Search Results

1 - 10 of 28 items :

  • "thermal expansion coefficient" x
Clear All

Abstract

The paper presents results of systematic tests of contraction and thermal expansion coefficients of materials based on polymer composites. The information on the above material properties is essential both at the design stage and during the use of finished products. Components for the samples were selected in such a way as to represent typical materials used for production of construction and moulding elements. The performed tests made it possible to monitor the analysed parameters at different stages of the technological process.

Abstract

The article describes the basic features of the lightweight floor system with heat-dissipating lamellas (LFS-L) that do not require screeds and are used in the design of radiant heating. It was assumed that reactive polyurethane adhesive constitute the connection layer between the ceramic tile floor and the thermal insulation substrate, which is covered with aluminium foil. This type of construction has not been fully tested for mechanical strength. To define it, for example, using the finite element method, strength indicators of the tested adhesives which were not used in any of the previous studies discussed in this paper should be determined, such as Young’s modulus E, Poisson’s ratio ν and linear thermal expansion coefficient α. This article presents research methods by which these data were determined. Module E and the ν ratio were determined in the compression strength test of cylindrical samples of polyurethane adhesive. Coefficient α was determined by using digital image correlation in the Aramis system, placing the prepared adhesive samples in a thermal chamber.

Abstract

Experimental structural data for liquid Bi were used for estimation of the main structure parameters as well as the thermal expansion coefficient both in supercooled and superheated temperature ranges. It was shown that the equilibrium melt had a positive thermal expansion coefficient within a temperature range upon melting and a negative one at higher temperatures. The former was related to structure changes upon melting, whereas the latter with topologic disordering upon further heating. It was found that the superheated melt had a negative thermal expansion coefficient. The results obtained from structural data were compared with the thermal expansion coefficient calculated from the data of density for liquid Bi.

, the occurrence of large negative volumetric thermal expansion coefficient is possible (very rough estimation leads to a V w -290 x 10 -6 K -1 ). Moreover, the distinct signature of the structural transition appears for V w 1116 a.u. 3 in the E-V curve at 700 K in our LSDA+DMFT calculations ( Fig. 4 ). On the other hand, rapid “softening” of the system is visible for the large volumes of V > 1307.050 a.u. 3 , as well. From the technological point of view, this could mean that the investigated Ce123 crystal structure undergoes very dramatic transitions during the

Abstract

Structural, elastic, electronic and thermodynamic properties of ternary cubic filled skutterudite compound were calculated. We have computed the elastic modulus and its pressure dependence. From the elastic parameter behavior, it is inferred that this compound is elastically stable and ductile in nature. Through the quasi-harmonic Debye model, in which phononic effects are considered, the effect of pressure P (0 to 50 GPa) and temperature T (0 to 3000 °C) on the lattice constant, elastic parameters, bulk modulus B, heat capacity, thermal expansion coefficient α, internal energy U, entropy S, Debye temperature θD, Helmholtz free energy A, and Gibbs free energy G are investigated.

Abstract

The paper presents an investigation on crystalline, elastic and electronic structure in addition to the thermodynamic properties for a CeRu4P12 filled skutterudite device by using the full-potential linear muffin-tin orbital (FP-LMTO) method within the generalized gradient approximations (GGA) in the frame of density functional theory (DFT). For this purpose, the structural properties, such as the equilibrium lattice parameter, bulk modulus and pressure derivatives of the bulk modulus, were computed. By using the total energy variation as a function of strain we have determined the independent elastic constants and their pressure dependence. Additionally, the effect of pressure P and temperature T on the lattice parameters, bulk modulus, thermal expansion coefficient, Debye temperature and the heat capacity for CeRu4P12 compound were investigated taking into consideration the quasi-harmonic Debye model.

Abstract

This paper demonstrates the stress free thermo-elastic problem of the FGM thick plate. Existence of such a purely thermal deformation is proved in two ways. First proof is based on application of the Iljushin thermo-elastic potential to displacement type system of equations. This reduces 3D problem to the plane stress state problem. Next it is shown that the unique solution fulfils conditions of simultaneous constant temperature and linear gradation of thermal expansion coefficient. Second proof is based directly on stress type system of equations which straightforwardly reduces to compatibility equations for purely thermal deformation. This occurs if only stress field is homogeneous in domain and at boundary. Finally an example of application to an engineering problem is presented.

Abstract

The aim of this work is a theoretical study of structural, elastic, electronic and thermal properties of CoGe compound in B20 structure using All-electron self-consistent Full Potential Augmented Plane Waves plus local orbital “FP(L)APW + lo” within the framework of Density Functional Theory DFT. GGA-PBEsol is the exchange-correlation potential selected in this work. This choice is motivated by the success of this functional in predicting structural and mechanical properties of solids. The values obtained by the study of structural properties are in very good agreement with those found previously. In this work, the elastic constants have been predicted for the first time and the obtained values confirm the mechanical stability of the CoGe compound in its B20 structure. The electronic part of this work shows that CoGe has metallic behavior with a mixed bonding between cobalt and germanium of covalent-metallic type. The effect of temperature and hydrostatic pressure on the lattice parameter - a0, heat capacity at constant volume - CV, thermal expansion coefficient - α and entropy - S of the CoGe have been studied using Debye model.

References [1] Ran Zhiguo, Yan Ying, Li Jianfeng, Qi Zhongxing, Yang Lei. Determination of thermal expansion coefficients for unidirectional fiber-reinforced composites. Chinese Journal of Aeronautics 2014 (27), No. 5, 1180 - 1187. DOI: 10.1016/j.cja.2014.03.010 [2] Zdeněk Vlasák, Výpočet tolerovaných rozměrů, Oddyseus, 2004, online: http://www.zvlasak.net/vvystupy/2_3_1/vypocet_tolerovanych%20_rozmeru.pdf [3] MSC-MENTAL, Advanced Nonlinear Simulation Solution, MSC Software Corporation, 2015. [4] R. Halama, A. Markopoulos, M. Šofer, Z. Poruba, P. Matušek. Cyclic

-electro-mechanical cantilever based biosensors, International Symposium on Electronic System Design (ISED) , 34-38. 14. Swartz C., Derrington C., Gragg J. (2004), Temperature compensation methods for the Motorola X-ducer pressure sensor element , Motorola Semiconductor application notes AN840. 15. TENMEX (2016), strain gauges producer webpage, http://www.tenmex.pl . 16. VISHAY Precision Group (2007), Measurement of thermal expansion coefficient using strain gages , technical note TN-513-1, http://www.vishaypg.com/docs/11063/tn5131tn.pdf .