Zhongmin Xiao¹, Wengang Zhang², Yanmei Zhang^{1, *}, Mu Fan³

CMC-Computers, Materials & Continua, Vol.62, No.1, pp. 267-280, 2020, DOI:10.32604/cmc.2020.06567

Abstract Fluctuated loadings from currents, waves and sea ground motions are observed on offshore steel pipelines, and they will result in small cracks to propagate continuously and cause unexpected damage to offshore/geotechnical infrastructures. In spite of the availability of efficient techniques and high-power computers for solving crack problems, investigations on the fatigue life of offshore pipelines with 3D interacting cracks are still rarely found in open literature. In the current study, systematic numerical investigations are performed on fatigue crack growth behaviours of offshore pipelines containing coplanar and non-coplanar cracks. Extended finite element method (XFEM) is adopted to simulate the fatigue crack… More >

Perissé P¹ y GM Tourn²

Phyton-International Journal of Experimental Botany, Vol.84, No.1, pp. 184-189, 2015, DOI:10.32604/phyton.2015.84.184

Abstract The morphological characteristics of the seeds of Vicia dasycarpa Ten. cv. Tolse FCA were studied in relation to the area of imbibition water entry and were considered the presence of areoles. Seeds were analyzed using a stereo, optical and scanning electron microscope (SEM). The determination of the initial water entry area was carried out by immersing the seeds in a solution of tetrazolium (1%). This study showed that this species has seeds with a halo framing the hilum, an inconspicuous dry aril and a deltoid micropyle. The seedcoat pattern is papillose. The tracheid bar is surrounded by a ring of… More >

Zhanqi Cheng¹, Dongdong Jin¹, Chengfang Yuan¹, Le Li^1,*

CMES-Computer Modeling in Engineering & Sciences, Vol.121, No.2, pp. 445-464, 2019, DOI:10.32604/cmes.2019.06374

Abstract In the research, the dynamic fracture failure problem of functionally graded materials (FGMs) containing two pre-cracks was analyzed using a bond-based Peridynamic (PD) method numerical model. The two convergence of decreasing the area of PD horizon (δ-convergence) and uniform mesh refinement (m-convergence) were studied. The effects of both crack position and distance between two cracks on crack propagation pattern in FGMs plate under tensile loads are studied. Furthermore, the effects of different gradient patterns on the dynamic propagation of cracks in FGMs are also investigated. The simulate results suggest that the cracks positions and the distance between them can significantly… More >

G. Dhondt¹, D. Bremberg²

Structural Durability & Health Monitoring, Vol.6, No.3&4, pp. 305-328, 2010, DOI:10.3970/sdhm.2010.006.305

Abstract In a previous article the K-distritubion along the crack front of several mixed-mode specimens was investigated [Dhondt, Chergui, and Buchholz (2001)]. Both the modified virtual crack closure integral method and the quarter point element stress field method yielded results close to the available reference solutions in the literature [Murakami (1987)]. The present paper extends these results in two aspects. First, the meshing procedure used to obtain a focused mesh at the crack front is modified in order to deal with highly curved cracks. Secondly, the K-distribution along the initial crack is used to perform a crack propagation calculation. The form… More >

H. Theilig¹

Structural Durability & Health Monitoring, Vol.6, No.3&4, pp. 239-272, 2010, DOI:10.3970/sdhm.2010.006.239

Abstract The aim of this paper is to give an overview to some problems and solutions of the fracture analysis of 2D structures. It will be shown that the common computer-aided two-dimensional fatigue crack path simulation can be considerably improved in accuracy by using a predictor-corrector procedure in combination with the modified virtual crack closure integral (MVCCI) method. Furthermore the paper presents an improved finite element technique for the calculation of stress intensity factors of mixed mode problems by the MVCCI Method. The procedure is devised to compute the separated strain energy release rates by using the convergence of two separate… More >

Pullela Mythravaruni¹, Konstantin Volokh^1,*

Molecular & Cellular Biomechanics, Vol.16, Suppl.2, pp. 87-87, 2019, DOI:10.32604/mcb.2019.07274

Abstract We present a theoretical approach to study the onset of failure localization into cracks in arterial wall. The arterial wall is a soft composite comprising hydrated ground matrix of proteoglycans reinforced by spatially dispersed elastin and collagen fibers. As any material, the arterial tissue cannot accumulate and dissipate strain energy beyond a critical value. This critical value is enforced in the constitutive theory via energy limiters. The limiters automatically bound reachable stresses and allow examining the mathematical condition of strong ellipticity. Loss of the strong ellipticity physically means inability of material to propagate superimposed waves. The waves cannot propagate because… More >

G. Savaidis¹, M. Malikoutsakis¹, A. Jagenbrein², A. Savaidis³, M. Soare⁴, M.V. Predoi⁴, A. Soare⁴, I.C. Diba⁴

Structural Durability & Health Monitoring, Vol.9, No.2, pp. 129-154, 2013, DOI:10.32604/sdhm.2013.009.129

Abstract Development of corrosion or/and fatigue crack propagation are the most common causes of structural degradation in road and railway tank vessels. An acoustic emission based monitoring procedure in conjunction with follow-up nondestructive testing is here proposed as a promising alternative to the conventional inspection processes enabling continuous health monitoring of the tank structures. Thereby, finite element analysis taking the respective ADR and RID tank design loads into account is proposed as a capable tool to be applied in early stages of development to reveal the hot spot areas, where acoustic emission sensors have to be positioned. The developed health monitoring… More >

S. Hadidi-Moud^1,2, H. Makari¹

Structural Durability & Health Monitoring, Vol.6, No.2, pp. 113-122, 2010, DOI:10.3970/sdhm.2010.006.113

Abstract A comprehensive numerical study has been carried out to investigate and to explore the impact of the presence of part through surface cracks of various size and orientation in a thick welded ferritic steel cylindrical vessel, on the beneficial effect of autofrettage loading. It is well known that autofrettage loading enhances the load carrying capacity of defect free pressure vessels. The results of this study suggest that in presence of cracks, the localised near crack tip residual stress fields interact with in service stresses and influence the enhancement in load carrying capacity of autofrettaged vessel. Furthermore it is concluded that… More >

J. Toribio¹, J.C. Matos², B. González¹, J. Escuadra²

Structural Durability & Health Monitoring, Vol.5, No.1, pp. 57-72, 2009, DOI:10.3970/sdhm.2009.005.057

Abstract In this paper an automatic (analytical-numerical) procedure is proposed to model the front of a transverse surface crack located in the circular section of a lineal structural element (wire, cable, strand, rod, shaft,..., i.e., a cylindrical geometry) by means of a fitting ellipse, obtaining the ellipse parameters from a series of points in therealcrack front and adjusting them to thetheoreticalfitting ellipse by a least square method. For symmetric cracks two modelling procedures are formulated: (i) in the first one, a fitting ellipse is used wit its centre belonging to the periphery of the circular section of the cylinder; (ii) in… More >

B. M. Singh, J. Rokne, R. S. Dhaliwal¹

Structural Durability & Health Monitoring, Vol.4, No.2, pp. 95-106, 2008, DOI:10.3970/sdhm.2008.004.095

Abstract Under the permeable electric boundary condition the problem of two collinear anti-plane shear cracks situated at the interface of two bonded dissimilar piezoelectric layers is considered. It is assumed that applied longitudinal shear stress and electric loading at the layer surfaces are prescribed. By the use of Fourier transforms we reduce the problem to solving a set of triple integral equations with a cosine kernel. The triple integral equations are further reduced to a Fredholm integral equation of the second kind whose iterative solution has been obtained. Analytical expressions for the stress intensity factors are obtained. Numerical results are presented… More >