Microstructural And Mechanical Properties Of Human Ribs Joseph

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CHAPTER 3 The Mechanical Characterization of Human Ribs Subjected to Dynamic Three-Point Bending Abstract Determining the risk of injury from an automobile collision to the thorax requires knowledge of the properties of the skeletal components that comprise the thorax. The purpose of this study was to investigate the strength of human ribs subjected to dynamic three-point bending. A total of four human cadavers were utilized by removing 16 rib sections from the right side of each thorax. One or two sections were removed from a single rib at the lateral, anterior and posterior locations of the thorax. The strain rates resulting from the dynamic loading ranged from 0.5 to 5.44 strains per second. Three-axis strain gage rosettes were used for one series of tests showing small variation of the principal strain axis from the direction of bending. For all subjects, the anterior specimens failed at a significantly lower peak stress than the lateral (p=0.01) and posterior (p=0.01) specimens. The average elastic modulus from all tests was 22 GPa. The average peak stress for all specimens was 115 MPa, with an average peak strain of 11,460 microstrain. Introduction Human ribs play an important role in the protection of vital organs essential to the life of an individual. In order to properly predict forces that will initiate rib fracture, the strength of each rib should be investigated. The rib response to dynamic loading is of particular interest for the development of injury criteria applied to automotive safety devices. Studies using restrained cadavers in impact sled tests have frequently found rib fracture to be the most common skeletal injury (Crandall 1997, Kallieris 1998, Cromack 28
1975, Patrick 1974, Ramet 1979). This study is an improvement to previous work due to the use of dynamic loading as well as the use of ribs from a wider range of locations on the thorax. Previous work on human ribs includes non-destructive tests performed by Shultz et al. (1974). These tests were performed using a cantilever end condition and resulted in force-displacement data showing no difference in stiffness among the ribs tested at different levels of the thorax. These included the second, fourth, sixth and the eighth through the tenth ribs. The use of a cantilever end condition is not an accurate way to recreate rib loading observed in vivo, however, this study provides useful information for model validation. Granik and Stein (1973) performed static three-point bending tests on lateral rib sections from the 6 th and 7 th ribs. For the ten cadavers tested, loading in the lateral/medial direction resulted in an average failure stress of 106 MPa and an average Young’s modulus of 11.5 GPa. Stein and Granik (1976) performed static three-point bending tests on a total of 79 male cadaver subjects, utilizing the 6 th and 7 th ribs from each. Quasistatic loading was performed in the medial/lateral direction at rates of 2.54, 0.508 and 12.7 mm/min. The average failure stress for all tests was 100.68 MPa, with a variance of 19% of the mean. More recently, Yoganandan and Pintar (1998) performed quasistatic three-point bending tests on the 7 th and 8 th ribs of 30 subjects. The authors found no significant difference between the strength parameter for the two ribs. An average Young’s modulus of 2318 MPa for the seventh rib and 1886 MPa for the eighth rib was determined. The average force at fracture was 153 and 137 N for the seventh and eight rib. Other studies include those consisting of geometric measurements as well as chest compression 29
Page 1 and 2: MICROSTRUCTURAL AND MECHANICAL PROP
Page 3 and 4: Acknowledgements The research descr
Page 5 and 6: Chapter 1 LIST OF FIGURES Figure 1:
Page 7 and 8: Introduction CHAPTER 1 The human th
Page 9 and 10: Background Thorax The thorax is com
Page 11 and 12: The joints between the vertebra and
Page 13 and 14: scale testing, whether it is perfor
Page 15 and 16: The objectives of this study are as
Page 17 and 18: Carter DR, Hayes WC: The Compressiv
Page 19 and 20: Martin R.B.: A Theory of Fatigue Da
Page 21 and 22: Abstract CHAPTER 2 Orientation of O
Page 23 and 24: previous researchers as the directi
Page 25 and 26: Reference Cuts Figure 2: Histologic
Page 27 and 28: In order to separate the canals int
Page 29 and 30: (θaverage) is then calculated (Equ
Page 31 and 32: to facilitate respiration and there
Page 33: References Black J, Richardson SP,
Page 37 and 38: Figure 1: Location of rib specimens
Page 39 and 40: during the application of the strai
Page 41 and 42: Strain Gage I Ixx xx Figure 4: Geom
Page 43 and 44: The strain rates resulting from the
Page 45 and 46: Table 4: Results for cadaver M1 wit
Page 47 and 48: (P=0.05), lateral (P=0.01) and post
Page 49 and 50: posterior region is finally compare
Page 51 and 52: These ribs were chosen for comparis
Page 53 and 54: References Crandall JR, Bass CR, Pi
Page 55 and 56: APPENDIX A: Matlab Algorithms for H
Page 57 and 58: end save 'osteoncoord08A.txt' xy -a
Page 59 and 60: end end end end xcenter(j+1)=(right
Page 61 and 62: % This is a subroutine algorithm th
Page 63 and 64: % extxy{i} and extxy01{i} represent
Page 65 and 66: end d=0; i=1; for i=1:8 ocorin2=int
Page 67 and 68: end d8=d8+1; ocorin7(d7,:)=ocorex1(
Page 69 and 70: save 'int7.txt' int7 -ascii -tabs s
Page 71 and 72: int01(k,1) & i == 1 65 if int02(j,1
Page 73 and 74: ext01(k,1) & i == 1 67 if ext02(j,1
Page 75 and 76: % The algorithm below creates image
Page 77 and 78: end bwo(xy(i,1)+1,xy(i,2)-1)=1; bwo
Page 79 and 80: %angle offset with horizontal axis
Page 81 and 82: end % Interior surface osteon coord
Page 83 and 84: save 'ext4.txt' ext4 -ascii -tabs s

Microstructural And Mechanical Properties Of Human Ribs Joseph

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