Search

To investigate the mechanical behavior of bidirectional spring units used as isolators in a kind of isolated floor system, three types of characterization tests were conducted--from spring components alone to the complete spring unit in its implemented configuration. The test results show that the behavior of the springs and spring units is stable when subjected to cyclic repeated motions, and is not sensitive to the velocity of motion. The hysteretic behavior of the spring units was found to be unconventional, with bilinear and different ascending (loading) and descending (unloading) branches. Based on the experimental behavior, a physical model was developed to replicate the unique behavior of such bidirectional spring units. Good agreement was found from the comparison between the results from the physical model and the corresponding tests. Finally, a sensitivity study, with respect to the model's four primary defining parameters, shows that this physical model is more sensitive to the sliding friction coefficient between the spring cable and the bushing in the spring unit than to the other three parameters. DOI: 10.1061/(ASCE)ST.1943-541X.0000187 CE Database subject headings: Structural engineering; Seismic design; Earthquakes; Isolation; Models; Floors. Author keywords: Structural engineering; Seismic design; Earthquake; Isolation; Models; Floor isolation; Spring unit.

Cylindrical compression spring behavior has been described in the literature using an efficient analytical model. Conical compression spring behavior has a linear phase but can also have a nonlinear phase. The rate of the linear phase can easily be calculated but no analytical model exists to describe the nonlinear phase precisely. This nonlinear phase can only be determined by a discretizing algorithm. The present paper presents analytical continuous expressions of length as a function of load and load as a function of length for a constant pitch conical compression spring in the nonlinear phase. Whal's basic cylindrical compression assumptions are adopted for these new models (Wahl, A. M., 1963, Mechanical Springs, Mc Graw-Hill, New York). The method leading to the analytical expression involves separating free and solid/ ground coils, and integrating elementary deflections along the whole spring. The inverse process to obtain the spring load from its length is assimilated to solve a fourth order polynomial. Two analytical models are obtained. One to determine the length versus load curve and the other for the load versus length curve. Validation of the new conical spring models in comparison with experimental data is performed. The behavior law of a conical compression spring can now be analytically determined. This kind of formula is useful for designers who seek to avoid using tedious algorithms. Analytical models can mainly be useful in developing interactive assistance tools for conical spring design, especially where optimization methods are used. [DOI: 10.1115/1.2338580] Keywords: constant pitch conical spring, analytical models, nonlinear, fourth order polynomial

This paper presents within the scope of the theory of static elasticity a derivation of soil spring constant in longitudinal direction of a buried pipeline in the seismic design. It is found that the spring constant depends on the shear modulus G of the soil deposits and the ratio (lambda) of the radius of zero displacement over the radius of a buried pipeline structure. When (lambda) increases, the soil spring constant decreases and the decreasing rate reduces remarkably when (lambda) is greater than about 10. The ratio of soil spring constant over G is 2.7 when (lambda) = 10. Furthermore, the dynamic effect of soil spring constants on buried pipeline structures is estimated analytically by the dynamic theory of elasticity. The soil spring constant that is derived, taking into account the boundary condition of ground surface, depends on the shear modulus G of the ground, nondimensional frequency (omega)b/V(sub s) ((omega) = circular frequency; b = radius of buried pipeline; V(sub s) = ground shear-wave velocity) and nondimensional depth d/b (d = depth of pipeline).

A tetrahedral three-spring system under a single load has been analyzed and a closed-form solution for the equilibrium positions is given. Each of the three springs is attached at one end to a fixed pivot in space while the other three ends are linked by a common pivot. The springs are assumed to behave in a linearly elastic way. The aim of the paper at hand was to find out what the maximum number of equilibrium positions of such a system might be, and how to compute all possible equilibrium configurations if a given force is applied to the common pivot. First a symmetric and unloaded system was studied. For such a system it was shown that there may exist a maximum of 22 equilibrium configurations which may all be real. Second the general, loaded system was analyzed, revealing again a maximum of 22 real equilibrium configurations. Finally, the stability of this three-spring system was investigated. A numerical example illustrates the theoretical findings.

A small perturbation theory helps study the joint effect of orifice flow and heat exchange on piston power release within a gas spring and establishes the association between piston displacement and gas spring pressure disturbance. The piston power depends separately on orifice dissipation and second-order transport when balanced in terms of pressure disturbances.

Scanning force microscopy springs, whose shape was modified to lower the influence of photon shot noise in the optimal beam deflection method, incorporated sharp tips. A process associated with the controlled fracture of micromachined structures was developed to incorporate these tips in the springs and the tips exhibited excellent performance when employed to image individual collagen molecules.

Experiments were performed on a piston-cylinder gas spring. Speed, cyclic mean pressure, gas, bore/stroke ratio, volume ratio, and internal extended surface geometry were varied. Hysteresis loss, pressure wave magnitude, and pressure-volume phase shift were measured. Nondimensional variables were found to correlate results, and a theoretical model was found to predict results well, over most of the operating range.

The results of a finite element analysis of the effects of material nonlinearity on the load-deflection curve and the stress field of conical disk springs is given. Two disk springs with a thickness of 2.7 mm and 5 mm are studied using finite element models with 4 nodes. Displacement loads are then applied at the upper inner edge of the spring. Results show that the material nonlinearity altered the load-deflection curve which is unlike the Almen-Laszlo curve. The stresses generated do not also agree with theoretical data. The tangential stress has a value between the yielding stress and the residual traction stress after the first cycle.

The coupled free vibration of helical springs is investigated. The study uses simple theories in which the spring behaves as a homogenous rod with altered elastic and mass characteristics. Results show that there are two waves spreading through the spring. The periodic ratio of the waves is almost a constant and the difference between the two period is small. This induces beat phenomenon in the free vibration causing it to look periodic.

Byline: M. Zigo In this paper we describe how to choose the physical properties and shape of rubber springs to each their extreme values. This choice would guarantee optimal dynamic properties of a resilient supported periodic vibration source, in the frequency range under audio-frequency.

Byline: Taehong Kim, Wonkyu Moon, Sungsoo Kim Influences of the shapes of spring leaves in a progressive multi-leaf spring were investigated using the semi-analytic model based on the Euler beam theory and the FEM model using ABAQUS. The trends in shifting of the locations of the contact point are found to change with the shapes of spring leaves. A change in the shapes of the spring leaves causes a change in the transition load of the stiffness of a progressive multi-leaf spring. If there is a quantum jump of the contact point locations, a noise, which was absent, can be generated. It is suggested from the analyses based on the models and verified experimentally that the noise is generated by a small collision between the main and the help spring leaves when the contact point between them is shifted to a location at a finite distance. The influences of the leaf shape can be predicted more efficiently with the Euler beam model used in this investigation.

The present study reports a theoretical analysis on Belleville springs with linearly variable thickness (radially tapered disk springs). The analysis aimed at the solution of two different problems: the realization of a spring with a zone of null slope in the stiffness curve (i.e. with the possibility of having different values of the deflection at a constant load, particularly useful in some regulation processes), and the definition of a disk spring with an almost constant stress state (with the stress linearly variable from the neutral axis to the upper and lower surfaces). Based on the hypothesis of Almen-Laszlo and CurtiOrlando-Podda, the theoretical analysis give the values of the stiffness curve and the stresses as a function of the geometrical parameters and allowed both problems to be resolved, clearly with different values of the geometric parameters. In order to Compare the stresses obtained for large deflections, the authors constructed a numerical model which validated the theoretical analysis. [DOI: 10.1115/1.1357162]

The steady-state response of the classic mass-spring-dashpot model when the spring stiffness decays exponentially with time (an aging spring) and the system is excited by a forcing function whose frequency is equal to the natural frequency of the system with the constant initial stiffness is investigated. The steady-state response is obtained in terms of the damping and decay constants of the system and exhibits an oscillation about a nonzero value. [DOI: 10.1115/1.1458559]