Torsional Amplitude Research Articles

Resonant capture and Sommerfeld effect due to torsional vibrations in a double Cardan joint driveline

The dynamics of a system comprising a heavy rotor which is coupled to a motor through a long and torsionally flexible drive shaft with universal joints (U-joints) at its both ends is studied numerically. The U-joints are arranged in Z-configuration to minimize the speed fluctuations between the input and output shafts. It is shown that for large parallel offset between the input and output shafts, Sommerfeld effect characterized by resonance capture and escape through resonance occur. The escape through resonance is associated with sharp jump in speed and reduction in torsional vibration amplitude. In fact, such jump phenomena occur at two different speed ranges, one near the natural frequency of the straight line arrangement of the U-joints and the other at half of that natural frequency. The nature of the dynamic response is affected by the rate at which the input shaft torque or power is varied.

Studying the Surface Layer Structure of 40Cr Steel after Rough and Semi-Finished Machining

The results of studies of the microstructure and local fields of internal stresses arising in the surface layer of 40Cr steel samples processed in two modes: rough and semi-finished (chip removal to a depth of 1.0 and 0.5 mm, respectively) are presented. The internal structure of all morphological steel components is investigated. The scalar dislocation density and the width of the bending extinction contours are measured and calculated, from which the amplitude of the curvature torsion of the crystal lattice of the forming phases, the excess dislocation density, and the amplitude of internal stresses in different sections of the material are determined. In the initial state, the 40Cr steel matrix is α phase, a solid solution of carbon and alloying elements in α-Fe with a body-centered cubic (bcc) lattice. The morphological components of the α phase are lamellar perlite and ferrite. Rough machining leads to the formation of secondary fragmented perlite. After semi-finishing, lamellar perlite is formed with curved cementite plates.

Technical analysis of adaptive neuron fuzzy intelligent system in tennis serve

Serving is the most important hitting technique in tennis, and a good service receiving can instantly reverse the active and passive relationship between serve and receive on the tennis court, and control the rhythm of the court. The purpose of this study is to use an adaptive neuron fuzzy intelligent system to analyze some techniques of tennis serve. In this study, eight male players from the school tennis team were selected as the experimental subjects, whose sports level was above the national tennis level II. Ten weeks before the simulation test, the training time and frequency of 8 subjects were the same. In other words, 5 times a week, 2.5 hours±0.5 hours. The work engineering of adaptive fuzzy system firstly, in the off-line modeling stage, the adaptive fuzzy system uses the rule self splitting technology to generate the initial fuzzy rules, and uses the improved adaptive neural network algorithm to optimize the calculation; then according to the error between the system input and the predicted output, the independent variable is adjusted and replaced; at the same time, the adaptive fuzzy system is further used for calculation In the process of tennis serving, the nonlinear control variables are obtained online and applied to the fuzzy system for control. Next, in the experiment, the system was used to record the body’s movement and service scores during service. The experimental results show that during the service process, the maximum trunk torsion amplitude can reach 48.26 ° and the minimum is only 5.41 ° and the service score accounts for 81.41% and 80.47% of the total scores of the two sections respectively. This shows that the fuzzy system in this study can effectively analyze the service posture and score of athletes. It is concluded that the accurate calculation and analysis of tennis serve by adaptive neuron intelligent fuzzy system in this study is conducive to improve the tennis serviceability and competition performance of players. This research has made a certain contribution to the intellectualization of sports.

Investigation of the generation mechanism of rail corrugation based on friction induced torsional vibration

Field measurements of Wuhan Metro Line 2 show that rail corrugation mostly occurs on the inner rail of curved tracks, and that the corrugation amplitude increases with the curvature of rail. To investigate this phenomenon, a theoretical model for the generation mechanism of rail corrugation based on friction induced torsional vibration is developed. This paper theoretically explains the reason why most rail corrugations occur on the inner rail. Furthermore, the simulation results of the model show that the torsional vibration amplitude of wheel axles increases with the curvature of rail, which can explain the reason why rail corrugation occurs on curved rail. In addition, it is found that vertical dynamics between wheel and rail is critical for the occurrence of torsional vibration for the case of large rail radius. Therefore, it seems that the generation mechanism of rail corrugation can be due to the friction induced vibration coupled with vertical dynamics.

Cyclic Response of Loose Anisotropically Consolidated Calcareous Sand under Progressive Wave–Induced Elliptical Stress Paths

Observations of the performance of coastal and marine structures in weather events that produce standing and/or progressive waves have pointed to liquefaction of the seabed as a contributing cause of damage. The cyclic response of marine sediments under wave loading can serve to improve the understanding of seabed liquefaction triggering and its consequences. This paper presents the results of an experimental study of the cyclic behavior of loose isotropically and anisotropically consolidated calcareous sand under elliptical stress paths representing progressive waves. Various ratios, λ, of the axial stress difference and torsional shear stress amplitudes were investigated in a hollow-cylinder torsional shear apparatus. The results indicate that the failure mode of isotropically and anisotropically consolidated (IC and AC, respectively) specimens are cyclic mobility and residual deformation failure, respectively. The difference in the observed failure mode appears to be related to particle shape and is independent of λ. However, the cyclic resistance of the calcareous sand is strongly influenced by λ and increases with decreasing consolidation stress ratio, Kc. The cyclic resistance of IC specimens is relatively independent of the orientation of elliptical stress paths, whereas the AC specimens exhibited a marked dependence. The terminal peak excess pore pressure ratio, ru,t, and shear work required for cyclic failure, Wf, are independent of λ; however, ru,t and Wf increases with increasing and decreasing Kc, respectively. Moreover, the relationship between the normalized peak excess pore pressure ratio and normalized shear work is related to the type of soil, but is independent of λ and Kc.

Torsional Vibration Stress and Fatigue Strength Analysis of Marine Propulsion Shafting System Based on Engine Operation Patterns

Modern merchant ships use marine propulsion systems equipped with an ultra-long-stroke diesel engine that directly drives a large slow-turning propeller. Such systems use fewer cylinders and generate greater power at slower shaft speeds, which affords improved propulsion performance as well as low repair and maintenance costs. However, this also results in higher torsional vibrations, which can lead to the fatigue of the shafting system. Tests performed on various marine propulsion systems with 5- to 7-cylinder engines have shown that engines with fewer cylinders exhibit a correspondingly wider barred speed range (BSR) and higher torsional vibration stresses. Thus, it is necessary to investigate the optimal engine operation patterns required to quickly pass the BSR with smaller torsional vibration. In this study, we carried out a series of BSR passage experiments during actual sea trials to evaluate the intermediate shaft performance under different engine operation patterns. The fractional damage accumulations due to transient torsional vibration stresses were calculated to estimate the fatigue lifetime of the shafting system. Our analysis results show that the torsional fatigue damage during BSR decelerations are small and negligible; however, the fractional damage during accelerations is a matter of concern. Our study determines the optimal main engine operation pattern for quick passage through the BSR with the smallest torsional vibration amplitudes and the least fractional damage accumulation, which can therefore extend the fatigue lifetime of the entire propulsion shafting system. Based on this analysis, we also suggest the optimum engine pattern for safe BSR passage.

Design and Experiment Study of Ultrasonic Longitudinal-Torsional Compound Consolidation Vibration System for Metal Foil

In order to realize the connection for metal foil, a longitudinal-torsional compound consolidation vibration system is proposed, and relative experiments are carried out. Firstly, the structure of longitudinal-torsional compound consolidation vibration system was designed, detailed structural design of the compound piezoelectric transducer and the compound horn in the vibration system was carried out, and torsional vibration analysis of the compound horn with spiral grooves was carried out based on mechanical principle. Secondly, modal calculation and harmonic response analysis of longitudinal-torsional compound consolidation vibration system were carried out, and corresponding vibration mode and harmonic frequency were obtained. The effect of structural parameters for the compound horn on the frequency of the consolidation vibration system was analysed, and structural parameters of the compound horn were optimized. Finally, the prototype was made, and the experimental platform was built to test the amplitude. When the frequency is near 20000 Hz, the resonance is achieved in three directions at the same time, and the resonance frequency is 19800 Hz. Through the frequency-scanning test, the maximum longitudinal amplitude of the consolidation vibration system is 16 μm, and the maximum torsional amplitudes of X and Y are 7.9 μm and 8.1 μm. The longitudinal-torsional compound consolidation vibration system can realize the connection of the same and different metal foils and has broad application prospects.

Preshearing is an in situ setting modification method for inorganic bone cements

AbstractThe flow behaviour and injectability of calcium phosphate cements are outcomes of the complex interplay between time‐dependent processes of dissolution, nucleation and crystal growth. Their dependence on shear strains, frequencies and rates has been revealed by rheological investigation of the setting processes of a brushite cement under torsional flow. Various oscillatory torsional strain amplitudes and frequencies were seen to promote dissolution or delay crystal intergrowth compared to quiescently set cement samples. Oscillatory torsional strain amplitudes higher than the linear viscoelastic strain limit resulted in a pronounced lag in crystal intergrowth. Dissolution was enhanced and setting was promoted with increasing frequency and strain amplitude within the linear viscoelastic strain range. Changing the preshearing mode to steady torsion increased energy spent to microstructural deformation, counteracting the beneficial vibratory effect on cement setting kinetics, and produced a net retardation by the disruption of the crystal network structure. Such deformation history can be created in the cement suspension prior to injection during clinical practice by precise adjustment of the preshearing modes and parameters to enable the orthopaedic surgeon tailor the setting time, flow behaviour and injectability of calcium phosphate cements in situ without altering the cement chemistry, hence bioactivity.

Dual-mass flywheels with tuned vibration absorbers for application in heavy-duty truck powertrains

As the heavy-duty combustion engine development goes towards lower rotational speeds and higher cylinder pressures, the torsional vibrations increase. There is therefore a need to identify and study new types of vibration absorbers that can reduce the level of torsional vibrations transmitted from the engine to the gearbox. In this work, the concept of a dual-mass flywheel combined with a tuned vibration absorber is analysed. The tuned vibration absorber efficiently reduces the vibration amplitudes for engine load frequencies near the tuning frequency, but it also introduces an additional resonance into the system. By placing the tuned vibration absorber on an intermediate flange between the two dual-mass flywheels, the introduced resonance frequency will be lower than the tuning frequency and a resonance in operating engine speed range can be avoided. Numerical simulations are used to show how the torsional vibration amplitudes in a heavy-duty truck powertrain are affected by the tuned vibration absorber and how the different parameters of the tuned vibration absorber and the dual-mass flywheel affect the torsional vibrations and the resonance frequencies.

The effects of meclizine on motion sickness revisited.

AimsAntihistamines make up the first line of treatments against motion‐sickness. Still, their efficacy and specific mechanism have come into question. The aim of this study was to investigate the effect of meclizine on motion‐sensitivity.MethodsThis study was carried out as a triple‐blinded randomized trial involving 12 healthy subjects who were exposed to (i) vestibular (VES), (ii) visual (VIS) and (iii) visual–vestibular (VIS+VES) stimulations in the roll plane. Subjects were divided into 2 groups by stratified randomization, receiving either meclizine or a placebo. Stimulations were carried out before, and after, drug administration, presented at 2 intensity levels of 14 and 28°/s2. Eye movements were tracked, and torsional slow‐phase velocities, amplitudes and nystagmus beats were retrieved. Subjects initially graded for their motion‐sickness susceptibility.ResultsSusceptibility had no effect on intervention outcome. Despite large variations, repeated ANOVAS showed that meclizine led to a relative increase in torsional velocity compared to placebo during vestibular stimulation for both intensities: 2.36 (7.65) from −0.01 (4.17) during low intensities, and 2.61 (6.67) from −3.49 (4.76) during high. The visual–vestibular stimuli yielded a decrease during low acceleration, −0.40 (3.87) from 3.75 (5.62), but increased during high, 3.88 (6.51) from −3.88 (8.55).ConclusionsMeclizine had an inhibitory effect on eye movement reflexes for low accelerations during VIS+VES trials. This indicates that meclizine may not primarily work through sensory‐specific mechanisms, but rather on a more central level. Practically, meclizine shows promise in targeting motion‐sickness evoked by everyday activities, but its use may be counterproductive in high‐acceleration environments.

Frequency coupling design of ultrasonic horn with spiral slots and performance analysis of longitudinal-torsional machining characteristics

Longitudinal-torsional (L-T) vibration in rotary ultrasonic machining (RUM) can further reduce the cutting force and improve the machining efficiency compared with the single longitudinal vibration in RUM. In this study, an ultrasonic step horn with spiral slots using the principle of mode conversion was designed to realize L-T vibration. The torsional amplitude to longitudinal amplitude (AT/AL) ratio is proposed to quantify the efficiency of mode conversion. Moreover, a simulation method was used to carry out the frequency coupling design of the ultrasonic horn with spiral slots. The influence of the step position and slot position with a spiral angle of 52° on the resonant frequency and amplitude of the ultrasonic horn were analyzed, respectively. Based on the simulation results, ultrasonic horns with different AT/AL were designed and fabricated. Finally, the results obtained through experiments with milling glass plane revealed that the cutting force was reduced by 48–73%, while the surface quality improved compared with single longitudinal vibration when the torsional vibration is coupled with the longitudinal vibration in RUM. The reasonable AT/AL ratio could effectively reduce the cutting force when the synthetic amplitude was the same. This indicates that the L-T vibration changes the trajectories of the diamond abrasives, which improves the machining performance.

Scoop and chop - A modified phaco-chop technique for pseudoexfoliation and cataract.

PURPOSE:The purpose is to evaluate the results of the modified direct phaco-chop technique of cataract surgery in eyes with pseudoexfoliation.METHODS:All patients with pseudoexfoliation and visually significant cataract with normal intraocular pressure (IOP) and optic nerve that underwent cataract surgery by the same surgeon using Infiniti®, OZil® Torsional handpiece (Alcon Labs), were included for this retrospective hospital-based study. Direct vertical or horizontal chop technique was used in all cases with parameters set as required for quadrant removal with high vacuum after the initial cleanup of cortex under the capsulorhexis. To allow better visualization of the hardness of the nucleus core, the sides of the lens were scooped out a central well with vacuum with maximum chopping done centrally within the rhexis as the first step to enable better assessment of the depth of burying the chopper for direct chop. Intraoperative details recorded and analyzed included ultrasound time and cumulative dissipated energy. The mean visual acuity and IOP before and after surgery were recorded at 1 day, 1 week, and 1 month. Complications during or after surgery were noted.RESULTS:A total of 138 patients with a mean age of 62 ± 6.7 years underwent phachop technique of phacoemulsification for nuclear cataract grades of nuclear sclerosis 2–4 with significant improvement in visual acuity from baseline (0.26) to 3 months (0.82), P < 0.001. The mean ultrasound torsional amplitude and cumulative dissipated energy (CDE) were greater for brown cataract of grading >3, P = 0.02. A total of 8 patients had intraoperative zonular dialysis in 1 quadrant (none in >1 quadrant), which was not associated with intraoperative vitreous prolapse in 6 eyes.CONCLUSIONS:Direct modified phaco-chop technique may be a safe technique in pseudoexfoliation due to minimal zonular stress with successful outcomes and reduced complications.

Torsional vibration induced by gyroscopic effect in the modified couple stress based micro-rotors

In this research, the small-scale effects in the torsional vibration of the micro-rotors with eccentric micro-disks are investigated based on the modified couple stress theory. The torsional deformation of the micro-shaft described by function φ(x,t) is considered to be independent of the flexural deformation described by functions v(x,t) and w(x,t). Using Hamilton's principle, the system of coupled nonlinear governing partial differential equations of motion and the associated boundary conditions are derived. The system of equations includes one corresponding to the torsional deformation and two others corresponding to the flexural deformation. By employing the Galerkin method, the system of governing equations is transformed into three coupled ordinary differential equations. The flexural-torsional nonlinear coupling due to the gyroscopic effect can excite the torsional mode. So, by utilizing the multiple scales method the non-resonant excitation and the torsional super-harmonic resonance are analytically investigated and in the special cases, the analytical results are compared with the numerical ones. Some parametric studies are presented to investigate the effects of various parameters, including the material length scale parameter, on the torsional natural frequency and the torsional super-harmonic resonance amplitude of the micro-rotors.

Effect of planar torsional deformation on the thermal conductivity of 2D nanomaterials: A molecular dynamics study

The thermal conductivity of nanoscale materials is largely dependent on the applied strain and deformations. In this paper, the effect of torsional deformation and consequent wrinkles on the thermal conductivity of graphene, hexagonal boron nitride (h-BN) and molybdenum disulfide (MoS2) nanostructures have been investigated by performing non-equilibrium molecular dynamics simulation. The nanostructure geometry is considered as a ring with different inner and outer radii so that the torsional deformation is applied on the inner boundary. It is found that the wrinkles caused by applying the torsion, result in reducing the thermal conductivity of nanostructures. Although the effect of created distortions is tangible, these wrinkles have the most influence on the thermal conductivity of MoS2 and the least on the thermal conductivity of h-BN. The effect of inner radius size is also studied and found that the reduction of the thermal conductivity is enhanced by increasing the inner radius size. The results of this study can be beneficial to thermal applications of 2D nanostructures under mechanical stress or strain and also for estimating the values of applied torsion and wrinkle amplitude by measuring the thermal conductivity variations.

Formation of Gradient Structure–Phase States in the Surface Layers of 100-m Differentially Quenched Rails

Abstract—The evolution of the structural-phase states in the surface layers of the head of differentially quenched DT350 rails to a depth of 10 mm are studied by optical microscopy and transmission electron diffraction microscopy along the central axis after the passage of a tonnage of 691.8 mln t gross in the experimental ring of AO VNIIZhT (proof ground for railway transport). The formation of a gradient structure is revealed. In this structure, the scalar and excess dislocation densities, the lattice curvature–torsion amplitude, and the degree of deformation-induced transformation of lamellar pearlite change gradually. The mechanisms of fracture of cementite lamellae are considered.

A Study on Nonlinear Model Predictive Control for Helicopter/Engine with Variable Rotor Speed Based on Linear Kalman Filter

Abstract A novel control method combining nonlinear model predictive control (NMPC) with linear kalman filter (LKF) and adaptive notch filter (ANF) for an integrated helicopter/engine system with variable rotor speed is proposed to enhance the response ability of turboshaft engine. Firstly, based on the integrated helicopter/engine model with variable rotor speed, an ANF combined with frequency estimation is introduced. Then, in order to estimate the significant and unmeasurable performance parameters utilized in model predictive control, such as temperature before turbine, a nonlinear model predictive controller based on LKF is presented. The simulation verifications demonstrate that the fundamental frequency of torsional vibration changes from 1.30 Hz to 2.70 Hz when the rotor speed varies continuously by 50 %. In this case, compared with the notch filter, all torsional vibration amplitudes are damped below 0.1 % by ANF. Meanwhile, in comparison with the PID controller, the NMPC can reduce the overshoot and droop of the power turbine speed to less than 1 % with steady-state error no more than 0.5 % at the off-design point of NMPC based on adaptive torsional vibration suppression. The applications of LKF and similar transformation improve the control accuracy and robustness performance of the NMPC designed at a single operating point.

Root cause analysis of locomotive wheel tread polygonisation

Periodic out-of-round or polygonised wheels were detected on a fleet of high adhesion locomotives operating within South Africa. The polygonised wheels increased the vertical load spectrum of the locomotive resulting in accelerated component failures. During the initial investigation it was found that torsional axle vibration could lead to the polygonisation of the wheels. The torsional vibration of the locomotive axle was confirmed theoretically and experimentally through various physics models and on-track measurements. Based on the results, two potential torsional vibration excitation mechanisms were identified. A link was also established between the torsional vibration frequency, vehicle operating speed and the polygonisation order. Based on the similarities of the two excitation mechanisms a vibration suppression system was considered and tested. A reduction in the torsional vibration amplitude was observed when the suppression system was active.

Drillstring Failure—Identification, Modeling, and Experimental Characterization

Abstract Drilling is one of the costliest and risky activities in oil and gas industry due to complexity of interactions with downhole formation. Under such conditions, the uncertainty of drillstring behavior increases, and hence, it becomes difficult to predict the causes, occurrences, and types of failures. Lateral and torsional vibrations often cause failure of bottom hole assembly (BHA), drillstring failure, drill bit, and wall borehole damages. In this work, a model is presented to determine the impact of lateral and torsional vibrations on a drillstring during the drilling operation. The model aims to mimic real drillstring behavior inside a wellbore with regards to its dynamic movements due to multiple real situations such as eccentricity of collars, drill pipe sections, and stick-slip phenomena occurring due to the interaction of the bit and the drillstring with the well formation. The work aims to develop a basis for determining critical operating speeds and design parameters to provide safe drilling procedures and reduce drillstring fatigue failure. Lagrangian approach is used in this study to attain drillstring lateral and torsional vibration coupling equations. The nonlinear equations are solved numerically to obtain the response of the system. In this work, we also present a brief description of an in-house constructed experimental setup. The setup has the capability to imitate the downhole lateral and torsional vibration modes. Parameters from the experimental investigations are incorporated for validation of the mathematical models and for prediction of the drillstring fatigue life. Such investigations are essential for oil/gas industries as they provide solutions as well as recommendations about operating speed, lateral and torsional amplitudes measurements and corrections, and the conditions for avoiding occurrence of natural frequency(ies) of the system.

Astrophysical detections and databases for the mono deuterated species of acetaldehyde CH2DCOH and CH3COD

Context. Detection of deuterated species may provide information on the evolving chemistry in the earliest phases of star-forming regions. For molecules with two isomeric forms of the same isotopic variant, gas-phase and solid-state formation pathways can be differentiated using their abundance ratio. Aims. Spectroscopic databases for astrophysical purposes are built for the two mono deuterated isomeric species CH2DCOH and CH3COD of the complex organic molecule acetaldehyde. These databases can be used to search and detect these two species in astrophysical surveys, retrieving their column density and therefore abundances. Methods. Submillimeter wave and terahertz transitions were measured for mono deuterated acetaldehyde CH2DCOH which is a non-rigid species displaying internal rotation of its asymmetrical CH2D methyl group. An analysis of a dataset consisting of previously measured microwave data and the newly measured transition was carried out with a model accounting for the large amplitude torsion. Results. The frequencies of 2556 transitions are reproduced with a unitless standard deviation of 2.3 yielding various spectroscopic constants. Spectroscopic databases for astrophysical purposes were built for CH2DCOH using the results of the present analysis and for CH3COD using the results of a previous spectroscopic investigation. These two species were both searched for and are detected toward a low-mass star-forming region. Conclusions. We report the first detection of CH2DCOH (93 transitions) and the detection of CH3COD (43 transitions) species in source B of the IRAS 16293−2422 young stellar binary system located in the ρ Ophiuchus cloud region, using the publicly available ALMA Protostellar Interferometric Line Survey.

Biomechanical test protocols to detect minor injury effects in intervertebral discs

Intervertebral discs (IVDs) maintain flexibility of the spine and bear mechanical load. Annulus fibrosus (AF) defects are associated with IVD degeneration and herniation which disrupt biomechanical function and can cause pain. AF puncture injuries can induce IVD degeneration but are needed to inject therapies. Identifying small AF defects with biomechanical testing can be difficult because IVDs have a complex, composite structure and nonlinear biomechanical properties that are dependent on AF fiber tension. It remains unclear how choice of biomechanical testing protocols affect the sensitivity of biomechanical properties to AF injuries. This study determined whether axial preload or magnitude of cyclic axial or torsional testing affected the ability to detect minor AF defects in rat caudal motion segments using ex vivo biomechanical testing. Intact and injured motion segments were subjected to a repeated measures study design with multiple biomechanical testing protocols that varied axial tension-compression force amplitude (±1.6 N, ±8.0 N, ±16.0 N), axial preload (−1.6 N, −8.0 N, −16.0 N, corresponding to −0.1 MPa, −0.5 MPa, and −1.0 MPa, respectively), and torsional rotation angle (±10°, ±15°, and ±20°). Biomechanical properties obtained from the lowest force testing conditions for axial tension-compression (±1.6 N), axial preload (−1.6 N), and angular rotation (±10°) exhibited the largest differences in biomechanical properties between intact and injured conditions. Biomechanical properties determined under low axial force or torsion amplitudes involve less AF fiber tension and were most sensitive to injury. Low force testing protocols are recommended for detecting minor structural AF defects and may enable more precise assessments of IVD injuries, healing or repair.