On Effective Stress Range Factor in Fatigue

1980 ◽  
Vol 102 (1) ◽  
pp. 147-152 ◽  
Author(s):  
K. M. Lal ◽  
S. B. L. Garg ◽  
I. Le May
Keyword(s):  
Fatigue Crack ◽  
Crack Closure ◽  
Effective Stress ◽  
Stress Ratio ◽  
Stress Amplitude ◽  
Simplified Model ◽  
Strain Hardening Exponent ◽  
Stress Range ◽  
Stress Cycles ◽  
Good Agreement

A detailed analysis of crack closure during fatigue crack propagation has been made using a simplified model. In addition, experimental work has been conducted using eddy current methods to determine crack closure. It was found that the effective stress range factor, U, depends on the applied stress range, stress ratio, yield strength and strain hardening exponent of the material, and that its value stabilizes in about 10 stress cycles for constant stress amplitude loading. Experimental and predicted results were seen to be in good agreement.

Effect of Stress Ratio on Fatigue Crack Growth in 95Pb-5Sn Solder

1999 ◽  
Vol 123 (3) ◽  
pp. 311-315 ◽  
Author(s):  
J. Zhao and ◽  
Y. Mutoh ◽  
T. Ogawa
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Crack Closure ◽  
Stress Ratio ◽  
High Stress ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Threshold Region ◽  
Test Conditions

The stress ratio effect on the fatigue crack growth behavior of 95Pb-5Sn solder has been investigated. It is found that both ΔJ and ΔK can correlate fatigue crack growth data well, which means that the crack growth behavior of the 95Pb-5Sn solder under the frequency of 10 Hz was dominantly cyclic dependent. The da/dN-ΔJ relationship can be expressed as: da/dN=1.1×10−11s˙ΔJ1.45. Low level of crack closure was found only in the near-threshold region. Except in this region, no crack closure was observed in the present test conditions. Both transgranular and intergranular fractures were observed on fracture surfaces: the former was dominant in most test conditions and the latter was dominant at the high stress ratio of 0.7. Striations and striation-like features were also found. Many slip bands and cavities along the grain boundary were observed on the crack wake and ahead of the crack tip in the high crack growth rate region.

Accounting for Negative R-Ratio (Crack Closure) in Fatigue Crack Growth Calculations on Stainless Steel Components

2015 ◽  
Author(s):  
Chris Watson ◽  
Chris Currie ◽  
Julian Emslie
Keyword(s):  
Stainless Steel ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Crack Closure ◽  
Crack Opening ◽  
Stress Range ◽  
Stress Cycle ◽  
R Ratio ◽  
Cylindrical Test

Negative R-ratio crack closure effects on Fatigue Crack Growth (FCG) are defined as the contribution of the compressive portion of the stress cycle to the crack extension, in addition to that contributed from the tensile portion of the cycle. Any potential decrease in FCG may be attributed to the mechanical effects of crack closure during the compressive part of the cycle. The overall effect is to decrease the crack opening portion of the stress range and to therefore reduce the crack growth rate compared to that obtained using the full stress range. This paper provides a brief overview of the treatment of negative R-ratio crack closure in FCG calculations on stainless steel components by reference to existing codes and standards. Then, using the results from crack closure tests on small cylindrical test specimens, a set of guidelines for the treatment of crack closure in the FCG assessment of stainless steel components are provided.

scholarly journals Modeling of Fatigue Crack Propagation in Aluminum Alloys Using an Energy Based Approach

2013 ◽  
Vol 3 (4) ◽  
pp. 488-496
Author(s):  
F. Khelil ◽  
B. Aour ◽  
M. Belhouari ◽  
N. Benseddiq
Keyword(s):  
Fatigue Crack ◽  
Aluminum Alloys ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Stress Ratio ◽  
Numerical Determination ◽  
Cracking Mechanisms ◽  
Load Pattern ◽  
Good Agreement

Materials fatigue is a particularly serious and unsafe kind of material destruction. Investigations of the fatigue crack growth rate and fatigue life constitute very important and complex problems in mechanics. The understanding of the cracking mechanisms, taking into account various factors such as the load pattern, the strain rate, the stress ratio, etc., is of a first need. In this work an energy approach of the Fatigue Crack Growth (FCG) was proposed. This approach is based on the numerical determination of the plastic zone by introducing a novel form of plastic radius. The experimental results conducted on two aluminum alloys of types 2024-T351 and 7075-T7351 were exploited to validate the developed numerical model. A good agreement has been found between the two types of results.

Sign in / Sign up

Export Citation Format

Share Document