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

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σ interf max [MPa] σ interf max [MPa] 1200 800 400 0 1200 800 400 0 Section 4 0 100 200 300 400 500 r [µm] a) 0 20 40 60 80 θ [°] b) 63 15 min 200h 15 min 200h Fig. 4.28. The σ interf max-values vs. (a) the distance between crack tip and particle, r, (b) the angle between the crack tip and the particle for different aging conditions of the PM-MMC.
Section 4 4.5. The relation between the local conditions for void initiation and global mechanical properties The average values of the maximum principal stresses in the particles are calculated for all specimens and inserted in Tables 4.8 and 4.9. For calculating the mean values, the near-zero CODvi-particles have been excluded. In Figure 4.29, the average σ max p fr - and σ max interf dec- values are plotted against the yield stress of the composites. One can see that these values are far from being equal in all specimens. The average of values of the maximum particle stresses and maximum stresses at the interface increase with increasing yield stress of the composites. The large differences in the average σ p max-values of about 400 MPa cannot be explained by methodogical uncertainties and computational inaccuracies of the analyzing procedure. This leads to the question: “What might be a reason for such a behavior?” A possible explanation could be that the onset of plastic deformation has a decisive influence on the particle fracture. Assume that void initiation would occur at the onset of gross plastic yielding in the matrix (not at the onset of local plastic yielding near some corners or edges of the particles). This would require that, considered at the meso-scale, the equivalent stress of the composite around the considered particle, σ c eq , reaches the composite yield stress, σy. For σ max [MPa] 1600 1200 800 400 0 0 100 200 300 400 σ y [MPa] 64 Al2O3 particles Al2O3 interface SiC particles Fig. 4.29. The dependence of the average σ max interf dec- and σ max p fr-values on the composite yield strength, σy, for all investigated MMCs.
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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
Page 13 and 14: Section 2 etched to mark the inclus
Page 15 and 16: Section 2 (4.) The specimen prepara
Page 17 and 18: Section 3 Fig. 3.1. The digital ele
Page 19 and 20: height [µm] height [µm] 10 0 -10
Page 21 and 22: Section 3 Fig. 3.5. The observation
Page 23 and 24: Section 3 3.3.2. The determination
Page 25 and 26: Section 3 The Eshelby tensor does n
Page 27 and 28: equivalent stress Section 3 Fig. 3.
Page 29 and 30: Assume σ m eq Calculate matrix sec
Page 31 and 32: Section 4 Table 4.1. Chemical compo
Page 33 and 34: 4.1.1.3. Fracture mechanics tests S
Page 35 and 36: Section 4 Fig. 4.4. A view of a com
Page 37 and 38: Section 4 Table 4.3. Mechanical pro
Page 39 and 40: εfr [%] εfr [%] N 16 12 8 4 0 150
Page 41 and 42: 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: σ interf max [MPa] σ interf max [
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 and 94: Section 7 Fig. 7.8. The fracture su
Page 95 and 96: 10 z [mm] 5 -10 -15 Section 7 0 -20
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
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Table 9.13. Data on stress for Spec
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Table 9.15. Data on stress for Spec
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Table 9.17. Results of the stereoph
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1 2 1 2 3 3 4 5 6 5 9 119 7 7 8 9 6
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8 9 10 6 10 122 11 12 13 14 11 12 1
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9 10 11 12 13 124 50 µm Fig. 9.6.
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1 2 1 2 3 3 4 4 126 5 5 6 9 7 50 µ
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1 1 2 2 3 4 3 4 5 5 128 6 7 6 7 50
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Fig. 9.12. Fracture surface with ma
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1 2 3 1 2 3 4 5 6 7 8 9 10 4 5 132
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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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