Bar Mechanism Research Articles

DESIGN AND SIMULATION OF TORSION BAR(ARB) FOR FSAE USING MATLAB

Formula SAE is a student design competition organized by SAE International (previously known as the Society of Automotive Engineers, SAE). The concept behind Formula SAE is that a fictional manufacturing company has contracted a student design team to develop a small Formulastyle race car. The prototype race car is to be evaluated for its potential as a production item. Each student team designs, builds and tests a prototype based on a series of rules, whose purpose is both ensuring on-track safety and promoting clever problem solving. An anti-roll bar is a part of automobile suspensions that helps reduce the body roll of a vehicle during fast cornering or over road irregularities. It connects opposite wheels together through short lever arms linked by a torsion spring. A sway bar increases the suspension's roll stiffness—its resistance to roll in turns, independent of its spring rate in the vertical direction. In this research paper, calculation for the anti-roll bar mechanism will be simpler, and more accurate than hand calculations. Calculation was done using MATLAB and further analysis using FEA in ANSYS.

FABRICATION OF MECHANISED CONVEYOR USING FOUR BAR MECHANISM

FABRICATION OF MECHANISED CONVEYOR USING FOUR BAR MECHANISM

Access Control in NB-IoT Networks: A Deep Reinforcement Learning Strategy

The Internet of Things (IoT) is a key enabler of the digital mutation of our society. Driven by various services and applications, Machine Type Communications (MTC) will become an integral part of our daily life, over the next few years. Meeting the ITU-T requirements, in terms of density, battery longevity, coverage, price, and supported mechanisms and functionalities, Cellular IoT, and particularly Narrowband-IoT (NB-IoT), is identified as a promising candidate to handle massive MTC accesses. However, this massive connectivity would pose a huge challenge for network operators in terms of scalability. Indeed, the connection to the network in cellular IoT passes through a random access procedure and a high concentration of IoT devices would, very quickly, lead to a bottleneck. The latter procedure needs, then, to be enhanced as the connectivity would be considerable. With this in mind, we propose, in this paper, to apply the access class barring (ACB) mechanism to regulate the number of devices competing for the access. In order to derive the blocking factor, we formulated the access problem as a Markov decision process that we were able to solve using one of the most advanced deep reinforcement learning techniques. The evaluation of the proposed access control, through simulations, shows the effectiveness of our approach compared to existing approaches such as the adaptive one and the Proportional Integral Derivative (PID) controller. Indeed, it manages to keep the proportion of access attempts close to the optimum, despite the lack of accurate information on the number of access attempts.

Analysis of temperature-induced spectral drift in the solar spectrometer driven by leadscrew and bar mechanism

A solar spectrometer is designed and developed, which uses a leadscrew and bar mechanism as the wavelength scanning mechanism, to achieve the accurate measurement of the solar spectrum in 170 nm–350 nm range. When measuring the standard spectrum of mercury lamp under laboratory conditions, there is a spectral drift due to temperature-induced deformation of the wavelength scanning mechanism. By using the finite element analysis method, the temperature sensitivity of each component in mechanism is analyzed. And then the linear superposition relationship between temperature rise and deformation is determined. Combined with the working principle of wavelength scanning mechanism, the corresponding relationship between temperature change and spectral drift is deduced.Spectral scanning and temperature monitoring were carried out simultaneously in instrument test to acquire temperature data of the wavelength scanning mechanism as it driving the gratings. Spectral drift was estimated according to the temperature variation and the maximum deviation between the predicted wavelength drift and the measured wavelength drift is 0.0016 nm, which is 6% of the measured wavelength. The experiment data validate the theoretical analysis results. The relationship between temperature change and spectral drift provides a theoretical reference for the correction of the measurement results and the thermal control of the instrument.

Durability of BFRP bars wrapped in seawater sea sand concrete

To investigate the durability of structures containing basalt fibre-reinforced polymer (BFRP) bars wrapped in seawater sea sand concrete (SWSSC) in marine environments, three sizes (including bare BFRP bars) of SWSSC-wrapped BFRP bars were subjected to laboratory accelerated corrosion tests in simulated seawater environments. The SWSSC thicknesses were set at 10 mm and 20 mm; the immersion temperatures were room temperature (~28 °C), 40 °C, and 60 °C; and the immersion media included a seawater, tap-water, and alkaline solution. The tensile properties of the SWSSC-wrapped BFRP bars after immersion were determined, and the degradation mechanism of the BFRP bars was investigated. Based on the results, the alkaline solution is more damaging to the BFRP bars than tap-water or seawater. Alkalinity is a key factor causing the degradation of the BFRP bars. Thus, the tensile strength retention of BFRP bars wrapped with thicker SWSSC, which has a higher alkalinity environment, could be lower than that of bare BFRP bars. In addition, prediction of the tensile strength retention of the SWSSC-wrapped BFRP bars based on Arrhenius relationship was conducted, and the prediction resutls agree well with the experimental results.

Electromechanical modelling of piezoelectric vibration energy harvester with a novel dynamic magnifier

Abstract In piezoelectric energy harvesting devices, the relative displacement between the two ends of the harvester beam decides the output power from the piezoelectric patch. A novel four bar mechanism with a helical spring is used as a dynamic magnifier to improve the relative displacement and thereby the output power from the harvester. This dynamic magnifier is placed between the base excitation location and the composite harvester beam to form two degrees of freedom (2DOF) piezoelectric energy harvester. Electromechanical coupled analytical equations for the voltage and output power are derived using a lumped electromechanical model. The model is developed assuming linear transverse vibrations of the harvester. A dynamic magnifier is fabricated for the required frequency range and the suitable dimensions of the harvester beam are estimated using commercially available software. Experiments are conducted for base excitation amplitude of 0.05 mm and the performance of the proposed 2DOF harvester is studied for the output voltage and power. The proposed 2DOF harvester has shown 110 % improvement in output power in first mode and 270 % improvement in second mode compared to the conventional single degree of freedom (SDOF) cantilevered harvester for given identical input conditions. The measured frequencies and output power are validated with analytical solutions and are found to be in good agreement. Further, the effect of mass ratio, stiffness ratio and base excitation amplitude on the output voltage and power is investigated using analytical expressions.

Corrosion behavior of low alloy steel bars containing Cr and Al in coral concrete for ocean construction

The corrosion resistance of carbon steel is poor in a harsh marine environment, and thus it is necessary to improve the durability of the structure. Coral concrete is a new cement-based composite material that exhibits excellent properties including local availability, high efficiency, good economy, and prospects for broad application in the construction of ocean-structures such as islands and reefs. Based on the corrosion mechanism of rebar, a low amount of Cr and Al are added to quantitatively analyse the corrosion time-varying performance of a low-alloy rebar in coral aggregate concrete. Based on XPS analysis, the corrosion resistance mechanism of Cr and Al low-alloy steel bars is determined, and the improvement value of steel bars' maintenance of passivity properties is quantitatively analysed. The polarization curves of reinforcement in coral aggregate concrete are obtained via the linear polarization method and electrochemical impedance spectroscopy to analyse the corrosion potential and corrosion current of low alloy reinforcement in coral aggregate concrete. A rebar performance improvement coefficient is defined to characterize the reinforcement durability improvement of alloy with Cr and Al elements. There is considerable scientific value and application significance attainable from the examination of the corrosion mechanism and behavior of corrosion-resistant steel bars in a harsh marine environment. It is essential to develop high strength corrosion-resistant low-alloy steel bars that are suitable for service in a harsh marine environment and to establish a rapid method to evaluate the corrosion resistance of steel bars.

Analysis of Geneva mechanism using dwell symmetrical coupler curve mechanism

Conveyor belt is a dedicated machine which is used in transporting the goods in assembly line area. This machine is driven by using a single mechanism for an operation. Here the focus is on the Geneva wheel which is used for this respective operation. Geneva Wheel mechanism here rotates and the index the roller in the conveyor belt one by one step. As we know there is the major drawback of a Geneva mechanism that jerk a lot while the operation is in process due to which it loses its acceleration. Here a symmetrical coupler curve of 4 bar mechanism which run on a Dwell curve is added to avoid the jerk as low as it can. The forces are analysed on the simulated mechanism with meshing method and the result to be presented in a graphical order, which represent the Von Mises stress and displacement.

Impact of Mechanical Reliability and Production Cost on the Thumbs Four Crossed Bar Mechanisms

Impact of Mechanical Reliability and Production Cost on the Thumbs Four Crossed Bar Mechanisms

Prediction of the Long-Term Performance and Durability of GFRP Bars under the Combined Effect of a Sustained Load and Severe Environments.

With the continuous development of production technology, the performance of glass-fiber-reinforced polymer (GFRP) bars is also changing, and some design codes are no longer applicable to new materials based on previous research results. In this study, a series of durability tests were carried out on a new generation of GFRP bars in laboratory-simulated seawater and a concrete environment under different temperatures and sustained loads. The durability performance of GFRP bars was investigated by analysing the residual tensile properties. The degradation mechanism of GFRP bars was also analysed by scanning electronic microscopy (SEM). Furthermore, the long-term performance of GFRP bars exposed to concrete pore solution under different stress levels was predicted using Arrhenius theory. The research results show that the degradation rate of GFRP bars was increased significantly at a 40% stress level. By comparing the test results, design limits, and other scholars’ research results, it is demonstrated that the GFRP bars used in this test have a good durability performance. It is found that the main degradation mechanism of the GFRP bars is the debonding at the fiber-matrix interface. In the range test, the effects of a 20% stress level on the degradation of GFRP bars were not obvious. However, the long-term performance prediction results show that when the exposure time was long enough, the degradation processes were accelerated by a 20% stress level.

Experimental investigation on shear steel bars in CRTS II slab ballastless track under low-cyclic reciprocating load

To study the seismic behavior of shear steel bar in high-speed railway CRTS II slab ballastless track, low-cycle reciprocating load tests were carried out on 6 high-speed railway CRTS II slab ballastless track specimens with different shear steel bar quantity and diameter. The failure mode, hysteretic curve, skeleton curve, energy dissipation capacity, ductility, stiffness degradation law and strength degradation law of the shear steel bars were examined. The influence of the quantity and diameter of shear steel bars on seismic performance of the track was analyzed, and the deformation process and failure mechanism of shear steel bar under the action of low-cyclic reciprocating load was revealed. Results showed that the deformation process can be divided into three stages: a) the interface between track slab and CA mortar layer cracks, and shear deformation of the shear steel bar occurs; b) the shear steel bar repeatedly compresses the CA mortar layer and adjacent track slab concrete around it, and bending deformation of the shear steel bar occurs; c) the CA mortar layer and track slab concrete around shear steel bar are crushed, and the shear steel bar undergoes tensile deformation until it fractures. The failure mechanism of shear steel bar under the action of low-cyclic reciprocating load was not instantaneous clipping, but a kind of “fracture” between clipping and a pull cut. The larger the quantity and diameter of the shear steel bar, the stronger the energy dissipation capacity of the specimen and the better the seismic performance of the ballastless track. Increasing the quantity and diameter of the shear steel bar can effectively reduce strength and stiffness degradation of track under the action of low-cycle reciprocating load.

Probing the Conformational Changes Associated with DNA Binding to PARP1.

Poly(ADP-ribose) polymerase 1 (PARP1) is an important first responder in the mechanism of DNA repair in eukaryotic cells. It is also a validated drug target, with four different PARP inhibitors (PARPi) approved for the treatment of BRCA-negative cancers. Despite past efforts, many aspects of PARPi are poorly understood, in particular their ability to trap PARP1 on chromatin and the relationships between their potencies, cellular toxicities, and trapping efficiencies. Because PARP trapping is widely believed to originate in allosteric coupling between DNA binding and the catalytic site, we further investigated the binding properties of PARP1 to a model for DNA with a double-strand break in the presence and absence of PARPi. Specifically, we have used sequential mixing stopped-flow spectroscopy to identify a slow conformational change that follows rapid DNA binding. Using a range of DNA concentrations and different mutants of PARP1 we demonstrate that this conformational change is one of the steps of the "monkey bar mechanism" that promotes DNA-dependent dissociation of DNA. This conformational change also corresponds to the previously identified conformational change associated with DNA-dependent activation of PARP1. Despite linking the conformational change associated with DNA binding and release to DNA activation, we find no evidence for PARPi perturbing this allosteric coupling.

Izado de torres provisionales de atirantamiento del viaducto de Almonte

Para el izado de las torres provisionales de atirantamiento del Viaducto de Almonte se ha utilizado un mecanismo de 4 barras más conocido como biela-deslizadera mediante el cual únicamente con la disposición de dos gatos de heavy lifting que accionan el mecanismo se pudo pasar de la torre en posición horizontal sobre el tablero a la torre en posición vertical sobre la pila. El fundamento de este mecanismo es conocido desde la Antigüedad y básicamente consiste en una deslizadera que mediante una acción exterior va desplazándose por un carril y a la que se une una biela biarticulada en sus dos extremos que es la que hace elevarse a la torre a la que está conectada.

Experimental Study and Mechanism on the Corrosion of Stressed Reinforcement Bars

In order to understand the influence of the tensile stress on the corrosion of reinforcement bars in civil engineering, the reinforcement bars specimens were put into the liquid corrosion tank made of hydrochloric acid and distilled water by applying the tension stress on the reinforcing frame to carry out rapid corrosion. The corrosion of reinforcement bars under different tension stresses was tested by using electrochemical polarization method. The metallographic examination of reinforcement bars was carried out through the section of reinforcement bars. The corrosion mechanism of the stressed reinforcement bar was tested and analyzed. It can be known from the experimental study: First in the same corrosion condition, the larger the tensile stress is, the faster the corrosion of steel bar will be; Second corrosion current density or corrosion rate are index for evaluating corrosion rate of reinforcement bars with different tensile stresses. Corrosion potential can not be used as an index for evaluating corrosion rate of reinforcement bars with different tensile stresses; Third intercrystalline corrosion occurs inside the reinforcement bar due to micro-defects after rolling and moulding, which directly affects the mechanical properties of reinforcement bar.

Optimal Synthesis of six bar Mechanism using Particle Swarm Optimization

This paper presents the optimal synthesis of a six-bar Watt-II mechanism with rotational joints in which a tracing point on the coupler traces a desired path. The objective of the work is to synthesize a six-bar mechanism whose coupler point generates the path as close to the given path as possible. The tracing path is the combination of two circular arcs with eighteen precision points with prescribed timing. A mathematical model is formed by two vector loop closure equations, and design constrained are imposed to improve the result quality. ‘Particle Swarm Optimization’ (PSO), an evolutionary technique, is used to obtain the optimal solution of the given six bar mechanism at first time, which has been used by various authors in case of four bar mechanism. Final design parameters and convergence rate of the optimal solutions are presented.

Corrosion Fatigue Crack Propagation Mechanism of High-Strength Steel Bar in Various Environments

AbstractThis paper investigated the corrosion fatigue crack propagation mechanism of high-strength steel bar HRB400 in various corrosive environments. Fatigue crack growth (FCG) tests were conducte...

Optimal Design and Redundancy Resolution of a Novel Robotic Two-Fingered Exoskeleton

This article deals with the optimal design and redundancy resolution of a seven DOF robotic two-fingered hand exoskeleton intended for rehabilitation purposes. The exoskeleton is designed to track the human digit motion accurately. As the human digit joint cannot be modeled by single revolute joint due to instantaneously varying center of rotation, a 4-bar mechanism is employed to model each phalanx of a finger. Optimal 4-bar linkages are designed by minimizing the error between the Cartesian trajectories of the human phalanx and those of the coupler points in respective 4-bar mechanisms. It is demonstrated that the designed 4-bar based exoskeleton can track the human digit motion accurately. Performance analysis of the developed device has been carried out by resolving its kinematic redundancy during a fine object translation motion by instantaneously optimizing manipulability measure.

Performance Analysis of LTE Random Access Protocol With an Energy Harvesting M2M Scenario

In this article, we analyze the performance of the long-term evolution random access procedure with the Third Generation Partnership Project's access class barring (ACB) mechanism in an energy harvesting (EH) machine-to-machine (M2M) scenario. To circumvent the state-space explosion in the conventional Markov-chain-based analysis due to time-dependent traffic pattern and data and energy buffer status, we develop an analytical model that combines mean-value analysis with the Markov-based analysis. Based on the analytical model, the random access success probability, the access delay of the network, and the average time duration between two successive successful transmissions are derived. Our analysis suggests that in the EH scenario, despite the lower number of the contending nodes in comparison with the non-EH scenario, the ACB parameters must be chosen in a more conservative way to avoid excessive collisions. The ACB parameters include access barring rate and mean barring duration. We also study an energy threshold-based activation policy and investigate the joint effects of this policy and the ACB mechanism on the random access success probability. The extensive simulations were conducted to evaluate the accuracy of the analytical model.

Design, development and modelling of single actuated, compliant and symmetrical multi link hopping mechanism

In this study, we present the design and development of a compliant multi-link hopping mechanism actuated by a single DC motor. Mechanism consists of torsional spring, two symmetrically arranged six bar mechanism connected through the bottom gears and a compliant preloaded pinned-pinned buckling beam serving as a nonlinear spring. Kinematic and dynamical analysis are performed using both Newtonian dynamics, vector closure loop equations and geometric constrains of the design to predict the motion of the mechanism. Adams simulations are performed to obtain the force-deflection curve for flexible beam and torque-angular displacement curve for flat spiral spring. Mechanism is built by 3D printing all parts using thermoplastic based polylactic acid PLA filament. Continuous hopping motion is created without requirement of any hydraulic and pneumatic actuators or mechanical springs to store and release energy during the complete motion. The actuator is connected to a 3D printed flat spiral spring to control the speed and pinned-pinned buckling beam is attached in between two symmetrical multi-link mechanism to increase the effect of impact.

A Comparative Study of Improved Harmony Search Algorithm in Four Bar Mechanisms

There are problems that are difficult to solve through mathematical programming or by classical methods. These problems are called hard problems due to their high complexity or high dimension. On the other hand, mataheuristics intends to seek a better solution to a problem. The Improvement Harmony Search algorithm is proposed under modification of the bandwidth parameter increasing the quality of the exploitation of the solutions. That is why within the state of the art, are mentioned several versions of harmonic search. The state of the art is supports the fact that the algorithm belongs to the category of those who make modifications to its parameters. This research demonstrates the ability of ImHS to solve a problem of high complexity focused on solving four-bar mechanism designs, whose solutions imply high dimension and which are also classified as hard problems. The two problems that are solved in this investigation, are problems very attacked within the state of the art by various metaheuristics. A comparison is then made against previous solutions with traditional metaheuristics and other versions of harmony search algorithm. Finally, the effectiveness of performance is demonstrated, where proposed algorithm it exceeded five metaheuristic algorithms and five harmony search versions. An optimum is provided in an easy and useful way, the parametric statistics are improved and the number of feasible solutions is exceeded in NP-hard problems as in the case of problems with four-bar mechanisms.