摘要:

A method developed previously for an analysis of the two‐dimensional excitation of an elastic cylindrical shell by a transverse, transient acoustic wave is extended to three‐dimensional applicability. In addition, some fluid‐structure interaction approximations are presented that follow naturally from the rigorous development. Application to finite element analysis of the transient response of submerged structures is discussed.

ISSN:0001-4966    

DOI:10.1121/1.1912526

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The frequency equation for trains of axisymmetric harmonic waves traveling in infinitely long three‐layered circular cylindrical shells and rods is established on the basis of the three‐dimensional theory of elasticity. The shells or rods are assumed to be made of three concentric cylinders, each of different isotropic material, bonded perfectly at their interfaces. The frequency equation has been evaluated numerically on an IBM 7044/7094 DCS system, and the effect of the geometric and physical parameters of the three‐layered shells on the frequency of the first few modes is illustrated. The limits that the phase velocities of the various modes of propagation approach asymptotically at large wavenumbers are established analytically and verified by the numerical results.

ISSN:0001-4966    

DOI:10.1121/1.1912527

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

This paper, motivated by the use of “bender” disks with underwater transducers, presents a complete solution of the elastic equations for freely supported thick disks that experience no net radial extension. The solution is complete in that all roots of the frequency equation, both real and complex, are considered when the boundary conditions are satisfied.

ISSN:0001-4966    

DOI:10.1121/1.1912528

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The effects of nonlinear (mixed) damping forces (such as viscous and dry friction damping, combined and separately, on the forced vibration response of a system) are discussed. A recursion procedure is developed to determine the coefficients of the general solution of the equation of motion. This method is then applied to solve asymmetrically damped systems, such as those for which the damping parameters assume different values for forward and backward motion. The results of representative calculations are presented and their significance is discussed.

ISSN:0001-4966    

DOI:10.1121/1.1912529

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

True dynamic similitude in the Newtonian sense proves often to be too restrictive in experimental investigations of dynamic characteristics of large shell structures by use of smaller models. Also, design information yielded by true similitude considerations is limited because of the usual requirement of total geometrical scaling. Thus, approximate similitude relationships were derived starting with Love's equations of motion for thin shells. Depending on the relative dominance of bending and membrane stress influences, selection is made between two similitude expressions. This allows the introduction of shell thickness as a parameter independent of the scaled surface geometry. Free as well as forced vibrations are examined. Some of the implications of approximate similitude are illustrated using as an example a simply supported circular cylindrical shell.

ISSN:0001-4966    

DOI:10.1121/1.1912530

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

A Kirchhoff‐type theory is established for axisymmetric motions of heterogeneous isotropic circular plates. It is shown that a coupled extensional‐flexural inertia term exists, in addition to the classical extensional and rotatory inertia terms. An analogy is found between the composite plate problem and the vibrations of homogeneous shallow spherical shells. The obtained sixth‐order system of equations is solved in closed form in terms of Bessel functions, with an argument determined from a characteristic cubic equation. A transcendental frequency equation is then derived for a circular composite plate with clamped edge conditions. Numerous examples are studied, showing the significant effect of plate heterogeneity on its vibrational response. Possibility of composite systems to transcend the frequencies of the individual constituents is clearly indicated by the theoretical results and checked experimentally.

ISSN:0001-4966    

DOI:10.1121/1.1912531

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

This paper presents a numerical approach to calculating the dynamic behavior of magnetostrictive transducers in the shape of a shell of revolution (for example, a cylindrical ring). The method accounts for the effects of saturation and loss, which are important in magnetostrictive devices. It is applicable to either biased or unbiased transducers. Since most transducers of this type are of a scroll construction, the effects of the alternating layers of magnetostrictive material and epoxy bond are included.

ISSN:0001-4966    

DOI:10.1121/1.1912532

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

For large‐amplitude oscillations, the work presented previously by the authors for single‐layer plates of composite materials, simply supported on all edges, is extended to include laminated plates and six combinations of clamped and simply supported edges. Berger's hypothesis is again used to obtain a set of simplified coupled equations which governs the nonlinear motion of plates. Solutions are obtained using a Ritz‐Galerkin method in which the assumed series are products of beam characteristic functions. In addition, small‐amplitude vibrations are treated as special cases. Numerical results for fully clamped as well as various combinations of clamped and simply supported boundary conditions are presented.

ISSN:0001-4966    

DOI:10.1121/1.1912533

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

A method for predicting underwater explosion shock‐wave pressure histories in caustic regions is described. This method involves the incorporation of various propagation effects, i.e., finite‐amplitude, absorption, and refraction effects, into a Fourier series representation of the initial shock wave from an underwater explosion. Refraction effects are accounted for by the use of a solution to the wave equation derived by Silbiger and Sachs. Pressure histories calculated using this method are compared with experimental results from ocean and flooded quarry tests. For the oceanic convergence zone case, quantitative agreement with the experimental pressure histories is demonstrated. This agreement is verified for a region 4000 ft wide surrounding the caustic. For the flooded quarry case, the peak pressure on and near the caustic is accurately predicted.

ISSN:0001-4966    

DOI:10.1121/1.1912534

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

Weighted‐Gaussian‐quadrature methods are applied to convergence‐zone range integrals without any severe caustic or multipath anomalies. Both flat and curved earth cases are examined. It is shown that in the convergence zone the curved‐earth effects are of the same order of magnitude as the thermocline effects and should be included for a meaningful calculation. Weighted‐Gaussian‐quadrature methods are compared to contemporary methods that approximate the sound‐velocity profile with a piecewise analytic segmented profile. Gaussian‐quadrature methods avoid the class of anomalies that are due to discontinuous derivatives of some finite order at the junction of two segments of the approximated profile. Illustrative numerical examples are included.

ISSN:0001-4966    

DOI:10.1121/1.1912535

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP