Gear Rattle during a start-up transient in a driveline equipped with a tuneable torsional Vibration Damper with Magneto-Rheological Elastomers

The paper reports a numerical investigation on the dynamic behaviour of a vehicle driveline, equipped with a Torsional Vibration Damper (TVD) based on Magneto-Rheological Elastomeric (MRE) spring elements, during the start-up transient considering an abrupt manoeuvre of clutch engagement. The TVD device consists of a flywheel and a damper disk, with interposed some elastomeric samples which react for relative angular displacements of the two disks. The dynamical parameters of the TVD can be properly tuned by varying the magnetic field surrounding the MRE springs to mitigate the torsional oscillations of the flywheel, causes of many undesired inconveniences as critical speeds or vibro-acoustic issues. The present study promotes the use of the MRE torsional vibration damper to reduce the annoying vibroacoustic phenomenon of “gear rattle” arising in the unloaded gear pairs of the gear box, during and after the rapid clutch engagement transients in the vehicle start-up phase and is conducted on a simplified automotive driveline equipped with a dry clutch. The possibility of quickly tuning the mechanical properties of the MRE-TVD, makes this device particularly eligible for suppressing the above disturbance, adapting to the various operative conditions of the automotive driveline. Results of the analysis, by the help of a Gear Rattle Index (GRI), demonstrate the effectiveness of the proposed device in reducing the vibroacoustic phenomenon during the transient phases of the vehicle start-up, until the vehicles speed conditions are reached.

THE IMPACT OF SELECTED PARAMETERS ON PRESSURE DISTRIBUTION IN THE FACE THROTTLE OF A CENTRIFUGAL PUMP AUTOMATIC BALANCING DEVICE

Face throttles are a necessary functional element of non-contact face seals and automatic balancing devices of centrifugal pumps of different constructions. To calculate the hydrodynamic forces and moments acting on the rotor and fluid flow through the automatic balancing device, it is necessary to know the pressure distribution in the cylindrical and face throttle when considering all important factors which predetermine fluid flow. The face throttle surfaces are moving, which leads to unsteady fluid flow. The movement of the walls of the face throttle causes an additional circumferential and radial flow, which subsequently leads to the additional hydrodynamic pressure components. The paper analyses viscous incompressible fluid flow in the face throttle of an automatic balancing device taking into account the axial and angular displacements of throttle’s surfaces and the inertia component of the fluid. The effect of local hydraulic losses as well as random changes in the coefficients of local hydraulic resistance at the inlet and outlet of the throttle is analysed.

THE STABILITY OF A FREELY FLOATING SHIP

The paper presents the problem of calculating the righting arms (GZ-curve) for a freely floating ship, longitudinally bal- anced at each heel angle. In such cases the GZ-curve is ambiguous, as it depends on the way the ship is balanced. Three cases are discussed: when the ship is balanced by rotating her around the trace of water in the midships, around a normal to the ship plane of symmetry (PS), and around a normal to the initial waterplane, fixed to the ship, identical with the curve of minimum stability. In all these cases the direction of the righting moment in space and area under the GZ-curves, which is the lowest possible, are preserved. Angular displacements (heel and trim) are the Euler's angles related to the relevant reference axis. The most important features of the GZ-curve with free trim are provided. Exemplary calculations illustrate how the way of balancing affects the GZ-curves.

Prediction of the spring-in of cylindrically orthotropic media and cross-ply laminates

The equation for prediction of the spring-in angle of a cylindrically orthotropic segment is shown to be independent of all material properties except for the anisotropic coefficients of thermal expansion and a stress-free state is insured for the corresponding unconstrained deformation. In contrast, the complete cylindrical geometry is shown to provide constraint to thermal deformation and thereby induce thermal residual stresses in the form of a moment. The method of superposition is demonstrated whereby traction-free conditions yield stress-free cylindrical elements with corresponding angular displacements at the element free boundaries. The first derivation of the spring-in equation is attributed to Radford, in contrast to the widely accepted view that the equation was first developed by Spencer et al. Finite-element methods, combined with the superposition approach, further validate the accuracy of the Radford equation for cylindrically orthotropic segments and explore its limitations for multiaxial composite laminates.

Kinematics of the head and associated vertebral artery length changes during high-velocity, low-amplitude cervical spine manipulation

Background Cervical spine manipulation (CSM) is a frequently used treatment for neck pain. Despite its demonstrated efficacy, concerns regarding CSM safety remain. The purpose of this study was to quantify the angular displacements of the head relative to the sternum and the associated vertebral artery (VA) length changes during the thrust phase of CSM. Methods Bilateral rotation and lateral flexion CSM procedures were delivered from C1 to C7 to three male cadaveric donors. For each CSM the force-time profile was recorded using a thin, flexible pressure pad (100-200Hz), to determine the timing of the thrust. Three dimensional displacements of the head relative to the sternum were recorded using an eight-camera motion analysis system (120-240Hz) and angular displacements of the head relative to the sternum were computed in Matlab. Positive kinematic values indicate flexion, left lateral flexion, and left rotation. Ipsilateral refers to the same side as the clinician's contact and contralateral, the opposite. Length changes of the VA were recorded using eight piezoelectric ultrasound crystals, inserted along the entire vessel. VA length changes were calculated as D=(L1-L0)/L0, where L0= length of the whole VA (sum of segmental lengths) or the V3 segment at CSM thrust onset; L1= whole VA or V3 length at peak force during the CSM thrust. Results VA length changes during the thrust phase were greatest with ipsilateral rotation CSM (producing contralateral head rotation): [mean ± SD (range)] whole artery [1.3 ± 1.0 (-0.4 to 3.3%)]; and V3 segment [2.6 ± 3.6 (-0.4 to 11.6%)]. For ipsilateral rotation CSM, head angular displacements relative to the sternum during the thrust were: flexion/extension [1.2 ± 3.4 (-6.6 to 7.6º)]; rotation [-10.2 ± 3.5 (-16.1 to -3.7º)]; and lateral flexion [8.8 ± 3.0 (2.5 to 14.1º)]. Conclusion Mean head angular displacements and VA length changes were small during CSM thrusts. Of the four different CSM measured, mean VA length changes were largest during rotation procedures. This suggests that if clinicians wish to limit VA length changes, consideration should be given to the type of CSM used.

Comparing the surgical efficacy of a newly designed endoscopic visualized trephine and a conventional trephine for percutaneous endoscopic lumbar discectomy with foraminoplasty for patients with single-segment lumbar disc herniation: A retrospective case -control study

Background Owing to the remarkable evolution of percutaneous endoscopic lumbar discectomy (PELD), the application of spinal endoscopy is shifting from the treatment of soft disk herniation to complex lumbar spinal stenosis. This study aim to compare the surgical efficacy of a newly designed endoscopic visualized trephine and a conventional trephine for PELD with foraminoplasty for patients with single-segment lumbar disc herniation (LDH). Methods A total of 54 patients who were diagnosed with single-segment LDH and received PELD with foraminoplasty at Xuzhou Central Hospital (Xuzhou, China) from January 2016 to June 2020 were included in this case-control study. Data related to the length of incision, amount of intraoperative bleeding, the time required to create the working channel, and intraoperative and postoperative complications were recorded. The Visual Analog Scale (VAS) score was used to assess low back pain and leg pain. Besides, the Oswestry Disability Index (ODI) and Japanese Orthopedic Association (JOA) scores were utilized to evaluate patients’ pain intensity and their sitting and standing abilities. The X-ray fluoroscopy was performed to measure the horizontal and angular displacements of lumbar extension-flexion, and to evaluate the stability of lumbar spine. Results All the patients successfully underwent surgical procedures, except for two patients with injuries in the spinal nerve root of the responsible segment in the conventional trephine group, who were given nutritional supplements for nerve treatment. Besides, there was no significant difference in incision length and operative blood loss between the modern trephine and the conventional trephine groups. However, the time required to create the channel and the duration of fluoroscopy in the modern trephine group were significantly less than those in the conventional trephine group (34.24 ± 5.38 vs. 44.76 ± 6.37 min, P < 0.05). In addition, the VAS, ODI, and JOA scores significantly decreased postoperatively in the two groups. We also found no significant difference in horizontal and angular displacements of lumbar extension-flexion between the two groups pre-operation and at 3- and 12-month post-operation. Conclusion In spite of similar surgical efficacy of the two techniques, the newly designed endoscopic visualized trephine outperformed in terms of operation time and duration of fluoroscopy.

Adaptive selective-invariant control of tracking electric drives with elastic kinematic transmissions

Currently, high quality indicators of adaptive versions of selective-invariant electromechanical systems designed to control the speed in a wide range have been obtained. Thus, it lays the groundwork for effective use of the proposed synthesis methods and obtained structural solutions in the systems of contour-positional and tracking control of angular displacements of the working elements of technological machines. The implemented structural-parametric synthesis is based on the methods of the theory of modal control, reduction of regulators, the principles of selective invariance, separation of the rates of movement of local subsystems, adaptive, contour-positional and tracking control. The study has been carried out by detailed computational experiments with models of synthesized electromechanical systems. The features of synthesis and functioning of adaptive selective-invariant systems with elastic kinematic links in the tracking and positioning modes are described. The combination of the principles of tracking, selective-invariant and adaptive control in the structure of a single electromechanical system makes it possible to fully provide new opportunities for the implementation of high-precision dynamic control of working machines.

Sensitivity enhanced roll-angle sensor by means of a quarter-waveplate

Attitude metrology (roll, pitch, and yaw) plays an important role in many different fields. Roll angle is considered the most difficult measurement quantity in angular displacements compared to pitch and yaw angles because the rotation axis of the roll angle is parallel to the probe beam. In this work, a sensitivity enhanced roll-angle sensor is presented. The principle is based on the polarization change of a sensing unit (quarter-waveplate). The polarization model is analyzed by Mueller matrix formalism. The Stokes parameters are detected by a Stokes polarimeter. The novel coaxial design improves the sensitivity and reduce the complexity of optical system alignment by means of a fixed quarter-waveplate. The proposed sensor provides a simple setup to measure roll angles with a high sensitivity of 0.006∘ and a long unambiguous measurement range of 180∘.

Effect of off-sized balls on contact stiffness and stress and analysis of the wear prediction model of linear rolling guideways

The characteristics between the rolling balls and raceways are the key to study a linear rolling guideway (LRG). In this paper, the contact stresses of an LRG with off-sized balls incorporating the variation of the contact angle are given by the established LRG joint model. Moreover, the effect of the location, number, and the deviation degree of the off-sized balls on the stress distribution are studied. In addition, the contact stress distribution between the balls and raceway for different arrangement cases of the off-sized balls are analyzed. The random arrangement case can improve the stiffness and service life of the LRG. Based on the Archard wear theory, the wear prediction model of the LRG is established and the displacements and angular displacements of the slider caused by wear in reciprocating motion are obtained. The effectiveness of the contact stiffness and wear prediction model of the LRG is verified by simulations and analysis.

Dynamic Responses of Female Volunteers in Rear Impact Sled Tests at Two Head Restraint Distances

The objective of this study was to assess the biomechanical and kinematic responses of female volunteers with two different head restraint (HR) configurations when exposed to a low-speed rear loading environment. A series of rear impact sled tests comprising eight belted, near 50th percentile female volunteers, seated on a simplified laboratory seat, was performed with a mean sled acceleration of 2.1 g and a velocity change of 6.8 km/h. Each volunteer underwent two tests; the first test configuration, HR10, was performed at the initial HR distance ∼10 cm and the second test configuration, HR15, was performed at ∼15 cm. Time histories, peak values and their timing were derived from accelerometer data and video analysis, and response corridors were also generated. The results were separated into three different categories, HR10C (N = 8), HR15C (N = 6), and HR15NC (N = 2), based on: (1) the targeted initial HR distance [10 cm or 15 cm] and (2) whether the volunteers’ head had made contact with the HR [Contact (C) or No Contact (NC)] during the test event. The results in the three categories deviated significantly. The greatest differences were found for the average peak head angular displacements, ranging from 10° to 64°. Furthermore, the average neck injury criteria (NIC) value was 22% lower in HR10C (3.9 m2/s2), and 49% greater in HR15NC (7.4 m2/s2) in comparison to HR15C (5.0 m2/s2). This study supplies new data suitable for validation of mechanical or mathematical models of a 50th percentile female. A model of a 50th percentile female remains to be developed and is urgently required to complement the average male models to enhance equality in safety assessments. Hence, it is important that future protection systems are developed and evaluated with female properties taken into consideration too. It is likely that the HR15 test configuration is close to the limit for avoiding HR contact for this specific seat setup. Using both datasets (HR15C and HR15NC), each with its corresponding HR contact condition, will be possible in future dummy or model evaluation.