Bolt Head Research Articles

Analytical study on mechanical behavior of friction grip joints with high strength countersunk head bolts and its geometrical configurations

Analytical study on mechanical behavior of friction grip joints with high strength countersunk head bolts and its geometrical configurations

Study on mechanical property of high durability friction grip joints with high strength countersunk head bolts for steel bridge structures

Study on mechanical property of high durability friction grip joints with high strength countersunk head bolts for steel bridge structures

Field measurements of anchored flexible systems for slope stabilisation: Evidence of passive behaviour

Flexible systems anchored to the ground constitute a technique for slope surface stabilisation. They are formed by membranes (cable nets, wire mesh, ring net), reinforcement cables and bolts tightly anchored to the ground forming regular patterns. Most manufacturers and independent researchers assume active behaviour of these systems when they propose their design models, which means that the system avoids occurrence of instability. To consider active behaviour, two conditions have to be fulfilled: the membrane has to be initially prestressed and the slope must present a convex shape. Neither of these two conditions has been verified so far, therefore, there are no guarantees that current design methods are adequate. Review of the technical brochures of manufacturers shows that applied prestress force on membranes and reinforcement cables is nonexistent or very low.In this paper, three field systems in north Spain with cable nets anchored to the ground have been instrumented. Net cables, reinforcement cables and bolt heads have been instrumented by using sensors based on electrical extensometry. Tensile forces on cables and compression forces on bolt heads have been monitored for more than a year from the beginning of installation. Initial tensile forces in net and reinforcement cables induced an average value of 0.7% and 2.1%, respectively, of the ultimate strength of each component. In relation to bolts, average compression force on bolt heads was 5.3% of their ultimate strength.These measurements demonstrate that prestress force on flexible systems is very low, and nearly negligible. Therefore, flexible systems anchored to the ground cannot be considered as active, but passive, which means that most current design methods are not adequate.

The Simulation Research on Assembly Deformation of Internal Combustion Engine Cylinder Liner

For the commonly used wet cylinder liner assembly characteristics and structure of water-cooled internal combustion engine, the influencing factors of wet cylinder liner deformation in the assembly conditions are calculated and analyzed using finite element method. Mainly from the matching stiffness of block-cylinder liner-gasket-cylinder head assembly, the local stiffness of the cylinder head, cylinder head bolt preload and the structure form of cylinder liner, get the influence laws of the various factors on the cylinder liner radial deformation and its each order Fourier series deformation, which provides guidance direction to control the cylinder liner deformation under assembly loading.

Finite Element Analysis and Optimization of S1110 Diesel Engine Body

In order to reduce the mass ratio of S1110 diesel engine, structural intensity and stiffness analysis are performed on the assembly parts of engine body by using the finite element method. Through comparative analysis of more than one calculation scheme, optimization scheme has been got. To ensure the intensity and stiffness of the engine body is not reduced under the premise, optimization scheme makes the body mass greatly reduced from the original engine body’s 38kg to 13.8kg and the engine mass ratio is reduced from 13.2kg/kW to 11.81kg/kW. The results show that, changing the body material from cast iron materials to cast aluminum materials, the body stress distribution trends are similar, but the cast aluminum body deformation increases; increasing the number of cylinder head bolts to 6 can reduce the deformation of the cylinder liner; a reasonable set of stiffeners can reduce the bearing bore deformation.

Geometrical Parameters Influencing a Hybrid Mechanical Coupling

Coupling techniques for components of different materials is spreading in mechanical industry; the test case studied in this work deals with the connection of an aluminium alloy component with a carbon fibre composite one. In particular, the first component is made of an aluminium-zinc alloy and exhibits an isotropic behaviour, while the second is made of a carbon fibre reinforced polymer (CFRP) and shows a strongly anisotropic behaviour; both materials are widely used in engineering applications. A titanium bolt connects the parts. This work is focused on the influence of the geometrical parameters which characterize the coupling between the components. In particular, a study has been carried out on the influence of the shank-hole clearance, the bolt head size, the bolt preload and the shape of the bolt head. A numerical model has been built and statically tested; the results have been compared with the experimental ones from literature. Once validated, the same numerical model has been used to evaluate the performance of the joint in presence of a change of the above mentioned characteristic parameters. The required numerical analyses have been performed using Abaqus/Standard® numerical code.

Al-Zn-Mg-Sc 알루미늄 합금 볼트 성형에 관한 연구

This paper is concerned with forming of Al-Zn-Mg-Sc aluminum alloy bolts, focusing on the effects of heat treatment and age-hardening on the formability and ductile damage evolution. Both experimental and finite element studies were performed. From the experiments, it is observed that the heat treatment or the normalization of Al-Zn-Mg-Sc aluminum alloy increases its formability dramatically resulting in successful bolt forming, while the effects of age-hardening at room temperature on the stress-strain relationship and formability are not very critical. Deformation characteristics such as distribution of effective stress and strain, material flow, and ductile damage evolution during bolt forming are examined using a commercial finite element package, Deform-2D. It should be noted that the extrusion load predicted by the finite element method matches well the experiment results. The finite element predictions on the deformation characteristics support the experimental observations such as fracture of bolt head flange, material flow, and distribution of hardness.

Finite Element Analysis of Large Capacity Endplate Steel Connections

Problem statement: Extended endplate connection is one of the most widely used beam-to column steel connections because of its fabrication simplicity, good overall performance and cost effectiveness compared with other connection types. The objective of this research is to develop three-dimensional finite element models to study the behavior of large capacity eight-bolt extended un-stiffened wide endplate steel connections, using current-technology elements instead of legacy elements which were previously used by other researchers. Approach: A finite element software package (ANSYS, version 11.0) was used to create and analyze three finite element models. Two of the finite element models were compared with previously reported experimental results to validate the accuracy of the finite element models. The third model was based on a modification of the second finite element model to improve bolt force distribution. Eight-node brick solid elements were used to model the connection members. The bolt shank was modeled using one three-dimensional spar element that connected the bolt head and nut together. Pretension in bolts, contact algorithm and material nonlinearity were considered in the finite element models. Results: Results of the first and the second finite element models were compared with experimental data. The comparison was based on moment-beam rotation and moment-endplate separation of the finite element models and the corresponding tested specimens. The results of the finite element models were used to compare the behavior of the bolts in the tension region adjacent to the beam bottom flange. Conclusion: The comparison showed good correlations between the finite element models and the corresponding tested specimens which confirmed the validity of the proposed models. Thus, a modified connection was proposed to improve the connection response. A finite element model of the modified connection was modeled, analyzed and compared to the original finite element model prior to modification to show their correlation.

Magnetic Memory Testing and Intensity Failure Analysis of Fractured Bolt of Cylinder Head on Hydrogen Gas Compressor

Along with the wide application of pressure energy, large scale reciprocating compressor unit is becoming one of the necessary key equipments in petrochemical industry. The reciprocating compressor has complicated structure and it is very difficult to carry out measurement & analysis to the operation status of various components. Above all, as the most important fastener of the compressor, once fracture of cylinder head bolt of the reciprocating compressor occurs, major disaster will occur. Metal magnetic memory testing technology is a nondestructive examination technology based on magneto-mechanical effect principle. Specific change of leakage magnetic field will occur in stress & deformation concentrated region under combined action of alternate work load and geomagnetic field, macroscopic cracking can be detected and stress concentration and early state damage can be evaluated by utilizing this specific change, We carried out on-site examination on the fractured bolt of cylinder head of hydrogen gas compressor unit in refinery of certain petrochemical corporation with latest metal magnetic memory testing technology. On the basis of intensity analysis and dynamic load calculation to cylinder head bolt of the reciprocating compressor, we analyzed the cause of bolt fracture by using metal magnetic memory testing technology and drew out the magnetic memory signal distribution characteristics of the bolt and its fracture. We verified the correctness of testing result of the metal magnetic memory technology on cylinder head bolt and its fracture with metallographic examination technology; furthermore, we studied the reliability of bolt fatigue crack & fracture analysis and investigation of accident cause by using magnetic memory characteristic distribution signal.

Three-Cylinder Gasoline Engine With Direct Injection

Market studies identified for this decade two segments that could be satisfied with a common base: : European volume segment around 74 to 92 kW : small car segments around 48 and 59 kW in Europe but also in rapidly expanding Asian and South American markets, with naturally aspirated 1.0-l engines. Initial engineering studies established that fuel economy and cost targets could best be met with a three-cylinder engine. Further studies then showed that a three-cylinder engine derived from existing architectures would not achieve the full functional potential and be more expensive than a dedicated small architecture. An all new small engine architecture was therefore developed with a 1.0-l in-line three-cylinder configuration as the basis. The challenge was to design an engine architecture that has excellent fuel economy using latest technologies in the turbo DI version, while offering an efficient but very low cost PFI engine for growth markets. One key element to achieving these conflicting goals is a cast iron block, with an unsurpassed combination of strength and low cost. To keep the weight competitive the engine block has to be designed as compact as possible. This requirement is largely met through the small displacement and three cylinders, and further supported by a long stroke configuration, which also improves combustion efficiency and knock resistance. Even in the highly charged turbo version (24 bar BMEP), the cast iron block enables cooling slots in the bore bridge, which is only 6.1 mm wide. Before this solution could be implemented, a compatible solution had to be found for the top end. Here the first challenge was to find an effective, low cost and compact solution for the valve train. By means of detailed friction breakdown studies and benchmarking, it was established that while the bucket tappet valve train in itself has higher friction than roller finger followers, this is only part of the losses. The primary drive also makes up a large part of the valve train friction, and here the belt-drive engines were typically much better. Hence a bucket tappet valve train was chosen, with a lifetime belt-in-oil drive. Through intensive development and implementation of polished tappets this valve train achieves friction levels similar to roller finger follower concepts, but at significantly lower cost. The small dimensions of the cylinder head created a packaging conflict between the tappets and the cylinder head bolts, which was solved by threaded steel inserts in the head, ❸. Open image in new window ❸ Requirements driving the concept choices Having settled the basic configuration of the engine, another major question was the configuration of intake, exhaust and accessory systems. Studies showed that keeping the accessories, turbocharger and catalyst on the same side of the engine offers significant advantages in crash performance and package. Putting them all on the front side provided easier thermal management as well as commonality with the diesel engines used in these vehicles. The thermal challenge of having the alternator close to the exhaust was substantially eased by the integrated exhaust manifold, which radiates significantly less heat versus a conventional manifold.

FEM Analysis on Block Vibration of Diesel Engine

In order to evaluate the vibration history of the engine block and predict its surface vibration status, a FEM model on 4102BZQ Diesel Engine block was constructed. Based on the cylinder pressure curve of 4102BZQ, some important exciting forces applied on the block were calculated. ANSYS software was used to compute and analyze dynamic response of the block. Simultaneously the node displacement history of the block model was obtained. The results of calculation and analysis showed that the vibration of the block skirts was more intense and the skirt was the main factor to influence the reliability of the engine. Cylinder head bolt force and piston slap force had significant effect on the top area of the block, and the surface vibration of the skirt was strongly influenced by the crank shaft load.

Effect of Conical Angle and Thread Pitch on the Self-Loosening Performance of Preloaded Countersunk-Head Bolts

This paper investigates the effect of the countersunk conical angle and thread pitch on the loosening performance of preloaded countersunk-head bolts that are subjected to harmonic transverse loading. A nonlinear mathematical model is used to predict the loosening performance. Cumulative differential loosening rotation of the bolt head is converted to a gradual loss in the bolt tension and joint clamp load. Model prediction of the self-loosening behavior is experimentally validated.

Ultrasonic measurement of self-loosening in bolted joints

Self-loosening of bolted joints in response to vibration can lead to the catastrophic failure of a range of engineering components and structures. Many techniques employed to study this phenomenon focus on directly measuring the pre-load remaining in the bolt itself, and offer little insight into the behaviour of the clamped interface. In this study, a non-intrusive ultrasonic reflection-based technique is used to first characterize interface pressure in the joint, and then determine the rate at which relaxation occurs. A key advantage of the technique is that it does not require the modification of the contact conditions, and rather utilizes the spring-like behaviour of a rough surface interface when subject to ultrasonic excitation. A series of different bolt torques were investigated, along with the inclusion of both plain and spring washers under the bolt head. All test samples were subjected to an oscillating fixed–displacement vibration cycle. An initial rapid reduction in interface clamping pressure was observed, followed by a more steady-state period. Increasing bolt torque was seen to enhance joint integrity, whereas both the plain and spring washers showed little improvement. The spring washer was observed to extend the secondary steady-state phase of loosening, though as the majority of pre-load was removed prior to this period any change was largely unbeneficial.

Continuous high strength aluminum bolt manufacturing by the spring-loaded ECAP system

Aluminum alloy 6061-T6 was used to produce an ultrafine-grained specimen by spring-loaded equal channel angular pressing (ECAP), which was continuously applied to a commercial multi-stage former at a production rate of 30 rpm at room temperature to manufacture high strength aluminum bolts. In order to increase the mechanical strength of the manufactured bolt, the bolt-forming process was introduced based on extrusion process in the present work. With the specimens processed by a single pass ECAP, underfilling at the bolt head and surface cracking at the flange of the produced bolts were observed due to the geometry of the ECAPed specimen and friction at the die interface, respectively. To remove these defects, modified route C for the second pass ECAP and aluminum fluoride coating with metal soap for the initial specimen were applied. Finally, the ultrafine-grained aluminum bolts were successfully manufactured in a continuous sequence. Both the ultimate tensile strength (UTS) and elongation to fracture of the manufactured bolts increased compared to the conventionally made bolts. According to the present investigation, an innovative approach utilizing the ECAP to develop high strength bolts without modifying conventional material is demonstrated.

A Novel Optical Method for Real-Time Control of Bolt Tightening

A digital speckle pattern interferometry (DSPI) system is developed for the real-time measurement and monitoring of the out-of-plane surface deformation around a preloaded bolt head or nut. The proposed system is specifically developed for the dynamic control of the bolt tightening process by continuously monitoring the out-of-plane joint surface deformation that will have been independently correlated to the bolt preload. Spatial phase shifting is employed to quantitatively determine the distribution of phase data by introducing a spatial carrier fringe pattern to the speckle interferogram. This is achieved by leading the object and reference beams through two separate apertures. The configuration is also suitable for collecting the real-time surface deformation during bolt tightening. The experimental DSPI system is set-up with optical components on a vibration-isolation table. A MATLAB software is developed for image acquisition and phase data calculations that yield the out-of-plane surface deformation caused by the bolt preload. The test fixture uses an M12 steel fastener and aluminum joint. For miniature screw applications, however, a plastic joint is used.

Reliability Analysis of a Small Pneumatic Cylinder Life

The reliability of the pneumatic cylinder was investigated by routine life test. The results show that the failures of the pneumatic cylinder can be described as a Weibull distribution and fatigue fracture of the aluminum end cap and the head of install bolt is the major failure for the pneumatic cylinder. The pneumatic cylinder life distribution parameters were estimated by the median rank method in combination with maximum likelihood method. The distribution model for the reliability of the pneumatic cylinder was also proposed here.

Electromagnetic Inspection Method of Slack of High Tension Bolt

The inspection of the slack of the steel high-tension bolt is important in the maintenance of various mechanical parts and buildings, etc. There occurs the difference of the magnetic property of the bolt head when the axis force of the fastened bolt is increased. Therefore, the evaluation of the slack of the bolt is possible by detecting the difference of the magnetic characteristics. In this paper, the electromagnetic method for measuring the slack of the steel high-tension bolt using an alternating magnetic field is proposed. The stress and flux density in the bolt head are estimated by 3-D stress analysis using the finite-element method and nonlinear electromagnetic finite element analysis taking account of the electromagnetic property under various compressive stresses. In addition, the experimental verification is also carried out.

Experimental Study on Composites with Single-Lap Countersunk Head Bolt Joints

An investigation was performed to study the response of laminated composites with bolt joints. The configuration was single-lap single countersunk head bolt. The major focus was to characterize bearing behavior of laminates and the effect of some parameters such as lap types, fastener types, hole diameter, and stiffness of lapped plate on the bearing strength and stiffness. For this purpose, hundreds of specimens were tested to obtain ultimate loads and stiffness of joints. According to different configurations of joints, three contrast tests were carried out, and some useful conclusions were drawn. Firstly, comparing the stiffness, the joints with protruding head bolts are slightly stiffer than those with countersunk head bolts. And bearing strength of the joints with protruding head bolts are about 10% higher than those with countersunk head bolts. Secondly, ultimate load and stiffness of single-lap double bolts are similar to double-lap single bolt, which are twice bigger than single-lap single bolt. Thirdly, the stiffness of joints can be improved by using bigger hole diameter or stiffer lapped plates. When the hole diameter and stiffer lapped plates are in a reasonable range, bearing strength increase. However, larger stiffness of joint structure may cause transient breaking, which is dangerous for the structure. So in engineering, it is needed to balance the bearing strength and stiffness of joints.

Research on the Parametric Designing for Thread Fasteners

For the purpose of improving the design automaticity for mechanical design, this paper explores the parameter designing for thread fasteners with SolidWorks as the operation platform and Visual Basic 6.0 as the development tool. The method and steps of parameter designing have been introduced here with the hexagonal head bolt as an example for users to conveniently transfer a series of hexagonal head bolt parts by inputting different parameter values on the man-machine dialogue window in the VB interface.

Longevity enhancement of bolted joints for aircrafts

New designs of bolted joints with bolt countersunk heads having high longevity in comparison with the used ones were proposed. One type of joint has the bolt heads with the reduced surface taper of the bolt head and in a joined part. Two other types have a spherical head surface, which is in contact with a tapered countersink surface. The rise in the fatigue life is achieved owing to the balance of the radial tension along the contact surfaces of the head and the countersink. Designs of a washer from the direction of a nut are proposed. These washers have ring bulges of wedge-shaped cross section that form areas of plastic deformations around a bolt body during the bolt tightening and reduce the concentration of contact stresses close to an edge of the contact surfaces of the bolt and joined parts. Procedures of fatigue tests were developed. Results of tests of the proposed bolted joints supporting their high longevity are presented. Findings of experimental investigations verify the efficiency of the application of proposed types of bolted joints in the designs of aircrafts.