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3 2017

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Numerical elastoplastic analysis of trabeculae in lumbar vertebral body

Maknickas A., Alekna V., Ardatov O., Kizilova N., Tamulaitiene M., Kacianauskas R.

Engineering Transactions

2017

Vol. 65, iss. 1

83--88

This paper presents a numerical modelling of lumbar vertebrae L1 by employing the finite element method. The three-dimensional model of vertebral body is derived by processing CT data and DICOM format files. The model includes cortical shell, trabecular bone and posterior elements. The formation of trabecular structure was performed by script-controlled ellipsoidal cut-outs. In order to define the nonlinear relationship between the stress and the strain, the Ramberg-Osgood equation was applied. Therefore, the von Mises stress was assumed to characterise the stressed state of bone tissue due to 1 and 7 MPa compression load. According to specific difficulties for “in vitro” and “in vivo” investigation methods, this “in silico” technique may provide new insight for further understanding of the trabecular bone behaviour in terms of plastic deformation.

The geometric model-based patient-specific simulations of turbulent aortic valve flows

Stupak E., Kačianauskas R., Kačeniauskas A., Starikovičius V., Maknickas A., Pacevič R., Staškūnienė M., Davidavičius G., Aidietis A.

Archives of Mechanics

2017

Vol. 69, nr 4-5

317--345

This paper presents the patient-specific simulations of the aortic valve based on the proposed geometric model. A structural analysis is performed by using the finite element method to determine the stress-strain state of the aortic valve. The study is focused on the investigation of various turbulence models crucial for the appropriate description of the flow in the deceleration phase, following the peak systole. A comparative study of the flow solution without a turbulence model and the numerical results obtained by using various turbulence models is also performed. The results yielded by the shear-stress transport k-ω model supplemented with the intermittency transition equation most closely match those of numerical simulations without a turbulence model.

The finite element analysis of osteoporotic lumbar vertebral body by influence of trabecular bone apparent density and thickness of cortical shell

Ardatov O., Maknickas A., Kačianauskas R., Alekna V., Tamulaitienė M.

Acta Mechanica et Automatica

2017

Vol. 11, no. 4

185--292

Osteoporosis causes the bone mass loss and increased fracture risk. This paper presents the modelling of osteoporotic human lumbar vertebrae L1 by employing finite elements method (FEM). The isolated inhomogeneous vertebral body is composed by cortical outer shell and cancellous bone. The level of osteoporotic contribution is characterised by reducing the thickness of cortical shell and elasticity modulus of cancellous bone using power-law dependence with apparent density. The strength parameters are evaluated on the basis of von Mises-Hencky yield criterion. Parametric study of osteoporotic degradation contains the static and nonlinear dynamic analysis of stresses that occur due to physiological load. Results of our investigation are presented in terms of nonlinear interdependence between stress and external load.