Bolt Torque Research Articles

Investigations on MWCNT Embedded Carbon/Epoxy Composite Joints Subjected to Hygrothermal Aging under Bolt Preloads

The present work emphasizes the effects of hygrothermal aging on the bolted joints prepared from carbon/epoxy nanocomposites at different bolt preloads. The effect of multiwalled carbon nanotubes (MWCNT) was investigated by incorporating 0.1 to 0.5 wt.% of MWCNT in composite laminates with 0.3 wt.% of MWCNT giving the best mechanical properties. The water absorption studies at three hygrothermal conditions i.e., 25 °C, 45 °C, and 65 °C for 30 days, were conducted for neat and 0.3 wt.% of MWCNT added composite specimens, as per ASTM D5229. The bolted joints were designed using ASTM D5961 having a width to diameter ratio (W/D) and edge to diameter ratio (E/D) equal to 6 and 5, respectively. The bolt torque effect at different levels i.e., 0, 2, and 4 Nm were studied to estimate the ultimate failure loads in the nanocomposite joints. In all aspects, incorporating MWCNT shows better results than neat configured composites. The statistical investigations were performed using the central composite design on different control factors i.e. temperature, duration, bolt torque, and material.

Effect of bolt tightening on the fatigue behavior of GLARE double shear lap joints

In this paper, the effect of bolt torque tightening has been investigated on the fatigue behavior of GLARE in double shear lap configuration. To do so, experimental fatigue tests were conducted using GLARE3-5/4-0.4 specimens with applied torques of 0 (finger tightened), 2 and 4 Nm at different cyclic longitudinal load ranges to achieve the stress-life (S-N) curves. The results revealed that applying and increasing the clamping force enhances the fatigue life of the GLARE specimens. Furthermore, comparison of fatigue test results of GLARE and available monolithic aluminum alloy 2024-T3 plates indicated when the applied load range is low, the effect of clamping force is more noticeable in GLARE specimens due to longer fatigue crack growth life of GLARE. Also, the occurrence of fretting fatigue didn’t reduce the fatigue life of GLARE specimens considerably in contrary to aluminum sheets because of the laminated structure of GLARE. The obtained results can provide insights in designing bolted GLARE joints with superior fatigue in-service performance.

Behavior of Mechanical Joints Prepared from EB Cured CFRP Nanocomposites Subjected to Hygrothermal Aging Under Bolt Preloads

In the present work, the hygrothermal aging effect was studied on the performance of bolted joints prepared from electron beam (EB) cured carbon/epoxy nanocomposites under varying bolt torques. The multiwalled carbon nanotubes (MWCNTs) at different wt.% varying from 0 to 0.5 were added into the composite laminates with 0.3 wt.% giving the maximum tensile strength. The comparison of mechanical properties was done for thermally cured, EB cured (without post curing) and EB cured (post curing) composites. For hygrothermal aging of neat and 0.3 wt.% MWCNT configurations, water absorption studies were conducted at three different water temperatures i.e., 25 °C, 45 °C, and 65 °C for 30 days, as per ASTM D5229. The mechanical strength retention of aged composite specimens were analysed. Using ASTM D5961, the bolted joint specimens were prepared to investigate the bearing response and ultimate failure loads in the composite bolted joints. The damage occurred due to hygrothermal conditions has been interpreted in the light of their morphological structures.

Analisa Posisi Peletakkan Baut terhadap Gaya Geser pada Sambungan Plat Baja

Research on analysis the effect of positioning the use of bolts on the connection process between the two steel plates against the other steel plates to determine the magnitude of the bolt torque moment and the magnitude of the force. The connection of the steel plate components where the joints are used are able to with stand shear forces, pressure and torsion. The research objective was to determine the effective placement of the bolt position and the distance of the load on the vertical and horizontal bolt position to the magnitude of the torque due to compression and the fracture model. Data collection was carried out in several tests of changes in the placement of the bolt joints, including the position of the bolts with three angles, in the vertical and horizontal position of the bolts. The findings of the placement of the three-angle bolt position at 2-4-11 the shear force experienced a shift / fracture of the bolt greater than the shear force that occurred in the horizontal and vertical bolts position, with a pressure of 92.66 bar (torsion moment 108,342 kg-mm). Testing the position of the three-angle bolt at 2-6-10 where the vertical bolt was broken with a pressure of 65.33 bar ( torque moment 76.401 kg-mm). The three-angle bolt placement test at 6-7-8 where the horizontal bolt was fractured at a pressure of 55.33 bar (torque moment 64,701 kg- mm). Comparison of the placement of the bolts in the position of three angles of the shear force between the vertical and horizontal positions, the shear forces experience the greatest shift / fracture of the bolts in the vertical position. The loading distance affects the amount of shear force that occurs on the bolt. the farther the loading distance, the greater the shear force that occurs.

Monitoring the looseness of a bolt through laser ultrasonic

laser ultrasonic was applied to monitor the looseness of a bolt, aiming at the phenomenon that bolts can be loose after being assembled in a machine. We expound the experimental principle to monitor the bolt looseness by wave energy dissipation based on Hertzian theory of contact, taking only the asperity elastic deformation into account in our research. In the experiment, guided wave was induced by the laser, which was stimulated on the plate, to realize the goal of non-contact excitation. A piezoelectric sensor was used to receive the guided wave signal in the experiment. The distribution of guided wave power with frequency was observed by a Welch power spectral density (WPSD) image, and then the power of guided wave was calculated by power spectral density(PSD). We found that the power of guided wave is positively correlated with bolt torque. This conclusion is feasible for plates of different roughness (Ra0.5 ∼ Ra1.5), clamped by a bolt, verifying the efficiency of the method to monitor the bolt looseness through laser ultrasonic.This was verified by numerical analysis. Finally, the formula between power and bolt torque was fitted for bolted-joints in our experiment.

Evaluation of the axial force in an FeCo bolt using the inverse magnetostrictive effect

Abstract The use of the magnetic flux density change as a diagnostic parameter in screw tightening torque of bolts is discussed in this study. The proposed methodology uses the inverse magnetostrictive effect, considering that the magnetic flux density changes according to the internal stress of the bolt. In the experiments, we measured the strain and magnetic flux density of the magnetostrictive material FeCo bolt under tightening. Moreover, theoretical and three-dimensional finite element analyses were performed, and the axial force, torque factor, strain, and magnetic flux density were calculated. The experimental, analytical and theoretical results were compared, and the relationship between the bolt’s internal axial force and the magnetic flux density was examined. Results show that the magnetic flux density in the FeCo bolt varies with changes in the magnitude of the bias magnetic field, and this study proposes the possibility of a new class of smart bolt. Keywords: Magnetic flux density, Inverse magnetostrictive effect, Internal axial force, FeCo alloy

Monitoring and Imaging of Bolted Steel Plate Joints Using Ultrasonic Guided Waves

Abstract Steel structures with bolted joints are easily dismantled and repurposed. However, maintaining joint integrity is a challenge. This paper reports a non-destructive methodology to monitor steel bolted joints. Piezoelectric ceramic patches have been surface bonded in the joint for transmission and reception of guided ultrasonic waves. Both single and multiple bolted joints have been investigated. It has been demonstrated that the variation in acoustic impedance due at the bolt interface can be discerned and calibrated with bolt torque level. The recorded reflections from interfaces are used as inputs for a newly developed imaging algorithm. The proposed method has the potential to be a reference-free and fully automated method.

Research on Torque Characteristics of Clamping Bolts for PEMFC Stack under Strengthened Durability Vibration

To investigate the bolt torque attenuation feature of PEMFC stack under static test and vibration test conditions, 2-hour static test and 300-hour enhanced road vibration test were carried out in turn. The results show that the attenuation of bolt torque are related to their locations during the static test, also the attenuation of bolt torque is obviously related to their locations during the 300-hour vibration test. Moreover, the test results also show that there are different regularities in different vibration test periods.

Spatially-Resolved Measurement of Current Distribution in Polymer Electrolyte Water Electrolyzers

Operational cost, primarily power consumption, is the one of the main obstacles for hydrogen produced by polymer electrolyte water electrolyzers (PEWE). Roughly 70% of the hydrogen production cost stems from electricity [1], thus overall electrochemical efficiency has a direct influence on the hydrogen price. Dominating sources of electrochemical loss in PEWE cells are the kinetic, electric, and mass transport overpotentials. Conventional research and diagnostic techniques, such as polarization curves and EIS measurements, predominantly probe macroscopic performance characteristics without any spatial resolution of electrochemical performance. These offer limited insight into the in-situ behaviors of the PEWE and its overpotentials. The work of Schuler, et al. [2] gives a detailed understanding of transport mechanisms inside a PEWE by drawing extensively on ex-situ techniques. Work carried out by Zhang et al. [3] has successfully shown the bubble formation of water electrolysis inside a PEWE by means of an in-situ, high-speed micro-scale visualization system (HMVS). However the HMVS does not explicitly capture the local electrochemical behavior of the cell. Therefore, complex CFD models have been implemented to shed light on the inner workings of PEWE; while insightful, such models need to be validated with experimental data. This work aims to provide a reliable source of experimental data by developing a technique that allows for in-situ spatial and temporal current distribution measurements which can be used to validate existing modeling efforts.Current distribution measurements are described extensively in the works of Bender et al. [4, 5]; a major innovation was the inclusion of a printed-circuit board (PCB) with an array of shunt resistors attached to each segment as shown in Figure 1a (4.5 mm x 4.5 mm segments in this work). The measured voltage drop across each shunt resistor is used to calculate the current in each segment. Data acquisition on the distributed current board is done simultaneously to electrochemical control of the electrolyzer. Thus the distributed current measurement occurs passively while a potentiostat controls the electrolyzer, without interrupting its operation. This setup is capable of using flow fields of both 5cm2 and 25cm2 active area. The 5 cm2 flow field has 16 segments while the 25cm2 has 100 segments that are electronically isolated, yielding high spatial resolution of the current distribution. The distributed current is then interpolated to obtain smoothed contours as shown in Figure 1b and 1c. Preliminary current distribution experiments were carried out at 85⁰C, water flow rate of 0.5 to 3 mL/min/cm2, at a cell compression under bolt torques of 5 Nm and 10 Nm. Experiments were also carried out with two sets of liquid-gas diffusion layers: iridium-coated titanium and bare titanium felts. The results show a relatively uniform current distribution across the electrolyzer with no significant impact of flow rate. The experiments also revealed that the spatial current distribution is highly sensitive to local cell compression, which is not captured in the overall cell performance of a polarization curve. This work demonstrates the benefit of a spatially-resolved current distribution measurement technique and the insights it offer which would otherwise be impossible to probe.

터보차저 V형 커플링의 체결 특성에 관한 유한요소 해석 및 실험적 연구

V-type coupling, which is often applied to turbochargers, is a mechanical fastener where radial forces close turbine housing and bearing housing together. It prevents leakage of exhaust gases by contact pressure of the backplate caused by the load transmitted from the bolt-tightening torque. Therefore, it is important to study the mechanical behaviors of the coupling system in order to establish more accurate sealing assessment technologies. In this study, an experiment was first conducted to obtain the relationship between torque and its resulting axial force in a specially designed gage bolt. Strains were then measured when the torque was applied using the gauge bolts on the turbocharger. Thus, the magnitude of the axial force due to the bolt torque can be obtained inversely. In addition, the circumference and width strains of the turbocharger coupling were measured under the assembly load, and theses results were compared with the finite element results. As a result, they tend to be very similar, but in the ring area, analysis results show a relatively small value, and near the bolt, the analysis results are larger than the experimental strains. This is thought to be due to the reduced strains around the bolt by the hammering process.

Bolt loosening detection in a jointed beam using empirical mode decomposition–based nonlinear system identification method

In this work, a state-of-art nonlinear system identification method based on empirical mode decomposition is utilized and extended to detect bolt loosening in a jointed beam. This nonlinear system identification method is based on identifying the multi-scale dynamics of the underlying system. Only structural dynamic response signals are needed to construct a reduced-order model to represent the system concerned. It makes the method easy to use in practice. A new bolt loosening identification procedure based on the constructed system nonlinear reduced-order model is proposed. A new damage feature to indicate bolt loosening is presented. Experimental works are carried out to validate the proposed method. The results show that the proposed damage detection method can detect bolt loosening effectively, and the proposed damage feature values increase with the increase of bolt torques. The damage feature calculated from the response solution of the reduced-order model can give robust and sensitive indication of bolt loosening.

Effect of secondary bending and bolt load on damage and strength of composite single-lap interference-fit bolted structures

The single-lap interference-fit bolted joint is widely used in composite structures. In order to get an accurate prediction of bearing strength, secondary bending and bolt load effects are studied in the present research via combination of experimental and numerical methods. The joint specimens with four levels of interference-fit size ( I) and bolt torque ( T) were tested according to ASTM standard D5961 to evaluate the bearing behavior and joint stiffness. Meanwhile, a finite element model considering the shear nonlinearity is built to simulate the bearing strength and evolution of intralaminar damage and delamination. Results show that the bearing behavior of composite joints is more sensitive to bolt load than interference-fit size, and the optimal pattern is I = 0.4% and T = 8 N-m, which can effectively improve bearing performance and alleviate secondary bending effect. Matrix failure and fiber–matrix shear-out failure accompanied with delamination are commonly observed and localized on the bearing side of joint-holes, indicating the desired non-catastrophic failure modes.

A bolt preload monitoring method based on the refocusing capability of virtual time reversal

Bolted joints are widely used in aerospace and civil structures. Nevertheless, bolts may easily lose preload because of inappropriate initial preloads or time-varying servicing loads. Hence, bolt loosening monitoring is important for ensuring the safety and reliability of the bolt-jointed structures. In this paper, a guided wave method based on virtual time reversal (VTR) and tightness index representing refocusing capability is developed for bolt preload monitoring and to mitigate the requirement of baseline. In VTR, a response signal acquired from the bolted structure in fully tightened condition is reversed and used as the excitation signal for the bolted structure in loosening states. On this basis, the ratio of the energy of the refocused wave packet in final received wave signal to the energy of the entire signal is defined as tightness index (TIE). In this way, the calculation of TIE does not need to compare with baseline acquired in fully tightened condition. The effects of roughness of contact surfaces on guided wave propagation and the refocusing capability are analyzed by a 2D FE model. The proposed method is also experimentally validated by bolt-jointed structures with single and multiple bolts. The experimental results show that TIE increased almost linearly with the decease of bolt preload and is effective at the early stage of bolt loosening. In addition, the effect of temperature on preload detection accuracy is weak. Furthermore, it is important to select a right frequency to ensure that the TIE is sensitive throughout the entire bolt torque range.

Hygrothermal effects on mechanical joints prepared from fiber reinforced plastic nanocomposites

The present work deals with the hygrothermal aging of the bolt joints prepared from glass fiber reinforced plastics. To investigate the effect of nanoclay on joint performance, nanoclay content was varied from 0 to 5 wt%, with laminates prepared from 3 wt% of nanoclay content demonstrating the best mechanical properties. Nanoclay acts as a mechanical interlock between the fiber and the epoxy and thus improves the interfacial bonding. A good dispersion of nanoclay also improves moisture barrier properties which in turn reduces the degradation of the composite material hygrothermal conditions. Bolt joints were prepared from woven glass fiber reinforced laminates incorporating 3 wt% of nanoclay content. To design the bolt joint, ASTM D5961 was used and the geometric parameters, i.e. edge distance to hole diameter (E/D) ratio and width to hole diameter (W/D) ratio were fixed to 5 and 6, respectively. Three different temperatures, i.e. 25℃, 50℃ and 75℃ were considered for the aging to three different duration of exposure, i.e. 1, 2 and 3 weeks. The effect of different levels of bolt torque, i.e. 0, 2 and 4 Nm were considered for the failure analysis of the joint. A full factorial design of experiment was conducted on important control factors, i.e. water temperature, exposure time, bolt torque and material variation. It was found that the hygrothermal conditions degraded the material with temperature as the most contributing factor.

Accelerated weathering of bolted joints prepared from woven glass fiber-reinforced nanocomposites

This work deals with the accelerated aging of the bolted joints prepared from glass fiber-reinforced nanocomposite laminates. ASTM D5961 was used to design the bolted joint, and the geometric parameters, i.e. width-to hole-diameter ( W/ D) ratio and edge distance-to-hole diameter ( E/ D) ratio were fixed to 6 and 5, respectively. ASTM D1544 was used for accelerated aging, and a maximum of 500 h cyclical ultraviolet exposure, 8 h of ultraviolet radiation at 60 ℃ followed by 4 h of condensation at 50 ℃, was given to the specimens. A full factorial design of experiment was conducted on important control factors, i.e. aging time, bolt torque, and material variation, using response surface methodology. To investigate the effect of nanoclay content, a range of 0–5 wt% was investigated. Specimens with 3 wt% of nanoclay demonstrated optimum tensile strength and were selected to manufacture the bolted joint. Nanoplatelets having high aspect ratio increased the specific surface area and thus the tensile strength of the nanocomposite. It was found that the strength of the joints prepared with and without the nanoclay content decreased with the increase in the duration of aging. However, the joints with the nanoclay content had higher failure loads. The strength retention in the joints with nanoclay content was more in comparison to the joints made with neat epoxy. Nanoclay acted as a mechanical interlock at the fiber–matrix interface and improved the interfacial bond strength. A good dispersion of nanoclay also acts as a barrier to the moisture, which eventually reduces the degradation of the composite material due to the lesser fiber–matrix de-bonding under accelerated aging conditions.

Experimental investigation of a passive direct ethanol fuel cell

Experimental investigation of a passive direct ethanol fuel cell (DEFC) is presented in this work. A passive DEFC of active area 25 cm2 with Nafion 115 membrane is developed and tested. Effect of several parameters such as ethanol feed concentration, ambient temperature, bolt torque, and operating orientation on the cell performance is investigated. It is found that all these parameters significantly affect the cell performance. The cell performance improves with initial increase in the ethanol feed concentration, reaches to a maximum, and then decreases on further increasing the ethanol feed concentration. A similar trend in the cell performance is observed on increasing the ambient temperature and on increasing the bolt torque too. In this study, the maximum cell performance is observed with 4 M ethanol feed concentration, 60 °C of ambient temperature, and 7 Nm of bolt torque. Cell orientation too affects the cell performance. Horizontal cell orientation is proved to deliver better cell performance compared to vertical orientation. This study depicts that an improved DEFC performance can be obtained by carefully selecting working parameters.

Experimental and analytical study of an CF-PEEK Fastener all composites single-lap shear joint under static and fatigue loading

This paper presents a detailed experimental study on carbon fibre (CF) polyether etherketone (PEEK) composite fasteners designed to join conventional high performance composites (CFRP). The failure mechanisms of two CF-PEEK fasteners with countersunk heads joining two laminate plates in a single-lap configuration were investigated under static (tensile) and cyclic loading (tension–tension). The failure process of the bolted joints is described in detail using acoustic emission and microscopic cut views. For comparison the CF-PEEK fasteners were replaced by metal fasteners (Titanium) under the corresponding conditions and loadings. The experimental results are in good agreement with the newly developed “closed-form” model up to the damage point of the joints. This enhanced analytical approach is a closed-form extension of the spring-based method, where bolts and laminates are represented by an arrangement of springs and masses. The model covers in all variables influencing the joint behaviour, such as fastener position, joint material, fastener type, hole diameter, joint thickness, bolt-hole clearance, and bolt torque.

Reduction of Sticking in a Linear-Guideway Type Recirculating Ball Bearing

This paper deals with the reduction of sticking in a linear-guideway type recirculating ball bearing (linear bearing), which is the significant increase in the required driving force for a linear bearing in a back-and-forth short stroke operation. First, the driving force of a linear bearing with five carriage-body types (A–E, having different dimensions and shapes) under rolling moment load was measured. Simultaneously, the ball's position in the load zone was observed. The experimental results showed that regardless of the carriage-body types, the increasing rate of the driving force and the interspace (space between balls around the center of the load zone on the raised side) decreases and sticking tends to hardly occur as the maximum linear velocity and the stroke length increase. Also, the occurrence of sticking was affected by the carriage-body types. Finally, to examine the relationship of carriage-body types, carriage-body deformation, and the occurrence of sticking, the carriage-body deformation (caused by preloading and tightening torque of bolts) was calculated by finite element method (FEM). The FEM results showed that carriage-body type, which is more deformable, had a tendency to reduce sticking.

Performance analysis of a transparent PEM fuel cell at theoptimized clamping pressure applied on its bolts

Experiments were carried out on a single transparent proton exchange membrane (PEM) fuel cell with titanium gas distributor plates. Effect of the clamping pressure due to torque applied on each bolt, anode and cathode humidification temperatures, fuel cell temperature and cathode flow rate on the performance of the fuel cell are discussed in this work. Results show that the performance of fuel cell increases first to a maximum and then decreases with further increase in bolt torque. The cell performance decreases with increase in cathode humidification temperature and increases with the cell temperature. Also, humidification of anode reactant is important to improve the performance of the fuel cell. The effect of cathode flow rate is less at activation and ohmic overpotential region but it is significant at concentration overpotential region.

Dynamic Friction Coefficient and Performance of Asymmetric Friction Connections

Modern steel structures are increasingly using friction connections to enhance energy dissipation and minimize damage. The Asymmetric Friction Connection (AFC) was developed to create a repeatable, efficient means of dissipating seismic response energy and reducing structural damage without yielding of structural frame elements. Testing has demonstrated stable efficient hysteretic behavior. However, no full characterization of their dynamic friction behavior exists, nor any specific information relating their clamping bolt assembly torque/force to the dynamic friction coefficient during cyclic testing. A deeper understanding of these design and implementation aspects adds greater certainty and precision to design.An experimental evaluation is performed, quantifying the effective dynamic friction coefficient as a function of connection clamping force from clamping bolt torque and input displacement, using torques from 20 to 500Nm and a series of sinusoidal input motions. Bolt elongation and associated clamping force are evaluated with the measured resistive sliding force of the connection to derive a dynamic coefficient of friction for the AFC. Overall results show that friction is weakly dependent on input motion amplitude, but is direction dependent for all torques with larger friction coefficients in the positive, tension direction of input motion, where larger assembly torques over 200Nm had larger direction dependence. Clamping bolt torques over 200Nm result in bolt yielding during input motions, which would necessitate post-earthquake inspection and potential repair, and reduce resistive sliding forces during a subsequent seismic event. The overall results present a generalizable analysis to guide design, which is extendable to similar friction connections or devices. Equally, the results also provide a better understanding to enhance adoption/uptake of these friction connections in steel structures.