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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]

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]

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]

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]

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]

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 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 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]

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]

Spring-assisted oscillating actuators allow the overall energy consumption of a system to be reduced. The concept relies on springs that store and release energy into the system when required. Conventional mechanical springs impose some limitations on a system, mainly in terms of compactness, friction, material fatigue, and failure. Magnetic springs have the potential to overcome these issues, especially for long-stroke high-frequency operation. We report here on the investigation of a magnetic spring into a linear oscillatory motor without any changes to the permanent magnet arrangement on the mover. We focus on a compact and highly integrated design with maximum energy storage capacity. Our analytic equations define the relevant geometrical parameters that exploit the potential of the system best and are on a par with a finite-element-based optimization. We also investigated the expected losses and demonstrate the importance of correct choice of materials to efficient operation. We validated our results using measurements from a prototype linear oscillatory motor featuring the proposed integrated magnetic spring. [ABSTRACT FROM PUBLISHER]

Abstract: This paper presents how the piston shape of an air‐spring can influence both its load‐deflection characteristic and the fatigue life. Two piston shapes are considered in this study for which load‐deflection characteristics and fatigue lives are compared. A method for the estimation of air‐spring fatigue life is upgraded by adding the influence of the mean stress level and afterwards used together with finite element analysis to predict the fatigue life and, ultimately, the timing and global location of failure within the air‐spring. These predictions are then compared with measured results and show good agreement thus proving the validity of the method used here for calculating fatigue life. Both experimental and predicted results show that the highest fatigue life can be expected if a noncylindrical, back tapered piston is used. This is only the case if the air‐spring is mounted at its optimal design height as the study also shows that moving away from optimal design height does have a detrimental effect on the fatigue life of back tapered air‐springs. This is due to the appearance of higher stress amplitudes in the flex member during operation. Such stress amplitudes and consequently fatigue damage can be reduced by avoiding sharp transitions in the piston design that cause additional bending of the flex member in a direction opposite to the deflection in the flex member fold. [ABSTRACT FROM AUTHOR]

We propose a new highly reliable and lightweight embedded optical torque sensor for biomimetic robot arm enabling the torque measurement in joints, which can measure torque of the joint by detecting torsion of its elastic element (mechanical structure or flexure element). Flexure spring is introduced as the elastic element of the torque sensor in this paper. Because of its curve modeling, flexure spring is not inclined to be broken contrast to crossbeam structure, which is commonly used in torque sensor. Thanks to this structure, we can build a torque sensor as an extremely compact and highly reliable size. Six types of flexure spring are proposed to be used as the elastic element of the torque sensor in this paper, which have the potential for the requirements of measurement range and multidimensional detection. The optical electronic, less influenced by electromagnetic interferences, is selected to measure the torsion displacement of the flexure spring. The proposed design is analyzed, which can obtain the successful measurement of the torque with a load capacity of 1 Nm. One of the designed optical torque sensors is optimized by FEM. The calibration and experiment are conducted to ensure its feasibility and performance. [ABSTRACT FROM AUTHOR]

A critical analysis of the scientific literature shows that, contrary to helical and other springs widely used in practice, slotted cylinder springs have been insufficiently documented to date. Currently, given the under exploited potential of their particular mechanical properties, a further investigation is much necessary in order to extend their use to as many as possible areas of technology. This is quite possible thanks to the most recent state of mechanical design research and technology. This paper is a part of a project that aims at developing specific computer software tools allowing precise analytic stress state determination. It develops a statically indeterminate approach of the problem of the stress behaviour of such springs, following which previously and three newly proposed models are compared one with another on the basis of ratios between Von Mises' stresses. Finally, for the case of two slots per section slotted cylinder springs, it is concluded that the analytical solution of the two degrees of freedom proposed primary system is in good agreement with empirical and Computer Aid Design res-olutions. A generalization to higher number of slots per section springs is foreseen using the same methodology. [ABSTRACT FROM AUTHOR]

We consider the identification of a single open crack in a simply supported beam having nonuniform smooth profile and undergoing infinitesimal in-plane flexural vibration. The profile is assumed to be symmetric with respect to the mid-point of the beam axis. The crack is modeled by inserting a rotational linearly elastic spring at the damaged cross-section. We establish sufficient conditions for the unique identification of the crack by a suitable pair of natural frequency data, and we present a constructive algorithm for determining the damage parameters. The result is proved under a technical a priori assumption on the zeros of a suitable function determined in terms of the eigenfunctions of the problem. Extensions to beams under different sets of end conditions are also discussed. Theoretical results are confirmed by an extensive numerical investigation, both on simulated and experimental data. [ABSTRACT FROM AUTHOR]

Primarily, two models are commonly used to describe rocking of rigid bodies; the Housner model, and the Winkler foundation model. The first deals with the motion of a rigid block rocking about its base corners on a rigid foundation. The second deals with the motion of a rigid block rocking and bouncing on a flexible foundation of distributed linear springs and dashpots (Winkler foundation). These models are two-dimensional and can capture some of the features of the physics of the problem. Clearly, there are additional aspects of the problem which may be captured by an enhanced nonlinear model for the base-foundation interaction. In this regard, what it is adopted in this paper is the Hunt-Crossley nonlinear impact force model in which the impact/contact force is represented by springs in parallel with nonlinear dampers. In this regard, a proper mathematical formulation is developed and the governing equations of motion are derived taking into account the possibility of uplifting in the case of strong excitation. The analytical study is supplemented by experimental tests conducted in the Laboratory of Experimental Dynamics at the University of Palermo, Italy. In this context, due to their obvious relevance for historical monuments, free-rocking tests are presented for several marble-block geometries on both rigid and flexible foundations. Numerical vis-à-vis experimental data are reported, supporting the usefulness and reliability of the proposed approach. [ABSTRACT FROM AUTHOR]

The objective of this paper is to investigate the springback of spatial tubes. The model for analyzing the springback of spatial tubes in [1] is extended to different loading modes and hardening materials. Comparisons among theoretical model, FEM model and experiments are performed to validate the effectiveness of the predictions. Results show that the new model is more effective to describe the springback behavior of spatial tubes, and the principles obtained by the new model are coincident with previous researches. Based on the theoretical model, the influence of loading modes on spatial tube springback is newly investigated. It is found that radii after springback and angles after springback will both increase accordingly with the increasing of loading index k . And evaluating the loading index k reasonably is beneficial for improving the precision of prediction results. [ABSTRACT FROM AUTHOR]

The resonance dynamics of a dissipative spring-mass and of a dissipative spring-pendulum system is studied. Internal resonance case is considered for the first system; both external resonances and simultaneous external and internal resonance are studied for the second one. Analysis of the systems resonance behavior is made on the base of the concept of nonlinear normal vibration modes (NNMs) by Kauderer and Rosenberg, which is generalized for dissipative systems. The multiple time scales method under resonance conditions is applied. The resulting equations are reduced to a system with respect to the system energy, arctangent of the amplitudes ratio and the difference of phases of required solution in the resonance vicinity. Equilibrium positions of the reduced system correspond to nonlinear normal modes; in energy dissipation case they are quasi-equilibriums. Analysis of the equilibrium states of the reduced system permits to investigate stability of nonlinear normal modes in the resonance vicinity and to describe transfer from unstable vibration mode to stable one. New vibration regimes, which are called transient nonlinear normal modes (TNNMs) are obtained. These regimes take place only for some particular levels of the system energy. In the vicinity of values of time, corresponding to these energy levels, the TTNM attract other system motions. Then, when the energy decreases, the transient modes vanish, and the system motions tend to another nonlinear normal mode, which is stable in the resonance vicinity. The reliability of the obtained analytical results is confirmed by numerical and numerical-analytical simulations. [ABSTRACT FROM AUTHOR]

This paper investigates the behavior of a non-linear mechanical model where a block is driven by an oscillating ground through Coulomb friction, a linear viscous damper and a linear spring. The governing equation is solved analytically for different partial configurations: friction only, friction with viscous damping, friction with a linear restoring force, and for the complete model. Using dimensionless groups, the analysis of the block motion provides a comprehensive set of information on the motion regime (stick, stick-slip or permanent sliding), on the dominant energies or forces, on the resonance and on the amplification of the ground oscillation by the system. The limit between the stick-slip regime and the permanent slipping regime is found either analytically or numerically. It is also shown that there exists a set of parameters for which the friction force, the viscous dissipative force and the elastic restoring force are equal. [ABSTRACT FROM AUTHOR]

The quality of springs depends on the rod surface. Requirements to the surface quality and depth of decarbonized layer of hot rolled coils are becoming stricter. Allowable depth of partial/complete decarbonization layer is 0,14/0,03 mm. The most common methods for preventing growth of decarbonized layer is controlled steel heating and metal forming control. Using controlled heating we can not always ensure that the depth of the decarbonization layer is not exceeded. The aim of the study is to control the uniformity of deformation to reduce the thickness of the decarbonized layer. This article focuses on roll pass design optimization (the width, height and angle of fillet) for intermediate stands and for finishing high-speed stands block (Danieli "BGV"). During experimental rolling in the new way of deformation in a volume of more than 50 tons, there was no sticking of metal in the stands, and final sizes of rolled round product with 14 mm diameter were within the existing tolerances for products (±0.3 mm). The result of using a new roll pass design configuration was the production of rolled products with high surface quality; and in the future, we have a possibility to produce automotive coil springs meeting high performance requirements. [ABSTRACT FROM AUTHOR]

The study of composite leaf springs has been popular in automotive light weighting. Particularly, the research on the fatigue reliability of composite leaf springs is crucial. This paper proposed the fatigue law inference of the parabolic composite leaf spring, which was validated by fatigue bench tests. On the bases of the ply scheme design method and the sandwich unit concept, the non-continuous layer section and the stacking order were presented. The stacking sequence was optimized using Genetic Algorithm. The production of composite leaf spring samples, on which the fatigue bench test was conducted, was based on the optimized ply scheme. Results indicate that the fatigue life of composite leaf springs can be improved by using the proposed ply scheme design method. [ABSTRACT FROM AUTHOR]

A model of a one-dimensional mass-spring chain with mass or spring defects is investigated. With a mass defect, all oscillators except the central one have the same mass, and with a spring defect, all the springs except those connected to the central oscillator have the same stiffness constant. The motion is assumed to be one-dimensional and frictionless, and both ends of the chain are assumed to be fixed. The system vibrational modes are obtained analytically, and it is shown that if the defective mass is lighter than the others, then a high frequency mode appears in which the amplitudes decrease exponentially with the distance from the defect. In this sense, the mode is localized in space. If the defect mass is greater than the others, then there will be no localized mode and all modes are extended throughout the system. Analogously, for some values of the defective spring constant, there may be one or two localized modes. If the two defected spring constants are less than that of the others, there is no localized mode. [ABSTRACT FROM AUTHOR]

Cam mechanisms are integral parts of many products. They are used in many applications from combustion engines through milling machines to fitness machines. As suggested by their range of applications, it is an important issue. In this article the configuration of a mechanism, comprising a flat faced follower, which is pressed to the surface of a radial cam by the coil spring, is studied. On the basis of the known lifting function (the results of previous work) a new cam profile will be proposed. Lifting functions are of a polynomial character. Particularly, a cubic polynomial, the fifth degree polynomial and the seventh degree polynomial will be studied. Subsequently, there will be proposed a methodology for the calculation of torque according to the desired angular velocity of the cam. This methodology will be used for choosing a suitable electric motor and for a proper selection of coil springs. The spring preload will be determined with intention to avoid the rebound of the follower from the cam surface. Based on the analytical analysis a new measuring stand will be proposed. In future, the analytical results will be complemented by experiment. [ABSTRACT FROM AUTHOR]

This paper considers an inverse mixed eigenvalue problem for a damped spring-mass system. The problem of reconstructing the vibration system from its partial physical parameters, complex mode and a real mode of the corresponding undamped system is considered. By solving a kind of quadratic inverse eigenvalue problems, the necessary and sufficient condition for the solvability of the problem is obtained, and a numerical method for solving the problem is proposed. The numerical example shows feasibility of the method. [ABSTRACT FROM AUTHOR]

To investigate the dynamic behavior of laminated plates with nonlinear elastic restraints, a varied constraint force model and a systematic numerical procedure are presented in this work. Several kinds of typical relationships of force-displacement for spring are established to simulate the nonlinear elastic restraints. In addition, considering the restraining moments of flexible pads, the pads are modeled by translational and rotational springs. The displacement- dependent constraint forces are added to the right-hand side of equations of motion and treated as additional applied loads. These loads can be explicitly defined, via an independent set of nonlinear load functions. The time histories of transverse displacements at typical points of the laminated plate are obtained through the transient analysis. Numerical examples show that the present method can effectively treat the geometrically nonlinear transient response of plates with nonlinear elastic restraints. [ABSTRACT FROM AUTHOR]

A model for randomly distributed, unidirectional, short-fiber composites with the spring layer model of interphases is presented and evaluated by means of numerical examples. It combines the notion of the energy-equivalent inhomogeneity and the method of conditional moments, proposed to evaluate the effective properties of random composites. The model leads to closed-form solution for effective properties of the composite. Given that the results for short-fiber composites with interphases do not appear to exist in the literature, the verification of the proposed methodology was possible through comparisons with the solutions for composites with infinite fibers. The limit values of the results developed here for short fibers are in an excellent agreement with those available in the literature for infinite fibers. [ABSTRACT FROM AUTHOR]

Free vibrations of elastic arches with rectangular cross sections are studied. The arches under consideration have piece wise constant dimensions of the cross section. Moreover, the arches are weakened with cracks of given extension. The influence of crack parameters on the natural frequencies is established by the method of a rotational spring. [ABSTRACT FROM AUTHOR]

The paper presents the design of a manipulator for servicing the elements of water and sewage infrastructure, in particular for installation and dismantling of pressure transducers without the need for earthmoving. To build this device the resilient elements, cold shaped, responsible for centering the manipulator in the technical tube were used. In their construction a method was applied of estimating the value of residual stresses in the cold shaped material, based on measurements of instrumental hardness. The experimental verification of numerical simulation of instrumental hardness measurements of flat springs made of 1.1274 steel is described. [ABSTRACT FROM AUTHOR]

This paper proposed a method used to analyze the motion of hammer-driven type penetrators and built a testbed for validating the result of structure optimization of the penetrator in deep space exploration. This method gave a clear understanding of the working principle of the penetrator. The penetrator mainly comprises five components: hammer element, suppressor element, housing element, brake spring, and force spring. Based on the structure of the penetrator, the maximum forward movement of housing element was chosen as optimal object. In order to describe the working process clearly and properly, the working stroke was divided into three phases: unlocking phase, colliding phase, and penetrating phase. In each phase, the displacement and velocity of hammer element, suppressor element, and housing element were described with equation sets when numerically solved. Then, the corresponding parameters of the penetrator were obtained in the testbed with high-speed camera. At last, comparing the parameters obtained by theoretical analysis with that obtained by experiment test with high-speed camera, the perfect ratio of mass element (hammer element, suppressor element, and housing element) and perfect ratio of stiffness of spring element (brake spring and force spring) were obtained. [ABSTRACT FROM AUTHOR]

In this paper, effect on spring back values of different materials before and after laser bending are studied. Four different alloys were selected for laser bending test: Aluminum Alloy Al-5052M, Stainless Steel Alloy-304M, Low Carbon Steel (perpendicular rolling direction) and Titanium Alloy Ti-6Al-4V (TCL4). Thickness of alloys sheet is almost same. The influence of different mechanical parameters like tensile strength and hardness on spring back values before and after pre-loaded laser bending were analyzed. The results were compared which showed that Al-alloys has large amount of spring back even at small amount of displacement before laser bending which is due to their low tensile strength. But after laser bending titanium alloys have high value of spring back as compare to before pre-loaded laser bending value proving that this laser bending technique can be a useful method for those alloys which are not easy to deform at normal temperature. [ABSTRACT FROM AUTHOR]

This work analyzes the influence of electromagnetic stiffness on coupled micro disturbance behavior of 32 and 64 subdivisions (SD) Solar Array Drive Assembly (SADA). The problem geometry consists of SADA supporting and operating rigid load through transmission shaft. Mathematical model of stepper motor, used as SADA, with two phases and four beats is developed to determine output excitation torque and electromagnetic stiffness. Keeping in view the reduction ratio, number of rotor teeth, beats and subdivisions; active and dead load SADA vibration model is developed. Rigid load operated by SADA is approximated into motor torsional spring moment of inertia dynamic system to obtain frequency response of mechanical configuration. The developed mathematical model contains information about moment of inertia of load, stiffness of electromagnetic spring, stiffness of transmission shaft and moment of inertia of SADA rotor. Results obtained from analytical calculations are validated by experimentation and simulations run in Matlab/Simulink. Analysis reveals that increase of electromagnetic stiffness, subdivisions number and rotor teeth leads to increase in stability of SADA operated system. The research lays a firm basis for study on vibration attenuation and analysis of SADA disturbances during in orbit operations. [ABSTRACT FROM AUTHOR]

A Power Assist Suit (PAS) for agricultural work was developed in this study. The objective is to reduce the strain involved in agricultural labor by mounting motor- and spring-assisted mechanisms on the PAS. However, such mounting might affect the operation of the PAS. Hence, an evaluation method that uses the degree of freedom (DOF) of the joint motions defined on the basis of the operable range of motion of the human body with the limbs in basic positions is proposed as an indicator of the ease of mobility. The articular structure of the PAS for agricultural work was evaluated using this method, and the feasibility of the labor-assist mechanisms was examined by analyzing the motions. The mechanisms reduced the labor involved in fruit tree pruning, which requires lesser joint motions. [ABSTRACT FROM AUTHOR]

This work is a comparison of the calculated and experimental natural frequencies of coil springs under the action of axial tension-compression. To calculate the coil springs, the finite element form of a single coil is proposed. The initial stiffness matrix and initial mass matrix are calculated by the differential equations of Kirchhoff-Clebsch. The co-rotational approach of single coil finite element is provided to make it applicable for calculating the changing stiffness matrix and changing mass matrix of the coil springs with initial deformations. The frequency and the form shape of the nature oscillation of coil spring are calculated as well. In addition, the comparison with experiment results show the high accuracy. [ABSTRACT FROM AUTHOR]

A general formulation of the static deflection under an axial force is required for accurate static, buckling and dynamic analyses. Even today, however, the helical spring formulas derived in 1960s still continue to be used in the spring design. So designers maintain to design helical springs with limited options in making a change in both the helix pitch angles and cross-section types. In this study, in order to carry out such formulation and get closed-form solutions for the vertical tip deflection, Castigliano's first theorem is directly employed to the linear elastic problem of cylindrical helical springs with large pitch angles. Derivation takes into account for the whole effect of the stress resultants such as axial and shearing forces, bending and torsional moments on the deformations. Cylindrical helical springs having doubly symmetric cross-sections such as a solid/hollow circle, a square, a horizontal/vertical rectangle, and a horizontal/vertical ellipse made of isotropic and homogeneous linear elastic materials are all handled in this work. For each shape of cross-section considered in the study, a closed form global formula in a compact form is offered for users with the common notations and common design parameters as currently used. These formulas may be directly used without hesitation for both closed-coiled (CC), α ≤ 10 ° , and open-coiled (OC), α ≥ 10 ° , cylindrical helical springs. That is one may use those formulas without the need for any extra information than he already has and without involving any design chart and correction factor. Some of formulas derived in this study are compared to the commonly used formulas in the available literature. It is verified that those formulas may be obtained readily from the present formulas by considering their certain assumptions. Benefits of this study related to previous ones are also discussed. Present global formulas are also verified with available recent experiments and finite element solutions. The groundwork for the data to be used directly in Castigliano's first theorem was obtained by using differential geometry of a helical structure from a general spatial rod, and governing equations derived by using equilibrium equations, constitutive equations and geometrical compatibility relations in vector forms. As a result, the author expects that a designer is to be free to design more accurate springs by using the global analytical formulas presented in this study. [ABSTRACT FROM AUTHOR]

A weak spring is connected to the end of a rotor rotating at constant angular velocity. The spring extends to a stretched length as determined by the spring mass, rest length, spring constant, rotor radius, and rotor angular velocity. When released from the rotor, captured video shows the inner end of the spring pulling away as expected, causing a wave to travel down the spring as it collapses. During this collapse, the outer end of the spring continues to move along its original circular path in uniform circular motion, as if the spring were still connected to the rotor. Values from a numerical model and measurements from video analysis show that after release the inner end travels along a circle of similar radius as the outer end. Simulation results are presented that agree with the video analysis. [ABSTRACT FROM AUTHOR]

A complex yet realistic nonuniform rolling friction force distribution of a spring-rolling isolation system could lead to great complexity in determining its seismic response. This paper investigates the isolation performance of a spring-rolling isolation system assuming that the rolling friction force gradually and linearly increases with the relative displacement between the isolator and the ground. A series of ground motions with different characteristics were applied to this system. The analysis results show that the considered concavely distributed friction force is capable of dissipating the earthquake energy, and it is also able to modify the structural natural period. These merits combined help to improve the isolating efficacy of the spring-rolling isolation system compared with scenarios with uniform distribution pattern, and more importantly lead to a relatively optimum isolation state, avoiding a sudden amplification of the structural seismic response, regardless of the input motion characteristics. [ABSTRACT FROM AUTHOR]

It proposes a variant of calculation which highlights the electrical nature Theory of Sonics. [ABSTRACT FROM AUTHOR]