scholarly journals Quantification of Thermal-Structural Uncertainties in Engine Combustor Composite Liners

1997 ◽  
Author(s):  
Shantaram S. Pai ◽  
Christos C. Chamis
Keyword(s):  
Mechanical Load ◽  
Coefficient Of Thermal Expansion ◽  
Thermal Gradients ◽  
Combined Stress ◽  
Liner Material ◽  
Shear Moduli ◽  
Local Stresses ◽  
Structural Uncertainties ◽  
Combustor Liner ◽  
Composite Liners

A typical hot structural component within an engine such as composite combustor liner is computationally simulated and probabilistically evaluated in view of the numerous uncertainties associated with the structural, material, and thermo-mechanical load variables (primitive variables) that describe the combustor. The combustor is evaluated for local stresses. Results show that the scatter in the combined stress near the support is significantly dependent upon the uncertainties in the through thickness thermal gradients, the liner material thickness, the coefficient of thermal expansion, and the axial and both the axial and shear moduli.

Probabilistic Assessment of Combustor Liner Design

1995 ◽  
Author(s):  
Shantaram S. Pai ◽  
Christos C. Chamis
Keyword(s):  
Thermal Load ◽  
Mechanical Load ◽  
Coefficient Of Thermal Expansion ◽  
Probabilistic Assessment ◽  
Vibration Frequencies ◽  
Combined Stress ◽  
Liner Material ◽  
Load Profile ◽  
Local Stresses ◽  
Combustor Liner

A typical hot structural component within an engine such as composite combustor liner is computationally simulated and probabilistically evaluated in view of the numerous uncertainties associated with the structural, material, and thermo-mechanical load variables (primitive variables) that describe the combustor. The combustor is evaluated for buckling (eigenvalue) loads, vibration frequencies, and local stresses. Results show that the scatter in the combined stress is not uniform along the length of the combustor. Furthermore, coefficient of thermal expansion, hoop modulus of the liner material, and the thermal load profile dominate stresses near the support and the intermediate location of the combustor liner. However, the liner thickness, the liner material hoop modulus, and pressure load profile have significant impact on stresses near the free end of combustor.

Auscultation d'une culée du pont de Portneuf à l'aide d'une inclusion de béton instrumentée (CIUS)

1996 ◽  
Vol 23 (5) ◽  
pp. 1129-1136
Author(s):  
Axel-Pierre Bois ◽  
Mohamed Lachemi ◽  
Gérard Ballivy
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Coefficient Of Thermal Expansion ◽  
Concrete Bridge ◽  
Thermal Gradients ◽  
Bridge Monitoring ◽  
Shrinkage And Creep ◽  
First Results ◽  
Short And Long Term

The Portneuf Bridge, built in 1992, is the first air-entrained high-performance concrete bridge in North America. To understand its short and long term behaviour, an auscultation program has been set. Hence, a cylindrical concrete inclusion of the Université de Sherbrooke was installed in one of the abutments of the bridge. The aim of this study is to present the first results thus acquired. The analysis of the results allowed to calculate the coefficient of thermal expansion of the concrete and to assess deformation variations due to shrinkage and creep and the effects of rebar–concrete interaction in the upper abutment region. Moreover, the presence of thermal gradients, which creates nonisotropic deformations, has been established. Key words: high-performance concrete, deformations, thermal gradients, instrumentation, bridge, monitoring. [Journal translation]

Microstructural Finite Element Modeling and Simulation on Al–MgO Composites

2015 ◽  
Vol 12 (05) ◽  
pp. 1550030 ◽  
Author(s):  
Satyanarayan Patel ◽  
Rahul Vaish ◽  
Vishal Singh Chauhan ◽  
Chris Bowen
Keyword(s):  
Finite Element ◽  
Volume Fraction ◽  
Filler Content ◽  
Coefficient Of Thermal Expansion ◽  
Object Oriented ◽  
Stress And Strain ◽  
Thermal And Mechanical Properties ◽  
Element Analysis ◽  
Local Stresses ◽  
Properties Of Composites

Object Oriented Finite Element Analysis (OOF2) is used to predict the thermal and mechanical properties of Al – MgO composites. In this work, three compositions of composites containing 5%, 10% and 15% MgO (by volume) are studied. The influence of MgO volume fraction is examined in terms of effective Young's modulus and coefficient of thermal expansion of the composites. In addition, the stress and strain contours are plotted, which are helpful to understand the mechanical behavior of these composites. It is noted that the properties of composites are improved because of the presence of MgO . However, local stresses increase with filler content.

Simulation of Combustor Damage Mechanisms and Material System Performance via a Sub-Element Configured Specimen Test

2011 ◽  
Author(s):  
Nagaraja Rudrapatna ◽  
Benjamin H. Peterson
Keyword(s):  
Gas Turbine ◽  
Thermal Fatigue ◽  
Bond Coat ◽  
Test Method ◽  
Material System ◽  
Engine Operation ◽  
Damage Mechanisms ◽  
Liner Material ◽  
Material Systems ◽  
Combustor Liner

Modern gas turbine combustors are made of high temperature alloys, employ effusion cooling and are protected by a Thermal Barrier Coating (TBC). Standard material characterization tests such as creep, oxidation and low cycle fatigue are indicators of a material’s potential performance but they neither fully represent the combustor geometric/material system nor fully represent the thermal fatigue conditions a combustor is subjected to during engine operation. Combustor rig tests and/or engine cyclic endurance tests to determine the suitability of new material systems for combustors are time consuming and costly. Therefore, a simple test method for screening material systems under representative combustor conditions is needed. This experimental system was recently developed at Honeywell Aerospace to characterize various gas turbine combustor damage mechanisms and assess state-of-the-art and developmental materials. A configured specimen is fabricated using materials and processes similarly to actual combustor hardware, including sheet metal forming, welding, TBC coating, and effusion hole laser drilling. The configured specimen is cyclically exposed to hot spot thermal gradients typically experienced by fielded hardware using a jet-fueled burner and heated cooling air. Damage mechanisms simulated include bond coat oxidation, TBC spallation, thermal fatigue and distortion. A summary of these damage mechanisms and lessons learned from test development are presented. Results from recent combustor liner, bond coat, and top coat material modifications are also discussed. The effect of combustor liner material creep and thermal fatigue resistance, bond coat composition and processing, and TBC composition and structure on combustor durability is presented.

Predicted Thermal Mismatch Stresses in a Cylindrical Bi-material Assembly Adhesively Bonded at Its Ends

1997 ◽  
Vol 64 (1) ◽  
pp. 15-22 ◽  
Author(s):  
E. Suhir
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Coefficient Of Thermal Expansion ◽  
Stress Model ◽  
Adhesively Bonded ◽  
Thermal Mismatch ◽  
Adhesive Material ◽  
Thermally Induced ◽  
Local Stresses ◽  
Material Assembly

A simple analytical stress model, based on the strength-of-materials approach, is developed for the evaluation of thermally induced shearing stresses in a long cylindrical bi-material assembly adhesively bonded at its ends and subjected to the change in temperature. The emphasis is on the interaction of the “global” thermal mismatch stresses, counted with respect to the mid cross section of the assembly as a whole, and the “local” stresses, counted with respect to the mid cross sections of the bonded regions. The effect of the coefficient of thermal expansion of the adhesive material itself is also considered. We show also how to evaluate the fundamental frequency of vibrations of the inner cylinder with consideration of the thermally induced tension, if any.

Constitutive Model Development for Thermo-Mechanical Fatigue Response Simulation of Haynes 230

2012 ◽  
Author(s):  
Raasheduddin Ahmed ◽  
Mamballykalathil Menon ◽  
Tasnim Hassan
Keyword(s):  
Stress Response ◽  
Constitutive Model ◽  
Kinematic Hardening ◽  
Isotropic Hardening ◽  
Large Set ◽  
Mean Stress ◽  
Liner Material ◽  
Mechanical Fatigue ◽  
Combustor Liner ◽  
Mean Strain

Turbine engine combustor components are subject to thermo-mechanical fatigue (TMF) during service. The combustor liner temperatures can sometimes reach as high as 1800°F. An accurate estimate of the strains at critical locations in the combustor liner is required for reliable lifing predictions. This demands the need for a detailed analysis of the TMF responses and a robust constitutive model capable of predicting the same. A large set of experiments have been carried out on the liner material, a nickel based alloy, HA 230, in an effort to understand its thermo-mechanical fatigue constitutive response. The out-of-phase strain-controlled TMF experiments with a negative mean strain show a positive mean stress response, while the in-phase TMF experiments with a positive mean strain show a negative mean stress response. A Chaboche based viscoplastic constitutive model is under development. It will have several essential features such as nonlinear kinematic hardening, isotropic hardening, strain range dependence, rate dependence, temperature dependence and static recovery. The constitutive model being developed for accurately calculating the stress-strain response is being carried out with the final objective of predicting the strains in an actual combustor liner in service through finite element simulation for fatigue lifing.

Thermoviscoelastic behavior of a short fiber-reinforced polymer hollow cylinder accounting for porosity

2016 ◽  
Vol 51 (19) ◽  
pp. 2779-2791 ◽  
Author(s):  
Hong-Liang Dai ◽  
Ting Dai ◽  
Wei-Feng Luo
Keyword(s):  
Hollow Cylinder ◽  
Integral Transform ◽  
Mechanical Load ◽  
Coefficient Of Thermal Expansion ◽  
Short Fiber ◽  
Fiber Reinforced Polymer ◽  
Fiber Reinforced ◽  
Cylindrical Structures ◽  
Reinforced Polymer ◽  
Hollow Cylinders

In this paper, thermoviscoelastic behavior of a hollow cylinder made of short fiber-reinforced polymer considering porosity is investigated by an analytical method. Material properties, except the Poisson’s ratio and coefficient of thermal expansion, are assumed to be changed with the volume of constituents and porosity. Utilizing the finite Hankle integral transform and Laplace transform, analytical solutions for thermoviscoelastic behaviors of short fiber-reinforced polymer hollow cylinders under thermal and mechanical loads are obtained. Numerical examples show the influences of thermal load, mechanical load, and material porosity on the thermoviscoelastic behaviors of short fiber-reinforced polymer cylindrical structures.

scholarly journals Probabilistic Study of Fluid Structure Interaction

2002 ◽  
Author(s):  
Rama S. R. Gorla ◽  
Shantaram S. Pai ◽  
Jeffrey J. Rusick
Keyword(s):  
Stress Responses ◽  
Hoop Stress ◽  
Coefficient Of Thermal Expansion ◽  
Cost Effective ◽  
Distribution Functions ◽  
Flow Coefficient ◽  
Cumulative Distribution ◽  
Design Variables ◽  
Probabilistic Study ◽  
Combustor Liner

A combustor liner was computationally simulated and probabilistically evaluated in view of the several uncertainties in the aerodynamic, structural, material and thermal variables that govern the combustor liner. The interconnection between the computational fluid dynamics code and the finite element structural analysis codes was necessary to couple the thermal profiles with structural design. The stresses and their variations were evaluated at critical points on the liner. Cumulative distribution functions and sensitivity factors were computed for stress responses due to the aerodynamic, mechanical and thermal random variables. It was observed that the inlet and exit temperatures have a lot of influence on the hoop stress. For prescribed values of inlet and exit temperatures, the Reynolds number of the flow, coefficient of thermal expansion, gas emissivity and absorptivity and thermal conductivity of the material have about the same impact on the hoop stress. These results can be used to quickly identify the most critical design variables in order to optimize the design and make it cost effective.

Effect of Polymer Liners in Different Via Shapes: Impact on Crosstalk Induced Delay

2021 ◽  
Author(s):  
Maya Chandrakar ◽  
Manoj Kumar Majumder
Keyword(s):  
Integrated Circuit ◽  
Coefficient Of Thermal Expansion ◽  
Electrical Network ◽  
Worst Case ◽  
Liner Material ◽  
Low Dielectric ◽  
Aspect Ratios ◽  
Cte Mismatch ◽  
Metal Liner ◽  
The Impact

Abstract The performance of a through silicon via (TSV) based 3D integrated circuit technology is primarily dependent on the choice of an appropriate liner material. The most commonly used liner material SiO2 is undergoing considerable reliability challenges such as coefficient of thermal expansion (CTE) mismatch, scallop formation, and interfacial delamination related problems. Therefore, TSVs employed with a polymer liner have achieved significant attention in recent years due to their low dielectric constant and excellent step coverage along the via surface that can effectively reduce thermal stress and crosstalk induced delay. This paper presents a comprehensive and accurate RLGC model for different via shapes considering the impact of various liner materials on the crosstalk induced delay. Considering an accurate via geometry and material properties at 32 nm and 45 nm technology, the proposed equivalent RLGC parameters include the cumulative effects of TSV metal, liner, bump, and the silicon substrate. The aforementioned parameters are used to model a novel T-type equivalent electrical network of cylindrical, tapered, and coaxial TSVs considering a coupled driver-via-load (DVL) setup. The proposed equivalent models of different via shapes are used to demonstrate the worst-case crosstalk induced delay in TSVs under the influence of various liner materials. Considering a tapered TSV, a significant improvement in crosstalk induced delay at 32 nm w.r.t. 45 nm technology is observed as 53.5%, 33.76%, and 19.12% at aspect ratios of 2.4, 3, and 4, respectively for the BCB liner.

Durability of Oxide/Oxide CMCs in Gas Turbine Combustors

2012 ◽  
Author(s):  
Mark van Roode ◽  
Arun K. Bhattacharya
Keyword(s):  
Water Vapor ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Rupture Strength ◽  
Aluminum Silicate ◽  
Inlet Temperature ◽  
Liner Material ◽  
Barrier Coating ◽  
Liner System ◽  
Combustor Liner

An integrated creep rupture strength degradation and water vapor degradation model for gas turbine oxide-based CMC (Ceramic Matrix Composite) combustor liners was expanded with heat transfer computations to establish maximum TRIT (Turbine Rotor Inlet Temperature) for gas turbines with 10:1 pressure ratio. Recession rates and average CMC operating temperatures were calculated for an existing baseline N720/A (N720/Al2O3) CMC combustor liner system, with and without protective Al2O3 FGI (Friable Graded Insulation) for 30,000-h liner service life. The potential for increasing TRIT by YAG (Y3Al5O12) substitution for the fiber, matrix and FGI constituents of the CMC system was explored, because of the known superior creep and water vapor degradation resistance of YAG compared to Al2O3. It was predicted that uncoated N720/A can be used as a combustor liner material up to a TRIT of ∼1200°C, offering no TRIT advantage over a conventional metal + TBC (Thermal Barrier Coating) combustor liner. A similar conclusion was previously reached for a SiC/SiC CMC liner with BSAS-type EBC (Barium Strontium Aluminum Silicate Environmental Barrier Coating). The existing N720/A + Al2O3 FGI combustor liner system can be used at a maximum TRIT of ∼1350°C, a TRIT increase over metal + TBC and uncoated N720/A of ∼150°C. Replacing the Al2O3 with YAG is predicted to increase the maximum allowable TRIT. Substitution of the fiber or matrix in N720/A increases TRIT by ∼100°C. A YAG FGI improves the TRIT of the 720/A + Al2O3 FGI by ∼50°C, enabling a TRIT of ∼1400°C, similar to that predicted for SiC/SiC CMCs with protective rare earth monosilicate EBCs.

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