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7353 |
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Friday, May 06, 2022, Hall G2 11:40 AM Characterization & Testing Methods I |
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Influence of ductility on fracture in tensile testing of cold gas sprayed deposits |
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Alexander List* / Helmut Schmidt University of the Federal Armed Forces, Germany Carl-Philipp Gieseler / Helmut Schmidt University, University of the Federal Armed Forces Hamburg, Germany, Germany Frank Gärtner/ Helmut Schmidt University, University of the Federal Armed Forces Hamburg, Germany, Germany Thomas Klassen/ Helmut Schmidt University, University of the Federal Armed Forces Hamburg, Germany, Germany |
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After many years of research and applications as conventional coating technique, cold gas spraying nowadays is under investigation for additive manufacturing with high deposition rate. To prove that additively manufactured parts meet the needs of the respective structural applications, more information on mechanical properties and respective failure modes is essential. Deposit strengths can be determined by micro-flat tensile (MFT) tests or tubular coating tensile (TCT) tests, according to DIN EN 17393. To compare results of both tests, a notch factor K is usually applied to TCT test results. However, in ductile systems, the stress concentration in pre-notched samples could be reduced by rounding off of originally sharp crack tips. Since TCT-tests offer geometries similar to pre-notched samples, a systematic investigation of the correlation factor can provide information on deposit ductility and fracture toughness. Taking copper and titanium as model systems, this study evaluates micro flat tensile and tubular coating tensile tests and influences on respective notch factors over a wide range of spray parameter sets. Reaching regimes in high pressure cold gas spraying that allow for coating quality parameters ? greater than 1.5, deposits can show certain ductility. The respective comparison between the results from micro flat tensile and tubular coating tensile tests reveal that the stress concentration factor depends on the coating quality parameter ? and could decrease to unity under ideal conditions. In turn, the correlation to respective strain to failure data can supply information on underlying deformation mechanisms. In summary, these preliminary results indicate strategies for tuning deposit toughness and respective tools for analyses. |