An Asymmetric Quasi-zero Stiffness Vibration Isolator with Long Stroke and Large Bearing Capacity

A novel passive asymmetric quasi-zero stiffness vibration isolator (AQZS-VI) comprising two linear springs acting in parallel with one negative stiffness element (NSE) is proposed, of which the NSE is mainly constructed by the combination of cantilever plate spring and L-shaped lever (CPS-LSL). The static model of the isolator is deduced considering the geometrical nonlinearity of the NSE and the bending deformation of plate spring. The nonlinear stiffness properties of the CPS-LSL and the AQZS-VI, as well as the nonlinear damping properties of the AQZS-VI are discussed. The absolute displacement transmissibility of the AQZS-VI under base displacement excitation is obtained using Harmonic Balance Method, and the effects of different excitation amplitudes and damping factors on the vibration isolation performance are analyzed. Better than other quasi-zero stiffness vibration isolators (QZS-VI) whose NSEs do not provide supporting force at zero stiffness point, the NSE of the AQZS-VI provides more supporting force than the parallel connected linear springs, which is very beneficial for improving the bearing capacity of the isolator. Compared with a typical symmetric QZS-VI with same damping property, the AQZS-VI has longer stroke with low stiffness and lower peak value of displacement transmissibility. The prototype experiments indicate that the AQZS-VI outperforms the linear counterpart with much smaller starting frequency of vibration isolation and lower displacement transmissibility. The proposed AQZS-VI has great potential for applying in various engineering practices with superior vibration isolation performance.

The Staple-Shape Plate Springs Engineering Calculation Method

The new types of elastic devices – staple-shape plate spring and leaf spring - have been developed at the Kyiv National University of Construction and Architecture. The staple-shape plate spring is an elastic plate where the ends are deflected from its middle part in the same direction and are made in the form of consoles equipped with hinge attachments. The middle part of the plate as a parallel to the line of the load action is designed with variable length section. In each section, the axis, relative to which the moment of the section inertia is a maximum, is perpendicular to the spring bending plane, designed as the equal resistance beam. This article substantiates the feasibility of using a staple-shape plate spring to improve the elastic suspension of truck cabs. The recommendations for choosing the most promising mass production directions, as well as the engineering calculation methods of such springs, have been developed. Objects of the study are devices intended for machines and their components dynamic loads shock absorption, differing in having a bracket shape and being a subject to bending in the plane of the highest rigidity of their cross sections, as well as shock absorbers using these springs, in particular KamAZ cabs suspension. This research implementation allows significantly reducing the metal consumption and elastic devices manufacture complexity, as well as can be useful in the design and operation of elastic car suspensions.Keywords: elastic device, staple-shaped plate spring, leaf spring, elastic suspension

Magnetic Pre-Loading for a Tonpilz-Type Acoustic Projector

This paper describes a new magnet-based method for applying a compressive pre-load to the piezoceramic elements of a Tonpilz-type acoustic projector, with the advantage of lower damping due to mechanical friction and a greater range of unhampered resonant motion since no plate spring is required. The Tonpilz-type acoustic projector can be applied to structural health monitoring studies involving air coupled ultrasound. Acoustic model predictions and the measured behaviour of a relaxor ferroelectric single crystal (RFSC) based prototype device, operating in air, are presented and show good correlation. With a 5 V drive, at 9420 Hz resonance, the prototype device generates a sound pressure level of 113 dB measured at an axial distance of 5 mm. The maximum peak tip displacement of the device’s head mass is predicted to be 0.7 µm at resonance. This is well within the 2 µm displacement produced by the 90 N magnetic pre-load, thus protecting the RFSC ceramic element from damaging tensile stress.

Efficient Design of the Sewing Machine's Shuttle Thread Tension Regulator

The paper presents the tension regulator of the Shuttle thread of the sewing machine, which consists of an arc-shaped plate spring, has two holes, the first for fixing the screw to the side surface of the bobbin cap and the second for the adjusting screw. In this case, the width of the plate spring along the entire length is the same. A disadvantage of the known design of the Shuttle thread tension regulator is that it is not possible to provide thread tension due to changes in the pressure force of the plate spring along its length in the areas of contact with the thread passing between the plate and the side surface.

A rapid prototyping-based methodology for patient-specific contouring of osteotomy plates

Purpose An important challenge of the osteotomy procedures, particularly in the case of large and complex corrections, is the fixation of the osteotomy site. The purpose of this study is to propose a practical and cost-effect methodology for the plate adapting problem of osteotomy surgery. Design/methodology/approach A novel patient-specific plate contouring methodology, based on rapid prototyping (RP) and multi-point forming (MPF) techniques, was developed and evaluated. In this methodology, a female mold is fabricated by RP, based on the geometry of the osteotomy site and estimation of the plate spring back. The mold is then used to configure a MPF die, which is then used for press forming of the factory-made locking plate. The applicability of the methodology was assessed in two case studies. Findings The results of implementing the methodology on a femoral and a tibial locking plate indicated very good conformity with the underlying bone, in both the frontal and sagittal planes. The surgical application of the pre-operatively contoured tibial plate facilitated the plate locating and screw inserting procedures, and provided a secure fixation for bone fragments. Practical implications The results are promising and provide a proof of concept for the feasibility and applicability of the proposed methodology in clinical practice, as a complementary to the existing surgical preplanning and patient-specific instrument preparations. Originality/value The advantageous features of RP and the MPF were used to provide a solution for the plate adapting problem of osteotomy surgery.

Investigation of vibration induced by moving cranes in high-tech factories

A finite element model was developed to simulate the crane induced vibration on the floor of high-tech factories, in which the mesh include beam, plate, spring-damper, and moving wheel elements. The finite element results were first compared with the experimental measurements in good agreement. The parametric studies were then performed to study the vibration behavior of high-tech factories due to the effects of rail irregularities, slab depth, and crane speed. The rail irregularities induce the vibration of the crane and slab at their natural frequencies, and both rail irregularities and the crane acceleration induce the crane rotation in its natural frequency, so that smoothing the wheel and rail should be the first priority to decrease slab vibration. The crane speed is another important issue to influence slab vibration, which decreases with the reduction of the crane speed clearly from the parametric study. Thus, decreasing the crane speed to reduce slab vibration is an alternative, and experiments are caused to find the optimal crane speed and acceleration. The crane induced vibration is the relatively largest and smallest at the column location and beam center, respectively. Therefore, increasing the slab and beam depth to decrease the slab vibration induced by the moving crane is an additional option.