9539743 Weight reduction method of connecting-rod by non-linear FEM analysis Susumu Numajiri (Mitsubishi Motors Corporation), Shinya Miura (MMC Computer Research Ltd.)

AIM: The purpose of this study is to compare the stress effects developed on the periodontal ligaments and teeth by three different types of mandibular advancement devices (MADs) using a finite element method (FEM) analysis. Introduction: Obstructive sleep apnea (OSA) is a disease with a high prevalence and, in recent years, the use of MADs as an alternative or support treatment to the continuous positive airway pressure (CPAP) has spread. Their use finds relative contraindications in the case of partial edentulism and severe periodontal disease. Given the widespread of periodontal problems, it is essential to know the effects that these devices cause on the periodontal ligament of the teeth. Materials and methods: Starting from the computed tomography (CT) scan of a patient’s skull, 3D reconstructions of the maxilla and mandible were implemented. Three different MADs were prepared for the patient, then 3D scanned, and lastly, coupled with the 3D models of the jaws. The devices have two different mechanics: One has a front reverse connecting rod (OrthoapneaTM), and two have lateral propulsion (SomnodentTM and HerbstTM). A FEM analysis was performed to calculate the stress applied on periodontal ligaments, on every single tooth and the displacement vectors that are generated by applying an advancement force on the mandible. Results: HerbstTM and SomnodentTM devices present very similar stress values, mainly concentrated on lateral teeth, but in general, the forces are very mild and distributed. The maximum stresses values are 3.27 kPa on periodontal ligaments and 287 kPa on teeth for SomnodentTM and 3.56 kPa on periodontal ligaments and 302 kPa on teeth for HerbstTM. OrthoapneaTM has, instead, higher and concentrated stress values, especially in the anterior maxillary and mandibular area with 4.26 kPa and 600 kPa as maximum stress values, respectively, on periodontal ligaments and teeth. Conclusions: From the results, it is concluded that devices with a bilateral mechanism generate less and more distributed stress than an anterior connecting rod mechanism. Therefore, they may be advisable to patients with compromised periodontal conditions in the anterior area.

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Damage-Involved Response of Two Colliding Buildings under Non-Uniform Earthquake Loading

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.577-578.197 ◽

2013 ◽

Vol 577-578 ◽

pp. 197-200

Author(s):

Robert Jankowski

Keyword(s):

Ground Motion ◽

Seismic Wave ◽

Damage Model ◽

Fem Analysis ◽

Stochastic Modelling ◽

Earthquake Loading ◽

Non Linear ◽

San Fernando ◽

The Difference ◽

Ground Motion Records

Pounding between insufficiently separated buildings, which may result in considerable damage or may even lead to the total collapse of colliding structures, has been repeatedly observed during earthquakes. Earthquake-induced collisions of buildings has been intensively studied applying various structural models. It was assumed in the analyses, however, that the seismic excitation is identical for all structural supports; whereas, in the reality, the ground motion differs from place to place due to spatial seismic effects connected with propagation of the seismic wave. The aim of the present paper is to conduct a detailed non-linear damage-involved analysis of pounding between two structures under non-uniform earthquake loading. A case of pounding between the Olive View Hospital main building and one of its stairway towers, observed during the San Fernando earthquake of 1971, has been considered in the study. In the numerical FEM analysis, non-linear material properties have been simulated using stiffness degradation (due to damage under cyclic loading) model of concrete and elastoplastic damage model of reinforcing steel. A method of conditional stochastic modelling has been used to generate the input ground motion records. The results of the study indicate that the incorporation of the non-uniform ground motion excitation may lead to substantial change of pounding-involved response of the structures. The difference between the uniform and non-uniform responses has been found to be relatively large considering the fact that the variation in the simulated input ground motion records was rather small. This shows the importance of incorporation in the damage-involved numerical analysis the effects connected with propagation of the seismic wave.

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