Spring System Research Articles

Theoretical evaluation of stack-based thermoacoustic refrigerators

Standing wave thermoacoustic refrigerator uses stack, is the heart of the thermoacoustic cooling system. The porous stack in the resonator tube develops temperature difference across the stack for heat pumping upon loudspeaker sound interaction of oscillating gas. In this paper, the optimization of stack-heat exchangers system and resonator is discussed using linear thermoacoustic theory for better COP and cooling power of refrigerator. The loudspeaker is assumed to provide the required acoustic power with the back volume gas spring system. Helium and air are chosen because of their better thermophysical properties and cost, compared to other competent gases. The 200 mm diameter stack is optimized for the temperature difference of 28 K. The theoretical results of the optimized refrigerator models are compared with the DeltaEC simulation results for deriving conclusions. DeltaEC predicts the cooling power and COP of 349 W at 0.998 for helium, and 139 W at 1.133 for air, respectively.

A multiparametric approach for rejuvenation of the Gaurikund geothermal spring system in the Northwest Himalayan region

The Gaurikund town falls on the way of the famous trekking route to Kedarnath that faced the wrath of the 2013 flood disaster. This fateful event severed more than 5000 casualties, demolished several infrastructures, and shifted the course of Gaurikund spring from its original position. Nevertheless, the Gaurikund geothermal spring system located in the Himalayan Geothermal Belt of the Garhwal region is preeminent for religious beliefs, balneotherapeutic values and a gateway to delve within the geothermal and hydrological characteristics of the area. In this perspective, restoration of Gaurikund geothermal spring system becomes a necessity. A multiparametric approach comprising geospatial, geology, hydrochemistry and geophysics has been used to study and justify these aspects at Gaurikund. The geological studies infer that the geothermal spring gets recharged by the steep, southerly dipping joints in granite gneiss. Subsequently, the deep percolated water heats up due to the high geothermal gradient and then emerge along the Vaikrita Thrust and its sympathetic minor fault-thrust system by advection. Moreover, four spring outlets are inventoried, with discharge varying from 7.46 to 95.54 L/min. The normal emissivity model uses the pre and post-disaster satellite data and generates maximum kinetic temperature images, showing a positive correlation between land surface temperature and spring discharge. Two-dimensional Electrical Resistivity Tomography (Schlumberger, Wenner and Gradient configurations) survey revealed two low resistivity zones proximal to the geothermal spring on the right bank of the Mandakini river. The engineering interventions carried out by bank protection and construction of small gully plugs in the catchment area is recommended along Gaurikund-Sonprayag section on the right bank of Mandakini river.

Energy Efficient Photovoltaic-Electric Spring for Real and Reactive Power Control in Demand-Side Management

Photovoltaic-electric spring (PV-ES) is a promising topology to utilize widespread residential roof-top photovoltaic systems in demand-side management. Power control for an integrated configuration of photovoltaic-electric spring system to achieve dynamic supply-demand balance in power distribution networks is presented. Extraction of maximum power from PV panel using Perturb and Observe algorithm along with boost converter are designed. This power is given as input to the DC link of the Electric Spring. The modeling and design of the integrated system are detailed. Extensive simulations are carried out in MATLAB/Simulink to observe the performance of the PV-ES system. The effectiveness of the proposed topology was verified for changes in line voltage, PV irradiation, and reference power. It was confirmed that the proposed PV-ES precisely controls the active power consumption of the critical load, rigidly regulates the voltage at the point of common coupling (PCC), and follows the variations in reference power available for the smart load. Finally, the expansive performance of ES fed with a PV source was confirmed to be superior over an ES system fed with a DC source.

Optimal control and performance evaluation of an inerter-based point absorber wave energy converter

This paper deals with optimal tuning, control and performance evaluation of an inerter-based point absorber (IPA) wave energy converter (WEC), which is a first step towards establishing an integrated offshore wind-wave energy system. An inerter–spring system is introduced into a conventional WEC, which can improve the system performance when properly tuned and controlled. Analytical expressions of the optimal IPA parameters have been derived under regular waves. Closed-form solution of the capture width ratio of the IPA under optimal control is obtained and verified by the theoretically optimal solution of a point absorber. Next, hybrid and passive control strategies for the IPA are also investigated, demonstrating superior energy absorption performance than the conventional point absorber under the same control strategy, due to the existence of an extra resonance and amplified motion of the inerter. Furthermore, the performance of passive IPA is evaluated under irregular waves, where parametric optimization has been performed with constraints on system modal frequencies. Single-mode and double-mode resonances have been observed for wave peak frequencies away from and close to the float natural frequency, respectively. This facilitates the frequency adaption of the IPA and the resulting superior performance in terms of more energy absorption and broader operational bandwidth.

Experimental investigation of a new self-centering shear wall with resilient hinge devices

In order to reduce the residual displacement of building structures caused by the damage on the reinforced concrete shear wall, this study develops a novel self-centering shear wall with resilient hinge devices. One device and three wall specimens are designed, and their hysteretic performance is investigated under low cyclic loading tests. The resilient hinge device which uses disc springs as the spring system is essentially a self-centering axial loaded device with an asymmetric flag-shaped hysteretic response. The experimental results demonstrate that the novel wall exhibits symmetrical flag-shaped hysteretic behavior and has a high self-centering performance. Its residual inter-story drift ratio is only 0.58% at a loading inter-story drift ratio reaching 3%. Compared with the conventional wall, the proposed self-centering shear wall has less wallboard damage, 10% degradation in peak bearing capacity, at least 50% improvement in deformation capacity, 26% degradation in equivalent viscous damping ratio, and 70% increase in total energy dissipation.

Comparative study of the variability and trends of phytoplankton biomass between spring and winter upwelling systems in the South China Sea

High phytoplankton biomass usually appears off the coastal waters southeast of Vietnam (SV) during summer and southwest of the Luzon Strait (SLS) in winter. Although this seasonal upwelling has been recognized in SV and SLS for more than half a century, there has been limited documentation comparing the characteristics and formation mechanisms of these two upwelling systems. To understand the dynamic features of phytoplankton growth in SV and SLS, seasonal and interannual variabilities of Chlorophyll-a (Chl-a) concentration were studied based on decadal-scale satellite-derived datasets (2003–2018). Bivariate wavelet coherence (BWC) and multiple wavelet coherence (MWC) were performed to evaluate the temporal variability of multiple controlling factors. The results demonstrated that there were different patterns of seasonal cycles and interannual variability of Chl-a concentrations in the two upwelling regions. In SV, high Chl-a concentrations during summer were primarily formed by the interactions of multiple factors, causing the mixed layer depth to increase during summer and sufficient nutrient concentrations on the surface (supplied by the mixed water column). In contrast, the high Chl-a concentrations in SLS are caused by a combination of deep mixing (induced by wind and buoyancy forcing) and enhanced upward advection (induced by strong eddy activities). These factors support intense levels of phytoplankton biomass during winter. The sea surface temperature (SST) was the best single factor to explain the Chl-a variance in both regions. The addition of more factors to the MWC analysis changed the main factors influencing the Chl-a variations. The two-factor combination of SST-Niño 3.4 in SV and the SST-mixed layer depth (MLD) in SLS controlled the Chl-a variations on an interannual scale. Moreover, the three-factor combination of SST-Niño 3.4-MLD was still meaningful for explaining the Chl-a variations. This indicated that the influencing the Chl-a variations differed in these two upwelling systems.

Optimization of Various Percentage of Fibers in Fiber Reinforced Composite Material Leaf Springs in Vehicles

A spring steel leaf spring is commonly used for suspension system in all types of loading vehicles due to its good stiffness and fatigue strength. Today, spring steel leaf springs are used in majority of applications but they are heavy in weight, poor in terms of gets corrosion resistance and average in ride comfort. Fiber reinforced composite material leaf spring represents a key application of composite materials in the field of automotive vehicles due to improved ride comfort and light in weight. Stiffness, fatigue life and damping capacity are the critical parameter of fiber reinforced composite leaf springs. CAE software and experimental analysis have been mainly used for design and analysis for composite material leaf springs. Saman Jolaiy et.al. [2021] focused on the damping characteristics of the composite leaf springs and worked out that fabrication of composite leaf spring with viscoelastic core(2mm) decreases the damping ratio of the leaf spring system, which results in a smooth ride. Few studies evaluated the stress distribution, deflection and fatigue life assessment of composite leaf springs reinforced with glass fibers or carbon fibers or combination of carbon lass and carbon fibers. The main objective of the present work is to optimize various percentage of fiber reinforced composite material leaf springs along with insertion of viscous core. The optimized results thus obtained show that the fiber reinforced composite leaf springs with viscous core can be a good replacement of spring steel leaf springs with overall weight reduction and better damping characteristics. Replacing spring steel leaf springs with fiber reinforced composite leaf springs will improve safety, comfort, high elastic strain energy storage capacity and durability.

Numerical analysis of tunnel segments strengthened by steel–concrete composites

In order to study the feasibility of strengthening of segmental tunnel linings by using steel–concrete composites (SCC), a three-dimensional (3D) finite element (FE) model is proposed in this paper. The nonlinear mechanical behavior of concrete is described by a plastic-damage model. The nonlinearity, resulting from the interface of the SCC and reinforced concrete (RC) segments, is simulated with the help of a system of springs. The analysis results are compared with those obtained from a full-scale test of a tunnel segment. Their agreement validates the usefulness of the 3D FE model. Numerical re-analysis of the test shows that the interfacial connectors govern both the strengthening effect of SCC and the failure pattern of the strengthened segments. Thus, the force-transmitting capacity of the interfacial connectors should be concerned in design activities. As regards the circular segments, the interfacial connectors refer to both the shearing and the stripping connectors. The composite effect of the SCC and RC segments increases with the increasing number of these connectors. The latter, therefore, results in the increases of the bearing capacities and stiffnesses of the strengthened segments. Those increases become insignificant as the number of these connectors is sufficient to ensure a perfect composite effect of the SCC and RC segments. In addition, the numerical simulations show that using high-performance steel shell (HPS) or/and ultra-high-performance concrete (UHPC) is an effective way to increase the strengthening effect of SCCs.

Successful establishment of endangered springsnails following habitat enhancement and translocations

Abstract Spring‐associated aquatic invertebrates tend to be narrow‐range endemics. Globally, they are threatened with extinction as a result of habitat loss caused by declining aquifers and by climate change. Extinction risks to narrow‐range endemics may be reduced by having multiple, separate populations, yet there have been few attempts to use conservation translocations to create new populations. Pyrgulopsis roswellensis (Roswell springsnail), Juturnia kosteri (Koster's springsnail) and Gammarus desperatus (Noel's amphipod) are range‐restricted, spring‐associated endangered species. Each species has lost one or more populations owing to habitat loss, and their distributions are now largely restricted to Bitter Lake National Wildlife Refuge, New Mexico. In 2014, Bitter Lake National Wildlife Refuge enhanced a series of springs by re‐routing a channelized section of river away from them. The goal was to create habitat suitable for establishing new populations of P. roswellensis and J. kosteri, and for expansion of G. desperatus. After assessing risks and benefits of translocations, approximately 6,177 P. roswellensis and 8,707 J. kosteri were introduced into the project area from 2015 to 2018. Efficacy was evaluated by comparing the abundance of invertebrates in the translocation site through time, and by comparing springsnail abundance with three reference spring systems. From 2014 to 2021, invertebrates were monitored twice annually in the translocation area. In reference spring systems, P. roswellensis and J. kosteri were monitored twice annually in 2020 and 2021. Counts of springsnails in the translocation area were comparable to one or more reference areas, which suggests that translocations were successful. In addition, the proportion of P. roswellensis, the less common springsnail, to J. kosteri was similar to references areas. G. desperatus did not increase, which may be because some measures of water quality have not stabilized. Globally, climate change and aquifer declines necessitate immediate consideration be given to conservation translocations as a means of keeping spring‐associated species from becoming extinct.

Analysis of Compliance and Kinetostatic of a Novel Class of n-4R Compliant Parallel Micro Pointing Mechanism.

A novel class of n-4R compliant parallel pointing mechanisms is proposed, and the compliance and kinetostatic model of the mechanism are established and analyzed successively. Firstly, the compliance model of a class of n-4R compliant parallel pointing mechanism is established based on the coordinate transformation. The model is verified by finite element analysis, and the influence of geometric parameter variations on the compliance performance of the mechanism is analyzed. Secondly, the mechanism is simplified to an equivalent spring system, and the governing equation of the equivalent spring system is constructed by utilizing the established compliance model. According to the governing equation, the mapping relationship between the input force and the output displacement of the mechanism is subsequently obtained, that is, the kinetostatic model. Then, the accuracy of the kinetostatic model is verified by two simulation examples: The spiral trajectory of the mobile platform center and the spatial pointing trajectory of the mechanism. The results of the two examples show that the deviations between the analytical results and the FE-results are within 0.038% and 0.857%, with the excellent consistency indicating the accuracy of the kinetostatic model. Finally, the influence of the geometric parameter values on the mapping matrix in the kinetostatic model is studied.

Ventricular Repolarization and Calcium Transient Show Resonant Behavior under Oscillatory Pacing Rate.

Cardiac EC coupling is triggered by rhythmic depolarizing current fronts originating from the sino-atrial node, and the way variability in rhythm is associated with variability in action potential duration (APD) and, in turn, in the variability of calcium transient amplitude (CTA) and contraction is a key determinant of beating stability. Sinusoidal-varying pacing rate is adopted here in order to establish whether APD and CTA oscillations, elicited in a human ventricular AP model (OR) under oscillatory pacing, are consistent with the dynamics of two coupled harmonic oscillators, e.g., a two-degree-of-freedom system of mass and springs (MS model). I show evidence that this is the case, and that the MS model, preliminarily fitted to OR behavior, retains key features of the physiological system, such as the dependence of APD and CTA oscillation amplitudes from average value and from beat-to-beat changes in pacing rate, and the phase relationship between them. The bi-directionality of coupling between APD and CTA makes it difficult to discriminate which one leads EC coupling dynamics under variable pacing. The MS model suggests that the calcium cycling, with its greater inertia chiefly determined by the SR calcium release, is the leading mechanism. I propose the present approach to also be relevant at the whole organ level, where the need of compact representations of electromechanical interaction, particularly in clinical practice, remains urgent.

How to Exploit the Glass Mass for Damping a Building?

The worlds spectacular skylines host tall and slender buildings to create a maximum of office, residential and commercial space on a minimized footprint. These structures need to cope with increasing wind forces at height and are additionally affected by wind-induced vibration due to their lower natural frequencies. The resulting vibrations make users uncomfortable. Therefore, heavy tuned mass dampers are installed in structures and occupy valuable space especially in the costliest top-floors. As an example, Taipei 101’s steel damper is located between the 87th and 91st floor and weights astonishing 660 metric tons. This raises the need for additional reinforcement which increases cost and carbon footprint.Most buildings in expensive metropolises are cladded with remarkable glass facades. Therefore, we asked the question if it was possible to use the existing mass – more specifically the glass mass in a Double‑Skin Facade – to dampen the building’s movement, create a comfortable space for the user, exploit more floor area for the investor and finally to minimize the amount of building material to reduce carbon footprint for society. The idea was realized in a collaborative research effort of TU Berlin, BTU Cottbus-Senftenberg and Josef Gartner GmbH that resulted in a full-scale mock-up of a Double‑Skin Facade. Its outer skin can move laterally on a guide rail system. As the building starts to move, the facade's inner skin remains fixed to the base structure while the outer skin follows the building’s movement in a delayed manner due to its mass inertia. The fixed inner skin and the moveable outer skin are connected by a spring system that is tuned to the first natural frequency of the base structure. During the motion of the facade’s outer skin, the spring system redirects the relative movement and generates a stabilizing force for the base structure in the opposite direction. Additionally, an electrical machine is placed in between to provide an adjustable damping effect for semi-active and passive control. It also serves the purpose of a generator to study the opportunity to harvest energy. The paper shows the structural design options for the novel facade concept in the context of a project review of Double-Skin and Closed-Cavity Facades. The function of a full-scale mock-up, its fabrication and installation are described to show feasibility and ongoing challenges. First test results reveal a close match between theoretical assumptions and the applied testing. This engineering-driven and experimentally validated design opens a new field of architectural options in sustainable facade design which is focused on tuning physical parameters that affect the damping properties of the global structure.

Analysis of the Vibration Characteristics of a Leaf Spring System Using Artificial Neural Networks.

The real-time vibrations occurring in a leaf spring system may cause undesirable effects, such as stresses, strains, deflections, and surface deformations over the system. In order to detect the most appropriate working conditions in which the leaf spring system will work more stably and also to design optimized leaf spring systems, these external effects have to be detected with high accuracy. In this work, artificial neural network-based estimators have been proposed to analyze the vibration effects on leaf spring systems. In the experimental studies carried out, the vibration effects of low, medium, and high-pressure values applied by a hydraulic piston on a steel leaf spring system have been analyzed by a 3-axial accelerometer. After the experimental studies, the Radial Basis Artificial Neural Network (RBANN) and Cascade-Forward Back-Propagation Artificial Neural Network (CFBANN) based nonlinear artificial neural network structures have been proposed to analyze the vibration data measured from the leaf spring system under relevant working conditions. The simulation results represent that the RBANN structure can estimate the real-time vibrations occurring on the leaf spring system with higher accuracy and reaches lower RMS error values when compared to the CFBANN structure. In general, it can be concluded that the RBANN and CFBANN network structures can successfully be used in the estimation of real-time vibration data.

Coulomb friction effect on the forced vibration of damped mass–spring systems

This paper aims at assessing the effect of dry friction on the dynamic behaviour of a damped mechanical system subject to harmonic forcing. Previous work on friction damped systems highlighted that not including other forms of damping in the dynamic analysis can lead to unrealistic results such as the presence of infinite resonances. In this contribution, an exact solution is derived for the continuous steady-state response of multi-degree-of-freedom systems with a contact between one of the masses and an external wall, using Coulomb’s law to model the friction force and a modal damping model to account for the system’s damping. Closed-form expressions are also derived for the amplitude and phase of the continuous responses, while stick–slip responses are investigated by using an ad-hoc numerical approach. In addition, analytical and numerical results are used for exploring the features and the motion regimes of the dynamic response, leading to the following conclusions: (i) system’s damping has a limited effect on low- and high-frequency behaviours, on the presence of invariant points and inversions across the transmissibility curves and can therefore be neglected, in non-resonant conditions, in the analysis of structures where dry friction is the main source of dissipation; (ii) when the damping of the system is accounted for in the mechanical models along with Coulomb damping, finite resonant peaks are also obtained in continuous sliding regime and their amplitude decreases linearly with the friction force generated in the contact.

Nonlinear Normal Modes of a Three Degrees-of-Freedom Cyclically Symmetric Piecewise Linear System

AbstractThis article investigates the nonlinear normal modes (NNMs) of a three degrees-of-freedom cyclically symmetric system with bilinear contact springs. Further, two different cases of zero and nonzero clearance are assumed for the contact model. These systems are found to exhibit qualitatively different characteristics. Interestingly, the former system admits positive-scaling of solutions, which is reminiscent of linear systems. Four classes of NNMs are found for both zero and nonzero clearance. The NNM solutions are calculated using analytical or numerical techniques. The analytical solution involves solving the equations of motion using appropriate ansatzes, while the numerical solution uses a shooting-based continuation scheme. The NNMs' features and their variations with contact spring stiffness and system energy are also studied. This study highlights certain simplifications applicable to cyclically symmetric structures with contact. These simplifications will be of practical interest for designing real-life structures.

Optimal Design of Leaf Springs Using Composite Materials

Abstract: The present work is to emphasizing the reduction in weight of suspension system by using composite materials instead of customary leaf springs. Also improve the level of suspension by using of composite materials. The leaf spring is one of the potential items for weight reduction in automobiles as it accounts for 10% - 20% of the unsprang weight. The process is beginning with the selection of composite materials. The selection process is focused to the checking of property of the material be chosen. After the verification, the manufacturing is done by the proper methods. Then the design calculation is done for both ordinary and novel spring system. Based on the results, the design calculation for deflection and weight of springs is compared. Keywords: Suspension Systems, Leaf Spring, Unsprung weight, Composite, Weight Reduction.

Holy springs and wells of the leningrad region

According to the results of the analysis of search queries an interest in information about holy springs has been revealed. An overview of 45 springs of the Leningrad region, attributed to the saints, is presented. Their map has been compiled (M: 1:200000). With the period of the population's self-isolation regime, Internet search queries for natural holy springs are also increasing. Statistical analysis of posts of thematic communities of the VKontakte social network by the tool "Khitalama" testifies to the social demand for information about holy springs references. These data serve as a promising source of information about behavioral geography. It is proposed to improve the network of specially guarding natural territories by including holy springs in it as objects of health, ecological, educational and pilgrimage tourism. On the example of the Leningrad Region, the foundations for the creation of a unified geoinformation system of holy springs are laid.

Mitigation of rotor thrust fluctuations through passive pitch

A rotor blade operating in an unsteady or a sheared stream experiences force fluctuations, which increase the structural requirements for both the blades and the rotor system as a whole. In this paper, we investigate whether force fluctuations can be passively mitigated without compromising the mean load. We consider a tidal turbine rotor in a shear current at a diameter-based Reynolds number of 2×107. The blades are rigid and can passively pitch. A mass–spring system acts on the spanwise axis of the blade governing the pitch kinematics. The effectiveness of this system is demonstrated with three methodologies: an analytical model based on blade element momentum theory and Theodorsen’s theory, and two sets of Reynolds-averaged Navier–Stokes simulations performed with two independent codes. The analytical and the numerical models are validated against experiments and simulations in the literature. All methodologies predict a reduction of more than 80% of the thrust fluctuations. Furthermore, because of the more uniform thrust force exerted on the current, the wake behind a passive pitch blade does not diffuse the onset shear flow. This results in a more sheared wake and faster wake recovery. The present results demonstrate the potential benefits of passive pitch and may underpin future applications of this concept for different types of turbines and compressors, including wind turbines, propellers, helicopter rotors, etc.

A multi-roller static model of the planetary roller screw mechanism considering load sharing

A multi-roller static model is proposed to calculate load sharing and load distribution in a planetary roller screw mechanism (PRSM) with axial loads and errors. Taking into the actual positions of rollers, the PRSM is discretized into a multi-roller spring system. The proposed model is validated by comparing the results from a finite element model. The load sharing, load distribution and elastic deformation behaviors of a PRSM under different part position errors and thread index errors are analyzed. The results show that load sharing is sensitive to the position errors of the screw and nut while being fairly insensitive to those of rollers. Part position errors and thread index errors have a great influence on the stiffness of the PRSM.

Finite-Time Stability of Polyhedral Sweeping Processes with Application to Elastoplastic Systems

We use the ideas of Adly-Attoych-Cabot [Adv. Mech. Math., 12, Springer, 2006] on finite-time stabilization of dry friction oscillators to establish a theorem on finite-time stabilization of differential inclusions with a moving polyhedral constraint (known as polyhedral sweeping processes) of the form $C+c(t).$ We then employ the ideas of Moreau [New variational techniques in mathematical physics, CIME, 1973] to apply our theorem to a system of elastoplastic springs with a displacement-controlled loading. We show that verifying the condition of the theorem ultimately leads to the following two problems: (i) identifying the active vertex ``A'' or the active face ``A'' of the polyhedron that the vector $c'(t)$ points at; (ii) computing the distance from $c'(t)$ to the normal cone to the polyhedron at ``A''. We provide a computational guide to implement steps (i)-(ii) in the case of an arbitrary elastoplastic system and apply the guide to a particular example. Due to the simplicity of the particular example, we can solve (i)-(ii) by the methods of linear algebra and minor combinatorics.