Andrzej Drzewiecki

Thermoelastic damping in an auxetic rectangular plate with thermal relaxation—free vibrations

This work describes an extended thermodynamical model to represent coupled thermomechanical interactions in continuum media having negative Poisson?s ratio. In particular, the Zener thermoelastic damping effect is considered for a plate with auxetic characteristics undergoing free vibrations. The extended thermodynamical model is characterized by a thermal relaxation time to avoid the propagation of thermal waves at infinite velocity. The thermal relaxation time used in this work is not Zener?s characteristic time constant. Strong dependence of the thermoelastic damping is observed for auxetic configurations, various plate thicknesses and ambient temperatures.

Anomalous Features of the Thermomagnetoelastic Field in a Vortex Array in a Superconductor: Propagation of Love'S Waves

A magnetic field enters a type-II superconductor along an arrangement of Abrikosov vortices. They interact with each other with the help of the Lorentz force creating a new mechanical field different from that coming from the crystal lattice of a superconducting material. That new field presents some anomalous properties as compared to the classical ones of the material. This article deals with a modeling and description of a number of those anomalous features of a vortex field in a superconductor.

Magnetoelastic surface waves in auxetic structure

In modern technologies searching materials of peculiar features is of a fundamental interest for many researchers and engineers. Negative Poissons ratio materials and structures expand transversely when stretching axially. Nowadays, there is an increasing interest in the development of these novel materials called auxetics. We are interested not only in their mechanical properties, but also in their interaction with external physical fields, e.g. electromagnetic field. It is expected that magnetoelastic surface waves propagation has essential meaning in many other physical and biomechanical applications. The paper aims at investigating propagation of magnetoelastic surface waves along an auxetic elastic halfspace in the presence of an external magnetic field of various orientations related to the limiting plane. Dispersion and existence conditions of those waves have been calculated and analyzed in order to present new features of described interactions. It has occurred that the dispersion properties in the case of the Rayleigh-like magnetoelastic surface waves are significantly different for the auxetic material compared to materials of positive Poissons ratio.

Thermoelastic Damping and Thermal Relaxation Time in Auxetics

The paper concerns description of the thermoelastic phenomenon in an auxetic rectangular plate within the extended thermodynamical model. Analyzing vibrations of that plate a dependence of elastic constants on the frequency, particularly of Poissons ratio of auxetic state of the body has been presented. Moreover, considered investigations allow to determine the thermal relaxation time analyzing resonance frequencies of the vibrating plate.

Mechanical (acoustic‐like) wave propagation along a vortex array in the superconducting heterostructure

Magnetic flux can penetrate the type ‐ II superconductor in the form of Abrikosov vortices (also called flux lines, flux tubes or fluxons) each carrying a quantum of magnetic flux. These tiny vortices of supercurrent tend to arrange themselves in a triangular or quadratic flux‐line lattice. Since the vortices are formed by the applied magnetic field, around of each of them the supercurrent flows. Moreover, there also exist some Lorentz force interactions among them. Those interactions form an origin of an additional mechanical (stress) field occurring in the type‐II superconductor. The paper deals with an analysis of elastic (acoustic‐like) wave propagation solely along vortices in a heterostructure consisted of the superconducting layer put on the superconducting substrate. Dispersion and the amplitude distribution of those waves in the vortex field existing in that structure has been presented.

Amplitude distribution of magnetoelastic waves propagating in a vortex field in a superconducting layer

Magnetic field enters the type ‐ II superconducting body along a discrete arrangement of magnetic vortex lines. In the dynamic case when the magnetic field vary in time, around each such a line a supercurrent flows. So, the vortices interact one to another with the help of the Lorentz force forming this way a new mechanical field of elastic properties. Moreover, those lines arrange themselves in a triangular or quadratic lattice. Such a set is observed if the intensity of the applied to the material magnetic field is close to its lower limiting value. The paper aims at investigating amplitude distributions of magnetoelastic waves propagating solely in the vortex field of the superconducting layer. Our attention have been focused on the applied magnetic field intensity influence on those amplitudes for various wave frequencies.