Papers by Keyword: Bolted Joint

Abstract: The difference signals, which between upper and lower shells of flange bolted joints structure, was applied to establish the autoregressive model for system condition identification. Firstly, an AR model is built by difference signals. The established AR model is used as a filter to process the difference signal in test state under the same condition and output residual series. Then the statistical parameters, such as Itakura distance, skewness, kurtosis and variance, are used to handle residual series. The results of experiment show that Itakura distance is a useful eigenvalue to identify the bolted joints condition.

Abstract: The disc-drum type rotors are commonly used in large gas turbine engines. In this paper, the dynamic characteristics of single stage disc-drum structure are studied based on the finite element model, where the connecting bolts are modeled using solid elements and the frictional contact at the joint interface is accommodated. In order to evaluate the nonlinearity resulting from the bolted joints, a finite element (FE) model fixing the disc and drum together is also established, and the simulation results based on the two models are compared. The effects of the bolt preload and the rotating speed on the dynamic characteristics of the disc-drum structure are also discussed. The works proposed in this paper help to enhance the understanding of the dynamics of the disc-drum type rotor.

Abstract: A three-dimensional model of bolted single-lap composite joint was developed to investigate the influence of ply angle on failure response of joint. This model can predict the failure mode and failure load of joint with arbitrary ply angle. The property analysis of joint was performed by using the ABAQUS FE code. Failure response and degradation of material properties were implemented using a progressive model, which is incorporated in ABAQUS USDFLD subroutine. The progressive model utilizes a set of stress-based three-dimensional Hashin criteria and a set of appropriate degradation rules.

Abstract: — In this paper thirty nine factors responsible for the dynamic loosening, under soft foot condition, of a bolted joint have been enumerated and its Interpretive Structural Modeling (ISM) has been developed. In this systematic approach of ISM, first of all a concept model of the problem has been formulated, followed by the formulations of Structural Self-Interaction Matrix (SSIM) and Reachability Matrix. The level of significance of each factor has been derived by level partitioning. The initial digraph is prepared on the basis of the canonical matrix. ISM based model is finalized after checking for conceptual inconsistency and necessary modifications. The MICMAC analysis is also conducted with the help of driving and dependence diagram, which states that factor 31 (vibration loosening) and 36 (additional stresses in the bolt) are the major threat for joint integrity and needs more attention.

Abstract: In order to properly simulate bolted joints and make the numerical modes as accurate as possible, this paper is focused on modeling methods for dealing with bolt connection structures composed of two sheets. Six methods are presented to establish the FE models using different element types(8-node brick elements and 4-node shell elements) and different constraints (such as contact interaction and coupling constraint). The models are solved in ABAQUS software and natural frequencies and vibration shapes are obtained. Then, the experiments of bolt fastening structures are performed and FE simulation results are compared with the experimental ones. Moreover, the methods which agree well with the experiments are selected as the FE model of bolted connection. Finally, the element layers in the through-thickness direction are discussed. FE models built in this paper can reflect the real situation of bolted joints and provide significant reference to FE analysis for the complex system connected by bolts.

Abstract: In this paper, discrete wavelet transform (DWT) is used to analyze the acceleration signals near to the loose bolt, in order to study the characteristics of bolted joint condition. Firstly, an experimental system is built based on the NI data acquisition equipment. Secondly, based on qualitative analysis of the loose process of the bolted joints and spectrum analysis of response signals, an appropriate wavelet function is chosen and decomposed levels are determined. Lastly, according to the amplitude of each level, the contour diagrams are drawn and the Root Mean Square (RMS) of detailed coefficients at the sensitive level is calculated. Experimental result shows that both DWT contour diagrams and RMS at sensitive level have significant difference when preload changes.

Abstract: Based on the vibration mechanics theory and system’s state equation, the state-space model of the flange bolted-joints structure is established. According to the dynamic characteristics of bolted connection, the parameters of the state-space model, such as rigidity and damping, can be identified. The accuracy of simulation model is validated, by comparing the simulation analysis results with the vibration test results, and an efficient method of recognition or fault diagnosis of bolted joints in vibratory environment is proposed.

Abstract: In this work, results from a study on bolted joints made of unidirectional, quasi isotropic Carbon Fiber Reinforced Polymer (CFRP) composites, subjected to tensile loads, are reported. CFRP composite materials are widely used in the mechanical industry, such as that of aerospace, where requirements of weight reduction and structural high performances are very compelling. Composite materials generally present a high resistance to fatigue and corrosion; however, the presence of joints produces the major problems and a poor design of joints leads to a drastic reduction of the reliability of structures made of these materials. A hybrid bolted joint involving a metal plate, made of aluminum alloy, and a CFRP composite plate has been considered; the plates are held together by a titanium bolt. Experimental results from literature are compared with those obtained through a numerical analysis developed with Abaqus code. Once the CFRP composite has been analyzed and the numerical model validated through numerical-experimental correlations, other possible configurations have been numerically analyzed in order to ensure the highest strength of the examined hybrid joint. Afterwards the effects of bolt-hole clearance on the stiffness and strength of the same joint have been investigated.

Abstract: The relationships between dynamics response and preload of bolted joint were studied. By using finite element analysis method, nonlinear model of flange structure with bolted joint was established. The transient analysis for different preload condition of bolted joint was employed to obtain steady state response. The energy of the difference signals between up and down mating surfaces was computed. The energy of the difference signals increased as preload of bolted joint decreased, and nonlinearity of bolted joint increased. The numerical results were compared with experimental measurements. The similarity was found to be satisfactory.

Abstract: This paper has proposed an improved formula for the torque-tension relationship of bolted joints with consideration of all forces and moments acting on fasteners. Finite element analysis (FEA) is used to analyze and evaluate the relationship. An effective finite element (FE) modeling scheme which considers the helical geometry is developed. Effects of contact radii ratios of the nut bearing surface on the percentages of component torques are investigated. Percentages of component torques are calculated according to present and conventional formula, to compare with FEA results.