Browsing by Author "Kamei, Khangamlung"

Now showing 1 - 5 of 5
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    Characterizing modal behavior of a cantilever beam at different heating rates for isothermal conditions
    (MDPI, 2021-05-12) Kamei, Khangamlung; Khan, Muhammad A.; Khan, Kamran A.
    The effect of temperature on structural response is a concern in engineering applications. The literature has highlighted that applied temperature loads change the system vibration behaviour. However, there is limited information available about temperature impacting the dynamic response. This paper investigated the heating rates effects on modal parameters for both with crack and without crack conditions in a cantilever beam. A beam subjected to three heating rates was considered: 2, 5, and 8 °C/min. The first one was assumed as a slow heating rate while the others were assumed as moderate and high, respectively. This controlled rate of heating was achieved by using a proportional-integral-derivative (PID) temperature controller. The results showed that heating at different rates has little impact on modal parameters. While this effect is minimal at lower temperatures and more evident at higher temperatures. The results of temperature ramped at 2, 5, and 8 °C/min were compared with the numerical and analytical results only for all the isothermal conditions. It was observed that the beam natural frequency and its modal amplitude decrease with the increase in temperatures and crack depths. Therefore, it is concluded that the rate of heating can make a slight impact on the dynamics response of any mechanical system.
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    Current challenges in modelling vibrational fatigue and fracture of structures: a review
    (Springer, 2021-01-22) Kamei, Khangamlung; Khan, Muhammad A.
    Fatigue damage is a concern in the engineering applications particularly for metal structures. The design phase of a structure considers factors that can prevent or delay the fatigue and fracture failures and increase its working life. This paper compiled some of the past efforts to share the modelling challenges. It provides an overview on the existing research complexities in the area of fatigue and fracture modelling. This paper reviews the previous research work under five prominent challenges: assessing fatigue damage accurately under the vibration-based loads, complications in fatigue and fracture life estimation, intricacy in fatigue crack propagation, quantification of cracks and stochastic response of structure under thermal environment. In the conclusion, the authors have suggested new directions of work that still require comprehensive research efforts to bridge the existing gap in the current academic domain due to the highlighted challenges.
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    Investigating the structural dynamics and crack propagation behavior under uniform and non-uniform temperature conditions
    (MDPI, 2021-11-21) Kamei, Khangamlung; Khan, Muhammad A.
    The robustness and stability of the system depend on structural integrity. This stability is, however, compromised by aging, wear and tear, overloads, and environmental factors. A study of vibration and fatigue cracking for structural health monitoring is one of the core research areas in recent times. In this paper, the structural dynamics and fatigue crack propagation behavior when subjected to thermal and mechanical loads were studied. It investigates the modal parameters of uncracked and various cracked specimens under uniform and non-uniform temperature conditions. The analytical model was validated by experimental and numerical approaches. The analysis was evaluated by considering different heating rates to attain the required temperatures. The heating rates were controlled by a proportional-integral-derivative (PID) temperature controller. It showed that a slow heating rate required an ample amount of time but more accurate results than quick heating. This suggested that the heating rate can cause variation in the structural response, especially at elevated temperatures. A small variation in modal parameters was also observed when the applied uniform temperatures were changed to non-uniform temperatures. This study substantiates the fatigue crack propagation behavior of pre-seeded cracks. The results show that propagated cracking depends on applied temperatures and associated mass. The appearance of double crack fronts and multiple cracks were observed. The appearance of multiple cracks seems to be due to the selection of the pre-seeded crack shape. Hence, the real cracks and pre-seeded cracks are distinct and need careful consideration in fatigue crack propagation analysis.
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    A machine learning approach to model interdependencies between dynamic response and crack propagation
    (MDPI, 2020-11-30) Fleet, Thomas; Kamei, Khangamlung; He, Feiyang; Khan, Muhammad A.; Khan, Kamran Ahmed; Starr, Andrew
    Accurate damage detection in engineering structures is a critical part of structural health monitoring. A variety of non-destructive inspection methods has been employed to detect the presence and severity of the damage. In this research, machine learning (ML) algorithms are used to assess the dynamic response of the system. It can predict the damage severity, damage location, and fundamental behaviour of the system. Fatigue damage data of aluminium and ABS under coupled mechanical loads at different temperatures are used to train the model. The model shows that natural frequency and temperature appear to be the most important predictive features for aluminium. It appears to be dominated by natural frequency and tip amplitude for ABS. The results also show that the position of the crack along the specimen appears to be of little importance for either material, allowing simultaneous prediction of location and damage severity
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    Structural dynamics and crack propagation behaviour under uniform and non-uniform temperature conditions.
    (Cranfield University, 2022-02) Kamei, Khangamlung; Khan, Muhammad Ali; Starr, Andrew
    The robustness and stability of machinery depend on structural integrity. This stability is, however, compromised by aging, wear and tear, overloads, and environmental factors. A study of vibration and fatigue crack growth for structural health monitoring is one of the core research areas in recent times. The research is yet to input sufficient explanations about the dynamic behaviour of the structure under distributed temperature. The structural dynamics can be influenced by material microstructure, temperature distribution, and duration of exposure to the thermal environment. The applied temperature can cause significant variations in the modal response. The existing studies are limited concerning temperature change and compel extensive investigation in a crack and uncracked condition. In this research, the structural dynamics and fatigue crack propagation behaviour when subjected to thermal and mechanical loads have been studied. It investigates the modal parameters of uncracked and various cracked specimens under uniform and non-uniform temperature conditions. An analytical model considering the effective length of the beam is developed to analyse the modal response of the beam. Then, the model is modified to enumerate the modal behaviour of the beam in the presence of crack. The model is validated by experimental and numerical approaches. The experimental evaluation is conducted by considering three heating rates to attain the required temperatures. In the first case, ramping at 2°C/min is assumed as a slow heating rate. While ramping at 5°C/min and 8°C/min are assumed as moderate and rapid heating rates respectively. The heating rates are considered to compare the structural response changes. A small variation on modal parameters is noticed for different heating rates and when the applied uniform temperatures are changed to non-uniform temperatures, especially at elevated temperatures. This signifies heating at different rates has a slight effect while measuring the dynamic response of any mechanical system. The results showed that changes in modal parameters of the beam are associated with the change in temperatures and heating rate. Furthermore, this research substantiates the fatigue crack propagation behaviour of pre-seeded cracks. The propagated crack depths are measured based on pixels contains in the crack. It is found that propagated crack depends on applied temperatures and associated mass. The appearance of double crack fronts and multiple cracks are observed. The multiple crack appearance seems due to the selection of pre-seeded crack shapes. Hence, the real crack and pre- seeded crack are distinct and need careful consideration in crack propagation evaluation.