Browsing by Author "Valente, R.A.F."
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- Determination of stress intensity factors along cracked surfaces in piping elbows structuresPublication . Fonseca, E.M.M.; Melo, F.J.M.Q. de; Valente, R.A.F.Piping elbows represent an essential role in pipework systems. These structures are part of the plant process in all industries. High safety standards in design are inherent to these projects due to complex mechanical or thermal loading. When these accessories carry defects, project engineers should assess their integrity in duty. This paper present a contribution in fracture mechanics applied to piping systems. Stress intensity factors are determined along cracked surfaces in piping elbows subjected to bending moment using a developed finite curved pipe element. This element is based in high order polynomial and trigonometric functions for rigid beam displacement and Fourier series modelling the transverse section warping or ovalization. Computational effort is saved with this element in the evaluation of the stresses or strains. Numerical tests are performed for different standard pipe elbows containing an axial or longitudinal crack. This study is compared with analyses reported by other authors.
- Determination of stress intensity factors along cracked surfaces in piping elbows structuresPublication . Fonseca, E.M.M.; Melo, F.J.M.Q. de; Valente, R.A.F.Pipe elbows play an essential role in pipework systems, once such structure elements are part of the plant process fluid conduction practically in all chemical or energy production industries. High safety standards in design are inherent to these projects due to complex mechanical or thermal loading. When these accessories carry defects, project engineers should assess their integrity in duty. This paper present a contribution in fracture mechanics applied to piping systems. Stress intensity factors are determined along cracked surfaces in piping elbows subjected to bending moment using a developed finite curved pipe element. This element is based in high order polynomial for rigid beam displacement and Fourier series modelling the transverse section warping or ovalization. Computational effort is saved with this element in the evaluation of the stresses or strains. Numerical tests are performed for different pipe elbows with thick or thin flanges, containing a circumferential crack. This study is compared with analyses reported by other authors.
- Modelo de deformação numérico e experimental em secções tubularesPublication . Fonseca, E.M.M.; Barreira, Luísa; Melo, F.J.M.Q. de; Valente, R.A.F.Neste artigo apresenta-se um modelo numérico e experimental para a análise de secções tubulares quando submetidas a carregamentos transversais. O objectivo consiste na avaliação da integridade estrutural destes elementos através da sua resistência à deflexão através do seu comportamento para além do domínio elástico. O modelo numérico baseia-se na utilização de elementos sólidos com características de não linearidade geométrica e material utilizando o programa Ansys. O modelo experimental resulta de ensaios efectuados em componentes com as mesmas características para a comparação de resultados. As estruturas tubulares têm elevada importância tecnológica em aplicações em várias áreas: em instalações de água, redes de segurança, ar comprimido, distribuição de gás. Uma tubagem submetida a uma pressão externa suficientemente elevada pode vir a traduzir-se num problema de estabilidade ou mesmo no seu colapso estrutural através das grandes deformações ocorridas. Este tipo de problemas podem surgir em tubagens submersas por água, em tubagens soterradas, em tubagens em contacto com outros materiais e ainda durante o seu transporte ou instalação. A ocorrência dos diferentes modos de falha em secções tubulares podem ocorrer devido à ovalização da secção recta. A utilização de técnicas numéricas, torna possíveis estudos complexos neste tipo de geometrias, com os problemas decorrentes da ovalização e empenamento quando as estruturas são solicitadas. Salientam-se alguns trabalhos realizados pelos autores nestas áreas [1]. A motivação do estudo e da análise deste tipo de estruturas traduz-se na verificação dos fenómenos de ovalização decorrentes do comportamento não linear e geométrico do material, em função de uma solicitação externa incremental, utilizando um modelo numérico e experimental com características similares.
- Modelo de deformação numérico e experimental em secções tubularesPublication . Fonseca, E.M.M.; Barreira, Luísa; Melo, F.J.M.Q. de; Valente, R.A.F.Neste artigo apresenta-se um modelo numérico e experimental para a análise de secções tubulares quando submetidas a carregamentos transversais. O objectivo consiste na avaliação da integridade estrutural destes elementos função da sua resistência à deflexão através do seu comportamento para além do domínio elástico. O modelo numérico baseia-se na utilização de elementos sólidos com características de não linearidade geométrica e material utilizando o programa Ansys. O modelo experimental resulta de ensaios efectuados em componentes com as mesmas características para a comparação de resultados.
- Stress intensity factors for notched round bars using FEMPublication . Fonseca, E.M.M.; Melo, F.J.M.Q. de; Valente, R.A.F.This study proposes alternative methods to estimate the stress intensity factors (SIF) of notched round components having an axial hole and subjected to an axial force or a bending moment. The method is based on analytical equations proposed by (Harris 1997) and on alternative formulation using finite element method (FEM). The objective of this work is a contribution in fracture mechanics applied to tubular systems with typical defects generated in service or a consequence of the fabrication method. Computational effort is saved with this element in the evaluation of the stress field across the section carrying the defect. Numerical examples are presented to illustrate the proposed method referring to tubular structures with different end constraints and containing a circumferential notch. The comparisons with the elastic finite element showed satisfactory results and good agreement with others references.
- Stress intensity factors for notched round bars using FEMPublication . Fonseca, E.M.M.; Melo, F.J.M.Q. de; Valente, R.A.F.This study proposes alternative methods to estimate the stress intensity factors (SIF) of notched round components having an axial hole and subjected to an axial force or a bending moment. The method is based on analytical equations proposed by (Harris 1997) and on alternative formulation using finite element method (FEM). The objective of this work is a contribution in fracture mechanics applied to tubular systems with typical defects generated in service or a consequence of the fabrication method. Computational effort is saved with this element in the evaluation of the stress field across the section carrying the defect. Numerical examples are presented to illustrate the proposed method referring to tubular structures with different end constraints and containing a circumferential notch. The comparisons with the elastic finite element showed satisfactory results and good agreement with others references.
- The flexibility of steel hollow tubular sections subjected to thermal and mechanical loadsPublication . Fonseca, E.M.M.; Melo, F.J.M.Q. de; Valente, R.A.F.Numerical analysis of hollow tubular sections is used as a starting tool to establish the reliability assessment of these elements when mechanically or thermally loaded. To quantify the material deformation behaviour of these elements resulting from ground motion, crack propagation, effects from high temperatures, theoretical and experiments analyses can be used for testing a service reliable guarantee. Structural hollow sections have excellent static properties, not only with regard to buckling and torsion, but also in the overall design of members. They can offer economic advantages compared to open sections. It is possible to change the strength by varying the wall thickness or filling the section with other material without changing the external geometry. Flexibility is an important parameter in hollow tubular systems when subjected to thermal or mechanical loads. This work presents a numerical analysis technique based on the finite element method for thermal and mechanical nonlinear behaviour. Temperature field will be calculated according to non-steady conditions when submitted to standard ISO834 and non-linear material properties foreseen in Eurocode standards (EC1 and EC3). This work will present a complete study of the flexibility analysis for a wide range of pipe dimensions, and the obtained results are then compared with design rules.