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(a) (b) Figure 2. 20. Crushing strength vs. foam density: a)Al-SiC and b)AlCu4 alloy closed cell foam, (Source: Santosa and Wierzbicki 1998b). Compression behavior of Al foams was simulated by using a unit cell geometry consists of two hemispheres and five layered multi-cell structure, Figure 2.21(Meguid, et al. 2002). Experimental density measurements showed certain density variations through the in-plane and transverse directions. In the simulations, the layer density was altered by varying the unit cell wall thickness. The crush behavior and load vs. deformation curves of the simulations and the experiments showed good agreement for both directions, transverse and in plane. The deformation behavior of a uniform density multiple cell model was also examined in the same study. In this case, the model could not accurately capture the localization behavior of the foam, and the resulting nominal stress–strain curves showed unrealistic numerical oscillations. Czekanski et al. (Czekanski, et al. 2005b) proposed a 3D unit cell geometry for modeling the deformation behavior of Al closed-cell foams. Proposed unit cell combined the ellipsoid small and pseudo-octagonal large cells as shown in Figures 2.22(a) and (b). Multi-cell finite element models were used to study the effect of individual cell size shape and the foam density on the collapse load and energy absorption. Simulation results showed geometrical parameters of multi-cell foam model had insignificant effects on the overall behavior of Al foam (Czekanski, et al. 2005a, Czekanski, et al. 2005b). 24
Figure 2. 21. Unit cell geometry and layered structure of Al foam simulation. (Source: Meguid, et al. 2002) The mechanical behavior of an Al foam was investigated at quasi-static and high strain rates under hydrostatic compression and tension,(Peroni, et al. 2008). Dynamic tests were performed using Taylor impact tester and Split-Hopkinson pressure bar. It was reported that yield stress values at quasi-static and dynamic uniaxial compression over a vast range of relative densities showed no dependence on the strain rate (Figure 2.23). Figure 2. 22. Unit-cell model: (a) graphical representation, and (b) 3D discredited geometry of representative unit-cell, (Source: Czekanski, et al. 2005b). 25
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 and 42: Figure 2.16. Shear strength, normal
Page 43: Figure 2. 19. Yield strength vs. re
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
Page 61: (a) (c) Figure 3.10. Deformation mo
Page 65 and 66: (a) (b) Figure 3.13. a) Schematic o
Page 67 and 68: (a) (b) (c) Figure 3.15. a) Load-di
Page 72 and 73: Figure 3.18. The crush terminology.
Page 75 and 76: The quasi-static compression behavi
Page 77 and 78: Figure 3.22. The variation of speci
Page 79 and 80: Figure 3.24. Deformation modes of e
Page 81 and 82: Figure 3.27. SEA values of empty an
Page 83 and 84: Figure 3.29. (cont.) 3.5. Motivatio
Page 85 and 86: CHAPTER 4 EXPERIMENTAL DETAILS 4.1.
Page 87 and 88: (a) (b) Figure 4.3.Pictures of a) f
Page 89 and 90: oxes are shown in Figure 4.6. The l
Page 91 and 92: Figure 4.7. The method of trigger m
Page 93 and 94: 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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