Behavior Of Bolted Joints Research Articles

Theoretical and experimental study on the damage behavior of bolted joints under cyclic loads

This paper presents a quasi-static and dynamic experimental study on the damage behavior of bolted joints. It proposes a 7-parameter theoretical model to accurately describe the damage properties of bolted joints during both micro- and macro-slip stages under cyclic loads. Results from quasi-static experiments indicate that under the preload of 12.4 kN, a ratcheting effect is observed during the micro-slip stage, reflecting the cumulative plastic damage process at the bolted interface. The macro-slip force exhibits a linear decrease with increased loading cycles. In the initiation of macro-slip, energy dissipation exhibits unstable characteristics, manifested as an "S"-shaped curve in the energy dissipation-applied force relationship. The proposed model can well describe bolted joints' observed energy dissipation characteristics.

Finite element analysis of bolted joints under torsional loads

The presence of service torque, which is generated after tightening, directly affects the mechanical properties of bolted joint. In this work, the mechanical behavior of bolted joints under torsional loads is investigated using finite element analysis (FEA). Models with two plates and multiple plates are established separately to investigate the mechanical properties of different kinds of bolted joints. Three analysis steps involving the entire process from tightening to torsional loading are adopted, namely tightening step, initial loss step and loading step. Torsional loads in two directions along the thread axis are considered and defined as loosening torsional load and tightening torsional load. The clamping force, as well as the friction torques of various contact surfaces, of the bolted joint are extracted in all the analysis steps. Different scenarios of friction torque combinations for bolted joints are obtained by means of adjusting the friction coefficient of the corresponding contact surfaces. On this basis, the mechanical properties of bolted joints and the corresponding torque thresholds are extracted on various scenarios. FEA results showed that how the service torque makes the directional characteristic of the mechanical properties of bolted joints under torsional loads. Moreover, the service reliability of bolted joint can be further improved based on the directional characteristics and the extracted torque thresholds.

A Dynamic Iwan Model to Describe the Impact Failure of Bolted Joints

Due to the nonlinearity of the contact interface, as well as the material, jointed structures exhibit complex mechanical behaviors under impact loading. In order to accurately characterize the dynamic response of a joint, this work presents a nonlinear dynamic model (DICF model). First, the effects of loading velocity, preload and friction coefficient on the displacement–load curve are discussed based on a validated finite element model. Numerical simulation results show that the critical load and critical displacement are linearly related to the normalized logarithmic velocity and linearly related to the normalized preload and friction coefficient. Subsequently, a DICF model that consists of sliding, collision and failure is proposed. The constitutive relations of the model are derived, and dynamic correction functions are introduced to characterize the effects of velocity, preload and friction coefficient. A parameter identification method for the model is also provided. Finally, the DICF model is compared with the finite element simulation results, with an error of 0.43% for quasi-static conditions, a minimum error of 0.17% and a maximum error of −1.41% for impact conditions, in addition to significantly improved accuracy compared to the EC3 model, which indicates that it can effectively capture the behavior of bolted joints under impact loading conditions.

An investigation of vibration responses for bolted composite flanged-cylindrical shells considering material and joint nonlinearity

In this paper, a thorough investigation into the vibration response of bolted composite flanged-cylindrical shell structures, considering the material nonlinearity of carbon fiber-reinforced polymer composites (CFRP) and the joint nonlinearity of bolt connections, is presented. Firstly, a general semi-analytical modeling method for bolted composite flanged-cylindrical shell is developed based on the first-order shear deformation theory (FSDT) and the energy method. In this method, material nonlinearity is introduced by accounting for the frequency-strain dependency of material parameters. A joint model with non-uniform distribution parameters and dynamic boundaries is proposed to simulate the interface pressure distribution and nonlinear mechanical behavior of bolted joints. Then, for the general numerical model that incorporates both types of nonlinearities, the ability to accurately predict the nonlinear vibration behavior of a bolted composite flanged-cylindrical shell is demonstrated through experimental testing. Finally, an in-depth discussion is conducted on the influence of fiber layup patterns and bolt numbers on the nonlinear vibration response of the bolted composite flanged-cylindrical shells. The conducted analysis indicates that the proposed method can offer utility to designers, empowering them with the insights necessary for the dynamic optimization of such structures.

Method of accumulation of preload loss of bolted joints due to rotational self-loosening caused by cyclic, transversal excitation

This paper presents a new method to experimentally characterize the rotational self-loosening behavior of bolted joints. Furthermore, a method to calculate the preload loss due to certain relative displacements of the clamped parts was developed. The method obtains all required calculation parameters from the experimental tests performed and neither needs further experimental determination of friction coefficients nor numerical simulations to predict the preload loss. The method accumulates the preload loss of load cycles. Thereby, it can be used to estimate the time a machine can operate until a critical amount of preload is lost. Non-linear dependencies of the preload loss to the displacement amplitude and the remaining preload are considered. The calculation method also applies to load cases with variable load amplitudes. This is validated experimentally.

Non-linear modeling and parameter identification of a bolted joint using substructure synthesis theory

Engineering applications require accurate modeling and parameter identification to anticipate bolted joint behavior under different loading circumstances. Bolted joints are extensively used in civil and mechanical structures. In this research study, cubic stiffness non-linearity is examined and a comprehensive model, which can exhibit the non-linearity of joint behavior, is developed. This is achieved by modeling the bolted joint which is connected at one end of a cantilever beam. Mathematical model is established using concept of sub structure synthesis theory by considering non-linear translational stiffness and non-linear rotational stiffness as a boundary condition. Non-dimensional natural frequencies are estimated by assuming stiffness parameters and joint parameter estimation for translational spring having nonlinear stiffness is calculated using second order curve fitting technique. Furthermore, estimated and exact value of cubic stiffness coefficient are compared. The experimental results shows that the percentage error of estimation for all the modes are less than 8%. The experimentally determined natural frequencies are further contrasted with an analytical results to validate a precision of generated model. Present work contributes in improving the bolted joint analysis by providing a solid non-linear modeling and parameter identification methodology. This methodology enhances design practices and ensures the durability of engineering structures and mechanical systems by improving bolted joint comprehension.

A Review of Cross-Scale Theoretical Contact Models for Bolted Joints Interfaces

Bolted joints structures are critical fastening components widely used in mechanical equipment. Under long-term loading conditions, the bolted joints interface generates strong nonlinearities within the system. The nonlinear stiffness inside the bolt leads to changes in the stiffness of the whole system. This affects the dynamic characteristics of the whole system. It brings challenges and difficulties to the performance prediction and reliability assessment of the equipment. A cross-scale theoretical model study based on the microscopic contact mechanism can provide a more comprehensive understanding and cognition of the degradation behavior of bolted joints interfaces. The current development status and deformation process of asperity models are summarized. The research progress of statistical summation model and contact fractal model based on microscopic contact mechanism is analyzed. The experimental methods for parameter identification of connection interfaces are reviewed. The study of numerical modelling of bolted joints structures from the surface contact mechanism is briefly described. Future research directions for cross-scale modelling of bolted joints structures are outlined.

Influence of fibre steering on the bearing performance of bolted joints in 3D printed pseudo-woven CFRP composites

Aiming to improve the bearing performance of bolted joints in carbon fibre reinforced polymer (CFRP) composites, this study investigates the impact of steered fibre paths around the hole edge within pseudo-woven (interlaced) composites that are manufactured by 3D printing. The influence of fibre steering on the crack initiation and propagation was examined through double-lap bearing tests performed on four distinct cases. Parallel to the comprehensive experimental study, digital image correlation (DIC) and X-ray computed microtomography (micro-CT) scans were performed to aid in understanding and identifying the various damage mechanisms in each specimen type. Results revealed that different patterns provided varying bearing abilities, with an employed pattern improving the initial bearing strength, initial fracture energy and ultimate fracture energy of the 3D printed pseudo-woven composite by 23.5%, 363.7% and 29.6%, respectively. Consequently, fibre steering in composites is found to be a promising method to tailor the bearing behaviour of bolted joints as required.

Guided wave-based damage assessment on bolt in precast beam-to-column joints

This paper deals with theoretical, numerical, and experimental investigations of guided wave-based damage assessment on bolts in the precast joints under cyclic loads. The mechanical behavior of precast bolted joints is analyzed, and the relationship between the force and drift ratio of the energy-dissipating (ED) bolt is derived. The propagation characteristic of guided wave in ED bolt is revealed through finite element simulation. The influence of tensile damage and looseness damage on the received signals is further studied, and two indexes are developed for evaluating the health status of ED bolts. Cyclic loading tests were carried out on four precast bolted beam-column joints with different precast beams, and the guided wave signals of ED bolts under each level of loading were monitored by arranging lead zirconate titanate (PZT) sensors. The bolt yield drift ratios were obtained by skeleton curves and FBG strain detectors respectively. The relationships between the two damage indexes and the drift ratio are obtained, and the two developed damage index trends were very well reproduced by analytical expressions. The health state assessment of ED bolts and precast bolted structures is realized by the proposed damage limit method, whether in daily maintenance or after the earthquake.

Critical load determination for preventing rotational loosening in bolted joints under dynamic transverse loads

To ensure the reliability of bolted joints, it is essential to accurately determine the critical load that prevents rotational loosening of the nuts. In this paper, the mechanical behavior of bolted joints during tightening, after tightening, and under transverse loading was analyzed. The contact status of two mating surfaces, including the thread and nut bearing surfaces, and their ability to withstand transverse loads were calculated. Based on the conditions leading to rotational loosening, defined by the occurrence of sliding across both sets of contact surfaces, the critical condition for transverse force that precipitates rotational loosening in bolted joints has been established. Furthermore, a systematic procedure for determining this critical state of rotational loosening in bolted joint assemblies has been developed. Finite element simulations on bolted joints subjected to dynamic transverse loads, using various combinations of friction coefficients, showed results in good agreement with theoretical predictions. Finally, experimental measurements of the critical rotational loosening loads were conducted. The experimental results highlight that the decrease in clamping force due to non-rotational factors has a significant impact on the critical loads. Considering this influence and adjusting the preload accordingly, the calculated results for the critical loads are in good agreement with the experimental data.

Coupled vibration analysis of bolted variable angle tow plates under combined nonlinear effects

To establish a dynamical modal of variable angle tow (VAT) plate accurately, the fiber path and fiber orientation of the VAT plate are described by high-order polynomials. Then, a simplified nonlinear joint model with interface dynamic partitioning is proposed to simulate the interface mechanical behavior of bolted joints. Based on these, a nonlinear semi-analytic dynamic model of the bolted VAT plate is built, which considers both material and joint nonlinearity and can accurately predict nonlinear vibration response. After verifying the proposed modeling method, a special bolted VAT plate is used as the analysis object for free vibration and forced vibration analysis. Firstly, the frequency veering behavior of the VAT plate caused by variations in boundary stiffness, connection stiffness, and fiber orientation is studied. Then, by analyzing the forced vibration response of the bolted VAT plate, it is found that under the combined effect of the modal interaction, material nonlinearity, and joint nonlinearity, the bolted VAT plate exhibited complex but rule-based nonlinear dynamic behavior. More importantly, the research work done in this paper has certain guiding significance for the optimization design of vibration resistance of a bolted VAT thin-walled structure with variable stiffness parameters and joint parameters as design variables.

Analysis of the mechanical behavior of bolted joints with slotted-in steel plate considering the move path of rotation center for single-layer timber reticulated shell

The mechanical behavior of the bolted joints with slotted-in steel plate plays an important role in maintaining the stability of single-layer timber reticulated shell, yet methods to estimate the mechanical behavior of the bolted joints still remains to be improved. Assuming that the ductile failure of the bolted joints and the compressive failure of the glulam beam end occurred, the move path of the rotation center was obtained through theoretical derivation and used to determine the ultimate moment and rotational stiffness of the bolted joints. The equations for calculating the ultimate moment of the bolted joints were derived based on the European Yield Modes, t. Moreover, employing the beam on elastic foundation theory, a simplified equation of slipping stiffness was obtained and used to calculate the rotational stiffness. Experimental investigations on bolted joints for single-layer timber reticulated shell were conducted to verify the accuracy of the proposed theoretical methods. The results showed the rotational stiffness and ultimate moment obtained from theoretical calculation were consistent with the results of experimental tests. Furthermore, by calculating the move path of the rotation center, it was found that the rotation center started from the geometrical center of bolts at earlier loading stage and moved towards the compressive region of the glulam beam end with the increase of the external force. And the moment-rotation curves predicted by the linear model was in good agreement with the moment-rotation curves obtained from experimental tests, showing a convenient and reliable way to the design of bolted joints for single-layer timber reticulated shell.

Experimental and numerical investigations on fatigue behavior of 42CrMo4 high-strength steel single lap double-bolted joints

Cold extrusion forming is a manufacturing technology that effectively extends the fatigue life of mechanical structures and has been widely used in the processing of ship components. The fatigue behavior of 42CrMo4 high-strength single lap double bolted joints is investigated based on fatigue experiment and numerical simulation. The stress-strain distribution of joint plates under cold extrusion, bolted tightening and longitudinal external loads are evaluated based on the nonlinear finite element software ABAQUS. The fractographic of fatigue specimens is detected by scanning electron microscopy (SEM) to research the initiation location and propagation type of fatigue cracks, and a prediction method for the stiffness of joint plate bolt connections is further proposed. The results indicate that fatigue cracks propagated tortuously and exhibits a more complex distribution state. The combination of cold extrusion forming and bolt preload can effectively improve the fatigue life of high-locked bolted joints. Smooth surface, beneficial residual stress field and cold extrusion hardening phenomenon are considered the main reasons for improving fatigue life.

Influence of bolt dynamic installation on topography characteristics and mechanical behaviors of CFRP interference-fit bolted joints

As the controlled research of Dynamic Installation (DI) and Static Installation (SI), a new interference installation method was developed based on electromagnetic loading to enhance the mechanical properties of composite structures. Four different interference-fit sizes were considered, ranging from a net fit to 2.0%. The experiments were conducted to evaluate the installation resistance and the mechanical behavior of the joint under external loads. Meanwhile, an FEA model to model the stress distribution and damage behavior of the bolt-hole contact interface was established. The load–displacement curve and damage modes of experiments were used to verify the FEA results. The results show that the installation resistance during DI process was remarkably lower than that of SI process corresponding to all interference-fit sizes, and the stress amplitudes induced by interference were larger and widely distributed. The damage of the hole wall was positively correlated with interference fit size, but DI can significantly reduce the damage compared to SI. In performance tests, DI enhanced the static bearing capacity and extended longer fatigue life of the joints than SI. DI methods can be an effective way to achieve highly reliable interference joints in composite structures.

Seismic behavior of composite bolted T-shaped exterior joints in modular steel construction

This paper presents a new joint that is connected by common friction high-strength bolts and blind bolts. To study the seismic behavior of the proposed joint, four full-scale joints were tested by quasi-static tests and simulated by the finite element method. According to the stiffness, resistance and ductility of the joints, the influences of column-to-column blind bolt connection, beam-to-beam common bolted connection, and arrangement of inner diaphragm are analyzed. The results show that the beam-to-beam bolted connection, column-to-column blind bolted connection, and the arrangement of inner diaphragms can obviously improve the bearing capacity of the joints, which are 24.9%, 39.2% and 44.6%, respectively. The ductility of each joint is between 1.86 and 2.74, with an average value of 2.15. The joints with cover plate and inner diaphragm plate can meet the requirements of special moment frames (SMF). Therefore, the modular steel construction (MSC) in the seismic zone should adopt cover plate and inner diaphragm plate, and the joint should meet the requirements of strong column-to-weak beam to obtain better ductility.

Prediction of Self-Loosening Mechanism and Behavior of Bolted Joints on Automotive Chassis Using Artificial Intelligence

The tightening torque values considered in the assembly of vehicle subparts are of great importance in terms of connection safety. The torque value to be selected is different for each bolted joint type with respect to mechanical features. While the tightening torque value is an important indicator, the bolt preloading value is always a more reliable parameter in terms of whether a secure tightening can be achieved or not. For this reason, when it is desired to create reliable joints, the preloading value that the tightening torque input will create on the connection package should be calculated well. This study presents an integrated approach using Taguchi method (TM) and neural network (NN) to predict the self-loosening mechanism of bolted joints in automotive chassis engine suspension connections. External loading acting on the joints of the engine suspension was collected from bench tests. NN was applied to establish the relationship between controlled factors and loosening rate. The results showed that the proposed approach can be used to predict mechanism of self-loosening and behavior of bolted joints without additional tests, and it is possible to make predictions with very low error rates using artificial intelligence techniques.

PDEM-based multi-component and global reliability evaluation framework for steel tubular transmission towers with semi-rigid connections

The conventional analysis and design of transmission towers usually ignore the effect of semi-rigid behaviors of bolted joints and simplify the joints as the rigid or pinned connection, which might overestimate or underestimate the structural response of transmission towers and the reliability of structural components and systems. To consider the effect of semi-rigid connections on the reliability of transmission towers in this paper, a stochastic dynamic finite element model of steel tubular transmission towers with semi-rigid connections (STTTs-SRCs) is established by deriving their stiffness matrix, where the uncertainties of dimensions, material and semi-rigid connections are considered and the wind loads are simulated as stochastic processes by the dimension-reduced probabilistic simulation approach. Then, based on the equivalent extreme-value event, the multi-component and global performance functions with stress and displacement failure modes for STTTs-SRCs are established, respectively. Further, a reliability evaluation framework for STTTs-SRCs is proposed based on the probability density evolution method (PDEM). Finally, a practical engineering transmission tower is regarded as an example to demonstrate the implementation process of the proposed reliability evaluation framework. Moreover, the reliability of steel tubular transmission towers with rigid and pinned connections is compared with that of STTTs-SRCs to investigate the effect of semi-rigid connections on the reliability of transmission towers. In general, the semi-rigid connections would mainly affect the value of the multi-component failure probability, however, it would not change the location where the maximum failure probability of components occurs. Additionally, the semi-rigid connection significantly affects the global failure probability of towers for the stress failure mode while slightly affects the global failure probability of towers for the displacement failure mode. Therefore, it may be more appropriate to consider the semi-rigid connections into the analysis and design of steel tubular transmission towers.

A nonlinear rheological shear constitutive model of bolted joints considering initial damage and damage evolution

Understanding the shear mechanics mechanism of bolted joints is of great significance for predicting and preventing geological disasters. Most current studies seldom consider the rheological effects of bolted joints. In this paper, a comprehensive rheological constitutive model is proposed, accounting for initial damage and damage evolution across different rheological stages and bolt characteristics. The model incorporates an elastoplastic Hooke body for instantaneous deformation, parametric nonlinear Kelvin and viscous models for attenuation and steady creep stages, and a visco-plastic model based on time-dependent shear strength for accelerated creep stage. Additionally, a bolt-rock cooperative deformation model is introduced, considering the evolution of the bolt's elastic modulus. The resulting elasto-viscoplastic constitutive model effectively describes the shear rheological behavior of bolted joints, with its validity and superiority demonstrated through comparisons with shear creep tests and the Maxwell model. This research aims to provide valuable theoretical guidance for the construction and reinforcement of rock mass engineering projects.

Experimental characterization and parameter identification of bolted joints under vibratory loading

The paper experimentally investigates the frictional behaviour of bolted joints with varying preload, inclined bolt head interface, and varying contact area between plates subjected to tangential loading. Experimental result shows a reduction macroslip force and energy dissipation with decrease in bolt preload. Similarly, increase in inclination of bolt bearing surface reduces macroslip force and energy dissipation. The reduction in contact area does not affect the tangential stiffness or frictional energy dissipation when contact pressure profile on plate interface is fully developed. For truncated pressure profile, the reduction in contact area reduces both the tangential stiffness and the energy dissipation. The experiments are conducted to determine the energy dissipation during pinning reveals differential pinning for lower displacements. At higher displacements, the crack initiates into the bolt shank which reduces the energy dissipation.

Experimental investigation on acoustic emission in fretting friction and wear of bolted joints

Fretting between bolted interfaces may change the dynamic characteristics of structures under vibration loading. The acoustic emission (AE) technique has been successfully used to investigate friction and wear mechanisms between different kinds of contact pairs. This paper experimentally investigates the AE signals of a bolted joint structure during friction and long-time fretting wear to explore the relationship between AE characteristics and interface fretting behaviors. A test apparatus dedicated to the study of fretting behaviors of bolted joints together with an AE acquisition system is used to carry out the experimental tests. Relative displacement, tangential friction force and the related AE waveform features are obtained simultaneously to better relate acoustic emission signals with hysteresis loops. The effects of external excitation amplitude and fretting wear cycles are investigated. The frequency signatures of the individual burst acoustic emission event under different excitation amplitudes and wear stages are analyzed. Results show that AE events mainly occur in the micro-slip and the gross-slip regime, and AE technique is more sensitive to the transition point from micro-slip to gross-slip regime. As the external excitation amplitude increases, the value of most AE parameters is gradually increased. As the fretting wear cycles increase, evolutions of bolt preload, frictional coefficients, and AE parameters first show a significant change and then become asymptotically stable. Furthermore, the frequency intensity and range will increase with the increase of excitation amplitude and decrease with the wear cycles.