Journal Sciences News
Theoretical and Applied Fracture Mechanics
August 2018
Flutter of multi-cracked laminated composite beams subjected to a non-conservative compressive load
Publication date: August 2018
Source:Engineering Fracture Mechanics, Volume 199 Author(s): H. Alidoost, J. Rezaeepazhand Free vibration and buckling instability of laminated composite beams and flutter instability of an isotropic beam with different defects have been investigated before, however, still dynamic stability of laminated composite beam with weak section subjected to follower forces has not considered. This paper presents a simple semi-analytical solution to the flutter instability of a laminated composite beam with multi open-edge cracks subjected to a tip follower force. Using classical lamination theory and Euler-Bernoulli beam theory, equation of motion of the beam is derived analytically and characteristic eigenvalue equations of the cracked laminated composite beam are obtained. A Matlab® code is used to solve these equations numerically. After validating the results, a numerical study is performed to investigate the effect of crack depth and stacking sequences on the dynamic stability of the cracked beam.
August 2018
An interaction factor to estimate the over-constraining effect in plates with co-planar cracks
Publication date: August 2018
Source:Engineering Fracture Mechanics, Volume 199 Author(s): Teik Tian Seah, Xudong Qian This paper reports an over-constraining effect on the near-tip stress field caused by the presence of a nearby coplanar crack, through detailed numerical investigations. The crack driving force, measured by the leading term in the near-tip stress solution, underestimates the stresses near the coplanar crack fronts. This study thus proposes a crack interaction factor based on the average Q-stress over a finite distance from the crack tip. The proposed interaction factor provides a close estimate of the near-tip stress for the coplanar cracks, and predicts successfully the interaction among coplanar elliptical crack-front locations, using an equivalent through-thickness coplanar crack model.
August 2018
Fatigue life prediction of nickel-based GH4169 alloy on the basis of a multi-scale crack propagation approach
Publication date: August 2018
Source:Engineering Fracture Mechanics, Volume 199 Author(s): Shen Ye, Cheng-Cheng Zhang, Peng-Yue Zhang, Xian-Cheng Zhang, Shan-Tung Tu, Run-Zi Wang This paper was concerned with an approach to predict fatigue life based on a multi-scale crack propagation model. The expressions of crack propagation rates in microstructurally small crack (MSC), physically small crack (PSC) and long crack (LC) stages were unified in the multi-scale crack propagation model. Its integral form presented a fatigue life prediction approach. The nickel-based GH4169 alloy was employed to validate the prediction capacity of present approach. The prediction results of lives of specimens with different initial defects sizes were compared with the experimental data.
August 2018
An efficient FE-implementation of implicit gradient-enhanced damage models to simulate ductile failure
Publication date: August 2018
Source:Engineering Fracture Mechanics, Volume 199 Author(s): Andreas Seupel, Geralf H
August 2018
Effect of fiber orientation on Mode-I delamination resistance of glass/epoxy laminates incorporated with milled glass fiber fillers
Publication date: August 2018
Source:Engineering Fracture Mechanics, Volume 199 Author(s): K. Saravanakumar, Nibras Farouk, V. Arumugam The present work is focused on improving the Mode-I delamination resistance of glass/epoxy composite laminates with milled glass fiber fillers. The influence of the interface fiber orientation and also the effect of fillers on the Mode-I interlaminar fracture toughness was experimentally investigated and the results were correlated with the baseline glass/epoxy samples. It was observed that the dispersion of milled glass fiber fillers by weight of 5% of the epoxy matrix into the resin rich domain improved the fracture toughness efficiently, in all the cases of interface fiber orientation. This improvement in interlaminar fracture toughness was due to additional toughening mechanisms through crack deflection, filler debonding, filler interlocking/bridging and filler pullout. The results showed that incorporation of milled glass fiber filler enhanced the GIC Initiation and GIC Propagation fracture toughness by 102% and 50% in 0–0° interply orientations over the baseline glass/epoxy samples. Besides, fracture surface analysis of the samples using Scanning Electron Microscope (SEM) indicates that the different damage mechanisms correspond to the deviation in fracture toughness.
August 2018
A Voronoi element based-numerical manifold method (VE-NMM) for investigating micro/macro-mechanical properties of intact rocks
Publication date: August 2018
Source:Engineering Fracture Mechanics, Volume 199 Author(s): Quansheng Liu, Yalong Jiang, Zhijun Wu, Jun He In this study, a two-dimensional Voronoi element based-numerical manifold method (VE-NMM) was developed as a new approach to investigate the micro- and macro- mechanical properties of intact rocks. The Voronoi technique was used to generate a polygonal grain assemblage to approximate the microstructure of sandstone samples from Gubei colliery of Huainan mining area in China. A modified contact model incorporating cohesion and tensile strength was adopted to interpret the interactions between rock grains. A series of laboratory tests, i.e. scanning electron microscope tests, uniaxial compression and Brazilian tests were carried out to obtain the microstructural information and macro-mechanical properties of the sandstone samples. To verify the proposed VE-NMM, simulations of Brazilian tensile splitting and uniaxial compressive tests were carried out and the results, in terms of strength, elastic constant and crack distribution, were compared to those of the laboratory tests. To investigate the effects of grain size on the micro-mechanical parameters and the representative elementary volume (REV) size, numerical uniaxial compression tests with different grain sizes (2mm, 3
August 2018