Recently Completed Projects
Determination of early age properties of cement composites using wave propagation techniques
Long-term service life performance of concrete structures are influenced to a great extent by the early age characteristics of concrete. During early age, the fluid multiphase structure of fresh cement composite transforms into a hardened one due to the hydration reactions. Owing to the various interrelated factors influencing this, fundamental physical mechanisms affecting the early age behaviour of cement composite have not been completely understood. In this regard, acoustic wave characteristics propagation through the cement composites undergoing hydration and their intrinsic frequency characteristics are examined. AE hits rate analysis, parameter-based AE approach and frequency based AE approach are applied to customise a procedure for classification of the detected signals and to identify the mechanisms and associated processes initiating AE in cement composite undergoing hydration. It is fascinating to note that the transition from fluid phase to solid phase can be captured from the change in character of the observed acoustic wave as hydration proceeds. Also, the dominant frequency in the power spectrum and its range of intensity for the detected acoustic waves are potentially related with occurrence of different physical-microstructural changes caused during hydration within the cement composite system. The alteration in the AE hits rate (low and high) has been observed to correspond to shift in the frequency towards high (above 300 kHz) range.
Further studies are being carried out on:
- Acoustic wave propagation in engineered material for evaluation of its structure and properties
- Exploring the microstructural activity and microstructural properties of fresh composites using AE and ultrasonic wave measurements
- Examining the effectiveness of engineered structures through AE method
Damage identification of structures by guided wave propagation technique
Timely maintenance is required in the critical structures such as pipes carrying oil and gas, ships, nuclear reactor, pressure vessels, aircraft etc., In these structures catastrophic failures continue to take place claiming valuable lives and assets, there comes the importance of health monitoring of structures. At CSIR-SERC, R&D activities are being carried out for detection of damage in thin-walled structures using lamb wave propagation. Numerical and experimental studies are being carried out in plate type structure to study the lamb wave propagation characteristics. PZT transducers are used for actuation and sensing the lamb waves. Time reversal process is explored for baseline free method for identification of damage. Experimental studies are being carried out on various types of thin walled structures to study the lamb wave characteristics and to identify the damage.
Investigations on the integrity of the concrete embedded anchor systems using wave propagation
The objective of this study is to assess the integrity of the steel anchor-concrete system using wave propagation Analytical formulation is developed for constructing the dispersion characteristics of multi-layer composite since the problem under consideration is also a multi layer composite (concrete-epoxy-steel-epoxy-concrete) composite. Transfer matrix method is used in the analytical formulation. Further, numerical simulations are being carried out for performing the wave propagation studies in multilayer composite. Concrete embedded anchor system with and without flaw was numerically simulated when the piezo actuator was used to excite at anchor head and the sensing was done through a series of piezo-electric sensors along the horizontal and vertical plane of the anchor block. To compare the intact and flawed system, change in wave amplitude and pattern are considered. From the results obtained from numerical and experimental studies, it is observed that for detection of the damage/flaw in the interface of anchor-concrete system, sensing the wave responses in horizontal direction is better than sensing the wave responses in the vertical direction. Frequency ( 100 kHz) with minimum 40 V peak- to – peak voltage is required as an input signal to obtain the reasonable wave responses in the sensor. Further studies are carried out on wave propagation in anchor system with different bonding length and thickness of polymer composite materials in the interface of steel –concrete, wave propagation behaviour in anchor in the presence of the initial stress and effect of group anchor in wave propagation.
An experimental setup for evaluation of flaw in anchor-concrete system using piezo actuation at anchor head and distributed sensing on concrete
Actuation and sensing in anchor system, (a) Input voltage signal applied to piezo patch on anchor top (b) Observed response on concrete surface