Experimental and theoretical studies of a bolted joint excited by a torsional dynamic load (original) (raw)
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Numerical and theoretical studies of bolted joints under harmonic shear displacement
Latin American Journal of Solids and Structures, 2015
A three-dimensional finite element model used to simulate the bolted joint is created using ABAQUS package. The stress concentration factors at the roots of the thread are first studied with a preload of 38.4 kN. Under harmonic transverse shear displacement, not only the stress variations at ten specified points of the first thread but also contact conditions between the contacting surfaces are studied. By changing the preload value, relative displacement, the coefficient of friction between the two clamped plates successively and the loading frequency, their effects on the hysteresis loops of the transverse load versus the relative displacement of the joint are then analyzed. Finally the hysteresis loops are produced by the Masing model. It is found that due to the greatest stress concentration factor, fatigue failure will occur at the root of the first thread. With the increase of preload value, the amplitude of displacement and the coefficient of friction, frictional energy dissipation of the joint increases. Very good agreement is achieved between the hysteresis loops produced from the fourth-order Masing model and the detailed ABAQUS model and therefore the fourth-order Masing model can replace the timeconsuming finite element model.
Simplified models of bolted joints under harmonic loading
Computers & Structures, 2005
Bolted joints are able to provide the majority of damping for an assembled structure when used to connect components. The dynamic frictional contact analysis of a bolted joint under harmonic loading is investigated by the finite element method. Then the detailed finite element model is replaced by a number of Jenkins elements and the Bouc-Wen model by fitting the hysteresis loops produced by the finite element method. These two latter models lead to much reduced computing load. The advantages and drawbacks of these two simplified models are discussed and this understanding is useful in choosing the right simplified model for a bolted joint.
Friction-Induced Vibrations during Tightening of Bolted Joints—Analytical and Experimental Results
Vibration
Bolted joints are one of the most used machine elements. Holding together structures of all sizes, the integrity rests on their shoulders. Thus, an accurate and reliable assembly of the joint is crucial. While it is the aim to not experience friction-induced vibrations at all, at some situations, it is unavoidable. These cases, however, have yet been out of the focus of control algorithms due to the volatile nature of the process. This contribution delivers analytical and experimental results for the occurrence of friction-induced vibrations during tightening of bolted joints. Previous findings of system characteristic constants could be validated, which can be used to monitor the tightening process even while strong vibrations during the tightening process occur. Additionally, a real-time algorithm is presented which allows for an advanced process monitoring and control by identifying process characteristics based on which predictions of the process can be made. These measures sign...
The effects of bolted joints on dynamic response of structures
IOP Conference Series: Materials Science and Engineering, 2013
Joint is an universal fastening technology for structural members; in particular bolted joints are extensively used in mechanical structures due to their simple maintenance and low cost. However, the components of bolted joints are imperative because failure could be catastrophic and endanger lives. Hence, in this study, the effects of bolted joints on vibrating structures are investigated by determining the structural dynamic properties, such as mode shapes, damping ratios and natural frequencies, and these are compared with the monolithic structures (welding). Two approaches of experimental rigs are developed: a beam and a frame where both are subjected to dynamic loading. The analysis reveals the importance of bolted joints in increasing the damping properties and minimizing the vibration magnitude of structures, this indicates the significant influence of bolted joints on the dynamic behaviour of assembled structures. The outcome of this study provides a good model for predicting the experimental variable response in different types of structural joints.
Implementation and Comparison of Damping in Jointed Structures
irjtas.com, 2018
Light weight structures generally have low connate basic damping. The damping instrument of different jointed structures can be clarified by considering the vitality misfortune because of contact and the dynamic slip delivered at the interfaces. The frictional damping is surveyed from the relative slip between the jointed interfaces and is believed to be the most supportive system for research the fundamental damping. The damping characteristics in jointed structures are affected by the intensity of weight movement, little scale slip kinematic coefficient of grinding and logarithmic decrements at the interfaces. The impacts of every one of these parameters on the system of damping have been broadly contemplated. All the above fundamental parameters are to a great extent impacted by the thickness proportion of the bar and subsequently influence the damping limit of the structures. What's more, shaft length of the structures and breadth of associating bolt and jolt additionally assume key parts on the damping limit of the jointed structures are assessable. For bolt jolt and welded joints the hypothetical examination proposes two unique strategies to ascertain damping: established technique and limited component strategy. The investigations depend on the suspicions of Euler-Bernoulli shaft hypothesis as the measurements of test examples fulfill the paradigm of thin bar hypothesis. The impacts of every one of these parameters are examined particularly in the present examination.
Nonlinear system identification of frictional effects in a beam with a bolted joint connection
Mechanical Systems and Signal Processing, 2013
We perform nonlinear system identification (NSI) of the effects of frictional connections in the dynamics of a bolted beam assembly. The methodology utilized in this work combines experimental measurements with slow-flow dynamic analysis and empirical mode decomposition, and reconstructs the dynamics through reduced-order models. These are in the form of single-degree-of-freedom linear oscillators (termed intrinsic modal oscillators-IMOs) with forcing terms derived directly from the experimental measurements through slow-flow analysis. The derived reduced order models are capable of reproducing the measured dynamics, whereas the forcing terms provide important information about nonlinear damping effects. The NSI methodology is applied to model nonlinear friction effects in a bolted beam assembly. A 'monolithic' beam with identical geometric and material properties is also tested for comparison. Three different forcing (energy) levels were considered in the tests in order to study the energy-dependencies of the damping nonlinearities induced in the beam from the bolted joint. In all cases, the NSI methodology employed was successful in identifying the damping nonlinearities, their spatial distributions and their effects of the vibration modes of the structural component.
Dynamic Response Analysis of Preloaded Bolted Joints Under Harmonic Excitation
Journal of emerging technologies and innovative research, 2020
Abstract: This study has been undertaken to investigate the dynamic response analysis of preloaded bolted joints with and without gasket under harmonic excitation. Mathematical model of preloaded bolted joint of pressure vessel is developed and various parameters such as stiffness of bolts, stiffness of combined plates and damping involved are determined. With the help of mathematical model and various parameters equations of motion for bolted joint with and without gasket are formulated and response of the system in the form of motion and force transmissibilities are determined.
Handbook on dynamics of jointed structures
2009
The problem of understanding and modeling the complicated physics underlying the action and response of the interfaces in typical structures under dynamic loading conditions has occupied researchers for many decades. This handbook presents an integrated approach to the goal of dynamic modeling of typical jointed structures, beginning with a mathematical assessment of experimental or simulation data, development of constitutive models to account for load histories to deformation, establishment of kinematic models coupling to the continuum models, and application of finite element analysis leading to dynamic structural simulation. In addition, formulations are discussed to mitigate the very short simulation time steps that appear to be required in numerical simulation for problems such as this. This handbook satisfies the commitment to DOE that Sandia will develop the technical content and write a Joints Handbook. The content will include: (1) Methods for characterizing the nonlinear stiffness and energy dissipation for typical joints used in mechanical systems and components. (2) The methodology will include practical guidance on experiments, and reduced order models that can be used to characterize joint behavior. (3) Examples for typical bolted and screw joints will be provided.
Applied Acoustics, 2010
The vibrations generated by friction are responsible for various noises such as squealing, squeaking and chatter. Although these phenomena have been studied for a long time, it is not well-understood. In this study, an experimental and numerical study of friction-induced vibrations of a system composed of two beams in contact is proposed. The experimental system exhibits periodic steady state vibrations of different types. To model and understand this experimental vibratory phenomenon, complex eigenvalue and dynamic transient analyses are performed. In the linear complex eigenvalue analysis, flutter instability occurs via the coalescence of two eigenmodes of the system. This linear study provides an accurate value of the experimental frequency of vibration. To understand what happens physically during frictioninduced instability, a dynamic transient analysis that takes account of the non-linear aspect of a frictional contact is performed. In this analysis, friction-induced instability is characterized by self-sustained vibrations and by stick, slip and separation zones occurring at the surface of the contact. The results stemming from this analysis show that good correlation between numerical and experimental vibrations can be obtained (in time and frequency domains). Moreover, time domain simulations permit understanding the physical phenomena involved in two different vibratory behaviours observed experimentally.
Numerical design and test on an assembled structure of a bolted joint with viscoelastic damping
Mechanical Systems and Signal Processing, 2016
Mechanical assemblies are subjected to many dynamic loads and modifications are often needed to achieve acceptable vibration levels. While modifications on mass and stiffness are well mastered, damping modifications are still considered difficult to design. The paper presents a case study on the design of a bolted connection containing a viscoelastic damping layer. The notion of junction coupling level is introduced to ensure that sufficient energy is present in the joints to allow damping. Static performance is then addressed and it is shown that localization of metallic contact can be used to meet objectives, while allowing the presence of viscoelastic materials. Numerical prediction of damping then illustrates difficulties in optimizing for robustness. Modal test results of three configurations of an assembled structure, inspired by aeronautic fuselages, are then compared to analyze the performance of the design. While validity of the approach is confirmed, the effect of geometric imperfections is shown and stresses the need for robust design.