Bolt Fastening Research Articles

Research on voice print recognition of loose state of transmission tower bolts based on MFCC feature vector

In order to monitor the loose state of transmission tower bolts, this study discusses the application of voice print recognition technology in this field. By collecting the sound signals under different loosening states of the transmission tower bolts and using Mel cepstrum coefficient (MFCC) feature extraction method, the sound signals are converted into feature vectors for analysis, and the loosening state of the bolts is effectively recognized. The experimental results show that the characteristic value obtained in the bolt loosening test is 4.3766, which is higher than the MFCC characteristic critical value 4.0, indicating that the bolt loosening problem exists. At the same time, in the bolt fastening test, the result obtained is 3.8364, which is lower than the MFCC characteristic critical value 4.0, indicating that the bolt is not loosened. It can be seen that whether the bolt loosening test or the bolt tightening test, the method based on MFCC feature vector has a considerable recognition effect, and can judge the bolt state through the eigenvalue method. This study provides a new non-contact technique for real-time monitoring of bolt loosening state of transmission tower, and provides important guarantee for the safe operation of transmission lines. This technology has a broad development prospect in practical application, and provides an important reference and guidance for further research and practice in related fields.

Analysis of torque variation in bolt fastening on coated steel surfaces

As the number of parts ever increases, the push for automation in assembly processes is intensifying in advanced manufacturing industries. The drive to improve productivity through manufacturing automation is relentless, and minimizing torque variation in automated bolt fastening is crucial for achieving successful assembly. Therefore, a precise understanding of the mechanisms of interfacial friction between bolts and coated steel plates, along with a torque analysis based on the interactions of various involved parameters, is essential. This study examines the interactions between surface topography and mechanical properties of bolts and coated steel plates. We explain three primary friction modes (plowing, sliding, and penetrating) within the defined contact areas and propose a prediction model based on contact mechanics to estimate the frictional torque under the bolt head on coated surfaces. Additionally, we quantitatively evaluate how the proportions of these friction modes change under various axial loads and coating conditions, and how these variations affect torque values. We also assess how variations in key parameters influence changes in friction modes, providing insights into the critical factors that should be monitored for effective control of fastening torque. This study presents methods for analyzing and calculating friction torque, offering guidelines for monitoring bearing surfaces to address bolt topography deviations and solving key industrial challenges in automated assembly.

A novel experimental method for bolt stress distribution during the assembly process

Bolt fasteners play a crucial role in modern engineering equipment, and understanding the stress distribution in the bolt during the assembly process is essential for enhancing its reliability. However, traditional experimental methods based on the principle of photoelasticity may not accurately reflect the actual assembly process and engineering materials. To address this issue, a novel experimental approach is proposed in this paper, which utilizes optical fibers to measure stress in the bolt during the assembly process. By affixing an optical fiber to the inside of the bolt and employing the optical frequency domain reflectometry (OFDR) technique, the axial stress distribution in the bolt can be obtained. In addition, the concept of an axial force gain factor is introduced to establish the relationship between the maximum axial force and preload. It is found that the calculated maximum axial force of the bolt is approximately 1.4 to 1.5 times the preload. The experimental results show that the stress distribution obtained through the proposed method is consistent with conventional photoelasticity experiments. Furthermore, a comparison with previous studies validates the accuracy of the experimental findings. The experimental approach presented in this paper can realize the real-time measurement of bolt stress distribution, which is of great significance for engineering application.

Research on the effect of manufacturing processes on the fatigue life of TC4 fasteners

Abstract TC4 fasteners have the characteristics of high specific strength and yield ratio, excellent high and low temperature performance, corrosion resistance, etc., and are widely used in many fastener fields, including aerospace. In long-term use, fatigue fracture has become the main failure mode of TC4 bolt fasteners. The common manufacturing processes of TC4 fasteners include shot peening, bottom corner rolling pressure, anodizing and molybdenum disulphide coating, etc. At present, few researchers have studied the effect of the stress level of the manufacturing process on the fatigue life of TC4 fasteners. Therefore, this paper designs the process and parameter influence test from the perspective of different manufacturing processes, and analyses the fatigue test results to reveal the influence mechanism of different processes on the fatigue life of TC4 fasteners. The research results show that the increase of residual compressive stress greatly improves the fatigue strength of fasteners, the shot peening process improves the fatigue life of TC4 fasteners by increasing the residual stress of fasteners, and rolling pressure also increases the surface residual compressive stress. However, it is necessary to find suitable rolling parameter values, and anodizing reduces the residual compressive stress of fasteners. The coating of molybdenum disulfide also reduces the residual stress value of the fastener surface and leads to a decrease in fatigue life. Therefore, in order to control the fatigue life of TC4 fasteners, it is necessary to carry out the shot peening process, and control the rolling pressure, anodizing time and the coating thickness of molybdenum disulfide. The research in this paper provides a reference for the subsequent research on fastener fatigue strength control.

Target reconstruction and process parameter decision-making for bolt intelligent assembly based on robot and multi-camera

Bolt assembly is widely used in modern manufacturing. And with the development of industrial automation, there is a growing demand for automatic assembly. To form a fully automatic and highly intelligent system for bolt assembly, a novel strategy based robot and multi-camera is proposed. In this strategy, a high assurance components reconstruction scheme is designed, wherein the Mask R-CNN is used for the identification and segmentation of the workpiece, then the shape, size and pose of the workpiece are determined by the local point cloud data and its envelope using basic geometries. The results show that the accuracy of workpiece recognition exceeds 96 %, the maximum positioning accuracy of the hole is 0.334 mm based on multi-camera system. Based on the historical fastening process data, an improved artificial jellyfish search optimizer (AJSO) BP neural network is proposed to automatically determine the optimal values for the bolt fastening speed and torque. The BP neural network optimized by AJSO reduces the maximum prediction error of process parameters from 0.117 mm/s to 0.051 mm/s for speed and from 0.052 N·m to 0.027 N·m for torque. Finally, the feasibility of the proposed strategy is demonstrated by an experimental case, which used a dual robot unit for the bearing seat assembly.

Examining the effect of threaded bolt fasteners on steel construction

This study investigated the effects of threaded bolt fasteners on the initial and final stiffness of bolted joints in special steel modular construction. A comprehensive set of 246 specimens, including 4, 7.6, and 12 mm thick plates with 20 and 30 mm diameter bolts and different end spacings, were tested. The results revealed that connections with threaded bolts exhibited lower initial stiffness compared to pure shaft connections. This study introduced a novel formula that significantly improved simulation results for bolted joints, surpassing previous modeling approaches. Following the American Society for Testing and Materials (ASTM) definition, the “elastic” stiffness values obtained from the laboratory tests were compared with those of Eurocode provisions. Additionally, ad hoc formulas were proposed for the stiffness of shank, lap connection with partially threaded, and fully threaded bolts. These results offer valuable insights for enhancing the stiffness of bolted shear connections.

Evaluation of the Influence of Bolt Fastener Spacing on the Elastic Critical Load from the Lateral-Torsional Buckling Condition of Built-Up Bending Members.

In an experimental study of two-branched beams bent transversely about the major stiffness axis, the elastic critical load from the lateral-torsional buckling condition was determined. The tests were conducted on simply supported two-branch beam models with a built-up section consisting of two cold-formed channel members (2C) bolted back-to-back. The bolts were located at the mid-height of the built-up cross-section. Five groups of members differing in longitudinal bolt spacing were examined. The models were gravitationally loaded (using ballast) at the centre of the beam span. This approach eliminated the undesirable effect of the lateral support of the beam, e.g., by the actuator head. The critical load, measured by the concentrated transverse force (Pz,cr), was determined using the modified Southwell method. It has been experimentally shown that, in built-up beams, there is an influence of bolt spacing on the elastic critical load from the lateral-torsional buckling condition. The lowest critical load capacity and the most non-linear behaviour of the built-up member were observed in beams bolted with only three bolts (at the supports and in the middle of the span). However, the experimental results obtained in this study show that increasing the number of bolts above a certain level (in the case of the tested models, it was seven bolts) does not result in a further increase in the critical load, which is a surprising result. The obtained values were 15 to 23% lower than the critical load determined numerically by the finite element method (LTBeamN) for an analogous element with a uniform I-section.

Synergistic Effects of Layered Double Hydroxide and MoS2 on the Performance of Lubricants

In this study, layered double hydroxide (LDH) and molybdenum disulfide (MoS2) were used as additives to prepare lubricants. The morphology and particle distribution of the LDH and MoS2 were characterized using a scanning electron microscope and a laser particle size analyzer, respectively. Thermogravimetric analysis was used to compare the performance of the lubricants at high temperature. The extreme pressure and wear resistance performance of the lubricants were tested using a four-ball machine and a fretting-wear machine. Then, the lubricants were applied in a bolt fastener. The loosening torque and surface wear condition at high temperature were compared. By adding LDH and MoS2 to the lubricants, the extreme pressure and wear resistance performance and anti-seize performance at high temperature were improved significantly. The LDH showed better anti-seize performance than the MoS2 because of its strong and stable structure at high temperature. The MoS2 showed better anti-wear performance under a high load because of its soft layered structure. The MoS2 with a larger particle size showed better extreme pressure performance under a high load. The LDH and MoS2 played a synergistic effect under the conditions of high temperature and high load.

Investigating seismic behaviour of cold-formed steel moment frames with the welded through-plate flexural connection

The Cold-Formed Steel (CFS) construction in seismic regions requires carefully selecting and designing an approved seismic-force resisting system. Among the available seismically-resistant structural systems, the bolted CFS moment frames have recently gained some attention. However, given the currently existing design issues associated with the bolted connections in CFS moment frames, this paper seeks to conduct a numerical investigation into the potential substitution of bolt fasteners with the weld materials in CFS frames. The objective is to explore the possibility of including the welded connection as an alternative to bolted connections in subsequent editions of the ASCE 7 code. To this end, finite element models, consisting of two built-up CFS beams and twenty-three flare-bevel-groove and fillet weld specimens, are initially validated against the cyclically and monotonically loaded tests with data available in the relevant literature. Subsequently, the verified weld and CFS beam models are incorporated in the simulation of thirty-four CFS beam-to-column welded moment connections, each differing in beam dimension, weld length and size, and gusset plate thickness. The built-up beams comprise back-to-back and lip-to-lip double C-section profiles. Stress variations along the weld lines, derived initially from nonlinear finite element analyses and then computed from the theoretical elastic analysis, are compared to establish a basis for categorizing stress distribution patterns in the longitudinal welds. Finally, six CFS frames assembled with the welded moment connection and subjected to a combined column axial compression and cyclic lateral drift are examined, resulting in an estimated seismic modification coefficient, R, equal to 3.8. Overall, the welded moment connections demonstrate a stable seismic response with an average ductility ratio, μ, of 2.7. The dominant failure mode is a locally developed ductile fracture in the two end segments of the longitudinal welds, identified as critical regions.

Evolution of corrosion degradation in galvanised steel bolts exposed to a tropical marine environment

The time-dependent degradation of galvanised steel bolts subjected to marine atmospheric exposure for a maximum period of 2 years in the Wenchang marine environment of Hainan province, South China, was investigated. The results showed that the zinc coating used as a protective surface finish deteriorated quickly due to the harsh environmental conditions. The deterioration of the zinc coating resulted in premature corrosion of the underlying steel substrate as early as 6 months. The main Zn corrosion products found at the initial exposure time were simonkollite (Zn5(OH)8Cl2·H2O), hydrozincite (Zn5(OH)6(CO3)2), and zincite (ZnO). At subsequent exposure times, major steel corrosion products such as lepidocrocite (γ-FeOOH), akaganeite (β-FeOOH), goethite (α-FeOOH), magnetite (Fe3O4), and maghemite (γ-Fe2O3) were detected. Fe3O4/γ-Fe2O3 was consistently found in the rust formed at both the exposed and crevice thread regions between 6 and 24 months of exposure. Based on the geometry of the bolt fastener, the corrosion rate and phase composition distribution varied between the two regions. Differences in oxygen exposure levels, corrosion kinetics, and electrochemical stability of the corrosion products were primary factors in these distinctive corrosion behaviours.

Bearing capacities and failure behaviors of bolt fasten wedge (BFW) active joints used in prestressed internal supports

In this paper, the bearing capacities and failure behaviors of bolt-fastened wedge active joints used in prestressed internal supports are studied. A thorough exploration of the design of the bolt-fastened wedge active joint is elaborated, and an overview, working mechanism, stiffness analysis, parameters, and strength checking are provided. Then, loading tests are conducted on four full-scale specimens. One test is an axial compression test, while the other three tests are performed to analyze the long-axis (Y-axis) eccentricity, short-axis (X-axis) eccentricity, and biaxial (XY-axis) eccentricity. The load–displacement curve, load–strain curve, bending moment-rotation curve, and failure mode of each specimen are obtained. The experimental results show that the samples have good compressive properties and bending resistance. The impact of the X-axis and Y-axis eccentricities on the compressive ultimate bearing capacity is investigated, revealing a significant reduction in the former, while the latter has a minimal effect. Under bidirectional eccentricity, the weakening of the axial bending performance is most apparent. Bidirectional eccentric loads lead to a reduction in the yield load and initial compression stiffness to approximately 90% of those observed under unidirectional eccentricity. Finally, a field test is carried out to compare the constructability and load-holding performances of bolt-fastened wedge active joints with those of commonly used steel wedge active joints. It is demonstrated that the bolt-fastened wedge active joint effectively maintains prestress through bolt fastening, substantially enhancing the safety of foundation pit excavation construction.

Experimental study of precast columns with a hybrid joint incorporating bolted couplers and grouted sleeves

The grouted sleeve (GS) splicing with mature technology is a favored wet-assembled connection in Chinese engineering. A technical interval is normally required to reach the design strength of the grouting material in the in-situ construction of GS splicing, increasing the demands of temporary bracing and reducing the on-site construction efficiency. In this paper, a hybrid joint was proposed by incorporating grouted sleeves and bolted couplers to improve the construction efficiency of GS splicing and reach a comparable performance to the joint with GS splicing. The bolted coupler was labeled CTB coupler, characterized by a combination of threaded connection and bolt fastening. Quasi-static tests were conducted to discuss the seismic performances of four columns, including two precast columns with a hybrid joint (labeled the hybrid column), one precast column using grouted sleeves, and one precast column using CTB couplers. The discussions illustrated that the hybrid column exhibited comparable stiffness degradation and strength to the precast concrete column with the GS splicing, while the former showed a decrease in inelastic deformation capacity and energy dissipated capacity compared to the latter. The energy dissipated capacity of the hybrid column can be improved in two feasible ways: increasing the distance from the hybrid joint to the foundation and using a higher strength rebar for the lower rebar (in the CTB coupler) with respect to its upper rebar. Finally, simplified numerical manners were proposed to consider the effects of CTB couplers and GS splicing. The experimental result of each specimen matched well with its numerical result, validating the effectiveness of the simplified manners.

Magnetostrictive Composite Bolt Fastening Characteristics and Internal Axial Force

Herein, the fastening characteristics and internal axial force of magnetostrictive composite bolts using magnetic flux‐density change are experimentally and theoretically examined. Magnetostrictive composite bolts are fabricated using FeCo wire and epoxy resin by applying magnetic field and preload. The advantage of using a bolt made of magnetostrictive composite materials is that it has reduced weight and can be applied to prestress. Tightening tests are conducted, with and without external‐bias magnetic fields, to measure bolt strain and magnetic flux‐density change. Then, theoretical and finite element analyses are performed to calculate the strain, axial force, and magnetic flux‐density. Theoretical results are compared with experimental results to determine the relationship between tightening torque, internal axial force, and magnetic flux‐density change. It is found that the applied magnetic field and preload conditions during fabrication, as well as the bias magnetic field during the tightening tests, have a significant effect on the magnetic flux‐density change of magnetostrictive composite bolts. The results of this study help propose new possibilities for internet of things and structural health monitoring nodes.

Transfer Learning-Based Object Detection Model for Steel Structure Bolt Fastening Inspection

As improper inspection of construction works can cause an increase in project costs and a decrease in project quality, construction inspection is considered a critical factor for project success. While traditional inspection tasks are still mainly labor-intensive and time-consuming, computer vision has the potential to revolutionize the construction inspection process by providing more efficient and effective ways to monitor the progress and quality of construction projects. However, previous studies have also indicated that the performance of vision-based site monitoring heavily relies on the volume of training data. To address the issues of challenging data collection at construction sites, this study developed models using transfer learning-based object detection models incorporating data augmentation and transfer learning. The performance of three object detection algorithms was compared based on average precision and inference time for detecting T/S bolt fastening of steel structure. Despite the limited training data available, the model’s performance was improved through data augmentation and transfer learning. The proposed inspection model can increase the efficiency of quality control works for building construction projects and the safety of inspectors.

Confirmation of Final Bolt Tightening via Deep Learning-Based Image Processing

In Japan, the final tightening of bolts in the bolt-tightening operations is guaranteed to have been performed correctly by visually determining the change in markings during the temporary tightening operation performed by the technician. However, the engineer must confirm many bolts; further, the amount of time needed for the confirmation work and the inability to keep an objective record of the confirmation results present problems. To solve these problems, we developed a system for automating the final tightening of bolts using deep learning-based image-processing technology. The proposed system takes as input videos of bolt fastening points, extracts individual bolts, extracts markings on the extracted bolts, and makes fastening decisions based on the markings. In the judgment stage, the system processes information on each bolt where a marking is detected; thus, it is possible to leave this information as objective data. In this paper, we evaluated the accuracy of each automated step using an actual bridge video. We also compared the confirmation time with human confirmation. As a result of the confirmation, our proposed method reduces the confirmation time by about 33% in comparison to human confirmation.

Optimal phase compensation for a rotor-AMB system considering interface contact

Rotor-Active magnetic bearing (rotor-AMB) systems offer significant advantages in power consumption and are increasingly being applied in fluid machinery. However, in such machinery, the impeller and the rotor are commonly connected by bolt fastening. Once a certain pre-tightening force is applied to the bolted connection and the interface contact between the rotor and the impeller is formed, the flexible modal vibration will be excited when the rotor is levitated. The conventional Proportional-Integral-Derivative (PID) controller is limited in this vibration suppression and it is essential to increase the damping at bending mode to inhibit vibration. However, the calculation of the optimal phase compensated is based on the rotor-AMB model considering interface contact. In this work, the effect of the interface contact is equivalent to massless spring units, and the disturbance generated by spring units is acted upon the mechatronic system in the way of positive feedback. The detailed description of the transfer function from the disturbance to rotor deformation at fourth bending mode is obtained by theoretical model and system identification. The optimal phase of the system needed to inhibit the disturbance is determined by minimizing the gain of the transfer function at fourth bending mode. A combination of PID control and phase compensation is implemented in the experiment. The results show that the optimal phase is 50° as the calculation and the optimal phase compensation control can sufficiently inhibit the modal vibration.

Insights into the characteristics of corrosion products formed on the contact and exposed regions of C1045 steel bolt and nut fasteners exposed to aqueous chloride environments

• Corrosion products on different regions of C1045 bolt are characterized for the first time. • Differential aeration/concentration effects induced heterogeneity in the corrosion products. • Reactive phases, γ-FeOOH and β-FeOOH dominated at the exposed and contact region, respectively. • Magnetite, Fe 3 O 4 was detected in both regions under low oxygen conditions. • Due to the low amount of α-FeOOH, the rusts in both regions lack stability and protectiveness. This study investigated the characteristics of corrosion products formed on the contact and exposed regions of C1045 steel bolt and nut fasteners used in structures exposed to aqueous chloride environments. The corroded surface morphology, rust compositions, and corrosion kinetics of the bolt specimen were studied by visual observation, optical microscopy (OM), scanning electron microscopy (SEM), X-Ray diffractometry (XRD), micro-Raman, electron probe micro-analyzer (EPMA), and potentiodynamic polarization techniques. Results obtained showed a variation in corrosion kinetics, morphology, and composition of the rust layer which were driven by differential aeration and concentration effects. Due to the availability of sufficient dissolved oxygen, the oxyhydroxide compound, lepidocrocite (γ-FeOOH) was detected in the outer rust layer in the exposed region, whereas the inner rust layer was composed of magnetite (Fe 3 O 4 ). However, the oxygen-deficient contact surface revealed the presence of akaganeite (β-FeOOH) and magnetite (Fe 3 O 4 ) as dominant oxide phases. The most stable phase, goethite (α-FeOOH) was also detected in the rust formed in both regions, though in significantly low amounts. Furthermore, owing to variation in environmental conditions, the amount and density of the rust layer varied in the different regions. The estimated corrosion stability values for the different regions revealed that the corrosion products formed on the steel surfaces were non-protective, suggesting the need for specific surface treatment as a protective measure.

Ratchetting-fatigue behavior of a 42CrMo steel under near-yield mean stress

42CrMo high-strength structural steel is widely used to manufacture the bolt fasteners of engineering machinery, which are subjected to cyclic loading with a near-yield pre-stress in service. In this contribution, we focused on the intrinsic correlation between macroscopic ratchetting-fatigue behavior and microscopic mechanisms in a quenching & tempering 42CrMo HSS steel under near-yield mean stress (σm) conditions. The results indicate that fatigue strength obviously decreases as σm increases from low level (51.9% of yield strength, σy) to near-yield range (80–95% of σy), which is followed by a slight decrease with σm increasing in near-yield σm range. Two distinct fracture patterns were found: (i) high-cycle fatigue failure under low σm and (ii) ratchetting-fatigue failure with plastic strain due to obvious ratchetting effect under near-yield σm. Compared to low σm, near-yield σm leads to the disappearance of fatigue striations, but emerging of some plastic micro-strains, sub-grains and high-density dislocation cells. Fatigue crack-path analysis demonstrates that the decreases in secondary crack size and crack deflection degree are favorable to fatigue crack propagation at a higher rate. Furthermore, fatigue crack tends to propagate along the high Schmid factor regions with the specific slip system of {110}<111> under near-yield σm, corresponding to quicken fatigue cracking behavior. However, it did not occur under low σm. Therefore, it can be concluded that near-yield σm and the resulting ratchetting effect play significant roles in fatigue cracking behavior of 42CrMo steel, which should be carefully taken into account for predicting fatigue lifetime of actual bolt fasteners.

Analisis Pergantian Alat Pengencang Baut-U 4 Spindel Menjadi 1 Spindel di Station Rear axle PT.Daimler Commercial Vehicles Manufacturing Indonesia

Bolt tightening is a process that is widely and important to use or do in the vehicle assembly process.. Power tools with synchronous systems are powerful equipment that is able to help the process of tightening several bolts simultaneously without human energy. This study aims to analyze the 1 spindle bolt fastener to fasten 4 U-bolts on Rear axle in Axor 4028TT type trucks at PT. Daimler Commercial Vehicles Manufacturing Indonesia.The experiment was conducted to test the fastening of the bolt 1 spindle with a replica method of the 4 spindle bolt fastening synchronization system. Sampling used is 6 units with each unit has 4 bolts on the right and left to be compared with the results of U-bolt tightening using the tool 4 spindles.The study used a digital moment key to measure the residual firmness value of the bolt. The data analysis technique is to compare the value of the bolt tightening deviation across two tool systems. The average deviation value on the 1 spindle bolt fastener is 0.31% while on 4 spindles it is 0.13%. The average value of deviations from the digital moment key verification results on 1 spindle is 2.4% while 4 spindles are 3.4%. The results of the comparison showed that the results of fastening bolts 1 spindle provide a deviation of no more than ± 18.6%. Despite having a deviation value greater than 4 spindles, but considering the capacity of units produced in the pandemic period and cost components if tool repairs are made, then the 1 spindle bolt tightening tool is worth considering for use..

Noise Identification for an Automotive Wheel Bearing

In this study, we identified the noise generated from automotive wheel bearings, which has recently emerged as a new problem in electric vehicles. The wheel bearing assembly considered in this study consists of a wheel bearing, dust shield, and knuckle, which are fastened with bolts. To obtain the noise characteristics of the wheel bearing, the noise and vibration were experimentally measured when the bearing rotated. Additionally, the natural frequencies and mode shapes of the main components of the bearing were acquired via modal testing. By comparing the obtained natural frequencies with the peak frequencies of the measured noise and vibration signals, we identified where the noise radiated. To specifically identify bearing defects, a finite element analysis model was established, and the deformation of the bearing under load was analyzed. Based on the analysis, we determined that the deformation of the outer ring in an outboard row, which resulted from bolt fastening, leads to noise and vibration in the wheel bearing.