In the development of modern machinetools for the automotive industry, higher productivity, higher metal removal rates and lower machining tolerances are increasingly calling for allowance to be made for misalignment...
In the development of modern machinetools for the automotive industry, higher productivity, higher metal removal rates and lower machining tolerances are increasingly calling for allowance to be made for misalignments due to thermal factors. Improving the accuracy of thermal simulation was the subject of a project conducted at the fraunhoferinstitute for machinetools and formingtechnology (IWU).
Finite element analysis (FEA) is a wide-spread method for studying the mechanical properties of structures. Finite element models (FE models) are being increasingly used in medical technology and biomechanics for calc...
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ISBN:
(纸本)9781615677368
Finite element analysis (FEA) is a wide-spread method for studying the mechanical properties of structures. Finite element models (FE models) are being increasingly used in medical technology and biomechanics for calculating dynamic problems with bones and artificial limbs. X-ray computer tomography data is used to create models that supply very precise information on morphology and tissue density. This article describes how experimental measurements of the dynamic behavior of the human hip bone can be obtained to verify different FE modeling approaches. Several mapping functions known from the literature will be used for material parameters in the FE models and the findings are compared. This paper specially focuses on the measuring method streamlined for fresh preparations using a 3-D laser vibrometer for the first time to capture oscillations threedimensionally.
Intermediate forming aimed at distributing the material volume contributes towards better utilization of the material, reducing the amount of energy necessary for heating and improving quality by near-net-shape geomet...
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ISBN:
(纸本)9783180920283
Intermediate forming aimed at distributing the material volume contributes towards better utilization of the material, reducing the amount of energy necessary for heating and improving quality by near-net-shape geometries. A range of different forming operations exists for realizing material distribution. This paper gives an overview of the process technologies used for distributing the material in an intermediate forming stage in the closed die forging of aero engine vanes and also illustrates their application areas. The development of a single cross wedge rolling operation will save two upsetting operations and one extrusion operation. A considerable reduction in cycle times and in manufacturing costs is the result of the shortened process chain. Additionally, the number of ancillary processes, such as heating, adjustment and lubricant application are reduced as well.
Because of the increasing demands for cost-effective and high-precision micro fluidic components the micro hot embossing technology becomes more and more important. An essential element of this technology is the requi...
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ISBN:
(纸本)9780955308253
Because of the increasing demands for cost-effective and high-precision micro fluidic components the micro hot embossing technology becomes more and more important. An essential element of this technology is the required micro forming tool. At the moment the requirements for the minimum tool sizes are in a range of 100 um with accuracy below 2 um. However, the exactness demands partially can reach to the sub micrometer area [1]. The required structural sizes and structure forms as well as the used tool materials limit the application of conventional processes like milling. The structuring with laser offers an alternative method because the material removal with a laser beam allows the manufacturing of very fine structures also in hard and brittle materials. For initial experimental investigations a high strength ceramic material (silicon carbide) was used to produce formingtools for micro fluid components. It succeeded to produce structures with dimensions smaller than 20 um and in a depth of 200 um. The evaluation showed very good surface qualities (roughness below RZ 2.55 um) and a high geometrical accuracy. First replication experiments in PMMA (polymethyl methacrylate) and polycarbonate also show good results and comparable structure qualities.
The fraunhoferinstitute for machinetools and formingtechnology has set itself the challenge of characterising the material behaviour of very recently developed sheet metal materials. To this end, an integrated conc...
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ISBN:
(纸本)9788957081525
The fraunhoferinstitute for machinetools and formingtechnology has set itself the challenge of characterising the material behaviour of very recently developed sheet metal materials. To this end, an integrated concept for the determination of material characteristics has been established. This consists in further developing well-known methods based on innovative characterisation concepts for describing phenomena such as springback, anistropy and the Bauschinger Effect. Using this approach, information relating to the interaction of sheet material, lubrication and forming tool can be derived.
During the hot pressing of glass (e.g. precision glass moulding, hot embossing) form deviations between the tool geometry and the manufactured glass formed part arise. Reasons for it are different thermal expansion be...
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ISBN:
(纸本)9780955308253
During the hot pressing of glass (e.g. precision glass moulding, hot embossing) form deviations between the tool geometry and the manufactured glass formed part arise. Reasons for it are different thermal expansion behaviour of the materials and technological parameters. The form deviation resulting from these measured variables gains more and more significance with a rising scale of miniaturization. For the hot embossing of flat glass substrates with several cavities (e.g. micro lens arrays, microfluidic components) at the fraunhofer IWU a method was developed, in order to determine the total form deviation with the help of uncomplex shaped dies experimentally. The obtained accuracy is sufficient in order to correct ordinary optical geometries, like spherical cavities, or the pitch of V-grooves and channel structures respectively. For different tool materials and inorganic glasses according to this method correction factors were determined to compensate the process inherent form deviation. In this way complex iteration steps in the manufacturing of the tool moulds can be minimized.
Aluminum foam sandwiches are laminates with an aluminum foam core and compact cover sheets. The foam cores possess a high energy absorption capacity. machine tool assemblies made of aluminum foam sandwiches offer very...
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ISBN:
(纸本)9781932078282
Aluminum foam sandwiches are laminates with an aluminum foam core and compact cover sheets. The foam cores possess a high energy absorption capacity. machine tool assemblies made of aluminum foam sandwiches offer very high flexural stiffness, together with comparatively light weight. Vibrations generated by machining are damped very well due to the cellular structure of foam. The manufacturing process of foam sandwiches is in general well understood, but there are still some open questions concerning the mechanisms of bonding and adhesion between cover sheets and foam core. This paper tries to give answers to these questions.
The need for high-aspect ratio micro structures in hard to machine materials is constantly growing. Electro-Physical machining processes such as EDM offer distinct advantages to conventional machining technologies suc...
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ISBN:
(纸本)9780955308253
The need for high-aspect ratio micro structures in hard to machine materials is constantly growing. Electro-Physical machining processes such as EDM offer distinct advantages to conventional machining technologies such as independence of material hardness, but are difficult to control for high-precision and micro applications [1]. It is therefore of great importance to provide means of fast and stable machining in Micro-EDM, e.g. optimize process and discharge efficiency. In this study, a novel approach to characterize erosion efficiency in Micro-EDM is made by recording erosion current and voltage with high resolution and long recording time. The paper presents the objectives of pulse shape classification for micro-EDM and lines out how a rating of erosion efficiency can be realized by studying the number and sequence of current and voltage of the erosion pulses. Thus, process analysis can be improved and optimized parameters can be adopted to the process state, eventually leading to an on-line process control.
In Jet Electrochemical Machining (Jet-ECM), the electrolytic current between the anodic work piece and the cathodic nozzle is supplied via an electrolyte jet which is ejected from a nozzle. The main advantage compared...
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ISBN:
(纸本)9780955308253
In Jet Electrochemical Machining (Jet-ECM), the electrolytic current between the anodic work piece and the cathodic nozzle is supplied via an electrolyte jet which is ejected from a nozzle. The main advantage compared to other EC processes is the restriction of the electrolytic current to a limited area by the jet. The dissolution rate and the machining position can easily be controlled by setting the electric current and the nozzle position. Higher dissolution rates compared to pulsed ECM are possible, because continuous direct current is applied. In this study the property of using an additional jet of compressed air to assist the procedure is presented. The additional jet of compressed air removes the electrolyte film enclosing the metallic nozzle, which is caused by surface tension. Thereby localisation is enhanced and working gaps of about 100 um (distance between work piece and nozzle) can be used. Furthermore a FEM model was developed to simulate selected processing results.
In today's mechanical engineering aluminum foam is no longer an unknown material. It is already used where lightweight construction and structural damping are required. Especially in sandwich composites with steel...
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ISBN:
(纸本)9781932078282
In today's mechanical engineering aluminum foam is no longer an unknown material. It is already used where lightweight construction and structural damping are required. Especially in sandwich composites with steel, the advantages of foam as rigid core become evident. For the production of aluminum foam often foamable semi-finished products are used that are fabricated by the molten powder metallurgical procedure. These semifinished products can be made with almost any cross section. During the foaming process the volume increases enormously so that it is possible to fill large volumes and gaps with the generated foam. Besides, aluminum foam is thermally resistant up to about 500C, it can be joined with metals during the foaming process, and it shrinks significantly during cooling. If one compares these facts with known applications of other materials the idea of "aluminum foam - a composite material" immediately comes to mind.
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