Axial Bolt Research Articles

Analiza trwałości zmęczeniowej połączeń śrubowych z wykorzystaniem oprogramowania ANSYS

The paper presents selected problems of fatigue life of bolt joints. An analysis of factors influencing fatigue life of bolt joints was performed and selected methods of improving life were described. Authors presents examples of numerical calculations with use of ANSYS software which depict influence of pre-tension in the bolt on fatigue life of the joint. Presented results of life calculation were carried out for bolt joint loaded along bolt axis and for bolt lap joint loaded perpendicular to bolt axis.

Failure of the threaded region of rockbolts in underground coal mines

HSAC 840 steel rockbolts were examined, all of which had failed in service through the threaded region exterior to the rock face by brittle fracture transverse to the bolt axis. The bolts had been in service in an Australian coal mine in which the groundwater had a pH of 7·5–8·5 and a relatively high bicarbonate level of 515–2200 mg l−1. All failures had occurred within the region comprising the domed washer and the end plate. The majority of the bolts showed a small thumbnail-shaped discoloured region 1.5-4.5 mm in length at the fracture origin, as is characteristic of stress corrosion cracking (SCC) in rockbolts. In half of these bolts, SCC had initiated immediately at the root of the thread, but in the other half of the bolts, SCC had initiated from a small pre-existing crack that had been produced in the thread as a result of a prior bending load.

Dynamic Response to Seismic Waves at the Shallow Slope Supported by Bolts

In the soil slope supported by bolts, longitude waves instead of transverse waves, generated by earthquakes, first reach the slope surface. With the dynamic response of the P (pressure) wave along the anchorage structure, first, a theoretical study was conducted to investigate the propagation characteristics of the interference superposition, generated by the SV (shear-vertical) and the P waves. The SV wave was formed by the wave, originating from the bottom and reflected from the free surface of the slope, whereas the latter was the incident P wave, propagating in the slope. In addition, the structural measures, restraining the seismic wave, and the characteristics of the restraint effect at the free segment of the bolt were investigated. According to the wave-way difference between the incident P wave and the reflected SV wave, the minimum critical slope angle, influenced by the interference at the shallow slope, and the maximum influencing depth of the dynamic response, acting vertically to the slope surface, were obtained. The results indicate that the maximum influencing depth linearly correlated with the slope angle. Furthermore, based on the propagation characteristics of the P wave along the bolt, and the coupled relation between the wave length and the anchorage design parameters, the axial acceleration of the wave propagating along the bolt axis was obtained. Then, the theoretical length of the anti-seismic bolt, subjected to seismic waves, and the compensation force of the anchorage structure were obtained. Finally, a numerical study, based on FlAC3D, properly verified the theoretical conclusions.

Effect by a Plain Washer on Reduction of Bolt Axial Tension in Bolted Joints in the case of Creep Deformation of Clamped Parts

Effect by a Plain Washer on Reduction of Bolt Axial Tension in Bolted Joints in the case of Creep Deformation of Clamped Parts

Deformation Analyses and Reductions of Bolt Axial Tension in the Bolted Joints with Creep of Clamped Parts

Deformation Analyses and Reductions of Bolt Axial Tension in the Bolted Joints with Creep of Clamped Parts

Causes of Failure of High-Tensile Stud Bolts Used for Joining Metal Parts of Tower Crane

The causes of the failure of a high-tensile stud 2M48-6gx500 10.9 made from steel grade 30HGSA which led to a temporary inoperability of a tower crane were investigated. The bolts were used to assemble the tower sections and collapsed after 45 days from the moment the crane was commissioned. The cracks in the fracture are identified as fatigue with the characteristic sites of nucleation, sustainable development and static dolomite. To determine the possible causes of stud bolts destruction, metallographic, durometric and mechanical tests were carried out from which it follows that the stud bolt material in its original state corresponded to the delivery conditions. The destruction of the stud bolt appears to have resulted from a combination of several unfavorable factors: uncertainty about the actual tension of the stud bolt due to the lack of information about the magnitude of the twist factor; partial displacement of the centers of the brackets holes and rotation of the stud bolt axis during the sections’ assembly; no tight contact on the support surfaces of the section brackets. All this led to a discrepancy between the actual design of the stud bolt, the appearance of additional forces and the destruction of the stud bolt.

Rotation Capacity of Bolted Flush End-Plate Stiffened Beam-to-Column Connection

One of the flexibility parameters of semi-rigid joints is rotation capacity. Plastic rotation capacity is especially important in plastic design of framed structures. Current design codes, including Eurocode 3, do not posses procedures enabling designers to obtain value of rotation capacity. In the paper the calculation procedure of the rotation capacity for stiffened bolted flush end-plate beam-to-column connections has been proposed. Theory of experiment design was applied with the use of Hartley’s PS/DS-P:Ha<sub>3</sub> plan. The analysis was performed with the use of finite element method (ANSYS), based on the numerical experiment plan. The determination of maximal rotation angle was carried out with the use of regression analysis. The main variables analyzed in parametric study were: pitch of the bolt “w” (120-180 mm), the distance between the bolt axis and the beam upper edge c<sub>g1</sub> (50-90 mm) and the thickness of the end-plate t<sub>p</sub> (10-20 mm). Power function was proposed to describe available rotation capacity of the joint. Influence of the particular components on the rotation capacity was also investigated. In the paper a general procedure for determination of rotation capacity was proposed.

Relationship between loading angle and displacing angle in steel bolt shearing

When subjected to shear loading condition, a steel rock bolt will become bent in the field close to the loading point in situ. The bolt is deformed as the joint displacement increases, which can mobilize a normal load and a shear load on the bolt accordingly. In this work, the relationship analysis between the displacing angle and loading angle is carried out. By considering elastic and plastic states of rock bolt during shearing, the rotation of bolt extremity can be calculated analytically. Thus, the loading angle is obtained from displacing angle. The verification of analytical results and laboratory results from reference research implies that the analytical method is correct and working. In terms of in-situ condition, the direction of the load acting on steel bolt can be predicted well according to the direction of the deformed rock bolt with respect to original bolt axis.

Decreasing of Bolt Axial Tension based on Creep Characteristic of Clamped Part in the Bolted Joint

Decreasing of Bolt Axial Tension based on Creep Characteristic of Clamped Part in the Bolted Joint

Flow switchability of motions in a horizontal impact pair with dry friction

Using the flow switchability theory of the discontinuous dynamical systems, the present paper is to develop mechanical complexity in a periodic-excited horizontal impact pair with dry friction. The impact pair studied models the motions of a single bolted connection which is vibrated in the plane perpendicular to the bolt axis. According to motion character, the phase space can be partitioned into several domains and boundaries, in which a continuous dynamical system is defined in each domain, and it possesses dynamical properties different from its adjacent subsystem, the boundaries have different properties and can fall into two kinds – displacement boundaries and velocity boundaries. In this paper, using G–functions defined on separation boundaries to study flow switching on corresponding boundaries, the analytical switching conditions on each boundary are developed: the sufficient and necessary conditions of occurrence and disappearance of sliding-stick motion and side-stick motion are obtained, the sufficient and necessary conditions of grazing motion appearing on velocity boundaries are also obtained, and the analytical conditions of appearance for grazing motion on displacement boundaries are preliminarily discussed. Thus it can be seen that dynamical behaviors of the horizontal impact pair with or without dry friction are essentially different, in particular flow switchability on displacement boundaries depend on whether the conditions of passable flows on velocity boundaries are satisfied. The numerical simulations are given to demonstrate the analytical results of two stick motions and grazing motions in such pair. More details of the motions for the object reaching the intersection point of displacement boundary and velocity boundary need to be considered further in the future.

温度変動における小口径管フランジ締結体のボルト軸力変化

温度変動における小口径管フランジ締結体のボルト軸力変化

Influence of Side-Pressure Coefficient on Deformation of Tunnel Surrounding Rock and Bolt Axial Force

Internal force and deformation of surrounding rock and supporting structure of the nonlinear research is the use of finite element software ADINA by ideal elastic-plastic constitutive model.Results show that the lateral pressure coefficient increased from 0 to 1, and even decrease sharply arch sedimentation of surrounding rock, side wall horizontal displacement towards the hole along the radial direction development gradually reduced to 0 and reverse to the hole, when the lateral pressure coefficient is less than 0.5, bolt axial force biggest change is not obvious, when lambda increases gradually, the largest bolt axial force significantly increased.

Performance of fully encapsulated rebar bolts and D-Bolts under combined pull-and-shear loading

The performance of two types of rock bolts, fully encapsulated rebar and D-Bolt, under combined pull and shear loading were studied in the laboratory. A new test approach was developed to apply the pull and shear loads to the rock bolt at the same time so that the bolt is displaced in a direction different from the bolt axis. Five displacing angles between 0° (pure pull) and 90° (pure shear) were employed in the tests. The test results show that the linear elastic stiffness of both the D-Bolt and the rebar bolt is mobilised quickly after a small displacement. When the displacing angle is larger than 40°, grout crushing may occur underneath the bolt shank, resulting in reduction in the stiffness of the bolt. The ultimate load of the bolts remains approximately constant no matter what the displacing angle is for both the D-Bolt and the rebar bolt. The displacement capacity of the D-Bolt, however, is dependent on the displacing angle. The ultimate displacement of a 1-m long D-Bolt section varies from 140mm under pure pull (0°) to approximately 70mm when the displacing angle is larger than 40°. The ultimate displacement of the rebar slightly increases from 29mm under pure pull to 53mm under pure shear. In general, the displacement capacity of the D-Bolt is larger than that of the rebar bolt. It is approximately 3.5 times the rebar under pure pull and 50% higher than rebar under pure shear. The test results show that the displacing angle of the bolt is larger than its loading angle, which is also confirmed by the analytical solutions.

Mechanism for a Bolt and Nut Self-Loosening under Repeated Bolt Axial Tensile Load

The mechanism for a bolt and nut self loosening under repeated bolt axial tensile load has yet to be clarified, despite much investigation into this phenomena. In this paper, the self loosening mechanism is derived from basic strength of materials equations, which results in the following conclusions. (1) When load is applied, a slip occurs on the screw thread surface, and the bolt shank twists clockwise, that is, it descends on the lead angle of the screw thread. At the end of this process, counterclockwise restitution torque TS1－ is generated by the twisted angle of the bolt shank. However, there is no rotation of the nut. (2) When the load is released, if TS1－ exceeds the friction torque TW0 on the nut bearing surface generated by the decreased bolt axial tension, a slip occurs on the nut bearing surface, and the bolt and the mating nut rotate counterclockwise as one unit. To satisfy the relationship TS1－> TW0, the maximum bolt axial tension F1 must be larger than cF0. Here F0 is the minimum bolt axial tension and the coefficient c depends on the bolt shape and the friction coefficient. The rotational behavior of the bolt and the nut derived from this analysis concurs with experimental and FEM calculation results of other researchers. For steel joints, it is believed that rotational loosening rarely occurs when there is no separation between joined parts.

Avoiding self-loosening failure of bolted joints with numerical assessment of local contact state

Fatigue and rotational self-loosening are two most widespread reasons for failure of dynamically loaded bolted joints, especially due to external loading perpendicular to the bolt axis (transverse loading). More and more component systems show self-loosening in light weight design. The aim of this paper is to provide a numerical design method with finite element analysis for detecting and understanding of the self-loosening process at bolted joints and the influences of the preload generation for the residual shank torque in the numerical simulation. A three-dimensional finite element (FE) model is established to study details of the rotational self-loosening process. Such processes are characterized by either complete or localized slip at the screw head and thread contact surfaces. Detailed information is given about the modelling. The computational results of the numerical simulation are compared with experimental investigations of the cyclic transverse load–displacement behaviour. These show that rotational self-loosening can also occur for only localized slip without complete slipping at the head contact surface.

Mechanism for a Bolt and Nut Self Loosening under Repeated Bolt Axial Tensile Load

The mechanism for a bolt and nut self loosening under repeated bolt axial tensile load has yet to be clarified, despite much investigation into this phenomena. In this paper, the self loosening mechanism is derived from basic strength of materials equations, which results in the following conclusions. (1) When load is applied, a slip occurs on the screw thread surface, and the bolt shank twists clockwise, that is, it descends on the lead angle of the screw thread. At the end of this process, counterclockwise restitution torque TS1－ is generated by the twisted angle of the bolt shank. However, there is no rotation of the nut. (2) When the load is released, if TS1－ exceeds the friction torque TW0 on the nut bearing surface generated by the decreased bolt axial tension, a slip occurs on the nut bearing surface, and the bolt and the mating nut rotate counterclockwise as one unit. To satisfy the relationship TS1－> TW0, the maximum bolt axial tension F1 must be larger than cF0. Here F0 is the minimum bolt axial tension and the coefficient c depends on the bolt shape and the friction coefficient. The rotational behavior of the bolt and the nut derived from this analysis concurs with experimental and FEM calculation results of other researchers. For steel joints, it is believed that rotational loosening rarely occurs when there is no separation between joined parts.

Design optimization of spring of a locking nut using design of experiments

The bolt and nut is a representative fastener used in a machine assembly. When a load is repetitively applied to the bolt and nut assembly in the perpendicular direction of the bolt axis, the nut gradually loosens. To address this problem, nuts of diverse structures and shapes have been developed. In this study, a loose-proof locking nut is developed using a spring. The spring prevents the loosening of the nut by augmenting the axial load of the bolt. Three dimensional finite element models for the bolt, nut, spring and vibration plate are generated, and the loosening performance of the nut is analyzed using MSC/Marc, a commercial finite element analysis program. With the optimization technique based on the design of experiments, the shape and material of the spring are optimized. The optimal results are applied to the bolt and nut connection. The performance of the newly developed locking nut with a spring is compared to that of the general nut and bolt connection without a spring and the effectiveness of the locking nut is verified.

A Mechanical Study to Investigate the Free Play of 3 Different Nail Designs Used for Fixation of Subtrochanteric Femoral Fractures

Patients with subtrochanteric fractures treated by intramedullary fixation frequently report marked post-treatment pain associated with movement. The free distance, clearly visible in the lateral view X-rays, between the inner cortex of the medullary cavity and outer implant surface shows that anterior-posterior movement is possible when using a single bolt for stabilisation of the nail position. The movement behaviour of three standard nail types (Proximal Femur Nail / Synthes, Gamma Nail / Howmedica, Trochanteric Nail / Howmedica) was investigated by mechanical testing and a mathematical model. The results of mechanical testing closely matched the mathematical model. The nail tip length from the locking bolt axis to its distal end was crucial in determining nail movement. The Proximal femur nail (60 mm) shows the least movement (best performance), the Trochanteric nail (20 mm) shows the largest movements, the movement associated with the Gamma nail (40 mm) was between those of the two other nails. We believe that the Trochanteric nail results in too large a movement and is the least suitable implant for stabilisation of subtrochanteric femoral fractures.

201 内圧作用下でのガスケット付ボルト・フランジ締結体の応力解析 : ボルト軸力のばらつきの影響(材料力学I)

201 内圧作用下でのガスケット付ボルト・フランジ締結体の応力解析 : ボルト軸力のばらつきの影響(材料力学I)

Cumulative Clamp Load Loss Due to a Fully Reversed Cyclic Service Load Acting on an Initially Yielded Bolted Joint System

The amount of clamp load loss due to a fully reversed cyclic service load is determined for a bolted assembly in which the fastener and the joint were both tightened initially beyond their respective proportional limits. The cyclic reversed load acts in a direction parallel to the bolt axis. During the first half of each cycle, the cyclic load acts as tensile separating force that increases the fastener tension further into the nonlinear range; it simultaneously reduces the joint clamping force. Thus, after the first one half of the cycle, the clamp load is reduced from its initial value due to the plastic elongation of the fastener. During the second half cycle, the cyclic load compresses the joint further into the plastic range; simultaneously, it reduces the fastener tension. Due to the permanent set in the compressed joint, the clamp load is decreased further at the end of the second half cycle of the service load. The cumulative clamp load loss due to the permanent set in both the fastener and the joint is analytically determined using a nonlinear model. Variables investigated in this study include the joint-to-fastener stiffness ratio, the ratio of the initial fastener tension to its elastic limit, and the ratio of the external force to its maximum tensile value that would trigger joint separation.