Spring System Research Articles

An Efficient Polynomial Chaos Method for Stiffness Analysis of Air Spring Considering Uncertainties

Traditional methods for stiffness analysis of the air spring are based on deterministic assumption that the parameters are fixed. However, uncertainties have widely existed, and the mechanic property of the air spring is very sensitive to these uncertainties. To model the uncertainties in the air spring, the interval/random variables models are introduced. For response analysis of the interval/random variables models of the air spring system, a new unified orthogonal polynomial expansion method, named as sparse quadrature-based interval and random moment arbitrary polynomial chaos method (SQ-IRMAPC), is proposed. In SQ-IRMAPC, the response of the acoustic system related to both interval and random variables is approximated by the moment-based arbitrary orthogonal polynomial expansion. To efficiently calculate the coefficient of the interval and random orthogonal polynomial expansion, the sparse quadrature is introduced. The proposed SQ-IRMAPC was employed to analyze the mechanic performance of an air spring with interval and/or random variables, and its effectiveness has been demonstrated by fully comparing it with the most recently proposed orthogonal polynomial-based interval and random analysis method.

Robotic grasping method of bolster spring based on image-based visual servoing with YOLOv3 object detection algorithm

In this paper, to address the problem of automatic positioning and grasping of bolster spring with complex geometric features and cluttered background, a novel image-based visual servoing (IBVS) control method based on the corner points features of YOLOv3 object detection bounding box is proposed and applied to the robotic grasping system of bolster spring. The YOLOv3 object detection model is used to detect and position the bolster spring and then based on the corner points features of the bolster spring bounding box, the IBVS controller is designed to drive the end effector of the robot to the desired pose. This method adopts the approach-align-grasp control strategy to achieve the grasping of the bolster spring, which is very robust to the calibration parameter errors of the camera and the robot model. With the help of Robotics and Machine Vision Toolboxes in Matlab, IBVS simulation analysis based on feature points is carried out. The results show that it is reasonable to use the corner points of the object detection bounding box as image features under the initial pose where the image plane is parallel to the object plane. The positioning and grasping experiments are conducted on the robotic grasping platform of bolster spring. The results show that this method is effective for automatic positioning and grasping of bolster spring with complex geometric features and cluttered background, and it has strong robustness to the change of illumination.

Analysis of the Dynamic Stiffness, Hysteresis Resonances and Complex Responses for Nonlinear Spring Systems in Power-Form Order

Power-form nonlinear contact force models are widely adopted in relatively moving parts of macro (e.g., rolling bearings considering Hertzian contact restoring force between rolling elements and bearing raceways) or micro (e.g., the micro cantilever probe system of atomic force microscopy) scale mechanical systems, and contact resonance could cause serious problems of wear, contact fatigue, vibration, and noise, which has attracted widespread attention. In the present paper, the softening/hardening stiffness characteristics of continuous and one-sided contact power-form nonlinear spring models are addressed, respectively, by the analysis of the monotone features of resonant frequency-response skeleton lines. Herein, the period-n solution branch and its stability characteristics are obtained by the harmonic balance and alternating frequency/time domain (HB–AFT) method and Floquet theory. Compared with previous studies, this paper will furtherly clarify the influences of externally normal load, the power form exponent term, and excitation amplitude on the softening/hardening stiffness characteristics of general power-form spring systems. In addition, for a power-form system with a one-sided contact, the phenomena of primary and super/sub-harmonic hysteretic resonances inducing period-doubling, folding bifurcation, the coexistence of multiple solutions are demonstrated. Besides, it gives the evolution mechanism of two types of intermittency chaos in a one-sided contact system. The overall results may have certain basic theoretical significance and engineering values for the control of vibration and noise in contact mechanical systems.

Development of a Combined Micro-Macro Mechanics Analytical Approach to Design Shape Memory Alloy Spring-Based Actuators and Its Experimental Validation.

In this work, an analytical procedure for the preliminary design of shape memory alloy spring-based actuators is investigated. Two static analytical models are considered and interconnected in the frame of the proposed procedure. The first model, based on the works from An, is able to determine the material properties of the SMA components by means of experimental test data and is able to size the SMA component based on the requirements of the system. The second model, based on a work from Spaggiari, helps to design and size an antagonist spring system that allows one to obtain the geometric characteristics of springs (SMA and bias) and the mechanical characteristics of the entire actuator. The combined use of these models allows one to define and size a complex SMA actuator based on the actuation load requirements. To validate the design procedure, static experimental tests have been performed with the entire SMA actuator.

Design and Characterization of an Electrostatic Constant-Force Actuator Based on a Non-Linear Spring System

In recent years, tissue engineering with mechanical stimulation has received considerable attention. In order to manipulate tissue samples, there is a need for electromechanical devices, such as constant-force actuators, with integrated deflection measurement. In this paper, we present an electrostatic constant-force actuator allowing the generation of a constant force and a simultaneous displacement measurement intended for tissue characterization. The system combines a comb drive structure and a constant-force spring system. A theoretical overview of both subsystems, as well as actual measurements of a demonstrator system, are provided. Based on the silicon-on-insulator technology, the fabrication process of a moveable system with an extending measurement tip is shown. Additionally, we compare measurement results with simulations. Our demonstrator reaches a constant-force of 79 ± 2 μN at an operating voltage of 25 V over a displacement range of approximately 40 μm, and the possibility of adjusting the constant-force by changing the voltage is demonstrated.

Hysteretic behavior and parametric studies of a self-centering shear wall with tension-compression disc spring devices

In order to achieve an earthquake-resilient structure, this study proposes a novel self-centering shear wall with disc spring devices (SCSW-DSDs). Cyclic loading tests were conducted on a conventional wall and an SCSW-DSD. Results indicate the satisfactory self-centering performance of the new wall, yet the initial stiffness and bearing capability of the current SCSW-DSD were significantly decreased compared to those of the conventional wall. Therefore, a compression-tension disc spring device (TCDSD) was designed to enhance the initial stiffness and bearing capacity of the SCSW. The establishment of the TCDSD equivalent spring systems allowed us to calculate the macro parameters of the device. The hysteretic behavior of both the TCDSD and SCSW-TCDSD were investigated under cyclic loadings. The TCDSD was observed to exhibit an asymmetric flag-shaped hysteretic response. Furthermore, the initial stiffness and bearing capacity of the SCSW-TCDSD were increased by approximately 25% compared to the previous SCSW-DSD. The increase in the first and second stiffness, as well as the pre-pressure and friction, can improve the bearing capacity of the wall. However, the residual displacement will inevitably increase with these four parameters, particularly the friction. Moreover, increasing the friction resulted in the greatest improvements in the SCSW-TCDSD energy dissipation capability.

Using StorAge Selection (SAS) functions to understand flow paths and age distributions in contrasting karst groundwater systems

Karst catchments have complex flow paths dynamics due to the unique, marked spatial heterogeneity of karst groundwater systems. We used the StorAge Selection (SAS) function framework to explore variations in age distributions of outflow and evapotranspiration from a small karst catchment in southwest China, as well as two hillslope spring systems within it. Daily hydrogen and oxygen stable isotopes (δD and δ18O) in precipitation and at corresponding discharge points were measured for 3 years in order to calibrate the model parameters. The seasonal variations in flux age of the three karst groundwater systems are similar, which indicates the generally strong hydrological connection between hillslope and depression at seasonal scales. The age distribution of outflow shows a “high-low–high” variation pattern in the whole catchment while a “high-low-low” pattern in hillslope system at the beginning of the wet season. In addition to sinkholes in depression, the distributions of soil and epikarst relating to the system storage capacity, resulting in variations of flow paths under different wetness conditions, is likely the main control on the age distributions in runoff for different karst system. The discharge selection preferences generally shift from for younger water in wet season to for older water in dry season in the whole catchment, while that for younger water in both wet and dry seasons in hillslope system. The dynamics of discharge selection preferences can be linked to the critical zone structure of karst underground system. The results in this study show that both hillslope and whole catchment preferentially release younger water to evapotranspiration in the study area.

How are oxygen budgets influenced by dissolved iron and growth of oxygenic phototrophs in an iron-rich spring system? Initial results from the Espan Spring in Fürth, Germany

Abstract. At present most knowledge on the impact of iron on 18O / 16O ratios (i.e. δ18O) of dissolved oxygen (DO) under circum-neutral conditions stems from experiments carried out under controlled laboratory conditions. These showed that iron oxidation leads to an increase in δ18ODO values. Here we present the first study on effects of elevated Fe(II) concentrations on the δ18ODO in a natural, iron-rich, circum-neutral watercourse. Our results show that iron oxidation was the major factor for rising dissolved oxygen isotope compositions in the first 85 m of the system in the cold season (February) and for the first 15 m during the warm season (May). Further along the course of the stream, the δ18ODO decreased towards values known for atmospheric equilibration around +24.6 ‰ during both seasons. Possible drivers for these changes may be reduced iron oxidation, increased atmospheric exchange and DO production by oxygenic phototrophic algae mats. In the cold season, the δ18ODO values stabilized around atmospheric equilibrium, whereas in the warm season stronger influences by oxygenic photosynthesis caused values down to +21.8 ‰. In the warm season from 145 m downstream of the spring, the δ18ODO increased again until it reached atmospheric equilibrium. This trend can be explained by respiratory consumption of DO combined with a relative decrease in photosynthetic activity and increasing atmospheric influences. Our study shows that dissolved Fe(II) can exert strong effects on the δ18ODO of a natural circum-neutral spring system even under constant supply of atmospheric O2. However, in the presence of active photosynthesis, with supply of O2 to the system, direct effects of Fe oxidation on the δ18ODO value become masked. Nonetheless, critical Fe(II) concentrations may indirectly control DO budgets by enhancing photosynthesis, particularly if cyanobacteria are involved.

Highly Selective Guiding Springs for Large Displacements in Surface MEMS

In this paper we introduce the concept, modelling and analysis of triangular and sinusoidal springs intended for large in-plane translational displacements for MEMS-guiding applications. The proposed spring systems combine the advantages of minimal space requirement, low stiffness in the axial direction and high mechanical resistance in off-axis directions. An analytical model for the description of the force-displacement characteristic of triangular springs is derived considering typical mechanical constraints. Based on the model, geometrical parameters of the springs influencing linearity and selectivity with respect to the in- and off-axis stiffness are analyzed. The validity of the models is demonstrated by finite element analysis and experimental verification realized by silicon-on-insulator demonstrators. [2020-0360]

Design and validation of a modular micro-robotic system for the mechanical characterization of soft tissues

The mechanical properties of tissues are critical design parameters for biomaterials and regenerative therapies seeking to restore functionality after disease or injury. Characterizing the mechanical properties of native tissues and extracellular matrix throughout embryonic development helps us understand the microenvironments that promote growth and remodeling, activities critical for biomaterials to support. The mechanical characterization of small, soft materials like the embryonic tissues of the mouse, an established mammalian model for development, is challenging due to difficulties in handling minute geometries and resolving forces of low magnitude. While uniaxial tensile testing is the physiologically relevant modality to characterize tissues that are loaded in tension in vivo, there are no commercially available instruments that can simultaneously measure sufficiently low tensile force magnitudes, directly measure sample deformation, keep samples hydrated throughout testing, and effectively grip minute geometries to test small tissues. To address this gap, we developed a micromanipulator and spring system that can mechanically characterize small, soft materials under tension. We demonstrate the capability of this system to measure the force contribution of soft materials, silicone, fibronectin sheets, and fibrin gels with a 5 nN – 50 µN force resolution and perform a variety of mechanical tests. Additionally, we investigated murine embryonic tendon mechanics, demonstrating the instrument can measure differences in mechanics of small, soft tissues as a function of developmental stage. This system can be further utilized to mechanically characterize soft biomaterials and small tissues and provide physiologically relevant parameters for designing scaffolds that seek to emulate native tissue mechanics. Statement of significanceThe mechanical properties of cellular microenvironments are critical parameters that contribute to the modulation of tissue growth and remodeling. The field of tissue engineering endeavors to recapitulate these microenvironments in order to construct tissues de novo. Therefore, it is crucial to uncover the mechanical properties of the cellular microenvironment during tissue formation. Here, we present a system capable of acquiring microscale forces and optically measuring sample deformation to calculate the stress-strain response of soft, embryonic tissues under tension, and easily adaptable to accommodate biomaterials of various sizes and stiffnesses. Altogether, this modular system enables researchers to probe the unknown mechanical properties of soft tissues throughout development to inform the engineering of physiologically relevant microenvironments.

Force-compensating spring modules of self-contained type for small phase error performance in in-vacuum undulators

In an in-vacuum undulator, the dynamic phase error, which is a kind of systematic phase errors, is increased because the out-of-vacuum girder is deformed with a strong magnetic force. As a result, the spectral performance of synchrotron radiation is deteriorated. A recommended solution for a problem of this kind is to adopt a spring system to compensate the magnetic force, but a conventional spring system has a problem in that the mechanical frame of the undulator is deformed by a reaction force from the springs. The new force-compensating spring module shown in this paper is a self-contained type that can treat the spring reaction force within the module, therefore, the side effects of the spring operation can be minimized. Three in-vacuum undulators with a length of 2–4 m are equipped with the spring modules of new type, so a small rms phase error of 1.7°–2.2° is obtained under the highest magnetic force at the minimum gap.

Dynamic simulation of a high-speed train with interconnected hydro-pneumatic secondary suspension

A secondary suspension configuration that integrates the Interconnected Hydro-Pneumatic Struts (IHPS) to the air spring system is proposed in this investigation for railway vehicles. Using the dynamic performance of IHPS, this suspension aims to provide smaller vertical supporting stiffness and larger anti-roll resistance compared to the traditional configuration, the air spring is connected to an emergency rubber spring in series with quite large stiffness. By replacing the rubber spring with IHPS, the proposed suspension configuration contributes to vibration absorption as well as anti-roll stiffness of the vehicle. The IHPS has two hydraulic cylinders installed in parallel to support the suspended mass. Each hydraulic cylinder has three oil chambers, and the oil chambers between the left and right struts are cross-connected through pipelines. Considering the oil compressibility and the vibration of liquid in the interconnected pipes, the mathematical model of IHPS is formulated and established in MATLAB. A multi-body dynamic railway vehicle model is built in SIMPACK, into which the IHPS is integrated through a co-simulation technique. Model validations on the IHPS are performed and its static and dynamic stiffness is examined. Numerical simulations show that the IHPS suspension reduces the vertical acceleration on the car body floor at a frequency between 1 and 3 Hz than the traditional air spring system with/without an anti-roll bar configuration. The vertical Sperling index of the vehicle using the IHPS suspension is smaller than that of the traditional suspensions, and it is more significant when the air spring deflates. However, the vertical acceleration with IHPS is larger than the traditional suspensions at 13∼55 Hz when the air spring deflates.

Spatial and Temporal Dynamics of Prokaryotic and Viral Community Assemblages in a Lotic System (Manatee Springs, Florida).

ABSTRACTFlow from high-magnitude springs fed by the Floridan aquifer system contributes hundreds of liters of water per second to rivers, creating unique lotic systems. Despite their importance as freshwater sources and their contributions to the state’s major rivers, little is known about the composition and spatiotemporal variability of prokaryotic and viral communities of these spring systems or their influence on downstream river sites. At four time points throughout a year, we determined the abundance and diversity of prokaryotic and viral communities at three sites within the first-magnitude Manatee Springs system (the spring head where water emerges from the aquifer, a mixed region where the spring run ends, and a downstream site in the Suwannee River). The abundance of prokaryotes and virus-like particles increased 100-fold from the spring head to the river and few members from the head communities persisted in the river at low abundance, suggesting the springs play a minor role in seeding downstream communities. Prokaryotic and viral communities within Manatee Springs clustered by site, with seasonal variability likely driven by flow. As water flowed through the system, microbial community composition was affected by changes in physiochemical parameters and community coalescence. Evidence of species sorting and mass effects could be seen in the assemblages. Greater temporal fluctuations were observed in prokaryotic and viral community composition with increasing distance from the spring outflow, reflecting the relative stability of the groundwater environment, and comparisons to springs from prior work reaffirmed that distinct first-magnitude springs support unique communities.IMPORTANCE Prokaryotic and viral communities are central to food webs and biogeochemical processes in aquatic environments, where they help maintain ecosystem health. The Floridan aquifer system (FAS), which is the primary drinking water source for millions of people in the southeastern United States, contributes large amounts of freshwater to major river systems in Florida through its springs. However, there is a paucity of information regarding the spatiotemporal dynamics of microbial communities in these essential flowing freshwater systems. This work explored the prokaryotic and viral communities in a first-magnitude spring system fed by the FAS that discharges millions of liters of water per day into the Suwannee River. This study examined microbial community composition through space and time as well as the environmental parameters and metacommunity assembly mechanisms that shape these communities, providing a foundational understanding for monitoring future changes.

Systematic Renovation Design of Surface Water Source Heat Pump for a Hot Spring Center Based on Thermodynamic Analysis

Currently, the application and renovation of surface water heat source pump (WHSP) mainly attempt to optimize heat exchangers, water pumps, the overall system, and economic frictional head loss. The mathematical model is often established and solved with such optimization objectives as optimization parameters, control forms, costs, and feasibility of investment and construction. There are relatively few studies that optimize the operating conditions with the minimal total energy consumption of system operations, and, on this basis, pursue global optimization design of the WSHP system. Therefore, this paper aims to carry out a systematic renovation design of the surface WSHP in a hot spring center in the national forest park of northern Guilin, southwestern China’s Guangxi Zhuang Autonomous Region. The project mainly covers the design of hot spring system, air-conditioning system, and hot water system, as well as the exergy analysis of WSHP system. Among them, the design of hot spring system includes the regulation of raw water, cold water, and warmed water; the constant temperature control of hot spring pools; the waste heat utilization of warmed water from the pools. The scientific nature of the design was proved through experiments.

The TLP 2-DOF as an alternative model for extreme wave application

Tension Leg Platform (TLP) is an offshore platform structure used for deep-sea oil and gas exploration. The main structure of the TLP consists of a deck, pontoon, mooring system, and foundation. TLP operates in a balance of buoyancy, structural weight, and mooring tension. The problem is the construction of TLP in the deep sea, where sometimes extreme waves appear could damage the TLP structure. This paper proposes a new model of TLP that is more stable to extreme waves. The method is to separate the mass of the deck and the mass of the pontoon into two flexible parts, which are connected by a cantilever spring system. Thus the TLP motion becomes two degrees of freedom (TLP 2-DOF). Using the dynamic vibration absorber (DVA) method, the ratio of the deck mass, pontoon mass, and spring stiffness are adjusted so that the primary mass movement is minimal. Furthermore, the ratio of the amplitude of the deck movement as the primary mass to the wave amplitude is analyzed, which is known as the operator response amplitude (RAO). The results showed that the TLP 2-DOF model was more stable. As an illustration, at resonance conditions, this model can reduce RAO to about 67%.

Design and Preliminary Testing of a Magnetic Spring as an Energy-Storing System for Reduced Power Consumption of a Humanoid Arm

The increasing use of robots in the industry, the growing energy prices, and higher environmental awareness have driven research to find new solutions for reducing energy consumption. In additional, in most robotic tasks, energy is used to overcome the forces of gravity, but in a few industrial applications, the force of gravity is used as a source of energy. For this reason, the use of magnetic springs with actuators may reduce the energy consumption of robots performing trajectories due their high-hardness magnetic properties of energy storage. Accordingly, this paper proposes a magnetic spring configuration as an energy-storing system for a two DoF humanoid arm. Thus, an integration of the magnetic spring system in the robot is described. A control strategy is proposed to enable autonomous use. In this paper, the proposed device is modeled and analyzed with simulations as: mechanical energy consumption and kinetic energy rotational and multibody dynamics. Furthermore, a prototype was manufactured and validated experimentally. A preliminary test to check the interaction between the magnetic spring system with the mechanism and the trajectory performance was carried out. Finally, an energy consumption comparison with and without the magnetic spring is also presented.

Study on dynamic characteristics of leaf spring system in vibration screen

By studying dynamic characteristics of the leaf spring system, a new elastic component is designed to reduce the working load and to a certain extent to ensure the linearity as well as increase the amplitude in the vertical and horizontal directions in vibration screen. The modal parameters, amplitudes, and amplification factors of the leaf spring system are studied by simulation and experiment. The modal results show that the leaf spring system vibrates in horizontal and vertical directions in first and second mode shapes, respectively. It is conducive to loosening and moving the particles on the vibration screen. In addition, it is found that the maximum amplitude and amplification factor in the horizontal direction appear at 300 r/min (5 Hz) while those in the vertical direction appear at 480 r/min (8 Hz), which are higher than those in the disc spring system. Moreover, the amplitude of the leaf spring system increases proportionally with the increase of exciting force while the amplification factors are basically the same under different exciting forces, indicating the good linearity of the leaf spring system. Furthermore, the minimum exciting force occurs in the leaf spring system under the same amplitude by comparing the exciting force among different elastic components. The above works can provide guidance for the industrial production in vibration screen.

Towing-tank measurement of unsteady wave elevation around two ships in head sea condition and comparison with computational results

Many studies on ship wave elevation measurement have been performed focusing on steady waves in calm water and unsteady wave-cut analysis near ships, and a reliable experimental database of unsteady wave elevation with incident waves is not enough for the validation of numerical computations. In this study, a non-contact scheme for capturing the instantaneous free surface near two ships is adopted to avoid any disturbance caused by measuring equipment. The applicability of the newly established unsteady measurement technique is examined during a standard seakeeping test with various wave amplitudes. Heave and pitch motions are set free, while the soft spring system is used for surge motion. The instantaneous free surface elevation is obtained on equally spaced positions. The mean value and higher harmonic components of measured wave elevation clearly show nonlinear characteristics for various incident wave amplitudes. Snapshots at several time instants and the magnitude of the first harmonic components of unsteady wave elevation are compared with those of numerical computations based on a Rankine panel method. The overall trend shows fair correspondence, whereas the detailed local flows are somewhat different because of the nonlinearity of waves.

Characterisation of an artesian groundwater system in the Valle de Iglesia in the Central Andes of Argentina

Despite its location in the “Arid Diagonal” of South America, the Valle de Iglesia contains a number of artesian springs, the most important of which are the Baños Pismanta thermal springs, which release water at ~ 45 °C. Despite the scarcity of water resources in the Valle de Iglesia, there have been few attempts to study these springs in any detail. In this study, > 50 springs are described, each characterised by small volcano-like mud structures up to 15 m tall. Hydrogeological and hydrochemical analyses of the groundwater system in the Valle de Iglesia were performed to improve our understanding of the subsurface water flow and of the connections between the subsurface water and the associated systems of faults and springs. Site measurements were made, and the concentrations of the main ions and trace elements were also determined by laboratory analysis of water samples. The samples obtained from the spring were rich in Na–HCO3–SO4 and Na–SO4–HCO3, but the surface water samples from the Agua Negra River were rich in Ca–SO4–HCO3. The temperature of the springs was in the range 20–45 °C. Both the temperatures and the ionic ratios are compatible with the presence of a deep hydraulic circulation system. The oxidation of sulphide minerals nearby the magmatic rocks and volcanic edifices causes the mobilisation of arsenic, which accumulates in the groundwater due to the low annual rainfall. The concentrations of arsenic in the spring water samples were therefore higher than the current limit set by the World Health Organisation, meaning that the water is not suitable for human consumption.

Evaluation of steel building structures with inerter-based dampers under seismic loading

One way of reducing damage to buildings from earthquakes is through the introduction of passive control devices. Many common passive control devices require relatively large masses to be effective, which increases cost and complicates design efforts. Inerter-based dampers are a promising alternative. Inerter-based dampers utilize inerters, mechanical devices that typically use a flywheel with a relatively small mass to provide large effective inertial mass. The evaluation of inerter-based dampers has typically been performed considering simple linear systems of masses and springs that are subjected to harmonic or random loads. While valuable information can be gained from these models, it is unclear if inerter-based dampers are effective at improving the performance of structures subjected to seismic ground motions, especially if the mechanics of the structure is modeled more explicitly and nonlinear behavior, such as yielding, is considered. This paper presents a numerical investigation on the behavior of structures with three different inerter-based dampers subject to seismic ground motions, including the effects of material and geometric nonlinearity. Designs for the three different inerter-based dampers were produced for 3-story and 9-story benchmark steel structures using existing design equations. The structures and devices were modeled in the OpenSees framework. The inerter-based dampers were found to remain effective outside of the elastic range, but at reduced efficiency. The inerter-based dampers were typically much more effective in the 3-story structure. These results show the potential for inerter-based dampers to reduce damage to structures subjected to earthquakes and will encourage the further study of these innovative devices.