Investigation of the Effects of Discontinuities on the Mechanical Properties of Micro Lattice Structures Produced by the Selective Laser Melting Method

Abstract

In this study, the effects of defects such as dust, voids and geometric distortions occurring in micro lattice structures produced by selective laser melting on mechanical properties were investigated. Micro lattice structures are made of 316L stainless steel material, in the form of a body-centered cubic (BCC) structure, with struts of 200 µm diameter. Defects occurring on the surface was modeled realistically using the scanning electron microscope images. The mechanical properties of the structure were examined by using the experimental and finite element method with compression tests. As a result of the tests carried out, it was observed that the finite element results converged to the experimental data by increasing the number of cells and increasing the number of wires accordingly. In the realistic modelling of the compression tests, considering the analysis time and the convergence to the experimental results, it is found out that at least two half-cells should be modeled. Although it is seen that the micro powders adhering on the part do not have much effect on the stress value, it has been determined that the strain value change makes it more realistic due to the early contact areas.

Keywords

• Micro Lattice Structures
• Selective Laser Melting
• Cellular Materials
• Additive Manufacturing
• Finite Element Analysis

Seçici Lazer Ergitme Yöntemi ile Üretilen Mikro Kafes Yapıların Yüzeyinde Meydana Gelen Kusurların Mekanik Özelliklere Etkilerinin İncelenmesi

Abstract

Bu çalışmada seçici lazer ergitme yöntemi ile üretilen mikro kafes yapılarda meydana gelen boşluklar, yüzeye yapışan tozlar ve geometrik çarpılmalar gibi kusurların mekanik özelliklere etkileri incelenmiştir. Mikro kafes yapılar 316L paslanmaz çelik malzemesinden, hacim merkezli kübik (BCC) yapı şeklinde, 200 µm çapında tellerden meydana gelecek şekilde üretilmiştir. Taramalı elektron mikroskobu görüntüleri kullanılarak yüzeyde meydana gelen kusurlar gerçeğe yakın katı modellenmiştir. Kafes yapıların mekanik özellikleri deneysel ve sonlu elemanlar yöntemi kullanılarak basma testleri ile incelenmiştir. Yapılan testler sonucunda hücre sayısının arttırılması, buna bağlı olarak tel sayısının arttırılması ile sonlu elemanlar sonuçlarının deneysel verilere yakınsadığı gözlemlenmiştir. Sıkışma bölgesinin gerçeğe yakın modellenmesinde, analiz süresi ve deneysel sonuçlara yakınsama göz önüne alındığında en az iki yarım hücrenin modellenmesi gerektiği görülmüştür. Parça üzerine yapışan mikro tozların gerilme değeri üzerinde çok etkisinin olmadığı görülse de erken temas bölgeleri oluşturmaları sebebi ile birim şekil değişiminin gerçeğe daha yakın hale getirdiği saptanmıştır.

Keywords

• Mikro Kafes Yapılar
• Seçici Lazer Ergitme
• Hücresel Malzemeler
• Eklemeli İmalat
• Sonlu Elemanlar Yöntemi

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