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

More documents

Recommendations

Info

a) b) Frequency [%] Frequency [%] Frequency [%] 30 25 20 15 10 5 0 30 25 20 15 10 5 0 30 25 20 15 10 5 0 Section 7 0 5 10 15 20 N q 0 5 10 15 20 N q 0 5 10 15 20 N q 87 Poisson distrubution experimental data Negative binomial distribution Poisson distribution experimental data Negative binomial distribution Poisson distribution experimental data Negative binomial distribution c) Fig. 7.5. Theoretical distribution curves and experimental results from the quadrat analysis of the PM MMC Al6061-20%Al2O3: a) in as-fabricated condition, b) after 4 ECAP passes, c) after 7 ECAP passes.
Section 7 It is important that no particle breaking during the ECAP is observed: the number of particles per quadrat, µ, are 6.2, 5.9, and 6.7 for the initial state, after 4, and 7 ECAP passes, respectively. It should be further noted that no voids are observed in the investigated material after 7 ECAP passes. 7.4.2. The effect of ECAP on the global fracture properties Grinded and polished tensile specimens with a gage length of 10 mm and a quadratic section of 2x2 mm are used for tensile tests. Disk-shaped compact specimens similar to that presented in Fig. 4.8 is used to perform fracture tests. Specimens for mechanical tests are annealed at 530°C for 1h, quenched in water, and aged at 175°C for 15min. which corresponds to an under-aged condition. This heat treatment is chosen because of the low fracture toughness of the MMC. As was already mentioned in Section 2, MMCs in the under-aged condition have the highest fracture toughness. In our case, a high fracture toughness would be advantageous to compare the fracture properties of the material. In Table 7.2, the results of mechanical tensile tests are listed. No significant difference between the yield strength, σy, ultimate tensile strength, σu, the strain hardening coefficient, N, and the fracture strain, εfr, is found for considered materials. In Figure 7.6, the J-∆a curves determined according to [70] for all tested disk compact specimens are given. The values of the fracture toughness, J0.2, the maximum extension of the stable crack propagation, ∆astab, the slope of the J-∆a-curve, dJ/d(∆a), in the range between the ∆a = 0.2 mm and ∆astab are listed in Table 7.2, as well. A tendency to increase of the J0.2-, the dJ/d(∆a)-, and the ∆astab-values with increasing homogeneity of the particle distribution can be noted. Evolution of the slope of the J-∆a curve, dJ/d(∆a), is especially interesting, as this parameter is a measure of the total crack growth resistance in material, Rtot, [50, 84]. In [50], the relation Number of ECAP passes Table 7.2. Data on mechanical properties of the PM-MMC Al6061-20%Al2O3. σy [MPa] σu [MPa] N εfr [%] 88 J0.2/Bl [kN/m] dJ/d(∆a) ∆astab [mm] 0 225 287 0.11 3.0 1.5 1.93 0.42 7.7 4 230 315 0.12 4.2 1.7 2.50 0.72 10.3 Rtot [kJ/m 2 ] 7 230 306 0.12 3.5 2.7 3.88 1.05 15.4
Page 1 and 2:
MONTANUNIVERSITÄT MONTANUNIVERSIT
Page 3 and 4:
TABLE OF CONTENTS 1. Introduction 5
Page 5 and 6:
7.4.4. The effect of ECAP on the lo
Page 7 and 8:
Section 1 The main results of this
Page 9 and 10:
Section 2 2.2. The influence of the
Page 11 and 12:
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 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: Section 7 a) b) c) Fig. 7.4. Micros
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
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
Page 139 and 140:
Fig. 9.20. Fracture surface with ma
Page 141 and 142:
Page 143 and 144:
Page 145 and 146:
Page 147 and 148:
Page 149 and 150:
Page 151 and 152:
Page 153 and 154:
Page 155 and 156:
Fig. 12.36. Fracture surface of the
Page 157 and 158:
[14] Lewandowski JJ, Liu C, Hunt WH
Page 159 and 160:
[42] Rice JR, Rosengren GF. Plane s
Page 161 and 162:
[70] ASTM E1820-01, “Standard Tes
show all

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

Create successful ePaper yourself

Delete template?

Save as template?