Vibration-Based Loosening Identification of Bolted Joints in Clamped Beams: A State-of-the-Art Review

Bolted connections are fundamental to the structural integrity of clamped beam assemblies across civil, aerospace, and mechanical engineering applications. The loosening of bolted joints due to dynamic loading, ambient vibrations, and thermal cycles remains one of the most prevalent failure mechanisms, leading to reduced load-bearing capacity and, in severe cases, catastrophic structural collapse. Vibration-based structural health monitoring (SHM) methods have emerged as particularly promising approaches for early loosening detection owing to their non-destructive nature, online implementability, and high sensitivity to localized stiffness changes. This paper presents a comprehensive review of vibration-based loosening identification techniques for bolted joints in clamped beams. The fundamental mechanisms of bolt loosening and their influence on the dynamic behavior of clamped beams are first elucidated. Current methodologies are systematically classified into four categories: modal parameter-based methods, frequency response function and time-frequency analysis methods, nonlinear methods, and data-driven machine learning approaches. Special emphasis is placed on recent advances in the identification of multiple simultaneous loosening, early-stage detection, and structural localization capabilities. The latest developments over the past five years (۲۰۲۱–۲۰۲۶) are critically reviewed with reference to more than ۳۰ authoritative international publications. Finally, key challenges including environmental effects, measurement noise, and practical implementation constraints are identified, and future research directions encompassing smart IoT-based monitoring systems, physics-informed machine learning, and quantitative severity assessment are discussed.

کلیدواژه ها:

Structural health monitoring ، bolt loosening identification ، clamped beam ، vibration analysis ، modal parameters ، machine learning ، nonlinear methods