Set Of Bolts Research Articles

Modelling of Multi-Bolted Systems at the Pretension Stage – Part 1: Mechanical Characteristics of the Contact between the Joined Elements

The subject of the paper is the modelling of multi-bolted connections that are at the pretensioning stage. Taking a systematic approach to the modelling issue, the connection was treated as a composite of four subsystems: a bolt set, a pair of joined elements and a contact layer between them. The first part of the paper describes experimental studies to determine the contact stiffness of a pair of elements separated from an exemplary asymmetric multi-bolted connection. The normal loading and unloading direction of the contact joint was considered. The tests were performed with the use of an INSTRON 8850 servo-hydraulic testing machine equipped with an extensometer. A normal stiffness characteristic in the form of an exponential function was proposed for the tested contact joint. It will be applied in the second part of the paper, in which finite element modelling of the multi-bolted connection will be presented.

Effect of Atmospheric Conditions on the Tightening Behaviour of HV Galvanised Bolts in Structural Bolt Sets

The aim of this article is to investigate the effect of atmospheric conditions on the tightening behaviour of HV bolts in structural bolt sets. The article describes the results of experimental tests carried out for bolt sets of a selected type. The parts of the joined sets were stored according to the specified six different conditions for four weeks before assembly. Paper, cardboard boxes and anticorrosion foils were used as protection against atmospheric conditions. The behaviour of unassembled and assembled bolt sets was also taken into account. The variation in the friction coefficient depending on the clamping force and storage conditions of the bolt sets was demonstrated. This applies both to the contact between the joining elements on the threaded surfaces and to the area between the bolt head and the bearing surface of the nut and washer.

A versatile approach for temporary storage and shipping of in vitro cultured cells, cell sheets and tissue engineered constructs – a preliminary report

• Device was made with readily available raw materials and can be used with ease in a DIY manner. • Device offers leak-proof and aseptic containment of the contents during storage and shipping process. • Device is versatile in its use where dishes having cell monolayers, cell sheets, cell encapsulated gels and cell seeded scaffolds can be stored or shipped. • Device is scalable, simple to handle, can be made for a single or multi-use purpose, and can be resizable to load other culture vessels. Temporary storage/ shipping of cell/ tissue engineering products from bench to bedside is a key aspect of regenerative medicine. The current proof-of-concept study presents a multipurpose device for temporary storage/ shipping of cell culture dishes containing cell/ tissue constructs. The device, made with readily available raw materials, contains three elements viz. a specialized lid, polymeric plates having grooves and a set of nuts and bolts. As part of the performance evaluation, the device was first subjected to a simulated storage/ shipping process, wherein the leak-proof and aseptic containment of the contents was demonstrated. Subsequently, the setup was used for temporary storage/ shipping of dishes having (a) L929 cell monolayers cultured on treated surfaces, (b) SIRC, HaCaT and A549 cell sheets cultured on thermo-responsive surfaces, (c) HOS-cell encapsulated agar gels and (d) HOS-cell seeded silk fibroin mats. The results showed that the health of cell monolayers/ cell sheets/ tissue constructs after the process was comparable to that before the process. The device was scalable, simple to handle, can be made for a single or multi-use purpose, and can be resizable to load other culture vessels. The design of the storage/ shipping device described in this report thus offers versatile features and applications.

Distribution of the friction coefficient in the tension connections by the HV set using the combined method

AbstractThe use of bolts in steel structures nowadays is one of the cheapest, fastest and easiest solutions for joining elements. HV high‐strength bolts used in tension connections are a special type of fasteners covered by supervision beginning with the selection of the material from which they will be made through the production process and quality confirmation, ending with clearly defined assembly requirements.The tests were focused on two assortments of M16 and M24 bolt assemblies made according to EN 14399. A test of the suitability of the connection was performed, expanding it with tests of the coefficient of friction on the bolt thread and between the nut head and washer according to EN ISO 16047. The dynamic joint load tests showed that the distribution of the coefficient of friction on the thread and between the nut and the washer affects the degree of tension through the preloading force.Tensile tests were carried out on the both aforementioned assortments. The determined yield point of the bolt was analyzed, which was referred to the stress causing plastic deformation in the test of connection suitability. Bolts in two systems of forces were compared with each other (simple ‐ stretching and complex ‐ stretching and torsion) and the difference between them was shown. Based on the correlation of results from both tests, the importance of the K‐factor on the mechanical properties of the HV set was emphasized. The dependence of the K‐factor on the coefficients of friction in a bolted joint has been demonstrated.HV high‐strength bolt sets consider assembly procedures using a combined method according EN 1090‐2. Cases of exceeding the yield point of the bolt during assembly and permanent deformation of the fastener have been shown. The scope of assembly was determined in the elastic range and the transition to the range of plastic deformations. Again, reference was made to the coefficient of friction and its effect on the difference in the obtained preloading force leading to risky assembly in the plastic range.

EFFECT OF ANCHORAGE REBARS APPLYING TO MID-STORY PIN COLUMN BASE CONNECTION ON STRESS TRANSFER MECHANISM AND ULTIMATE SHEAR STRENGTH UNDER HORIZONTAL FORCE

Mid-story pin column system has been proposed to realize beam yielding mechanism of a steel moment-resisting frame. In this system, a pin connection system is applied inbetween the upper steel column and the lower RC column extended from the base beam to control moment demands on both ends of the first story column. An exposed-type column base has been adopted as a pin connection connected by a single anchor bolt. Static cyclic horizontal loading tests of a partial frame consisting of the first story column and the second floor beams showed a frame with the proposed column base system exhibited stable hysteresis performance up to a story drift angle of 0.05 rad, remaining column in elastic. In addition, the RC column with the connection of a single anchor bolt exhibited slippage at the connection while this problem was solved when an anchor bolt was stiffened by cross-shaped four shear plates. A cover plate was also welded on the top of the shear plates to cover the top surface of the RC column from bearing pressure of the upper steel column. An anchor bolt with the welded plates are called an anchor bolt set, or ABS, hereinafter. Ensuring a reliable seismic performance of an upper steel frame, damages at the proposed connection have to be minimized. So far, compressive stress transfer mechanism was clarified, and the ultimate compressive strength of the connection was evaluated in the previous study.

Testing of bolted base connections for wide-flange columns under combined axial compression and weak-axis lateral forces

This paper focuses on a new type of base connection for wide-flange columns. The base connection consists of a pair of steel angles and a shear plate that connect the flanges and the web of a wide-flange column to the foundation through a set of high-strength bolts, respectively. To investigate the response of the bolted base connection under the combined column axial compression and weak-axis lateral load, three specimens were prepared and tested. The test parameter varied in the specimens was the technology used to develop the angles in the bolted base connection. The three specimens adopted the hot rolled angles, the angles cold folded from steel plates, and the angles welded from steel plates, respectively. All the specimens were tested with the same axial compression and the same cyclic lateral loading protocol. It was found that all the specimens behaved in the same ductile manner while dissipating significant amounts of hysteretic energy. Moreover, all the specimens sustained the weak-axis rotation of 0.06 rad without developing any in-cycle strength degradations. The tests provided clear evidence that the cold folded and welded angles can be used as the surrogates to the hot rolled angles in the bolted base connection under the considered combined loading. This research further established a simplified model to approximate the backbone response of the lateral resistance of the bolted base connection under the considered combined loading. Result comparisons show that the simplified model can provide reasonable estimates.

Numerical Analysis of the Influence of Bolt Set on the Shear Resistance of Jointed Rock Masses

Bolt reinforcement is a standard reinforcement method for jointed rock masses. However, regarding rock anchoring, the mechanical characteristics of the joint surface, as well as the angle between the bolt and the joint sliding surface, are important factors that affect rock support. Therefore, to understand the influence of a set angle, length, normal load, and other conditions that affect the shear strength of bolt joints, this study uses numerical software to establish the shear sliding model of bolt rock masses and analyzes the influence of the setting conditions of the bolt on the shear strength of a bolt rock mass, which can be done by changing the setting method of the bolt and normal mechanical conditions of the sliding surface. The results show that the shear strength of the anchor joint is not affected after the anchor reaches a certain length. The angle of the anchor strongly influences the shear strength of the anchor joint, and the shear strength curve is V-shaped, where the anchor angle is less than 90°. Moreover, the shear strength curve indicates a downward trend when the anchor angle is greater than 90°, and the shear strength of the anchorage joint increases with the increase of the normal load. Under the same anchor length (4 cm) in the anchor angle and shear strength coordinate system, the shear strength curve of the single anchor is above the shear strength curve of the double anchor, which is exclusively in the local anchor angle section under the condition of a large normal load and a large anchor angle. The shear strength curve of the double anchor is above the shear strength curve of the single anchor.

Environmental Assessment of Electrochemical Energy Storage Device Manufacturing to Identify Drivers for Attaining Goals of Sustainable Materials 4.0

Electricity from the combination of photovoltaic panels and wind turbines exhibits potential benefits towards the sustainable cities transition. Nevertheless, the highly fluctuating and intermittent character limits an extended applicability in the energy market. Particularly, batteries represent a challenging approach to overcome the existing constraints and to achieve sustainable urban energy development. On the basis of the market roll-out and level of technological maturity, five commercially available battery technologies are assessed in this work, namely, lead–acid, lithium manganese oxide, nickel–cadmium, nickel–metal hydride, and vanadium redox flow. When considering sustainable development, environmental assessments provide valuable information. In this vein, an environmental analysis of the technologies is conducted using a life cycle assessment methodology from a cradle-to-gate perspective. A comparison of the environmental burden of battery components identified vanadium redox flow battery as the lowest environmental damage battery. In terms of components, electrodes; the electrolyte; and the set of pumps, motors, racks, and bolts exhibited the greatest environmental impact related to manufacturing. In terms of materials, copper, steel, sulphuric acid, and vanadium were identified as the main contributors to the midpoint impact categories. The results have highlighted that challenging materials 4.0 are still needed in battery manufacturing to provide sustainable technology designs required to the future urban planning based on circular economy demands.

Prediction of bolt fastening state using structural vibration signals

We have proposed a new method to predict the state of bolt fastening connection using time-domain structural vibration signal and experimentally validated its effectivness. To obtain the structural vibration signal, non-contact type laser displcement sensor and contact type piezo film sensor were used, respectively. Two-beam structures with holes were prepared and fastened with a set of bolt and nut. By applying a random initial displacement at the free end of the cantilever beam structure, vibration signals were measured for three different bolt fastening states: fully fastened, half-loosened and 90 %-loosened. After extraction of features from the obtained vibration signals, the bolt fastening state was classified based on the k-nearest neighbor (k-NN) algorithm. It is experimentally verified that the bolt fastening state can be accurately predicted by using the structural vibration signals and machine learning algorithm.

Impact of Nonlinearity of The Contact Layer Between Elements Joined in a Multi-Bolted System on Its Preload

The paper deals with modelling and calculations of asymmetrical multi-bolted joints at the assembly stage. The physical model of the joint is based on a system composed of four subsystems, which are: a couple of joined elements, a contact layer between the elements, and a set of bolts. The contact layer is assumed as the Winkler model, which can be treated as a nonlinear or linear model. In contrast, the set of bolts are modelled using simplified beam models, known as spider bolt models. The theorem according to which nonlinearity of the contact layer has a negligible impact on the final preload of the joint in the case of its sequential tightening has been verified. Results of sample calculations for the selected multi-bolted system, in the form of diagrams of preloads in the bolts as well as normal contact pressure between the joined elements during the assembly process and at its end, are presented.

Detection of structural bolt detorquing using direct acoustic measurement

A method for detecting loosened bolts in a structural joint based upon open-loop acoustic measurement is presented. The acoustic measurement is taken direclty on the bolt head. The response of the bolt to a proximal hammer impact is evaluated and characterised using wavelet decomposition of the signal measured from the bolt head. Results are presented from a set of structural bolts in several conditions of preload and looseness. The study could enable a quick and simple method for detecting and evaluating detorqued bolts in structural joints.

Modelling Nonlinear Multi-Bolted Systems on the Assembly State

Modelling and calculations of asymmetrical nonlinear multi-bolted connections treated as a system composed of four subsystems are presented. These subsystems are: a couple of joined elements (a flange and a support), a contact layer between the elements, and a set of bolts. The physical model of the system on the assembly state is described taking into account the bolt preloading conducted according to a specific sequence. For the modelling the finite element method is used. The flange and the support are built with spatial finite elements. The contact layer is formed as a nonlinear Winkler model, and the set of bolts are modelled using simplified beam models (named as rigid body bolt models). The calculation model is presented, by means of which changing force values in the bolts during the preloading of the system and at its end can be determined. Results of calculations for the exemplary multi-bolted system are presented.

Non-linearity of the contact layer between elements joined in a multi-bolted connection and the preload of the bolts

The paper presents modeling and calculations of multi-bolted connections at the assembly stage on an example of the engine cylinder head-block connection. The physical model of the connection was introduced as a combination of three subsystems: the set of bolts, the joined element and the contact layer between the joined element and the rigid support. The finite element method (FEM) was used for the modeling. Bolts were replaced with hybrid elements. The joined element was modeled with spatial finite elements. The Winkler model of the contact layer has been taken into consideration. The truth of the theorem has been examined, according to which non-linearity of the contact layer has a negligible impact on the final values of the bolt forces in the case of sequential preloading of the multi-bolted connection. The results of the calculations of a selected multi-bolted connection have been compared with the experimental results.

Experimental study of post-fire performance of high-strength bolts under combined tension and shear

Purpose This study aims to verify whether the reduction factors for the post-fire performance of Grade 10.9 bolts stated in an earlier study at the TU Darmstadt are also valid for shear and combined tension and shear. Design/methodology/approach Tests on Grade 10.9 bolt sets under combined tension and shear were carried out. The tested bolts were heated and cooled without being stressed by an additional mechanical load before being tested. Findings The test results show that the reduction factors can also be adopted for bolts under combined tension and shear, but the tension-shear-ratio has an influence on the load bearing capacity. Originality/value The post-fire performance of high-strength bolts is of special interest when a building structure is evaluated after an event of fire. In contrast to conventional structural steel, high-strength bolts do not recover their original strength and material properties.

발전용 축계 결합용 커플링 볼트 설계에 관한 연구

Coupling bolts have replaced conventional fitted bolts in applications where the operator's safety during assembly/disassembly is of concern or where the cost of process interruption is significant. Coupling bolts have been installed on rotating flange couplings in a wide range of marine and power applications worldwide. Their use has been approved by all leading international and national classification societies and regulatory bodies. A coupling bolt is a hydraulically tensioned fitted bolt that creates a stable and rigid link between coupling flanges and simplifies assembly and disassembly. We measure the bolt dimensions for reverse engineering and study the standard of assembly-load using a mechanical formula in order to localize a coupling bolt for a shaft in a power plant. We experimentally obtain the friction coefficient and confirm the condition of bolt sets through structure analysis. We show the variation of contact pressure for the shape parameter in order to consider the result when redesigning a bolt.

The ITER EC H&CD upper launcher: Design, analysis and testing of a bolted joint for the Blanket Shield Module

The final design of the structural system for the ITER EC H&CD upper launcher is in progress. Many design features of the preliminary design are under revision with the aim to achieve the built-to-print-status. This paper deals with design and analysis of a bolted joint for the Blanket Shield Module with special perspective on Remote Handling capability. The BSM of the ECH Launcher is attached to the Launcher Main Frame by a bolted joint conceived so that in the Hot Cell Facility, RH maintenance can be performed on internal components. The joint must be capable to resist very high Electro-Magnetic loads from disruptions, while it has to sustain substantial thermal cycling during operation. Thus the need for a rigid and reliable design is essential. Beside the set of pre-stressed bolts the flanges were therefore equipped with additional shear keys to divert radial moments away from the bolts. Main focus of the work performed was the mechanical design of the joint and the assessment of the structural integrity with respect to the loads applied and its capability for maintenance by RH procedures. To fulfill a major aspect of the RH requirements, the bolts were designed as “captive” in order to avoid their accidental removal from the joint. The captive bolt design is based on a concept that uses a dedicated spring ring, a standard spiral spring and a tensioning screw with two threads to secure the bolts in a form-locking stop. The final approval phase of the RH compatibility foresees simulations in Virtual Reality and physical tests on prototypes.

高温加熱を受けた高力ボルトセットのロックウェル硬さに基づく受熱温度推定方法

The Rockwell hardness of high-strength bolt sets subjected to high temperature was measured. According to these data, the equation that Rockwell hardness decreased at 7HRC per 100℃ above the tempering temperature was proposed as a conservative simple estimation method for fire-damaged investigation. The temperature of high-strength bolt sets was decided by averaging three temperatures, which estimated by applying the proposed equation to bolt, nut and washer. The proposed method was applied to the fire resistance test on full-scale beam and the measured temperatures of bolt sets could be estimated with adequate accuracy.

Frictional systems under periodic loads — History-dependence, non-uniqueness and energy dissipation

Nominally static contacts such as bolted or shrink-fit joints typically experience regions of microslip when subjected to oscillatory loading. This results in energy dissipation, reflected as apparent hysteretic damping of the system, and also may cause the initiation of fretting fatigue cracks. Early theoretical studies of the Hertzian contact problem by Cattaneo and Mindlin were confirmed experimentally by Johnson, who identified signs of fretting damage in the slip annulus predicted by the theory.For many years, tribologists assumed that Melan's theorem in plasticity could be extended to frictional systems — i.e. that if there exists a state of residual stress associated with frictional slip that is sufficient to prevent periodic slip in the steady state, then the system will shake down, regardless of the initial condition. However, we now know that this is true only if there is no coupling between the normal and tangential loading problems, as will be the case notably when contact occurs on a symmetry plane.For all other cases, periodic loading scenarios can be devised such that shakedown occurs for some initial conditions and not for others. The initial condition here might be determined by the assembly protocol — e.g. the order in which a set of bolts is tightened — or by the exact loading path before the steady cycle is attained. This non-uniqueness of the steady state persists at load amplitudes above the shakedown limit, in which case there is always some dissipation, but the dissipation per cycle (and hence both the effective damping and the susceptibility to fretting damage) depends on the initial conditions. This implies that fretting fatigue experiments need to follow a well-defined assembly protocol if reproducible results are to be obtained. We shall also present results showing that when both normal and tangential forces vary in time, the energy dissipation is very sensitive to the relative phase of the oscillatory components, being greatest when they are out of phase.With sufficient clamping force, 'complete' contacts (i.e. those in which the contact area is independent of the normal load) can theoretically be prevented from slipping, but on the microscale, all contacts are incomplete because of surface roughness and some microslip is inevitable. In this case, the local energy dissipation density can be estimated from relatively coarse-scale roughness models, based on a solution of the corresponding 'full stick' problem.

Not Another Set of Nuts and Bolts

Not Another Set of Nuts and Bolts

극한 상태에서 A490 고장력 볼트 세트의 체결 품질 연구

This test focuses on the correlation between the lubrication, ductility and strength through the change of nut lubricant which decides joining angle for A490 bolt sets required in the AASHTO (American Association of State Highway & Transportation Officials). Because the lubrication of high tension bolt, nut, washer sets becomes an important factor to ductility and joining load, the quality improvement is required for improving reliability and securing enough lubrication of maker and user. This study examines the quality characteristics required in the specification through tests because only this standard specifies joining quality in the extreme conditions (as much about two times of the joining angle on site as normal condition). Moreover, this study is limited to the test on joining axial force required in the AASHTO for the three nut lubrication conditions of A490 bolt set. It is concluded that the nuts should be coated or waxed enough for the improvement of the joining axial force and ductility of bolts required in the standards. It is shown that in the case of plain high tension bolt sets, a rust preventing lubricative oil shall be applied and the torque coefficient value for A490 bolt sets should be maintained below 0.175.