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Design and performance analysis of a mechanically coupled spring compliant to out-of-plane oscillation

Nguyen Duong Van, Nguyen Chien Quoc, Dang Hieu Van, Chu Hoang Manh

Archive of Mechanical Engineering

2022

LXIX, nr 4

629--643

In this paper, a spring system symmetrically arranged around a circular plate compliant to out-of-plane oscillation is proposed. The spring system consists of single serpentine springs mutually coupled in a plane. Three theoretical mechanical models for evaluating the stiffness of the spring system are built, which are based on the flexural beam, Sigitta, and serpentine spring theories and equivalent mechanical spring structure models. The theoretically calculated results are in good agreement with numerical solutions using the finite element method, with errors less than 10% in the appropriate dimension ranges of the spring. Compared to similar spring structures without mechanical coupling, the proposed mechanically coupled spring shows advantage in suppressing the mode coupling.

On prediction of the compressive strength and failure patterns of human vertebrae using a quasi-brittle continuum damage finite element model

Nakhli Zahira, Hatira Fafa Ben, Pithioux Martine, Chabrand Patrick, Saanouni Khemais

Acta of Bioengineering and Biomechanics

2019

Vol. 21, no. 2

143--151

Damage of bone structures is mainly conditioned by bone quality related to the bone strength. The purpose of this work was to present a simple and reliable numerical treatment of a quasi-brittle damage constitutive model coupled with two different elastic modulus and to compare the numerical results with the experimental ones. Methods: To achieve this goal, a QCT based finite element model was developed within the framework of CDM (Continuum Damage Mechanics) and implemented in the FE code (ABAQUS). It described the propagation of brittle cracks which will help to predict the ultimate load fracture of a human vertebra by reproducing the experimental failure under quasi-static compressive loading paths of nineteen cadaveric lumbar vertebral bodies. Results: The numerical computations delivered by the proposed method showed a better agreement with the available experimental results when bone volume fraction related Young’s modulus (E(BV/TV)) is used instead of density related Young’s modulus (E(ρ)). Also, the study showed that the maximum relative error (%) in failure was 8.47% when E(BV/TV) was used, whereas the highest relative error (%) was 68.56% when E(ρ) was adopted. Finally, a mesh sensitivity analysis revealed that the element size has a weak incidence on the computed load magnitude. Conclusions: The numerical results provided by the proposed quasi-brittle damage model combined with E(BV/TV) are a reliable tool for the vertebrae fracture prediction.

Parametric instability of stiffened plates

Srivastava A. K. L., Datta P. K., Sheikh A. H.

International Journal of Applied Mechanics and Engineering

2004

Vol. 9, no 1

169-180

The parametric instability behavior of a stiffened plate subjected to uniform in-plane edge loading is studied using the finite element analysis. The method of Hill's infinite determinants is applied to analyze the dynamic instability regions. Numerical results are presented to demonstrate the effects of various parameters, such as the aspect ratio, boundary condition, stiffening scheme, on the dynamic stability of stiffened plates. The results show that the location, size and number of stiffeners have a significant effect on the location of the boundaries of the principal instability regions when compared with those of a flat unstiffened plate.