KIc Determination of a 7075 T6 Aluminum Alloy by Critical Distances Theory and LEFM

The Critical Distances Theory has been used in engineering field as a less expensive method to predict failures. Thus, this research aims to evaluate its methods in other materials, like the aluminum alloy 7075 T6, and notches. Two different notches were machined: a sharp and a blunted, with radius of 0,025 mm and 0,045 mm, respectively. The first in specimens of tests tension and the last in bend tests specimens. The DCT methods analyzed exhibited low percent differences and predictions mutually consistent. However, the Line Method stood out when presented 3% to percent difference. The analysis to stress field around of sharp notch tip, LM achieved a value of 12 MPa√m para KIc. Although, when these same results were applied in the Traditional Fracture Mechanics equations, a fracture toughness of 34 MPa√m was found. This last result is one of the best predictions achieved until the present moment in this research group. Mainly when compared with other works which determined the same property using the same thermal treatment conditions to this alloy

Anomalous Strain Rate Effect in Ultrafine Grained Titanium

An anomalous effect was found in the strain rate dependence of severe plastic deformed commercially pure titanium with ultrafinegrained structure. A maximum tensile strength was obtained for ϵ˙=10−3s−1. This did not allow a single strain rate sensitivity parameter to be defined in the interval from ϵ˙=10−5to10−1s−1. Distinct deformation mechanisms for lower and higher strain rates might be the reason for this anomaly

ANÁLISE DA FALHA DE PARAFUSOS CLASSE 10.9 UTILIZADOS EM GUINDASTE OFFSHORE

Neste trabalho foram avaliadas as propriedades mecânicas de dois parafusos que têm como função a fixação de um guindaste utilizado nas plataformas offshore. Foram retiradas duas seções de cada elemento para a realização de análises de composição química, da fratura e microestrutural e ensaios mecânicos de dureza e de tração. Os resultados obtidos nas análises da composição química mostraram-se condizentes com as normas e que o material utilizado para fabricação dos parafusos trata-se de um aço ASTM 4140, sendo apropriado para fabricação de parafusos da classe 10.9. Através das fraturas foi possível verificar que o parafuso 1 provavelmente foi submetido a um esforço por torção, tendo uma alta concentração de tensão na região da raiz do filete, assim como a existência de marcas de catraca, o que possibilitou a criação da trinca e propagação por fadiga. No parafuso 2 foram observadas marcas de praia originadas em cavidades e uma região de fratura final pequena como indicativo de baixa tensão nominal. Identificou-se que ambos possuem uma matriz microestrutural martensítica, contudo foi encontrada a presença de austenita retida e também inclusões não metálicas, as quais apresentam maior concentração no parafuso 2, indicando que provavelmente estariam presentes nas cavidades produzidas na fratura. Os valores de dureza determinados são apropriados para os valores mínimos estabelecidos por normas técnicas. No entanto, verificou-se que o parafuso 2 não apresenta as porcentagens mínimas de ductilidade estipuladas por uma das normas técnicas analisadas. ABSTRACTThe purpose of this article was evaluate the mechanical properties of two bolts that has as function the fixing of a crane used at oil offshore platforms. Two specimens were removed of each bolt for analysis such of chemical composition, fracture and hardness and tensile testing. The results obtained from analysis of the chemical composition proved to be consistent with the standards and the material used to manufacture the bolts consists of a steel ASTM 4140, being appropriate for manufacturing class 10.9 bolts. Through the fractures it was found that the bolt 1 was probably subjected to a load of torsion with a high concentration of stress in the region of bolt’s root, well as the existence of ratchet marks, which enabled the creation of fatigue crack. Beach marks were observed originating from cavities and a small final fracture region indicated a low nominal stress on bolt 2. It was identified that both have the martensitic microstructure matrix, however it was found the presence of retained austenite and also non-metallic inclusions, which are more concentrated on the bolt 2, indicating that probably would be present in cavities produced in the fracture. The hardness values are appropriate to the minimum values established by technical standards. However, it was found that the bolt 2 does not show the minimum ductility percentages prescribed by technical standards analyzed

Femoral Orthopedic Implants in Dogs with Titanium - Mechanical Evaluation

ABSTRACTBackground: Orthopedic implants are commonly used for different types of surgical procedures to gain optimal function and to provide stability to both bones and tendon structures. When inserting these implants, the characteristics of the material are important for surgical success, and the ideal implant must be biocompatible and nonallergenic. However, when molding an implant to the bone structure, its resistance can change significantly. Implants can be temporary or permanent in the body, and metal possesses properties that make it acceptable for bone repair. In biomedical implants, 2 types are most common, commercially pure (CP)-Ti and Ti-6A1-4V. They both provide stable fixation and low risk of loosening. Implants made with the same material and composition can perform differently if the material has been altered by processing techniques for different scenarios. Stress, strain and elastic modulus are the primary metrics used in the description of implant materials. They can be calculated based on mechanical tests of specimens with defined geometry, most commonly tensile, bending and torsional tests. In order to better evaluate those changes, we compared the mechanical characteristics of titanium bone plates, before and after they were molded to the bone, to verify and quantify the loss of stiffness and resistance after molding the plate.Materials, Methods & Results: The study was prospective. Orthopedic implant made of commercially pure titanium (CP-Ti) were divided into 2 groups, one group without plate molding and the other with plate molding to a dog femora bone. Thirty-six plates of different sizes (5.0, 6.5, 8.0, 9.0, 10.0 and 11.0-mm diameter) were divided into 6 groups containing 6 plates of each size and submitted to the 4-point flexion test of resistance, using a piece of dog femur (weights of 5, 10, 15, 20 and 25 kg) as the bone in which the molding was performed. The evaluations were tabulated and analyzed using the program GraphPad Prism version 5.0. Corrections of the normal distribution curve were made using the Bartlett test. After the corrections, one-way analysis of variance (ANOVA) was performed with P < 0.05. Assessments were made within the group and between groups. Subsequently, the Newman-Keuls test was performed, adopting P < 0.05. For analyses in 2 groups, Student's t-test was performed as a post-test, also with P < 0.05. When the plates were compared between equal sizes of groups 1 and 2, the non-molded plate group (G1) obtained the best results in the flexural stiffness and structural flexion tests. However, in the flexural resistance test, most plates obtained similar results and the plates with diameters of 8 mm, 9 mm and 10 mm of the molded plate group (G2) obtained the best results.Discussion: Our results show that the implants had adequate mechanical characteristics, but the unmolded plates had greater flexural and structural stiffness than the molded plates. This difference was significant, thus demonstrating a large loss of stiffness in relation to the original conformation. However, when we tested the flexural resistance, no significant differences were observed, and although without significant statistical changes, there was an increase in the resistance of the plate with the new conformation obtained by molding. In the results of the mechanical tests, we observed that after the molding, the implants gained greater resistance, although the difference was not statistically significant. This suggests that the architecture of the implants should have slight curvature in the medial direction of the bone, since this would lead to a better adaptation to the anatomy of the bone, and possibly greater resistance, as indicated by the new configuration after molding.Keywords: bone implants, titanium, orthopedic implants, femur, dogs

Modelagem de processos de negócio: efeito do método de notação no nível de ambiguidade

Resumo A proposta deste estudo experimental controlado e aleatorizado foi analisar a especificação de requisitos funcionais. Avaliaram-se os possíveis impactos do método de notação de modelagem de processo no nível de ambiguidade presente na especificação em linguagem natural. As notações foram utilizadas como instrumento para manifestar as necessidades do usuário quanto ao processo de compra em aplicações de comércio eletrônico - caso de uso típico de sistemas de informação empresarial. A partir de um protótipo de baixa fidelidade, que representa o processo de compra numa loja virtual, 43 estudantes de graduação em ciência da computação foram agrupados de acordo com as notações desempenhadas: grupo controle linguagem natural (GC); grupo experimental máquina de estados finitos (GEMEF); e o grupo experimental notação combinada (GENC), que utilizou anotação manual de papéis semânticos baseados em máquina de estados finitos. Foi utilizado o conceito que trata da ambiguidade como informações inconsistentes que levam a múltiplas interpretações do documento de especificação dos requisitos funcionais. Pela técnica de leitura baseada em teste, associada à utilização da métrica de qualidade apropriada, foi conduzida uma análise de variância de fator único com delineamento completamente casualizado para saber se o método de notação, como fator primário, afeta o nível de ambiguidade. A comparação intergrupo sugere que: a notação combinada é o melhor método para reduzir o nível de ambiguidade da especificação de requisitos; e que a especificação de requisitos expressa em máquina de estados finitos gera o maior o nível de ambiguidade dentre as notações avaliadas. No entanto, estas tendências não são estatisticamente significativas. De forma geral, observou-se que a variável independente, método de notação, não afeta o nível de ambiguidade do processo descrito na especificação de requisitos funcionais

Oficinas de turbomáquinas no Brasil e a contribuição da Rede Brasileira de Turbinas a Gás e do PROMINP

A Rede de Pesquisa e Desenvolvimento de Turbinas a Gás (RTG) surgiu como inspiração para a busca de uma alavancagem tecnológica frente às diversas incertezas no ano de 2001, com uso nas áreas de geração elétrica em termelétricas e na área offshore, buscando-se a construção de uma base nacional de serviços e reparos à frota de turbinas existente através do Programa Nacional de Mobilização da Indústria Nacional de Petróleo e Gás Natural (PROMINP). O artigo busca o status atual desses dois vetores de desenvolvimento à tecnologia, sua aplicação ao campo e se existiria alguma conexão entre eles. A RTG pouco avançou e o PROMINP apontou empresas com potencial de suporte em oficinas, o que também não se concretizou. As empresas indicadas como baixo potencial pelo programa foram as que mais se desenvolveram e não indicam conexão com a RTG. A atividade de suporte às turbinas a gás permanece sob gestão dos fabricantes, tendo seus laboratórios e oficinas concentrados na região Sudeste

Femoral Orthopedic Implants in Dogs with Titanium - Mechanical Evaluation

ABSTRACTBackground: Orthopedic implants are commonly used for different types of surgical procedures to gain optimal function and to provide stability to both bones and tendon structures. When inserting these implants, the characteristics of the material are important for surgical success, and the ideal implant must be biocompatible and nonallergenic. However, when molding an implant to the bone structure, its resistance can change significantly. Implants can be temporary or permanent in the body, and metal possesses properties that make it acceptable for bone repair. In biomedical implants, 2 types are most common, commercially pure (CP)-Ti and Ti-6A1-4V. They both provide stable fixation and low risk of loosening. Implants made with the same material and composition can perform differently if the material has been altered by processing techniques for different scenarios. Stress, strain and elastic modulus are the primary metrics used in the description of implant materials. They can be calculated based on mechanical tests of specimens with defined geometry, most commonly tensile, bending and torsional tests. In order to better evaluate those changes, we compared the mechanical characteristics of titanium bone plates, before and after they were molded to the bone, to verify and quantify the loss of stiffness and resistance after molding the plate.Materials, Methods & Results: The study was prospective. Orthopedic implant made of commercially pure titanium (CP-Ti) were divided into 2 groups, one group without plate molding and the other with plate molding to a dog femora bone. Thirty-six plates of different sizes (5.0, 6.5, 8.0, 9.0, 10.0 and 11.0-mm diameter) were divided into 6 groups containing 6 plates of each size and submitted to the 4-point flexion test of resistance, using a piece of dog femur (weights of 5, 10, 15, 20 and 25 kg) as the bone in which the molding was performed. The evaluations were tabulated and analyzed using the program GraphPad Prism version 5.0. Corrections of the normal distribution curve were made using the Bartlett test. After the corrections, one-way analysis of variance (ANOVA) was performed with P < 0.05. Assessments were made within the group and between groups. Subsequently, the Newman-Keuls test was performed, adopting P < 0.05. For analyses in 2 groups, Student's t-test was performed as a post-test, also with P < 0.05. When the plates were compared between equal sizes of groups 1 and 2, the non-molded plate group (G1) obtained the best results in the flexural stiffness and structural flexion tests. However, in the flexural resistance test, most plates obtained similar results and the plates with diameters of 8 mm, 9 mm and 10 mm of the molded plate group (G2) obtained the best results.Discussion: Our results show that the implants had adequate mechanical characteristics, but the unmolded plates had greater flexural and structural stiffness than the molded plates. This difference was significant, thus demonstrating a large loss of stiffness in relation to the original conformation. However, when we tested the flexural resistance, no significant differences were observed, and although without significant statistical changes, there was an increase in the resistance of the plate with the new conformation obtained by molding. In the results of the mechanical tests, we observed that after the molding, the implants gained greater resistance, although the difference was not statistically significant. This suggests that the architecture of the implants should have slight curvature in the medial direction of the bone, since this would lead to a better adaptation to the anatomy of the bone, and possibly greater resistance, as indicated by the new configuration after molding.Keywords: bone implants, titanium, orthopedic implants, femur, dogs

Nanosatellites: Space and Ground Technologies, Operations and Economics

Nanosatellites: Space and Ground Technologies, Operations and Economics comprehensively presents the latest research on the fast-developing area of nanosatellites. Divided into three distinct sections, the book begins with a brief history of nanosatellites and introduces nanosatellites technologies and payloads, also explaining how these are deployed into space. The second section provides an overview of the ground segment and operations, and the third section focuses on the regulations, policies, economics, and future trends. Key features: Payloads for nanosatellites Nanosatellites components design Examines the cost of development of nanosatellites. Covers the latest policies and regulations. Considers future trends for nanosatellites. Nanosatellites: Space and Ground Technologies, Operations and Economics is a comprehensive reference for researchers and practitioners working with nanosatellites in the aerospace industry