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Matéria (Rio de Janeiro), Volume: 29, Issue: 1, Published: 2024
  • Prediction of autoclaved aerated cement block masonry prism strength under compression using machine learning tools Articles

    Muthukumar, Soundar Rajan; Jegatheeswaran,

    Abstract in English:

    ABSTRACT When the only information available is the issue parameters, and the intended outwards, machine learning techniques like ANN (Artificial Neural Networks) and ANFIS (Adaptive neuro-fuzzy inference system) been proven to address the complex problems without duplicating the phenomena under investigation. The main prompting characteristics are the height-to-the-thicknesses ratio of prisms and the strength under compression of prisms and mortar were analyzed. As inputs, the prototypes are used as blocks and mortars. Both prototypes were accomplished and evaluated. Thirty-six data sets were gathered for testing in addition to verified technical and subsequently comparison with other empirical computation methods served to validate. The outwards show that the suggested prototypes have good forecast capabilities with negligible error rates. To assess and compare the structural behavior of structural completion of AAC block with the other types. At last, both the machine learning tools are good application and dependability.
  • Microstructural evaluation of welded joints of ASTM Mar-M247 superalloy using ERNiCrMo-3 filler alloy Articles

    Alomairi, Bassam Salman; Driss, Zied; Abood, Adnan Naama

    Abstract in English:

    ABSTRACT ASTM Mar-M247 is one of the superalloys used to manufacture gas turbine blades in power stations. This paper studies the microstructure across welded joints of a turbine blade made of a high-strength material (Mar-M247 alloy) employing AWS ERNiCrMo-3 as a filler alloy. This process was carried out using gas tungsten arc welding (GTAW). The dendritic and interdendritic structures were observed in the fusion zone. The results also showed the presence of epitaxial growth at the interface between the weld metal and the base alloy without solidification cracks. Al and Co concentrations gradually decrease towards the weld metal zone during the solidification process, while Cr content increases towards the fusion zone. Vickers hardness revealed that the hardness in the heat-affected zone (HAZ) is higher than that of the base metal and the weld metal zone, the average in the HAZ is 340HV, while in the base metal and the fusion zone is 322HV, 284HV respectively. Coarse grains in the HAZ were found with an agglomeration of carbides at the grain boundaries due to the input heat of the welding process.
  • Analysis of water absorption in industrial waste of superabsorbent polymer and cellulosic fiber Articles

    Barth, Mateus Essvein; Pistore, Mateus Ripol; Brehm, Feliciane Andrade; Mancio, Mauricio; Souza, Vitória da Luz de

    Abstract in English:

    abstract Proper curing of concrete is one of the most important processes in the post-concreting period so that concrete can achieve the desired mechanical strength and durability. However, part of the construction works perform this procedure for inadequate periods or often do not perform it; as a result, surface characteristics are commonly affected, resulting in increased porosity and, consequently, increased permeability, cracking and carbonation. Materials that have water retention capacity and subsequent gradual release may be effective as internal curing agents. Superabsorbent polymers (PSA) are already used and widely studied for this purpose, but usually with commercial origin. The objective of this research is to evaluate different water absorption methods in industrial waste of superabsorbent polymer and cellulosic fiber (PSAR) for later use as an internal curing agent in Portland cement matrices. PSAR was homogenized by a process at two different times. The material in its natural state and homogenized had its absorption capacity evaluated using two methods: ISO 17190:2001 and sieve method. For the sieve method, the influence of hydration time on absorption was analyzed. The ISO 17190:2001 method did not show representativeness in the results due to the high absorption variation. The sieve method was more representative and demonstrated efficiency in the homogenization processes, reducing the coefficient of variation by up to 43%. The material with the highest potential for use was PSAR60, with an absorption value of 68.26 g of water per g of PSAR, since the absorption test showed the highest homogeneity and, from this absorption, no longer had significant variations.
  • Mathematical model of a plenum to obtain the dynamic characteristics of the mass flow of a turbo-charger Artículos

    Bermúdez Santaella, José Ricardo; Suárez Sierra, Oscar Javier; Cabello Eras, Juan José

    Abstract in Spanish:

    RESUMEN Los turbocargadores en la actualidad han demostrado ser imprescindibles en el campo automotriz por ser máquinas que se encargan de aumentar la potencia, reducir el consumo de combustible y generar menos dióxido de carbono en un motor de combustión interna. En este artículo se presenta el desarrollo de un modelo matemático en base a un plenum, con el propósito de obtener las características dinámicas del flujo másico que genera un turbocargador. Para cumplir con lo propuesto se fundamentó en el conocimiento teórico-práctico de las leyes y conceptos que conforman un turbocargador, dando como resultado la simulación de un modelo matemático utilizando la herramienta Simulink. Para el desarrollo del modelo matemático se utilizaron datos teóricos y de pruebas en régimen estable y dinámico, así como el comportamiento del plenum sometido al sistema de compresión. Este modelo planteado contribuirá a la comunidad científica a través de la obtención de las características entre la relación de compresión y el flujo de masa del compresor de un turbocargador, también, aportará en el futuro al campo de la detección y diagnósticos de fallos orientados a los turbocargadores vehiculares.

    Abstract in English:

    ABSTRACT Turbochargers have proven to be essential in the automotive field as they are machines responsible for increasing power, reducing fuel consumption, and generating less carbon dioxide in an internal combustion engine. This article presents the development of a mathematical model based on a plenum to obtain the dynamic characteristics of the mass flow generated by a turbocharger. To comply with the proposal, it was based on the theoretical-practical knowledge of the laws and concepts that make up a turbocharger, resulting in the simulation of a mathematical model using the Simulink tool. For the development of the mathematical model, theoretical and test data in stable and dynamic regimes were used, as well as the behavior of the plenum subjected to the compression system. This proposed model will contribute to the scientific community by obtaining the characteristics between the compression ratio and the compressor mass flow of a turbocharger and will also contribute to the field of detection and diagnosis of targeted failures in vehicle turbochargers.
  • Physical-mechanical characterization of tuturubá wood (Pouteria oblanceolate Pires) Articles

    Lima, Vinícius de Sousa; Silva, Maria Gabriela Sales da; Menezes, Gabriel Cruz; Cunha, Rita Dione Araújo; César, Sandro Fábio; Pereira, Andrea Ferraz Silva; Dias, João Miguel Santos

    Abstract in Portuguese:

    RESUMO O conhecimento das propriedades físicas e mecânicas da madeira é crucial para a segurança e eficácia do dimensionamento das estruturas. Além de favorecer a diversificação e abastecimento do mercado madeireiro, a determinação de tais propriedades, para diferentes espécies nativas, pode contribuir para a redução da exploração concentrada de madeiras tropicais. Entre as madeiras disponíveis para a construção civil na Região Tocantina do Maranhão encontra-se o tuturubá (Pouteria oblanceolata Pires). Neste contexto, este estudo teve como objetivo determinar as propriedades físicas e mecânicas da madeira de tuturubá, visando o seu uso em estruturas de edificações. Foram determinados: o teor de umidade, a densidade aparente, as resistências à compressão paralela e perpendicular às fibras, a resistência ao cisalhamento paralelo às fibras, a resistência à flexão e os módulos de elasticidade à compressão paralela às fibras e à flexão. Obteve-se um teor de umidade médio de 13,88%, uma densidade aparente média de 992,04 kg.m-3, o valor médio da resistência à compressão paralela às fibras igual a 60,03 MPa e o valor característico de 56,86 MPa, sendo o módulo de elasticidade à compressão paralela às fibras de 22761 MPa. A resistência média à compressão perpendicular às fibras foi de 10,74 MPa e a resistência média ao cisalhamento paralelo às fibras foi igual a 10,47 MPa. A resistência à flexão média foi de 154,82 MPa e o valor característico igual a 128,37 MPa, enquanto o valor médio do módulo de elasticidade à flexão foi de 21026 MPa. Os resultados permitiram classificar a madeira de tuturubá como pertencente à classe de resistência mecânica D50. Comparativamente com outras espécies disponíveis no mercado madeireiro, a madeira de tuturubá apresentou propriedades mecânicas superiores às madeiras de pequiá (Caryocar villosum) e tauari (Couratari oblongifolia). Esta caracterização físico-mecânica evidencia o potencial da madeira de tuturubá para utilização em estruturas de edificações.

    Abstract in English:

    ABSTRACT Knowledge of the physical and mechanical properties of wood is crucial for the safety and efficiency of structural design. In addition to promoting diversification and supply in the timber market, determining these properties for different types of native woods can contribute to reduce the concentrated overexploitation of tropical woods. Among the woods available for construction purposes in the Tocantina region of Maranhão State is tuturubá (Pouteria oblanceolata Pires). In this context, the present study aimed to evaluate the physical and mechanical properties of tuturubá wood for its use in building structures. The characterizations carried out were: moisture content, apparent density, compressive strength parallel and perpendicular to the grain, shear strength parallel to the grain, flexural strength, modulus of elasticity in compression parallel to the grain and three-point bending test. For the average moisture content, a percentage value of 13.88% was checked, and for the average apparent density, a value of 992.04 kg.m-3 was obtained. For the compressive strength parallel to the grain, an average value of 60.03 MPa was determined, while the characteristic value was 56.86 MPa. The compressive modulus of elasticity parallel to the grain determined was equal to 22761 MPa. The average values for compressive strength perpendicular to the grain and shear strength parallel to the grain were 10.74 MPa and 10.47 MPa, respectively. For flexural strength, average and characteristic values were 154.82 and 128.37 MPa, respectively. For the flexural modulus of elasticity, an average value of 21026 MPa was determined. The results allowed tuturubá wood to be classified in mechanical resistance class D50. Compared to other commercially available wood species, tuturubá has better mechanical properties than pequiá (Cary-ocar villosum) and tauari (Couratari oblongifolia) woods. This physical-mechanical characterization high-lights the potential of tuturubá wood for use in building structures.
  • Mechanical and chemical analysis of degraded plastic bags exposed in air, water, and soil Artigos

    Oliveira, Warlen Librelon; Uliana Junior, Paulo Sérgio.; Lins, Vanessa de Freitas Cunha

    Abstract in English:

    ABSTRACT This study is aimed at analyzing the mechanical behavior of low-density polyethylene (LDPE) plastic bags exposed for three years to air, immersed in polluted and tap water, buried in soil, and exposed on the soil surface. The pH and conductivity analyses for polluted water resources, clean water and soil extract were performed. Semi-quantitative chemical analysis of soil using X-ray fluorescence spectrometry (XRF) was performed. For the mechanical assay, a 100 kN load cell was used subjected to a traction with obtaining strain curve x deformation. The aqueous soil extract is rich mainly in nitrate, sulfate, and calcium. The polluted water in which the bags were immersed had a high concentration of chlorides, and contained nitrate, sodium, and calcium. Finally, tap water contained mostly sulfate, sodium, calcium, and chloride ions. However, the chloride content of polluted water is ten times the content of tap water. The tensile strength and elongation of degraded samples are lower than the reference, confirming the process of degradation. An exception was the deformation of plastic bag buried in soil which was the highest.
  • Experimental and theoretical investigation on the bond strength between high-strength and lightweight concrete Articles

    Eisa, Ahmed S.; Aboul-Nour, Louay A.; Mohamad, Asmaa

    Abstract in English:

    ABSTRACT The appropriate bond strength between the layers with different concrete strengths is considered the most important concern for the layered elements. An experimental study has been approved to produce structural lightweight concrete with a compressive strength not decreasing by 18 MPa and a unit weight not increasing by 2000 kg/m3 and high-strength concrete with a compressive strength not decreasing by 60 MPa and then investigate the bond strength between new high-strength concrete and old lightweight concrete with different treatment cases and different compressive concrete strengths. Mix with 0% perlite meets the requirements of the targeted high-strength concrete, and mixes with 30%, 40%, and 50% perlite meet the requirements of the targeted structural lightweight concrete, and they can be used for testing bond strength with different treatment methods. The new concrete jackets have a concrete strength of 62.5 MPa, and the old concrete cube's strength is varied between 18.4, 21.8, and 38.08 MPa. A total of eleven bond strength test specimens were cast with different parameters. The specimen interface was arranged by different systems: roughness, agent material, and nails. The roughness techniques used were hand-wire brushing, grinding, or hand chiseling. Theoretical results were compared with the experimental data. It was concluded that using a new high-strength concrete with two times the strength of the old lightweight concrete and treating it with nails is the best technique to achieve an economic and acceptable value of bond strength. The nails achieved a good bond between the fresh and hardened concrete owing to the developed shear friction. The hand-chiseling roughness method gives the best bond strength results. The high difference in concrete strengths between the fresh high-strength jackets and the hardened lightweight cube isn’t mandatory to enhance the interface bond strength between them.
  • Characteristics of pore structure and permeability prediction in binary blended pervious concrete Articles

    Muthaiyan, Uma Maguesvari

    Abstract in English:

    ABSTRACT This study primarily focuses on analyzing the pore structure characteristics and predicting permeability in binary blended pervious concretes, both with and without fines. The pervious concretes included fly ash, a class 'C' material, as a partial cement replacement (10% and 20%). The aggregates consisted of a mix of coarse aggregates, with sizes ranging from 19–9.5 mm and 9.5–4.75 mm, and fine aggregates substituted a portion of the coarse aggregates at specific levels (5–15%). The area fraction (ϕA) and volumetric methodology (ϕV) were used for assessing the porosity of the binary blended pervious concrete mixtures. The properties of the pore size were measured through morphological techniques. The Katz-Thompson (K-T) relationship utilized porosity and pore size data from image analysis to predict permeability in pervious concretes. Comparing the two porosity calculation methods, the porosities obtained through image analysis (area fraction) were slightly higher than those obtained through the volumetric technique. The pore characteristics identified through techniques like Two-Point Correlation and granulometry were found to be quite similar. Results indicated a strong agreement between the experimentally determined and predicted permeability values.
  • Strength properties of engineered cementitious composites containing pond ash and steel fiber Articles

    Kandasamy, Yuvaraj; Thangavel, Bragadeeswaran; Sukumar, Kamal Kannan; Ravi, Babu

    Abstract in English:

    ABSTRACT Concrete technology has seen a recent advancement with the widespread adoption of Engineered Cementitious Composite (ECC). Typically, ECC consist of cement, fly ash, fine sand, fibers, and occasionally other additives or mineral admixtures. However, there has been no exploration into the effects of combining pond ash with steel fibers on emerging cementitious materials like ECC. In this study, seven ECC specimens were made. One was a control mix, and the other six included pond ash with increments of 10% from 10% to 60%. All seven mixes were maintained at a fixed ratio of fly ash 40% and water-to-binder ratio of 0.3. To boost the fresh mix of the ECC mixes, superplasticizer was introduced at a rate of 1% by volume, and steel fiber was incorporated at a rate of 2% by volume of ECC. Addition of pond ash into ECC results exhibits superior properties than control mix.
  • Effect of heat treatment on the microstructure and surface damage evolution of selective-laser-melted IN718 alloy Articles

    Li, Lei; Li, Xiaodong; Liu, Qiao; Mao, Dexin

    Abstract in English:

    The microstructure and damage evolution behavior of IN718 alloy prepared by selective laser melting (SLM, referred to as SLM IN718 alloy) under different heat treatment processes were studied using optical microscopy, scanning electron microscopy, electron backscatter diffraction, microhardness tests, and other material tests, combined with digital image correlation. The heat treatment of the SLM IN718 alloy achieved different degrees of recrystallization and transformed the microstructure from dendritic crystals to bulk crystals with the precipitation of a large number of γ′ and γ′′ phases. As the heat-treatment temperature was increased, the δ phase of the SLM IN718 alloy was precipitated and then dissolved, the microhardness and strength of SLM IN718 alloy increased and then decreased, the elongation decreased and then increased, and toughness fracture was the main fracture mode. Therefore, heat treatment can be used to alter the relative proportions of recrystallized and substructured grains in the SLM IN718 alloy, thereby modulating its overall mechanical properties. After heat treatment, the damage factor entered the rapid damage stage earlier, and the critical damage factor increased as the critical plastic strain was increased. Further, the damage evolution equations of the SLM IN718 alloy under different heat treatment processes were established.
  • Influence of nano silica on impact resistance and durability of fly ash concrete in structural buildings Articles

    Ramasamy, Saravanakumar; Deivasigamani, Vivek; Soundararajan, Elango Krishnan; Sridhar, Jayaprakash

    Abstract in English:

    ABSTRACT The impact of integrating Nano Silica (NS) on mechanical characteristics, resistance towards impact, and chloride penetration on concrete having Fly Ash (FA) are investigated in this research. The NS particles are subsequently mixed into concrete at one, two, three, four, and five percent of the binder’s mass, respectively. The performance of the specimens under an impact load is assessed by utilizing the drop weight impact technique, frequency on strikes, and impact force variation has been used to evaluate the specimen's impact resistance. The concrete's ability to withstand damage from chloride penetration was evaluated by determining the chloride diffusion coefficient of the samples. The test findings demonstrated that adding NS to concrete may significantly increase its mechanical characteristics as well as chloride penetration resistance. The optimum amount of NS substitution in concrete is two to three percent and it is discovered that if the proportion of NS is too large, the benefits of incorporating NS into the characteristics of the concrete are diminished, and might even have a detrimental effect on the resistance towards impact and durability of the concrete. Moreover, the experimental compressive strength and split tensile is compared with existing gene expression programming model.
  • Investigation on microstructural and compressive strength characteristics of a novel bio-admixture comprising Cassava Starch-Xanthan gum with cement mortar for building application Articles

    Selvakumar, Paramathmeka; Kumarasamy, Vidhya

    Abstract in English:

    ABSTRACT Developing high-performing bio adhesives for enhancing the bonding strength of cement-based materials is highly desirable as they improve workability, corrosion resistance and durability of the concrete. The present effort aims at stemming a novel bio admixture comprising agricultural products Cassava starch and Xanthan gum as well examines the effect of incorporation of it into the cement. The composition of xanthan gum is varied in the starch mixture systematically in the ratios namely 1:0.25, 1:0.5 and 1:0.75. As-prepared bio admixtures are characterized through Fourier Transform Infra-Red spectroscopy, X-Ray Diffraction, Thermo Gravimetric Analysis, contact angle and Scanning Electron Microscopy-Energy Dispersive X-ray studies. These results demonstrated that presence of optimal amount of xanthan gum facilitates the binding nature of starch and promotes better bond strength as it significantly improved the bonding capacity as well as hydrophilic nature of starch thereby augmenting the bonding strength when used in cement mortar. The bio admixture filler material occupied the voids between the mortar matrix, thus reducing the porosity. The beneficial effect of as-prepared bio admixture has been reflected in the compressive strength that has been enhanced by 16.6% when optimized quantity (1.5 wt.%) of the bio admixture is added to the mortar.
  • Chemical modifications of activated carbons prepared from different Ganoderma residues, their adsorption, and catalytic application Articles

    Chen, Bo Jie; Liu, Yang; Liu, Bai Cheng; Huang, Rong Bing; Wu, Pei Ling; Jiang, Tiemin; Dong, Xinhong; Li, Xia; Khoo, Hock Eng; Lee, Say Wah

    Abstract in English:

    ABSTRACT This study aimed to prepare Ganoderma-based activated carbons for chemical adsorption and catalyzing N-(phosphonomethyl)iminodiacetic acid to glyphosate. The activated carbons were prepared by applying different activation conditions. These carbon samples were applied to catalyze N-(phosphonomethyl)iminodiacetic acid to glyphosate. The results showed that the black Ganoderma char activated at 800 °C for 90 min using 40% phosphoric acid had the highest methylene blue adsorption capacity and DPPH scavenging activities, but the methylene blue adsorption capacity of the black Ganoderma sample activated at 800 °C for 90 min using 40% acid-base solution was lower than the red AC sample. These carbon samples had high thermal stability. Chemical modifications of these chars with the carbon modifiers at an optimized activation condition increased the Langmuir-specific surface areas of these carbon samples up to 2055.09 m2/g. The carbon sample of black Ganoderma activated using the 40% acid-base solution at 800 °C for 90 min and coupled with the addition of hydrogen peroxide during ultrasonication and microwave-assisted reactions had the highest glyphosate catalyzing rate. The glyphosate yield obtained from the catalyzing at atmospheric pressure was 58.78 ± 0.28%. These Ganoderma-based activated carbons can replace other carbon materials for catalysis applications and as adsorbents in food and pharmaceutical industries.
  • Synergistic effect of graphene oxide and coloidalnano-silica on the microstructure and strength properties of fly ash blended cement composites Articles

    Subramani, Kalaiselvi; Ganesan, Arun Kumar

    Abstract in English:

    Cement concretes are widely used and very effective in the construction industry. Micro-scale problems such as porosity, micro-cracks, etc. Many researchers have done research work globally to address this issue. This research investigation also addresses this by using colloidal nano-silica along with Graphene oxide (GO) particles in fly ash-based cement compounds. The change in the behaviour of cement matrix experimentally observed with 10% replacement of FA with cement, 2.5% replacement of Nano-silica with cement, and GO of variable dosage in this research investigation, GO as additive of dosages 0.02%, 0.03%, 0.04%, 0.05%, and 0.06% by mass of cement has been used. GO and Nano-silica were sonicated for 30 minutes to get uniform dispersion of nanoparticles. The material characterization and cement blended composite characterization has been performed using Energy-dispersive X-ray analysis, Scanning Electron Microscopy, X-Ray diffraction, and Fourier transform infrared tests. From the Test results, it is found that the addition of 0.03% of GO is the optimum dosage of the cement composites. It is observed that GO+NS with FA affects the overall hydration process of the cement composites. GO, and NS fills the pores, causing a reduction in pore volume and promoting the more compact and dense microstructure.
  • A study of the reverse martensitic transformations in austenitic stainless steels by calorimetry and isothermal heat treatments Articles

    Salgado, Jorge; Fava, Javier; Spinosa, Cristina

    Abstract in English:

    The objective of this work was to study the reversion of the strain-induced α-martensite to γ-austenite in three sets of AISI 304, 316-L and 347 stainless steels specimens. To obtaining a high amount of αʹ-martensite (γ → αʹ ), the samples were submitted to 63% reduction in thickness by cold rolling at a temperature of –70 ºC. The reversion of martensite to austenite was made by means of 1-hour isothermal heat treatments between 200 and 1000 ºC (αʹ → γ). Martensite amounts were determined by measurements made with a commercial feritscope. The main analysis of reversion was performed by differential scanning calorimetry (DSC) studies with heating rates of 10, 20 and 40 °C/min. It was determined that under continuous heating the deformation-induced reversion is carried out by a superposition of the diffusional and shear mechanisms, for the heating rates tested. The reversion begins via diffusion-controlled mechanism at temperatures between 414 and 453 °C and ends via non-diffusional mechanism between 557 and 633 °C. On the other hand, the energy per unit mass of the transformation turned out to be between 37 and 63 J/g; and it was found that this depends on the heating rate.
  • The electrochemical behavior of an Al-Cu-Li alloy Artigos

    Araujo, João Victor de S.; Silva, Rejane Maria Pereira da; Viveiros, Bárbara Victoria Gonçalves de; Klumpp, Rafael Emil; Costa, Isolda

    Abstract in Portuguese:

    RESUMO Ligas Al-Cu-Li têm apresentado vantagens em relação às ligas Al-Cu-Mg convencionais usadas na indústria aeroespacial devido as suas propriedades, como alta resistência à fadiga e baixa densidade. As propriedades mecânicas destas ligas dependem de sua microestrutura. Neste trabalho, a atividade eletroquímica associada a microestrutura e comportamento à corrosão da liga Al-Cu-Li 2198-T8 foi investigada por testes eletroquímicos e ensaios de imersão em soluções contendo íons cloreto (Cl–). Os resultados obtidos mostraram que o comportamento eletroquímico e a susceptibilidade a corrosão desta liga são fortemente influenciados pela fase T1(Al2CuLi), a qual é a principal responsável pelo endurecimento da mesma. Foi observado ainda que esta fase é eletroquimicamente mais ativa do que a matriz de alumínio e, que quando exposta ao meio corrosivo, resulta em corrosão localizada severa (CLS), devido ao ataque cristalográfico. Nestas regiões foi observada intensa acidificação, principalmente dentro dos pites, resultando na evolução de gás hidrogênio, o que foi confirmado pelos ensaios de visualização em gel. Os resultados obtidos por técnicas eletroquímicas globais e técnica de varredura do eletrodo vibratório (SVET) confirmaram as observações dos ensaios de imersão e de visualização em gel.

    Abstract in English:

    ABSTRACT Al-Cu-Li alloys present interesting advantages over conventional Al-Cu-Mg alloys used in the aerospace industry, due to their excellent properties, such as high fatigue resistance and low density. The mechanical properties of these alloys depend on their microstructure. In this work, the electrochemical activity associated with the microstructure and corrosion behavior of the AA2198-T8, Al-Cu-Li alloy, was investigated through electrochemical and immersion tests, in chloride ions (Cl–) containing solutions. Results obtained showed that the electrochemical behavior and susceptibility to corrosion of this alloy are strongly influenced by the T1(Al2CuLi) phase density which is mainly responsible for its hardening. It was also observed that this phase is electrochemically more active than the aluminum matrix and when exposed to corrosive environments, it results in severe localized corrosion (SLC), due to crystallographic attack. In these regions, intense acidification was observed, within the pits, resulting in hydrogen gas evolution, which was confirmed by gel visualization tests. The results obtained through global electrochemical techniques and scanning vibrating electrode technique (SVET) confirmed the observations from the immersion and gel visualization tests, where increased values of anodic current densities were related to the SLC regions.
  • Potential for using oiticica fruit residue in the development of thermoplastic matrix composites Artigos

    Borba, Caroline Henrique de Souza; Lima, Pablo Freire; Vieira, Jamile Almeida; Cerqueira, Grazielle Rozendo de; Santos, Zora Ionara Gama dos; Ueki, Marcelo Massayoshi

    Abstract in Portuguese:

    RESUMO Nos últimos anos a preocupação de ambientalistas vem crescendo devido ao grande uso de produtos que tem como matéria-prima fontes fósseis não renováveis. Uma alternativa adotada entre os pesquisadores é a produção de compósitos de matriz termoplástica com fibras de resíduos de lignocelulósicas. A oiticica ou oiti é um fruto rico em óleo e é muito utilizado para a produção de sabão. O co-produto gerado desse processo é rico em fibras, óleo e impurezas e atualmente é muito utilizado para ração animal e adubo para solo. O objetivo do presente trabalho é a produção e avaliação das propriedades de compósitos de PEAD com Torta de Oiticica. Como matriz foi utilizado um PEAD verde fornecido pela Braskem e a fase dispersa foi a Torta de oiticica fornecida por uma fábrica de sabão. As composições com 5, 10 e 20% de Torta de oiticica foram processadas por extrusão dupla rosca e os corpos de provas confeccionados pelo processo de injeção. Os compósitos foram caracterizados através do ensaio de tração uniaxial para avaliação de propriedades mecânicas (deformação até a ruptura, módulo e tensão na força máxima). A interação entre torta e matriz foi analisada através da superfície de fratura utilizando microscopia eletrônica de varredura e a análise térmica foi avaliada através de DSC. Os resultados mostraram diminuição na deformação para composições com 10 e 20% de torta. Houve uma queda gradativa na tensão na força máxima nos compósitos quando comparada com a do PEAD. As micrografias mostraram pouca interação entre fibra e matriz e a presença de vazios. As análises térmicas apresentaram uma diminuição no grau de cristalinidade. concluindo-se que a presença da torta pode ter dificultado a organização das cadeias, gerando maior número de regiões amorfas.

    Abstract in English:

    ABSTRACT In recent years the concern of environmentalists has been growing due to the large use of products that have non-renewable fossil sources as raw material. An alternative adopted by the researchers is the production of thermoplastic matrix composites with lignocellulosic waste fibers. The oticica or oiti is a fruit rich in oil and is widely used for soap production. The co-product generated from this process is rich in fiber, oil and impurities and is currently widely used for animal feed and soil fertilizer. The objective of the present work is the production and evaluation of the properties of HDPE composites with Oiticica waste. As matrix was used a green HDPE supplied by Braskem and the dispersed phase was the pie de oiticica supplied by a soap factory. Compositions with 5, 10 and 20% of waste de oiticica were processed by double screw extrusion and the specimens made by the injection process. The composites were characterized by uniaxial tensile test to evaluate mechanical properties (deformation to rupture, modulus, and stress at maximum force). The interaction between pie and matrix was analyzed through the fracture surface using scanning electron microscopy and the analysis. Thermal analysis was assessed by DSC. The results showed decrease in the deformation for 10 and 20% waste compositions. There was a gradual decrease at the stress at the maximum strength of the composites when compared to HDPE. The micrographs showed little interaction between fiber and matrix and the presence of voids. Thermal analysis showed a decrease in the degree of crystallinity, concluding that the presence of the oiticica may have made it difficult to organize the chains, generating a greater number of amorphous regions.
  • Development of an optical sensor for acidic environments from Pani/LDHs composites Artigos

    Raffa, Francine Andrea; Schons, Aline Boarolli; Maria, Arthur Leonhardt Santa; Marangoni, Rafael; Castro, Eryza Guimarães de

    Abstract in Portuguese:

    RESUMO Materiais híbridos formados entre polianilina e hidróxidos duplos lamelares de Zn e Al (Pani/ZnAlHDL) foram obtidos adicionando a Polianilina (Pani) previamente preparada ao meio reacional da síntese dos HDLs e também HDLs modificado com os surfactantes aniônicos dodecilsulfato de sódio e dodecilbenzenosulfato de sódio. Os compósitos apresentaram cor azul que é característica da fase base esmeraldina da Pani. Os difratogramas de raios X destes compostos apresentaram deslocamento dos picos (003) e (006) do ZnAlHDL para menores valores de 2θ, indicando a presença das duas fases nos compósitos. Além disso, foi constatado também que os surfactantes aniônicos também exercem influência nas características estruturais dos compósitos. Os espectros de FTIR corroboram os resultados do DRX. Os compósitos obtidos com os surfactantes foram submetidos à testes de sensor colorimétrico para HCl. Após 5 minutos apenas de exposição aos vapores do HCl, os materiais apresentaram mudança na sua coloração de azul para verde, indicando a formação da fase da Pani, sal esmeraldina. Esse indício foi confirmado por espectroscopia na região do UV-Vis, uma vez que os espectros após interação com ácido, apresentaram novas bandas, nas regiões de 400 nm e 820 nm, que são características do sal esmeraldina, forma estrutural da Pani de coloração verde. Esses resultados mostram a viabilidade da utilização destes materiais no sensoriamento de ambientes ácidos, apresentando resposta rápida e eficaz.

    Abstract in English:

    ABSTRACT Hybrid materials formed between polyaniline and layered double hydroxides of Zn and Al (Pani/ZnAlHDL) were obtained by adding previously prepared polyaniline (Pani) to the reaction medium during the synthesis of the HDLs, including HDLs modified with the anionic surfactants sodium dodecyl sulfate and sodium dodecylbenzenesulfonate. The composites exhibited a blue color characteristic of the emeraldine base phase of Pani. X-ray diffraction (XRD) patterns of these compounds showed a shift of the peaks (003) and (006) of ZnAlHDL to lower 2θ values, indicating the presence of both phases in the composites. Additionally, it was observed that the anionic surfactants also influence the structural characteristics of the composites. Fourier-transform infrared (FTIR) spectra support the XRD results. Composites obtained with surfactants were subjected to colorimetric sensor tests for HCl. After only 5 minutes of exposure to HCl vapors, the materials changed their color from blue to green, indicating the formation of the Pani emeraldine salt phase. This indication was confirmed by UV-Vis spectroscopy, as spectra after acid interaction showed new bands in the 400 nm and 820 nm regions, characteristic of the emeraldine salt, the green-colored structural form of Pani. These results demonstrate the feasibility of using these materials in acid sensing, providing a rapid and effective response.
  • FE simulation of uniaxial tensile behavior of SiC reinforced AA5083 alloy Articles

    Songa, Hemanth Kumar; Suman, Koka Naga Sai; Manyala, Anjani Raj

    Abstract in English:

    ABSTRACT Reinforcements added to pure AA5083 alloy are known to lower the overall weight while improving the strength of the Metal Matrix Composite (MMC). In this work, Silicon carbide (SiC) particles are added to pure AA5083 in varying quantities (3%, 5%, 7% and 10%), and tested to failure using tensile testing. The stress-strain behavior is decomposed into the elastic and plastic behavior and is validated using Finite Element (FE) modeling. The results exhibited an increase in ultimate tensile strength (UTS) of the MMC up to 5% of SiC. The formation of intermetallic compounds due to reactions at high concentrations of SiC resulted in debonding in the MMC and thus reduction in UTS. In this work, the response of the material between yield and complete failure is characterized using VOCE nonlinear model in FE analysis. It is observed that MMC with 5% SiC has shown maximum UTS (340.34 Mpa), while MMC with 10% SiC content has resulted in the most ductility (27% plastic strain) of all the compositions. Further, MMC with 7% SiC has highest saturation stress (R0 = 653.09 Mpa) and lowest ductility, while MMC with 10% SiC has lowest saturation stress (R0 = 115.57 Mpa) and highest ductility.
  • Optimizing flow, strength, and durability in high-strength self-compacting and self-curing concrete utilizing lightweight aggregates Articles

    Kadhar, Syed Abdhaheer; Gopal, Elangovan; Sivakumar, Vivek; Anbarasu, Naveen Arasu

    Abstract in English:

    ABSTRACT This comprehensive study undertaken to investigate the properties and performance of M60 grade self-compacting and self-curing concrete mix designs. The research involved an in-depth analysis of various concrete compositions labeled as M1 to M16, each with specific aggregate combinations and percentages. The primary focus was on assessing critical properties such as flow-ability, mechanical, durability and micro structural properties. The mix labeled as M6, featuring a balanced incorporation of fine aggregate alternatives (FAA) and natural coarse aggregates (NCA), exhibited noteworthy behavior in terms of the evaluated properties. This indicated the potential advantages of judiciously combining different types of aggregates to achieve desired concrete characteristics. The research underscored the critical role of aggregate selection and substitution in determining the overall durability, strength, and structural performance of M60 grade concrete. These findings contribute to an improved understanding of optimizing concrete mix designs for achieving enhanced mechanical properties, micro structural and long-term structural sustainability. The mix M12 is more superior compared to all the mix in the form of fresh concrete properties, mechanical properties and durability properties of concrete. This study’s outcomes have implications for the construction industry, offering valuable insights into formulating concrete blends tailored for specific structural requirements and desired performance outcomes.
  • Experimental and analytical analysis of spot-welded cold form steel built up section under axial compression Articles

    Tamilarasa, Anitha Ranee Ramasamy; Gurusamy, Srisanthi Vellalapalayam

    Abstract in English:

    ABSTRACT The widespread adoption of Cold-Formed Steel (CFS) sections for constructing cost-effective housing and lightweight industrial structures is attributed to their ease of assembly and earthquake-resistant properties. Substantial research efforts have focused on enhancing the cost efficiency of structures by utilizing assembled CFS sections. The effectiveness of these BU-C sections relies on their ability to function in a composite manner, a function influenced by the type and arrangement of connections. The study encompasses both experimental and finite element analysis, involving 27 axial compression tests. These tests were conducted on specimens with varying cross-sections and thicknesses, each tested at different pitches. The experimental findings indicate a significant increase in axial compression load when number of pitch is increased. An ABAQUS-based Finite Element Model (FEM) was formulated and validated against the experimental data, demonstrating consistency in both axial compression load and buckling behavior. This authenticated FEM was subsequently employed for a parametric investigation, exploring the impact of pitch, spot welding thickness, and length on the axial compression capacity of BU-C. The observation was that an increase in pitch enhances the composite behavior of CFS BU-C, leading to a corresponding augmentation in compression capacity.
  • Fiber reinforced self compacting concrete workability properties prediction and optimization of mix using machine learning modeling Articles

    Periyasamy, Muthaiyan; Kanagaraj, Ramadevi

    Abstract in English:

    ABSTRACT Self Compacting Concrete (SCC) is an engineered concrete manufactured in such a way that it can compact itself independently, without any external vibrations or equipment. The self-weight of the SCC is specifically higher than that of the Conventionally Vibrated Concrete (CVC) because of more fines in the SCC. The fines help to achieve self-compaction, but at the same time, it creates more shrinkage in the SCC. The fibers were used in the SCC to reduce these shrinkages. This investigation uses, various percentages of natural kenaf fibers such as 0.1%, 0.2%, 0.3% and 0.4%. Due to this variation in the fiber fractions, the workability properties are affected in the SCC. If the workability gets affected, the concrete does not have the self-compaction property and behaves as CVC. Hence the current research focuses on the SCC Workability Properties (WP) and optimization of SCC mix utilizing machine learning techniques. Considering the advantages of past research, a model was developed with a fusion approach that incorporates Principal Component Analysis (PCA) for SCCWP. Initially, the dataset is processed with the help of standardization using an SCC mix. The processed output is fed into principal component analysis for a dimensional shift from high to low. Then the low dimensional data is given as input to the effect of various workability properties of Fiber Reinforced Self Compacting Concrete (FRSCC) which was modeled using a Support Vector Machine (SVM) and Logistic Regression (LR). A comparison has been made, logistic regression produces a more reliable outcome compared to support vector machine in terms of all the evaluation metrics used.
  • Evaluation of the mechanical performance and capillary absorption of concretes with incorporation of crystallizing admixtures and subjected to damage at early ages Articles

    Tambara, Rafael Fumaco; Júnior, Luis Urbano Durlo Tambara; Venquiaruto, Simone Dornelles; Costa, Fernanda Bianchi Pereira da

    Abstract in Portuguese:

    RESUMO Esta pesquisa avaliou o fenômeno de autocicatrização nas propriedades mecânicas e absorção capilar de concretos estruturais. Foram avaliados dois aditivos cristalizantes em pó, dosados de acordo com o teor recomendado pelos fabricantes. Aditivos cristalizantes aumentam a densidade do gel C-S-H e formam cristais insolúveis, bloqueando fissuras. Três traços de concreto foram produzidos: referência, aditivo-X com 0,8% e aditivo-Y com 2,0% em relação a massa do cimento. Aplicou-se 75% da carga de ruptura aos 3- e 14-dias para gerar microfissuras e comparar com a referência. Posteriormente, a autocicatrização foi avaliada aos 28- e 76-dias. A propriedade de resistência à compressão axial foi determinada aos 28-dias, revelando que os aditivos cristalizantes contribuíram para um aumento médio de 12% desta propriedade. A idade do carregamento dos concretos não apresentou um impacto significativo na resistência à compressão axial, mas apontou resultados significativos entre os tipos de aditivos estudados, conforme ANOVA. As propriedades de absorção de água por capilaridade foram avaliadas aos 28- e 76-dias, indicando uma redução de absorção de água média de 42% devido ao uso dos aditivos cristalizantes. Em conclusão, a incorporação dos aditivos cristalizantes contribuiu de maneira positiva para a autocicatrização dos concretos estudados, indicando uma recuperação parcial das microfissuras.

    Abstract in English:

    ABSTRACT This study assessed the self-healing phenomenon in the mechanical properties and capillary absorption of structural concretes. Two crystalline powder additives were evaluated, dosed according to the manufacturers’ recommendations. Crystalline additives increase the density of the C-S-H gel and form insoluble crystals, effectively blocking fissures. Three concrete mixes were produced: a reference mix, additive-X with 0.8%, and additive-Y with 2.0%, relative to the mass of cement. 75% of the rupture load was applied at 3- and 14-days to induce microfissures for comparison with the reference mix. Subsequently, self-healing was assessed at 28- and 76-days. The property of axial compressive strength was determined at 28-days, revealing that crystalline additives contributed to an average increase of 12% in this property. While the age of loading did not significantly impact axial compressive strength, there were significant variations among the types of additives studied, as indicated by ANOVA. Water absorption properties through capillarity were evaluated at 28- and 76-days, showing an average reduction of 42% in water absorption due to the use of crystalline additives. In conclusion, the inclusion of crystalline additives positively contributed to the self-healing of the studied concretes, suggesting a partial recovery of microfissures.
  • Mechanical analysis of concrete with partial replacements of aggregates by steel filings Articles

    Mello, Paulo Henrique Carvalho; Altoé, Silvia Paula Sossai; Gdirão, Gustavo Saleme de Miranda; Ribeiro, Otávio Gandolphi do Nascimento; Thomazotti, Pietro Marquette

    Abstract in Portuguese:

    RESUMO O presente trabalho teve por objetivo apresentar os resultados obtidos para o comportamento mecânico do concreto considerando a substituição parcial dos teores dos agregados por resíduo industrial provenientes da usinagem de aço. Conhecidas as propriedades mecânicas dos metais, considera-se que a substituição parcial dos agregados em concretos por resíduos dessa natureza possa atuar não apenas como um fator de melhora no comportamento do material, mas também como uma maneira de se produzir uma destinação eficiente ao resíduo em questão, além de que, a substituição de agregados por materiais alternativos contribui para mitigar a escassez desses recursos. Dessa forma, o trabalho justifica-se pelas suas potencialidades em relação à engenharia de materiais cimentícios e impactos ligados à sustentabilidade das edificações. Para se investigar o material foram adotados três teores de substituições em relação ao peso de cimento, 5%, 10% e 15%, sendo efetuados ensaios para obtenção da absorção de água e consistência, além das resistências à tração indireta, compressão e módulo de elasticidade estático. A que a substituição dos agregados por resíduo de usinagem leva a maior qualidade do concreto produzido além de acréscimo de resistências, essa melhora se mostrou mais expressiva para a substituição do agregado miúdo, com aumento na resistência média à compressão e tração de até 73,70% e 73,71% respectivamente, obtendo-se através de aproximações não lineares o teor ótimo próximo a 12%, para as substituições de agregado graúdo teores acima dos estudados tendem a ser mais interessantes.

    Abstract in English:

    ABSTRACT The present study aimed to present the results obtained for the mechanical behavior of concrete, considering the partial replacement of aggregate content with industrial waste from steel machining. Given the mechanical properties of metals, it is considered that the partial substitution of aggregates in concrete with waste of this nature can act not only as an improvement factor in the material’s behavior but also as an efficient way to dispose of the specific waste. Additionally, the substitution of aggregates with alternative materials contributes to mitigating the scarcity of these resources. Thus, the work is justified by its potential in relation to cementitious materials engineering and impacts related to the sustainability of buildings. To investigate the material, three replacement levels were adopted concerning the weight of cement, namely 5%, 10%, and 15%. Tests were conducted to obtain water absorption and consistency, as well as indirect tensile strength, compression, and static elasticity modulus. The replacement of aggregates with machining waste was found to lead to higher quality concrete production and increased strengths. This improvement was more pronounced for fine aggregate replacement, with an increase in average compression and tensile strength of up to 73.70% and 73.71%, respectively. Through nonlinear approximations, the optimal content was found to be around 12% for fine aggregate replacement. For coarse aggregate replacements, levels above those studied tend to be more interesting.
  • Experimental study of the production of resin granite and marble using their solid waste Articles

    Santos, Vinicius Rodrigues dos; Genova, Luís Mateus; Soares, Silvete Mari; Cabral, Thiago Baltor; Lovo, João Fiore Parreira; Carmo, Devaney Ribeiro do

    Abstract in English:

    ABSTRACT Structural materials play an essential role in equipment and constructions, with properties such as strength and stability. Granite and marble are widely used for structural building materials such as cladding, sinks and countertops. It is possible to recycle waste from these rocks in the production of new parts, reducing the environmental impact. In Brazil, there is a high amount of construction and demolition waste, with most of the raw material becoming waste before the product is finished. Studies indicate that the incorporation of ornamental stone waste into cementitious products can significantly reduce environmental impact and improve its sustainability. The present work presents an experimental study for the manufacture of resin granite test specimens with residues from different dosages and resin epoxy levels. Flexural strengths of up to 7, 11, 24 and 28 MPa are achieved for resin contents of 5%, 10%, 15% and 20% respectively. The material has anisotropic characteristics and makes good use of almost all of the size ranges of waste used. Future reverse engineering studies of the resin are also necessary to expand knowledge and further optimize its application.
  • Experimental and numerical analysis of reinforced concrete beams strengthened in shear with steel bars using the near-surface mounted (NSM) technique Artigos

    Costa, Leonardo Medeiros; Pires, Tiago Ancelmo de Carvalho; Silva, José Jéferson do Rêgo; Vasconcelos, Geilson Márcio de Alburquerque

    Abstract in Portuguese:

    RESUMO Há uma necessidade crescente de intervenção nas estruturas de concreto armado existentes para recuperar ou aumentar a sua capacidade resistente. O uso de materiais compósitos, como a fibra de carbono, tem sido eficiente, mas o custo ainda é um entrave. A aplicação de barras de aço como elemento de reforço apresenta-se como material alternativo e tecnicamente viável, porém existem poucos trabalhos na literatura. Desse modo, este trabalho realizou uma série experimental com três vigas de concreto armado sem armadura transversal, e reforçadas ao cisalhamento com barras de aço utilizando a técnica near-surface mounted (NSM). Foram monitorados no experimento a carga, o deslocamento e o padrão de fissuração. Os resultados demonstraram a eficiência do reforço com aumento de 69% da carga última e 63% da carga para surgimento das primeiras fissuras comparados a viga de referência. O reforço também aumentou a ductibilidade das vigas antes da ruptura brusca por cisalhamento. Modelos numéricos via método dos elementos finitos (MEF) foram realizados no software ABAQUS utilizando diferentes tipos de elementos e malhas. Os resultados numéricos foram validados com os resultados experimentais e foi observado que o uso de elementos quadráticos comparados a elementos lineares consegue representar melhor o padrão de fissuração e a capacidade de carga das vigas. A relação média dos resultados numérico/experimental para carga máxima das vigas reforçadas foi de 0,94.

    Abstract in English:

    ABSTRACT There is a growing need for intervention in existing structures to recover or increase strength capacity. The use of composite materials, such as carbon fiber, has been efficient, but cost is an obstacle. The application of steel bars as a strengthening element is an alternative and technically viable material, but there are few studies in the literature. This work carried out an experimental series with three reinforced concrete beams without transverse reinforcement, and strengthened in shear with steel bars using the near-surface mounted (NSM) technique. The load, displacement and cracking pattern were monitored in the experiment. The results demonstrated the efficiency of the strengthening with an increase of 69% in the ultimate load and 63% in the load for the appearance of the first cracks compared to the reference beam. The strengthening also increased the ductility of the beams before sudden shear failure. Numerical models via the finite element method (FEM) were carried out in the ABAQUS software using different elements and meshes. The numerical results were validated with the experimental results, and it was observed that the use of quadratic elements compared to linear elements can better represent the cracking pattern and the load capacity of the beams. The mean ratio of numerical/experimental results for maximum load of strengthening beams was 0.94.
  • Static and cyclic behaviour of fibre-reinforced pavement concrete with copper slag as fine aggregate Articles

    Kamalasekar, Athiappan; Murugasan, Rajiah; Makendran, Chandrakasu; Francis, Michael Raj

    Abstract in English:

    ABSTRACT The objective of this research was to assess the performance of pavement-quality concrete having 100% copper slag as fine aggregate in the presence of steel fibre. In this research, the crimped steel fibre of two lengths (30 mm and 50 mm) and different dosages such as 0.5%, 1.0%, 1.5%, and 2.0% by weight of concrete are included in the concrete having 100% copper slag as fine aggregate and compared with the concrete having river sand and copper slag as fine aggregate without fibre. The mechanical characteristics that are being examined include fatigue performance, bond strength, impact strength, flexural strength, stress-strain behaviour, abrasion resistance, and slabs exposed to both static and cyclic loading. According to the experimental findings, pavement concrete that contains 100% copper slag as fine aggregate and 1% crimped steel fibre in both 30 and 50 mm diameters performs better and is more optimal. An inventive way to manage copper slag waste and create durable, stiff pavement construction is with copper slag in concrete road construction. Utilising copper slag in concrete road construction offers a novel approach to waste management and the creation of environmentally friendly concrete road construction.
  • Residual stress analysis in AISI 347L steel coating welding on Cr-Mo steel using coordinate measurement method Artigos

    Silva, Gleryston Thiago Gomes da; Hermenegildo, Tahiana Francisca da Conceição; Torres-López, Edwar Andrés; Santos, Tiago Felipe de Abreu; Urtiga Filho, Severino Leopoldino

    Abstract in Portuguese:

    RESUMO Este estudo avaliou a qualidade do revestimento de aço inoxidável AISI 347L em substrato de aço Cr-Mo produzido pelo processo GMAW, levando em consideração a influência dos parâmetros de soldagem e dos tratamentos térmicos de alívio de tensão. Para a análise de tensão residual, foi utilizado o método de Deslocamento de Pontos Coordenados (DCP). Foram confeccionados três (3) corpos de prova com dimensões de 300 × 150 × 12,7 mm, variando a composição do gás de proteção (100% Ar, 98% Ar + 2%CO2 e 96% Ar + 4% CO2), e realizados tratamentos térmicos pós-soldagem em conformidade com a norma ASME BPVC VIII. Para avaliar a microestrutura do revestimento, foram realizadas análises de microscopia óptica, ensaio macrográfico e ensaio de dureza. Os resultados obtidos indicam que os tratamentos térmicos de alívio de tensão foram eficazes na redução da tensão residual, melhorando a qualidade do revestimento. A análise de microscopia óptica revelou uma microestrutura homogênea e sem trincas ou porosidades, indicando um bom desempenho do processo GMAW. Os resultados desses ensaios são de grande importância para a qualificação do procedimento de soldagem e para garantir a qualidade do revestimento em aplicações práticas.

    Abstract in English:

    ABSTRACT This study evaluated the quality of AISI 347L stainless steel coating on Cr-Mo steel substrate produced by GMAW process, considering the influence of welding parameters and stress-relieving heat treatments. The Coordinated Point Displacement (CPD) method was used for residual stress analysis. Three (3) specimens with dimensions of 300 × 150 × 12.7 mm were fabricated with variations in shielding gas composition (100% Ar, 98% Ar + 2% CO2, and 96% Ar + 4% CO2), and post-weld heat treatments were performed following ASME BPVC VIII standard. Optical microscopy, macrographic examination, and hardness testing were performed to evaluate the microstructure of the coating. The results indicate that the stress-relieving heat treatments effectively reduce residual stresses and improve coating quality. Optical microscopy analysis revealed a homogeneous microstructure without cracks or porosity, indicating satisfactory performance of the GMAW process. These test results are important for qualifying the welding process and ensuring the quality of the coating in practical applications.
  • Influence of tensile strength on the load bearing capacity of tall reinforced masonry walls Articles

    Padilha, Tiago Montanha; Parsekian, Guilherme Aris; Nascimento Neto, Joel Araújo do

    Abstract in English:

    Rupture by geometric instability is a common characteristic in slender walls. Codes for the design of slender walls use the slenderness ratio (λ) as a parameter for which their methods are valid. The Brazilian standard has a specific method for the design of highly slender walls with λ > 30 that does not take into account the tensile strength of the masonry. To evaluate the behavior of high slenderness walls and the sensitivity to tensile strength, a finite element model was developed using Abaqus to simulate three experiments from the literature. The results proved the ability of the modeling to represent the behavior of slender walls with 20% error for the out-of-plane displacements and vertical load bearing capacity. It was concluded that the post buckling behavior of the walls is sensitive to tensile strength and negligible for determining the critical buckling load.
  • Investigating the properties of ternary-blended self-compacting concrete with fibre Articles

    Muthaiyan, Uma Maguesvari

    Abstract in English:

    Self-Compacting Concrete (SCC) is the designation for concrete that flows under its own weight. By creating or introducing SCC, the flow ability of ordinary concrete can be enhanced. This study’s primary focus is on the creation of SCC utilizing ternary blends of cementitious additives. Several tests were carried out to assess the SCC’s mechanical, fresh, and durability characteristics. Energy Dispersive X-ray Analysis (EDAX) and Scanning Electron Microscope (SEM) were used to examine micro level characteristics. The mechanical and durability qualities of SCC have been improved by using a ternary blended SCC mix that contains seventy percentage of Ordinary Portland Cement, twenty percentage of Fly Ash, and ten percentage of Silica Fume. The workability of fresh concrete got reduced by increasing the fly ash, silica fume and glass fibre content that can be improved by adding super plasticizer. The strength and durability performance of hardened concrete were increases with increase in fly ash, silica fume and glass fibre in conventional concrete. The glass fiber reinforced SCC mixes with 0.4 and 0.6% of GF have a strong connection with the cement matrix, as shown by SEM pictures. As fiber dosage is increased, peak load of ternary mixed SCC increases significantly.
  • Performance analysis of bacterial self-compacting concrete – workability, mechanical, durability and micro analysis Articles

    Vadamalai, Priyadharshini; Paramasivam, Suresh Kumar

    Abstract in English:

    ABSTRACT Concrete may develop micro cracks and contains pores, both of which are extremely undesirable since they allow water and other harmful chemicals to enter the material easily. The Bacterial Self Compacting (BSCC), which continually deposits calcite in concrete, is one efficient method for sealing fissures. Microbiologically Induced Calcite Precipitation, or MICP, is the term used to describe this occurrence. The urease enzyme assists bacteria in the deposition of calcium carbonate (CaCO3). Because it is bio-based, environmentally safe, and long-lasting, the bacterial remediation method outperforms other methods. The high pH of concrete and the mechanical forces that occur during mixing require bacteria to provide resistance. The MICP-induced concrete has become a significant topic of study for high performance building. The utilization of bacteria for the production of bacterial SCC has received very little attention in India, and the durability properties of these mixtures have also received inadequate attention. Bacterial Self-Compacting Concrete (BSCC) of M60 grade, with bacteria as admixture along with flyash and silica fume. This research is to know about the workability, mechanical properties, durability and micro analysis of bacterial self-compacting concrete. The test results shows the bacteria of size 106 shows the best results in bacterial self-compacting concrete.
  • Enhancing PVCC beam performance through PVA fiber and basalt fabric in sustainable construction: ductility, strength, and energy absorption improvements Articles

    Prasanthni, P.; Priya, B.; Palanisamy, T.; Dineshkumar, G.

    Abstract in English:

    This study evaluates the performance of PVCC (Polyvinyl Alcohol Cementitious Composite) layered beams (BP1 to BP5), basalt fiber fabric-wrapped beams (BB1 and BB2), and a control beam (B0). Results show that specimen BP3, with 1.2% PVA fiber in PVCC layered beam, and BB2, with basalt fiber fabric wrapped at the bottom up to the neutral axis, exhibit superior performance. BP3 delays first crack initiation, increases the ultimate load-carrying capacity by 19.87%, and achieves a remarkable 54.57% increase in maximum ductility compared to B0. BP3 also demonstrates 54.54% higher stiffness and notable energy absorption. Similarly, BB2 outperforms BB1 and B0 in first crack load, ultimate load carrying capacity, ductility, stiffness, energy absorption, and energy index. BB2 exhibits 2.10 times increase in ductility compared to B0. Incorporating PVA fiber in PVCC layered beams and basalt fiber fabric wrapping offers better improvements in crack resistance, load capacity, ductility, stiffness, and energy absorption, contributing to innovative and sustainable beam design in construction.
  • The influence of MoS2 and SiC reinforcement on enhancing the tribological and hardness of aluminium matrix (Al6061-T6) hybrid composites using Taguchi’s method Articles

    Kuppusamy, Ragupathy; Thangavel, Anand; Manickam, Arun; Sathiyamoorthy, Vishvanathperumal

    Abstract in English:

    The current study has examined the dry sliding wear behaviour of MoS2 and SiC reinforced aluminium composites. An aluminium matrix reinforced with SiC and MoS2 was used for this investigation. Silicon carbide (SiC) and molybdenum disulphide (MoS2) particles are employed as reinforcements, and the matrix is made of the aluminium alloy series Al6061. Three weight steps were used to adjust the SiC and MoS2 reinforcements in the Al6061 matrix from 3% to 5%. Dry sliding wear behaviour is examined using a pin-on-disc apparatus. Additionally, the test was further validated using a suitable set of parameters that confirmed Taguchi’s findings. The Brinnell hardness test is used to determine the composite material’s hardness. When the percentage of reinforcement reaches 3% SiC and 5% MoS2, wear is less compared to a combination of 5% SiC and 3% MoS2.By increasing the MoS2 percentage of reinforcement, wear was consequently decreased. The microstructure of AL6061/SiC/MoS2 composites is evident from the scanning electron microscopy images, where the silicon carbide (SiC) phase and the molybdenum disulfide (MoS2) phase are evenly distributed throughout the matrix.
  • Evaluation of machinability performance of T51603 using response surface methodology and grey relational analysis Articles

    Kumar, R. Suresh; Vinodh, S.; Satishkumar, P.; Seenivasan, S.

    Abstract in English:

    The goal of this study is to increase material removal rate (Mrr), and minimize consumption of power (Pc) and surface integrity (Sr) while using the least amount of resources thereby addressing sustainable manufacturing and optimization in machining operation. Box Behnken Design (BBD) and Grey Regression Analysis (GRA) are systematically followed in the machining process on UNS T51603. The experimental runs were performed based on BBD followed by multi-objective optimization using GRA. The practical applicability and reliability of the optimized parameters is evaluated by confirmatory runs, and the optimal solution of single and multi-objective solution for Sr, Mrr, and Pc, is verified. The lowest Sr was achieved when Ss was maintained at 2000 rpm, with Dc at 0.6 mm, Fr at 750 mm/min, and Cfr 6 l/min. maximum Mrr was attained when Ss assigned at 1750 rpm, with Dc at 0.6 mm, Fr at 750 mm/min, and Cfr 8 l/min. When compared to confirmatory runs, the optimized set of parameters for BBD and GRA reveals a 10% variance, demonstrating the validity of the optimization strategies used. In terms of Pc the optimized parameters were found to be 1750 rpm, 0.2 mm, 500 mm/min, and 6 l/min.
  • Utilizing binary ternary blended metakaolin and ground pond ash for reduced carbon footprint emissions and improved mechanical properties in concrete Articles

    Kandasamy, Yuvaraj; Kumarasamy, Vidhya; Murugan, Sakthivel; Singaraj, Ramkumar

    Abstract in English:

    ABSTRACT In this empirical investigation, the effect of four concrete mixtures was examined, namely, control concrete (CC), binary blended metakaolin concrete (BBMC), binary blended pond ash concrete (BBPC), and ternary blended metakaolin and pond ash concrete (TBMPC). In this study, a total of 288 specimens were manufactured, including CC, BBMC, BBPC, and TBMPC, which were subjected to curing for 28 and 90 days. The mix compositions used were in a ratio of 1:1.75:2.22, with a water-binder ratio of 0.44. The study delved into an extensive examination of both the fresh and mechanical properties of these concrete mixtures. Additionally, the sustainability analysis for all mix proportions were computed. The results demonstrate significant enhancements in compressive strength (fcs), split tensile strength (fsts) and flexural strength (ffs) with an increase of 17.82% and 19.81%, 12.32% and 13.50%, 13.34% and 14.39%. These improvements were observed specifically in the M6P6 mix, composed of 88% PC, 6% MK, and 6% PA. In the context of sustainability analysis, the PA20 mix displayed the lowest carbon footprint emissions, measured at 351 kgCO2/m3. On the other hand, the MK6PA6 mix demonstrated the highest CO2 intensity, with values of 0.095 MPa/kgCO2·m3 and 0.114 MPa/kgCO2·m3.
  • Experimental study and assessment of the structural performance of laced reinforced concrete beams against reverse cyclic loading Articles

    Johnson, Blessy Grant Christian; Ramasamy, Murugesan; Narayanan, Anandavalli

    Abstract in English:

    This experimental research evaluates the structural performance of laced reinforced concrete beams (LRC-45) in comparison to conventional reinforced concrete beams (RC-90) under reverse cyclic loading. Visual inspection revealed that LRC-45 exhibited superior crack resistance, even at high displacements, unlike RC-90, which displayed vertical cleavages and diagonal tension cracks. RC-90 demonstrated minimal ductility, initiating cracking at lower loads. Hysteresis response curves showed LRC-45 outperforming RC-90 in terms of cracking load and maximum load, with higher displacement capacity. The ductility factor of LRC-45 was 56.39% higher. Notably, LRC-45 exhibited a substantial 143.43% increase in cumulative energy dissipation, highlighting its superior energy-absorbing capacity. Additionally, stiffness analysis indicated significantly higher stiffness in LRC-45. The numerical analysis supported experimental findings, emphasizing the potential of laced reinforcement in enhancing structural resilience, energy dissipation, and stiffness. The novelty lies in the remarkable improvements offered by LRC-45, particularly its enhanced energy-absorbing capacity and stiffness, which are crucial for structures subjected to dynamic loads, such as seismic events.
Laboratório de Hidrogênio, Coppe - Universidade Federal do Rio de Janeiro, em cooperação com a Associação Brasileira do Hidrogênio, ABH2 Av. Moniz Aragão, 207, 21941-594, Rio de Janeiro, RJ, Brasil, Tel: +55 (21) 3938-8791 - Rio de Janeiro - RJ - Brazil
E-mail: revmateria@gmail.com