Bolt Structure Research Articles

Contact Resistance Model and Thermal Stability Analysis of Bolt Structure

This paper introduces a contact resistance model of bolt structures based on virtual material method. The main idea of the model is to interpose a virtual layer between the overlapped bus bar and define properties including equivalent resistivity and equivalent modulus of elasticity to describe the dynamic characteristics of the distributed contact resistance. The determining method of these properties is introduced, and the validity of the model is demonstrated by comparing the calculated contact resistance with the measured results. The model is further applied to the coupled electromagnetic–stress–thermal finite-element calculation to analyze the thermal stability of the bolt structure. The temperature rise process inside the bolt structure is studied, and the strengthening effect of the electrodynamic force on the thermal field is revealed. Besides, the influences of contact loosening and oxidation are also researched with the method.

Bending fatigue behaviour and microstructure in welded high-strength bolt structures

Welded high-strength bolts are recently being applied to automobile part fixations, and it is important to clarify their fatigue behaviours and to carry out the fatigue strength designs for preventing fatigue failures. Using the spot and full-circled welded bracket samples in four kinds of weld shapes, bending fatigue strength properties of welded high-strength bolt structures were examined. Factors affecting fatigue to failure, such as weld bead shapes and metal structures, were identified through local stress measurements with strain gauges and X-ray diffractions, microscope observations and chemical composition analyses, as well as stress concentrations of finite element method computational simulation. Differences of bending fatigue strengths at 2 × 105 cycles in welded bolt structure samples when based on nominal stress are 15% to 60% compared with the bolt itself. Fatigue strengths corresponded to four kinds of fracture modes and did not decline greatly in the full-circled welded structure. The spot P sample, in which the connecting line between the two centres of the weld beads was perpendicular to the load direction, has higher strength due to the crack initiating from the weld zone of the gap between the plate and the bolt flange which has hard mixed phases of ferrite + martensite + bainite with high fatigue resistance, and its strength divided by weld length does not deteriorate. The strengths and fracture modes were analysed from the viewpoints of the shape effect relating to the stress concentration and residual stress and the material effect relating to the microstructure of the weld as well.

IWSHM 2017: Structural health monitoring of the loosening in a multi-bolt structure using linear and modulated nonlinear ultrasound acoustic moments approach

Applying highly accurate clamp loads in bolted joints during assembly and inspections is essential for estimation of the integrity of a joint and reduction of disastrous failures. Non-destructive post-assembly and in-service inspections of joint integrity are vital and significantly reduce maintenance and associated repair costs. Therefore, a bolt control technology able to provide precise direct measurement of bolt loosening state during assembly and in-service is needed. This work proposes an in situ structural health monitoring approach based on the evaluation of linear and nonlinear modulated acoustic moments for the assessment of the loosened state of bolts in a multi-bolted structure. Linear and nonlinear ultrasound methods’ detection accuracy and robustness can be highly dependent on correct frequency selection. The structural health monitoring method suggested uses material resonance and a frequency sweep methodology coupled with a cross-correlation method which identifies significant frequency pairs or higher harmonics used to determine bolt loosening. The proposed approach was tested and successfully validated on three different bolted structures showing that loosening of the structure can be identified accurately with a limited number of transducers. The solution provides a qualitative solution, which identifies degradation in the torque of a bolted structure; furthermore, the developed structural health monitoring method has the potential to become an automatic tool for monitoring the loosened state of bolts in critical complex structural components.

Conceptual Design Study on Bolts for Self-Loosing Preventable Threaded Fasteners

Threaded fasteners using bolts is widely applied in industrial field as well as various fields. However, threaded fasteners using bolts have loosing problems and cause many accidents. In this study, the purpose is to obtain self-loosing preventable threaded fasteners by applying spring characteristic effects on bolt structures. Helical-cutting applied bolt structures is introduced through three dimensional (3D) CAD modeling tools. Analytical approaches for evaluations on the spring characteristic effects helical-cutting applied bolt structures and self-loosing preventable performance of threaded fasteners were performed using finite element method and results are reported. Comparing slackness test results with analytical results and more details on evaluating mechanical properties will be executed in future study.

Parametric Study of Single Bolted Composite Bolted Joint Subjected to Static Tensile Loading

The use of composites is increasing in the engineering applications in order to reduce the weight, building energy efficient systems, designing a suitable material according to the requirements of the application. But at the same time, building a structure is possible only by bonding or bolting or combination of them. There are limitations for the bonding methods and problems with the bolting such as stress concentration near the neighborhood of the bolt hole, tensile or shear failure, delamination etc. Hence the design of a composite bolted structure needs a special attention. This paper focuses on the performance of the composite bolted joint under static tensile loading and the effect of variation in the parameters such as the bolt pitch, plate width, thickness, bolt tightening torque, composite material, coefficient of friction between the bolt and plate etc. A simple spring mass model is used to study the single bolted composite bolted joint.The influencing parameters are identified through the developed model and compared with the results from the literature. The best geometric parameters for the applied load are identified for the composite bolted joints.

Clamping force diagnosis during bolting process using acoustic signatures

The method of measuring the fastening force of the bolt in a non-contact manner during the fastening of the bolt is of great value in the industry. In this study, the fastening force was measured by changing the dynamic characteristics as the bolts were fastened. Experiments were carried out by measuring the vibration generated when bolts with load cells were fastened. When the bolt is fastened, the vibration characteristics of the bolt are measured by the accelerometer attached to the joint structure of the bolt by the fastener. The measured vibration signals are classified using cepstrum of bolt. Learning was performed by recognizing different axial force as each speaker. The clamping force was predicted in such a manner as to determine which studied clamping force is most similar to the present clamping force. The proposed method is verified by applying it to actual bolt structure.

Experimental Analysis of Anchor Bolt in Concrete under the Pull-Out Loading

The design of pull-out strength of anchor bolt in concrete is generally based on standards which are assumed to have a single crack failure and the uniform stress. However, in real phenomenon these assumptions are not reliable and a combination of failure modes between the cone and bond failure is commonly found. This research was conducted to analyze the failure mechanism and the strength of the anchor bolt under static pull-out load. Normal strength of concrete-mortar block and the shallow depth of anchor bolt was used in this research. The failure mode, reaction force, and concrete cone stress will be discussed and compared to the design standards. The experimental results clearly show that a combination failure mode between the cone and bond failure of anchor bolt was found, consequently the depth of the cone failure part reduced and the angle of cone slope narrowed. The cone stress and loading capacity of the experimental result is extremely lower than the design standards, which is around a half. Therefore a certain safety factor is required to guarantee the safety of anchor bolt structures.

Identification of damage based on frequency response function (FRF) data

Mechanical joints, particularly fasteners such as bolted joints have a complex non-linear behaviour. The non-linearity might emerge from the material, geometry or by the contacts in the joints. However, damage to a structure can be happened either their connections or the material of components. The effect of damage can change the dynamic properties of the structure such as natural frequencies and mode shapes and structural performance and can cause premature failure to structure. This paper presents a damage detection method using a vibration based damage detection method based on the frequency response function (FRF) data. A combination of numerical model and physical bolted jointed structure of damaged and undamaged structure will be investigated. The validation is employed to detect the presence of damage in the structure based on the frequency response function (FRF) data from the parameter values used in the benchmark model and damaged model. The comparisons of the undamaged and damaged structure of the FRF have revealed the damaged structure was shifted from the undamaged structure. The effect of the FRF between undamaged and damaged structure is clearly affected by the reduction of stiffness for the damaged structure.

Modal Analysis of Monolithic and Jointed Type Cantilever Beams with Non-Uniform Section

Modal analysis of non-uniform bolted structures are of significance in modeling many complex mechanical structures. There are vast literatures available related with the analytical as well as numerical modeling of bolted joint. However, most of the analytical model discuss about the modeling of first mode of uniform structures with single bolted joint. In this paper, we present the modeling of single as well as bolted non-uniform beams using approximate mode shapes. To develop the model, we first carry out experiments to measures the modal frequencies and shapes of the test structures. Subsequently, we also do numerical modeling of non-uniform beams in ANSYS to verify the validity of the Euler-Bernoulli beam theory in developing the analytical models. Finally, using the Euler-Bernoulli beam theory, we obtain the analytical values of frequencies using the approximate the mode shapes. The analytical results are found to be closer to the experimental results with a maximum percentage error of about 15 %. The model presented in the paper can be extended to the mechanical structures with many non-uniform sections with or without bolted joints.

Stiffness Analysis of Curvic Coupling in Tightening by Considering the Different Bolt Structures

AbstractCurvic couplings are extensively used in aerospace machinery, such as helicopter, aero-engine, or other aircrafts. The aim of this paper is to reveal new insights into the behavior of bolted joint with curvic couplings according to the bolt geometry and physical parameters by an analytical model. The different cases are focused mainly on the different geometry characters of the bolt. The analytical results show that the compression stiffness of both the curvic and the ring part of the disc has some relationship with the curvic rotation. The curvic rotation angle and the curvic compression stiffness show a slight difference during the tightening regardless of the bolt structural parameters. However, the stiffness of the other disc parts present a more obvious difference in tightening because of the various bolt structural parameters.

Convoluted solutions in supergravity

Inspired by the convoluted solutions for two intersecting M2 branes in elevendimensional supergravity, in which one brane in the system is completely localized along the overall and relative transverse coordinates while the other brane in the system is localized only along the overall transverse coordinates, we construct two classes of exact solutions to Einstein-Maxwell theory in six and higher dimensions. We show that the membrane configuration preserves four supersymmetries and upon dimensional reduction, the solutions provide intersecting configurations of three D-branes in type IIA supergravity. Moreover, we show that the metric functions in six and higher dimensions can be written as convolution-like integrals of two special functions. The solutions are regular everywhere and show a bolt structure on a single point in any dimensionality. Also, we find the exact nonstationary solutions to the Einstein-Maxwell theory with positive cosmological constant. We show that the cosmological solutions are expanding patches in asymptotically de Sitter spacetime.

Exact convoluted solutions in higher-dimensional Einstein-Maxwell theory

We construct two classes of exact solutions to six and higher dimensional Einstein-Maxwell theory in which the metric functions can be written as convolution-like integrals of two special functions. The solutions are regular everywhere and show a bolt structure on a single point in any dimensionality. Moreover, we find the exact nonstationary solutions to the Einstein-Maxwell theory with positive cosmological constant. We show that the cosmological solutions are expanding patches in asymptotically de Sitter spacetime.

Research to the Tension Monitoring Instrument of Bolt and Cable in Multi-Point

Since safety of roadway and steady of rock depend on bolt and cable supporting quality [~[, it is important to evaluate timely bolt and cable supporting quality that monitors tension state of bolt and cable. With separated type design, the monitoring instrument, which is to monitor tension of multiple survey point and separation type Bolt and Cable, is made up of tension of bolt and cable sensor and secondary measuring instrument. This paper focuses on the composition and the basic principle of the tension of bolt and cable sensor structure, the composition of secondary measuring instrument structure and functional partition of the chips and circuit theory of the monitoring instrument. This paper introduces the concrete implementation way and the conditions of usage of the monitoring instrument and introduces the monitor in the application of the auxiliary slot of 22301 working face of Shen Dong coal group Shi Ge Tai ore.

Structural performance evaluation of circular steel bands for PC column–beam connection

The aim of this study was to evaluate the performance of steel bands used for connecting centrifugal hollow precast concrete (PC) columns to steel beams. A steel band and centrifugal hollow PC column were connected together to produce specimens using two methods: stud bolt connection and rib connection. While the stud bolt connecting method produces interference between the stud bolt and column rebar structure during the production of a centrifugal hollow PC column, causing a delay in the process, the rib connecting method does not cause interference with the rebar structure, simplifying the production process. The results of the study indicated that, compared with the stud bolt connecting method, the specimen produced by the rib connecting method produced a 12·8% greater yield strength and a 9·7% greater horizontal displacement. The strain of the steel band was 0·0013 until the inter-floor displacement angle reached 0·04 rad, and thus the steel band remained in elastic regions even after significant deformation occurred at the joint.

Numerical Analysis of Deeply Buried Small Net Distance Tunnels on Rock Stability under Different Construction and Methods

Based on the background of a highway, for tunnels with small spacing of complex stress condition, adopt various construction schemes for numerical simulation using Midas Gts finite element software under the condition of deep-buried small net distance tunnel. Use full-face excavation method, benching tunneling construction method and both side heading method to compare surrounding rock stress, surrounding rock deformation, internal force of bolt and shotcrete support system structure, lateral-wall displacement and stability of surrounding rock. Analyse displacement and stress change laws before and after the excavation of tunnel surrounding rock and supporting structure under different schemes.

Reliability Study on Bolt Support Systems of Coal Roadway under Group Failure Modes Based on Maximal Entropy Principle

Currently, there are several failure modes in the blot structure of coal roadway. Existing reliability analysis method of blot support structure of coal roadway does not consider the relevance existing among these methods, thus reducing reliability of the blot structure. In order to fix this defect, we put forward the group failure mode of coal roadway bolt structure analysis method taking the relevance issue into consideration. At the same time, we analyze the probability characteristic of blot structure parameters based on the maximum entropy principle; through the normal distribution curve express the coal - rock characterization of cohesion and the friction angle. The Monte Carlo simulation method calculates reliability of the model with the matlab. The results show that the maximum entropy can effectively reflect the probability characteristic of variables in coal roadway bolt structure. Furthermore, Group failure modes allow for the relevance among existing failure modes in the same group, thus in the general, providing more scientific and accurate responses evaluating the overall reliability of the system. Under the group failure modes, the results of reliability are larger than those under traditional reliability analysis method with same conditions.

Damping capacity of various materials with non-uniform intensity of pressure distribution at the interfaces of a layered and jointed structure

The present work investigates the mechanism of damping in layered and jointed bolted structures of aluminium, copper and mild steel materials with non-uniform intensity of pressure distribution at the interfaces. Extensive experiments are conducted to validate the numerical analysis. The interface pressure, diameter of the bolts, material, coefficient of friction and dynamic slip ratio at the interfaces, washer, and frequency of excitation are found to play major roles on the damping capacity of structures. It is established that the damping capacity of bolted structures can be enhanced substantially with an increase in number of layers and decrease in diameter of the bolts along with use of washers. It is further found that the aluminium material in layers contribute more to the damping of structures and this design concept can be effectively used to select a proper material depending on the required damping capacity in real industrial applications.

Cosmological solutions on Atiyah-Hitchin space in five-dimensional Einstein-Maxwell-Chern-Simons theory

We construct non-stationary exact solutions to five dimensional Einstein-Maxwell-Chern-Simons theory with positive cosmological constant. The solutions are based on four-dimensional Atiyah-Hitchin space. In asymptotic regions, the solutions approach to Gibbons-Perry-Sorkin monopole solutions. On the other hand, near the four-dimensional bolt of Atiyah-Hitchin space, our solutions show a bolt structure in five dimensions. The c-function for the solutions shows monotonic increase in time, in agreement with the general expected behaviour of c-function in asymptotically dS spacetimes.

Use of a submodel method to check the bolt strength of marine equipment

A submodel method was proposed that works from computational models of marine gear cases to verify that the proposed bolts will give it sufficient structural integrity. Calculations for marine equipment using this system accorded well with conventional results. As an example, an anti-shock computation was processed for a gear case, and the submodel was then employed to check the strength of individual components. The results showed that the gear case connecting structure can satisfy relative anti-shock requirements, and the dynamic response characteristics seen in the bolt structures had a close relationship with the method used for attaching the bolt. This provides a new means for checking the strength of connecting structures on large-scale equipment and thus has significant reference value.

Geometric parameters and chemical corrosion effects on bearing strength of polyphenylenesulphide (PPS) composites

The pin-bearing strength of polymer composites has been the focus of a significant research effort. In bolted composite structures, the presence of bolt holes induces high stress concentrations, which are hence recognized to be a source of damage developed during loading. In this study we aim to investigate the bearing performance of random oriented short fibre reinforced polyphenylenesulphide (PPS) composites which are widely used in various engineering applications. Both geometric parameters and chemical corrosion effects on the bearing performance of the material were investigated. It is concluded that the load bearing performance of the materials strictly depends on the geometric parameters of the joints. Chemical corrosion was also found an important environmental factor which was affecting the load bearing performance remarkably.