Mechanical Behavior Of Materials

The Brazilian Test is the most used test to determine the indirect tensile strength for brittle materials like concrete. It has been observed that the success of the test depends on the cracks initiation point position and therefore the arch loading angle; a crack appears in the center of the disk when the test is valid. To this effect, using Fast Lagrangian of Continua code FLAC2D; numerical analyses were performed to study the impact of the arch loading angle on the initial crack’s position in a 70 mm diameter Brazilian disk of concrete and mortar under loading arch 2α which varies from 5–45°. The distribution of stresses and the tensile strength at the center of the Brazilian disk obtained numerically was closely similar to analytical and experimental existing solutions. The results showed that to obtain a meaningful and validated test with the most accurate indirect tensile strength, it is recommended to take a loading arch 2α ≥ 20° for the concrete and 2α ≥ 10° for the mortar.

The decision on sequencing of operations, tool travel and machining time calculations is done in microplanning. After a set of processes has been selected for all the features of part, the sequencing task begins by searching and analysing relationship between features. This is done by rule to detect geometrical interactions and the appropriate precedence relationship in knowledge base. For deciding sequence of operations precedence relationship among the different operations is developed using decision rules. CNC program is generated based on the process plan of a given component. The generated CNC program is then validated by simulation software before giving it to CNC machine.

Composite microstructures of ferrite and 30 to 76% martensite have been obtained by intermediate Quenching (IQ) heat treatment of a boron-vanadium micro-alloyed steel. Welding parameters were established for shielded metal are welding (SMAW) using bead on plate experiments. Test coupons were prepared as per AWS D1.1 (Structural welding code). The microstructural studies were correlated with microhardness, tensile, bend, impact and fracture toughness values. A Scanning Electron Microscope analysis of the broken welded tensile specimens and ½ CT specimens were carried out. The results indicate that as the percentage of martensite content increases in the welded specimens, there has been increase in the ultimate tensile strength, yield strength, percentage of elongation, impact and fracture toughness values. The fractographic observation of welded tensile specimens indicates predominantly cleavage to predominantly dimpled fracture surface. Where as, ½ CT welded specimens indicate a cle...

In the Piezoelectric behaviour refers that conversion of mechanical impact to electrical power, or electrical impact to mechanical changing. The presence of piezoelectricity has been scientifically discovered in 1880 as a result of the work of Jacques and Pierre Curie brothers. They found that some naturally occurring crystals such as quartz and Rochelle salt produced a surface charge when subject to a compressive load. Piezoelectric energy has a wide range of application areas by providing sustainable energy. One of these areas is the textile industry which has been moving towards higher value added production in recent years. Piezoelectric materials are divided into four groups: piezoelectric crystals (quartz, rochelle salt, tourmaline, topaz etc.), piezoelectric ceramics (lead zirconate titanate, barium titanate, etc.), piezoelectric polymers (PVDF, odd numbered nylons etc.) and piezoelectric composites. Because of different characteristics of these piezoelectric materials, each of them is preferred with regard to projected purpose. This study reviews piezoelectric polymers and highlights its properties such as elasticity, lightness, strength, etc. where the desired characteristics are needed in textile products. These features make easier to use of piezoelectric polymers in smart textile applications. They are generally used to energize from human movements or different regions of the human body. Power generation can be achieved by various textile structures such as fibre, yarn, weaving and knitting. In this review some polymers, for example polyvinylidene difluoride (PVDF), Polyamide 11 (PA11), Polypropylene (PP), are especially chosen to give more detail on their piezoelectric characteristics which are considered in the textile applications.

Ancient stone masonry is a composite structure, mainly comprised of stone elements. During restoration, stone elements are sometimes found to present serious fragmentation, and their structural continuity must be re-established. In such cases, an adhesive material can be applied to reattach the detached fragment to its original position, with or without the use of pins or anchors, according to the size of the fragment and its position. However, many considerations must be taken into account regarding compatibility with the ancient material and the performance and longevity of the intervention. In the current study, a series of pastes are designed for the reattachment of stone fragments, with and without the concurrent use of titanium pins, aiming to re-establish the continuity of the porous stone elements of the Acropolis circuit wall. The designed pastes are examined in terms of physical and mechanical characteristics and assessed in relation to their compatibility with the original stone material, while their effectiveness as adhesive and/or anchoring materials is evaluated through a real-time and-scale pilot application on site at the Acropolis monument work site using fragments of the original ancient stone material. The natural lime-metakaolin paste presents the optimum results as an adhesive and anchoring material.

Worldwide Increasing demand for sustainable energy calls for flexible solutions depending on the local conditions. Even wind power and solar energy capacity are expanding all over the world high efficient fossil fuel power plant will continue to be the basic concept in development countries where the need for new energy is large and coal is cheap. The potentials for improved coal fired plants are revealed. In the western countries especially Europe the massive increase in renewable energy is challenging the future energy system and high degree of flexibility may only be establish in the long run using gas turbines as back up for the intermitting out put from wind and solar generation.

As propriedades da madeira são influenciadas pela do comprimento e do diâmetro madeira permitiria seu uso mais adequado e racional, pois a destinação de peças em função das necessidades de rigidez exigida. verificar se o ensaio de ultrassom retiradas de diferentes posições ao longo das toras. longitudinal, de cada árvore foram retiradas três toras identificadas como tora da base, tora de retirada da peça o desdobro quais foram denominadas de A (vigas m próximas da medula). Após o processo de realizados os ensaios de ultrassom e de flexão, os quais permitiram o cálculo do de rigidez (C LL ), do módulo de elasticidade verificar que o uso de peças de dimensões estruturais dificulta a metodologia, pois não permite, em alguns casos, retirar as vigas integralmente em uma mesma região. Apesar do problema metodológico foi possível verificar que o uso do coeficiente de rigidez, provenie do ensaio de ultrassom, permite avaliar as variações de propriedades nas diferentes posições de retirada da peça ao longo do tronco, tanto longitudinal quanto radial Palavras-chave: Módulo de elasticidade, coeficiente de rigidez, densidade.

This research presents an experimental study of analysis of stress strain state SSS of X-60 pipe weld joints employing magnetic anisotropy indicator of mechanical stresses Stress Vision (IMS) using of "before and after" comparison approach taking readings on pipe base metal, weld area and heat affected zone (HAZ) before and after hydrotest. Test results were compared with X-ray testing results for welded joints and with metallographic testing. Test results demonstrate the relevance of applied test conditions and redistribution of residual stresses. A new equation was established for estimating the residual (technological) and operating stresses in other pipelines with a tolerance of 15% in the field of elastic deformation (up to the yield point), according to Hooke law.

For steel structures to be installed in the Arctic region, the risk of brittle fracture represents a primary concern due to the ductile to brittle usually transition taking place at sub-zero temperatures. Therefore, the present investigation addressed the heat affected zone and weld metal toughness of two extra low carbon steels of 420 MPa yield strength grade, supplied in 20 and 50 mm thickness. The testing included tensile, Charpy V and CTOD. The results obtained showed that the Charpy V toughness was relatively high at -60°C, but that some low values may occur for the fusion line position. The fracture toughness at -60°C, based on SENB05 (a/t=0.5) geometry, appeared to be low for both weld metal and fusion line positions. More specific measures may be taken into account in welding procedure qualification of the current steels, such as using lower crack length (e.g., a/t=0.2), tension instead of bending (SENT testing) or a full engineering critical assessment.

Knowledge about the mechanical properties of lower-limb prosthetic sockets fabricated with resin infusion lamination and composite materials is limited. Therefore, sockets can be subject to mechanical failure and overdimensioning, both of which can have severe consequences for patients. For this reason, an exploratory study was conducted to analyze the effect of stratigraphy (layup and fibers), matrix (resin) and mechanical connection (socket distal adapter) on socket static strength, with the objectives of: 1) implementing a mechanical testing system for lower-limb prosthetic sockets based on ISO 10328:2016 and provide the mechanical design of the loading plates, 2) apply the testing system to a series of laminated sockets, and 3) for each type of distal adapter, identify the combinations of stratigraphy and matrix with acceptable strength and minimum weight. Twenty-three laminated sockets were produced and tested. Sixteen met the required strength, with ten exhibiting an excessive weight. Among the remaining six, four combinations of stratigraphy and resin were identified as best option, as they all overcame ISO 10328 P6 loading level and weighted less than 600 g. The selected stratigraphies had limited or absent amount of Perlon stockinettes, which seems to increase weight without enhancing the mechanical strength. Sockets based on Ossur MSS braids and connector show the best compromise between strength and weight when the amount of carbon braids is halved.

The purpose of this study was to investigate the effect of using ultrasound waves at 24 kHz on surface topography of three stainless steel coupons during soil film removal. Atomic force microscopy (AFM), a major discovery as a non-destructive analysis tool was used in the analysis of surface topography and morphology in non-contact (tapping) mode. Coupons before and after treatment with ultrasound waves (after 9 adhesion-cleaning cycles) were used and quantified in the study. Quantitative measurements according to topographic and morphological parameters: average roughness (Ra), root-mean-square profile height (Rq), maximum peak-to-valley height(Rmax), surface skewness(Rskw) and surface kurtosis (Rkur) were studied on (7x5cm 2 ) coupons for AFM scanning area of 25x25m 2 . The results revealed that normal surfaces (surfaces not welded) had pits/valleys which were good lubrication whilst welding (heat treatment) processes modified the surface by introducing peaks resulting in rougher...

An attempt has been made in this research work to probe the sequel of initial grain size of the steel and its impact on tensile strength. Low carbon-manganese steel in respect of initial grain size and final grain size has been deliberately investigated. Two steel samples having similar chemical composition were austenized at temperatures of 925°C and 1100°C respectively with same holding time in the box furnace followed by quenching. Initial microstructure at 925°C and 1100°C were calculated as 62.34 um and 124.4 um respectively. Just after heat treatment both the samples were prepared for tensile testing as per standard. UT machine was used with a cross head speed of 0.5 mm/min. The raw data obtained from the UT were analyzed stress and strain equations and stress-strain diagram was plotted by using origin software. It was concluded that the sample with initial grain size of 62.34 um showed high elongation curve and large plastic range. The large grain sized samples having initial...

Microstructured optical fibers (MOF) can be seen as next generation fiber of significance in advancing the compact optics because of its excellent compatibility in integrated optics. However, the degradation of their physicochemical properties limits their efficiency and lifetime. Atmospheric moisture is responsible for the degradation of amorphous systems especially chalcogenide glasses. In the light of previously reported studies, in order to clarify the aging process continuously evolving in sulfide microstructured optical fiber over time, a detailed investigation of this phenomenon has been conducted. The timedependent transmission and glass chemical deterioration have been studied for As 2 S 3 MOF with regard to their exposure to different atmospheric conditions. Results show a substantial impact of atmospheric moisture through an interaction with the glass network. Significant improvement has been registered by storing the fibers under dry atmosphere.

The efficiency and the stability of As 2 S 3 microstructured optical fibres (MOFs) are limited by the shift of their optical properties that occurs over time due to a naturally induced aging process. Such sensitivity becomes more crucial for long optical path. Among the variety of fibre designs, the MOFs are developed for promising photonics applications such as supercontinuum generation for example. In the present work, we carried out an extensive aging study on As 2 S 3 chalcogenide MOFs in ambient atmosphere. The evolution of the fibre transmission spectrum has been studied with regards to exposure time. The analysis of the transmission line profile was performed in terms of different spectral components Gaussian in shape and the infrared absorption bands have been attributed to the corresponding chemical groups' vibration modes or overtones. The timedependent evolution of fibre attenuation has been studied as well as its longitudinal evolution for a given exposure time. Previous knowledge of extinction coefficient inherent to vibration components allows to predict their corresponding concentration. The content of hydroxyl groups tightly bonded to the glass network of the sulphide MOF core decreases exponentially with distance away from the MOF extremity. The report results show that a deleterious aging effect occurs over the first hours and days of exposure. This have crucial implications for storage and employment techniques and requires holes airproofing technique.

Ni-based superalloy is widely used for high performance components in power generation turbine due to its excellent mechanical properties. However, Ni-based superalloy has low oxidation resistantance. Therefore, surface coating is required to improve oxidation resistance at high temperatures. Al-Si as a coting material was successfully co-deposited on Nibased substrate by pack cementation method at 900 °C for about 4 hours. The oxidation test was carried out at high temperature of 1000 °C for 100 hours. Micro structural characterization and analysis on crystal orientation were perfomed by using Field Emission Scanning Electron Microscope (FE-SEM) and Electron Back Scatter Diffraction (EBSD) technique, respectively. The results showed that the coating layer with a homogenous layer and had a thickness of 53 m consisting of β-NiAl with cubic structure and Ni 2 Al 3 with hexagonal structure. TGO layer was developed after oxidation and had a thickness of about 5 m consisting of α-Al 2 O 3 and spinel NiCr 2 O 4. The phase composition map and crystal orientation acquired by EBSD technique was also discussed both in TGO and coating layers.

Crack growth data obtained from ASTM load shedding method for different R values show some fanning especially for aluminum alloys. It is believed by the authors and it has been shown before that the observed fanning is due to the crack bifurcation occurs in the near threshold region which is a function of intrinsic properties of the alloy. Therefore, validity of the ASTM load shedding test procedure and results is confirmed. However, this position has been argued by some experimentalists who believe the fanning is an artifact of the test procedure and thus the obtained results are invalid. It has been shown that using a special test procedure such as using compressively pre-cracked specimens will eliminate the fanning effect. Since not using the fanned data fit can result in a significantly lower calculated cyclic life, design of a component, particularly for rotorcraft and propeller systems will considerably be impacted and therefore this study is of paramount importance. In this effort both test procedures i.e. ASTM load shedding and the proposed compressive pre-cracking have been used to study the fatigue crack growth behavior of compact tension specimens made of aluminum alloy 2524-T3. Fatigue crack growth paths have been closely observed using SEM machines to investigate the effects of compression pre-cracking on the crack bifurcation behavior. The results of this study will shed a light on resolving the existing argument by better understanding of near threshold fatigue crack growth behavior.

Loading flat coated specimens with tensile forces is a universal method to determine the nature of fracture of hard coatings in maritime applications. Such an approach allows the determination of the shear strength at the interfaces between layers and the cohesive properties. Thus, the authors studied the fracturing processes of plasma-sprayed yttria-stabilized zirconia two-layer coatings under the action of tensile forces. The results revealed cracking characteristics in the outer ceramic layer and delamination of flat metal specimens. An analytical method led to normal stress determination in the coating. It also exhibited shear stresses at the bond coat-substrate interface and the top coat-bond coat interfaces. The results include normal and shear stress distributions before and after fragmentation of the ceramic top layer. Tested substrate, the metal bond coat, and the ceramic top coat exhibit a modulus of elasticity of 196, 142, and 47 GPa, respectively. Engineers could apply t...

Se prepararon compuestos de aluminio reforzados con nanotubos de carbono de pared múltiple (NTCPM) utilizando la técnica de pulvi-metalurgia. Los NTCPM se sintetizaron por deposición química de vapor (DQFV), utilizando C 2 H 2 como gas precursor, Ar como gas de arrastre y Fe-Co / CaCO 3 como catalizador. El polvo de aluminio se mezcló con NTCPM en un dispositivo de molienda de bolas planetaria para diferentes relaciones de peso, de 0% a 2% y diferentes etapas de tiempo en el proceso de mezcla (3 min y 60 min). Los compuestos en polvo se prensaron en caliente, recocidos en atmosfera inerte y analizados usando un microscopio electrónico de barrido de emisión de campo (MEB-EC), difracción de rayos X en polvo y dureza Vickers. Se examinaron un total de 80 muestras para evaluar el efecto de los NTCPM sobre la dureza. Los resultados mostraron un aumento de la dureza para los compuestos de ~ 15% a 24%. Se consideró la desviación estándar de las medidas de dureza para evaluar la dispersión de MWCNT en los compuestos. Se aplicó un ajuste lineal a los datos de dureza para evaluar la influencia de la temperatura en el proceso de consolidación de granos y un análisis de varianza. Los resultados exhibieron una dispersión sustancial de la dureza de 13.13% a 24.57% de error. El análisis de los resultados obtenidos en varias condiciones sugirió condiciones óptimas para un tiempo de mezcla de 3 min y una temperatura de sinterización de 760 ° C.

In this study AISI 304 L type of austenitic stainless steels were welded using 308 L consumable electrodes by the process of Gas Metal Arc Welding (GMAW). The aim of current study is to examine effects of shielding gas compositions on mechanical properties and microstructure of AISI 304 L weldments. A detailed study of gas metal arc welding of AISI 304 L stainless steel was carried out with different shielding gas compositions such as 100% argon, 80% argon + 20% CO2, 50% Argon + 50% argon and 100% CO2. The mechanical properties were determined by performing different tests, viz. Charpy V notch impact test, tensile test, hardness test, bend test. Surface morphology had been analyzed by Scanning Electron Microscope (SEM). The results indicated that the shielding gas compositions have great influence on mechanical properties. Results revealed that increase in amount of CO2 in shielding gas resulted in higher tensile strength and hardness values than the base metal. The study also indic...

Les fluctuations de la température à l'intérieur des bâtiments sont causées soit, par un important apport solaire en période d'été ou bien par une baisse de la température extérieure durant l'hiver. Ces fluctuations peuvent être atténuées par l'emploi de matériaux à changement de phase (MCPs) permettant d'assurer une situation de confort thermique durant tous les mois de l'année. Ce travail est relatif à l'étude du comportement thermique de deux toits multicouches pendant deux périodes différentes : estivale et hivernale. Le 1 er toit est constitué par des matériaux usuels en bâtiment, alors que le second est muni en plus de deux matériaux à changement de phase placés en différentes positions et des épaisseurs variables afin d'optimiser une toiture capable de minimiser l'impact des conditions climatiques annuelles externes. Un modèle numérique unidimensionnel validé analytiquement et expérimentalement, a été développé. Il permet de simuler le comportement de la toiture selon les paramètres de l'étude. L'objectif étant de déterminer la configuration et la disposition relatives des différentes couches de la toiture permettant de générer un confort thermique optimal durant les périodes estivale et hivernale.

We investigate light-induced patterning of a monodomain side-chain liquid crystal elastomer (SC-LCE) doped with light-sensitive azobenzene moiety in the temperature region close to the nematic-paranematic phase transition. We show that a strongly nonlinear relationship between the concentration of the cis isomers of the azomesogens and the refractive index modification of the material, which is characteristic for the phase transition region, results in nonmonotonous time dependence of the diffraction efficiency of a probe beam. From this effect we determine the sensitivity of the nematic transition temperature on the molar fraction of the cis isomers. The relation between the cis isomer molar fraction and nematic order also provides a possibility for recording hidden holograms, which can be made visible by cooling the sample from the paranematic to the nematic phase.

A comparative study of UV-irradiation-induced refractive index modulation in two analogous monodomain nematic side-chain liquid-crystalline elastomer materials is conveyed. In one of them, mesogenic azobenzene derivatives are incorporated as pendant co-monomers, and in the other as crosslinking units. The dependence of the optical diffraction properties on the polarization state of the probe beam reveals that diffraction is predominantly of a bulk origin for both materials. For prolonged UV exposures, the material with pendant azobenzene derivatives exhibits practically constant diffraction properties, while the material with cross-linking azobenzene units shows a profound decrease of diffraction effi ciency with increasing exposure time. The difference is attributed to photoinduced alignment of the azobenzene molecules, which is much stronger in the material with the crosslinking azobenzene units.

The optical mechanism for imprinting one-dimensional grating structures into thin films of a light-sensitive monodomain liquid crystal elastomer is investigated by analyzing the time dependence of optical diffraction properties. The recording kinetics shows an irregular oscillatory behavior, which is most expressed at small grating spacings and at temperatures close to the nematic-isotropic phase transition. The oscillations are attributed to the opto-mechanical response of the film, i.e., to contraction of the film during the recording process. At temperatures far below the nematic-isotropic phase transition, the spontaneous erasure kinetics exhibits exponential relaxation with relaxation time following the Arrhenius activation law. However, at temperatures close to the nematic-isotropic phase transition, the erasure process shows an interesting nonmonotonic behavior that we

Tris(pentafluorophenyl)borane (TPFPB) is a unique Lewis acid that catalyzes the condensation between hydrosilanes (Si-H) and alkoxysilanes (Si-OR), leading to the formation of siloxane bonds (Si-OSi) with the release of hydrocarbon (R-H) as a byproduct—the so-called Piers–Rubinsztajn reaction. The analogous reactions of hydrosilanes with silanols (Si-OH), alcohols (R-OH), ethers (R-OR′) or water in the presence of TPFPB leads to the formation of a siloxane bond, alkoxysilane (Si-OR or Si-OR′) or silanol (Si-OH), respectively. The above processes, often referred to as Piers–Rubinsztajn reactions, provide new synthetic tools for the controlled synthesis of siloxane materials under mild conditions with high yields. The common feature of these reactions is the TPFPB-mediated hydride transfer from silicon to carbon or hydrogen. This review presents a summary of 20 years of research efforts related to this field, with a focus on new synthetic methodologies leading to numerous previously d...

A madeira sempre foi e continua sendo importante material, quer seja para uso na construção civil ou na confecção de móveis; entretanto, o Brasil sempre foi marcado pelo desmatamento indiscriminado e pela falta de preocupação com a preservação e recuperação das espécies nativas. Esta devastação se deve a vários fatores, dentre eles, a falta de preparo técnico da indústria madeireira. Aliado a isto, a falta de conhecimento do material, por parte dos profissionais que se utilizam da madeira, faz com que haja tendência de se utilizar as mesmas espécies até seu total desaparecimento. Neste cenário, surge a perspectiva do uso das espécies de reflorestamento e, com ela, um desafio: conhecer e divulgar suas características e possibilidades de emprego. Neste contexto, a proposta deste trabalho avalia a utilização do ultra-som como método auxiliar na determinação de propriedades mecânicas da madeira, com vistas à classificação; para isto, verificou-se a existência de correlação entre os resu...

TThis paper presents a novel theoretical framework that redefines the fundamental concepts of mass, charge, energy, and time through the lens of space compression. We propose that space itself, conceived as "neutral mass", is the eternal fundamental substance from which all physical phenomena emerge. Time is defined as the rate of conversion of mass into charge, while moving mass constitutes charge, and moving charge represents energy. This framework provides a mechanistic explanation for the observed 10⁸ jump in magnitude between fundamental physical scales. Key mathematical relationships and testable predictions are presented.

Various steel pipes that are exposed to corrosion, are protected with the cathodic protection where thermite welding of a copper conductor on a steel pipe is used. During the welding process and due to the nature of it, steel in the solid state comes in contact with liquid copper. Contact of steel with liquid metal in some cases cause phenomenon known as the liquid-metal embrittlement or LME. Phenomenon was previously studied in cases such as soldering, but for thermite welding no records were found in accessible literature. The purpose of this paper is to draw attention to some irregularities and consequences arising from it, which in this type of welding can occur. At the end of article some measures to reduce these risks are given.

The researchers are working towards to find out the best replacement for the fossil fuel; if not at least to offset the total fuel demand. In regards to emission, the fuel in the form of gaseous state is much than liquid fuel. By considering the various aspects of fuel, hydrogen is expected as a best option when consider as a gaseous state fuel. It is identified as a best alternate fuel for internal combustion engines as well as power generation application, which can be produced easily by means of various processes. The hydrogen in the form of gas can be used in the both spark ignition and compression ignition engines for propelling the vehicles. The selected fuel is much cleaner and fuel efficient than conventional fuel. Hydrogen internal combustion engine (ICE) vehicles present much of the same promise as hydrogen fuel cell vehicles (FCVs): Reduced reliance on imported oil and reduced carbon dioxide emissions. Proponents envision hydrogen ICE as a bridging technology from gasolin...

Over the last decade, the first principle study, has achieved a great importance in the field of quantum chemistry, solid state physics and material science. This study is about to investigate the different prosperities of many-body electronic systems and it is a quantum mechanical simulation approach. Eventually, this approach has a tool to predict some new materials and their properties computationally. This method can save the use of chemical methods, which can be harmful to the environment. In this review article, the research field of first principle techniques has been explored for some important semiconductor materials.

The fuel modelling code FUROM (FUel ROd Model), suitable for calculating the normal operation condition behaviour of PWR and WWER fuels, has been developed at AEKI for several years. The validation of the code has so far been based on the individual calculation of many relevant experiments. This, however, was a time consuming process that could give rise to errors both at the input and at the comparison stage. A new methodology is implemented to build up a uniform database from the IFPE data and run automated validation tasks depending on the model or phenomenon of interest. The general problems encountered and some results are presented here.

Microstructured optical fibers (MOF) can be seen as next generation fiber of significance in advancing the compact optics because of its excellent compatibility in integrated optics. However, the degradation of their physicochemical properties limits their efficiency and lifetime. Atmospheric moisture is responsible for the degradation of amorphous systems especially chalcogenide glasses. In the light of previously reported studies, in order to clarify the aging process continuously evolving in sulfide microstructured optical fiber over time, a detailed investigation of this phenomenon has been conducted. The timedependent transmission and glass chemical deterioration have been studied for As 2 S 3 MOF with regard to their exposure to different atmospheric conditions. Results show a substantial impact of atmospheric moisture through an interaction with the glass network. Significant improvement has been registered by storing the fibers under dry atmosphere.

In this paper, forced convective heat transfer in a water based nanofluid has experimentally beencompared to that of pure water in an automobile radiator. Five different concentrations of nanofluids inthe range of 0.1-1 vol.% have been prepared by the addition of TiO2 nanoparticles into the water. Thetest liquid flows through the radiator consisted of 34 vertical tubes with elliptical cross section and airmakes a cross flow inside the tube bank with constant speed. Liquid flow rate has been changed in therange of 90-120 l/min to have the fully turbulent regime. Results demonstrate that increasing the fluid circulating rate canimprove the heat transfer performance. Meanwhile, application of nanofluid with low concentrations can enhance heat transfer efficiency up to45% in comparison with pure water. Keywords— Nanofluid, Heat transfer coefficient, TiO2, Radiator, Cooling performance, Experimental

1 Research student Department of Mechanical Engineering, P.V.P.I.T, Budhgaon, Sangli, Maharashtra, India 2 Associate Professor, Department of Mechanical Engineering, P.V.P.I.T, Budhgaon, Sangli, Maharashtra, India ---------------------------------------------------------------------***---------------------------------------------------------------Abstract—The Parabolic Dish Solar Collector technology is very useful as it is used for approximately all solar energy applications such as steam and power generation, water heating, air heating etc. In this paper work the performance analysis of parabolic solar dish collector is done with the use of different reflecting materials. In this work a Parabolic Dish Solar Collector system is fabricated for hot water production. Water is used as a working fluid and is recirculates from the storage tank to the absorber tank with the help of a pump. The main aim in the work is to increase the temperature of water in the storage tank to a maximum va...

Component failures due to the hydrogen embrittlement (HE) were observed in different industrial systems, including high-pressure hydrogen storage tanks, aircraft components, highstrength alloy components, and high-strength steel fasteners. The contemporary approach in studying the effects of hydrogen on the mechanical properties of steels and iron at different scales is based on the implementation of various multiscale (macro, micro-meso, and nano-atomic) modeling approaches and the applications of advanced experimental methods. A large number of contemporary studies confirmed the multiple effects and activity of different HE mechanisms in steels and iron. The coexistence and synergistic activity -concurrent action and effects in a cooperative manner of different HE mechanisms, including the hydrogen-enhanced localized plasticity (HELP) and the hydrogen-enhanced decohesion (HEDE), were recently detected and confirmed through computations-simulations, as well as experimentally in different grades of steel. However, the critical evaluation and quantification of synergy between the HELP and HEDE mechanisms, enhanced plasticity and decohesion, hydrogen-deformation/dislocation interactions and their simultaneous effect on the mechanical properties (hardening and softening), still do not exist. In this review paper, the multifaceted nature of the synergistic interplay of HE mechanisms is covered through extensive literature overview regarding the chronological development of ideas related to the HELP + HEDE concept and HELP mediated HEDE model. The particular emphasis is given to the proposal of the novel and unified HELP + HEDE model based on the specific microstructural mapping of the dominant HE mechanisms with implications on the fracture process and resulting hydrogen-assisted fracture modes. Most of up-to-date experimental and modeling approaches, current trends and future challenges in the investigation of the synergistic interplay of HE mechanisms in different grades of steel, including the most advanced, and iron, are also included and critically discussed. The multifaceted nature of hydrogen embrittlement (HE) and both electrochemical and non-electrochemical control of different hydrogen damage in metals and alloys are broadly covered in the reference world literature [1-10] and within the recent review papers . These references discussed the HE phenomenon from different points of view, depending on numerous influencing factors which can be generally grouped as environmental, mechanical, and materials influences . Still, there is a strong

This is the transforming era in which human involvement is going to be eliminate day by day and computer controlled machines have to be performed all the work to remove human idleness and fatigue. Aluminium is essentially used in aircraft industry, mainly in fighter planes and space shuttles because of its high strength and very light weight. The aim of this paper is to explain the Taguchi method to find the best process parameters and improved quality results in incremental sheet forming (ISF). Taguchi technique is used to investigate the variation in number of experiments, parameters and focus on acceptance in improved quality of the workpiece. The optimum possible performance of parameters is obtained by determining the optimum combination of design factors by this technique. The present work was focused on design of experiment by using L 9 Orthogonal Array (OA) on the different steps for optimal values by conducting machining on CNC machining centre. Analysis of variance (ANOVA)...

This paper presents a methodology to determine tool forces, distribution of temperatures to estimate distribution of stresses and deformation on the single point cutting tool in the process of metal cutting. In mechanism of metal cutting a cutting tool exerts a compressive force on the work piece. Under this compressive force the material of the work piece is stressed beyond its yield point causing the material to deform plastically and shear off. The sheared material begins to flow along the cutting tool face in the form of small pieces called chips .The flowing chips causes the wear of cutting tool. Heat is produced during shearing action the heat generated raises the temperature of tool, work and chips. The temperature rise in cutting tool tends to soften it and causes loss of keenness in the cutting edge leading to its failure. This temperature during metal cutting is to be maximum at the tip of the tool, is too measured by experimental set up and which are required as input to ...

In this work, we try to point out the influence of annealing prior to chemical strengthening on the mechanical strength of thin ion exchangeable alkali borosilicate glass. The effect of annealing at 425 °C on density, hardness and cracking behaviour were investigated. Then, as-received and annealed samples were subjected to ion exchange in a molten potassium nitrate bath at the same temperature for 4 h and the generation of compressive stress in glass was analyzed as well as the bending strength. Annealing makes the glass denser, improves hardness and enhances the compressive stress build-up. However, bending strength of as-received and annealed glass after ion-exchange is substantially the same, this being probably attributed to the limited case depth if compared to surface flaws. Annealing before ion exchange does not appear to be a crucial factor in improving chemical strengthening efficiency in thin borosilicate glass.

A simple viscoplastic model for the stress-strain behaviour of filled rubber is presented. It consists, for a given strain, of additive contributions to stress from hyperviscoelasticity and time independent hysteresis. Rubber components are often subjected to scragging, i.e. preconditioning to a large strain, before carefully assessing their load deflection behaviour and comparing it to specification. The choice of scragging strain, however, affects the load deflection behaviour. It is found that this effect may be approximately captured, for modelling purposes, by regarding the modulus of the time-independent hysteresis contribution to be a function of the scragging strain and the time elapsed since scragging.

Disc brake noise and vibration control in vehicle has received significant attention in the last years, The Noises are generated in Disc and Drum Brakes where there is a transition from static to dynamic condition or vice versa. The Eigen Value characteristics of a brake child parts is the important tool to detect brake noises. Frequency response measurement is frequently used countermeasures for eliminating or reducing squeal ,by getting high excitation frequencies, The Experimentation has been done on disc brake child parts (i.e. caliper, rotor, pad, bracket) by FRF testing and by knowing Eigen values, results will be compared with the CAE results .To verify the Frequency Modes.

Nowadays, Aluminium (Al) based hybrid surface composites are amongst the fastest developing advanced materials used for structural applications. Friction Stir Processing (FSP) has emerged as a clean and flexible solid-state surface composites fabrication technique. Intensive research in this field resulted in numerous research output; which hinders in finding relevant meta-data for further research with objectivity. In order to facilitate this research need, present article summarizes current state of the art and advances in aluminium based hybrid surface composites fabrication by FSP with in-situ and ex-situ approach. Reported literature were read and systematically categorized to show impacts of different types of reinforcements, deposition techniques, hybrid reinforcement ratio and FSP machine parameters on microstructures, mechanical and tribological characteristics of different Al alloys. Challenges and opportunities in this field have been summarized at the end, which will be beneficial to researchers working on solid state FSP technique.

The influence of tempering on the mechanical performance of pottery is assessed. Emphasis is placed on the examination of the impact of temper shape (low vs. high sphericity) and extent of vitrification on the strength and toughness of the ceramic material. Measurements on experimental briquettes show that the replacement of platy phyllitic temper with bulky granitic temper results in a reduction in strength but, at least at very high firing temperatures, in an increase in toughness. The observed differences in strength reduction with different temper shapes is semi-quantitatively assessed by adapting the damaged zone model, developed previously to disk-shaped particles. The effect of temper shape on toughness is particularly pronounced at high firing temperatures, where platy temper results in significantly lower fracture toughness of the corresponding material.

The composite prepreg waste is still an environmental challenge. In the last decade, several researchers have been studying the recycling and reuse processes of composite components, mainly to use in secondary (non-structural) components. In this paper, uncured aerospace grade prepreg scraps resulted from the production waste were used to manufacture laminates. The carbon reinforcement of the prepreg presented plain weave style fabric. To manufacture the laminates the hand-lay up process was used, randomly positioning the scraps and without respecting the preferred directions of the warp and weft. Therefore, the resulting laminate is multidirectional (in the plane) and orthotropic. The cure was performed in autoclave at the maximum temperature of (180 ± 1)°C and pressure of 100 psi. This laminate was tested in compression according to standard SACMA SRM 1R-94. The results show an average compression resistance equivalent to that of laminates produced with continuous layers, although...

In this work, the effect of building direction on the microstructure evolution of laser-powder bed fusion (LPBF) processed AlSi10Mg alloy was investigated. The building direction, as shown in experimentally fabricated parts, can influence the solidification behavior and promote morphological transitions in cellular dendritic microstructures. We develop a thermal model to systemically address the impact of laser processing conditions, and building direction on the thermal characteristics of the molten pool during laser processing of AlSi10Mg alloy. We then employ a multi-order parameter phase field model to study the microstructure evolution of LPBF-AlSi10Mg in the dilute limit, using the underlying thermal conditions for horizontal and vertical building directions as input. The phase field model employed here is designed to simulate solidification using heterogeneous nucleation from inoculant particles allowing to take into account morphological phenomena including the columnar-to-equiaxed transition (CET). The phase field model is first validated against the predictions of the previously developed steady-state CET theory of Hunt [1]. It is then used under transient conditions to study microstructure evolution, revealing that the nucleation rate is noticeably higher in the horizontally built samples due to larger constitutional undercooling, which is consistent with experimental observations. We further quantify the effect of building direction on the local cooling conditions, and consequently on the grain morphology.

Material properties controlled by evolving defect structures, such as mechanical response, often involve processes spanning many length and time scales which cannot be modeled using a single approach. We present a variety of new results that demonstrate the ability of phase field crystal (PFC) models to describe complex defect evolution phenomena on atomistic length scales and over long, diffusive time scales. Primary emphasis is given to the unification of conservative and nonconservative dislocation creation mechanisms in three-dimensional FCC and BCC materials. These include Frank-Read-type glide mechanisms involving closed dislocation loops or grain boundaries as well as Bardeen-Herring-type climb mechanisms involving precipitates, inclusions, and/or voids. Both source classes are naturally and simultaneously captured at the atomistic level by PFC descriptions, with arbitrarily complex defect configurations, types, and environments. An unexpected dipole-to-quadrupole source transformation is identified, as well as various new and complex geometrical features of loop nucleation via climb from spherical particles. Results for the strain required to nucleate a dislocation loop from such a particle are in agreement with analytic continuum theories. Other basic features of FCC and BCC dislocation structure and dynamics are also outlined, and initial results for dislocation-stacking fault tetrahedron interactions are presented. These findings together highlight various capabilities of the PFC approach as a coarse-grained atomistic tool for the study of three-dimensional crystal plasticity.

This scientific work was initiated as a result of many concerns facing most researchers on the nature, properties and characteristics of the clay materials northern Cameroon. Including the city of Maroua in the Far North Region Cameroon. The specific case of Makabaye is indeed the object of this science. This work can serve as a guide, and why not valuable source of information useful to a deeper understanding of the chemical and mineralogical characteristics of Makabaye clay. Judicious use of the results of this work may also lead to the formulation of the products in terracotta, with a valuation of its clays in the cosmetics industry, real estate, pharmaceuticals, and purification of vegetable oils. To achieve our results, we basically made of chemical and mineralogical analysis in the laboratory, along with a team of sworn laboratory for major tests we have done. In particular, it is the XRD X-ray analysis for the determination of mineral elements, and finally, the geochemical analysis by X-ray fluorescence, to better identify the specific chemical characteristics of the clay. We believe the views of the results obtained, absorbent properties of the clay materials, properties that can be put to good use in the purification of vegetable oils and waste water treatment.

The mechanical behavior of hybrid (bolted/bonded) joints is investigated. The joints under study are balanced single-lap joints, and an elastic behavior of the materials is assumed. A fully parametric analytical two-dimensional model, based on the Finite Element Method, is presented. A special Finite Element ("Bonded Beams" element) is computed in order to simulate the bonded adherends. The simulation of fasteners is examined through experimental and numerical approaches. Good agreement was found between the experimental and numerical results.