Evaluation of the Behaviour of Steel Bar in the Concrete under Cyclic Loading Using Magnetic Flux Leakage and Acoustic Emission Techniques.

The behaviour of the steel bar in concrete under cyclic loading has been evaluated using magnetic flux leakage associated with acoustic emission monitoring technique. Visual observation was used to observe the deformation of the beam under cyclic loading. The sensors of metal magnetic memory were scanned in the middle of the beam at a distance of 320 mm at the bottom part. Twenty-two cyclic ranges were performed for cyclic loading of 100 or 200 cycles for each range, with a frequency of 1 Hz and a sinusoidal wave mode. The magnetic flux leakage signal, acoustic emission characteristics and crack width were measured and analysed to evaluate the behaviour of the steel bar in the concrete beam. The magnetic flux leakage signal and acoustic emission energy results were well matched with the occurrence of cracks at the centre of the beam. It was found that the relationship between the magnetic leakage flux signal and crack opening showed a strong correlation with R2 of 0.969. A high acoustic emission energy of 1300 nVs is observed at the centre of the beam. Based on the results, the behaviour of the steel in the concrete beam can be determined by the integrity assessment of a structure.

Fatigue Life Assessment of API Steel Grade X65 Pipeline Using a Modified Basquin Parameter of the Magnetic Flux Leakage Signal.

This paper presents a modified fatigue life model of the Basquin equation using the stress parameter of the magnetic flux leakage signal. Most pipeline steels experience cyclic loading during service and the influence of the load history makes assessing fatigue behaviour more difficult. The magnetic flux leakage signal's response to a uniaxial cyclic test of API X65 steel was measured with eight levels of ultimate tensile stress loads. The influence of dH(y)/dx on fatigue failure was the main concern in this study, the aim being to represent localised stress parameters in the modified Basquin equation. Both fatigue lives, experimental and predicted from the modified Basquin equation, were validated through reliability analysis, producing a 60% value when approaching 1.8 × 105 cycles. The fatigue data from the experiment produced a higher mean-cycle-to-failure value than the prediction data, with slightly different values of 3.37 × 105 and 3.28 × 105. Additionally, the modified Basquin equation's predicted and the experimental fatigue lives were found to have a high R2 correlation value of 0.9022. The Pearson correlation also showed a good relationship between the fatigue lives, with an r value of 0.9801. Finally, the modified Basquin equation based on dH(y)/dx signals provided an accurate and alternative method for durability assessment.