Mechanistic Studies of High-Temperature Crack Initiation in Single Crystal Materials

2009 ◽  
pp. 81-81-12
Author(s):  
E. P. Busso ◽  
N. P. O'Dowd ◽  
K. Nikbin
Keyword(s):  
High Temperature ◽  
Crack Initiation ◽  
Single Crystal ◽  
Mechanistic Studies ◽  
Temperature Crack

Crack initiation mechanisms during very high cycle fatigue of Ni-based single crystal superalloys at high temperature

2020 ◽  
Vol 188 ◽  
pp. 131-144 ◽  
Author(s):  
A. Cervellon ◽  
S. Hémery ◽  
P. Kürnsteiner ◽  
B. Gault ◽  
P. Kontis ◽  
...  
Keyword(s):  
High Temperature ◽  
Crack Initiation ◽  
Single Crystal ◽  
High Cycle Fatigue ◽  
Cycle Fatigue ◽  
Very High Cycle Fatigue ◽  
Very High

scholarly journals Fatigue Life Prediction Modeling for Turbine Hot Section Materials

1989 ◽  
Vol 111 (2) ◽  
pp. 279-285 ◽  
Author(s):  
G. R. Halford ◽  
T. G. Meyer ◽  
R. S. Nelson ◽  
D. M. Nissley ◽  
G. A. Swanson
Keyword(s):  
High Temperature ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Single Crystal ◽  
Life Prediction ◽  
Fatigue Crack Initiation ◽  
Prediction Method ◽  
Nasa Lewis Research ◽  
Prediction Modeling ◽  
Cyclic Damage

This paper presents a summary of the life prediction methods developed under the NASA Lewis Research Center’s Hot Section Technology (HOST) program. A major objective of the fatigue and fracture efforts under the HOST program was to significantly improve the analytic life prediction tools used by the aeronautical gas turbine engine industry. This has been achieved in the areas of high-temperature thermal and mechanical fatigue of bare and coated high-temperature superalloys. Such technical improvements will eventually reduce life cycle costs. The cyclic crack initiation and propagation resistance of nominally isotropic polycrystalline alloys and highly anisotropic single crystal alloys have been addressed. A sizeable data base has been generated for three alloys [cast PWA 1455 (B–1900 + Hf), wrought Inconel 718, and cast single-crystal PWA 1480] in bare and coated conditions. Two coating systems, diffusion aluminide (PWA 273) and plasma-sprayed MCrAlY overlay (PWA 286), were employed. Life prediction modeling efforts were devoted to creep-fatigue interaction, oxidation, coatings interactions, multiaxially of stress-strain states, mean stress effects, cumulative damage, and thermomechanical fatigue. The fatigue crack initiation life models developed to date include the Cyclic Damage Accumulation (CDA) Model of Pratt & Whitney and the Total Strain Version of Strainrange Partitioning (TS-SRP) of NASA Lewis for nominally isotropic materials, and the Tensile Hysteretic Energy Model of Pratt & Whitney for anisotropic superalloys. The fatigue model being developed by the General Electric Company is based upon the concepts of Path-Independent Integrals (PII) for describing cyclic crack growth under complex non-linear response at the crack tip due to thermomechanical loading conditions. A micromechanistic oxidation crack extension model has been derived by researchers at Syracuse University. The models are described and discussed in the paper. Only limited verification has been achieved to date as several of the technical programs are still in progress and the verification tasks are scheduled, quite naturally, near the conclusion of the program. To date, efforts have concentrated on developement of independent models for cyclic constitutive behavior, cyclic crack initiation, and cyclic crack propagation. The transition between crack initiation and crack propagation has not been thoroughly researched as yet, and the integration of these models into a unified life prediction method has not been addressed.

Standardisation of High Temperature Crack Growth Testing of Weldments

2006 ◽  
Author(s):  
B. Dogan ◽  
U. Ceyhan ◽  
K. Nikbin ◽  
D. Dean
Keyword(s):  
High Temperature ◽  
Crack Initiation ◽  
Crack Growth ◽  
Structural Integrity ◽  
Material Selection ◽  
International Institute ◽  
Select Committee ◽  
Subject Field ◽  
High Temperature Testing ◽  
Temperature Crack

A European collaborative effort has been made to produce a Code of Practice (CoP), with participation from the European Structural Integrity Society (ESIS) TC11-Working Group on High Temperature Testing of Weldments (WG on HTTW) and EC project CRETE. The prepared CoP is based on the authors’ and project partners’ long years of experience in the subject field of high temperature testing, deformation studies and crack growth on various materials studied in internal, European and international projects. The code is being processed for ISO standardization by the International Institute of Welding (IIW), Select Committee Standardization (SC STAND). Guidelines are established for material and specimen selection. The document aims at giving advice on testing, measurements and analysis of creep crack initiation and growth data for a range of creep brittle to creep ductile materials. It may be used for material selection criteria and inspection requirements for damage tolerant applications. In quantitative terms, it can be used to assess the individual and combined effects of metallurgical, fabrication, operating temperature, and loading conditions on welded components for high temperature service. The present paper reports on the standardisation of high temperature crack initiation and crack growth testing in weldments. The material behaviour in service, including significance of creep and loading, substantiates the testing and data analyses procedure for design as well as fitness-for-purpose assessment.

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