24 research outputs found

    Estimation of load history by residual stress relaxation

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    Focusing on the impact of machining on structural integrity and fatigue life of components the surface and subsurface properties are of major importance. It is well known that machining induced residual stresses have a significant influence on the fatigue life of a component. Due to thermal and mechanical loads during a product's life cycle these stresses relax, which is undesired in most cases. The presented approach utilizes relaxations due to mechanical load to estimate the load history of a component. It is intended to qualify residual stress relaxation as a load sensor and to determine the limits of this approach. Therefore, it is demonstrated, how the residual stress state induced by turning of AISI 1060 determines the critical load causing relaxation. Subsequently, the influence of load stress and the number of load cycles is used to build up a model. The presented approach accesses load information from mass production components. Until now, this information is typically limited to prototypical developments or high price parts equipped with external sensors. One application of life cycle data is condition-based maintenance. This technology allows to extend service intervals and prevent a premature replacement of undamaged components. Thus, cost and resource efficiency are augmented. It is demonstrated that based on the changes of residual stress, possible mechanical loads and number of load cycle combinations can be identified. The changes are used to estimate the experienced loads.DFG/CRC/65

    Finite strain viscoplasticity with nonlinear kinematic hardening: phenomenological modeling and time integration

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    This article deals with a viscoplastic material model of overstress type. The model is based on a multiplicative decomposition of the deformation gradient into elastic and inelastic part. An additional multiplicative decomposition of inelastic part is used to describe a nonlinear kinematic hardening of Armstrong-Frederick type. Two implicit time-stepping methods are adopted for numerical integration of evolution equations, such that the plastic incompressibility constraint is exactly satisfied. The first method is based on the tensor exponential. The second method is a modified Euler-Backward method. Special numerical tests show that both approaches yield similar results even for finite inelastic increments. The basic features of the material response, predicted by the material model, are illustrated with a series of numerical simulations.Comment: 29 pages, 7 figure

    Enabling of Component Identification by High Speed Measuring of Grinding Wheel Topography

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    The machining process affects quality and function of components. For this reason, it is an important key competence of the manufacturer. Over the past years, counterfeit products have been threatening the user and damaged the reputation of the original manufacturer. On this account, a method of fingerprinting of ground surfaces was developed in the Collaborative Research Center 653 to protect components against plagiarism. However, this method needs the measuring of every single ground surface, which means a huge expenditure of time in the production chain. If it were possible to predict the grinding surface of the grinding tool precisely, occasional measurements of the grinding tool during the setup time would be sufficient to assign the right tool to the component‘s surface and the manufacturer behind it. The presented paper is focusing on methods for the determination of the topography of grinding tools. These topographies enable the manufacturer to predict and thus identify the surface of components

    Verschleissfeste PVD-/CVD-Trockenschmierstoffschichten fuer die umweltschonende und innovative Fertigung. Teilprojekt 3: Kohlenstoffbasierte Trockenschmierstoffschichten (TSS-C) Abschlussbericht

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    The partners Bosch, Metaplas Ionon and Roth and Rau developed dry lubricant coatings on a carbon coating base. The cutting tools used for the testing were developed in former dry cutting projects especially for cutting with minimum quantity lubrication (MQL). The coatings were tested in cutting and metal forming. After tribological testing at the coating companies the deposited coatings were evaluated by machining tests in drilling, thread forming and metal forming at the universities of Darmstadt and Kassel. The best coatings were tested in production field tests (laboratory) or, if possible, in the production at company Bosch and at other end users of the joint project. It was possible to show that carbon coatings are very good at punching and sheet bending. Also at drilling and thread forming in cast iron and low alloyed steels the results are good enough for production. The results at drilling and thread forming in aluminium alloys and high alloyed steels (X90CrMoV18) were not good enough for production under dry conditions. But testing with a reduced amount of MQL (6ml/h) showed better cutting parameters than commercial coatings. Also cutting length and quality of the parts are better. Even with the best coatings it was not possible to make dry massive forming with reduced temperature. At these high temperatures and high surface pressures it was not possible to work without lubricants. (orig.)Im Projekt wurden von den Partnern Bosch, Metaplas Ionon und Roth and Rau Trockenschmierstoffschichten auf Kohlenstoffbasis entwickelt. Diese wurden auf Werkzeuge abgeschieden, deren Geometrien in bereits abgeschlossenen Projekten fuer die Trockenzerspannung mit Minimalmengenschmierung optimiert wurden. Die Schichten sind fuer die Zerspannung und Umformtechnik vorgesehen. An tribologische Tests bei den Beschichtern schlossen sich Filtertests an den Hochschulen Darmstadt und Kassel an, bei denen die Schichten in Bohr-, Gewindeform- und Umformtests untersucht wurden. Geeignete Schichten kamen in fertigungsnahe Feldtests bzw. in die Fertigung beim Endanwender Bosch und projektuebergreifend bei anderen Endanwendern des Gesamtprojektes. Es zeigte sich, dass die Kohlenstoffschichten bei Stanz- und Blechumformungsoperationen hervorragende Ergebnisse liefern. Auch beim Bohren und Gewindeformen in Gusswerkstoffen und niedrig legierten Staehlen konnten trocken fertigungsrelevante Ergebnisse erzielt werden. Bohren und Gewindeformen in Aluminiumlegierungen und hochlegierten Staehlen war trocken mit fertigungsrelevanten Schnittwerten nicht moeglich. Vergleichsversuche mit Minimalmengenschmierung haben jedoch aufgezeigt, dass trotz Reduzierung der Minimalmenge auf 6 ml/Std. deutlich hoehere Schnittwerte gefahren werden konnten, als mit bisher am Markt erhaeltlichen Beschichtungen. Auch die Standmenge und die Qualitaet der Bearbeitungen konnte verbessert werden. Der Versuch, besonders gute Beschichtungen auch in der Halbwarm-Massivumformung einzusetzen, ist leider gescheitert. Bei den hohen Temperaturen und Flaechenpressungen war ein Arbeiten ohne Schmiermittel grundsaetzlich nicht moeglich. Die Arbeiten wurden deshalb zur Mitte des Projektes abgebrochen. (orig.)SIGLEAvailable from TIB Hannover: F03B70 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung und Forschung, Berlin (Germany)DEGerman

    Moeglichkeiten zur quantitativen Erfassung des Beitrags der Kinderlosen zu den oeffentlichen Aufwendungen fuer die nachwachsende Generation

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    SIGLETIB Hannover: RO 5633(6) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

    Moeglichkeiten zur quantitativen Erfassung des Beitrags der Kinderlosen zu den oeffentlichen Aufwendungen fuer die nachwachsende Generation

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    Bibliothek Weltwirtschaft Kiel A 167311 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

    CVD-Diamantbeschichtung von Stahl. Teilprojekt: Zerspanungsverhalten diamantbeschichteter HSS-Werkzeuge bei der Bearbeitung von Weichmetallen, Verbundwerkstoffen und Glas Abschlussbericht

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    In order to enable diamond deposition onto steel, interlayers have been deposited and investigated. These interlayers have been developed on the base of multilayered systems and have proven to increase adhesion between the diamond film and the relatively soft substrate. Optimization was performed by taking into account the following points: - necessary thickness, gradient of layer hardnesses, sufficient toughness - minimization of carbon- and iron-interdiffusion - promotion of diamond nucleation - matching of thermal expansion coefficients. Diamond coatings have been tested under laboratory conditions, and the critical parameters necessary to perform quality assurance have been evaluated - comparative lab testing of diamond layers - evaluation of test procedures - characterization of structure, composition and adhesion. Finally, diamond-coated tools have been tested by machining of numerous materials. Functionality and lifetime have been assesed, tool wear and quality of the treated surface investigated. (orig.)Available from TIB Hannover: F98B249+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

    CVD-Diamantbeschichtung von Stahl. Teilprojekt: Zerspanungsverhalten diamantbeschichteter HSS-Werkzeuge bei der Bearbeitung von Weichmetallen, Verbundwerkstoffen und Glas Abschlussbericht

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    In order to enable diamond deposition onto steel, interlayers have been deposited and investigated. These interlayers have been developed on the base of multilayered systems and have proven to increase adhesion between the diamond film and the relatively soft substrate. Optimization was performed by taking into account the following points: - necessary thickness, gradient of layer hardnesses, sufficient toughness - minimization of carbon- and iron-interdiffusion - promotion of diamond nucleation - matching of thermal expansion coefficients. Diamond coatings have been tested under laboratory conditions, and the critical parameters necessary to perform quality assurance have been evaluated - comparative lab testing of diamond layers - evaluation of test procedures - characterization of structure, composition and adhesion. Finally, diamond-coated tools have been tested by machining of numerous materials. Functionality and lifetime have been assesed, tool wear and quality of the treated surface investigated. (orig.)Available from TIB Hannover: F98B249+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman
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