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2018
Pereira, F. A. M., M. F. S. F. de Moura, N. Dourado, J. J. L. Morais, J. Xavier, and M. I. R. Dias. "Determination of mode II cohesive law of bovine cortical bone using direct and inverse methods." International Journal of Mechanical Sciences. 138-139 (2018): 448-456. AbstractWebsite

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.

2017
Pereira, F. A. M., M. F. S. F. de Moura, N. Dourado, J. J. L. Morais, J. Xavier, and M. I. R. Dias. "Direct and inverse methods applied to the determination of mode I cohesive law of bovine cortical bone using the DCB test." International Journal of Solids and Structures. 128 (2017): 210-220. AbstractWebsite

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.

Silva, F. G. A., M. F. S. F. de Moura, N. Dourado, J. Xavier, F. A. M. Pereira, J. J. L. Morais, M. I. R. Dias, P. J. Lourenço, and F. M. Judas. "Fracture characterization of human cortical bone under mode II loading using the end-notched flexure test." Medical {&} Biological Engineering {&} Computing. 55 (2017): 1249-1260. AbstractWebsite

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.

2016
Silva, F. G. A., M. F. S. F. de Moura, N. Dourado, J. Xavier, F. A. M. Pereira, J. J. L. Morais, and M. I. R. Dias. "Mixed-mode I+II fracture characterization of human cortical bone using the Single Leg Bending test." Journal of the Mechanical Behavior of Biomedical Materials. 54 (2016): 72-81. AbstractWebsite

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.

2015
Silva, F., M. de Moura, N. Dourado, J. Xavier, F. Pereira, J. Morais, M. Dias, P. Lourenço, and F. Judas. "Fracture Characterization of Human Cortical Bone Under Mode I Loading." Journal of Biomechanical Engineering. 137 (2015): 121004. AbstractWebsite

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.

Dourado, N., M. F. S. F. de Moura, J. Xavier, and F. A. M. Pereira. "A New Procedure for Mode I Fracture Characterization of Cement-Based Materials." Strain. 51 (2015): 483-491. AbstractWebsite

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–displacement curves was obtained, which validates the procedure.

2014
Silva, F. G. A., J. J. L. Morais, N. Dourado, J. Xavier, F. A. M. Pereira, and M. F. S. F. de Moura. "Determination of cohesive laws in wood bonded joints under mode II loading using the ENF test." International Journal of Adhesion and Adhesives. 51 (2014): 54-61. AbstractWebsite

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Xavier, J., P. Monteiro, J. J. L. Morais, N. Dourado, and M. F. S. F. de Moura. "Moisture content effect on the fracture characterisation of Pinus pinaster under mode I." Journal of Materials Science. 49 (2014): 7371-7381. AbstractWebsite
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2013
Dias, G. F., M. F. S. F. de Moura, J. A. G. Chousal, and J. Xavier. "Cohesive laws of composite bonded joints under mode I loading." Composite Structures. 106 (2013): 646-652. Abstract
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Silva, F., J. Xavier, F. A. M. Pereira, J. Morais, N. Dourado, and M. F. S. F. de Moura. "Determination of cohesive laws in wood bonded joints under mode I loading using the DCB test." Holzforschung. 67 (2013): 835-959. AbstractWebsite
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2011
Xavier, J., J. Morais, N. Dourado, and M. F. S. F. de Moura. "Measurement of mode I and mode II fracture properties of wood-bonded joints." Journal of Adhesion Science and Technology. 25 (2011): 2881-2895. Abstract
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2010
Morais, J. J. L., M. F. S. F. de Moura, F. A. M. Pereira, J. Xavier, N. Dourado, M. I. R. Dias, and J. M. T. Azevedo. "The double cantilever beam test applied to mode I fracture characterization of cortical bone tissue." Journal of the Mechanical Behavior of Biomedical Materials. 3 (2010): 446-453. Abstract

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Catalanotti, G., P. P. Camanho, J. Xavier, C. G. Dávila, and AT Marques. "Measurement of resistance curves in the longitudinal failure of composites using digital image correlation." Composites Science and Technology. 70 (2010): 1986-1993. Abstract
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