Browsing by Author "Jothi Saravanan T."

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Assessing cement paste strength evolution under curing: An experimental and numerical investigation through equivalent stiffness parameter identified by embedded piezo sensors
(2025) Bansal T.; Azam A.; Morwal T.; Talakokula V.; Jothi Saravanan T.
Equivalent stiffness is one of the most important mechanical parameters of any concrete structure which allows engineers to predict the behaviour of the structure. This paper identifies the equivalent stiffness parameter through an embedded piezo sensor (EPS) in the strength development of cement paste using the electro-mechanical impedance (EMI) technique through experimental and numerical investigation. The experiments were conducted on the cement paste specimens
Elastic wave methods for non-destructive damage diagnosis in the axisymmetric viscoelastic cylindrical waveguide
(2021) Jothi Saravanan T.
The popular technique for damage detection in a cylindrical waveguide is the ultrasonic guided wave propagation based acoustic emission (AE) monitoring method. It comes under the dynamic non-destructive evaluation (NDE) category, primarily established on the fluctuations in AE signal features to detect the structural damage in real-time. In this paper, the numerical modeling of wave scattering by a structural discontinuity in axisymmetric high strength steel wire - viscoelastic waveguide medium for analyzing the wave interaction by inhomogeneity is presented. The hybrid standard three-dimensional finite element (3D FE) method and semi-analytical finite element (SAFE) method for numerical analysis of guided ultrasonic wave propagation are employed. For the simulation of waveguide media with arbitrary defect shapes, the hybrid 3D FE-SAFE method can be used. The basic idea is to express the frequency response of the cross-section at the two ends of the 3D FE part as a modal superposition calculated by the semi-analytical method. A case study on a steel wire is conducted to calculate the displacement response under a narrow-band external force excitation. The AE signal characteristics are used to understand the wave interaction of the pitting corrosion and tapered section in steel wire. The investigation of the amplitude of elastic waves passing through the discontinuity for the both undamped and damped cylindrical waveguide is proposed to understand the distribution of energy at points of reflections or refraction and the ratio between the amplitudes arriving at that point. Another contribution of the research work includes the robust algorithm for wave reflection and scattering based on the hybrid element method, which can effectively improve the calculation competence using an internal degree of freedom condensation and modal acceleration. It is suitable for models with multiple damages in the 3D FE area, and the accuracy of the results on wave-damage interactions can be achieved. The recommended method can be used to distinguish damages present in a viscoelastic cylindrical waveguide. � 2021 Elsevier Ltd
Guided ultrasonic wave-based investigation on the transient response in an axisymmetric viscoelastic cylindrical waveguide
(2021) Jothi Saravanan T.
The analysis of ultrasonic wave propagation in an axisymmetric viscoelastic cylindrical waveguide under time-dependent preload is presented. It requires investigation of the transient response for understanding the dynamics of a multi-wire structure for non-destructive evaluation and health monitoring applications. The purpose of this research is to establish a platform for calculating the time-transient response of waveguides for propagating acoustic emission (AE) signals using a semi-analytical finite element (SAFE) method. The time-transient response analysis is carried out in the frequency domain, which combines the Fourier transform and Cauchy residue theorem. The fundamental idea is to use the modal superposition method to calculate the frequency response at each point and then utilize the inverse Fourier transform to convert the response to the time domain. For the numerical investigation, an axisymmetric SAFE method is utilized to simulate the AE signal for propagating in an infinitely long, high-strength steel wire with a diameter of 5 mm. The time-dependent loads used in the numerical investigation for analyzing time-transient responses are narrowband and broadband excitations. A nonlinear model for transient response analysis is developed to consider the contact state and friction effects of the surrounding steel wires in the multi-wire environment. A nonlinear device consisting of contact springs and friction-type dampers is considered to account for the contact state and friction effects of the surrounding steel wires. The investigations are carried out with a single set and two sets of nonlinear devices under various stiffness values and preload conditions to understand the response characteristics. The estimated value of the contact spring stiffness is based on calculating the Hertz semi-width between the steel wires when the seven-wire steel strands are under tension. From observation, the standard nonlinear features input high-frequency fluctuation components into the original ideal linear system and cause extended high-frequency fluctuation at the tail of the waveform. The proposed nonlinear model for analyzing the preload condition in the axisymmetric viscoelastic waveguide showed a possible way for guided wave propagation-based health monitoring applications for prestressed cables. � 2021 Elsevier B.V.
Investigation of guided wave dispersion characteristics for fundamental modes in an axisymmetric cylindrical waveguide using rooting strategy approach
(2022) Jothi Saravanan T.
Guided wave propagation and its dispersion phenomenon in infinite solid elastic rods are encountered in several applications including, mechanical and civil engineering fields. A robust root finding method based on the Pad� approximation is presented for studying the dispersion characteristics of guided wave motion in a solid cylindrical rod with a circular cross-section. The theoretical analysis is conducted in the context of the theory of elasticity for deriving the simplified solution for the classic Pochhammer frequency equation. In this research work, dispersion curves of fundamental modes, namely, torsional (Formula presented.) longitudinal (Formula presented.) and flexural (Formula presented.) modes, are studied adequately. Based on the Pad� approximants, the solution strategy for the original Pochhammer frequency equation is improved. The calculation results herein show that this method is stable and efficient under the condition of guaranteeing an absolute wavenumber calculation accuracy, which can avoid the leakage of its close root in the curve. The dispersion curves obtained from the root-finding method by Pad� approximation are compared with the theoretical ones obtained by solving the corresponding Pochhammer frequency equation. It is observed that they coincide well with each other even in the region where the slope changes sharply, meaning that the proposed rooting strategy can be favorable for the rapid convergence of the theoretical solution. It is also extended to the solution of the wavenumber-frequency curve of the complex wavenumber domain in the viscoelastic waveguide. Henceforth, the proposed rooting approach can be employed to determine the dispersion characteristics of multiple modes in a cylindrical waveguide. � 2020 Taylor & Francis Group, LLC.
Retraction notice to �Elastic wave methods for non-destructive damage diagnosis in the axisymmetric viscoelastic cylindrical waveguide� [Measurement 177 (2021) 109253] (Measurement (2021) 177, (S0263224121002633), (10.1016/j.measurement.2021.109253))
(2022) Jothi Saravanan T.
This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the author. The author notes that experimental data carried out by another research group was used in the paper without their permission. The author wishes to sincerely apologize for the inconvenience caused. � 2022 Elsevier Ltd
Retraction notice to �Guided ultrasonic wave-based investigation on the transient response in an axisymmetric viscoelastic cylindrical waveguide� [Ultrasonics 117 (2021) 106543] (Ultrasonics (2021) 117, (S0041624X21001712), (10.1016/j.ultras.2021.106543))
(2023) Jothi Saravanan T.
This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/policies/article-withdrawal). This article has been retracted at the request of the Editor-in-Chief, for the unauthorized use of third party research data by the author. The author apologizes for the violation of the journal's code of ethics. One of the conditions of submission of a paper for publication in Ultrasonics is that authors must declare explicitly that their work is original. Use of research outcomes from others without formal permission or without appropriate citation is regarded as an ethical violation. The scientific community takes a very strong view on this matter and apologies are offered to readers of Ultrasonics that this was not detected during the submission process. � 2023 Elsevier B.V.