K. S. C. Kuang

• PhD, BEng(Hons), MBA
• Associate Professor at National University of Singapore

This paper presents a novel sensor for monitoring concrete surrounding the rebar for chlorides ingress, which is one the main precursors for rebar corrosion. The sensor consists of an optical probe housing a camera and electrical units. It also consists of a sacrificial metal foil, which is representative of the rebar material. The thickness range...

Corrosion of reinforcement in concrete is one of the major causes for deterioration of concrete structures. This work presents an approach in the monitoring of concrete structures for damage induced by corrosion of steel in concrete using a lens-based plastic optical fiber (LPOF) strain sensor. The optical fiber sensor offers the advantage of being...

This paper presents a novel fatigue crack monitoring method for steel specimens based on the smoothness priors method (SPM) and Tsallis entropy (TE) of strain measurements. The aim of the study is to detect initiation of a crack in steel specimens and subsequently to monitor its propagation under the fatigue load, based on real-time strain measurem...

One of the key parameters monitored in structural health monitoring applications is strain. In this work an extrinsic plastic optical fiber (POF) sensor developed previously has been optimised to increase its strain sensitivity. The extrinsic POF sensor basic design used here and previously comprises of two fiber units. As the distance of separatio...

A non-intrusive method is proposed in this study with details showing the steps to convert rail pad into a load sensor for train wheel damage detection applications. The fabrication process is simple, requiring only the addition of a thin PVDF-based multilayered sensing device (approximately 0.7 mm) beneath the rail pad. An alternating-strip config...

Noncontact measurement techniques in structural dynamics field have progressed significantly in the past few decades. Vision-based measurement techniques are unique in that they have the ability to achieve full-field measurement and possess the typical advantages associated with noncontact measurement techniques. Recently, vision-based techniques h...

Taking the role of a team of civil engineers, students working in a group of five prepare a bid for a civil infrastructural project for the government to address a pressing need in society. Students were guided using a framework where they identify, define, set goals, generate solutions, and evaluate alternatives from the financial, economic, envir...

This paper presents a framework for segmentation of imaging probe corrosion sensor data using a deep learning algorithm and estimation of the remaining service life of the structure using the segmented data. The sensor consists of a sacrificial metal foil that is imaged using the optical probe and the changes in the images as corrosion develops can...

Optical fibre sensors have shown their excellent potential for structural monitoring in a variety of engineering structures. This paper discussed the feasibility of real-time monitoring of fatigue crack using an extrinsic plastic optical fibre sensor. This intensity-based plastic optical fibre (POF) sensor was fabricated by connecting two cleaved o...

This article focuses on the rail crack monitoring using acoustic emission technique in the field typically with complex cracking conditions and high operational noise. A novel crack monitoring strategy based on Tsallis synchrosqueezed wavelet entropy was developed, where synchrosqueezed wavelet transform was introduced to explore the time–frequency...

A novel sensing application based on chemiluminescence was designed and tested in the laboratory for deformation monitoring in soil. The device, containing the reactants stored in separate chambers, on activation when deformed under load, result in an almost instantaneous production of light which could be readily detected using low-cost optoelectr...

Plastic optical fiber (POF) sensors have shown excellent potential for damage detection and structural health monitoring in a variety of engineering structures. This paper discusses the feasibility of using POF sensors in conjunction with a signal-processing algorithm capable of detecting and monitoring fatigue-induced cracks in train track steel s...

This paper investigates the capability of a novel piezoelectric sensor for low-frequency and low-amplitude vibration measurement. The proposed design effectively amplifies the input acceleration via two amplifying mechanisms and thus eliminates the use of the external charge amplifier or conditioning amplifier typically employed for measurement sys...

The acoustic emission (AE) technique is a promising approach for detecting and locating fatigue cracks in metallic structures such as rail tracks. However, it is still a challenge to quantify the crack size accurately using this technique. AE waves can be generated by either crack propagation (CP) or crack closure (CC) processes and classification...

This paper summarizes a study of a low-cost device capable of crack sensing and healing intended for smart concrete developments. Crack sensing capability of the device was achieved via a wire-crack sensor, while healing of concrete cracks was realized through an embedded healing tube containing a copolymer adhesive which was released following fra...

Taking advantage of the high sensitivity and long-distance detection capability of acoustic emission (AE) technique, this paper focuses on the crack detection in rail head, which is one of the most vulnerable parts of rail track. The AE source location and noise cancellation were studied on the basis of practical rail profile, material and operatio...

Coupled structures are widely seen in civil and mechanical engineering. In coupled structures, monitoring the translational motion of its key components is of great importance. For instance, some coupled arms are equipped with a hydraulic piston to provide the stiffness along the piston axial direction. The piston moves back and forth and a distanc...

In this paper, results demonstrating the use of plastic optical fibre (POF) sensors for crack detection and localisation in tensile steel specimen are presented. POF is employed to detect cracks using a high-resolution photon-counting optical time-domain reflectrometer (-OTDR). Although OTDR is an established technique in the telecommunication indu...

In this paper, results demonstrating the use of plastic optical fibre (POF) sensors for crack detection and localisation in tensile steel specimen are presented. POF is employed to detect cracks using a high-resolution photon-counting optical time-domain reflectrometer (v-OTDR). Although OTDR is an established technique in the telecommunication ind...

A novel application of chemiluminescence, a chemical reaction which generates light, is being developed in view of its potential use for landslide monitoring. The light emission from the device is detected using an array of inexpensive photodetectors and the signal transmitted via a wireless node to a base station. Since the light is emitted on det...

Acoustic emission (AE) technique has a promising application for crack detection in rail tracks. However, it is still a challenging task to identify the size of fatigue cracks from AE signals. This paper proposes an index based on wavelet coefficients to accurately distinguish AE waves induced by crack propagation and crack closure, and a novel met...

A novel application of chemiluminescence resulting from the chemical reaction in a glow-stick as sensors for structural health monitoring is demonstrated here. By detecting the presence of light emitting from these glow-sticks, it is possible to develop a low-cost sensing device with the potential to provide early warning of damage in a variety of...

The paper presents the fabrication and testing of a low-cost fibre optic accelerometer designed for wind turbine monitoring. The accelerometer was fabricated using plastic optical fibre enclosed in a plastic casing made from 3D printing. Nine fabricated accelerometers were mounted along a cantilever beam w a non-rotating wind turbine blade under wi...

The measurement of large strains in geotextile sheets in the order of a few tens of percentage strain (up to 40% in this study) has been achieved using plastic optical fibre (POF) sensors. These instrumented geotextile sheets were manufactured in a form of geotextile tubes which were strategically dumped from a barge into water depth of up to 25m....

Temperature is an important process control, but is a difficult parameter to measure in the microwave processing of concrete. Owing to their metallic nature, conventional thermocouples are not suitable for temperature measurement in microwave fields. Some of the most popular sensors known to be immune to electromagnetic interference are based on op...

Sensors based on plastic optical fibres have received significant attention for various applications in engineering. This paper illustrates some applications of plastic optical fibre sensors in civil engineering, in particular their use in structural health monitoring. Here, a brief overview of their current development and challenges in their impl...

A breathing rate sensor has been developed using plastic optical fiber and the test results are presented in this letter. The principle of coupling loss was used in designing this sensor to take advantage of the large core size of plastic optic fiber. The sensor was placed near the nostril to determine the rate of breathing as air was exhaled. The...

In this paper, plastic optical fibres are embedded in a natural fibre composite to provide a means to monitor the curing process and post-cure vibration. The composite specimens were made from kenaf fibre and a low-viscosity epoxy resin via liquid composite moulding technique. The potential of applying this integrated-sensing capability for process...

The measurement of large strain of up to 40% strain in geotextile materials has been achieved using extrinsic plastic optical fiber sensor (POF). Typical fiber optic sensors can measure strain up to 5% based on fiber stretching, but this cost-effective high-strain optical fiber sensor system allows strains to be measured even after exceeding strain...

It is important to ensure the safe and reliable use of massive engineering structures such as offshore platforms, including all aspects of safety and design code compliance. Although routine inspection is an integral part of the safety protocol in operating and maintaining these structures, regular assessment of the effectiveness and efficiency of...

While a number of literature reviews have been published in recent times on the applications of optical fibre sensors in smart structures research, these have mainly focused on the use of conventional glass-based fibres. The availability of inexpensive, rugged, and large-core plastic-based optical fibres has resulted in growing interest amongst res...

This paper reports a study of the use of nickel-titanium shape memory alloy (Ni-Ti SMA) sheet and carbon fibre reinforced composite to produce a novel smart fibre-metal laminate (FML). Investigations into the morphing response and control using integrated heaters and plastic optical fibre sensors have shown the potential to accurately control the a...

This article investigates the activation characteristics of a novel fiber-metal laminate (FML) based on a nickel–titanium (Ni–Ti) shape memory alloy. Initial attention focuses on manufacturing this smart FML in which a woven glass fiber reinforced epoxy material is sandwiched between two shape memory alloy (SMA) outer skins. Activation tests on can...

This paper summarises an effort in the development of a remote flood monitoring system based on plastic optical fibre (POF) sensors and a wireless mote network. The wireless mote, comprising of a network of MICA2DOT™ units, was used as a platform to monitor and record the signal from the POF sensors and transmit this information to a base station w...

A high-strain optical fiber sensor system has been developed to provide a cost-effective solution for measurement of very large strain. The measurement of large strain in the order of a few tens of % strain (up to 40 % strain) in geotextile materials has been achieved using an extrinsic plastic optical fiber sensor (POF). Based on this design, the...

This paper investigates the interfacial, tensile, and fatigue properties of a novel smart fiber-metal laminate (FML) based on a nickel-titanium (Ni-Ti) shape memory alloy and a woven glass fiber reinforced epoxy. Initial tests, using the single cantilever beam (SCB) geometry, have shown that this unique system offers high values of metal-composite...

This article demonstrates the potential of a new extrinsic plastic optical fiber (POF) sensor for vibration-based structural health monitoring (SHM) applications. A simple genetic algorithm (GA) is used in conjunction with the POF sensor. The construction and principle of operation of the intensity-based POF sensor used in the study is described, h...

In this paper, packaged fibre Bragg grating (PFBG) sensors were fabricated by embedding them in 70mm x 10mm x 0.3mm carbon-fibre composites which were then surface-bonded to an aluminium beam and a steel I-beam to investigate their strain monitoring capability. Initially, the response of these packaged sensors under tensile loading was compared to...

This paper reports the use of fibre Bragg gratings (FBGs) as sensors for structural integrity assessment by monitoring the reduction in the flexural stiffness of a novel sandwich structure based on thermoplastic fibre-metal laminate (FML) skins and an aluminum-foam core. By monitoring the reduction in the structural flexural stiffness, the techniqu...

This paper describes the design of an extrinsic optical fibre sensors based on poly(methamethycrylate) for structural health monitoring applications. This polymer-based optical fiber sensor relies on the modulation of light intensity and is capable of monitoring the response of the host structure subjected to either static or dynamic load types. A...

Plastic optical fibre sensors offer remarkable ease of handling and recent research has shown their potential as a low-cost sensor for damage detection and structural health monitoring applications. This paper presents details of a novel plastic optical fibre sensor and the results of a series of mechanical tests conducted to assess its potential f...

This paper reports the use of fibre Bragg gratings (FBGs) for monitoring the fabrication process in a novel sandwich structure based on thermoplastic fibre–metal laminate (FML) skins and an aluminum-foam core. The FBG sensors were embedded between two plies of glass fibre reinforced polypropylene within the FML and the shift in the Bragg wavelength...

Plastic optical fibre sensors offer remarkable ease of handling, and recent research has shown their potential as a low-cost sensor for damage detection and structural health monitoring applications. This paper presents details of a novel extrinsic polymer-based optical fibre sensor and the results of a series of mechanical tests conducted to asses...

The static and dynamic response of a cantilever composite beam was investigated using polymer-based sensors. Polymeric materials which exhibit optical properties such as PMMA are being used to produce plastic optical fibers (POF). The POF and the PVDF film were bonded to the composite beam using a cyanoacrylate adhesive. The composite beam was subj...

This paper reports the feasibility of using embedded Fabry–Pé rot fiber optic sensors to detect and monitor the propagation of cracks and delamination within concrete beams induced by corrosion of the reinforcing bars. In this research, four series of reinforced concrete beams were subjected to varying degrees of corrosion-induced damage by modifyi...

The use of intensity-based optical fiber systems and fiber Bragg grating sensor for damage detection in composite structures was investigated. These optical fiber systems were found to be capable of detecting impact damage, transverse cracking and delamination and also have the ability to monitor strain in structures. It was found that it is import...

Two long-term environmental monitoring plastic optical fibre (POF) sensors are described, using light intensity modulation. An evanescent field biofouling sensor was developed and characterised with sensitivity ±0.007 refractive index units or 0.5% below n = 1.4 and ±0.002 refractive index units or 0.15% above n = 1.4. A tapered POF was developed a...

This paper reports the use of a plastic fibre sensor for detecting impact damage in carbon fibre epoxy cantilever beams by monitoring their damping response under free vibration loading conditions. The composite beams were impacted at impact energies up to 8 J. The residual strengths and stiffnesses of the damaged laminates were measured in order t...

Step-index multi-mode optical fibers have been embedded in a thermoplastic glass fiber polypropylene (GF/PP). Three types of commercially available optical fibers have been investigated to evaluate their potential for detecting impact-induced damage in thermoplastic-based composite structures. Preliminary findings have confirmed the feasibility of...

This paper reports the findings of an evaluation of a low-cost, intensity-based plastic optical fibre (POF) sensor for monitoring the dynamic response of both cantilever and simply supported beams subjected to dynamic loading conditions. The sensors were either surface bonded to a plastic beam or embedded in a carbon-fibre composite and subjected t...

Plastic optical fibres have been employed to detect initial cracks, monitor post-crack vertical deflection and detect failure cracks in concrete beams subjected to flexural loading conditions. The intensity-based sensor system relies on monitoring the modulation of light intensity within the optical fibre as the sensor is loaded. The sensor design...

This paper reports the use of optical fibres to obtain real-time information during the processing of thermoplastic-based glass fibre-reinforced polypropylene. The technique used to monitor the melting and solidification process in this study is based on monitoring the modulation of the refractive index of the polymer matrix. Before embedding the s...

This paper reports the use of a low cost, intensity-based plastic optical fibre sensor for curvature and strain measurements in samples subjected to flexural and tensile loading conditions respectively. This simple and robust sensor exhibits a high signal-to-noise ratio and excellent repeatability, rendering the system cost effective for operation...

In this paper we describe the use of an inexpensive standard communication-grade optical fiber for the purpose of detecting damage in glass fiber reinforced thermoplastic composite materials and hybrid fiber metal laminates based on the same composite constituent. These multi-mode, step-index optical fibers were embedded at different locations with...

Conventional glass optical fibers were used to detect impact damage in a thermoplastic-based fiber-metal laminate (FML) system. The results suggest that for a higher fracture sensitivity, optical fibers should be embedded close to the impact surface in order to be sufficiently sensitive to detect energies of 1 to 2 Joules in these systems.

Fibre Bragg grating (FBG) sensors have been embedded in a number of advanced composite materials and fibre/metal laminates (FMLs). The post-fabrication FBG spectra were studied to examine the influence of manufacturing variables (such as composite stacking sequence and resin flow during processing) on the final profile of the spectrum and the funct...

Recently, optical fibre Bragg gratings have attracted a significant amount of attention as optical fibre sensors for measuring strain in composite structures. Indeed, the growth of optical fibre technology has spurred the development of smart composites capable of measuring real-time internal strain within structures and an assortment of measurands...

Thesis (Ph.D.)--University of Liverpool, 2002.

The concept of smart structures with integrated optical fibre sensors capable of performing real-time structural health-monitoring has attracted much attention in recent years due to the potential safety and economic benefits they offer. In addition, optical fibres have also been employed as in-situ sensors to monitor the fabrication cycle of polym...