Bolt Head Research Articles

Analysis of the influence of geometric accuracy on the preload and stress of engine connecting rod bolts

The pitch deviation, non-parallel end face, and middle diameter deviation generated during the machining process of connecting rod bolts will lead to changes in bolt preload and stress distribution under ideal conditions, and their effects under individual or interaction are not fully understood. The finite element simulation model of connecting rod bolt tightening was established by Abaqus finite element simulation analysis software. The Yamamoto analysis method verified the finite element model of connecting rod bolts. The effects of pitch deviation, non-parallel end face, and middle diameter deviation on the preload, stress distribution, and fatigue safety factor of connecting rod bolts under tightening load were studied. The results show that increasing pitch deviation and middle diameter deviation or decreasing non-parallel end face will increase the bolt preload under the same torque. When the pitch is 1 mm, the middle diameter is 8.3505 mm, and the non-parallel end face is 0.5°, the fatigue safety factor of the bolt failure area is the largest, and the fatigue failure does not quickly occur during the working process. The bolt connection structure of a U-shaped cutting groove can significantly improve the fatigue strength of the joint between the bolt head and the screw, and its average fatigue safety factor is 1.71.

Comparison of Epoxy Resin and Rigid Polyurethane Foam as a Bone Substitute to Study Implant Biomechanics.

Introduction The study of biomechanical factors is crucial for discerning the solutions relating to implant failures. These factors are analyzed using in vitro models. These models help us to understand the relation of these variables with implant biomechanics. Multiple materials are available for use as bone substitutes for in vitro studies. Each material has its own pros and cons, and there is no single material that can ideally replicate bone behavior under intra-oral conditions. Objectives The objective of this study was to synthesize and compare the two synthetic bone substitute materials as a biomechanical bone model to evaluate the stress distribution in the peri-implant region using strain gauge analysis. Materials and methods The two bone substitutes used were polyurethane (PU) foam (Sawbones, Vashon, Washington, United States) and epoxy resin (Polycraft ClearTop 35 Epoxy Water Clear Resin System, MB Fibreglass, Newtownabbey, Northern Ireland). The PU models were designed in two densities to mimic bone type 2 as per the Mischclassification. A mold was used for the epoxy resin models. Dental implants of two different thread designs were used for biomechanical load transfer. The implants were placed in both types of models using the manufacturer's instructions.A strain gauge was bonded over each model adjacent to the upper third (coronal) region of each implant. The strain gauge was connected to the strain meter. A combined (axial and non-axial) loading ranging from 50 N to 300 N magnitude was applied using a universal testing machine (UTM). The load was applied using a porcelain fused to a metal prosthesis bonded over a bolt head which was fixed in the crosshead of the UTM. The strain rate was 0.95 mm/min, and the strain values were recorded using a strain meter. The collected data was organized and analyzed usingIBM SPSS Statistics for Windows, Version 22.0 (Released 2013; IBM Corp., Armonk, New York, United States). Results All strain values recorded were less than 3000 µε and within the physiological loading zone per the Frost theory. The difference between the strains produced in both models was statistically significant (p≤0.05). The strain values recorded were higher in the PU model as compared to epoxy resin. Conclusions PU foam can be preferred as a bone substitute in biomechanical studies as it provides a more accurate estimation of strain in the peri-implant region. Its wide range of available densities can allow researchers to mimic various types of bones, facilitating the analysis of stress and strain distribution produced by the implants under study.

Effect of the washers on the bearing resistance of the bolted connections

Abstract Bolted connections are the most common method of joining thin-walled galvanized sheets on site. Small diameter bolts (M8, M10 or M12) and the corresponding nuts are used for this purpose. Washers should be provided both under the heads of the bolts and the nuts in case of a single shear connection with one row of bolts, according to the standard BDS EN 1993-1-8. I.e. it is unnecessary to place washers under the bolt head in case of two or more rows of bolts. In laboratory tests of bolted connections with two rows of bolts without washers under the nuts, is accounted bearing capacity lower than the theoretically determined one. The initial explanation is that the lack of flat washers results in high bolt rotations and hence reduced load resistance. To verify this seemingly logical explanation, the authors has conducted series of finite element analyses (FEA) on connections with two rows of bolts. It turned out that this was not the reason for the reduced bearing resistance. The presence of washers under the bolt head and the nut had a negligible effect.

Analysis of torque variation in bolt fastening on coated steel surfaces

Analysis of torque variation in bolt fastening on coated steel surfaces

Study on bolt loosening mechanism under transverse load considering slip and adhesion status of contact surfaces

Study on bolt loosening mechanism under transverse load considering slip and adhesion status of contact surfaces

Experimental and numerical investigation of novel triangular headed one-sided bolted T-stub connections

Experimental and numerical investigation of novel triangular headed one-sided bolted T-stub connections

Analysis of relaxation characteristics of multi-bolted connections under the transverse cyclic load

A modeling method under lateral cyclic loading is proposed for the complex multi-bolt connection loosening problem. Firstly, the thread stress surface is divided into n small sectors, and the self-relaxation mechanical model of multi-bolt connection is established considering the interaction between bolts. Secondly, the self-relaxation model is solved by MATLAB software and compared with Nassar model to verify the correctness of the model. Finally, considering the influence of different bolt number, hole clearance and connection spacing, the relaxation characteristics of multi-bolt connection are studied. The results show that during the loosening process, the bolt head undergoes a bending-sliding-bending cycle process, and the bolt tension shows a wave downward trend. When multiple bolts are connected, the number of loosening cycles decreases linearly with the increase of hole clearance. With the equidistant increase of bolt connection spacing, the number of bolt loosening cycles shows a decreasing trend. Compared with the number of bolts, the change of bolt hole clearance and connection spacing is more likely to affect bolt loosening.

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.

Early Bolt Loosening Detection Method Based on Digital Image Correlation.

Bolt loosening can significantly impact the accuracy, stability, and safety of equipment. The detection of bolt loosening in a timely manner is crucial for ensuring the safety, reliability, performance, and service life of equipment, structures, and systems. Various methods exist for detecting bolt loosening, such as strain gauges and ultrasonic waves. However, these technologies have some limitations that impede their widespread application. In this paper, for the high-pressure pipe manifolds that may experience leakage accidents due to the loosening of bolts, an early bolt loosening detection method based on digital image correlation is proposed. Initially, a model is established through tensile tests to relate the average strain on the side of the bolt head to the axial force. Subsequently, an industrial camera captures images of bolts with random speckles under operational conditions. Using digital image correlation technology, the average strain in a specific region on the side of the bolt head is calculated. By integrating the average strain into the established relationship model between the average strain and axial force, the axial force of the bolt under operational conditions can be predicted, enabling the early assessment of bolt loosening. The findings show that the average strain on the side of the bolt head increases proportionally with the axial force, indicating a strong linear relationship. This method enables accurate prediction of the bolt's axial force, offering a new approach for identifying the early loosening of bolts in high-pressure manifolds and monitoring structural health.

Bolt Force Monitoring Method Used in Maglev Structure Maintenance Based on Radial Strain on the Surface of Bolt Head

Bolt Force Monitoring Method Used in Maglev Structure Maintenance Based on Radial Strain on the Surface of Bolt Head

Analysis of damage evolution in single‐lap and double‐lap bolted joints of carbon fiber reinforced polymer plates based on load distribution

AbstractIt is important to study damage evolution as well as failure of carbon fiber reinforced polymer (CFRP) plates bolted joints. Therefore, the quasi‐static tensile test on single‐lap and double‐lap CFRP plates bolted joints was conducted. Meanwhile, the tensile strength prediction model for titanium alloy bolted joint of CFRP plates was established based on the improved 3D Hashin failure criterion, then a theoretical model was proposed to accurately predict the load distributions and tilt angle of bolted joints. Thus, the load–displacement curves were divided into four stages, and load distributions at different stage points as well as the relationship between tilt angle of bolt and load variation were obtained. The damage evolution of single‐lap and double‐lap at different stage points was analyzed respectively, and failure mechanisms were revealed based on load distribution. The results show that the ultimate failure of single‐lap is caused by the intrusion of bolt head into CFRP plates, while double‐lap is caused by the compression deformation of central plate. The numerical simulation works are in high agreement with the experimental results.Highlights Calculate the load distribution at single‐lap and double‐lap bolted joints. Obtain the relationship between bolts tilt angle and load variation. Analysis of damage evolution in bolt‐hole wall of carbon fiber reinforced polymer (CFRP) plates. Using loads to reveal the failure mechanisms of single‐lap and double‐lap bolted joints of CFRP plates.

Experimental investigation on the effect of forced assembly on fatigue behavior of single-lap, countersunk composite bolted joints

Experimental investigation on the effect of forced assembly on fatigue behavior of single-lap, countersunk composite bolted joints

Effect of Excessive Clamping Force on Bolted CFRP Composite Plates

Friction-type bolted joints are widely used in both the civil and aerospace industries. Uncontrolled excessive bolt clamping force can cause damage to the laminated fiber-reinforced polymeric (FRP) composite through the thickness and damage the joint before applying the service loads. The effect of the friction coefficient (between 0 and 0.3), bolt clearance, joint type, and other parameters on failure modes and the maximum bolt clamping force of the carbon FRP lapped joint is studied. A three-dimensional finite element (FE) model consisting of a bolt, a washer, a laminate FRP composite plate, and steel plates was developed for the simulation of the double- (3DD) and single (3DS)-lapped bolted joint. The FE model was validated by using experimental results and was able to predict the experimental results by a difference of between 2.2 and 6.7%. The joint capacity of the clamping force was found to be greatly increased by adopting the double lap technique, which involves placing an FRP composite plate between two steel plates. Also, it was recommended to use an internal washer diameter less than or equal to the FRP composite plate hole diameter since a larger washer clearance can produce higher contact pressure and reduce the resistance by 22%. In addition, reducing the bolt head diameter can lead to a 65% reduction in the 3DS joint clamping strength.

Mechanical performance of elliptical one-sided bolted joints for T-stub and hollow section members under tension

This paper presents experimental and numerical investigations on the tensile performance of the elliptical one-sided bolted joints in building applications. Two types of joints are examined including the T-stub joints and T-hollow joints, where T-stub joints are formed by two T-stubs connected together through elliptical one-sided bolts at their flanges; and T-hollow joints are formed by two T-stubs connected to a square hollow section (SHS) member with the help of the elliptical one-sided bolts. A group of T-stub joints with ordinary bolts is also comparatively studied. Similar failure modes were observed for either elliptical one-sided or ordinary bolted joints while the yield capacity for elliptical one-sided joints was 9% lower than that of ordinary bolted joints for the T-stub joints. Parametric studies are further carried out on the key parameters such as flange thickness of the T-stubs and wall thickness of the hollow section members in the T-stub and T-hollow joints. It is found that the joint stiffness and strength can be improved with the increase of flange thickness or wall thickness for T-stub and T-hollow joints. Analytical models based on the yield line mechanisms are then presented, providing mechanism-based understanding for such elliptical one-sided joints in structural assembly. Detailed finite element (FE) models were constructed with considerations of bolt pre-tensioning and contact behaviours such as those between T-stub flange and bolt head. The deformed configurations of specimens can be successfully described by the FE modelling and the differences on initial stiffness and yield capacity between experimental and FE results are within about 10%.

Prediction of Pre-Loading Relaxation of Bolt Structure of Complex Equipment under Tangential Cyclic Load.

Bolts have the advantages of simple installation and easy removal. They are widely applied in aerospace and high-speed railway traffic. However, the loosening of bolts under mixed loads can lead to nonlinear decreases in pre-loading. This affects the safety performance of the structure and may lead to catastrophic consequences. Existing techniques cannot be used to monitor the bolt performance status in time. This has caused significant problems with the safety and reliability of equipment. In order to study the relaxation law of bolt pre-loading, this paper carries out an experimental analysis for 8.8-grade hexagonal bolts and calibrates the torque coefficient. We also studied different loading waveforms, nickel steel plate surface roughnesses, tangential displacement frequencies, four different strengths and bolt head contact areas of the bolt, the initial pre-loading, and the effects of tangential cyclic displacement on pre-loading relaxation. This was done in order to accurately predict the degree of bolt pre-loading loosening under external loads. The laws are described using the allometric model function and the nine-stage polynomial function. The least squares method is used to identify the parameters in the function. The results show that bolts with a smooth surface of the connected structure nickel steel flat plate, high-frequency working conditions, half-sine wave, and a high-strength have better anti-loosening properties. Taking 5-10 cycles of cyclic loading as a boundary, the pre-loading relaxation is divided into two stages. The first stage is a stage of rapid decrease in bolt pre-loading, and the second stage is the slow decrease process. The performance prediction study shows that the allometric model function is the worst fitted, at 71.7% for the small displacement condition. Other than that, the allometric model function and the nine-stage polynomial function can predict more than 85.5% and 90.4%, which require the use of least squares to identify two and ten unknown parameters, respectively. The complexity of the two is different, but both can by better indicators than the pre-loading relaxation law under specific conditions. It helps to improve the monitoring of bolt loosening and the system use cycle, and it can provide theoretical support for complex equipment working for a long time.

Bearing Capacity Characteristic Analysis of Anti-floating Bolts in Unsaturated Soil Based on Mindlin Solution

AbstractBased on Mindlin solution and the theory of unsaturated soil mechanics, the theoretical solutions of shear stress and axial force distribution in the elastic stage of full-length binding-type anti-floating bolts were derived, and the bearing capacity characteristics of such bolts and the influencing factors were analyzed. In this paper, the design parameters of anti-floating anchor in a negative two-floor basement of a commercial square are substituted into the formula derived in this paper. The results show that, in unsaturated soil, the shear stress and axial force of the full-length bonded anti-floating anchor are distributed along the total length of the anchor, but neutral points appear in both of them, which is mainly due to the reduction of the axial force and shear stress of the anti-floating anchor caused by the matric suction. The formula derived in this paper is used to analyze the factors affecting the bearing capacity of anti-floating anchor bolt in unsaturated soil. The results show that: the greater the elastic modulus of soil mass, the greater the peak value of shear stress curve, the closer the peak value is to the head of anchor bolt, and the greater the axial force decline rate. With the increase of anchor solid diameter D, the peak value of shear stress decreases, the peak value moves backward, the neutral point moves forward, the negative shear stress value increases, the decline rate of axial force distribution curve decreases, but the negative axial force increases. With the increase of the additional shear stress τ0, the peak value of the shear stress curve decreases, the peak value moves to the hole of the anchor rod, the neutral point moves to the hole, the negative shear stress increases, the decline rate of the axial force distribution curve increases, and the negative axial force increases.

Head surface strain measurement based wireless bolt sensor with self temperature compensating

Bolt loosening detection is crucial for ensuring the safe operation of equipment. Loosened bolts are hard to detect, and if left undetected, it can lead to catastrophic failures, especially for numerous bolts in large-scale structures. Therefore, the development of distributed bolt monitoring method and related sensors is highly necessary. In this paper, a novel bolt preload sensor with self-temperature compensation is proposed, based on the strain distribution of the bolt head end face. This study enhances previous research by conducting a detailed analysis of strain distribution at the edge of the bolt head surface. The finite element analysis results show that the bolt preload has almost no effect on the circumferential strain in the edge region of bolt head surface. Based on this feature, the strain gauge is applied circumferentially along the edge of the bolt head face as a temperature compensation gauge. In this way, the measuring strain gauge and the temperature compensation gauge can be integrated on the surface of the bolt head, thus achieving self-temperature compensation for the sensor. An experimental device has been established and the experimental results show that the designed sensor has excellent linearity to the bolt preload and effective temperature compensation. For the monitoring of numerous bolts with a wide distribution, a wireless sensing network utilizing the proposed sensor has been designed. The proposed wireless bolt sensor is easy to install and replace, without redesigning or changing the existing structure, thus providing a simple and effective way to monitor large number of bolts with wide distribution.

Three-dimensional reconstruction of industrial parts from a single image

This study proposes an image-based three-dimensional (3D) vector reconstruction of industrial parts that can generate non-uniform rational B-splines (NURBS) surfaces with high fidelity and flexibility. The contributions of this study include three parts: first, a dataset of two-dimensional images is constructed for typical industrial parts, including hexagonal head bolts, cylindrical gears, shoulder rings, hexagonal nuts, and cylindrical roller bearings; second, a deep learning algorithm is developed for parameter extraction of 3D industrial parts, which can determine the final 3D parameters and pose information of the reconstructed model using two new nets, CAD-ClassNet and CAD-ReconNet; and finally, a 3D vector shape reconstruction of mechanical parts is presented to generate NURBS from the obtained shape parameters. The final reconstructed models show that the proposed approach is highly accurate, efficient, and practical.

Experimental and numerical study on mechanical performance of single shear bolted connections with novel elliptical one-sided bolts

Experimental and numerical study on mechanical performance of single shear bolted connections with novel elliptical one-sided bolts

Failure Analysis of Drive Head Bolt by Seam Defect

Failure Analysis of Drive Head Bolt by Seam Defect