Showing papers in "Advances in Manufacturing in 2018"
TL;DR: In this article, a review of the progress of thermochromic smart coatings to solve the above obstacles has been surveyed, and future development trends have also been given to promote the goal of commercial production of VO2-based coatings, such as the high phase transition temperature, optical properties, environmental stability in a long-time period, as well as mass production.
Abstract: With an urgent demand of energy efficient coatings for building fenestrations, vanadium dioxide (VO2)-based thermochromic smart coatings have been widely investigated due to the reversible phase transition of VO2 at a critical transition temperature of 68 °C, which is accompanied by the modulation of solar irradiation, especially in the near-infrared region. As for commercial applications in our daily life, there are still some obstacles for VO2-based smart coatings, such as the high phase transition temperature, optical properties (luminous transmittance and solar modulation ability), environmental stability in a long-time period, as well as mass production. In this review, recent progress of thermochromic smart coatings to solve above obstacles has been surveyed. Meanwhile, future development trends have also been given to promote the goal of commercial production of VO2 smart coatings.
99 citations
TL;DR: Most biomaterials used for bio-implants are reviewed in this article, and typical manufacturing processes are discussed in order to provide a perspective on the development of manufacturing fundamentals and latest technologies.
Abstract: Bioimplants are becoming increasingly important in the modern society due to the fact of an aging population and associated issues of osteoporosis and osteoarthritis. The manufacturing of bioimplants involves an understanding of both mechanical engineering and biomedical science to produce biocompatible products with adequate lifespans. A suitable selection of materials is the prerequisite for a long-term and reliable service of the bioimplants, which relies highly on the comprehensive understanding of the material properties. In this paper, most biomaterials used for bioimplants are reviewed. The typical manufacturing processes are discussed in order to provide a perspective on the development of manufacturing fundamentals and latest technologies. The review also contains a discussion on the current measurement and evaluation constraints of the finished bioimplant products. Potential future research areas are presented at the end of this paper.
84 citations
TL;DR: In this article, the effects of the process variables, viz. raster angle, layer height, and raster width on the flexural properties of FFF-printed polylactic acid (PLA) is studied.
Abstract: Fused filament fabrication (FFF) has been widely used to develop prototypes as well as functional parts owing to its capability for creating parts with complex geometries in a short time without the specific requirement of tooling. The mechanical properties of parts produced by FFF exhibit 70%–80% of the mechanical properties of parts produced by injection molding. The mechanical properties of FFF-produced parts are primarily dependent on the selection of various process variables. The mechanical properties of the part can be enhanced through the proper selection of process variables. In the present experimental investigation, the effects of the process variables, viz. raster angle, layer height, and raster width on the flexural properties of FFF-printed polylactic acid (PLA) is studied. The result shows that flexural strength is primarily influenced by layer height followed by raster angle. The sample printed with 100-µm layer height and 0° raster angle exhibits a higher tensile strength. Further, the microscopic examination of the deformed specimen is performed to understand the mode of failure. Specimens printed at different raster angles show different modes of failure.
61 citations
TL;DR: In this paper, a comparative machinability assessment for the hard turning of hardened AISI D2 steel by coated and uncoated carbide insert in a dry environment was performed.
Abstract: The investigation of low cost uncoated and coated carbide insert in the hard turning of hardened AISI D2 steel (≥ 55 HRC) will definitely open up a new arena as an economical alternative suitable to industrial machining sectors. Thus, this paper reports the comparative machinability assessment for the hard turning of AISI D2 steel ((55 ± 1) HRC) by coated and uncoated carbide insert in a dry environment. Micro hardness and abrasion tests were carried out to assess resistance capability against wear. The above test results confirmed the greater wear resistance ability of Al2O3 coated carbide insert over uncoated carbide. Based on the extensive investigation of comparative machinability, the coated carbide insert (TiN-TiCN-Al2O3) outperformed the uncoated carbide insert with regard to surface roughness, flank wear, chip-tool interface temperature, and chip morphology. Abrasion and diffusion were observed as the principal tool wear mechanisms in the investigated range. The uncoated carbide failed completely due to the severe chipping and quick dulling of the cutting edge, which led to its unsuitability for machining hardened steel.
55 citations
TL;DR: In this paper, the effect of material type (i.e., neat PLA and PLA/wood fibres) and the number of shells on tensile, flexural and impact strengths of material samples was investigated via design of experiments (DoE).
Abstract: 3D printing in additive manufacturing is considered as one of key technologies to the future high-precision manufacturing in order to benefit diverse industries in building construction, product development, biomedical innovation, etc The increasing applications of 3D printed components depend primarily on their significant merits of reduced weight, minimum used materials, high precision and shorter production time Furthermore, it is very crucial that such 3D printed components can maintain the same or even better material performance and product quality as those achieved by conventional manufacturing methods This study successfully fabricated 3D printed mechanical testing samples of PLA and PLA/wood fibre composites 3D printing parameters including infill density, layer height and the number of shells were investigated via design of experiments (DoE), among which the number of shells was determined as the most significant factor for maximising tensile strengths of PLA samples Further, DoE work evaluated the effect of material type (ie, neat PLA and PLA/wood fibres) and the number of shells on tensile, flexural and impact strengths of material samples It is suggested that material type is the only predominant factor for maximising all mechanical strengths, which however are consistently lower for PLA/wood fibre composites when compared with those of neat PLA Increasing the number of shells, on the other hand, has been found to improve almost all strength levels and decrease infill cavities
45 citations
TL;DR: In this paper, the authors focused on mathematical modeling, multi response optimization, tool life, and economical analysis in finish hard turning of AISI D2 steel ((55 ± 1) HRC) using CVD-coated carbide (TiN/TiCN/Al2O3) and uncoated carbonide inserts under dry environmental conditions.
Abstract: The present study focused on mathematical modeling, multi response optimization, tool life, and economical analysis in finish hard turning of AISI D2 steel ((55 ± 1) HRC) using CVD-coated carbide (TiN/TiCN/Al2O3) and uncoated carbide inserts under dry environmental conditions. Regression methodology and the grey relational approach were implemented for modeling and multi-response optimization, respectively. Comparative economic statistics were carried out for both inserts, and the adequacy of the correlation model was verified. The experimental and predicted values for all responses were very close to each other, implying the significance of the model and indicating that the correlation coefficients were close to unity. The optimal parametric combinations for Al2O3 coated carbide were d1–f1–v2 (depth of cut = 0.1 mm, feed = 0.04 mm/r and cutting speed = 108 m/min), and those for the uncoated tool were d1–(0.1 mm)–f1 (0.04 mm/r)–v1 (63 m/min). The observed tool life for the coated carbide insert was 15 times higher than that for the uncoated carbide insert, considering flank wear criteria of 0.3 mm. The chip volume after machining for the coated carbide insert was 26.14 times higher than that of the uncoated carbide insert and could be better utilized for higher material removal rate. Abrasion, diffusion, notching, chipping, and built-up edge have been observed to be the principal wear mechanisms for tool life estimation. Use of the coated carbide tool reduced machining costs by about 3.55 times compared to the use of the uncoated carbide insert, and provided economic benefits in hard turning.
40 citations
TL;DR: In this paper, a grey relational grade (GRG) was calculated to simultaneously minimize the cutting force and surface roughness of high chrome white cast iron with a cubic boron nitride (CBN) insert.
Abstract: High chrome white cast iron is particularly preferred in the production of machine parts requiring high wear resistance. Although the amount of chrome in these materials provides high wear and corrosion resistances, it makes their machinability difficult. This study presents an application of the grey relational analysis based on the Taguchi method in order to optimize chrome ratio, cutting speed, feed rate, and cutting depth for the resultant cutting force (FR) and surface roughness (Ra) when hard turning high chrome cast iron with a cubic boron nitride (CBN) insert. The effect levels of machining parameters on FR and Ra were examined by an analysis of variance (ANOVA). A grey relational grade (GRG) was calculated to simultaneously minimize FR and Ra. The ANOVA results based on GRG indicated that the feed rate, followed by the cutting depth, was the main parameter and contributed to responses. Optimal levels of parameters were found when the chrome ratio, cutting speed, feed rate, and cutting depth were 12%, 100 m/min, 0.05 mm/r, and 0.1 mm, respectively, based on the multiresponse optimization results obtained by considering the maximum signal to noise (S/N) ratio of GRG. Confirmation results were verified by calculating the confidence level within the interval width.
39 citations
TL;DR: In this paper, an efficient implementation of the multi-frequency solution and the construction of an approximate solution is presented, which is significantly more efficient than an explicit calculation at all random parameter points.
Abstract: The occurrence of chatter in milling processes was investigated in this study. The prediction of the stability lobes of metal cutting processes requires a model of the cutting force and a model of the dynamic machine tool behavior. Parameter uncertainties in the models may lead to significant differences between the predicted and measured stability behavior. One approach towards robust stability consists of running a large number of simulations with a random sample of uncertain parameters and determining the confidence levels for the chatter vibrations, which is a time-consuming task. In this paper, an efficient implementation of the multi frequency solution and the construction of an approximate solution is presented. The approximate solution requires the explicit calculation of the multi frequency solution only at a few parameter points, and the approximation error can be kept small. This study found that the calculation of the robust stability lobe diagram, which is based on the approximate solution, is significantly more efficient than an explicit calculation at all random parameter points. The numerically determined robust stability diagrams were in good agreement with the experimentally determined stability lobes.
26 citations
TL;DR: In this paper, the microstructure evolution of Al-Si-10Mg alloy in DMLS process is studied with the help of the phase field modeling, where the simulation parameters include temperature gradient, laser power and scan speed.
Abstract: Direct metal laser sintering (DMLS) has evolved as a popular technique in additive manufacturing, which produces metallic parts layer-by-layer by the application of laser power. DMLS is a rapid manufacturing process, and the properties of the build material depend on the sintering mechanism as well as the microstructure of the build material. Thus, the prediction of part microstructures during the process may be a key factor for process optimization. In addition, the process parameters play a crucial role in the microstructure evolution, and need to be controlled effectively. In this study, the microstructure evolution of Al-Si-10Mg alloy in DMLS process is studied with the help of the phase field modeling. A MATLAB code is used to solve the phase field equations, where the simulation parameters include temperature gradient, laser power and scan speed. From the simulation result, it is found that the temperature gradient plays a significant role in the evolution of microstructure with different process parameters. In a single-seed simulation, the growth of the dendritic structure increases with the increase in the temperature gradient. When considering multiple seeds, the increasing in temperature gradients leads to the formation of finer dendrites; however, with increasing time, the dendrites join and grain growth are seen to be controlled at the interface.
25 citations
TL;DR: In this paper, a 3D finite element model is developed to investigate the drilling process of AISI 1045 steel, and particularly, the heat and wear on the drill faces.
Abstract: In this study, a 3D finite element model is developed to investigate the drilling process of AISI 1045 steel, and particularly, the heat and wear on the drill faces. To model drill wear, a modified Usui flank wear rate is used. Experiments are used for the verification of the simulated model and the evaluation of the surface roughness and built-up edge. A comparison of the predicted and experimental thrust forces and flank wear rates revealed that the predicted values had low errors and were in good agreement with the experimental values, which showed the utility of the developed model for further analysis. Accordingly, a heat analysis indicated that approximately half the generated heat in the cutting zone was conducted to the drill bit. Furthermore, material adhesion occurred in localized heat areas to a great extent, thus resulting in wear acceleration. A maximum flank wear rate of 0.026 1 mm/s was observed when the rotary speed and feed rate were at the lowest and highest levels, respectively. In the reverse cutting condition, a minimum flank wear rate of 0.016 8 mm/s was observed.
20 citations
TL;DR: In this article, a support vector machine (SVM) algorithm using a normalized poly-kernel and a radial-basis flow kernel is recommended for modeling the wire electric discharge machining process.
Abstract: The current study investigates the behavior of wire electric discharge machining (WEDM) of the super alloy Udimet-L605 by employing sophisticated machine learning approaches. The experimental work was designed on the basis of the Taguchi orthogonal L27 array, considering six explanatory variables and evaluating their influences on the cutting speed, wire wear ratio (WWR), and dimensional deviation (DD). A support vector machine (SVM) algorithm using a normalized poly-kernel and a radial-basis flow kernel is recommended for modeling the wire electric discharge machining process. The grey relational analysis (GRA) approach was utilized to obtain the optimal combination of process variables simultaneously, providing the desirable outcome for the cutting speed, WWR, and DD. Scanning electron microscope and energy dispersive X-ray analyses of the samples were performed for the confirmation of the results. An SVM based on the radial-basis kernel model dominated the normalized poly-kernel model. The optimal combination of process variables for a mutually desirable outcome for the cutting speed, WWR, and DD was determined as T
on1, T
off2, I
P1, WT3, SV1, and WF3. The pulse-on time is the significant variable influencing the cutting speed, WWR, and DD. The largest percentage of copper (8.66%) was observed at the highest cutting speed setting of the machine compared to 7.05% of copper at the low cutting speed setting of the machine.
TL;DR: An improved tracking and localization algorithm of an omni-directional mobile industrial robot is proposed to meet the high positional accuracy requirement, improve the robot’s repeatability positioning precision in the traditional trilateral algorithm, and solve the problem of pose lost in the moving process.
Abstract: In this paper, an improved tracking and localization algorithm of an omni-directional mobile industrial robot is proposed to meet the high positional accuracy requirement, improve the robot’s repeatability positioning precision in the traditional trilateral algorithm, and solve the problem of pose lost in the moving process. Laser sensors are used to identify the reflectors, and by associating the reflectors identified at a particular time with the reflectors at a previous time, an optimal triangular positioning method is applied to realize the positioning and tracking of the robot. The experimental results show that positioning accuracy can be satisfied, and the repeatability and anti-jamming ability of the omni-directional mobile industrial robot will be greatly improved via this algorithm.
TL;DR: In this article, an experimental study is performed for examining the electroplated copper thickness of the plastic EDM electrode and its performances in the field of electro discharge machining (EDM), and it is found that the electrode can be regarded as a viable tool for rough cutting or semi-finishing cut EDM functions.
Abstract: The importance of rapid tooling (RT) and additive manufacturing (AM) appears to be indispensable for boosting the process of manufacturing and expanding the horizon of production technology worldwide. This concept draws the attention of numerous scholars to arrive at a conclusive theory for the widespread utilization of RT. This study attempts to determine the viability and performance of an RT electrode in the field of electro discharge machining (EDM). The electrode prototype is made using an acrylonitrile butadiene styrene (ABS) plastic by fused deposition modeling (FDM), an AM technique, electroplated with copper of desired thickness, and used in die sinking EDM of D2 steel. The scanning electron microscope analysis of the electroplated samples confirms that it is possible to obtain the desired thickness of the metal by electroplating on any electrically conductive surface. In the present work, an experimental study is performed for examining the electroplated copper thickness of the plastic EDM electrode and its performances. It is found that the electroplated ABS plastic EDM RT electrode successfully performs the machining operation of D2 steel, and the results are comparable with a solid electrode. The study reveals that the RT electrode can be regarded as a viable tool for rough cutting or semi-finishing cut EDM functions. The experimental results are thoroughly discussed, examined, analyzed, and evaluated for the purpose of developing the appropriate form of the concept.
TL;DR: In this paper, a particle flow friction system with the set of parallel plates and the model parameters according to the abrading processing equipment and processing materials is constructed, and the simulation results show that the shear dilatancy can be divided into three stages: plastic strain, macroscopic failure, and granular recombination stages.
Abstract: Abrading is a very important sub-technology of the surface treatment technology with vast applications in the industry. This study aims at analyzing the inherent laws of friction systems during abrading. In particle flow code modeling, the abrading process can be simplified to the movement of particles in a parallel-plate shear friction system. In this study, the PFC2D software is used to construct the particle flow friction system with the set of parallel plates and the model parameters according to the abrading processing equipment and processing materials, control the simulation of a single variable, and compare the output data to estimate the impact of change of parameters on the force chain. The simulation results show that the shear dilatancy can be divided into three stages: plastic strain, macroscopic failure, and granular recombination stages. The distribution and load rates of the weak force chains depend on the load, velocity, friction coefficient between granules, granular diameter, and number of granular layers. The number of granular layers and the load increase cause the direction of the force chain to be oriented with the vertical direction, and the force chains move toward the horizontal direction as the velocity increases. The increase in load does not cause the shear dilatancy stage to occur; the velocity, friction coefficient between granules, and granular diameter increase cause the shear dilatancy to occur gradually.
TL;DR: In this paper, an approach for determining the optimal cutting condition for milling thin-walled elements with complex shapes is presented, based on the interaction between the thinwalled detail and its periodic excitation by tooth passing, taking into account the high intermittency of a process.
Abstract: This paper presents an approach for determining the optimal cutting condition for milling thin-walled elements with complex shapes. The approach is based on the interaction between the thin-walled detail and its periodic excitation by tooth passing, taking into account the high intermittency of such a process. The influence of the excitation frequency on the amplitude of the detail oscillation during milling was determined by simulation and experiments. It was found that the analytical results agreed with experimental data. The position of the detail when the tooth starts to cut was evaluated through experiments. The influence of this parameter on the processing state is presented herein. The processing stability is investigated and compared with the proposed approach. Thereafter, spectral analyses are conducted to determine the contribution of the vibrating frequencies to the detail behavior during processing.
TL;DR: In this paper, a thermal resistance network model of the motorized spindle system is established based on the heat transfer theory, and the heat balance equations of the critical thermal nodes are established with Kirchhoff's law.
Abstract: In the motorized spindle system of a computer numerical control (CNC) machine tool, internal heat sources are formed during high-speed rotation; these cause thermal errors and affect the machining accuracy. To address this problem, in this study, a thermal resistance network model of the motorized spindle system is established based on the heat transfer theory.
The heat balance equations of the critical thermal nodes are established according to this model with Kirchhoff’s law. Then, they are solved using the Newmark-β method to obtain the temperature of each main component, and steady thermal analysis and transient thermal analysis of the motorized spindle system are performed. In order to obtain accurate thermal characteristics of the spindle system, the thermal-conduction resistance of each component and the thermal-convection resistance between the cooling system and the components of the spindle system are accurately obtained considering the effect of the heat exchanger on the temperature of the coolant in the cooling system. Simultaneously, high-precision magnetic temperature sensors are used to detect the temperature variation of the spindle in the CNC machining center at different rotational speeds. The experimental results demonstrate that the thermal resistance network model can predict the temperature field distribution in the spindle system with reasonable accuracy. In addition, the influences of the rotational speed and cooling conditions on the temperature increase of the main components of the spindle system are analyzed. Finally, a few recommendations are provided to improve the thermal performance of the spindle system under different operational conditions.
TL;DR: In this paper, a hybrid laser/arc welding (HLAW) was employed to join 8mm-thick high-strength quenched and tempered steel (HSQTS) plates in the butt- and T-joint configurations.
Abstract: In this investigation, hybrid laser/arc welding (HLAW) was employed to join 8-mm-thick high-strength quenched and tempered steel (HSQTS) plates in the butt- and T-joint configurations. The influences of welding parameters, such as laser power, welding speed, stand-off distance (SD) between the arc of gas metal arc welding, and the laser heat source on the weld quality and mechanical properties of joints, were studied to obtain non-porous and crack-free fully-penetrated welds. The weld microstructure, cross-section, and mechanical properties were evaluated by an optical microscope, and microhardness and tensile tests. In addition, a finite element model was developed to investigate the thermal history and molten pool geometry of the HLAW process to join the HSQTS. The numerical study demonstrated that the SD had a paramount role in good synergy between the heat sources and the stability of the keyhole. For the butt-joint configuration, the results showed that, at a higher welding speed (35 mm/s) and optimum SD between the arc and laser, a fully-penetrated sound weld could be achieved. A non-porous weld in the T-joint configuration was obtained at a lower welding speed (10 mm/s). Microstructural evaluations indicated that the formation of residual austenite and the continuous network of martensitic structure along the grain boundary through the heat affected zone were the primary reasons of the softening behavior of this area. This was confirmed by the sharp hardness reduction and failure behavior of the tensile coupons in this area.
TL;DR: In this article, the frequency response function for the micro-end mill is obtained by finite element method modal analysis, which is used for chatter prediction in high-speed micromilling operations.
Abstract: High-speed micromilling (spindle speeds 100 000 r/min) can create complex three-dimensional microfeatures in difficult-to-machine materials. The micromachined surface must be of high quality, to meet functional requirements. However, chatter-induced dynamic instability deteriorates the surface quality and can be detrimental to tool life. Chatter-free machining can be accomplished by identifying stable process parameters via stability lobe diagram. To generate accurate stability lobe diagram, it is essential to determine the microend mill dynamics. Frequency response function is required to determine the tool-tip dynamics obtained by experimental impact analysis. Note that application of impact load at the microend mill tip (typically 100 – 500 μm) is not feasible as it would invariably end with tool failure. Consequently, alternative methods need to be developed to identify the microend mill dynamics. In the present work, the frequency response function for the microend mill is obtained by finite element method modal analysis. The frequency response function obtained from modal analysis has been verified from the experimentally obtained frequency response function. The experimental frequency response function was obtained by impacting the microend mill near the taper portion with an impact hammer and measuring the vibration of the tool-tip with a laser displacement sensor. The fundamental frequency obtained from finite element method modal analysis shows a difference of 6.6% from the experimental fundamental frequency. Microend mill dynamics obtained from the finite element method is used for chatter prediction in high-speed micromilling operations. The stability lobe diagram predicts the stability boundary accurately at 60 000 r · min–1 and 80 000 r/min; however, a slight deviation is observed at 100 000 r/min.
TL;DR: In this paper, a three-dimensional finite element model was developed, and a coupled field analysis was conducted to study the effect of four parameters, i.e., cutting depth, support length, applied voltage, and pulse-on time, on the maximum normal stress in the region where the edge-chipping initiates.
Abstract: The problem of eliminating edge-chipping at the entrance and exit of the hole while drilling brittle materials is still a challenging task in different industries. Grinding-aided electrochemical discharge machining (G-ECDM) is a promising technology for drilling advanced hard-to-machine ceramics, glass, composites, and other brittle materials. Edge-chipping at the entrance of the hole can be fully eliminated by optimizing the machining parameters of G-ECDM. However, edge-chipping at the exit of the hole is difficult to eliminate during the drilling of ceramics and glass. This investigation suggests some practical ways to reduce edge-chipping at the exit of the hole. For this purpose, a three-dimensional finite element model was developed, and a coupled field analysis was conducted to study the effect of four parameters, i.e., cutting depth, support length, applied voltage, and pulse-on time, on the maximum normal stress in the region where the edge-chipping initiates. The model is capable of predicting the edge-chipping thickness, and the results predicted by the model are in close agreement with the experiment results. This investigation recommends the use of a low voltage and low pulse-on time at the hole entrance and exit when applying G-ECDM to reduce the edge-chipping thickness. Moreover, the use of a full rigid support in the form of a base plate or sacrificial plate beneath the workpiece can postpone the initiation of chipping by providing support when the tool reaches the bottom layer of the workpiece, thereby reducing the edge-chipping thickness.
TL;DR: A point-based method for modeling the rotating tool considering its deflections is presented and, with this method, tools with complex shapes and runout can be simulated in an efficient and flexible way.
Abstract: Geometric physically-based simulation systems can be used for analyzing and optimizing complex milling processes, for example in the automotive or aerospace industry, where the surface quality and process efficiency are limited due to chatter vibrations. Process simulations using tool models based on the constructive solid geometry (CSG) technique allow the analysis of process forces, tool deflections, and surface location errors resulting from five-axis machining operations. However, modeling complex tool shapes and effects like runout is difficult using CSG models due to the increasing complexity of the shape descriptions. Therefore, a point-based method for modeling the rotating tool considering its deflections is presented in this paper. With this method, tools with complex shapes and runout can be simulated in an efficient and flexible way. The new modeling approach is applied to exemplary milling processes and the simulation results are validated based on machining experiments.
TL;DR: In this article, the authors investigated the relationship between the external potential and the discharge voltage for both EDM and ECDM and found that the former is useful for machining while the latter is useful only for nonconducting materials.
Abstract: Electric discharge is a common tool nowadays for machining of materials. It may be through a liquid medium or through air. Any metals, hard alloys, and non-metals can be machined using the energy of electric discharge. In electric discharge machining (EDM), the discharge occurs between two electrodes through a liquid medium and it is applicable only for electrically conducting materials and alloys. In electrochemical discharge machining (ECDM), the medium is an aqueous electrolyte and it is of two types. In the first type, the discharge occurs between two electrodes. One of the electrodes is the workpiece, and the other is the tool. In the second type, the discharge occurs between one electrode and an electrolyte. It is used for electrically nonconducting materials and the discharge energy is utilized maintaining the nonconducting workpiece in proximity of the discharge. All these electrical discharges are transient phenomena and do not result in a stable discharge in the form of arc. The output parameters depend on the discharge energy that requires precise control to maintain the accuracy of the machining. For micromachining, the control of the discharge is paramount both in terms of energy and pattern. Using various shaped tools, machining media with additives, different types of applied potentials, and supporting mechanical motions are some of the attempts made to improve the machining output. Optimization of these parameters for machining particular materials (or alloys) is a popular field of research. The present work is directed toward the investigation of discharge initiation and development by analyzing the cell current and discharge voltage relationship for both EDM and ECDM. The rectangular direct current (DC) pulse with different frequencies and the duty factor (on–off time ratio) are used for investigation. Observations on the voltage–current relationship are made for the external potential prior to discharge at discharge and above the discharge potential. Though the external potential above the discharge voltage is useful for machining, these observations elucidate the mechanism regarding the initiation of the electric discharge under different conditions. The manner of discharge development in dielectrics and electrolytes is observed to be different. This understanding will aid in deciding the design of the discharge circuit including the external potential and its pattern for certain desired outputs in machining.
TL;DR: In this article, the authors investigated the room temperature creep-deformation of KDP crystals with the aid of nanoindentation and found that the creep rate and creep depth decrease with decrease in peak force and loading rate.
Abstract: It has been a tremendous challenge to manufacture damage-free and smooth surfaces of potassium dihydrogen phosphate (KDP) crystals to meet the requirements of high-energy laser systems. The intrinsic issue is whether a KDP crystal can be plastically deformed so that the material can be removed in a ductile mode during the machining of KDP. This study investigates the room temperature creep-deformation of KDP crystals with the aid of nanoindentation. A stress analysis was carried out to identify the creep mechanism. The results showed that KDP crystals could be plastically deformed at the nano-scale. Dislocation motion is responsible for creep-deformation. Both creep rate and creep depth decrease with decrease in peak force and loading rate. Dislocation nucleation and propagation bring about pop-ins in the load-displacement curves during nanoindentation.
TL;DR: In this article, a finite element model of chip formation in a 2D milling process is used to predict the occurrence of chatter vibrations, and to investigate the effects of various machining parameters on this phenomenon.
Abstract: Chatter vibration is a major obstacle in achieveing increased machining performance. In this research, a finite element model of chip formation in a 2D milling process is used to predict the occurrence of chatter vibrations, and to investigate the effects of various machining parameters on this phenomenon. The dynamic properties of the machine tool at the tool tip are obtained based on experimental modal analysis, and are used in the model as the cutter dynamics. The model allows for the natural development of vibration as the result of the chip-tool engagement, and accounts for various phenomena that occur at the chip-tool interface ultimately leading to stable or unstable cutting. The model was used to demonstrate the effects of the machining parameters, such as the axial depth of cut, radial immersion, and feed rate, on the occurrence of chatter. Additionally, the phenomenon of jumping out of the cut region could be observed in this model and its effect on the chatter process is demonstrated. The numerical model is verified based on comparisons with experimental results.
TL;DR: This study constructed an automatic chatter suppression system with optimal pitch control for shared-surface parallel turning with rigid tools and a flexible workpiece, integrating in-process chatter monitoring based on the cutting force estimation.
Abstract: Simultaneous processes such as parallel turning or milling offer great opportunities for more efficient manufacturing because of their higher material removal rates. To maximize their advantages, chatter suppression technologies for simultaneous processes must be developed. In this study, we constructed an automatic chatter suppression system with optimal pitch control for shared-surface parallel turning with rigid tools and a flexible workpiece, integrating in-process chatter monitoring based on the cutting force estimation. The pitch angle between two tools is tuned adaptively in a position control system in accordance with the chatter frequency at a certain spindle speed, in a similar manner as the design methodology for variable-pitch cutters. The cutting force is estimated without using an additional external sensor by employing a multi-encoder-based disturbance observer. In addition, the chatter frequency is measured during the process by performing a low-computational-load spectrum analysis at a certain frequency range, which makes it possible to calculate the power spectrum density in the control system of the machine tool. Thus, the constructed system for automatic chatter suppression does not require any additional equipment.
TL;DR: In this paper, the Al-Fe-Mn ternary system is reassessed by the CALPHAD method and three new ternaries intermetallic compounds are initially described and a reasonable and self-consistent set of thermodynamic parameters are established to describe this system.
Abstract: In this study, the Al-Fe-Mn ternary system is reassessed by the CALPHAD method. Three new ternary intermetallic compounds are initially described and a reasonable and self-consistent set of thermodynamic parameters are established to describe this system. The 973 K, 1 073 K, 1 173 K, 1 273 K, 1 373 K, and 1 473 K isothermal sections and the 1 073 K, 1 013 K, 968 K and 913 K isothermal sections at the Al corner as well as the liquidus projection at the Al corner are calculated. It is shown that the calculated results are in good agreement with almost all of the experimental results previously reported.
TL;DR: In this paper, a combined model of the surface regeneration effect and chip formation is used to predict the stability of turning processes in a chip segmentation sub-model, the primary shear zone is described with a corresponding material model along layers together with the thermodynamic behavior.
Abstract: The prediction of chatter vibration is influenced by many known complex phenomena and is uncertain We present a new effect that can significantly change the stability properties of cutting processes It is shown that the microscopic environment of chip formation can have a large effect on its macroscopic properties In this work, a combined model of the surface regeneration effect and chip formation is used to predict the stability of turning processes In a chip segmentation sub-model, the primary shear zone is described with a corresponding material model along layers together with the thermodynamic behavior The surface regeneration is modeled by the time-delayed differential equation Numerical simulations show that the time scale of a chip segmentation model is significantly smaller than the time scale of the turning process; therefore, averaging methods can be used Chip segmentation can decrease the average shear force leading to decreased cutting coefficients because of the non-linear effects A proper linearization of the equation of motion leads to an improved description of the cutting coefficients It is shown that chip segmentation may significantly increase the stable domains in the stability charts; furthermore, by selecting proper parameters, unbounded stability domains can be reached
TL;DR: In this article, a pulsed magneto-oscillation (PMO) technique during the solidification of a commercial high melting point medium carbon steel ingot (φ140mm×450mm) produced fully equiaxed grains in the cast ingot, indicating that the PMO process significantly promotes heterogeneous nucleation near the solid-liquid interface.
Abstract: The application of a pulsed magneto-oscillation (PMO) technique during the solidification of a commercial high melting point medium carbon steel ingot (φ140 mm × 450 mm) produced fully equiaxed grains in the cast ingot, indicating that the PMO process significantly promotes heterogeneous nucleation near the solid-liquid interface. The vigorous convection induced by PMO forced the partly solidified grains to move from the solid-liquid interface and became randomly distributed throughout the melt, which resulted in the formation of uniformly sized equiaxed dendrites throughout the whole ingot. Building on the developed nucleation mechanism and a flow field simulation of pure aluminum, a PMO-induced grain refinement model for steel is proposed.
TL;DR: A method for combining both the spindle speed and chatter detection methods along with an online chatter detection algorithm is proposed for efficient determination of stability lobe diagrams in milling.
Abstract: The experimental determination of stability lobe diagrams (SLDs) in milling can be realized by either continuously varying the spindle speed or by varying the depth of cut. In this paper, a method for combining both these methods along with an online chatter detection algorithm is proposed for efficient determination of SLDs. To accomplish this, communication between the machine control and chatter detection algorithm is established, and the machine axes are controlled to change the spindle speed or depth of cut. The efficiency of the proposed method is analyzed in this paper.
TL;DR: When compared with the analysis results of production line capacity, the key parameters possess the same optimal values, and this proves the accuracy of the production line 3D visualization monitoring system.
Abstract: New production line management technologies are required and adopted recently with the development of modern manufacturing industry. In this study, a production line three-dimensional (3D) visualization monitoring system based on OpenGL modeling, open database connectivity (ODBC), and database management technology is established on a VC++6.0 platform to satisfy effective production. A client/server model is adopted in the system, and data on processing information, interactive operation, and failure process are stored in the server side database. A client reads the workpiece process information from the server, and the machining process of every workpiece is visually represented in the form of 3D visualization. Production line 3D visualization provides production capacity simulation to optimize the parameter settings. When compared with the analysis results of production line capacity, the key parameters possess the same optimal values, and this proves the accuracy of production line 3D visualization monitoring system. The system provides effective data support for production line monitoring and management in enterprises.
TL;DR: The inverse stability solutions and their use for such purposes are discussed through relevant examples and case studies and specific areas include identification of process damping at low cutting speeds and variations in spindle dynamics at high rotational speeds.
Abstract: Research on dynamics and stability of machining operations has attracted considerable attention. Currently, most studies focus on the forward solution of dynamics and stability in which material properties and the frequency response function at the tool tip are known to predict stable cutting conditions. However, the forward solution may fail to perform accurately in cases wherein the aforementioned information is partially known or varies based on the process conditions, or could involve several uncertainties in the dynamics. Under these circumstances, inverse stability solutions are immensely useful to identify the amount of variation in the effective damping or stiffness acting on the machining system. In this paper, the inverse stability solutions and their use for such purposes are discussed through relevant examples and case studies. Specific areas include identification of process damping at low cutting speeds and variations in spindle dynamics at high rotational speeds.