Dynamic Finite Element Modelling and Vibration Analysis of Prestressed Layered Bending–Torsion Coupled Beams

Free vibration analysis of prestressed, homogenous, Fiber-Metal Laminated (FML) and composite beams subjected to axial force and end moment is revisited. Finite Element Method (FEM) and frequency-dependent Dynamic Finite Element (DFE) models are developed and presented. The frequency results are compared with those obtained from the conventional FEM (ANSYS, Canonsburg, PA, USA) as well as the Homogenization Method (HM). Unlike the FEM, the application of the DFE formulation leads to a nonlinear eigenvalue problem, which is solved to determine the system’s natural frequencies and modes. The governing differential equations of coupled flexural–torsional vibrations, resulting from the end moment, are developed using Euler–Bernoulli bending and St. Venant torsion beam theories and assuming linear harmonic motion and linearly elastic materials. Illustrative examples of prestressed layered, FML, and unidirectional composite beam configurations, exhibiting geometric bending-torsion coupling, are studied. The presented DFE and FEM results show excellent agreement with the homogenization method and ANSYS modeling results, with the DFE’s rates of convergence surpassing all. An investigation is also carried out to examine the effects of various combined axial loads and end moments on the stiffness and fundamental frequencies of the structure. An illustrative example, demonstrating the application of the presented methods to the buckling analysis of layered beams is also presented.

Anteroinferior Bundle of The Acromioclavicular Ligament Plays a Substantial Role in The Joint Function During Shoulder Elevation and Horizontal Adduction: A Dynamic Finite Element Model.

Background: Postoperative acromioclavicular (AC) ligament deficiency has been identified as a common cause of failure after isolated coracoclavicular reconstruction. The two-bundle arrangement of the acromioclavicular ligament has recently been reported in histological and anatomical research. In addition, a clear structural advantage of the superoposterior bundle (SPB) over the less consistent anteroinferior bundle (AIB) was also found. However, the current understanding of the function of the acromioclavicular ligament in joint stability is based on uniaxial bone loading experiments and sequential ligament sectioning. Consequently, these rigid biomechanics models do not reproduce the coupled physiological kinematics, neither in the normal joint nor in the postoperative condition. Therefore, our goal was to build a dynamic finite element model to study the function of the acromioclavicular ligament based on its biomechanical performance patterns using the benefits of computational models.Methods: A three-dimensional bone model is reconstructed using images from a healthy shoulder. The ligament structures were modeled according to the architecture and dimensions of the bone. The kinematics conditions for the shoulder girdle were determined after the osseous axes aligned to simulate the shoulder elevation in the coronal plane and horizontal adduction. Three patterns evaluated ligament function. The peak von Mises stress values were recorded using a clock model that identified the stress distribution. In addition, the variation in length and displacement of the ligament during shoulder motion were compared using a two-tailed hypotheses test. P values < 0.01 were considered statistically significant.Results: The peak von Mises stress was consistently observed in the AIB at 2:30 in coronal elevation (4.058 MPa) and horizontal adduction (2.323 MPa). Except in the position 2:00, statistically significant higher deformations were identified in the two bundles during shoulder elevation. The highest ligament displacement was observed on the Y- and Z- axes. Conclusions: The AIB has the primary role in restricting the acromioclavicular joint during shoulder motion, even though the two bundles of the AC ligament have a complementary mode of action. During horizontal adduction, the SPB appears to prevent anterior and superior translation.

Vessel-Bridge Collision Reliability Assessment Based on Structural Dynamic Analysis

Reliability analysis of vessel-bridge collision plays an important role in the construction of inland bridges. In this paper, a new method is proposed based on structural dynamic analysis. The random characteristics of three factors—impact angle, deadweight tonnage of vessels, and impact velocity—are considered. This method combines the method of moments with nonlinear dynamic finite element analysis, which can enhance the efficiency of calculating failure probability.

Dynamic finite-element simulations reveal early origin of complex human birth pattern

Human infants are born neurologically immature, but whether this originates from conflicting selection pressures between bipedal locomotion and encephalization as suggested by the obstetrical dilemma remains controversial. Australopithecines are ideal for investigating this trade-off as they have a bipedally adapted pelvis, yet relatively small brains. Our finite-element birth simulations based on different pelvic reconstructions and a range of fetal head sizes indicate that australopithecines already possessed a human-like rotational birth pattern. Since only newborn head sizes smaller than those predicted for non-human primates leave adequate space for soft tissue between the bony pelvis and fetal skull, our data imply that australopithecines had secondarily altricial newborns and likely evolved cooperative breeding to care for their helpless infants. These prerequisites for advanced cognitive development therefore seem to have been corollary to skeletal adaptations to bipedal locomotion that preceded the appearance of the genus Homo and the increase in encephalization.

Effect of the Location of Strut Chordae Insertion on Computational Modeling and Biomechanical Evaluation of Mitral Valve Dynamics

The strut chordae (SC) have a unique structure and play an important role in reinforcing the tunnel-shaped configuration of the mitral valve (MV) at the inflow and outflow tracts. We investigated the effect of varying the SC insertion location on normal MV function and dynamics to better understand the complex MV structures. A virtual parametric MV model was designed to replicate a normal human MV, and a total of nine MV modes were created from combinations of apical and lateral displacements of the SC insertion location. MV function throughout the full cardiac cycle was simulated using dynamic finite element analysis for all MV models. While the leaflet stress distribution and coaptation showed similar patterns in all nine MV models, the maximum leaflet stress values increased in proportion to the width of the SC insertion locations. A narrower SC insertion location resulted in a longer coaptation length and a smaller anterior coaptation angle. The top-narrow MV model demonstrated the shortest anterior leaflet bulging distance, lower stresses across the anterior leaflet, and the lowest maximum stresses. This biomechanical evaluation strategy can help us better understand the effect of the SC insertion locations on mechanism, function, and pathophysiology of the MV.