Tap Bolts Research Articles

Analyses of Tightening Characteristics and Cyclic Stress Amplitude of Studs and Tap Bolts

Analyses of Tightening Characteristics and Cyclic Stress Amplitude of Studs and Tap Bolts

Mechanical Behaviors of Bolted Joint in Various Clamping Configurations

In a bolted joint, failures usually initiate at the first root of the bolt thread. However, rupture around the bolt head is sometimes reported for a tap bolt because of high stresses produced by tightening torque applied to the bolt head. It is also well known that manufacturing errors of internal threads in a tapped hole are generally much larger than those of external threads, thus leading to the failures concerned. In this paper, mechanical behaviors of bolted joints in various clamping configurations are analyzed using FEM as multi-body elastic contact problem, and the effects of nominal diameter, friction and pitch error upon stress concentrations are evaluated for through bolts, studs, and tap bolts. It is then quantitatively estimated on the effectiveness of “recessed internal threads” for reducing the stress concentration occurred around the far end of bolt hole. In addition, the tightening process and strength of a bottoming stud, which have seldom been studied despite favorable performance in preventing stress concentration at the runout of threads, are also investigated.

Stress Analysis and the Strength for Slipping of Bolted Joints of Hollow Cylinders Subjected to Torsion.

This paper deals with the strength characteristics of bolted joints subjected to torsional loads. The joints are composed of two hollow cylinders which are clamped by a bolt and a nut or a threaded tap bolt. The stress distributions at the contact surfaces and the variation in torsional loads occuring in the bolts are analyzed using an axisymmetrical theory of elasticity. A method for cstimating the joint strength for slipping is proposed. Analytical results concerning the variation of the torsional loads in the bolt and the joint strength are in fairly good agreement with the experimental ones. It is found that the joint strength for slipping increases as the initial clamping force increases. It is also found that the strength of joint using a bolt and a nut is greater than that using a threaded tap bolt. The joint strength when a torsional load is applied in the same direction as the screw fastening direction is greater than that in the inverse direction.

Mechanical Behaviors of Bolted Joint in Various Clamping Configurations.

In a bolted joint, failures usually initiate at the first root of the bolt thread. However, rupture around the bolt head is sometimes reported for a tap bolt because of high stresses produced by tightening torque applied to the bolt head. It is also well known that manufacturing errors of internal threads in a tapped hole are generally much larger than those of external threads. In this paper, mechanical behaviors of bolted joints in various clamping configurations are analyzed using FEM as an axisymmetric elastic contact problem, and the effects of nominal diameter, friction and pitch error upon stress concentrations are evaluated for through bolts, studs and tap bolts. In addition, the tightening process and strength of bottoming studs, which have seldom been studied despite of its good performance in preventing stress concentration at the runout of threads, are also investigated.

Characteristics of Bolted Flanged Joints with a Flat Cover by Tap Bolts in a Pressure Vessel Subjected to Heat Conduction.

When a bolted joint is under thermal change, where the material of clamped parts is different from that of the bolts, a variation in axial bolt force is produced due to the difference in thermal properties between the bolts and the clamped parts. In this paper, a variation of axial bolt force in a bolted joint under thermal change, in which a hollow cylinder manufactured from aluminum alloy is fastened to a body (hollow cylinder) with a tap bolt manufactured from steel, is examined both theoretically and experimentally. In addition, mechanical behaviors of a bolted flanged joint with a flat cover in which the cover, the gasket and the flange are manufactured from aluminum alloy and tap bolts of steel are examined when the inner circumference of the joint is subjected to heat conduction. With the use of the finite difference method, the temperature distribution in the connection is analyzed. A variation of axial bolt force and a maximum stress produced in the tap bolts are analyzed. In the experiments, temperature distribution was measured by thermocouples, the variation in axial bolt force and the maximum stress produced in the tap bolts by strain gauges when the inner circumference of vessel was heated (cooled). The numerical results are in fairly good agreement with the experimental results.

The Strength of Joints Combining Adhesives with Tap Bolts : Cases where Adherends are Hollow Cylinders and Rectangular T-Shape Flanges

This paper deals with the strength of joints that combine adhesion and tap bolts. When an external load was applied to a combination joint, which was constructed by joining two hollow cylinders by adhesion and the clamping them together using a tap bolt with an initial clamping force, the stress distributions in the adhesives and the variation of the bolt axial force were analyzed using an axisymmetric theory of elasticity. In addition, a method for estimating the strength of the combination joint was proposed. Experiments were performed and the analytical results were consistent with the experimental results concerning the variation of the bolt axial force and the joint strength. It is seen that, as compared with the adhesive joint in which two tap bolts are used, as the length of the tap bolt increases, the strength of the combination joint increases. Furthermore, the strength in the case where rectangular T-shape flanges were used was examined by both analyses and experiments. The characteristics of the combination joint were elucidated.

The Strength of Joints Combinging Adhesion with Tap Bolts. The Case where Adherends are Hollow Cylinders and T-Flanges.

This paper deals with the strength of joints that combine adhesion and tap bolts. When an external load was applied to a combination joint formed after joining two hollow cylinders by adhesion, they were clamped by a tap bolt with an initial clamping force, and the stress distributions in the adhesives and the variation of the bolt axial force were analyzed using an axisymmetric theory of elasticity. In addition, a method to estimate the strength of the combination joint was proposed. Experiments were performed. The analytical results are consistent with the experimental results concerning the variation of the bolt axial force and the joint strength. It is seen that the strength of the combination joint increases as the length of the tap bolt increases. Furthermore, the strength of the T-type butt adhesive joint combined with tap bolts was examined from both analyses and experiments. The characteristics of the combination joint were clarified.

Features of bolted joints with tap bolts (The case where a clamped part with a metallic gasket is the cover of a pressure vessel)

This paper deals with the distribution of contact stress and the load factor (the ratio of an increment of bolt axial force to an external load) of bolted joints fastened with tap bolts, when a clamped part with a raised face metallic gasket is the cover of a pressure vessel. The distribution of contact stress is analyzed as a three-body contact problem, using the axisymmetrical theory of elasticity. The effects of the stiffness and the position of the gasket are shown on the distribution of contact stress by numerical computations. The contact stress has been measured by means of an ultrasonic technique. The load factor and the maximum stress produced in the bolts are analyzed. For verification, experiments have been performed. The analytical results are in fairly good agreement with the experimental results. In addition, the analytical results of the effective gasket seating width and the moment arm are compared with those obtained from JIS (Japanese Industrial Standard).

On the characteristics of bolted joints with tap bolts. The case where clamped parts are hollow cylinders with a full-face metallic gasket.

In designing bolted joints, it is important to know the contact stress and the force ratio (the ratio of an increment of the bolt axial force to an external load). Up to now, some investigations have been carried out on the characteristics of bolted joints with gaskets. However, the compressive spring constants Kcg of the bolted joint in which a clamped part is fastened to a base with a tap bolt including a gasket have not been studied. In the present paper, the characteristics of the bolted joint with a full-face metallic gasket are examined. Replacing a clamped part, a gasket and a base with finite hollow cylinders, respectively, the contact stress distribution, the force ratio and the compressive spring constants are analyzed using a three-dimensional theory of elasticity. In the experiments, the force ratio is measured and the contact stress is measured by an ultrasonic wave. Analytical results are in fairly good agreement with experimental results. In addition, a simple calculation method to obtain Kcg is proposed.

A simple calculation method of the spring constant in bolted joints using tap bolts.

In designing bolted joints, it is necessary to know the compressive spring constants for clamped parts more exactly. Up to now, simple calculation method to obtain the compressive spring constants for clamped parts have been suggested. However, they are mainly for bolted joints in which nuts and bolts are used. A simple calculation method to obtain compressive spring constants for bolted joints in which tap bolts are used, has not yet been satisfactorily established. In this paper, deformations of bolted joints, in which hollow cylinders are clamped to a base by a tap bolt, are analyzed using a three-dimensional theory of elasticity. Using the numerical results, the spring constants can be calculated .The effects of certain factors on the spring constants are thus examined. A simple calculation method to obtain the spring constant in a bolted joint using a tap bolt is thus derived. Furthermore, experiments are carried out in order to verify this simple calculation method.

Features of bolted joints with tap bolts. (The case where a clamped part with a raised face metallic gasket is the cover of a pressure vessel).

This paper deals with the distribution of contact stress and the force ratio (the ratio of an increment of bolt axial force to an external load) of bolted joints fastened with tap bolts, when a clamped part with raised face metallic gasket is the cover of a pressure vessel. The distribution of contact stress is analyzed as a three-body contact problem, using the three-dimensional theory of elasticity. The effects of the stiffness and the position of gaskets are shown on the distribution of contact stress in numerical computations. The contact stress is measured by means of ultrasonic-waves. Next the force ratio and the maximum stress caused in bolts are analyzed. For verification, experiments are performed. The analytical results are in fairly good agreement with the experimental ones. In addition, concerning the effective gasket yielding width and the moment arm standardized in JIS, the analytical results are compared with the values obtained from JIS.

The characteristics of bolted joints with tap bolts subjected to external bending moments. (The case where a clamped part is T-flange with a full face metallic gasket or a filler plate)

Few investigations have been carried out on the characteristic of a bolted joint with tap bolts subjected to external bending moments. In this paper, the characteristics of a T-flange connection with tap bolts, including a full face metallic gasket or a filler plate, are examined. For analysis, a T-flange, gasket (filler plate) and base were replaced with finite strips. Contact stress distribution, the force ratio for the external bending moment (the relationship between an increment (decrement) of the bolt axial force and the external bending moment) and the maximum stress produced in the bolts are analyzed using a two-dimensional theory of elasticity. Furthermore, the characteristics of a circular flange connection are estimated by using the two-dimensional model. For verification, experiments were performed with respect to the force ratio for the external bending moment, contact stress distribution and the maximum stress in the bolt. Analytical results are in fairly good agreement with experimental ones.

Features of Bolted Joints with Tap Bolts : Case where a Clamped Part with a Full Face Metallic Gasket is the Cover of a Pressure Vessel and a Circular Flange

The design method of bolted joints with gaskets is generally based on experience, and the sealing performance is not made clear by theoretical analyses. In the present paper, discussion is made on 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 force ratio (the ratio of an increment of the bolt axial force to an external load) and the maximum stress caused in bolts are analyzed in taking account of the bending moment. For verification, experiments are carried out, and the analytical results are found in fairly good agreement with the experimental ones.

Features of bolted joints with tap bolts (Cases where a clamped part with a full face metallic gasket is the cover of a pressure vessel and a circular flange)

The design method of bolted joints with gaskets is almost based on experience, and the sealing performance is not made clear by theoretical analyses. In the present paper, discussion is made on the distribution of contact stress in the bolted joints fastened with tap bolts, when a clamped part with a gasket is the cover of a pressure vessel and a circular flange. The distribution of contact stress 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 force ratio (the ratio of an increment of the bolt axial force to an external load) and the maximum stress caused in bolts taking account of a bending moment are analyzed. For verification, experiments are carried out, and the analytical results are in fairly good agreement with the experimental ones.

Considerations on the improvement of the stiffness of bolted joints in machine tools.

The present paper deals with an improvement of the stiffness of bolted joints in machine tools. In the design of bolted joints, the stiffness, the bolt axial force and the distribution of the contact stress are important characteristics, and they have been investigated by many researchers. But the effects of the tightening position of the thread in a base, the height of clamped parts and the configuration of contact surfaces are not taken into consideration sufficiently. Thus, in the present paper, the effects of the tightening position of the thread in the base on the stiffness and the distribution of the contact stress are examined experimentally in the case where a beam is fastened partially to the base with tap bolts. As a result, it is shown that these effects contribute to the improvement of the stiffness of bolted joints.

Considerations on the Improvement of the Stiffness of Bolted Joints in Machine Tools

The present paper deals with an improvement of the stiffness of bolted joints in machine tools. In the design of bolted joints, the stiffness, the bolt axial force and the distribution of the contact stress are important characteristics, and they have been investigated by many researchers. But the effects of the tightening position of the thread in a base, the height of clamped parts and the configuration of contact surfaces are not taken into consideration sufficiently. Thus, in the present paper, the effects of the tightening position of the thread in the base on the stiffness and the distribution of the contact stress are examined experimentally in the case where a beam is fastened partially to the base with tap bolts. As a result, it is shown that these effects contribute to the improvement of the stiffness of bolted joints.

On the Characteristics of Bolted Joints with Tap Bolts (The Case Where a Clamped Part with a Full Face Metallic Gasket or a Filler Plate is a T-flange

A design of bolted joints with gaskets almost depends on experience and a sealing performance is not made clear by theoretical analyses. In the present paper, discussion is made on the distribution of contact stresses when a clamped part with a gasket or a filler plate is fastened with two tap bolts to a base which is large enough comparing with the clamped part. The distribution of contact stresses is analyzed as a three body contact problem using the two-dimensional theory of elasticity. Moreover, the contact stress is measured by means of ultrasonic waves. Next, the force ratio (a ratio of an increment of bolt axial force to a load) and the maximum stress caused in bolts taking a bending moment into account are analyzed. For verification, experiments are carried out. The analytical results are in fairly good agreement with the experimental ones.

The Behaviour of Fasteners under External Loading : Force Ratio of Threaded Connections

In the design of fasteners subjected to an external service load, it is very important to know the relationship between bolt tensile load and service load and to assure a good tightening. However, there are many difficult points in the analysis of fasteners, because the shape of threaded parts of bolts and nuts is very complex and a threaded fastener is, from a view point of the theory of elasticity, equivalent to a contact problem of many elastic bodies. This paper introduces a finite element technique to numerically analyze the the threaded fastener subjected to external loads. As concrete examples of standard threaded fasteners, the results for the force ratios of the through bolt, the tap bolt, the stud and the T-type flange are numerically obtained by using an axi-symmetric and a three-dimensional model.

On the Characteristics of a Bolted Joint with Tap Bolts : the case where a clamped part is a cover of a pressure vessel

This paper discussed on a distribution of contact stresses when the cover of a pressure vessel is fastened with tap bolts to a vessel. In the analysis, by replacing the cover and the vessel by a finite hollow cylinder the distribution of contact stresses is analyzed by three dimensional theory of elasticity. In addition, the force ratio, which is the ratio of an increment of a bolt axial force to a load when a pressure is applied, is analyzed by using three dimensional theory of elasticity and theory of beam on an elastic foundation. Moreover, the maximum stress caused in bolts when a pressure is applied, is also analyzed. Then, a method to estimate the pressure causing a separation of the interface and a leakage of fluid from the joint is proposed. For verification, experiments are carried out. Analytical results are in a fairly good agreement with experimental ones.

On the Characteristics of a Bolted Joint with Tap Bolts : The Case where a Clamped Part is a Circular Flange

円形フランジをこれに比べて大きな本体にN本のねじ込みボルトによって締結した時の接合面の応力分布に関して検討した。全体的には有限円柱どおし、ボルト穴近傍では有限円筒どおしの二体接触問題として三次元弾性論により解析した。さらに内力係数(ボルト軸力の増加分と外力との比)およびボルトに生じる曲げモーメントを考慮した最大応力についても解析を行い、実験結果と比較し、両者はかなりよく一致することを示した。