Bolt Preloads Research Articles

電磁加振法によるボルト軸力測定の適用性評価

The integrity and safety of a bolted joint are to be guaranteed by applying and maintaining an appropriate amount of bolt preloads. However, the variation of bolt preloads inevitably occurs in the service condition due to various reasons, even if the initial bolt forces are properly applied. Accordingly, the monitoring of bolt forces in the service condition is significantly important. From the practical point of view, it is preferably conducted without disassembling the objective bolted joint.In this paper, Electromagnetic Vibration Method is introduced for monitoring the variation of bolt preloads in the service condition, and its performance is examined by experiments using bolted joints with various geometric configurations. Electromagnetic Vibration Method estimates the magnitude of bolt force by measuring the resonant frequencies of the bolted joint, which vary in accordance with the contact pressure of the joint interface. Electromagnetic Vibration Method is found to be effective to estimate the bolt force with a reasonable accuracy, except for the bolted joint including the interface under very high contact pressure. In addition, the characteristics of the method are evaluated as a vibration problem by constructing a free vibration model composed of two masses and three springs.

Experimental and theoretical studies of a bolted joint excited by a torsional dynamic load

This paper presents the experimental work on a single joint rig and the analytical models for representing the experimental results. A bolted joint connecting two beams is shaken at two resonant frequencies. These experiments have illustrated microslip and macroslip phenomena from measurements taken locally to the joint interface in the time domain. Hysteresis loops of the torque versus the relative angular displacement of the joint have been generated from the time-domain data of the rig subjected to multiple bolt preloads and amplitudes of excitation. Damping behaviour evolving from linear viscous type to nonlinear frictional type is clearly shown in the plots of the hysteresis loops and the frequency spectra of the relative angular displacement of the joint. As microslip in the joint develops, the hysteresis loops deviate from an ellipse and the contribution from superharmonics in the frequency spectra becomes stronger. The presence of odd superharmonics in the frequency spectra seems to suggest that the nonlinearity due to friction in the joint can be represented by a cubic stiffness term. The Jenkins-element model for the friction torque in the joint has been used to fit the hysteresis loops of the experimental joint.

Measurement of Bolt Pre‐load in Torqued Composite Joints

StrainVolume 41, Issue 3 p. 109-112 Measurement of Bolt Pre-load in Torqued Composite Joints M. A. McCarthy, M. A. McCarthy Composites Research Centre, Materials and Surface Science Institute, Department of Mechanical and Aeronautical Engineering, University of Limerick, Limerick, IrelandSearch for more papers by this authorV. P. Lawlor, V. P. Lawlor Composites Research Centre, Materials and Surface Science Institute, Department of Mechanical and Aeronautical Engineering, University of Limerick, Limerick, IrelandSearch for more papers by this authorP. C. O'Donnell, P. C. O'Donnell Composites Research Centre, Materials and Surface Science Institute, Department of Mechanical and Aeronautical Engineering, University of Limerick, Limerick, IrelandSearch for more papers by this authorK. Harris, K. Harris Composites Research Centre, Materials and Surface Science Institute, Department of Mechanical and Aeronautical Engineering, University of Limerick, Limerick, IrelandSearch for more papers by this authorP. Kelly, P. Kelly Composites Research Centre, Materials and Surface Science Institute, Department of Mechanical and Aeronautical Engineering, University of Limerick, Limerick, IrelandSearch for more papers by this authorJ. P. Cunningham, J. P. Cunningham Composites Research Centre, Materials and Surface Science Institute, Department of Mechanical and Aeronautical Engineering, University of Limerick, Limerick, IrelandSearch for more papers by this author M. A. McCarthy, M. A. McCarthy Composites Research Centre, Materials and Surface Science Institute, Department of Mechanical and Aeronautical Engineering, University of Limerick, Limerick, IrelandSearch for more papers by this authorV. P. Lawlor, V. P. Lawlor Composites Research Centre, Materials and Surface Science Institute, Department of Mechanical and Aeronautical Engineering, University of Limerick, Limerick, IrelandSearch for more papers by this authorP. C. O'Donnell, P. C. O'Donnell Composites Research Centre, Materials and Surface Science Institute, Department of Mechanical and Aeronautical Engineering, University of Limerick, Limerick, IrelandSearch for more papers by this authorK. Harris, K. Harris Composites Research Centre, Materials and Surface Science Institute, Department of Mechanical and Aeronautical Engineering, University of Limerick, Limerick, IrelandSearch for more papers by this authorP. Kelly, P. Kelly Composites Research Centre, Materials and Surface Science Institute, Department of Mechanical and Aeronautical Engineering, University of Limerick, Limerick, IrelandSearch for more papers by this authorJ. P. Cunningham, J. P. Cunningham Composites Research Centre, Materials and Surface Science Institute, Department of Mechanical and Aeronautical Engineering, University of Limerick, Limerick, IrelandSearch for more papers by this author First published: 26 July 2005 https://doi.org/10.1111/j.1475-1305.2005.00201.xCitations: 9Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume41, Issue3August 2005Pages 109-112 RelatedInformation

Finite Element Analysis of the Thermal and Mechanical Behaviors of a Bolted Joint

Mechanical and thermal behaviors of the bolted joint subjected to thermal load are analyzed using axisymmetric FEM, where the effects of thermal contact resistance at the interface and heat flow through small gap are taken into account in order to accurately evaluate the variations of bolt preloads. It is expected that the numerical procedure proposed here provides an effective means for estimating the strength of such critical structures as pressure vessels, internal combustion engines, steam and gas turbines, etc. An experimental equation that can compute the thermal contact coefficient at the interface composed of common engineering materials has been proposed in the previous paper. In this study, a simple equation for evaluating the amount of heat flow through small gap is shown by defining apparent thermal contact coefficient. Accordingly, a numerical approach has been established, which can accurately analyze the thermal and mechanical behaviors of a bolted joint, by incorporating the two kinds of thermal contact coefficients into FE formulation. By use of the FE code thus developed, it is shown that only a slight difference in coefficients of linear expansion among the joint members significantly affects the variations of bolt preloads. The validity of the numerical approach is demonstrated by experimentation.

Stress Analysis and Sealing Performance Evaluation of Pipe Flange Connections under Internal Pressure (Effects of Scatter in Bolt Preloads)

The effects of scatter in bolt preloads of pipe flange connections with gaskets subjected to internal pressure are examined. The scatter in the bolt preloads tightened by a torque wrench was measured in the experiments. The contact gasket stress distributions at the interfaces of the pipe flange connections with the gaskets were calculated under the measured bolt preloads using elastoplastic finite element method (FEM) taking into account hysteresis and non-linearity in the stress-strain curves of the gaskets. The effects of the scatter in the bolt preloads on the gas leakage were also exmained using actual pipe flange connections. As the result a difference in an amount of measured gas leakage was found to be substantial between our study and PVRC (ASME) procedure. By using the calculated contact gasket stress distributions in the connections under the internal pressure and the results of the leakage tests, the sealing performance was evaluated. The effect of the scatter in the bolt preloads is found to be substantial on the leakage. It is found that the sealing performance is worse in the actual pipe flange connection than that evaluated by PVRC procedure. The tightening efficiency was proposed taking account the leakage due to the scatter in bolt preloads.

Bolt-Up Guideline for Pipe Flange Connections

Numerical simulations are systematically executed for pipe flanges with wide variety of nominal size by using finite element analysis, which can simulate the bolt-up process of a pipe flange connection. Effects of the gasket modeling method on the bolt-up simulation and the bolu-up procedure which can prevent open up deformation are evaluated. It is indicated that the simplified linear modeling of gasket, in which two different Young's moduli are used in loading and unloading, is valid for estimating the variations, of mean bolt preloads during bolting up operations. The bolt-up procedure, in which four bolts located 90 degrees apart each other are tightened uniformly with the target bolt preload at the installation process, is effective to prevent the open up deformation. Finally, the methodical guideline for bolt-up operation of pipe flange connections with joint sheet gasket or spiral wound gasket is proposed.

Elastic Plastic Finite Element Analysis of Bolted Joint During Tightening Process

Mechanical behavior of bolted joints during the tightening process with torque control is analyzed by FEM as elastic plastic contact problems. Three-dimensional analysis was conducted employing two-dimensional model with each node having three degrees of freedom that attains high computation efficiency. Such important factors as development of plastic zones, variations of load distributions along engaged threads, the relationships between axial bolt stress and nut rotation angle were analyzed in order to provide an effective guideline when tightening critical structures with high bolt preloads. It was also shown that the proposed numerical method can be applied to evaluate the tightening process by “plastic region tightening” used extensively in recent years. The validity of the numerical method is demonstrated by comparing the calculated bolt elongation with that obtained from experiment.

Finite Element Simulation of Bolt-Up Process of Pipe Flange Connections With Spiral Wound Gasket

It is well known that a large amount of scatter in bolt preloads is observed when bolting up a pipe flange connection, especially in the case of using a spiral wound gasket. In this study, a numerical approach is proposed, which can simulate the bolt-up process of a pipe flange connection with a spiral wound gasket inserted. The numerical approach is designed so as to predict the scatter in bolt preloads and achieve uniform bolt preloads at the completion of pipe flange assembly. To attain the foregoing purposes, the stress-strain relationship of a spiral wound gasket, which shows highly nonlinear behavior, is identified with a sixth-degree polynomial during loading and with an exponential equation during unloading and reloading. Numerical analyses are conducted by three-dimensional FEM, in which a gasket is modeled as groups of nonlinear one-dimensional elements.

Stress Analysis and Determination of Bolt Preload in Pipe Flange Connections With Gaskets Under Internal Pressure

The stresses of a pipe flange connection with a spiral-wound gasket under internal pressure are analyzed taking account a nonlinearity and a hysteresis of the gasket by using an axisymmetric theory of elasticity and the finite element method (FEM). The leakage tests were also conducted using an actual pipe flange connection with a spiral-wound gasket. Using the contact stress distribution of the pipe flange connection with 3-in. nominal diameter under internal pressure and the tightness parameter, the values of the new gasket constants are obtained by taking into account the changes in the contact stress. A difference in the new gasket constants between the estimated values obtained from the actual pipe flange connection and the values obtained by the PVRC procedure is small. In addition, a method to determine the bolt preload for a given tightness parameter is demonstrated. The obtained results of the bolt preload for the pipe flange connection are in a fairly good agreement with those obtained by the PVRC procedure under a lower pressure application. However, a difference in the bolt preload is about 10% when an internal pressure is increased.

BOLJAT: a tool for designing composite bolted joints using three-dimensional finite element analysis

This paper discusses the development of a software tool for design of composite bolted joints, using three-dimensional finite element analysis. The tool allows the user to create the joint geometry through a menu-driven interface and then generate a customised mesh according to the user's needs. Contact parameters are defined automatically, which shields the user from the most difficult part of the process. Boundary conditions, bolt pre-loads, and material properties can also be set. Only a few manual steps are necessary to complete the finite element code generation process. By automating the time-consuming model creation process, the tool facilitates the increased use of three-dimensional finite element analysis in the design of composite bolted joints. A case study is shown to demonstrate the usefulness of the tool.

Three-Dimensional Finite Element Analysis of Pipe Flange Connections. In Case of Using Compressed Asbestos Sheet Gasket.

The most important factors for the leakage problem of pipe flange connection is considered to be contact pressure distribution at the gasket bearing surface in service. In this study, the mechanical behaviors of pipe flange connection are evaluated using FEM as a three-dimensional contact problem, in which a gasket is modeled as a nonlinear one-dimensional gasket element. Here, the contact pressure distributions at the gasket bearing surface and the variations of bolt stress are estimated under uniform bolt preloads or nonuniform ones due to the elastic interaction during bolting up. The numerical procedure proposed here can successively deal with the processes of bolt-up, applying inner pressure and applying bending moment. The analytical objects are pipe flanges specified in JIS B 2238 with compressed asbestos sheet gaskets being inserted. The validity of the numerical method is ascertained by experiment.

マリンエンジニアリングにおける安全管理に対する計算力学の可能性

The safety management in marine engineering has long been supported with the help of skilled workers. Meanwhile, the lack of such skilled workers is of growing problem in marine engineering field and related areas. Incidentally, Computational Mechanics has attained remarkable progress in this decade, and it is expected to be effective means to solve the problem stated above.In this paper, the tightening procedure of pipe flange connection is adopted, as an example of its engineering application. The most critical problem concerned is the estimation of scatter in bolt preloads, when tightening bolts one by one. Such complicated problem could now be analyzed by FEM. In addition, a numerical method offering an optimal tightening procedure is presented here, which estimates how much initial bolt preload is needed for each bolt to achieve uniform bolt preloads in the final state. The numerical method proposed here is expected to partly compensate the lack of skilled workers and contribute the safety management in marine engineering.

Finite Element Simulation of Bolt-Up Process of Pipe Flange Connections

Achieving uniform bolt preload is difficult when tightening a pipe flange with a number of bolts. Several bolt-tightening strategies have been proposed so far for achieving uniform bolt preloads. It seems, however, that effective guidelines for tightening pipe flange connections have not been established. In this study, a numerical approach is presented for estimating the scatter in bolt preloads and achieving the uniform bolt preloads when tightening each bolt one by one in an arbitrary order. Numerical analyses are conducted using three-dimensional FEM as an elastic contact problem. The analytical objects are pipe flanges specified in JIS B 2238 with an aluminum gasket inserted. The validity of the numerical procedures proposed here is ascertained by experiment.

Determination of bolt forces in a circular flange joint under tension force

Formulae for the calculation of bolt forces in circular flange joints under tension are developed and tables and a chart are created to simplify their use. Bolt forces obtained can be used for the design of bolts and flanges in the joints. A range of joints with different dimensions and different bolt preloads are analysed using the formulae and very good agreement between the results and those obtained using finite element analyses has been found.

Experimental study of circular flange joints in tubular structures

Four circular bolted joints with blank flanges have been tested under static tension forces. Different tension forces and bolt preloads have been applied to the joints and bolt forces, displacements and stresses in the joints have been measured. The influences of bolt preloads and flange dimensions on the behaviour of the joints have been investigated. The results obtained have been compared with the results from finite element analyses and mathematical analyses and good agreement has been found.