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A constitutive model for rubbers providing temperature dependent behavior and self-heating
Published in Bertrand Huneau, Jean-Benoit Le Cam, Yann Marco, Erwan Verron, Constitutive Models for Rubber XI, 2019
In order to render the temperature-dependence predictable, the antagonizing physical effects have to be considered. While the rubber matrix stiffens, the strain moderation of the filler is supposed to be less pronounced at elevated temperatures. As a result, depending on the respective recipe, different trends can be observed. Despite crystallization, inelastic effects are attributed to the filler, which introduces weak bonds into the system. With increasing temperature these physical bonds are supposed to be successively overpowered by thermal fluctuations. This is embodied in form of temperature sensitive viscous and plastic stress contributions resulting in a realistic prediction of temperature dependent hysteretical loss.
Influence of alkali activators on thermo-physical properties of ecofriendly unfired clay bricks from anthill mounds
Published in European Journal of Environmental and Civil Engineering, 2022
Banjo A. Akinyemi, Blessing O. Orogbade, Ayavoro Ogheneyome, Mohamed A. Abeer, Anish Khan, Ali H. Mahmoud, Abdullah Asiri
One of the greatest advantage of using earth as a building material is the thermal comfort it affords to the users when utilised either as a walling material or as bricks. In this case, anthill mounds have been adjudged to be one of the best examples of a thermal regulated material (Gouttefarde et al., 2017). Table 2 shows that sample with 1% weight of sodium hydroxide and silicate had the least thermal conductivity at 0.671 W/mK while the highest is at mix with 1% and 1.5% weight of SS and calcium chloride with 0.712 W/mK, respectively. A lower value of thermal conductivity is an indication of good insulation property which denotes that it could be used for structural applications where thermal fluctuations are to be kept small (Oluyimika & Mijinyawa Yahaya, 2015). The least thermal conductivity of mix G is within the range of the result of a study conducted by El Fgaier et al. (2015) on unfired clay bricks. It has also been reported that the more the pores within the microstructure of a material, the lower the thermal conductivity because the voids are filled with air which is a poor conductor (Ng & Low, 2010).
On the mechanical response and intermetallic compound formation in Al/Fe interface: molecular dynamics analyses
Published in Philosophical Magazine, 2020
Zeina El Chlouk, Wassim Kassem, Mutasem Shehadeh, Ramsey F. Hamade
The stress required to initiate dislocation nucleation and movement in the iron crystal at low temperature is expected to be large in order to overcome the large lattice friction which is strongly sensitive to temperature [36–41]. As temperature increases, the magnitude of lattice friction decreases. This is partly the reason behind the decrease of yield point associated with nucleation of dislocations in the BCC Fe. Temperature increase in BCC iron is also associated with an increase in phonon drag [42–46]. These competing phenomena, namely the softening behaviour due to a decrease in nucleation barrier and lattice friction and the hardening behaviour due to the increased phonon drag, result in the overall weak temperature sensitivity of yielding behaviour in Fe above a temperature of 340 K. Similarly, the relaxation stress, associated with dislocation nucleation in the FCC aluminium region, from the misfit sites as well as from the bulk, also decreases with increasing temperature [30]. This is largely attributed to the effect of thermal fluctuations in the crystal which facilitates the nucleation of dislocations and their movement. The mechanical contribution to the energy barrier is compensated by the thermal energy. Finally, the interfaces and their types have been shown to play a major role in strain hardening and strain hardening rate as they were found to increase in incoherent interfaces [8].