Influence of minimum temperature on the thermomechanical fatigue of a directionally-solidified Ni-base superalloy

被引:19
作者
Kupkovits, Robert A. [1 ]
Smith, Daniel J. [2 ]
Neu, Richard W. [2 ,3 ]
机构
[1] Exponent Failure Anal Associates, Los Angeles, CA 90034 USA
[2] Georgia Inst Technol, Sch Mech Engn & Mech Properties Res Lab, Atlanta, GA 30332 USA
[3] Georgia Inst Technol, Sch Mat sci & Engn, Atlanta, GA 30332 USA
来源
FATIGUE 2010 | 2010年 / 2卷 / 01期
关键词
Thermomechanical fatigue; creep; rafting; Ni-base superalloy;
D O I
10.1016/j.proeng.2010.03.074
中图分类号
TH [机械、仪表工业];
学科分类号
0802 ;
摘要
It is well understood that thermomechanical fatigue (TMF) lives are significantly influenced by the maximum temperature of the cycle since increasing temperature accelerates both creep and the coupled fatigue-oxidation effects, usually exponentially with increasing temperature. Hence, most TMF experiments focus on the impact of the maximum temperature of the cycle along with the phasing of the temperature and strain. Very little focus has been placed on the role of the minimum temperature of the TMF cycle. Usually the minimum temperature is chosen for experimental expediency and is not based on minimum temperature experienced in actual components. For example, in a gas turbine, the minimum temperature for an extended shutdown is near room temperature. This paper shows that out-of-phase TMF with lower minimum temperature while maintaining the same mechanical strain results in lower life. Possible explanations for the reduction in life include the increase in inelastic strain range due to the increase in elastic modulus at lower temperatures and microstructural changes that occur at elevated temperature, reducing the lower temperature yield strength. Both experiments and simulations using crystal viscoplasticity modeling show that the increase in elastic modulus with decreasing temperature leads to greater inelastic strain range and a commensurate reduction in fatigue life. This effect is just as important to consider as the influence of microstructure changes occurring at the elevated temperatures of the cycle. (C) 2010 Published by Elsevier Ltd.
引用
收藏
页码:687 / 696
页数:10
相关论文
共 11 条
[1]  
[Anonymous], 2007, ASTM standard D698-07
[2]  
Arrell D, 2004, SUPERALLOYS 2004, P291, DOI 10.7449/2004/Superalloys_2004_291_294
[3]  
HASELQVIST M, 2007, P ASME TURB EXP 2007
[4]  
KUPKOVITS RA, 2010, INT J FATIG IN PRESS
[5]  
KUPKOVITS RA, 2009, THESIS GEORGIA I TEC
[6]  
Mughrabi H, 2000, ADV ENG MATER, V2, P319, DOI 10.1002/1527-2648(200006)2:6<319::AID-ADEM319>3.0.CO
[7]  
2-S
[8]  
NEUNER FC, 2002, ASTM STP, V1428
[9]  
OTT M, 1996, P FATIGUE 96, V2, P789
[10]   Thermomechanical fatigue behavior of a directionally solidified Ni-base superalloy [J].
Shenoy, MM ;
Gordon, AP ;
McDowell, DL ;
Neu, RW .
JOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY-TRANSACTIONS OF THE ASME, 2005, 127 (03) :325-336