The transient waves caused by a line heat source with a uniform velocity inside isotropic homogeneous thermoelastic perfectly conducting half-space permeated into a uniform magnetic field are studied. The formulation is applied under three theories of generalized thermoelasticity: Lord-Shulman theory with one relaxation time, Green-Lindsay theory with two relaxation times, as well as the classical dynamical coupled theory. The problem is reduced to the solution of three differential equations by introducing the elastic and thermoelastic potentials. The normal mode analysis is used to obtain the expression for the temperature, displacement components and the thermal stresses. Numerical results are given and illustrated graphically. Comparisons are made with the results predicted by the three theories in the presence and absence of magnetic field and the internal heat source.
In the context of Lord and Shulman theory, the generalized thermoelastic theory with thermal relaxation is used to investigate the thermoelastic interaction in an infinite fibre-reinforced anisotropic plate containing a circular hole. Thermoelastic interactions are caused by a uniform step at temperature applied to the boundary of the hole which is stress-free. The problem is solved numerically using a finite element method and the numerical solutions of the non-dimensional governing partial differential equations of the problem are shown graphically. The effects of the presence and absence reinforcement on temperature, stress and displacement are studied.
We describe here structure and temperature dependences of conductivity σ(T), the Seebeck coefficient α(T), thermal conductivity λ(T) and figure-of-merit ZT(T) in Ca_3Co_4O_9 ceramics, doped with Fe and Y, depending on compacting pressure (0.2 or 6 MPa) and temperature (300 < T < 700 K). It is shown that introduction of iron and yttrium to ceramics does not alter the crystalline structure of the material. Increasing the pressure in the compacting process before the additional diffusion annealing leads to a smaller-grained structure and increase σ and λ due to reducing of the synthesized samples porosity. The Seebeck coefficients of nanocomposite ceramics Ca_3Co_{3.9}Fe_{0.1}O_9 and (Ca_{2.9}Y_{0.1})(Co_{3.9}Fe_{0.1})O_9 have linear dependences on temperature is not changed after increase of compacting pressure. Electrical-to-heat conductivity ratio (σ/λ) for the samples compacted at high (6 GPa) pressure increases not more than 20-30% in comparison with ones compacted at low (0.2 GPa) pressure, whereby ZT is increased more than 50%. The main reason for this effect is samples porosity reduction with the compacting pressure increase.
In the paper the results of investigation on tensile stresses dependence of magnetoelastic characteristics of cores made of 13CrMo4-5 constructional steel are presented. In the investigation step-cooling test treated samples were used. The step-cooling test process is a type of heat treatment simulating effects of passing time and environmental conditions (temperature and stress) on the sample. In the paper the method of testing the influence of stresses on the magnetic characteristics is presented. Frame shaped samples ensured a closed magnetic circuit and homogeneous distribution of stress. It was found that step-cooling test does not significantly influence the magnetoelastic characteristics and the structure of the samples. On the other hand, then tensile stresses significantly change the magnetic characteristics of 13CrMo4-5 constructional steel. That confirms the possibility of using measurements based on the magnetoelastic effect in the stress assessment for industrial non destructing testing of steel constructions.
The paper presents results of research on the effects of mechanical stresses on the magnetostrictive properties of 13CrMo4-5 steel. Measurements of stress dependence of magnetostriction fill the gap in the state of the art enabling description of relationships between stresses applied to the samples and its magnetoelastic and magnetostrictive properties. Performed studies represent the starting point for development of unified model of both Villari (magnetoelastic) and Joule (magnetostrictive) effects under stresses in steels. The formulated model will be the basis for the development of generalized methods of interpreting the results of non-destructive testing of the state of the internal stresses in steels based on these phenomena.
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.