A Stabilised High-Order Finite Element Model for the Linearised Euler Equations

The flexural and dynamic behavior of tapered cross-section steel-concrete composite material beams frequently used in structural engineering is strongly influenced by the type of shear connection between the steel beam and the concrete slab. The numerical model must account for the partial interaction (interlayer slip) in order to get accurate analytical predictions. The 1D high order finite element model for variable cross-section steel-concrete composite beams with interlayer slip were established in this paper. The displacement field of kinematic model is obtained by introducing the constraint condition on interface between those two components based on classical Newmark model. The high order finite element with 16 degrees of freedom (DOF) is chosen to overcome the slip-locking problem in low order finite element which has been reported in published literatures so much. The established element can be used in flexural and dynamic analysis of tapered cross-section steel-concrete composite material beams directly.

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Wavefront aberrations induced from biomechanical effects after customized myopic laser refractive surgery in finite element model

10.21203/rs.3.rs-189830/v1 ◽

2021 ◽

Author(s):

Ruirui Du ◽

Lihua Fang ◽

Weijian Peng ◽

Ruizhi Yang ◽

Shifeng Nie ◽

...

Keyword(s):

Finite Element ◽

Finite Element Model ◽

Refractive Surgery ◽

Element Model ◽

High Order ◽

Spherical Equivalent ◽

Wavefront Aberrations ◽

Material Parameters ◽

Ablation Profile ◽

High Order Aberrations

Abstract Purpose A customized myopic refractive surgery was simulated by establishing a finite element model of the human eye,after which we studied the wavefront aberrations induced by biomechanical effects and ablation profile after wavefront-guided LASIK surgery. Methods Thirty myopia patients (i.e., 60 eyes) without other eye diseases were selected. Their ages, preoperative spherical equivalent, astigmatism, and wavefront aberration were then obtained, in addition to the mean spherical equivalent error range − 4 to -8D. Afterward, wavefront-guided customized LASIK surgery was simulated by establishing a finite element eye model, followed by the analysis of the wavefront aberrations induced by the surface displacement from corneal biomechanical effects, as well as customized ablation profile. Finally, the preoperative and induced aberrations were statistically analyzed. Results Comatic aberrations were the main wavefront abnormality induced by biomechanical effects, and the wavefront aberrations induced by the ablation profile mainly included coma and secondary-coma, as well as sphere and secondary-sphere aberrations. Overall, the total high-order aberrations (tHOAs), total coma (C31), and sphere () increased after wavefront-guided customized LASIK surgery. According to our correlation analyses, coma, sphere, and total high-order aberrations were significantly correlated with decentration. Additionally, the material parameters of ocular tissue were found to affect the postoperative wavefront aberrations. When the material parameters of the sclera remained constant but those of cornea increased, the induced wavefront aberrations were reduced. Conclusion All biomechanical effects of cornea and ablation profile had significant effects on postoperative wavefront aberrations after customized LASIK refractive surgery; however, the effects of the ablation profile were more notorious.Additionally,the characteristics of biomechanical materials have influence on the clinical correction effect.

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