Axial Impulse Research Articles

Study on the Performance of Spiral-Grooved Semi-Spherical Air Bearings Using Taguchi Method.

A self-acting air bearing draws surrounding air into the gap between the stator and rotor, and does not need any air pressurizing equipment. This type of air bearing has wide potential application. In this study, parametric and interaction effects on the bearing performance are investigated experimentally and optimal conditions are found for self-acting spiral grooved semi-spherical air bearings using the Taguchi method. The three design parameters are clearance, groove depth and out-of-sphericity. The performance factors are axial runout and axial impulse stiffness. Investigation of the effects of the design parameters shows that high performance is achieved generally for a small clearance. Optimal conditions are found to depend on a performance factor.

Binaural equalization for loudspeaker systems

On-axis equalization methods for loudspeaker systems can be found everywhere. In these schemes, the axial impulse responses are taken as the objects to be equalized. However, the generated equalizers will display unsatisfactory off-axis distortions and different equalization effects at left and right ears. In this paper, a new criterion, which combines the considerations of the distortions at left and right ears and the binaural difference, is presented. A binaural equalization method applying this criterion is introduced and the comparison with normal on-axis equalization methods is also given.

Annular binary filters for controlling the axial behaviour of optical systems

The one-dimensional (1D) version of the iterative Fourier transform algorithm (IFTA) and a modified error diffusion algorithm are proposed for binarizing rotationally symmetric pupil filters designed to shape the axial impulse response of optical system. The resulting binary masks consist of a set of transparent and opaque annular zones of equal area or equal width. A numerical experiment in which we examine the performance of the binarization methods is carried out. In this experiment the resemblance between the axial diffractive behaviour of the binary version of an axially superresolving pupil filter, and that of the original continuous-tone filter is evaluated. It is shown that the performance of the binary mask obtained with 1D IFTA is much better than that of the annular binary filters obtained by other digital half-toning techniques which preserve the rotational symmetry of binarized pupils.

Dynamic buckling of an imperfect spherical shell under an axial impulse

In this paper we determine the dynamic buckling load of an imperfect spherical shell under an impulse and also examine the effects of non-linear terms on the initial post dynamic buckling behaviour of the structure. The results show that: (a) neglecting the axisymmetric and non-axisymmetric imperfections implies neglecting, respectively, the effects of the axisymmetric and non-axisymmetric non-linear buckling mode contributions, and (b) the coupling effects of the buckling modes are felt only if none of the imperfections are zero.

An evaluation of the Kirchhoff approximation in predicting the axial impulse response of hard and soft disks

To test the ability of the Kirchhoff approximation for estimating the various components in the near-field impulse response of a circular disk, the predictions from a time domain formulation of the Helmholtz–Kirchhoff solution [Trorey, Geophys. 35, 762–864 (1970)] are benchmarked against results obtained via the Fourier synthesis of highly accurate frequency domain solutions [Kristensson and Waterman, J. Acoust. Soc. Am. 72, 1612–1625 (1982)]. In these numerical experiments, a collocated point source and receiver lie on the symmetry axis of an acoustically hard (rigid) or soft (pressure release) disk. A time-domain analysis is carried out in order to unambiguously evaluate the Kirchhoff approximation for different components of the scattered field. It is found that, while Helmholtz–Kirchhoff predicts the correct reflected component, it fails to accurately predict the strength of the diffracted component. The magnitude of the error depends on whether the disk is soft or hard and on the source/receiver height above the disk. The error in the diffracted component exceeds, in some cases, 100%. Furthermore, it is observed that the Helmholtz–Kirchhoff approach does not include the secondary or multiply diffracted arrivals which are more pronounced for the hard disk.

Detection of Cracks in Rotating Timoshenko Shafts Using Axial Impulses

A rotating Timoshenko shaft with a single transverse crack is considered. The crack opens and closes during motion and is represented by generalized forces and moments. The shaft has simply supported ends, and the six coupled, piecewise-linear equations of motion (including longitudinal, transverse, and torsional displacements) are integrated numerically after application of Galerkin’s method with two-term approximations for each of the six displacements. Time histories and frequency spectra are compared for shafts with no crack and with a crack for which the crack depth is one-fifth of the shaft diameter. Free vibrations and the responses to a single axial impulse and periodic axial impulses are analyzed. The last case appears to provide an effective means for detecting cracks in rotating shafts.

Influence of side unloading on the radial axial impulse distribution of the explosion of an explosive cylinder

Influence of side unloading on the radial axial impulse distribution of the explosion of an explosive cylinder