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Repositório do Instituto Politénico de Castelo Branco (13.947 recursos)

O Repositório Científico do Instituto Politécnico de Castelo Branco tem como objectivos fundamentais a divulgação, a preservação em formato digital e a partilha do conhecimento científico gerado na instituição, constituindo-se numa ferramenta de valor acrescentado porque permite aumentar a visibilidade e o impacto da investigação desenvolvida.

ESTCB - Artigos em revistas com arbitragem científica

Mostrando recursos 1 - 20 de 39

  1. Empirical model for plasticity-induced crack closure based on Kmax and ΔK

    Antunes, F.V.; Chegini, A.G.; Camas, D.; Correia, L.
    The mean stress has a significant effect on crack propagation life and must be included in prediction models. However, there is no consensus in the fatigue community regarding the dominant mechanism explaining the mean stress effect. The concept of crack closure has been widely used and several empirical models can be found in literature. The stress ratio, R, is usually the main parameter of these models, but present numerical results showed a significant influence of Kmax. A new empirical model is therefore proposed here, dependent on Kmax and ΔK, with four empirical constants. The model also includes the effect of material's yield stress, and two...

  2. Potential toxic elements in stream sediments, soils and waters in an abandoned radium mine (central Portugal)

    Antunes, I. M. H. R.; Neiva, A. M. R.; Albuquerque, M. T. D.; Carvalho, P. C. S.; Santos, A. C. T.; Cunha, P. P.
    The final publication is available at Springer via http://dx.doi.org/10.1007/s10653-017-9945-2

  3. A numerical study of non-linear crack tip parameters

    Antunes, F.V.; Branco, R.; Correia, L.; Ramalho, A.L.
    Crack closure concept has been widely used to explain different issues of fatigue crack propagation. However, different authors have questioned the relevance of crack closure and have proposed alternative concepts. The main objective here is to check the effectiveness of crack closure concept by linking the contact of crack flanks with non-linear crack tip parameters. Accordingly, 3D-FE numerical models with and without contact were developed for a wide range of loading scenarios and the crack tip parameters usually linked to fatigue crack growth, namely range of cyclic plastic strain, crack tip opening displacement, size of reversed plastic zone and total plastic dissipation per cycle, were...

  4. Effect of compressive loads on plasticity induced crack closure

    Antunes, F. V.; Correia, L.; Camas, D.; Branco, R.
    Compressive stresses play an important role on tension-compression fatigue which can be attributed to plasticity induced crack closure (PICC). The objective here is to study numerically the effect of compressive stresses on PICC and to discuss the applicability of PICC to explain the effect of negative stress ratios on fatigue crack growth rate. The compression produces reversed plastic deformation at the crack tip, reducing linearly the crack opening level. The incursion to negative stress ratios did not produce sudden changes in the behavior of PICC and no saturation with the decrease of minimum load was observed for δKeff. Crack closure was able to collapse da/dN-δK...

  5. Finite element meshes for optimal modelling of plasticity induced crack closure

    Antunes, F. V.; Camas, D.; Correia, L.; Branco, R.
    The main goal here is to optimise the finite element mesh used to predict plasticity induced crack closure (PICC). A numerical model was developed for a M(T) specimen made of 6016-T4 aluminium alloy. The parameters studied were the size of most refined region perpendicularly to crack flank (ym) and along propagation direction (xr), the size of finite elements near crack tip (L1) and the vertical size of refinement close to crack flank (yA/B). A maximum size of about 1.3mm was found for ym, but a smaller value has a limited impact on PICC. An analytical expression was proposed for xr, dependent on δK and...

  6. Effect of crack closure on non-linear crack tip parameters

    Antunes, F.V.; Sousa, T.; Branco, R.; Correia, L.
    Crack closure concept has been widely used to explain different issues of fatigue crack propagation. However, some authors have questioned the relevance of crack closure and have proposed alternative concepts. The main objective here is to check the effectiveness of crack closure concept by linking the contact of crack flanks with non-linear crack tip parameters. Accordingly, 3D-FE numerical models with and without contact were developed for a wide range of loading scenarios and the crack tip parameters usually linked to fatigue crack growth, namely range of cyclic plastic strain, crack tip opening displacement, size of reversed plastic zone and total plastic dissipation per cycle were...

  7. A parameter for quantitative analysis of plasticity induced crack closure

    Antunes, F.V.; Correia, L.; Ramalho, A.L.
    Numerical models have been successfully developed to predict plasticity induced crack closure (PICC). However, despite the large research effort a full understanding of the links between physical parameters, residual plastic wake and PICC has not been achieved yet. The plastic extension of material behind crack tip, Dyp, obtained by the integration of vertical plastic deformation perpendicularly to crack flank, is proposed here to quantify the residual plastic field. The values of Dyp and PICC were obtained numerically in a M(T) specimen using the finite element method. An excellent correlation was found between PICC and Dyp which indicates that this parameter controls the phenomenon, and can be...

  8. Uncalibrated eye-to-hand visual servoing using inverse fuzzy models

    Gonçalves, P.J.S.; Mendonça, L.F.; Sousa, J.M.C.; Pinto, J.R.C.
    (c) 2007 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.

  9. Portuguese UGM characterisation using cyclic triaxial tests

    Luzia, Rosa; Santos, Luís Picado; Neves, José; Gardete, Dinis
    Disponível apenas o resumo

  10. Comportamiento de esquistos en los terraplenes y explanadas de los firmes de carreteras en Portugal

    Luzia, Rosa; Santos, Luis Picado
    Disponível apenas o resumo

  11. Documentary evidence of past floods in Europe and their utility in flood frequency estimation

    Kjeldsen, T. R.; Macdonald, N.; Lang, M.; Mediero, L.; Albuquerque, M.T.D.; Bogdanowicz, E.; Brazdil, R.; Castellarin, A.; David, V.; Fleig, A.; Gül, G.O.; Kriauciuniene, J.; Kohnova, S.; Merz, B.; Nicholson, O.; Roald, L. A.; Salinas, J. L.; Sarauskiene, D.; Sraj, M.; Strupczewski, W.; Szolgay, J.; Toumazis, A.; Vanneuville, W.; Veijalainen, N.; Wilson, D.
    This review outlines the use of documentary evidence of historical flood events in contemporary flood frequency estimation in European countries. The study shows that despite widespread consensus in the scientic literature on the utility of documentary evidence, the actual migration from academic to practical application has been limited. A detailed review of flood frequency estimation guidelines from dierent countries showed that the value of historical data is generally recognised, but practical methods for systematic and routine inclusion of this type of data into risk analysis are in most cases not available. Studies of historical events were identied in most countries,...

  12. Water distribution network’s modeling and calibration: case study based on scarce inventory data

    Alves, Z.; Muranho, J.; Albuquerque, M.T.D.; Ferreira, A.
    Under a Creative Commons license

  13. Tiny programming language to improve assembly generation for automation equipment

    Metrôlho, J.C.M.M.; Costa, Mónica; Ribeiro, F. Reinaldo
    The development time in industrial informatics systems, within industry environments, is a very important issue for competitiveness. The usage of adequate targetspecific programming languages is very important because they can facilitate and improve developers’ productivity, allowing solutions to be expressed in the idiom and at the level of abstraction of the problem’s domain. In this paper we present a target-specific programming language, which was designed to improve the design cycle of code generation, for an industrial embedded system. The native assembly code, the new language structure and their constructs, are presented in the paper. The proposed targetspecific language is expressed using words and terms that are related to the...

  14. Smart content selection for public displays in ambient intelligence environments

    Ribeiro, F. Reinaldo; José, Rui
    A public display that is able to present the right information at the right time is a very compelling concept. However, realising or even approaching this ability to autonomously select appropriate content based on some interpretation of the surrounding social context represents a major challenge. This article provides an overview of the key challenges involved and an exploration of some of the main alternatives available. It also describes a novel place-based content adaptation system that autonomously selects from web sources the content deemed more relevant according to a dynamic place model. This model is based on a tag cloud that...

  15. A survey on IP-based wireless sensor networks solutions

    Rodrigues, Joel; Neves, P.A.C.S.
    Wireless sensor networks can be composed of thousands of smart sensing nodes that capture environment data in a cost-efficient way. Such networks present new challenges when compared to traditional computer networks, namely in terms of smart node processing power and very limited energy resources. Ubiquitous computing can benefit from wireless sensor networks, from the perspective that sensed data can be used on behalf of the user without explicit intervention, turning ubiquitous computing into a reality. For the data to be available everywhere wireless sensor networks must be connected to the Internet. Two main approaches can be considered: proxy-based or sensor...

  16. Body sensor network mobile solutions for biofeedback monitoring

    Pereira, Orlando; Caldeira, J.M.L.P.; Rodrigues, Joel
    Body sensor networks (BSN) appeared as an application of Wireless Sensor Networks (WSN) to medicine and biofeedback. Such networks feature smart sensors (biosensors) that capture bio-physiological parameters from people and can offer an easy way for data collection. BSNs also need suitable interfaces for data processing, presentation, and storage for latter retrieval. As a result, Bluetooth technology can be used to communicate with several more powerful and graphical user interface (GUI)-enabled devices such as mobile phones or regular computers. Taking into account that people currently use mobile and smart phones, it offers a good opportunity to propose a suitable mobile system for BSN networks. This paper presents a BSN mobile solution for biofeedback...

  17. Core-body temperature acquisition tools for long-term monitoring and analysis

    Caldeira, J.M.L.P.; Moutinho, José A. F.; Rodrigues, Joel J. P. C.; Gilg, Marc; Lorenz, Pascal
    The detection of fertile and ovulation periods may be performed by women’s body temperature variations. These variations are more accurate if a core-body temperature for their detection is used. Previous medical studies concluded that the use of skin temperature could be influenced by environmental conditions. Since the increasing of the body temperature in this period is only about 0.5 ºC, it is crucial that measurements should be the most accurate as possible. Due to the lack of solutions to realize that in order to measure and analyze the core-body temperature, this paper presents a system to capture, display, and monitoring...

  18. Toward ubiquitous mobility solutions for body sensor networks on healthcare

    Caldeira, J.M.L.P.; Rodrigues, Joel; Lorenz, Pascal
    Toward ubiquitous mobility solutions for body sensor networks on healthcare

  19. Impact of vehicle movement models on VDTN routing strategies for rural connectivity

    Soares, Vasco N. G. J.; Farahmand, Farid; Rodrigues, Joel J. P. C.
    Vehicular delay-tolerant networks (VDTNs) appear as an alternative to provide low cost asynchronous internet access on developing countries or isolated regions, enabling non-real time services, such as e-mail, web access, telemedicine, environmental monitoring and other data collection applications. VDTNs are based on the delay-tolerant network (DTN) concept applied to vehicular networks, where vehicles mobility is used for connectivity. This paper considers a rural connectivity scenario and investigates how different mobility patterns and vehicle densities influence the performance of DTN routing protocols applied to VDTN networks. Moreover, routing protocols parameters are also changed in the present study. We analyse their effect on...

  20. Artificial neural networks and neuro-fuzzy systems for modelling and controlling real systems: a comparative study

    Vieira, José; Dias, Fernando; Mota, Alexandre
    This article presents a comparison of artificial neural networks andneuro-fuzzy systems appliedfor modelling andcontrolling a real system. The main objective is to model and control the temperature inside of a kiln for the ceramic industry. The details of all system components are described. The steps taken to arrive at the direct and inverse models using the two architectures: adaptive neuro fuzzy inference system and feedforward neural networks are described and compared. Finally, real-time control results using internal model control strategy are resented. Using available Matlab software for both algorithms, the objective is to show the implementation steps for modelling and controlling a real system....

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