Disc Springs Research Articles

New applications for shape memory alloys in angular - contact ball bearings preloading systems

Shape Memory Alloys (SMA) have been researched extensively in the past forty years. The different available compositions of these alloys can make them suitable for certain applications with specific requirements. The increasing demand for high precision machinery and equipment brought forward the need to search for alloys that that can perform better under stress than conventional materials. This is the case of Shape Memory Alloys. As their name suggests, these alloys can regain their initial shape after being subjected to external stresses, up to a specific degree. Due to the research carried out over the past two decades on these alloys, they became better known and more accessible, being tested in order to be integrated in various applications. One such application consists of using a shape memory alloy formed into disc springs in order to optimize the preloading of angular contact ball bearings. The tests were conducted using a device especially developed for this research, with the purpose of recording the friction torque evolution and the preload induced by disc springs during the operation of the rolling bearings in order to assess the possibility of using elastic elements for active ball bearings preloading systems.

The longitudinal vibration characteristics and parametric analysis of a ship thrust bearing integrated with internal disc springs

To reduce the transmission of shafting longitudinal vibration in surface ships, a design of thrust bearing integrated with internal disc springs is proposed and the longitudinal vibration characteristics of the shafting are studied. According to the structural characteristics of thrust bearing and the deformation characteristics of disc springs, the specific size and combination forms of disc springs in the thrust bearing are designed, and the effective disc springs schemes are achieved according to the static and dynamic design requirements. With the integration of the disc springs into the thrust bearing, the peak of longitudinal displacement response at the base of thrust bearing can be reduced by 10 dB by two schemes of disc springs. The proposed design can effectively suppress the transmission of shaft longitudinal vibration to the hull, which has engineering significance for the longitudinal vibration control of the shafting of the surface ship.

Concept and analysis of resilient frictional shear connector for coupled system

Buildings designed using current seismic codes typically undergo significant structural damage and residual deformations under a design-level earthquake. To avoid this drawback in coupled structural systems, a novel resilient frictional shear connector (RFSC) that can improve both the energy dissipation capacity and structural resilience was proposed in this study. The RFSC is comprised of two T-shaped sections and two cover plates, which are clamped together by two arrays of pre-stressed high-strength bolts and disc springs. The equations governing the hysteretic loop of the coupled system using RFSC are first derived. Then three-dimensional finite element models were developed in Abaqus software for validating the RFSC and predicting the hysteretic response of the RFSC in the coupled system, respectively. Finally, a group of computational investigations of the RFFC in the coupled system subjected to static cyclic load are conducted to analyze the effect of varying key design variables such as the slope angle, the bolt preload, the spring stiffness and the friction coefficient. The parametric analysis confirmed the expected resilient behavior of the RFSC and explored the sensitivity of different parameters on the system responses such as stiffness, strength and equivalent damping ratio.

Effect of the temperature increase in oil-immersed electric reactor on the stress loss of the fastening rods of core limb

The noise and vibration of large oil-immersed reactor is usually controlled and reduced by using high-strength pretensioned steel rods to fasten iron cores. But the effect of uneven temperature increase in the reactor on the pretension relaxation of steel rods is rarely discussed in previous literatures. A combined fastening device of high-strength steel rod and disc spring is designed to conduct temperature experiment in this paper. And three-dimensional (3D) finite element model is developed to reproduce the experiment process. After the numerical simulation method is verified, finite element analysis of a real BKD-6700/20 oil-immersed reactor is performed. The prestress loss proportion of the high-strength pretensioned steel rods in the oil-immersed reactor under practical operating state is 17.91 % owing to its uneven temperature rise, which can result in significantly weakening of its vibration and noise reduction function.

Assembled self-centering energy dissipation braces and a force method-based model

A pre-pressed spring self-centering energy dissipation (PS-SCED) bracing system has significant energy dissipation and re-centering abilities, although many welds result in a lengthy manufacturing process and reduce the machining accuracy to an unacceptable level. An assembled pre-pressed spring self-centering energy dissipation (A-PS-SCED) bracing system that uses disc spring groups to provide a re-centering ability and a friction device to dissipate energy, is presented in this paper to simplify production and maintenance. A novel force method-based (FMB) hysteretic analysis model governing the distribution of the internal force is proposed and verified by a numerical model of the A-PS-SCED brace and tests of the PS-SCED brace specimen. The simulation results indicate that the A-PS-SCED brace exhibits sufficient and steady energy dissipation and re-centering capacities. The FMB model agrees well with the numerical model with a maximum bearing force difference of 2% and has steady hysteretic responses under random excitations. The FMB model is used to determine the mechanisms of the stiffness and contact status change during a typical loading process. Additionally, the FMB model accurately predicts the cyclic loading test results of an existing PS-SCED brace specimen, and the average bearing force differences are 6% and 2% at friction force of 200 kN and 300 kN, respectively.

ANALYSIS OF SCREW CONNECTION IN AIR CONDITIONING SYSTEMS

Air conditioning systems in vehicles require long-term reliability during their entire service life. Especially, a good sealing function is needed for the prevention of coolant leaking. Unfortunately, in specific cases, after a particular time, screw connections of the air conditioning circuit lose their tightness, and the coolant starts to leak. Therefore, this paper focuses on the analysis and design optimisation of screw connections. We used the finite element method for describing the sealing, screw and disc spring behaviour. Then, we proposed a new design of the disc spring to obtain the proper force-deformation characteristics of the connection and ensure the tightness of the screw connection.

Research and Development of Three-Dimensional Isolation System for SFR

The development of a SFR(:Sodium-cooled Fast Reactor) is carried out by Japan Atomic Energy Agency and others. Not only the decrease of horizontal seismic loads, but also the decrease of vertical seismic loads is important in SFR which has thin wall structures. Accordingly, the three-dimensional isolation system is developed for the seismic design of the components. This isolation device consists of a thick rubber bearing, four coned disc spring units, four vertical oil dampers, eight sliding functions and a supporting function. Furthermore, horizontal oil dampers are installed for damping force. This isolation device has few critical development elements and no additional function such as the rocking suppression device. In this isolation system, the natural frequency in the horizontal direction is 0.29Hz, the natural frequency in the vertical direction is 3.0 Hz. This isolation device is premeditatedly developed from 2017. This project has carried out load tests with full and half scale coned disc springs. The design method of coned disc spring units has been confirmed. Furthermore, this project has developed the horizontal oil damper of high allowable velocity and the vertical oil damper. This project is carrying out load tests of the half scale three-dimensional seismic isolation device, which consist of the thick rubber bearing, the coned disc spring units, the supporting function and so on. The development of this isolation device will be continued sequentially. The fundamental design method of this isolation device is confirmed in this project.

Design and Research of Operating Repulsion Mechanism Suitable for 252kV High-Speed Breaking Circuit Breaker

This paper proposes a high-speed operating repulsive force mechanism suitable for 252kV high-voltage circuit breakers. The mechanism draws on the working principle of the electromagnetic repulsion operating mechanism of the medium voltage circuit breaker, and combines the new electromagnetic fast repulsion device with the traditional disc spring hydraulic mechanism to realize the fast action of the circuit breaker. This paper first introduces the working principle of the electromagnetic repulsion operating mechanism, and proposes the initial design scheme of the mechanism. Subsequently, the digital twin technology was used to establish the rigid-flexible coupling multi-body dynamics model of the mechanism, and the defects of the initial scheme were analyzed based on simulation. Finally, the paper optimized the design of the initial scheme and verified it by simulation. The test shows that the 252kV high-voltage circuit breaker with the improved scheme as the operating mechanism works normally and can complete the fault breaking within 20.1ms, which is twice as fast as the current products of the same type.

Design of Composite Disc Spring for Automotive Suspension with using Numerical Simulation

This paper investigates the replacement of a conventional steel coil spring with a composite disc spring with the aim of minimizing its weight. Simulation in the CAD system Siemens NX 12 was used to determine the composite disc spring’s behavior. The regression functions were stated based on the numerical simulation. Based on the regression functions the solution with the minimum weight was found using software programmed in Matlab. The prototype discs were manufactured from carbon fibre prepreg. Their load-deflection characteristics were tested and compared with the designed values. The experimental results show that using this solution reduces the weight by about 30% in this case.

Vertical Seismic Isolation Device for Three-Dimensional Seismic Isolation of Nuclear Power Plant Equipment—Case Study

The purpose of this study was to develop a vertical seismic isolation device essential for the three-dimensional seismic isolation design of nuclear power plant equipment. The vertical seismic isolation device in this study has a concept that can be integrally combined with a conventional laminated rubber bearing, a horizontal seismic isolator with a design vertical load of 10 kN. To develop the vertical seismic isolation device, the vertical spring and the seismic energy dissipation device capable of limiting the vertical displacement of the spring were designed and their performances were verified through actual tests. In this study, the target elevation of the floor is 136 ft, where safety-related nuclear equipment, such as cabinet and remote shutdown console, etc., is installed. The sensitivity studies were carried out to investigate the optimal design vertical isolation frequencies for the target building elevation. Based on the results of the sensitivity study, a disc spring and a helical coil spring were selected for the vertical stiffness design, and the steel damper was selected for the seismic energy dissipation, and their performance characteristics were tested to confirm the design performance. For the steel damper, three types were designed and their energy dissipation characteristics by hysteretic behavior were confirmed by the inelastic finite element analyses and the tests in static fully reversed cyclic conditions. Through the study of the vertical seismic isolation device, it was found that 2.5 Hz~3.0 Hz is appropriate for the optimal design vertical isolation. With results of the vertical seismic isolation performance analysis, the appropriate number of steel dampers are proposed to limit the vertical seismic displacement of the spring within the static displacement range by the design vertical load.

Discussion on the Factors Affecting the Service Life of Rolling Mill Damping Body and the Application Optimization of Disc Spring in Rolling Mill

Discussion on the Factors Affecting the Service Life of Rolling Mill Damping Body and the Application Optimization of Disc Spring in Rolling Mill

Cyclic tests of a precast restrained rocking system for sustainable and resilient seismic design of bridges

Letting a column uplift and sustain rocking motion has been suggested as a seismic design method for bridges. In an effort to increase the redundancy of a rocking bridge, most researchers use ungrouted restraining tendons passing through the columns. However, it has been argued that these tendons unnecessarily increase the design forces of the superstructure and of the foundation, and that rocking systems should be designed to be unrestrained.In an effort to combine the benefits of both approaches this paper suggests the use of flexible restraining systems comprising a tendon in series with disc springs, essentially forming a seismic isolation method for precast structures. It presents cyclic tests of two 1:5 scale RC columns with ends protected either with steel jackets or with steel discs. The columns are able to sustain drifts of more than 15% (and in some cases 30%) without any significant damage – hence they are resilient. The behavior of the disc springs is well predicted by analytical models. The strength (i.e. uplift force) and post uplift stiffness of the system can be predicted with a reasonable accuracy using a rigid body model. However, the rigid body model does not predict well the pre-uplift behavior. As the tendon is anchored within the column, the design moment of the foundation drastically decreases, therefore costly and material intensive pile foundations could be avoided – hence the design concept contributes to sustainability.

Theoretical and experimental research on a new rotating standing wave ultrasonic motor

In this paper, a new rotating standing wave ultrasonic motor with multiple driving teeth is proposed. Using the method of adding additional teeth, the correction of the B06 surface of the ultrasonic motor vibrator is expected, the design of the optimum position of the drive tooth is realized. At the same time, a method of reducing the stiffness of the rotor is proposed, and the flexibility is met, the integrated design of the rotor and the pressure device can be realized by removing the disc spring. The accuracy of the finite element analysis is verified by the vibration test of the prototype oscillator. The finite element analysis of the main structure parameters of the influence oscillator mode and natural frequency is carried out. It provides theoretical basis for the design and machining of vibration.

Cyclic response of a self-centering RC wall with tension-compression-coupled disc spring devices

A strong self-centering ability and robust ductility have previously been observed in the pseudo-static cyclic loading test conducted on a self-centering shear wall (SCSW) with disc spring devices (DSD). However, the bearing capacity and initial stiffness of the wall are reduced by 34.18% and 53.72% respectively compared with the conventional reinforced concrete wall. Therefore, this paper develops a tension–compression-coupled DSD (TCCDSD) to enhance the bearing capacity of the SCSW. The static cyclic responses of the TCCDSD and the SCSW-TCCDSD are investigated through numerical models. TCCDSD exhibits high first and soft second stiffness values during loading, as well as an asymmetric flag-shaped cyclic response. The mechanical model proposed in the paper demonstrates a high accuracy. Compared with the previous SCSW-DSD, the bearing capacity and initial stiffness of the SCSW-TCCDSD increase by 18.12% and 43.53%, respectively, yet the maximum residual drift ratio only increases by 0.044%. Parametric analysis reveals that increasing the first tensile stiffness or the first compressive stiffness of the TCCDSD can enhance the initial stiffness of the wall. Increasing the second compressive stiffness of the TCCDSD can reduce the residual drift of the SCSW, while a higher second tensile stiffness will result in an obvious residual drift. Moreover, a steel plate reinforcer (SPR) is designed to control the damage of the wall. Despite the reduction damage of the region covered by the SPR, severe shear deformation is concentrated on the interface between the wall and foundation as the SPR is not embedded into the foundation.

Development of an End-Toothed Disc-Based Quick-Change Fixture for Ultra-Precision Diamond Cutting

With its standardized and unified interface, the quick-change fixture is an important part for maintaining high efficiency without compensation of precision in the metal-turning process because it can conveniently realize high-precision repeated clamping and multi-station conversion without complex positioning and adjustment steps. However, the existing quick-change fixture products and related research cannot fully meet the needs of repeatability and applicability raised from ultra-precision, single-point diamond turning with ultra-high accuracy and ultra-small depth of cut. In this paper, we develop a quick-change fixture for ultra-precision diamond turning, in which the end-toothed disc acts as the positioning element. Specifically, the main parameters of two key components of the end-toothed disc and slotted disc spring are calculated analytically to ensure the positioning accuracy of the designed fixture used in the rotation condition, which is further ensured by controlling the machining tolerance of the tooth profile of the end-toothed disc. Additionally, finite element simulations are performed to investigate the static and modal states of the quick-change fixture, which demonstrate a maximum deformation of about 0.9 μm and a minimum natural frequency of 5655.9 Hz for the designed fixture. Two high-precision sensors are used to detect the radial jump and end run-out values after repeated clamping actions, which are employed to verify the repetitive positioning accuracy of the fixture. Subsequent finite-element simulation of the clamping of small-diameter copper bar, as well as the diamond turning experiment, jointly demonstrate that the designed fixture can achieve a precision of 1 μm. Current work provides an effective quick-change fixture to reduce the deformation of a weak-stiffness workpiece caused by clamping deformation in ultra-precision diamond cutting.

Nonlinear behavior of disk spring with complex contact state.

Disk springs are widely used as preload and isolation due to their unique mechanical properties. In the prior research, the effect of linear friction on the disk spring was considered, but contact stiffness, another nonlinear contact factor, is ignored. Accordingly, in this paper, the asymmetric displacements of the contact edges are first derived, and the accurate friction dissipations are obtained, as a way to evaluate the effect of friction on the system. Then the velocity of the edges was obtained to establish a dynamic friction model. Meanwhile, the contact displacement and contact stiffness of the edge are obtained by fractal contact theory. Then the nonlinear static and dynamic models of disk spring with friction and contact stiffness are established by the energy method. The load-deflection relationship, stiffness, and hysteresis of disk spring are studied with different contact states. The results show that the model considering contact stiffness and asymmetric friction dissipation can effectively evaluate the static properties of the disk spring. Friction reinforces the nonlinear behavior of the system, while contact stiffness weakens the nonlinearity of the system. And due to the influence of nonlinear contact factors, the transmissibility curves produce multiple resonance peaks.

Experimental investigation on static and dynamic energy dissipation characteristics of composite sandwich structure with entangled metallic wire materials and disc springs

In this paper, a novel composite sandwich structure with entangled metallic wire materials and disc springs (EMWM/DS) was proposed to improve the high temperature resistance and energy absorption characteristic of disc spring structure (DSS). The performance superiority of the proposed structure was verified by a series of quasi-static and low-velocity impact tests. On the one hand, the static energy dissipation characteristics of the EMWM/DS and DSS are compared through quasi-static test. Furthermore, the influences of the key experimental parameters and the densities of EMWM sandwich layers on the dynamic energy absorption characteristics of EMWM/DS are respectively studied by associating the mechanical properties of EMWM/DS with the helix wires based on curved cantilever beam of variable length. The experimental observations show that by increasing the density of the EMWM sandwich layer or increasing the compression deformation, the energy dissipation characteristics of EMWM/DS can be effectively enhanced. The composite sandwich structures still have good compression resistance and energy dissipation characteristics at high temperatures with increased environmental temperature. On the other hand, the dynamic energy absorption performance of the EMWM/DS and the DSS via low-velocity impact (LVI) is evaluated. The experimental results show that the complete impact energy absorption, specific energy absorption, and impact energy loss rate of the EMWM/DS can be increased by more than 93% compared with the DSS under the low-velocity impact (0.5 m s−1–2 m s−1).

Modeling of Disc Spring Self-Centering Energy Dissipation Braces from Inactive State to Design Limit State

AbstractThis paper focuses on modeling the hysteretic behavior of disc spring self-centering energy dissipation braces (DS-SCEDBs) from the inactive state to the design limit state, and proposes tw...

Experimental Study on Instability and Load Transfer Mechanism within Multi-Pillar System

In order to study the instability and load transfer mechanism among multiple parallel pillars during underground mining, compressive tests on single- and treble-pillar specimens were conducted under soft loading condition with adjustable stiffness. Disc spring group was used to realize the adjustable stiffness of the test machine. Experimental results showed that the instability of rock specimen was determined by the stiffness of test machine, where the sudden jump displacement Δd exponentially decreases with the increase of loading stiffness. The load transfer behavior of treble-pillar specimen could only be reproduced under this soft loading condition. Under the soft loading condition, the failure of single pillar in multi-pillar system induces the sudden increase of cumulative AE counts not only in itself, but also in adjacent pillars, which indicates the accelerated damage in adjacent pillars accelerated by load transfer effect. Finally, it was concluded that the soft loading condition was the necessary condition for the load transfer of multi-pillar system. Results of this study may contribute to the better understanding of load transfer mechanism and to optimizing the design of room-and-pillar stopes during underground mining.

RESTORING FORCE MODEL OF DISC SPRING DEVICES AND ITS APPLICATION IN SELF-CENTERING RC SHEAR WALL

The working principle and mechanics behavior of disc spring device are analyzed to accurately simulate the mechanics performance of disc spring device and the self-centering RC shear wall. Furthermore, the restoring force model of disc spring device is proposed and developed. The accuracy of the restoring force model is verified through experiments. The hysteretic performance of the self-centering RC shear wall with disc spring device is numerically simulated and compared with the experimental results due to cyclic reversed loading. Results indicate that the numerical model using a restoring force model of disc spring device can effectively simulate the hysteretic behavior, self-centering performance and energy dissipation capability of the self-centering RC shear wall. The bearing capacity of the self-centering RC shear wall increases with the increase of the pre-pressed force of disc springs, the additional friction force and the stiffness of disc spring device. The energy dissipation capacity increases with the increase of the additional friction force. The residual displacement increases with the increase of additional friction and decreases with the increase of the pre-pressed force of disc springs and the stiffness of disc spring device.