Hexagonal Bolt Research Articles

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.

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

One-sided bolts, which typically employed for connecting components with closed cross section, often present complexities in both construction and installation. Addressing the limitations of conventional one-sided bolts, this study introduces a novel variant distinguished by its elliptical head, offering ease of installation without the need for specialized tools. Due to the special shape of the bolt head, the mechanical properties of the bolt need to be studied in depth. To investigate the shear properties of the novel elliptical one-sided bolts, three sets of single lap shear experiments were conducted. Subsequently, finite element numerical analyses were employed to simulate these experiments, facilitating the development of a reliable finite element model. Furthermore, parametric analyses were undertaken to examine the influence of various parameters on the ultimate shearing capacity and displacement of joints. The findings indicate that the shear capacity of the single lap joint employing novel elliptical one-sided bolts closely rivals that of ordinary hexagonal bolts with equivalent diameters. However, an enhancement in slip resistance capacity is observed in the novel elliptical one-sided bolt joints compared to hexagonal bolts. Notably, the parameters of the bolt exert a more pronounced impact on the ultimate shearing capacity and displacement of joints when contrasted with parameters associated with the plates. The recommended torque coefficient for the novel elliptical one-sided bolt is established as 0.2, and it is recommended to use appropriate torque to ensure the slip performance of the joint during practical application.

Design research on the unmeshed thread section structure of engine conrod bolts

In the design standard for hexagonal flange bolts, the reliability of the bolt connection structure varies when different structural forms of bolts are selected. However, there are few studies on the design and selection of bolts with different structural forms, and the design law of the bolt connection structure cannot be summarized comprehensively. In this paper, a finite element model of conrod bolt tightening was established based on the mesh convergence criterion, and the model was verified by comparing the simulation curve of tightening torque-bolt preload with the theoretical curve. The influence of the length of unmeshed thread, the length of thin rod and the diameter of thin rod section on the stress and deformation of conrod bolt was studied, it is found that the increase of the three kinds of structural parameters will reduce the stress concentration and radial deformation at the first thread of engagement, which can guarantee the structural strength of the bolt. At the same time, the fatigue safety factor of the bolt easy-to-failure region was analyzed, and the reliability of different structural forms of bolts was evaluated comprehensively. The results show that when the structure of bolt conforms to the design standard of full thread hexagonal flange bolt, the length of unmeshed thread is 27 mm, the stress value and radial deformation of the first thread are the smallest, and the fatigue safety factor of the bolt easy-to-failure region is the largest, which is not easy to damage. In the design of hexagonal flange bolts, full thread hexagonal flange bolts are used as much as possible.

PETA KENDALI MULTIVARIAT np

In general, a production process requires the control of multiple quality characteristics (variables). Multivariate control charts can be used to control many quality attributes and identify the root cause of an out-of-control condition or signal. It was used in the production of Hexagon Bolt M16x75mm. However, research regarding the theory of multivariate control charts remains limited. The np multivariate control chart is obtained by combining the processes of parameter estimate, control limit determination, and out-of-control signal detection. Keywords: Control Charts, Multivariate np, Out of Conrol Signal.

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.

Influence of Geometry on Failure Modes of Hybrid Metal-Composite Protruding Bolted Joints

This article presents the influence of joint geometry on the damage mode in the CFRP (Carbon Fiber Reinforced Polymer) composite plate of the single-lap, protruding, hybrid metal-composite joints. A detailed 3D finite element model incorporating geometric, material and friction-based contact full nonlinearities is developed to numerically investigate the geometry effects on the progressive damage analysis (PDA) of the orthotropic material model. The PDA material model integrates the nonlinear shear response, Hashin-tape failure criteria and strain-based continuum degradation rules being developed using the UMAT user subroutine in Nastran commercial software. In order to validate the geometry effects on the failure modes of the joints with hexagonal head bolts, experiments were conducted using the SHM (Structural Health Monitoring) technique. The results showed that the plate geometry is an important parameter in the design process of an adequate bolted joint and its effects on damage initiation and failure modes were quite accurately predicted by the PDA material model, which proved to be computational efficient and can predict failure propagation and damage mechanism in hybrid metal-composite bolted joints.

Optimization of trimming process in cold forging of steel bolts by Taguchi method

In this study, die-service life analysis of hexagonal trimming dies with different edge radius and cutting width was performed. The trimming dies were prepared by grinding the front face of the die due to desired cutting width and edge radius. Prepared dies were used in cold forging of steel M6x25 hexagonal bolts and service life of each die were determined in terms of number of bolts that they can produce until they experience fracture. Numerical models of trimming operation with varying cutting width were also prepared in finite element software simufact.forming to conduct stress analysis. Production trials and finite element analysis showed that service life of trimming die was significantly affected by cutting width. It was seen that die-service life increases linearly with increasing cutting width within an optimum range of 0.8 and 1.2 mm. Similarly, the die-service life improved with increasing edge radius values. Moreover, the trimming operation carried out by using hexagonal trimming die was optimized with Taguchi method by defining 5 design parameters and 3 levels for each parameter. Minimizing the peak trimming load and maximizing the peak damage value were determined as the objective functions to find the most effective design parameters. According to the Taguchi results, the cutting width and stopping distance were seen to have significant impact on peak trimming load while the edge radius was determined to be effective on the peak damage value.

Influence of Preload on Failure Modes of Hybrid Metal-Composite Protruding Bolted Joints

This paper presents the effects of torque preload on the damage initiation and growth in the CFRP (Carbon Fiber Reinforced Polymer) composite laminated adherent of the single-lap, single-bolt, hybrid metal-composite joints. A detailed 3D finite element model incorporating geometric, material and friction-based contact full nonlinearities is developed to numerically investigate the preload effects on the progressive damage analysis (PDA) of the orthotropic material model. The PDA material model integrates the nonlinear shear response, Hashin-tape failure criteria and strain-based continuum elastic properties degradation laws being developed using the UMAT user subroutine in Nastran commercial software. In order to validate the preload effects on the failure modes of the joints with hexagonal head bolts, experiments were conducted using the SHM (Structural Health Monitoring) technique. The results showed that the adherent torque level is an important parameter in the design process of an adequate bolted joint and its effects on damage initiation and failure modes were quite accurately predicted by the PDA material model, which proved to be computational efficient and can predict failure propagation and damage mechanism in hybrid metal-composite bolted joints.

Design Analysis of a Portable Manual Tyre Changer

In this paper, an efficient, affordable, and portable manual automobile tyre changing tool was designed. The tool operates on the principle of second-class levers, where the load to be overcome is situated between the fulcrum and the effort point. The mechanical advantage (MA) of the bead breaker arm and pry bar assembly of the tool was determined to be 11.5. The standard tube size of the bead breaker arm that can withstand stress due to bending moment was determined to be a 2” (50mm) diameter Schedule 80 steel tube. Also, the dimensions of the standard hexagonal bolts to be used at the fulcrum and load point of the bead breaker arm are M12 × 1.5 × 75 mm, while the standard size of hexagonal nuts to be used with the bolts is M12 × 1.5 mm with a height of 10mm. Moreover, the mechanical advantage (MA) of the mount/demount arm and pry bar assembly of the tool was determined to be 5.22. Also, by comparing the angles of twist of two sizes of the mount/demount arm when the tool is used in mounting or demounting a tyre on a 16” × 7” wheel rim, the standard size of the mount/demount arm that can withstand stresses due to bending moment and torsional moment was determined to be a 60mm × 60mm × 5mm square tube. The cost of materials needed to fabricate the tyre changer summed up to ?21,000. Ergo, the design provides an alternative portable and relatively affordable tyre changing tool that can be afforded by tyre technicians across Nigeria, and other developing or underdeveloped countries.

Design Analysis of a Portable Manual Tyre Changer

In this paper, an efficient, affordable, and portable manual automobile tyre changing tool was designed. The tool operates on the principle of second-class levers, where the load to be overcome is situated between the fulcrum and the effort point. The mechanical advantage (MA) of the bead breaker arm and pry bar assembly of the tool was determined to be 11.5. The standard tube size of the bead breaker arm that can withstand stress due to bending moment was determined to be a 2” (50mm) diameter Schedule 80 steel tube. Also, the dimensions of the standard hexagonal bolts to be used at the fulcrum and load point of the bead breaker arm are M12 × 1.5 × 75 mm, while the standard size of hexagonal nuts to be used with the bolts is M12 × 1.5 mm with a height of 10mm. Moreover, the mechanical advantage (MA) of the mount/demount arm and pry bar assembly of the tool was determined to be 5.22. Also, by comparing the angles of twist of two sizes of the mount/demount arm when the tool is used in mounting or demounting a tyre on a 16” × 7” wheel rim, the standard size of the mount/demount arm that can withstand stresses due to bending moment and torsional moment was determined to be a 60mm × 60mm × 5mm square tube. The cost of materials needed to fabricate the tyre changer summed up to ₦21,000. Ergo, the design provides an alternative portable and relatively affordable tyre changing tool that can be afforded by tyre technicians across Nigeria, and other developing or underdeveloped countries.

Research and Application of Locking Strip for Inter-Hexagon Screw in Main Pump for Nuclear Power Station

The loosening of inter- hexagonal screws connecting internal parts in main pump for nuclear power station causes some nuclear safety problem due to medium erosion at present. Aim at the problem, a special locking strip for inter- hexagonal screws is put forward and the structure of the locking strip, the bending process and the forming die of the locking strip are designed and calculated in this paper. Furthermore, the fastening tool of the locking strip is designed, and the feasibility of the locking strip is verified in the experiment so as to improve the anti-loosening reliability. The locking strip for inter- hexagonal bolts can be widely applied to the locking and fastening industry application fields.

A Split Die Design for Forging of Hexagonal Bolt Head

A Split Die Design for Forging of Hexagonal Bolt Head

Research on Performance of Grounding Conductor Based on Multi-Physics

The performance analysis of the grounding conductor is of great significance for improving the design and construction level of the grounding grid and rationally selecting the grounding conductor specifications.Based on the multi-physics analysis and calculation software COMSOL, this paper establishes a three-dimensional simulation model of the grounding conductor with the standard hexagonal M8 bolt as the research object.Firstly, the contact resistance of the grounding copper bus contact surface is calculated, and the influence of contact resistance is analyzed according to different factors. Then, the influence of different tightening torque on the maximum temperature of the contact surface under the condition of short-circuit current is calculated. Finally, the normal condition of the contact surface under different tightening moments and the pressure distribution characteristics during short-circuit are calculated. The results show that the bolt tightening torque, the surface roughness of the copper row, the selected grounding copper row material, and the overlapping area all have an effect on the contact resistance; When the grounding conductor is short-circuited, the maximum temperature on the contact surface decreases with the increase of the tightening torque. It is recommended to use copper as the material of the grounding conductor, and apply a tightening torque to the bolt at 24∼28N•m; At the same time, the distribution characteristics of the contact surface of the conductor under normal conditions are analyzed. Finally, based on the research results, the method of reducing the grounding resistance at the grounding conductor joint in practical engineering is proposed.

Experimental and Finite Element Research on the Failure Mechanism of C/C Composite Joint Structures under Out-of-Plane Loading.

The loading and the failure mode of metal hexagon bolt joints and metal counter-sunk bolt joints of C/C composites were investigated. The joints were tested for out-of-plane loading at two temperatures (600 °C and 800 °C). The failure morphology of a lap plate was investigated, and the main failure modes were determined. The typical load–displacement curve was characterized and the test was simulated using ABAQUS non-linear finite element software. Furthermore, progressive damage was induced, and comparison of the finite element simulation with the experimental data revealed that the failures mainly occurred in the lower lap plate and were dominated by cracking and delamination of the matrix, accompanied by the pull-out of a small number of piercing fibers. Finally, the influences of the temperature, nut radius, and fixture geometry on the critical load were determined via simulation.

Integrated process design of Al6061 alloy bolts for fastening offshore platforms

In this study, we design an integrated manufacturing process for Al6061 alloy bolts to fasten offshore platforms. The proposed scheme includes the theoretical design and numerical study for the heading, trimming, and thread-rolling process. For the theoretical design, the initial rod diameter and the penetration depth (PD) in the thread-rolling process are calculated according to thread standards and geometric relation. The dimensions of the initial workpiece for the heading process are obtained using the volume constancy law. Considering process limitations to predict the defects, the number of stages is set, and the preform is then determined using the design rule in the heading process. Based on the theoretical design, finite-element (FE)-analysis is conducted. In order to predict the defects and fracture phenomena, the ductile fracture criterion was applied during the heading and trimming processes. The Taguchi method is used to optimize the trimming and thread-rolling process with the set of design parameters, such as the PD, transfer velocity, and revolutions per minute in the thread-rolling process, and the blade radius (BR), land width, and stop distance in the trimming process, respectively. Results show that the PD and BR have the most significant effect on the dimensional accuracy and forming load. To validate the proposed design, the aluminum alloy bolt-forming experiment is performed. We obtain the sound Al6061 alloy M12 hexagonal bolt shaped with highdimensional accuracy. Therefore, this research provides valuable guidelines for the design of the integrated forming process in actual bolt production.

Preload Effects on Failure Mechanisms of Hybrid Metal-Composite Bolted Joints

This paper presents the effects of torque preload on the damage initiation and growth in the CFRP (Carbon Fiber Reinforced Polymer) composite laminated adherent of the single-lap, single-bolt, hybrid metal-composite joints. A detailed 3D finite element model incorporating geometric, material and friction-based contact full nonlinearities is developed to numerically investigate the preload effects on the progressive damage analysis (PDA) of the orthotropic material model. The PDA material model integrates the nonlinear shear response, Hashin-tape failure criteria and strain-based continuum elastic properties degradation laws being developed using the UMAT user subroutine in Nastran commercial software. In order to validate the preload effects on the failure modes of the joints with hexagonal head bolts, experiments were conducted using the SHM (Structural Health Monitoring) technique. The results showed that the adherent torque level is an important parameter in the design process of an adequate bolted joint and its effects on damage initiation and failure modes were quite accurately predicted by the PDA material model, which proved to be computational efficient and can predict failure propagation and damage mechanism in hybrid metal-composite bolted joints.

Shaping the Hexahedral Head of a 12Kh18N10T Stainless Steel Bolt

The manufacture of 12Kh18N10T austenitic stainless steel bolts with a hexahedral head is analyzed. The mechanical properties of 12Kh18N10T steel are tested after tempering and calibration to the initial dimensions. Two production technologies are considered: cold stamping with trimming of the hexahedral head; and cold flash-free stamping of a hexahedron. The quality of the head is better in the latter case. The best depth of the depression in the hexagonal bolt head made by flash-free stamping is determined.

Study on Analysis of Heat Conduction of SUS Materials for Peeling Machine

SUS bars such as 304, 316 series have been widely used to manufacture the adapters and fittings, which include many hexagonal bolts and nuts. The purpose of this study is to investigate the characteristics of heat conduction of SUS bar according to rotation of cutting tool. Temperature distribution in SUS bar can be achieved by using numerical analysis of heat conduction, thus it may be of help to the optimal operation of peeling machine. As the results, as the rotation of cutting tool is increased, both maximum cutting temperature and depth of heat conduction are decreased. Moreover as the angle of SUS bar is increased, it shows that maximum cutting temperature is decreased, on the other hand, depth of heat conduction is increased.

Design and Fabrication of Mechanically Controlled Pedorthosis to Treat Congenital Talipes Equino Varus (CTEV)

Objectives: Clubfoot scientifically coined as Congenital Talipes Equino Varus (CTEV) is a deformity in which the afflicted foot appears to be rotated internally at the ankle and shape the subject to walk on the sides of their foot. To diagnose clubfoot deformity non-surgical technique such as serial casting and implementing an Ankle Foot Orthosis (AFO) is preferred over surgical method. This paper aims at developing a mechanically governed non-surgical corrective mechanism that rectifies clubfoot deformity in infants. Methodology: To design the supportive device, following three parameters, are to be considered: Foot Bi-Malleolar angle (FBM), Angle of Plantar Flexion (PF), Angle of Dorsi Flexion (DF). The FBM, PF and DF angle for a healthy infant ranges from 85 - 90˚, 0 - 40˚ and 0 - 22˚ but for a child with clubfoot it is constrained within 50 - 65˚, 0 - 22˚, 0 - 12˚. This deformation can be corrected with the help of mechanically controlled hinge joint and sliding pair mechanism. The orthosis predominantly consists of two main parts sole and cylindrical pair joint. The sole part which is connected to the lower link using a hexagonal nut and bolt creates a hinge joint and thus providing movement along PF. The bottom link in-turn is connected with the cylindrical pair joint and thus allowing 360˚ movement along FBM. Thus hinge joint provides the counter force on the forefoot. Similarly, cylindrical pair joint provides the counter force on mid and hind foot thus directing the bone growth to its pristine. Findings: The initial wearable prototype of the pedorthosis has been proposed, designed and fabricated using thermoforming process. Applications: This wearable orthosis can be fitted to a subject and the growth pattern can be studied. Feasibility of the concept can be understood by virtually evaluating using finite element analysis.