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The creep and plateau stress-temperature behavior of Al foams was previously studied by few researchers (Andrews, et al. 1999a, Andrews, et al. 1999b, Haag, et al. 2003). The secondary creep strain rate and the time to failure of Alporas closed cell Al foam were determined (Andrews, et al. 2001). Al foam showed comparable creep activation and power law exponent values with those of pure Al under relatively low stresses and at low temperatures. However, at high stresses, higher activation energy and power law number were found. This behavior was attributed to the cell wall breakage at very high creep rates due to the high local stresses caused by the inhomogeneous cell microstructure. The plateau stresses of Al closed cell foams decreased with increasing ,Figure 2.18 (Haag, et al. 2003). The energy absorbing capacity and the plateau stresses of pure Al and solution hardened Al-10% magnesium alloy (AlMg10) foams were previously compared (Han, et al. 1998). The solution treated AlMg10 foam showed less number of load oscillations than untreated foams. This behavior was explained by phase of Al and Mg compound partially or wholly dissolved in phase by solution treatment. However, as-cast AlMg10 foams showed higher plateau stresses and energy absorption than pure Al and solution treated AlMg10 foams (Figure 2.19). Figure 2. 18. Plateau stress vs. temperature at a strain rate of 3.4 X 10 -4 s -1 . (Source: Haag, et al. 2003) 22
Figure 2. 19. Yield strength vs. relative density of pure Al, AlMg10 and solution treated AlMg10 foam (Source: Han, et al. 1998) One of the earliest metal foam modeling studies using an unit cell geometry was performed by Santosa and Wierzbicki (Santosa and Wierzbicki 1998b). The unit cell geometry was a truncated cube comprising cruciform web and pyramidal sections. The crushing of truncated cube unit cell model was progressive folding initiated at the cruciform section and followed by plastic collapse in the pyramidal section. Good agreements between the simulation, analytical modeling and experimental uniaxial compression of HYDRO and IFAM Al closed-cell foam were found (Figure 2.20). However, CYMAT and ALCAN foams showed experimentally much lower crushing strength than the predicted values. This was attributed to the differences in the foam morphological structures between the investigated Al foams, leading to the difference in the crushing strengths. 23
Page 1 and 2: OPTIMIZATION OF THE AXIAL CRUSHING
Page 3 and 4: ACKNOWLEDGEMENTS My PhD quest has b
Page 5 and 6: ÖZET KAPALI HÜCRELİ ALUMİNYUM K
Page 7 and 8: CHAPTER 4 EXPERIMENTAL DETAILS ....
Page 9 and 10: CHAPTER 8 ALUMINUM CRASH BOX OPTIMI
Page 12 and 13: Figure 3.7. Simulations of the defo
Page 14 and 15: Figure 4.9. Dimensions of tensile t
Page 16 and 17: Figure 6.21. Sequential deformation
Page 18 and 19: Figure 7.20. Sequential deformation
Page 20 and 21: LIST OF TABLES Table Page Table 4.1
Page 22 and 23: Figure 1. 1. The body in white stru
Page 24 and 25: Figure 1. 4. Commercial crash boxes
Page 26 and 27: CHAPTER 2 AL CLOSED CELL FOAMS: PRO
Page 28 and 29: The processing methods and mechanic
Page 30 and 31: Figure 2. 5 The preferred particle
Page 32 and 33: Figure 2. 8. Typical cellular struc
Page 34 and 35: Figure 2. 10. Manufacturing cost of
Page 36: Figure 2. 12. Laser assisted foamed
Page 41: Figure 2.16. Shear strength, normal
Page 45 and 46: Figure 2. 21. Unit cell geometry an
Page 47 and 48: Figure 2. 24. Load-displacement cur
Page 49 and 50: Figure 2. 26. The photographs of a
Page 51 and 52: CHAPTER 3 CRUSHING BEHAVIOR OF TUBU
Page 53 and 54: Figure 3.2. Diamond deformation mod
Page 57 and 58: deformation mode transition from ax
Page 59 and 60: Figure 3.8. Energy absorption of qu
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Page 72 and 73: Figure 3.18. The crush terminology.
Page 75 and 76: The quasi-static compression behavi
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Page 83 and 84: Figure 3.29. (cont.) 3.5. Motivatio
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4.4. Compression Tests of Crash Box
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4.5.2. Uniaxial Compression Testing
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Table 4.1 (Cont.) G1 T3 F2 G1T3F2 3
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Table 4.2 (Cont.) G1 T2.5 WP F2 G1T
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CHAPTER 5 SIMULATION AND OPTIMIZATI
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considered in axial and transverse
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were constrained. Since the width o
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5.4. The Crashworthiness Optimizati
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great effect on the crushing behavi
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CHAPTER 6 EXPERIMENTAL RESULTS 6.1.
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Figure 6.3.Tensile stress-strain cu
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(a) (b) Figure 6.5. Sequential defo
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plate (Figure 6(b)). The trigger is
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(a) (b) Figure 6.9. Deformation seq
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Figure 6.12. Sequential deformation
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Figure 6.18. (cont.) (c) (a) (b) Fi
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Figure 6.20.(cont.). (b) (c) 6.5.4.
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Figure 6.21.(cont.) (b) (c) 122
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Figure 6.22.(cont.) (c) Figure 6.23
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Figure 6.24.(Cont.) (b) (c) (a) Fig
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Figure 6.26.(cont.) (b) (c) 6.6. Dy
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Figure 6.27. (cont.) (b) (c) 130
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CHAPTER 7 MODELING RESULTS OF FOAM,
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experimental tensile stress-strain
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significant effect of weld seem ope
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Figure 7.7. Deformation photo of fi
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Figure 7.11. Deformation photos of
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(a) (b) (c) Figure 7.14. Load-displ
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7.4. Simulation of Empty and Partia
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Figure 7.16. (cont.) (c) (a) Figure
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(a) (b) Figure 7.18. Sequential def
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Figure 7.19. (cont.) (b) (c) 150
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Figure 7.20. (cont.) (c) (a) Figure
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(a) (b) Figure 7.26. Experimental a
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The constructed response surface of
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Table 8.1. R 2 , Radj 2 and RMSE va
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(a) (b) Figure 8.7. Response surfac
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an empty tube wall thickness higher
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where, K is a dimensionless constan
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The dynamic simulation and analytic
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Figure 9.4. (cont.) (c) (d) Figure
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Figure 9.6. (cont.) (c) (d) (a) Fig
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Equation 9.7 can also be rewritten
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(a) (b) Figure 9.10. Energy-absorbi
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Figure 9.11. (cont.) (d) The variat
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foam filling were evaluated. The re
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13. The interaction between foam fi
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Arora, J. S.,2004,Introduction to O
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Dannemann, K. A. and Lankford, J.,
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Hall, I. W., Guden, M. and Yu, C. J
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Kim, D-K. and Lee, S., 1999, Impact
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Mamalis, A. G., Manolakos, D. E., I
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Pugsley, A. G. and Macaulay, M., 19
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T. Miyoshi, M. Itoh S. Akiyama A. K
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Zhao, H., Elnasri, I. and Girard, Y
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