# Comparing Bol Implementation Methods in Vibration Testing for Accurate Dynamic Behavior Analysis
###### Abstract  
Vibration testing is crucial for understanding structural dynamics, yet conventional modeling of bolt connections often leads to significant inaccuracies. This study systematically compares six bolt connection methods--bonded, adaptive bonded, joint, beam, screw, and fixed bolt--using a finite element analysis of a headlamp vibration test jig. The six bolt connection methods were selected based on approaches adopted in previous studies. The experimental results identified the joint connection method as the most accurate, minimizing deviations in natural frequency to 7.6 Hz compared to experimental tests at 493.2 Hz, while bonded methods overestimated the frequency at 544.1 Hz due to excessive stiffness assumptions. Efficiency analyses highlighted bonded methods as the most computationally streamlined, offering preprocessing times as short as 30 s and shorter overall analysis times. These findings emphasize the importance of selecting appropriate bolt connection methods in the early design phase to ensure accurate natural frequency predictions and mode shape representations. Although this study does not consider bolt preload forces, the work shows the possibility of offering practical guidelines for improving the reliability and efficiency of vibration test jig designs by bridging the gap between analysis and experimental results. blbl 2025155  
connections, leading to discrepancies between the analysis and test results [14; 15; 16]. This hinders the derivation of accurate test results and increases the likelihood that the jig design properties will not meet expectations under real-world conditions. The bolt connection method significantly affects the natural frequencies and mode shapes of a vibration test jig. Therefore, differences may arise between the analysis and experimental results depending on the contact conditions and connection method chosen [11]. Numerous studies have analyzed the effects of bolt connection methods on the natural frequencies and mode shapes of structures through experiments and numerical analysis, emphasizing their critical role in ensuring design accuracy and appropriateness [17; 18]. For instance, a study showed that failing to reflect the actual contact conditions of the bolts during vibration testing can reduce the consistency between the analysis and experimental results, highlighting the importance of proper bolt implementation methods to improve design accuracy [19]. Additionally, a study that experimentally demonstrated the impact of bolt connection methods on natural frequencies and mode shapes suggested that selecting the correct connection method during the initial design stage is essential [20]. To address the discrepancy between analysis and test results, various bolt implementation methods have been proposed [21]. For example, connecting a line body under rigid conditions can improve analysis efficiency by providing shorter analysis times in vehicle engine vibration testing [22]. Furthermore, the simplified connection approach has been effectively applied in the vibration analysis of diesel engine cylinders, streamlining bolt implementation while maintaining adequate accuracy [23]. However, research on bolt implementation methods in vibration testing remains fragmented, and a systematic comparison and evaluation of the performance and limitations of each method are lacking. This study analyzes the natural frequencies, mode shapes, and efficiency of various bolt implementation methods using a vibration test jig to determine the most suitable method for design and analysis. To achieve this, a headlamp jig and M6 standard tapped bolts currently in use were selected as the research materials. The bolts were modeled using six different implementation methods, and their natural frequencies, mode shapes, analysis times, and preprocessing efficiency were compared. Additionally, the natural frequencies obtained from vibration tests were compared with those of the analysis models to evaluate the effectiveness of each method.