In this article the physical principles which explain divergences of calculated and experimental values of thermal streams and temperatures of building envelope are considered. In this work the simplest thermal conduction through building envelope is considered.

The stress regions where amplitude-modulated oscillations (AMO) appear, intensify, weaken, and disappear were determined for PET, Armos, SVM, Terlon synthetic fibres and monofilament PET fibres. The reappearance of AMO caused by the structure of the random copolymer was also found in Armos synthetic fibre. It was found for all fibres investigated that AMO do not appear at temperatures close to the glass transition temperature or any other softening point. A method is proposed for determining the temperature after which AMO do not appear. AMO were also not observed in many synthetic fibres (for example, polypropylene, polyethylene) in the devitrified state. The various explanations of AMO with respect to the structural and kinetic features of oriented polymers, related to the inhomogeneity of the supramolecular structure of oriented polymers, combined with the activating effect of an external load on the relaxation spectrum are examined.In studying the mechanical properties of synthetic fibres by the free longitudinal vibration method, it was found that in rigid-and semirigid-chain oriented polymers SVM, Terlon, Armos, poly(ethylene terephthalate) (PET), a complex form of the oscillation process in the form of amplitude-modulated oscillations (AMO) is observed in a limited load range. The study of this phenomenon shows that after appearing, as the load increases, AMO are initially monotonically intensified, then attenuated and then disappear at some mechanical load. Outside of this load zone, classic damped oscillations, i.e., oscillations without the appearance of AMO, are observed.The shape of the experimentally observed AMO is shown in Fig. 1 for SVM synthetic fibre with a linear density of 29.4 tex. The reappearance of AMO at a higher load was also found for Armos fibre. The stress and strain ranges within which AMO are observed are reported in Table 1.In addition to the load, the temperature affects the character of AMO. It was found that amplitude-modulated oscillations always disappeared at a temperature close to the glass transition temperature. Such an effect can be used for determining this temperature boundary. The validity of the method of determining the indicated temperature boundary is also confirmed by the fact that AMO are not observed in many oriented polymers (for example, in polyethylene and polypropylene fibres) whose glass transition temperature is below room temperature where the free oscillations were measured.Finding AMO in monofilament PET fibres shows that the analyzed phenomenon is not due to the complex structure of the synthetic fibres investigated. The effect of the appearance of AMO in SVM and Terlon fibres with 58.8 tex linear density is also not due to their cross-sectional dimensions.In the stress range within which AMO appear and disappear, the following are observed: the monotonicity of the change in the frequency increases with an increase in the load (Fig. 2a), the mechanical loss characteristic has a sharp maximum (Fig. 2b), and the monotonicity changes twice for the dynamic...

No abstract

No abstract

No abstract