Analysis on circumpelvic muscle force and spatial position and orientation of bone traction needle for pelvic fracture reduction

Traditional pelvis fracture reduction suffers from some disadvantages. Robot-assisted pelvis fracture reduction offers some promise in solving these problems. However, the reduction reference to guide robot motion is a key issue that must be resolved. In this paper, we propose a physical symmetry and virtual plane-based reduction reference and adopt the method of registration to calculate the virtual plane for the reference, which were verified via experiments. The results of the position symmetry experiments of the original pelvis and virtual plane-based position symmetry experiments were similar; both showed that the symmetry errors of the pelvis were less than 4[Formula: see text]mm and 2.5[Formula: see text]. The results indicated that the proposed method could be used as a reference for robot-assisted pelvis fracture reduction.

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Rearfoot Kinematics during Initial Takeoff of Elite High Jumpers: Estimation of Spatial Position and Orientation of Subtalar Axis

Journal of Applied Biomechanics ◽

10.1123/jab.19.1.13 ◽

2003 ◽

Vol 19 (1) ◽

pp. 13-27 ◽

Cited By ~ 3

Author(s):

Bart Van Gheluwe ◽

Philip Roosen ◽

Kaat Desloovere

Keyword(s):

High Speed ◽

Elite Athletes ◽

Angular Displacement ◽

Frontal Plane ◽

Analytical Techniques ◽

Spatial Position ◽

Anatomical Location ◽

Kinematic Behavior ◽

High Speed Cinematography ◽

Position And Orientation

As the spatial position and orientation of the subtalar ankle axis documented in biomechanical literature has mainly been estimated in unloaded conditions, it was hypothesized that high loads on the subtalar joint during very dynamic movements may force the respective axis away from its normal anatomical location. Therefore, high jump takeoffs of two elite athletes were selected to estimate and analyze the kinematic behavior of the subtalar axis during initial takeoff. The subtalar motion of the calcaneus was reconstructed using 3-D high-speed cinematography and a three-segment ankle model expressing subtalar pronation as the movement of the calcaneus around the talus. Results revealed that the subtalar axis moved away from its initial orientation and position at first heel impact, respectively more horizontally and laterally. The pronational angular displacement and velocity were calculated for all jumps and reached maximal values close to 30°, respectively 2000°/s. They compared surprisingly well with values obtained from frontal plane projections as used in a conventional cinematographical approach. But values corresponding to a subtalar axis fitting conventional anatomical descriptions showed consistently larger discrepancies, up to 10° for pronational displacement and close to 600°/s for pronational velocity. Finally, a comparison with results obtained from helical or screw axes produced nearly identical findings, suggesting good validity of the analytical techniques applied in this study for the 3-D reconstruction of the subtalar axis.

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Enhancing Strength and Toughness of Hierarchical Composites through Optimization of Position and Orientation of Nanotubes: A Computational Study

Journal of Composites Science ◽

10.3390/jcs4020034 ◽

2020 ◽

Vol 4 (2) ◽

pp. 34 ◽

Cited By ~ 1

Author(s):

Qiang Liu ◽

Stepan V. Lomov ◽

Larissa Gorbatikh

Keyword(s):

Computational Study ◽

Spatial Position ◽

Matrix Cracking ◽

Strength Increase ◽

Stress Concentrations ◽

Transverse Tensile ◽

Design Variables ◽

Hierarchical Composites ◽

Position And Orientation ◽

Strength And Toughness

Hierarchical composites that combine microscopic fibers and carbon nanotubes (CNTs) offer opportunities to further improve mechanical properties. Motivated by the experimental evidence that the spatial distribution of CNTs has a significant effect on the strength and toughness of these composites, we developed a novel modelling tool to help us explore mechanisms of strengthening and toughening in an efficient way. The spatial position and orientation of CNTs are chosen as design variables and their optimization is performed on the example of a unidirectional fiber-reinforced composite (FRC) subjected to transverse tensile loading. The model relies on the use of genetic algorithm and finite element method. Our modelling results show that the CNT network with an optimized morphology suppresses stress concentrations in the matrix near the fibers. The optimized morphology is shown to activate a new strengthening and toughening mechanism—diffusion of damage at micro-scale. It allows substantial increase in the consumption of the strain energy by matrix cracking, delocalization of damage, and with it, improvement of the strength and toughness. When the network morphology of 1.0 wt% of CNTs is optimized, the strength and toughness are increased by 49% and 65%, respectively, compared to the pristine FRC. The same amount of homogenously distributed CNTs in the composite leads to only 2% of the strength increase accompanied by a 13% decrease in toughness. The work emphasizes the importance of optimizing spatial position and orientation of CNTs for the strength and toughness improvements of composites.

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