Variable-Amplitude Fatigue Tests of Aluminum-Alloy Specimens

2009 ◽  
pp. 125-125-14 ◽  
Author(s):  
Herbert F. Hardrath ◽  
Eugene C. Naumann
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Tests ◽  
Variable Amplitude ◽  
Variable Amplitude Fatigue

Fatigue of Stabilized SS and 316 NG Alloy in PWR Environment

2006 ◽  
Author(s):  
Jussi P. Solin
Keyword(s):  
Stainless Steels ◽  
Fatigue Tests ◽  
Test Results ◽  
Constant Amplitude ◽  
Low Oxygen ◽  
Variable Amplitude ◽  
Variable Amplitude Fatigue ◽  
Reduction Factors

Strain controlled constant and variable amplitude fatigue tests for 316NG and Titanium stabilized stainless steels in low oxygen PWR waters were performed. The stabilized steel has been plant aged for 100 000 hours. Constant amplitude test results at 0,01 Hz sinusoidal straining comply with predicted lives according to the Fen approach for both materials. Spectrum straining both in air and in environment caused predicted life reduction factors (about 3) for the stabilized steel, but for the 316NG steel spectrum straining in environment resulted to a larger reduction in life.

Corrosion Fatigue of AZ91E-T6 Cast Magnesium Alloy in a 3.5 Percent NaCl Aqueous Environment

1995 ◽  
Vol 117 (3) ◽  
pp. 293-298 ◽  
Author(s):  
R. I. Stephens ◽  
C. D. Schrader ◽  
K. B. Lease
Keyword(s):  
Fatigue Life ◽  
Magnesium Alloy ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Mean Stress ◽  
Constant Amplitude ◽  
Variable Amplitude ◽  
Cast Magnesium Alloy ◽  
Cast Magnesium ◽  
Variable Amplitude Fatigue

The objective of this research was to obtain and compare constant and variable amplitude fatigue behavior of AZ91E-T6 cast magnesium alloy in both an air and 3.5 percent NaCl aqueous corrosive environment. An additional objective was to determine if commonly used models that describe fatigue behavior and fatigue life are applicable to this material and test environment. Fatigue tests included constant amplitude strain-controlled low cycle fatigue with strain ratio, R, equal to 0, −1 and −2, Region II constant amplitude fatigue crack growth with load ratio, R, equal to 0.05 and 0.5 and variable amplitude fatigue tests using keyhole notched specimens. In all fatigue tests, the corrosion environment was significantly detrimental relative to the air environment. Mean strains influenced fatigue life only if accompanied by significant mean stress. The Morrow and Smith, Watson, and Topper mean stress models provided both accurate and inaccurate fatigue life calculations. Likewise, variable amplitude fatigue life calculations using the local strain approach and based upon the formation ofal mm crack at the keyhole notch were both accurate and fairly inaccurate depending on the specific model used.

scholarly journals Effects of variable amplitude loading on fatigue life

2015 ◽  
Vol 6 (3) ◽  
pp. 10 ◽  
Author(s):  
Niels Laseure ◽  
Ingmar Schepens ◽  
Nahuel Micone ◽  
Wim De Waele
Keyword(s):  
Offshore Structures ◽  
Fatigue Tests ◽  
Variable Amplitude Loading ◽  
Variable Amplitude ◽  
Industrial Sectors ◽  
Closure Mechanism ◽  
Physical Phenomena ◽  
Published Research ◽  
Variable Amplitude Fatigue ◽  
Plasticity Induced Crack Closure

This paper is a review of published research on variable amplitude loading of steels. The use of service spectra for different industrial sectors and specifically for offshore applications is first considered. Constant amplitude fatigue failure models are not representative for these applications. The JONSWAP spectrum shows potential to be used as service spectrum for offshore structures. Further investigation of variable amplitude fatigue is needed to get insight in the various phenomena linked to the variable amplitude. Observed trends in fatigue crack growth rate in variable amplitude fatigue tests on steels, such as the effects of overloads and underloads (occurring as single events, sequential events or block loadings), are discussed. Furthermore, suggestions of the underlying physical phenomena behind the load interaction effects due to variable amplitude loading are presented. It can be concluded that the plasticity induced crack closure mechanism is the most profound explanation for the acceleration effect in overloads and the retardation effect observed in underloads.

scholarly journals Experimental Study on Variable-Amplitude Fatigue of Welded Cross Plate-Hollow Sphere Joints in Grid Structures

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Jin-Feng Jiao ◽  
Hong-Gang Lei ◽  
Y. Frank Chen
Keyword(s):  
Fatigue Life ◽  
Hollow Sphere ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Metallographic Analysis ◽  
Variable Load ◽  
Random Loading ◽  
Variable Amplitude ◽  
Different Types ◽  
Variable Amplitude Fatigue

The fatigue stress amplitude of the welded cross plate-hollow sphere joint (WCPHSJ) in a grid structure varies due to the random loading produced by suspending cranes. A total of 14 specimens considering three different types of WCPHSJs were prepared and tested using a specially designed test rig. Four typical loading conditions, “low-high,” “high-low,” “low-high-low,” and “high-low-high,” were first considered in the tests to investigate the fatigue behavior under variable load amplitudes, followed by metallographic analyses. The experimental and metallographic analysis results provide a fundamental understanding on the fatigue fracture form and fatigue mechanism of WCPHSJs. Based on the available data from constant-amplitude fatigue tests, the variable-amplitude fatigue life of the three types of WCPHSJs was estimated using the Miner rule and Corten-Dolan theory. Since both accumulative damage theories yield virtually same damaging results, the Miner rule is hence suggested to estimate the fatigue life of WCPHSJs.

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