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.

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.

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.

Elasto-Plastic Stress Analysis of the Characteristics for T-Flange Bolted Joints Under External Loading

2013 ◽  
Author(s):  
Yuya Omiya ◽  
Toshiyuki Sawa
Keyword(s):  
Stress Analysis ◽  
Tensile Load ◽  
Bending Moment ◽  
Bolted Joints ◽  
External Loading ◽  
Load Factor ◽  
Bolted Joint ◽  
Bearing Surface ◽  
Permanent Set ◽  
Bolt Preload

In designing bolted joints, it is necessary to know the contact stress distributions in bolted joints. Recently, high strength bolts have been used with a higher bolt preload. As the results, the permanent set occurs sometimes at the bearing surfaces of clamped parts in the bolted joint. In addition, when external loads such as tensile loads, transverse loads and bending moments are applied to the bolted joint, the permanent set can be extended at the bearing surfaces. As the permanent set increases, the reduction in the bolt preload increases. Thus, it is important to estimate the reduction in the bolt preload from the reliability stand point. However, no study on the permanent set at the bearing surface under the external loading taking into account the bending moment has been carried out. In this study, the stress distribution and the extension of the permanent set at the bearing surface of the T-flange bolted joint under the external tensile loading are examined using Finite Element Method (FEM), where two T-flanges are clamped with a hexagon bolt and a nut. Using the obtained results, an increment in the axial bolt force and the reduction in the bolt preload are estimated. For verification of the FEM stress analysis, the load factor of hexagon bolt was measured. The FEM results of the load factor (the ratio of the increment in the axial bolt force to the tensile load) and the axial bolt force are in a fairly good agreement with the experimental results.

FEM Stress Analysis of the Characteristics of Bolted Joints Under External Loadings (In the Case Where Two Hollow Cylinders Are Clamped)

2011 ◽  
Author(s):  
Toshiyuki Sawa ◽  
Kengo Kuwaki ◽  
Yukio Morozumi ◽  
Masahiko Okumura
Keyword(s):  
Stress Analysis ◽  
Theory Of Elasticity ◽  
Bolted Joints ◽  
External Loading ◽  
Load Factor ◽  
Bolted Joint ◽  
Bearing Surface ◽  
Permanent Set ◽  
Bolt Preload ◽  
Hollow Cylinders

In designing bolted joints, it is necessary to know the stress distributions in bolted joints. Recently, high strength bolts have been used with a higher bolt preload. As the results, the permanent set occurs sometimes at the bearing surfaces of clamped parts in a bolted joint. In addition, when an external load is applied to the bolted joint, the permanent set can be extended at the bearing surfaces. As the permanent set increases, the reduction in the bolt preload increases. Thus, it is important to estimate the reduction in the bolt preload from the reliability stand point. However, no study on the permanent set at the bearing surface under the external loading has been carried out. In this study, the stress distribution and the extension of the permanent set at the bearing surface of the bolted joint under the external tensile loading are examined using finite element Method (FEM), where two hollow cylinders are clamped with a hexagon bolt and a nut. The spring constants for the hexagon bolt and the clamped parts are analyzed using an axi-symmetrical theory of elasticity. Using the obtained results, an increment in the axial bolt force and the reduction in the bolt preload are estimated. For verification of the FEM stress analysis, the load factor of hexagon bolt was measured. The FEM results of the load factor (the increment in the axial bolt force) and the axial bolt force are in a fairly good agreement with the experimental results and the reduction of the axial bolt force. Finally, discussion is made on the appreciate bolt preload.

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.

A Tetraparametric Metamodel for the Simulation and Optimization of Bolting Sequences for Wind Generator Flanges

2010 ◽  
Author(s):  
Mikel Abasolo ◽  
Josu Aguirrebeitia ◽  
Rafael Avile´s ◽  
Igor Fernandez de Bustos
Keyword(s):  
Computational Cost ◽  
Nonlinear Behavior ◽  
Elastic Interaction ◽  
Bolted Joints ◽  
Experimental Measurements ◽  
Assembly Process ◽  
Simulation And Optimization ◽  
Wind Generator ◽  
Bolt Preload ◽  
Contact Surfaces

In the bolted joints of wind generator flanges there is a gap between the contact surfaces of the flanges. This involves a nonlinear behavior of the system during the tightening sequence of the joint. This phenomenom, in addition with the elastic interaction, makes it difficult to achieve a uniform bolt preload at the end of the assembly process. This work presents a methodology which, based on a metamodel created for such purpose, enables the optimization of the tightening sequence; i.e. it calculates the load to be applied to each bolt in order to achieve a desired uniform preload at the end of the tightening sequence. This optimization is done with a minimum computational cost, avoiding costly experimental measurements or nonlinear FE simulations. Besides, the methodology also takes into account that the load for any bolt must be below its yield point, and therefore calculates a two-pass sequence if necessary.

FEM Contact Stress Analysis at the Bearing Surfaces in Bolted Joints With Washer Under Tensile Loadings

2013 ◽  
Author(s):  
Toshiyuki Sawa ◽  
Yuya Omiya ◽  
Kengo Kuwaki
Keyword(s):  
Contact Stress ◽  
External Load ◽  
High Reliability ◽  
High Strength ◽  
Bolted Joints ◽  
Load Factor ◽  
Stress Distributions ◽  
Bolted Joint ◽  
Bolt Preload ◽  
Plastic Displacement

High strength bolts with washers are utilized widely for high reliability. The usage of the high strength bolts enables higher bolt preload, thus the contact stress at the bearing surfaces increase. When a bolted joint is under external axial load W, the axial bolt force increases by Ft and the contact stress increases at the bearing surface. This may cause the plastic deformation and a decrease in the axial bolt force. Consequently, it is important to determine the initial axial bolt force (bolt preload) considering external load. In this paper, The characteristics of hollow cylindrical bolted joints with plain washers under external tensile loadings are analyzed using elasto-plastic FEM such as the contact stress distributions, plastic displacement (permanent set) at the bearing surfaces and the load factor Φ = (Ft/W). The effect of thickness of the plain washers on the contact stress distributions and the plastic displacements are clarified. It is found that the effect of the plain washer specified in JIS B 1256 is small on the contact stress distributions and the plastic displacements. Also, the effect of the external load on the changes in the contact stress distributions and the plastic displacements at the bearing surfaces using the values of load factor is observed to be small. The prediction for the reduction in axial bolt force was compared with the experiment. As a result, it was found that a higher bolt preload shows a small reduction in axial bolt force.

scholarly journals Experimental investigation on self-loosening of a bolted joint under cyclical temperature changes

2021 ◽  
Vol 13 (8) ◽  
pp. 168781402110394
Author(s):  
Oybek Maripjon Ugli Eraliev ◽  
Yi-He Zhang ◽  
Kwang-Hee Lee ◽  
Chul-Hee Lee
Keyword(s):  
Experimental Investigation ◽  
Stainless Steel ◽  
Temperature Variation ◽  
The Self ◽  
Experimental Results ◽  
Bolted Joints ◽  
Bolted Joint ◽  
Temperature Changes ◽  
Threaded Fasteners ◽  
Bolt Preload

The most commonly used part in engineering fields is threaded fasteners. There are a lot of advantages of fasteners. One of them is that they can be easily disassembled and reused, but a bolted joint can loosen easily when a transversal load is applied. The clamp load of a bolted joint can also loosen slowly when subjected to repeated temperature changes. This paper presents an experimental investigation of the self-loosening of bolted joints under cyclical temperature variation. Experiments are carried out under several cyclical temperature changes with different bolt preloads. Rectangular threaded bolted joints with M12 × 1.75 bolts and nuts are tested in a specially designed testing apparatus. Material of bolt, nut, and plates is a stainless steel. The experimental results show that the high initial bolt preload may prevent the joint from self-loosening and the bolted joint has loosened significantly in the first cycle of temperature changes. From this investigation, the loosening of the bolted joint can be considered as a first stage self-loosening.

scholarly journals Bolted Joint Preload Distribution from Torque Tightening

2021 ◽  
Vol 71 (2) ◽  
pp. 329-342
Author(s):  
Welch Michael
Keyword(s):  
Friction Coefficient ◽  
Static Friction ◽  
Bolted Joints ◽  
Dynamic Friction ◽  
Bolted Joint ◽  
Classical Analysis ◽  
Joint Design ◽  
Static Friction Coefficient ◽  
Bolt Preload ◽  
Torque Wrench

Abstract The purpose of this paper is to develop an understanding of how bolt preloads are distributed within a joint as each bolt is tightened in turn by the use of a calibrated torque wrench. It discusses how the order that the joints nuts/bolts are tightened can affect the final bolt preload. It also investigates the effect on incrementally increasing the bolt preload through a series of applications of the controlled torque tightening sequence. Classical analysis methods are used to develop a method of analysis that can be applied to most preloaded bolted joints. It is assumed that the static friction coefficient is approximately 15% less than the dynamic friction. It is found that the bolt preload distribution across the joint can range from slightly above the target preload to significantly less than the target preload. The bolts with a preload greater than the target preload are found to be those tightened towards the end of the tightening sequence, usually located close to the outer edges of the joint’s bolt array. The bolts with a preload less than the target preload are those tightened early in the tightening sequence, located centrally within the joints bolt array. The methods presented can be used to optimise bolted joint design and assembly procedures. Optimising the design of preloaded bolted joints leads to more efficient use of the joints.

A METHOD TO REDUCE THE NUMBER OF ASSEMBLY TIGHTENING PASSES IN BOLTED FLANGE JOINTS

2021 ◽  
pp. 1-29
Author(s):  
Linbo Zhu ◽  
Abdel-Hakim Bouzid ◽  
Jun Hong
Keyword(s):  
Oil And Gas ◽  
Elastic Interaction ◽  
Pressure Vessels ◽  
Flange Joint ◽  
Linear Elastic ◽  
Bolt Preload ◽  
Leakage Failure ◽  
Bolted Flange ◽  
Number Of Passes ◽  
Nuclear Applications

Abstract Bolted flange joints are extensively used in the pressure vessels and piping equipment and rotating machinery. Achieving a uniform bolt preload during the assembly process is particularly important to satisfy in bolted flange connection of oil and gas and fossil and nuclear applications. However, it is a very difficult task when tightening all bolts one by one due to elastic interaction. The risk of leakage failure under service loading is consequently increased because of the scatter of the bolt preload. This paper takes the advantage of a developed analytical model based on the theory of circular beams on linear elastic foundation that simulate the elastic interaction of bolted flange joints to reduce the number of passes while achieving bolt load uniformity. As such, a novel methodology for the optimization of the tightening sequence strategies is suggested to obtain uniform bolt tension while avoiding yield under minimum tightening passes. In this regards, based on the target preload, the load applied to each bolt in each pass is suggested. The developed approach is validated both numerically using FEM (finite element method) and experimentally on a NPS 4 class 900 welding neck flange joint using the criss-cross tightening and sequential patterns.

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