End Clamp Research Articles

Boundary discontinuous Fourier analysis of thick cross-ply clamped plates

A new analytical solution to the problem of deformation of a finite-dimensional general cross-ply thick rectangular plate , modeled using a higher order shear deformation theory (HSDT), is presented. A solution methodology, based on a boundary-discontinuous generalized double Fourier series approach, is used to solve a system of five highly coupled linear partial differential equations , generated by the HSDT-based laminated plate analysis, with the C3-type clamped boundary condition prescribed at all four edges. The numerical accuracy of the solution is ascertained by studying the convergence characteristics of deflections and moments of a cross-ply plate. The primary focus of the present study is to investigate the effect of end clamping on the response of a thick laminated plate, while keeping the in-plane end constraints unaltered. Important numerical results presented include sensitivity of the predicted response quantities of interest to lamination , material property, thickness effects and end clamping as well as their interactions.

Asymmetrical properties of a vibrating wire and their effects

Some effects of the asymmetries causing a splitting of the fundamental natural vibrating frequency of a wire have previously been reported [Hanson et al., J. Acoust Soc. Am. 103, 2873 (1998)]. It has been demonstrated in this work on brass harpsichord wire that the splitting of the frequency is due to intrinsic properties of the wire itself and not of asymmetries in the end clamps. The two frequencies are associated with two definite orientations with respect to the wire. These two vibrational directions have been determined to be orthogonal within one degree experimental uncertainty. This orthogonality is in agreement with predictions of a simple model which assumes that, for small-amplitude free vibrations, the observed portion of the wire moves under the action of a linear anisotropic conservative restoring force. Measured splittings for several samples of harpsichord wire have ranged from 0.12 to 0.30 Hz for a frequency of about 70 Hz. The nonlinear effects of generation of motion perpendicular to the driving direction [Hanson et al., J. Acoust. Soc. Am. 96, 1549–1556 (1994)] and generation of higher harmonics are profoundly influenced by the orientation of the driving direction with respect to these vibrational orientations for low-driving forces. Related effects for plucked strings will be discussed.

Mechanical performance of 5-cm-aperture, 15-m-long SSC dipole magnet prototypes

The authors summarize the mechanical performance of the most recent 5-cm-aperture, 15-m-long SSC dipole magnet prototypes. The magnets were produced at Brookhaven National Laboratory (BNL) and Fermi National Accelerator Laboratory (FNAL) under contract with the Superconducting Super Collider Laboratory (SSCL). The BNL magnets rely on a horizontally split yoke with collared ends, while the FNAL magnets rely on a vertically split yoke with collet-style end clamps. Magnets of both designs are equipped with strain gauges enabling measurement of the azimuthal pressures exerted by the coils against the collar poles as well as the axial forces transmitted from the coil ends to the end plates. A comparison of the mechanical behaviors measured by the strain gauges is presented. How the behavior of the 5-cm-aperture magnets compares to that of the 4-cm-aperture prototypes is also discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Mechanical behavior of Fermilab-built 1.5 m model SSC collider dipoles

Several model SSC (Superconducting Super Collider) dipole magnets (50-mm aperture, 1.5-m magnetic length) have been built and tested at Fermilab. These magnets are instrumented with strain gauges to measure stresses in the coil, the cold mass shell, and the coil end clamp assembly. Measurements are made of these quantities during assembly, cooldown, excitation, and warmup. The collar vertical deflection with prestress and the shell azimuthal tension agree quantitatively with design expectations. Coil prestresses within the desired range have been achieved without pole shims. Prestress loss with cooldown compares favorably with 40-mm models. Most of the axial I*B force is transmitted to the shell via collar-yoke-shell friction, and not by compressive loading of the coil end. The yoke parting plane gap remains closed to well above the operating point, and end clamp deflections are >

Tests of Fermilab built 40 mm aperture full length SSC dipole magnets

Several 40-mm-aperture, 17-m-long dipoles have been built by Fermilab as developmental prototypes for the Superconducting Super Collider (SSC). These magnets have an external inner-outer coil splice design, a collet style end clamp assembly, a new, analytically designed minimum stress coil end design, and a new insulation system which does not employ shims or 'shoes'. In addition, the magnets were built using production-style tooling. The magnets were tested at the Fermilab Magnet Testing Facility. Quench testing and mechanical measurement results are presented and analyzed with emphasis on the new design and fabrication features of these magnets. The performance of these magnets was very good from a quench and mechanical behavior standpoint. The magnets did not exhibit excessive training behavior and only one training quench was below the nominal operating current. The coil prestress remained positive to >7 T in both magnets and most of the quenches originated in the high field region of the pole turn.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Localized Intrinsic Strengthening Approach (LISA): A Practical Method for Determining the Tensile Strength of Multistrand Cables

Abstract The problem of stress concentration and the associated premature failure in tension test specimens of multistrand conductors and wire ropes has been overcome through localized cooling of the end fitting with liquid nitrogen. A reliable measurement of the true tensile strength (TTS) of a range of multistrand bodies of interest to electrical utilities has been achieved using a number of commercially available end fittings and clamps. Measured values of TTS have been found to be as much as 22.9% higher than the calculated rated tensile strength (RTS). A standard test method is proposed that is simple and cost effective. The localized intrinsic strengthening approach (LISA) is invaluable in a quantitative evaluation of the efficiency of end fittings and splices, in determining the residual strength of multistrand bodies, and for optimizing the design of conductors and wire ropes.

Section 4-vibration of conductors and overhead ground wires

Among the problems connected with the 220-kv. lines, that of the vibration of conductors and ground wires has claimed its share of attention. On account of the larger diameter of the conductors this phenomenon is clearly visible, and exaggerated reports are frequently received that the conductors are jumping up and down 6 in. or more. There have also been complaints of the rattling of towers, even on still nights. In one instance a conductor failed at the outer end of a dead end clamp and the appearance of the broken strands indicated that vibration might have caused the break. A second conductor was discovered with 28 aluminum strands out of a total of 54 broken at the end of a dead end clamp. Numerous rases of broken ground wires have been found, the strands breaking at the point of attachment to the towers. In a few cases ground wires have fallen but a larger number of broken strands has been discovered by inspection and repaired before complete failure of the cable. These troubles led to an investigation of the vibration problem as it appears in the spans of the Big Creek and Eagle Bell lines. While this investigation has not yet led to definite conclusions as to the cause of vibration and method of preventing it, the information obtained is presented here as a part of the operating record.