#1Chen Xing(NUAA: Nanjing University of Aeronautics and Astronautics)H-Index: 1
#2Chuwei Zhou(NUAA: Nanjing University of Aeronautics and Astronautics)H-Index: 7
Abstract A combination of sub-partition and substructure methods in finite element is developed to simulate the crack propagation in plate and shell structures. This method allows modeling arbitrary shape crack independent of element mesh and only the elements overlapping crack need to be operated. An element cut apart by a crack is sub-partitioned into ordinary sub-elements while an element enveloping crack tip is sub-partitioned into several singular sub-elements. The whole sub-elements consti...
Fatigue is one of the main causes of failures in mechanical and structural systems. Offshore installations, in particular, are susceptible to fatigue failure due to their exposure to the combination of wind loads, wave loads and currents. In order to assess the safety of the components of these installations, the expected lifetime of the component needs to be estimated. The fatigue life is the sum of the number of loading cycles required for a fatigue crack to initiate, and the number of cycles ...
An overview of integrity management of offshore structures, with emphasis on the oil and gas energy sector, is given. Based on relevant accident experiences and means to control the associated risks, accidents are categorized from a technical-physical as well as human and organizational point of view. Structural risk relates to extreme actions as well as structural degradation. Risk mitigation measures, including adequate design criteria, inspection, repair and maintenance as well as quality ass...
Last. Ivar Langen(University of Stavanger)H-Index: 7
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Abstract The structural integrity assessment of ageing structures for possible life extension has been identified as a growing challenge in the oil and gas industry worldwide. Although the available guidelines provide a general assessment process, it is necessary to have more detailed guidelines. This can be achieved by adding relevant theories and models which can capture time-dependent structural degradation more precisely. To address this, a new framework for possible life extension is propos...
Abstract The linear elastic fracture mechanics (LEFM) based remnant fatigue life (RFL) assessment of offshore pipeline is used to determine the inspection interval frequency of the aforementioned asset. One of the vital factors of the LEFM approach that determines the accuracy of the RFL estimate (and in turn of the inspection interval frequency) is the Stress Intensity Factor (SIF), which must be evaluated as accurately as possible. For simple crack geometries numerous closed-form equations ava...
Last. Fabio Scenini(University of Manchester)H-Index: 17
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Abstract This paper reports the results of an extensive series of finite element calculations to provide normalised T-stress solutions for through-wall cracked pipes under bending for a range of crack sizes and pipe radius to wall thickness ratios. Comparisons with the limited solutions in the literature are used to give confidence in the numerical solutions obtained, which are shown to be sensitive to mesh refinement. The results are provided in a form that is suitable for use in practical cons...
Abstract This study aims to experimentally investigate fatigue growth behaviour in AA7075-T651 under proportional and non-proportional mixed mode I and II loads. Fatigue tests were performed under cyclic tension and torsion using a thin-walled tubular specimen with a key-hole style crack starter. After the generation of a single-side mode I pre-crack, varied forms of mixed mode loads were applied, which in most cases led to coplanar growth for a short distance followed by a long and stable crack...
Last. A. Deylami(AUT: Amirkabir University of Technology)H-Index: 7
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Abstract In this study a cylindrical cracked aluminium pipe is considered. Fatigue crack growth behaviour of the pipe is observed through experimental tests. Stress intensity factors are computed for the pipe with an inclined crack under axial tensile load. Fatigue crack trajectory and also the crack growth curves versus number of cycles of load, are extracted. Validation of results is then achieved through the extended finite element method (XFEM). A stand-alone MATLAB programming package is de...
When a crack is detected in a piping line during in-service inspections, failure estimation method provided in ASME Boiler and Pressure Vessel Code Section XI or JSME Rules on Fitness-for-Service for Nuclear Power Plants can be applied to evaluate the structural integrity of the cracked pipe. The failure estimation method in the current codes accounts for the bending moment and axial force due to pressure. The torsion moment is not considered.Recently, analytical investigations have been carried...
Abstract In this study, a systematic three-dimensional finite element analyses (3D FEA) are performed to evaluate the Mode II stress intensity factor (SIF) for circumferential through-wall cracked pipe under torsion moment. A wide range of crack lengths and pipe radius over thickness ratios are considered. Empirical solution of the mid-thickness Mode II SIF is developed as functions of crack lengths and pipe sizes. The deviating angle and the effective SIF regarding a through-wall crack (TWC) un...
An increasing number of the offshore structures in the North Sea are being operated in a life extension phase, which means that their original design life has been exceeded. As the structures age, they are deteriorating, mainly due to fatigue and corrosion. In order to ensure that the structural integrity is maintained during the life extension phase, the remaining fatigue life of the structures needs to be assessed. While simple and conservative approximations are used in fatigue design, it wil...
Abstract Environmental loads acting on structures usually cause fatigue crack propagation under variable amplitude mixed-mode conditions. In order to better estimate the remaining fatigue life, the fatigue crack growth behaviour under these conditions needs to be studied. In this paper, an experimental study where mixed-mode I and II overloads are applied to a fatigue crack propagating under mixed-mode I and II constant amplitude loading, is presented. The overloads are found to cause fatigue cr...
Abstract In this paper, the optical method of transmitted caustics is extended to study the stress singularity at the tip of a circumferential crack in a PMMA cylindrical shell. First, a new theoretical analysis of light path is presented based on local deformations around the circumferential crack tip and geometry condition of the cylindrical shell. Second, governing equations of transmitted caustics are established, and the effects of material properties, radius of curvature, shell thickness a...