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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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    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.