High-speed Face Research Articles

High-speed face milling features of deformable aluminum alloys

High-speed face milling features of deformable aluminum alloys

Surface integrity and modification of SA508Gr.3Cl.2 RPV steel induced by high-speed face milling process

Surface integrity and modification of SA508Gr.3Cl.2 RPV steel induced by high-speed face milling process

Experimental study and mathematical modelling of face milling forces of high-strength high-viscosity shipbuilding steel

Mechanical processing of hole edges in large-size hull structures of single and double curvature for welding saturation parts into them is an urgent task of shipbuilding. A considerable amount of such machining has to be performed directly on the slipway on a fully assembled structure. To perform such works non-stationary technological machining complexes are used, which have reduced rigidity in comparison with stationary equipment. The article summarizes the results of mathematical modeling of cutting forces during face milling of a workpiece made of high-strength high-viscosity shipbuilding steel. The application of high-speed face milling in order to reduce the value and non-uniformity of cutting forces is theoretically substantiated. Recommendations for selection of technological cutting modes and tool geometry are determined. The obtained experimental data confirm the possibility and expediency of high-speed face milling of hull structures made of hard-to-machine materials under conditions of a low-rigid technological system.

Wear mechanisms of coated carbide tools during high-speed face milling of Ti2AlNb intermetallic alloys

Wear mechanisms of coated carbide tools during high-speed face milling of Ti2AlNb intermetallic alloys

A YOLO-NL object detector for real-time detection

In recent years, YOLO object detection models have undergone significant advancement due to the success of novel deep convolutional networks. The success of these YOLO models is often attributed to their use of guidance techniques, such as expertly tailored deeper backbone and meticulously crafted detector head, which provides effective mechanisms to tradeoff between accuracy and efficiency. However, these sluggish-reasoning models are not capable of handling false detection and negative phenomena, facing challenges include improving the robustness of scaled objects detection against occlude and densely sophisticated scenarios.To address these limitations, we propose a novel object detector, You Only Look Once and None Left (YOLO-NL). Our model includes a novel global dynamic label assignment strategy, which allocates labels for specific anchors to maintain a balance between higher precision detection and finer localization. To enhance the detection capability of multi-scale objects in complex scenes, we separately upgrade CSPNet and PANet using the shortest-longest gradient strategy and self-attention mechanism. To meet the need for fast inference, we propose the Rep-CSPNet network using the reparameterization method to convert residual convolutions to ghost linear operations. Additionally, we accelerate the feature extraction process by deploying the serial SSPP structure. The proposed model is robust to scale objects against negative effectives such as dust, dense, ambiguous, and obstructed scenes. YOLO-NL achieved a mAP of 52.9% on the COCO 2017 test dataset, exhibiting a significant improvement of 2.64% compared to the baseline YOLOX. It is worth noting that YOLO-NL can perform high-accuracy and high-speed face mask detection in real-life scenarios. The YOLO-NL model was employed on self-built FMD and large open-source datasets, and the results show that it outperforms the other state-of-the-art methods, achieving 98.8% accuracy while maintaining 130 FPS.

RESEARCH ON WIDE SPECTRUM FULL-COLOR NIGHT VISION ELDERLY FACIAL VIDEO HEART RATE AUTOMATIC MEASUREMENT AND WARNING SYSTEM

In recent years, the prevalence of cardiovascular diseases has been growing geometrically, especially among the elderly. Real-time heart rate monitoring becomes an effective measure for preventing cardiovascular diseases. Traditional contact-based real-time heart rate measurement methods require long-term wearing of contact electrodes, which can cause inconvenience to the elderly population. In this study, a wide spectrum full color night vision elderly face video heart rate automatic measurement and early warning system was designed and developed by combining imaging photoplethysmography (IPPG), video acquisition equipment based on starlight wide spectrum camera and high-speed face recognition signal processing algorithm based on deep learning. By constructing a software and hardware platform, a comprehensive evaluation of the system’s application in elderly facial video heart rate measurement experiments was conducted.

Modeling of heat partitioning and temperature rise at the tool-chip interface in diamond turning of the PBX surrogate

To predict the heat partition ratio and chip temperature rise in the diamond turning of a PBX surrogate, a comprehensive model is built in this work. The newly created model takes into account the removal and friction law of powder chips at the tool tip in addition to the diamond tool and important process parameters. The cutting heat generation and distribution rule are clearly outlined thanks to the successful integration of the momentum theorem (related to cutting force) and energy conservation theory (related to cutting heat). The following findings came from the high-speed face turning experiment based on simultaneous force-thermal monitoring: 1) The friction heat at the tool-chip interface is the primary cause of the temperature increase in the chip, and decreasing the heat partition ratio is advantageous for lowering the risk of thermochemical reactions of powder chips. 2) It is effective to suppress the proportion of heat obtained from powder chips by optimizing the diamond tool with a negative rake angle and reducing the equivalent cutting friction coefficient. 3) The most important aspect affecting the chip temperature rise is the cutting speed. Improving the tool-chip friction conditions and lowering the maximum cutting speed are essential for ensuring PBX machining safety.

A High Performance Dual Stage Face Detection Algorithm Implementation using FPGA Chip and DSP Processor

A dual stage system architecture for face detection based on skin tone detection and Viola and Jones face detection structure is presented in this paper. The proposed architecture able to track down human faces in the image with high accuracy within time constrain. A non-linear transformation technique is introduced in the first stage to reduce the false alarms in second stage. Moreover, in the second stage pipe line technique is used to improve overall throughput of the system. The proposed system design is based on Xil¬inx’s Virtex FPGA chip and Texas Instruments DSP processor. The dual port BRAM memory in FPGA chip and EMIF (External Memory Interface) of DSP processor are used as interface between FPGA and DSP processor. The proposed system exploits advantages of both the computational elements (FPGA and DSP) and the system level pipelining to achieve real time perform¬ance. The present system implementation focuses on high accurate and high speed face detec¬tion and this system evaluated using standard BAO image database, which include images with different poses, orientations, occlusions and illumination. The proposed system attained 16.53 FPS frame rate for the input image spatial resolution of 640X480, which is 23.4 times faster detection of faces compared to MATLAB implementation and 12.14 times faster than DSP implementation and 2.1 times faster than FPGA implementation.

High-speed face milling of AZ91 Mg alloy: Surface integrity investigations

Magnesium (Mg) alloys are popular in the aerospace and automotive sector owing to their light-weight aspects. Amongst various Mg alloys, AZ91 alloy behaviour under machining has been trending and needs to be completely explored. The selection of optimal machining parameters is an important decision making process to achieve highest quality along with reduced cost and time. In this regard, this article describes experimental investigations to evaluate the performance of face milling operations on the surface characteristics of AZ91 magnesium alloy. The experiments were carried out with uncoated and PVD (Physical Vapour Deposition) coated carbide inserts at three levels of cutting speed (500, 700 and 900 m/min), feed rate (0.1, 0.2 and 0.3 mm/teeth) and depth of cut (0.5, 1.0 and 1.5 mm) under dry machining conditions. Major surface integrity indicators, such as roughness, hardness, residual stresses and microstructure are analysed. Chip morphology is also analysed and the correlation between chips and machined surface roughness is established. Face milling operation significantly improved surface roughness and microhardness of this alloy. Roughness improvement up to 85% (0.067 μm) and hardness improvement up to 33% (91.8 HV) is observed from the use of uncoated carbide inserts. Whereas, from PVD coated inserts, roughness improvement up to 81% (0.083 μm) and hardness improvement up to 60% (111.2 HV) is achieved. A similarity in behaviour between the two types of insert conditions are observed with increase in roughness from feed increase and decrease in hardness from cutting speed increase. Microstructural analysis showed PVD coated insert conditions producing surface with no defects, when compared to the crack observed in the surface from the use of uncoated carbide inserts. Marginally higher compressive residual stresses are detected at the surfaces from use of the uncoated inserts. Overall, due to no surface defect and the significant improvement in hardness and roughness from the PVD coated inserts, they are recommended for use in face milling operation for the cutting conditions investigated in this study.

Waviness at dry high-speed face milling of some hard steels

Waviness at dry high-speed face milling of some hard steels

Analysis of tool wear and surface roughness in high-speed milling process of aluminum alloy Al6061

In this study, the influence of cutting parameters and machining time on the tool wear and surface roughness was investigated in high-speed milling process of Al6061 using face carbide inserts. Taguchi experimental matrix (L9) was chosen to design and conduct the experimental research with three input parameters (feed rate, cutting speed, and axial depth of cut). Tool wear (VB) and surface roughness (Ra) after different machining strokes (after 10, 30, and 50 machining strokes) were selected as the output parameters. In almost cases of high-speed face milling process, the most significant factor that influenced on the tool wear was cutting speed (84.94 % after 10 machining strokes, 52.13 % after 30 machining strokes, and 68.58 % after 50 machining strokes), and the most significant factors that influenced on the surface roughness were depth of cut and feed rate (70.54 % after 10 machining strokes, 43.28 % after 30 machining strokes, and 30.97 % after 50 machining strokes for depth of cut. And 22.01 % after 10 machining strokes, 44.39 % after 30 machining strokes, and 66.58 % after 50 machining strokes for feed rate). Linear regression was the most suitable regression of VB and Ra with the determination coefficients (R2) from 88.00 % to 91.99 % for VB, and from 90.24 % to 96.84 % for Ra. These regression models were successfully verified by comparison between predicted and measured results of VB and Ra. Besides, the relationship of VB, Ra, and different machining strokes was also investigated and evaluated. Tool wear, surface roughness models, and their relationship that were found in this study can be used to improve the surface quality and reduce the tool wear in the high-speed face milling of aluminum alloy Al6061

Optimum Hydrodynamic Journal Bearing Performance Characteristics in High-Speed and High-Power Gearboxes

Application of hydrodynamic journal bearings such as pressure dam and offset in high-speed and high-power gearboxes face immense challenges to deliver optimum static and dynamic performances under various operating conditions. Stability, efficiency and oil flow are critical to quality (CTQ) requirements for these gearboxes, and hence, optimum design of journal bearings is required to meet all the performance requirements. For example, bearings designed for optimum static performance at full load and full speed conditions could not deliver the stable dynamic performance at no load conditions. In this study, offset and pressure dam geometries are combined into same bearing and analyzed if the combination can deliver the optimum performance characteristics. The governing mathematical models of Reynold’s equation and energy equation include turbulent and adiabatic thermal effects. The analytical study found that combined offset pressure dam bearing delivers optimum performance at all operating conditions.

Comparative evaluation of soybean oil–based MQL flow rates and emulsion flood cooling strategy in high-speed face milling of Inconel 718

Comparative evaluation of soybean oil–based MQL flow rates and emulsion flood cooling strategy in high-speed face milling of Inconel 718

Chip formation and tribological behavior in high-speed milling of IN718 with ceramic tools

Advanced ceramics exhibit excellent mechanical properties at elevated temperatures suggesting them as plausible cutting tool materials for machining of heat-resistant superalloys. However, despite numerous efforts to date, relative brittleness of ceramic tools can result in chipping or catastrophic failure, especially during an intermittent process where excessive thermo-mechanical alteration occurs, like high-speed face milling. Previous studies by the authors revealed that in high-speed milling of inconel with SiAlON tools, after surpassing a certain cutting speed where extreme levels of strain rates and temperatures exist, the IN718 machinability transforms drastically, showing a significant reduction in cutting force, chipping and tool wear. Following this observation, in the current paper, an attempt has been made to further investigate the phenomena acting at the shear deformation zones through analysis of chip formation mechanisms and tool-workpiece tribosystem. Numerous characterization techniques have been used in this research, such as cutting force measurements, chip cross-section studies, SEM/EDS, TEM, and nanoindentation. Results suggest that a reduction in material flow strength occurs at the extreme conditions of the cut, showing similarities to fluid flow in TEM images of the tool face. Increasing the cutting speed generally facilitates chip formation; However, a rise in cutting force by further increasing the speed, and excessive generation of unstable built-up layers practically limits the cutting speed. Additional XPS studies show that variation in cutting speed also changes the frictional response of the tool-workpiece tribosystem by forming lubricious and thermal-barrier tribofilms.

Cutting performance and wear mechanism of Sialon ceramic tools in high speed face milling GH4099

This work aims to reveal the cutting performance and wear mechanisms of Sialon ceramic tools for the high-speed face-milling of GH4099, with the goal of improving this process as well as designing more advanced ceramic cutting tools in the future. At the outset of this study, several single-factor experiments were designed with speed as a variable to gather various data on such tools. Failure patterns and tool life curves were first obtained through cutting tests. Afterwards, the tools were split at their place of wear (middle of notch and 1/2 depth of cut) to prepare for further analysis. Wear morphology and element composition distribution in the depth direction of the corresponding interface were then analyzed using a field emission scanning electron microscope (FE-SEM) and energy dispersive spectrometer (EDS) to explore potential diffusion and/or chemical wear. Finally, studies were conducted into the tools’ chemical wear under specific cutting conditions, finishing with a theoretical verification based on the thermodynamic principle of chemical reactions. This research discovered that notch wear was the main failure pattern for the high-speed face-milling of GH4099 under the suitable cutting conditions. Overall, the optimal cutting speed was 1000 m/min, with a tool life of about 3 min. Compared with cemented carbide tools, the machining efficiency for Sialon ceramic tools increased by over a factor of 16. The wear mechanisms for such tools demonstrated a mixture effect of abrasive, adhesive, diffusive and chemical wear. Diffusive wear mainly occurred in their flank faces, but did not constitute the main mechanism of notch wear; chemical wear proved to be a key reason for notch wear at higher temperatures. Based on the aforementioned research, this paper concludes with a proposed comprehensive model for notch wear.

Influence of process parameters on the cutting performance of SiAlON ceramic tools during high-speed dry face milling of hardened Inconel 718

Heat-resistant superalloys (HRSAs) exhibit excellent mechanical strength and structural stability at elevated temperatures. Hence, aerospace and power industries have consistently chosen nickel-based superalloys over the years for manufacturing hot-section components. However, poor machinability of these alloys has always been a challenge. This paper investigates the cutting performance of new-generation SiAlON ceramics under extreme conditions of dry high-speed face milling of hardened Inconel 718. Comprehensive characterization of the ceramic tool and its milling performance were conducted using instrumented micro/nano-mechanical indentations, tool life studies, optical 3D imaging, and SEM/EDS investigation of wear patterns. Also, experimental results were linked to the finite element analysis (FEA) of temperature and stress profiles. It is demonstrated that a few major factors govern the ceramic tool life under the outlined cutting conditions: (1) High temperature at the cutting edge exceeding 1250 °C. This temperature is close to the melting point of Inconel 718, and moreover, it is highly localized around the cutting edge-chip interface. (2) High resultant mechanical stress on the tool of around 5.8 GPa. (3) Thermal and mechanical fatigue loading due to the discontinuity of the milling process, combined with (4) intensive built-up edge formation caused by severe weldability of the softened workpiece to the tool. Combination of these phenomena results in a significant change in the machinability of the workpiece material after surpassing a certain limit of cutting speed. The cutting forces, tool wear, and chipping show a significant decline with increasing the speed high enough, which is attributed to the change in the material properties of the workpiece and dissolution of the hard particles within the Inconel microstructure.

Analysis of cutting forces and surface quality during face milling of a magnesium alloy

This paper presents an experimental study carried out in order to assess the effects of the cutting parameters (cutting speed, feed and depth of cut) and also of cooling conditions on the cutting force and the surface quality during high speed face milling of a magnesium alloy. With its high ratio of strength to weight, good machinability and overall physico – mechanical properties magnesium has attracted a large interest upon itself, especially in fields such as automotive, aeronautics, electronics or biomaterials. On the other hand, there has been lately an increased interest for cooling techniques that are more environmentally friendly, which is why in this study two cooling systems were used: dry machining and minimum quantity lubrication (MQL). The tests have been organised according to design of experiment technique. By using the response surface methodology (RSM), a central composite experimental matrix was designed. Statistical analysis (ANOVA) has allowed to create mathematical models of the cutting force and surface roughness and to analyse the effects of the effects of the input parameters on these outcomes. It was thus revealed that the depth of cut and the feed, and the interactions feed – depth of cut and feed direction – cooling, respectively, have the most significant influence on the main cutting force, whereas when it comes to the surface roughness, the most significant factors were the feed, the feed direction and the interaction between feed direction and cooling type.

Experimental study on the chip morphology, tool–chip contact length, workpiece vibration, and surface roughness during high-speed face milling of A6061 aluminum alloy

In this study, experiments of high-speed face milling of A6061 aluminum alloy with a carbide insert milling cutter under dry cutting conditions were conducted. The contact length between tool and chip, the workpiece vibration amplitude, and the arithmetic average surface roughness were measured under varying cutting conditions (cutting speed, feed rate, and depth of cut). The characteristics of chip morphology were observed using scanning electron microscope. Experimental results showed that the increasing cutting speed reduced the tool–chip contact length, the workpiece vibration, and the surface roughness. The tool–chip contact length, the workpiece vibration, and the surface roughness were all increased with increasing cutting depth and feed rate. The results of chip morphology showed that the chips with serrated form were generated under high-speed cutting conditions. Moreover, scratch lines, plastic deformation cavities, and local molten chip material were observed on the slide chip surface.

Numerical Simulation Investigation on the Windage Power Loss of a High-Speed Face Gear Drive

Reducing the energy consumption and improving the efficiency of high-speed transmission systems are increasingly common goals; the windage power loss is not negligible in these methods. In this work, the multi-reference frame (MRF) and periodic boundary conditions (PBC) based on the computational fluid dynamics (CFD) method were adopted to investigate the windage phenomena of a single face gear with and without a shroud, and the impact of the gear speed on the windage power loss was analyzed. Furthermore, the effects on the distribution of static pressure due to the distances between the shroud and the gear body in different directions, including the outer radius direction, the inner radius direction, and the addendum direction were investigated. The results indicate that the gear speed significantly affected the windage loss, as the higher the gear speed was, the greater the windage power loss. Additionally, the shroud could effectively reduce the windage power loss, where the optimal distance from the addendum to the shroud was not the minimum distance; however, for the distances from the shroud to the inner radius and the outer radius, the smaller the distance was, the smaller the windage loss. The results can provide a theoretical basis and technical reference for reducing the windage power loss of various face gear drives.

Evaluation of tool wear in high-speed face milling of Al/SiC metal matrix composites

In recent years, a new generation of composite materials has been introduced as metal matrix composites (MMCs) in order to simultaneously provide higher strength and stiffness. Industrial interests resulted in deep investigations and researches on machinability of MMCs and especially in the field of high-speed machining. High-speed machining processes offer a higher machining efficiency and reduced cost of the process, which made them the process of interest in many manufacturing industries. However, matrix reinforcement by addition of hard particle phases to the MMCs significantly increases machining difficulty, tool wear, surface quality deterioration and overall fabrication costs. In the current research, the cutting speed, feed rate, depth of cut, presence of cryogenic coolant and their effect on the tool wear of high-speed machining of Al/SiC MMC reinforced with 15 wt% SiC particles have been investigated. The results have shown that silicon carbide particles in the aluminum matrix cause a severe tool wear. However, the severity of tool wear has decreased by applying a cryogenic cooling.