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Loosening failure of bolted joints often occurs in a vibration environment. This may induce the separation of clamped components and even result in catastrophic consequences in certain situations. Various anti-loosening bolted connections have been developed and widely applied to prevent loosening. Tightening and fatigue resistance performances are also two important characteristics of anti-loosening bolted connections. However, a comprehensive comparison study of the tightening, anti-loosening, and fatigue resistance performances of typical anti-loosening bolted connections is lacking, meaning that there is a lack of material to assist in the selection of anti-loosening bolted connections in engineering. In this study, accurate three-dimensional finite element models of typical anti-loosening bolted connections with the forms of washers or nuts are established. The processes of tightening, vibration-induced loosening, and fatigue are simulated via finite element analysis (FEA). Based on the results of FEA, the tightening, anti-loosening, and fatigue resistance performances of regular bolted joints and several anti-loosening bolted connections are comprehensively compared. The results reveal that bolted joints installed with both a variable-diameter nut and an eccentric double nut are difficult to tighten. We confirm that the researched structures all have superior anti-loosening capacities compared to regular bolted joints. Additionally, the results show that the regular bolted joint achieved the worst fatigue resistance performance, i.e., the application of anti-loosening bolted connections improves fatigue resistance. Finally, the effects of preload distributions on the two nuts in bolted joints with double nuts are discussed in terms of tightening, anti-loosening, and fatigue resistance performances. [ABSTRACT FROM AUTHOR]

There is bolt preload loss under vibration in the aircraft rudder, of which the connected parts are steel beam and CFRP panel, and the fastener is bolts and self-lock jet nuts. Based on the above phenomenon, this paper analyzes rotational loosening, washer wear, composite progressive damage, and plastic deformation condition of CFRP-steel hybrid self-lock bolted joint under transverse cyclic loading by experiments and finite element simulations, and subsequently analyzes the preload loss mechanisms. The results showed that washer wear was the main factor leading to the preload loss under long-term loading, and even this factor accounted for 70% of the total preload loss when the aluminum washer was used. During short-term loading, local slip and stress redistribution among threads, plastic deformation, and composite damage accounted for 30%, 50%, and 20% of the total preload loss respectively. To prevent preload loss, the wear-resistance of the washer should be improved, and the plastic deformation on the bolt and the damage in the composite material should be reduced. [ABSTRACT FROM AUTHOR]

Self-loosening of bolted joints can occur in a vibration environment, and it may induce bolt fatigue fracture with catastrophic consequences. It is essential to clarify the self-loosening mechanism, based on which novel anti-loosening thread structures can be developed. In this paper, we propose the concept of radial slippage propagation and provide new insights into the self-loosening process. The new theory states that the slippage along the radial direction of the thread surface induces more slippage areas (slippage propagation), and self-loosening occurs due to the dynamic evolution and propagation of contact states on the thread and bearing surfaces with an increase in the number of vibration cycles. Finite element analysis (FEA) was used to validate the propagation process of slippage areas on the thread surface. A novel bolted joint with step thread engagement was developed, which could prevent the occurrence of relative motion of the external and internal threads in the radial direction and thus block slippage propagation. A three-dimensional (3D) finite element model (FEM) of the novel thread structure was established, and a test specimen was manufactured using two special tools. FEA and experiments validated its superior anti-loosening and anti-fatigue performances, and the convenience of installation and removal. Experimental validation of the radial slippage propagation theory and the performance optimisation of the step-thread structure should be performed in the future. [ABSTRACT FROM AUTHOR]

Loosening failure of bolted joints often occurs in a vibration environment. This may induce the separation of clamped components and even result in catastrophic consequences in certain situations. Various anti-loosening bolted connections have been developed and widely applied to prevent loosening. Tightening and fatigue resistance performances are also two important characteristics of anti-loosening bolted connections. However, a comprehensive comparison study of the tightening, anti-loosening, and fatigue resistance performances of typical anti-loosening bolted connections is lacking, meaning that there is a lack of material to assist in the selection of anti-loosening bolted connections in engineering. In this study, accurate three-dimensional finite element models of typical anti-loosening bolted connections with the forms of washers or nuts are established. The processes of tightening, vibration-induced loosening, and fatigue are simulated via finite element analysis (FEA). Based on the results of FEA, the tightening, anti-loosening, and fatigue resistance performances of regular bolted joints and several anti-loosening bolted connections are comprehensively compared. The results reveal that bolted joints installed with both a variable-diameter nut and an eccentric double nut are difficult to tighten. We confirm that the researched structures all have superior anti-loosening capacities compared to regular bolted joints. Additionally, the results show that the regular bolted joint achieved the worst fatigue resistance performance, i.e., the application of anti-loosening bolted connections improves fatigue resistance. Finally, the effects of preload distributions on the two nuts in bolted joints with double nuts are discussed in terms of tightening, anti-loosening, and fatigue resistance performances.

Abstract Self-loosening of bolted joints can occur in a vibration environment, and it may induce bolt fatigue fracture with catastrophic consequences. It is essential to clarify the self-loosening mechanism, based on which novel anti-loosening thread structures can be developed. In this paper, we propose the concept of radial slippage propagation and provide new insights into the self-loosening process. The new theory states that the slippage along the radial direction of the thread surface induces more slippage areas (slippage propagation), and self-loosening occurs due to the dynamic evolution and propagation of contact states on the thread and bearing surfaces with an increase in the number of vibration cycles. Finite element analysis (FEA) was used to validate the propagation process of slippage areas on the thread surface. A novel bolted joint with step thread engagement was developed, which could prevent the occurrence of relative motion of the external and internal threads in the radial direction and thus block slippage propagation. A three-dimensional (3D) finite element model (FEM) of the novel thread structure was established, and a test specimen was manufactured using two special tools. FEA and experiments validated its superior anti-loosening and anti-fatigue performances, and the convenience of installation and removal. Experimental validation of the radial slippage propagation theory and the performance optimisation of the step-thread structure should be performed in the future.

Helical milling (HM) is a developing hole-making technology in aircraft assembly. Nevertheless, fundamental problems, such as tool deflection and chip evacuation, when helical milling small-diameter or deep holes still exist. To solve these problems and improve the machining quality of Ti-6Al-4V holes, an ultrasonic transversal vibration-assisted helical milling (UTVHM) method is developed. The motion paths of the peripheral cutting edges are established, and the tool-workpiece contact behaviour is analysed to explore how transversal vibration affects the material removal of UTVHM. The hole surface strengthening mechanisms in the UTVHM were revealed and explored. Moreover, the verification experiments were conducted, and the results suggested that the transverse force and thrust force in the UTVHM reduced up to 38.1% and 13.9%, respectively, because of the intermittent cutting mode realised in the UTVHM compared to HM. Significantly improved surface integrity, excellent chip evacuation conditions, and narrow hole geometric tolerances were obtained using UTVHM. A maximum depth of 9.7 µm for the plastic deformation layer was generated in the UTVHM, which was 6.5 times that of HM. The maximum increases in surface microhardness and residual compressive stresses in the UTVHM were 184.7% and 150.2%, respectively. Electron backscattered diffraction (EBSD) analysis showed that a higher plastic strain and smaller grain size occurred in the UTVHM. This study enhances the understanding of the surface and subsurface formation and material removal mechanisms of UTVHM, providing a theoretical basis and practical method for machining holes with high precision and excellent surface integrity in aircraft structures. [Display omitted] • A novel hole-making method of ultrasonic transversal vibration-assisted helical milling (UTVHM) is proposed. • UTVHM exhibits superior cutting performance compared to conventional helical milling. • Lower cutting force and higher hole precision are obtained in UTVHM. • Strengthening effect for the machined surface is realized in UTVHM. [ABSTRACT FROM AUTHOR]

In twist drilling, severe extrusion is unavoidable at the chisel edge zone and results in high thrust force and poor surface integrity. Traditional axial vibration-assisted twist drilling only modifies the material removed from the continuous extrusion to the interrupted extrusion for the chisel edge centre, and must satisfy the chip-breaking conditions to ensure that the cutting edge is periodically separated from the workpiece. Hence, transversal vibration, has been introduced in twist drilling to overcome the severe extrusion behaviour of the chisel edges of the twist drills, referred to as ultrasonic transversal vibration-assisted drilling (UTVD). Theoretical models revealed that the material removal behaviour of the chisel edge centre changed from extrusion in CD to cutting in UTVD. Experiments were performed on UTVD of Ti-6Al-4V to confirm the feasibility with this novel method. The results indicated that transverse vibration significantly affected the thrust force and torque, and the maximum decline was 29.4% and 31.5%, respectively, compared with CD. Generated chips verified the material removal behaviour of the chisel edge centre zone changed from extrusion in CD to cutting in UTVD. Therefore, the hole quality and surface integrity were improved significantly by UTVD. Deeper plastic deformation (∼2.5 times), higher surface microhardness and compressive residual stress were realised using UTVD. This study enhanced the understanding of material removal and formation mechanisms of the surface and subsurface in UTVD, thereby providing a novel method and theoretical basis for the high-performance twist drilling of difficult-to-cut alloys. [ABSTRACT FROM AUTHOR]

• An improved Riccati transfer matrix method for closed-loop systems is developed. • A spatial dynamics model for a tracked vehicle is established. • Two simplified contact models between the sprocket, track and rollers are proposed. • The effect of the track pre-tension on the transversal vibration of upper track is analyzed. In order to analyze the effect of track pre-tension on the transversal vibration of the upper track, a multibody dynamics model of a tracked vehicle needs to be established. In view of the complex structure of tracked vehicles, the computational efficiency of conventional methods cannot meet engineering design requirements. In this paper, the Riccati Transfer Matrix Method for nonlinear closed-loop multibody systems is proposed and applied to the modeling and simulation of tracked vehicle systems. It avoids the overall dynamic equations of the system and achieves efficient computation with a smaller matrix scale. By selecting accelerations and forces as elements of the state vectors instead of coordinates and forces, linearization is avoided. The track chain is cut in a revolute joint. Its effect on the closed-loop system is represented by a set of constraint equations and internal constraint forces. An improved Riccati transformation for closed-loop systems is proposed to connect the internal force and acceleration parts in the state vector with the system constraint internal forces. The track pre-tension can be adjusted by moving the position of the idler relative to the chassis. The root mean square of vertical acceleration of mid-span with respect to the chassis is selected to evaluate the transversal vibration of the upper track. Simulation of a tracked vehicle driving on different road conditions is carried out with different idler displacements. Finally, a reasonable adjustment strategy for the track tensioner is proposed corresponding to different running conditions. [ABSTRACT FROM AUTHOR]

• A new dynamic model of the upper span of the track is established. • The transversal vibration of the upper track is captured taking into account the track's axial velocity and the torsional stiffness of the track pin. • The complex transfer matrix method is proposed to derive the calculation equation of the natural vibration frequency of the track. • The effect of chassis vibration and polygon effect on steady-state response of the upper track is studied. Distinct from traditional metal hinge tracks, a new structure with tubular rubber bushing in the track pin has been used in the modern track. Vibration analysis of the track is indispensable to evaluate the vibration energy transmitted to the vehicle. The upper span of the track is modeled as a coupled multi-span axially moving Euler-Bernoulli beam. Based on the Hamiltonian principle, the transversal vibration differential equation of beam element is established, and its transfer matrix is derived. Dividing the state vector into real and imaginary parts, a complex transfer matrix method is proposed to establish the overall transfer equation of the system. Natural vibration characteristics of the system are discovered. Simulation results indicate that the first and second transversal vibration frequencies of the upper track increase monotonously as the axial speed decreases or tension increases. This study also analyses the steady-state response characteristics of forced vibration caused by chassis vibration and polygon effect. The results illustrate that the increasing tension can effectively reduce the vibration amplitude as the track is subjected to high-frequency excitation. This study contributes to the literature by providing the theoretical basis for the transversal vibration and stability control of the upper track. [ABSTRACT FROM AUTHOR]

Sufficient preload in a bolted joint is key to ensuring the reliability of mechanical products; however, under vibration, preload decrease often occurs. The mechanism of preload decrease has not yet been fully clarified. In this study, finite element models of bolted joints with and without helix angles were constructed to study the mechanism of preload decrease under transversal vibration. Based on the finite element analysis results, a new cause of preload decrease, denoted as stress release and redistribution, was discovered and explained in detail. The mechanism of preload decrease caused by stress release and redistribution, cyclic plasticity deformation and rotation loosening is studied systematically, and the typical mode of preload decrease is proposed. Based on the preload decrease curve, more comprehensive evaluation criteria are established, quantified using three parameters to represent the locking behavior of bolted joints. Finally, experiments were conducted to verify the reliability of the preload decrease results. [ABSTRACT FROM AUTHOR]

An understanding of conditions that trigger the loosening of bolted joints is essential to ensure joint reliability. In this study, a three-dimensional finite element model of a typical bolted joint is developed, and a new simulation method is proposed to quantitatively identify the critical transverse force for initiating loosening. This force is used to evaluate the anti-loosening capacity of bolted joints. Using the proposed simulation method, the effects of factors affecting critical loosening are systematically studied. It is found that the preload, frictional coefficients at the thread and the bearing surfaces, clamped length, and fit tolerance mainly affected loosening. When the preload and friction coefficients are increased, and the clamped length and fit tolerance are reduced, loosening is inhibited. Experiments are performed to demonstrate the reliability of the results. Finally, a suggestion is proposed to improve the design guideline VDI 2230 for bolted joints, which considers the requirement of avoiding loosening under vibrational loading. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to study the effect of lateral wind excitation on the transversal vibration of orchard chain ropeway system. The proposed chain system has been proved to be flexible and efficient, which can meet the demands of cargo transportation in mountainous orchards. The axially moving chains always work in a non-steady state and inevitably produce periodic transversal vibrations. The wind excitation exerted on the moving chain makes the transversal vibrations more complex. The transversal vibrations affect the safety and reliability of the moving chain system, and even lead to a disaster with high-amplitude vibrations. It is necessary to find an effective method for reducing wind-induced vibrations to an acceptable level imposed by the boundary conditions. In this paper, the Hamilton principle was applied to develop the dynamic differential functions of one-span moving chain under the lateral wind excitation. Mean lift and drag coefficients were used to characterize the susceptibility of moving chain to the galloping effect since the wind velocity was not normal to the chain axis. Long-span chain system may be subjected to the vortex-induced vibration seriously. The differential equations of axially moving chain system were proposed and discretized, which were based on the force equilibrium considering the chain boundary conditions with polygon effect. The formulation of transversal vibration subjected to the wind excitation was valid for the entire range of chain speeds and all points of the chain span. The solution of the differential equation governing the motion of the moving chain was obtained by using the Crank-Nicolson method and fourth order Ronge-Kutta method. The accuracy of the solution depended on the taken number of terms for the wind-induced chains. The time-history of wind speed was simulated by using harmonic superposition method, and the vibration properties of the axially moving chain with different mean wind speeds were numerically simulated. An experiment set-up was built for wind excitation test and 2 high speed cameras were used to capture the transversal vibration of the moving chain system. The LabWindows/CVI program was designed to process the captured vibration images. The wind speeds were simultaneously measured under different wind excitations generated by the experiment set-up. The wind speed profiles of mean wind speed with additional turbulence components were adopted. The turbulence component could be treated as a stationary random process with a mean value of zero. The equations describing the wind in the atmospheric boundary layer were represented by the proposed wind profile. The results of simulations and experiments showed that the lower mean wind speed could result in the decreasing of the amplitude of transversal vibration, which had a good aerodynamic stability for the moving chain system. At very high mean wind speeds, the negative damping effect would be exerted on the moving chain and cause the vibration to have considerable divergence and instability. This finding is useful for the development of active wind-induced vibration controller considering the chain polygon effect. This study can provide a reference for the transversal vibration control of the axially moving chain or string system under the lateral wind excitation. [ABSTRACT FROM AUTHOR]

• Transversal vibrations in cantilever beams are a good predictor of MOE of wood. • MOE prediction by transversal vibrations was more accurate than ultrasound method. • Five wood species with a wide density range (243 kg/m3 to 766 kg/m3) were tested. • This method could be further developed into a useful tool for timber grading. The prediction of the modulus of elasticity (MOE) of five species of different spectrum density woods, namely, Populus × euramericana I-214 (Poplar), Fagus sylvatica L. (Beech), Quercus pyrenaica L. (Oak), Paulownia elongata S.Y.Hu (Paulownia) and Pinus sylvestris L. (Scots pine) were examined through the natural frequency of vibration on cantilevered beams (transverse direction) and ultrasound (longitudinal direction). Cantilever beams are commonly used for other materials but limited information is available for wood materials tested in this manner. A total of 60 specimens with nominal dimensions of 40 × 60 × 1200 mm3 were tested, which were visually graded according to UNE 56544:2022 and UNE 56546:2022 as first class, and finally the global bending stiffness was obtained from a four-point bending test. Utilising this data, a regression model was presented to predict the MOE. Also, Picea sitchensis Trautv. & G.Mey (Sitka spruce) has been chosen as a blind species in order to validate the regression model of prediction of the MOE as a function of the dynamic MOE by ultrasound. Bending strength, modulus of elasticity and density were obtained according to the EN 408. In the prediction model using the dynamic MOE with vibrations, an r2 of 95.9% was achieved for the induced vibration technique which was found to be slightly higher than the model for the ultrasound prediction which had an r2 of 93.7%. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study of the nonlinear characteristics of an axially moving string. An experimental system with a simple configuration, which is similar to a practical application, was built. Two laser sensors were used to monitor the vertical and horizontal vibrations of the moving string under different conditions. Using the Hilbert-Huang transform method, the detailed results of a typical measured data series, which include intrinsic mode decomposition, Hilbert spectrum and marginal spectrum, are introduced. For comparison, marginal spectra for almost all test cases are also given. Based on the results, several observed nonlinear phenomena, which include whirling motion, resonances, quasiperiodical and a beating motion, torus doublings and one chaotic motion, are presented. The quantitative nonlinear vibrating details and the observed rich behaviors help explain the great complexity of a single moving string. [ABSTRACT FROM AUTHOR]

The equations of motion of a star graph of Stieltjes strings with prescribed number of masses on each edge, with or without a mass at the central vertex, lead to a system of second order difference equations. At the central vertex Dirichlet or Neumann conditions are imposed while all pendant vertices are subject to Dirichlet conditions. We establish necessary and sufficient conditions on the location and multiplicities of two (finite) sequences of numbersandto be the corresponding Dirichlet and Neumann eigenvalues. Moreover, we derive necessary and sufficient conditions for one (finite) sequenceto be the Neumann eigenvalues of such a star graph. Here the possible multiplicities play a key role; the conditions on them are formulated by means of the notion of vector majorization. Our results include, as a special case, some earlier results for star-patterned matrix inverse problems where only multiplicities, not the location of eigenvalues, are prescribed. [ABSTRACT FROM PUBLISHER]

Transverse vibrations of a rotating annular disk composed of two annular disks of different materials are studied in this paper. The disk is clamped at the inner edge, while at the outer edge is free. Differential equations of small vibrations are solved exactly by series expansion using the Frobenius method. The solutions are separately presented for three cases corresponding to vibration with zero, one or two nodal diameters. The influence of angular velocity, moduli of elasticity and the volume densities of the materials of disks on vibration frequency is analyzed. Vibration frequencies are obtained for the disk composed of aluminum and steel. Influences of the inner radius and the radius of the connection on the vibration frequencies are also obtained. [ABSTRACT FROM AUTHOR]

To suppress the transverse vibration of an axially moving chain system with concentrated inertial masses in hilly orchard, the important factors affecting frequency characteristic of moving chain and their interaction are required to be studied. Based on the string theory and dynamics of chain transmission, the differential equation of transverse vibration was developed in the Laplace domain and the critical transport velocity was obtained in this paper. The stable condition for transport velocity corresponding to resonance was determined by considering the polygon effect causing speed variation when the moving chain link engaging with supporting end. With solutions for the second-order homogeneous partial differential equation, the effects of initial tension, transport velocity and load mass on the frequency of transverse vibration were numerically and experimentally analyzed. The difference between measured data and calculated data yielded values from 1.4% to 27.6% for various transport velocities, from 6.1% to 14.2% for various load masses, and from 14.7% to 24.3% for various initial tensions. The results show that the frequency of transverse vibration of axially moving chain increases with the increase in initial tension. The negative effect of transport velocity and load mass on vibration frequency in the case of forced nonlinear vibration is found. The proposed differential equation is proved valid to predict the effects of operation parameters on vibration frequency. It is conformed that this approach to transverse vibration of an axially moving chain can be used for parameter optimization under a certain constraint condition. The solution provides the theoretical basis for the vibration analysis and stability control of moving chain by consideration of wind-induced and rain-induced effects. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the transversal vibration characteristics of an axially moving string with unilateral constraints were examined using the Hilbert–Huang transform (HHT), due to its wide range of applications. Experiments were conducted on five test cases, and the subsequent analyses were discussed. The experimental results show that the introduction of a guide has the effect of causing low-frequency vibration suppression. The vibration behaviors of the guided segment and the free portion are highly sensitive to the initial tension, the initial clearance between the string and the guide, the transport speed and the guiding length. The details of the string vibrations revealed in this work will be used as a reference for engineering designs and relative system identifications. [Copyright &y& Elsevier]

This work considers passive dynamic absorber (without additional energy source) of the simplest type: a non-controlled spring with one degree of freedom. Object of vibration suppression is transversal vibrations of rigid cantilever beam. The inertial element is connected to the vibration protection object by means of elastic metal element - nonlinear conical coil spring. Experiments were performed on the universal vibration system TM 150. [ABSTRACT FROM AUTHOR]

In the paper, transversal vibration of the annular plate related to the toothed gear is studied using finite element representation. The plate is fixed in the hollow shaft. The base model contains all essential construction of the aviation engine toothed gear. The algorithm to identify the proper distorted mode shapes is presented. The pre-stress effect is included using the FE code system standard procedure. It is important to note that the data presented in the paper is brought the practical advice to design engineers. [ABSTRACT FROM AUTHOR]

Mean dynamics of light granular matter in liquid in the rotating horizontal cylinder subjected to transversal vibrations is experimentally investigated. The excitation of outstripping and lagging azimuth motion of the interface with respect to the cavity is revealed at definite ratios of rotation and vibration frequencies ${\Omega _\upsilon } \mathord{\left/ {\vphantom {{\Omega _\upsilon } {\Omega_r }}} \right. \kern-\nulldelimiterspace} {\Omega _r }$ . The motion is generated by the inertial oscillations arising in the system in a resonant way. The formation of regular spatial structures on the interface is revealed at intensive outstripping motion. These structures have azimuth and axial periodicity and their shape depends on the type of inertial waves arising in the cavity. Intensity and direction of azimuth flows as well as shape of patterns on the granular matter–liquid interface are determined by the ratio $ {\Omega _\upsilon } \mathord{\left/ {\vphantom {{\Omega _\upsilon } {\Omega _r}}} \right. \kern-\nulldelimiterspace} {\Omega _r }$ . It is shown, that the lagging motion exists at $ {\Omega _\upsilon } \mathord{\left/ {\vphantom {{\Omega _\upsilon } {\Omega _r }}} \right. \kern-\nulldelimiterspace} {\Omega _r }<1$ , and the outstripping one exists at $ {\Omega _\upsilon } \mathord{\left/ {\vphantom {{\Omega _\upsilon } {\Omega _r }}} \right. \kern-\nulldelimiterspace} {\Omega _r }>1 $ . Combined action of vibrations and rotation provides an efficient mechanism of mass transfer control, the intensity of mean flows in the cavity frame can be of the same order of magnitude as the rotation velocity. [ABSTRACT FROM AUTHOR]