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    A Novel Approach for Modelling Crack Paths in Plate Structures for Dynamic Response Analysis
    (Trans Tech Publications Ltd, 2026) Alshammari, Yousef Lafi A.; Khan, Muhammad Ali; He, Feiyang; Kati, Hilal Do?anay
    Cracks significantly affect the structural integrity and functionality of mechanical components. While most existing studies focus on identifying straight cracks using dynamic response (DR) data, the characterisation of crack paths, especially curved ones, remains limited. This gap is critical, as the path of crack propagation plays a vital role in determining the severity of structural damage, particularly in critical regions of plate structures. The large number of possible crack paths has made systematic research in this area difficult. Therefore, this study proposes a novel methodology for modelling both straight and curved crack paths in plate structures to analyse their DR using the Finite element method (FEM). Straight cracks are represented by coordinate pairs, while curved cracks are defined using second-order polynomial equations. A combination-based approach is employed to generate feasible curved paths within a bounded region, allowing variation in crack shapes, lengths, and geometries. The results demonstrate that the proposed methodology effectively reduces the total number of crack path configurations from 7140, an impractically large set for detailed analysis, to a manageable subset of 288. This reduction facilitates more efficient implementation in both numerical simulations and experimental investigations without compromising the representational diversity of crack path geometries. They also show that the crack path has a greater influence on the dynamic response than crack length, offering a more comprehensive framework for crack path identification and evaluation. © 2026, Trans Tech Publications Ltd. All Rights Reserved.
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    Analytical Modeling and Experimental Validation of Wear and Frictional Noise Under Lubricated Conditions
    (Asme, 2026) Kalifa, Mohamed; Khan, Muhammad; He, Feiyang; Basit, Kanza; Doganay Kati, Hilal
    Understanding the dynamics of friction, wear, and noise under lubricated conditions is crucial for the predictive maintenance of mechanical systems; however, existing models often overlook the role of lubrication in modulating these interactions. This research presents an analytical model that combines single-degree-of-freedom (SDOF) vibration theory, Hertz contact mechanics, the Archard wear model, and the principles governing acoustic emission to predict both wear depth and sound pressure level emitted in a lubricated pin-on-disc system. Contact stiffness and wear-induced geometric changes are dynamically updated by the model, considering viscous damping from thin-film lubrication. Experiments were conducted using an Anton Paar TRB3 tribometer under lubricated conditions at realistic loads of 15, 20, and 30 N and a rotational speed of 300 rpm (corresponding to a linear sliding velocity of approximately 0.314 m/s at a 10-mm track radius). The friction noise was recorded by a microphone that was free-standing. The analytical predictions were closely aligned with the measurements taken during the tests. For mild steel, wear depth errors remained below 22%, while sound pressure predictions deviated by 14-21%. Due to its softer nature, aluminum exhibited higher wear deviations (up to 32%). Track analyses showed that lubrication decreases wear depth compared to dry sliding, and sound pressure levels are closely related to wear depth. Track analysis revealed that lubrication decreases wear depth by up to 50% compared to dry sliding, and sound pressure levels closely follow wear progression. This work improves prognostic health management systems by incorporating lubrication dynamics and tribo-acoustic phenomena, which allow for effective real-time wear and noise monitoring in industrial applications.
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    Crack path effects on vibration characteristics in structural beams and plates
    (British Institute of Non-Destructive Testing, 2025) Alshammari, Yousef Lafi A.; Khan, Muhammad Mansoor; He, Feiyang; Kati, Hilal Do?anay; Buhari, Jamilu
    Accurately assessing and forecasting damage development is essential for maintaining safety, enhancing maintenance efficiency, and prolonging the service life of components in sectors like aerospace, automotive and civil infrastructure. This study examines the impact of crack characteristics—including path, length, and orientation—on the vibration characteristics of metallic and polymeric structures using both numerical and experimental methods. Using aluminium (AL) cantilever beams, numerical simulations were employed to determine the natural frequencies and associated amplitude using 13 different crack propagation paths. Results show that changes in crack orientation in the beam's depth significantly affected frequency and amplitude trends. Complementing this, experimental modal analysis (EMA) and the half-power bandwidth method were conducted on 10 crack paths on AL and 3D-printed ABS plates to examine how surface crack length and orientation influence damping ratios. Findings indicated that longer cracks increased damping due to reduced stiffness and microslip, resulting in more energy dissipation, while orientation, especially along the primary deformation axis, had a more substantial effect. ABS plates exhibited higher damping than aluminium due to their viscoelastic properties. Overall, the study highlights the critical role of crack paths in dynamic behaviour, which enhances damage identification and advanced structural health monitoring. © NDT 2025.All right reserved.
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    Effect of Printing Parameters on the Dynamic Characteristics of Additively Manufactured ABS Beams: An Experimental Modal Analysis and Response Surface Methodology
    (Mdpi, 2025) Doganay Kati, Hilal; He, Feiyang; Khan, Muhammad; Gokdag, Hakan; Alshammari, Yousef Lafi A.
    This study investigates the dynamic characteristics of three-dimensional (3D) printed acrylonitrile butadiene styrene (ABS) cantilever beams using Experimental Modal Analysis (EMA). The effects of Fused Deposition Modelling (FDM) process parameters-specifically infill pattern, infill density, nozzle size, and raster angle-on the natural frequency, mode shapes, and damping ratio were examined. Although numerous studies have addressed the static mechanical behaviour of FDM parts, there remains a significant gap in understanding how internal structural features and porosity influence their vibrational response. To address this, a total of seventy-two specimens were fabricated with varying parameter combinations, and their dynamic responses were evaluated through frequency response functions (FRFs) obtained via the impact hammer test. Damping characteristics were extracted using the peak-picking (half power) method. Additionally, the influence of internal porosity on damping behaviour was assessed by comparing the actual and theoretical masses of the specimens. The findings indicate that both natural frequencies and damping ratios are strongly influenced by the internal structure of the printed components. In particular, gyroid and cubic infill patterns increased structural stiffness and resulted in higher resonant frequencies, while low infill densities and triangle patterns contributed to enhanced damping capacity. Response Surface Methodology (RSM) was employed to develop mathematical models describing the parameter effects, providing predictive tools for applications sensitive to vibration. The high R2 values obtained in the RSM models based on the input variables show that these variables explain the effects of these variables on both natural frequency and damping ratio with high accuracy. The models developed (with R2 values up to 0.98) enable the prediction of modal behaviour, providing a valuable design tool for engineers optimizing vibration-sensitive components in fields such as aerospace, automotive, and electronics.
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    Numerical Analysis of Crack Path Effects on the Vibration Behaviour of Aluminium Alloy Beams and Its Identification via Artificial Neural Networks
    (Mdpi, 2025) Kati, Hilal Doganay; Buhari, Jamilu; Francese, Arturo; He, Feiyang; Khan, Muhammad
    Understanding and predicting the behaviour of fatigue cracks are essential for ensuring safety, optimising maintenance strategies, and extending the lifespan of critical components in industries such as aerospace, automotive, civil engineering and energy. Traditional methods using vibration-based dynamic responses have provided effective tools for crack detection but often fail to predict crack propagation paths accurately. This study focuses on identifying crack propagation paths in an aluminium alloy 2024-T42 cantilever beam using dynamic response through numerical simulations and artificial neural networks (ANNs). A unified damping ratio of the specimens was measured using an ICP (R) accelerometer vibration sensor for the numerical simulation. Through systematic investigation of 46 crack paths of varying depths and orientations, it was observed that the crack propagation path significantly influenced the beam's natural frequencies and resonance amplitudes. The results indicated a decreasing frequency trend and an increasing amplitude trend as the propagation angle changed from vertical to inclined. A similar trend was observed when the crack path changed from a predominantly vertical orientation to a more complex path with varying angles. Using ANNs, a model was developed to predict natural frequencies and amplitudes from the given crack paths, achieving a high accuracy with a mean absolute percentage error of 1.564%.