Complex Cavity Research Articles

Formation and Optimization of Electrical Discharge Coatings Using Conventional Electrodes

An emerging topic is electrical discharge (ED) coating with its application on complex shapes and cavities to repair components or act as functional coatings. Because it is a variant process of an electric discharge machine (EDM) with the ability to coat on electrically conductive substrates, there is a possibility that next-generation electrical discharge machining components may exploit the attachment phenomenon to enhance recast layer properties. Previously, researchers have obtained ED coating by mixing the powder in a dielectric medium and/or by using powder metallurgy electrodes. In this work, primarily, an insight in the formation of ED coating on-die sinks electrical discharge machine, using conventional electrode materials viz., bronze on titanium alloy (Ti-6Al-4V) is made. The bronze electrode on the titanium substrate obtained a crack-free copper coating of ~20 microns thickness. In order to perform the experiments, three combinations were made using five parameters: current (Amps), ton (µs), Toff (µs), duty cycle (%), and flushing pressure as constant (bar). After obtaining the coating, a combination of input parameters was selected by optimizing the output performance parameters, viz., the electrical discharge deposition rate, coating thickness, micro-cracks, and elemental coating composition. Secondarily, different optimization techniques viz., grey relational analysis, the technique for order of preferences by similarity to ideal solution, −nD angle method and information divergence method were implemented to find out the suitable combination of parameters where the latter two methods were introduced for the first time in this area of EDM optimization. A study was conducted to check whether the latter two methods are optimization techniques or multi-criteria decision-making techniques. The optimization of existing reactor types and the development of new reactors in wastewater treatment through EDC, by which energy could be saved by replacing the conventional techniques.

Dental amalgam: a practical guide

Historically, dental amalgam is the world's most commonly used restorative material. Its use is declining due to patient and professional demand for tooth-coloured restorations that are adhesive and promote minimally invasive tooth preparation techniques. Significant reduction has also resulted from environmental concerns relating to dental amalgam's ~50% mercury content. This paper provides a comprehensive review of the status of dental amalgam including its advantages and disadvantages, amalgam safety, regulations and legislation and a comparison with alternative restorative materials. As the undergraduate teaching of amalgam procedures has progressively declined, this paper also provides an illustrated step-by-step revision guide to the materials, equipment and clinical techniques that will optimize the restoration of challenging, complex cavities, where amalgam is still considered by many to be the material of choice. CPD/Clinical Relevance: Amalgam remains an excellent restorative material for long-lasting restorations in large/complex cavities and where moisture control presents challenges.

Distinctive Supramolecular Features of β-Cyclodextrin Inclusion Complexes with Antidepressants Protriptyline and Maprotiline: A Comprehensive Structural Investigation.

Depression, a global mental illness, is worsened due to the coronavirus disease 2019 (COVID-2019) pandemic. Tricyclic antidepressants (TCAs) are efficacious for the treatment of depression, even though they have more side effects. Cyclodextrins (CDs) are powerful encapsulating agents for improving molecular stability, water solubility, and lessening the undesired effects of drugs. Because the atomic-level understanding of the β-CD–TCA inclusion complexes remains elusive, we carried out a comprehensive structural study via single-crystal X-ray diffraction and density functional theory (DFT) full-geometry optimization. Here, we focus on two complexes lining on the opposite side of the β-CD–TCA stability spectrum based on binding constants (Kas) in solution, β-CD–protriptyline (PRT) 1—most stable and β-CD–maprotiline (MPL) 2—least stable. X-ray crystallography unveiled that in the β-CD cavity, the PRT B-ring and MPL A-ring are aligned at a nearly perfect right angle against the O4 plane and primarily maintained in position by intermolecular C–H···π interactions. The increased rigidity of the tricyclic cores is arising from the PRT -CH=CH- bridge widens, and the MPL -CH2–CH2- flexure narrows the butterfly angles, facilitating the deepest and shallower insertions of PRT B-ring (1) and MPL A-ring (2) in the distorted round β-CD cavity for better complexation. This is indicated by the DFT-derived complex stabilization energies (ΔEstbs), although the complex stability orders based on Kas and ΔEstbs are different. The dispersion and the basis set superposition error (BSSE) corrections were considered to improve the DFT results. Plus, the distinctive 3D arrangements of 1 and 2 are discussed. This work provides the first crystallographic evidence of PRT and MPL stabilized in the β-CD cavity, suggesting the potential application of CDs for efficient drug delivery.

Simulation of Polymer Melt Injection Molding Filling Flow Based on an Improved SPH Method with Modified Low‐Dissipation Riemann Solver

AbstractSimulations are performed for the polymer melt injection molding filling flow using an improved SPH (smoothed particle hydrodynamics) method. For improving the numerical stability of the high‐pressure and high‐viscosity injection molding filling simulation, a modified low‐dissipation Riemann solver is proposed, and the Tait equation of state and several improvements are adopted in the improved SPH method. Simulations with three cavities are performed for verification of the SPH method, including a simple long rectangular cavity and two relatively complex cavities for study of injection flow balancing. For each cavity, the pressure and velocity results of the injection molding filling simulation are demonstrated, discussed, and compared with the results of the corresponding Moldflow simulation. Furthermore, results of particle motion tracking are also analyzed for an insight into the fountain flow effect. The SPH simulation results indicate that the improved SPH method can well weaken the non‐physical pressure oscillation with reasonable pressure results and controlled melt compressibility, and the SPH results are in good agreement with the Moldflow results.

Fabrication and properties of silica-based ceramic cores modified by mullite powders with different particle sizes

Ceramic cores provide complex internal cavity structures in the investment precision castings of hollow blades for aero-engine. The silica/mullite ceramic cores were fabricated by hot injection molding, adding fused mullite powders with different particle sizes as mineralizers. The particle size of mullite mineralizers on the crystallization and properties of ceramic cores was investigated in the paper. The result shows that the mullite mineralizers promote the crystallization of cristobalite in ceramic cores, and finer mullite powders can further improve the heterogeneous nucleation, and generate larger quantities of cristobalite. Mullite mineralizers with large particle size can lead to low sintering degree, poor mechanical properties and creep resistance of ceramic cores. While the particle size of mullite mineralizers is too small, the core contains too much quartzite crystal phase, and the microcrack occurs during the phase transformation during cooling, which also causes the deterioration of the strength at room temperature and the high temperature deformation resistance ability. The ceramic cores with mullite powders in particle size of 19 μm show excellent comprehensive performance, with linear shrinkage of 0.65%, porosity of 31.8%, room temperature strength of 17.8 MPa, high temperature creep deformation of 0.4 mm, and leaching rate of 0.06 g/min.

Multi-tonal low frequency noise control using Helmholtz resonators with complex cavity designs for aircraft cabin noise improvement

The noise control at multiple tonal frequencies simultaneously, in the low frequency range, is a challenge for aerospace, ground transportation and building industries. In the past few decades, various low frequency noise control solutions based on acoustic metamaterial designs have been presented in the literature. These solutions showed promising performance and are considered a better alternative to conventional sound insulation materials. In the present investigation, it was noticed that subdividing the cavity of a Helmholtz resonator allowed the control of multi-tonal noise at several resonance frequencies simultaneously and a shift of the resonance peaks towards the low frequencies. This paper proposes concepts of Helmholtz resonators with subdivided cavities to improve the sound transmission loss (STL) performance and simultaneously control the noise at several tonal frequencies. HRs with cylindrical shaped cavities were embedded in a layer of porous material. The STL of the metamaterial noise insulation configuration was predicted using serial and parallel assemblies of transfer matrices (TMM) incorporating a thermo-viscous-acoustic approach to accurately account for the viscous and thermal losses of acoustic wave propagation within the metamaterial. The STL calculated using the proposed TMM approach were observed to be in excellent agreement with the finite element method (FEM) numerical results.

Binder jetting 3D printing process optimization for rapid casting of green parts with high tensile strength

Binder jetting 3D printing is a rapid, cost effective, and efficient moulding/core making process, which can be applied to a large variety of materials. However, it exhibits a relatively low green-part strength. This may cause the collapse of the printed parts during de-caking and the pick-up procedure, especially in the case of small-scale structures, such as thin walls, tips, and channels. In this work, polyvinyl alcohol (PVA) was used as the additive in coated sand powder. By exploiting the binding effect between the two composites (thermoplastic phenolic resin and PVA) triggered by the binder, bonding necks firmly form among the sand particles, improving the green-part strength of the coated sand printed parts. Experiments based on the Taguchi method were used to investigate the relationship between the process parameters and the green-part tensile strength. The following set of optimal process parameters was identified: 50wt.% alcoholicity of the binder, 75% binder saturation, 0.36 mm layer thickness and 4.5wt.% PVA content. Further, the effect of such parameters on the green-part tensile strength was determined via statistical analysis. The green part of an engine cylinder head sand pattern with complex cavity structures was printed, and the green-part tensile strength reached 2.31 MPa. Moreover, the ZL301 aluminum alloy impeller shape casting was prepared using sand molds printed with the optimal process parameters. The results confirm that the proposed binder jetting 3D printing process can guarantee the integrity of the printed green parts and of small-size structures during decaking and the pick-up procedure. Furthermore, the casting made from the printed sand molds exhibits a relatively high quality.

Slanted septum and multiple folded cavity liners for broadband sound absorption

The design of acoustic liners with complex cavities for a wide frequency range of attenuation using numerical method is investigated in this paper. Three novel liner concepts are presented, demonstrating predicted improvements in broadband sound absorption when compared with that for conventional designs. The liners include a slanted septum core, a slanted septum core with varying percentage open area, and a MultiFOCAL concept. A finite element model of a normal incidence impedance tube is developed using COMSOL Multiphysics modeling software to predict the acoustic properties (resistance and reactance) of liners at medium and high sound pressure levels, and to study the impact of variations in the liner design parameters. The impedance tube finite element model incorporates non-linear semi-empirical impedance equations, validated by comparing numerical results with measurements performed on a single-degree-of-freedom liner, with a perforated face sheet, at high sound pressure level. The design variables of the novel liner concepts are optimized using a hybrid automated optimisation procedure. The low-frequency optimum slanted septum core concept with an open area of 4.5% for the face sheet and 18% for the short slanted septum is predicted to have an absorption level of at least 14 dB in the frequency range of 400–1000 Hz for normally incident pure tone excitations at 150 dB. The slanted septum core concept with varying percentage open area, with broadband optimum design variables, is predicted to have good broadband sound absorption levels of at least 10 dB in the frequency range of 570–3800 Hz. Finally, the MultiFOCAL liner concept with optimised percentage open areas is predicted to have an excellent broadband sound absorption levels of at least 14 dB, for pure tone excitations at 150 dB, in the frequency range of 900–5300 Hz. This work will be followed by optimisation of the face sheet geometries of these novel liner designs in order to maximise lined duct attenuation for aircraft engine applications.

Exploring of an open hammer die life with an expanding gutter using information technologies

Currently, open dies with a parallel bridge are widely used. The design of such stamps is carried out according to proven methods. However, the dimensions of the bridges obtained do not always provide a sufficiently high durability of the dies. The decrease in the durability of the dies caused by the overestimated resistance of the bridge is especially noticeable in the manufacture of simple forgings that do not have complex cavities filled by extrusion. Thus, industries need more durable tooling that can provide a large number of stamped parts, as well as save money on the development, design and manufacture of a new stamp. To this end, in this paper, an analysis of the application of an expanding burr groove in a tool is considered. Practical experience of how the tooling is worn out with the number of stampings, the geometry of the tooling is measured, an analysis is carried out, and a mathematical model of the behavior of wear based on the experiment is presented. The same equation was obtained using Excel, which indicates that the mathematical model was obtained correctly. In addition, the paper considers the value of individual parameters of the tool geometry on the overall tool life.

Technical Considerations and Outcome Analysis of Using Extended Bipaddle Pectoralis Major Myocutaneous Flaps for Reconstructions of Large and Complex Oral Cavity Defects: Expanding the Horizons.

The online version contains supplementary material available at 10.1007/s13193-021-01345-1.

One-pot fabrication of dual-redox sensitive, stabilized supramolecular nanocontainers for potential programmable drug release using a multifunctional cyclodextrin unit

Facile engineering of β-cyclodextrin (β-CD)-based supramolecular nanocontainers with simultaneous enhanced extracellular stability and efficient intracellular biosignals-triggered destabilization generally suffers from multistep synthesis and tedious purification process, thus remains a significant challenge for the scale-up production and clinical translation of β-CD-based supramolecular nanomedicine. To address these issues, we reported in this study a one-pot preparation of dual-redox sensitive, stabilized supramolecular nanocontainers for potential programmable drug release by self-crosslinking of a multifunctional β-CD unit that integrates a host cavity for oxidation-mediated reversible complexation with ferrocence (Fc) guest molecule and lipoic acids (LAs)-decorated primary and secondary faces for reversible in-situ crosslinking by the reducible disulfide links. The resulting doxorubicin (DOX)-loaded nanoparticles showed, on one hand, enhanced colloidal stability and high DOX loading capacity with a drug loading content (DLC) of approximately 11.3% due to the crosslinked structure, and on the other hand, a programmable destruction of the supramolecular micelles triggered by a simultaneous adoption of intracellular glutathione (GSH) and reactive oxygen species (ROS) toward a complete structural destruction for promoted drug release with enhanced therapeutic efficiency. Notably, an optimized DOX-loaded micelle formation, DOX@CL P1 showed greater cytotoxicity with an IC50 of 2.94 ± 0.25 μg/mL than free DOX (6.00 ± 0.56 μg/mL) in Bel-7402 cancer liver cells, but a significantly reduced side effect relative to free DOX in L02 normal liver cells. In vivo animal study in Bel-7402 tumor-bearing BALB/c mice further confirmed prolonger elimination half-life time, efficient tumor accumulation, enhanced therapeutic efficiency and compromised systemic toxicity of this micelle construct. Therefore the multifunctional CD unit developed in this study offers an extremely straightforward and robust strategy with respect to dual-redox responsive, stabilized supramolecular nanocontainers with potential programmable controlled release properties for clinical translations.

Effect of permeability and MHD on nanoparticle transportation

Complex cavity permeated with permeable media was influenced by magnetic field in current modeling. The flow encounters resistance in existence of Lorentz force and to improve thermal features, water was equipped with nano powders. Induce magnetic was ignored and to harness the permeability effect, non-Darcy approach was used. Current model acquired large attention in industry. For examine the correctness of code, the results of θ was compared with previous basic article and achieved graph illustrates nice conformity of current modeling. Two straight wall were adiabatic, lower and upper walls were confined to hot and cold temperature bath. Laminar flow was established and maximum of Ra is 105 and carrier fluid is incompressible. To incorporate the gravity force, Boussinesq principle was utilized. The bottom surface was subjected to hot source and gravity enforces the nanomaterial to go up and create rotating cell. The complex shape of isotherms pertains to stronger convection which is attributed to greater permeability. Involve of MHD, declines the distortion of isotherms and conduction becomes stronger in greater Ha. Rise of Ha leads to decrease in Ψ about 60% when Da = 100. Ψ augments about 100% with augment of Da when Ha = 0. Rise of Ha provides reduction in Nu about 11.48% and 9.37% when Da = 100 and 0.01, respectively. Rise of Rd offers 106.6% augmentation in Nu when Ha = 0. When Ha = 20 and Da = 100, rise of Ra leads to 99% augmentation in Nu.

Modeling and simulation of material distribution in the sequential co-injection molding process

Abstract In co-injection molding, the properties and distribution of polymers will affect the application of products. The focus of this work is to investigate the effect of molding parameters on the skin/core material distribution based on three-dimensional (3-D) flow and heat transfer model for the sequential co-injection molding process, and the flow behaviors and material distributions of skin and core melts inside a slightly complex cavity (dog-bone shaped cavity) are predicted numerically. The governing equations of fluids in mold are solved by finite volume method and Semi-Implicit Method for Pressure Linked Equations (SIMPLE) algorithm on collocated meshes, and the domain extension technique is employed in numerical method for this cavity to assure that the numerical algorithm is implemented successfully. The level set transport equation which is used to trace the free surfaces in co-injection molding is discretized and solved by the 5th-order Weighted Essentially Non-Oscillatory (WENO) scheme in space and 3rd-order Total Variation Diminishing Runger-Kutta (TVD-R-K) scheme in time respectively. Numerical simulations are conducted under various volume fraction of core melt, skin and core melt temperatures, skin and core melt flow rates. The predicted results of material distribution in length, width and thickness directions are in close agreement with the experimental results, which indicate that volume fraction of core melt, core melt temperature and core melt flow rate are principal factors that have a significant influence on material distribution. Numerical results demonstrate the effectiveness of the 3-D model and the corresponding numerical methods in this work, which can be used to predict the melt flow behaviors and material distribution in the process of sequential co-injection molding.

Processing behavior and surface quality control of the engine fuel nozzle precision machining by AFM containing magnetic particles

As a flexible processing technology, the abrasive flow machining (AFM) technology can effectively finish the complex cavities and inner channels surface. In order to improve the inner surface quality of the engine fuel nozzle, optimize the ejection quality and atomization performance of the nozzle, and realize the precision machining surface of the nozzle, this paper explores the precision machining behavior and surface quality control of the nozzle by AFM containing magnetic particles through theoretical analysis, numerical simulation, and experimental research. After machining, the Ra value of inner surface roughness of the nozzle bore area was significantly improved, from the initial 0.336 μm to 0.065 μm. Based on the experimental statistical analysis, the significant factors affecting AFM were established, the optimal process combination of AFM was established, and the prediction of AFM on the inner surface of the nozzle was realized. Then, the quantitative cutting of nozzle and the quality control of AFM are realized.

Innovation Strategy of 3D Printing in Industrial Design Based on Vision Sensor

3D printing is becoming increasingly integrated across all disciplines affecting traditional manufacturing. Traditional subtractive and isomaterial processing techniques make it difficult to process and manufacture complex structures such as spatial surfaces and complex cavities. Traditional processing and manufacturing processes are complex. Cumbersome clamps are also a drawback of traditional machining. Compared to traditional processing and manufacturing, 3D printing has significant advantages in manufacturing processes and manufacturing complex structures. Based on this, this paper studies the application of visual sensor 3D printing technology in industrial design and further studies the innovative free design methods under the implementation of 3D printing to provide a design basis for solving industrial product processing troubles and complex structures. This paper first provides a theoretical analysis of the combination of 3D printing of vision sensors and innovative design of industrial products. Next, take two classic industrial parts, a mechanical hydraulic valve block, and a crankshaft, as an example, and adopt an innovative and free design method to get an optimized pipeline of hydraulic valve blocks. The crankshaft molding structure integrated with the structure of the lightweight block demonstrates the superiority of 3D printing technology over the innovative design and manufacture of industrial products. Experiments have proved that the molding direction 1 consumes the least time and consumables (5 h 3 min, 24.44 m), but the inner channel is a blind hole, and it is difficult to remove the support after processing. The molding direction 2 consumes a little more consumable but not too much, but the channel supports are all easy to remove, and molding direction 3 has no advantage in all aspects. Research on industrial design innovation strategy of vision sensor 3D printing technology not only leads to the realization of vision sensor 3D printing technology and its equipment. It also provides a specific reference for the green and intelligent development of the future high‐end equipment manufacturing industry.

Poly(methyl methacrylate) bone cement, its rise, growth, downfall and future

AbstractPoly(methyl methacrylate) (PMMA)‐based bone cements (BCs) can be defined as a family of materials that consist of powder and liquid phases which after mixing form a plastic paste that can self‐set once implanted in the human body. PMMA‐based BCs are easily molded and adapted to complex bone cavities or used in orthodontic applications to restore dental damage. The main advantages of the use of cement are the excellent primary fixation between bone and implant and, therefore, the faster recovery of the patient. Despite the initial success rate of implant fixation with BCs, they have some disadvantages such as local tissue damage due to exothermic polymerization reactions, mechanical mismatch between native bone and cement, lack of bone regeneration and bioactivity and poor mechanical properties which may cause the failure of the BCs. BCs are still considered as a top option for bone repair. Due to the disadvantages highlighted, research has focused on alternative materials used with PMMA‐based BCs. This review aims to critically review the BCs and emerging materials used in combination with PMMA‐based BCs. These materials include titania, apatite–wollastonite (A‐W), glass ceramic (GC) and hydroxyapatite (HA). The review discusses the properties of these materials and their pathway to clinical study. Among the various kinds of reinforcement, HA has been extensively used. So, in this review, we compare the effects of HA as reinforcement in PMMA‐based BCs. Upcoming study of PMMA‐based BCs should concentrate on trialing combinations of these reinforcing agents as this might improve beneficial characteristics. © 2020 Society of Industrial Chemistry

Multi-variable optimization in die-sinking EDM process of AISI420 stainless steel

ABSTRACT Die-Sink Electric Discharge Machining (DS-EDM) is a preferred advanced method, used to produce the complex geometry, cavities, die, and mold facing difficult in cutting the materials. In the current research work, machining of AISI420 stainless steel with copper electrode has been performed. Gap voltage (V), Pulse current (A), and Pulse on time (T) are considered as machine control variables (MCV) and material removal rate (MRR) and electrode wear rate (EWR) as measured machining performance. Experiments have been designed with the assistance of the Taguchi technique and further, Taguchi-Grey Relational Analysis (T-GRA) is executed to optimize the MCV. Parametric analysis is carried out to observe the implications of MCV on the measured machining performance. After interpretation the observations, it has been analyzed that the factors A, V, and T influenced 63.71%, 13.26%, and 10.88%, respectively, on the optimal explication. The fittest method positions have been confirmed by conducting a validation test. It has been explicitly proved that multiple performance characteristics in the DS-EDM method have been considerably enhanced by the T-GRA technique. The rise in grey relational grade is 0.086 by using the T-GRA technique.

Improved catalytic performance of CrOx catalysts supported on foamed Sn-modified alumina for propane dehydrogenation

To better understand influences of surface properties of supports on distributed Cr active sites of Cr-based catalysts with high Cr loading, foamed alumina modified by Sn was prepared to support CrO x catalysts for propane dehydrogenation. N 2 adsorption-desorption, TEM, XRD, FTIR, UV–vis, Raman, XPS, NH 3 -TPD, Py-IR and H 2 -TPR were carried out to elucidate catalyst structures. The foamable alumina is formed by using soft template, and tin added in preparing process changes micro-micelle formation to generate more complex cavity structure. The Sn doped into alumina framework and dispersed on support surface changes the surface properties, such as surface hydroxyl group and isoelectric point, promoting the formation of more active polymeric chromate on the surface, thus the CrO x supported on modified alumina presents high activity of propane dehydrogenation and good catalyst stability, comparing with unmodified CrO x /alumina catalyst. The added Sn obviously inhibits the formation of coke deposition due to decreased strong acid sites, Cr sites density and Cr 3+ content on the surface of the catalysts. • Foamed alumina modified by tin is prepared for supporting CrO x catalysts. • The adding tin increases the pore size and develops more complex cavity structure. • Doped and dispersed tin on surface change interaction between Cr and support. • Propane dehydrogenation performance is enhanced by using modified alumina as support. • Tin obviously inhibits formation of coke and increases catalyst stability.

Distribution model of the surface roughness in magnetorheological jet polishing

Magnetorheological jet polishing (MJP) plays an important role in polishing complex cavities and special optical elements with high precision. However, the roughness distribution function that describes the variation with polishing time of the roughness value of every area in the polishing area has not been studied deeply. In this paper, the influence of the roughness distribution on the removal function of MJP in optics (with a roughness of less than 10 nm) and its evolution model in the spatial and time domains are studied. With the increase of polishing time, the surface roughness of the central area linearly increases, forming surface defects, such as pits. The roughness of the polishing area exhibits a limited growth trend. Verification experiments are carried out on BK7 glass. The results of the roughness distribution on the removal function prove the correctness of the model. The model laid a foundation; therefore, it has important guidance and reference value for the application to the whole aperture polishing.

Recent Patents on Micro-EDM Milling

Background: Micro-Electrical Discharge Machining (EDM) milling is widely used in the processing of complex cavities and micro-three-dimensional structures, which is a more effective processing method for micro-precision parts. Thus, more attention has been paid on the micro-EDM milling. Objective : To meet the increasing requirement of machining quality and machining efficiency of micro- EDM milling, the processing devices and processing methods of micro-EDM milling are being improved continuously. Methods: This paper reviews various current representative patents related to the processing devices and processing methods of micro-EDM milling. Results: Through summarizing a large number of patents about processing devices and processing methods of micro-EDM milling, the main problems of current development, such as the strategy of electrode wear compensation and the development trends of processing devices and processing methods of micro-EDM milling are discussed. Conclusion: The optimization of processing devices and processing methods of micro-EDM milling are conducive to solving the problems of processing efficiency and quality. More relevant patents will be invented in the future.