Aluminium matrix composites (AMC) do combine a high lightweight potential with a wide range of specific mechanical or thermal properties, depending on their material composition or the content of ...reinforcement particles, respectively. Currently, the three main production technologies for manufacturing such AMC are powder metallurgy, semi-solid processes and casting. Here, the AMC´s reinforcement proportion that can be processed depends on the chosen manufacturing strategy and is therefore often limited to a maximum value of 30 vol. %, due to agglomeration and porosity problems. In this context, the main objective is to understand the fundamental mixing behaviour of powder mixtures for AMC green body production having reinforcement contents of up to 50 vol.% SiC
p
. For this purpose, powder mixtures of monomodal AlSi7Mg0.6 and different SiC
p
fractions were prepared with different mixing times and speeds to investigate the influence of these mixing parameters on the homogeneity of the particle distribution. Afterwards, the influence of powder size on the mixing process was investigated. The results showed that a slower mixing speed resulted in faster homogenisation as well as a larger particle size can be faster mixed. Furthermore, a regression model was developed using mixing time, speed and particle loading, to determine sufficient mixing parameters.
Today, design and operation of manufacturing processes heavily rely on the use of models, some analytical, empirical or numerical i.e. finite element simulations. Models do reflect reality as best as ...their design and structure may appear, but in many cases, they are based on simplifying assumptions and abstractions. Reality in production, i.e. reflected by measures such as forces, deflections, travels, vibrations etc. during the process execution, is tremendously characterised by noise and fluctuations revealing a stochastic nature. In metal forming such kind of impact on produced product today in detail is neither explainable nor supported by the aforementioned models. In industrial manufacturing the game to deal with process data changed completely and engineers learned to value the high significance of information included in such digital signals. It should be acknowledged that process data gained from real process environments in many cases contain plenty of technological information, which may lead to increase efficiency of production, to reduce downtime or to avoid scrap. For this reason, authors started to focus on process data gained from numerous metal forming technologies and sheet metal blanking in order to use them for process design objectives. The supporting idea was found in a potential combination of conventional process design strategies with new models purely based on digital signals captured by sensors, actuators and production equipment in general. To utilise established models combined with process data, the following obstacles have to be addressed: (1) acquired process data is biased by sensor artifacts and often lacks data quality requirements; (2) mathematical models such as neural networks heavily rely on high quantities of training data with good quality and sufficient context, but such quantities often are not available or impossible to gain; (3) data-driven black-box models often lack interpretability of containing results, further opposing difficulties to assess their plausibility and extract new knowledge. In this paper, an insight on usage of available data science methods like feature-engineering and clustering on metal forming and blanking process data is presented. Therefore, the paper is complemented with recent approaches of data-driven models and methods for capturing, revealing and explaining previously invisible process interactions. In addition, authors follow with descriptions about recent findings and current challenges of four practical use cases taken from different domains in metal forming and blanking. Finally, authors present and discuss a structure for data-driven process modelling as an approach to extent existing data-driven models and derive process knowledge from process data objecting a robust metal forming system design. The paper also aims to figure out future demands in research in this challenging field of increasing robustness for such kind of manufacturing processes.
In this contribution, a new forming method is presented for high-strength steel sheet metal materials called Transversal Compression Drawing (TCD). For TCD, the blankholder of the conventional deep ...drawing process is replaced by sliders introducing a vertical force along the blank edge. Compared to conventional deep drawing, compressive stresses are thereby superimposed in the flange area of the sheet metal material, reducing the springback of formed components and the forces required during the process. Proof of this is provided here on the basis of numerical investigations in which conventional deep drawing and TCD are compared using the example of an “S-Rail” component made from DP980. Results of these investigations reveal that with TCD a maximum reduction in springback by more than 5 mm is achieved, leading to an improvement in the component´s overall shape accuracy of more than 55%. Furthermore, frictional work is decreased by − 6.92 kJ/kg, resulting in an overall reduction of maximum forming forces by 67.4%. Besides, TCD enables a trim-free net shape forming of the final part contour in a single operation and an increased material utilization of 4.5% from coil to part. Not least, no sheet thinning occurs with TCD, whereas a maximum thinning of 12% is observed with the conventional deep drawing process.
The production of irregularly shaped deep drawing parts with high quality requirements, which are common in today’s automotive car body production, consistently challenges production processes. The ...more and more complex requirements of design, light weight construction and crashworthiness lead to a more narrow process window for deep drawing production and thus the manufacturing process robustness is decreasing and hence the necessary use of high strength steels. Modern metal forming technologies deals with these challenges using highly sophisticated methods to control the material flow or adjustable process parameters by use of controllable machine or tool axis. Multiple control loop methods in deep drawing technology have been investigated during the recent two decades in order measure and to control the material flow in deep drawing processes. These methods only allow any control intervention between two strokes which itself is regarded as a simple open loop control system because a none process variable is a feed back to the controller. The method that was developed at the Institute for Metal Forming Technology (IFU) at the University of Stuttgart allows any control intervention during the deep drawing stroke for every blank holder design.
Ecological aims and political requirements today are increasing demands on lubricants in sheet metal forming and their impact on environment. For that reason, metal forming industry wants to reduce ...the amount of lubricants containing polluting additives with a long-term goal of avoiding lubrication entirely. Additionally, dry metal forming will reduce the cleaning steps after the forming operation. This paper shows a new tribological system in which lubrication is replaced by CO2 in a liquid state. Here, CO2 is expanding directly into contact area between workpiece and tool surface and changes its state from gas to solid. The combination of this particular dry ice as well as the pressure of approximately 57 atm affects resulting friction coefficient significantly. After forming operation, CO2 medium vaporizes and a dry component can be used immediately for the next process steps. In this case, the lubricant is applied directly into the contact area. Therefore, laser drilled micro holes are located in the contact area of the tool. Very first gained experimental results disclose such feasibility, the effects and the potential of this new lubrication system at that moment is based on strip draw tests. Different numbers of micro holes are examined to support blank holder pressure ranging between 5 MPa and 6 MPa. In this investigation a mild strength steel DC04 is used as sheet material. This knowledge is aimed to be used for further investigation and later transfer into real deep and stretch forming processes.
Multicomponent processes for production of high performance gearwheels combines both high power density and high lightweight potential. In this paper, the focus is on manufacturing an assembled ...gearwheel using cold forging and simultaneously joining the gearwheel body and a gear ring. In this study, FEA results regarding the joining process of two different materials for assembled gearwheels are presented. The aim of the numerical investigation is to achieve a robust forging process and define appropriate tool parameters.
Deep drawing is the most important manufacturing process in order to produce sheet metal parts in mass production. In this study, volatile carbon dioxide (CO2) is used as lubricant in order to ...replace mineral oil-based lubricants. CO2 is injected into the void between the forming tool and the metal part through laser drilled microholes in the forming tool and acts there as a highly efficient lubricant. In order to investigate the tribological conditions during the drawing process, a new test bench having optical access to the CO2 lubricant is designed, built and used in this study. Additionally, the CO2 flow through the microholes is modeled using CFD simulation. Both the experimental and the theoretical study reveal a critical influence of the geometry of the microholes on the phase of the CO2 in the forming tool and on the friction during the drawing process. Thereby, these investigations confirm that the CO2 is in solid and/or gaseous state dependent on the surface pressure and the geometry of the microholes. Consequently, these results support the concept of microstructure-designed forming tools allowing dry metal forming for locally adjusted and environmentally friendly friction conditions.
Cold formed sheet metal parts made of advanced high-strength steels (AHSS) offer a high potential for a lightweight, durable and economic design. However, manufacturing dedicated, high-strength parts ...with cold forming technologies such as conventional deep-drawing often results in unacceptable shape deviations due to elastic springback after unloading the part from the forming tools. Therefore, various springback compensation methods have been established to ensure dimensional quality of such sheet metal parts. At the Institute for Metal Forming Technology (IFU Stuttgart), deep-drawing with alternating blank draw-in was developed in this context as a new approach to reduce springback and enhance cold forming of AHSS sheet metal parts. Presented work provides numerical sensitivity analysis as well as experimental studies about this new forming method. The asymmetric and alternating blank draw-in, which is changed within a multistage forming process sequence, results in an alternated bending over tool radii and leads to a beneficial stress superposition in the part wall area with reduced springback phenomena. Compared to conventional deep-drawn sheet metal components, springback of a benchmark part geometry could thus be reduced over 75 % by a three-stage forming process with an optimized blank draw-in kinematic.
Hollow or tubular preforms are used to meet lightweight requirements and reduce production costs of cold formed components. In order to increase efficiency of manufacturing, a combined forming ...process was developed, which will be presented in this paper: manufacturing of hollow preforms by combining processes backward cup extrusion and piercing. With regard to combined forming processes in the field of cold forging, disclosed work consists of numerical identification of significant process input variables, process outcomes, and the process limits.
Against the background of today's lightweight design, an innovative joining technique has been developed at the Institute for Metal Forming Technology/Stuttgart for combining aluminium sheet ...structures with carbon fabrics. During the process of Joining of Carbon Fibres with Aluminium Structures (JOCA process), two or more aluminium sheets with carbon fabric layers in-between are initially conductively heated up into the semi-solid material state by means of two adjacent electrodes of a welding gun. If heated up to a liquid share of 30% to 60%, the aluminium matrix infiltrates the carbon fabric resulting into a firm joint after solidification of the metal material. This publication provides an overview of the research results obtained by experimental and numerical investigations of the infiltration process achieved so far.
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