Browsing by Author "Abbas, Muntazir"

Now showing 1 - 9 of 9
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    An advanced Wigner-Ville time-frequency analysis of lamb waves signals based upon AR model for efficient damage inspection
    (IOP, 2021-03-16) Rizvi, Syed Haider; Abbas, Muntazir
    The generation and acquisition of the ultrasonic guided wave in metallic or composite structures to investigate the structural defects are quite straightforward; however, the interpretation and evaluation of the reflected/transmitted signal to extract the useful information is a challenging task. It is primarily due to the dispersion, and multi-modal behavior of the Lamb waves which is dependent on the exciting wave frequency and thickness of the material under investigation. These multi-modes and dispersion behavior lead to a complex waveform structure, and therefore, require an advanced signal processing technique to decipher the useful information in time and frequency domain. For this purpose, Wigner-Ville Distribution, due to its desirable mathematical properties, is considered as a powerful tool for estimating temporal and spectral features of this type of complex signals. However, because of its quadratic nature, the undesirable cross-terms and spurious energies are also generated, which limit the readability of the spectrum. To suppress this effect, the autoregressive model based upon Burg's Maximum Entropy method was employed that modified the kernels of the discrete Wigner-Ville Distribution. This technique was applied to ultrasonic Lamb wave signals, obtained numerically and experimentally, to extract useful discriminating spectral and temporal information that was required for mode identification, damage localization, and its quantification. For damage localization, based upon excellent time-frequency energy distribution, the proposed method precisely estimated the distance between two closely spaced notches in a plate from different simulated noisy signals with a maximum uncertainty of 5%. Moreover, time-frequency energy concentration in a combination with variation of its instantaneous frequency was also effective in identifying the overlapping modes of the Lamb wave signal. Lastly, for damage quantification, three time-frequency based damage indices namely, energy concentration, time-frequency flux, and instantaneous frequency were extracted from the five sets of specimens using the proposed time-frequency scheme and trained them for the regression model. The model testing proved that the damage indices has the potential to predict the crack sizes precisely and reliably.
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    A dimensional metrology-based approach for corrosion measurement of ship grade steels exposed to various marine environmental conditions
    (Taylor and Francis/Maney, 2021-04-04) Abbas, Muntazir; Simms, Nigel; Laoa, Liyun; Malik, Owais A.; Syed, A. U.; Sarfraz, Syed Ali; Ashraf, Luqman; Rizvibar, Syed Haider M.
    Corrosion-induced degradation in marine steel structures is highly dependent on the surrounding environmental conditions and sea water compositions that varies significantly around global sea water bodies. This research investigates the corrosion behaviour of ship-grade steels exposed under different sea water compositions and environmental conditions typical of the Arabian Sea. More, environmental conditions spanning those anticipated for the shipping structures operating in the highly saline and warmest regions in the Arabian Sea have been simulated in laboratory-based experiments by using heated and aerated artificial sea water. Following their exposures, the corrosion performance of coupons has been investigated using the standard weight loss and a new dimensional metrology-based approach. Besides, the corrosion products formed on the steel surfaces have been characterised using various analytical techniques. Considerably higher corrosion losses and maximum corrosion depths were observed in the nutrient-rich polluted sea waters than those recorded in the natural sea waters, as well as in the simulated artificial sea water conditions.
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    Environmental impact on the corrosion behavior of marine grade steel in the Arabian Sea conditions - a comparative analysis of field and laboratory based corrosion tests
    (UCTEA Chamber Of Metallurgical and Materials Engineers, 2021-06-12) Abbas, Muntazir; Simms, Nigel; Lao, Liyun; Malik, Owais A.; Ashraf, Luqman
    Corrosion-induced degradation of marine steel structures is highly dependent on the surrounding environmental conditions and so varies significantly around global seawaters. This research has investigated the dependence of corrosion of carbon steel alloy for marine service on seawater composition and climatic conditions typical of the Arabian Sea. Natural and polluted seawater sites in the Arabian Sea were selected for field exposures. In addition, environmental conditions spanning those anticipated for the shipping structures operating in the Arabian Sea have been simulated in laboratorybased experiments by using heated and aerated artificial seawater. Following their exposures, the performance of samples have been investigated using the weight-loss and dimensional metrology methods. High overall corrosion losses were observed in the polluted seawaters than in the natural seawater conditions of Arabian Sea.
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    Evaluation of the effects of highly saline and warm seawaters on corrosivity of marine assets
    (DECHEMA, 2019-09-13) Abbas, Muntazir; Simms, Nigel; Syed, Ali Sarfaraz; Malik, Owais Ahmed; Sumner, Joy
    In marine environment, the corrosion rate of metallic structures vary remarkably with the change in climatic conditions and seawater composition across geographical locations. The corrosion in brackish and polluted seawaters is even more complicated due to the presence of different chemical species and untreated effluents. The complex correlation between the above average temperature and salinity with the high nutrient content in polluted seawater tends to accelerate the rate of biological activities and microbiological induced corrosion (MIC). This research paper has investigated the short-term corrosion of cupronickel (Cu-Ni) 90/10 alloy, and mild steel in the highly saline and warm seawaters. Field experiments for general corrosion under fully immersed condition were conducted at two site locations, represented as site 1 for pollutantrich seawaters and site 2 for natural seawaters in the North Indian Ocean. The experiments were conducted for a period of up to two months and coupons for each metal alloy were recovered from both sites after an exposure period of 15, 30, 45, and 60 days, respectively. In both environmental conditions, significantly high mass loss and corrosion rates were recorded for each metal alloys. Despite the same temperature of seawater and immersion depth at both sites, average corrosion losses at site 1 were found to be 5 and 3 times higher than that of site 2 for Cu-Ni alloy 90/10, and mild steel coupons, respectively.
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    Evaluation of the influence of dissolved nitrates on corrosion behaviour of ship structural steel exposed to seawater environment
    (Elsevier, 2024-02-29) Abbas, Muntazir; Rizvi, Syed Haider Mehdi; Sarfraz, Shoaib; Raza, Asif; Khan, Asif; Loya, Adil; Najib, Antash
    Corrosion rates in marine structural steels differ significantly with the varying compositions of seawater particularly near harbours or coastal regions primarily due to the presence of untreated chemically active species from various sources. The reviewed literature reports accelerated steel corrosion losses in coastal seawater exposure conditions, which has widely been attributed to the presence of aggressive chemical compounds e.g., dissolved inorganic nitrogenous (DINs) compounds, sulphur containing compounds, in combination with various other environmental factors and their interdependent complex relationships. This paper aims to investigate the influence of nitrates, a DIN compound, on the corrosion behaviour of a low carbon ship structural steel, by exposing surface the cleaned coupons to an artificial seawater solution in a controlled laboratory environment. The uniform and localised corrosion damages were measured on steel coupons by using the standard weight loss and the dimensional metrology methods. A significant increase in corrosion losses was observed on coupons exposed to the nitrate-added artificial seawater than those exposed to similar seawater compositions with no additional nitrate content. Elemental compositions of corrosion deposits and corrosion morphologies investigated using various analytical tools such as SEM, EDS and Raman scattering techniques have shown different types of corrosion products in both exposure conditions.
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    Lamb wave damage severity estimation using ensemble-based machine learning method with separate model network
    (IOP Publishing, 2021-10-08) Rizvi, Syed Haider; Abbas, Muntazir
    Lamb wave-based damage estimations have great potential for structural health monitoring. However, designing a generalizable model that predicts accurate and reliable damage quantification result is still a challenge due to complex behavior of waves with different damage severities. In recent years machine learning algorithms have been proven to be an efficient tool to analyze damage-modulated Lamb wave signals. In this study, ensemble-based machine learning algorithms are employed to develop a generalizable crack quantification model for thin metallic plates. For this, the scattering of Lamb wave signals due to different configurations of crack dimension and orientation is extensively studied. Various finite-element simulation signals representing distinct crack severities in terms of crack length, penetration, and orientation are acquired. Realizing that both temporal and spectral information of the signal is extremely important to damage quantification, three time-frequency-based damage-sensitive features, namely energy concentration, time-frequency flux, and coefficient of variance, are proposed. These damage features are extracted by employing smoothed-pseudo Wigner-Ville distribution. After that, data augmentation technique based on the spline-based interpolation is applied to enhance the size of the dataset. Eventually, these fully developed damage dataset is deployed to train ensemble-based machine learning models. Here, we propose a separate model network (SMN), in which different models are trained and then link together to predict new and unseen datasets. The performance of the proposed model is demonstrated by two cases: first, simulated data incorporated with high artificial noises and in the second scenario, experimental data in raw form are employed to test the model. Results indicate that the proposed framework has the potential to develop a general model that yields reliable results for crack estimation.
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    A new approach for quantification of corrosion losses on steels exposed to an artificial seawater environment
    (Taylor & Francis, 2023-03-13) Abbas, Muntazir; Simms, Nigel; Rizvi, Syed Haider Mehdi
    The selection methodology for thickness loss measurement is very important to determine the extent of corrosion damage, as well as in formulation of corrosion prediction models and inspection/maintenance plans for offshore structures. This paper introduces a more accurate corrosion measurement technique, based on the pre-exposure dimensional metrology and post-exposure optical microscopy/image analysis on the cross-sections of steel samples. During this corrosion test, the surface grinded and uncoated steel samples were submerged vertically in an artificial seawater solution, for a duration of up to a maximum of 365 days. The corrosion damage experienced on the steel samples means that the dimensional metrology can be more accurate, and useful approach to measure both uniform and localised corrosion losses simultaneously than the conventional average mass loss method.
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    Performance evaluation of Cu-Ni 90/10 alloyed structures exposed to various seawater compositions and their remaining service life estimation
    (Cranfield University, 08/11/2022) Sarfraz, Syed Ali; Abbas, Muntazir; Sarfraz, Shoaib; Ashraf, Farhan
    The Cu-Ni 90/10 alloy is extensively used in seawater applications mainly because of its excellent heat transferability, resistance toward corrosion and marine fouling. The corrosion resistance of Cu-Ni 90/10 has been found to be far superior in open natural seawater, however, several premature failures have often been reported during their exposure in the pollutant-rich seawater typically found near harbours, jetties and coastlines. This paper investigates the corrosion behaviour of Cu-Ni 90/10 alloyed coupons exposed to natural seawater, and pollutant-rich harbour seawater in a submerged position. Moreover, this research also investigates the corrosion mechanism on marine heat exchanger tubes of material that failed prematurely while operating in similar seawater compositions. The field experimental results for short-term corrosion results from coupons, and the long-term corrosion results from heat exchanger tubes have been evaluated, to formulate a relationship and corrosion modelling.
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    Structural health monitoring (SHM) and determination of surface defects in large metallic structures using ultrasonic guided waves
    (MDPI, 2018-11-15) Abbas, Muntazir; Shafiee, Mahmood
    Ultrasonic guided wave (UGW) is one of the most commonly used technologies for non-destructive evaluation (NDE) and structural health monitoring (SHM) of structural components. Because of its excellent long-range diagnostic capability, this method is effective in detecting cracks, material loss, and fatigue-based defects in isotropic and anisotropic structures. The shape and orientation of structural defects are critical parameters during the investigation of crack propagation, assessment of damage severity, and prediction of remaining useful life (RUL) of structures. These parameters become even more important in cases where the crack intensity is associated with the safety of men, environment, and material, such as ship’s hull, aero-structures, rail tracks and subsea pipelines. This paper reviews the research literature on UGWs and their application in defect diagnosis and health monitoring of metallic structures. It has been observed that no significant research work has been convened to identify the shape and orientation of defects in plate-like structures. We also propose an experimental research work assisted by numerical simulations to investigate the response of UGWs upon interaction with cracks in different shapes and orientations. A framework for an empirical model may be considered to determine these structural flaws.