Process For Various Applications Research Articles

Individualized and controlled laser beam pre-treatment process for adhesive bonding of fiber-reinforced plastics. III. Effects of contaminants

Adhesive bonding of plastic components is a well-established process for various applications. Specifically for thermoplastic parts, surface pre-treatment is required to achieve optimum bonding quality. However, automated surface pre-treatment is not established yet. Reasons are missing process monitoring and significant challenges arising from conventional monitoring techniques that hardly identify surface contaminants. In a recent research project, the authors investigated how process monitoring by spectrometry during a laser-based surface pre-treatment might solve this challenge for fiber-reinforced plastics and generic surface contaminants. This article describes experiments conducted on two composite materials with different contaminants. A nanosecond-pulsed UV-laser was used to pretreat a glass-fiber reinforced 2C-polyurethane (GF-PUR) and a glass-fiber reinforced polyamide 6 (GF-PA6). Each composite had coupons contaminated with an industry standard mould release agent or artificial silicate-based dust as well as uncontaminated samples. The samples were laser pretreated and compared to reference coupons that did not receive laser treatment. The samples were analyzed after laser pre-treatment for their free surface energies by the detection of the contact angle and measured for the surface roughness. The bonding improvement due to the laser process was determined by shear strength and peel resistance tests. The results show that UV-laser pre-treatment has an advantageous impact on the bonding strength of GF-PUR and GF-PA6. Combined with a fast spectrometric process monitoring that robustly identifies contaminants during the laser process, an inline process control is feasible.

Printing parameters and materials affecting mechanical properties of FDM-3D printed Parts: Perspective and prospects

Additive Manufacturing has become one of the primary advances of the fourth industrial revolution. Fused Deposition Modelling (FDM) is one of the most widely used additive manufacturing processes for various applications. In light of the growing demand for environmentally friendly developments, this article provides a comprehensive review of the printing parameters directly influencing the mechanical properties such as tensile strength, stress, Young’s modulus on the parts produced by FDM. In this article, the most crucial printing parameters, namely layer thickness, infill density and pattern, printing speed, build orientation, and raster angle affecting mechanical properties, are considered for the study. The information regarding various materials used in the FDM process is also given in detail. The article details the effect of different printing parameters on tensile strength, flexural strength, and Young's modulus.

Analysis of optical emission spectroscopy data during silicon etching in SF6/O2/Ar plasma

Silicon etching is an essential process in various applications, and a major challenge for etching process is anisotropic high aspect ratio etching characteristics. The etch profile is determined by the plasma parameters and process parameters. In this study, the plasma state with each process parameters were analyzed through the optical emission spectroscopy (OES) plasma diagnostic sensor by both chemical and physical approaches. Electron temperature and electron density were additionally acquired using the corona model with OES data that provides chemical species information, and the etch profile was evaluated through scanning electron microscope measurement data. The results include changes in profile with gas ratio, bias power, and pressure. We figure out that factors like ion energy and ion angular distribution as well as chemical reaction affect the anisotropic profile.

Controllable peeling of an elastic strip on a viscoelastic substrate

Controllable peeling is one of the core requirements of the adhesive applications needing high-precision detachment. In this paper, the peeling of an elastic strip on a viscoelastic substrate is analyzed theoretically focusing on the controllability of the peeling process, especially the interfacial detaching speed. The effects of the speed dependence of the work of adhesion, the substrate viscoelastic property and the peeling angle on the controllability of the detaching speed are systematically explored. Assuming a constant work of adhesion, the controllable detaching speed range is strongly limited and the maximum controllable speed is independent on the zero-frequency/high-frequency modulus ratio of the substrate as well as the peeling angle. The controllable detaching speed range can be substantially enlarged when a speed dependent work of adhesion is considered, which indicates a great improvement of the controllability of peeling and is of particular significance to applications needing quick detachment. The tunability of the controllable detaching speed range is also significantly improved when considering the speed dependence of the work of adhesion that the maximum controllable speed can be effectively tuned through modulating the viscoelasticity of the substrate as well as the peeling angle. The results presented here help to comprehensively understand the influences of the material properties and loading parameters on the peeling of an elastic strip on a viscoelastic substrate, which can be exploited to precisely control the peeling process in various applications needing high-precision detachment.

Study of process conditions on surface roughness in Incremental Forming Process

The employment of a green manufacturing process can directly save energy and materials in industrial sectors. Single Point Incremental Forming (SPIF) is an agile and flexible method of fabricating sheet material components and exempts the use of dedicated die-sets which further makes it a choice of green manufacturing. Furthermore, the customized components can be easily fabricated by SPIF economically. The surface quality of fabricated parts can greatly decide the suitability and sustainability of the process in various applications. This work investigates the impact of significant process factors on the roughness of the parts during the SPIF process. The average roughness has been considered to determine the surface quality. The increment in the value of wall angle and step size resulted in the increment in Ra value of formed components drastically. It was also observed that as the forming angle was raised from a lower level (60°) to a higher level (68°), the Ra value was found to increase significantly.

Exploration of wall angle and tool rotation on surface roughness in Negative Incremental Forming Process

A significant augmentation in the obsolescence of traditional forming techniques results in the strong requirement of developing an emerging and flexible process to fabricate the user-ready parts in the manufacturing units. Single Point Incremental Forming (SPIF) also known as “negative incremental forming” has shown its viability as a novel and emerging forming method for fabricating the customized and batch-type products of sheet materials to satisfy the need of various potential sectors including medical, automobile, and aerospace. This method directly exempts the involvement of dedicated die-sets and turns into the choice of green manufacturing. The surface quality of fabricated parts can greatly decide the suitability and sustainability of the process in various applications. In the current study, the impact of wall angle and tool rotation have been explored for surface roughness during SPIF. Results revealed that the increase in spindle speed resulted in the decrease of Ra value of formed components. Moreover, the Ra value of formed components was found to decrease by 50 % when the experimental condition was changed from the combination of higher levels of wall angle and “free-to-rotate” condition of spindle speed to the combination of lower levels of wall angle (60°) and a higher level of spindle speed (1500 rpm).

Selected Aspects of Cohesive Zone Modeling in Fracture Mechanics

This review paper discusses the basic problems related to the use of cohesive models to simulate the initiation and development of failure in various types of engineering issues. The most commonly used cohesive zone models (CZMs) are described. Recent achievements in the field of cohesive modeling are characterized, with particular emphasis on the problem of mixed mode loading, the influence of the strain rate, the stress state triaxiality, and fatigue. A separate chapter of the work is devoted to the identification of cohesive parameters. Examples of the use of CZMs for the analysis of the fracture and failure process in various applications, both on the macro and microscopic scale, are given. The directions of CZMs development were indicated as well as the issues that are currently under particularly intensive development.

Relevance of Matrices and Image Processing

An image is formed by the small bit of information namely pixel which is stored in the form of an array or a matrix. An image is converted into a digital form and some operations are carried out on this so that an improved image can be obtained and some specific information regarding the same can be recovered too; this procedure is known as image processing. Different processes in image processing involve different methods and operations applied. Matrix Theory has great importance in the operations applied in image processing. This manuscript is focused on the relationship of matrix theory and image processing in various applications of image processing. In order to understand the higher dimension matrices in image processing, some applications are considered to give a good insight.

Recent Advances on High-Entropy Alloys for 3D Printing.

Boosted by the success of high-entropy alloys (HEAs) manufactured by conventional processes in various applications, the development of HEAs for 3D printing has been advancing rapidly in recent years. 3D printing of HEAs gives rise to a great potential for manufacturing geometrically complex HEA products with desirable performances, thereby inspiring their increased appearance in industrial applications. Herein, a comprehensive review of the recent achievements of 3D printing of HEAs is provided, in the aspects of their powder development, printing processes, microstructures, properties, and potential applications. It begins with the introduction of the fundamentals of 3D printing and HEAs, as well as the unique properties of 3D-printed HEA products. The processes for the development of HEA powders, including atomization and mechanical alloying, and the powder properties, are then presented. Thereafter, typical processes for printing HEA products from powders, namely, directed energy deposition, selective laser melting, and electron beam melting, are discussed with regard to the phases, crystal features, mechanical properties, functionalities, and potential applications of these products (particularly in the aerospace, energy, molding, and tooling industries). Finally, perspectives are outlined to provide guidance for future research.

Highly efficient neoteric histogram–entropy‐based rapid and automatic thresholding method for moving vehicles and pedestrians detection

Thresholding for segmentation is an important key step and necessary process in various applications. Estimating an accurate threshold value for a complex and coarse image is computationally expensive and lacks accuracy and stability. This study is aimed at developing a general histogram–entropy-based thresholding method, referred as our HEBT method, for fast and efficient automatic threshold value evaluation. In the proposed method, the probability density function and Shannon entropy derived from 1D bimodal histogram have been used to find the optimal threshold values automatically. The proposed method implemented with a three-frame differencing segmentation technique has been tested on real-time datasets – change detection 2012, change detection 2014, and Wallflower – to identify pedestrians and vehicles. The performance of our HEBT method has been compared with six state-of-the-art automatic thresholding methods. The experimental segmented image results confirmed that our HEBT method is more adaptable and better suited for real-time systems with severe challenging conditions of great variations. Further, the new HEBT method achieved the best segmentation results with highest values of several performance parameters, i.e. recall, precision, similarity, and f-measure. Interestingly, the computation time is the lowest for the proposed method than the state-of-the-art methods, promising its application for a fast and effective image segmentation.

Carbon-based materials for photo- and electrocatalytic synthesis of hydrogen peroxide.

The high demand for hydrogen peroxide (H2O2) has been dominantly supplied by the anthraquinone process for various applications globally, including chemical synthesis and wastewater treatment. However, the centralized manufacturing and intensive energy input and waste output are significant challenges associated with this process. Accordingly, the on-site production of H2O2via electro- and photocatalytic water oxidation and oxygen reduction partially is greener and easier to handle and has recently emerged with extensive research aiming to seek active, selective and stable catalysts. Herein, we review the current status and future perspectives in this field focused on carbon-based catalysts and their hybrids, since they are relatively inexpensive, bio-friendly and flexible for structural modulation. We present state-of-the-art progress, typical strategies for catalyst engineering towards selective and active H2O2 production, discussion on electro- and photochemical mechanisms and H2O2 formation through both reductive and oxidative reaction pathways, and conclude with the key challenges to be overcome. We expect promising developments would be inspired in the near future towards practical decentralized H2O2 production and its direct use.

Distributed compressive and collaborative sensing data collection in mobile sensor networks

Compressive sensing (CS) supports emergent paradigms for data processing in various applications in different fields. In this paper, a distributed compressive and collaborative sensing algorithm is proposed for mobile sensor networks (MSN) to build a scalar field map that significantly reduces power consumption for the sensor movements and communications. Based on CS a certain number of mobile sensors deployed randomly on a field can build a map themselves. They collect sensory data from the others through their neighborhoods to generate CS measurements and then recover all data from the network based on a small number of CS measurements compared to the total readings in the network. All transmission power consumption for the network are analyzed and formulated. We also analyze the convergence time and the trade-off with the sensor communication range and suggest an optimal range for the mobile sensor to consume the least power.

Control of Direct Written Ink Droplets Using Electrowetting.

Here, we investigate the feasibility and effectiveness of electrowetting in the motion control of droplets of different liquids, which are widely used as inks in direct writing (DW)-based three-dimensional (3D) printing processes for various applications. To control the movement of DW ink droplets on dielectric substrates, the electrodes were embedded in the substrate. It is demonstrated that droplets of pure liquid inks, aqueous polymer solution inks, and carbon fiber suspension inks can be moved on multi-angled surfaces. Also, experimental results reveal that droplets of a commercial hydrogel, agar-agar, alginate, xanthan gum, and gum arabic can be moved by electrowetting. Droplets of sizes 200 μm-3 mm were manipulated and moved by the electric field on different dielectric substrates accurately and repeatedly. Effective electrowetting-based control and movement of droplets were observed on horizontal, vertical, and even inverted substrates. These findings imply the feasibility and potential application of electrowetting as a flexible, rapid, and new method for ink droplet control in 3D printing processes.

An atom probe analysis of self-assembled monolayers: A novel approach to investigate mixed and unmixed self-assembled monolayers (SAMs) on gold

Atom probe tomography was used to analyze self-assembled monolayer of octanethiol and (1H,1H,2H,2H) perfluoro decanethiol (PFDT) in a mixed and unmixed state on a gold surface. The first part of this report, we have analyzed the two SAMs with a direct comparison, whereas in the second part, a binary mixture of these two SAMs (with a 1:1 ratio) are analyzed. Au was taken as a metal substrate in both cases. It has been observed that, although having similar structure and belongs from the same SAMs group, the sequence of evaporation of both chains appeared significantly different molecular fractions in the first case, while in the mixed phase condition the two SAMs chains were arranged in a patchy domain by forming a small nanoscale cluster on the gold surface. Primarily, this study gives an overall understanding of evaporation sequence and surface morphology of the SAMs in an unmixed and mixed condition on the gold substrate, which may lead to the further design process in various applications.

Computational discovery of nanoporous materials for energy- and environment-related applications

ABSTRACTOur society is currently facing critical energy and environment issues, due to the consistent increase in the usage of fossil fuels and anthropogenic activities. One of the viable solutions is to develop better materials to enable more energy-efficient processes for various applications, including gas separations, energy storage, desalination, etc. Nanoporous materials such as zeolites, metal–organic frameworks (MOFs), and nanoporous graphene have drawn considerable attention as promising candidates in these applications owing to many of their favourable properties. Moreover, the tunability of porous materials results in essentially infinitely large number of possible candidates. While such vast materials space provides great opportunities, it also imposes a significant challenge on the selection of promising candidates. To this end, computational methods, such as molecular simulations, can play an important role in facilitating the discovery and design of optimal materials. In this review, we introduce several computational studies conducted for large-scale materials screenings for gas separations and for the discovery of novel membranes for water filtrations. Furthermore, in light of the importance of molecular force fields for reliable computational predictions, we also discuss some recent developments in this field. Overall, this article discusses the recent advances of computational material discoveries and methodology developments.

Solid-state compounding of immiscible PCL-PEO blend powders for molding processes

Solid-state milling is a promising ecologically friendly method for fabricating polymeric blend and composite powder raw materials for several subsequent manufacturing processes. Biodegradable polymers, blends, and composites are expected to find extensive use by industry due to their environmental friendliness and acceptable mechanical and thermal properties for several applications. Poly-ε-caprolactone (PCL), poly-ethylene-oxide (PEO), and their blends have attracted so much attention to replace commodity polymers in future applications. Therefore, in the current research, bulk compounding of PCL-PEO blends with various compositions using solid-state cryomilling was investigated. Structural, mechanical, thermal, and hydrophilicity properties were examined on samples obtained by compression molding to explore the capabilities of the milling process for various applications. Morphology of the blends was explored by scanning electron microscopy (SEM), which showed a clear phase separation in blends after heating. Dispersed as well as co-continuous morphologies were achieved by varying composition. Differential scanning calorimetry (DSC) and x-ray diffraction (XRD) of the blends indicated insignificant amorphization by milling. Tensile strength, modulus, and percentage elongation at break of the blends demonstrated significant variations due to processing parameters.

Limit theorems for non-Markovian marked dynamic contagion processes

In this paper, we study a general dynamic contagion process that includes several standard point processes as special cases. We have developed (i) the corresponding large deviation principle; (ii) the corresponding law of large numbers; (iii) the corresponding central limit theorem, all of which are critical in describing the essential of this type of processes, and are not available in current literature. The proposed model provides a broader framework in the study of contagion processes in various applications. In particular, we obtain the finite-horizon and infinite-horizon ruin probability asymptotics for the risk model with marked dynamic contagion claim arrivals as an application.

Surface modification of ion‐exchange membranes: Methods, characteristics, and performance

Considerable effort has been made to improve ion‐exchange membrane (IEM) properties in order to achieve better performance of IEM‐based processes in various applications. Surface modification is one of the effective ways to improve IEM properties. Various methods have been used to modify IEM surfaces, for example, plasma treatment, polymerization, solution casting, electrodeposition, and ion implantation. These methods are able to produce a thin and fine distributed layer and also to modify the chemical structure of the surface. The new layer can be adsorbed, deposited, or chemically bonded on a membrane surface. By using these methods, IEM properties are improved, and the desired or specific characteristics such as high monovalent ion permselectivity, low fuel crossover, and anti‐organic‐fouling property can be obtained. In this paper, methods for surface modification of IEMs are reviewed. Moreover, the effects of modification on IEM properties and performance are discussed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45540.

Effect of Laser Preheating AISI 4140 Specimens for Micro-Forging

Abstract Many high performance and permanent service parts require suitable material characteristics-high fatigue strength is one of the most important characteristics. For this reason, surface treatment processes are essential to increase the material performance and avoid the use of costly ineffective material. There exist various surface treatment processes for various applications. Each process has advantages and disadvantages and hybridization can solve various problems. The micro-forging process delivers a controlled and uniform surface hardness, but the depth of the forged surface is limited. On the other hand, laser heat treatment can increase the hardness drastically, but the surface may become brittle, which reduces the fatigue life. Laser-assisted micro-forging is a novel hybrid process of laser heat treatment and micro-forging that has the potential to increase the forging depth and relax the stress caused by the high temperature of the forging process. This study examines the effect of laser preheating in the micro-forging of AISI 4140. The processes were varied as follows: no treatment, micro-forging only, and laser-assisted micro-forging. The fatigue strength of the specimens was examined by means of an ultrasonic fatigue tester and then compared. The microstructural changes were investigated with respect to the processes by using scanning electron microscopy. In conclusion, it was confirmed that the laser preheating auxiliary forging affects the fatigue life. It was confirmed that the fatigue life was the mostly increased in 550°C temperature laser preheating micro forging process and the temperature was identified as the most important factor.

Probing nanoscale oxygen ion motion in memristive systems

Ion transport is an essential process for various applications including energy storage, sensing, display, memory and so on, however direct visualization of oxygen ion motion has been a challenging task, which lies in the fact that the normally used electron microscopy imaging mainly focuses on the mass attribute of ions. The lack of appropriate understandings and analytic approaches on oxygen ion motion has caused significant difficulties in disclosing the mechanism of oxides-based memristors. Here we show evidence of oxygen ion migration and accumulation in HfO2 by in situ measurements of electrostatic force gradient between the probe and the sample, as systematically verified by the charge duration, oxygen gas eruption and controlled studies utilizing different electrolytes, field directions and environments. At higher voltages, oxygen-deficient nano-filaments are formed, as directly identified employing a CS-corrected transmission electron microscope. This study could provide a generalized approach for probing ion motions at the nanoscale.