Academic literature on the topic 'Axial compression-extension'
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Journal articles on the topic "Axial compression-extension"
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Shirazi-Adl, A., and G. Drouin. "Nonlinear Gross Response Analysis of a Lumbar Motion Segment in Combined Sagittal Loadings." Journal of Biomechanical Engineering 110, no. 3 (August 1, 1988): 216–22. http://dx.doi.org/10.1115/1.3108434.
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A 3-D nonlinear mathematical model is used to analyze the mechanical response of a lumbar L2–3 motion segment including the posterior elements when subjected to combined sagittal plane loads. The loadings consist of axial compression force, anterior and posterior shear forces, and flexion and extension moments. The facet articulation is modelled as a general moving contact problem and the ligaments as a collection of uniaxial elements. The disk nucleus is considered as an inviscid fluid and the annulus as a composite of collagenous fibers embedded in a matrix of ground substance. The presence of axial compression force reduces the segmental stiffness in flexion whereas a reverse trend is predicted in extension. In the presence of axial compression with and without sagittal shear force, flexion considerably increases the intradiscal pressure while extension reduces it. In other words, under an identical compression force, disk pressure is predicted to be noticeably larger in flexion than in extension. The segmental mechanical response in extension loadings is markedly influenced by the changes in the relative geometry of the articular surfaces at the lower regions. Finally, the deformation of the bony structures plays a significant role in the segmental mechanics under relatively large loads.
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Godzik, Jakub, Bernardo de Andrada Pereira, Anna G. U. Sawa, Jennifer N. Lehrman, Randall J. Hlubek, Brian P. Kelly, and Jay D. Turner. "Impact of dual-headed pedicle screws on the biomechanics of lumbosacral junction multirod constructs." Journal of Neurosurgery: Spine 34, no. 5 (May 2021): 691–99. http://dx.doi.org/10.3171/2020.8.spine191545.
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OBJECTIVE The objective of this study was to evaluate a novel connector design and compare it with traditional side connectors, such as a fixed-angle connector (FAC) and a variable-angle connector (VAC), with respect to lumbosacral stability and instrumentation strain. METHODS Standard nondestructive flexibility tests (7.5 Nm) and compression tests (400 N) were performed using 7 human cadaveric specimens (L1–ilium) to compare range of motion (ROM) stability, posterior rod strain (RS), and sacral screw bending moment (SM). Directions of motion included flexion, extension, left and right lateral bending, left and right axial rotation, and compression. Conditions included 1) the standard 2-rod construct (2R); 2) the dual-tulip head (DTH) with 4-rod construct (4R); 3) FACs with 4R; and 4) VACs with 4R. Data were analyzed using repeated-measures ANOVA. RESULTS Overall, there were no statistically significant differences in ROM across the lumbosacral junction among conditions (p > 0.07). Compared with 2R, DTH and FAC significantly reduced RS in extension, left axial rotation, and compression (p ≤ 0.03). VAC significantly decreased RS compared with 2R in flexion, extension, left axial rotation, right axial rotation, and compression (p ≤ 0.03), and significantly decreased RS compared with DTH in extension (p = 0.02). DTH was associated with increased SM in left and right axial rotation compared with 2R (p ≤ 0.003) and in left and right lateral bending and left and right axial rotation compared with FAC and VAC (p ≤ 0.02). FAC and VAC were associated with decreased SM compared with 2R in right and left lateral bending (p ≤ 0.03). CONCLUSIONS RS across the lumbosacral junction can be high. Supplemental rod fixation with DTH is an effective strategy for reducing RS across the lumbosacral junction. However, the greatest reduction in RS and SM was achieved with a VAC that allowed for straight (uncontoured) accessory rod placement.
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Lin, H. D., and W. C. Chen. "Anisotropic Strength Characteristics of Composite Soil Specimen Under Cubical Triaxial Conditions." Journal of Mechanics 23, no. 1 (March 2007): 41–50. http://dx.doi.org/10.1017/s1727719100001064.
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AbstractThis paper provides 41 cubical triaxial test results to examine the influence of the stress path angle and the improvement ratio on the anisotropic strength of the composite soil specimens consisting of remolded soft clay and grout columns. Pictures of failed samples shown in this paper are especially enlightening in demonstrating failure mechanisms. Results from this study can be summarized as follows. The composite soil specimens exhibited different failure patterns depending on the stress path angle, axial compression failure for 0°, 30° and 60°; lateral compression for 120° and 150°; and axial extension for 90° and 180°. Consistently, diagonal shear cracks through the grout column were observed for axial compression failure samples. On the other hand, tension cracks were observed for samples which failed due to lateral compression and axial extension. The composite soil specimens exhibited apparent anisotropic behavior. In general, the anisotropic strength ratio increased with the improvement ratio. The equivalent strength formula commonly used in practice may give erroneous results, especially when the stress paths are those of tension failure. In such a case, the anisotropic strength ratio suggested in this paper can significantly improve its accuracy.
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LI, ZHI-MIN, and HUI-SHEN SHEN. "POSTBUCKLING OF SHEAR-DEFORMABLE ANISOTROPIC LAMINATED CYLINDRICAL SHELLS UNDER AXIAL COMPRESSION." International Journal of Structural Stability and Dynamics 08, no. 03 (September 2008): 389–414. http://dx.doi.org/10.1142/s0219455408002715.
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A postbuckling analysis is presented for a shear-deformable anisotropic laminated cylindrical shell of finite length subjected to axial compression. The material of each layer of the shell is assumed to be linearly elastic, anisotropic and fiber-reinforced. The governing equations are based on a higher order shear-deformable shell theory with the von Kármán–Donnell type of kinematic nonlinearity and including the extension/twist, extension/flexural and flexural/twist couplings. The nonlinear prebuckling deformations and initial geometric imperfections of the shell are both taken into account. A singular perturbation technique is employed to determine the buckling loads and postbuckling equilibrium paths. The numerical illustrations concern the postbuckling response of perfect and imperfect, moderately thick, anisotropic laminated cylindrical shells with different values of shell parameters and stacking sequence. The results confirm that there exists a compressive stress along with an associate shear stress and twisting when the anisotropic shell is subjected to axial compression. The postbuckling equilibrium path is unstable for the moderately thick cylindrical shell under axial compression and the shell structure is imperfection-sensitive.
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Leighton, Matthew P., Laurent Kreplak, and Andrew D. Rutenberg. "Chiral phase-coexistence in compressed double-twist elastomers." Soft Matter 17, no. 19 (2021): 5018–24. http://dx.doi.org/10.1039/d1sm00181g.
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Quaglierini, Jacopo, Alessandro Lucantonio, and Antonio DeSimone. "Mechanics of tubular helical assemblies: ensemble response to axial compression and extension." Acta Mechanica Sinica 37, no. 2 (February 2021): 173–86. http://dx.doi.org/10.1007/s10409-021-01068-0.
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Abstract Nature and technology often adopt structures that can be described as tubular helical assemblies. However, the role and mechanisms of these structures remain elusive. In this paper, we study the mechanical response under compression and extension of a tubular assembly composed of 8 helical Kirchhoff rods, arranged in pairs with opposite chirality and connected by pin joints, both analytically and numerically. We first focus on compression and find that, whereas a single helical rod would buckle, the rods of the assembly deform coherently as stable helical shapes wound around a common axis. Moreover, we investigate the response of the assembly under different boundary conditions, highlighting the emergence of a central region where rods remain circular helices. Secondly, we study the effects of different hypotheses on the elastic properties of rods, i.e., stress-free rods when straight versus when circular helices, Kirchhoff’s rod model versus Sadowsky’s ribbon model. Summing up, our findings highlight the key role of mutual interactions in generating a stable ensemble response that preserves the helical shape of the individual rods, as well as some interesting features, and they shed some light on the reasons why helical shapes in tubular assemblies are so common and persistent in nature and technology. Graphic Abstract We study the mechanical response under compression/extension of an assembly composed of 8 helical rods, pin-jointed and arranged in pairs with opposite chirality. In compression we find that, whereas a single rod buckles (a), the rods of the assembly deform as stable helical shapes (b). We investigate the effect of different boundary conditions and elastic properties on the mechanical response, and find that the deformed geometries exhibit a common central region where rods remain circular helices. Our findings highlight the key role of mutual interactions in the ensemble response and shed some light on the reasons why tubular helical assemblies are so common and persistent.
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Weerheijm, J. "Axial Dynamic Tensile Strength of Concrete under Static Lateral Compression." Key Engineering Materials 324-325 (November 2006): 991–94. http://dx.doi.org/10.4028/www.scientific.net/kem.324-325.991.
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The rate effect on concrete tensile strength can be modeled by the description of crack extension in a fictitious fracture plane [1,2].The plane represents the initial, internal damage and the geometry of the final fracture plane. In the paper, the same approach is applied to model the failure envelope for the biaxial loading condition of static lateral compression and axial impact tensile load. The predicted failure envelope is compared with data from experimental work.
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Wang, Feng Chi, Feng Qi Liu, Jun Sheng Ding, and Zhi Pan Wang. "Experimental Research on Damage of Rubberized Cement-Soil." Applied Mechanics and Materials 256-259 (December 2012): 394–97. http://dx.doi.org/10.4028/www.scientific.net/amm.256-259.394.
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In order to analyze rubber powder influencing on cement-soil, axial compression stress-strain curves and a series of damage relationship curves are obtained by unconfined compression test and circulating load-unload test. The damage process of rubberized cement-soil could be divided into four phases including internal tiny crack closing, cracking, crack stable extension and crack unstable extension. Rubber powder increased stress and strain threshold values of cement-soil. 10% was the best rubber powder content. Rubber powder can impede cement-soil inner tiny holes and crakes to occur and develop, so that damage resistance and deformation capability are improved.
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Bhaskar, K., and L. Librescu. "Buckling under axial compression of thin-walled composite beams exhibiting extension-twist coupling." Composite Structures 31, no. 3 (January 1995): 203–12. http://dx.doi.org/10.1016/0263-8223(95)00010-0.
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Rodriguez-Martinez, Nestor G., Luis Perez-Orribo, Samuel Kalb, Phillip M. Reyes, Anna G. U. S. Newcomb, Jeremy Hughes, Nicholas Theodore, and Neil R. Crawford. "The role of obesity in the biomechanics and radiological changes of the spine: an in vitro study." Journal of Neurosurgery: Spine 24, no. 4 (April 2016): 615–23. http://dx.doi.org/10.3171/2015.7.spine141306.
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OBJECT The effects of obesity on lumbar biomechanics are not fully understood. The aims of this study were to analyze the biomechanical differences between cadaveric L4–5 lumbar spine segments from a large group of nonobese (body mass index [BMI] < 30 kg/m2) and obese (BMI ≥ 30 kg/m2) donors and to determine if there were any radiological differences between spines from nonobese and obese donors using MR imaging. METHODS A total of 168 intact L4–5 spinal segments (87 males and 81 females) were tested using pure-moment loading, simulating flexion-extension, lateral bending, and axial rotation. Axial compression tests were performed on 38 of the specimens. Sex, age, and BMI were analyzed with biomechanical parameters using 1-way ANOVA, Pearson correlation, and multiple regression analyses. MR images were obtained in 12 specimens (8 from obese and 4 from nonobese donors) using a 3-T MR scanner. RESULTS The segments from the obese male group allowed significantly greater range of motion (ROM) than those from the nonobese male group during axial rotation (p = 0.018), while there was no difference between segments from obese and nonobese females (p = 0.687). There were no differences in ROM between spines from obese and nonobese donors during flexion-extension or lateral bending for either sex. In the nonobese population, the ROM during axial rotation was significantly greater for females than for males (p = 0.009). There was no significant difference between sexes in the obese population (p = 0.892). Axial compressive stiffness was significantly greater for the obese than the nonobese population for both the female-only group and the entire study group (p < 0.01); however, the difference was nonsignificant in the male population (p = 0.304). Correlation analysis confirmed a significant negative correlation between BMI and resistance to deformation during axial compression in the female group (R = −0.65, p = 0.004), with no relationship in the male group (R = 0.03, p = 0.9). There was also a significant negative correlation between ROM during flexion-extension and BMI for the female group (R = −0.38, p = 0.001), with no relationship for the male group (R = 0.06, p = 0.58). Qualitative analysis using MR imaging indicated greater facet degeneration and a greater incidence of disc herniations in the obese group than in the control group. CONCLUSIONS Based on flexibility and compression tests, lumbar spinal segments from obese versus nonobese donors seem to behave differently, biomechanically, during axial rotation and compression. The differences are more pronounced in women. MR imaging suggests that these differences may be due to greater facet degeneration and an increased amount of disc herniation in the spines from obese individuals.
Dissertations / Theses on the topic "Axial compression-extension"
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Lin, Jian-Hung, and 林建宏. "Study on the Axial Extension Mechanical Property of Soils Between Jet Grouted Soil Column After Lateral Compression." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/29628652844972876056.
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碩士國立臺灣科技大學
營建工程系
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Soils between grouted soil column are subjected to lateral compression during the grouting process. Because jet grouting proceeds in sequence, the grouting pressure is often not symmetrical. The ungrouted soils are then subjected to axial extension in subsequent excavation stage.As a result, the construction factors may influence the mechanical property of the ungrouted soil. In general, designers should consider the above factors. A series of triaxial stress path test were performed on undisturbed Taipei silty clay and true triaxial test were performed on remoulded Taipei silty clay in order to understand the ungrouted soil’s mechanical property of axial extension after jet grouting. Results from three triaxial test indicate that（1）the influence of jet grouting on the undrained axial extension behavior is very little.（2） the available undrained strength may be reduced in the process of jet grouting.（3）the deformation modulus decreases with increasing amount of lateral compression, but increases with lateral extension. Results from true triaxial test indicate that（1）one-way lateral compression has little influence on the axial extension behavior, two way compression may reduce undrained shear strength.；（2）for different types of lateral compression, with the same compression magnitude, the excited excess pore pressure may exhibit different behavior depending on the amount of lateral compression.
Book chapters on the topic "Axial compression-extension"
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Bayly, Brian. "Overview and Preview of Conclusions." In Chemical Change in Deforming Materials. Oxford University Press, 1993. http://dx.doi.org/10.1093/oso/9780195067644.003.0005.
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The purpose of this book is to fill something of a gap. In general, thermodynamics has been a great success and has provided a means of understanding and predicting material behavior of almost all kinds at the macroscopic level. Even when thermodynamic statements were limited to equilibrium states they were widely useful, and with extension to nonequilibrium states almost all behaviors that a person might observe directly became accessible to theory. But there has been and is one resistive point: if a cylinder of material is more strongly compressed along its length than radially, it is in a nonequilibrium state no matter how ideal its condition in other respects, and the effect of this type of nonequilibrium has not been successfully explored. The physical consequences are, of course, well known; the cylinder deforms in ways successfully described in almost all respects by the methods of continuum mechanics. But the chemical consequences are less well known. For example, suppose the cylinder contains iron and is surrounded by some second iron-bearing phase; suppose further that before the cylinder is compressed axially, the cylinder and its surroundings are in equilibrium. When the axial compression is imposed, how is the equilibrium disturbed and what processes begin to run? The purpose of the book is to provide the outline of a comprehensive approach to this question. The question has been discussed extensively in technical journals and in complicated ways. The stimulus for this book is the belief that the topic need not be so complicated. There are two equations that describe the stresses in the cylinder that have up to now not been used; using these neglected equations provides a point of view not taken by other writers, and it is the fresh point of view that permits certain simplicities to be seen (the key equations are 6.3 and 8.10). Of course, we make headway only to a limited extent; not all problems are answered, not all complications are resolved. The existence of a central and unresolvable complication is recognized toward the end of this overview, in the section on Continuum Behavior and Atoms.
Conference papers on the topic "Axial compression-extension"
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Siegmund, Gunter, and Barry S. Myers. "Human Cervical Motion Segment Flexibility and Facet Capsular Ligament Strain Under Combined Posterior Shear, Extension and Axial Compression." In 44th Stapp Car Crash Conference (2000). 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2000. http://dx.doi.org/10.4271/2000-01-sc12.
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Langrana, Noshir A., Robert D. Harten, David C. Lin, Mitchell F. Reiter, and Casey K. Lee. "Fracture Patterns and Strain Information in Thoracolumbar Burst Fractures." In ASME 2000 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/imece2000-2584.
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Abstract A combined loading of axial compression and anterior shear on a spinal motion segment causes the severe form of burst fracture. Thoracolumbar motion segments were instrumented with a strain gage on the middle of the anterior wall and one near the base of the pedicles. Two samples were subjected to high-speed axial compression in the neutral position while two were tested in extension to maximize facet joint loading. The specimens tested in extension exhibited the more severe fracture pattern, indicated by failure of the middle column and an increase in interpedicular distance. Failure loads and ratio of strain at the base of the pedicles to strain at the anterior wall were higher in this group. The results suggest that the shear force transmitted through the facet joint and the pedicles to the posterior upper half of the vertebral body is an essential component of the injury mechanism.
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Kumaresan, Srirangam, Narayan Yoganandan, Frank A. Pintar, and Dennis J. Maiman. "Regional Load Sharing in Cervical Spine Intervertebral Disc." In ASME 1998 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/imece1998-0100.
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Abstract An anatomically accurate, fully three-dimensional, geometrically and materially nonlinear, and experimentally validated finite element model of the human lower cervical spine was used to study the intervertebral disc biomechanics. The internal axial and shear forces resisted by the ventral, middle and dorsal regions of the intervertebral disc under the axial and eccentric loading modes were quantified. The ventral region resisted higher axial forces with considerable variation from compression-flexion to compression-extension loading. This may explain the higher incidence of osteophytes in this region of the cervical spine. The higher shear forces resisted by the dorsal region of the disc coupled with the presence of bilateral uncovertebral joint anatomy may account for the occurrence of disc herniation in the dorso-lateral region of the spine.
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DiSilvestro, Mark R., Qiliang Zhu, Marcy Wong, Jukka Jurvelin, and Jun-Kyo Suh. "Biphasic Poroviscoelastic Model Simultaneously Predicts Axial Reaction Force and Lateral Displacement of Articular Cartilage During an Unconfined Compression-Stress Relaxation Experiment." In ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-0452.
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Abstract Articular cartilage lining the articulating surfaces in diarthrodial joints is composed of an extracellular matrix and interstitial fluid. The complex mechanical behavior of this tissue has been successfully modeled by the linear biphasic poroviscoelastic (BPVE) model first introduced by Mak (1986). This model, a simple extension of the well-known biphasic theory first proposed by Mow et al. (1980), accounts for both fluid flow-dependent and fluid flow-independent viscoelastic mechanisms which contribute to the overall mechanical behavior exhibited by the tissue. Despite the success of the linear BPVE model for indentation (Suh and Bai, 1997), as well as that described for unconfined compression (Suh and DiSilvestro, 1997, 1998), the model’s ability to account for more than one measurable variable with a single parameter set has not been established. Therefore, the objective, of this study was to assess the ability of the linear BPVE model to account for both the axial reaction force and lateral deformation of a cylindrical plug of articular cartilage subjected to unconfined compression under a stress relaxation protocol.
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Bahramshahi, N., H. Ghaemi, and K. Behdinan. "Finite Element Study of Spinal Cord Mechanics During Biomechanical Response of Middle Cervical Spine." In ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-40573.
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The present study is conducted to develop a detailed FE model of spinal cord and to study its behaviour under various loading conditions. To achieve the goal, a previously developed and validated FE model of the middle cervical spine (C3-C5) is utilized. The model is further modified to investigate the stresses that the spinal cord in experiences during cervical spine motion segment in compression and flexion/extension loading modes. The resulting Von Misses stress and axial strain of the anterior and posterior surfaces of the cervical spinal cord are obtained from a set of elements along the C4-C5 disc space of the dural sheath, CSF and cord. The results show that in compression, the anterior surface of spinal cord experiences larger displacement, stress, and strain than those of the posterior surface. Conversely, the analyses show that in flexion\extension, the stresses, strains, and displacements are more pronounced in posterior segment of the spinal cord. In extension, the posterior disc bulge applies pressure onto the Posterior Longitudinal Ligament and thereby, applying local pressure on the spinal cord. The FE results show a stress concentration at the point of contact between disc and spinal cord. Furthermore, the FE results of flexion test show similar stress concentration characteristic at the point of contact. However, the local stress on spinal cord is more pronounced in flexion than extension at the C4-C5 area of spinal cord. It was also determined the compressive load resulted in the highest stress concentration on the spinal cord.
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Needham, Dusty A., Jeffrey P. Rouleau, Dennis J. Buchanan, Robert L. Conta, and Jack E. Parr. "Evaluation of a Modular Polyaxial Spinal Component With Interlocking Tapers." In ASME 1997 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/imece1997-0317.
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Abstract The use of tapers in orthopaedic applications for the fixation of one implant component to another is well documented, such as in femoral head fixation to a hip stem. By providing sufficient interference between the two components, hoop stresses and friction forces are generated which hold the assembly together. Under normal physiological conditions, the spine is subjected to a variety of loading regimes, including tension, compression, torsion, bending, and combinations of all four. With the addition of instrumentation, these spinal loads are shared with the fixation device. The resulting construct must be strong enough to maintain correction of the spinal deformity during healing. To examine the strength of a spinal instrumentation system which includes the new locking mechanism of tapers, several tests were utilized, including flexion-extension, axial rod gripping capacity, torsional rod gripping capacity, anterior-posterior pull, and fatigue flexion-extension tests.
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Wang, Rick, Richard Kania, Robert J. Smyth, and Ian R. Smyth. "Cyclic Pressure Testing a Section of 34” Pipe Repaired Using the PETROSLEEVE Technology to Determine the Effect on a 50% Crack." In 2012 9th International Pipeline Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/ipc2012-90674.
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TransCanada Pipelines operates a large mainline pipeline transportation system. Engineering analysis and severe testing was performed to confirm that the PETROSLEEVE© Steel Compression Reinforcement Technology would arrest crack extension in large diameter pipe. This testing involved putting a 50% crack into a section of 862 mm diameter, 9.5mm wall thickness grade 448 pipe. Then a compression sleeve was installed while the pipe was pressurized to 3800 kPa (38% SMYS). Following sleeve installation, the test vessel was subjected to 9000 cycles 7880 to 2960 kPa (80%–30% SMYS); 200 cycles 7800 to 0 kPa (80%–0% SMYS); hold pressures of 8870 kPa (90% SMYS) for 4 hours and 10840 kPa (110% SMYS) for 2 hours. Following the cyclic pressuring, the crack was metallurgically inspected. It was reported by third party inspection that the compression sleeve reinforcement “can effectively suppress fatigue crack growth of an axial flaw (100mm long × 50% of the wall thickness deep) in the API X65 pipe.” This paper reviews the engineering and cyclic testing undertaken.
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DeVries, Nicole A., Anup A. Gandhi, Douglas C. Fredericks, Joseph D. Smucker, and Nicole M. Grosland. "In Vitro Study of the C2-C7 Sheep Cervical Spine." In ASME 2011 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2011. http://dx.doi.org/10.1115/sbc2011-53167.
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Due to the limited availability of human cadaveric specimens, animal models are often utilized for in vitro studies of various spinal disorders and surgical techniques. Sheep spines have similar geometry, disc space, and lordosis as compared to humans [1,2]. Several studies have identified the geometrical similarities between the sheep and human spine; however these studies have been limited to quantifying the anatomic dimensions as opposed to the biomechanical responses [2–3]. Although anatomical similarities are important, biomechanical correspondence is imperative to understand the effects of disorders, surgical techniques, and implant designs. Some studies [3–5] have focused on experimental biomechanics of the sheep cervical functional spinal units (FSUs). Szotek and colleagues [1] studied the biomechanics of compression and impure flexion-extension for the C2-C7 intact sheep spine. However, to date, there is no comparison of the sheep spine using pure flexion-extension, lateral bending, or axial rotation moments for multilevel specimen. Therefore, the purpose of this study was to conduct in vitro testing of the intact C2-C7 sheep cervical spine.
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Chirvi, Sajal, Frank A. Pintar, and Narayan Yoganandan. "An Examination of Isolated and Interaction-Based Biomechanical Metrics for Potential Lower Neck Injury Criteria." In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-52108.
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Lower neck injuries inferior to C4 level, such as fractures and dislocations, occur in motor vehicle crashes, sports, and military events. The recently developed interaction criterion, termed Nij, has been used in automotive safety standards and is applicable to the upper neck. Such criterion does not exist for the lower neck. This study was designed to conduct an analysis of data of lower neck injury metrics toward the development of a mechanistically appropriate injury criterion. Axial loads were applied to the crown of the head of post mortem human subject (PMHS) head-neck complexes at different loading rates. The generalized force histories at the inferior end of the head-neck complex were recorded using a load cell and were transformed to the cervical-thoracic joint. Peak force and peak moment (flexion or extension) were quantified for each test from corresponding time histories. Initially, a survival analysis approach was used to derive injury probability curves based on peak force and peak moment alone. Both force and moment were considered as primary variables and age a covariate in the survival analysis. Age was found to be a significant (p<0.05) covariate for the compressive force and flexion moment but insignificant for extension moment (p>0.05). A lower neck Nij formulation was done to derive a combined interactive metric. To derive cadaver-based metrics, critical intercepts were obtained from the 90% injury probability point on peak force and peak moment curves. The PMHS-based critical intercepts derived from this study for compressive force, flexion, and extension moment were 4471 N, 218 Nm, and 120 Nm respectively. The lower cervical spine injury criterion, Lower Nij (LNij), was evaluated in two different formulations: peak LNij and mechanistic peak LNij. Peak LNij was obtained from the LNij time history regardless of when it occurred. Mechanistic peak LNij was obtained from the LNij time history only during the time when the resulting injury mechanism occurred. Injury mechanism categorization included compression-flexion, compression-extension, and those best represented by a more pure compression-related classification. Mechanistic peak LNij was identified based on the peak timing of the injury mechanism. Peak LNij and mechanistic peak LNij were found to be significant (p<0.05) predictors of injury with age as a covariate. The 50% injury probability was 1.38 and 1.13 for peak LNij and mechanistic peak LNij, respectively. These results provide preliminary data based on PMHS tests for establishing lower neck injury criteria that may be used in automotive applications, sports and military research to advance safety systems.
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Uppala, Subramanya, Robert X. Gao, Scott Cowan, and K. Francis Lee. "A Biomechanical Model of Lumbar Spine." In ASME 2000 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/imece2000-2282.
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Abstract The strength and stability of the lumbar spine are determined not only by the bone and muscles, but also by the visco-elastic structures and the interplay between the different components of the spine, such as ligaments, capsules, annulus fibrosis, and articular cartilage. In this paper we present a non-linear three-dimensional Finite Element model of the lumbar spine. Specifically, a three-dimensional FE model of the L4-5 one-motion segment/2 vertebrae was developed. The cortical shell and the cancellous bone of the vertebral body were modeled as 3D isoparametric eight-nodal elements. Finite element models of spinal injuries with fixation devices are also developed. The deformations across the different sections of the spine are observed under the application of axial compression, flexion/extension, and lateral bending. The developed FE models provided input to both the fixture design and experimental studies.