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Gear transmission errors are influenced by temperature especially in the aerospace field. A model is proposed to investigate the influence of temperature on cylindrical gear transmission errors based on the thermal network (TETN). The gear temperature field distribution model is established based on the thermal network method, and gear thermal deformation can be calculated along the gear meshing line. Regarding the gear single-flank rolling process, the variation of gear transmission errors under temperature is determined. In numerical calculations in MATLAB, the variation of gear transmission errors at 100 ℃ compared to 20 ℃ is -4.20 μm, which decreases almost linearly while the thermal expansion coefficient of the gear material increases. The simulation of the gear transmission errors variation of temperatures using the finite element method (FEM) were carried out in Workbench software under Ansys and the average difference of the TETN model results between calculations and FEM for different temperatures was 0.24 μm. Experiments were carried out on the gear tester in temperatures ranging from 0℃ to 100℃, the TETN model results in calculations were compared with the results of the tester, and the average difference was -1.15 μm. The results show that the proposed TETN can be used as an algorithm to determine the variation of gear transmission errors under the influence of temperature. [ABSTRACT FROM AUTHOR]

This paper focuses on the thermal properties of R-Glass/Epoxy laminate in response to temperature variations. The elastic properties and coefficient of thermal expansion in the material's principal direction were measured across the temperature range from room temperature to the cure temperature. These properties were then characterized as functions of temperature. Using the characterized properties and the principles of classical lamination theory, a method was proposed to predict the changes in the coefficient of thermal expansion for a general laminate subjected to temperature variations. The measured values of the coefficient of thermal expansion for laminates with varying angle plies were compared with the predicted values. The experimental results demonstrate that the proposed method accurately predicts the changes in the coefficient of thermal expansion for a general laminate under temperature variations. Additionally, an analytical formulation was proposed and validated to predict the changes in the coefficient of thermal expansion for R-Glass/Epoxy laminates subjected to temperature variations. [ABSTRACT FROM AUTHOR]

Large negative thermal expansion (NTE) was achieved at room temperature using the structural phase transition in Zn2P2O7. Particularly, Zn1.6Mg0.4P2O7 has a negative coefficient of linear thermal expansion αL of about –60 ppm/K at temperatures of 289–374 K. Co-doping of Mg and another element at the Zn site was found to be effective for control of NTE properties and for improvement of thermal expansion compensating ability. The present phosphates are expected to have widely various practical applications as thermal expansion compensators because they contain no toxic or expensive elements. Moreover, they can be prepared using a simple solid-state reaction method in air. [ABSTRACT FROM AUTHOR]

Thermoresponsive self-crimping polybutylene terephtlate (PBT)-based bicomponent fibers were fabricated by melt-spinning to serve as primary constituents for textiles, such as nonwoven battings, for an adaptive single insulting layer. Due to the intrinsically mismatching modulus and coefficient of thermal expansion (CTE), the fibers curl or straighten with temperature, similar to the concept of Timoshenko's bimetallic strip. Maximizing the curvature is driven by an optimum of fiber diameter, overall CTE, and fiber moduli, which are all affected by drawing ratio and, consequently, fiber's microstructure. A draw ratio of 2.33 yielded the best combination of mechanical and thermal properties; it was observed that increasing the draw ratio does not necessarily increase the self-crimping behavior. Tests performed on non-woven battings of these fibers exhibited comparable thermoreponsive behaviors to polypropylene-based thermoresponsive fibers from previous studies in the −20 °C to 20 °C temperature range, which has potential for wearable insulations for both commercial and defense sectors alike. [ABSTRACT FROM AUTHOR]

In this review article, we have investigated the credibility and suitability of the lanthanum gallium silicate (La3Ga5SiO14, LGS) crystals in the application of high-temperature sensing. All the basic properties of the langasite family piezoelectric crystals, such as elastic properties, are taken into consideration and discussed. The crosstalk effects between different vibration modes of LGS crystal are investigated to optimize the crystal cuts. Thereafter, dependences of properties, such as electroelastic properties, resistivity, and electromechanical coupling coefficients of langasite family crystals on higher temperatures, are discussed. Finally, thermal-related properties of langasite family crystals, such as specific heat as well as thermal expansion coefficients, are studied for higher temperature ranges and a comparison with other piezoelectric crystals has also been presented. [ABSTRACT FROM AUTHOR]

Thermal, thermo-mechanical and mechanical properties of four different commercially available polyetheretherketones (PEEK) based materials were investigated. PEEK matrix was either modified and/or reinforced with carbon fibres, graphite and/or PTFE. Impact strength was measured at three different temperatures: 25 °C, −100 °C, and −195 °C. At 25 °C, thermal stability and mechanical properties, including the elastic modulus, compression, and impact strength, were enhanced with the addition of carbon fibres. Matrix modification had a minor impact on thermal stability, while the mechanical properties decreased, except for impact strength. At −100 °C, the mechanical properties of the neat polymers were improved, including increased impact strength by 20% compared to values at 25 °C. Addition of fillers hindered the rise of impact strength due to complex mechanisms caused by different coefficients of thermal expansion of reinforcements and matrix. At −195 °C, the significant increase of impact strength was revealed for unmodified PEEK reaching 30 times higher values than at 25 °C, while matrix modification suppressed the rise of impact strength. The scratch test indicated the superior behaviour of unfilled PEEK during the tested load range (up to 15 N), while the effect of the fillers was observed at much lower load threshold of 7 N. • Cryogenic temperatures have a significant impact on mechanical properties. • Self-toughening mechanisms at cryogenic temperatures retained by matrix modification. • Difference of filler/matrix CTEs affects impact strength at cryogenic temperatures. • Scratch resistance is governed by fillers until a load threshold reached. [ABSTRACT FROM AUTHOR]

First-principles calculations were used to examine the mechanical and thermodynamic properties of Ti 2 AX (A = Al,Ga; X = C,N) M 2 AX phase at various pressures and temperatures. The calculated values of elastic constants show that Ti 2 AlC, Ti 2 AlN, Ti 2 GaC and Ti 2 GaN are mechanically stable under pressures of 0–50 GPa. The changes of thermal expansion coefficient, Debye temperature, heat capacity and Grünesen constant were investigated at 1200 K temperature and 50 GPa pressure. The results of temperature and pressure on constant heat capacity (C v) and elastic constant are exactly the opposite, which indicates that Ti 2 GaN has the largest heat release or heat storage capacity, and the order of the final Debye temperature are: Ti 2 AlN > Ti 2 AlC > Ti 2 GaN > Ti 2 GaC. • The effect of Ti 2 AX's C 11 and C 33 with increasing pressure is more pronounced. • Ti 2 GaN has greater deformation resistance than Ti 2 AlC, Ti 2 AlN, Ti 2 GaC. • Ti 2 GaN first exhibits ductile behavior when the pressure exceeds 30 GPa. • The Ti 2 GaN phase has the most stable thermodynamic properties. • Ti 2 GaN has the most optimal heat release or heat storage capacity. [ABSTRACT FROM AUTHOR]

• Negative thermal expansion of PbTiO 3 compound is tailored by simultaneous substitution at the Pb and Ti sites. • The choice of substitutional elements with appropriate proportions produces materials with very low thermal expansion. • PT-L, and PT-N shows very low thermal expansion in the temperature regions, 15–400 K, and 15–420 K, respectively. • PT-P shows intermediate thermal expansion in the temperature range 15–380 K. [Display omitted] The article deals with the thermal expansion properties of some diluted PbTiO 3 (PT) based ceramic compounds. We have tailored the negative thermal expansion (NTE) coefficient of PT by substituting both at the Pb and Ti sites with different elements, with an intention to achieve very low thermal expansion coefficient. The choice of substitutional elements with appropriate proportions gives us materials with very low thermal expansion, operative over a wide range of temperature (from well above the room temperature to well below it). Moreover, we have shown an effective way to select the operative temperature region of their performance, even without performing the actual dilatometric experiment. [ABSTRACT FROM AUTHOR]