Abstract
The spreading use of cellular structures brings the need to speed up manufacturing processes without deteriorating mechanical properties. By using Selective Laser Melting (SLM) to produce cellular structures, the designer has total freedom in defining part geometry and manufacturing is simplified. The paper investigates the suitability of Selective Laser Melting for manufacturing steel cellular lattice structures with characteristic dimensions in the micrometer range. Alternative lattice topologies including reinforcing bars in the vertical direction also are considered. The selected lattice structure topology is shown to be superior over other lattice structure designs considered in literature. Compression tests are carried out in order to evaluate mechanical strength of lattice strut specimens made via SLM. Compressive behavior of samples also is simulated by finite element analysis and numerical results are compared with experimental data in order to assess the constitutive behavior of the lattice structure designs considered in this study. Experimental data show that it is possible to build samples of relative density in the 0.2456–0.4367 range. Compressive strength changes almost linearly with respect to relative density, which in turns depends linearly on the number of vertical reinforces. Specific strength increases with cell and strut edge size. Numerical simulations confirm the plastic nature of the instability phenomena that leads the cellular structures to collapse under compression loading.
Highlights
Layer manufacturing (LM) technologies produce 3D physical parts directly from CAD solid models.Since 3D Systems Inc. introduced the first rapid prototyping (RP) system in the late 1980s, many layer manufacturing technologies and systems have been developed
This paper presented a comprehensive study on fabrication and mechanical testing of 18Ni Marage
The pillar texile micro-lattice structure, comprised of four vertical strut columns and four couples of struts inclined at ±45°with respect to cell axes of symmetry, was selected for being further developed in the second phase of the study as it realizes the best compromise in terms of relative density, area density, and mechanical strength amongst the most commonly used micro-lattice structures described in literature
Summary
Layer manufacturing (LM) technologies produce 3D physical parts directly from CAD solid models. The increasing demand of CMS for engineering applications has led to develop a relevant number of fabrication processes From this stand point, cellular materials can be classified in terms of variability in cell size (i.e., regular or stochastic), topology of pores (i.e., open or closed), relative density of structure and cell size. In spite of the above mentioned advantages, technical literature does not present many systematic investigations on properties of SLM-built lattice structures to assess relative merits of different cell topologies in terms of relative density, thermal dissipation and mechanical strength. For this reason, the article presents a comprehensive study on the performance of micro-lattice structures fabricated via SLM using 18Ni Marage 300 powder. Experimental tests and finite element simulations are performed in order to compare the compression behavior of micro-lattice structures and micro-lattice structures reinforced by bars
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