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When the car suddenly collides, the webbing bunching phenomenon will occur at the upper guide ring (D-ring) of the height adjuster of the seat belt, causing serious damage to the human chest by local positive pressure. In this paper, finite element method is used to calculate lateral displacement of seat belt. The BP neural network training method was used to fit the relationship between the displacement response and the random parameters, and the reliability function was established. The reliability and reliability sensitivity of random parameters were calculated by first-order second-moment method, and the influence rule of belt guide ring and belt parameters on reliability was obtained, which provided a theoretical basis for the parameter reliability design of safety belt guide ring. [ABSTRACT FROM AUTHOR]

Highlights • Build vibration transmission path system models according to the concept of vibration source, transfer path and receiving structure. • Define transmission reliability pattern of resonance problem. • Define transmission reliability sensitivity to distribution characteristics of path parameters. • Explore theoretical analysis method of transmission reliability and reliability sensitivity and derive general calculation formulas. Abstract The vibration transmission path systems are generally composed of the vibration source, the vibration transfer path and the vibration receiving structure. The transfer path is the medium of the vibration transmission. Therefore, the uncertainty of path parameters influences the system reliability greatly. In order to avoid the resonance failure, the transmission reliability analysis and the reliability sensitivity analysis are both very important. Based on the reliability theory, the absolute value difference of natural frequency and excitation frequency of random vibration transmission path system was limited and the reliability pattern of the resonance problem was defined in this paper. Applying the generalized second moment technique of vector-valued functions and the stochastic finite element theory, the theoretical analysis method of the transmission reliability and reliability sensitivity was presented. The corresponding vibration transmission path system with uncertain path parameters including mass, stiffness and path position was analyzed theoretically and computed numerically, and then the correlated mathematical expressions were obtained. Thus, in practical project, most of uncertain factors in the vibration systems can be analyzed so that the effective way can be given to avoid resonance failure. [ABSTRACT FROM AUTHOR]

This study was designed to investigate the modal characteristics of the human spine. A 3-D finite element model of the spine T12-Pelvis segment was used to extract resonant frequencies and modal modes of the human spine. By finite element modal analysis and harmonic response analysis, several lower vibration modes in the flexion–extension, lateral bending, and vertical directions were obtained and its vibration configurations were shown in this paper. The results indicate that the lowest resonant frequency of the model is in the flexion–extension direction. The second-order resonant frequency is in the lateral bending direction and the third-order resonant frequency of the T12-Pelvis model is in the vertical direction. The results also show that lumbar spinal vertebrae conduct the rotation action during whole body vibration (WBV). The vibration configurations of the lumbar spine can explore the motion mechanism of different lumbar components under WBV and make us to understand the vibration-induced spine diseases. The findings in this study will be helpful to understand WBV-related injury of the spine in clinics and the ergonomics design and development of mechanical production to protect human spine safety. [ABSTRACT FROM AUTHOR]

Abstract: This study attempts to determine the influence of anteroposterior (A-P) shifting of trunk mass from the upright sedentary posture on dynamic characteristics of the human lumbar spine. A three-dimensional finite element (FE) model comprising of the T12–Pelvis spine unit was used to mimic the human spine system. It is not clear how the A-P shifting of the upper part of human upper body affect on vibrational modality of the human lumbar spine under whole body vibration. Five trunk mass point locations were assumed by 2.0cm anterior, 1.0cm anterior, 1.0cm posterior and 2.0cm posterior to the upright sedentary posture including no shifting posture. FE modal analysis was used to extract the resonant frequencies and vibration modes of the human spine. The analytical results indicate that trunk mass centroid shifting onwards or rearwards may result in a reduction of vertical resonant frequency of the human spine. The human spine has the highest vertical resonant frequency at the normal upright sedentary posture with the trunk mass locating around 1.0cm anterior to the L3–L4 vertebral centroid. Larger A-P deformations and rotational deformations were also found at the spine motion segments L3–L4 and L4–L5, which imply higher compressive stress and shear stress at the disc annulus of those spinal motion segments. The findings in this study may explain why long-term whole body vibration might induce the degeneration of human spine at the relevant spinal motion segments. [Copyright &y& Elsevier]