Characterization of shear stress at the tool‐part interface during autoclave processing of prepreg composites

In this article, shear stress between an aluminum tool and a carbon fiber‐epoxy prepreg is characterized during cure using polymeric release agent and release film at the tool‐part interface. The effects of surface roughness, release materials, pull‐out speed, temperature, and normal force (autoclave pressure) on the shear stress are investigated using a customized friction rig. Results show that the interfacial shear stress decreases as the temperature increases and it increases as the normal force increases when using either the release film or the release agent. Additionally, changes in surface roughness from 1.35 to 0.18 μm decrease the shear stress 10–27% while the use of release agent shows a decrease between 23% and 51% in the shear stress. Furthermore, strong adhesion between the tool and the part is observed when using release agent and pull‐out speeds of 0.05 mm/min (static/dynamic friction ratio of 5.29 ± 0.19). Using the experimental data, a mathematical approach based on the Coulomb's friction model is proposed to predict the friction force at the tool‐part interface. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Ausgleich der Volatilität der Erneuerbaren Energien mittels Wärmespeichern auf Salzbasis

To compensate for the volatility of renewable energies, solutions beyond fossil reserve power plants are needed. One approach is salt-based heat storage with phase change materials (PCM). In order to achieve economic efficiency, ambitious targets are required. A sensible and latent heat storage system for the temperature range around 400 °C based on salts and thermal oils with high development potential is presented.     

Numerical and experimental investigations of the dynamic response of bonded beams with a single-lap joint

The need to design lightweight structures and the increased use of lightweight materials in industrial fields, have led to wide use of adhesively bonding in recent years. In the design of mechanical systems, which consist of adhesively bonded joints, for minimum vibration response, a specific knowledge of the damping capacity of the component materials and joints is important. It is believed that adhesively bonded joints act to augment the system damping capacity in view of the increasing use of viscoelastic materials in their design. The aim of this paper is to provide an efficient numerical technique for the prediction of the dynamic response of bonded beams with a single-lap joint and to validate the predictions via experimental tests. The finite element method was used to predict the natural frequencies, mode shapes and frequency response functions of the beams. The dynamic test software and the data acquisition hardware were used in the experimental measurement of the dynamic response of the joints. The frequency response functions of the joints of different adherend widths and of different adhesive layer thickness were measured. The frequency response functions and mode shapes predicted using the finite element method were compared with those measured experimentally. The coordination of the numerical and experimental techniques makes it possible to find an efficient tool for studying the dynamic response of bonded beams with a single-lap joint.     

In-situ monitoring of the resin transfer molding impregnation and cure process

Resin transfer molding (RTM) of advanced fiber architecture materials promises to be a cost effective process for obtaining composite parts with exceptional strength. However there are a larger number of material processing parameters that must be observed, known, and/or controlled during the resin transfer molding process. These include the viscosity both during impregnation and cure. In-situ sensors which can observe these processing properties within the RTM tool during the fabrication process are essential. This paper will discuss recent work on the use of frequency dependent electromagnetic sensing (FDMS) techniques to monitor these properties in the RTM tool. Our objective is to use these sensing techniques to address problems of RTM scaleup for large complex parts and to develop a closed loop, intelligent, sensor controlled RTM fabrication process.     

Production of unfired ceramic materials by strengthening with chemical activation of the contact bonds

Conclusions New principles of a process for making unfired ceramic materials using strengthening by chemical activation of contact bonds (CACB ceramic) have been formulated. Additional strengthening of ceramic materials is achieved with virtually unchanged porosity, i.e., without filling the pore space and clearly with the retention of the original geometrical system of contact bonds.The mechanical properties of the SCACB ceramic are fully comparable with the properties of the fired materials. By comparison with other unfired ceramics or refractory materials obtained using various binders or bondings (phosphate, silicoorganic, water glass, alumina, cement, resins, etc.), the structure of the SCACB ceramic which on the whole determines the properties of the ceramic, is outstanding in its low concentration or virtual absence of additional components.It would be sensible to carry out some studies to give a fuller explanation of the strengthening process and also how to introduce into production unfired materials of this type.Translated from Ogneupory, No. 4, pp. 50–56, April, 1981.     

304不锈钢管焊缝区碱性腐蚀的电化学噪声检测

利用电化学电位噪声检测304不锈钢管焊缝区在50%NaOH碱液沸腾温度下腐蚀过程的电位噪声谱,观测相应的腐蚀形貌,分析电化学噪声谱特征参数。结果表明：实验过程中焊缝处腐蚀电位呈下降趋势;发生局部腐蚀裂纹时,电位噪声时域谱振幅较大,出现暂态峰;经快速傅里叶变换（FFT）后的功率密度（PSD）谱出现高频白噪声水平,PSD谱高频线性部分的斜率K>-20 dB·dec^-1。测试室温碱液中304不锈钢管焊缝处的电化学噪声表明,不同腐蚀状态的焊缝试样腐蚀电位及噪声时域谱特征不同,可利用K值定性判定是否发生局部腐蚀,为现场检测奠定基础。     

Solid-state NMR as a probe of porous catalysts and catalytic processes

The power of solid-state NMR for the interrogation of porous catalytic materials is illustrated using three examples. First, for the investigation of catalytic processes occurring within the confines of a microporous catalyst NMR is shown to reveal both the details of shape-selectivity and the nature of internal surface species. Second, NMR is shown to be a powerful short-range tool to reveal precise structural information on highly disordered microporous titanosilicates. Despite long-range disorder the short-range order is maintained and can be easily studied. Finally, the same utility of probing short-range chemical phenomena is shown to be crucial for the investigation of novel-ordered-amorphous-mesoporous materials known generically as M41S. This class of material is currently one of the most important with potential catalytic application.     

Unsteady Mixing Characteristics in a Vessel with Forward‐Reverse Rotating Impeller

Usually, mixing is carried out in a vessel with four baffles and a single impeller. In some applications, however, the use of a baffled vessel is not recommended. One of the stirring methods used instead is unsteady agitation with forward‐reverse rotating impellers. The aim of this work was to characterize the agitation characteristics in a baffled and an unbaffled vessel with a turbine impeller. Mixing time and mixing power were evaluated in relation to the presence of baffles and the frequency of forward‐reverse rotation. It was found that the frequency of oscillation does not affect either the mixing time and mixing power values or the drag and added mass coefficients. Power requirements and mixing time were higher compared to the steady mixing conditions in a baffled vessel. The results showed that it is not recommended to use baffles because they have no influence on unsteady mixing.     

A rotating sphere viscometer

The use of a rotating sphere viscometer for the measurement of parameters in the flow curves of inelastic as well as viscoelastic liquids is examined. An experimental investigation of the primary flow around a sphere rotating in Newtonian and viscoelastic liquids is carried out by using a new “three-dimensional particle technique.” Currently available theoretical analyses of rotation of a sphere in viscoelastic liquids are shown to be inadequate to describe the experimental primary velocity distribution data. Theoretical results for the primary distribution derived on the basis of a creeping flow of a power law liquid are found to describe the experimental data well. This distribution is then used to derive torque–angular velocity relationships, which are then confirmed experimentally for both inelastic and viscoelastic liquids. The results of this work justify the use of a rotating sphere viscometer as a useful tool for the measurement of parameters of flow curves of inelastic and viscoelastic liquids.     

Application of High-Power Ultrasound for Dehydration of Vegetables: Processes and Devices

High-intensity ultrasound is a tool with a great potential for vegetable dehydration. Airborne ultrasonic waves have been used for drying materials in combination with hot air systems to obtain adequate drying rates at lower temperatures. Nevertheless, the extension of this technique has been limited because of practical difficulties in the efficient generation of high-intensity ultrasound in air. The implementation of a new technology of plate-transducer power ultrasonic generators has opened up new possibilities in this area. This article reviews the development and testing of an ultrasonic technology for vegetable dehydration based on the application of the new power ultrasound generators. Two experimental procedures have been carried out by airborne ultrasound and ultrasonic vibration in direct contact with the vegetable.     

Application of High-Power Ultrasound for Dehydration of Vegetables: Processes and Devices

High-intensity ultrasound is a tool with a great potential for vegetable dehydration. Airborne ultrasonic waves have been used for drying materials in combination with hot air systems to obtain adequate drying rates at lower temperatures. Nevertheless, the extension of this technique has been limited because of practical difficulties in the efficient generation of high-intensity ultrasound in air. The implementation of a new technology of plate-transducer power ultrasonic generators has opened up new possibilities in this area. This article reviews the development and testing of an ultrasonic technology for vegetable dehydration based on the application of the new power ultrasound generators. Two experimental procedures have been carried out by airborne ultrasound and ultrasonic vibration in direct contact with the vegetable.     

New emissions targeting strategy for site utility of process industries

A new procedure for environmental targeting of co-generation system is presented. The proposed method is based on the concepts of pinch technology for total site targeting of fuel, power, steam, environmental impacts and total annualized cost with considering emissions taxes. This approach provides a consistent, general procedure for determining mass flow rates and efficiencies of the applied turbines. This algorithm utilizes the relationship of entropy with enthalpy and isentropic efficiency. Also, the life cycle assessment (LCA) as a well-known tool for analyzing environmental impacts on a wide perspective with reference to a product system and the related environmental and economic impacts have been applied. In this regard, a damage-oriented impact analysis method based on Eco-indicator 99 and footprints analysis was considered. In addition, the present work demonstrates the effect of including both sensible and latent heating of steam in the extended Site Utility Grand Composite Curve (ESUGCC). It is shown that including sensible heating allows for better thermal matching between the processes. Furthermore, the other representation YSUGCC as the other form of Site Utility Grand Composite has been proposed. Two case studies were used to illustrate the usefulness of the new environmental targeting method.     

Quantifying alignment in carbon nanotube yarns and similar two-dimensional anisotropic systems

The uniaxial orientational order in a macromolecular system is usually specified using the Hermans factor which is equivalent to the second moment of the system's orientation distribution function (ODF) expanded in terms of Legendre polynomials. In this work, we show that for aligned materials that are two-dimensional (2D) or have a measurable 2D intensity distribution, such as carbon nanotube (CNT) textiles, the Hermans factor is not appropriate. The ODF must be expanded in terms of Chebyshev polynomials and therefore, its second moment is a better measure of orientation in 2D. We also demonstrate that both orientation parameters (Hermans in three dimensional (3D) and Chebyshev in 2D) depend not only on the respective full-width-at-half-maximum of the peaks in the ODF but also on the shape of the fitted functions. Most importantly, we demonstrate a method to rapidly estimate the Chebyshev orientation parameter from a sample's 2D Fourier power spectrum, using an analysis program written in Python which is available for open access. As validation examples, we use digital photographs of dry spaghetti as well as scanning electron microscopy images of direct-spun carbon nanotube fibers, proving the technique's applicability to a wide variety of fibers and images.     

Deep precision machining of SiC ceramics by picosecond laser ablation

Silicon carbide (SiC) ceramic is becoming widely used in multiple industrial applications, owing to its exceptional high-temperature properties. Yet it is still a challenge to machine SiC using traditional means without causing damage due to its high hardness and brittleness. In this study, a subtractive manufacturing technique based on the use of a fiber picosecond laser was employed to remove material from the reaction bonded SiC surface or create micro-patterns with the minimum damage to the surface, maximum surface quality and precision. Multiple laser processing parameters were investigated with the purpose of obtaining deep high-quality cuts with the minimum surface roughness and the minimum amount of the re-deposited material. The heat affected zone was analyzed by grazing angle X-ray diffractometry, cross-sectional scanning electron microscopy, energy dispersive and micro Raman spectroscopy techniques. The cut shape, depth, surface roughness as well as the kerf width and re-deposition height were assessed using a 3D laser scanning microscopy. The optimum values were established for the focal position, the laser power, linear speed, wobble frequency, wobble pattern, and number of passes. This study also identified the processing parameters for shallow and deep high-precision SiC cutting at a material removal rate of ～2 mm³/min. The work demonstrated that the developed laser machining process is an efficient subtractive manufacturing tool that can be integrated into the automated precision cutting systems for machining hard ceramic materials such as SiC and alumina.     

FE fracture analysis,using the integral J and tearing energy T parameters,of a natural rubber NR

Fracture of rubber-like materials under quasi-static loadings is of a great interest since the use of such materials has been widespread in many industrial applications. Thus, the aim of this work is to study the fracture behavior of a carbon-black filled natural rubber using the finite elements method. In the first step, we have identified a hyperelastic potential of the virgin material, using equibiaxial and pure shear tests, for the Finite Element (FE) calculations. In the second step, two numerical models with pre-cracked specimens, using Ansys software, are developed. The investigated parameters, based upon energy concepts, are carried out on Single Edge Notched in Tension and Pure Shear specimens. Finally, the evolution and the comparison of obtained results will be examined as a function of the integral J, of Rice, and the tearing energy T, of Rivlin and Thomas.     

Electrochemical performance of NiFe2O4 nanostructures incorporating activated carbon as an efficient electrode material

The quest for cost-efficient electro-active materials exhibiting high specific capacitance is currently a key focus in energy-related research. Owing to their high capacitance values, metal oxides (MOs) are preferably being utilized for energy storage applications as electrode materials in supercapacitors. However, the electrochemical performance of MOs is hindered due to less specific surface area and high tendency towards aggregation. Therefore, tuning in electrochemical activity of MOs is essential. In this framework, NiFe₂O₄ was prepared using a facile and cost-effective citrate-gel followed by auto-ignition method, and was incorporated with activated carbon contents to tune the electrochemical performance. Formation of inverse spinel structure of NFO and its stability throughout the compositions was examined using X-ray diffraction analysis. Well-dispersed, spherical and porous morphological features were visualized using a field emission scanning electron microscope. The electrochemical analysis was conducted using CH instruments 660 E via freshly prepared 4 M KOH solution. Cyclic voltammetry was carried out at constant potential window of 0.25–0.65 V and different scan rates (0.009–0.08 Vs^-1). The pseudo-capacitive behavior was perceived from occurrences of oxidation/reduction peaks. In addition, charge/discharge curves revealed cyclic stability over long range cycles. Specific capacitance, discharge time, energy and power density values were also measured for all the compositions and NFO with 1% activated carbon was found to be the most suitable candidate for use as electrode materials in the present work.     

A Box–Behnken Design-Based Model for Predicting Power Performance in Microbial Fuel Cells Using Wastewater

Although modeling is regarded as a useful tool to understand the performance of microbial fuel cells (MFCs), the number of MFC models remains very low compared with the number of experimental works available in the literature. Moreover, there are very few MFC modeling attempts dealing with the use of wastewater as fuel in these devices, which is essential for the practical implementation of MFCs since the potential of this technology lies in the two-fold benefit of wastewater treatment and bioenergy generation. In this work, a four-factor three-level Box–Behnken design was developed to model the electrochemical power generation in two-chamber MFCs using wastewater as fuel. The optimum values of temperature, external resistance, feed concentration and anodic pH that maximized power output were investigated. Optimum conditions were found at T = 35°C and R = 1 kΩ, corresponding to a maximum power density of 0.88 W·m^?3, while feed concentration and pH did not show statistical significance in the ranges studied. Thus, a Box–Behnken design-based model as empirical approach could provide an effective tool for the optimization study of MFC systems.     

Effect of process parameters on the energy requirement in ultrasonical treatment of waste sludge

Mechanical treatment methods are used as pre-treatment methods in order to enhance the efficiency of conventional sludge treatment processes and the sludge becomes more suitable for its complete treatment. The ultrasound is an alternative method among other methods, but because of its high energy requirement it should be optimized before utilization. This work gives the optimized parameters such as sonication time, sonication power (these parameters are the two factors which play part for energy calculations), type of sludge, cooling requirements and solid content in the sludge solution. Even if the previous researchers prefer to use the energy (specific energy usually), we have found out that both the sonication time and the sonication power have individual importance. For municipal sludge the main conclusion can be summarized as: “high power-short retention time” is more effective than “low power-long retention time”. As this phenomenon may alter from sludge to sludge, various combinations of power and retention time should be tried while keeping the volume small and the concentration below a certain level. The process should be performed at moderate temperatures and the efficiency increases if the sludge is as homogeneous as possible.     

混合供电系统中退役电池的模块化储能操作优化

将退役的动力电池用于混合供电系统可有效地降低投资成本，而针对退役电池储能系统的操作优化则可降低混合供电系统的操作费用，并提升混合供电系统的运行收益。以多个初始容量存在差异的电池组构成的退役电池储能系统为对象，在综合考虑退役电池容量衰退特性和电池组初始状态差异的基础上，构建了以年总费用最小为目标的混合供电系统操作优化模型，并将该方法用于一个由光伏发电和储能电池系统构成的混合供电系统的操作优化中。研究表明：储能电池系统中多组退役电池初始状态的差异，使得各电池组在操作过程中的充放电顺序和频率存在显著差异；储能电池系统的操作优化可有效缓解电池容量衰退，与固定比例调度流程相比，该储能电池系统的年总费用更低。     

Contactless field enhanced sintering (cFES): A spot glaze repair technology (SGRT)

We report the successful development of a novel Contactless Field Enhanced Sintering (cFES) process for sanitaryware repair: “Spot Glaze Repair Technology (SGRT)”. A hot glaze melt system has been applied on sanitaryware bodies without the use of a kiln. The faults were re-glazed using a mixture of 50 vol% original glaze and 50 vol% low temperature glaze developed in house. Surface faults with diameters of 1–2 mm were successfully repaired using a custom built cFES rig and special low temperature glaze, without any sign of surface cracking. Using a combination of a hot flame and a low frequency electric field, the repairs required just 3 s. The flame provided the thermal energy required to reduce the dielectric breakdown voltage of the surrounding air, leading to the generation of plasma under applied potential. This setup is simple enough to be industrially scaled, and does not require expensive electrode materials.