An Accurate Method of Evaluating Relaxation in Bolted Flanged Connections

1997 ◽  
Vol 119 (1) ◽  
pp. 10-17 ◽  
Author(s):  
A. Bouzid ◽  
A. Chaaban
Keyword(s):  
Accurate Method ◽  
Bolted Joints ◽  
Fe Modeling ◽  
Test Results ◽  
Bolted Joint ◽  
Asme Code ◽  
Thermal Dilatation ◽  
Joint Rigidity ◽  
Analytical Tools ◽  
Leakage Assessment

Bolted flanged joint assemblies may begin to leak some time following a successful hydrostatic test. One of the reasons is that the gasket experiences a drop in its initial compressive stress due to creep, thermal dilatation, and thermal degradation. The need to pay attention to the relaxation behavior of bolted joints for high-temperature applications is recognized by the ASME Code, but no specific guidelines are given to help engineers, neither at the design nor maintenance levels. This paper deals with the basic analytical tools that have been used to develop a computer program “SuperFlange” that can be used to make accurate predictions of the relaxation of bolted flanged joints, and hence be able to provide a reasonable leakage assessment over time. A simplified analytical method of relaxation analysis will also be presented. These proposed methods are supported by test results obtained on a real bolted joint fixture and by FE modeling. A strong emphasis will be put on flanged joint rigidity, which is one of the major controlling parameters of relaxation besides the material properties involved.

Accurate Evaluation of Bolt and Clamped Members Stiffnesses Of Bolted Joints

2021 ◽  
Author(s):  
Rashique Iftekhar Rousseau ◽  
Abdel-Hakim Bouzid ◽  
Zijian Zhao
Keyword(s):  
Finite Element ◽  
Joint Stiffness ◽  
Element Model ◽  
Fe Analysis ◽  
Bolted Joints ◽  
Analytical Models ◽  
Fe Modeling ◽  
Bolted Joint ◽  
A New Technique ◽  
External Loads

Abstract The axial stiffnesses of the bolt and clamped members of bolted joints are of great importance when considering their integrity and capacity to withstand external loads and resist relaxation due to creep. There are many techniques to calculate the stiffnesses of the joint elements using finite element (FE) modeling, but most of them are based on the displacement of nodes that are selected arbitrarily; therefore, leading to inaccurate values of joint stiffness. This work suggests a new method to estimate the stiffnesses of the bolt and clamped members using FE analysis and compares the results with the FE methods developed earlier and also with the existing analytical models. A new methodology including an axisymmetric finite element model of the bolted joint is proposed in which the bolts of different sizes ranging from M6 to M36 are considered for the analysis to generalize the proposed approach. The equivalent bolt length that includes the contribution of the thickness of the bolt head and the bolt nominal diameter to the bolt stiffness is carefully investigated. An equivalent bolt length that accounts for the flexibility of the bolt head is proposed in the calculation of the bolt stiffness and a new technique to accurately determine the stiffness of clamped members are detailed.

Non-Linear Analysis and Modeling of the Structure with Bolted Joints

2015 ◽  
Vol 656-657 ◽  
pp. 694-699
Author(s):  
Xin Liao ◽  
Jian Run Zhang ◽  
Dong Lu
Keyword(s):  
Dynamic Stiffness ◽  
Element Model ◽  
Outer Radius ◽  
Bolted Joints ◽  
Structure Model ◽  
Test Results ◽  
Bolted Joint ◽  
Joint Structure ◽  
Non Linear ◽  
Simulation Results

In this study, a non-linear finite element model for a simplified single-bolted joint structure model is built. Static analysis on the structure under different shear force and pretension effect is done, and the non-linear contact behavior is analyzed. Through comparing datum, it is found that interface area of each bolted joint region can be described an annular region around bolt hole, whose outer radius has increased by 85% compared with radius of bolt hole. Also, the frequency responses of the multi-bolted joint structure under sinusoidal excitation are investigated. Simulation results show that the resonance regions basically remain unchanged in different pretension effect and the largest amplitude will increase with the increasing preloads. Finally, the vibration experiments are conducted. Interface nonlinear affect dynamic stiffness considerably. The test results illustrate that dynamic behaviors of bolted joint agree with the simulation results and the proposed non-linear contact model was reasonable.

scholarly journals Shear Strength of Flat Joint considering Influencing Area of Bolts

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Hang Lin ◽  
Penghui Sun ◽  
Yifan Chen
Keyword(s):  
Shear Strength ◽  
Jointed Rock ◽  
Calculation Model ◽  
Bolted Joints ◽  
Rock Joints ◽  
Joint Surface ◽  
Influence Coefficient ◽  
Test Results ◽  
Bolted Joint ◽  
Joint Shear Strength

Bolt is popular in the reinforcement of geotechnical engineering, which can significantly improve the strength and stability of jointed rock mass. For bolted joint, the bolting area is a certain scope instead of the entire joint surface; therefore, it is necessary to study the effect of bolt influencing area on the shear strength of rock joints. In this paper, a series of laboratory direct shear tests were executed on the bolted joints to explore the influence of bolts on the joint shear strength, as well as the influencing area of bolt. Via successively changing bolting angle and bolt number, the shear stress-shear displacement curves of bolted joints were recorded and the variation law of shear strength was analyzed. Based on the assumption of the circular influencing area of bolt, the influence coefficient m (defined as the diameter ratio of the influencing area to the bolt) was introduced to establish the theoretical calculation model of the shear strength of bolted joint, which was verified by test results. Furthermore, the value of m was changed, and the shear strengths of bolted joints under different bolting condition were calculated to compare with the test results. The average relative error Eave was selected to determine the optimal value of m under the corresponding bolting condition, and it tends to sufficiently small values under the case of m > 30 for one-bolted joint and m > 25 for two-bolted joint, as well as m > 20 for three-bolted joint, which demonstrates that m can be applied to effectively calculate the actual influencing area of bolt.

Parametric modeling and updating for bolted joints of aeroengine casings

2016 ◽  
Vol 230 (16) ◽  
pp. 2940-2951 ◽  
Author(s):  
Xue Zhai ◽  
Cheng-Wei Fei ◽  
Jian-Jun Wang ◽  
Xing-Yu Yao
Keyword(s):  
Thin Layer ◽  
Model Updating ◽  
Parametric Modeling ◽  
Bolted Joints ◽  
Maximum Relative Error ◽  
Fe Model ◽  
Fe Modeling ◽  
Bolted Joint ◽  
Static Stiffness ◽  
Fe Model Updating

To establish accurate finite element (FE) model of bolted joint structures of aeroengine stator system (casings), this work implements the parametric FE modeling and updating of bolted joints of aeroengine stator system with multi-characteristic responses (multi-object). Firstly, the parametric FE modeling approach of bolted joint structure was developed based on the thin layer element method. And then the FE model updating thought of aeroengine stator system was developed based on the probabilistic analysis method. Finally, the parametric modeling and updating of the bolted joints of aeroengine stator system with multi-characteristic responses was completed by the optimization iteration calculation of objective function based on the proposed methods and the static stiffness testing data. Through the parametric modeling of bolted joint structures based on the thin layer method, the complexity of FE model of aeroengine casings with many bolted joint structures is reduced. As shown in the FE model updating of casings with multi-characteristic responses analysis, the static stiffness from the updated model are very close to the test data, in which the maximum relative error decreases to 3.9% from 30.52% and the others are less than 3%, so that the design precision of aeroengine stator system with the many and wide variety of bolted joints gets a great improvement. Moreover, the proposed methods of parametric modeling and model updating for multi-characteristic responses are validated to be effective in the simulation and equivalent of the mechanical characteristics of bolted joints in complex systems like aeroengine stator system.

Gasket Catastrophic Failure Modes

2018 ◽  
Author(s):  
Warren Brown ◽  
Nathan Knight
Keyword(s):  
Failure Modes ◽  
The Body ◽  
Bolted Joints ◽  
Test Results ◽  
Bolted Joint ◽  
Critical Factors ◽  
Test Set ◽  
Set Up ◽  
Industry Experience ◽  
Corrugated Metal

This paper outlines how, under certain scenarios, gaskets may catastrophically blow out of pressure boundary bolted joints. Supporting the observations on industry occurrences of such failures, attempts were made to re-create one of the failure modes in a test set-up. The tests managed to highlight critical factors for blow out of Corrugated Metal with Covering Layer (CMCL) gaskets. A summary of the known industry experience with gasket blow out and the CMCL test results are included in the body of this paper. Conclusions and recommendations for considering these failure modes in both pressure boundary bolted joint design and also risk assessment are made.

EXPERIMENTAL ANALYSIS OF THE LOAD CAPACITY AND REPEATABILITY OF PRELOADED BOLTED JOINTS

Tribologia ◽  
2020 ◽  
Vol 292 (4) ◽  
pp. 71-77
Author(s):  
Marcin Szczęch ◽  
Wojciech Horak
Keyword(s):  
Axial Force ◽  
Experimental Analysis ◽  
Load Capacity ◽  
Bolted Joints ◽  
Test Results ◽  
Bolted Joint ◽  
Breaking Force ◽  
Torque Wrench ◽  
The Common ◽  
Lubrication Conditions

Bolted joints are among the most widespread and most important detachable connections used in mechanical engineering and construction. The common use of this connection group is reflected in the variety of types of screw connections. There are several geometric and material factors, and consequently tribological ones, that determine the load capacity and, which is often of key importance, the repeatability of the bolted joint. The paper presents a description of the test stand and the test results of preloaded bolted joints for different lubrication conditions. The measured parameters were the breaking force value of a double lap bolted joint and its repeatability and the axial force repeatability of the bolts tightened by an electronic torque wrench.

Optimized Bolt Tightening Sequences in Bolted Joints Using Superelement FE Modeling Technique

2018 ◽  
Author(s):  
Ibai Coria ◽  
Iñigo Martín ◽  
Hakim Bouzid ◽  
Iker Heras ◽  
Josu Aguirrebeitia
Keyword(s):  
Elastic Interaction ◽  
Bolted Joints ◽  
Fe Modeling ◽  
Bolted Joint ◽  
Assembly Time ◽  
Load Variations ◽  
Computational Costs ◽  
Bolt Preload ◽  
Optimization Methodology ◽  
Number Of Passes

A lot of effort is put to achieve bolt preload uniformity during the assembly process of offshore bolted joint connections resulting in potentially high economic costs and project delays. The complexity of this operation is due to the effect of the elastic interaction between the different joint elements which causes load variations of adjacent bolts whenever a bolt is tightened. As a consequence, it is difficult to achieve a uniform target load in the bolts. In order to avoid this phenomenon, tightening sequences of a large number of passes are usually carried out until a uniform target load is achieved. This solution is neither practical nor efficient when treating hundreds or even thousands of bolted joints due to the large assembly time needed. Several methods were developed to study the effect of the elastic interaction and minimize the assembly time. These methods usually predict the loss of load of every bolt during the tightening sequence, and thus calculate the tightening loads that will provide a uniform final load at the end of the sequence. As a result, an optimized tightening sequence is achieved, which provides a uniform final load distribution in only one or two tightening passes. However, several complex and costly analyses are previously necessary for such purpose. Based on these traditional methods, this paper presents a new and more efficient optimization methodology to achieve assembly bolt load uniformity. The method is based on the use of superelement technique and is capable of producing similar results with computational costs reduced by 30 times as compared to the more conventional Finite Element (FE) modeling. The results were satisfactorily validated with the latter as well as with tests conducted on a NPS 4 class 900 bolted joint.

Finite Element Study of Double-Gasket Bolted Joint Connection for Different Gaskets and Bolt Torques

2017 ◽  
Author(s):  
Reza Ghafouri-Azar ◽  
Rosha Banan ◽  
Miodrag (Mike) Stojakovic
Keyword(s):  
Finite Element ◽  
Bolted Joints ◽  
Analysis Tool ◽  
Fe Model ◽  
Fe Modeling ◽  
Bolted Joint ◽  
Modeling And Analysis ◽  
Joint Connection ◽  
Size Type ◽  
The Right

In order to understand the behavior of bolted joints and select a right size, type and gasket load combination, a detailed analysis tool is very helpful. However, the modeling and analysis of a bolted joint connection is a complicated, complex process; particularly if multiple parts are considered in the Finite Element (FE) modeling. Analysis results are often sensitive to bolt pre-torque, gasket type, gasket thickness and other challenges of Finite Element (FE) modeling. In addition, often credible and reliable gasket deflection-load data are not readily available. The bolted joint under study was a double-gasket joint with inner gasket leakoff. The joint has leaked on several occasions, sometimes after several years of service due to warmup/cooldown cycling and sometimes immediately after installation and pressurization. A 3-D FE model was developed for assembly of tubesheet, bolt, two inner and outer gaskets, and vessel cover. Different cases were studied by changing gasket load-deflections for different gasket materials, gasket thicknesses and bolt loads. The outcome of the analyses was used to predict the behavior of bolted joints and understand the root cause of leakage. The results provided guidance for choosing the right combination of bolt pre-torque and gasket type.

Gaskets and Bolted Joints

1950 ◽  
Vol 17 (2) ◽  
pp. 169-179
Author(s):  
Irving Roberts
Keyword(s):  
Elastic Recovery ◽  
Fluid Pressure ◽  
Design Procedure ◽  
Bolted Joints ◽  
Approximate Theory ◽  
Bolted Joint ◽  
Recovery Curves ◽  
Internal Fluid ◽  
Asme Code ◽  
System Equations

Abstract This paper consists of a study of the loading requirements of gaskets in bolted joints, with the object of developing a rational basis for design of such joints. Starting with an analysis of gasket conditions for tightness, the gasket factor m is defined, and its variation with initial gasket stress and gasket width is predicted. These trends are confirmed by a survey of the available literature data. In a bolted joint, gasket stress becomes a function of the elastic constants of the system. Equations are derived to predict gasket and bolt stresses resulting from application of internal fluid pressure, and typical elastic recovery curves for an asbestos gasket are presented. Consideration is given to the effect of gasket creep in a bolted joint, and to the problem of distribution of bolt load, for which an approximate theory is derived. On this basis, defects in the ASME Code are pointed out, and a tentative new design procedure is proposed. Finally, a summary of data which should be obtained for use with the new design procedure is given.

Representation of bolted joints in a structure using finite element modelling and model updating

2020 ◽  
Vol 14 (3) ◽  
pp. 7141-7151 ◽  
Author(s):  
R. Omar ◽  
M. N. Abdul Rani ◽  
M. A. Yunus
Keyword(s):  
Finite Element ◽  
Dynamic Behaviour ◽  
Model Updating ◽  
Complex Structure ◽  
Bolted Joints ◽  
Model Parameters ◽  
Fe Model ◽  
Bolted Joint ◽  
Fe Modelling ◽  
Joint Structure

Efficient and accurate finite element (FE) modelling of bolted joints is essential for increasing confidence in the investigation of structural vibrations. However, modelling of bolted joints for the investigation is often found to be very challenging. This paper proposes an appropriate FE representation of bolted joints for the prediction of the dynamic behaviour of a bolted joint structure. Two different FE models of the bolted joint structure with two different FE element connectors, which are CBEAM and CBUSH, representing the bolted joints are developed. Modal updating is used to correlate the two FE models with the experimental model. The dynamic behaviour of the two FE models is compared with experimental modal analysis to evaluate and determine the most appropriate FE model of the bolted joint structure. The comparison reveals that the CBUSH element connectors based FE model has a greater capability in representing the bolted joints with 86 percent accuracy and greater efficiency in updating the model parameters. The proposed modelling technique will be useful in the modelling of a complex structure with a large number of bolted joints.

Sign in / Sign up

Export Citation Format

Share Document