Luca Vecchiato , Alberto Campagnolo , Matteo Cova , Giovanni Meneghetti
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Abstract
This study investigates potentials and limitations of the Direct Current Potential Drop (DCPD) method for monitoring fatigue crack size in single-edge-crack round bars made of 42CrMo4 steel. Specimens with a semi-elliptical crack-starter notch were tested under axial fatigue loading, with DCPD applied in various configurations to evaluate the impact of current and potential probe positions on measurement overall accuracy. Therefore, experimental DCPD calibration data were developed by correlating the measured signals with the corresponding crack fronts identified through beach marking. Eventually, experimental data were compared with calibration curves obtained from electrical FE analyses, where semi-elliptical cracks were modelled using crack fronts best fitted to the beach-marked experimental fronts. The results confirmed the reliability and accuracy of DCPD for monitoring fatigue crack growth in single-edge-crack round bars, provided that the propagating crack shape is known a priori. Moreover, the effect of probe positioning was highlighted: current injection near the crack plane with potential probes at the crack symmetry plane improved measurability, while the highest sensitivity was achieved with probes near the crack tip. Both local and remote current injections, with current and potential probes at the crack symmetry plane, provided comparable accuracy, making these setups promising for experimental fracture mechanics testing.
期刊介绍：
Typical subjects discussed in International Journal of Fatigue address:
Novel fatigue testing and characterization methods (new kinds of fatigue tests, critical evaluation of existing methods, in situ measurement of fatigue degradation, non-contact field measurements)
Multiaxial fatigue and complex loading effects of materials and structures, exploring state-of-the-art concepts in degradation under cyclic loading
Fatigue in the very high cycle regime, including failure mode transitions from surface to subsurface, effects of surface treatment, processing, and loading conditions
Modeling (including degradation processes and related driving forces, multiscale/multi-resolution methods, computational hierarchical and concurrent methods for coupled component and material responses, novel methods for notch root analysis, fracture mechanics, damage mechanics, crack growth kinetics, life prediction and durability, and prediction of stochastic fatigue behavior reflecting microstructure and service conditions)
Models for early stages of fatigue crack formation and growth that explicitly consider microstructure and relevant materials science aspects
Understanding the influence or manufacturing and processing route on fatigue degradation, and embedding this understanding in more predictive schemes for mitigation and design against fatigue
Prognosis and damage state awareness (including sensors, monitoring, methodology, interactive control, accelerated methods, data interpretation)
Applications of technologies associated with fatigue and their implications for structural integrity and reliability. This includes issues related to design, operation and maintenance, i.e., life cycle engineering
Smart materials and structures that can sense and mitigate fatigue degradation
Fatigue of devices and structures at small scales, including effects of process route and surfaces/interfaces.
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