dissertation global and local fracture properties of metal matrix ...

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Section 7 particle cluster area area without particle clusters CODi = 0.2...0.5µm Fig. 7.9. Schematic view of the fracture surface of the the PM-MMC Al6061-20%Al2O3 in as- fabricated condition. local CODi-values is found. In front of the particle cluster, they have near-zero values 0.2…0.5 µm. In Figure 7.10, such a profile is presented. In front of the region with homogeneous particle distribution on the fracture surface, the CODi-values lie in the range 2…3 µm (Fig. 8.11). On the contrary, in the specimen from the MMC after 7 ECAP passes, no significant scatter of the CODi-values is observed: the local CODi-values measured at six different positions vary in the range of 2…3 µm (Table 7.3). An improvement of the global fracture toughness and the total crack growth resistance of the MMC with increasing homogeneity of the particle distribution might be explained by results of estimation of the local fracture properties. Such a difference in local fracture properties at regions with different local particle distribution can be caused by a different amount of energy required for crack propagation in this region. It is clear that at particle clusters, where no matrix between the particles is observed (Fig. 7.7b), no energy is needed for the void initiation and void growth: the local values of the crack growth resistance are extremely low, since the local values of the void initiation fracture toughness is almost equal zero. At the same time, in regions with homogeneous particle distribution, some amount of energy is required for the void initiation and following void growth that results in relative high values of the local fracture toughness. CODi = 2...3 µm 93 fracture surface crack tip pre-fatigued region
10 z [mm] 5 -10 -15 Section 7 0 -20 -10 0 10 20 30 40 x [mm] -5 COD i = 0.5 µm crack tip Fig. 7.10. Profiles through a particle cluster at specimen from the as-fabricated material: CODi = 0.5 µm (Profile 1 in Table 7.3). 94
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MONTANUNIVERSITÄT MONTANUNIVERSIT
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TABLE OF CONTENTS 1. Introduction 5
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7.4.4. The effect of ECAP on the lo
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Section 1 The main results of this
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Section 2 2.2. The influence of the
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Section 2 high strength, fine reinf
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Section 2 etched to mark the inclus
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Section 2 (4.) The specimen prepara
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Section 3 Fig. 3.1. The digital ele
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height [µm] height [µm] 10 0 -10
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Section 3 Fig. 3.5. The observation
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Section 3 3.3.2. The determination
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Section 3 The Eshelby tensor does n
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equivalent stress Section 3 Fig. 3.
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Assume σ m eq Calculate matrix sec
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Section 4 Table 4.1. Chemical compo
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4.1.1.3. Fracture mechanics tests S
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Section 4 Fig. 4.4. A view of a com
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Section 4 Table 4.3. Mechanical pro
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εfr [%] εfr [%] N 16 12 8 4 0 150
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Section 4 4.2. The effect of the he
Page 43 and 44: Section 4 It should be noted that n
Page 45 and 46: CODi [µm] 40 30 20 10 0 Section 4
Page 47 and 48: Section 4 Table 4.4. Results of the
Page 49 and 50: CODi [µm] COD i [µm] CODi [µm] 2
Page 51 and 52: Cast MMCs 10%-RT 10%-8h 10%-24h 10%
Page 53 and 54: COD vi [µm] COD vi [µm] CODvi [µ
Page 55 and 56: CODvi [µm] CODvi [µm] 80 60 40 20
Page 57 and 58: Section 4 Table 4.6. The values of
Page 59 and 60: σ p max [MPa] σ p max [MPa] σ p
Page 61 and 62: σ p max [MPa] σ p max [MPa] 1200
Page 63 and 64: σ interf max [MPa] σ interf max [
Page 65 and 66: Section 4 4.5. The relation between
Page 67 and 68: Section 4 Table 4.9. Conditions for
Page 69 and 70: Ln(Ln(1/(1-F σ))) Ln(Ln(1/(1-F σ)
Page 71 and 72: Section 5 diameter of 2…8 µm and
Page 73 and 74: MnS-inclusion r θ MnS-inclusion Se
Page 75 and 76: σ interf [MPa] σ interf [MPa] σ
Page 77 and 78: Section 6 where n is the number of
Page 79 and 80: Ji [kN/m] J i [kN/m] 25 20 15 10 5
Page 81 and 82: Section 7 7.2. A model by Tan and Z
Page 83 and 84: Section 7 its initial length, li. O
Page 85 and 86: 1 µm Section 7 5 µm Fig. 7.3. A s
Page 87 and 88: Section 7 a) b) c) Fig. 7.4. Micros
Page 89 and 90: Section 7 It is important that no p
Page 91 and 92: Section 7 between the Rtot and the
Page 93: Section 7 Fig. 7.8. The fracture su
Page 97 and 98: Section 7 Table 7.3. Data on measur
Page 99 and 100: 8. Summary Section 8 This work deal
Page 101 and 102: Section 8 The effect of the homogen
Page 103 and 104: Table 9.1. Data on stress for Speci
Page 113 and 114: Table 9.11. Data on stress for Spec
Page 119 and 120: Table 9.17. Results of the stereoph
Page 121 and 122: 1 2 1 2 3 3 4 5 6 5 9 119 7 7 8 9 6
Page 123 and 124: 8 9 10 6 10 122 11 12 13 14 11 12 1
Page 125 and 126: 9 10 11 12 13 124 50 µm Fig. 9.6.
Page 127 and 128: 1 2 1 2 3 3 4 4 126 5 5 6 9 7 50 µ
Page 129 and 130: 1 1 2 2 3 4 3 4 5 5 128 6 7 6 7 50
Page 131 and 132: Fig. 9.12. Fracture surface with ma
Page 133 and 134: 1 2 3 1 2 3 4 5 6 7 8 9 10 4 5 132
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Fig. 9.26. Fracture surface with ma
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Fig. 12.36. Fracture surface of the
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[14] Lewandowski JJ, Liu C, Hunt WH
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[42] Rice JR, Rosengren GF. Plane s
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[70] ASTM E1820-01, “Standard Tes
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