AN INVESTIGATION OF 3-D CURLED CHIP IN MACHINING-PART 1: A MECHANICS-BASED ANALYTICAL MODEL

This paper presents an analytical model of the 3-D curled chip that is commonly produced in oblique machining. The chip model is based on a 3-D spiral with continuously varying center and curl radius. Stresses in the chip are analyzed by an energy-based approach. Bending and torsional shear stresses in the chip are generated based on input reaction forces. A case study with typical input values of reaction forces is analyzed for finding the magnitude and location of the maximum stresses. Also, the octahedral shear stress is proposed as a comprehensive 3-D chip failure criterion, because it combines the individual effects of the bending and shear stresses.     

声发射监测切屑状态的可行性研究

金属切削过程中产生丰富的声发射。用声发射技术监测切屑状态是一个很有潜力的新方法。本文通过实验研究了车削时切屑状态和声发射信号间的相互关系,结果表明：1.声发射DC包络信号脉冲能准确反映断屑情况;2.声发射加权计数率波形和包络信号均值能反映切屑形状和异常切屑状态;3.不同类型切屑的形成过程具有不同的声发射信号波形。     

SIMULATION OF CHIP FORMATION IN ORTHOGONAL METAL CUTTING PROCESS: AN ALE FINITE ELEMENT APPROACH

Lagrangian and Eulerian finite element formulations have been traditionally used for modeling of the orthogonal metal cutting process. In this paper it is shown that a more general formulation, the arbitrary Lagrangian-Eulerian method (ALE), may be used to combine the advantages and avoid the drawbacks of both methods in a single analysis. Due to the characteristics of the cutting process, ALE formulation offers a very efficient modeling approach for the cutting process. A comprehensive ALE model along with strain rate and temperature dependent constitutive equations and a contact/friction algorithm is used to analyze the thermo-elasto-plastic process of plane strain orthogonal cutting. Simulation results for cutting of low carbon free cutting steel are presented and compared with available experimental data obtained under similar cutting conditions. Good agreement between the numerical and experimental results is observed.     

NUMERICAL SIMULATION AND EXPERIMENTAL VALIDATION OF THE TEMPERATURE FIELD IN SURFACE GRINDING

Three-dimensional numerical simulations are carried out to investigate the temperature field in the contact zone due to the thermal loading of the workpiece in surface grinding. This technique considers that the thermophysical properties of the workpiece material are non-linear according to temperature, the contact zone between the wheel and the workpiece is assumed as an arc surface, and the heat flux entering the workpiece is assumed as proportional to the local undeformed chip thickness. A good agreement is found between the simulated results and the experimental observations. The high grinding temperature leads to the thermal expansion of the workpiece material, which causes the thickness of the actual material removal layer to be larger than the cutting depth. The grinding temperature at the central portion is higher than that on the side of the workpiece during the wet grinding, thus the material removal layer in the central zone is thicker than that on the side zone, and the workpiece surface is concave across the grinding width.     

ATOMIC SCALE LEVEL CHIP FORMATION OF AMORPHOUS METAL INVESTIGATED BY USING AFM AND MD-RPFEM SIMULATION

A cutting device has been developed by utilizing the scanning system of atomic force microscope (AFM) in machining, which aims at clarifying the ultimately small size removal as well as observing them in high resolution. As an application of the proposed method, the micro-chip deformation is investigated by cutting an amorphous metal Fe₇₈B₁₃Si₉. It is shown that a lamellar structure, which is formed due to the localized shear occurred in a very narrow region and at very high strain rate, appears even at nanometer scale cutting. The simulation of this process using combined molecular dynamics (MD) and rigid-plastic finite element method (RPFEM) is also presented in this paper. The simulation shows that the localized shear would occur at the atomic scale by the cooperative group-movement of atoms. The high kinetic state of atoms would play a role of advancing this process for causing such localized shear.     

偏心圆孔板弯曲时的三维应力集中

根据一种修正的余能原理所建立的具有一个无外力圆柱表面的 12结点三维杂交应力元 ,与一般的 8结点假定位移等参元配合 ,可十分有效地分析具有偏心圆孔厚 (薄 )板承受弯曲时的三维 (或二维 )应力集中。数值算例表明 ,对小偏心问题 (偏心距与板宽比e/2b≤ 0 .15时 ) ,厚板的三维应力集中系数大于相应二维应力集中系数。所以 ,将具有偏心圆孔薄板在弯曲时的应力集中系数用于厚板是偏于不安全的 ;但对大偏心问题 (e/2b >0 .15 ) ,厚、薄板均可应用二维应力集中系数     

太阳辐射下乘员舱温度场的数值模拟研究

针对太阳辐射对乘员舱内部热环境影响较大的问题,根据雷诺平均(RANS)的方法,采用射线追踪的方法计算了太阳辐射对乘员舱内部温度场的影响,并定量地分析了隔热玻璃的使用对乘员舱温度场的影响。计算结果表明太阳辐射和人体散热对车内温度场均存在明显的影响,采用隔热玻璃能有效地降低太阳透射辐射强度,使得太阳透射辐射平均强度降低了14.4%,仪表盘区域的最高温度降低了3.5℃。研究结果为乘员舱内部热环境的优化提供了新的思路和手段。     

失配渐开线圆柱蜗杆传动的弹性啮合分析、加工仿真及相关技术的理论与试验研究

综合应用多项先进技术,进行失配蜗轮副的理论与试验研究,包括虚拟制造蜗杆蜗轮,齿接触的计算机三维动态模拟,应用弹性啮合原理进行载荷变形下的齿接触分析,应用人工神经网络和基因遗传法优化传动参数,试验验证模拟和分析结果.以提出符合失配蜗轮副啮合特性,适于实际应用的强度分析和优化设计方法.研究对象以渐开线圆柱蜗杆蜗轮为主.并对渐开线失配圆柱蜗杆传动的传动效率和工作温度试验结果进行了分析,说明了失配蜗轮副优于线接触蜗轮副的原因.     

刨煤机不同位置刨刀的载荷模拟研究及其强度验证

刨刀是刨煤机落煤的执行工具,其工作载荷直接影响刨煤机的刨削能力和生产效率。为研究刨煤机的载荷特性,基于Matlab和VC开发出了刨煤机载荷计算程序,可根据不同模拟煤层的赋存条件,计算出不同位置刨刀的随机载荷;基于仿真软件Adams,对不同位置刨刀进行模拟,并对其进行了强度验证。通过分析得出:在相同截深时,不同位置刨刀的载荷具有随机性,其中,短腰刀的三向载荷均值与标准差最小,与其他位置的刨刀相比受力较稳定均匀,其次为长腰刀、顶刀、底刀;随着刨削深度的增加,刨刀所受的三向力均有不同程度的增大,当刨深超过一定值以后,刨削阻力会出现明显的增大;当刨刀间距超过一定截线距时,刨削力急剧增加;刨刀在工作过程中,长、短腰刀所受最大应力分别位于刀体薄厚位置过渡连接处和刀体与片状合金头镶嵌处,主要失效方式为断裂和磨损;顶刀和底刀在与刀座连接部分做倒角处理可缓和应力集中。分析结果为研究动载荷作用下刨刀可靠性及其结构优化设计提供了理论依据。     

结构光三维测量中的亚像素级特征提取与边缘检测

提高采样频率和检测精度是目前结构光三维测量研究中的关键问题。传统的结构光测量主要通过提取光条中心线来求取物体表面轮廓特征。以激光线光源为结构光光源,提出了针对单条线型激光光束的双特征线提取方法,从而使采样频率提高一倍。同时在算法中引入亚像素检测思想,实现对激光光束的亚像素级特征提取,提高了测量精度。对激光光束宽度与物体表面倾角的关系进行分析,利用Lambert漫反射模型,给出了物体表面倾斜时的阈值修正算法,试验结果验证了算法对提高测量精度的有效性。     

容栅磁翻柱液位计中电容传感器的数值仿真及试验

以容栅磁翻柱液位计的单个电容传感器为研究对象,分别用远场单元法和Trefftz有限元法对具有开放边界的静电场建立数学模型,并在此两种模型的基础上,运用ANSYS软件分析容栅磁翻柱液位计在工作中由于磁翻柱翻转引起的电场变化,计算出电容传感器中电极板间的电容变化量.将运用两种方法仿真所得到的结果与试验测试值进行比较,发现用Trefftz有限元法所得仿真值的相对误差只为3.3%,从而验证了运用Trefftz有限元法处理具有开放边界条件的静电场问题是一种有效而精确的方法.     

3D FINITE ELEMENT MODELLING OF CHIP FORMATION PROCESS FOR MACHINING INCONEL 718: COMPARISON OF FE SOFTWARE PREDICTIONS

Many efforts have been focused on the development of Finite Element (FE) machining models due to growing interest in solving practical machining problems in a computational environment in industry. Most of the current models are developed under 2D orthogonal plane strain assumptions, or make use of either arbitrary damage criterion or remeshing techniques for obtaining the chip. A complete understanding of the material removal process together with its effects on the machined parts and wear behaviour of the cutting tools requires accurate 3D computational models to analyze the entire physical phenomenon in materials undergoing large elastic-plastic deformations and large temperature changes as well as high strain rates. This work presents a comparison of 3D machining models developed using commercially available FE softwares ABAQUS/Explicit^© and DEFORM?3D Machining. The work material is chosen as Inconel 718, a difficult-to-cut nickel-based alloy material. Computational results of temperature, strain and stress distributions obtained from the FE models for the effect of cutting speed are presented in comparison with results obtained from experimental tests. In addition, modified material model for Inconel 718 with flow softening is compared with the Johnson-Cook model. The predictions of forces and chip formation are improved with the modified material model.     

MEASUREMENT OF 2-DIMENSIONAL DISPLACEMENT USING 2-D ZERO-REFERENCE MARKS

Several 2-D displacement sensing methods are reviewed. As to the cross diffraction grating, there is no absolute zero-reference. In regards to the optical fiber method, the output signal is affected greatly by the quality of the reflecting surface and it is hard to get high resolution. Considering the concentric-circle gratings, the displacement can only be gained with complicated calculating of the experiment data. Compared with the advantages and limitations of the methods above, a novel 2-D zero-reference mark is especially proposed and demonstrated. This kind of mark has an absolute zero-reference when used in pair, and the experimental result is simple to dispose. By superimposing a pair of specially coded 2-D marks, the correct alignment position of the two marks can be detected by the maximum output of the sharp intensity peak. And each slope of the peak is of good linearity which can be used to achieve high resolution in positioning and alignment in two dimensions. Design and fabrication of such     

偏心圆孔板的三维应力集中

根据1种修正的余能原理,建立了具有1个无外力圆柱表面的12结点三维杂交应力元,其单元内的应力场满足三维柱坐标平衡方程及无外力圆柱面边界条件;当元退化为二维时,也满足协调条件。数值算例表明用这种特殊杂交应力元能十分有效地分析具有偏心圆孔厚（薄）板的三维及二维应力集中。     

OPTIMISATION OF BEARING DIAGNOSTIC TECHNIQUES USING SIMULATED AND ACTUAL BEARING FAULT SIGNALS

In this paper, bearing fault vibrations are modelled as a series of impulse responses of a single-degree-of-freedom system. The model incorporates slight random variations in the time between pulses so as to resemble actual vibration signals. Although the bearing fault harmonics in the raw spectrum are caused by the random fluctuations to smear over one another, they remain quite clear in the spectrum of the envelope. However, the envelope spectrum is still prone to masking by discrete and random noise. Therefore, the simulated bearing fault signals were used to investigate the efficient application of self-adaptive noise cancellation (SANC) in conjunction with envelope analysis in order to remove discrete frequency masking signals. Two ways of combining these techniques have been suggested, both of which require the original signal to be band-pass filtered and frequency-shifted in order to reduce the number of samples to be processed by SANC. The subsequent envelope analysis can then be performed by using the Hilbert transform technique or band-pass rectification. Band-pass rectification is simpler but requires extra zero padding above and below the demodulation band, making the length of the signal processed by SANC twice as long as with the former method, but still only a fraction of the length of the original signal. On the other hand, the Hilbert technique requires an extra forward and inverse discrete Fourier transform operation compared with band-pass rectification. These two methods reduce the masking effects in the envelope spectrum by removing pseudo-sum frequencies or placing them outside the frequency range of interest. This is illustrated with examples of simulated and actual vibration signals. The removal of discrete frequency noise using SANC is also demonstrated for actual vibration signals. The threshold for which analysing the squared envelope or its higher powers gives an improvement in the envelope spectrum has also been defined using simulated and actual vibration signals. The treatment in the paper is qualitative and non-mathematical for purposes of clarity, but reference is made to a quantitative treatment of the effects of masking.     

卧式柴油机主轴润滑特性及参数影响分析

针对卧式两缸柴油机,在AVL Excite pu软件中建立其主轴承弹性动力润滑仿真模型,在考虑主轴瓦及轴颈粗糙度因素下,分析了在最大扭矩工况条件下(1 600 r/min)主轴承的润滑特性并对主轴承结构参数进行了优化。研究结果表明:各主轴承最小油膜厚度,最大油膜压力符合设计限值;第二主轴承最大油膜压力接近150 MPa的车用柴油机油膜压力极限值,其轴心轨迹有明显偏向运动,表明该轴承存在明显的轴承弯矩;以轴承弯矩为分析目标,采用试验设计方法得到对轴承弯矩影响的主轴承结构参数顺序为主轴承宽度、轴承间隙、油槽宽度、进油口位置。     

ESTIMATION OF TOOL WEAR OF CARBIDE TOOL IN ORTHOGONAL CUTTING USING FEM SIMULATION

In metal cutting, tool wear on the tool-chip and tool-workpiece interfaces (i.e. flank wear and crater wear) is strongly influenced by the cutting temperature, contact stresses, and relative sliding velocity at the interface. These process variables depend on tool and workpiece materials, tool geometry and coatings, cutting conditions, and use of coolant for the given application. Based on the predicted temperatures and stresses on the tool face from the finite element analysis (FEA) simulation, tool wear may be estimated with acceptable accuracy by incorporating an empirical wear model.

The overall objective of this study is to develop a methodology to predict the tool wear evolution and tool life in orthogonal cutting using FEM simulations. To approach this goal, the methodology is proposed with three different parts. In the first part, a tool wear model for the specified tool-workpiece pair is developed via a calibration set of tool wear cutting tests in conjunction with cutting simulations. In the second part, modifications are made to the commercial FEM code used to allow for tool wear calculation and tool geometry updating. The last part includes the validation of the developed methodology. This paper is mainly focused on the modifications made to the commercial FEM code in order to make reasonable tool wear estimates (the second part).     

ESTIMATION OF TOOL WEAR OF CARBIDE TOOL IN ORTHOGONAL CUTTING USING FEM SIMULATION

In metal cutting, tool wear on the tool-chip and tool-workpiece interfaces (i.e. flank wear and crater wear) is strongly influenced by the cutting temperature, contact stresses, and relative sliding velocity at the interface. These process variables depend on tool and workpiece materials, tool geometry and coatings, cutting conditions, and use of coolant for the given application. Based on the predicted temperatures and stresses on the tool face from the finite element analysis (FEA) simulation, tool wear may be estimated with acceptable accuracy by incorporating an empirical wear model.

The overall objective of this study is to develop a methodology to predict the tool wear evolution and tool life in orthogonal cutting using FEM simulations. To approach this goal, the methodology is proposed with three different parts. In the first part, a tool wear model for the specified tool-workpiece pair is developed via a calibration set of tool wear cutting tests in conjunction with cutting simulations. In the second part, modifications are made to the commercial FEM code used to allow for tool wear calculation and tool geometry updating. The last part includes the validation of the developed methodology. This paper is mainly focused on the modifications made to the commercial FEM code in order to make reasonable tool wear estimates (the second part).     

STRATEGIES AND CHALLENGES IN METHOD DEVELOPMENT AND VALIDATION FOR THE ABSOLUTE QUANTIFICATION OF ENDOGENOUS BIOMARKER METABOLITES USING LIQUID CHROMATOGRAPHY‐TANDEM MASS SPECTROMETRY

Metabolomics is a dynamically evolving field, with a major application in identifying biomarkers for drug development and personalized medicine. Numerous metabolomic studies have identified endogenous metabolites that, in principle, are eligible for translation to clinical practice. However, few metabolomic‐derived biomarker candidates have been qualified by regulatory bodies for clinical applications. Such interruption in the biomarker qualification process can be largely attributed to various reasons including inappropriate study design and inadequate data to support the clinical utility of the biomarkers. In addition, the lack of robust assays for the routine quantification of candidate biomarkers has been suggested as a potential bottleneck in the biomarker qualification process. In fact, the nature of the endogenous metabolites precludes the application of the current validation guidelines for bioanalytical methods. As a result, there have been individual efforts in modifying existing guidelines and/or developing alternative approaches to facilitate method validation. In this review, three main challenges for method development and validation for endogenous metabolites are discussed, namely matrix effects evaluation, alternative analyte‐free matrices, and the choice of internal standards (ISs). Some studies have modified the equations described by the European Medicines Agency for the evaluation of matrix effects. However, alternative strategies were also described; for instance, calibration curves can be generated in solvents and in biological samples and the slopes can be compared through ratios, relative standard deviation, or a modified Stufour suggested approaches while quantifying mainly endogenous metabolitesdent t‐test. ISs, on the contrary, are diverse; in which seven different possible types, used in metabolomics‐based studies, were identified in the literature. Each type has its advantages and limitations; however, isotope‐labeled ISs and ISs created through isotope derivatization show superior performance. Finally, alternative matrices have been described and tested during method development and validation for the quantification of endogenous entities. These alternatives are discussed in detail, highlighting their advantages and shortcomings. The goal of this review is to compare, apprise, and debate current knowledge and practices in order to aid researchers and clinical scientists in developing robust assays needed during the qualification process of candidate metabolite biomarkers. © 2019 John Wiley & Sons Ltd. Mass Spec Rev     

直齿圆柱齿轮动力学特性分析与ADAMS仿真研究

在考虑时变啮合刚度、啮合阻尼、齿面摩擦等因素的基础上,采用集中参数法建立了圆柱齿轮传动系统平移-扭转耦合动力学模型。根据齿轮箱设计参数,使用龙格-库塔法求得各齿轮的振动位移,计算了齿轮副的动态啮合力。并在Adams中建立齿轮传动系统的多体接触动力学模型并进行仿真,获得齿轮啮合传动过程中的动态啮合力和振动位移、振动速度。通过台架试验,测量齿轮传动系统的振动加速度,采用数值积分计算振动速度和位移,并分析其振动特性。结果表明,在齿轮的振动速度与位移方面,集中参数求解结果与实验数据具有良好的一致性;啮合力方面两种方法均得到与理论计算值一致的结果,验证了采用两种方法对比分析研究方法的可行性。