Acoustic emission (AE) technique is used for monitoring and evaluating the influence of corrosion on the structural behaviour of steel reinforced concrete (RC) beams under three-point flexure test. In this study, steel corrosion was accelerated by electro-chemical method utilising a direct current (DC) power supply and 5% sodium chloride (NaCl) solution. The steel corrosion that was induced into beam specimens casting were estimated at 0%, 4.55% and 32.37%, respectively, according to mass loss of steel reinforcement. Based on observations during static load test, the damage developed in the specimens could be classified into four different stages, namely, micro-cracking, first visible cracks, cracks distribution, as well as damage localization and yielding. Analysis of the AE data reveals distinguishable trends for RA value and average frequency (AF) registered for different corrosion levels, respectively. Moreover, the index of damage (ID) derived from the AE energy parameters obtained during the first stage of damage was found to be useful as an indicator for evaluating the extent of corrosion damage of RC beam specimens at initial loadings. In addition, to provide a practical application of AE toward life span estimation of corroded beam specimen, a Weibull damage function was introduced to estimate the remaining flexural capacity of the beam specimens. Based on analysis as well, it is noted that tensile fracture became more dominant with an increase in corrosion level.

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In this paper, we present a high-speed direct pattern fabrication on hard materials (e.g., a tungsten-coated quartz substrate) via mechanical plowing. Compared to other probe-based nanolithography techniques based on chemical- and/or physical-reactions (e.g., the Dip-pen technique), mechanical plowing is meritorious for its low cost, ease of process control, and capability of working with a wide variety of materials beyond conductive and/or soft materials. However, direct patterning on hard material faces two daunting challenges. First, the patterning throughput is ultimately hindered by the "writing" (plowing) speed, which, in turn, is limited by the adverse effects that can be excited/induced during high-speed, and/or large-range plowing, including the vibrational dynamics of the actuation system (the piezoelectric actuator, the cantilever, and the mechanical fixture connecting the cantilever to the actuator), the dynamic cross-axis coupling between different axes of motion, and the hysteresis and the drift effects related to the piezoelectric actuators. Secondly, it is very challenging to directly pattern on ultra-hard materials via plowing. Even with a diamond probe, the line depth of the pattern via continuous plowing on ultra-hard materials such as tungsten, is still rather small (<0.5 nm), particularly when the "writing" speed becomes high. To overcome these two challenges, we propose to utilize a novel iterative learning control technique to achieve precision tracking of the desired pattern during high-speed, large-range plowing, and introduce ultrasonic vibration of the probe in the normal (vertical) direction during the plowing process to enable direct patterning on ultra hard materials. The proposed approach was implemented to directly fabricate patterns on a mask with tungsten coating and quartz substrate. The experimental results demonstrated that a large-size pattern of four grooves (20 μm in length with 300 nm spacing between lines) can be fabricated at a high speed of ~5 mm/s, with the line width and the line depth at ~95 nm and 2 nm, respectively. A fine pattern of the word "NANO" is also fabricated at the speed of ~5 mm/s.

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