stretching to uniaxial tension of aluminium alloy sheets, and compared with the experimental results. The predicted limit strains are in good agreement with the measured ones not only just at the fracture site but also at outside of the fracture site. It is demonstrated that the forming limit diagrams are successfully predicted by the present approach.     

Analysis of strain localization for ductile materials with effect of void growth

In the framework of thermodynamics and damage mechanics, an elastoplastic constitutive relation of ductile materials is developed. Based on this constitutive relation, the properties of strain localization for ductile materials are investigated with the effect of void growth included. The influences of void growth on strain localization are analyzed based on the unified strength criterion. Finally, the effects of yield criteria on the properties of strain localization are discussed.     

Numerical modelling of ductile plastic damage in bulk metal forming

This work addresses the computational aspects of a model for rigid–plastic damage. The model is a modification of a previous established model formulated by Perzyna (Recent Advances in Applied Mechanics, Academic Press: New York, 1966, p. 243–377 (Chapter 9)) which is here extended to include isotropic damage. Such an extension is obtained by incorporating the constitutive equations introduced by Lemaitre (J. Eng. Mater. Technol. 107 (1985) 83; Comput. Meth. Appl. Mech. Eng. 51 (1985) 31; A Course on Damage Mechanics, Springer, Berlin, Heidelberg, New York, 1996) for ductile plastic damage into the original model. In its original version (J. Eng. Mater. Technol. 107 (1985) 83; Comput. Meth. Appl. Mech. Eng. 51 (1985) 31) this model does not distinguish tension and compression in the damage evolution law, so it was necessary to introduce a refinement proposed by Ladevèze (in: J.P. Boehler, (Ed.), Proceedings of CNRS International Colloquium 351 Villars-de-Lans, France (Failure Criteria of Structured Media, 1983, p. 355) and Lemaitre (A Course on Damage Mechanics, Springer, Berlin, Heidelberg, New York, 1996) which takes into account the partial crack closure effect with isotropic damage. The accuracy of the computational model, developed for the analysis of the material degradation in bulk metal forming processes, is shown through the discussion of the results of two examples, allowing to compare the simulation results with experimental and numerical results obtained by other authors.     

焊接技术在金属切削刀具中的应用

目前我国刀具焊接基本上分为两种:摩擦焊和闪光对焊。本文主要介绍了焊接技术在金属切削刀具中的应用及其在生产加工中相关的知识。     

硬质合金圆柄止动槽成型刀设计

针对加工止动槽用硬质合金焊接刀刃磨时,其宽度难以控制、对刀困难、无法加工倒角等问题,设计了圆柄止动槽成型刀代替硬质合金焊接刀,只需刃磨排屑槽,节约了磨刀时间,保证了止动槽宽度尺寸,节省了倒角工序,提高可产品质量和经济效益。     

Experimental research on ductile fracture criterion in metal forming

Ductile fracture criterion is key limitation parameter in material forming. Accuracy predicting surface and internal failure in plastic deformation process affects on the technology design of workpiece and die greatly. Tension, compression, torsion and shearing test on 45# steel are utilized for providing the experimental values of the critical values at fracture, and 11 widely used ductile fracture criterion are selected to simulate the physical experiments and their relative accuracy for predicting and quantifying fracture initiation sites are investigated. The comparing results show that metal forming process under high triaxiality can be estimated successively using both Normalized Cockcroft-latham and the Brozzo ductile fracture criteria, but the Ayada and general Rice-Tracey model work very well for the low triaxiality cases.     

Effect of conical angle on the hydraulic properties of orifice plate flows: A numerical approach

Orifice flowmeters are widely used in industry due to their simple design, ruggedness, and easy installation. However, high-pressure losses, measurement accuracy, and long pipe length requirements are still significant concerns. Typically, conical entry orifice plates at a 45-degree conical angle are recommended by orifice standards, especially for low Reynolds numbers instead of the sharp-edged orifice plates, which pose stability. The primary goal here is to develop the conical entry orifice plates further over a broader range of Reynolds numbers. In this case, a 45-degree conical angle may seem questionable since the optimization of conical angles has not been studied so far. To clarify that point and reach the new technical data about the conical entry orifice plates, orifice plates in different orifice diameter ratios (0.4, 0.5, 0.63) and beveled with different conical angles (15°, 30°, 45°) were tested numerically through water flow simulations inside a pipe with an inner diameter of 50.8 mm at different Reynolds numbers (5000,18,400, 91,100, 240,000).According to the analysis made, the 30-degree conical angle orifice plate was the best in reducing pressure losses, resulting in pressure losses 37–52% less than that of sharp-edged orifice plates in the min-max range. Furthermore, it reduced the pressure losses by 13–21 % more than that of the 45-degree conical angle. These last outcomes indicate that current orifice standards needs a modification into the recommended conical angles. Through these findings, pressure losses in multi-hole plate flow conditioners can be reduced considerably when the holes are beveled at the 30-degree conical angle.Also in the study, the axial characteristic lengths relevant to recirculation region, flow recovery and vena contracta were predicted approximately, along with the derived numerical correlations resulting with constants. Moreover, the effect of orifice plates exposed to an upstream distorted velocity profile on orifice flows was tested numerically. According to this evaluation, the lowest measurement errors were observed at the 30-degree conical angle orifice plate, about 30–70 % less than that of the sharp-edged orifice plate in the min-max range.     

圆锥滚子摆动从动件圆锥凸轮机构压力角的解析方法

以单参数包络面理论为基础,建立了圆锥凸轮机的数学模型,通过坐标变换,推导出了圆锥凸轮的廓面方程,进一步求出了压力角的计算公式,为空间凸轮的精确设计和制造提供了理论基础。     

奥－贝球墨铸铁切削加工性的研究

分析研究了切削用量三要素对奥－贝球铁主切削力Ｆ２和刀具寿命的影响规律；从降低切削力的观点出发，优选了刀具材料。本文得出的结论及实验数据对奥－贝球铁的切削加工有指导意义，可作为有关部门切削加工的参考。     

奥－贝球墨铸铁切削加工性的研究

分析研究了切削用量三要素对奥－贝球铁主切削力Ｆ２和刀具寿命的影响规律；从降低切削力的观点出发，优选了刀具材料。本文得出的结论及实验数据对奥－贝球铁的切削加工有指导意义，可作为有关部门切削加工的参考。     

Analytical and numerical investigation of wrinkling for deep-drawn anisotropic metal sheets

An analysis of the onset of wrinkling is first developed for a doubly curved, elastic–plastic shell element submitted to a biaxial plane stress loading. Plastic yielding is described using a criterion recently proposed for anisotropic sheet metals. The wrinkling limit curves obtained with this analysis are compared with previous results based on different yield criteria. Finite element (FE) simulations of a deep-drawing experiment are also performed using the Abaqus/Explicit code with the aim of comparing the FE results relating to the initiation of wrinkling with the predictions of the analytical model and with experiments from the literature.     

新型大柔度锥面高速刀柄的性能研究

设计了具有分锥体结构的新型大柔度锥面高速刀柄.利用有限元软件对该高速刀柄的静态和高速性能进行了分析,具体研究了刀柄锥面与端面的压力分布特点以及主轴的膨胀变形规律.研究结果表明,大柔度锥面高速刀柄比常用的HSK刀柄具有更高的极限转速,在高转速下能够保证良好的定位精度和连接刚度,特别适合于高速加工.     

Survival life analysis applied to tool life estimation with variable cutting conditions when machining titanium metal matrix composites (Ti-MMCs)

A survival analysis methodology is employed through a novel approach to model the progressive states of tool wear under different cutting conditions during machining of titanium metal matrix composites (Ti-MMCs). A proportional hazards model (PHM) with a Weilbull baseline is developed to estimate the reliability and hazard functions of the cutting inserts. A proper criterion is assigned to each state of tool wear and used to calculate the tool life at the end of each state. Accounting for the machining time and different stages of tool wear, in addition to the effect of cutting parameters, an accurate model is proposed. Investigating the results obtained for different states, it was shown that the evolution of the time-dependent phenomena, such as different tool wear mechanisms, throughout the whole machining process were also reflected in the model. The accuracy and reliability of the predicted tool lives were experimentally validated. The results showed that the model gives very good estimates of tool life and the critical points at which changes of states take place.