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A Slinky is a loose helical coil spring and is a well-known educational toy. In this paper a model for a Slinky is presented. The Slinky is represented as a sequence of rigid half coils connected by torsional springs. A range of Slinky configurations in static equilibrium are calculated. Where possible the torsion spring model is compared with the much simpler point mass model of a Slinky, and a more sophisticated model that includes axial and shear deformation. The torsional spring model is shown for the most part to produce similar qualitative behaviour as the more complex model. The simplicity of the torsional spring model makes it a candidate for a discrete stair walking dynamic model of a Slinky, The point mass model is straightforward to derive and solve and makes it possible for an undergraduate engineering student in the early part of their degree course to understand. The torsional spring model is a useful tool for showing what can be done in a more advanced mechanics course to model a system that most students would have previous experience of. [ABSTRACT FROM AUTHOR]

The NiTi open coil spring is commonly accustomed to creating spaces for crowded teeth. It is difficult to anticipate the length of the open coil spring desired to open up the exact quantity of space; sometimes, the length of the open spring falls short of opening up the space required. In such a case, the base arch wire must be taken out and replaced with an expanded open coil spring, which is both difficult and time-consuming. There are various reactivation methods available, such as split tubings, cutting a C-shaped tube to the desired length, adding extra length to the spring, creating C-rings, and using composite beads. Hence, we have designed a very simple yet effective chairside method to reactivate NiTi open coil spring with the removal of base arch wire. [ABSTRACT FROM AUTHOR]

A simple method is described for measuring liquid density based on stretching of the spring and equilibrium of weight and elastic force. The method involves placing a container with liquid under test on the spring causing a stretch of the spring that is directly proportional to the weight of the liquid. With this technique, the liquid density can be determined without measuring its mass and volume, and it should help students comprehend the concept of density more easily. The design of the measuring setup in this study is made using tools and materials that are simple and easy to obtain, such as spring, ruler, and small plastic or metallic container (tube). Two liquids used to test the measuring method were ethanol and glycerol. A test showed that the density of the test liquids at room temperature could be measured with the relative uncertainty of 3%, hence the reliability of the described method was confirmed. [ABSTRACT FROM AUTHOR]

Due to their robustness, compactness, simplicity, and the possibility of nonlinear torque curves, spiral springs are being increasingly contemplated for industrial application. Recent manufacturing technologies and materials allow for the creation of spiral springs of various shapes and geometries able to provide the required torque curves. Modeling the behavior of this kind of springs is highly complex due to the strong nonlinearities arisen from large deflections and the possibility of coiling of strip length around the spring barrel or arbor. For this reason, up to our knowledge, existing models only provide design features such as deflection and torque curve for the simplest strip geometries, and fewer models supply, only if no strip coiling occurs, reactions at the strip-barrel and strip-arbor clampings. In addition, to our knowledge, just semi-empirical models for strip-barrel, -arbor and -strip contact forces or friction torques were available. In this work, we introduce a novel general, an analytical quasistatic model for the calculation of all the above spring characteristics for any length-dependent strip material and initial geometry and strip cross-sectional shape and for any barrel and arbor radii. The strip deflection curvatures are calculated minimizing the sum of elastic and gravitational potential energies under geometrical constraints associated with eventual strip coiling. Once the curvatures are calculated, the spring internal, contact, and reaction forces can be straightforwardly calculated by solving the elastica differential equations. Friction is taken into account by evaluating the contact conditions at the strip coiled sections. [ABSTRACT FROM AUTHOR]

This article describes a novel approach to the design of linear machines that are not run at a steady-state operating point. The focus lies on minimizing the power loss to achieve highest possible efficiency. First analytical considerations reveal the potential of designing electrical machines and spring mechanisms for periodic, accelerated motion. It shows the influence of the machine size on the power losses due to the dependence of machine force as well as moving mass on this parameter. Based on these findings, a simulation model was created that can be used with an optimization algorithm. The simulation consists of a stationary and a time-dependent finite-element analysis of the linear machine in conjunction with an operational model that includes a given movement cycle. It was used to design a flat-type linear machine for a free-piston linear generator. The simulation results validate the analytical calculations and illustrate the differences to conventional design approaches for linear machines. [ABSTRACT FROM AUTHOR]

As a novel voltage control device, electric spring (ES) can effectively suppress the voltage fluctuations across critical loads (CLs), and solve the various problems with electrical quality induced by the grid access of renewable energy resources (RES). However, the traditional controllers for the ES system can no longer meet the control requirements, as the environment is complicated by the growing number of load-side nonlinear loads and uncertain disturbances. To solve the problem, this paper proposes a control system based on finite control set-model predictive control (FCS-MPC), and applies it to the ES. Firstly, a load-side circuit prediction model was established and analyzed. Next, a control system was designed based on FCS-MPC. Finally, the proposed system was proved feasible and effective through MATLAB/Simulink simulation and dSPACE physical experiment. The results show that the proposed FCS-MPC system can directly control the ES, easily handle system constraints, achieve robust dynamic and static performance, eliminating the need for pulse width modulation (PWM). [ABSTRACT FROM AUTHOR]

The decline of Arctic sea ice extent has created a pressing need for accurate seasonal predictions of regional summer sea ice. Recent work has shown evidence for an Arctic sea ice spring predictability barrier, which may impose a sharp limit on regional forecasts initialized prior to spring. However, the physical mechanism for this barrier has remained elusive. In this work, we perform a daily sea ice mass (SIM) budget analysis in large ensemble experiments from two global climate models to investigate the mechanisms that underpin the spring predictability barrier. We find that predictability is limited in winter months by synoptically driven SIM export and negative feedbacks from sea ice growth. The spring barrier results from a sharp increase in predictability at melt onset, when ice‐albedo feedbacks act to enhance and persist the preexisting export‐generated mass anomaly. These results imply that ice thickness observations collected after melt onset are particularly critical for summer Arctic sea ice predictions. Plain Language Summary: Observations over the past 40 years have documented a significant decline in Arctic sea ice extent and thickness. These rapid changes and their implications for Northern communities, shipping industries, wildlife, fisheries, and natural resource industries have created an emerging operational need for regional summer sea ice predictions. This study is motivated by the following question: How far in advance can accurate predictions of regional summer sea ice be made? Recent work has shown evidence for an Arctic sea ice spring predictability barrier, which may fundamentally limit the accuracy of predictions made before May. However, the physical mechanism for this barrier has remained elusive. In this study, we investigate this mechanism using a sea ice mass (SIM) budget analysis, which allows for a process‐based attribution of summer sea ice predictability. We considerthe relative roles of ice growth and melt (thermodynamics) and ice motion (dynamics) in determining the spring predictability barrier. We find that predictability is limited by ice motion and growth in winter and increases rapidly in spring due to melt processes. These results imply that ice thickness observations collected after spring melt onset are particularly critical for summer Arctic sea ice predictions. Key Points: The Arctic sea ice spring predictability barrier is investigated using a daily mass budget analysisA mechanism for the spring predictability barrier is proposed, involving three distinct predictability regimesThe spring barrier is expected to shift earlier under Arctic warming due to shifts in melt onset timing [ABSTRACT FROM AUTHOR]

Several self-centering systems have been developed and tested so far, and all of them confront problems. Several problems like stress relaxation, elongation capacity and high post-yield stiffness are some of the problems, which should be addressed. The aim of this study is to find a solution to these problems. To this end, a new pre-compressed self-centering system has been proposed, tested and studied. Pre-compressed springs have been used to provide the required restoring force. Since the spring is under pressure and it has a high elastic capacity, the problem related to limited elongation capacity no longer exists. The experimental result indicates that the proposed self-centering brace has complete self-centering behaviour and low postyield stiffness. The proposed self-centering system produces less secondary stiffness compared to other systems. The effect of secondary stiffness on the drift and base shear was studied. Results of the numerical models indicate that high secondary stiffness does not decrease the drift of the structure, it only increases the base shear. Therefore, to attain an economical design, using the proposed self-centering system with slight secondary stiffness is suggested. [ABSTRACT FROM AUTHOR]

Soil compaction is an important procedure of precision seeding operation. In this paper, a precise downforce control system based on fuzzy PID was proposed in order to improve the quality of the soil compaction and the accuracy of setting working parameters. The conventional mechanism of seeders for soil compaction was optimised. The compressing spring of the compaction mechanism was replaced by a linear motor, which is actively controlled to adjust downforce in real time. A force sensor was connected in series with the linear motor to detect the actual downforce from a press wheel acting on soil. The detected downforce was employed as feedback for the fuzzy PID model. A slave real-time control system was constructed by using an STM32 microcontroller. A user interface was designed for the portable master computer system based on the ForLinx embedded platform to facilitate the setting of target downforce and display the actual downforce in real time. Meanwhile, it was able to adjust the system for different operating requirements, such as soil stiffness, moisture, and crop species. Experiments were conducted on a soil bin, and the results indicated that the active control system has better performance than the conventional passive system in downforce control. The downforce was stable with a variance less than 2.6% under different conditions, and it was 8.11% less than the conventional passive system. [ABSTRACT FROM AUTHOR]

The maximum displacement from equilibrium of a ballistic pendulum is analyzed as a function of projectile mass. The displacement can be determined according to the conservation laws of energy and momentum, which are applied in three stages. For an ideal spring-gun, the pendulum's maximum displacement height should increase monotonically with the mass of the projectile until the mass of the projectile and the effective mass of the pendulum are equal, after which the displacement height decreases monotonically with projectile mass. The additional mass of the spring and driver mechanism shifts this peak towards higher projectile masses. This relationship was tested using a cup-catcher and a set of blocks of varying mass as the projectiles, and the pendulum maximum displacement does indeed increase with mass to a point before slowly decreasing. [ABSTRACT FROM AUTHOR]

This study proposes a coil current model and an energy storage motor current (ESMC) model of circuit breakers (CBs) with spring operated mechanism. To make sure the signals generated by the models are identical to the actual ones, this study proposes a stochastic optimisation algorithm to optimise the model parameters. Based on the data produced by the optimised models, two fault diagnosis methods are proposed to assess operational condition and detect faults. The first method is based on fast template matching, which adopts K-means clustering algorithm to cluster the data and form a template library. The second one combines deep belief network and Softmax classifier, which can not only extract high level information of the characteristic signals, but also avoid the negative impact of the large dimension on classification results. In the simulation studies, the two methods are tested on various scenarios and their merits are demonstrated, respectively, where the latter one shows superior performance. [ABSTRACT FROM AUTHOR]

Hayabusa2 is a current sample return mission spacecraft developed by JAXA. One of the most important scientific objectives of Hayabusa2 is to investigate the chemical and physical properties of the internal materials and structures of the asteroid Ryugu. To achieve this goal, we developed a new device called the small carry-on impactor (SCI). The SCI is a kinetic impactor that is being used to create an artificial crater on the surface of Ryugu. It has no attitude or orbit control device. The helical spring in the separation mechanism provides both separation force and spin torque to the SCI. The impact accuracy of the SCI depends heavily on the separation accuracy. Repeating a large number of separation tests is a straightforward approach to evaluate the separation accuracy. However, that is not realistic. Hence, first we performed several element tests to understand the separation dynamics. Then, the final separation accuracy was evaluated through a small number of separation tests, and this was followed by simulations that used the results of the element tests. This paper provides an overview of the separation mechanism, the results of development testing analyzed in detail, and a summary of the separation performance. [ABSTRACT FROM AUTHOR]

This study determines the practicality and feasibility of the application of pneumatic artificial muscles (PAMs) in a pneumatic therapy robotic system. The novel mechanism consists of a single actuated pneumatic artificial muscle (single-PAM) robotic lower limb that is driven by only one PAM combined with a torsion spring. Unlike most of previous studies, which used dual-actuated pneumatic artificial muscles (dual-PAMs) to drive joints, this design aims to develop a novel single-PAM for a one degree-of-freedom (1-DOF) robotic lower-limb system with the advantage of a mechanism for developing a multi-axial therapy robotic system. The lower limb robotic assisting system uses the stretching/contraction characteristics of a single-PAM and the torsion spring designed by the mechanism to realize joint position control. The joint is driven by a single-PAM controlled by a proportional pressure valve, a designed 1-DOF lower-limb robotic system, and an experimental prototype system similar to human lower limbs are established. However, the non-linear behavior, high hysteresis, low damping and time-variant characteristics for a PAM with a torsion spring still limits its controllability. In order to control the system, a fuzzy sliding mode controller (FSMC) is used to control the path tracking for the PAM for the first time. This control method prevents approximation errors, disturbances, un-modeled dynamics and ensures positioning performance for the whole system. Consequently, from the various experimental results, the control response designed by the joint torsion spring mechanism can also obtain the control response like the design of the double-PAMs mechanism, which proves that the innovative single-PAM with torsion spring mechanism design in this study can reduce the size of the overall aid mechanism and reduce the manufacturing cost, can also improve the portability and convenience required for the wearable accessory, and is more suitable for the portable rehabilitation aid system architecture. [ABSTRACT FROM AUTHOR]

The HP³ Mole system is part of the HP³ payload on the InSight discovery class mission, which will place a geophysical lander onto the surface of Mars in 2018. DLR's HP³ - instrument (Heat Flow and Physical Properties Package) will measure Mars' interior heat flux and thermal gradient down to a depth of 5 m and thus penetrates deeper below the Martian surface than any other instrument before. Being the locomotion system of the instrument, the HP³ Mole acts as a self-impelling nail in order to accomplish this goal. The inner hammering mechanism is spring driven and periodically loaded by a cylindrical cam mechanism. The innovative impact driven locomotion principle enables a minimum in required energy and mass, but leads to complex system behaviour and dependence of the inner mechanism dynamics on the outer force conditions exerted by the soil. The scope of this paper is to provide an overview of the Mole, its role in the mission and payload, as well as to give a brief overview about its subsystems, its interfaces and working principle. • Detailed presentation of a flight design subsurface access device ("mole"). • This mole is a contribution to the recently landed InSight mission on Mars. • Presentation of the design process, i.e. testing alongside with simulation. [ABSTRACT FROM AUTHOR]

Copyright of Oil Drilling & Production Technology / Shiyou Zuancai Gongyi is the property of Shiyou Zuancai Gongyi Bianjibu and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• A method for static balancing of spherical mechanisms using springs is proposed. • The mechanisms are constructed using spherical chains and other types of chains. • Mass moment substitution approach is adopted. • Bennett plano-spherical hybrid linkage and 3-RRS parallel mechanism are balanced. A geometric method to the static balancing of mechanisms constructed using spherical chain units is presented. A (serial) spherical kinematic chain unit is composed of n moving links, whose masses are considered, connected by revolute (R) joints the axes of which intersect at a fixed point. The mass of each link can be balanced using one spring without any auxiliary parallelogram. The balancing can be achieved readily with almost no calculation. One end of each spring is fixed right above the intersection of the joint axes and the other end is attached to the point that is on the line defined by the intersection and the equivalent center of mass of the corresponding link (combining the masses of the link and the payload). This method is then applied to the mechanisms constructed using spherical kinematic chain units, and the ones constructed using spherical kinematic chain units and other types of kinematic chain units. By distributing the mass of a link onto its adjacent links, the static balancing of the mechanism is reduced to those of several spherical kinematic chain units, which can be balanced using the proposed method. Two examples are given, including a Bennett plano-spherical hybrid linkage and a 3-RRS parallel mechanism to illustrate the proposed method for static balancing. [ABSTRACT FROM AUTHOR]

This technical note presents a numerical corrective technique that allows control of nonlinearity in a mass-spring system (MSS) independent of its spring constants or system topology. The governing equations of MSS in the form of ordinary differential equations or a regular function accompanied by any boundary or initial condition as known constraints, are employed to modify the results. A least-squares algorithm coupled with the finite difference method is used to discretize the basic residual function implemented in this corrective technique. This numerical solution is applicable to both static and dynamic MSS. This technique is easy to implement and has accuracy similar to that of the equivalent finite element method (FEM) solution to the same system whereas solutions are obtained in a fraction of the CPU time. The proposed technique can also be used to smooth solutions from other methods such as FEM or boundary element method (BEM). [ABSTRACT FROM AUTHOR]

Aim: The Forsus fatigue-resistant device spring is a 3-piece telescoping compression spring used for Class II correction. The aims of this study were: (1) to measure the mean force delivered at different amounts of deflection; (2) to determine and compare the mean stiffness between loading and unloading; and (3) to determine the resilience of the fatigue-resistant device springs. Material and methods: Twelve fatigue-resistant device springs were tested with a universal testing machine and Winrcon software, with the load cell of 100 N, crosshead speed at 0.5 mm/second. Force-deflection data during loading and unloading were recorded at 2-mm intervals up to 12 mm compression. Results: (1) The mean force-deflection loading and unloading curves generally were linear, with a small area of hysteresis; (2) the loading mean stiffness (19.4 g/mm) was significantly greater than the unloading mean stiffness (18 g/mm), although this is clinically insignificant; (3) fatigueresistant device springs exhibited good resiliency. A calibrated table of force-deflection of fatigue-resistant device springs is presented for clinicians to select the appropriate length of the device for the particular orthodontic force needed. [ABSTRACT FROM AUTHOR]

In this study, we used the method of finite element analysis to investigate the mechanical stiffness of single nanoscale helical springs with two different configurations—square and round—in order to answer two questions. (1) Is the classic macroscopic-based theoretical prediction still valid to nanoscale springs? (2) What is the effect of boundary conditions on the spring stiffness? Our results indicated that the classic prediction is valid and applicable to predicting the relationship between the spring stiffness and the spring section diameter and coil width in nanoscale springs, and that boundary conditions applied to the nanosprings will significantly affect the deformation of the springs and their stiffness values. The strict boundary condition of radial symmetry used in the classic development is responsible for producing high stiffness values. When used as a stand-alone mechanical component, a nanospring will be 2–3 times stiffer than that used as part of a film structure. With equivalent dimensions, a square helical spring will be stiffer than its round counterpart. In a square configuration, the spring stiffness can be maximized at a rising angle of 30°. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In this paper, the performance of a multi-unit friction damper with high-tension bolts tightened via coned disc springs was experimentally investigated, and the response control effects achieved by the friction damper were numerically assessed. Elemental tests were performed to obtain the basic characteristics of dampers composed of two friction units. The dampers exhibited a stable rigid-plastic restoring force characteristic without significant degradation of the frictional force even under repetitive loading operations. In full-scale tests, the performance of a brace-type damper composed of eight or 10 friction units and incorporated into a steel frame was investigated. The brace-type damper demonstrated stable performance and showed no remarkable decrease in the sliding force, even under repeated loading. The damper was shown to produce a total frictional force approximately proportional to the number of the friction units. Thus, the total frictional force of the damper can be estimated as the sum of the contributions of the friction units. Moreover, adopting multiple friction units and assembling them permit the damper to achieve a high total frictional force capacity. Earthquake response analysis was conducted using a 30-story high-rise building model incorporating the brace-type dampers to assess their performance against various earthquake motions, including long-period, long-duration motions and pulse-like motions. By installing the high-capacity brace-type dampers into the two spans out of 12 spans for each floor of the main frame, a response reduction effect was obtained in most analytical cases compared to the model without dampers. [ABSTRACT FROM AUTHOR]

A quasi-zero stiffness (QZS) isolator is devised to acquire the feature of high-static-low-dynamic stiffness. Cam–roller–nonlinear spring mechanisms, where two horizontal dampers are installed symmetrically, are employed as a negative stiffness provider to connect in parallel with a vertical spring. From the static analysis, the piecewise restoring force in the vertical direction of the system is inferred considering possible separation between the cam and roller. The stiffness characteristics and parameters for offering zero stiffness at the equilibrium position are then determined. The dynamic equation is established and used for the deduction of the amplitude–frequency equation by means of the Harmonic Balance Method. The definitions of force and displacement transmissibility are introduced, and their expressions are derived for subsequent investigations of the effects of horizontal spring's nonlinearity, excitation amplitude, horizontal damping, and vertical damping on the transmissibility performance. The comparative study is implemented on the isolation performance afforded by the QZS isolator and an equivalent linear counterpart, whose static bearing stiffness is same as the QZS isolator. Results indicate that the system with softening nonlinear horizontal spring can exhibit better performance than that with opposite stiffness spring. With the increase in horizontal damping ratio, the force transmissibility is further suppressed in resonance frequency range but increased in a small segment of higher frequencies and tends to unite in high frequency range. However, the horizontal damper deteriorates the ability to isolate the displacement excitation to a certain extent. Besides, the isolation capability of the QZS system depends on the magnitude of excitation amplitude. The quasi-zero stiffness system possesses lower initial isolation frequency and better isolation ability around resonance frequency compared with the linear system. Therefore, the quasi-zero stiffness isolator has superior low-frequency ability in isolating vibration over its linear counterpart. [ABSTRACT FROM AUTHOR]

We present a setup that is excellently suited to measure the electrical and thermoelectrical transport across single-molecule junctions at both room temperature and low temperatures. It employs a sandwich configuration of two silicon carbide chips each equipped with metallic electrodes. Upon compression with an external piezo/spring mechanism, fine-tuned displacement control is achieved such that ultrastable atomically thin nanojunctions can be established. As a consequence of its stability, the setup gives access to point-by-point comparisons of electrical and thermoelectrical transport across single-molecule contacts. As a first demonstration of the capabilities of our setup, we present experiments with gold-molecule-gold contacts. Investigating a large ensemble of nanojunctions, each fully characterized by current-voltage characteristics and thermovoltage, correlations between these quantities are uncovered which can be rationalized within the Landauer transport picture. When including characteristics with resonant features, the Seebeck coefficient adds the decisive parameter to fully describe datasets within a resonant tunneling model. The setup provides further potential of controlling additional parameters as it is optically fully transparent. It also allows for nearly arbitrary material combinations for electrode-nanoobject object-electrode nanojunctions. [ABSTRACT FROM AUTHOR]

Summary: Objectives: Three different types of lancets have been compared to identify and implement the one that causes the least pain. Simple manoeuvres during the lancing procedure have been evaluated to determine their effectiveness in reducing the intensity of perceived pain. Background: Pre‐donation haemoglobin estimation is performed by pricking the donor's finger with a lancet. Pain associated with the procedure causes fear and anxiety, which dissuades the donors from donating blood. Methods: In 100 subjects, finger prick was performed using three different lancets, and the subjects were asked to score their pain on a numerical rating scale (NRS). A further 150 blood donors were subjected to routine finger pricking for Hb estimation and were asked to score their pain on an NRS. After 15 min, they underwent a second prick with application of a manoeuvre (breath holding, coughing trick or looking away) and again marked their pain scores on the NRS. Results: Participants reported the least pain scores with lancing devices that have a spring mechanism to retract the lancets soon after penetration into the skin. Breath holding and the cough trick manoeuvre reduced the perceived pain scores significantly. Conclusion: Lancing devices merit consideration for routine use, and a simple manoeuvre may be applied to reduce perceived pain. [ABSTRACT FROM AUTHOR]

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Graphical abstract Highlights • An innovative design of speed amplified electromagnetic oscillation energy harvester. • Analysis of the harvester for its parameter study and performance optimization. • A non-linear oscillator used for enhancing the performance through magnetic springs. • Analytical/simulation method considering the rotational inertia of the pulley wheels. • The dimensionless expressions of the output voltage and harvested power. Abstract This paper proposes a novel design of speed amplified nonlinear electromagnetic vibration energy harvester through fixed pulley wheel mechanisms and magnetic springs. The new vibration energy harvester consisting of fixed pulley wheel mechanisms, nonlinear magnetic springs, inner and outer rectangular ring Halbach arrays of magnets and a four-phase coil connection has potential to generate more output voltage than that with the speed amplified linear electromagnetic vibration energy harvester and conventional non-speed amplified nonlinear electromagnetic vibration energy harvester. By so far no one has worked on increasing the relative speed of the magnets with respect to the coils by adopting the fixed pulley wheel mechanisms. The nonlinear vibration was achieved by adopting repulsive magnetic springs with nonlinear spring stiffness. Analytical and simulation solutions of the speed amplified nonlinear electromagnetic vibration energy harvester system considering the effects of the rotational inertia of the pulley wheels have been verified by experimental results. The dimensionless formulae of the relative displacement, output voltage and harvested power of the speed amplified nonlinear electromagnetic vibration energy harvester system have been established and experimentally validated. [ABSTRACT FROM AUTHOR]

Highlights • A FE model of the SKL-1 system was developed and experimentally validated. • The mechanical response and the fatigue behavior were satisfactorily reproduced. • A novel method was implemented to assess the influence of mean stress on fatigue. • The FE model shows that fatigue alone cannot be the failure mechanism of spring clips under in-service conditions. Abstract The fastening system that links the rail and the sleeper in railway lines is an element of high responsibility, since its failure may lead to the derailment of the train. This paper combines an experimental approach and a Finite Element model to assess the structural integrity of the spring clip of the SKL-1 fastening system, used assiduously in high-speed lines. Our results prove that fatigue is not the failure mechanism that explains the fractures of clips as pointed out by other authors, provided the following requirements: the material has received the appropriate thermomechanical treatments; the assembly of the clip has been carried out with precision; and the system has not suffered anomalous in-service overloads. [ABSTRACT FROM AUTHOR]

Observations from two research cruises made in 2008 and 2012 to east of New Zealand are put into context with satellite data to contrast and compare surface chlorophyll a evolution in the two years in order to explore mechanisms of phytoplankton bloom development in the southwest Pacific Ocean. In 2008, surface chlorophyll a largely followed the long-term climatological cycle, and 2008 can be considered a canonical year, where the autumn bloom is triggered by increasing vertical mixing at the end of summer and the spring bloom is triggered by decreasing vertical mixing at the end of winter. In contrast, 2012 was anomalous in that there was no autumn bloom, and in early spring there were several periods of sustained increase in surface chlorophyll a that did not become fully developed spring blooms. (In this region, we consider spring blooms to occur when surface chlorophyll a exceeds 0.5 mg m-3). These events can be related to alternating episodes of increased or decreased vertical mixing. The eventual spring bloom in October was driven by increased ocean cooling and wind stress (i.e. increased mixing) and paradoxically was driven by mechanisms considered more appropriate for autumn rather than spring blooms. [ABSTRACT FROM AUTHOR]

Screw mechanism fixing bolt fracture failure of a 500kV circuit breaker spring mechanism running process. By analyzing the installation position and operating environment, and by means of chemical analysis, metallographic examination and other means, the microstructure macro and micro fracture morphology of the fracture bolt were analyzed. The results show that the surface of the bolt is hydrogen-rich and produces hydrogen embrittlement during surface treatment. [ABSTRACT FROM AUTHOR]

Abstract Disk springs have been widely used in machine tools, aerospace vehicles, and automobiles. Pioneering work by Almen -Laszlo has inspired a deeper understanding of the nonlinear behavior over the last eight decades. There is a need for extending the analysis for stepped section disk springs. In this paper, we report the effect of the stepped section on the force-deflection and variable stiffness characteristics. A simplified method for predicting load deflection of the stepped disk spring has been developed incorporating the geometric non-linearity. Extending the work of Almen-Laszlo, Curti, and Rosa, we present a theoretical analysis that predicts the force deflection characteristic as function of the geometric parameter and the theoretical model is verified using finite element results. Highlights • Methodology to enhance energy absorption in disk spring by addition of stepped section has been presented. • Theoretical formulation available in the paper helps designer to choose the section parameters for optimum energy storage. • Results of theoretical formulation are verified by FE results. • Results from the present paper has been compared with the previous published work. [ABSTRACT FROM AUTHOR]

The detrainment of organic matter from the mixed layer, a process known as the mixed layer pump (ML pump), has long been overlooked in carbon export budgets. Recently, the ML pump has been investigated at seasonal scale and appeared to contribute significantly to particulate organic carbon export to the mesopelagic zone, especially at high latitudes where seasonal variations of the mixed layer depth are large. However, the dynamics of the ML pump at intraseasonal scales remains poorly known, mainly because the lack of observational tools suited to studying such dynamics. In the present study, using a dense network of autonomous profiling floats equipped with bio‐optical sensors, we captured widespread episodic ML pump‐driven export events, during the winter and early spring period, in a large part of the subpolar North Atlantic Ocean. The intraseasonal dynamics of the ML pump exports fresh organic material to depth (basin‐scale average up to 55 mg C·m−2·day−1), providing a significant source of energy to the mesopelagic food web before the spring bloom period. This mechanism may sustain the seasonal development of overwintering organisms such as copepods with potential impact on the characteristics of the forthcoming spring phytoplankton bloom through predator‐prey interactions. Key Points: The density of BGC‐Argo float network enables identification of episodic mixed layer pump events on a basin scaleIntraseasonal dynamics of the mixed layer pump drives episodic inputs of fresh organic material to the mesopelagic during the winter to spring transitionThis mechanism provides a significant source of energy to the mesopelagic food web before the spring bloom period [ABSTRACT FROM AUTHOR]

Abstract Composite springs have been used in many engineering applications, particularly in the transportation industry. This is due to their light weight, good stiffness, good strength, good corrosion and fatigue resistances. Normally special molds need to be prepared in the manufacturing of these springs. The molds have curvatures which fit into the shape of the final product. Recently the concept of 4D printing of composites was introduced. This concept is a combination of 3D printing together with the reconfiguration of the part upon the activation of some mechanism such as heat, light, or the absorption of moisture. This concept allows the ability to make structures of complex shapes without the need to have complex molds. Layers of composites can be laid on a flat mold. Upon curing, the layers reconfigure into curved structures. As such, curved composite structures can be made using only flat molds. The mechanism for this reconfiguration depends on the anisotropic nature of layered composite materials. This paper presents the fundamental study, as part of a larger project intended to use the concept of 4D printing to develop complex composite structures without the need for complex curved molds. The fundamental study examines the mechanical characteristics of curved composite beams made by 4D printing. [ABSTRACT FROM AUTHOR]

The paper deals with designing a control force to create nodal point(s) having zero displacements and/or zero slopes at selected locations in a harmonically excited vibrating structure. It is shown that the steady-state vibrations at desired points can be eliminated using feedback control forces. These control forces are constructed from displacement and/or velocity measurements using sensors located either at the control force position or at some other locations. Dynamic Green's function is exploited to derive a simple and exact closed from expression for the control force. Under a certain condition, this control force can be generated using passive elements such as springs and dampers. Numerical examples demonstrate the applicability of the method in various cases. [ABSTRACT FROM AUTHOR]

Abstract In order to investigate the microstructure evolution of spring stress relaxation under different conditions, a microscopic analysis is carried out for the austenitic AISI 304 stainless steel spring. The microstructure and remanence of spring samples are obtained. Based on this, the stress relaxation mechanisms at different temperatures and loads are studied. The research shows that, for AISI 304 springs, the main stress relaxation mechanism at low temperatures and light loads is martensitic transformation. When the environmental temperature exceeds the creep temperature of spring material, the main stress relaxation mechanism is changed to the formation and growth of austenite twins. The rise of temperature will accelerate the spring stress relaxation. Within the elastic limit, the applied load only changes the relaxation rate instead of the relaxation mechanism. Thus, for the safety and reliability of springs, the environmental temperature should not exceed the creep temperature of spring material and the applied load should not exceed the spring elastic limit. Highlights • At room or low temperatures, the SSR microscopic mechanism is deformation-induced martensitic transformation. • Above the creep temperature of spring material, the SSR microscopic mechanism is formation and growth of austenite twins. • The boundary martensite amount for consistent SSR microscopic mechanism is provided. • The boundary environmental temperature and applied load for consistent SSR microscopic mechanism is determined. [ABSTRACT FROM AUTHOR]

Mechanical vibrations in buildings are ubiquitous. Such vibrations limit the performance of sensitive instruments used, for example, for high-precision manufacturing, nanofabrication, metrology, medical systems, or microscopy. For improved precision, instruments and optical tables need to be isolated from mechanical vibrations. However, common active or passive vibration isolation systems often perform poorly when low-frequency vibration isolation is required or are expensive. Furthermore, a simple solution such as suspension from common bungee cords may require high ceilings. Here we developed a vibration isolation system that uses steel springs to suspend an optical table from a common-height ceiling. The system was designed for a fundamental resonance frequency of 0.5 Hz. Resonances and vibrations were efficiently damped in all translational and rotational degrees of freedom of the optical table by spheres, which were mounted underneath the table and immersed in a highly viscous silicone oil. Our low-cost, passive system outperformed several state-of-the-art passive and active systems in particular in the frequency range between 1 and 10 Hz. We attribute this performance to a minimal coupling between the degrees of freedom and the truly three dimensional viscous damping combined with a nonlinear hydrodynamic finite-size effect. Furthermore, the system can be adapted to different loads, resonance frequencies, and dimensions. In the long term, the excellent performance of the system will allow high-precision measurements for many different instruments. [ABSTRACT FROM AUTHOR]

Abstract The breakage of spring of a valve causes the non functionality of a hydraulically operated system which pours steel into tundish (controls the flow of steel before putting into a caster) in a steel manufacturing plant. The valve is operated with two springs of diameter 0.3 mm among which one was broken. The spring failed after 5 years of service which had expected life of 10 years. The fracture surface under SEM showed striations confirming fatigue failure. The chemistry of the spring was confirmed to be o be a plain high carbon steel consistent with the requirements of ASTM A228 "Steel wire,Music quality" which is a cold drawn steel wire for mechanical spring. The microstructural analysis showed crack associated with scale and crow feet. The presence of crow feet like surface defect acted as stress concentration for fatigue crack initiation. The valve spring activated100 times per hour causing fatigue loading of the spring. The etched condition shows drawn pearlite typical structure of cold drawn spring and hardness was also found to be satisfactory. The presence of crow feet surface defect came from the wire drawing stage due to insufficient lubrication and considered to be manufacturing defect. The inspection of a spring this kind for critical applications should be robust to avoid future failures Highlights • Spring failed in fatigue. • Fatigue crack initiated from surface defect during spring wire drawing. • Calculated stress intensity factor crosses fracture toughness causing failure. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of factors essential to air spring and undercarriage design to determine their influence on air spring fatigue life. Two sets of factors were chosen for the investigation: those relating to the design of the air spring itself (cord angle, diameter difference) and those relating to the design of the undercarriage (lever length, eccentricity, lever eccentricity, inclination). A full factorial experiment, whereby interactions between all the factors are investigated, would demand 729 experiments. Using Taguchi methods, the number of experiments required is dramatically reduced, using only 27 experiments to determine the influence of 6 factors and 3 interactions. Taguchi analysis shows here that factors inherent to air spring design have a much greater influence on fatigue life than those factors inherent to undercarriage design. Interaction between these factors has also revealed that there is no optimal cord angle for all air springs. [ABSTRACT FROM AUTHOR]

Abstract The physical properties of arteries are important in the research of the circulatory system dynamics. Moreover, in order to build Virtual Reality Simulators, it is crucial to have a tissue model able to respond in real time. A reduced mesh size results in shorter processing times, which can be achieved using a two-dimensional grid. In this work, a triangular topology is considered and the nodes are connected by three kinds of linear springs (one normal and two angular ones). The spring stiffnesses depend on the mesh geometry and on the elastic properties of the artery. The model linearizes the material response, but it still contemplates the geometric nonlinearities. Comparisons showed a good match with a nonlinear model and with our previous model based on a quadrilateral topology. However, the proposed model extension is more flexible and easier to implement than the previous one. [ABSTRACT FROM AUTHOR]

Mechanical characteristic parameter can be used to evaluate circuit breaker performance, traditional test method for measuring characteristic parameter cannot be applied on-line, also the application process is complicated. To solve this problem, a new method for Timing parameters extraction from vibration signal of circuit breaker in opening process is proposed. First, based on the principle of spring operating mechanism, the vibration event caused by components impact in the opening process is analyzed. Then, in order to eliminate noise, variation mode decomposition is adopted to decompose vibration signal, reconstruct the signal by components whose waveform change is consistent with original signal. Finally, timing parameters in the opening process of circuit breaker (CB) are detected by double threshold method based on short time energy entropy ratio. Through comparison of the timing parameters extracted from vibration signal and experimental travel curve, the correctness of proposed method is verified. This study provides a new method for on-line detection of high voltage circuit breaker characteristic parameters. [ABSTRACT FROM AUTHOR]

There are many engineering design problems that call for rubber components as the best solution. Vulcanized rubber has found its way into all sorts of devices, from the universal automobile pneumatic tire to the ubiquitous compliant bushing. Some high-speed rail vehicle suspensions make use of rubber, not only in the air spring itself, but also in the auxiliary spring. The mechanical characteristics of this component influence vehicle dynamics and, therefore, accurate spring models with which to conduct dynamic analysis would make for powerful design tools. Nevertheless, the mechanical behavior of rubber defies simple modeling on account of stress relaxation, creep, set, viscosity, internal friction, and nonlinear stress–strain relations. Despite the advances in the micromechanical understanding of these phenomena, as well as in the macroscopic modeling of rubber spring behavior, there is ample room for refinement, and this is precisely the goal of this paper. The mechanical behavior of a particular rubber spring for high speed rail vehicles has been characterized. The results reveal the necessary components of the model, and suggest the appropriate procedure for parameter extraction. Our model proposal consists of three elements in parallel: a nonlinear elastic spring; a “soft friction” element; and a Maxwell viscous component. The characterization procedure takes into account both stress relaxation and nonlinear elasticity. The proposed model accurately reproduces experimental results and may then be used with confidence in any type of numerical simulation. Nevertheless, for this statement to be true, the problem of “numerical softening” potentially induced by soft friction models should be resolved. The paper will show that a trailing moving average filter, seamlessly tied to the model, wipes out the softening effect. [ABSTRACT FROM AUTHOR]

Presents a study which described scanning force microscopy springs optimized for optical-beam deflection and with tips made by controlled fracture. Noise calculation and optimization; Details of spring design; Discussion of spring fabrication.