The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform

K.f. Wang - One of the best experts on this subject based on the ideXlab platform.

A.b. De Morais - One of the best experts on this subject based on the ideXlab platform.

  • Analysis of the metal adhesively bonded double cantilever Beam specimen
    International Journal of Adhesion and Adhesives, 2015
    Co-Authors: A.b. De Morais
    Abstract:

    Abstract The double cantilever Beam specimen is currently standardized for measuring the mode I fracture energy of adhesive joints. In addition, it has been increasingly employed to evaluate the adhesive traction-separation law by the direct method, which involves crack tip separation measurements. The three-dimensional finite element analyses here conducted showed that significant anticlastic deformations of the metal adherends compromise the accuracy of the direct method in the elastic domain. It was also seen that the adherend plane stress and adhesive uni-axial strain hypotheses are adequate for the typical specimen geometries. Finally, the new elastic crack length correction derived from a Beam model can be used to predict accurately the initial specimen compliance, to obtain conservative fracture energy values and to gain additional insight into the adhesive fracture behaviour.

  • Beam analysis of the double cantilever Beam specimen with fibre bridging
    Journal of Composite Materials, 2014
    Co-Authors: A.b. De Morais
    Abstract:

    The fibre bridging phenomenon commonly seen in double cantilever Beam tests is considered an artifact of the standard unidirectional specimen. Therefore, it limits the scope of the test to the measurement of the critical strain energy release rate GIc for crack initiation. This paper presents a Beam model based on a linear traction–separation law that has been shown to be a good approximation to the early stages of fibre bridging. The present model enables the evaluation of accurate propagation GIc values through the fitting of experimental load–displacement curves. Furthermore, fairly good fits can be obtained without employing sophisticated optimization algorithms by considering simple relations between model parameters and curve features. Therefore, the present model is able to extract a broader set of results from a single test, thereby increasing the confidence in toughness measurements.

  • A new fibre bridging based analysis of the Double Cantilever Beam (DCB) test
    Composites Part A-applied Science and Manufacturing, 2011
    Co-Authors: A.b. De Morais
    Abstract:

    Abstract A new analysis was developed for the Double Cantilever Beam (DCB) test. Its main objective is to compute mode I critical strain energy release rates G Ic unaffected by fibre bridging. In fact, the latter phenomenon often observed in standard unidirectional specimens is not considered representative of most structural applications. The analysis developed applies a relatively simple numerical procedure to experimental load–displacement data for the initial crack propagation stages. Moreover, it does not require monitoring crack propagation during the tests. Application to experimental data for carbon and glass fibre composites gave consistent propagation G Ic that were similar to initiation values, thereby supporting the main assumptions of the proposed model.

  • Double cantilever Beam testing of multidirectional laminates
    Composites Part A-applied Science and Manufacturing, 2003
    Co-Authors: A.b. De Morais
    Abstract:

    Abstract Several difficulties in the double cantilever Beam (DCB) tests of multidirectional laminates often prevent valid measurements of the mode I critical strain energy release rate G Ic . In this paper, several DCB specimens were analysed with 3D finite element models. The results showed that the undesired effects of residual stresses and of mode-mixity can be minimised. An interlaminar stress based fracture criterion predicts that the G Ic of multidirectional specimens is typically 10–40% higher than the G Ic of unidirectional [0°] n laminates. This agrees with the few valid experimental data available.

  • Analysis of crack propagation in double cantilever Beam tests of multidirectional laminates
    Mechanics of Materials, 2003
    Co-Authors: A.b. De Morais, J P M Goncalves, M.f.s.f. De Moura, Pedro P. Camanho
    Abstract:

    Abstract This paper presents numerical analyses of crack propagation in double cantilever Beam (DCB) tests of multidirectional laminates. Three-dimensional finite element models were used for application of the virtual crack closure technique and for simulation of crack growth with a progressive damage model. The analyses were concerned with three features that may affect the measurements of the mode I critical strain energy release rate G Ic : residual stresses, mode-mixity and curved delamination fronts. The results showed that the effects of those features could be minimised by a proper selection of specimen stacking sequences. The suitability of other DCB specimens proposed in the literature to avoid intralaminar damage and crack jumping was also evaluated.

M.f.s.f. De Moura - One of the best experts on this subject based on the ideXlab platform.

  • Estimate of resistance-curve in wood through the double cantilever Beam test
    Holzforschung, 2010
    Co-Authors: N Dourado, M.f.s.f. De Moura, José Morais, M.a.l. Silva
    Abstract:

    Numerical and experimental studies involving the double cantilever Beam test to estimate the resistance-curve under mode I loading in wood (Pinus pinaster Ait. – RL fracture system) are presented. Two data reduction schemes based on the specimen compliance and crack equivalent concept are proposed to obtain accurate values of fracture energy. The methods do not require crack length monitoring and mitigate the influence of scatter of wood elastic properties on the measured fracture energy. A finite element analysis to validate the proposed methodologies was performed. Good agreement was achieved in both cases, especially for one case. Experimental tests were also carried out to determine the fracture energy of this wood species. Application of both data reduction schemes provided consistent values.

  • a new data reduction scheme for mode i wood fracture characterization using the double cantilever Beam test
    Engineering Fracture Mechanics, 2008
    Co-Authors: M.f.s.f. De Moura, J J L Morais, N Dourado
    Abstract:

    This paper describes experimental and numerical studies on double cantilever Beam test applied to fracture characterization of wood in mode I. A new data reduction scheme based on the Beam theory and specimen compliance is proposed in order to overcome the difficulties inherent to crack monitoring during propagation. A cohesive damage model adapted to wood is used to simulate the test. The cohesive properties are evaluated using an inverse method based on a developed Genetic Algorithm through an optimisation strategy. The results demonstrate the effectiveness of the proposed methodology as a suitable data reduction scheme for the double cantilever Beam test.

  • Analysis of crack propagation in double cantilever Beam tests of multidirectional laminates
    Mechanics of Materials, 2003
    Co-Authors: A.b. De Morais, J P M Goncalves, M.f.s.f. De Moura, Pedro P. Camanho
    Abstract:

    Abstract This paper presents numerical analyses of crack propagation in double cantilever Beam (DCB) tests of multidirectional laminates. Three-dimensional finite element models were used for application of the virtual crack closure technique and for simulation of crack growth with a progressive damage model. The analyses were concerned with three features that may affect the measurements of the mode I critical strain energy release rate G Ic : residual stresses, mode-mixity and curved delamination fronts. The results showed that the effects of those features could be minimised by a proper selection of specimen stacking sequences. The suitability of other DCB specimens proposed in the literature to avoid intralaminar damage and crack jumping was also evaluated.

Baolin Wang - One of the best experts on this subject based on the ideXlab platform.

Zhong Chen - One of the best experts on this subject based on the ideXlab platform.

  • INTERFACE FRACTURE TOUGHNESS ASSESSMENT OF SOLDER JOINTS USING DOUBLE CANTILEVER Beam TEST
    International Journal of Modern Physics B, 2010
    Co-Authors: Natalia Yantara, Zhong Chen
    Abstract:

    In the current work, a test scheme to evaluate solder joint interface fracture toughness using double cantilever Beam (DCB) test has been successfully demonstrated. The obtained results, in terms of critical energy release rate, predict the joint failure based on the principle of fracture mechanics. The results can be used as a materials property in the reliability design of various types of solder-ball joined packages. DCB specimens made of 99.9 wt% copper were selected in the current work. Eutectic Sn-37Pb and lead-free Sn-3.5Ag-0.5Cu solders were used to join two pieces of the copper Beams with controlled solder thickness. The test record showed steady propagation of the crack along the solder / copper interface, which verifies the viability of such a testing scheme. Interface fracture toughness for as-joined, extensively-reflowed and thermally aged samples has been measured. Both the reflow treatment and the thermal aging lead to degradation of the solder joint fracture resistance. Reflow treatment was more damaging as it induces much faster interface reaction. Fractographic analysis established that the fracture has a mixed micromechanism of dimple and cleavage. The dimples are formed as a result of the separation between the hard intermetallic compound (IMC) particles and the soft solder material, while the cleavage is formed by the brittle split of the IMCs. When the IMC thickness is increased due to extended interface reaction, the proportion of IMC cleavage failure increases, and this was reflected in the decrease of the critical energy release rate.

  • The essential work of fracture and JR curves for the double cantilever Beam specimen: an examination of elastoplastic crack propagation
    Proceedings of The Royal Society A: Mathematical Physical and Engineering Sciences, 1998
    Co-Authors: A. G. Atkins, Zhong Chen, Brian Cotterell
    Abstract:

    The propagation of a crack in a Double-Cantilever Beam (DCB) geometry where there is extensive remote plastic flow both preceding and accompanying fracture is analysed. Experiments show that there ...