A Five Variable Refined Plate Theory For Thermal Buckling Analysis Uniform And Nonuniform Of Cross-Ply Laminated Plates

This research is devoted to investigating the thermal buckling analysis behaviour of laminated composite plates subjected to uniform and non-uniform temperature fields by applying an analytical model based on a refined plate theory (RPT) with five unknown independent variables. The theory accounts for the parabolic distribution of the transverse shear strains through the plate thickness and satisfies the zero-traction boundary condition on the surface without using shear correction factors; hence a shear correction factor is not required. The governing differential equations and associated boundary conditions are derived by using the virtual work principle and solved via Navier-type analytical procedure to obtain critical buckling temperature. Results are presented for: uniform and linear cross-ply lamination with symmetry and antisymmetric stacking, simply supported boundary condition, different aspect ratio (a/b), various orthogonality ratio (E1/E2), varying ratios of coefficient of uniform and linear thermal expansion (α2⁄α1), uniform and linearly varying temperature thickness ratio (a/h) and numbers of layers on thermal buckling of the laminated plate. It can be concluded that this theory gives good results compared to other theories.

The linear thermal expansion coefficient of Inconel 617 alloy

The experimental results of a study of the thermal expansion of Inconel 617 alloy in the temperature range of 293.15-1460 K are presented. An anomalous change in the thermal expansion coefficient at high temperatures was detected. The initial data are obtained with an error within 3%. The approximation equations and the table of reference values for the temperature dependence of the volumetric properties are obtained.

Setup of high resolution thermal expansion measurements in closed cycle cryostats using capacitive dilatometers

We present high resolution thermal expansion measurement data obtained with high relative sensitivity of ΔL/L = 10-9 and accuracy of ±2% using closed cycle refrigerators employing two different dilatometers. Experimental details of the set-up utilizing the multi-function probe integrated with the cold head of two kinds of closed cycle refrigerators, namely, pulse tube and Gifford-McMahon cryocoolers, has been described in detail. The design consists of decoupling the bottom sample puck and taking connections from the top of the multi-function probe to mitigate the vibrational noise arising from the cold heads, using which smooth and high quality thermal expansion data could be obtained. It was found that dilatometer #2 performs a better noise mitigation than dilatometer #1 due to the constrained movement of the spring in dilatometer #2. This was confirmed by finite element method simulations that were performed for understanding the spring movement in each dilatometer using which the effect of different forces/pressures and vibrations on the displacement of the spring was studied. Linear thermal expansion coefficient α obtained using both dilatometers was evaluated using derivative of a polynomial fit. The resultant α obtained using dilatometer #2 and either of the closed cycle cryostats on standard metals silver and aluminium showed excellent match with published values obtained using wet cryostats. Finally, thermal expansion measurements is reported on single crystals of two high temperature superconductors YBa2Cu3-xAlxO6+δ and Bi2Sr2CaCu2O8+x along the c-axis with very good match found with published data obtained earlier using wet liquid helium based cryostats.

Thermal analysis of Kevlar/basalt reinforced hybrid polymer composite

Use of lightweight composite materials in automobile applications such as doors, bonnets, and bumpers and also the utilization of composite materials in building insulations require superior mechanical and thermal properties. This study attempts to determine the thermal conductivity, linear thermal expansion coefficient, heat deflection temperature and thermo gravimetric analysis of hybrid composite containing reinforcement fibers stacked in seven different combinations in an epoxy matrix as per ASTM standards. Each composite contained two different fibre materials, i.e., Kevlar and basalt. The study revealed that the stacked layers of basalt fibers had more influence on the thermal properties. It was observed that the hybrid composite made of least quantity layers of Kevlar and most of basalt exhibited the maximum thermal conductance of 0.219W/mK, while with vice versa laminate developed 0.191W/mK which was least thermal conductance. The composition prepared by made Kevlar as core layer and basalt as its outer layers exhibited coefficient of linear thermal expansion above 11.5x10-6/oC. Maximum decomposition weight loss of 76.92% occurred in the composition prepared by keeping basalt as core and Kevlar as outer layer. The differential thermal graph showed that the said hybrid composite exhibited the peak decomposition rate of 1wt.%/oC. The thermal properties of the laminate prepared by keeping two layers of Kevlar sandwiched between the basalt were excellent when compared to other six hybrid composites investigated in this study.

Anorthite-reducing glass-crystalline materials synthesized in plasma

The paper presents the experimental results of the glass-ceramic material production using the low-temperature plasma. The dependences are suggested for the main physical-and-mechanical properties (compressive and flexural strengths, density, linear thermal expansion coefficient) of products and the mixture compositions. The centers of secondary recrystallization are identified for the anorthite phase (CaAl2Si2O8). These inclusions chaotically locate on the surface of the synthesis products and resemble dendritic microinclusions up to 90 nm in size. A comparative analysis is given to the properties of glass-ceramic materials produced by the low-temperature plasma and traditional methods.

Strong π-stacking causes unusually large anisotropic thermal expansion and thermochromism

π-stacking in ground-state dimers/trimers/tetramers of N-butoxyphenyl(naphthalene)diimide (BNDI) exceeds 50 kcal ⋅ mol−1 in strength, drastically surpassing that for the *3[pyrene]2 excimer (∼30 kcal ⋅ mol−1; formal bond order = 1) and similar to other weak-to-moderate classical covalent bonds. Cooperative π-stacking in triclinic (BNDI-T) and monoclinic (BNDI-M) polymorphs effects unusually large linear thermal expansion coefficients (αa, αb, αc, β) of (452, −16.8, −154, 273) × 10−6 ⋅ K−1 and (70.1, −44.7, 163, 177) × 10−6 ⋅ K−1, respectively. BNDI-T exhibits highly reversible thermochromism over a 300-K range, manifest by color changes from orange (ambient temperature) toward red (cryogenic temperatures) or yellow (375 K), with repeated thermal cycling sustained for over at least 2 y.

Glass formation and properties of glasses in the system SrO–B2O3–SiO2–xAl2O3 (x=0; 10 mol.%)

The paper shows the prospects of the system SrO–Al2O3–B2O3–SiO2 as a basis for the synthesis of new vitreous and glass-ceramic materials, which are widely used as electrical insulated and high-temperature coatings, for sealing of solid oxide fuel cells, and in the production of heat resistant materials. We experimentally established the conditions of glass formation, regions of glass-forming melts and properties of glasses, the chemical composition of which is limited by the following content of components (mol.%): SrO 30–80, B2O3 10–60, SiO2 10–60, and Al2O3 0–10. It is shown that during the synthesis of glasses in the corundum crucible at the temperature of 13500С the region of glass formation in the system SrO–B2O3–SiO2 is limited by the following content of components (mol.%): SrO 30–60, B2O3 10–60, and SiO2 10–50. It is found that the introduction of Al2O3 to the composition of these glasses expands the region of glass formation towards increase of the SiO2 content in the glass up to 60 mol.%. Experimentally determined values of glass properties are within the following limits: coefficient of linear thermal expansion (67–118)10–7 К–1; glass transition temperature 570–6600С; dilatometric softening point 580–7000С; and density 2.62–3.71 g cm–3. The established patterns of influence of the components and conditions of glass formation on the physical and chemical characteristics of glasses may serve as an experimental basis for designing of new materials with a complex of specified properties, which allows solving the problems of their practical use.

Possibilities of Additive Technologies for the Manufacturing of Tooling from Corrosion-Resistant Steels in Order to Protect Parts Surfaces from Thermochemical Treatment

The structure and physical–mechanical properties of products made from powders of corrosion-resistant steel 12X18H10T by the laser-beam powder bed fusion (LB-PBF) and subsequent ion-plasma nitriding in the work were investigated. Comparative studies of the physical mechanical properties of specimens made by the LB-PBF and conventional method from steel of the same grade were carried out. The density of the specimens and the coefficient of linear thermal expansion (CLTE) after the LB-PBF are almost the same as those of the conventionally manufactured specimens. Our analysis of the obtained dilatograms in the temperature range from 20 to 600 °C showed that the CLTE of steel after the LB-PBF is within acceptable limits (18.6 × 10−6 1/°C). Their hardness, tensile strength, yield strength and elongation are higher than those of a conventionally manufactured specimen. The phase composition and structure of specimens of steel 12X18H10T made by the LB-PBF after the process of ion-plasma nitriding were investigated. The obtained results show that the mode of ion-plasma nitriding used in this case (stage 1—570 °C for 36 h; stage 2—540 °C for 12 h) does not lead to deterioration of the characteristics of the selected steel. A technological process for the manufacture of modified tooling from 12X18H10T steel by the LB-PBF was developed. It protects the surfaces that are not subject to nitriding and makes it possible to obtain a uniform high-quality nitrided layer on the working surface of the part made from spheroidal graphite iron.

Humidity-Sensing Properties of an 1D Antiferromagnetic Oxalate-Bridged Coordination Polymer of Iron(III) and Its Temperature-Induced Structural Flexibility

A novel one-dimensional (1D) oxalate-bridged coordination polymer of iron(III), {[NH(CH3)(C2H5)2][FeCl2(C2O4)]}n (1), exhibits remarkable humidity-sensing properties and very high proton conductivity at room temperature (2.70 × 10−4 (Ω·cm)−1 at 298 K under 93% relative humidity), in addition to the independent antiferromagnetic spin chains of iron(III) ions bridged by oxalate groups (J = −7.58(9) cm−1). Moreover, the time-dependent measurements show that 1 could maintain a stable proton conductivity for at least 12 h. Charge transport and magnetic properties were investigated by impedance spectroscopy and magnetization measurements, respectively. Compound 1 consists of infinite anionic zig-zag chains [FeCl2(C2O4)]nn− and interposed diethylmethylammonium cations (C2H5)2(CH3)NH+, which act as hydrogen bond donors toward carbonyl oxygen atoms. Extraordinarily, the studied coordination polymer exhibits two reversible phase transitions: from the high-temperature phase HT to the mid-temperature phase MT at T ~213 K and from the mid-temperature phase MT to the low-temperature phase LT at T ~120 K, as revealed by in situ powder and single-crystal X-ray diffraction. All three polymorphs show large linear thermal expansion coefficients.