표제지
국문요약
영문요약
목차
제1장 서론 15
1.1. 연구배경 16
1.2. 연구목적 20
1. SLM 공정을 이용한 CoCrMo sheet TPMS lattice 제조 20
2. SLM-built CoCrMo sheet TPMS lattice의 구조적 특징 및 미세조직 분석 20
3. SLM-built CoCrMo sheet TPMS lattice의 기계적 특성 비교 및 고찰 20
4. SLM-built CoCrMo sheet TPMS lattice의 기계적 특성에 미치는 unit cell 형상, parent materials, 미세조직의 영향 규명 20
제2장 이론적 배경 21
2.1. 적층제조 공정 22
2.1.1. Powder Bed Fusion 24
2.1.2. Directed Energy Deposition 26
2.2. 격자구조체 28
2.3. Triply Periodic Minimal Surface Lattice 30
2.4. CoCrMo 합금 33
제3장 실험 방법 35
3.1. 격자구조체의 설계 36
3.2. CoCrMo 분말 및 적층제조 공정 38
3.3. 격자구조체의 구조 분석 39
3.4. 미세조직 및 상 분석 40
3.5. 기계적 물성 시험 41
제4장 연구 결과 43
4.1. 제조된 격자구조체의 구조 및 형태 분석 44
4.2. 초기 미세조직 및 상 분석 52
4.3. 인장 기계적 특성 및 인장 변형 거동 57
4.4. 압축 기계적 특성 62
4.5. 압축 에너지 흡수 특성 67
제5장 결과 고찰 73
5.1. 인장 변형 거동 74
5.1.1. μ-CT 및 DIC 74
5.1.2. 단순 정역학 모델 78
5.2. 압축 변형 거동 및 에너지 흡수 특성 81
5.2.1. 변형 이미지를 이용한 현상학적 해석 81
5.2.2. 미세조직학적 효과 84
제6장 결론 87
참고문헌 91
연구실적 100
발표실적 101
수상실적 103
Table 4-1. Measured values of lattice parameters 51
Table 4-2. Tensile mechanical properties of sheet TPMS lattices and real bone 58
Table 4-3. Compressive mechanical properties 64
Table 4-4. Energy absorption characteristic parameters of TPMS lattices (BD samples) 72
Figure 2-1. Schematic diagram of SLM 25
Figure 2-2. Schematic diagram of DED 26
Figure 2-3. Schematic diagram of TPMS 30
Figure 3-1. isometric view images of computer aided design (CAD) models for (a) Neovius unit cell and (b) IWP unit cell 37
Figure 4-1. Macrophotographs of Co-Cr-Mo TPMS sheet lattice specimens with various topology and unit cell sizes: (a) Neovius, (b) IWP. The legend on the right shows the directions of the three axes in the Cartesian coordinate system (BD: building direction, TD: tensile... 45
Figure 4-2. Cross-sectional and 3D reconstructed μ-CT images of the fabricated (a) Neovius 1, (b) Neovius 2.5, (c) Neovius 5 and (e) IWP 1, (f) IWP 2.5, (g) IWP 5 sheet TPMS lattices. Diagrams of the geometrical structures of the (d) Neovius and (h) IWP lattices,... 46
Figure 4-3. 3D reconstructed μ-CT images of (a) Neovius (b) IWP and (c) Cross sectional images of IWP with indicating the rectangular coordination system of three axis (1. building direction (BD) 2. perpendicular direction 1 (PD₁) 3. perpendicular direction 2 (PD₂)) 47
Figure 4-4. SEM showing the morphologies of the top surfaces of the (a) Neovius 1, (b) Neovius 2.5, (c) Neovius 5 (c), and (d) IWP 1, (e) IWP 2.5, (f) IWP 5 TPMS sheet lattices 50
Figure 4-5. SEM observing on the top and bottom surfaces: (a) Neovius 2.5 top surface, (b) Neovius 2.5 bottom surface, (c) IWP 2.5 top surface, (d) IWP 2.5 bottom surface 50
Figure 4-6. SEM showing the sheet (wall) thicknesses of the different unit cell topologies and sizes: (a) Neovius 1, (b) Neovius 2.5, (c) Neovius 5, (d) IWP 1, (e) IWP 2.5, and (f) IWP 5. 51
Figure 4-7. SEM showing typical microstructures of SLM-built CoCrMo sheet TPMS lattices: (a-b) Neovius 2.5 and (c-d) IWP 2.5. (e) X-ray diffraction patterns of SLM-built CoCrMo sheet TPMS lattices 54
Figure 4-8. EBSD results: IPF maps, KAM maps and phase maps of as-fabricated sheet TPMS lattices; (a) Neovius, and (b) IWP 56
Figure 4-9. Engineering stress-strain curve (results of tensile test) of (a)unit cell size=1mm, (b)unit cell size=2.5 mm and unit cell size=5 mm and macro-images of tensile... 58
Figure 4-10. Estimated Young's modulus ((a): Equation (4)) and yield stress ((b): Equation (5)) of sheet TPMS lattices after insertion of our data in the Gibson-Ashby model. 61
Figure 4-11. Engineering stress-strain curve (results of compressive test) of (a) sheet Neovius, sheet IWP lattices and (b) SLM-built bulk CoCrMo 63
Figure 4-12. Comparison of the compressive mechanical properties based on relative density (ρ) with other SLM-built CoCrMo lattices; (a) 0.2% yield strength, (b) First peak strength, and (c) young's modulus 66
Figure 4-13. Stress-strain and energy absorption efficiency-strain curve for calculating energy absorption parameters; (a)Neovius, (b)IWP(σy and εD indicating yield stress and densification strain, respectively)[이미지참조] 69
Figure 4-14. Ideality Energy absorption efficiency (Ideality) of Neovius BD and IWP BD 70
Figure 5-1. μ-CT images of the specimens scanned before and after tensile testing. In each set of images, those on the left were scanned before the as-fabricated specimens were tested, and those on the right were scanned after the deformed samples were subjected to tensile... 75
Figure 5-2. In-situ tensile deformation behavior of CoCrMo lattices analyzed by the digital image correlation method; (a1-a6) Neovius and (b1-b6) IWP lattices. The DIC results show the distribution of local strains; (a5,b5) at maximum tensile strain without fracture, and...[이미지참조] 76
Figure 5-3. Schematic diagrams showing the decomposition of the stress load along the tensile direction in the normal direction (ND) and the transverse direction (TD) for the Neovius unit cell (a) and the IWP unit cell (b). μ-CT images of the tensile deformed specimens: (c)... 80
Figure 5-4. Deformation processes of sheet TPMS lattices during compression test : (a) Neovius, and (b) IWP. The plateau stage is indicated by the area in red parentheses 83
Figure 5-5. EBSD results: IPF maps, KAM maps and phase maps of compressive deformed sheet Neovius lattices 85
Figure 5-6. EBSD results: IPF maps, KAM maps and phase maps of compressive deformed sheet IWP lattices 86