FEM Stress Analysis and the Load Factor of Bolted Joints Consisting of Dissimilar Hollow Cylinders Under Tensile Loads

2017 ◽  
Author(s):  
Shunichiro Sawa ◽  
Mitsutoshi Ishimura ◽  
Yasuhisa Sekiguchi ◽  
Toshiyuki Sawa
Keyword(s):  
Hollow Cylinder ◽  
Design Method ◽  
Tensile Load ◽  
Bolted Joints ◽  
Load Application ◽  
Load Factor ◽  
Application Point ◽  
Bolt Preload ◽  
Hollow Cylinders ◽  
Bolt Diameter

In designing a bolted joint consisting of dissimilar hollow cylinders, the load factor (the ratio of an increment in axial bolt force to an external tensile load) is important. In the present paper, the effect of the load application point, the ratio b/a of the outside diameter to the inside diameter of dissimilar hollow cylinders, Young’s modulus ratio between the dissimilar hollow cylinders on the load factor and the interface stress distribution are examined using FEM calculations. As a result, it is found that the values of the load factor decrease as the ratio b/a increases and the positions where the load application point approaches the interfaces while the value of the load factor is independent of the bolt preload. In addition, it is found that the value of the load factor is less than 0.1 for steel and steel hollow cylinder joints, it is less than 0.2 for aluminum and aluminum hollow cylinder joints and it is less than 0.15 for aluminum and steel hollow cylinder joints while the material of bolt is steel in the present study. For verification of the FEM calculations, experiments to measure the load factor and a load when the interfaces start to separate were carried out. The FEM results are in a fairly good agreement with the experimental results. Finally, based on the obtained results, a design method for bolted joints with dissimilar hollow cylinders is demonstrated for determining the nominal bolt diameter and the bolt strength grade.

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.

Finite-Element Analysis of the Load Factor and Design for Bolted Circular Flange Joints Consisting of Dissimilar Clamped Parts Under Tensile Loadings

2019 ◽  
Author(s):  
Shunichiro Sawa ◽  
Yasuhisa Sekiguchi ◽  
Toshiyuki Sawa
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Design Method ◽  
Bolted Joints ◽  
Load Factor ◽  
Bending Stress ◽  
Element Analysis ◽  
Bolt Stress ◽  
Bolt Diameter ◽  
Circle Diameter

Abstract The load factor for bolted circular flange joints where two dissimilar material (steel-aluminum) of circular flanges are clamped by a lot of bolts and nuts under external tensile loadings is examined newly using Finite Element analysis. Furthermore, the effects of the bolt pitch circle diameter D and number of tightened bolts N on the load factor and a load when the interfaces start to separate are examined. The value of the load factor for steel-aluminum circular flange joint is a little bit larger than that for steel-steel circular flange joints and it increases as the value of D decreases. In addition, it decreases as the value of N increases. A maximum bending stress is also found newly about 5% larger than the bolt stress due to the load factor. The experiments to measure the load factor, the maximum bending bolt stress and a load when the interfaces start to separate were carried out. The FEM results are fairly coincided with the experimental results. Finally, based on the obtained load factor, a design method for bolted joints with dissimilar circular flanges is demonstrated for determining the nominal bolt diameter and the bolt strength grade and the effect of bolt number N is examined. It is found that the contact stress at the bearing surfaces of aluminum circular flange is critical and it is shown that washers are needed in some cases.

New Design Formula for Bolted Joints Under Tensile Loads

2013 ◽  
Author(s):  
Toshiyuki Sawa ◽  
Yuya Omiya
Keyword(s):  
Tensile Load ◽  
Theoretical Background ◽  
Theory Of Elasticity ◽  
Experimental Results ◽  
Spring Constant ◽  
Load Factor ◽  
Outer Diameter ◽  
Hollow Cylinders ◽  
The Difference ◽  
Good Agreement

In designing a bolted joint, it is important to estimate an increment in axial bolt force when an external tensile load is applied to an assembly. The ratio of the increment Ft in the axial bolt force to the external tensile load W is called the load factor φ(= Ft/w). The formula φ = Kt/(Kt+Kc) proposed by Thum has been applied for estimating the value of the load factor φ, where Kt is the spring constant of bolt-nut system and Kc is the compressive spring constant of clamped parts. It has been found that the value of the load factor varies with the position of load application to the assembly. Then, a method to compensate Thum’s formula was proposed. However, this compensation is made empirically and the theoretical background is not made clear. In this paper, the concept of the tensile spring constant Kpt for clamped parts is introduced newly when an external load is applied to the outer circumference of clamped parts (hollow cylinders) and a method for estimating the value of the load factor exactly is proposed by using Kpt. The value of Kpt is analyzed using an axisymmetric theory of elasticity. For verification of the proposed method, experiments were carried out to measure the load factor. A fairly good agreement is seen between the analytical and the experimental results of the values of the load factor while the values of the load factor obtained from Thum’s formula were so different with the experimental results. The reason why the difference in the values of the load factor is substantial between values and the values obtained from Thum’s formula is elucidated. It is found that the value of the load factor decreases as the outer diameter of the hollow cylinder increases and the as thickness of the clamped parts decreases. In addition, FEM calculations for the load factor are carried out. The FEM results are in a fairly good agreement with the theoretical results.

An Estimation of the Load Factor and Sealing Performance Evaluation for Bolted Pipe Flange Connections With Gaskets Under Internal Pressure

2017 ◽  
Author(s):  
Toshiyuki Sawa ◽  
Koji Sato
Keyword(s):  
Internal Pressure ◽  
Plate Theory ◽  
Design Method ◽  
Spring Constant ◽  
Leak Rate ◽  
Load Factor ◽  
Real Rate ◽  
Simple Method ◽  
Gas Leakage ◽  
Bolt Preload

In designing bolted pipe flange connections with gaskets, It is necessary to know the actual residual gasket contact stress in the connections under internal pressure. However, the actual reduced gasket stress in the connection has not been sufficiently estimated. In estimating the actual residual contact gasket stress more precisely, it is needed to know the load factor (the ratio of an increment in axial bolt force to the axial force due to the internal pressure per bolt) of the connections with gaskets. The new formula for obtaining the load factor was proposed by one of the authors using the tensile spring constant Ktg and the compressive spring constant Kcg, while the spring constant of bolt-nut system is designated as Kt. In the present paper, for estimating the load factor of the connections with gaskets, the circular plate theory is applied for obtaining the values of Kcg and Ktg and then the load factor is obtained for pipe flanges specified JIS 10K flanges and ASME B 16.5 flanges. The obtained results are in a fairly good agreement with the FEM results. Using the obtained load factor for the connections, a design method is demonstrated taking account of the allowable leak rate. Using the residual contact gasket stress and the fundamental gasket leak rate, an amount of gas leakage is predicted. The predicted amount of gas leakage for 3” and 20” pipe flange connections is fairly coincided with the experimental results and the FEM results. In addition, a design method for determining the bolt preload for a give allowable real rate is demonstrated using the simple method for obtaining the load factor.

The Load Factor and Permanent Set at the Bearing Surfaces in Hollow Cylindrical Bolted Joints Under External Axial Loads

2011 ◽  
Author(s):  
Yukio Morozumi ◽  
Masahiko Okumura ◽  
Toshiyuki Sawa ◽  
Kengo Kuwaki
Keyword(s):  
Contact Stress ◽  
High Reliability ◽  
Fem Analysis ◽  
High Strength ◽  
Theory Of Elasticity ◽  
Bolted Joints ◽  
Load Factor ◽  
Axial Forces ◽  
Bolt Preload ◽  
Plastic Displacement

High strength bolts are utilized widely for high reliability and to reduce the weight of the bolted joints. The usage of the high strength bolts may increase the contact stress at the bearing surfaces. 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, (load factor) Φ = (Ft/W) is investigated by axi-symmetrical theory of elasticity, FEM analysis and experiments. The results obtained from these methods showed in a fairly good agreement. Then the contact stress distributions and the plastic displacement distributions under external loads were studied for three different initial axial forces by elasto-plastic FEM analyses. The prediction for the reduction in axial bolt force, which is obtained by multiplying the setting factor by the mean plastic displacement, was compared with the experiment. As a result, it was found that a higher bolt preload shows a small reduction in axial bolt force.

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.

FEM Stress Analysis and Design for Bolted Circular Flange Joints Under Tensile Loading

2015 ◽  
Author(s):  
Shunichiro Sawa ◽  
Mitsutoshi Ishimura ◽  
Yasuhisa Sekiguchi ◽  
Toshiyuki Sawa
Keyword(s):  
Design Method ◽  
Tensile Loading ◽  
Theory Of Elasticity ◽  
Load Factor ◽  
Bolted Joint ◽  
Analysis And Design ◽  
Bolt Preload ◽  
Experimental Values ◽  
New Formulation ◽  
Circle Diameter

In designing a bolted joint, it is necessary to know a ratio of increment Ft in axial bolt force to an external tensile loading W, that is, the load factor φ=Ft/W. In our previous paper, the new formulation for obtaining the value of the load factor φ for a bolted joint in which two hollow cylinders and two T-shape flanges were clamped was proposed by introducing the tensile spring constant Kpt for clamped parts. Then, the values of the load factor of bolted joint obtained from our formulation are shown to be in a fairly good agreement with the experimental values. In the present paper, the mechanical characteristics of bolted circular flange joints are analyzed by Finite Element Method (FEM) and axi-symmetrical theory of elasticity such as the load factor, the contact stress distributions at the interfaces and a load when a separation occurs at the interfaces. For verification of the analyses, experiments were carried out to measure the load factor, the maximums stress and a load when a separation occurs. In the analyses, the effect of the bolt pitch circle diameter D on the value of the load factor is examined. The numerical results of the load factor are fairly coincided with the experimental results. As the results, it is found that the load factor decreases as the bolt pitch circle diameter D increases and that the value of the load factor is less than 0.1. It is also found that the load when the interfaces start to separate decreases as the value of D increases. Based on the obtained results, a design method for the bolted circular flange joints under tensile loadings is demonstrated, that is, the method how to determine the bolt nominal diameter, bolt strength grade, the bolt preload for the external tensile loading are described.

scholarly journals Dynamic Analysis and Looseness Evaluation of Bolted Connection Under Vibration of Machine Tools

2021 ◽  
Author(s):  
Wenxiang Xu ◽  
Qiang Cheng ◽  
Congbin Yang ◽  
Ying Li
Keyword(s):  
Dynamic Analysis ◽  
Machine Tools ◽  
Design Method ◽  
Bolted Joints ◽  
Quadratic Regression ◽  
Bolted Connection ◽  
Bolt Preload ◽  
Attenuation Rate ◽  
Experimental Design Method ◽  
Analytical Result

Abstract Bolted connections are widely used in the machine tool manufacturing and equipment. As it is well known, bolt preload will be attenuated by the vibration of machine tools, which will degenerate the working life of machine tools. In this paper, a new experimental design method is introduced into the study on bolt preload attenuation: the quadratic general rotary unitized design. The dynamic analysis of the bolted connection is carried out based on a finely fragmented numerical model to interpret the generation of fretting slip and the reason for the loosening of bolts. The alternating load cyclic vibration test, implemented on the bolted joints, can provide the vibration response under the influence of different working factors. Statistical test and analysis are performed on the quadratic regression mathematical model of the bolt preload attenuation, and the principal working factor that affecting the bolt preload attenuation under vibration can be obtained. Based on the analytical result, the combination of the working factors at the lowest bolt preload attenuation rate, which can effectively slow the bolt looseness, is investigated. The results of this study can provide an experimental basis for improving the machining stiffness of machine tools.

A Normalized Stress of Pull-Out Action on Bolted Joints Under Eccentric Load

2018 ◽  
Author(s):  
Makoto Imura ◽  
Takayuki Koyama ◽  
Motonobu Iizuka ◽  
Takayuki Suzuki
Keyword(s):  
Axial Direction ◽  
Bolted Joints ◽  
Eccentric Load ◽  
Stress Evaluation ◽  
Centrifugal Load ◽  
Pull Out ◽  
Bolt Preload ◽  
Structural Interface ◽  
Bolt Stress ◽  
Bolt Diameter

Our objective is to evaluate precisely a life-cycle of bolted joints under an eccentric load against a bolt axis. Many approaches to achieve the objective based on a lot of theories and practices have been proposed so far [1–12]. As we can refer from their approaches, the opening of the structural interface between clamped plates of bolted joints occurs by the eccentric load, which is over a bolt preload, and then the opening gradually propagates as the eccentric load increases. In the case, nonlinearity appears remarkably on the tensional and bending stress of bolts in the axial direction. In addition to the above, the axial bolt stress larger than expected occurs due to the principle of leverage depending on the load position and the bolted joints layout in the early phase of the pull-out action. Accordingly, the stress evaluation of bolted joints under the eccentric load is very important in order to ensure the safety of industrial machines. If dimensionless quantities of the bolt stress are found out considering the influence of the structural opening and the load eccentricity, we can have a few advantages as follows. First, bolt stress evaluations can be conducted by easily converting the dimensionless quantities of the bolt stress to the physical dimension quantities in a lot of cases where the bolt preload and the load eccentricity are different. Second, the number of times of verification tests can be reduced. We are developing a lot of industrial machines which have bolted joints used under eccentric load. In such development [13], bolt stress analyses are usually conducted under the combinations of the following conditions: (i) tapped thread joints, (ii) thin clamped plates than the bolt diameter, (iii) large eccentric loads, (iv) permitting the opening of the structural interface. Therefore, we propose a concept of a normalized bolt stress considering the effect of the structural opening and the load eccentricity. We validated this concept through theoretical studies, finite element analyses, and experiments under the direct load and the centrifugal load. As a result, the dimensionless quantities of the bolt stress caused by the bolt preload and a lever ratio of bolted joints under combined conditions was determined in this study. We can easily evaluate the bolt stress by simple conversions in a lot of cases in which the bolt preload and the load eccentricity differ.

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