Formation of hydrogen blisters during the solution treatment for aluminum alloys

The solution treatment of aluminum alloys can be restricted by the presence of porosity defects caused by the moisture present in the process or by the hydrated front on the material surface. Hydrogen blisters cause deleterious effects on mechanical properties and surface finish. However, the formation of bubbles in solid aluminum is not caused only by the known reaction 2Al+3H2 O=3H2 +Al2 O3 , as it does not explain the interaction of the aluminum oxide layer with the formation mechanisms. In addition, the literature approaches show that there is more than one mechanism for the formation of these defects, but no work has made an association between them. Thus, the objective of this work is to carry out extensive research on the state of the art of hydrogen blister formation in aluminum alloys during the solubilization heat treatment. Contemplating different proposed mechanisms of bubble formation on the surface and structure, the analysis of this association of approaches indicated that the mechanisms depend on both permeability, where the hydrated oxide front creates passage for the formation of blister in the sublayer, as well as diffusion and hydrogen solubility in the microstructure

Analysis of non-uniform expansion behavior of injected EVA

Currently the sports footwear market is very competitive, in which it is sought to produce products that provide high performance, using technology in the production processes as well as in the materials used. One of the main materials used in the composition of soles and midsole of these products is EVA (Ethylene-Vinyl Acetate), which brings several benefits such as cost reduction, comfort, lightness and softness. The injection molding process is the most efficient for obtaining EVA soles, however, EVA undergoes large expansions that may vary according to its formulation and geometry of the desired model. The objective of this work is to analyze the non-uniform deformation of EVA, used in the injection molding processes, as well as one method used to correct such distortions that occur in the expansion of this material. For this, a bibliographic review was carried out to analyze the chemical composition of the EVA, whose composition will determine the characteristics of expansion and softness. The work also addresses the steps of the injection process by analyzing the temperatures and pressure employed and an analysis of how to predict and correct the distortion in EVA expansion. It is proposed to use a section of a 3D model, where it is determined where compensations should be applied and using 3D modeling software. To analyze the generation of smaller bubbles in less thick regions of an EVA sole, a scanning electron microscope (SEM) analysis was performed. In addition, the measurements of the analyzed model were compared with the virtual model through a 3D scan. Hardness tests on the Asker C scale and injection simulations were also performed to analyze the cooling time of the part after leaving the mold, volumetric contraction that occurs in the extraction of the mold part, and the thicknesses of the walls of the product. The results indicate that the comparison of the models was within the accepted tolerance, which allows a variation in the expansion of up to 1mm in the length of the evaluated points. From the analyzes made in the scanning electron microscope and in the hardness test, it was possible to verify that in regions of smaller thickness and smaller volume, the EVA blend cannot have its total expansion, i.e., micro bubbles of gases generated in the expansion are smaller in these regions when compared to regions of greater volume and thickness. Consequently, these regions become denser and less soft. Simulations indicated that in regions where bubbles do not expand, there is also an early cooling of the material when compared to regions with higher volume, proving that the cooling time is directly linked to the EVA expansion rate

Análise e seleção de materiais para garrafas térmicas

Neste artigo, três diferentes marcas de garrafas térmicas foram analisadas, segundo a norma ABNT NBR 13282 (garrafa térmica com ampola de vidro – requisitos e métodos de ensaio). Testes de capacidade volumétrica real, estabilidade, resistência a choques térmicos, eficiência térmica e resistência ao impacto foram realizados. Além disso, foi feita uma engenharia reversa, onde se utilizou ensaios de Espectrofotometria de Infravermelho - FTIR para a identificação dos materiais utilizados no corpo externo, copo, tampa e fundo. Uma vez que os resultados mostraram que, em grande parte, os materiais utilizados nos produtos eram os mesmos, foi feita uma seleção computadorizada de materiais, a fim de verificar se haveria outros materiais que pudessem apresentar melhores propriedades frente às exigências de fabricação e uso de uma garrafa térmica ou custo mais baixoIn this article, three different trademarks of thermal bottles were analyzed, according to ABNT NBR 13282 norm (thermal bottle with silvery glass – requirements and test methods). Tests of real volumetric capacity, stability, thermal shock resistance, thermal efficiency and impact resistance were carried out. In addition, a reverse engineering was done, where it was applied the Fourier Transform Infra-red Spectroscopy - FTIR tests for the identification of the external body, cup, lid and bottom materials. Since the results showed that, to a great extent, the materials utilized were the same, a computerized material selection was carried out, in order to verify if there would be other materials that could present better properties to the demands of a thermal bottle manufacturing and use or lower cost

Cement matrix containing lightweight aggregate based on Non-Metallic Fraction Printed Circuit Boards (NMFPCB'S)

Materials such as river sand, used in construction, have a high demand, and thus generate great environmental impacts while being extracted, such as erosion of the rivers banks and your siltation. With the increasing restriction of river sand extraction which can generate a reduction in the product's offer in the civil construction sector, it is necessary to develop waste recycling technologies for the production of sands with less environmental impact. One of the alternatives for the production of mortar for construction is the replacement of sands extracted from rivers by waste from other industries, such as the electronics industry that presents large and growing production worldwide, due to technological advances. Thus, this work aims to evaluate the influence of partial replacement of quartz sand by lightweight aggregate based non-metallic fraction of printed circuit boards (NMFPCB's) on the properties of cementitious matrix in the fresh and hardened states. For this, the electronic components of the printed circuit boards (PCBs) were removed, they were grinded and then through magnetic and electrostatic separation processes to separate the most valuable and abundant part of metals. The water to cement ratio was 0.48 in all the experiments, the Portland cement to sand ratio was 1:3 (in mass) for the control, and the mortars with NMFPCB's replacement of sand by volume of 25% and 50% were also made. These were characterized mechanically by axial compressive strength test at different ages. The partial results showed that with the increase of sand substitution by NMFPCB's there was a reduction of the mortar consistency index in the fresh state. Results showed that matrix that suffered the substitution of sand by light aggregate, decreased the compressive strength in relation to the reference, but have potential to use in construction industry as blocks or non-structural elements

Selection of thermoplastics and multishot process for bi-component household design

Introduzir novos materiais e transformá-los em produtos diferenciados, por meio de processos adequados, é um dos desafios da área de desenvolvimento de produtos. Este estudo detalha o projeto de utensílio doméstico - colher para preparo alimentos - com propostas de substituição dos materiais empregados convencionalmente no mercado, com a premissa de explorar o toque suave e a flexibilidade da forma que os Elastômeros Termoplásticos (TPEs) podem proporcionar. O presente trabalho descreve diferentes tipos de processos industriais de injeção multimateriais, destacando critérios para a seleção adequada do processo. Foi empregada a metodologia de seleção de materiais de Ashby, complementando métodos projetuais de design de Bonsiepe. Foi realizada uma comparação de materiais computadorizada com o software Cambridge Engineering Selector, a fim de comparar propriedades relevantes para a função estrutural e pelas restrições de resistir a temperaturas elevadas, decorrente do uso no processo de cozimento de alimentos. Além disso, foram realizadas análises com o software CAE SolidWorks Plastics, para simular o preenchimento das cavidades do molde com diferentes polímeros, analisando o tempo de preenchimento e resfriamento, pressão, temperatura, cisalhamento e rechupes. Os resultados encontrados com o software CES Selector, permitiram destacar duas possibilidades de seleção focada principalmente na resistência térmica. Os candidatos mais promissores encontrados foram o PA6 para a parte rígida e o TPA para a parte flexível ou PBT para a parte rígida e TPC para a parte flexível. Contudo, a classe de TPEs encontrou dificuldade em substituir o silicone com a mesma performance no critério de temperatura máxima de trabalho. Mesmo assim a combinação PA6 com TPA mostrou-se satisfatória. Já o resultado da simulação do processo de injeção apresentou-se promissor, devido ao bom preenchimento da cavidade. Os resultados indicam que a união do PA6 com o TPA é a melhor escolha, considerando o valor de mercado da resina, o módulo de elasticidade, a energia incorporada, a temperatura de trabalho e o processamento simulado da co-injeção da dupla de materiais.Introduce new materials and turn them into differentiated products through applicable processes and one of the challenges of product development. This study details the design of the household utensil - food preparation spoon - with proposals for replacing conventionally used materials on the market, with the premise of exploring the soft feel and flexibility of how thermoplastic elastomers (TPEs) can use. This paper describes different types of industrial multi-material injection processes, highlighting the requirements for proper process selection. Ashby's material selection methodology was employed, complementing Bonsiepe's design design methods. A computerized material comparison was performed with the Cambridge Engineering Selector software, a comparison that includes the requirements for structural functions and high temperature resistance constraints resulting from use in the food cooking process. In addition, they were analyzed using CAE SolidWorks Plastics software to simulate or fill mold cavities with different polymers, analyze fill and cool time, pressure, temperature, shear and reapplication. The results found with CES Selector software allowed to highlight two selection possibilities focusing mainly on thermal resistance. The most promising candidates found were the rigid part PA6 and the flexible part TPA or the rigid part PBT and the flexible part TPC. However, one class of TPEs found it difficult to replace silicone with the same performance at the maximum working temperature criterion. Even so, the combination PA6 with TPA was satisfactory. It is already the result of the simulation of the injection process displayed, if due to the good filling of the cavity. The results that determine the union of PA6 with TPA are the best choice considering the resin market value, elastic modulus, incorporated energy, working temperature and simulated co-injection processing of the material pair.KEYWORDSproduct development; materials selection; household items; Thermoplastic Elastomers; multi-material injection process

Tratamento térmico em Zamac visando diminuir defeitos de porosidade

O Zamac tem sido utilizado na indústria galvânica, principalmente, devido ao seu baixo ponto de fusão, o que permite a obtenção de peças com riqueza de detalhes, tais como peças do setor moveleiro, moda e metais sanitários. No entanto, os processos de sua obtenção, por injeção sob pressão e injeção centrífuga, geram porosidade e, consequentemente, aumento de sucata. Por outro lado, estudos mostraram que fusão por gravidade não apresenta tais problemas. Nesse sentido, o objetivo deste artigo foi tratar termicamente peças de Zamac injetadas sob pressão, com a finalidade de obter comportamento semelhante às peças fundidas por gravidade. Para tanto, peças injetadas sob pressão foram tratadas termicamente, abaixo da temperatura de fusão. A caracterização morfológica dessas amostras foi obtida por MEV. Observou-se que o tratamento térmico acima da temperatura eutetoide apresentou melhor resultado com respeito à porosidade observada.The Zamac has been used in the galvanic industry mainly due its low fusing point properties, which allows obtaining very detailed parts, like parts for furniture industry, fashion and health metals. However, its production processes, like pressure injection and centrifugal injection, generate an increase in porosity as well as waste. On the other hand, studies show that die casting leaked Zamac doesn’t show the same problems. In this sense, the goal for this work is to perform heat treatment in Zamac parts produced by pressure injection in order to obtain similar properties as the ones produced by die casting leakage. For this, the parts injected under pressure were thermally treated under their fusion temperature. It was observed that thermic treatment over the eutectoid temperature showed the best result, regarding the observed porosity

Reuse of waste printed circuit boards as fillers in polypropylene composites

As placas de circuito impresso (PCIs) são as partes mais valiosas dos resíduos eletrônicos, pois possuem uma considerável quantidade de metais com potencial de recuperação. Processos de reciclagem com o intuito de recuperar metais de PCIs têm despertado interesse ultimamente. Contudo, uma fração destes resíduos não é completamente aproveitada e tem destino incerto, como ocorre para a fração não-metálica e o pó gerados durante os processos de recuperação de metais. O foco deste estudo foi o emprego do pó gerado nos processos de cominuição mecânica, separação granulométrica, magnética e eletrostática de PCIs controladoras e indicadoras de temperatura de câmaras frias, para obter compósitos de matriz de polipropileno (PP) com diferentes teores de pó de PCIs, 5, 10 e 20% em massa. Os materiais foram pesados, misturados, moldados por injeção e posteriormente caracterizados por ensaios de tração, dureza Shore D, espectroscopia de infravermelho, análise termogravimétrica e microscopia eletrônica de varredura. Os resultados dos ensaios de tração e dureza indicaram propriedades levemente superiores às do PP puro, exceto para a deformação na ruptura, que foi reduzido em até 2,7 vezes para a amostra com 20% de resíduo. O desenvolvimento de compósitos utilizando o pó de PCIs se mostrou viável em aplicações onde as propriedades resistência à tração, rigidez e dureza são determinantes, mesmo para um elevado teor de resíduo (20%) agregado.Printed Circuit Boards (PCBs) are the most valuable parts of e-waste because they have a considerable amount of metals with recovery potential. Recycling processes aimed at recovering metals from PCBs have aroused great interest recently. However, there is a fraction of this waste that is not utilized and has uncertain destination, e.g. the non-metallic fraction and the dust generated during metal recovery processes. The focus of this study was to employ the powder generated in the mechanical comminution, granulometric, magnetic and electrostatic separation processes of controller and temperature indicator PCBs of cold rooms to obtain polypropylene (PP) matrix composites with distinct PCBs powder content, 5, 10 and 20% in weight. The sample was collected during the mechanical comminution processes. The materials were weighed, mixed, injection molded and later characterized using tensile tests, Shore D hardness, infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. Results of the tensile and hardness tests showed properties slightly superior to pure PP, except for strain at break, which was reduced up to 2.7 times for the sample with 20% of residue. In all, the development of composites using the powder of PCBs was considered feasible for applications where tensile strength, stiffness and hardness are important, even for a large amount of residue added (20%)

Essential oil of the leaves of Eugenia sulcata preserve myocardial contractility and does not present immunotoxicity

The essential oil of the leaves of Eugenia sulcata, in the Myrtaceae family, has a demonstrated antihypertensive effect, but its effects on heart muscle and its toxicity have not yet been elucidated. Little chemical or biological data are available for E. sulcata, whether emphasizing the beneficial effects or the pharmacological security of this species. This study aims to evaluate myocardial contractility and to analyze angiotensin converting enzyme (ACE) and myosin ATPase activities associated with use of this essential oil. In addition, we evaluated the immunotoxicity of E. sulcata essential oil. Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR) were treated daily for 30 days (10 mg/kg of oil) to evaluate the isometric force of the papillary muscle, ACE measured by fluorimetry, and myosin ATPase activities by inorganic phosphate. Lymphocyte cultures were used to evaluate cytotoxicity, DNA damage, and mutagenicity of the essential oil. The results demonstrate that the treatment did not change the cardiac contraction force and did not alter the functioning of the sarcoplasmic reticulum, extrusion of the membrane calcium, or modify the membrane calcium channels or β-adrenergic receptor activity. Tetanic contractions were potentiated in the SHR animals. Myosin ATPase activity was also increased in the SHR animals. Cardiac ACE activity was reduced in both animal strains, and the serum ACE was reduced only in the SHR animals. The essential oil did not cause cytotoxicity or mutagenicity and presented low DNA damage. Our results demonstrated that the essential oil does not change myocardial contractility and does not present relevant immunotoxicity

Analysis of the processes of chromium plating, nickel plating, zinc plating and tin plating

A cada ano, surge um grande interesse em combater a corrosão sobre peças, componentes e máquinas utilizadas em diversos setores das engenharias, e tendo em vista isto, investe-se nos processos de recobrimentos de prevenção contra a corrosão. O objetivo deste trabalho é apresentar aspectos básicos nesta área de recobrimentos metálicos, com enfase nos processos de cromagem, niquelagem, Zincagem e estanhagem. Para tanto, foi realizada uma revisão bibliográfica que aborda os principais recobrimentos utilizados nas indústrias, e também suas vantagens, desvantagens e aplicações. Também foi realizada uma comparação destes materiais utilizados nos processos de recobrimentos com o software Cambridge Engineering Selector® a fim de comparar os custos e valores de durezas associados aos mesmos. Os resultados indicam que os recobrimentos possuem diversas vantagens sob os processos convencionais de prevenção contra a corrosão, que tem aumentado cada vez mais seu campo de aplicação. Entretanto, assim como vantagens, possuem desvantagens, que são a geração de efluentes líquido e gasosos, que ao serem liberados no meio ambiente, geram impactos ambientais severos. Por isso, junto com o aumento de suas aplicações, tem crescido os estudos sobre formas de tratar e reutilizar estes efluentes.Each year, there is a great interest in fighting corrosion on parts, components and machines used in various engineering sectors, and in view of this, it is invested in the processes of prevention coatings against corrosion. The objective of this paper is to present basic aspects in this area of metallic coatings, with emphasis on the processes of chromium plating, nickel plating, zinc plating and tin plating. To this end, a literature review was carried out that approaches the main coatings used in the industries, as well as their advantages, disadvantages, and applications. A comparison of these materials used in the coating processes was also performed using the Cambridge Engineering Selector® software to compare the costs and hardness values associated with them. The results indicate that coatings have several advantages over conventional corrosion prevention processes, which have increasingly increased their field of application. However, as well as advantages, they have disadvantages, which are the generation of liquid and gaseous effluents, which when released into the environment, generate severe environmental impacts. Therefore, along with the increase of its applications, there has been a growing number of studies on ways to treat and reuse these effluents