Improving the comprehensive performance of miniature MR rotary actuators using a lamellar excitation structure

Miniaturization has increasingly become a crucial prerequisite in various magnetorheological (MR) drive application scenarios. Owing to their high controllability and low response time, MR rotary actuators are developed for numerous feasible actuation solutions. However, the incident low degradation efficiency in the miniaturization limits the application of MR rotary actuators. In addition to torque capacity, structural simplification and easy machinability are also essential for miniaturization. In this study, a novel lamellar excitation structure (LES), which is interleaved with induction coils and ring-shaped iron cores, is proposed to improve the comprehensive performance of a miniature MR rotary actuator. The optimisation of the magnetic field distribution is realised by adopting an equivalent magnetic modelling method. The miniature MR actuator is incorporated into a turbine generator to evaluate the torque capability of the proposed LES-incorporated MR actuator via a kinematic model of the rotating shaft. The LES-incorporated MR rotary actuator demonstrates more favourable deceleration efficiency and torque capacity than conventional MR rotary actuators. The speed reduction per unit power Δn/P can be increased by 500% at most. The torque enhancement ratio-to-volume ratio (TEVR) value of LES is approximately 80 times higher than that of other optimised structures. We believe that this study is significant in improving the comprehensive performance of miniature MR rotary actuators, expanding the applications of MR actuators in miniaturised scenarios.

Torque capacity of multidisc wet clutch with reference to friction occurrence on its spline connections

In this article developed mathematical model that includes friction occurrence on spline connections is presented. The work also contains results of experimental research on torque capacity of multidisc wet clutch. These results are expressed as a function of contact pressure for different number of friction surfaces. Due to increased interest in research concerning multidisc wet clutches it is essential to determine impact of friction on fit connections on transmitted torque. Analytical calculations that include both known loss coefficient and assumed lack of friction on fit connections are compared to results of experiments. The paper contains detailed description of test stand and methodology of experiment. As a result of conducted tests it was found that correction coefficients known from literature are highly inaccurate. Measured values of torque indicate that transmitted torque reach significantly higher values. It was also revealed that after slippage appeared, the pressure plate usually moved in the direction of exerted clamping force, but movement in reversed direction also took place for some experiments. While movement corresponding to clamping force reached ca. 0.08 mm, in opposite direction amounted to 0.02 mm. Furthermore, studies presented that lapping of adjacent friction surfaces greatly affects differences between respective results obtained for a specific experiment.

Railway Axle and Wheel Assembly Press-Fitting Force Characteristics and Holding Torque Capacity

Nowadays, press-fitting is widely used in the manufacturing industry because it allows easy and fast installation and is repetitive, strong, and inherently reliable. The quality of a press-fitting assembly can be verified from the press-fitting curves and forced monitoring. This study aims to investigate the characteristics of the press-fitting curve with various interference railway wheelset models and determine the interference limit that axles can withstand at the maximum holding torque without slipping and without plastic deformation. A three-dimensional finite element analysis examined the maximum press-fitting force and stress distributions using Abaqus FEA software. The press-fitting curves of the railway wheel and axle assembly obtained from finite element simulation were classified following European Standard EN 13260. The press-fitting curves showed whether they fell within the boundary limits in the EN standard to allow their practical application. This study also showed when plastic deformation would occur, within the recommended interferences in the EN standard. Moreover, the effect of interference was numerically simulated for the maximum holding torque capacity within the EN standard interference range. Numeric simulation was compared with the theory: the deviation was 15–6%.

Torque capacity of the multilayer interference fit based on a friction coefficient prediction model

This paper proposes the theoretical model of a multilayer interference fit and gives out the relational expression between radial interference and friction coefficient. Taking the typical wind turbine's shrink disk of a three-layer interference fit structure as an example, special experimental equipment is developed to test the torque capacity. Based on experimental results and the theoretical model, the mathematical expressions of radial interference and assembly stroke for friction coefficient are obtained by polynomial fitting, and the prediction model of friction coefficient is established. The three-dimensional finite element model of a shrink disk is constructed by applying the friction coefficient prediction model. With the mathematical expressions of radial interference and assembly stroke for the torque capacity, the rules of main dimension parameters and torque capacity are analyzed. The maximum relative error between experiment and simulation is 8.2%, which shows the feasibility of finite element simulation. The results of our study have certain guidance for the prediction of friction coefficient and the manufacture of the multilayer interference fit.

Analysis of Screw Extrusion of Thermoplastics for AM

3D printing is an Additive Manufacturing (AM) process that enables physical realization of a CAD (Computer-Aided Design) model. 3D printing can be classified into several variants; Material Extrusion Additive Manufacturing (MEAM) is the most versatile and widely used. MEAM is a continuous extrusion and selective deposition process commonly used for thermoplastics. Screw Extrusion Additive Manufacturing (SEAM), a sub-domain of MEAM, uses an extruder screw to push the polymer-melt out of the nozzle. Computational Fluid Dynamics (CFD) analysis of a single screw extrusion of thermoplastics is presented in this paper. The effect of various control parameters like screw rotation, wall heat flux/temperature profile, screw geometry, etc., has been studied on the required output parameters like productivity, torque capacity, power requirement, metering efficiency, etc. It is found that the incrementally-variable-pitch screw geometry provides the best metering characteristics. However, every screw design is a compromise between melt temperature, productivity, and power requirements.

On the Design of Continuously Variable Transmissions with Bidirectional Bridge Structures for Hybrid Vehicles

To increase the energy efficiency of road vehicles, an ideal transmission system should have a wide ratio coverage, a high torque capacity, and a high mechanical efficiency. Continuously variable units (CVUs) have been successfully implemented due to the smooth ratio variation, sufficient torque capacity, and ratio coverage. Hence, it will be beneficial to develop a hybrid powertrain comprising a CVU. In this paper, a design method called the “basic path diagram” (BPD) is proposed. It provides a simplified schematic of the system and represents the generic connections among the mechanical components. The system configurations synthesized by the BPD can be sorted according to three characteristics: Direction of power flows through the CVU, coupling pattern of the power inputs, and number of transmission paths parallel to the CVU. The first characteristic determines the number of times the CVU ratio coverage can be exploited, the second characteristic determines whether the torque of the power inputs can be independently controlled, and the third characteristic can help reduce the torque loading of the CVU. With the aid of a BPD, one of the possible system configurations is provided as an example. The result shows that the system can exploit twice the ratio coverage of the CVU and reduce the torque and power transmitted by the CVU in combination with planetary gearsets.

Analysis on the Interference Assembly of Camshaft With Knurled Tube and Cam

Interference joint is one of the most advanced assembly methods for camshaft. In this paper, the mechanism of camshaft interference assembly is analyzed by thick-wall cylinder model. Joining/tortion experiments are done to estimate the joining force and connection strength. The relationship between the torque capacity, joining force and interference of the camshaft is established by the experiment results. Joining force linear increase with the interference, and torque exponential increase with it. The plastic deformation characteristics of knurled teeth on the tube during the joining process are obtained by metallographic observation. The results reveal the metal line changes continuously of the knurled tube. The knurled tooth tip turns over after joining. And elastic limit would be reached in the extrusion region.

Preliminary Study of the Effects of Eccentric-Overload Resistance Exercise on Physical Function and Torque Capacity in Chronic Kidney Disease

The purpose of this preliminary study was to describe changes in physical function and torque capacity in adults with chronic kidney disease (CKD) in response to a novel progressive eccentric-overload resistance exercise (ERE) regime. Participants included men (n = 4) diagnosed with CKD according to estimated glomerular filtration rate (eGFR) between 59 and 15 mL/kg/1.73 m2 and not requiring dialysis. Physical function was determined by the Short Physical Performance Battery (SPPB), five repetitions of a sit-to-stand (STS) task, and timed-up and go (TUG). Knee extensor strength was assessed using both isometric and isokinetic contractions and performance fatigability indexes were calculated during a 30-s maximal isometric test and a 30-contraction isokinetic test at 180°/second. None of the patients exhibited significant worsening in their health status after training. Participants demonstrated improvements in several measures of physical function and torque capacity following 24 sessions of ERE. Following training, performance fatigability remained relatively stable despite the increases in torque capacity, indicating the potential for greater fatigue resistance. These findings provide initial evidence for ERE as a potential treatment option to combat declines in physical function and neuromuscular impairments in people with CKD. Future research is required to determine optimal progression strategies for maximizing specific neuromuscular and functional outcomes when using ERE in this patient population.

Torsional Strengthening of Low-Strength RC Beams with Post-Tensioned Metal Straps: An Experimental Investigation

This article investigates the behaviour of low-strength reinforced concrete beams under pure torsion with and without strengthening. Four beams were cast and tested in torsion: i) a control beam without vertical reinforcement, ii) two beams with internal stirrups designed for shear and torsion demands using different stirrup spacing (50 and 100 mm), and iii) a beam having steel stirrups with a spacing of 100 mm strengthened using high ductile post-tensioned metal straps (PTMS). The main objective of the PTMS strengthening solution was to investigate the enhancement of torsional strength confined along the beam. The failure modes, torsional capacities, rotation, and strengthening performance in torsion are discussed in in this study. The experimental results indicate that the PTMS improved the cracking torque capacity by up to 15 % compared to the control beam. Moreover, the PTMS also increased the ultimate torque by up to 19 % compared to the unstrengthened beam. Current code equations to predict the torsional capacity of RC beams are also compared with the experimental results. It is found that the predictions obtained by current ACI equation gives a good agreement and yield in general conservative values compared to the experimental ones.

An experimental investigation on the installation and loading performance of model-scale deep helical piles in very dense sand

The use of helical piles has grown over the years owing to different advantages, such as large uplift capacity due to the anchor effect of the helix, and installation torque-capacity correlation. Although the use of helical foundations is expanding worldwide, some key aspects fundamental to the design are not well understood to date. The practical experience indicates that the installation forces and loading performance of helical piles in sand are dependent on the helices characteristics and confining stresses. Therefore, for a better understanding of these dependencies, the effects of the helix-to-shaft diameter ratio (wing ratio) and vertical confining stress on the installation torque and forces, and on the uplift and compression capacities of helical piles, were evaluated from nine calibration chamber tests, conducted on instrumented single-helix piles in very dense sand. Among other findings, this study indicated that for a certain shaft diameter: (i) the wing ratio influences the installation torque but does not affect the installation vertical force; (ii) the ultimate uplift pressure mobilized on the helix decreases with the increase of the wing ratio; (iii) for vertical stresses higher than 100 kPa the growth rate of the helix bearing resistance with the confining pressure become reduced for piles with larger wing ratio.