High-speed Process Research Articles

Optimization of Milling Aluminum Alloy 6061-T6 using Modified Johnson-Cook Model

Finite element (FE) simulation is an efficient and time-saving method to optimize the high-speed machining process of aluminum (Al) alloy. The constitutive model accurately described the dynamic mechanical behavior of materials at cutting conditions is the premise of obtaining high-precision simulation results. In this study, the flow stress-strain relationship of AA 6061-T6 is obtained at a high temperature (up to 400 °C) and a high strain rate (up to 1 × 104 s−1). Temperature-dependent Johnson-Cook (J-C) model is proposed by considering dynamic recrystallization effect. By the modified J-C model, a two-dimensional simplified FE model is established to optimize the high-speed milling process of AA 6061-T6 hard drive head (HDH) access arm. The results show that the modified J-C constitutive model has a good prediction accuracy, and the predicted cutting forces are in good agreement with the experimental results. By the finite element simulations, the influences of both cutting parameters and tool geometric parameters on cutting force, chip morphology, cutting temperature, effective stress and effective strain are analyzed during cutting processes of AA 6061-T6. Optimized range of cutting parameters and tool geometric parameters are obtained, which provides a theoretical guidance for the optimization of the cutting processes of Al alloy precision parts.

MICRONIZED CONCRETE POWDER AS MIRCOFILLER IN CEMENT PASTE: INFLUENCE ON HYDRATION AND STRUCTURE

The reuse of old concrete as a coarse and fine recycled aggregate in cement composites is relatively well researched, and therefore a very fine fraction of recycled concrete was used in this paper. When using a very fine fraction of recycled concrete, it is appropriate to focus primarily on less technologically demanding treatment processes with minimal costs and environmental impact. Therefore this paper focus on using the fine fraction of recycled concrete as a microfiller. For this purpose, the material is treated by high-speed milling process and micronized concrete powder (MCP) is produced. Using several micronized concrete powder types that differ by origin, separation process and fineness of grinding should help understand how MCP influences the hydration process and cement paste structure. The samples with 0, 10, 20, 30, 40 and 50 wt. % of MCP were made to determine proper dosage in cement paste. Specific surface, matrix density and DTG analysis of micronized concrete powder were carried out. The calorimetric measurement was used to confirm how microfiller affects the hydration process. Finally, bulk density and porosity measurements were performed to determine the effect of MCP and its amount on the cement paste structure.

Roughness and Near-Surface Porosity of Unsupported Overhangs Produced by High-Speed Laser Powder Bed Fusion.

Laser powder bed fusion (LPBF) is a promising technology that requires further work to improve productivity to be adopted more widely. One possible approach is to increase the laser power and scan speed. A customized high-speed and high-power LPBF system has been developed for this purpose. The current study investigated the surface roughness and near-surface porosity as a result of unsupported overhangs at varying inclination angles and orientations during the manufacturing of Ti6Al4V parts with this custom high-speed and high-power LPBF system. It is known that surface roughness and porosity are among the main drawbacks for parts manufactured by LPBF, and that supports are required for overhang regions with low inclination angles relative to the powder bed, typically in commercial LPBF systems requiring supports for regions with inclination angles less than 45°. However, the appropriate inclination angles for this custom system with high power and speed requires investigation. In this article, a simple benchmark test artefact with different inclination angles was manufactured in different orientations on the build platform and characterized by X-ray tomography, touch probe roughness meter, optical microscopy, and scanning electron microscopy. The analysis of surface roughness and near-surface porosity at upskin and downskin regions was performed as a function of inclination angle. The results indicate that the high-speed LPBF process produces relatively high roughness in all cases, with different porosity distributions at upskin and downskin areas. Both roughness and porosity vary as a function of inclination angle. Significant warping was observed, depending on build orientation relative to laser scanning direction. These are the first reported results of the detailed surface roughness and porosity characterization of part quality from such a high-speed, high-power LPBF process.

Fabrication of food-grade Pickering high internal phase emulsions stabilized by the mixture of β-cyclodextrin and sugar beet pectin

Food-grade Pickering high internal phase emulsions (HIPEs) stabilized by a mixture of β-cyclodextrin (β-CD) and sugar beet pectin (SBP) were fabricated for the first time. The factors affecting the microstructures, mechanical properties, and stabilities of the Pickering HIPEs were systematically investigated. The corresponding hybrid particles were also separated and characterized to reveal the formation mechanism. The results indicated that the mixture could induce the formation of HIPEs with an oil phase volume fraction (φ) of 75% using a one-step high-speed shearing process at room temperature. The composition (the mass ratio of β-CD to SBP, Rc/s) and concentration (W) of the mixture had significant effects on the formation and properties of HIPEs. When W ≥ 1.0% and Rc/s = 2:2 or 3:1, HIPEs had smaller oil droplets, higher gel strengths, better centrifugation stabilities and lutein protection effects. The spectral analysis suggested that SBP could adhere to the surface of β-CD particles to form hybrid particles during the homogenization. Compared with native β-CD particles, these hybrid particles had higher ζ-potential absolute values, and the SBP could also increase the viscosity of the aqueous phase, which contributed to the formation and properties of these HIPEs.

Low-Autocorrelation Random Number Generator Based on Adiabatic Quantum-Flux-Parametron Logic

We propose a true random number generator (TRNG) based on adiabatic quantum-flux-parametron (AQFP) logic. This AQFP TRNG corresponds to an AQFP buffer chain with the input current removed, which enables the generation of random bits via thermal fluctuation. To realize ultralow autocorrelation, several isolation inductors are inserted between adjacent buffers in the AQFP TRNG, thereby reducing the impact of the back action between buffers. We design and fabricate an AQFP TRNG using the AIST 10 kA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> Nb high-speed standard process and evaluate the quality of the generated random bit streams. For a 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">17</sup> -bit random stream obtained from the AQFP TRNG at 100 kHz, the autocorrelation function is 5.00 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> . Furthermore, we evaluate a 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sup> -bit random stream from the AQFP TRNG using a statistical test suite provided by the National Institute of Standards and Technology. The bit stream passed 14 out of 15 tests, which suggests that the proposed AQFP TRNG can be used for applications such as stochastic computing and stochastic local search algorithms.

Features of temperature measurement of short thermal pulses

Short thermal impulses are typical for the explosions, glowing combustion products, which are accompanied by high pressure and destructive force. The most suitable thermocouples for measuring temperature values of a high-speed thermal process are thermocouples with known dynamic characteristics, which record the value of the output EMF during the temperature change transient process. Hourly dependence of the input temperature is calculated by converting from the operator to hourly form or from the hourly dependence through the inverted convolution of the output signal with the pulse transient characteristic by numerical methods.&#x0D; Restoration of the values of temperature acting on them is done by EMF measured values processing using the well-known dynamic characteristics of thermocouples, which are suggested to be pre-determined in the form of magnitude and phase frequency response, by heating the thermocouple with a sinusoidal electric current of the appropriate frequency. To be able to implement the method of determining the characteristics of thermocouple dynamics, a model of the processes that occur in the thermocouple when electric current is passing through it is presented. The use of sinusoidal electric current to heat up the thermocouple leads to the appearance of a DC component and a component with second harmonic in the output of EMF. On the basis of the proposed model, the algorithm of obtaining the magnitude and phase frequency response of the thermocouple by means of determining the ratio of the amplitudes of the EMF variable of the thermocouple in the form of a composition at the double frequency of the input current to the amplitude of the second harmonic of the input current, obtained by means of elevation to the square of output EMF instantaneous values by the calculating method, is developed.&#x0D; The methodology was developed, a research system was created, and experimental samples of the fast thermocouples were made. The obtained dynamic characteristics allow, by applying the inverse function, to adequately measure the current temperature of thermal impulses using the data of the output thermal EMF of thermocouples.&#x0D; &#x0D; Keywords: measurement; temperature; thermal pulse; thermocouple; dynamic characteristics; Nyquist plot.

Joining of Sheets with Tubes by Electrohydraulic Forming

Electrohydraulic forming is a high-speed process, which is based on a force transmission by a working media. In this process, shock waves transmit the punching force in a very short period of time. These shock waves are applied to accelerate the workpiece towards a passive die. Besides forming and embossing of sheets and tubes, joining of sheets with tubes is enabled as a novel application presented in this contribution. Thereby, the tube is embedded temporarily in the die as a functional part. By accelerating the sheet towards the tube end, the joint is formed. This study deals with the question of how this joint is formed in sense of process kinematics and material flow. Therefore, the loading energy, the distance of sheet and tube as well as the sheet thickness was varied and the influence of these parameters and geometric conditions of the tube on the process and resulting joints was observed. Joining of EN AW-1050 aluminum alloy sheets to EN AW-6060 aluminum alloy tubes was performed. These joints were analyzed by microsections and head tension tests. The investigations introduce the new joining process regarding its process behavior and show first joining results.

Prediction of cutting power and surface quality, and optimization of cutting parameters using new inference system in high-speed milling process

During the actual high-speed machining process, it is necessary to reduce the energy consumption and improve the machined surface quality. However, the appropriate prediction models and optimal cutting parameters are difficult to obtain in complex machining environments. Herein, a novel intelligent system is proposed for prediction and optimization. A novel adaptive neuro-fuzzy inference system (NANFIS) is proposed to predict the energy consumption and surface quality. In the NANFIS model, the membership functions of the inputs are expanded into: membership superior and membership inferior. The membership functions are varied based on the machining theory. The inputs of the NANFIS model are cutting parameters, and the outputs are the machining performances. For optimization, the optimal cutting parameters are obtained using the improved particle swarm optimization (IPSO) algorithm and NANFIS models. Additionally, the IPSO algorithm as a learning algorithm is used to train the NANFIS models. The proposed intelligent system is applied to the high-speed milling process of compacted graphite iron. The experimental results show that the predictions of energy consumption and surface roughness by adopting the NANFIS models are up to 91.2% and 93.4%, respectively. The NANFIS models can predict the energy consumption and surface roughness more accurately compared with other intelligent models. Based on the IPSO algorithm and NANFIS models, the optimal cutting parameters are obtained and validated to reduce both the cutting power and surface roughness and improve the milling efficiency. It is demonstrated that the proposed intelligent system is applicable to actual high-speed milling processes, thereby enabling sustainable and intelligent manufacturing.

Recovery of undersampled force measurement from high-speed milling process using approximate sparsity in frequency domain

During the monitoring of high-speed milling, the anti-aliasing filter is of great significance for the test signal to truly reflect the cutting state of the machine tool. The cutting force measurement of high-speed milling is similar to the sum of a series modulated sinusoidal waves (MSWs). In the frequency domain, the energy concentrated on several narrow bands, which show approximate sparsity. Aim to recover the information of the undersampled force measurement from the monitoring of aluminum alloy high-speed milling, this paper proposed a spectrum sensing algorithm based on this approximate sparsity. The principle of spectrum aliasing caused by undersampling was derived mathematically and the aliasing map was established. Based on the approximate sparsity of the force measurement, the proposed sensing algorithm divided the aliasing spectrum into several frequency subbands, and calculated the real frequency range of each subband according to the aliasing map. Bins of the spectrum were corrected to establish a new spectrum. The Inverse Fast Fourier Transform (IFFT) was used to reconstruct the actual signals. Numerical simulations and cutting experiments of aluminum alloys were conducted to verify the effectiveness of the proposed method. The maximum relative error of envelope is less than 4% in the engineering test signal application.

Research on hydrodynamic characteristics of cylinder planing

This paper selects SST k-w turbulence model and VOF wave to construct a numerical calculation model of moving body planning on a flat free surface based on STAR-CCM+ numerical simulation software. The construction model is checked through foreign classic literature, and the numerical simulation results are in good agreement with the experimental results. The hydrodynamic numerical errors are less than 5%, which is within the engineering error range. The model can be used for the numerical simulation of the planning cylinder. In this paper, it is used to simulate the planing process of cylinder with different speeds and different submerged depths, and the flow field characteristics and hydrodynamic characteristics in the planing process are obtained. The results show that waves appear at the tail and the tail liquid splashes to form a water splash during the planing process of the cylinder on a flat surface. The higher the speed of the planning cylinder is, and the deeper the submersion depth, the more pronounced waves at the tail. When the cylinder has a Fr number Cv≥8, the hydrodynamic force of the cylinder is almost unchanged, and it is not affected by the speed. But when Cv=3, the hydrodynamic characteristic coefficient is higher. The drag coefficient is 20% higher than that in the high-speed (Cv≥8) planing process. The lift coefficient is 3 times of high-speed planing lift coefficient. It is related to the surface pressure and frictional force distribution of cylinder during the low-speed planing. There is a linear relationship between the drag coefficient and the submerged depth during the cylinder planing at different submerged depths.

Homo-layer hafnia-based memristor with large analog switching window

The fast development of high-accuracy neuromorphic computing requires stable analog memristors. While filamentary memory switching is very common in binary oxides, their resistive switching usually involves abrupt changes due to the rupture or reformation of metallic filaments. In this work, we designed a memristor consisting of dual-layer HfOy/HfOx, with different concentrations of oxygen vacancies (y &amp;gt; x). During the electroforming process, both the migration of existing oxygen vacancies in HfOx and the generation of new oxygen vacancies in HfOy occur simultaneously, leaving a semiconducting part close to the HfOy/HfOx interface. The resulting filament is not metallic as a whole, as revealed by first principles calculations. Such a device demonstrates excellent switching uniformity as well as highly gradual resistance change, ideal for neuromorphic computing. Through fine tuning of the filament structure, the device achieves low variation, high speed, gradual SET and RESET processes, and hundreds of stable multi-level state behaviors. The long-term synaptic plasticity was further achieved, showing good linearity and large analog switching window (ΔG as high as 487.5 μS). This works affords a route toward a gradual resistance change in oxide-based memristors.

Roll-to-roll nanoimprint lithography using a seamless cylindrical mold nanopatterned with a high-speed mastering process

The advanced optical and wetting properties of metamaterials, plasmonic structures, and nanostructured surfaces have been repeatedly demonstrated in lab-scale experiments. Extending these exciting discoveries to large-area surfaces can transform technologies ranging from solar energy and virtual reality to biosensors and anti-microbial surfaces. Although photolithography is ideal for nanopatterning of small, expensive items such as computer chips, nanopatterning of large-area surfaces is virtually impossible with traditional lithographic techniques due to their exceptionally slow patterning rates and high costs. This article presents a high-throughput process that achieves large-area nanopatterning by combining roll-to-roll (R2R) nanoimprint lithography (NIL) and nanocoining, a process that can seamlessly nanopattern around a cylinder hundreds of times faster than electron-beam lithography. Here, nanocoining is used to fabricate a cylindrical mold with nanofeatures spaced by 600 nm and microfeatures spaced by 2 μm. This cylindrical drum mold is then used on a R2R NIL setup to pattern over 60 feet of polymer film. Microscopy is used to compare the feature shapes throughout the process. This scalable process offers the potential to transfer exciting lab-scale demonstrations to industrial-scale manufacturing without the prohibitively high cost usually associated with the fabrication of a master mold.

High temporal resolution electrical characterization technology of single-molecule devices

<p indent=0mm>Single-molecule electronics is a cross-discipline which aims at employing the individual molecule as the functional element for further miniaturization of the silicon-based microelectronics, and also focuses on the physical and chemical phenomena at single-molecule level. With the development of the single-molecule electronics, numerous novel physical and chemical effects such as Kondo physics, superconductivity and chemical reactions catalyzed by local strong electric fields, and single-molecule electronic devices including filed-effect transistors, diodes, and photo-switches have been widely explored. However, most of the abovementioned investigations are implemented at the millisecond level owing to the low temporal resolution of the measurement instrument, which makes it difficult to monitor the reaction events at faster time scales as well as meet the requirement of the high operating speed of the single-molecule devices. As a result, more attentions have been paid to develop the high temporal resolution electrical characterization techniques. In conventional single-molecule electrical measurement techniques, there is a big challenge that the extremely weak current signal through the single-molecule junction puts higher demands on the current amplification system of the instrument. However, the response speed of such amplifying circuits is relatively low, which limits the temporal resolution for single-molecule electrical measurements. In order to break through the limitation of temporal resolution, much efforts have been made in recent years. On the one hand, the low response speed caused by DC circuits can be improved through increasing the response speed of the current amplifying circuits. On the other hand, AC signal provides a promising approach to improve the temporal resolution, considering that the AC signal has already proven its application potential in the study of other micro-scale high-speed processes. This method requires the addition of AC signal measurement equipment in the circuit, including AC-DC separation circuits, RF amplifiers and lock-in amplifiers, etc., in addition, how to conduct effective data analysis is also a challenge worth considering. In this article, we will give a comprehensive review on the high temporal resolution electrical characterization techniques in the field of single-molecule electronics. This review will describe the challenges, developments, and applications of high temporal resolution electrical characterization techniques. We will briefly explain the significance of the research on the high temporal resolution electrical characterization techniques in the first part, the second part will describe the technical bottleneck of conventional single-molecule electrical measurement techniques, the third part will focus on the applications of the high temporal resolution electrical characterization techniques, and we will draw some expectations and conclusions in the fourth part. Although the high temporal resolution electrical characterization technology of single-molecule devices is still staying at the primary stage for its high requirements for circuit technology and measurement equipment, but this characterization technology can provide us with effective means to study higher-speed processes and more essential properties at the single-molecule scale, which includes the rearrangement of atoms, the structural transformation of molecules, and even the charge or energy transfer at the molecule-electrode interface. Those properties are also the guarantee for the manufacture of high-performance single-molecule electronic devices in the future. Therefore, we believe that the high temporal resolution electrical characterization techniques of single-molecule devices is full of development prospects and will be employed widely in the future.

Development and Testing of a High-Frequency Dynamometer for High-Speed Milling Process

Cutting forces are strongly associated with the mechanics of the cutting process. Hence, machining forces measurements are very important to investigate the machining process, and numerous methods of cutting forces measurements have been applied. Nowadays, a dynamometer is the most popular tool for cutting forces measurements. However, the natural frequency of a dynamometer has a direct impact on the accuracy of measured cutting forces in the machining process. Therefore, few dynamometers are appropriate and reliable to measure the cutting forces at high frequencies. In this work, a new strain-gauge-based dynamometer (SGBD) with a special structure was designed, manufactured, and put to the test to ensure the measurement of high-frequency dynamic forces in the milling process. The main structure of the SGBD is symmetrical and mainly consists of a center quadrangular prism surrounded by four force sensing elastic elements, an upper support plate, and a lower support plate. The dynamic identification test was conducted and indicated that the SGBD′s natural frequency could be stabilized at a high value of 9.15 kHz. To automatically obtain the milling force data with a computer during high rotational speed milling, a data acquisition system was devised for the dynamometer. To reduce the effects of cross-sensitivity and acting point of force, an innovative model based on a conversion matrix was established for the dynamometer. Furthermore, the cutting tests were conducted at high rotational speeds (10,000–18,000 rpm), and it was found that the difference of cutting forces between the SGBD and a Kistler dynamometer are 2.3–5.8% in the X direction and 3.5–8.8% in the Y direction. The experimental findings disclosed that the new kind of dynamometer is reliably for the measurement of high-frequency dynamic forces in milling at high rotational speeds.

Determining the Power Consumption of the Automatic Device for Belt Perforation Based on the Dynamic Model

The subject of the dynamic analysis presented in the article is the linear drive system with a timing belt utilized in the automatic device for polymer composite belt perforation. The analysis was carried out in two stages. In the first stage, the timing belt was modeled with all the relevant dynamic phenomena; subsequently, the tension force of the belt required for the correct operation of the belt transmission was determined. The necessary parameters for belt elasticity, vibration damping, and inertia are based exclusively on the catalog data provided by the manufacturer. During the second stage, equations of motion were derived for the designed drive system with a timing belt, and characteristics were identified to facilitate the optimal selection of electromechanical drives for the construction solution under analysis. The presented methodology allows for designing an effective solution that may be adapted for other constructions. The obtained results showed the influence of the kinematic parameters on the motor torque and proved the importance of reducing the mass of the components in machines that perform high-speed processes.

Online monitoring and multi-objective optimisation of technological parameters in high-speed milling process

Online monitoring and multi-objective optimisation of technological parameters in high-speed milling process

Real-Time Human Detection in a Restricted Area for Safety in Truck Dumper Control System Using Deep Learning

A process to receive raw materials from suppliers in an animal feed industry utilizes both automatic and semi-automatic machine control systems. The process called “truck dumper system” is the procedure that the suppliers provide raw materials carried by trucks; then, their tailgates open, and the raw materials are discharged by raising front end part of a truck to gather raw materials in a collection area. In general, the truck dumper system has been controlled manually by staff in a control room, not by a truck driver. However, serious accidents may occur during the process because when the dumper lifts up, the staff's vision has been blocked by the raised part of a truck. Therefore, if the staff controls the dumper to lift down by lacking safety awareness, people in the restricted area can be endangered. In this study, we proposed a framework of automatic human detection to prevent any accident that may occur from the truck dumper in the restricted area. The human detection model was developed to detect humans possibly in different blind corners that are difficult for staff in a control room to monitor these unseen areas for safety-awareness. The main technology of the proposed framework was the real-time human detection with fully convolutional neural network architecture called You Only Look Once, or YOLO. The framework has been designed to send a signal to terminate the truck dumper system immediately after the model detects people in the restricted area. In experiments, we discovered that the model could detect a human in all blind corners, including the corners that the staff's sight was completely bloacked by some barriers. The overall efficiency of this framework in an aspect of speed was high. The average time to process per image was 397 milliseconds by using CPUs and only 52 milliseconds by using GPUs. The results also showed that the model was effectively applicable to detect human in real-time due to its high-speed process.

Design and Development of Database System for Turning and Milling Compound high-speed Machining

In order to realize the advantages of high-speed cutting machine and improve the efficiency of high-speed cutting, a turning and milling compound high-speed machining process database was studied. According to the data information of cutting lathes, workpiece materials, tools and high-speed machining parameters, the functional requirements, system roles and system data relationships of the database system were analyzed. Based on the above information, the functional module, basic database, user permission and system architecture were designed, and a compound high-speed machining database system which is suitable for lathes and milling machines was developed.

High-speed milling Inconel 718 using Electrostatic Minimum Quantity Lubrication (EMQL)

Inconel 718 superalloy is widely used in the aerospace and nuclear industries. It is a difficult-to-cut material representing short tool life and high machining costs. Minimum Quantity Lubrication (MQL) is adopted to extend tool life and minimize machining costs. However, it is not effective in high-speed milling processes. A new Electrostatic Minimum Quantity Lubrication (EMQL) nozzle design is presented. The performance of the EMQL system in end milling Inconel 718 is assessed in terms of tool life, specific cutting energy and, surface roughness; and is benchmarked against MQL.

Robustness of Weld Appearance on High-speed Arc-assisted Laser Welding Process on Titanium Sheet

Robustness of Weld Appearance on High-speed Arc-assisted Laser Welding Process on Titanium Sheet