185 research outputs found

    Control charts for the on-line diagnostics of CMM performance

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    The quality of a production process is increasing its dependence on both the manufacturing technology, and the production control. In most applications controls are operated by relying on intelligent instrumentation to 'automatically' perform the programmed checks. However, the performance systems that verify the product's quality can deteriorate, as can the production process. This paper presents a method for the on-line verification of the performance of a coordinate measuring machine (CMM) using statistically based control charts. The method is automated and performed on-line during a normal measurement cycle. Some experimental results are then presented and discussed

    On the Choice of Tool Material in Friction Stir Welding of Titanium Alloys

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    Friction Stir Welding (FSW) is a solid state welding process patented in 1991 by TWI; initially adopted to weld aluminum alloys, is now being successfully used also for magnesium alloys, copper and steels. The wide diffusion the process is having is due to the possibility to weld both materials traditionally considered difficult to be welded or "unweldable" by traditional fusion welding processes due to peculiar thermal and chemical material properties, and complex geometries as sandwich structures and straightening panels. Recently, research is focusing on titanium alloys thanks to the high interest that such materials are getting from the industry due to the extremely high strength-weight ratio together with good corrosion resistance properties. At the moment, the main limit to the industrial applicability of FSW to titanium alloys is the tool life, as ultra wear and deformation resistant materials must be used. In this paper a, experimental study of the tool life in FSW of titanium alloys sheets at the varying of the main process parameters is performed. Numerical simulation provided important information for the fixture design and analysis of results. Tungsten and Rhenium alloy W25Re tools are found to be the most reliable among the ones considered

    Micro-Drilling of ZTA and ATZ Ceramic Composit: Effect of Cutting Parameters on Surface Roughness

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    Ceramics are a class of materials widely used during last fifteen years for orthopaedic applications. It is well known that they are characterized by low wear rate, and friction coefficient. However, these materials are very difficult to machine into complex shapes because of their brittleness and high hardness. The most effective method to increase the crack resistance is the formation of a composite structure. This class of materials, composed by two or more different ceramics, can present higher characteristic respect to the single component, like fracture toughness and flexural strength. This paper presents a study of the influence of cutting parameters (cutting speed, feed rate and step number) onto the hole surface roughness and deformation due to the drill operation. The ceramic composite materials AZT (alumina toughened zirconia) and ZTA (zirconia toughened alumina) were first characterized in terms of hardness and roughness. After the drilling test, the holes were analyzed using scanning electron microscope (SEM) and an advanced 3-dimensional non-contact optical profilomete

    Finite Element Modeling of Microstructural Changes in Turning of AA7075-T651 Alloy and Validation

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    The surface characteristics of a machined product strongly influence its functional performance. During machining, the grain size of the surface is frequently modified, thus the properties of the machined surface are different to that of the original bulk material. These changes must be taken into account when modeling the surface integrity effects resulting from machining. In the present work, grain size changes induced during turning of AA 7075-T651 (160 HV) alloy are modeled using the Finite Element (FE) method and a user subroutine is implemented in the FE code to describe the microstructural change and to simulate the dynamic recrystallization, with the consequent formation of new grains. In particular, a procedure utilizing the Zener-Hollomon and Hall-Petch equations is implemented in the user subroutine to predict the evolution of the material grain size and the surface hardness when varying the cutting speeds (180 - 720 m/min) and tool nose radii (0.4 - 1.2 mm). All simulations were performed for dry cutting conditions using uncoated carbide tools. The effectiveness of the proposed FE model was demonstrated through its capability to predict grain size evolution and hardness modification from the bulk material to machined surface. The model is validated by comparing the predicted results with those experimentally observed

    conceptual framework for evaluating the environmental awareness and eco efficiency of smes

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    Abstract Environmental problems are increasingly impacting society and nature. For this reason, companies are expected to become aware of the importance of seeking strategies and measures to mitigate and prevent environmental impacts. The growing concern about the availability of natural resources for future generations and their survival has been the premise for decision making in the industrial sector to improve the quality of life and preserve the environment. In this domain, important concepts such as sustainable development and eco-efficiency have been developed. They represent the trend to achieve a balanced use of resources and a reduction of environmental pollution by preventing waste and establishing economic returns. The aim of this paper is to present a conceptual framework for evaluating the eco-efficiency of small and medium-sized enterprise (SMEs) through four main factors: analysis, identification and evaluation, integration, and an action plan. As a result of the analysis, sustainability strategies are proposed to decrease the negative impact and increase the cost-effectiveness and the competitiveness of the SMEs

    Additive manufacturing for the automotive industry: on the life-cycle environmental implications of material substitution and lightweighting through re-design

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    The automotive sector has recently been taking measures to reduce fuel consumption and greenhouse gas emissions for the mobility of ground vehicles. Light-weighting, via material substitution, and the re-designing of components or even a combination of the two, have been identified as a crucial solution. Additive manufacturing (AM) can be used to technologically complement or even replace conventional manufacturing in several industrial fields. The enabling of complexity-for-free (re) designs is inherent in additive manufacturing. It is expected that certain benefits can be achieved from the adoption of re-design techniques, via AM, that rely on topological optimisation, e.g., a reduced use of resources in both the material production and use phases. However, the consequent higher specific energy consumption and the higher embodied impact of feedstock materials could result in unsustainable environmental costs. This paper investigates the case of the light-weighting of an automobile component to quantify the outcomes of the systematic integration of re-designing and material substitution. A bracket, originally cast in iron, has been manufactured by means of a powder bed-based AM technique in AlSi10Mg through an optimized topology. Both manufacturing routes have been evaluated through a comparative Life Cycle Assessment (LCA) within cradle-to-grave boundaries. A 69%-lightweighting has been achieved, and the carbon dioxide emissions and energy demands of both scenarios have been compared. Besides the use-phase-related savings in terms of both energy and carbon footprint due to the lightweighting, the results highlight the environmental trade-offs and prompt the consideration of such a manufacturing process as an integral part of sustainable product development