61 research outputs found

    Formability of Polymer-coated Metals

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    This project was undertaken to explore the viability of manufacturing polymer-coated cans using current drawing-wall-ironing methods, and centres around exploring polymer-coated alternatives to lacquered food and beverage cans. A full process FEA model was developed in Abaqus, and a polymer coating characterisation was attempted via tensile and compressive tests of available PET. As an alternative, the polymer was modelled as a force/over-closure con-tact definition in finite element analysis models, using force data derived from existing polymer data. The contact definition demonstrated an effective alter-native to modelling a finite element meshed polymer layer but needed opti-mising to match physical results. A tensile test machine rig was designed and manufactured capable of ironing strip metal specimens for otherwise unavail-able ironing metrology. The rig was calibrated using uncoated steel, then used to gain data on force and resulting geometry for polymer coated steel during and after ironing. Rig data was used in a finite element analysis automated feedback loop to optimise the force/over-closure and friction coefficients for the contact definition. Finally, a full-process drawing-wall-ironing simulation on polymer coated steel was implemented in a design of experiments study, which mapped the previously unexplored design space. The most significant parameters in resulting can geometry were the percentage of redraw and iron-ing during the respective forming phases, as well as the redraw radius. De-creasing the diameter of both redraw and ironing tooling rings resulted in a longer and thinner can, as did decreasing the redraw radius. Whilst not an ex-haustive study, the project ultimately demonstrated the viability of modelling polymer-coatings using contact definitions in finite element analysis and paves the way for further study into the polymer-coated steel can

    Flow forming : a review of research methodologies, prediction models and their applications

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    After years of largely academic interest and niche applications, a new generation of high duty CNC machines is enabling the flow forming process find increasing application in aerospace, automotive and defense industries. The versatility of digital control has made it economically viable to deliver weight and cost savings for small to medium batch sizes while simultaneously improving quality and material proprieties. To better understand the capabilities of flow forming this review surveys the reported research over last fifty years and summarizes both theoretical models and experimental investigations. Where possible the contributions of different researchers are described and assessed in terms of the accuracy of their predictive capabilities. In some cases practice has preceded the development of theory for example: the ratio of circumferential to axial contact is widely used as a defect prediction parameter, even if the process' failure mechanism is still not fully understood. In other areas, such as forming forces and powers, the literature provides a clear rational based on experimentally validated analytical models. In addition to summarizing current knowledge the review also identifies gaps in current literature where more research is required. For example: the evolution of stress/strain tensors during a flow forming process has not been reported due to the high computational cost and a lack of consensus on the most appropriate finite elements modeling approach to adopt. Similarly while the final microstructure of a formed part is often evaluated models of its development (during the series of plastic deformations created by a flow forming process) have not been reported. Likewise residual stress and final material proprieties, such as corrosion behaviour, have been not studied numerically or experimentally. It is also noted that the impact of tool paths (e.g. their geometry and topology) has not been deeply explored. Lastly the authors note, the surprising observation, that only a few researchers have reported the experimental optimization and characterization of flow forming process parameters using a 'Design of Experiments' methodology

    Framework for process improvement in manufacturing of metal packaging

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    Thesis (MEng)--Stellenbosch University, 2022.ENGLISH ABSTRACT: Due to increased competitiveness in the packaging industry, process improvement is important to give businesses an edge over their competition. This thesis represents a study of the application of machine learning for process improvement in metal can manufacturing. A five step process improve ment framework based on the Six Sigma process improvement methodology and the CRISP-DM data science framework was developed. The framework consisted of different steps that included steps used in the Six Sigma process improvement methodologies as well as steps used in data science processes.The five steps were; Define, Understand, Model, Evaluate and Deploy (DUMED). The DUMED framework was used in a case study that predicted the axial load resistance of 2-piece metal food cans during the manufacturing process. The objective is to understand how axial load resistance relates to other factors in the process with the outcome that any changes made in the process will still deliver cans with suitable axial load resistance. A predictive model on axial load resistance will give enhanced capability to control axial load resistance, and will lead to less rejections and therefore less waste. A predictive model on axial load resistance can also supply valuable information on the possible viability for light weighting of material, which will have a decreased cost of raw material as a result and therefore hold financial benefit for the manufacturer. Various data science and machine learning principles were applied during the study related to data understanding, data assessing, data preparation, data modelling and model assessing. The framework was successfully applied in the case study, with the exception of the fifth step, deployment. The deployment phase will be dependent on further improvement of the predictive model. Machine learning was successfully used in the case study to develop a predictive model; the axial load resistance could be predicted within 2.3% of the actual values. The best results were obtained from using feature selected data obtained from a random forest feature selection algorithm that was modelled by using a gradient boost ensemble regression model. Machine learning was successfully applied to a metal package manufacturing line to predict quality characteristics of the final product and possibly bring about process improvement.AFRIKAANSE OPSOMMING: As gevolg van die toenemende kompetisie in die verpakkings industrie is proses verbetering belangrik om besighede ’n voorsprong oor hulle kompetisie te gee. Hierdie tesis is ’n studie van die gebruik van masjienleer vir proses verbetering in metaal blik vervaardiging. ’n Vyf stap proses verbeterings raamwerk wat gebaseer was op die Ses Sigma proses verbeterings metodologie an die CRISP-DM data wetenskap raamwerk was ontwikkel. Die vyf stappe was; definieer, verstaan, modeleer, eval ueer, en ontplooi (DUMED, na aanleiding van die engelse akroniem). Die DUMED raamwerk was gebruik vir ’n gevallestudie wat die aksiale ladings weerstand van 2-stuk metaal kos blikke voorspel gedurende die vervaardigings proses. Verskeie data wetenskap en masjienleer beginsels was toegepas gedurende die studie relevant tot die verstaan van die data, assessering van die data, voorbereiding van die data, modelering van die data en die assessering van die data modelle. Die raamwerk was suk sesvol toegepas vir die gevallestudie, behalwe vir die vyfde stap, naamlik die ontplooing. Die ontploo ings fase sal afhanklik wees van verdere verbeteringe op die voorspellende data model. Masjienleer was suksesvol gebruik in die gevallestudie om ’n voorspellende model te ontwikkel; die aksiale lad ings weerstand kon voorspel word tot binne 2.3% van die werklike waardes. Die beste resultaat was verkry deur die ’gradient boost’ masjienleer algoritme toe te pas op ’random forest feature selected’ data. Masjienleer was suksesvol toegepas op ’n metaal verpakkings vervaardigings lyn om kwaliteits eienskappe op die finale produk te voorspel en so moontlikke proses verbetering te bewerkstellig.Master

    Innovative mathematical and numerical models for studying the deformation of shells during industrial forming processes with the Finite Element Method

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    The doctoral thesis "Innovative mathematical and numerical models for studying the deformation of shells during industrial forming processes with the Finite Element Method" aims to contribute to the development of finite element methods for the analysis of stamping processes, a problematic area with a clear industrial application. To achieve the proposed objectives, the first part of this thesis covers the solid-shell elements. This type of element is attractive for the simulation of forming processes, since any type of three-dimensional constitutive law can be formulated without the need to consider any additional conjecture. Additionally, the contact of both sides can be easily treated. This work first presents the development of a triangular prismatic solid-sheet element, for the analysis of thick and thin sheets with capacity for large deformations. This element is in total Lagrangian formulation, and uses neighboring elements to compute a field of quadratic displacements. In the original formulation, a modified right Cauchy tensor was obtained; however, in this work, the formulation is extended obtaining a modified strain gradient, which allows the concepts of push-forward and pull-back to be used. These concepts provide a mathematically consistent method for the definition of temporary derivatives of tensors and, therefore, can be used, for example, to work with elasto-plasticity. This work continues with the development of the contact formulation used, a methodology found in the bibliography on computational contact mechanics for implicit simulations. This formulation consists of an exact integration of the contact interface using mortar methods, which allows obtaining the most consistent integration possible between the integration domains, as well as the most exact possible solution. The most notable contribution of this work is the consideration of dual augmented Lagrange multipliers as an optimization method. To solve the system of equations, a semi-smooth Newton method is considered, which consists of an active set strategy, also extensible in the case of friction problems. The formulation is functional for both frictionless and friction problems, which is essential for simulating stamping processes. This frictional formulation is framed in traditional friction models, such as Coulomb friction, but the development presented can be extended to any type of friction model. The remaining necessary component for the simulation of industrial processes are the constitutive models. In this work, this is materialized in the formulation of plasticity considered. These constitutive models will be considered plasticity models for large deformations, with an arbitrary combination of creep surfaces and plastic potentials: the so-called non-associative models. To calculate the tangent tensor corresponding to these general laws, numerical implementations based on perturbation methods have been considered. Another fundamental contribution of this work is the development of techniques for adaptive remeshing, of which different approaches will be presented. On the one hand, metric-based techniques, including the level-set and Hessian approaches. These techniques are general-purpose and can be considered in both structural problems and fluid mechanics problems. On the other hand, the SPR error estimation method, more conventional than the previous ones, is presented. In this area, the contribution of this work consists in the estimation of error using the Hessian and SPR techniques for the application to numerical contact problems.La tesis doctoral "Modelos matemáticos y numéricos innovadores para el estudio de la deformación de láminas durante los procesos de conformado industrial por el Método de los Elementos Finitos" pretende contribuir al desarrollo de métodos de elementos finitos para el análisis de procesos de estampado, un área problemática con una clara aplicación industrial. De hecho, este tipo de problemas multidisciplinares requieren el conocimiento de múltiples disciplinas, como la mecánica de medios continuos, la plasticidad, la termodinámica y los problemas de contacto, entre otros. Para alcanzar los objetivos propuestos, la primera parte de esta tesis abarca los elementos de sólido lámina. Este tipo de elemento resulta atractivo para la simulación de procesos de conformado, dado que cualquier tipo de ley constitutiva tridimensional puede ser formulada sin necesidad de considerar ninguna conjetura adicional. Además, este tipo de elementos permite realizar una descripción tridimensional del cuerpo deformable, por tanto, el contacto de ambas caras puede ser tratado fácilmente. Este trabajo presenta en primer lugar el desarrollo de un elemento de sólido-lámina prismático triangular, para el análisis de láminas gruesas y delgadas con capacidad para grandes deformaciones. Este elemento figura en formulación Lagrangiana total, y emplea los elementos vecinos para poder computar un campo de desplazamientos cuadráticos. En la formulación original, se obtenía un tensor de Cauchy derecho modificado (¯C); sin embargo, en este trabajo, la formulación se extiende obteniendo un gradiente de deformación modificado (¯F), que permite emplear los conceptos de push-forward y pull-back. Dichos conceptos proveen de un método matemáticamente consistente para la definición de derivadas temporales de tensores y, por tanto, puede ser usado, por ejemplo, para trabajar con elasto-plasticidad. El elemento se basa en tres modificaciones: (a) una aproximación clásica de deformaciones transversales de corte mixtas impuestas; (b) una aproximación de deformaciones impuestas para las Componentes en el plano tangente de la lámina; y (c) una aproximación de deformaciones impuestas mejoradas en la dirección normal a través del espesor, mediante la consideración de un grado de libertad adicional. Los objetivos son poder utilizar el elemento para la simulación de láminas sin bloquear por cortante, mejorar el comportamiento membranal del elemento en el plano tangente, eliminar el bloqueo por efecto Poisson y poder tratar materiales elasto-plásticos con un flujo plástico incompresible, así como materiales elásticos cuasi-incompresibles o materiales con flujo plástico isocórico. El elemento considera un único punto de Gauss en el plano, mientras que permite considerar un número cualquiera de puntos de integración en su eje, con el objetivo de poder considerar problemas con una significativa no linealidad en cuanto a plasticidad. Este trabajo continúa con el desarrollo de la formulación de contacto empleada, una metodología que se encuentra en la bibliografía sobre la mecánica de contacto computacional para simulaciones implícitas. Dicha formulación consiste en una integración exacta de la interfaz de contacto mediante métodos de mortero, lo que permite obtener la integración más consistente posible entre los dominios de integración, así como la solución más exacta posible. La implementación también considera varios algoritmos de optimización, como la optimización mediante penalización. La contribución más notable de este trabajo es la consideración de multiplicadores de Lagrange aumentados duales como método de optimización. Estos permiten condensar estáticamente el sistema de ecuaciones, lo que permite eliminar los multiplicadores de Lagrange de la resolución y, por lo tanto, permite la consideración de solvers iterativos. Además, la formulación ha sido adecuadamente linealizada, asegurando la convergencia cuadrática del problema. Para resolver el sistema de ecuaciones, se considera un método de Newton semi-smooth, que consiste en una estrategia de set activo, extensible también en el caso de problemas friccionales. La formulación es funcional tanto para problemas sin fricción como para problemas friccionales, lo que es esencial para la simulación de procesos de estampado. Esta formulación friccional se enmarca en los modelos de fricción tradicionales, como la fricción de Coulomb, pero el desarrollo presentado puede extenderse a cualquier tipo de modelo de fricción. Esta formulación de contacto es totalmente compatible con el elemento sólido-lámina introducido en este trabajo. El componente necesario restante para la simulación de procesos industriales son los modelos constitutivos. En este trabajo, esto se ve materializado en la formulación de plasticidad considerada. Estos modelos constitutivos se considerarán modelos de plasticidad para grandes deformaciones, con una combinación arbitraria de superficies de fluencia y potenciales plásticos: los llamados modelos no asociados. Para calcular el tensor tangente correspondiente a estas leyes generales, se han considerado implementaciones numéricas basadas en métodos de perturbación. Otra contribución fundamental de este trabajo es el desarrollo de técnicas para el remallado adaptativo, de las que se presentarán distintos enfoques. Por un lado, las técnicas basadas en métricas, incluyendo los enfoques level-set y Hessiano. Estas técnicas son de propósito general y pueden considerarse tanto en la aplicación de problemas estructurales como en problemas de mecánica de fluidos. Por otro lado, se presenta el método de estimación de errores SPR, más convencional que los anteriores. En este ámbito, la contribución de este trabajo consiste en la estimación de error mediante las técnicas de Hessiano y SPR para la aplicación a problemas de contacto numérico. Con los desarrollos previamente introducidos, estaremos en disposición de introducir los casos de aplicación centrados en el contexto de procesos de estampado. Es relevante destacar que estos ejemplos son comparados con las soluciones de referencia disponibles en la bibliografía como forma de validar los desarrollos presentados hasta este punto. El presente documento está organizado de la siguiente manera. El primer capítulo establece los objetivos y revisa la bibliografía acerca de los temas clave de este trabajo. El segundo capítulo hace una introducción de la mecánica de medios continuos y los conceptos relativos al Método de los Elementos Finitos (MEF), necesarios en los desarrollos que se presentarán en los capítulos siguientes. El tercer capítulo aborda la formulación del elemento sólido-lámina, así como del elemento de lámina sin grados de libertad de rotación que inspira el sólido-lámina desarrollado. Esta parte muestra varios ejemplos académicos que son comúnmente empleados en la bibliografía como problemas de referencia de láminas. El cuarto capítulo presenta la formulación desarrollada para la resolución de problemas de contacto numérico, consistente en una formulación implícita de integración exacta mediante métodos mortero y multiplicadores de Lagrange aumentados duales. Este capítulo incluye, asimismo, varios ejemplos comúnmente encontrados en la bibliografía, que generalmente son considerados para su validación. El quinto capítulo presenta la formulación de plasticidad empleada, incluyendo algunos detalles técnicos desde el punto de vista de la implementación, así como varios ejemplos de validación. El sexto capítulo muestra los algoritmos de remallado adaptativo desarrollados en el contexto de este trabajo, y presenta varios ejemplos, que incluyen no solo casos estructurales, sino también de mecánica de fluidos. El séptimo capítulo encapsula algunos casos de validación y aplicación para procesos de estampado. El capítulo final comprende las conclusiones, así como los trabajos que podrían continuar el presente estudio.Postprint (published version

    Investigating the current and future role of paraffin in South Africa

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    This research investigates what the future of paraffin could and should be in South Africa, in particular whether this could be envisioned as transforming paraffin into a safe fuel for households. Alternatively, might South Africa look to assist households with a transition towards other modern fuels

    Experimental study and optimization of the machining parameters in ultrasonic vibrationassisted turning (UVT)

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    In recent year’s applications of hard materials in different industries, like aviation, defense and petrochemicals sectors etc. have been increased remarkably. The machining of these hard materials is very difficult in conventional turning process. Ultrasonic assisted turning is a suitable and advanced process for machining hard and brittle material because of its periodic cutting mechanism. In the present work, an ultrasonic vibratory tool (UVT) is designed and analyzed using ANSYS® environment for calculation of its natural frequency and working amplitude of vibration. An ultrasonic assisted turning system is designed in consideration of cutting tool as a cantilever beam. Experimental study has been carried out to find the difference between ultrasonic-assisted turning and conventional turning at different cutting conditions taking Stainless steel (a general purpose engineering material) as the work piece material. It is found that ultrasonic assisted turning reduces the surface roughness and cutting forces in comparison with conventional turning. It is well known that cutting forces and surface finish/ roughness are two major parameters which affect the productivity of the turning process. In the present work, Taguchi with TOPSIS method is used to optimize both forces and surface roughness to find the best possible machining parameters under the used experimental working conditions

    Analysis and Optimisation of Carcass Production for Flexible Pipes

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