A Numerical Investigation About Shrink Line Formation in TPMS Lattice Structures During LPBF Process

Öz

Thermal nature of laser powder bed fusion process (LPBF) causes residual stress formation on the part during printing which may cause penetration of some layers towards inside or outside of the nominal geometry called shrink line. Shrink line affects dimensional accuracy and fatigue life of produced parts. The prediction of shrink line formation via numerical methods is important to mitigate the high cost of trial-and-error printing. This study focused on shrink line formation prediction in triply periodic minimum surface (TPMS) lattices produced by LPBF process. The effect of TPMS type, volume fraction, unit cell size, inclination angle of the lattice with respect to build platform, functional grading and material on shrink line formation were investigated. Numerical results revealed that shrink lines were formed only on Primitive lattices and input or control parameters used in this study directly influence the shrink line penetration depth due to different thermally induced stress formation between successive layers.

Anahtar Kelimeler

• shrink line
• laser powder bed fusion
• process simulation
• TPMS lattices

Lazer Toz Yataği Füzyon Prosesi Sırasında, Tpms Kafes Yapılarında Oluşan Büzülme Çizgilerinin Sayısal İncelenmesi

Öz

Lazer toz yatağı füzyon işleminin (LTYF) termal doğası, üretim sırasında parça üzerinde artık gerilim oluşumuna neden olur ve bu da bazı katmanların büzülme çizgisi adı verilen nominal geometrinin içine veya dışına nüfuz etmesine neden olabilir. Büzülme çizgisi, üretilen parçaların boyutsal doğruluğunu ve yorulma ömrünü etkiler. Büzülme çizgisi oluşumunun sayısal yöntemlerle tahmin edilmesi, deneme yanılma üretiminin yüksek maliyetini azaltmak için önemlidir. Bu çalışma, LTYF yöntemi ile üretilen üçlü periyodik minimum yüzey (TPMS) kafeslerinde büzülme çizgisi oluşumunun tahmin edilmesine odaklanmıştır. TPMS tipinin, hacim oranının, birim hücre boyutunun, kafesin üretim platformuna göre eğim açısının, fonksiyonel derecelendirmenin ve malzemenin büzülme çizgisi oluşumuna etkisi araştırılmıştır. Sayısal sonuçlar, büzülme çizgilerinin yalnızca Primitif kafeslerde oluştuğunu ve bu çalışmada kullanılan kontrol parametrelerinin, ardışık katmanlar arasındaki, ısı kaynaklı gerilim oluşumu nedeniyle büzülme çizgisi penetrasyon derinliğini doğrudan etkilediğini ortaya çıkardı.

Anahtar Kelimeler

• Büzülme çizgisi
• lazer toz yatağı füzyon yöntemi
• proses simülasyonu
• TPMS kafes yapısı

Kaynakça

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