Design Space Exploration of a Beam Flexible Hub Concept for an Inside-Out Ceramic Turbine Using a Simplified Rotordynamic Finite Element Model

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Céderick Landry ◽  
Patrick K. Dubois ◽  
Jean-Sébastien Plante ◽  
François Charron ◽  
Mathieu Picard
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Design Space Exploration ◽  
Design Space ◽  
Space Exploration ◽  
Element Model ◽  
Inlet Temperature ◽  
Blade Tip ◽  
Hoop Stresses ◽  
Inside Out

This paper presents a new flexible hub design for the inside-out ceramic turbine (ICT) rotor configuration. This configuration is used in microturbines to integrate ceramic blades in order to increase turbine inlet temperature (TIT), which leads to higher cycle efficiency values. The ICT uses an outer composite rim to load the ceramic blades in compression by converting the centrifugal loads of the blades into hoop stresses in the composite rim. High stresses in the composite rim lead to high radial displacement of the blades. This displacement is compensated by using flexible hub in order to maintain the contact with the blades. However, hub flexibility can lead to rotordynamic problems as heavy hub deformation will induce high stresses in it. Thus, stresses in the hub are induced by both rotordynamics and centrifugation, requiring a multi-objective design process, which has yielded geometries that limited, until now, the blade tip speed to 358 m/s. In this paper, a simplified rotordynamics finite element model of a flexible hub is developed to allow quick design iterations. Using the model, a design space exploration of this hub concept is done while considering centrifugation and rotordynamics. Experimental validation is conducted on a simplified ICT prototype up to 129 krpm, i.e., an equivalent blade tip speed of 390 m/s. Finally, predictions from the experimentally calibrated model show that the tested prototype hub could reach a blade tip speed of 680 m/s.

Finite-Element Simulations and Probabilistic Fracture Assessments of the Response of Alternate Rifling Geometries

2007 ◽  
Author(s):  
A. E. Segall ◽  
R. Carter
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Thermal Stresses ◽  
Rotational Symmetry ◽  
Element Model ◽  
Time Dependent ◽  
Uniform Heating ◽  
Thermal Pressure ◽  
Single Firing ◽  
Hoop Stresses

A 3-D finite-element model was used to simulate the severe and localized thermal/pressure transients and the resulting stresses experienced by a rifled ceramic-barrel with a steel outer-liner; the focus of the simulations was on the influence of non-traditional rifling geometries on the thermoelastic- and pressure-stresses generated during a single firing event. In order to minimize computational requirements, a twisted segment of the barrel length based on rotational symmetry was used. Using this simplification, the model utilized uniform heating and pressure across the ID surface via a time-dependent convective coefficient and pressure generated by the propellant gasses. Results indicated that the unique rifling geometries had only a limited influence on the maximum circumferential (hoop) stresses and temperatures when compared with more traditional rifling configurations because of the compressive thermal stresses developed at the heated (and rifled) surface.

A Multilevel Hierarchical Finite Element Model for Capillary Failure in Soft Tissue

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
Ian R. Grosse ◽  
Lu Huang ◽  
Julian L. Davis ◽  
Dennis Cullinane
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Volume Fraction ◽  
Element Model ◽  
Capillary Wall ◽  
Failure Stress ◽  
The Third ◽  
Human Arm ◽  
Hoop Stresses ◽  
Hierarchical Finite Element

Bruising, the result of capillary failure due to trauma, is a common indication of abuse. However, the etiology of capillary failure has yet to be determined as the scale change from tissue to capillary represents several orders of magnitude. As a first step toward determining bruise etiology, we have developed a multilevel hierarchical finite element model (FEM) of a portion of the upper human arm using a commercial finite element tool and a series of three interconnected hierarchical submodels. The third and final submodel contains a portion of the muscle tissue in which a single capillary is embedded. Nonlinear, hyperelastic material properties were applied to skin, adipose, muscle, and capillary wall materials. A pseudostrain energy method was implemented to subtract rigid-body-like motion of the submodel volume experienced in the global model, and was critical for convergence and successful analyses in the submodels. The deformation and hoop stresses in the capillary wall were determined and compared with published capillary failure stress. For the dynamic load applied to the skin of the arm (physiologically simulating a punch), the model predicted that approximately 8% volume fraction of the capillary wall was above the reference capillary failure stress, indicating bruising would likely occur.

scholarly journals Non-Linear Modeling of Centrifugal Stiffening Effects for Accurate Bladed Component Reduced-Order Models

2017 ◽  
Author(s):  
Elias Khalifeh ◽  
Elsa Piollet ◽  
Antoine Millecamps ◽  
Alain Batailly
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Angular Speed ◽  
Reduced Order Models ◽  
Order Model ◽  
Reduced Order ◽  
Linear Finite Element ◽  
Centrifugal Stiffening ◽  
Blade Tip

The modeling of centrifugal stiffening effects on bladed components is of primary importance in order to accurately capture their dynamics depending on the rotor angular speed. Centrifugal effects impact both the stiffness of the component and its geometry. In the context of the small perturbation framework, when considering a linear finite element model of the component, an assumption typically made in the scientific literature involves a fourth-order polynomial development of the stiffness matrix in terms of the angular speed. This polynomial development may fail to provide an accurate representation of the geometry evolution of a blade. Indeed, the error on the blade-tip displacement associated to the use of a linear finite element model quickly reaches the same order of magnitude as the blade-tip/casing clearance itself thus yielding a 100 % error on the blade-tip/casing clearance configuration. This article focuses on the presentation of a methodology that allows for creating accurate reduced order models of a 3D finite element model accounting for centrifugal stiffening with a very precise description of the blade-tip/casing clearance configuration throughout a given angular speed range. The quality of the obtained reduced order model is underlined before its numerical behaviour in the context of non-linear dynamic simulations be investigated. It is evidenced that the new reduced order model features specific interactions that could not be predicted with a linear model. In addition, results highlight the limitations of numerical predictions made for high angular speeds with a linear model. Finally, a particular attention is paid to the numerical sensitivity of the proposed model. As a downside of its increased accuracy, it is underlined that its computation must be done carefully in order to avoid numerical instabilities.

Finite Element Simulation of Tire-Rim Interface

1989 ◽  
Vol 17 (4) ◽  
pp. 305-325 ◽  
Author(s):  
N. T. Tseng ◽  
R. G. Pelle ◽  
J. P. Chang
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Finite Element Simulation ◽  
Contact Pressure ◽  
Element Model ◽  
Experimental Measurements ◽  
Inflation Pressure ◽  
Interference Fit ◽  
Element Simulation ◽  
Rubber Composite

Abstract A finite element model was developed to simulate the tire-rim interface. Elastomers were modeled by nonlinear incompressible elements, whereas plies were simulated by cord-rubber composite elements. Gap elements were used to simulate the opening between tire and rim at zero inflation pressure. This opening closed when the inflation pressure was increased gradually. The predicted distribution of contact pressure at the tire-rim interface agreed very well with the available experimental measurements. Several variations of the tire-rim interference fit were analyzed.

Torsional Analysis of a Steel Cord-Rubber Tire Belt Structure

1996 ◽  
Vol 24 (4) ◽  
pp. 339-348 ◽  
Author(s):  
R. M. V. Pidaparti
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Composite Structures ◽  
Three Dimensional ◽  
Element Model ◽  
Torsional Stiffness ◽  
Element Analysis ◽  
Rubber Belt ◽  
Steel Cord ◽  
Torsional Analysis

Abstract A three-dimensional (3D) beam finite element model was developed to investigate the torsional stiffness of a twisted steel-reinforced cord-rubber belt structure. The present 3D beam element takes into account the coupled extension, bending, and twisting deformations characteristic of the complex behavior of cord-rubber composite structures. The extension-twisting coupling due to the twisted nature of the cords was also considered in the finite element model. The results of torsional stiffness obtained from the finite element analysis for twisted cords and the two-ply steel cord-rubber belt structure are compared to the experimental data and other alternate solutions available in the literature. The effects of cord orientation, anisotropy, and rubber core surrounding the twisted cords on the torsional stiffness properties are presented and discussed.

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