Local Heat Treatment in Draw Bending for Profiles of Manganese Boron Steel 22MnB5

Due to the increasing demand for vehicles with a low fuel consumption and consequently low emissions, lightweight construction is an important task in the automotive industry. High-strength profile parts reduce the total weight of the vehicle while maintaining a high bending-resistance. Draw bending combined with inductive sheet heating and subsequent cooling represents a cost-effective and economic concept for producing partially hardened profiles for small batch sizes. This paper deals with experimental investigations to optimize and examine heating and cooling in the process chain of draw bending. After designing the process by numerical simulation, the existing draw bending machine of the IFUM was expanded by an inductive heating unit and a cooling system. Subsequently, new experiments on the implementation of a heat treatment during draw bending were carried out with this machine. In the course of these experiments, the determined process limits were recorded based on the required drawing force, the temperature courses in the process and the respective hardness values. These values served to evaluate and validate the results of the numerical simulation. By means of heating the material before it enters the forming die, it could be shown that it is possible to form super high-strength-profile components through draw bending. The material was heated up to austenitization temperature by a surface inductor and cooled by the draw bending tool and the additional air cooling. The material used was the uncoated manganese-boron steel 22MnB5. Good results with regard to process and part quality were obtained by means of an upstream heating. The comparison with the simulation also showed a high degree of similarity and consequently confirmed the results of the numerical representation of the process. Thus the general feasibility of integrating a heat-treatment into a draw bending operation was successfully proved.DFG/BE 1691/146-

Numerical product design: Springback prediction, compensation and optimization

Numerical simulations are being deployed widely for product design. However, the accuracy of the numerical tools is not yet always sufficiently accurate and reliable. This article focuses on the current state and recent developments in different stages of product design: springback prediction, springback compensation and optimization by finite element (FE) analysis. To improve the springback prediction by FE analysis, guidelines regarding the mesh discretization are provided and a new through-thickness integration scheme for shell elements is launched. In the next stage of virtual product design the product is compensated for springback. Currently, deformations due to springback are manually compensated in the industry. Here, a procedure to automatically compensate the tool geometry, including the CAD description, is presented and it is successfully applied to an industrial automotive part. The last stage in virtual product design comprises optimization. This article presents an optimization scheme which is capable of designing optimal and robust metal forming processes efficiently

Multi-scale friction modeling for manufacturing processes: The boundary layer regime

This paper presents a multi-scale friction model for largescale forming simulations. A friction framework has been developed including the effect of surface changes due to normal loading and straining the underlying bulk material. A fast and efficient translation from micro to macro modeling, based on stochastic methods, is incorporated to reduce the computational effort. Adhesion and ploughing effects have been accounted for to characterize friction conditions on the micro scale. A discrete model has been adopted which accounts for the formation of contact patches ploughing through the contacting material. To simulate metal forming processes a coupling has been made with an implicit Finite Element code. Simulations on a typical metal formed product shows a distribution of friction values. The modest increase in simulation time, compared to a standard Coulomb-based FE simulation, proves the numerical feasibility of the proposed method

Tube and Sheet Metal Forming Processes and Applications

At present, the manufacturing industry is focused on the production of lighter weight components with better mechanical properties and always fulfilling all the environmental requirements. These challenges have caused a need for developing manufacturing processes in general, including obviously those devoted in particular to the development of thin-walled metallic shapes, as is the case with tubular and sheet metal parts and devices.This Special Issue is thus devoted to research in the fields of sheet metal forming and tube forming, and their applications, including both experimental and numerical approaches and using a variety of scientific and technological tools, such as forming limit diagrams (FLDs), analysis on formability and failure, strain analysis based on circle grids or digital image correlation (DIC), and finite element analysis (FEA), among others.In this context, we are pleased to present this Special Issue dealing with recent studies in the field of tube and sheet metal forming processes and their main applications within different high-tech industries, such as the aerospace, automotive, or medical sectors, among others

Towards 3D Process Simulation for In-Situ Hybridization of Fiber-Metal-Laminates (FML)

Fiber-metal-laminates (FML) provide excellent fatigue behavior, damage tolerant properties, and inherent corrosion resistance.To speed up manufacturing and simultaneously increase the geometrical complexity of the produced FML parts, Mennecart et al. proposed a new single-step process combining deep-drawing with infiltration (HY-LCM). Although the first experimental results are promising, the process involves several challenges, mainly originating from the Fluid-Structure-Interaction (FSI) between deep-drawing and infiltration. This work aims to investigate those challenges to comprehend the underlying mechanisms. A new close-to-process test setup is proposed on the experimental side, combining deep-drawing of a hybrid stack with a linear infiltration. A process simulation model for FMLs is presented on the numerical side, enabling a prediction of the dry molding forces, local Fiber Volume Content (FVC) within the three glass fiber (GF) interlayers, and simultaneous fluid progression. The numerical results show that the local deformation of the hybrid stack and required forces are predictable. Furthermore, lateral sealing of the hybrid stacks leads to deviations from the intended initially one-dimensional fluid progression. Eventually, the numerical results demonstrate that most flow resistance originates from geometrically critical locations. Future experimental and numerical work will combine these insights to focus on the flow evaluation during deformation and a successful part-level application

Study, modelling, and dynamic analysis of construction solutions for doors and windows of buildings

Dissertação de mestrado em Engenharia MecânicaRecentes exigências do mercado levaram a que portas e janelas compostas por vidros e caixilhos com corte térmico sejam produzidas pela JFAN Steel com dimensões não abrangidas pelas classes de certificação dadas pelo fornecedor do caixilho (Secco). As classes de certificação, acompanhadas pela marcação CE, são dadas com base num conjunto de testes que uma porta ou uma janela deve suportar. Para aumentar as hipóteses destes sistemas passarem nos testes estruturais, foi selecionado um caso de estudo de um sistema porta com duas folhas para testar a influencia de diferentes reforços. Os testes à resistência do sistema às cargas verticais, à torção estática, e à carga de vento foram escolhidos como os mais críticos. Foi também criado um critério para avaliar o desempenho do sistema exposto a um terramoto, devido à preocupação relativamente ao comportamento vibratório dos sistemas em certas regiões geográficas do mercado. Primeiramente, os caixilhos, que têm uma secção composta por dois componentes metálicos (latão, aço corten, aço galvanizado, ou aço inoxidável) separados por um núcleo polimérico (poliamida no meio e poliuretano nos lados), tiveram algumas propriedades do latão, aço inoxidável, e poliamida verificadas através de ensaios de tração e densidade, enquanto as propriedades dos outros materiais foram verificadas em paralelo pela empresa. Um caixilho foi testado à flexão em três pontos após ter sido utilizado para uma análise modal experimental, e os dados destas experiências foram utilizados para avaliar os modelos do caixilho. Um modelo analítico, um de elementos de viga, um de elementos sólidos, e um que utiliza elementos de viga e de casca foram utilizados para capturar o comportamento estático e dinâmico do caixilho. Este último mostrou os resultados mais promissores, e foi selecionado para integrar o modelo do caso de estudo. Em seguida, os três testes mencionados foram simulados com o modelo do sistema caso de estudo, onde foram testadas diferentes configurações de reforços colocados dentro do caixilho com módulos de elasticidade distintos, bem como algumas melhorias da vidraça. As melhorias da vidraça, apesar de aumentarem muito o peso do sistema, provaram ser a melhor opção para aumentar o seu desempenho. Simulações simplificadas através de análises harmónicas deram confiança na resistência do sistema a um terramoto de intensidade instrumental V, no entanto, foram utilizadas algumas simplificações no próprio modelo. Finalmente, uma análise térmica numérica baseada na normalização europeia mostrou alterações insignificantes na transmitância térmica do sistema com a introdução dos reforços internos de aço.Recent market demands require JFAN Steel to produce doors and windows comprised of glazing and frames with a thermal break and with dimensions that are not covered by the certification classes given by the frame’s supplier (Secco). The certification classes, accompanied by the CE marking, are given based on a set of tests that a door or a window must endure. To increase the structural test passing rate, a case study of a double leafed door system was selected and used in this work to test out the influence of different reinforcements. The tests of the system’s resistance to vertical loads, static torsion, and wind load were isolated as the most critical ones. Additionally, a criterion to evaluate the performance of the system exposed to an earthquake was created as a concern regarding the vibratory behaviour of the systems in certain geographic regions of the company’s market. Firstly, the multi-material beams, that have a section comprised of two metallic components (brass, corten steel, galvanized steel, or stainless steel) separated by a polymeric core (polyamide in the middle and polyurethane at the sides) had some properties of brass, stainless steel, and polyamide verified through tensile and density tests, while the properties of the other materials were parallelly verified by the company. A multi-material beam underwent a three-point bending experiment after being used for experimental modal analysis, and the data from these experiments was later used to evaluate the models of the beam. An analytical model, a beam elements model, a solid elements model, and a model that uses beam and shell elements were used to capture the static and dynamic behaviour of the multi-material beam. The latter showed the more promising results and was selected to integrate the model of the case study system. Then, the three mentioned tests were simulated with the model of the case study system, where different configurations of reinforcements placed inside the frames with distinct elastic modulus as well as some glazing improvements were tested. Despite increasing the weight of the system, the glazing improvements proved to be the best option for increasing the overall performance. Simplified simulations through harmonic analyses gave confidence in the strength of the system to withstand an earthquake of instrumental intensity V, however, some simplifications were used in the model itself. Lastly, a numerical thermal analysis based on the European standardization showed insignificant changes in the thermal transmittance of the system with the introduction of the internal steel reinforcements

Study of the structural behavior of hybrid elements of carbon fiber reinforced polymer and concrete

Creating sustainability and public infrastructure is a fairly recent subject the engineering community has been debating. Introducing new building materials or introducing new structural designs is a strategy for constructing buildings that have long-term reliability and low maintenance requirements. Fiber-reinforced polymers (FRP) are one of the innovative approaches in the field of civil engineering that offer promising results in this regard. In order to maximize the usage of FRP forms, researchers suggested the development of hybrid structural structures by mixing composite materials with standard materials, such as concrete, to enhance the stability, ductility and buckling resistance of single FRP members. Nevertheless, these composite solutions need more preliminary research to prove its feasibility due to the complexity and large range of hybrid components. However, as there is a current shortage of compulsory codes for the design of composite structures and consequently FRP-concrete members, accurate predictive models need to be created. Thus, the present work aims at testing the structural efficiency of hybrid slabs made of CFRP sheets under a concrete layer in bending and shear configurations by carrying an experimental and analytical analysis. Using Carbon Fiber Reinforced Polymer (CFRP) bonded with resin is usual to strengthen concrete slabs or other elements. This thesis introduces a novel technological definition of thin CFRP-concrete unidirectional hybrid slabs. In bending part, experimental quasi-static three-points bending tests and modal analysis tests were carry out to analyze the influence of the connection systems on the dynamic response. Moreover, the corresponding analytical methodology to calculate their response are presented. Four different connection strategies between CFRP sheet and concrete were tested. These included flexible mesh embedding and particle-based frictional enhancement. The maximum bending moment, the evolution of the neutral axis, the comparison between external moment (calculated from applied load) and internal moment (calculated from strain distribution), the CFRP-concrete interface shear stress, and the evolution of the vertical displacement at the loading point are the main results obtained from the tests. In shear part, this work investigates the shear behavior of hybrid slabs that used different types of particles and/or a flexible high strength fabric to connect both materials: concrete and CFRP sheet. Several pure-shear experiments have been carried out to characterize the interface shear response of these hybrid elements. These increase the experimental database on CFPR-concrete shear connection systems. Experimental results showed that the improvement resulting from fabric embedding is far more significant than other tested connection elements at increasing the shear connection strength between the parts of the composite slabs. Results are divided with technological and scientific contributions. The feasibility of using CFRP sheets in hybrid unidirectional slabs instead of steel sheets is the main technological contribution, which also offers the following advantages: lighter weight and resistance to corrosion. Qualitative and quantitative analysis of the CFRP-concrete connection alternatives point out that combining adherence and frictional based strategies is the most promising method. An analytical method for the modelling of concrete slabs with CFRP was developed. In function of full cross-section interaction some equations for bending ultimate limit states were suggested. The possibility of using simpler formulas for quantifying interlayer slip effects was analyzed in assessing deflections, flexural stiffness, bending efficiency and normal and shear stress distributions. The proposed analytical method was able to capture the structural behavior and performance of the specimens.La creació d'infraestructura pública i sostenible és un tema de plena actualitat que la comunitat de l¿enginyeria ha estat debatent des de fa anys. Els polímers reforçats amb fibra (FRP) són un dels materials innovadors en el camp de l'enginyeria civil que ofereixen resultats prometedors en aquest sentit. Per maximitzar l'ús de formes de FRP s'estan desenvolupant estructures híbrides barrejant materials compostos amb materials tradicional, com el formigó, per millorar l'estabilitat, ductilitat i resistència al vinclament de membres individuals de FRP. A més, com hi ha una escassetat actual de codis obligatoris per al disseny d'estructures compostes i, en conseqüència, elements de formigó FRP, cal crear models predictius necessaris perquè es puguin estandarditzar. Abordar els problemes esmentats anteriorment és essencial per augmentar la introducció de materials compostos avançats en tipus comuns d'obres i construccions públiques. Així, el present treball té com a objectiu provar l'eficiència estructural de lloses híbrides de làmines de CFRP amb una capa de formigó, en configuracions de flexió i tallant, mitjançant la realització d'un anàlisi experimental i analític. L'ús de polímers reforçats amb fibra de carboni (CFRP) unit amb resina és habitual per reforçar lloses i altres elements de formigó. Aquesta tesi introdueix una definició tecnològica innovadora de lloses híbrides unidireccionals de formigó-CFRP de làmina prima. A la part de flexió es van realitzar assajos experimentals de flexió quasiestàtics, de tres punts, i assajos d'anàlisi modal per analitzar la influència dels sistemes de connexió en la resposta dinàmica. Així mateix, es presenta la metodologia analítica corresponent per calcular la seva resposta. Es van provar quatre estratègies de connexió diferents entre la làmina de CFRP i el formigó. Aquestes van incloure l¿embegut de malla flexible en el formigó i la millora de la fricció basada en partícules. El moment flector màxim, l'evolució de l'eix neutre, la comparació entre el moment extern (calculat a partir de la càrrega aplicada) i el moment intern (calculat a partir de les deformacions), l'esforç tallant de la interfície CFRP-formigó i l'evolució del desplaçament vertical en el punt de càrrega, són els principals resultats obtinguts de les proves. Aquest treball investiga el comportament rasant de lloses híbrides on els materials de CFRP i formigó es van connectar mitjançant diferents tipus d'agregats i tèxtils flexibles d'alta resistència. S'han dut a terme experiments de tall pur per caracteritzar la resposta de la interfície d'aquests elements híbrids. Aquests assajos augmenten la base de dades experimental sobre sistemes de connexió de tall de formigó-CFPR. Els resultats experimentals van mostrar que la tela embeguda produeix una millora en l'augment de la resistència estructural de manera molt més significativa que amb altres sistemes de connexió provats. La viabilitat d'utilitzar xapes de CFRP en lloses unidireccionals híbrides, en lloc de xapes d'acer, és la principal aportació tecnològica que, a més, ofereix els següents avantatges: menor pes i major resistència a la corrosió. Els anàlisis qualitatiu i quantitatiu de les alternatives de connexió CFRP-formigó assenyalen que la combinació d'estratègies basades en adherència i fricció és el mètode més prometedor. Així mateix, es va desenvolupar un mètode analític per a la modelització de lloses de formigó amb CFRP. En funció dels principis de la interfície completa, es suggereixen equacions per calcular els estats límit últims. La possibilitat d'utilitzar fórmules més simples per quantificar els efectes de lliscament entre capes va ser analitzada en l'avaluació de deflexions, rigidesa de flexió, eficiència de flexió i distribucions d'esforços normals i tallants. El mètode analític proposat va ser capaç de capturar el comportament estructural i el rendiment mecànic de les mostres.La creación de infraestructura pública y sostenible es un tema de plena actualidad que la comunidad de ingenieros ha estado debatiendo desde hace años. La introducción de nuevos materiales de construcción o la introducción de nuevos diseños estructurales es una estrategia eficiente para construir edificios que tengan fiabilidad a largo plazo y requisitos de bajo mantenimiento. Los polímeros reforzados con fibra (FRP) son uno de los materiales innovadores en el campo de la ingeniería civil que ofrecen resultados prometedores en este sentido. Para maximizar el uso de formas de FRP se están desarrollando estructuras híbridas mezclando materiales compuestos con materiales estándar, como el hormigón, para mejorar la estabilidad, ductilidad y resistencia al pandeo de miembros individuales de FRP. Sin embargo, estas soluciones compuestas necesitan más investigación preliminar para demostrar su viabilidad debido a la complejidad y la amplia gama de componentes híbridos. Además, como existe una escasez actual de códigos obligatorios para el diseño de estructuras compuestas y, en consecuencia, elementos de hormigón FRP, es necesario crear modelos predictivos precisos para que puedan estandarizarse. Abordar los problemas mencionados anteriormente es esencial para aumentar la introducción de materiales compuestos avanzados en tipos comunes de obras y construcciones públicas. Así, el presente trabajo tiene como objetivo probar la eficiencia estructural de losas híbridas de láminas de CFRP con una capa de hormigón, en configuraciones de flexión y cortante, mediante la realización de un análisis experimental y analítico. El uso de polímeros reforzados con fibra de carbono (CFRP) unido con resina es habitual para reforzar losas y otros elementos de hormigón. Esta tesis introduce una definición tecnológica novedosa de losas híbridas unidireccionales de hormigón-CFRP de lámina delgada. En la parte de flexión se realizaron ensayos experimentales de flexión cuasi estáticos, de tres puntos, y ensayos de análisis modal para analizar la influencia de los sistemas de conexión en la respuesta dinámica. Asimismo, se presenta la metodología analítica correspondiente para calcular su respuesta. Se probaron cuatro estrategias de conexión diferentes entre la lámina de CFRP y el hormigón. Estos incluyeron el embeber una malla flexible en el hormigón y la mejora de la fricción basada en partículas. El momento flector máximo, la evolución del eje neutro, la comparación entre el momento externo (calculado a partir de la carga aplicada) y el momento interno (calculado a partir de la distribución de deformaciones), el esfuerzo cortante de la interfaz CFRP-hormigón y la evolución del desplazamiento vertical en el punto de carga, son los principales resultados obtenidos de las pruebas. En el estudio del cortante, este trabajo investiga el comportamiento rasante de losas híbridas donde los materiales de CFRP y hormigón se conectaron mediante diferentes tipos de agregados y textiles flexibles de alta resistencia. Se han llevado a cabo experimentos de corte puro para caracterizar la respuesta de la interfaz de estos elementos híbridos. Estos ensayos aumentan la base de datos experimental sobre sistemas de conexión de corte de hormigón-CFPR. Los resultados experimentales mostraron que la tela embebida produce una mejora en el aumento de la resistencia estructural de manera mucho más significativa que con otros sistemas de conexión probados. Los resultados de la tesis se dividen en contribuciones de tipo tecnológico y científico. La viabilidad de utilizar chapas de CFRP en losas unidireccionales híbridas, en lugar de chapas de acero, es el principal aporte tecnológico, que además ofrece las siguientes ventajas: menor peso y mayor resistencia a la corrosión. Los análisis cualitativo y cuantitativo de las alternativas de conexión CFRP-hormigón señalan que la combinación de estrategias basadas en adherencia y fricción es el método más prometedor. Asimismo, se desarrolló un método analítico para el modelado de losas de hormigón con CFRP. En función de los principios de la conexión completa se sugieren ecuaciones conceptuales para calcular los estados límite últimos. La posibilidad de utilizar fórmulas más simples para cuantificar los efectos de deslizamiento entre capas fue analizada en la evaluación de deflexiones, rigidez de flexión, eficiencia de flexión y distribuciones de esfuerzos normales y cortantes. El método analítico propuesto fue capaz de capturar el comportamiento estructural y el rendimiento mecánico de las muestras.Postprint (published version