Abstract
The present paper deals with an experimental determination of fatigue crack growth rate (FCGR) of microalloyed steel (38MnVS6) to study the crack propagation in forged automobile crankshafts. The criterion based on crack tip opening displacement range (∆CTOD) is used to investigate the fatigue crack growth rate. In the current work use of 2D-digital image correlation (DIC) technique for the measurement of crack tip opening displacement (CTOD) and crack length (a) is proposed. Digital Image Correlation (DIC) is a full field displacement and strain measurement technique. It is easier to measure the crack tip opening displacement (CTOD) and crack length (a) with this technique than other. Fatigue crack growth curve based on crack tip opening displacement (CTOD) criteria is presented using DIC.
Highlights
Several models are suggested in literature to evaluate fatigue crack growth rate of a material [1]-[4]
Fatigue crack growth analysis based on the stress intensity factor range (∆K), as in equation (1), is applicable only for linear elastic fracture mechanics, under constant amplitude loading and only for long cracks
The concepts of J integral range (ΔJ), crack tip opening displacement range (ΔCTOD) and the energy release rate range (ΔG) are suggested in the literature to be used in place of stress intensity factor range (ΔK) in Paris law under large scale yielding [8], [9]
Summary
Several models are suggested in literature to evaluate fatigue crack growth rate of a material [1]-[4]. Fatigue crack growth analysis based on the stress intensity factor range (∆K), as in equation (1), is applicable only for linear elastic fracture mechanics (small scale yielding condition), under constant amplitude loading and only for long cracks. When these assumed requirements are not met Paris law is not applicable for prediction of the crack growth rate under cyclic condition [6],. Digital image correlation (DIC) is a non-contact optical technique which gives full field displacement and strain measurement in a deformed body This technique starts with taking an image prior to loading (reference image) in an un-deformed position and a series of pictures are captured throughout the deformation process (deformed images). Detailed information regarding DIC can be found in the literature [10]-[13]
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