Bolt Nut Research Articles

The Tightening and Untightening Modeling and Simulation of Bolted Joints

Although bolted joints may appear simple and are easy to manipulate, they are challenging to model and analyze due to their complex structural patterns and statically indeterminate nature. Ensuring the structural integrity of these joints requires maintaining proper bolt preload and clamping force, which is crucial for preventing failures such as overload, excessive bearing stress, fatigue, and stripping caused by seizing or galling. Achieving the necessary clamping force involves carefully controlling the input tightening torque, which is divided into the pitch torque and the friction torques at the bolt or nut bearing surfaces and in the engaged threads. The resulting clamping force is critical for generating the required force within the bolt. However, the achieved bolt force depends on several factors, such as friction at the joint’s contact surfaces, grip length, and the relative rotation between the bolt and nut during tightening. Friction at the contact surfaces, particularly beneath the bolt head or nut and between the threads, consumes a significant portion of the applied tightening torque—approximately 90%. This paper explores the three existing bolt internal pitch, bearing, and thread friction torques that are generated by the external applied torque in a bolted joint, as well as their contributions and variations throughout a loading cycle composed of three phases: tightening, settling, and untightening. An analytical model is developed to determine these torque components, and its results are compared with those obtained from finite element (FE) modeling and experimental testing from previous studies. Finally, this study examines the torque–tension relationship during bolt tightening, offering insights into the required accuracy of bolt and clamped member stiffness. The bolt samples used in this study include M12 × 1.75 and M36 × 4 hex bolts.

High-strength preload indicator inner washer forward design method

The preload indicator bolt assembly is a fastener that achieves the desired preload effect by simply tightening the preload nut within a specified range without additional measuring tools. The inner washer is a critical component in this assembly, with its outer diameter and height serving as crucial design parameters. In this paper, an equivalent mechanical model is established for the preload indicator bolt assembly. Utilizing this model, an iterative search process is developed to determine the optimal outer diameter and height of the inner washer. The analytical relationship between the bolt preload force and nut displacement is compared and validated against finite element analysis and experimental results, yielding favorable agreement. Notably, the nut tightening angle can vary within the range of 187°–242°, while the preload force exhibits a minimal variation of only ±2% for type 10-0A bolt connection (Bolt diameter and bolt pitch are φ16 mm and 1.41 mm, respectively. The material of bolt, inner ring, and flat ring are GH4169, 40CrNiMoA, and 30CrMo, respectively). This feature significantly simplifies the installation process of the preload indicator bolt assembly in real-world applications, offering great convenience. The increment in tension force on preloaded bolts under external loads exhibits an almost identical trend for both connection methods. Under the same preload force and the same eccentric working load conditions, the thickness of the connected components follows the same trend as their contact area.

Analytical and Numerical Study of Mechanical Behaviour of Bolted Joints –A Review

Any component that is subjected to excessive heat or cold experiences behavioural changes. The nut bolt assembly at the flange joint may not function as planned or may fail under such circumstances. Temperature fluctuations tend to cause the inner and outer threads to react differently, resulting in the pair becoming looser. Flange materials have a propensity to flex, applying unneeded additional stress on the bolt head and nut. Notably, liquid propellant rocket engines display this type of temperature variation. To assess mechanical performance while accounting for different nut factors and flange materials, analytical and numerical approaches are applied.

Detection of Missing Bolts for Engineering Structures in Natural Environment Using Machine Vision and Deep Learning

The development of an accurate and efficient method for detecting missing bolts in engineering structures is crucial. To this end, a missing bolt detection method that leveraged machine vision and deep learning was developed. First, a comprehensive dataset of bolt images captured under natural conditions was constructed, which improved the generality and recognition accuracy of the trained bolt target detection model. Second, three deep learning network models, namely, YOLOv4, YOLOv5s, and YOLOXs, were compared, and YOLOv5s was selected as the bolt target detection model. With YOLOv5s as the target recognition model, the bolt head and bolt nut had average precisions of 0.93 and 0.903, respectively. Third, a missing bolt detection method based on perspective transformation and IoU was presented and validated under laboratory conditions. Finally, the proposed method was applied to an actual footbridge structure to test its feasibility and effectiveness in real engineering scenarios. The experimental results showed that the proposed method could accurately identify bolt targets with a confidence level of over 80% and detect missing bolts under different image distances, perspective angles, light intensities, and image resolutions. Moreover, the experimental results on a footbridge demonstrated that the proposed method could reliably detect the missing bolt even at a shooting distance of 1 m. The proposed method provided a low-cost, efficient, and automated technical solution for the safety management of bolted connection components in engineering structures.

Pembuatan Lift Barang Untuk Rumah Dua Lantai

Limited land availability is a major obstacle to occupancy in Indonesia. In addition, residential owners who have constraints on physical limitations will have difficulty going up and down stairs by carrying loads. Based on these problems, the manufacture of a goods elevator with a carried out for a two-story house. The process of making a goods elevator starts from the process of re-design, preparation of materials tools and manufacturing process. Manufacturing processes in the manufacture of elevators include cutting, welding and pouring processes. Furthermore, the manufacturing process is divided into three parts, namely the manufacture of the main frame, the manufacture of cages and the place of electrical hoist as a drive pulley. The results of the elevator have dimensions of 6 meters in length of 0.8 meters and a width of 0.8 meters, while the cage has a height dimension of 1.5 meters long 0.74 meters and a width of 0.74 meters. The main frame construction uses the UNP 65×40×4 profile and the L 40×40×2 profile which is connected through part of the SMAW welding process and bolt nut connection. While in the cage using hollow profile baja 30×30×2, UNP 65×35×4 and wire mesh wire. Tempat electrical hoist uses UNP 85×45×5 profile and L 70×70×5 profile. The drive system in the elevator uses a 1200 kg PA electrical hoist with a single-phase 1800 watt electric power specification with a voltage of 220 V.

Experimental study on influence of different tightening positions on bolt preload

Aiming at the typical bolted flange connection structure in aero-engine, based on the principle of acoustic elasticity, the supersonic method is used to measure the bolt f preload, and the influence of different tightening positions on the bolt preload and stability is studied. The tightening positions are divided into bolt head and nut, and each tightening position is set with several tightening torques and different lubrication conditions. The test results show that in the full torque range of the bolt without lubrication, the torque coefficient is smaller when the bolt head is tightened, and the distribution of preload under each torque is more uniform and the standard deviation is smaller. Lubricating bolts and nuts, the torque coefficient is also smaller when tightening the bolt head, but under each torque, the preload distribution is more uniform when tightening the nut, and the standard deviation is smaller.

Anti-loosening mechanism of pitch difference bolt nut connections based on Junker loosening test

Bolt nut connections are essential elements and widely used in industry. The authors have verified that introducing a slight pitch difference between the bolt and the nut may improve the anti-loosening performance and fatigue life of the bolt nut connections. Besides, the effect of residual torque of pitch difference bolt-nut connections on the loosening resistance performance was discussed. In this study, the Junker loosening test was investigated experimentally and analytically to confirm the anti-loosening performance of pitch difference bolt nut connections directly. The FEA results are in good agreement with the experiments. It is confirmed that, for pitch difference bolt nut connections, the threads contact status is different from the common bolt nut connections, and the torque between the thread contact surface friction is the main reason of anti-loosening performance improvement of the pitch difference bolt nut connections. In addition, the results showed that if the pitch difference is large enough, the nut loosening angle equals the tightening angle for each vibration, and nut loosening does not occur. If the pitch difference is relatively small but just large enough to provide a prevailing torque, with increasing of the vibrations number of the nut, the loosening speed decreases gradually and finally the clamping force remains steady, which means the bolt nut connections retain anti-loosening performance to some extent.

Detection of Nut–Bolt Loss in Steel Bridges Using Deep Learning Techniques

The early detection of bolts and nuts’ loss on bridges has a huge tendency of averting bridge collapse. The aim of this research is to develop a novel framework for the detection of bolt–nut losses in steel bridges using deep learning techniques. The objectives include: to design a framework for the detection of nuts and bolts and nut holes using deep learning techniques, to implement the designed framework using Python programming, and to evaluate the performance of the designed framework. Convolutional neural network (CNN) and long- and short-term memory (LSTM) techniques were employed using 8 × 8 blocks of images of bridges as inputs. Based on the proposed models, which considered the CNN in its ordinary form, and combined with the LSTM and You Only Look Once (YOLOv4) algorithms, the CNN achieved average classification accuracy of 95.60% and the LSTM achieved an accuracy of 93.00% on the sampled images. The YOLOv4 algorithm, which is a modified version of the CNN with single forward propagation, was utilized, and the detection accuracy was 76.5%. The relatively high level of detection accuracy recorded by the CNN is attributed to its stepwise extraction by convolution and pooling processes. However, a statistical test of the hypothesis at the 5.0% level of significance revealed that there was no statistically significant difference between object detection and classifications among the models used in the built framework. Therefore, the use of the CNN model is recommended for the detection of nuts and bolts and nut holes on steel truss bridges for effective structural health monitoring (SHM) purposes based on its high level of detection accuracy and speed.

Alignment Error Modelling, Analysis and Experiment of the Deep-Water Bolt Flange Automatic Connection Tool

A deep-water bolt flange automatic connection tool plays a very important role in the process of offshore oil exploitation and transportation. In the connection process, the alignment error of bolts and nuts is the key factor to ensure the connection process is successful. Using the kinematics modeling method, this paper created the alignment error model of the deep-water bolt flange automatic connection tool and analyzed the influence of manufacturing accuracy on the alignment error of bolts and nuts through computer simulation software. Based on the error matching design method, the manufacturing accuracy of parts were optimized with a part-size-based priority sequence to ensure the bolt–nut alignment error was within the allowable limits. The land tests, the pool tests and the sea test were carried out. The test results showed that the bolt and nut can be connected in the subsea environment reliably.

Loosening Test of a Bolted Joint by Axial Impact Load

Loosening of the screw can be classified into types depending on the cause and the phenomenon, there is a "loose by the fluctuation of the axial load" as one of them. Loosening mechanism according to fluctuation the axial load are the sliding of the bearing surface caused by sliding of the threaded portion by fluctuation the axial force and a rotation of the nut by torsion torque accumulated in the bolt shaft. In this study, the effect of preventing "loosening due to changes in axial load" of bolts and nuts that have been developed aimed at loosening prevention effect was investigated from these viewpoints. As a result, regarding the axial impact load, the impact load of the hexagon bolt and hexagon nut with flange increased and the impact load of Active-X bolts and nuts decreased compared to the hexagon bolt and hexagon nut. Furthermore, regarding the amount of decrease in axial force after impact, the decrease in axial force was alleviated for hexagon bolts and hexagon nuts with flanges and Active-X bolts and nuts compared to hexagon bolts and hexagon nuts.

Investigation of loosening resistance based on Junker loosening test of bolt nut connections with pitch differences

Investigation of loosening resistance based on Junker loosening test of bolt nut connections with pitch differences

Consideration of optimum pitch difference for different diameters of bolt nut connections with pitch difference

The pitch difference nut can be used in automobiles and other industries to improve anti-loosening and fatigue strength with low cost. In this paper, based on the suitable pitch difference α experimentally obtained previously for JIS M12 and M16, the suitable pitch difference is discussed for other bolt nominal diameters. Here, the overlap thread length is calculated from the suitable α obtained for M12. Then, the same value of is assumed to estimate the suitable α for other diameters. The validity of this theory is confirmed through calculating the prevailing torque for other diameter by applying FEM analysis.

Behavior of end plate connection for steel angles

This study investigated the behavior of bolted end plate connection for structural angle sections. For the splice of angles under tensile loading, thick end plates attached to the end of angles are connected by one single high-tension bolt. To improve connection performance and reduce required plate thickness, plate washers made of the same material as that of the end plates are used under the bolt head and nut. Tensile tests of twenty-two specimens with different connection details were conducted. The tests showed that the governing failure mode was bolt rupture and the connection performance was affected by the thickness of the plates. The minimum thickness of end plate and plate washer determined by the yield line theory was conservative. Due to prying action, the connection strength (i.e., the tensile load of angles) was reduced to about 85% of the tensile strength of high-tension bolt. The force transfer behavior of the end plate connection with and without plate washer was investigated in detail through finite element analysis.

Tensile behavior of different anchor channel connections

This paper compares the behavior of two T-shaped bolts in a cold-formed anchor channel system under tension loads, typically used to connect precast reinforced concrete elements. A new sliding block patented bolt is compared with a standard commercially available one. The comparison of the mechanical behavior of the two bolts is supported by experimental investigations, analytical evaluations, and numerical analyses. The tensile load bearing capacity of the connection is examined with reference to two different working configurations: one with the bolt in the middle of the anchor channel, and the other one with the bolt aligned with the anchor embedded in concrete. The comparison of the obtained results shows a higher efficiency of the newest bolt nut thanks to the better spread of the applied tensile load along the lips of the cast-in channel. Furthermore, the results also show that the weakest working configuration of the connection is, as expected, the one above the anchor. Both the analytical and numerical models support the experimental studies, allowing a better understanding of both deformation and stress distributions in the materials.

How to improve both anti-loosening performance and fatigue strength of bolt nut connections economically

In this paper, how to improve both anti-loosening and fatigue strength with low cost is newly proposed for bolt-nut connection. The authors’ previous study clarified that the most suitable pitch difference α=α1 for the fatigue strength is smaller than the most suitable pitch difference α=α2 for the anti-loosening. In this paper, toward improving both fatigue strength and anti-loosening, a larger nut height coupled with pitch difference is studied through experiment and FEM analysis. It is found that with increasing the nut height, the suitable pitch difference for the anti-loosening α=α3 decreases without changing the suitable pitch difference for the fatigue strength. Therefore, a larger nut height with the pitch difference α=α3≈α1<α2is suitable for improving both fatigue strength and anti-loosening.

Effects of root radius and pitch difference on fatigue strength and anti-loosening performance for high strength bolt–nut connections

The fatigue strength improvement and anti-loosening performance are studied experimentally and analytically for JIS M16 bolt–nut connections. Three different root radii are considered coupled with three different pitch differences. The enlarging the bolt root radius improves the fatigue limit of the bolt by more than 30% because both stress amplitude and mean stress can be reduced. Furthermore, suitable pitch difference improves the fatigue limit by more than 25%. This is because under no pitch difference the crack initiation always occurs at No.1 or No.2 threads close to the bolt head causing the final failure; however, under a suitable pitch difference the crack initiation occurs at No.6 or No.7 threads far away from the bolt head. Good anti-loosening performance can be expected for the bolt–nut connections having enlarged root radius because the prevailing torque [Formula: see text] = 19 Nm and the residual prevailing torque [Formula: see text] are not smaller compared to other special bolt–nut connections.

Reconsideration on Theoretical Self-loosening Mechanism of Bolt Nut Units under Repeated Axial Tensile Loads

Reconsideration on Theoretical Self-loosening Mechanism of Bolt Nut Units under Repeated Axial Tensile Loads

Cyclic tests and analyses of extended endplate composite connections to CFDST columns

ABSTRACT Many existing investigations have focused on the performance of concrete filled double skin steel tubular (CFDST) members. However, there is a lack of research on the behavior of beam to CFDST column joints. This paper presents an experimental investigation and a numerical analysis of the CFDST column to composite beam joint with extended end plates. A series of joint specimens, that were composed of composite beams and square and circular CFDST columns connected by extended end plates and blind bolts, were tested under lateral cyclic loads. In addition, analytical models for this type of connection were established by ABAQUS software. The bolt washer and nut were idealized as circular parts to solve the convergence problem induced by the complex interactions. Nonlinear springs were employed to simulate the behavior of shear studs. The predicted results from the analytical models coincided well with the test results in terms of the failure modes and hysteretic curves. Furthermore, a total of sixteen parameters were analyzed to assess their influence on the structural behavior of typical square and circular CFDST column composite connections with extended end plates. The experimental and analytical results demonstrate that the extended end plate composite connections to square and circular CFDST columns have excellent seismic performance and are applicable in high-intensity earthquake regions.

Loosening Behavior of Ripped Nuts Based on the Fastener Tightening Strategy and Plate Hardness

Within the scope of this study, loosening behavior under vibration was investigated depending on the plate hardness, clamp length and tightening strategy of M8x1.25 10.9 quality nuts with rip form under flange. Two different plate hardness were used and two different types of tightening strategy, i.e. application of torque to either from bolt head or nut, were carried out by using bolts with 29 mm and 40 mm clamp length. During tightening, the effects created by rips on the plate were examined. A parametric study was also carried out to understand loosening behavior of fasteners depending on the plate hardness. Based on the experimental study, it was shown that plate hardness, clamp length and tightening strategy played a key role on the loosening behavior of fasteners. To decrease the loosening rate of the assembly on softer plate, nut with rip form should be tightened from the bolt element. However, for harder plates the selection of tightening strategy was less significant compared to that of softer plate.

Relationship between bolt stress and nut rotation angle during tightening and untightening processes

Relationship between bolt stress and nut rotation angle during tightening and untightening processes