On the Propagation of Twin-Fault-Induced Stress in Platelet Fau-Framework Zeolites

1987 ◽  
Vol 111 ◽  
Author(s):  
M. M. J. Treacy ◽  
J. M. Newsam ◽  
D. E. W. Vaughan ◽  
R. A. Beyerlein ◽  
S. B. Rice ◽  
...  
Keyword(s):  
Internal Stress ◽  
Fault Zone ◽  
Stress Gradients ◽  
Induced Stress ◽  
Twin Fault ◽  
Rhombohedral Distortion

AbstractA model describing the propagation of a rhombohedral distortion in platelet CSZ–1 zeolites is presented. It is proposed that internal stress gradients grown into CSZ–1 platelets at synthesis are responsible for this distortion of the cubic FAU framework, where the spacings of 111 planes parallel to the platelet surfaces are elongated relative to the {111} planes. The presence of inhomogeneities is suggested by the presence of thin bands of twin faults which are invariably observed near the central layers of each platelet. Elastic modelling confirms that the effects of any stress associated with such twin faults will be most pronounced in the thinnest platelets, where the effects of elastic relaxation are minimal, and where the width of the fault zone relative to the platelet thickness is maximal. Platelet CSZ–3 and Y-type zeolites, which are considerably thicker, are therefore not expected to show significant rhombohedral distortion despite the presence of similar twin fault bands.

scholarly journals Diamond Heteroepitaxial Lateral Overgrowth

2015 ◽  
Vol 1734 ◽  
Author(s):  
Y-H Tang ◽  
B. Bi ◽  
B. Golding
Keyword(s):  
Internal Stress ◽  
Diamond Films ◽  
Diamond Surface ◽  
Threading Dislocation ◽  
Thermally Induced ◽  
Structural Improvement ◽  
Lateral Overgrowth ◽  
Induced Stress ◽  
Initial Stage ◽  
Threading Dislocation Density

ABSTRACTA method of diamond heteroepitaxial lateral overgrowth is demonstrated which utilizes a photolithographic metal mask to pattern a thin (001) epitaxial diamond surface. Significant structural improvement was found, with a threading dislocation density reduced by two orders of magnitude at the top surface of a thick overgrown diamond layer. In the initial stage of overgrowth, a reduction of diamond Raman linewidth in the overgrown area was also realized. Thermally-induced stress and internal stress were determined by Raman spectroscopy of adhering and delaminated diamond films. The internal stress is found to decrease as sample thickness increases.

Experimental and Numerical Investigation on the Influence of Thermally Induced Stress Gradients on Fatigue Life of the Nickel-Base Alloy Mar-M247

2019 ◽  
Author(s):  
Marcus Thiele ◽  
Stefan Eckmann ◽  
Min Huang ◽  
Uwe Gampe ◽  
Kathrin A. Fischer ◽  
...  
Keyword(s):  
High Temperature ◽  
Fatigue Life ◽  
Base Alloy ◽  
Low Cycle Fatigue ◽  
Heat Fluxes ◽  
Cycle Fatigue ◽  
Thermally Induced ◽  
Stress Gradients ◽  
Induced Stress ◽  
Nickel Base

Abstract Today’s and future parameters of stationary gas turbines and aircraft engines require intensive and highly efficient cooling of hot gas path components. High temperature and thermally induced stress gradients with impact on fatigue life are the consequence. Thermally induced stress gradients differ from geometrically induced stress gradients with respect to stress mechanics by the independence from external loads and material mechanics by the influence of temperature on material properties and strength. Regarding the contribution and evaluation on damage, the latter characteristic feature in turbomachinery is currently not fully understood. Therefore, a test facility has been designed, set up, and reported in GT2018-76519 for the investigation of the influence of stationary temperature, and thus thermally induced stress gradients, on the damage evolution of cooled high-temperature components. To achieve high temperature and thermally induced stress gradients, large heat fluxes are required. A unique radiation heating has been developed allowing very high heat fluxes of q̇ ≥ 1.5 MW/m2 for testing of hollow cylindrical specimens. The conventional cast nickel-base alloy Mar-M247 has been chosen to study the influence of thermally induced stress gradients on fatigue life. The low-cycle fatigue testing of the hollow cylindrical specimens has been conducted both with and without superimposed stationary temperature gradients. In addition, Complex Low-Cycle Fatigue (CLCF) tests with symmetric and nonsymmetric loading conditions have been performed to provide the necessary database for the adaptation of a viscoplastic deformation model. To calculate the local stress-strain field and service life of the test specimens, linear elastic and viscoplastic finite element studies have been performed and were assessed by means of a fracture mechanics-based lifetime model. The test results show the considerable influence of the temperature gradient on the low-cycle fatigue life for the investigated material. Both the radial temperature variation over the specimen wall with a hot outer surface and a cooled inner surface as well as the thermally induced stresses are stated to be the main drivers for the change in low-cycle fatigue life. The test results enhance the understanding of fatigue-damage mechanisms under local unsteady conditions and can be used as a basis for improved service life predictions.

Influence of Thermally Induced Stress Gradients on Fatigue Life

MTZ worldwide ◽  
2021 ◽  
Vol 82 (12) ◽  
pp. 66-70
Author(s):  
Marcus Thiele ◽  
Stefan Eckmann ◽  
Min Huang ◽  
Uwe Gampe
Keyword(s):  
Fatigue Life ◽  
Thermally Induced ◽  
Stress Gradients ◽  
Induced Stress

Novel Test Facility for Investigation of the Impact of Thermally Induced Stress Gradients on Fatigue Life of Cooled Gas Turbine Components

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Marcus Thiele ◽  
Uwe Gampe ◽  
Kathrin A. Fischer
Keyword(s):  
Service Life ◽  
Gas Turbine ◽  
Heat Fluxes ◽  
Temperature Gradients ◽  
Test Facility ◽  
Test Results ◽  
Thermally Induced ◽  
Stress Gradients ◽  
Induced Stress ◽  
The Impact

A novel test facility has been designed and setup for the investigation of the influence of stationary temperature, and thus thermally induced stress gradients with respect to the damage evolution of cooled gas turbine components. Thermally induced stress gradients differ from geometrically induced stress gradients. From the point of view of stress mechanics, they are independent from external loads. From the perspective of material mechanics, their impact on service life is influenced by locally different material properties and strength. However, the impact of thermally induced stress gradients on the cyclic life of high loaded, cooled components is not precisely known. In order to increase knowledge surrounding these mechanisms, a research project was launched. To achieve high temperature gradients and extended mechanical stress gradients, large heat fluxes are required. The authors developed a test bench with a unique radiant heating to achieve very high heat fluxes of q˙ ≥ 1.6 MW/m2 on cylindrical specimen. Special emphasis has been placed on homogenous temperature and loading conditions in order to achieve valid test results comparable to standard low-cycle or thermo-mechanical fatigue tests. Different test concepts of the literature were reviewed and the superior performance of the new test rig concept was demonstrated. The austenitic stainless steel 316 L was chosen as the model material for commissioning and validation of the test facility. The investigation of thermally induced stress gradients and, based on this analysis, low-cycle fatigue (LCF) tests with superimposed temperature gradients were conducted. Linear elastic finite element studies were performed to calculate the local stress–strain field and the service life of the test specimens. The test results show a considerable influence of the temperature gradient on the LCF life of the investigated material. Both the temperature variation over the specimen wall and thermally induced stresses (TIS) are stated to be the main drivers for the change in LCF life. The test results increase the understanding of fatigue damage mechanisms under local unsteady conditions and can serve as a basis for improved lifetime calculation methods.

Experimental and Numerical Investigation on the Influence of Thermally Induced Stress Gradients on Fatigue Life of the Nickel-Base Alloy Mar-M247

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Marcus Thiele ◽  
Stefan Eckmann ◽  
Min Huang ◽  
Uwe Gampe ◽  
Kathrin A. Fischer ◽  
...  
Keyword(s):  
High Temperature ◽  
Fatigue Life ◽  
Base Alloy ◽  
Low Cycle Fatigue ◽  
Heat Fluxes ◽  
Cycle Fatigue ◽  
Thermally Induced ◽  
Stress Gradients ◽  
Induced Stress ◽  
Nickel Base

Abstract Today's and future parameters of stationary gas turbines and aircraft engines require intensive and highly efficient cooling of hot gas path components. High temperature and thermally induced stress gradients with impact on fatigue life are the consequence. Thermally induced stress gradients differ from geometrically induced stress gradients with respect to stress mechanics by the independence from external loads and material mechanics by the influence of temperature on material properties and strength. Regarding the contribution and evaluation on damage, the latter characteristic feature in turbomachinery is currently not fully understood. Therefore, a test facility has been designed, setup, and reported in GTP-18-1482 for the investigation of the influence of stationary temperature, and thus thermally induced stress gradients, on the damage evolution of cooled high-temperature components. To achieve high temperature and thermally induced stress gradients, large heat fluxes are required. A unique radiation heating has been developed allowing very high heat fluxes of q˙ ≥ 1.5 MW/m2 for testing of hollow cylindrical specimens. The conventional cast nickel-base alloy Mar-M247 has been chosen to study the influence of thermally induced stress gradients on fatigue life. The low-cycle fatigue testing of the hollow cylindrical specimens has been conducted both with and without superimposed stationary temperature gradients. In addition, complex low-cycle fatigue (CLCF) tests with symmetric and nonsymmetric loading conditions have been performed to provide the necessary database for the adaptation of a viscoplastic deformation model. To calculate the local stress–strain field and service life of the test specimens, linear elastic and viscoplastic finite element studies have been performed and were assessed by means of a fracture mechanics-based lifetime model. The test results show the considerable influence of the temperature gradient on the low-cycle fatigue life for the investigated material. Both the radial temperature variation over the specimen wall with a hot outer surface and a cooled inner surface as well as the thermally induced stresses are stated to be the main drivers for the change in low-cycle fatigue life. The test results enhance the understanding of fatigue-damage mechanisms under local unsteady conditions and can be used as a basis for improved service life predictions.

Novel Test Facility for Investigation of the Impact of Thermally Induced Stress Gradients on Fatigue Life of Cooled Gas Turbine Components

2018 ◽  
Author(s):  
Marcus Thiele ◽  
Uwe Gampe ◽  
Kathrin A. Fischer
Keyword(s):  
Fatigue Life ◽  
Low Cycle Fatigue ◽  
Heat Fluxes ◽  
Test Facility ◽  
Test Results ◽  
Cycle Fatigue ◽  
Thermally Induced ◽  
Stress Gradients ◽  
Induced Stress ◽  
The Impact

A novel test facility has been designed and set up for the investigation of the influence of stationary temperature, and thus thermally induced stress gradients with respect to the damage evolution of cooled gas turbine components. Thermally induced stress gradients differ from geometrically induced stress gradients. From the point of view of stress mechanics, they are independent from external loads. From the perspective of material mechanics, their impact on service life is influenced by locally different material properties and strength. However, the impact of thermally induced stress gradients on the cyclic life of high loaded, cooled components is not precisely known. In order to increase knowledge surrounding these mechanisms, a research project was launched. To achieve high temperature gradients and extended mechanical stress gradients, large heat fluxes are required. The authors developed a test bench with a unique radiant heating to achieve very high heat fluxes of q̇ ≥ 1.6MW/m2 on cylindrical specimen. Special emphasis has been placed on homogenous temperature and loading conditions in order to achieve valid test results comparable to standard low cycle or thermo-mechanical fatigue tests. Different test concepts of the literature were reviewed and the superior performance of the new test rig concept was demonstrated. The austenitic stainless steel 316L was chosen as the model material for commissioning and validation of the test facility. The investigation of thermally induced stress gradients and, based on this analysis, low-cycle fatigue tests with superimposed temperature gradients were conducted. Linear elastic finite element studies were performed to calculate the local stress-strain field and the service life of the test specimens. The test results show a considerable influence of the temperature gradient on the low-cycle fatigue life of the investigated material. Both the temperature variation over the specimen wall and thermally induced stresses are stated to be the main drivers for the change in low-cycle fatigue life. The test results increase the understanding of fatigue damage mechanisms under local unsteady conditions and can serve as a basis for improved lifetime calculation methods.

Topographic measurement of electromigration-induced stress gradients in aluminum conductor lines

2000 ◽  
Vol 76 (25) ◽  
pp. 3726-3728 ◽  
Author(s):  
P.-C. Wang ◽  
I. C. Noyan ◽  
S. K. Kaldor ◽  
J. L. Jordan-Sweet ◽  
E. G. Liniger ◽  
...  
Keyword(s):  
Stress Gradients ◽  
Induced Stress ◽  
Topographic Measurement
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