Spring Relaxation Research Articles

The impact of pre-compression and temperature on perfluoroalkoxy alkane springs: Insights into spring relaxation.

A predictive model was proposed for determining the high-temperature free height of perfluoroalkoxy alkane springs in air-operated double-bellow pumps with the aim of investigating their relaxation. The model incorporates classical spring deformation theory and considers the material, structure, and real-world operating conditions of the perfluoroalkoxy alkane springs. Experimental validation of the model is also conducted. This study examines the effects of varying temperatures and pre-compression values on the relaxation of perfluoroalkoxy alkane springs' free height. It collects relaxation curves under different temperatures and various pre-compression conditions. The results indicate that spring relaxation increases with higher temperatures when there is no pre-compression. Furthermore, increasing pre-compression at the same temperatures leads to greater spring relaxation. Pre-compression has a more significant impact on spring relaxation. By comparing the experimental data with the simulated curve generated by the model, it is evident that the predicted spring free height relaxation closely aligns with the actual measurements. This verification demonstrates the effectiveness and accuracy of the proposed model in evaluating the relaxation of perfluoroalkoxy alkane springs' free height. Moreover, the model provides a valuable tool for predicting the lifespan of similar perfluoroalkoxy alkane springs in engineering applications.

Experiments on the localized interaction at the interface fuel rod/spacer grid in pressurized water reactors

The release of fissile material into the coolant caused by fretting of the fuel rods at the interface with spacer grids is a significant safety issue and cause of financial losses in the operation of Pressurized Water Reactors (PWRs). Each fuel rod is kept in position inside spacer grids through friction from the preload exerted by retaining elements (springs and dimples). Fretting of the fuel rods occurs at the contact with the springs and dimples. In severe fretting cases the integrity of the fuel rod cladding is compromised and fission byproducts enter the primary coolant circuit. The reciprocating motion at the contact interface of the fuel rods and spacer grids resulting in material fretting is due to the Flow-Induced Vibrations (FIV) of fuel rods, caused by the unstable surrounding coolant flow, which in PWRs is predominantly parallel to the length of fuel rods (axial flow). Under specific flow conditions, fretting develops rapidly. The vibrations of fuel rods, as well as the relationship of fretting wear mechanisms with several factors associated with the fission process and coolant flow dynamics and stability (vibration amplitude, preload, oscillating loads, irradiation, axial slip, spring relaxation, temperature, oxidation, material of spacer grids and fuel rods), have been considered in the literature. However, direct experimental measurements of the contact force and axial slip during FIV have not been treated in the literature, likely because of the absence of suitable measurement methods. This gap in experimental measurement techniques is addressed in this work, specifically for the analysis of PWR fuel assemblies, by installing a piezoelectric stack and aiming laser Doppler vibrometers on a one-meter-long fuel rod, supported by two full-scale spacer grids, in-air or immersed in quiescent water. In the presence of small- and large- amplitude forced vibrations, the signal of the piezoelectric force transducer increases with the amplitude of vibration, but it is also affected by vibrations perpendicular to the excitation, which appear for large-amplitude excitations. The axial motion of the fuel rod at the spacer grid has a complex evolution and is significant for large-amplitude vibrations only. At any rate, the time histories of contact force and axial motion display the effects of impacts and slips, particularly during the tests in water. The measurement system shows that the severity of the interaction at the spacer grid interfaces is influenced strongly by the amplitude of the forced fuel rod vibrations. Since fuel rods and fuel assemblies are prone to several nonlinear phenomena, as demonstrated by recent studies, it follows that the usage of nonlinear models will be essential to numerically estimating the severity of fretting.

EQUALITY: Quality-aware intensive analytics on the edge

Our work is motivated by the fact that there is an increasing need to perform complex analytics jobs over streaming data as close to the edge devices as possible and, in parallel, it is important that data quality is considered as an optimization objective along with performance metrics. In this work, we develop a solution that trades latency for an increased fraction of incoming data, for which data quality-related measurements and operations are performed, in jobs running over geo-distributed heterogeneous and constrained resources. Our solution is hybrid: on the one hand, we perform search heuristics over locally optimal partial solutions to yield an enhanced global solution regarding task allocations; on the other hand, we employ a spring relaxation algorithm to avoid unnecessarily increased degree of partitioned parallelism. Through thorough experiments, we show that we can improve upon state-of-the-art solutions in terms of our objective function that combines latency and extent of quality checks by up to 2.56X. Moreover, we implement our solution within Apache Storm, and we perform experiments in an emulated setting. The results show that we can reduce the latency in 86.9% of the cases examined, while latency is up to 8 times lower compared to the built-in Storm scheduler, with the average latency reduction being 52.5%.

Perspectives for the reconstruction of 3D chromatin conformation using single cell Hi-C data.

Construction of chromosomes 3D models based on single cell Hi-C data constitute an important challenge. We present a reconstruction approach, DPDchrom, that incorporates basic knowledge whether the reconstructed conformation should be coil-like or globular and spring relaxation at contact sites. In contrast to previously published protocols, DPDchrom can naturally form globular conformation due to the presence of explicit solvent. Benchmarking of this and several other methods on artificial polymer models reveals similar reconstruction accuracy at high contact density and DPDchrom advantage at low contact density. To compare 3D structures insensitively to spatial orientation and scale, we propose the Modified Jaccard Index. We analyzed two sources of the contact dropout: contact radius change and random contact sampling. We found that the reconstruction accuracy exponentially depends on the number of contacts per genomic bin allowing to estimate the reconstruction accuracy in advance. We applied DPDchrom to model chromosome configurations based on single-cell Hi-C data of mouse oocytes and found that these configurations differ significantly from a random one, that is consistent with other studies.

Irreversibility and entropy production of a thermally driven micromachine

We discuss the non-equilibrium properties of a thermally driven micromachine consisting of three spheres which are in equilibrium with independent heat baths characterized by different temperatures. Within the framework of a linear stochastic Langevin description, we calculate the time-dependent average irreversibility that takes a maximum value for a finite time. This time scale is roughly set by the spring relaxation time. The steady-state average entropy production rate is obtained in terms of the temperatures and the friction coefficients of the spheres. The average entropy production rate depends on thermal and/or mechanical asymmetry of a three-sphere micromachine. We also obtain the center of mass diffusion coefficient of a thermally driven three-sphere micromachine as a function of different temperatures and friction coefficients. With the results of the total entropy production rate and the diffusion coefficient, we finally discuss the efficiency of a thermally driven micromachine.

Indoor Visible Light Positioning Using Spring-Relaxation Technique in Real-World Setting

GPS has limitations in indoor applications. Consequently, other indoor localization techniques and systems are active areas of research. Visible Light Positioning (VLP) is a promising option, especially given the growing popularity of LED-based lighting and the expected adoption of the forthcoming Visible Light Communication (VLC). This paper reports a novel VLP technique. The developed technique uses received signal strength for ranging. It is followed by the iterative estimation of a location using spring relaxation. The performance of the proposed technique was experimentally evaluated in indoor settings and benchmarked against the lateration- and fingerprint-based localization approaches in multiple scenarios. The obtained results demonstrate that the proposed VLP approach offers an opportunity to outperform the existing techniques in terms of localization accuracy and precision.

SpringLoc: A Device-Free Localization Technique for Indoor Positioning and Tracking Using Adaptive RSSI Spring Relaxation

Device-free localization (DFL) algorithms using the received signal strength indicator (RSSI) metrics have become a popular research focus in recent years as they allow for location-based service using commercial-off-the-shelf (COTS) wireless equipment. However, most existing DFL approaches have limited applicability in realistic smart home environments as they typically require extensive offline calibration, large node densities, or use technology that is not readily available in commercial smart homes. In this paper, we introduce SpringLoc and a DFL algorithm that relies on simple parameter tuning and does not require offline measurements. It localizes and tracks an entity using an adaptive spring relaxation approach. The anchor points of the artificial springs are placed in regions containing the links that are affected by the entity. The affected links are determined by comparing the kernel-based histogram distance of successive RSSI values. SpringLoc is benchmarked against existing algorithms in two diverse and realistic environments, showing significant improvement over the state-of-the-art, especially in situations with low-node deployment density.

Elastic Three-Sphere Microswimmer in a Viscous Fluid

We discuss the dynamics of a generalized three-sphere microswimmer in which the spheres are connected by two elastic springs. The natural length of each spring is assumed to undergo a prescribed cyclic change. We analytically obtain the average swimming velocity as a function of the frequency of the cyclic change in the natural length. In the low-frequency region, the swimming velocity increases with the frequency and its expression reduces to that of the original three-sphere model by Najafi and Golestanian. In the high-frequency region, conversely, the average velocity decreases with increasing the frequency. Such a behavior originates from the intrinsic spring relaxation dynamics of an elastic swimmer moving in a viscous fluid.

Effects of γ′ Precipitation, Dislocation Density, and Grain Size on Stress-Relaxation Properties of INCONEL X-750 Helical Springs

INCONEL X-750 specimens were manufactured into helical springs by drawing and coiling followed by aging. They were subsequently subjected to stress-relaxation tests. Stress relaxation is the important property of springs that are compressed at elevated temperatures. To understand stress relaxation, this study investigated the effect of the drawing ratio (DR) on the γ′ size and volume fraction, grain size, carbide volume fraction, and dislocation density. Small-angle neutron scattering was used to measure the size and volume fraction of γ′ phase, and X-ray diffraction was employed to analyze the dislocation density in the springs as a function of the DR. The smallest DR specimen (DR0) had a longer free length than the larger DR specimens (DR17 and DR42) after the stress-relaxation test was completed at 773 K (500 °C) for 300 hours. However, the size and volume fraction of γ′, along with the dislocation density, had no influence on the stress relaxation of the INCONEL X-750 springs. The decreased grain size (d) due to an increase in the DR was the main factor in the increase in the stress relaxation of the springs. The decrease in grain size displayed a nonlinear relationship with the increase in stress relaxation. The stress-relaxation behavior relationship was d −3. Grain boundaries were determined to play a role in dislocation sink via transmission electron microscopy (TEM) observations. Grain boundary diffusion accommodated by slip was responsible for the stress-relaxation properties of the spring at an elevated temperature (773 K = 500 °C).

Noise-aware localization algorithms for wireless sensor networks based on multidimensional scaling and adaptive Kalman filtering

The range-based MDS-MAP (multidimensional scaling-MAP) localization algorithm has been widely applied to the estimation of node position in wireless sensor networks (WSNs). However, the range for the MDS-MAP is often influenced by measurement noise so that there is an error, which will greatly reduce the positioning precision of MDS-MAP. Although the current improved MDS-MAP algorithms, such as MDS-MAP(P) and MDS-MAP(P,R), and the algorithms based on the theory of the rigid graph can obtain higher accuracy compared to the MDS-MAP, they are not suitable for the occasion where there are large errors in distance measurements between most nodes, namely the non-rigid graph. Therefore, Kalman filter (KF) is employed to refine the node coordinates from the MDS-MAP on this occasion, but it requires obtaining accurate noise statistics in advance and cannot adapt to the change of noise statistics. In the real WSN localization scenario with unknown or time-varying noise statistics, the inaccurate statistical parameter of noise will seriously weaken the refinement effect of KF on the MDS-MAP, especially under large noise-statistic bias. In this work, we propose two types of two-stage noise-aware localization algorithms for WSNs based on MDS-MAP and adaptive KF (AKF), i.e. an existing adaptive extended KF and an innovative adaptive unscented KF. The positioning accuracy and the time complexity of the AKF for the proposed algorithms are better than those of the spring relaxation for the rigid-graph based localization and the least square optimization for the improved MDS-MAP in the noisy environment. The results of extensive simulations show that compared with the present algorithms for refining the MDS-MAP, our proposed algorithms can always achieve higher positioning accuracy and lower time complexity regardless of the placement way of node, the shape of network topology, the communication radius of node, the node degree of network, and the deviation of noise statistics.

Analysis of Helical Stainless Steel 08X18H10 Spring Relaxation at High Temperature

Analysis of Helical Stainless Steel 08X18H10 Spring Relaxation at High Temperature

Relaxation and creep in twist and flexure

Purpose– The purpose of this paper is to derive the exact analytical expressions for torsion and bending creep of rods with the Norton-Bailey, Garofalo and Naumenko-Altenbach-Gorash constitutive models. These simple constitutive models, for example, the time- and strain-hardening constitutive equations, were based on adaptations for time-varying stress of equally simple models for the secondary creep stage from constant load/stress uniaxial tests where minimum creep rate is constant. The analytical solution is studied for Norton-Bailey and Garofalo laws in uniaxial states of stress.Design/methodology/approach– The creep component of strain rate is defined by material-specific creep law. In this paper the authors adopt, following the common procedure Betten, an isotropic stress function. The paper derives the expressions for strain rate for uniaxial and shear stress states for the definite representations of stress function. First, in this paper the authors investigate the creep for the total deformation that remains constant in time.Findings– The exact analytical expressions giving the torque and bending moment as a function of the time were derived.Research limitations/implications– The material isotropy and homogeneity preimposed. The secondary creep phase is considered.Practical implications– The results of creep simulation are applied to practically important problem of engineering, namely for simulation of creep and relaxation of helical and disk springs.Originality/value– The new, closed form solutions with commonly accepted creep models allow a deeper understanding of such a constitutive model's effect on stress and deformation and the implications for high temperature design. The application of the original solutions allows accurate analytic description of creep and relaxation of practically important problems in mechanical engineering. Following the procedure the paper establishes closed form solutions for creep and relaxation in helical, leaf and disk springs.

A multi-stage wear model for grid-to-rod fretting of nuclear fuel rods

The wear of fuel rod cladding against the supporting structures in the cores of pressurized water nuclear reactors (PWRs) is an important and potentially costly tribological issue. Grid-to-rod fretting (GTRF), as it is known, involves not only time-varying contact conditions, but also elevated temperatures, flowing hot water, aqueous tribo-corrosion, and the embrittling effects of neutron fluences. The multi-stage, closed-form analytical model described in this paper relies on published out-of-reactor wear and corrosion data and a set of simplifying assumptions to portray the conversion of frictional work into wear depth. The cladding material of interest is a zirconium-based alloy called Zircaloy-4 which rubs against dimples or springs on the supporting grid which may be composed of the same or a different alloy. The model involves an incubation stage, a surface oxide wear stage, and a base alloy wear stage. The wear coefficient, which is a measure of the efficiency of conversion of frictional work into wear damage, can change to reflect the evolving metallurgical condition of the alloy. Wear coefficients for Zircaloy-4 and for a polyphase zirconia layer were back-calculated for a range of times required to wear to a critical depth. Inputs for the model, like the friction coefficient, are taken from the tribology literature in lieu of in-reactor tribological data. Concepts of classical fretting were used as a basis, but are modified to enable the model to accommodate the complexities of the PWR environment. Factors like grid spring relaxation, pre-oxidation of the cladding, multiple oxide phases, gap formation, impact, and hydrogen embrittlement are part of the problem definition but uncertainties in their relative roles limits the ability to validate the model. Sample calculations of wear depth versus time in the cladding illustrate how GTRF wear might occur in a discontinuous fashion during months-long reactor operating cycles. A means to account for grid/rod gaps and repetitive impact effects on GTRF wear is proposed.

Mesh optimisation methods for unstructured transmission‐line modelling

Transmission-line modelling (TLM) is a valuable technique for numerical simulation of electromagnetic fields. Recently, investigations have been successfully carried out into the use of the TLM approach on unstructured meshes However, as the local characteristics of mesh geometry will clearly make an impact upon the fidelity of simulations, it is necessary to examine suitable techniques for mesh optimisation. Three different methods have been investigated here to find optimal meshes for subsequent TLM simulations: the centroidal Voronoi Tessellation method, the optimal Delaunay triangulation method and a spring relaxation method. These different techniques are assessed in terms of maximum efficiency of the subsequent TLM simulations and the computational cost that is incurred to identify them. Several different canonical examples of mesh are considered to determine the generality of the conclusions drawn.

Hybrid RF Mapping and Kalman Filtered Spring Relaxation for Sensor Network Localization

An accurate and low-cost hybrid solution to the problem of autonomous self-localization in wireless sensor networks (WSN) is presented. The solution is designed to perform robustly under challenging radio propagation conditions in mind, while requiring low deployment efforts, and utilizing only low-cost hardware and light-weight distributed algorithms for location computation. Our solution harnesses the strengths of two approaches for environments with complex propagation characteristics: RF mapping to provide an initial estimate of each sensor's position based on a coarse-grain RF map acquired with minimal efforts; and a cooperative light-weight spring relaxation technique for each sensor to refine its estimate using Kalman filtered inter-node distance measurements. Using Kalman filtering to pre-process noisy distance measurements inherent in complex propagation environments, is found to have significant positive impacts on the subsequent accuracy and the convergence of our spring relaxation algorithm. Through extensive simulations using realistic settings and real data set, we show that our approach is a practical localization solution which can achieve sub-meter accuracy and fast convergence under harsh propagation conditions, with no specialized hardware or significant efforts required to deploy.

A self-organizing localization reference grid

We propose a non-persistent localization system using a self-organizing reference grid of autonomous robot systems. The key idea is to continuously maintain accurate relative positions between the robots using an enhanced mass spring relaxation model. The robots estimate distances between neighboring systems using an ultrasonic system, measuring both the time of flight based distance and the angle between the systems. The algorithm then adapts the local position of the robot in the grid according to its neighbors. We developed a mass spring relaxation model allowing to maintain a completely self-organizing reference grid. In mass spring, newly arriving nodes can introduce oscillations and self-localization might fail or take a long time to converge. Therefore, we first use the available grid to localize the arriving system with reference to the grid before including the robot as a new reference point. Misplaced nodes are detected and corrected by our enhancements. In turn, the grid is able to provide accurate localization services, e.g. for flying robots.

Rheological Properties of Egg Yolk Subjected to High Hydrostatic Pressure

A high hydrostatic pressure of 100-400 MPa was applied to fresh egg yolks. The rheological properties 、of the resulting egg yolks were evaluated by measuring viscosity at a high shear rate (10-'103 S:-I) in steady-state and at a very low shear rate (10-1 -lO-:J S-I) in spring relaxation. The f10w curves for the egg y61ks showed non-thixotropic behavior after the application of 200-300 MPa ，but thixotropic behavior after 400 MPa. The thixotropic property and yield values were then evaluated. The thixotropic parameter Th of the egg yolk pressurized at 400 MPa (12.8X 103 Pa's-') was larger than that of egg yolk pressurized at 100 MPa (0.09X 10:1 Pa's-1). The viscosity of allpressurized egg yolksobeyed the power law. While the consistency index K was increased ，the f10wbehavior index n was d 巴creased with increasing pressure and time applied. Casson'syield value in the spring relaxation was 140 MPa for the egg yolk which had been pressur 包 ed at 400 MPa for 10 min. This value is less than the 340 MPa which was evaluated for the steady state. This result indicates that a spring relaxation study would be useful for evaluating theyield value (Rec 巴ived October 20 ，1999;Accepted in revised form July 19 ，2000)

SDIPR: A Generic P2P Semantic Distance Inference Approach Based on Spring Relaxation System

Large-scale P2P applications can benefit from the ability to predict semantic distances to other peers without having to contact them first. In this paper, we propose a generic semantic distance inference scheme, SDIPR, in P2P network, which, through measuring semantic distances from peers to a handful of other peers and the current coordinates of those peers, assigns synthetic coordinates to each peer, and can approximately predict the semantic distance between any two peers. Specifically, in our paper, the semantic distance between peers is quantitatively characterized through vector space model based on peers’ semantic profiles and weighted with the number of documents in each peer. Then, we adopt the spring relaxation method, mimicking the physical massspring system, to simulate the semantic embedding procedure, which can find minimal energy configuration corresponding to relatively accurate semantic embedding. Simulation results show that a 3-dimension Euclidean model can embed these peers with relatively high accuracy. Moreover, we compare SDIPR with the influential existing Locality Sensitive Hashing (LSH) based multi-dimension indexing approaches, and show that SDIPR performs much better than one index scheme (that is, one group of hash functions with same dimensions as our approach), and are comparable with LSH-based schemes using three indexes (total 9 dimensions).

Stress relief effect on fatigue and relaxation of compression springs

In the manufacturing process of mechanical springs, high tensile residual stresses are generated which reduces considerably the spring strength and service life. These unfavorable residual stresses are partially eliminated by the heat treatment. In this process, the spring is heated uniformly below the material transformation temperature. An experimental investigation has been conducted to assess the stress relief influence on helical spring fatigue properties. First, S– N curves were determined for springs treated under different conditions (times and temperatures) on a testing machine specially designed to do this task. Next the stress relief effect on spring relaxation induced by cyclic loading was evaluated. Finally, residual stresses were measured on the inner and outer coil surfaces to analyze the effect of heat treatment. The most suitable heat treatment conditions (time range and temperature level) were obtained, these parameters give rise to the highest fatigue resistance with minimum spring relaxation.

Spontaneous Oscillation by Hair Bundles of the Bullfrog's Sacculus

One prominent manifestation of mechanical activity in hair cells is spontaneous otoacoustic emission, the unprovoked emanation of sound by an internal ear. Because active hair bundle motility probably constitutes the active process of nonmammalian hair cells, we investigated the ability of hair bundles in the bullfrog's sacculus to produce oscillations that might underlie spontaneous otoacoustic emissions. When maintained in the normal ionic milieu of the ear, many bundles oscillated spontaneously through distances as great as 80 nm at frequencies of 5-50 Hz. Whole-cell recording disclosed that the positive phase of movement was associated with the opening of transduction channels. Gentamicin, which blocks transduction channels, reversibly arrested oscillation; drugs that affect the cAMP phosphorylation pathway and might influence the activity of myosin altered the rate of oscillation. Increasing the Ca 2+ concentration rendered oscillations faster and smaller until they were suppressed; lowering the Ca 2+ concentration moderately with chelators had the opposite effect. When a bundle was offset with a stimulus fiber, oscillations were transiently suppressed but gradually resumed. Loading a bundle by partial displacement clamping, which simulated the presence of the accessory structures to which a bundle is ordinarily attached, increased the frequency and diminished the magnitude of oscillation. These observations accord with a model in which oscillations arise from the interplay of the hair bundle's negative stiffness with the activity of adaptation motors and with Ca 2+-dependent relaxation of gating springs.