scholarly journals Analysis of the limit states of ship composite shafts using numerical models

2020 ◽  
pp. 89-96
Author(s):  
В.А. Коршунов ◽  
Д.А. Пономарев ◽  
А.А. Родионов
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Nonlinear Analysis ◽  
Numerical Models ◽  
Multilayer Shell ◽  
Homogeneous Material ◽  
Limit States ◽  
Initial Imperfections ◽  
Model Based ◽  
Shell Finite Element

В работе продемонстрированы возможности применения МКЭ для исследования процессов деформирования судовых валов, выполненных из композитных материалов, для анализа предельных состояний. Рассмотрены конечно-элементные модели композитных валов на основе многослойного оболочечного и многослойного твердотельного элемента, а также модель с гомогенным представлением материала. Анализ несущей способности композитного вала выполнен в линейной и нелинейной постановках при действии крутящего момента. Результаты линейного анализа показали, что наименьшую погрешность с экспериментальным и данными имеет модель на основе многослойного оболочечного конечного элемента. Нелинейный анализ выполнен с учетом геометрической нелинейности и начальных несовершенств геометрии вала. Начальные несовершенства определены масштабированием первой формы линейной потери устойчивости. В результате нелинейного анализа получены кривые нагружения, характеризующие зависимость крутящего момента от угла поворота сечения вала и определяющие предельные нагрузки. Полученные значения предельных нагрузок всех рассматриваемых моделей вала близки к экспериментальными данными. По результатам работы рекомендуется в качестве оптимальной модели, для анализа напряженно-деформированного состояния и предельных состояний тонких композитных валов, использовать модель, на основе многослойного оболочечного конечного элемента. The paper demonstrates the possibility of using FEM to study the processes of deformation of ship composite shafts for the analysis of limiting states. Finite element models of composite shafts based on a multilayer shell and multilayer solid element, as well as a model with a homogeneous material representation, are considered. The analysis of the bearing capacity of the composite shaft is carried out in linear and non-linear formulations under the action of a torque. The results of linear analysis showed that the model based on a multilayer shell finite element has the smallest error with experimental data. Nonlinear analysis is performed taking into account geometric nonlinearity and initial imperfections of the shaft geometry. The initial imperfections are determined by scaling the first form of linear buckling. As a result of nonlinear analysis, loading curves were obtained that characterize the dependence of the torque on the angle of rotation of the shaft section and determine the ultimate loads. The obtained values of the ultimate loads of all the considered shaft models are close to the experimental data. Based on the results of the work, it is recommended to use a model based on a multilayer shell finite element as an optimal model for analyzing the stress-strain state and limit states of thin composite shafts.

Cemented Wellbore Experiments Reveals That Cement Interface Debonding Modeling Overestimate Potential Leakage Rates

2020 ◽  
Author(s):  
Zachary Speer ◽  
Jarrett Wise ◽  
Runar Nygaard ◽  
Geir Hareland ◽  
Eric Ford ◽  
...  
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Numerical Models ◽  
Interface Debonding ◽  
Finite Element Models ◽  
Wellbore Integrity ◽  
Cement Interface ◽  
Abandoned Wells ◽  
Numerical Finite Element ◽  
Physical And Chemical

Abstract Leakage pathways may develop in wellbores during construction, production, or during and after plug and abandonment (P&A). These pathways are created due to events and conditions during cementing operations, or because of physical and chemical changes after cementing such as changes in temperature and wellbore pressures, and deterioration of the cement. Common leakage pathways develop inside the cement sheath, or as microannuli along the cement-tubing interface. Numerous evidence exists showing that wellbores leak, but there is no verified method to determine if a well will leak or not. To ensure long term wellbore integrity, leakage risks need to be evaluated for plugged and abandoned wells. To evaluate leakage risks from plugged and abandoned wells, numerical finite element models have been developed and used to investigate leakage scenarios during the life of the well. Currently, little work has been done to verify finite element numerical models with experimental data regarding flowpath size in cement sheaths. The aim of this paper is to model previously published experimental data to determine if the finite element models can accurately predict leakage potentials. Two lengths of cemented annuli were modeled, each with conventional and expanding cement to replicate the Aas et. al. [1] experiments. The numerical results show that the simulated microannuli overestimate flow rate compared to experimental data, indicating that flow path dimensions and/or fluid friction factor does not accurately represent the fluid flow in the experiments.

scholarly journals Experimental and numerical investigations on glass fragments: shear-frame testing and calibration of Mohr–Coulomb plasticity model

2021 ◽  
Author(s):  
Alexander Pauli ◽  
Michael A. Kraus ◽  
Geralt Siebert
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Numerical Models ◽  
Failure Criteria ◽  
Test Results ◽  
Load Bearing ◽  
Frictional Contacts ◽  
Numerical Investigations ◽  
Shear Frame ◽  
Bearing Behavior

AbstractThe numerical treatment of the residual load-bearing behavior of laminated glasses (LG) in the post-fractured state is highly topical. Nevertheless, currently only few numerical approaches for an accurate representation of the experimentally observed behavior are existent. In order to model the characteristics of the load-bearing behavior of glass laminates in the post-fractured state, the behavior of the interlayer, the behavior of the glass fragments as well as the bonding between glass and interlayer need to be characterized correctly. This paper focuses on the modeling of the frictional contacts between the glass fragments itself. In order to allow for the calibration of failure criteria for the fractured glass particles, framed shear tests which are a common experimental technique in geomechanical testing to determine the shear strength of soils, are performed on glass fragments of different thicknesses and levels of thermal pre-stress. The test results are subsequently used to calibrate non-associated Mohr–Coulomb criteria, which are widely applied to the description of failure and frictional sliding of soils, to the experimental data of four distinct kinds of glass fragments. The obtained parameters of the Mohr–Coulomb models are in magnitude similar to the parameters of standard soils such as sand or gravel. The experimental data further show, that the Mohr–Coulomb model in general can be used to approximate the stress failure plane of the glass fragments but lacks for capturing correctly the plastic volumetric strains (dilation) in Finite Element modelling. Numerical investigations by the Finite Element method showed, that it is possible to reproduce experimental data by using Mohr–Coulomb plasticity models and hence the numerical models are validated for further investigations.

Stiffness Simulation Analysis of Rubber Bush Mountings Subjected to Tilting Deflection

2013 ◽  
Vol 765-767 ◽  
pp. 341-344
Author(s):  
Bai Qin ◽  
Chao Wu ◽  
Bo Zhang ◽  
Quan Fu Wang ◽  
Ya Juan Ji
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Finite Element Model ◽  
Simulation Model ◽  
Axial Length ◽  
Simulation Analysis ◽  
Element Model ◽  
Simulation Data ◽  
Model Based ◽  
The Finite Element Model

The finite element model of rubber bush mountings is built up. And the value of the reduced tilting stiffness is obtained directly by solving the model. The simulation data and the experimental data can be seen to agree very closely. This fully proves the reliability of the simulation model. Based on this simulation model, which has been parameterized, the influence of the axial length and inner and outer radii on the reduced tilting stiffness of rubber bush is studied by using the co-simulation of MATLAB and ANSYS.

Remaining Collapse Capacity of Corroded Pipelines

2011 ◽  
Author(s):  
Qishi Chen ◽  
Mark Marley ◽  
Joe Zhou
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Wall Thickness ◽  
Numerical Models ◽  
Substantial Reduction ◽  
Assessment Method ◽  
Full Scale ◽  
Finite Element Models ◽  
Pipe Material ◽  
Corrosion Defects

It is known that, for given pipe material and diameter, collapse capacity of a plain pipe subjected to external pressure is proportional to the second or third power of wall thickness. In lieu of sophisticated numerical models and experimental data, conservative approaches such as those in which thickness losses at corrosion defects are extended to the entire circumference have been adopted in practices to assess the collapse resistance of corroded pipes. This reduced wall thickness is then used in the design equation of plain pipe to predict remaining collapse capacity. Such conservative assumptions result in substantial reduction of collapse capacity for pipelines with localized corrosion defects. During the course of a multiple-year PRCI research project, results of full-scale collapse tests and three-dimensional finite element analysis demonstrated that the reduction of collapse capacity was less than 10% for defects with a depth of 50% wall thickness, an axial length of one diameter and a circumferential width of half a diameter. These findings illustrated that the actual collapse capacity of corroded pipes is significantly higher than that estimated according to the conservative assumptions. This paper presents the development of a reliability-based, practical assessment method that allows remaining collapse capacity of corroded pipelines be determined based on defect size data obtained from in-line inspections. Work involved included characterization of corrosion defects, full-scale collapse tests, validation of finite element models using experimental data, analysis of parametric cases using finite element models, development of empirical equation based on experimental and numerical results, and calibration of partial safety factors which addressed the uncertainties associated with model error, load variation, and sizing inaccuracy of corrosion defects. Practical implications of the proposed assessment method were evaluated based on selected examples.

Instability Analysis of Torispherical Pressure Vessel Heads with Triangular Thin-Shell Finite Elements

1977 ◽  
Vol 99 (1) ◽  
pp. 64-74 ◽  
Author(s):  
V. L. Kanodia ◽  
R. H. Gallagher ◽  
H. A. Mang
Keyword(s):  
Finite Element ◽  
Nonlinear Analysis ◽  
Thin Shell ◽  
Experimental Result ◽  
Elastic Instability ◽  
Nonlinear Load ◽  
Linearized Problem ◽  
Shell Finite Element ◽  
Doubly Curved ◽  
Alternative Solutions

The elastic instability of an internally-pressurized cylindrical tank with a torispherical head is investigated using a triangular, doubly curved, thin-shell finite element. The formulation of the finite element, which is based upon cubic displacement functions and a modified principle of potential energy, is first described. Then, the element is verified by comparing numerical results for the linear, stable analysis to alternative solutions for the same problem. The subsequent instability investigation includes the solution of the linearized problem of equilibrium bifurcation, that is, of the classical eigenvalue problem, and a general nonlinear analysis, based on tracing the nonlinear load-displacement path. The critical pressure, obtained with use of the general nonlinear analysis, agrees closely with an experimental result as well as with a numerical solution stemming from an axisymmetric formulation.

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