Rethinking fatigue crack growth: Crack growth at constant R and strain energy

2017 ◽  
Vol 41 (3) ◽  
pp. 700-707 ◽  
Author(s):  
K. Walker
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Strain Energy ◽  
Growth Crack

Three Stages of Fatigue Crack Growth in GFRP Composite Laminates

2000 ◽  
Vol 123 (1) ◽  
pp. 139-143 ◽  
Author(s):  
Jie Tong
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Energy Release ◽  
Crack Growth ◽  
Strain Energy ◽  
Strain Energy Release ◽  
Release Rates ◽  
Energy Release Rates ◽  
Three Stages ◽  
Strain Energy Release Rates

Multiple fatigue crack growth behavior has been studied in model transparent GFRP laminates. Detailed experimental observations have been made on the growth of individual fatigue cracks and on the evolution of cracks in off-axis layers in 0/90/±45S and ±45/90S laminates. Three stages of fatigue crack growth in the laminates have been identified: initiation, steady-state crack growth (SSCG), crack interaction and saturation. The results show that SSCG rate is essentially constant under constant load, independent of crack length and crack spacing. Finite element models have been developed and used to calculate the strain energy release rates associated with the off-axis matrix cracking. A correlation has been achieved between fatigue crack growth rates in off-axis layers and the total strain energy release rates.

scholarly journals Improved computation method in residual life estimation of structural components

2013 ◽  
Vol 40 (2) ◽  
pp. 247-261
Author(s):  
Stevan Maksimovic ◽  
Katarina Maksimovic
Keyword(s):  
Fatigue Crack ◽  
Energy Density ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Crack Closure ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Computation Method ◽  
Structural Components

This work considers the numerical computation methods and procedures for the fatigue crack growth predicting of cracked notched structural components. Computation method is based on fatigue life prediction using the strain energy density approach. Based on the strain energy density (SED) theory, a fatigue crack growth model is developed to predict the lifetime of fatigue crack growth for single or mixed mode cracks. The model is based on an equation expressed in terms of low cycle fatigue parameters. Attention is focused on crack growth analysis of structural components under variable amplitude loads. Crack growth is largely influenced by the effect of the plastic zone at the front of the crack. To obtain efficient computation model plasticity-induced crack closure phenomenon is considered during fatigue crack growth. The use of the strain energy density method is efficient for fatigue crack growth prediction under cyclic loading in damaged structural components. Strain energy density method is easy for engineering applications since it does not require any additional determination of fatigue parameters (those would need to be separately determined for fatigue crack propagation phase), and low cyclic fatigue parameters are used instead. Accurate determination of fatigue crack closure has been a complex task for years. The influence of this phenomenon can be considered by means of experimental and numerical methods. Both of these models are considered. Finite element analysis (FEA) has been shown to be a powerful and useful tool1,6 to analyze crack growth and crack closure effects. Computation results are compared with available experimental results.

Fatigue crack propagation prediction of a pressure vessel mild steel based on a strain energy density model

2017 ◽  
Author(s):  
P. J. Huffman ◽  
J. Ferreira ◽  
J.A.F.O. Correia ◽  
A.M.P. De Jesus ◽  
G. Lesiuk ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Energy Density ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Pressure Vessel ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Propagation Model ◽  
Crack Growth Rates

Fatigue crack growth (FCG) rates have traditionally been formulated from fracture mechanics, whereas fatigue crack initiation has been empirically described using stress-life or strain-life methods. More recently, there has been efforts towards the use of the local stress-strain and similitude concepts to formulate fatigue crack growth rates. A new model has been developed which derives stress-life, strain-life and fatigue crack growth rates from strain energy density concepts. This new model has the advantage to predict an intrinsic stress ratio effect of the form ?ar=(?amp)?·(?max )(1-?), which is dependent on the cyclic stress-strain behaviour of the material. This new fatigue crack propagation model was proposed by Huffman based on Walkerlike strain-life relation. This model is applied to FCG data available for the P355NL1 pressure vessel steel. A comparison of the experimental results and the Huffman crack propagation model is made.

Fatigue Processes in Silicon MEMS Devices

2001 ◽  
Vol 682 ◽  
Author(s):  
Emily D. Renuart ◽  
Alissa M. Fitzgerald ◽  
Thomas W. Kenny ◽  
Reinhold H. Dauskardt
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Crack Extension ◽  
Stable Crack Growth ◽  
Growth Stress ◽  
Mems Devices ◽  
Beam Geometry ◽  
Growth Crack ◽  
Crack Growth Curve

ABSTRACTMEMS devices may experience significant alternating loads during service, associated with both applied and vibrational loading. Long-term reliability and lifetime predictions require understanding of possible fatigue mechanisms in these structures. Although silicon is not generally considered susceptible to fatigue crack growth, recent studies suggest that there may be fatigue processes in silicon MEMS structures. The phenomenon, however, has still not been extensively studied. In this work, we used a compressive double cantilever beam geometry to examine stable crack growth. Crack length and loads were carefully monitored throughout the test in order to distinguish between the apparent role of environmentally assisted crack growth (stress corrosion) and mechanically induced fatigue. Results revealed similar step-like crack extension versus time for the cyclic and monotonic tests. The fatigue crack-growth curve extracted from the crack extension data exhibited a nearly vertical slope with no evidence of fatigue crack-growth. Fracture surfaces for the monotonic and cyclic tests were similar, further suggesting that a true mechanical fatigue crack-growth mechanism did not occur.

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