Repositório Comunidade: DEM
https://hdl.handle.net/1822/1189
DEM2024-03-28T22:54:42ZWear behavior of a new composite formulation, with TEOS addition, for abrasive vitrified grinding wheels
https://hdl.handle.net/1822/90204
Título: Wear behavior of a new composite formulation, with TEOS addition, for abrasive vitrified grinding wheels
Autor: Capela, Paulina Araújo; Costa, Sharlane Maria; Souza, M. S.; Carvalho, Sérgio Manuel Freitas; Pereira, Mário; Carvalho, L.; Gomes, J. R.; Soares, Delfim
Resumo: Vitrified grinding wheels are used in many manufacturing industries to shape and finish metals and other materials in an efficient way. This work addresses a new approach with the use of tetraethyl orthosilicate solution (TEOS solution or silica sol), as an additive, in vitrified abrasive composites for grinding wheels. Different types of composite were produced using always the same materials and processing methods, but with different TEOS contents. Compared with a reference abrasive grinding wheel, the addition of TEOS promoted an improvement in the abrasive tool performance. The new formulation for vitrified abrasive composites showed better dimensional stability during processing (drying and sintering), and could be applied to the production of grinding tools with high dimensional accuracy. With the addition of 3.75 wt% of TEOS there was an increase in the strength of the matrix bonds. The porosity of the composite increased by 7% (from 43.6 to 46.9%), also improving its wear properties, with the quadrupling of the grinding ratio of the abrasive composite. In addition, the surface roughness of the composite decreased (from Ra = 22.9 to 8.4 μm) allowing to improve the surface finish of the workpieces.
<b>Tipo</b>: article2024-03-27T17:59:53ZIntroduction of lean management in product development process in an automotive company
https://hdl.handle.net/1822/89755
Título: Introduction of lean management in product development process in an automotive company
Autor: Gomes, Margarida Gonçalves da Silva
Resumo: O Processo de Desenvolvimento do Produto é conhecido na indústria e, particularmente, em empresas
do ramo automóvel. No entanto, com o avanço da tecnologia e a necessidade de melhorar a eficiência
dos produtos, as empresas começaram a aplicar metodologias Lean. A aplicação dos princípios Lean é
universal, uma vez que atualmente encontra-se aplicada a diversas áreas. Os benefícios associados a
esta prática levam muitas empresas a implementar ferramentas, como Value Stream Design in Indirect
Areas, Obeya, Just-in-time (JIT) que se baseia no sistema de produção desenvolvido pela Toyota.
No entanto, a implementação do pensamento Lean revela-se bastante desafiante, uma vez que esta
abordagem deve ser considerada desde as fases iniciais do desenvolvimento do produto. Em particular,
a autora desta dissertação encontrou vários desafios à sua implementação na empresa onde foi
desenvolvida. Assim, o objetivo desta dissertação foi medir o impacto do Lean Product & Process
Development no atual Processo de Desenvolvimento de Produto e desenvolver um modelo de design de
fluxo de valor que pudesse ser útil para a empresa.
A pesquisa realizada iniciou-se com a revisão bibliográfica sobre os princípios do pensamento Lean, o
processo de desenvolvimento de produto da organização e a necessidade de integrar o primeiro no
modelo de negócios adotado pela organização. A análise realizada através do estado atual e a
visualização das etapas do processo foi relevante para identificar falhas e problemas, com foco no lado
da manufatura. Os resultados do estudo mostraram a existência de obstáculos na implementação do
Lean, o que reforçou a necessidade da existência de um modelo para ultrapassar estes obstáculos. Neste
modelo foram propostas ferramentas como Value-stream mapping e Quality Function Deployment.
Com este modelo espera-se melhorias nos tempos de atraso, qualidade e custo. Espera-se ainda que os
engenheiros possam tomar decisões imediatas, atender aos requisitos dos clientes com mais facilidade,
melhorar o desempenho do desenvolvimento de produtos e processos, e ainda a redução do lead time
de 700 para 500 dias.; Product Development Process is widely known among industry and automobile companies. However, the
advance of technology and the need to improve product efficiency, the companies started applying lean
techniques. The application of Lean Thinking principles is considered universal since they are currently
fully disseminated in other areas. The benefits associated with Lean principles lead many companies to
implement and apply their concepts and tools, like Value Stream Design in Indirect Areas, Obeya, Just in-time (JIT) which is based on, the production control system developed and implemented by Toyota.
However, the implementation of the lean management reveals to be very challenging, as this approach
should be considered since the early stages of the product development. In particularly, the author of this
dissertation found multiple barriers to its implementation in the company where she works, and where
the case study was developed. Thus, the objective of this dissertation was to measure the impact of Lean
Product & Process Development on the current Product Development Process and develop a value stream
design model that could be a useful and successfully contribution for the company. The implementation
of the new standard plan must become the normal way of doing the business and must be lived
consequently.
The conducted research began with the literature understanding of the main Lean thinking principles, the
organization product development process and the need to integrate the Lean Product Development on
the first steps of the Product Development Process. The performed analysis through the current state and
the visualization of process steps was relevant to identify disturbances and problems that occur, focusing
on the manufacturing side. The results of the study showed the existence of barriers in the implementation
of Lean and pull that overcame technical barriers, which further reinforced the need of the model. In this
model, tools such as Value-stream mapping and Quality Function Deployment were proposed.
This dissertation presents a different approach of the lean management on the automobile industry. It is
expected improvements on time, quality and costs. Engineers should be able to take faster decisions,
meet customers’ requirements more easily, improve performance of the product and process
development, and also the reduction of the lead time from 700 to 500 days.
Descrição: Dissertação de mestrado em Engenharia Mecânica (área de especialização em Conceção e Construção
Mecânica)
<b>Tipo</b>: masterThesisCorrosion and tribocorrosion behaviour of Ti-B4C composites processed by conventional sintering and hot-pressing technique
https://hdl.handle.net/1822/89713
Título: Corrosion and tribocorrosion behaviour of Ti-B4C composites processed by conventional sintering and hot-pressing technique
Autor: Sousa, L.; Alves, Alexandra Manuela Vieira Cruz Pinto; Guedes, A.; Toptan, Fatih
Resumo: In this work, low volume reinforcement ex-situ Ti-B4C composites were produced using two different routes: conventional powder metallurgy (PM) and hot-pressing (HP). The effect of reinforcement phases and processing method on corrosion and tribocorrosion behaviour were studied. Composites processed by
PM lost the typical passive behaviour of Ti matrix, while composites processed by HP presented similar
behaviour to unreinforced Ti. Tribocorrosion tests showed that both composite groups presented two times
decrease in corrosion kinetics under sliding compared to pure titanium. An antagonistic effect between
wear and corrosion was observed for composites with at least two times decrease in wear volume compared
to titanium.
<b>Tipo</b>: article2024-03-19T14:07:44ZElectrochemical response of Ti joints vacuum brazed with TiCuNi, AgCu, and Ag fillers
https://hdl.handle.net/1822/89711
Título: Electrochemical response of Ti joints vacuum brazed with TiCuNi, AgCu, and Ag fillers
Autor: Marinho, C.; Toptan, Fatih; Guedes, A.; Alves, Alexandra Manuela Vieira Cruz Pinto
Resumo: The properties of the joints are dictated by the nature, distribution, and morphology of the phases formed at the interface. The mechanical properties of brazed joints are well documented in the literature, contrarily to their electrochemical behaviour. Thus, the main objective of this study was to understand the influence of the phases formed at the interface on the corrosion behaviour of commercially pure Ti brazed joints, produced by using TiCuNi, eutectic AgCu, and Ag filler foils. The electrochemical behaviour of the Ti joints was accessed by open circuit potential and potentiodynamic polarization tests in phosphate buffer saline solution electrolyte at body temperature. Results showed that Ag-based fillers induced susceptibility to micro-galvanic corrosion between the Ag-rich and Ti phases formed at the interface and commercially pure Ti base metal. However, no significant differences were observed between the joint system and the base material when brazing with TiCuNi filler.
<b>Tipo</b>: article2024-03-19T14:00:26ZMicrostructure, mechanical properties and corrosion behaviour of Ti6Al4V/Al2O3 joints brazed with TiCuNi filler
https://hdl.handle.net/1822/89707
Título: Microstructure, mechanical properties and corrosion behaviour of Ti6Al4V/Al2O3 joints brazed with TiCuNi filler
Autor: Alves, Alexandra Manuela Vieira Cruz Pinto; Pinto, A. M. P.; Simões, S.; Guedes, A.
Resumo: Ti6Al4V and Al2O3 were successfully vacuum brazed at 980 °C using TiCuNi filler foil. The microstructure and the chemical composition of the interface were analysed by SEM (scanning electron microscopy) and EDS (energy dispersive spectros- copy), respectively. The hardness profile across the interface and the mechanical strength of joints were assessed by Vickers microhardness tests and shear tests, respectively. The fracture surfaces were analysed by SEM, EDS and XRD (X-ray dif- fraction). The corrosion behaviour of joints was evaluated by OCP (open circuit potential), potentiodynamic polarisation tests and EIS (electrochemical impedance spectroscopy). Brazing produced a layered interface, free of pores and cracks, essentially composed of α-Ti, Ti2(Cu,Ni) and TixOy. The shear strength of joints was 168 ± 13 MPa, and fracture occurred partially through the hardest zone of the interface (1261 HV0.01.), located in the vicinity of the Al2O3 sample, and partially through the ceramic sample. The brazed joint did not significantly affect the corrosion behaviour of Ti6Al4V.
<b>Tipo</b>: article2024-03-19T13:37:56Z