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 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.

Stress Analysis of Bolted Joints of Flat Cover With Tap Bolts in a Pressure Vessel

1999 ◽  
Author(s):  
Toshiyuki Sawa ◽  
Akihiro Karasawa ◽  
Akihiro Shimizu
Keyword(s):  
Contact Stress ◽  
Pressure Vessel ◽  
Three Dimensional ◽  
Bending Moment ◽  
Theory Of Elasticity ◽  
Contact Stresses ◽  
Ultrasonic Waves ◽  
Bolted Joints ◽  
Load Factor ◽  
Sealing Performance

Abstract Bolted joints with gaskets have been designed empirically, and the sealing performance is not made clear by theoretical analyses because the contact stress distribution between the gasket and the flanges are not clarified when an internal pressure is applied to the joint. The present paper, discusses the distribution of contact stresses in the bolted joints fastened with tap bolts, when a clamped part with a gasket is the cover of a pressure vessel and is a circular flange. The distribution of contact stresses is analyzed as a three-body contact problem, using the three-dimensional theory of elasticity. Moreover, the contact stress is measured by means of ultrasonic waves. In addition, the load factor (the ratio of an increment of the axial bolt force to an external load) and the maximum stress caused in bolts are analyzed taking into account the bending moment. For verification, experiments are carried out, and the analytical results are found in fairly good agreement with the experimental ones. It was found that the sealing performance was improved when Young’s modulus of the gaskets was decreased and the gasket thickness was increased.

FEM Contact Stress Analysis at the Bearing Surfaces in Bolted Joints Under External Loadings

2018 ◽  
Author(s):  
Atsushi Shirakawa ◽  
Toshiyuki Sawa ◽  
Tomohiro Naruse
Keyword(s):  
Stress Analysis ◽  
Contact Stress ◽  
Permanent Deformation ◽  
Bolted Joints ◽  
External Loading ◽  
Bearing Surface ◽  
Stress Strain ◽  
Bolt Preload ◽  
Plastic Displacement ◽  
Critical Contact

The higher bolt preload is better for increasing the integrity of bolted joints. However, the bearing surface could be permanently deformed with too much high preload and the bolt preload decreases with permanent deformation. Thus, an upper limit of bolt preload per contact area at the bearing surfaces, which is called as the critical contact stress, must be examined for various materials of clamped parts. In the previous research, the critical contact stresses were obtained by compressing a cylindrical bar. However, the contact stress distribution of compressing a cylindrical bar is much different to that of an actual bolted joint. In addition, a lot of previous researches used the stress-strain curves under tensile loadings for analyzing the contact stress distributions at the bearing surfaces. In this study, the Finite Element Method is used for contact stress analysis at the bearing surfaces in clamped bolted joints under external loading. Various materials for clamped part are chosen such as steel, aluminum alloy, cast iron and stainless steel. Firstly, the stress-strain curves for the above materials were measured under compressive loadings. The differences in the stress-strain curves under tensile and compressive loadings are evaluated with the above materials. Next, using actual bolts, the displacements at the bearing surfaces in cylindrical clamped parts consisting of the above materials were measured. Finally, elasto-plastic FEM contact stress analyses are carried out for analyzing the plastic displacements at the bearing surfaces under compressive loadings. The mean displacement at the bearing surfaces are compared with those obtained from the experiments for each material. The FEM results of the relationship between the contact stress and the plastic displacement at the bearing surface are in a fairy good agreement with the experimental results for each clamped material. In addition, the critical contact stress at the bearing surface is discussed for each material. Two proposals for the critical contact stress at the bearing surface are described and compared with the critical contact stress of VDI2230.

Stress Analysis and the Characteristics of T-Shape Bolted Joints Under Tensile Loadings

2005 ◽  
Author(s):  
Toshiyuki Sawa ◽  
Seiichi Hamamoto
Keyword(s):  
Bending Moment ◽  
Theory Of Elasticity ◽  
Bolted Joints ◽  
Load Factor ◽  
Two Dimensional ◽  
Bolted Joint ◽  
Dimensional Theory ◽  
Matching Method ◽  
Point Matching ◽  
Bolt Stress

In designing a bolted joint, it is important to examine the interface stress distribution (clamping effect) and to estimate the load factor, that is the ratio of an additional axial bolt force to a load. In order to improve the clamping effect raised faces of the interface have been used. But these interfaces in bolted joints have been designed empirically and the theoretical grounds are not made clear. In the present paper, in the case of T-shaped flanges with raised faces the clamping effect is analyzed by a two-dimensional theory of elasticity and the point matching method. Then, the load factor is analyzed. Moreover, with the application of the load a bending moment is occurred in bolts and the stress is added due to this bending moment. The bending moment in the bolt is also analyzed. In order to verify these analyses experiments to measure the load factor and the maximum bolt stress were carried out. The values of the load factor and the load when interface start to separate are compared with those of the joints with flat-faces. The analytical results are in fairly good agreements with the experimental ones.

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.

A Stress Analysis of a Taper Hub Flange With a Bolted Flat Cover

1997 ◽  
Vol 119 (3) ◽  
pp. 293-300
Author(s):  
T. Sawa ◽  
N. Higurashi ◽  
T. Hirose
Keyword(s):  
Stress Distribution ◽  
Contact Stress ◽  
Theory Of Elasticity ◽  
Load Factor ◽  
Bolted Connection ◽  
Body Contact ◽  
The Moment ◽  
Flat Cover ◽  
The Relationship ◽  
Contact Stress Distribution

A bolted connection consisting of a cover on a pressure vessel flange with a metallic flat gasket on raised faces is analyzed as a four-body contact problem using axisymmetrical theory of elasticity. The contact stress distribution, the load factor (the relationship between an increment of bolt axial force and an internal pressure), and the gasket properties (the gasket seating width and the moment arm) are examined. In the analysis, the cover is replaced with a finite solid cylinder. The metallic flat gasket, the flange, and the hub are replaced with finite solid cylinders. The effects of the stiffness and the thickness of various size gaskets on the contact stress distribution are obtained by numerical calculations. Experiments were carried out to obtain the load factor, the maximum stress produced in bolts, and the stress produced on the hub. The analytical results obtained are shown to be consistent with the experimental results.

scholarly journals Paint Coating Removal by Heating for High-Strength Bolted Joints in Steel Bridge and Its Influence on Bolt Axial Force

2021 ◽  
Vol 2 (4) ◽  
pp. 728-738
Author(s):  
Tomonori Nakahara ◽  
Mikihito Hirohata ◽  
Shinsuke Kondo ◽  
Toru Furuichi
Keyword(s):  
High Strength ◽  
Bolted Joints ◽  
Maximum Temperature ◽  
Steel Bridge ◽  
Bolted Joint ◽  
Paint Coating ◽  
Axial Forces ◽  
Ceramic Heater ◽  
Coating Removal ◽  
Series Of Experiments

A series of experiments were carried out for developing a paint coating removal method for high-strength bolted joints in steel bridges. The paint-coated bolted joint specimens were heated to the target temperature of 200 °C by using a sheet-type ceramic heater. The maximum temperature of specimens could be controlled within 10% of the target value. The paint coating was easily removed by using general tools after heating. The behaviour of bolts with thermal expansion and shrinkage was monitored by strain gauges attached to the bolts during heating. It was estimated that the axial forces of the bolts were reduced by 2.6% of the initially installed axial forces, on average.

An Analysis of Circular Bolted Flanged Joints on Solid Round Bars Subjected to External Bending Moments

2000 ◽  
Author(s):  
Toshiyuki Sawa ◽  
Tsuneshi Morohoshi ◽  
Akihiro Shimizu
Keyword(s):  
Stress Distribution ◽  
Contact Stress ◽  
Three Dimensional ◽  
Bending Moment ◽  
Theory Of Elasticity ◽  
Load Factor ◽  
Bending Moments ◽  
Sealing Performance ◽  
Contact Stress Distribution ◽  
Good Agreement

Abstract In designing bolted joints, it is important to know the contact stress distribution which governs the clamping effect or the sealing performance and to estimate the load factor (the ratio of an increment in axial bolt force to an external load) from bolt design standpoint. The clamping force by bolts and the external bending moment are axi-asymmetrical loads and not many investigations have seen reported which treat axi-asymmetrical. In this paper, the clamping effect, and the load factor for the case of solid round bars with circular flanges, subjected to external bending moments, are analyzed as an axi-asymmetrical problem using the three-dimensional theory of elasticity. Experiments were carried out concerning the contact stress distribution, and the load factor for the external bending moment (a relationship between an increment in axial bolt force, and external bending moment). The analytical results were in fairly good agreement with the experimental ones.

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