Estimating Local Part Thickness in Midplane Meshes for Finite Element Analysis

Within the development of motor vehicles, crash safety (e.g. occupant protection, pedestrian protection, low speed damageability), is one of the most important attributes. In order to be able to fulfill the increased requirements in the framework of shorter cycle times and rising pressure to reduce costs, car manufacturers keep intensifying the use of virtual development tools such as those in the domain of Computer Aided Engineering (CAE). For crash simulations, the explicit finite element method (FEM) is applied. The accuracy of the simulation process is highly dependent on the accuracy of the simulation model, including the midplane mesh. One of the roughest approximations typically made is the actual part thickness which, in reality, can vary locally. However, almost always a constant thickness value is defined throughout the entire part due to complexity reasons. On the other hand, for precise fracture analysis within FEM, the correct thickness consideration is one key enabler. Thus, availability of per element thickness information, which does not exist explicitly in the FEM model, can significantly contribute to an improved crash simulation quality, especially regarding fracture prediction. Even though the thickness is not explicitly available from the FEM model, it can be inferred from the original CAD geometric model through geometric calculations. This paper proposes and compares two thickness estimation algorithms based on ray tracing and nearest neighbour 3D range searches. A systematic quantitative analysis of the accuracy of both algorithms is presented, as well as a thorough identification of particular geometric arrangements under which their accuracy can be compared. These results enable the identification of each technique’s weaknesses and hint towards a new, integrated, approach to the problem that linearly combines the estimates produced by each algorithm.

Improving FEM crash simulation accuracy through local thickness estimation based on CAD data

In this paper, we present a method for estimating local thickness distribution in nite element models, applied to injection molded and cast engineering parts. This method features considerable improved performance compared to two previously proposed approaches, and has been validated against thickness measured by di erent human operators. We also demonstrate that the use of this method for assigning a distribution of local thickness in FEM crash simulations results in a much more accurate prediction of the real part performance, thus increasing the bene ts of computer simulations in engineering design by enabling zero-prototyping and thus reducing product development costs. The simulation results have been compared to experimental tests, evidencing the advantage of the proposed method. Thus, the proposed approach to consider local thickness distribution in FEM crash simulations has high potential on the product development process of complex and highly demanding injection molded and casted parts and is currently being used by Ford Motor Company.

The influence of the dispersion method on the electrical properties of vapor-grown carbon nanofiber/epoxy composites

The influence of the dispersion of vapor-grown carbon nanofibers (VGCNF) on the electrical properties of VGCNF/ Epoxy composites has been studied. A homogenous dispersion of the VGCNF does not imply better electrical properties. In fact, it is demonstrated that the most simple of the tested dispersion methods results in higher conductivity, since the presence of well-distributed nanofiber clusters appears to be a key factor for increasing composite conductivity.

Thoracic wall reconstruction using ultrasound images to model/bend the thoracic prosthesis for correction of pectus excavatum

Pectus excavatum is the most common congenital deformity of the anterior thoracic wall. The surgical correction of such deformity, using Nuss procedure, consists in the placement of a personalized convex prosthesis into sub-sternal position to correct the deformity. The aim of this work is the CT-scan substitution by ultrasound imaging for the pre-operative diagnosis and pre-modeling of the prosthesis, in order to avoid patient radiation exposure. To accomplish this, ultrasound images are acquired along an axial plane, followed by a rigid registration method to obtain the spatial transformation between subsequent images. These images are overlapped to reconstruct an axial plane equivalent to a CT-slice. A phantom was used to conduct preliminary experiments and the achieved results were compared with the corresponding CT-data, showing that the proposed methodology can be capable to create a valid approximation of the anterior thoracic wall, which can be used to model/bend the prosthesis

Utilização do método Multicritério AHP, na aquisição de um sistema ERP

The selection of an Enterprise Resource Planning (ERP) system is one of the most sensitive and highest impact processes in the area of information systems and technologies, because it supports and integrates the whole business of an organization. Hence the importance of deciding the best solution in order to contribute to the organization's competitiveness in a global and increasingly demanding market. Therefore, it is essential to provide tools to support decision making, turning complex and often intangible decisions into simple and quantifiable scenarios. This study addressed the adoption of the Analytical Hierarchy Process (AHP) multicriteria decision method to support the selection of an ERP system. The literature review was the source used to obtain the set of the most relevant criteria to be considered in this decision, which were subsequently validated through systematic application of various surveys of experts and people related to the field of ERP systems. To support the application of AHP, according to the model obtained in the study, it was developed a web application that will be available to the general public. The responsible for the acquisition of ERP systems can use it to easily apply the AHP method based on validated decision model. On the other hand, the web application can be used as a validation tool, allowing collecting data for future developments of the decision model.

A Divulgação de Informação sobre Responsabilidade Social nas paginas web dos Municípios Portugueses- Factores determinantes

Este estudo pretende conhecer o nível de divulgação de informação sobre responsabilidade social(RS) e analisar possíveis factores determinantes em 60 municípios portugueses. Assumindo que os municípios utilizam cada vez mais Internet como meio de comunicação com seus stakholders, a metodologia de estudo consistiu na analise de conteúdo dos websites e dos documentos disponíveis para download. com vista a determinar se para cada item de informação necessária é elaboração dos Índices de Divulgação de Informação, que permitissem medir o nível de divulgação de informação de cada município. Como forma de analisar a associação existente entre os índices de divulgação de informação criados e os potenciais factores determinantes, foram efectuados diversos testes ás hipóteses formuladas. Os resultados apontam para níveis de divulgação médios na maioria dos índices analisados. O Índice de Divulgação Total(IDT) apurado foi de 0,46. Para cada bloco de informação, o índice que apresentou um valor mais alto foi o da Informação Económica(IDE) com 0,66, seguindo-se o da Informação Social(IDS) com 0,61 e o Ambiental(IDA) com 0,36. O Índice de divulgação de informação genérica(IDG) sobre o RS foi o qeu apresentou valores mais reduzidos, 0,22. Foi efectuada uma analise univariada e bivariada que surgem vários factores como explicativos dos níveis de divulgação de informação. Da aplicação do Modelo de Regressão Linear Multiplica resulta que o IDG é influenciado pelo facto e o município implementar a Agenda 21 Local(A21L) e a pela percentagem de despesas ambientais nas despesas totais(DAMB);que apenas a elevada percentagem de despesas de licenciados(ESCOL)influência o IDE; e a localização do município(LOC, a A21L e a Carga Fiscal(FISC) tem influência no IDA e que a percentagem de habitantes com idade <19 anos e >65 anos(POPID) influencia negativamente o IDA; por ultimo e no que diz respeito ao Índice de Divulgação Total, a CARAT, a A21L, o possuir Certificação e a FISC influenciam positivamente o IDT, enquanto que a POPID influencia negativamente.

Modelo para avaliação da qualidade de conteúdos de sítios Web de Unidades de Saúde

Os sítios Web são a face das instituições, mas há evidências de frequentemente serem pouco cuidados, sobretudo ao nível dos seus conteúdos. Nesta tese apresentamos uma investigação que desenvolve um modelo de avaliação da qualidade dos conteúdos de sítios Web de unidades de saúde. A revisão bibliográfica, realizada neste trabalho, permitiu identificar as dimensões e atributos de avaliação da qualidade de conteúdos de sítios Web mais considerados pelos diversos autores dos trabalhos mais importantes da área, mas não um modelo que, a partir deles, fosse capaz de os avaliar objetivamente. Assim, levantou-se o problema de saber se todos os atributos têm a mesma importância. Atributos mais importantes devem dar maior contributo na avaliação pretendida e o modelo a ser considerado deve refletir isso, adicionalmente a ferramenta de avaliação deveria ser intuitiva e rápida na aplicação. Para determinar a importância de cada atributo aplicou-se o Método Delphi tendo sido necessário três rondas para encontrar consenso relativamente à importância dos atributos a que se seguiu a aplicação de um conjunto de modelos estatísticos de forma a determinar uma métrica consistente e que permitisse a comparação de pontuações entre sítios web. De acordo com as questões de investigação e os objetivos definidos foi possível encontrar um modelo que fornecesse uma medida objetiva, normalizada e consistente acerca da qualidade de conteúdos de sítios web de unidades de saúde

Towards a model for the measurement of data quality in websites

Websites are, nowadays, the face of institutions, but they are often neglected, especially when it comes to contents. In the present paper, we put forth an investigation work whose final goal is the development of a model for the measurement of data quality in institutional websites for health units. To that end, we have carried out a bibliographic review of the available approaches for the evaluation of website content quality, in order to identify the most recurrent dimensions and the attributes, and we are currently carrying out a Delphi Method process, presently in its second stage, with the purpose of reaching an adequate set of attributes for the measurement of content quality.