scholarly journals Influence of fluid-structure interaction modelling on the stress and fatigue life evaluation of a gas turbine blade

2020 ◽  
pp. 095765092096755
Author(s):  
Iroizan Ubulom
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Stress State ◽  
Turbine Blade ◽  
Stress History ◽  
Turbine Wheel ◽  
Fluid Structure ◽  
Stress Fluctuation ◽  
Fully Coupled ◽  
Mean Stresses

A computational method of fluid-structure coupling is implemented to predict the fatigue response of a high-pressure turbine blade. Two coupling levels, herein referred to as a “fully coupled” and “decoupled” methods are implemented to investigate the influence of multi-physics interaction on the 3 D stress state and fatigue response of a turbine blade. In the fully-coupled approach, the solutions of the fluid-flow and the solid-domain finite element problem are obtained concurrently, while in the decoupled approach, the independently computed aerodynamic forces are unilaterally transferred as boundary conditions in the subsequent finite element solution. In both cases, a three-dimensional unsteady stator-rotor aerodynamic configuration is modelled to depict a forced-vibration loading of high-cycle failure mode. Also analyzed is the low-cycle phenomenon which arises due to the mean stresses of the rotational load of the rotating turbine wheel. The coupling between the fluid and solid domains (fully-coupled approach) provides a form of damping which reduces the amplitude of fluctuation of the stress history, as opposed to the decoupled case with a resultant higher amplitude stress fluctuation. While the stress amplitude is higher in the decoupled case, the fatigue life-limiting condition is found to be significantly influenced by the higher mean stresses in the fully-coupled method. The differences between the two approaches are further explained considering three key fatigue parameters; mean stress, multiaxiality stress state and the stress ratio factors. The study shows that the influence of the coupling between the fluid and structures domain is an important factor in estimating the fatigue stress history.

scholarly journals Unsteady Flow and Vibration Analysis of the Horizontal-Axis Wind Turbine Blade under the Fluid-Structure Interaction

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Rui Zhu ◽  
Da-duo Chen ◽  
Shi-wei Wu
Keyword(s):  
Unsteady Flow ◽  
Wind Turbine ◽  
Turbine Blade ◽  
Wind Turbine Blade ◽  
Horizontal Axis ◽  
Leeward Side ◽  
Horizontal Axis Wind Turbine ◽  
Fluid Structure ◽  
Fluid Field ◽  
Stress Fluctuation

A 1.5 MW horizontal-axis wind turbine blade and fluid field model are established to study the difference in the unsteady flow field and structural vibration of the wind turbine blade under one- and two-way fluid-structure interactions. The governing equations in fluid field and the motion equations in structural were developed, and the corresponding equations were discretized with the Galerkin method. Based on ANSYS CFX fluid dynamics and mechanical structural dynamics calculation software, the effects of couplings on the aerodynamic and vibration characteristics of the blade are compared and analyzed in detail. Results show that pressure distributions at different sections of the blade are concentrated near the leading edge, and the leeward side of two-way coupling is slightly higher than that of one-way coupling. Deformation along the blade span shows a nonlinear change under the coupling effect. The degree of amplitude attenuation in two-way coupling is significantly greater than that in one-way coupling because of the existence of aerodynamic damping. However, the final amplitude is still higher than the one-way coupling. The Mises stress fluctuation in the windward and leeward sides is more obvious than one-way coupling, and the discrepancy must not be ignored.

Finite Element Analysis of the Effect of Twist on Chain Fatigue Performance

2019 ◽  
Author(s):  
Justin Jones
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Fatigue Life ◽  
Stress State ◽  
Element Analysis ◽  
Contact Patch ◽  
Multiaxial Stress State ◽  
Twisted State ◽  
Residual Stress State ◽  
Proof Testing

Abstract Mooring chains may be installed with twist or become twisted during service. This paper describes an investigation of the effect of a range of twist angles on the fatigue life of studless chain through the use of detailed finite element analysis. The analysis includes the local contact patch deformation and residual stress state that results from plasticity during the proof testing of the chain. The effect of high in-service tension resulting from storms that produces additional plasticity when the chain is loaded in the twisted state is also included. The change in fatigue life at the crown, inner bend and around the contact patch are assessed. Local to the contact patch the fatigue life calculation includes an assessment of the multiaxial stress state. For small angles of twist the calculated fatigue life at the crown and around the contact increases and that at the inner bend sees a marginal reduction. At twist angles above 12 to 14 degrees per link the calculated inner bend and contact patch fatigue lives reduce markedly with increasing twist, but the crown fatigue life continues to increase.

scholarly journals Application of Spectral Method for Vibration-Induced High-Cycle Fatigue Evaluation of an HP Turbine Blade

2020 ◽  
Author(s):  
Iroizan Ubulom
Keyword(s):  
Fatigue Life ◽  
Frequency Domain ◽  
Turbine Blade ◽  
Euler Angle ◽  
Mean Stress ◽  
Critical Plane ◽  
Life Estimation ◽  
Fatigue Life Estimation ◽  
The Mean ◽  
Fully Coupled

Abstract A method of fluid-structure interaction coupling is implemented for a forced-response, vibration-induced fatigue life estimation of a high-pressure turbine blade. Two simulations approaches; a two-way (fully-coupled) and one-way (uncoupled) methods are implemented to investigate the influence of fluidsolid coupling on a turbine blade structural response. The fatigue analysis is performed using the frequency domain spectral moments estimated from the response power spectral density of the two simulation cases. The method is demonstrated in light of the time-domain method of the rainflow cycle counting method with mean stress correction. Correspondingly, the mean stress and multiaxiality effects are also accounted for in the frequency domain spectral approach. In the mean stress case, a multiplication coefficient is derived based on the Morrow equation, while the case of multiaxiality is based on a criterion which reduces the triaxial stress state to an equivalent uniaxial stress using the critical plane assumption. The analyses show that while the vibration-induced stress histories of both simulation approaches are stationary, they violate the assumption of normality of the frequency domain approaches. The stress history profile of both processes can be described as platykurtic with the distributions having less mass near its mean and in the tail region, as compared to a Gaussian distribution with an equal standard deviation. The fully-coupled method is right leaning with positive skewness while the uncoupled approach is left leaning with negative skewness. The directional orientation of the principal axes was also analyzed based on the Euler angle estimation. Although noticeable differences were found in the peak distribution of the normal stresses for both methods, the predicted Euler angle orientations were consistent in both cases, depicting a similar orientation of the critical plane during a crack initiation process. It is shown that the fatigue life estimation was conservative in the fully-coupled solution approach.

scholarly journals STRESS AND FATIGUE LIFE PREDICTION OF THE H-TYPE DARRIEUS VERTICAL AXIS TURBINE FOR MICRO-HYDROPOWER APPLICATIONS

2021 ◽  
Author(s):  
Intizar Ali
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Fatigue Life ◽  
Turbine Blade ◽  
Cfd Simulation ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Speed Ratio ◽  
Analysis Model ◽  
Element Analysis

The present study aims to analyze the structural behavior of the Darrieus Hydro-kinetic turbine at different upstream velocity values and rotational rates. For that purpose, one-way fluid-structure interaction is performed to predict stresses, deformation and fatigue life of the turbine. To determine real-time fluid loads three-dimensional fluid flow simulations were performed, the obtained fluid loads were transferred to the structural finite element analysis model. CFD simulation results were validated with experimental results from literature where the close agreement was noticed. Structural analysis results revealed that the highest stresses are produced in the struts and at the joint where the shaft is connected with struts. Moreover, it was also found that the stress produced in the turbine is highly non-linear against Tip Speed Ratio (TSR) i.e inflow water velocity. Finite Element Analysis (FEA) results showed that maximum values of stresses were found in the turbine strut having a value 131.99MPa, which lower than the yield strength of the material, the fatigue life of 117520 cycles and factor of safety 1.89. The study also found that increased inflow velocity results increase in stress and deformation produced in the turbine. Additionally, the study assumed Aluminum Alloy as turbine blade material, further; it was found that the blade which confronts flow, experience higher stresses. Moreover, the study concluded that strut, blade-strut joint and strut-shaft joint are the critical parts of the turbine, require careful design consideration. Furthermore, the study also suggests that the turbine blade may be kept hollow to reduce turbine weight; hence inertia and turbine struts and shaft should be made of steel or the material having higher stiffness and strength.

A New Fully-Detailed Finite Element Model of Spiral Strand Wire Ropes for Fatigue Life Estimate of a Mooring Line

2019 ◽  
Author(s):  
Federico Bussolati ◽  
Martin Guiton ◽  
Pierre-Alain Guidault ◽  
Yann Poirette ◽  
Michael Martinez ◽  
...  
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Stress State ◽  
Finite Element Model ◽  
Limit State ◽  
Element Model ◽  
Offshore Wind Turbine ◽  
Mooring Lines ◽  
Wire Ropes ◽  
The Wire

Abstract Spiral strand wire ropes are commonly used in the mooring system of offshore structures. When dealing with the fatigue limit state, engineers have to consider many different load cases, according to the variability of the environmental state. This usually prevents the use of any detailed numerical model of the mooring lines. In this paper, we propose a new method to evaluate with an affordable computational cost the detailed mechanical stress state in different parts of the wire ropes used for mooring a floating offshore wind turbine. We first compute tension and bending history in the mooring, with the hydrodynamic software Deeplines™, assuming for simplification stationary aerodynamic loads on the floater. These time series are then accounted for in a novel Finite Element Model of the spiral strand, with small sliding among the wires. The obtained kinematics and stress state of the wires can then feed a fatigue law based on fretting fatigue, which has been experimentally evidenced to condition the fatigue life of spiral strand wire ropes. The potential of this method is illustrated with an application to a cylinder-like shape floater equipped with 3 pairs of catenary mooring lines. It is shown that bending and tension histories do not significantly depend on the wire rope bending stiffness.

A simplified numerical and analytical study for assessing the seismic response of a gravity concrete lock

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Neander Berto Mendes ◽  
Lineu José Pedroso ◽  
Paulo Marcelo Vieira Ribeiro
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Analytical Study ◽  
Two Dimensional ◽  
The Finite Element Method ◽  
Fluid Structure ◽  
Analytical Formulation ◽  
Acoustic Cavity ◽  
Water Chamber ◽  
Structure Problem

ABSTRACT: This work presents the dynamic response of a lock subjected to the horizontal S0E component of the El Centro earthquake for empty and completely filled water chamber cases, by coupled fluid-structure analysis. Initially, the lock was studied by approximation, considering it similar to the case of a double piston coupled to a two-dimensional acoustic cavity (tank), representing a simplified analytical model of the fluid-structure problem. This analytical formulation can be compared with numerical results, in order to qualify the responses of the ultimate problem to be investigated. In all the analyses performed, modeling and numerical simulations were done using the finite element method (FEM), supported by the commercial software ANSYS.

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