Spring Force Research Articles

CHARACTERIZING SPINAL LOAD-DISPLACEMENT BEHAVIOUR USING REPRESENTATIVE COMPONENTS

AbstractObjectivesSpinal stiffness and flexibility terms are typically evaluated from linear regression of experimental data and are then assembled into 36-element matrices. Summarising in vitro test results in this manner is quick, computationally cheap and has the distinct advantage of outputting simple characteristic values which make it easy to compare results. However, this method disregards many important experimental features such as stiffening effects, neutral and elastic zones magnitudes, extent of asymmetry and energy dissipation (hysteresis). Alternatives to the linear least squares method include polynomials, separation of the load-displacement behaviour into the neutral and elastic zones using various deterministic methods and variations on the double sigmoid and Boltzmann curve fits. While all these methods have their advantages, none provide a comprehensive and complete characterisation of the load-displacement behaviour of spine specimens. In 1991, Panjabi demonstrated that the flexion-extension and mediolateral bending behaviour of functional spinal units could be approximated using the viscoelastic model consisting of a nonlinear spring in series with a linear Kelvin element. Nowadays viscoelastic models are mainly used to describe creep and stress relaxation, rather than for cyclic loading. The aim of this study was to conclusively prove the viscoelastic nature of spinal behaviour subject to cyclic loading. Being able to describe the behaviour of spine specimens using springs and dampers would yield characterising coefficients with recognisable physical meaning, thus providing an advantage over existing techniques.MethodsSix porcine isolated spinal disc specimens (ISDs) were tested under position and load control. Visual inspection of the load-displacement graphs from which the principal terms of the stiffness and flexibility matrices are derived suggest that the load-displacement behaviour could be idealised by a nonlinear spring system with damping. It was hypothesised that the contributions arising from non-linear spring-like behaviour and damping could be separated for each of the principal load-displacement graphs.ResultsThe principal elements from position and load control tests were plotted with load on the vertical axis and displacement on the horizontal axis, and a polynomial representing spring force was fitted to the data. This polynomial was subtracted from the experimental data. The remainder - representing damping force - was plotted against displacement and velocity and compared to idealised plots for different types of damping behaviour. Applying this reasoning to the six principal load-displacement plots obtained from stiffness and flexibility tests revealed that four of six exhibit behaviour which is a combination of a nonlinear hardening spring and viscous damper. However, for flexion-extension and mediolateral bending, the damping behaviour is more akin to coulomb damping with viscous influences, characterised by a steep central linear region and near horizontal regions at the extremes. These trends were common amongst all six specimens within the study sample size.ConclusionsThe unique approach described here has allowed the characterisation of the load-displacement behaviour of ISDs in terms of characteristic mass-spring-damper systems. This is an important development which allows experimental findings to be framed in terms of mechanical contributions to a given load-displacement behaviour.Declaration of Interest(b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Resonance control to eliminate reactive power of an improved dual-port direct-drive wave energy converter

The single-port direct-drive wave energy converter (SPDDWEC) is widely utilized for harvesting ocean power among the existing wave energy converters (WECs) designs. Due to its working principle of generating reactive power inevitably and intermittent nature of the waves, the SPDDWEC is unable to provide continuous and stabilized energy to the grid. This paper proposed a dual-port resonance (DPR) control, which can achieve an improved dual-port direct-drive WEC (DPDDWEC) resonance by adjusting the dual electromagnetic force and electromagnetic spring force. The proposed DPR control can effectively avoid reactive power flow of the DPDDWEC, which can generate more energy than the SPDDWEC. Based on the established DPDDWEC kinematic state space model, the proposed DPR control is simulated and verified. The study results confirm the effectiveness of the proposed control method and correctness of theoretical analysis.

Design and analysis of a tunable electromagnetic lever-type anti-resonant vibration isolator

To broaden the effective vibration suppression band of a typical dynamic anti-resonant vibration isolator (DAVI), a tunable lever-type anti-resonant vibration isolator has been designed, theoretically investigated, and experimentally verified. An anti-resonant frequency occurs within the device when the inertial force generated by the levered mass cancels the spring force. By controlling the electromagnetic spring so as to adjust the system’s equivalent stiffness, the anti-resonant frequency of the electromagnetic lever-type anti-resonant vibration isolator (EM-LVI) can be tuned to coincide with the excitation frequency in real time. A broad stopband where the vibration is sufficiently suppressed can be provided by the EM-LVI for low-frequency applications. Due to the lever’s amplifying effect, the EM-LVI can modify the equivalent stiffness of the system with a small electromagnetic stiffness, which provides a viable approach to the design of lightweight isolators. Theoretical and experimental results demonstrate that the tuning bandwidth increases along with the lever amplification ratio. With the advantages of a wide stopband and a high vibration suppression level, the proposed EM-LVI exhibits significant advantages in suppressing low-frequency vibration in a finite-frequency band and has been successfully validated by experimental prototypes for its beneficial performance in low-frequency vibration suppression.

Tailored nonlinear stiffness and geometric damping: Applied to a bistable vibration absorber

A novel device is proposed to obtain arbitrary restoring force characteristics and nonlinear geometric damping. It consists of linear springs and dampers that are compressed along a track. The obtained nonlinear damping and stiffness law depend on the track’s shape. The device is then applied to obtain a nonlinear energy sink (NES) to damp the vibrations of a host system. Both the case of transient vibrations, induced by shock loads, and sustained vibrations, induced by harmonic loads, are studied. For arbitrary stiffness and damping, slow flow dynamics and slow invariant manifolds (SIMs) are derived by applying harmonic balancing and multiple timescales techniques. Under transient vibrations, two performance measures are derived from the SIM, the relative residual energy and the pumping time, and are found for generic nonlinear spring force and nonlinear geometric damping. For sustained vibrations, a load-dependent frequency response (FR) is derived from the SIMs. This FR predicts the occurrence of the efficient strongly modulated responses but also the occurrence of the unfavorable detached responses called isolas, where the NES fails to mitigate and even amplifies vibrations.This research investigates the performance of a conventional cubic NES and a bistable NES (BNES) with nonlinear damping obtained from the proposed device. Especially the BNES with nonlinear damping shows attractive properties, with a high degree of robustness over a wide energy range and a low vibration threshold under transient loading. Under harmonic loads, the nonlinear damping helps reduce the effect of isolas. A novel tuning methodology is proposed to avoid isolas for a range of load magnitudes. The new device opens up a whole range of possibilities regarding energy dissipation through nonlinear damping.

Investigations of aged metal seals for interim storage

Abstract. The storage of spent fuel and high-level radioactive waste in Germany is performed in interim storage containers with double-lid systems. The lids are bolted and equipped with metal seals (e.g. Helicoflex®) to ensure the safe containment of the inventory. The used metal seals have a layered structure consisting of three components as can be seen schematically in the cross-sectional view in Fig. 1. In the centre, a helical spring is positioned that is surrounded by two C-shaped jackets and is mainly responsible for generation of the required restoring force. The inner jacket is made of stainless steel and homogenises the restoring force of the helical spring. The outer jacket is made of silver or aluminium which are both soft metals in comparison to the contact partners (lid and container body). During bolting of the lid to the container body, the seal is compressed. The generated restoring force of the helical spring causes a plastic deformation of the outer jacket and adapts to the surfaces of the lid and the container body. Hence, leakage paths are closed, and the sealing function is generated. Typical durations for existing interim storage licenses in Germany are 40 years, but it can be expected that they have to be extended to longer periods as a final repository will not be available before the end of the running licence periods. This extension of licence periods requires a solid understanding of the long-term behaviour of the seals under storage conditions. To meet this challenge, long-term investigations were started at the Bundesanstalt für Materialforschung und -prüfung (BAM) in 2009. These tests focus on seals assembled in test flanges which are stored at temperatures ranging from room temperature to 150 ∘C for accelerated ageing. The aged seals are tested repeatedly after certain ageing steps, and the leakage rate (as indicator for sealing performance), the remaining seal force, and the useable resilience upon decompression are determined. An update on the performed investigations with respect to earlier publications (Grelle et al., 2019; Goral et al., 2023) will be given, and the implications of the results for resilient, long-term safety will be presented. Additionally, there will be a focus on the currently planned further investigations, and the following question will be addressed. What is additionally needed for evaluation of an interim storage period extension in regard to the used metal seals?

Development of Simplified Seedling Transplanting Device for Supporting Efficient Production of Vegetable Raw Materials

Efficient greenhouse production has a great supporting role in the development of vegetable agricultural and sideline product processing. In this paper, a simplified automatic transplanting device was designed and evaluated in a laboratory. The device mainly consists of a seedling pick-up gripper, a transplanting manipulator, two conveyors and a control system. The flexible multi-pin gripper was designed to effectively grasp, hold, and release seedlings. Through a combination innovation of the linear modules, the transplanting manipulator was designed to move the seedling gripper to the desired working position. The conveyors were the pallet-type double-row chain transmission system for automatic feeding of plug trays and growth pots. The control system was developed to coordinate each of the aforementioned function units. The multi-factor orthogonal and transplanting performance experiments were carried out under the standard seedling agronomy. The results showed that the transplanting frequency and the pick-up depth significantly affected the transplanting quality. When the transplanting frequency was 15 plants/min, the tightened spring force was 1.2 N, and the pick-up penetration depth was 35 mm, the optimum effects of automatic transplanting seedlings could be achieved. The maximum success in transplanting seedlings was 95.47% for local vegetable crops. The developed prototype could realize less waste of seedling resources at the farm level.

Measures to Improve Seismic Resistance by Fuse Mechanism in Pier Structures

AbstractIn Japan, temporary pier structures are designed to withstand earthquakes in consideration of their short service life, and seismic inputs exceeding the design are also expected. In order to confirm the deformation behavior of the fuse mechanism in this temporary pier structure, a fundamental study was conducted using a model specimen. The strength test results showed that the fuse mechanism behaved similar to a rigid body, and then the mortar fuse failed. After the failure of the mortar fuse, the reaction force was generated by the addition of the residual bearing capacity of the mortar fuse and the reaction force of the coil spring. The dynamic loading test results showed that the CFT columns contacted the remaining portion of the fuse after the mortar fuse ruptured, temporarily increasing the maximum response acceleration to 35 m/s2, but the response period became longer, indicating the deformation behavior of the fuse mechanism. In addition, the maximum load of the mortar fuse mechanism and the natural period after the mortar fuse rupture were calculated from the design values of the mortar fuse strength and the spring constant of the coil spring.

Solving the constitutive equation of dilute polymeric flows: A general Fokker–Planck approach for linear elastic dumbbell models

We present a mesoscopic numerical solver for the constitutive equation of dilute polymer solutions, as described by the Fokker–Planck equation of bead-spring dumbbell models with linear spring forces, such as Oldroyd-B, FENE-P (finitely extensible nonlinear elastic with Peterlin closure), and C-FENE-P (charged FENE-P). The configuration density function of the Fokker–Planck equation is expanded into a series of Hermite polynomials, and we show that only a second order in the expansion is needed to describe the evolution of the polymer-induced stresses. The polymer-induced stress tensor is given exactly through a discrete representation of the configuration distribution function, which is obtained from a finite set of Gauss–Hermite quadrature points. In addition, we derive the conformation tensor equation, which serves as a mathematical quality check for the method. We solve the time evolution of the extra stress tensor for homogeneous flows of dilute polyelectrolyte solutions, conceptualized by the C-FENE-P model, which is a generalization of the FENE-P dumbbell model. The results are shown to be in excellent agreement with analytical and semi-analytical reference results for simple shear and extensional flows. While in this paper the focus is on linear connector forces, we believe that the principles of the derivation are extendable to other force laws.

Influence of NiTi Spring Dimensions and Temperature on the Actuator Properties

Nitinol (NiTi) is used in many medical applications, including hard tissue replacements, because of its suitable characteristics, including a close elastic modulus to that of bones. Due to the great importance of the mechanical properties of this material in tissue replacements, this work aims to study the hysteresis response in an attempt to explore the ability of the material to remember its previous mechanical state in addition to its ability to withstand stress and to obtain the optimal dimensions and specifications for the manufacturer of NiTi actuators. Stress-strain examination is done in a computational way using a mutable Lagoudas MATLAB code for various coil radii, environment temperatures, and coil lengths. The computational methodology was done by varying the dimensions and the ambient temperature of the simulated NiTi spring actuator. The hysteresis loop is studied by increasing the external stress for a reversible martensitic transformation. The coil radius, spring height, and wire radius affect the spring force and deformations. In the same way, these parameters affect the strain and stress point values. These changes are shown through the martensite and austenite start and finish values. The NiTi hysteresis loop narrows with increasing ambient temperature or initial spring height. At a higher temperature, the force supplied to the actuator must be less for the same deformation; therefore, a higher ambient temperature provides more efficiency for the shape memory devices and a longer lifetime for the actuator.

Minimum Free Energy Pathways of Reactive Processes with Nudged Elastic Bands.

The determination of minimum free energy pathways (MFEP) is one of the most widely used strategies to study reactive processes. For chemical reactions in complex environments, the combination of quantum mechanics (QM) with a molecular mechanics (MM) representation is usually necessary in a hybrid QM/MM framework. However, even within the QM/MM approximation, the affordable sampling of the phase space is, in general, quite restricted. To reduce drastically the computational cost of the simulations, several methods such as umbrella sampling require performing a priori a selection of a reaction coordinate. The quality of the computed results, in an affordable computational time, is intimately related to the reaction coordinate election which is, in general, a nontrivial task. In this work, we provide an approach to model reactive processes in complex environments that does not require the a priori selection of a reaction coordinate. The proposed methodology combines QM/MM simulations with an extrapolation of the nudged elastic bands (NEB) method to the free energy surface (FENEB). We present and apply our own FENEB scheme to optimize MFEP in different reactive processes, using QM/MM frameworks at semiempirical and density functional theory levels. Our implementation is based on performing the FENEB optimization by uncoupling the optimization of the band in a perpendicular and tangential direction. In each step, a full optimization with the spring force is performed, which guarantees that the images remain evenly distributed. The robustness of the method and the influence of sampling on the quality of the optimized MFEP and its associated free energy barrier are studied. We show that the FENEB method provides a good estimation of the reaction barrier even with relatively short simulation times, supporting that its combination with QM/MM frameworks provides an adequate tool to study chemical processes in complex environments.

Integration of a gas pressure chamber on a reciprocal tribometer for experiments at ambient pressures up to 10 bar

PurposeThis study aims to focus on the development of an experimental setup for testing tribological pairings under a gas atmosphere at pressures up to 10 bar.Design/methodology/approachA pressure chamber allowing oscillating movement through an outer shaft was constructed and mounted on an oscillating tribometer. Due to a metal spring bellows system, a methodology for the evaluation of the coefficient of friction values separately from the spring forces was developed.FindingsThe selected material concept was qualitatively and quantitatively assessed. An evaluation of the static and the dynamic coefficient of friction was performed, which was crucial for the understanding of the adhesion effects of the tested material pairing. The amount of information that is lost due to averaging the measured friction values is higher than one would expect.Originality/valueThe developed experimental setup is unique and, compared with the existing tribometers for testing under gas ambient pressures, allows testing under contact conditions that are closer to real applications, such as compressors and expanders. An in-depth observation of the adhesion and stick–slip effects of the tested material pairings is possible as well.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-06-2023-0173/

Effective viscosity and elasticity in dense suspensions under impact: Toward a modeling of walking on suspensions.

The elastic response of dense suspensions under an impact is studied using coupled lattice Boltzmann method and discrete element method (LBM-DEM) and its reduced model. We succeed to extract the elastic force acting on the impactor in dense suspensions, which can exist even in the absence of percolating clusters of suspended particles. We then propose a reduced model to describe the motion of the impactor and demonstrate its relevancy through the comparison of the solution of the reduced model and that of LBM-DEM. Furthermore, we illustrate that the perturbation analysis of the reduced model captures the short-time behavior of the impactor motion quantitatively. We apply this reduced model to the impact of a foot-spring-body system on a dense suspension, which is the minimal model to realize walking on the suspension. Due to the spring force of the system and the stiffness of the suspension, the foot undergoes multiple bounces. We also study the parameter dependencies of the hopping motion and find that multiple bounces are suppressed as the spring stiffness increases.

Quasi-static cyclic loading experiment and analysis of mechanical properties of the Sc-FSB

In order to improve the seismic performance of a continuous bridge, we propose to install self-centering functional separation bearings (Sc-FSB) between the fixed pier and the girder in the bridge. Following the design idea of separating functionalities, the Sc-FSB device is primarily composed of a sliding bearing to bear vertical load, a friction cable to carry horizontal seismic force and dissipate the seismic energy input into the superstructure, and self-centering springs to achieve post-earthquake self-centering effects. In this study, the Sc-FSB device's hysteretic model is established, and its theoretical formula is deduced. The quasi-static cyclic tests of 10 Sc-FSB device specimens were performed to verify their promising mechanical performances, in which we consider parameters of two friction cables with different diameters and three self-centering springs with different stiffnesses. The results show that the Sc-FSB device holds excellent characteristics of a typical friction damper, such as relatively stable outputs, good energy dissipation and deformation capacity under all working conditions, and its fatigue performance meets the requirements of typical specifications. In addition, several unique features of the Sc-FSB are identified as follows. The maximum damping force is independent of the loading frequency, and it increases with the displacement amplitude. The damping force is significantly affected by the pre-tension force of the friction cable and the number of winding coils, and as a result, the energy dissipation performance is promising. The stiffness and pre-tension force of the self-centering spring significantly improve the self-centering ability of the Sc-FSB device. The design of friction cable and self-centering spring effectively separates the functions of bearings. This study can serve as a foundation for the further study of Sc-FSB device and as a reference for the research of other similar friction dampers.

Chilling and forcing proceed in parallel to regulate spring leaf unfolding in temperate trees

AbstractAimTemperature is the main driver of growth reactivation in plants of extratropical regions. Accumulations of chilling and forcing units during dormancy co‐regulate spring phenology. Here, we aimed to answer whether chilling and forcing proceed in parallel or sequentially to regulate spring phenology in temperate trees.LocationEurope.Time Period1951–2016.Major Taxa StudiedNine temperate woody species.MethodsUsing long‐term and large‐scale records of in situ leaf unfolding dates of temperate tree species at more than 2300 sites, we analysed the rolling partial correlations between leaf unfolding dates and chilling and forcing in winter and spring using a weekly smoothing window. Through process‐based modelling, we further identified the start of forcing accumulation and the end of chilling accumulation using the Unified model and compared the model efficiency of the Parallel and the Sequential models.ResultsWe observed negative responses of leaf unfolding dates to accumulations of both chilling and forcing units for most of winter and spring across successional types of species (early‐ and late‐successional taxa), elevations and periods. Using the Unified model, we also found overlapping windows for chilling and forcing accumulations. Moreover, the Parallel model performed better than the Sequential model. These findings suggested that chilling and forcing requirements may be fulfilled simultaneously in temperate trees.Main ConclusionsOur study not only provides a guideline for identifying the effective periods of chilling and forcing, but also a general and robust perspective that accumulations of chilling and forcing act in parallel to regulate spring leaf unfolding in temperate trees, promoting more precise and reasonable predictions of temperature‐driven phenological shifts under future climate change.

The stable and unstable oscillations of a rod attached to many springs

The oscillation equations of a multi-spring system connected to a rod are developed. Oscillations can be stable or unstable depending on the distribution of the spring constant and the number of springs. The symmetrical spring distribution with respect to the rod center tends to stabilize. The system becomes more stable as the number of springs increases. The equations of motion are identified to satisfy the Mathieu’s equation. The system could be thought of as a rough imitation of the crazy bamboo attraction, a traditional attraction by old civilization that is frequently associated with the mystical phenomenon. One spring represents one performer. The behavior of the performer’s force (opposite to the direction of the bamboo movement and providing a stronger force as the displacement of the bamboo increases) is similar to that of the spring force.

Neural Control of a Robotic Manipulator in Contact with a Flexible and Uncertain Environment

Abstract This article presents the synthesis of a neural motion control system of a robot caused by disturbances of constraints limiting the movement, which are the result of flexibility and disturbances of the contact surface. A synthesis of the control law is presented, in which the knowledge of the robot’s dynamics and the parameters of a susceptible environment is not required. Moreover, the stability of the system is guaranteed in the case of an inaccurately known surface of the environment. This was achieved by introducing an additional module to the control law in directions normal to the surface of the environment. This additional term can be interpreted as the virtual viscotic resistance and spring force acting on the robot. This approach ensured the self-regulation of the robot’s interaction force with the compliant environment, limiting the impact of the geometrical inaccuracy of the environment.

Open-source 3-D printable autoinjector: Design, testing, and regulatory limitations.

Autoinjectors have become popular modern injectable medical devices used as drug delivery systems. Due to their ease, capability and reliability compared to other conventional injectable medical devices, the market and manufacturing demand for autoinjector devices are increasing rapidly and expected to reach a market of $37.5 billion globally by 2025. Although autoinjectors can offset healthcare treatment costs through self-administered medication, they can be expensive for consumers, which limit their accessibility. This study describes the design and manufacture of a spring-driven and 3-D printed autoinjector to overcome this economic accessibility challenge. The digitally replicable device is released as open-source hardware to enable low-cost distributed manufacturing. The bill of materials and assembly instructions are detailed, and the effectiveness of the autoinjector is tested against the current standard (ISO 11608-1:2022) for needle-based injection systems. The safety and dosing accuracy was tested by measuring the weight of 100% ethyl alcohol expelled from six BD Insulin syringes with varying capacities or needle lengths. A one-way analysis assessed the variability between the dose delivery efficiency of 1mL, 0.5mL, and 0.3mL syringes. Testing indicated that the entire dose was delivered over 97.5% of the time for 1mL and 0.5mL syringes, but the autoinjector's loaded spring force and size exceeded structural limitations of 0.3mL or smaller syringes. Components can be manufactured in about twelve hours using an open-source desktop RepRap-class fused filament 3-D printer. The construction requires two compression springs and 3-D printed parts. The total material cost of CAD$6.83 is less than a tenth of comparable commercial autoinjectors, which makes this approach promising. The autoinjector, however, is a class two medical device and must be approved by regulators. Future work is needed to make distributed manufacturing of such medical devices feasible and reliable to support individuals burdened by healthcare costs.

Robotic check of a subassembly, and its simulation

This paper discusses a quality inspection process of a subassembly of a battery cover, which is performed with an industrial robot equipped with an intelligent end-effector. The subassembly has a plastic pin and a torsion spring part. During intended use of the unit, the necessary force to actuate the pin is determined with measurements and simulations. In the measurement a self-devised intelligent end-effector is equipped with a microcontroller and a beam type load cell in order to measure the spring force. The main aim is to make an automatic decision without operator intervention at the quality check process, which is related to the quality of the subassembly. In the simulation deformation of the spring part is modeled with geometrically nonlinear 2D beam finite elements in the course of assembly and intended use. Co-rotational approach is used to consider the large displacements and rotations with small strains. Penalty method is applied to treat the contact between the spring and pin parts.

Mechanism of active acetylcholinesterase inhibition by organic sulfanes in garlic: Non-covalent binding and covalent modifications

Numerous secondary metabolites in medicinal food homology plants such as Allium inhibit the activity of acetylcholinesterase (AChE), but the current understanding of the inhibition mechanism is limited. In this study, we employed ultrafiltration, spectroscopic, molecular docking, and matrix-assisted laser desorption ionization time-of-flight tandem mass spectrometry (MALDI-TOF-MS/MS) techniques to investigate the inhibition mechanism of AChE by garlic organic sulfanes, including diallyl sulfide (DAS), diallyl disulfide (DADS), and diallyl trisulfide (DATS). The results of UV-spectrophotometry and ultrafiltration experiments showed the inhibition of AChE activity by DAS and DADS was reversible (competitive inhibition), but inhibition by DATS was irreversible. Molecular fluorescence and molecular docking indicated DAS and DADS changed the positions of key amino acids inside the catalytic cavity through hydrophobic interactions with AChE. By using MALDI-TOF-MS/MS, we found DATS irreversibly inhibited AChE activity by opening disulfide-bond switching of disulfide bond 1 (Cys-69 and Cys-96) and disulfide bond 2 (Cys-257 and Cys-272) in AChE, as well as by covalently modifying Cys-272 in disulfide bond 2 to generate AChE–SSA derivatives (strengthened switch). This study provides a basis for further exploration of natural AChE inhibitors using organic active substances in garlic and presents a hypothesis of U-shaped spring force arm effect based on the disulfide bond-switching reaction of DATS that can be used to evaluate the stability of disulfide bonds in proteins.

Development and seismic behavior of an assembly composite damping self‐centering brace

AbstractA new type of assembly composite damping self‐centering brace is proposed to simplify the configuration, reduce the manufacturing cost, and improve its energy dissipation capacity, which is assembled by several modules in parallel with different functions. A brace specimen with a total length of 1.843 m was designed and numerically analyzed. The brace exhibits stable and full flag‐shaped hysteretic responses, and dissipates adequate energy during cyclic motion, with a high bearing capacity. When the brace is unloaded, the viscous damping force disappears, and the residual displacement can be basically eliminated. The hysteretic envelope area increases with the increase in loading frequency. When the frequency is 0.5 Hz and the target displacement is 30 mm, the activation force, ultimate bearing capacity, residual displacement, energy dissipation during one cycle, and equivalent viscous damping ratio are 622.5 kN, 1018.7 kN, 9.11 mm, 41.10 kJ, and 0.214, respectively. Under random loading, the damping force provided by the viscous module ensures a fuller hysteretic loop than the existing displacement‐type energy dissipation self‐centering brace. The influences of design parameters on the hysteretic performances of the brace were studied. When the disc spring stiffness increases from 3.27 to 9.80 kN/mm, the ultimate bearing capacity, residual displacement, and equivalent viscous damping ratio change by 18%, −24%, and −15%, respectively. The viscous damping coefficient and flow index of the viscous module should be increased, and the prepressed force and stiffness of disc springs in recentering module should also be appropriately increased.