Liquid–(Solid + Liquid) Transitions in a Two-Component System of (CH 3 )CCl 3 + CCl 4

Liquid–(solid + liquid) transitions are studied in (CH3)CCl3 + CCl4 by using the Landau phenomelogical model. The Gibbs energy is expanded in terms of the orientational disorder (OD) parameters for the transitions of the liquid–(rhombohedral + liquid) and liquid–(face-centered cubic + liquid) in a two component system of (CH3)CCl3 + CCl4. From the Gibbs energy, the phase line equations are derived for the transitions studied and they are fitted to the observed T–X phase diagram of (CH3)CCl3 + CCl4 for the concentration (X) CCl4. Temperature and concentration dependences of the OD parameters (Ψ and η) and the inverse susceptibility ($$\chi_{\psi }^{ - 1}$$ and $$\chi_{\eta }^{ - 1}$$) for the two transitions of interest, are predicted by using the melting curves of (CH3)CCl3 + CCl4 on the basis of the Landau phenomenological model. Our predictions, which can be compared with the experimental data, indicate that the first order transition of the liquid–(solid + liquid), in particular, for (CH3)CCl3 + CCl4 can be described satisfactorily by the Landau mean field model.     

Acoustic radiation from the elastic impact of a sphere with a slab

The transient sound radiation from the impact of a spherical object with a slab is analysed theoretically and compared with experimental results. It is shown that the major source of sound radiation when a sphere impinges on a massive plate is due to the sudden change of velocity of the sphere. By using the method of images, an analytical expression predicting the sound pressure waveform is obtained. Experimental results confirm the theoretical analysis and provide further explanation of this rigid body type of acoustic radiation.     

Radial oscillations of nonhomogeneous,thick-walled cylindrical and spherical shells subjected to finite deformations

The infinitesimal breathing motions of long cylindrical tubes and hollow spherical shells of arbitrary wall thickness subjected to a finite deformation field caused by uniform internal and/or external pressures are investigated. A neo-Hookean material with a material constant varying continuously along the radial direction is used. The shell is first subjected to finite static deformations and is then exposed to a secondary dynamic displacement field. Based on the theory of small deformations superposed on large deformations, closed form expressions are obtained for the frequency of small oscillations about the highly prestressed state. Frequency versus initial deformation parameter curves are given for several nohomogeneity functions and for various wall thicknesses.     

Accuracy and convergence of element-by-element iterative solvers for incompressible fluid flows using penalty finite element model

The ability of two types of Conjugate Gradient like iterative solvers (GMRES and ORTHOMIN) to resolve large-scale phenomena as a function of mesh density and convergence tolerance limit is investigated. The flow of an incompressible fluid inside a sudden expansion channel is analysed using three meshes of 400, 1600 and 6400 bilinear elements. The iterative solvers utilize the element-by-element data structure of the finite element technique to store and maintain the data at the element level. Both the mesh density and the penalty parameter are found to influence the choice of the convergence tolerance limit needed to obtain accurate results. An empirical relationship between the element size, the penalty parameter, and the convergence tolerance is presented. This relationship can be used to predict the proper choice of the convergence tolerance for a given penalty parameter and element size.     

Shock measurement with non-contacting fiber optic levers

The displacement, velocity, and acceleration performance limits of a non-contacting fiber optic lever vibration transducer are quantified. Performance characteristics are experimentally verified and measurements of displacement, velocity, and acceleration obtained from impacted plates are compared with those obtained by using conventional accelerometers. It is shown that all relevant transducer quantities, i.e., absolute maximum and minimum levels, dynamic range, and frequency response, lend themselves to quantification (or optimization) on a single graphic representation. The transducer is particularly useful for measuring high frequency shock parameters.     

Unstable capillary flow of reinforced polymer melts

The injection capillary flow of various unfilled and glass fibre or calcium carbonate filled polypropylene and nylon 6.6 melts is studied using either a single capillary of five capillaries in series, separated by small reservoirs. Only unfilled nylon 6.6 yields instability during flow through a single capillary due to mechanochemical degradation in the capillary at extremely high shear rates above 5 × 10⁵ s^?1. It is found that only short glass fibre reinforced polypropylene yields high frequency oscillations in the reservoir pressure and extrudate diameter and has discontinuity in the flow curve when the apparent shear rate is above 4 × 10⁵ s^?1 and the flow is through multiple capillaries. Further increase in the shear rate restores the stable flow. The intensity of the oscillations and the range of shear rate during which unstable flow occurs are increased with increasing melt temperature. The mechanism of this unstable flow is investigated by studying fibre orientation at the capillary entrance and exit using mouldings simulating capillary entry-exit flows.     

Frequency intermittency and energy pumping by linear attachments

The present paper considers the problem of realizing an effective targeted energy pumping from a linear oscillator to a set of ungrounded linear resonators attached to it. Theoretical as well as numerical results demonstrate the efficacy of using a complex attachment as a passive absorber of broadband energy injected into the primary structure. The paper unveils also the existence of an instantaneous frequency associated with the master response characterized by intermittency: a rather surprising result for a linear autonomous system. Comparison with nonlinear energy sinks demonstrates that the two systems have some analogies in this respect and that the linear complex attachment is a very efficient energy trap.