Latest Hydroforming Technology of Metallic Tubes and Sheets

This Special Issue and Book, ‘Latest Hydroforming Technology of Metallic Tubes and Sheets’, includes 16 papers, which cover the state of the art of forming technologies in the relevant topics in the field. The technologies and methodologies presented in these papers will be very helpful for scientists, engineers, and technicians in product development or forming technology innovation related to tube hydroforming processes

Metal Micro-forming

The miniaturization of industrial products is a global trend. Metal forming technology is not only suitable for mass production and excellent in productivity and cost reduction, but it is also a key processing method that is essential for products that utilize advantage of the mechanical and functional properties of metals. However, it is not easy to realize the processing even if the conventional metal forming technology is directly scaled down. This is because the characteristics of materials, processing methods, die and tools, etc., vary greatly with miniaturization. In metal micro forming technology, the size effect of major issues for micro forming have also been clarified academically. New processing methods for metal micro forming have also been developed by introducing new special processing techniques, and it is a new wave of innovation toward high precision, high degree of processing, and high flexibility. To date, several special issues and books have been published on micro-forming technology. This book contains 11 of the latest research results on metal micro forming technology. The editor believes that it will be very useful for understanding the state-of-the-art of metal micro forming technology and for understanding future trends

Analysis of single stage SPIF process applied to the hole flanging operation.

Tradicionalmente, las operaciones de rebordeado se llevan a cabo en la industria mediante técnicas de prensado convencionales utilizando punzón y troquel. Sin embargo, investigaciones recientes en conformado incremental (ISF) han señalado ventajas significativas de esta operación con respecto a los procesos convencionales. Entre otras son, la flexibilidad, la relación coste-efectividad y una importante mejora aparente en la confomabilidad del material. En este sentido, la presente tesis doctoral ofrece un análisis crítico de la operación de rebordeado de agujero cilíndrico mediante el conformado incremental mono punto (SPIF), realizada en una etapa, desde el punto de vista de la conformabilidad del material y las capacidades geométricas del proceso. Para comprender y cuantificar las ventajas de las operaciones de SPIF de una sola etapa, se llevó a cabo una campaña experimental de rebordeado de orificios cilíndricos mediante conformado incremental y convencional. Esto se realizó sobre una lámina de aleación de aluminio 7075-O. Se proporciona un estudio detallado de la evolución de las deformaciones en el flanco. Éstos se midieron utilizando métodos avanzados de videogrametría y fotogrametría. Los mecanismos y modos de fallo de la lámina y la caracterización de la capacidad de rebordeado en ambas operaciones se analizan usando el diagrama límite de conformado (FLD). El efecto de flexión inducido por la herramienta en SPIF y el radio de esquina en el caso convencional ha sido claramente dilucidado, junto con la geometría del flanco y las fuerzas de conformado involucradas. Finalmente, la comparación llevada a cabo permite extraer las ventajas y limitaciones tecnológicas en el proceso de rebordeado de orificios mediante SPIF de una sola etapa, y descubrir futuras líneas de investigación para mejorar su aplicación práctica.Traditionally, flanging operations are performed in industry by conventional press working techniques using a punch and die. However, recent investigations in incremental sheet forming (ISF) have highlighted the significant advantages of this operation with respect to conventional processes. These advantages include flexibility, cost-effectiveness and a significant apparent enhancement in the formability of a material. This PhD thesis offers a critical analysis of the hole flanging operation by Single Point Incremental Forming (SPIF), which is performed in one stage, from the point of view of material formability and the geometrical capabilities of the process. To understand and quantify the advantages of a single-stage SPIF operation, experimental campaign of hole flanging tests by both incremental forming and conventional forming was performed on an aluminium alloy 7075-O sheet. A detailed study of the evolution of the strains in the flange is provided. These strains were measured using advanced videogrammetric and hotogrammetric methods. The mechanisms and modes of failure of the sheet and characterization of the flangeability in both operations were analysed using a forming limit diagram (FLD). The effect of bending induced by the tool in SPIF and the punch edge radius in conventional forming was clearly elucidated with the flange geometry and the forming forces. The comparison performed in this study enables the identification of the technological advantages and limitations in the hole flanging process by singlestage SPIF and the future research lines for improving its practical application

Efeito da estampagem incremental de ponto simples na microestrutura e propriedades mecânicas do alumínio e do aço

Mestrado em Ciência e Engenharia de MateriaisNeste trabalho foi investigado o efeito da deformação plástica por estampagem incremental de ponto simples (SPIF) na textura cristalográfica, estrutura de deslocações e propriedades mecânicas de chapas de alumínio, aço com baixo teor em carbono e aço de fase dupla. Foram realizados ensaios de tração nos materiais iniciais para caracterizar as suas propriedades mecânicas. Além disso, foram realizadas análises por difração de eletrões retrodispersados (EBSD), observações por microscopia eletrónica de transmissão (TEM) e cálculos utilizando o modelo viscoplástico autoconsistente para caracterizar a influência da textura cristalográfica e da microestrutura no comportamento mecânico dos materiais. Foram também realizadas medidas de deformação e de espessura, bem como ensaios de microdureza nos materiais deformados por SPIF. Em todos os materiais, a textura cristalográfica inicial revelou-se muito estável durante o processo de SPIF e foi observado um acentuado aumento da densidade de deslocações bem como o desenvolvimento de células equiaxiais de deslocações durante a deformação de ambos os aços. No entanto, na chapa de alumínio, não foram observadas alterações significativas da microestrutura inicial de laminagem. Em todos os materiais foi observado um bom acordo entre a espessura das peças obtidas por SPIF e o valor previsto pela lei do seno.In this work, was investigated the effect of the plastic deformation by single point incremental forming (SPIF) on the crystallographic texture, dislocation structure and mechanical properties of aluminum, low carbon steel and dual phase steel sheets. Tensile tests were conducted on the initial materials to characterize their mechanical behavior. Furthermore, electron backscattering diffraction (EBSD), transmission electron microscopy (TEM) observations and calculations using a polycrystalline viscoplastic self-consistent (VPSC) model were carried to characterize the influence of the crystallographic texture and microstructure on the mechanical behavior of the materials. Strain and thickness measurements and microhardness tests were also conducted on the SPIF deformed materials. The initial crystallographic texture was very stable during the SPIF of all materials and a strong increase of dislocation density and the development of equiaxed dislocation cell structure was observed during the deformation of both steels. However, for the aluminum sheet, no major change was observed on the initial rolling microstructure. For all materials, it was observed a good agreement between the thickness of the SPIF pieces and the value predicted by the sin law

Otimização de parâmetros de lubrificação e velocidade em SPIF

With the rising competitiveness in industry, it is mandatory to develop new methods and processes in order to fill some gaps, and at the same time ameliorate the existing ones. Incremental forming appears from the necessity to produce functional and usable prototypes, or alternatively, to produce small batches or replacement parts. In fact, the traditional use of press technology represents a very high cost when the number of parts in a batch is not big enough. Within incremental forming, the cost of tools is reduced to a minimum as just a punch and a clamping frame are needed to produce a part from the CAD model, which brings high interest to this technology. This work is part of the SPIF-A project (Single Point Incremental Forming at Aveiro). From many possible parameters, focus will be given to lubrication and federate (the travel speed of the forming tool). These two parameters are utmost importance either for the quality of parts and for the process time efficiency. After experimental tests, results will allow for conclusions that will certainly constitute a vital contribute for a better implementation of incremental forming processes into industrial environment.Com a constante competitividade da indústria, existe a necessidade de criar novos métodos e processos que colmatem lacunas dos já existentes, assim como procurar soluções com rendimentos superiores, tanto quantitativamente como qualitativamente. A estampagem incremental surge aliada à dificuldade de produção de protótipos funcionais e reais. A necessidade de produção de pequenos lotes de peças a um custo competitivo é outro fator preponderante para a evolução deste tipo de tecnologia, visto que os métodos de estampagem tradicionais implicam custos muito elevados para a conceção das ferramentas necessárias. Esta tecnologia permite à indústria produzir uma grande variedade de produtos com custos reduzidos e numa janela de tempo bastante mais curta que a generalidade dos processos convencionais, o que torna a estampagem convencional numa tecnologia muito flexível proporcionando à industria uma vertente bastante interessante trazendo novas soluções para os vários tipos de mercado. Neste trabalho, inserido no projeto SPIF-A (Single Point Incremental Forming at Aveiro) são estudados com recurso a testes experimentais, duas classes de parâmetros importantes quer para a qualidade, quer para o rendimento do processo: i) o efeito dos lubrificantes na qualidade superficial dos componentes produzidos e forças geradas durante a conformação e ii) o efeito do aumento da velocidade do punção conformador nas forças geradas e formabilidade das peças produzidas. Face ao conhecimento gerado, considera-se que esta tese teve um contributo importante do desenvolvimento do processo de estampagem incremental com vista à sua melhor implementação industrial.CENTRO-01-0145-FEDER-022083Mestrado em Engenharia Mecânic

Advances in Plastic Forming of Metals

The forming of metals through plastic deformation comprises a family of methods that produce components through the re-shaping of input stock, oftentimes with little waste. Therefore, forming is one of the most efficient and economical manufacturing process families available. A myriad of forming processes exist in this family. In conjunction with their countless existing successful applications and their relatively low energy requirements, these processes are an indispensable part of our future. However, despite the vast accumulated know-how, research challenges remain, be they related to the forming of new materials (e.g., for light-weight transportation applications), pushing the boundaries of what is doable, reducing the intermediate steps and/or scrap, or further enhancing the environmental friendliness. The purpose of this book is to collect expert views and contributions on the current state-of-the-art of plastic forming, thus highlighting contemporary challenges and offering ideas and solutions

AN INVESTIGATION OF SIZE EFFECTS ON THIN SHEET FORMABILITY FOR MICROFORMING APPLICATIONS

The increasing demand for powerful miniaturized products for all industrial applications has prompted the industry to develop new and innovative manufacturing processes to fabricate miniature parts. One of the major challenges facing the industry is the dynamic market which requires continuous improvements in design and fabrication techniques. This means providing products with complex features while sustaining high functionality. As a result, microfabrication has gained a wide interest as the technology of the future, where tabletop machine systems exist. Microforming processes have the capability of achieving mass production while minimizing material waste. Microforming techniques can produce net-shape products with intricacy in fewer steps than most conventional microfabrication processes. Despite the potential advantages, the industrial utilization of microforming technology is limited. The deformation and failure modes of materials during microforming is not yet well understood and varies significantly from the behavior of materials in conventional forming operations. In order to advance the microforming technology and enable the effective fabrication of microparts, more studies on the deformation and failure of materials during microforming are needed. In this research work, an effort to advance the current status of microforming processes for technologies of modern day essentials, is presented. The main contribution from this research is the development of a novel method for characterizing thin sheet formability by introducing a micro-mechanical bulge-forming setup. Various aspects of analyzing microscale formability, in the form of limiting strains and applied forces, along with addressing the well known size effects on miniaturization, were considered through the newly developed method. A high temperature testing method of microformed thin sheets was also developed. The aim of high temperature microforming is to study the material behavior of microformed thin sheets at elevated temperatures and to explore the capability of the known enhancement in formability at the macroscale level. The focus of this work was to develop a better understanding of tool-sheet metal interactions in microforming applications. This new knowledge would provide a predictive capability that will eliminate the current time-consuming and empirical techniques that, and this in turn would be expected to significantly lower the overall manufacturing cost and improve product quality