Removal Mode Research Articles

Experimental investigations to improve the electrical efficiency of photovoltaic modules using different convection mode

Solar energy is the most frequently used renewable energy source which receives the light energy from the sun, and it transform in to electric energy with the help of photovoltaic cell as a module. The flow of electrons or electrical energy is produced by making the sunlight photons to fall on the collector. Which produce the electrical energy, but the power generation is not completely produced because due to various losses. The most commonly occurred power loss is due to heat formed under the solar panel which affects the solar panel performance. Induced electrical energy is inversely proportional to the base panel temperature. Our main scope of the work is to remove the heat, which are accumulated under the solar panel by using different convection mode. In this paper, an experimental analysis is conducted in four different convection mode for heat removal for three days from sunrise 8.00 a.m. to 5.00 p.m. for calculating the maximum current, voltage generation and maximum heat removal. Four experiments namely, without rectangular duct under free convection, with rectangular duct under free convection, with rectangular duct under forced convection and duct with L shaped barrier and forced convection are conducted for three days. The maximum voltage induced in solar panel without duct, with duct under free convection, duct under forced convection and duct under forced convection & L shaped barrier was obtained at 11:00 a.m. as 18.54 V, 19.05 V, 21.04 V and 22.56 V. Results indicate that the maximum voltage induced is significantly increased in all the modifications such as duct under free convection, duct under forced convection and duct under forced convection & L shaped barrier by 2.75%, 13.48% and 21.68% as compared to conventional solar panel without duct condition. The inclusion of duct under free convection, duct under forced convection and duct under forced convection & L shaped barrier in solar panel base limits the maximum temperature as 44℃, 41℃ and 38℃, however the maximum temperature in the solar panel base is 49℃ for solar panel without duct condition. Reduction in solar panel base maximum temperature for duct under free convection, duct under forced convection and duct under forced convection & L shaped barrier are 10.20%, 16.33% and 22.45% as compared to conventional solar panel without duct condition. The results also indicate that the induced voltage and solar panel base panel temperature for four experiments was compared and found the maximum electrical efficiency enhancement of 21.68% with duct and L shaped barrier under forced convection than conventional method and the corresponding base panel temperature reduction is 19.15% is obtained than conventional type. The proposed system significantly increased the photovoltaic panel performance and output voltage due to enhanced evaporation rate and reduction in photovoltaic panel temperature.

Biochar from waste Sterculia foetida and its application as adsorbent for the treatment of PAH compounds: Batch and optimization

Polyaromatic hydrocarbons (PAHs) are organic pollutants with known health hazards and have been reported worldwide in many water sources. The present study reports the easy and green formulation of KOH-modified biochar from Sterculia foetida shells capable of adsorbing acenaphthene and naphthalene from water. To elevate process efficiency, response surface methodology (RSM) was applied to optimize the sorption process. Batch study data were also analysed to understand the process isothermal, thermodynamic and kinetic characteristics. Characterization of the biochar was done using SEM, EDS, BET, FT-IR and XRD. The results display that the formulated biochar was able to remove approximately 92% and 94% of acenaphthene and naphthalene respectively from aqueous solutions. Further the process was found to follow Langmuir and Temkin isotherms and pseudo-second-order kinetics. The thermodynamic study suggested that the adsorption was endothermic and spontaneous in nature. The activation energy of the process suggested that chemical adsorption was the mode of PAH removal.

Longitudinal amplitude effect on material removal mechanism of ultrasonic vibration-assisted milling 2.5D C/SiC composites

The anisotropic, heterogeneous, brittle and hard nature of ceramic matrix composites (CMCs) challenge machining process. Ultrasonic vibration-assisted machining may be an excellent method for processing these CMCs. The paper aims to investigate the effect of longitudinal amplitude on material removal mechanism of ultrasonic vibration-assisted milling (UVAM) 2.5D C/SiC composites. Firstly, the UVAM experiments of 2.5D C/SiC composites are performed at different longitudinal amplitudes. Secondly, the machined surface defects, surface roughness and cutting force are measured and analyzed. The UVAM experimental results show that the longitudinal amplitude of tool changes the ratio of local fragmentation fracture and abrupt macro fracture in carbon fiber removal modes to affect surface quality. Finally, a novel micro-mechanical model of UVAM carbon fiber in 2.5D C/SiC composites is proposed. The proposed model demonstrates that the longitudinal amplitude induces alternate impact load in carbon fiber and is positively correlated with alternate impact load frequency. The strain rate increases with the alternate impact load frequency, which leads to the embrittlement and local fragmentation of the carbon fiber at the stress point. On the other hand, the cutting force increases at the excessive longitudinal amplitude, which makes the carbon fiber more prone to abrupt macro fracture during machining process. A comprehensive evolution mapping of the carbon fiber fracture process is established to explain the relationship between machining process, removal mechanism, and surface defects. This work suggest that the machined quality of CMCs component can be improved by selection of optimized longitudinal amplitude by control fracture-mode percentage in UVAM.

Evolution and control of deformation mechanisms in micro-grooving of Zr-based metallic glass

The evolution of deformation mechanisms with increasing depth of cut (DOC) in micro-grooving of Zr-based metallic glass was deeply investigated in this study for the first time. The micro-grooving characteristics of metallic glass were initially studied by nanoscratch test, which verified that the material removal mode abruptly changes from extrusion mode to cutting mode with increase of DOC. Based on the free-volume theory, a dynamic model coupling stress, temperature and free volume concentration was used to simulate the change of deformation characteristics with DOC. The results showed that the deformation mechanism of metallic glass is closely related to free volume flow, which is significantly affected by average strain rate and free volume flow coefficient in deformation zone and can be tuned with different DOC. Considering that free volume flow is determined by its flow coefficient and concentration, we proposed to control the deformation characteristics of metallic glass in micro-grooving by heat treatment and verified its effectiveness experimentally. • Materials removal mode of metallic glass changes with the increase of depth of cut. • The evolution of deformation mechanisms was studied using a dynamic model. • Free volume flow affects the evolution of deformation mechanisms significantly. • Deformation characteristics of metallic glass were experimentally modulated.

Surface generation in high-speed grinding of brittle and tough ceramics

Grinding induced sub-surface defects substantially impair the functionality of ceramic components. Effective control of such defects is possible through identification and understanding the governing factors. The present work investigates the interaction of abrasive grits over the ground surface to identify the governing factors for effective control of such defects during high-speed grinding of a brittle (alumina) and a tough (yttria-stabilized zirconia (YSZ)) ceramic. High-speed grinding was carried out using single-layer electroplated diamond grinding wheels in the speed range of 40–200 m/s. The important grinding characteristics, such as material removal mode, residual stress, surface roughness, etc., were correlated with the maximum uncut chip thickness (hm) and the scallop height (Sg). The hm represents the interaction of active grits at the exit of the grinding zone, whereas the interaction of active grits while entering the grinding zone (at ground surface) leads to the formation of scallops. Instead of hm, material removal mode and other related grinding characteristics are found to be governed by the Sg. An efficient reduction of approximately 90 % in Sg is realized by increasing the grinding speed from 40 m/s to 200 m/s. For a brittle ceramic like alumina, such a drastic reduction in Sg reduced grinding induced defects by more than 75 %. For a tougher ceramic like YSZ, a reduction of more than 30 % in the magnitude of compressive residual stress is observed with a reduction in Sg at a higher grinding speed of 200 m/s. This study manifests Sg as a predominant factor in governing the ground surface characteristics during ceramic grinding, which can be effectively utilized to control grinding induced defects in ground ceramic parts.

Single diamond scribing of SiCf/SiC composite: Force and material removal mechanism study

SiC fiber-reinforced SiC ceramic matrix (SiCf/SiC) is an advanced high-temperature material widely used in the heat-resistant componets of the aerospace engine and nuclear reactor, which are generally precisely ground to achieve the designed dimensional and geometrical tolerances. This research investigates the scribing force and material removal mechanism of 2.5D woven SiCf/SiC with the flat and sharp diamond grits, which present the new dressed and worn grinding wheel. The results show that the sharp grit has larger wear on the cutting edge and generates lower force than that of the flat grit at the same scribing depth and groove cross-section area. In both sharp and flat grits, the SiC matrix is mainly removed by the fracture cracks, peeling off, fiber exposure and powdering. In transverse diamond scribing of the SiCf, the fiber debonding and shear breakage are dominant removal feature for the flat grit scribing. Two additional removal patterns, the ductile scratch and fiber cracking, are observed for the sharp grit. In parallel diamond scribing of the SiCf, the shear and bending fractures in the cut-in and cut-out points are two key material removal modes, respectively, especially in the fiber woven structure. This research provides a fundamental understanding of interaction force and the material removal process of SiCf/SiC in grinding.

Grain flash temperatures in diamond wire sawing of silicon

Diamond wire sawing has obtained 90% of the single-crystal silicon–based photovoltaic market, mainly for its high production efficiency, high wafer quality, and low tool wear. The diamond wire wear is strongly influenced by the temperatures in the grain-workpiece contact zone; and yet, research studies on experimental investigations and modeling are currently lacking. In this direction, a temperature model is developed for the evaluation of the flash temperatures at the grain tip with respect to the grain penetration depth. An experimental single-grain scratch test setup is designed to validate the model that can emulate the long contact lengths as in the wire sawing process, at high speeds. Furthermore, the influence of brittle and ductile material removal modes on cutting zone temperatures is evaluated.

Microstructural influence on damage-induced zirconia surface asperities produced by conventional and ultrasonic vibration-assisted diamond machining

Zirconia surface asperities associated with machining-induced damage and deformation jeopardize the quality of zirconia products. Conventional and emerging ultrasonic vibration-assisted machining processes are used to shape zirconia materials. However, a deep understanding of how zirconia microstructures and ultrasonic vibration amplitudes affect material removal mechanisms and surface quality in these processes is missing, rendering the proper mechanical process selection challenging. This paper reports on the 3D characterization of damage-induced surface asperities and the investigation of material removal mechanisms of pre-sintered porous and sintered dense zirconia materials in conventional and ultrasonic vibration-assisted diamond machining processes. 3D white light profilometry was used to measure surface asperities in terms of texture parameters, together with scanning electron microscopy (SEM) for imaging damage and deformation morphologies. The results show that removal mechanisms and damage-induced zirconia surface asperities depended on material microstructures and ultrasonic vibration amplitudes. Both porous and dense zirconia materials had a brittle-ductile mixed removal mode in conventional and ultrasonic vibration-assisted diamond machining processes. However, brittle fracture was dominant for the porous state and ductile deformation was presiding for the dense state. Thus, there were significantly higher fracture damage area ratios with much higher average and maximum roughness values, and maximum peak and valley heights on machined porous surfaces than dense ones. Ultrasonic assistance at an optimal vibration amplitude promoted brittle-ductile transitions on both porous and dense zirconia surfaces, resulting in reduced brittle fracture damage areas with reduced surface asperities. This microstructure-process-surface quality relation provides insights into manufacturing processes for zirconia products.

The removal mechanism and force modelling of gallium oxide single crystal in single grit grinding and nanoscratching

Gallium oxide (Ga2O3) single crystals are an ultrawide bandgap semiconductor with wide industrial applications. Ultra-precision grinding is an essential shaping process in the fabrication of high quality Ga2O3 substrates. However, due to the lack of understanding of their removal mechanism, the development of high efficiency and low-damage grinding technology for Ga2O3 substrates faces great challenges. In this work, the removal mechanism of (010) β-Ga2O3 was systematically investigated by use of single grit grinding and nanoscratching. The results showed that its removal involved both ductile cutting and brittle fracture under conventional grit-grinding conditions. The ductile deformation of β-Ga2O3 was dominated by the formation of stacking faults, while in its brittle removal region microcracks were initiated and propagated mainly along the (200) lattice plane. A theoretical force model that reflects the combined effects of ductile and brittle removal was developed to further elucidate the removal mechanism. The calculated force was in good agreement with the experimental results, clearly indicating that the transition of removal modes was affected by the chip cross-sectional area.

BiFeO3 immobilized within liquid natural rubber-based hydrogel with enhanced adsorption-photocatalytic performance

Semiconductor materials have shown a good photocatalytic behaviour for the photodegradation of organic pollutants. In this work, maleated liquid natural rubber (MLNR) based hydrogel supported bismuth ferrite (BiFeO3) as photocatalyst was successfully synthesized by crosslinking with acrylic acid (AAc) assisted by the ultrasonication method to study the efficiency for the removal of methylene blue (MB) dye in wastewater. Response surface methodology (RSM) was used to optimize the parameters for adsorption of the methylene blue (MB) dye compound, whereby the effects of the initial concentration of MB and the adsorption time were examined to obtain a quadratic model for the respective hydrogel composite. The prepared composite sample was characterized by Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy-Energy Dispersive X-ray (SEM-EDX) and X-ray Diffraction (XRD) analysis. Remarkable improvement for removal of methylene blue (99% removal) was found within 3 h adsorption time with a MLNR/AAc-BiFeO3 hydrogel composite as compared to the pristine hydrogel. A synergistic mode of dye removal by adsorption and photodegradation is proposed. Based on the isotherm and kinetic study conducted, it was found that Freundlich isotherm model and a pseudo second-order kinetic model was best fitted for adsorption of MB dye. The MLNR/AAc-BiFeO3 composite maintains its removal efficiency after 5 cycles without the necessity of post-treatment separation. Therefore, it is crucial to note that the resultant low-cost MLNR/AAc-BiFeO3 hydrogel composite in this study offers excellent potential for water and wastewater treatment applications with improved recyclability and recovery.

Simulation of the ductile machining mode of silicon

Diamond wire sawing has been developed to reduce the cutting loss when cutting silicon wafers from ingots. The surface of silicon solar cells must be flawless in order to achieve the highest possible efficiency. However, the surface is damaged during sawing. The extent of the damage depends primarily on the material removal mode. Under certain conditions, the generally brittle material can be machined in ductile mode, whereby considerably fewer cracks occur in the surface than with brittle material removal. In the presented paper, a numerical model is developed in order to support the optimisation of the machining process regarding the transition between ductile and brittle material removal. The simulations are performed with an GPU-accelerated in-house developed code using mesh-free methods which easily handle large deformations while classic methods like FEM would require intensive remeshing. The Johnson-Cook flow stress model is implemented and used to evaluate the applicability of a model for ductile material behaviour in the transition zone between ductile and brittle removal mode. The simulation results are compared with results obtained from single grain scratch experiments using a real, non-idealised grain geometry as present in the diamond wire sawing process.

Fundamental study on material removal mechanism in single-crystal germanium

In this study, vary-loads and const-load nano-scratching tests were performed to investigate the material removal mechanism in single-crystal germanium. Based on the indentation size effect, the cutting force in the ductile regime was modelled analytically considering the elastic recovery and sliding friction. Subsequently, a novel specific cutting energy (SCE) model was proposed to quantitatively determine the ductile to brittle transition (DBT) depth. The surface topography of the workpiece was observed and measured using a scanning electron microscope (SEM) and an atomic force microscope (AFM). The surface morphology revealed the existence of a ductile regime, DBT regime, and brittle regime in the nano-scratching process. The DBT depth was calculated analytically using the proposed SCE model, which had a prediction error of less than 4.02%. Thus, the model results were in good agreement with the experimental results. The phase transitions of different material removal modes were characterised using Raman spectroscopy, which revealed that the phase transition from the crystalline phase to the amorphous phase dominated the material removal process. In addition, the feasibility of high-efficiency machining by increasing the cutting speed was verified: the surface integrity improved and the subsurface damage reduced at high cutting speeds. These findings provide a fundamental understanding of the ductile regime machining process for single-crystal germanium.

Forecasting the Microstructure of a Microalloyed Steel Plate Strip

A description of the experience in the development and implementation of a model for forecasting the microstructure of rolled tubular products steel during thermomechanical processing of a semi-finished product and the relative IT-solution for the plate mill 5000 of PJSC MMK is presented. This solution is based on modeling the kinetics of structure formation in the mill technological line. The article describes briefly the result of analysis of a number of existing kinetics models of phase and structural transformations from the point of view of their application under the conditions of interest to us. An empirical study of the thermal effects of phase transformations and the influence of the heat removal mode on the kinetics of structure formation is described. The process of development of an empirical kinetics model and implementation of IT-solution, that implements this model, is also described.

Utilization of sewage sludge derived magnetized geopolymeric adsorbent for geogenic arsenic removal: A sustainable groundwater in-situ treatment perspective

Highly compressible sewage sludge (SS) derived geopolymer was magnetized with impregnation of magnetite (Fe3O4) nanoparticles (NPs), and these newly developed and characterized adsorbents were tested in a batch mode for the sorptive removal of metalloid arsenic (As) from a significant potable water resource (groundwater). Various sorption experiments were performed under variable pH (4.0–9.0), magnetized geopolymer dosages (0.1–3 g L−1), contact time (0–180 min), initial As concentrations (10–100 μg L−1) and co–existing anions to develop a critical understanding of the optimal experimental requirements and to assess the sorption kinetics and isotherms. Magnetized geopolymer had better monolayer sorption capacity (∼51.6 μg g−1, after 3 h) for As(V) than only geopolymer (∼9.81 μg g−1, after 3 h) at near neutral pH (∼6.0). The sorption process onto magnetized geopolymer was facilitated by intraparticle diffusion as well as surface complexation mechanisms and was best explained by the pseudo second order kinetic model (R2 ≥ 0.95) and Freundlich and Temkin isotherm models (R2 ≥ 0.90). The exhausted composite adsorbent was sufficiently regenerated up to five sorption–desorption–regeneration cycles using 0.1 M NaOH. Further, it also displayed an excellent As(V) removal capacity from the cocktail mixture of the common geogenic anions and their antagonistic effect follows the order of: NO3− < Cl− < SO42− < F− < PO43−. The proposed waste derived sustainable composite material was proved to be a promising sorbent for economic As(V) removal under simulated complex environmental conditions.

Experimental Investigation and Analysis on Borosilicate Glass Using Electrochemical Discharge Machining Process

Electrochemical discharge machining process (ECDM) is a non-traditional machining process which has widely used in medical, electronics and aerospace industry. This paper discuss about the various different methods using same process i.e. electrode immersion depths along with electrolytic stirring effects in ECDM are discussed. The various process parameters considered during the experiment (applied voltage, electrolyte concentration and electrode immersion depths); on the other side response parameters consider as material removal, tool wear and surface finish. Experimental results indicate the adequate material removal with equivalent electrode cross sectional areas as well as fine immersion depths. Electrode immersion depth ratios, electrolyte concentration and electrolyte-stirring effect on borosilicate glass using NaOH as the electrolyte mediums show some improvement in process results. The addition of stirring effect to the electrolyte along with proper immersion depths of the electrodes resulted in improvement of the process performance mainly the improvement in surface finish values up to around four times than the normal ECDM process. The FESEM micro graphs of the fabricated micro channels reveal some interesting modes of material removal. EDS were studied for analysis of debris through this process.

Multi-phase modeling of SiC particle removal mechanism in ultrasonic vibration–assisted scratching of SiCp/Al composites

A micromechanics model based on multi-phase modeling was established by using ABAQUS software. The material removal mechanism of SiC particle and the interactions among the cutting tool, SiC particle, Al matrix, and interface were studied, and the simulation results were compared to the experimental results. Different relative positions between the cutting tool and SiC particles can lead to different removal modes of SiC particles, including rolled or penetrated in Al matrix mode, fractured mode, and pulled out mode. Among them, fractured mode can be further divided into partial fractured mode and complete fractured mode. In complete fractured mode and pulled out mode, the SiC particle and its surrounding interface are seriously destroyed. Therefore, in the actual machining process, a small value of cutting depth should be chosen to make the SiC particle removed in rolled or penetrated in Al matrix mode or partial fractured mode for a better structural integrity of SiCp/Al composites. The pit as a result of SiC particle fractured and pulled out from Al matrix is the main defect on the machined surface. With the assistance of ultrasonic vibration, friction coefficient between the cutting tool and workpiece can be decreased. Thus, a better surface integrity of SiCp/Al composites can be obtained. The simulation results agree well with the experimental results.

Process Parameters Optimization Using Taguchi-Based Grey Relational Analysis in Laser-Assisted Machining of Si3N4.

Despite extensive research over the past three decades proving that laser-assisted machining (LAM) is effective for machining ceramic materials, which are affected by many machining parameters, there has been no systematic study of the effects of process parameters on surface quality in LAM ceramic materials. In this paper, the effects and optimization of laser power, spindle speed, feed rate, and cutting depth on surface roughness and work hardening of LAM Si3N4 were systematically studied, using grey relational analysis coupled with the Taguchi method. The results show that the combination of machining parameters determines the material removal mode at the material removal location, and then affects the surface quality. In ductile material removal mode, both the value of surface roughness and work hardening degree are smaller. Decreased surface roughness and work hardening degree can be obtained with smaller cutting depth and higher laser power.

Investigation on nanoscale material removal process of BK7 and fused silica glass during chemical‐mechanical polishing

AbstractUnderstanding the nanoscale material removal process in chemical mechanical polishing (CMP) is of fundamental importance for the operation and further development of CMP. In this study, the nanoscale material removal processes of both fused silica glass and BK7 glass were investigated based on single‐pad‐asperity polishing experiments. The results indicate that the material removal characteristics are highly dependent on the composition and structure of glass materials. In the mechanically induced chemical bonding removal mode, only atoms locate near the outermost several layers can participate in the formation and breakage of interfacial bridge bonds. Moreover, the force on the abrasive particle must exceed a threshold value to induce significant removal of Si atoms from the glass substrate, because as the breakage of Siglass–O backbonds does not occur in low‐stress conditions. We reveal for the first time that the chemical and mechanical properties of the topmost layer, which is recognized as densification, hydrated, or redeposition layer, have not been significantly affected by the mechanical action of the abrasive particles when polishing in this kind of material removal mode. The results are expected to provide a deeper insight into the nanoscale material removal mechanism during glass CMP.

Slurry Erosion Resistance of Microwave Derived Ni-SiC Composite Claddings

Hydro machinery components such as turbines, pipes, guide vanes, and pumps suffer from severe slurry erosion caused by the abrasive particles entrained in working fluid. In the current work, an array of systematic slurry erosion tests were executed to study the influence of impact angle on slurry erosion rates of Ni-SiC based composite claddings developed on SS 316 L through microwave hybrid heating. Various microstructural and mechanical characterizations such as micro and nano-indentation, x-ray diffraction (XRD), and scanning electron microscopy (SEM) were performed on the developed claddings. The claddings contain 5 wt.% of SiC particles of different size fractions from nano to micro (unimodal) and combination of both in the matrix (bimodal). Slurry erosion studies were performed on the developed claddings at different impingement angles. The claddings exhibited good metallurgical bonding with the substrate without any pores throughout. The developed claddings exhibited high hardness and elastic modulus compared to the substrate material. A significant improvement in the erosion resistance of the claddings was observed with the addition of bimodal sized SiC secondary particles. The enhanced erosion resistance of the claddings could be attributed to the higher fracture toughness and hardness of the developed coating. Among the developed coatings, the bimodal sample with 5% SiC claddings showed at least two times better erosion resistance than hydro-turbine steel at almost all the impact angles. SEM studies performed on the eroded samples showed micro-cutting and plowing as the main modes of material removal at lower impact angles.

Experimental investigation on cutting mechanisms in fixed diamond wire sawing of bone

Bone sawing has been widely used in performing bone surgery. However, thermal necrosis, loss of cutting precision and surface damage may occur in cutting process. The primary objective of this research is to improve cutting performance of bone by advantages of diamond wire sawing. Mechanism of material removal, cutting force, temperature and surface quality are analyzed based on experimental results. It is indicated that wire sawing provides small depth of cut, which is effective to obtain ductile material removal mode. Due to small material removal rate per abrasive, thermal energy is low and most of the heat can be taken away by the cyclic wire and bone chips. Consequently, cutting force and temperature in cutting zone are lower than that of traditional sawing. Due to the high efficiency of chip ejection, burrs and fracture are reduced and a significant improvement in surface quality is achieved. Based on cutting experiments with various values of cutting parameters, it is observed that better performance is achievable at higher wire speeds. These results provide a valuable basis for application of wire sawing and understanding of bone cutting mechanisms.