Microstructural effects and crack closure during near Threshold Fatigue Crack Propagation in a High Strength Steel

Ravichandran, K.; Rao, H. C. Venkata; Dwarakadasa, E. S.; Nair, C. G. Krishnadas

doi:10.1007/bf02646928

Cited by 25 publications

(2 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Crack closure can also be used to explain the effect of prestrain on near-threshold FCGR [50][51][52][53]. In this case, the crack closure values of pre-strained materials go down as compared to the corresponding non pre-strained materials.…”

Section: Effect Of R Ratio and Pre-strain On Fcgrmentioning

confidence: 99%

Statistical modeling of fatigue crack growth rate in pre-strained 7475-T7351 aluminum alloy

Al-Rubaie

Barroso

Godefroid

2008

Materials Science and Engineering: A

View full text Add to dashboard Cite

Section: Effect Of R Ratio and Pre-strain On Fcgrmentioning

confidence: 99%

Statistical modeling of fatigue crack growth rate in pre-strained 7475-T7351 aluminum alloy

Al-Rubaie

Barroso

Godefroid

2008

Materials Science and Engineering: A

View full text Add to dashboard Cite

“…This single slip mechanism leads to a zigzag crack path. Formation of secondary cracks (indicated by arrow mark) is ascribed to the liberation of atomic hydrogen from moist air in the laboratory air environment (Ravichandran et al 1986;Ravichandran and Dwarakadasa 1987). The secondary cracks are responsible for the deceleration of crack growth.…”

Section: Influence Of Microstructure On Fractographic Featuresmentioning

confidence: 99%

A study on fatigue crack growth in dual phase martensitic steel in air environment

Sudhakar

Dwarakadasa

2000

Bull Mater Sci

Self Cite

View full text Add to dashboard Cite

Dual phase (DP) steel was intercritically annealed at different temperatures from fully martensitic state to achieve martensite plus ferrite, microstructures with martensite contents in the range of 32 to 76%. Fatigue crack growth (FCG) and fracture toughness tests were carried out as per ASTM standards E 647 and E 399, respectively to evaluate the potential of DP steels. The crack growth rates (da/dN) at different stress intensity ranges (∆ ∆K) were determined to obtain the threshold value of stress intensity range (∆ ∆K th). Crack path morphology was studied to determine the influence of microstructure on crack growth characteristics. After the examination of crack tortuosity, the compact tension (CT) specimens were pulled in static mode to determine fracture toughness values. FCG rates decreased and threshold values increased with increase in vol.% martensite in the DP steel. This is attributed to the lower carbon content in the martensite formed at higher intercritical annealing (ICA) temperatures, causing retardation of crack growth rate by crack tip blunting and/or deflection. Roughness induced crack closure was also found to contribute to the improved crack growth resistance at higher levels of martensite content. Scanning electron fractography of DP steel in the near threshold region revealed transgranular cleavage fracture with secondary cracking. Results indicate the possibility that the DP steels may be treated to obtain an excellent combination of strength and fatigue properties. Keywords. Dual phase (DP) steel; fatigue crack growth; fracture toughness; stress intensity range; intercritical annealing; crack closure.

show abstract

Prediction of fatigue crack growth rate in steels

Zheng

1992

Int J Fract

View full text Add to dashboard Cite

It has been recognized that the fatigue life of a cyclically loaded engineering element containing a crack-like defect depends upon the growth rate of the defect from its original size to the critical one which causes the final fracture of the element under service loading [1]. In recent years, the fracture mechanics approach has been widely applied in predicting the fatigue life of engineering elements and the fatigue crack growth rate (FCGR) curve, in which the FCGR, i.e. da/dN, is presented as a function of the stress intensity factor range, AK (see Fig. 1), and is now commonly used as a measure for comparing the crack growth resistance of metals, as well as a part of engineering standard and design codes. Most test data reported in the literature for crack growth behavior of metals were obtained in the intermediate region, i.e. da/dN = 108 -10 ~ m/cycle, and were correlated through Paris' formula [2,3]: da ~v = C (~) " (I)Though Paris' formula gives good fit to the test data in the intermediate rate region, it fails to so in the near-threshold region. It is well known that, however, the major part of the crack growth life of an engineering element is expended in the near-threshold fatigue crack growth because of the small size of the initial crack or defect [1,4]. The crack growth threshold AK,~ is an important factor governing the FCGR in the near-threshold region. Unfortunately, the experimental determination AK~ is rather difficult and expensive, although great efforts have been made to simplify the testing procedure. Therefore, an accurate expression for prediction of the FCGR both in the near-threshold and intermediate regions is very desirable for the structural damage tolerance design and the life prediction. In this paper a method for prediction of the FCGR in structural steels was tentatively proposed and checked by the test results. Based upon the modified static fracture model of the crack tip, Zheng and Hirt developed an expression for the FCGR in metals [5], da = B (AK -AK,h) 2 dN (2) Int Journ of Fracture 55 (1992)

show abstract

Microstructural effects and crack closure during near Threshold Fatigue Crack Propagation in a High Strength Steel

Cited by 25 publications

References 30 publications

Statistical modeling of fatigue crack growth rate in pre-strained 7475-T7351 aluminum alloy

Statistical modeling of fatigue crack growth rate in pre-strained 7475-T7351 aluminum alloy

A study on fatigue crack growth in dual phase martensitic steel in air environment

Prediction of fatigue crack growth rate in steels

Contact Info

Product

Resources

About