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The dynamics of a machine tool ball screw is an important topic in high-precision machining. Capturing the axial and torsional dynamics of the ball screw has an important guiding significance to the stable processing of the machine tool. The traditional methods mainly involve a mounted sensor or direct embedment into the structure and hybrid finite element methods (FEMs), which are inconvenient. The FEM accuracy is limited by the accuracy of the model. This paper reports that feed-drive system vibration is excited by the interactive impact of a screw, ball, and nut, whose interaction is the core of the feed-drive system dynamics. Under the action of current, the ball screw serves as the transmission component of the executive component to control the working condition of the sliding table. This paper proposes a new method that uses the inertia force sequence caused by random idle running of the sliding table to identify the natural frequency of a feed-drive system based on the feed motor current response. First, the corresponding relationship between the current and the vibration of the feed-drive system is studied. The accuracy of the new method based on the current response is analysed by the experiment, which is performed to identify the natural frequency of the feed-drive system. Then, the incentive region is changed to study the identification effect under different interactive impact conditions, where the contact condition of the ball screw is different. [ABSTRACT FROM AUTHOR]

Microstructure features directly reflect mechanical responses during material deformation and can influence the surface integrity of machined components, which is of great interest to both academic communities and industries. This paper summarizes the state of the art in modeling approaches for the effect of the microstructures and its evolution during metal-cutting processes. The aim of this paper is to analyze the advantages and drawbacks of current methods to improve modeling work and direct future orientations. First, dominant numerical modeling approaches for metal-cutting processes are reviewed. The finite element method (FEM) and mesh-free methods widely applied in professional research are discussed. Following this, approaches to modeling the effect of microstructures and their evolution are reviewed for two major categories—homogeneous field distribution and heterogeneous characteristics. Both the advantages and disadvantages of these two categories are analyzed and discussed in detail. Experimental techniques based on advanced characterization approaches to the validation of pertinent models are also discussed. Finally, a brief summary is presented and an outlook for future work is delineated. [Display omitted] • Numerical modeling approaches with the consideration of microstructure features towards metal cutting are reviewed. • Modeling through treating microstructures as homogeneous characteristics and pertinent validation techniques are reviewed. • Modeling of heterogeneous microstructure evolution in metal-cutting and pertinent characterization techniques are reviewed. • Future orientations of modeling the effect of the microstructure and its evolution in metal-cutting are recommended. [ABSTRACT FROM AUTHOR]

Abstract: This paper provides a comprehensive review of literature, mostly of the last 10–15 years, on modeling of machining of composite materials with a focus on the process of turning. The paper discusses modeling of both fiber reinforced and particle reinforced composites. Modeling studies include molecular dynamic simulations, 2-D and 3-D finite element models and the emerging field of multi-scale models. In fiber reinforced composites the focus is on glass and carbon fiber reinforced polymeric composites as well as long fiber reinforced metal matrix composites. On the other hand modeling of particulate composites is restricted to that of metal matrix composites (MMC). The paper includes recent modeling work to predict cutting forces, tool–particle interaction, cutting temperatures and machined sub-surface damage. A case study on the machining of the MMC A359 aluminum matrix composite reinforced with 20% by volume fraction silicon carbide particles is included to showcase the hierarchical multi-scale machining model. [Copyright &y& Elsevier]

Abstract: In the conventional mechanical punching, the size of punched holes is limited due to the difficulties of tool fabrication and punch-to-die alignment and the increasing costs of tool fabrication. In order to overcome these problems, this paper presents a novel laser-driven flyer punching technology. A flyer with a high speed punch pressure was achieved after being irradiated by a short and intense laser pulse. When the flyer loaded on the workpiece, bending and axial stretching of workpiece would take place, and the workpiece could be sheared off around the corner of die. In this paper, a single micro-hole mold was machined by the micro-milling cutter on printed circuit board and a die-opening with three holes was produced by electrical discharge machining(EDM) using the copper electrode. The micro-punching experiments were conducted on copper successfully by controlling the laser energy and good edge quality was obtained. Experimental results were observed under a XTZ-FG stereo-microscope and an AxioCSM700 scanning microscope. The novel process of punching was also numerically studied by Finite Element Mesh (FEM) and Smoothed Particle Hydrodynamics (SPH), which on the one hand, confirms this punching method could work, on the other hand, lays the foundation for optimizing the process parameters and reducing the number of experiments. With further development, the laser-driven flyer punching technology may become an important micro-punching method, which is characterized by non-contact, low cost, and high efficiency. [Copyright &y& Elsevier]

Abstract The need of fine finishing of gears with high shape accuracy increases in various industrial, military and scientific instruments applications for enhancing the working performance, power transmission capability, service life, reliability as well as decreasing noise and vibrations at high speed. The surface asperities, dimensional inaccuracy, rough surface and shape inaccuracy of a gear tooth profile occur because of the high speed of material removal mechanism which leads to undesirable effect such as noise and vibration in the gearbox. Therefore, utilizing the conventional tool for finishing of gears at high material removal rates may increase inaccuracy in gear teeth profile shape due to the transverse grinding lines, burns, fine cracks, uneven stress, and thermal distortion. This paper reports on a novel design of a magnetorheological gear profile finishing (MRGPF) tool and its performance analysis to finish the gear teeth profile with more precisely and accurately. The MRGPF tool is made likely similar to the gear grinding profile wheel tool. To analyze the uniform finishing at the gear tooth profile, the magnetostatic finite element analysis (FEA) is performed to predict the uniform magnetic flux density at the proposed tool surface using Maxwell Ansoft. On the basis of the result obtained of magnetic flux density distribution on its finishing surface, the MRGPF tool is designed and fabricated. Further, the experiments are performed to examine the finishing performance of the newly designed tool on the EN-24 steel spur gear teeth profile. The results attest the significant improvement in finishing of gear teeth profile surface with high shape accuracy (DIN standard). This may result in improvement in scuffing performance, reducing noise and vibrations at high speed, reducing wear rate on gear teeth profile and also provides lower friction and temperature during its functional operation. Highlights • Designed a new magnetorheological gear profile finishing tool for fine finishing of gears with high shape accuracy. • Uniform distribution of magnetic flux density with significant magnitude on gear tool profile helps in uniform finishing. • Experimentally demonstrated effectiveness of new tool for fine finishing of gear teeth profile with high shape accuracy. • Magnetorheological finished gears can reduce noise and vibrations during its functional application at high rpm. [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates the grinding–hardening both theoretically and experimentally with a plunge surface-grinding process. Theoretically, the paper presents a temperature-dependent finite element heat transfer model, incorporating a triangular moving heat source and various cooling conditions, to investigate the phase transformation kinetics, thus to predict the thickness of a layer hardened. The temperature variation and thickness of the hardened layer were also investigated experimentally on quenchable steel 1045 using dry air and liquid nitrogen as the cooling media. The predictions were in good agreement with the experimental results. It was found that the phase transformation follows the martensitic kinetics. The application of liquid nitrogen enhances the transformation of retained austenite to martensite and results in a refinement of the martensitic structure. [ABSTRACT FROM AUTHOR]

Abstract: As a volumetric heat source, YAG laser can penetrate through the glass, and has many advantages in cutting of glass with controlled fracture compared with CO2 laser cutting of glass. This work lays great emphasis on studying the technique of YAG laser cutting of multi-layer glasses. This paper indicates the experiments of YAG laser cutting of two-layer and four-layer soda-lime glasses with controlled fracture. Optical microscope photographs of the separation surface are obtained to examine the surface quality. The impact of laser power, scanning speed and laser beam size on the cutting quality is studied and the optimum processing parameters are presented in the paper. A theoretical model of a thermal laser shock method for separation of two-layer glasses is developed, and the fracture propagation mechanism is studied by examining the temperature and stress fields using finite element software ANSYS. In YAG laser cutting of multi-layer glasses, the temperature distribution is uniform across the thickness of the glass and the fracture propagates from the top and bottom surface to middle so that better separation surface quality can be acquired and multi-layer glasses can be cut simultaneously. [ABSTRACT FROM AUTHOR]

Abstract: This paper aims to study innovative structure solutions for Ultra High Precision (UHP) Machine Tools (MT) within machining applications at micro/mesoscale level (10–10000μm range). There are many aspects that can affect the accuracy of UHP machining performance. The most important issues are related to the static, dynamic and thermal behaviour of the machines. This paper shows a complete study and thermal testing validation on a set of prototypes (plates and beam) based on sandwiches with core made of metal foam (open cells) material impregnated by phase change materials. The proposed multifunctional structure (which provides high stiffness to weight ratio, good damping properties together with thermal stability) consists of a machine tool part, a beam (Z-axis) of a precision milling machine. The authors have designed, realised and tested prototypes developing thermal trials and then evaluating the experimental data. The trials consisted to test the prototype thermal stability when the environmental temperature varies in a specified range (20–50°C), in order to assess the PCM proprieties to absorb heat and maintain performances for a long duration. Furthermore, a numerical-experimental validation through finite element analysis on the beam prototype is presented. [Copyright &y& Elsevier]

Abstract: The influence of tool roughness on roughness transfer in skin-pass or temper rolling of steel strip is investigated, focusing on loading under combined normal and tangential displacement of tool relative to the workpiece. The calculated roughness transfer by an elasto-plastic finite element (FE) simulation of plane strain indentation in authors’ previous paper [H. Kijima, N. Bay, Skin-pass rolling I—studies on roughness transfer and elongation under pure normal loading, International Journal of Machine Tools and Manufacture, May 2008, accepted for publication] is verified by experimental measurements in this paper. The experiment shows a significant influence on roughness transfer of tangential displacement of workpiece in the sticking and the sliding region. The FE calculations modelling the sticking and sliding region reveal the mechanisms of plastic deformation and roughness transfer. [Copyright &y& Elsevier]

Abstract: This paper presents a finite element model for white layer formation in orthogonal machining of hardened AISI 52100 steel under thermally dominant cutting conditions that promote martensitic phase transformations. The model explicitly accounts for the effects of stress and strain, transformation plasticity and the effect of volume expansion accompanying phase transformation on the transformation temperature. Model predictions of white layer depth are found to be in agreement with experimental values. The paper also analyzes the effect of white layer formation on residual stress evolution in orthogonal cutting of AISI 52100 hardened steel. Model simulations show that white layer formation does have a significant impact on the magnitude of surface residual stress and on the location of the peak compressive residual stress. [Copyright &y& Elsevier]

Abstract: Knowledge of the physics behind the separation of material at the tip of the tool is of great importance for understanding the mechanisms of chip formation. How material separates along the parting line to form the chip and cut surface is still not well understood, yet it is of great importance for improving the robustness, enhancing the predictability and extending the application of currently existing finite element computer programs. This paper attempts to provide some answers to these issues by means of a combined numerical and experimental investigation of the transient beginning to machining and the transition to steady-state orthogonal metal cutting. Numerical modelling was performed by means of an updated-Lagrangian approach based on the finite element flow formulation and experiments were carried out on lead specimens under laboratory-controlled conditions. Forces and displacements are given for the initial indentation phase during which material is displaced up the rake face of the tool. Ductile damage begins to accumulate, eventually leading to separation at the tool tip. This marks the onset of a second stage during which further displacement of material along the rake face is accompanied by separation of material at the tool tip (i.e. cracking), which now continues in all subsequent deformation. The displaced material, although not yet attaining its fullest extent, now begins to take on the appearance of a continuous chip. A third stage begins when the material, which up till now has been in intimate contact with the rake face, develops curvature and leaves the tool. This does not, however, mark the beginning of steady-state cutting, because chip curl continues to increase until a steady value is attained. During this period, the contact length with the tool then reduces somewhat, before settling down to a steady value. The thrust force is a maximum at the point of greatest chip contact length. The paper demonstrates that material separation is caused by shearing rather than tension. The specific distortional energy is an appropriate criterion for evaluating ductile damage in shear and the onset of separation ahead of the cutting edge. In turn this determines the value of the fracture toughness in shear. [Copyright &y& Elsevier]

Abstract: This paper investigates Atkins’ idea that the modelling of metal cutting must include the significant work involved in the formation of new surfaces as well as the traditional components of plastic flow and friction. New finite element and algebraic calculations are presented together with specially designed orthogonal metal cutting experiments performed on lead specimens under laboratory-controlled conditions. Independent determinations of the mechanical properties of lead were made and comparisons are given between theoretical predictions and experimental results. Calculations cover a wide range of topics such as material flow, chip-compression factor, primary shear plane angle, cutting force and specific cutting pressure. It is shown that the choice of lead as workpiece material reveals important facts that would be obscured were the usual sort of workpiece metals to be cut. The paper demonstrates quantitatively that while material flow, chip formation and the distribution of the major field variables can be modelled successfully by traditional ‘plasticity and friction only’ analyses, the contribution of ductile fracture mechanics is essential for obtaining good estimates of cutting forces and of the specific cutting pressure. [Copyright &y& Elsevier]

Abstract: This paper aims to evaluate the properties of tubular materials by hydraulic bulge tests combined with a newly proposed analytical model. Annealed AA6011 aluminum tubes and SUS409 stainless steel tubes are used for the bulge test. The tube thickness at the pole, bulge height and the internal forming pressure are measured simultaneously during the bulge test. From above experimental data, the effective stress–effective strain relations can be derived by this analytical model assuming the profile of the free bulge region as an elliptical surface. The flow stresses of the tubular materials by this approach are compared with those obtained by the tensile test and Fuchizawa''s model. The finite element method is used to conduct the simulations of hydraulic bulge forming with the flow stresses obtained by the above-mentioned models. The analytical results of forming pressures versus bulge heights are compared with the experimental results to validate the approach proposed in this paper. [Copyright &y& Elsevier]

Abstract: Kinematic roughness-based surface finish prediction is known to often under-predict the measured surface roughness in turning process, especially at small (micron level) feed rates. It has also been observed that the surface roughness in micro-turning decreases with feed, reaches a minimum, and then increases with further reduction in feed. This paper presents a model for predicting the surface roughness in micro-turning of Al5083-H116 alloy that takes into account the effects of plastic side flow, tool geometry, and process parameters. The model combines these effects with more accurate estimation of the average flow stress of Al5083-H116 at micron scale of deformation with the help of a previously reported strain gradient-based finite element model. The surface roughness model is evaluated through a series of micro-turning experiments. The results show that the model can predict the surface roughness in micro-turning quite well. It is shown that the commonly observed discrepancy between the theoretical and measured surface roughness in micro-turning is mainly due to surface roughening caused by plastic side flow. Further, it is shown that the increase in roughness at low feed can be attributed to the increased side flow caused by strain gradient-induced strengthening of the material directly ahead of the tool. [Copyright &y& Elsevier]

Abstract: This paper presents an expert spindle design system strategy which is based on the efficient utilization of past design experience, the laws of machine design, dynamics and metal cutting mechanics. The configuration of the spindle is decided from the specifications of the workpiece material, desired cutting conditions, and most common tools used on the machine tool. The spindle drive mechanism, drive motor, bearing types, and spindle shaft dimensions are selected based on the target applications. The paper provides a set of fuzzy design rules, which lead to an interactive and automatic design of spindle drive configurations. The structural dynamics of the spindle are automatically optimized by distributing the bearings along the spindle shaft. The proposed strategy is to iteratively predict the Frequency Response Function (FRF) of the spindle at the tool tip using the Finite Element Method (FEM) based on the Timoshenko beam theory. The predicted FRF of the spindle is integrated to the chatter vibration stability law, which indicates whether the design would lead to chatter vibration free cutting operation at the desired speed and depth of cut for different flutes of cutters. The arrangement of bearings is optimized using the Sequential Quadratic Programming (SQP) method. [Copyright &y& Elsevier]

It is a known fact that it is very difficult to implement the algorithm of plasticity of porous materials in FEM commercial programs for different types and characteristics. The aim of this paper is to put forward a flexible model of plasticity of porous materials by implementing it into the general purpose finite element program ABAQUS®. A modified algorithm is developed in this paper which takes into account the effect of an isotropic work hardening of the porous material. This is incorporated into the FEM program to yield a flexible solution for different yielding criterion. The present criterion is compared with other known published work and was found to be in good agreement. It was found that all the failure criteria used were successfully implemented using the newly developed algorithm. Also, the present criterion is adequately adjusted to fit all other results obtained from other criteria of failure. Finally, some of these published criteria had not been implemented previously for use in the FEM programs, but in this paper were made to do so. Other theoretical results will also be presented. [Copyright &y& Elsevier]

This bibliography contains references to papers, conference proceedings and theses/dissertations dealing with machining simulated by the finite element methods that were published in 1996–2002. Three hundred and seventy-two references are listed. The paper is an addendum to the author’s bibliography published in J Mater Process Technol 86 (1999) 17–44, which listed references on subjects published between 1976–1996. [Copyright &y& Elsevier]

Temperature variations in the machine tool structural components may lead to relative pose variations between the tool tip and the workpiece. Different thermal layouts may lead to various temperature distributions and generate various thermal deformations. Thermal symmetric design is often used to complete thermal balancing of machine tools. Studies on theoretical methods to guide the layout design of the heat sources (HS) and cooling sources (CS) in machine tools are insufficient. To address this problem, a novel analytical approach for characterising the equivalent cuboid thermal response of machine tool structural components is presented in this paper. The proposed analytical modelling method can realise analytical temperature field modelling with Green's function, calculating the equivalent thermal moment with Reissner's theory, and matching the thermal power-deformation mapping coefficient (TPDMC) using the finite element method (FEM). The explicit and correlative formulation between the thermal power of the HSs and CSs and the guideway thermal deviations is deduced. Furthermore, the layout principles of the CSs are presented according to the maximum efficiency of the thermal moment and the characterisation matching of the TPDMC curves. Afterwards, power matching of the CS is obtained with the aid of the minimum deformation principles of the key positions. Simulated and experimental results illustrated that the proposed method can be used to rapidly and accurately analyse the temperature and thermal deformation responses of the machine tool, as well as to provide a thermal balancing strategy according to specific thermal conditions. The analytical approach proposed in this paper is a general method suitable for the thermal balancing design of machine tools, and it is of great value for improving the thermally induced accuracy stability of machine tools. [Display omitted] • Analytical modelling method for thermal characterizing of machine tool structural components is presented. • Effects of heat sources powers on temperature and deformation are theoretically investigated. • Layout principle of heat/cooling sources is summarised. • Thermal balancing strategy to reduce thermal deformation is developed. [ABSTRACT FROM AUTHOR]

Rehbinder effect on ductile materials is observed when surfactant is applied on the material surface, which reduces the strength of material due to reduction in surface energy. Application of Rehbinder effect in conventional machining of ductile materials was studied previously which resulted in significant reduction in chip thickness and cutting forces. In this paper, the Rehbinder effect on ultraprecision microcutting of ductile materials is presented. Microcutting experiments were conducted on annealed copper, hardened copper, aluminium alloys AA-6061-T6 and RSA-6061 of different grain sizes at varying uncut chip thickness and cutting speed. Permanent metal marker ink was used as a surfactant to induce Rehbinder effect. As a result, cutting and thrust forces were reduced by 50% for pure copper whereas a 30% reduction was observed on aluminium alloys along with a reduction in chip thickness for the sections where ink was applied. It is also evident that the Rehbinder effect contributes towards an improvement in surface roughness. The underlying mechanism responsible for the reduction in cutting forces and chip thickness is explained in relation to a dislocation density model and explored further by a finite element method simulation. Positive results of Rehbinder effect on microcutting demand further studies to characterise the effect on other surfactant-material pairs for the applications in ultraprecision machining. [ABSTRACT FROM AUTHOR]

In tube free-bending, the connection of the bending die to the guide has a great influence on the stability of mechanical movement and the forming limit of the bent tube. The general connection of the bending die to the guide cannot realize the continuous stable movement of the bending die. Spherical connection of the bending die to the guide can guarantee a continuous changed tipping of the bending die, but has a limited minimal bending ratio (ratio of bending radius to tube outer diameter) of R/D 0  ≥ 3 depending on the geometrical constrains. In this paper, a new spherical connection of the bending die to the guide was designed through geometric derivation, which can lead to a greater deflection of the bending die, to realize the bending ratio of down to R/D 0  = 2.5. Based on the designed spherical connection, the bending ratio of down to R/D 0  = 2.43 and R/D 0  = 2.78 of brass tube were realized in the finite element simulation and bending test respectively. And with the analytical model, simulation model and experimental bending results, the forming characteristics of bent tube with small bending radii based on the spherical connection structure were investigated. The main results show that the equivalent stress, displacement of the strain neutral layer (NL) increase with the decrease of bending radius, and the wall thickness thinning in outer bend shows little differences under tight and big bending radii due to the increased axial thrust. [ABSTRACT FROM AUTHOR]

Tool tip frequency response function (FRF) is essential for chatter stability diagram in machining. But new modal tests are required for different tool-holder-spindle assemblies. To avoid these tests, receptance coupling substructure analysis (RCSA) method has been developed. Previous research proved that the full receptance matrix, which contains rotational and moment contributes, influences the RCSA accuracy. By improving the accuracy and efficiency in acquiring the full receptance matrix, this paper presents a new RCSA methodology to predict the tool tip dynamics when a new tool is selected. To identify the contact dynamics between the tool and tool holder, one required receptance matrix is experimentally measured with a reference tool attached on the machine. Comparing to the classical RCSA technique, an enhanced approach is proposed to better estimate the receptance matrix. Only one impact positon is required in the experiment. The enhanced approach introduces two compensation strategies to process the measuring data from impact test. Each compensation strategy can be chosen to improve the estimation accuracy. The measured receptances, together with the finite element models of the reference tool and the new tool, are used to predict the unknown tool tip FRF. Both numerical simulation and practical experiment are conducted to validate the proposed methodology. The results show that the proposed method is preferred when multiple modes should be considered. [ABSTRACT FROM AUTHOR]

Modeling method investigation about spindle thermal errors is significant for spindle thermal optimization in design phase. To accurately analyze the thermal errors of motorized spindle unit, this paper assumes approximately that 1) spindle linear thermal error on axial direction is ascribed to shaft thermal elongation for its heat transfer from bearings, and 2) spindle linear thermal errors on radial directions and angular thermal errors are attributed to thermal variations of bearing relative ring displacements. Based on prerequisites, an analytical modeling method is developed to analyze these spindle thermal errors. Firstly, thermal-mechanical models of rotating ring geometry and interference assembled rotating ring geometries are established, for thermal variation modeling of relative ring displacements of short cylindrical roller bearing and angular contact ball bearing. Secondly, these thermal variation models are associated with heat-fluid-solid coupling FE (finite element) simulation technique, to model spindle linear thermal errors on radial/axial directions and angular thermal errors by the analytical simulation method. Consequently, verification experiments clarify that the presented method is accurate for spindle thermal errors modeling, and can be effectively applied into the design and development phases of motorized spindle units. [ABSTRACT FROM AUTHOR]

An easy-to-produce sawtooth chip is the main feature of the high-speed milling of hardened steel. In previous works, a theoretical geometric model was proposed for the sawtooth chip formation to predict the strain and strain rate in the shear band during chip formation; these properties are important when describing the deformation characteristics for the cutting of hardened steel materials. In the cutting process, however, the changes and distributions of stress and strain can hardly be obtained using a theoretical model. This paper modifies the conventional empirical Johnson–Cook constitutive equation by employing stress–strain curves at high temperature and a high strain rate obtained using split Hopkinson pressure bar technology and considering the negative strain rate effect and temperature effect of the material, especially for SKD11 (62 HRC) hardened steel. A thermo-mechanical coupled two-dimensional planar strain finite element model for the high-speed milling of SKD11 hardened steel with a modified Johnson–Cook constitutive equation is presented. The geometric characteristics of chip formation during the high-speed milling of SKD11 are predicted and the results are in good agreement with experimental results. Employing the modified finite element model, the stress and strain in the shear band during high-speed cutting are quantitatively analyzed and found to be in close agreement with the results of a theoretical model analysis. It is found that the cutting speed has a critical value at which the stress and strain reach a certain value and the distributions of stress and strain change in the shear band, resulting in the generation of a sawtooth chip. Moreover, the cutting force, cutting temperature, and selection of a coated tool are discussed according to results obtained with the modified finite element model. The cutting force and difference in temperature decrease while the temperature increases as the cutting speed increases. Compared with a TiAlN-coated tool, a TiSiN-coated tool performs better in cutting SKD11 hardened steel in terms of the cutting temperature. [ABSTRACT FROM AUTHOR]

This paper proposes a new approach to improving the machining precision based on dynamic sensitivity analysis. Firstly, the movement transmission chain of machine tools is analyzed to establish the error propagation model. The model can be used to calculate the error sensitive coefficient of each component. Secondly, the deformation of each component is acquired depending on the finite element analysis. Combining the error sensitive coefficient and deformation, the sensitive error components of machine tools are identified. Thirdly, according to the sensitive error components, the layout of the machine tool is modified and the stiffness of sensitive error component is improved to reduce the machining error of machine tools. A simulation example about globoidal cam machine tools is conducted. Comparing the machining error of vertical globoidal cam machine tool and horizontal globoidal cam machine tool in the simulation, the feasibility of the method is verified. This method not only increases the stiffness of the sensitive error component, but also changes the layout of the machine tool based on dynamic sensitivity analysis results. Therefore, it can provide a new approach to improving the machining accuracy. Finally, an experiment was conducted to verify the validity the correctness of the conclusions. [ABSTRACT FROM AUTHOR]

In this paper a new approach is presented for predicting the milling stability based on the Simpson method. Generally the milling dynamic process is described as a linear time-periodic system with a single discrete time delay. By dividing the tooth passing period equally into a finite set of time intervals, the Simpson method is utilized in each time interval to estimate the state items. Then the state transition matrix over one tooth passing period is constructed, and the milling stability could be predicted by the Floquet theory. The convergence rate of the proposed method is discussed, and two benchmark examples are conducted. The results show that the proposed method achieves satisfactory accuracy and efficiency. [ABSTRACT FROM AUTHOR]

Hydraulic forming (HF) has good forming accuracy, but causes the material to break easily. Electromagnetic forming (EMF) can greatly improve the forming limit of materials, but its shape control ability is poor. In this paper, the two techniques were combined, i.e., electromagnetic hydraulic forming (EMHF), to obtain a new high-strain-rate forming method, which was investigated through experimental and simulation studies. Three kinds of specimens were designed, and the forming limits of 5052 aluminum alloy were determined. The results show that EMHF specimens have higher forming height and limit strain compared with HF specimens. The increase in forming limit is due to the uniform dislocation distribution at microscopic level and inertia effect at macroscopic level. The simulation results show that the deformation velocity exceeds 55.6 m/s and strain rate exceeds 689.7 s−1. The experimental results are consistent with the simulated deformation contours, which proves the reliability of simulation. Flat bottom die and wave shape die were used to investigate the shape control ability of EMF and EMHF. The sheet and die can be closely fitted in EMHF. However, EMF has significant rebound effect and poor forming accuracy. Thus, better forming accuracy can be obtained if liquid is added in high-speed forming. The difference between EMHF and EMF formation mechanisms is essentially the difference of force action. EMHF not only retains the strong shape control ability of HF, but also greatly improves the forming limit of materials. It is a potential forming process that can be widely used in industrial manufacturing field in the future. [Display omitted] • Electromagnetic hydraulic forming (EMHF) method can greatly improve the forming limit of AA5052. • Compared with electromagnetic forming, EMHF has better shape control ability. The scientific implications are discussed. • The finite element model of EMHF is established, and the simulation results agree with the experimental results. • The mechanism of EMHF improving forming limit was analyzed. Theoretical models are established. [ABSTRACT FROM AUTHOR]

The proposal of erosion models to predict the jet footprint during abrasive waterjet machining is a key element for the development of this technology, but it is very challenging because of the inherent fluctuations of the process. This issue becomes critical when the size of the cutting systems is reduced, since the relative size of these deviations increases. The present paper considers for the first time a modelling framework capable of predicting the average shape of AWJM footprints and, of great novelty, the variability along the trench, combining finite element analysis and Monte Carlo methods, and verifying the model using different feed speeds and tilt angles. For that purpose, the relevance of each random parameter, such as shape (sharpness), size and relative orientation of the abrasive particles, has been investigated through parametric studies on these variables. Multiple particle simulations with randomly generated input were performed to determine the effect of operating parameters in the overall variability of the jet footprint. The process was simulated using Abaqus 6.14 as multiple garnet particles hitting a target of Ti–6Al–4V at very high velocity, eroding the target by plastic deformation and material removal. The model shows successfully the influence of single particle parameters, such as the shape, on the surface variability. The results for the footprint variability show that stochastic methods are suitable to model these fluctuations, and it is also shown that this approach yields accurate estimates of the average profile after multiple jet passes with error less than 5%. [ABSTRACT FROM AUTHOR]

This paper presents an integrated error propagation analysis method to estimate the measurement uncertainty using Monte Carlo method in order to analyze the measurement accuracy of an H-drive stage with air bearing during high acceleration subjected to the influence of a variety of errors, including straightness errors, thermal errors, deformation errors and air bearing gap change errors caused by acceleration force. Firstly, the integrated error propagation model of an H-drive stage is built combined with the effects of the various error sources based on the multi-body system and instrument precision theory. Then these errors are identified by experiments and finite element analysis and the influence of each error in six degrees of freedom displacement is obtained. Finally, the displacement measurement uncertainty of the stage in the reference coordinate system is evaluated by Monte Carlo method, within 95% probability, the displacement measurement results and the expanded uncertainty in x and y directions are calculated x =(165.000±0.064) mm and y =(195.000±0.054) mm respectively. The proposed method can be used in the error budget of precise machine design and applied in error compensation to improve the measurement and control accuracy of precise machine workpiece stage. [ABSTRACT FROM AUTHOR]

In this paper, a sheet metal forming simulator (SMFS) is used for evaluation of the frictional behaviour of AZ80 and ZE10 magnesium alloys under lubricated contact conditions. The results showed that the friction coefficient increases by increasing the contact pressure and decreasing the sliding velocity. A friction model is further developed for lubricated contact taking into account the surface roughness characteristics and the viscosity of lubricant. The proposed model showed very good agreement with the results of experiments. Finite element (FE) simulations were also carried out to investigate the effect of key process parameters on the results of SMFS. Based on the results of the FE model, the coefficient of friction increases by increasing the bending angle and pin diameter; however, these increases are not significant. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a multi-particle microfinite element model with a random particle distribution in SiCp/Al composites was developed using ABAQUS software. The formation mechanism of edge defects near the exit of orthogonal cutting was analyzed, and the effects of cutting parameters on the sizes of edge defects were investigated. The results indicate that both the brittle fracture of SiC particles and the plastic flow of Al matrix occur in the process of the edge defects formation. Additionally, the cutting speed has little effect on the sizes of edge defects but the cutting depth has a significant effect on the height and length of edge defects. The numerical results were also compared to the orthogonal cutting experimental data and found to be in reasonable agreement. [Copyright &y& Elsevier]

Abstract: Flexible forming technology provides significant application potential in various areas of manufacturing, particularly at a miniaturized level. Simplicity, versatility of process and feasibility of prototyping makes forming techniques by using flexible tools suitable for micro sheet metal forming. This paper reports the results of FE simulation and experimental research on micro deep drawing processes of stainless steel 304 sheets utilising a flexible die. The study presents a novel technique in which an initial gap (positive or negative) is adopted between an adjustment ring and a blank holder employed in the developed forming system. The blank holder is moveable part and supported by a particular spring that provides the required holding force. The forming parameters (anisotropy of SS 304 material, initial gap, friction conditions at various contact interfaces and initial sheet thickness) related with the forming process are in details investigated. The FE models are built using the commercial code Abaqus/Standard. The numerical predictions reveal the capability of the proposed technique on producing micro metallic cups with high quality and large aspect ratio. To verify these results, number of micro deep drawing experiments is conducted using a special set up developed for this purpose. As providing a fundamental understanding is required for the commercial development of this novel forming technique, hence the optimization of the initial gap in accordance with each sheet thickness, thickness distribution and punch force/stroke relationship are detected. [Copyright &y& Elsevier]

Abstract: This paper addresses a key theoretical problem in the mechanics of ultra-precision machining – shear angle prediction and cutting force variation induced by crystallographic anisotropy. The constitutive equation of crystal plasticity is implemented in the finite element modelling of the chip formation at micro-scale to take into account the effect of crystallographic orientations of the work piece to be cut. The theoretical prediction of shear angle and cutting force variation reveals two distinguished phases of pre-compression and steady-state cutting in ultra-precision diamond turning. The predicted patterns of cutting force variation are in good agreement with published experimental results. [Copyright &y& Elsevier]

Abstract: The cutting process stability depends on machine tool dynamics that is strongly influenced by the tool. Receptance coupling substructure analysis (RCSA) can be used to estimate the tool tip dynamic compliance and consequently the chatter free cutting conditions when the machine is equipped with a tool that has not been previously tested. This methodology can be particularly useful on real shop–floors where a lot of different tool–tool holder configurations are generally used. RCSA typically combines experimental dynamic compliance measurements performed on a machine equipped with a selected tool and the finite element (FE) models of both the already tested tool and the new ones. This paper presents a new receptance coupling substructure analysis (RCSA) approach that overcomes the drawbacks in the estimation of the receptances that contain rotational and moment contributes. This indeed often limits the accuracy of the RCSA techniques presented in other scientific works. The proposed formulation allows to better estimate both the matrices of receptances of the spindle–tool holder assembly and the tool–tool holder connection stiffness. Those quantities are used, together with the FE model of the new tool, to predict the unknown tool tip dynamic compliance. Some useful guidelines to implement the proposed RCSA are also defined: they allow to manage the procedure accuracy considering the experimental methodology typically used to measure dynamic compliances. The proposed innovative RCSA is experimentally tested and validated. [Copyright &y& Elsevier]

Abstract: The helical-wedge rolling (HWR) process is a new metal forming technique for producing spherical parts of various dimensions. In this paper, the overall details of the HWR process are described and the important process parameters that control the HWR process are systematically discussed. A new experimental method, developed under laboratory conditions, showed that the HWR process can produce spherical steel parts (balls) with high manufacturing quality. Numerical simulations of the HWR process were carried out using a commercially available FEM software (Simufact) to show the stress, strain, and temperature distributions in the rolled balls. In addition, the variation of forces and rolling moments during the process are analyzed. Based on the experimental and numerical investigations, the HWR technique has been found to be a viable process for enhancing the quality and productivity of formed spherical products. [Copyright &y& Elsevier]

Abstract: The chip segmentation process has a significant effect on the cutting force fluctuation during machining which could affect tool vibration and tool wear. This paper deals with a quantitative analysis of the chip segmentation phenomenon in metal machining. The notion of intensity of the phenomenon has been introduced. Various parameters have been proposed for this purpose. These parameters are based on dimensional characteristics of the segmented chip and the strain distribution within the chip. A Finite Element based modelling has been developed to simulate the chip formation process in the case of machining aeronautical aluminium alloy AA2024-T351 with WC-Co based cutting tools. From the simulated chip morphologies, introduced chip segmentation parameters are assessed. The impact of the cutting speed and tool geometry on the chip segmentation intensity is clearly highlighted. The relevance of each parameter is discussed. Cutting force and contact length fluctuations with respect to the cutting speed variation when segmentation occurs are discussed and deeply analysed. A correlation between average cutting force reduction and segmentation intensity when the cutting speed increases as well as between chip formation process and cutting force oscillation has been established thanks to the introduced parameters, showing thus their usefulness. [Copyright &y& Elsevier]

Abstract: A nanofinishing process using ball end magnetorheological (MR) finishing tool was developed for finishing 3D workpiece surfaces. In this process a ball end shape of MR polishing fluid is generated at the tip surface of the rotating tool which is used as a finishing spot. This paper is focused on surface finishing and performance evaluation of a typical three-dimensional ferromagnetic workpiece using a ball end magnetorheological finishing process. A typical 3D workpiece surfaces were made by milling process at different angles of projection such as flat, 30°, 45° and curve surfaces. The experiments were performed on these typical workpiece surfaces by ball end MR finishing setup to study the effect of number of finishing passes on final surface roughness. The experiments were also performed on a flat ground surface to study the process performance as compared with the milled workpiece surfaces. The finite element analysis has been done to study the distribution of magnetic flux density at tip surface of the tool with an inserted typical 3D workpiece surfaces. When these typical workpiece surfaces were finished by proposed MR finishing process, the surface roughness were reduced as low as 16.6nm, 30.4nm, 71nm and 123.7nm respectively on flat, 30°, 45° and curve surfaces for 60 passes of finishing. The roughness of flat ground surface was reduced as low as 19.7nm for 120min of finishing. The experimental results demonstrated that the newly developed ball end magnetorheological finishing process was effective in finishing typical 3D ferromagnetic workpiece surfaces. [Copyright &y& Elsevier]

Abstract: Laser forming is a noncontact forming method that has received considerable attention in recent years. Compared to mechanical bending, no hard tooling, dies, or external force is used. Within laser forming, laser thermal adjustment is an important industrial activity with applications in critical microsystems such as electrical switches, computer devices, etc. This process utilizes the thermal stresses generated during laser heating to achieve the desired deformations. The parameters varied to control the process are usually laser power, beam diameter, heating time, and the number of pulses. The thermal stresses generated during laser heating are strongly dependent upon sample geometry. This paper investigates the effects for cut-out and its geometries on laser thermal adjustment. Finite element modeling has been used for the study of the process with some results also validated by experiments. [Copyright &y& Elsevier]

Abstract: This work is motivated by the fact that the conventional cutting parameters optimization in milling process has been widely investigated based on the assumption that the dynamics of the milling system is deterministic. Since there are many uncertain factors in a practical milling process, nominal cutting parameters derived from the deterministic cutting parameters optimization formulation cannot guarantee the stability of milling process and cannot lead to actual maximization of material removal rate and minimization of surface location error at the shop floor level. We develop a robust spindle speed optimization formulation, in which the upper bound of surface location error and lower bound of Lobe diagram are adopted as the optimization object and the constraint condition, respectively. For a comparison, we also give a deterministic spindle speed optimization formulation, without uncertainties. Time finite element approach is employed as the conventional deterministic model to obtain the Lobe diagram and surface location error. The upper and lower bounds of Lobe diagram and surface location error due to the model parameters uncertainties are calculated using the sensitivity analysis. The optimization problems are solved by an augmented Lagrangian function method. Experiments of milling of blades with spindle speeds derived from the deterministic and robust optimization results are implemented. The robust optimization result leads to stable milling process, while the deterministic one does not. The experimental results validate the proposed method. The robust optimization formulation given in this paper is helpful to the decision making in a practical milling process. [Copyright &y& Elsevier]

Abstract: This paper presents a new approach for chatter modelling in micro-milling. The model takes into account: the nonlinearity of the uncut chip thickness including the run-out effect; velocity dependent micro-milling cutting forces; the dynamics of the tool-holder-spindle assembly. The uncut chip thickness is determined after considering the full kinematics of the cutting tool including the run-out effect. The micro-milling cutting forces are determined by: (i) a finite element (FE) prediction of the cutting forces in orthogonal cutting at different cutting velocities and uncut chip thicknesses; (ii) describing the relationship between cutting forces, cutting velocities and uncut chip thicknesses into a nonlinear equation; (iii) incorporating the uncut chip thickness model into the relationship of the cutting forces as function of the cutting velocity and the uncut chip thickness. The modal dynamic parameters at the cutting tool tip are determined for the tool-holder-spindle assembly and used for solving the equation of motion. The micro-milling process is modelled as two degrees of freedom system where the modal dynamic parameters for the tool-holder-spindle assembly and the micro-milling cutting forces are considered. Due to nonlinearities in the micro-milling cutting forces, the equation of motion is integrated numerically in the time domain using the Runge–Kutta fourth order method. The displacements in the x and y directions are obtained for one revolution-per-tool. Statistical variances are then employed as a chatter detection criterion in the time-domain solution. Scanning electron microscope (SEM) inspection is carried out to observe potential chatter marks on the micro-milled AISI 4340 steel surfaces at different spindle speeds and depths of cut. The predicted stability lobes and the experimentally obtained stability limits resulted in satisfactory agreement. The influence of the run-out effect on the stability lobes at different feed rates was investigated, which demonstrated the capability of the developed chatter model to consider quantitatively the run-out phenomenon. The results showed that the stability limits decrease by increasing the run-out length. [Copyright &y& Elsevier]

Abstract: Friction under lubricated conditions is known to depend on pressure, and experimental determination of this dependence has typically quantified pressure as a uniform value over the contact area. However, non-uniform pressure distributions at the contact interfaces of draw-bend tests have been reported from various experiments and simulations. A previous study by the authors had evaluated the conventional methodology, which assumes uniform pressure distribution to estimate friction coefficients from draw-bend friction tests, and has concluded that the conventional methodology is only valid for measuring an average friction coefficient over the pressure range, which exists in a specific draw-bend system. In this paper, a new methodology to determine friction coefficients from draw-bend friction tests considering the pressure non-uniformity is suggested. In the methodology, contact pressure maps obtained from simulations, instead of the uniform pressure assumption, are included in the analysis of test data to measure the pressure dependency of friction coefficient. The proposed method is applied to friction measurement of aluminum sheets with anisotropic mill-finish surface and friction coefficients were obtained as functions of contact pressure, sliding velocity and sliding direction. Lastly, the obtained friction data were implemented into a finite element code, and circular cup drawing experiments and simulations were performed to validate the methodology. [Copyright &y& Elsevier]

Abstract: This paper presents a model for the three-dimensional (3D) dynamic response of endmills while considering the actual fluted cross-sectional geometry and pretwisted shape of the tools. The model is solved using the spectral-Tchebychev (ST) technique. The bending and the coupled torsional-axial behavior of four different fluted endmills is compared to finite element model (FEM) predictions and experimental results obtained using modal testing under free-free boundary conditions. For the first eight modes, including six bending and two torsional/axial modes, the difference between the 3D-ST and experimental natural frequencies is shown to be 3% or less for all four tools tested during this study. For the same modes, the 3D-ST and FEM predictions agree to better than 1%. To demonstrate its application, the 3D-ST model for the fluted section of a commercial endmill is coupled to the spindle–holder to predict the tool-point dynamics using receptance coupling substructure analysis (RCSA) with a flexible connection. The coupled model is validated through experiments. [Copyright &y& Elsevier]

Abstract: A major challenge in laser fusion cutting of thick-section ceramics is to overcome the thermal-stress induced cracking, which leads to catastrophic breakdown of the material integrity. In order to achieve crack-free cutting of ceramics, it is important to understand the mechanism of the transient temperature field and resulting stress distribution effect on crack formation. In this paper, both experimental and theoretical investigations are reported to understand crack formation characteristics in fibre laser cutting of thick-section Al2O3 ceramics. A three-dimensional (3D) finite element (FE) model for simulation of the transient temperature field and thermal-stress distribution together with material removal in laser cutting was developed. Crack formation characteristics were predicted by the model and validated by experiments. The effects of four process parameters i.e. laser peak power, pulse duration, pulse repetition rate and feed rate on temperature field, resulting stress distribution and potential crack formation were also investigated in this work. The study indicates that a transition from compressive to tensile stresses can be resulted in as the laser cutting parameters change, which is beneficial to resist the crack formation. Based on the experimental and numerical investigations, the process parameters were optimised and the fibre laser crack-free cutting of 6-mm-thick alumina was demonstrated for the first time. [Copyright &y& Elsevier]

Abstract: In machine tools such as numerical control machines, thermal error in the ball screw induces a direct position error. A high-speed ball screw system naturally generates more heat and results in greater thermal expansion, adversely affecting the accuracy of positioning. In this paper, we discussed the placement of an air cooling system in a ball screw shaft to overcome thermal errors and achieve temperature equilibrium faster. In order to estimate the thermal error of the ball screw system and effectiveness of the air cooling system, thermal behavior models using the finite element method (FEM) and a modified lumped capacitance method (MLCM) were developed separately. This included heat generation from the main heat source of the ball screw system and other boundary conditions. The completed models were used to simulate temperature distribution, thermal deformation and air cooling performance. Comparing the experiments shows that these methods can well predict thermal behavior of the ball screw system and air cooling performance. And the positioning accuracy will significantly improve with the use of the air cooling system in the ball screw drive system. [Copyright &y& Elsevier]

Abstract: Titanium and nickel alloys represent a significant metal portion of the aircraft structural and engine components. When these critical structural components in aerospace industry are manufactured with the objective to reach high reliability levels, surface integrity is one of the most relevant parameters used for evaluating the quality of finish machined surfaces. The residual stresses and surface alteration (white etch layer and depth of work hardening) induced by machining of titanium alloys and nickel-based alloys are very critical due to safety and sustainability concerns. This review paper provides an overview of machining induced surface integrity in titanium and nickel alloys. There are many different types of surface integrity problems reported in literature, and among these, residual stresses, white layer and work hardening layers, as well as microstructural alterations can be studied in order to improve surface qualities of end products. Many parameters affect the surface quality of workpieces, and cutting speed, feed rate, depth of cut, tool geometry and preparation, tool wear, and workpiece properties are among the most important ones worth to investigate. Experimental and empirical studies as well as analytical and Finite Element modeling based approaches are offered in order to better understand machining induced surface integrity. In the current state-of-the-art however, a comprehensive and systematic modeling approach based on the process physics and applicable to the industrial processes is still missing. It is concluded that further modeling studies are needed to create predictive physics-based models that is in good agreement with reliable experiments, while explaining the effects of many parameters, for machining of titanium alloys and nickel-based alloys. [Copyright &y& Elsevier]

Abstract: The paper describes an experimental investigation of the surface error generation in machining of thin-walled structural parts. The influences of process induced temperatures and deflections were experimentally investigated for a peripheral milling process with an endmill. The resulting surface error is discussed in consideration of the thermal and mechanical influences on surface generation. A FE-simulation is used to separate the influence of thermal deviations from process-force induced deflections. Finally, a process model is presented, which is able to predict the generation of shape deviations based on the workpiece deflections measured. The simulation result will be compared to the surface measured and the surface error is separated into main shape dominances affected by thermal and mechanical loads. [ABSTRACT FROM AUTHOR]

Abstract: Machining chatter is an inherently nonlinear phenomenon that is affected by many parameters such as cutting conditions, tool geometry e.g., nose radius and clearance angle and frictional conditions at the tool/workpiece interface. Models for chatter prediction often ignore nonlinearities or introduce them through simple models for friction and geometry. In particular, the effect of chip–tool interaction on the occurrence of chatter is not investigated thoroughly. This paper presents a novel approach for prediction of chatter vibration and for investigation of the effects of various conditions on the onset of chatter. This approach uses finite element simulation to investigate the inter-relationship between the chatter vibration and the chip formation process. Simulation of chip formation is combined with dynamic analysis of machine tool to determine the interaction between the two phenomena. Mesh adaptation technique is used to move the tool inside the workpiece to form the chip, while a flexible tool is used to allow the tool to vibrate under variable loading conditions. By repeating the simulations under various widths of cut, it is shown that the onset of chatter can be detected, and the simulation is able to realistically predict various phenomena observed in actual machining process such as variation of shear angle and the increase of stability at lower speeds known as process damping. The stability map obtained from simulations is compared with experimental data attained through orthogonal cutting tests. Reasonable agreement observed between the two sets of results demonstrates the effectiveness of the simulation approach. [Copyright &y& Elsevier]

Abstract: Thermally induced errors account for the majority of fabrication accuracy loss in an uncompensated machine tool. This issue is particularly relevant in the micro-machining arena due to the comparable size of thermal errors and the characteristic dimensions of the parts under fabrication. A spindle of a micro-milling machine tool is one of the main sources of thermal errors. Other sources of thermal errors include drive elements like linear motors and bearings, the machining process itself and external thermal influences such as variation in ambient temperature. The basic strategy for alleviating the magnitude of these thermal errors can be achieved by thermal desensitization, control and compensation within the machine tool. This paper describes a spindle growth compensation scheme that aims towards reducing its thermally-induced machining errors. The implementation of this scheme is simple in nature and it can be easily and quickly executed in an industrial environment with minimal investment of manpower and component modifications. Initially a finite element analysis (FEA) is conducted on the spindle assembly. This FEA correlates the temperature rise, due to heating from the spindle bearings and the motor, to the resulting structural deformation. Additionally, the structural deformation of the spindle along with temperature change at its various critical points is experimentally obtained by a system of thermocouples and capacitance gages. The experimental values of the temperature changes and the structural deformation of the spindle qualitatively agree well with the results obtained by FEA. Consequently, a thermal displacement model of the high-speed micro-milling spindle is formulated from the previously obtained experimental results that effectively predict the spindle displacement under varying spindle speeds. The implementation of this model in the machine tool under investigation is expected to reduce its thermally induced spindle displacement by 80%, from 6microns to less than 1 micron in a randomly generated test with varying spindle speeds. [Copyright &y& Elsevier]

Abstract: Machining of copper-based alloys tends to produce irregularly spaced chip serration. However, turning cold-rolled material could sometimes produce regularly spaced chip serration. The regularly spaced chip serration is indeed layers of shear bands that grow and agglomerate to become chip serration. In this paper, an investigation into the formation of shear bands in the microcutting process of single point diamond turning is presented. The experimental results reveal how shear bands are initiated at the free edge of the chip and then propagated towards the tool tip. A new finite element model is developed to simulate the initiation and formation of these shear bands and to provide evidence for how these shear bands are induced by the elastic strain concentration. In contrast to the popular assumption that materials behave as rigid plastic during machining, the results reveal that elastic strain is one of the dominant factors leading to the formation of shear bands. Finally, an analytical model is proposed to reveal the influence of shear bands on the cutting force and on the formation of serrated chips. [Copyright &y& Elsevier]

Abstract: Simulating the transient temperature field in additive layer manufacturing (ALM) processes has presented a challenge to many researchers in the field. The transient temperature history is vital for determining the thermal stress distribution and residual stress states in ALM-processed parts that utilise a moving laser heat source. The modelling of the problem involving multiple layers is equally of great importance because the thermal interactions of successive layers affect the temperature gradients, which govern the heat transfer and thermal stress development mechanisms. This paper uses an innovative simulation technique known as element birth and death, in modelling the three-dimensional temperature field in multiple layers in a powder bed. The results indicate that the heated regions undergo rapid thermal cycles that could be associated with commensurate thermal stress cycles. Deposition of successive layers and subsequent laser scanning produces temperature spikes in previous layers. The resultant effect is a steady temperature build-up in the lower layers as the number of layers increases. [Copyright &y& Elsevier]

Abstract: In developing micro-spindle units, a critical problem is miniaturization of the tool clamp. Approaches for scaling down conventional tool clamps, such as the collet-chuck, hydraulic chuck, and shrink-fit methods may be limited by their inherently complicated mechanisms. This study developed a novel tool clamp based on shape memory alloy (SMA), which allows further miniaturization. The tool clamp can be simplified by using an SMA ring, which is all that is needed for clamping. The SMA-based tool clamp does not require any collet, and its structural configuration is axisymmetric. Furthermore, the SMA makes it possible to switch between the clamped and unclamped states by using a simple device to regulate small changes in temperature. This paper first describes the operating principle of the SMA-based tool clamp. Second, it presents the finite element method (FEM) analyses that were conducted to investigate the characteristics of the clamping/unclamping operations and the effect of centrifugal force. Third, it describes a prototype of the SMA-based tool clamp, which was designed and built for applications in micro-spindle units. Fourth, it presents an evaluation of the time needed for the clamping/unclamping operations and the tool-clamping force, which were both evaluated experimentally. Finally, it describes a mill-machining test conducted with the prototype, which confirmed that the tool clamp is little affected by centrifugal force at high rotational speeds. The experimental results confirm that the proposed SMA-based tool clamp can be successfully applied to micro-machining. [Copyright &y& Elsevier]