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CHAPTER 10 CONCLUSIONS The present thesis focused on the optimization of the crushing behavior of partially foam filled commercial 1050H14 Al crash boxes in 2, 2.5 and 3 mm wall thickness. The boxes were partially filled, 50% of the total length of the box, with commercially available closed-cell Al foam (Alulight AlSi10) with two relative densities, 0.11 and 0.15. In the first part the thesis, empty and foam filled boxes with various configurations, with and without trigger and with and without corrugations were crushed at a quasi-static strain rate in order to determine the box crushing behavior and to provide experimental data for the subsequent modeling and optimization studies. Few filled and empty boxes were also compression tested at a relatively high velocity (5.5 mm/s) using a drop-weight impact tester. In the second part of the thesis, the quasi- static crushing of empty and filled boxes was simulated using LS-DYNA explicit finite element program. In the simulations, the box material was modeled with plastic- kinematic material card (Mat 3) and the foam filler with the Honeycomb model (Mat26). To simulate quasi-static crushing, the material mass density was scaled down by a factor of 1000 and the deformation speed was increased to 2 m/s. The final part of the thesis focused on the optimization of partially foam filled 1050H14 Al crash box crushing using the response surface methodology to maximize the specific energy absorption. A full factorial design was used to create the sample mesh. Dynamic test simulations were also run in accord with the design points of the sampling mesh. In the optimization, the wall thickness and foam filler relative density were selected as independent variables, while a mean crushing load of less than 55 kN, a box wall thickness between 1 and 3 mm and a foam filler density ranging between 0 and 0.2 were considered as constraints. The used optimization methodology was also applied to the boxes made of a stronger Al alloy, 6061T4 Al, and filled with a higher strength Al foam, Hydro Al closed cell foam, in order to clarify the effect of box material and foam filler strength on the crush behavior of the filled boxes. Finally, the benefits of partially 190
foam filling were evaluated. The results of crash analysis of the studied 1050H14 Al boxes were also compared with those of commercially available other boxes made from 6061T4 Al and steel. Following conclusions can be made based on the experimental, simulation and optimization studies on the partially filled crash boxes: 1. Honeycomb model of Alulight AlSi10 aluminum foam was successively captured the foam compression behavior at varying foam relative densities and also the deformation of the foam filler in the filled boxes. 2. The triggers and corrugations formed/machined on the box surface and the montage plate changed the folding initiation site on the box wall. The folding started from one of the ends of the box near the compression plate in the boxes without triggers and corrugations, while the folding started from the triggers and /or corrugations in the boxes with triggers and corrugations. The triggers, corrugations and the montage plate decreased the initial peak load and mean load values of empty boxes. The trigger induced a more uniform folding in empty box, by lowering the differences between initial peak load and the subsequent peak load values in the load-displacement curves. 3. In the filled boxes without montage plates, the fold formation was observed to change from regular to irregular as the box thickness decreased and the foam filler relative density increased. The SEA values of filled crash boxes were similar to those of empty crash boxes between 20 and 40 mm displacement; however, the SEA values of filled boxes increased over those of empty boxes after about 40 mm displacement. 4. Similar to the crash boxes without montage parts, the SEA values of partially filled crash boxes increased over those of empty boxes after about displacement between 40-60 mm. 5. In empty crash boxes tested without and with montage plates, two regular symmetric folds formed. Although, the foam filler microscopically was found to not completely enter in between the folds, it increased the number of folds to 3 in the filled boxes both with and without montage plates. 6. The initial peak load values of dynamically tested boxes were found to be higher than those of quasi-statically tested boxes. However, the mean load values of dynamically and quasi-statically tested empty and filled boxes were almost the 191
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OPTIMIZATION OF THE AXIAL CRUSHING
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ACKNOWLEDGEMENTS My PhD quest has b
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ÖZET KAPALI HÜCRELİ ALUMİNYUM K
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CHAPTER 4 EXPERIMENTAL DETAILS ....
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CHAPTER 8 ALUMINUM CRASH BOX OPTIMI
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Figure 3.7. Simulations of the defo
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Figure 4.9. Dimensions of tensile t
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Figure 6.21. Sequential deformation
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LIST OF TABLES Table Page Table 4.1
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Figure 1. 1. The body in white stru
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Figure 1. 4. Commercial crash boxes
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CHAPTER 2 AL CLOSED CELL FOAMS: PRO
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The processing methods and mechanic
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Figure 2. 5 The preferred particle
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Figure 2. 8. Typical cellular struc
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Figure 2. 10. Manufacturing cost of
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Figure 2. 12. Laser assisted foamed
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Figure 2.16. Shear strength, normal
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Figure 2. 19. Yield strength vs. re
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Figure 2. 21. Unit cell geometry an
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Figure 2. 24. Load-displacement cur
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Figure 2. 26. The photographs of a
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CHAPTER 3 CRUSHING BEHAVIOR OF TUBU
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Figure 3.2. Diamond deformation mod
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deformation mode transition from ax
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Figure 3.8. Energy absorption of qu
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(a) (c) Figure 3.10. Deformation mo
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(a) (b) Figure 3.13. a) Schematic o
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(a) (b) (c) Figure 3.15. a) Load-di
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Figure 3.18. The crush terminology.
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The quasi-static compression behavi
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Figure 3.22. The variation of speci
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Figure 3.24. Deformation modes of e
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Figure 3.27. SEA values of empty an
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Figure 3.29. (cont.) 3.5. Motivatio
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CHAPTER 4 EXPERIMENTAL DETAILS 4.1.
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(a) (b) Figure 4.3.Pictures of a) f
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oxes are shown in Figure 4.6. The l
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Figure 4.7. The method of trigger m
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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 6.18. (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
Page 160 and 161: Figure 7.11. Deformation photos of
Page 162 and 163: (a) (b) (c) Figure 7.14. Load-displ
Page 164 and 165: 7.4. Simulation of Empty and Partia
Page 166 and 167: Figure 7.16. (cont.) (c) (a) Figure
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Page 172 and 173: Figure 7.20. (cont.) (c) (a) Figure
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Page 182 and 183: The constructed response surface of
Page 184: Table 8.1. R 2 , Radj 2 and RMSE va
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Page 189 and 190: an empty tube wall thickness higher
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Page 194 and 195: The dynamic simulation and analytic
Page 196: Figure 9.4. (cont.) (c) (d) Figure
Page 199 and 200: Figure 9.6. (cont.) (c) (d) (a) Fig
Page 203 and 204: Equation 9.7 can also be rewritten
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Page 209: Figure 9.11. (cont.) (d) The variat
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Page 215 and 216: Arora, J. S.,2004,Introduction to O
Page 217 and 218: Dannemann, K. A. and Lankford, J.,
Page 219 and 220: Hall, I. W., Guden, M. and Yu, C. J
Page 221 and 222: Kim, D-K. and Lee, S., 1999, Impact
Page 223 and 224: Mamalis, A. G., Manolakos, D. E., I
Page 225 and 226: Pugsley, A. G. and Macaulay, M., 19
Page 227 and 228: T. Miyoshi, M. Itoh S. Akiyama A. K
Page 229: Zhao, H., Elnasri, I. and Girard, Y
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