In dieser Arbeit wurde eine Bewertungsmethodik untersucht, mit der das komplexe Versagensverhalten von geschweißten Verbindungen beschrieben werden kann. Die Bewertung erfolgt dabei auf Basis eines Zwei-Phasen-Modells, in dem die Berechnung der Anrisslebensdauer und der Rissfortschrittslebensdauer getrennt durchgeführt wird. Die Anrisslebensdauer wird basierend auf dem Kerbspannungskonzept mit Spannungsmittelung nach Neuber sowie der Theorie des kritischen Abstandes nach Taylor berechnet. Die Makro-Rissfortschrittslebensdauer wird ausgehend von FE-Analysen unter Verwendung von bruchmechanischen Kennwerten bestimmt. Die untersuchten Methoden lieferten bei der Abschätzung der Anrisslebensdauer gute Ergebnisse. Beim Vergleich der berechneten Spannungsintensitätsfaktoren zeigen sich Unterschiede in Abhängigkeit von den verwendeten Berechnungsansätzen. Es zeigte sich, dass die eingesetzten Methoden für den industriellen Einsatz weiter verbessert werden sollten.
In this study, an additive manufacturing process based on digital light processing was employed for quick, flexible, and economical fabrication of resin-bonded SiC grinding tools. The grinding wheel has been fabricated using laboratory manufacturing processes that utilize ultraviolet-curable resins and conventional abrasives. Also, desirable geometries and features like integrated coolant holes, which are difficult or even almost impossible to manufacture by conventional processes, are easily achievable. Grinding experiments were carried out by different process parameters, and with two different grinding wheels, i.e. with and without cooling channels with different concentrations (25 wt.% and 50 wt.% grains) to evaluate the grinding efficiency of the produced tools. Grinding forces, tool wear, tool loading, and ground surface quality were measured and analyzed. The wear rates of the grinding wheels with cooling channels were generally less than those without cooling channels, particularly in the deep grinding processes with large contact areas. Grinding tests on a hardened steel have shown that the integration of cooling lubricant channels almost prevents the wheel loading. In addition, by increasing the cutting speed (from 15 to 30 m/s) and decreasing the feed rate (from 10 to 2 m/min) the grinding wheel wear was significantly reduced. Furthermore, surface grinding of aluminum resulted in surface roughness values (Ra) in the range of 1 µm to 2.5 µm, while a Ra of about 0.2 µm was achieved by grinding hardened steel (100Cr6) with the same grinding conditions. Using the higher SiC-grain concentration (50 wt.%), it was determined that the surface roughness was 50% finer. Additionally the tool wear was significantly reduced (up to 30 times depending on the process parameters). The wear characteristics of the grinding wheel was analyzed through a novel image processing system. Significant correlations were found between wear flat of grains and the increase in grinding forces due to the tool wear.
In this study, an additive manufacturing process based on digital light processing was employed for a quick, flexible, and economical fabrication of resin bonded SiC grinding tools. The grinding wheel has been fabricated using laboratory manufacturing processes that utilize ultraviolet-curable resins and conventional abrasives. Also, desirable geometries and features like integrated coolant holes, which are difficult or even almost impossible to manufacture by conventional processes, are easily achievable. Grinding experiments were carried out by different process parameters, and with two different grinding wheels, i.e., with and without cooling channels with different concentrations (25 wt.% and 50 wt.% grains) to evaluate the grinding efficiency of the produced tools. Grinding forces, tool wear, tool loading, and ground surface quality were measured and analyzed. The wear rates of the grinding wheels with cooling channels were generally less than those without cooling channels, particularly in the deep grinding processes with large contact areas. Grinding tests on a hardened steel have shown that the integration of cooling lubricant channels almost prevents the wheel loading. In addition, by increasing the cutting speed (from 15 to 30 m/s) and decreasing the feed rate (from 10 to 2 m/min), the grinding wheel wear was significantly reduced. Furthermore, surface grinding of aluminum resulted in surface roughness values (Ra) in the range of 1 μm to 2.5 μm, while a Ra of about 0.2 μm was achieved by grinding hardened steel (100Cr6) with the same grinding conditions. Using the higher SiC-grain concentration (50 wt.%), it was determined that the surface roughness was 50% finer. Additionally the tool wear was significantly reduced (up to 30 times depending on the process parameters). The wear characteristics of the grinding wheel were analyzed through a novel image processing system. Significant correlations were found between the wear flat of grains and the increase in grinding forces due to the tool wear.
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