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URI permanente para esta coleçãohttps://repositorio.fei.edu.br/handle/FEI/5123
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Artigo de evento 0 Citação(ões) na Scopus Plastic eta factors to determine experimental J-integral and ctod using homogeneous and mismatched SE(T) specimens(2010-07-26) MOREIRA, F. C.; OLIVEIRA, G. P. DE; Gustavo DonatoThis work presents procedures for experimental estimation of J - integral and CTOD (d) using the eta (h) method and SE(T) specimens in clamped and pin-loaded conditions. Homogeneous materials and also specimens containing mismatched welded joints are considered. The conceptual background is presented, followed by the details of the various finite element models developed for the analyses. As results, are presented h factors for J and CTOD experimental estimation. The main objective is to allow fracture toughness experimental evaluation using SE(T) specimens to reduce the conservatism in integrity assessments of pipelines and pressure vessels, which present very similar fracture conditions. Consequently, the results contribute for a better understanding of SE(T) specimens and encourage further developments since they are not available in current standards.Artigo de evento 1 Citação(ões) na Scopus A novel scroll expander for flank leakage investigation: preliminary tests(2016-07-19) FANTI, G. R.; Gustavo Donato; Paulo de Mello© 2016 University of Ljubljana.The isentropic efficiency of the expander is a concern for organic Rankine cycle (ORC) and compressed air energy storage (CAES) implementation. In these applications, the expander alone has a great influence over the whole system efficiency. Scroll expanders are particularly interesting for the low power range comprehended between 1 and 10 kW. Many previous works have attributed to internal leakages a great importance to obtain high isentropic efficiency in these machines. We present herein experimental results obtained with a novel scroll expander constructed to investigate the effect of internal leakages. We discuss the geometry definition and design of the prototype in detail. The maximum mechanical power produced by the prototype was 923 W at 2690 rpm but its isentropic efficiency was only 30.6%. Filling factor as high as 4.9 reveals that internal leakage must be reduced to obtain a more efficient expander.Artigo de evento 0 Citação(ões) na Scopus Effects of plasticity on the elastic unloading compliance of C(T), Se(B) and clamped SE(T) specimens(2017-06-18) Gustavo Donato; ANDRADE, L. G. F.© 2017 Chinese Society of Theoretical and Applied Mechanics. All Rights Reserved.This paper investigates how plasticity affects instantaneous crack size predictions based on the elastic unloading compliance technique applicable to SE(B), C(T) and clamped SE(T) fracture mechanics specimens. Since this method assumes linear-elastic constitutive model, plasticity ahead of the crack may alter crack-size predictions due to residual stresses, local deformations, among other reasons. In order to better understand such effects and develop corrections, three materials were modeled with different hardening and same elastic modulus to represent modern high strength steels. Specimens were loaded, unloaded and reloaded considering large geometry change for varying CMOD values in order to induce varying levels of plasticity. Results show that for all specimens, specially for clamped SE(T), compliance will increase for larger CMOD values, showing that plasticity may affect crack size predictions and deserve further attention. A trend was found for the three geometries under investigation, being SE(T) the most affected.Artigo de evento 1 Citação(ões) na Scopus Effects of crack tunneling on the elastic unloading compliance of C(T), Se(B) and clamped SE(T) specimens(2017-06-18) Gustavo Donato; ANDRADE, L. G. F.© 2017 Chinese Society of Theoretical and Applied Mechanics. All Rights Reserved.This paper investigates how crack front curvature affects instantaneous crack size predictions based on the elastic unloading compliance technique applicable to SE(B), C(T) and clamped SE(T) specimens. Relative crack depths (a/W) of 0.2, 0.5 and 0.7, alongside five levels of crack curvature were considered. Crack front was modeled as a semi-ellipse. It was shown that for the same ASTM equivalent straight crack [1] compliance decreases as tunneling increases. Since the maximum crack curvature allowed by ASTM is very restrictive, compliance did not change much within that limit, but if violated, a remarkable deviation may occur. As a step to improve such techniques, a new formulation to determine the equivalent straight crack was developed. The new proposal shows reduced errors on compliance as crack curvature grows when compared to current ASTM proposal.