FEM and BEM Analysis of a Human Mandible with Added Temporomandibular Joints

Mathematical modelling of human mandible and its temporomandibular joints (TMJs) is one of the most important steps for developing a powerful forecasting tool to analyse the stress/strain behaviour of a human masticatory system under occlusal loads. In this work the structural behaviour of a mandible with articular discs, undergoing a unilateral occlusion, is numerically analysed by means of both Finite Element Method (FEM) and Boundary Element Method (BEM). The mandible is considered as completely edentulous and its anisotropic and non-homogeneous bone material behaviour is modelled. The material behaviour of the articular discs was assumed to be either elastic or hyper-elastic. The loads applied to the mandible are related to the active muscle groups during a unilateral occlusion. The results of FEM and BEM analyses are presented mainly in terms of stress distribution on the mandible and on the articular discs. Due to the uncertainty in the determination of the biological parameters, a sensitivity analysis is provided, which demonstrates the impact of the variation of articular disc stiffness and TMJ friction coefficient on the mandible stress peaks and on the occlusal loads (for a given intensity of muscle loads). Moreover a comparison between the effectiveness of the BEM and FEM numerical approaches on this kind of problem is provided

Comfort Driven Redesign: The Case of Library Chairs

AbstractUniversity students spend most of their time in a sitting position. Prolonged sitting on ill-fitted furniture and the resulting lousy posture is making students having different musculoskeletal disorders and is strictly related to students learning outcomes. This study aims to improve postural comfort of chairs placed inside the Science & Technology Library at the University of Salerno. A previous study about these library chairs showed that the lumbar area was the most suffering part while perceived (dis)comfort was dependent on time. Based on this, an ergonomic redesign and, consequently, manufacturing of the chair has been done. A perceived-comfort comparison between the library chair and the redesigned one has been performed. A statistical sample of 28 healthy students performed a 20-min experiment two times, alternatively on the library chair and the redesigned one. The 20-min experiment was divided into two 10-min tasks ("Reading & Writing" and "Laptop use") to simulate a study day. The participants' postures were acquired non-invasively using cameras and processed by Kinovea; questionnaires were used to rate the perceived subjective (dis)comfort. A procedure for improving an existing product through a comfort-driven redesign is proposed. Results showed the redesigned library chair lead on increasing postural comfort (particularly in the lumbar area) thanks to the new design and modifications

Optimization and solution approximation of design problems formulated by axiomatic design and paracomplete logic

Of primary importance in Axiomatic Design (AD) theory is Suh‘s first axiom, stating that the independence of functional requirements should be maintained throughout the design process. Para-complete logics, such as fuzzy logic, can be used to express the relationship between functional requirements (FRs) and design parameters (DPs) in AD. This is especially true in cases where this relationship can only be codified using linguistic variables. In fact, para-complete logics violate the principle of the excluded third party, allowing for the effects of changes in DP within the same FR to be considered partially independent of each other. Recently, a paper was published investigating changes in the concept of decoupled design when para-complete logics are applied to FRs-DPs link definition. Using an example case, this paper evaluated the impact of a designer‘s decoupling capability using composition rules for FRs, in order to make the design matrix diagonal or lower triangular by decoupling the effects of several DPs on different FRs using fuzzy formulation. -cut is a powerful instrument used to modify membership functions in order to approximate a non- optimized solution to an optimized one, by simply modifying the membership values. In this paper, we attempt to elaborate a simple optimization method based on a controlled approximation given by several values applied to different membership functions. We then introduce a new method to control and evaluate the amount of that approximation

Axiomatic Design of a car bonnet: a new decoupling method based on Fuzzy Logic application

In Axiomatic Design Approach, the first axiom, states that independence of functional requirements should be maintained throughout the design process. Para-complete logics, such as Fuzzy logic, represents a powerful instrument to express “mathematical/functional” interaction between Functional Requirements (FRs) and Design Parameters (DPs). Para-complete logics violate the principle of the excluded third party, so that the effects of DPs’ changes on the same FR can be considered partially independent each other. Our paper investigates the changes in Decoupled Design’s concept when para-complete logics are applied in FRs-DPs matrix definition. Paper evaluates the impact of decoupling capability of designer using composition rules on FRs, in order to make the design matrix diagonal or lower triangular by decoupling effects of several DPs on different FRs using Fuzzy formulatio