Publication: Direkt Metal Lazer Sinterleme Metodu İle Ti-6Al-4V Proses Haritalarının Çıkartılması Ve Geçici Hal Eriyik Havuz Geometrisinin Analizi
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Date
2019-01-07
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Abstract
Direkt Metal Lazer Sinterleme (DMLS) metoduyla proses parametrelerinin tek tek etkileriniincelemek ve bunu parçanın farklı geometrileri için tekrarlamak tasarlanmıs parça içinparametrelerin bulunması sürecini uzatır ve maliyetleri arttırır. Imalat sırasında ısıl kaynaksebebiyle olusan eriyik havuz kontrolü parça kalitesinde etkin rol oynamaktadır. Bugeometrinin kontrol edilebilmesi ana proses parametreleri olan ısın gücü ve ısın hızı ilesaglanabilir. Proje kapsamında tek paso eriyik havuz geometri deneyleri ve sonlu elemananaliz (SEA) termal modelleri proses haritalarının olusturulmasında kullanılmıstır. Prosesharitaları sayesinde kompleks parça üretiminde hedeflenen kalitedeki üretime ulasma süreleriçok daha kısalabilir.Proses haritaları tek paso deneylerinin kararlı hal durumu için yürütülmesiyle ortayakonmustur. Elde edilen eriyik havuz geometrileri termal SEA modellerin karsılastırılmasındave kalibrasyonunda kullanılmıstır. Olusturulan SEA modeli lazer absorpsiyon verimliligidegisimini ve 3B ısı kaynagı geometrisini parametrelere göre degistiren bir model olarakmeydana getirilmistir. Elde edilen güvenilir model kararlı hal dısında ve tek paso kosullarıharicinde de kullanılabilir. Imalatın hızını arttırabilmek için farklı lazer çaplarının eriyik havuzaetkileri yine tek paso deneyleri ve modelleri ile incelenmistir. Lazer çapı artısı ve katmankalınlıgı artısı ile yıgma oranı yaklasık 3 kat aratabilecegi analiz edilmistir. Eriyik havuzderinlik-genislik oranı 0.85?den düsük kaldıgı durumlarda imalatın hatasız ürünlere imkantanıdıgı ortaya konmustur. Gözenekli yapı esik degerleri için hacimsel enerji yogunlugu venormalize entalpi lazer çapına baglı olarak çalısılmıstır. Normalize entalpi degeri lazer çapıetkisinden bagımsız kullanıcıya hatalı üretim hakkında bilgi verebilmektedir. Parametredegisimi sırasında eriyik havuz davranısı incelenmis ve sitemdeki lazer performansı anlıkdegisimine karsı veya parametre degisimi sırasındaki eriyik havuz degisim bölgesinikısaltmaya yönelik ikinci lazer ısın etkileri modellenerek çalısılmıstır.Bu projenin çıktıları olan proses haritaları konu üzerinde çalısan arastırmacılara deneysel verisunacaktır ve kullanıcılara da kaliteli parça imalatı için referans olacaktır. Projede sunulantermal modelleme yöntemi de farklı proses ve malzemeler adapte edilebilecek sekildearastırmacıların faydalanabilecegi bir yöntem olarak sunulmustur. Lazer çap degisimi etkileride imalat verimliligini arttırma potansiyeli nedeniyle gelecek daha detaylı çalısmalara açıktır.
Investigating process parameter effects of direct metal laser sintering (DMLS) andrepeating the procedure on different geometries of the part extends the procedure duration forfinding final process parameters for the designed part and increases the cost. Controlling the meltpool geometry, which is formed due to heat source, plays an important role on part quality. Thisgeometry can be controlled by main process parameters such as beam power and beam speed.Single bead experiments and thermal finite element analysis models for different processparameter were conducted during the project. Developed process maps may help decreasing thepreparation stage to find the optimum parameters for complex shaped partsProcess maps for single bead tracks were developed after running the experiments. Meltpool geometry results of the experiments were used to calibrate the thermal models and comparewith it. A unique thermal model approach has been developed because it varies the laserabsorption efficiency and heat source geometry as a function of the process parameters. Thisaccurate model can also be used for different alloys and geometries. To investigate the potentialof higher deposition rates, different beam diameters experiments and models were investigated.Increasing the layer thickness and beam diameter potentially has increased the deposition rateby a factor of three. Melt pool depth over width ratio was found to be less than 0.85 to avoid theporosity defects. To find the thresholds of the void defects, volumetric energy density andnormalized enthalpy were utilized. Normalized enthalpy was useful to inform the user about thethresholds independent from the beam diameter variation. Moreover, melt pool for parameterchange was modeled during laser single scan, and second laser effects to reduce the transitionregion was further investigated.Process maps as a result of this study will provide experimental data to the researcherswork on this topic and a reference for the additive manufacturing users for quality partmanufacturing. Developed thermal model can be utilized for various alloys and part geometries.Variation of the beam diameter has a potential to increase the manufacturing efficiency.Keywords: additive manufacturing, process parameter mapping, melt pool geometry,thermal finite element analysis, transient melt pool geometry, direct metal laser sintering(DMLS), selective laser melting
Investigating process parameter effects of direct metal laser sintering (DMLS) andrepeating the procedure on different geometries of the part extends the procedure duration forfinding final process parameters for the designed part and increases the cost. Controlling the meltpool geometry, which is formed due to heat source, plays an important role on part quality. Thisgeometry can be controlled by main process parameters such as beam power and beam speed.Single bead experiments and thermal finite element analysis models for different processparameter were conducted during the project. Developed process maps may help decreasing thepreparation stage to find the optimum parameters for complex shaped partsProcess maps for single bead tracks were developed after running the experiments. Meltpool geometry results of the experiments were used to calibrate the thermal models and comparewith it. A unique thermal model approach has been developed because it varies the laserabsorption efficiency and heat source geometry as a function of the process parameters. Thisaccurate model can also be used for different alloys and geometries. To investigate the potentialof higher deposition rates, different beam diameters experiments and models were investigated.Increasing the layer thickness and beam diameter potentially has increased the deposition rateby a factor of three. Melt pool depth over width ratio was found to be less than 0.85 to avoid theporosity defects. To find the thresholds of the void defects, volumetric energy density andnormalized enthalpy were utilized. Normalized enthalpy was useful to inform the user about thethresholds independent from the beam diameter variation. Moreover, melt pool for parameterchange was modeled during laser single scan, and second laser effects to reduce the transitionregion was further investigated.Process maps as a result of this study will provide experimental data to the researcherswork on this topic and a reference for the additive manufacturing users for quality partmanufacturing. Developed thermal model can be utilized for various alloys and part geometries.Variation of the beam diameter has a potential to increase the manufacturing efficiency.Keywords: additive manufacturing, process parameter mapping, melt pool geometry,thermal finite element analysis, transient melt pool geometry, direct metal laser sintering(DMLS), selective laser melting
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