@article {PEREIRA2020105482, title = {Low and ultra-low-cycle fatigue behavior of X52 piping steel based on theory of critical distances}, journal = {International Journal of Fatigue}, year = {2020}, note = {n/a}, pages = {105482}, abstract = {

The cyclic failure observed in structural components such as pipelines subjected to extreme loading conditions highlights some limitations concerning the application of existing fatigue damage models. The evaluation and prediction of this type of failure in these steel components under large-scale plastic yielding associated with high levels of stress triaxiality are not sufficiently known nor explored. This fatigue domain is conventionally called ultra-low-cycle fatigue (ULCF) and damage features are representative of both low-cycle fatigue (LCF) and monotonic ductile fracture. Thus, in order to understand the ULCF damage mechanisms both monotonic and LCF tests are required to get representative bounding damage information to model the material damage behaviour under such extreme loading conditions. This paper aims at exploring the Theory of Critical Distances (TCD) in the LCF and ULCF fatigue regimes, including the application of the point, line and area methods. The application of the TCD theories has not been explored so far in the ULCF fatigue regimes, despite its promising results in the LCF and high-cycle fatigue. An experimental program was carried out on several specimens{\textquoteright} geometries made of X52 piping steel. In detail, smooth plane specimens and notched plane specimens were cyclic loaded under tension/compression loading in order to obtain fatigue lives within the range of 101-104 cycles. In addition, cyclic bending tests on notched plane specimens were also incorporated in this study. Finite element simulations of all small-scale tests were conducted allowing to derive elastoplastic stress/strain fields along the potential crack paths. The numerical data were subjected to a post-processing in order to find characteristic lengths that can be treated as a fatigue property according to the TCD. A unified strain-life relation is proposed for the X52 piping steel together with a characteristic material length, consisting of a practical relation for pipeline strain-based design under extreme cyclic loading conditions.

}, keywords = {cyclic plasticity, LCF, piping steel, Theory of Critical Distances, ULCF}, issn = {0142-1123}, doi = {https://doi.org/10.1016/j.ijfatigue.2020.105482}, url = {http://www.sciencedirect.com/science/article/pii/S014211232030013X}, author = {J.C.R. Pereira and A.M.P. de Jesus and J. Xavier and J.A.F.O. Correia and L. Susmel and A.A. Fernandes} } @article {doi:10.1177/1464420718799116, title = {Fracture characterization of a cast aluminum alloy aiming machining simulation}, journal = {Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications}, volume = {233}, number = {3}, year = {2019}, note = {n/a}, pages = {402-412}, abstract = {

Despite extensive research regarding metal cutting simulation, the current industrial practice very often relies on empirical data when it comes to tool design. In order accurately simulate the cutting process it is not only important to have robust numerical models that closely portray the phenomenon, but also to properly characterize the material taking into account the cutting conditions. The goal of this investigation focuses on the mechanical characterization of the cast aluminum alloy AlSi9Cu3 by conducting both compression and fracture tests. Due to its very good castability, machinability, and attractive mechanical properties, this alloy is widely used in casting industry for the manufacture of automotive components, among others. Besides the experimental characterization, a numerical methodology is proposed for the modeling of the cast alloy, making use of the Johnson{\textendash}Cook constitutive material model, in Abaqus/CAE. The material model is calibrated based on compression tests at multiple conditions (quasi-static, incremental dynamic and high temperatures). The identified model is then validated by simulation of the ductile fracture tests of notched specimens. The obtained numerical results were consistent with the experimentally obtained, contributing to the validity of the presented characterization technique.

}, doi = {10.1177/1464420718799116}, url = {https://doi.org/10.1177/1464420718799116}, author = {TEF Silva and S Gain and D Pinto and A.M.P. de Jesus and J. Xavier and Reis, A. and P. A. R. Rosa} } @article {Fernandes201819, title = {Durability of bond in NSM CFRP-concrete systems under different environmental conditions}, journal = {Composites Part B: Engineering}, volume = {138}, year = {2018}, note = {

n/a

}, pages = {19 - 34}, abstract = {

Abstract This paper addresses the durability of bond between concrete and carbon fibre reinforced polymer (CFRP) strips installed according to the near-surface mounted (NSM) technique (NSM CFRP-concrete systems) under the effects of two main groups of environmental conditions: (i) laboratory-based ageing conditions; (ii) real outdoor ageing conditions. The bond degradation was evaluated by carrying out direct pullout tests on aged specimens that were previously subjected to distinct environmental conditions for different periods of exposure. Moreover, the degradation of the mechanical properties of the involved materials was investigated. The digital image correlation (DIC) method was used to document the evolution of the deformation fields at the surface over the whole region of interest consisting of concrete and epoxy adhesive at the ligament region. This information supported the discussion about the evolution of the bond resistant mechanism developed in \{NSM\} CFRP-concrete specimens during testing, as well as the assessment of the bond quality of the system. In general, the results obtained from the durability tests conducted have shown that the different exposure environments, which may be considered as quite severe, did not result in significant damage on \{NSM\} CFRP-concrete system. The maximum decrease of about 12\% on bond strength was obtained for real outdoor environments. Conversely, a maximum increase of 8\% on bond strength was obtained on the specimens exposed to the temperature cycles between -15��C and +60��C. \{DIC\} allowed to document the stress transfer mechanisms established between the \{CFRP\} and the concrete substrate, revealing the crack patterns and the influence widths of the \{CFRP\} reinforcement strips, which were shown to be important for avoiding group effect when using multiple parallel strengthening \{CFRP\} strips.

}, keywords = {Carbon fibre, Debonding, Environmental degradation, Mechanical testing, Near-surface mounted systems}, doi = {https://doi.org/10.1016/j.compositesb.2017.11.022}, url = {https://www.sciencedirect.com/science/article/pii/S1359836817311332}, author = {Pedro Fernandes and Jos{\'e} Sena-Cruz and Jos{\'e} Xavier and Patr{\'\i}cia Silva and Eduardo Pereira and Jos{\'e} Cruz} } @article {doi:10.1177/0309324718791087, title = {Measuring orthotropic bending stiffness components of Pinus pinaster by the virtual fields method}, journal = {The Journal of Strain Analysis for Engineering Design}, volume = {53}, number = {8}, year = {2018}, note = {

n/a

}, pages = {556-565}, abstract = {

Orthotropic stiffness components of Pinus pinaster Ait. wood are simultaneously determined by means of a heterogeneous plate bending test. The proposed inverse identification approach couples full-field slope measurements provided by deflectometry with the virtual fields methods. Wooden plates oriented in the longitudinal{\textendash}radial and longitudinal{\textendash}tangential material planes were manufactured. A procedure was implemented to allow suitable specular reflective coating of the wooden plates, required in the deflectometry technique. Reconstructed curvature fields, applied load and plate dimensions were input in virtual fields methods for material parameter identification, assuming Kirchhoff{\textendash}Love classical plate theory. Several virtual fields and load cases were analysed to address the identifiability of the method. The values of the orthotropic elastic constants obtained from the proposed approach were found in good agreement with regard to reference ones for the same species and determined from classical tensile, compression and shear mechanical tests.

}, doi = {10.1177/0309324718791087}, url = {https://doi.org/10.1177/0309324718791087}, author = {J. Xavier and F. Pierron} } @article {Pereira2018448, title = {Determination of mode II cohesive law of bovine cortical bone using direct and inverse methods}, journal = {International Journal of Mechanical Sciences}, volume = {138-139}, year = {2018}, note = {n/a}, pages = {448 - 456}, abstract = {

This study presents two alternative methods to determine the cohesive law of bovine cortical bone under mode II loading, employing the End Notched Flexure (ENF) test. The direct method results from the combination of the progress of the mode II strain energy release rate with the crack tip shear displacement, obtained by digital image correlation. The resulting cohesive law is determined by differentiation of this relation relatively to the crack shear displacement. The inverse method employs finite element analyses with cohesive zone modelling, in association with an optimization procedure. The resulting strategy enables determining the cohesive law without establishing a pre-defined shape. The significant conclusion that comes out of this work is that both methods offer consistent results regarding the estimation of the cohesive law in bone. Given that the inverse method dispenses the use of sophisticated equipment to obtain the cohesive law in bone, it can be used as a more convenient procedure to accomplish efficient studies in the context of bone fracture characterization under mode II loading.

}, keywords = {Bovine cortical bone, Cohesive law, End notched flexure, Mode II}, issn = {0020-7403}, doi = {https://doi.org/10.1016/j.ijmecsci.2018.02.009}, url = {http://www.sciencedirect.com/science/article/pii/S0020740317327479}, author = {F.A.M. Pereira and de M.F.S.F. Moura and N. Dourado and J.J.L. Morais and J. Xavier and M.I.R. Dias} } @article {Kuhn2018276, title = {Determination of the crack resistance curve for intralaminar fiber tensile failure mode in polymer composites under high rate loading}, journal = {Composite Structures}, volume = {204}, year = {2018}, note = {n/a}, pages = {276-287}, abstract = {

This paper presents the determination of the crack resistance curve of the unidirectional carbon-epoxy composite material IM7-8552 for intralaminar fiber tensile failure under dynamic loading. The methodology, proposed by Catalanotti et al. (2014) for quasi-static loading conditions, was enhanced to high rate loading in the order of about 60 ?s-1. Dynamic tests were performed using a split-Hopkinson tension bar, while quasi-static reference tests were conducted on a standard electromechanical testing machine. Double-edge notched tension specimens of different sizes were tested to obtain the size effect law, which in combination with the concepts of the energy release rate is used to measure the entire crack resistance curve for the fiber tensile failure mode. Digital image correlation is applied to further verify the validity of the experiments performed at both static and dynamic loading. The data reduction methodology applied in this paper is suitable for intralaminar fiber failure modes without significant delamination. Sufficient proof is given that quasi-static fracture mechanics theory can also be used for the data reduction of the dynamic tests. It is shown, that the intralaminar fracture toughness for fiber tensile failure of UD IM7-8552 increases with increasing rate of loading.

}, keywords = {Dynamic fracture, Fiber-reinforced composites, R-curve, Size effect}, doi = {https://doi.org/10.1016/j.compstruct.2018.07.039}, url = {http://www.sciencedirect.com/science/article/pii/S0263822318308079}, author = {P. Kuhn and G. Catalanotti and J. Xavier and M. Ploeckl and H. Koerber} } @article {Pereiraetal2018, title = {Identification of transverse elastic properties of the diaphysis of cortical bone}, journal = {Journal of Mechanical Engineering and Biomechanics}, volume = {2}, number = {5}, year = {2018}, note = {n/a}, pages = {50-55}, abstract = {n/a}, doi = {10.24243/JMEB/2.5.172}, url = {https://doi.org/10.24243/JMEB/2.5.172}, author = {B. Pereira and J. Xavier and Pereira, F. and Morais, J} } @article {Xavier2018462, title = {Non-linear shear behaviour of bovine cortical bone by coupling the Arcan test with digital image correlation}, journal = {Optics and Lasers in Engineering}, volume = {110}, year = {2018}, note = {n/a}, pages = {462-470}, abstract = {

The non-linear shear behaviour of bovine cortical bone is measured by coupling the Arcan test with digital image correlation. The experimental study is carried out on specimens taken from bovine femur and oriented along the longitudinal-tangential material plane. An ad hoc Arcan fixture is built to transfer the cross-head displacement of the testing machine into a shear loading at the centre of the V-notched section. A validation of predominant shear behaviour at the gauge section is shown from full-field deformation measurements. Moreover, direct evaluation of the shear modulus is obtained by integrating the shear strain component along the V-notches, avoiding numerical correction factors required in the classical data reduction scheme. The shear modulus of bovine cortical bone is found in good agreement with references from literature. Moreover, the shear stress at maximum load is understood as a suitable estimation of the shear strength. Furthermore, the Ramberg�Osgood model is found to provide an accurate description of the non-linear shear behaviour of bone tissue.

}, keywords = {Arcan shear test, Cortical bone, Digital Image Correlation, Finite element method, Non-linear shear behaviour}, doi = {https://doi.org/10.1016/j.optlaseng.2018.07.004}, url = {http://www.sciencedirect.com/science/article/pii/S0143816618302288}, author = {J. Xavier and Morais, J and Pereira, F.} } @article {doi:10.1177/0309324718786351, title = {On the identification of earlywood and latewood radial elastic modulus of Pinus pinaster by digital image correlation: A parametric analysis}, journal = {The Journal of Strain Analysis for Engineering Design}, volume = {53}, number = {8}, year = {2018}, note = {n/a}, pages = {566-574}, abstract = {

This work addresses the reconstruction of strain gradient fields at the wood growth ring scale from full-field deformation measurements provided by digital image correlation. Moreover, the spatial distribution of the earlywood and latewood radial modulus of elasticity is assessed. Meso-scale tensile tests are carried out on Pinus pinaster Ait. wooden specimens oriented in the radial{\textendash}tangential plane under quasi-static loading conditions. A parametric analysis of the two-dimensional digital image correlation extrinsic and intrinsic setting parameters is performed, in a balance between spatial resolution and resolution. It is shown that the parametric module is an effective way to quantitatively support the choice of digital image correlation parameters in the presence of the high deformation gradient fields generated by the structure{\textendash}property relationships at the scale of observation. Under the assumption of a uniaxial tensile stress state, the spatial distribution of the radial elastic modulus across the growth rings is obtained. It is observed that the ratio of the radial modulus of elasticity between latewood and earlywood tissues can vary significantly as a function of the digital image correlation parameters. It is pointed out, however, that a convergence value can be systematically established. Effectively, earlywood and latewood stress{\textendash}strain curves are obtained and elastic properties are determined assuming the converged digital image correlation setting parameters.

}, doi = {10.1177/0309324718786351}, url = {https://doi.org/10.1177/0309324718786351}, author = {Jo{\~a}o Lu{\'\i}s Pereira and Jos{\'e} Xavier and Bahman Ghiassi and Jos{\'e} Lousada and Morais, Jos{\'e}} } @article {Rodrigues2017183, title = {Numerical analysis of a double shear standard bolted connection considering monotonic loadings}, journal = {Engineering Structures and Technologies}, volume = {9}, number = {4}, year = {2017}, note = {

n/a

}, pages = {183-194}, publisher = {Taylor \& Francis}, abstract = {

AbstractThe behaviour of standard boltedsteel connections submitted to monotonic loads, through the use of numerical models, is presented in the current paper.The bolted connections allow speed up constructive processes in an increasingly competitive and globalized world in which the costs are a decisive factor in the development of a project. The use of computational tools in the analysis of bolted connections becomes determinant, mainly for new solutions or solutions less explored in terms of design codes.Throughout the years, bolted connections have been suffering transformations resulting from research activities performed by many authors. Rivets have been replaced by bolts, the main achievement being the pre-stressed bolts. Methodologies based on finite element analyses were proposed for double shear bolted connection. The non-linear behaviour of these connections is investigated and their performances are compared. In the numerical modelling of the bolted connection, linear elastic and elastoplastic analyzes reveal that there are two slip levels associated with local non-linearities caused by the contact pairs, which vary with clamping stresses.

}, doi = {10.3846/2029882X.2017.1414638}, url = {https://doi.org/10.3846/2029882X.2017.1414638}, author = {M.F. Rodrigues and J. Correia and B. Pedrosa and A. de Jesus and B. Carvalho and C. Rebelo and J. Xavier and R. Cal{\c c}ada} } @article {Pereira2017663, title = {ULCF assessment of X52 piping steel by means of cyclic bending tests}, journal = {Journal of Constructional Steel Research}, volume = {138}, year = {2017}, note = {

n/a

}, pages = {663 - 674}, abstract = {

Abstract Pipelines and piping components may experience large cyclic deformations during a reduced number of cycles (Ni = 1�100 cycles), when subjected to extreme cyclic loading events (e.g. hurricanes, support settlements, earthquakes). In accordance with these loading scenarios, a lateral movement can be applied to the pipeline inducing bending stresses that gradually promotes strain localization, due to progressive plastic instabilities (buckling), damage evolution and final failure. This work aims at characterizing ultra-low cycle fatigue (ULCF) behaviour of the \{X52\} piping steel under bending and local buckling state. An experimental program was carried out to derive \{ULCF\} data for smooth, notched and flat-grooved specimen geometries under cyclic bending. Furthermore, the small-scale tests were simulated in ABAQUS� with the objective of computing the parameters governing the fatigue damage models. The classical Coffin-Manson strain-life relation commonly used in the low cycle fatigue (LCF) regime is proposed to model the fatigue lives. In addition, the Xue model, particularly dependent of the monotonic fracture strain was also used for the prediction of the number of cycles until the crack initiation. The numerical data obtained with these models are compared, being achieved similar fatigue lives predictions for notched plane specimens. For the case of flat-grooved specimens which provides plain strain conditions, an overestimation from the Coffin-Manson relation was observed while the Xue model reproduces very good results for both specimens{\textquoteright} series.

}, keywords = {Cyclic bending, Experimental techniques, Numerical modelling, ULCF, X52 piping steel}, doi = {https://doi.org/10.1016/j.jcsr.2017.08.020}, url = {http://www.sciencedirect.com/science/article/pii/S0143974X17304352}, author = {J.C.R. Pereira and A.M.P. de Jesus and J. Xavier and A.A. Fernandes} } @article {Pereira2017210, title = {Direct and inverse methods applied to the determination of mode I cohesive law of bovine cortical bone using the DCB test}, journal = {International Journal of Solids and Structures}, volume = {128}, number = {Supplement C}, year = {2017}, note = {n/a}, pages = {210 - 220}, abstract = {

Abstract This work addresses the determination of the cohesive law under mode I loading of bovine cortical bone tissue using the Double Cantilever Beam (DCB) test. Direct and inverse methods were proposed to assess the cohesive laws representative of bone fracture under mode I loading. The direct method combines the evolution of the strain energy release rate under mode I loading with the crack tip opening displacement that is monitored by digital image correlation technique. According to this method, the cohesive law is obtained by differentiation of such relation with respect to the crack opening. The inverse procedure is performed through a finite element analysis including cohesive zone modelling, conjointly with a developed optimization algorithm. This identification strategy does not require a pre-established shape of the cohesive law as with the conventional inverse based procedures, which is viewed as a novelty of this work. It was concluded that both methods provide consistent results, being appellative tools concerning systematic and methodical studies dedicated to bone fracture characterization.

}, keywords = {Bovine cortical bone, Cohesive law, Double cantilever beam test, Mode I}, doi = {https://doi.org/10.1016/j.ijsolstr.2017.08.028}, url = {http://www.sciencedirect.com/science/article/pii/S002076831730392X}, author = {F.A.M. Pereira and de M.F.S.F. Moura and N. Dourado and J.J.L. Morais and J. Xavier and M.I.R. Dias} } @article {Pinto201763, title = {Dispersion and failure analysis of PLA, PLA/GNP and PLA/CNT-COOH biodegradable nanocomposites by SEM and DIC inspection}, journal = {Engineering Failure Analysis}, volume = {71}, year = {2017}, note = {n/a}, pages = {63 - 71}, abstract = {

Biodegradable polymers such as PLA have been studied for medical applications, human ligament repair is one of such cases. However, these materials can be applied in other sectors as aerospace, aeronautics, automotive, food packaging. PLA presents a relatively brittle on the mode I fracture behavior, being often blend with other biodegradable or non-degradable polymers to improve its fracture energy. For some existing applications, PLA components exhibit accumulated permanent deformation resulting from dynamic mechanical inputs, resulting on failure by laxity of parts. Aiming the improvement of PLA mechanical properties, the inclusion of carbon nanofillers into PLA matrix, in particular, CNT-COOH and GNP have been developed, due to their strong sp2 carbon-carbon bondings and their geometric arrangement that enhance mechanical properties of the polymer matrix. PLA and nanocomposites were produced by melt blending followed by compression moulding in a hot press, with small weight percentages of nanofillers added to the matrix. Nanocomposites dispersion was evaluated by SEM. Quasi static tensile tests were performed on a mechanical testing machine (Instron� ElectroPuls E1000) along with strain field measurements of specimens with centred crack with digital image correlation, revealing strain distribution along specimens.

}, keywords = {Composite(s), Failure analysis, Mechanical testing, Non-destructive testing, Static failure}, doi = {https://doi.org/10.1016/j.engfailanal.2016.06.009}, url = {http://www.sciencedirect.com/science/article/pii/S1350630716304745}, author = {V.C. Pinto and T. Ramos and A.S.F. Alves and J. Xavier and P.J. Tavares and P.M.G.P. Moreira and R.M. Guedes} } @article {Silva2017, title = {Fracture characterization of human cortical bone under mode II loading using the end-notched flexure test}, journal = {Medical {\&} Biological Engineering {\&} Computing}, volume = {55}, number = {8}, year = {2017}, note = {n/a}, pages = {1249-1260}, abstract = {

Fracture characterization of human cortical bone under mode II loading was analyzed using a miniaturized version of the end-notched flexure test. A data reduction scheme based on crack equivalent concept was employed to overcome uncertainties on crack length monitoring during the test. The crack tip shear displacement was experimentally measured using digital image correlation technique to determine the cohesive law that mimics bone fracture behavior under mode II loading. The developed procedure was validated by finite element analysis using cohesive zone modeling considering a trapezoidal with bilinear softening relationship. Experimental load-displacement curves, resistance curves and crack tip shear displacement versus applied displacement were used to validate the numerical procedure. The excellent agreement observed between the numerical and experimental results reveals the appropriateness of the proposed test and procedure to characterize human cortical bone fracture under mode II loading. The proposed methodology can be viewed as a novel valuable tool to be used in parametric and methodical clinical studies regarding features (e.g., age, diseases, drugs) influencing bone shear fracture under mode II loading.

}, doi = {10.1007/s11517-016-1586-6}, url = {https://doi.org/10.1007/s11517-016-1586-6}, author = {F.G.A. Silva and de M.F.S.F. Moura and N. Dourado and J. Xavier and F.A.M. Pereira and J.J.L. Morais and M.I.R. Dias and P.J. Louren{\c c}o and F.M. Judas} } @article {Silva201672, title = {Mixed-mode I+II fracture characterization of human cortical bone using the Single Leg Bending test}, journal = {Journal of the Mechanical Behavior of Biomedical Materials}, volume = {54}, year = {2016}, note = {n/a}, pages = {72-81}, abstract = {

Abstract Mixed-mode I+II fracture characterization of human cortical bone was analyzed in this work. A miniaturized version of the Single Leg Bending test (SLB) was used owing to its simplicity. A power law criterion was verified to accurately describe the material fracture envelop under mixed-mode I+II loading. The crack tip opening displacements measured by digital image correlation were used in a direct method to determine the cohesive law mimicking fracture behavior of cortical bone. Cohesive zone modeling was used for the sake of validation. Several fracture quantities were compared with the experimental results and the good agreement observed proves the appropriateness of the proposed procedure for fracture characterization of human bone under mixed-mode I+II loading.

}, keywords = {Fracture characterization, Human cortical bone, Mixed-mode I+II, Single Leg Bending test}, issn = {1751-6161}, doi = {http://dx.doi.org/10.1016/j.jmbbm.2015.09.004}, url = {http://www.sciencedirect.com/science/article/pii/S175161611500332X}, author = {F.G.A. Silva and de M.F.S.F. Moura and N. Dourado and J. Xavier and F.A.M. Pereira and J.J.L. Morais and M.I.R. Dias} } @article {Pinto2015635, title = {Comparative Failure Analysis of PLA, PLA/GNP and PLA/CNT-COOH Biodegradable Nanocomposites thin Films}, journal = {Procedia Engineering}, volume = {114}, year = {2015}, note = {

{\.I}CSI\} 2015 The 1st International Conference on Structural Integrity Funchal, Madeira, Portugal 1st to 4th September, 2015

}, pages = {635-642}, abstract = {

Abstract Biodegradable polymers such as poly(lactic) acid (PLA) have been studied for biomaterials applications such as natural human ligament replacement, however these materials could be applied to other sectors as aerospace, aeronautics, automotive, food packaging. \{PLA\} presents a relatively brittle with a mode I fracture behavior, being often blend with other biodegradable or non-degradable polymers to improve its fracture energy. For some existing applications, \{PLA\} components exhibit accumulated permanent deformation resulting from dynamic mechanical inputs, resulting on failure by laxity of parts. Aiming the improvement of \{PLA\} mechanical properties, the inclusion of carbon nanofillers into \{PLA\} matrix, in particular, CNT-COOH and \{GNP\} have been developed, due to their strong sp2 carbon-carbon bondings and their geometric arrangement that enhance mechanical properties of the polymer matrix. \{PLA\} and nanocomposites were produced by melt blending followed by compression molding in a hot press, with small weight percentages of nanofillers added to the matrix. Quasi static tensile tests were performed on a mechanical testing machine (Instron{\texttrademark} ElectroPuls E1000) along with failure analysis of specimens with centered crack with digital image correlation, revealing strain distribution along specimens.

}, keywords = {biodegradable nanocomposites, Biodegradable polymers, CNT-COOH, DIC, FTM, GNP, mechanical failure, PLA}, doi = {http://dx.doi.org/10.1016/j.proeng.2015.08.004}, url = {http://www.sciencedirect.com/science/article/pii/S1877705815016434}, author = {V.C. Pinto and Tiago Ramos and Sofia Alves and J. Xavier and Paulo Tavares and P.M.G.P. Moreira and Rui Miranda Guedes} } @article {Silva2015, title = {Fracture Characterization of Human Cortical Bone Under Mode I Loading}, journal = {Journal of Biomechanical Engineering}, volume = {137}, number = {12}, year = {2015}, note = {n/a}, pages = {121004-121004}, publisher = {ASME}, abstract = {

A miniaturized version of the double cantilever beam (DCB) test is used to determine the fracture energy in human cortical bone under pure mode I loading. An equivalent crack length based data-reduction scheme is used with remarkable advantages relative to classical methods. Digital image correlation (DIC) technique is employed to determine crack opening displacement at the crack tip being correlated with the evolution of fracture energy. A method is presented to obtain the cohesive law (trapezoidal bilinear softening) mimicking the mechanical behavior observed in bone. Cohesive zone modeling (CZM) (finite-element method) was performed to validate the procedure showing excellent agreement.

}, doi = {10.1115/1.4031846}, url = {http://dx.doi.org/10.1115/1.4031846}, author = {F. Silva and M. de Moura and N. Dourado and J. Xavier and Pereira, F. and Morais, J and Dias, M. and P. Louren{\c c}o and F. Judas} } @article {Dourado2015483, title = {A New Procedure for Mode I Fracture Characterization of Cement-Based Materials}, journal = {Strain}, volume = {51}, number = {6}, year = {2015}, note = {n/a}, pages = {483-491}, abstract = {

Fracture characterization under mode I loading of a cement-based material using the single-edge-notched beam loaded in tree-point-bending was performed. A new method based on beam theory and crack equivalent concept is proposed to evaluate the Resistance-curve, which is essential to determine fracture toughness with accuracy. The method considers the existence of a stress relief region in the vicinity of the crack, dispensing crack length monitoring during experiments. A numerical validation was performed by finite element analysis considering a bilinear cohesive damage model. Experimental tests were performed in order to validate the numerical procedure. Digital image correlation technique was used to measure the specimen displacement with accuracy and without interference. Excellent agreement between numerical and experimental load{\textendash}displacement curves was obtained, which validates the procedure.

}, keywords = {cement-based materials, cohesive zone modelling, fracture toughness, mode I loading, single-edge-notched test}, doi = {10.1111/str.12165}, url = {http://dx.doi.org/10.1111/str.12165}, author = {N. Dourado and de M.F.S.F. Moura and J. Xavier and F.A.M. Pereira} } @article {Silva201454, title = {Determination of cohesive laws in wood bonded joints under mode II loading using the ENF test}, journal = {International Journal of Adhesion and Adhesives}, volume = {51}, year = {2014}, note = {

n/a

}, pages = {54-61}, abstract = {

n/a

}, keywords = {Bonded joints, Cohesive laws, Digital Image Correlation, End notched flexure (ENF), Wood}, doi = {http://dx.doi.org/10.1016/j.ijadhadh.2014.02.007}, url = {http://dx.doi.org/10.1016/j.ijadhadh.2014.02.007}, author = {F.G.A. Silva and J.J.L. Morais and N. Dourado and J. Xavier and F.A.M. Pereira and de M.F.S.F. Moura} } @article {Pereira2014107, title = {Assessing wood quality by spatial variation of elastic properties within the stem: Case study of Pinus pinaster in the transverse plane}, journal = {Canadian Journal of Forest Research}, volume = {44}, number = {2}, year = {2014}, note = {n/a}, pages = {107-117}, abstract = {n/a}, author = {J. Pereira and J. Xavier and Morais, J and J. Lousada} } @article {Xavier2014142, title = {Characterisation of steel components under monotonic loading by means of image-based methods}, journal = {Optics and Lasers in Engineering}, volume = {53}, year = {2014}, note = {n/a}, pages = {142-151}, abstract = {n/a}, doi = {http://dx.doi.org/10.1016/j.optlaseng.2013.09.004}, url = {http://www.sciencedirect.com/science/article/pii/S0143816613002807}, author = {J. Xavier and J.C.R. Pereira and A.M.P. de Jesus} } @article {Pereira2014214, title = {Ultra low-cycle fatigue behaviour of a structural steel}, journal = {Engineering Structures}, volume = {60}, year = {2014}, note = {n/a}, pages = {214-222}, abstract = {n/a}, keywords = {Experimental techniques, Finite element modelling, Structural steel, Ultra low-cycle fatigue}, doi = {http://dx.doi.org/10.1016/j.engstruct.2013.12.039}, url = {http://www.sciencedirect.com/science/article/pii/S0141029614000030}, author = {J.C.R. Pereira and A.M.P. de Jesus and J. Xavier and A.A. Fernandes} } @article {Xavier2013423, title = {Characterisation of the bending stiffness components of MDF panels from full-field slope measurements}, journal = {Wood Science and Technology}, volume = {47}, number = {2}, year = {2013}, note = {n/a}, pages = {423-441}, abstract = {n/a}, doi = {10.1007/s00226-012-0507-6}, author = {J. Xavier and U. Belini and F. Pierron and Morais, J and J. Lousada and M. Tomazello} } @article {Fernandes201371, title = {Comparison between neural networks and partial least squares for intra-growth ring wood density measurement with hyperspectral imaging}, journal = {Computers and Electronics in Agriculture}, volume = {94}, year = {2013}, note = {n/a}, pages = {71-81}, abstract = {n/a}, doi = {10.1016/j.compag.2013.03.010}, author = {Fernandes, A. and J. Lousada and Morais, J and J. Xavier and J. Pereira and P. Melo-Pinto} } @article {Silva2013Holz, title = {Determination of cohesive laws in wood bonded joints under mode I loading using the DCB test.}, journal = {Holzforschung}, volume = {67}, number = {8}, year = {2013}, note = {n/a}, pages = {835-959}, abstract = {n/a}, doi = {http://dx.doi.org/10.1515/hf-2013-0012}, url = {http://www.degruyter.com/view/j/hfsg.2013.67.issue-8/hf-2013-0012/hf-2013-0012.xml}, author = {F. Silva and J. Xavier and F.A.M. Pereira and Morais, J and N. Dourado and de M.F.S.F. Moura} } @article {Fernandes201359, title = {Measurement of intra-ring wood density by means of imaging VIS/NIR spectroscopy (hyperspectral imaging)}, journal = {Holzforschung}, volume = {67}, number = {1}, year = {2013}, note = {n/a}, pages = {59-65}, abstract = {n/a}, doi = {10.1515/hf-2011-0258}, author = {Fernandes, A. and J. Lousada and Morais, J and J. Xavier and J. Periera and P. Melo-Pinto} } @article {Xavier2012207, title = {Stereovision measurements on evaluating the modulus of elasticity of wood by compression tests parallel to the grain}, journal = {Construction and Building Materials}, volume = {26}, number = {1}, year = {2012}, note = {n/a}, pages = {207-215}, abstract = {n/a}, doi = {10.1016/j.conbuildmat.2011.06.012}, author = {J. Xavier and A.M.P. de Jesus and J.J.L. Morais and J.M.T. Pinto} } @article {Morais2010446, title = {The double cantilever beam test applied to mode I fracture characterization of cortical bone tissue}, journal = {Journal of the Mechanical Behavior of Biomedical Materials}, volume = {3}, number = {6}, year = {2010}, note = {

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}, pages = {446-453}, abstract = {

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}, doi = {doi:10.1016/j.jmbbm.2010.04.001}, author = {J.J.L. Morais and de M.F.S.F. Moura and F.A.M. Pereira and J. Xavier and N. Dourado and M.I.R. Dias and J.M.T. Azevedo} } @article {Xavier2009217, title = {Measurement of the shear properties of clear wood by the Arcan test}, journal = {Holzforschung}, volume = {63}, number = {2}, year = {2009}, note = {n/a}, pages = {217-225}, abstract = {n/a}, doi = {10.1515/HF.2009.034}, author = {J. Xavier and Oliveira, M. and Morais, J and Pinto, J.} } @article {Xavier2009b, title = {Variation of transverse and shear stiffness properties of wood in a tree}, journal = {Composites Part A: Applied Science and Manufacturing}, volume = {40}, number = {12}, year = {2009}, note = {n/a}, pages = {1953-1960}, abstract = {n/a}, doi = {10.1016/j.compositesa.2009.09.023}, author = {J. Xavier and S. Avril and F. Pierron and Morais, J} } @article {Xavier2007, title = {Novel experimental approach for longitudinal-radial stiffness characterisation of clear wood by a single test}, journal = {Holzforschung}, volume = {61}, number = {5}, year = {2007}, note = {n/a}, pages = {573-581}, abstract = {n/a}, doi = {10.1515/HF.2007.083}, author = {J. Xavier and S. Avril and F. Pierron and Morais, J} } @article {Xavier2004, title = {A comparison between the Iosipescu and off-axis shear test methods for the characterization of {\i}t Pinus pinaster Ait.}, journal = {Composites Part A: Applied Science and Manufacturing}, volume = {35}, number = {7-8}, year = {2004}, note = {

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}, pages = {827-840}, abstract = {

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}, doi = {doi:10.1016/j.compositesa.2004.01.013}, author = {J.C. Xavier and N.M. Garrido and Oliveira, M. and J.L. Morais and P.P. Camanho and F. Pierron} }