Temperature-dependent Material Properties Research Articles

Optimization of Brake Disc Profile Based on the Thermal Performance for Electric Vehicles

The brake disc market has reached the value of USD 20.9 billion in 2021 at a CAGR of 4.9% and it is expected to grow to USD 26.5 billion by 2026. However, the difficulties associated with the brake discs are significant rise in the temperature which results in, early wear, thermal cracks and brake fade leading to uneven braking and premature replacement. In this context many researchers have been studying the parameters like brake disc material and type of ventilation. The objective of the work was to study of the effect of ventilation types on thermal responses and optimize the brake disc profile for better thermal performances. Center of gravity and dynamic load transfer were calculated for two wheeler electric vehicle experimentally which was followed by computing the force required for braking process and heat flux on the brake disc analytically. Ventilation of type cross drilled holes (CD) was adopted in brake disc modelling, and was carried out in SOLIDWORKS 2022 and finite element model for the brake disc was created in ANSYS 17.2 with mesh size of 2 mm for lamellar graphite iron (LGI) with temperature dependent material properties. The transient thermal analysis for three braking cycles were carried out with the considerations such as: initial velocity of the vehicle of 96 km/h, ambient temperature of 22°C, conduction and convection modes of heat transfer and 5 s of deceleration and acceleration time. Transient thermal analysis was carried out by applying the heat flux on the frictional surface of the brake disc. For the solid disc without ventilation, it was found that the maximum temperature at the end of first braking cycle (0 to 5 s) was 157.72°C, at end of second braking cycle (10 to 15 s) was 256.95°C and at the end of third braking cycle (20 to 25s) was 349.73°C. As the wear rate for lamellar graphite iron grows exponentially beyond 300°C, ventilations were provided on the brake disc to reduce the temperature on the disc. For the optimized brake disc with ventilation type VT-12, it was found that maximum temperature at the end of first braking cycle (0 to 5 s) was 139.43°C, at end of second braking cycle (10 to 15 s) was 222.68°C and at the end of third braking cycle (20 to 25s) was 299°C. The overall character of these shows a quick rise in temperature at the start of the process, followed by the achievement of the maximum value and, eventually there is a drop in temperature. In this research the future work can be carried out by implementing the noise, vibration and harness studies which would benefit the industry with better braking system.

Thermal model for nanosecond laser ablation Al2O3 considering temperature dependence

This paper presented a thermal model based on heat-conduction and vaporization to predict the ablation profile by nanosecond pulsed laser in Al2O3. The temperature distribution is estimated by heat transfer in the laser irradiated zone, considering temperature dependence of material properties. The ablation profile was analyzed and predicted, which has considered the laser spatial and time-distribution and the effective number of laser pulses within the irradiated area. To validate the accuracy of thermal model proposed, micro-channel experiment has been performed. The morphology and profile of micro-channel was measured by Scanning electron microscope (SEM) and an 3D microscope. The difference in microstructure of SEM can be attributed to the laser-material interaction associated with the temperature distribution. Good agreement between calculated depth and width of microchannel and that of experimentally measured and its dependence on incident laser parameters validated theoretical model. Whereas, the degree of error marginally increases at high laser power fluences due to the model proposed ignored the optical properties. The errors of side-wall of micro-channel can be attributed to the effect of multi-reflection and plasma on the channel side-wall.

System-Level Robust Design Optimization of a Permanent Magnet Motor Under Design Parameter Uncertainties

In the presence of design parameter uncertainties, a system-level robust design optimization method for a permanent magnet motor is proposed to enhance the dynamic and steady performances of a whole motor drive system. To achieve the goal, the influence of individual motor parameters on transient system responses is first investigated with the method of Taguchi experimental planning. The temperature-dependent material property of each motor component is then examined around an operating temperature. A conventionally customized motor drive system is fully simulated based on the finite element method. Finally, it is optimized by the univariate dimension reduction method to ensure the robustness of system performances against the manufacturing tolerance and operating temperature fluctuation.

Torsional postbuckling characteristics of functionally graded graphene enhanced laminated truncated conical shell with temperature dependent material properties

Buckling and postbuckling characteristics of laminated graphene-enhanced composite (GEC) truncated conical shells exposed to torsion under temperature conditions using finite element method (FEM) simulation are presented in this study. In the thickness direction, the GEC layers of the conical shell are ordered in a piece-wise arrangement of functionally graded (FG) distribution, with each layer containing a variable volume fraction for graphene reinforcement. To calculate the properties of temperature-dependent material of GEC layers, the extended Halpin-Tsai micromechanical framework is used. The FEM model is verified via comparing the current results obtained with the theoretical estimates for homogeneous, laminated cylindrical, and conical shells, the FEM model is validated. The computational results show that a piece-wise FG graphene volume fraction distribution can improve the torque of critical buckling and torsional postbuckling strength. Also, the geometric parameters have a critical impact on the stability of the conical shell. However, a temperature rise can reduce the crucial torsional buckling torque as well as the GEC laminated truncated conical shell's postbuckling strength.

Temperature-Dependent Thermal Parameter Identification of Ceramic Nanorod Aerogels Composite in the Ultrahigh Temperature Environment

The identification of the thermal properties of advanced materials is of great importance in engineering application. In this work, an inverse scheme is proposed to identify the temperature-dependent thermal parameters of ceramic nanorod aerogels (CNRAs) composite in the ultrahigh temperature environment up to 1873 K. The feasibility of the proposed method is successfully tested by an analytical solution for CNRAs with known material properties. Furthermore, the temperature-dependent thermal properties of CNRAs are successfully obtained using the experimental data acquired from the heat conduction experimental testing for a CNRAs plate. Lastly, the obtained thermal properties are used to simulate an arc-heated wind tunnel (AHWT) test of a receiving satellite antenna assembly using the FEM method. The simulated temperature at measured data has a very good agreement with the experimental data. This further demonstrates the strong capability of the proposed inverse method. In summary, the proposed approach provides an important approach for the identification of nonlinear and temperature-dependent thermal properties of advanced materials.

Effect of thermal expansion on the high temperature wear resistance of Ni-20%Cr detonation spray coating on IN718 substrate

The temperature-dependent materials properties on the dry sliding wear resistance of the detonation sprayed Ni-20%Cr coating have been studied. In-situ high-temperature X-ray diffraction (HT-XRD) was used to investigate high-temperature properties such as stress relieving, recrystallization, and thermal expansion. The dry sliding wear test was performed by using a ball-on-disc tribometer by sliding velocities (0.1 m/s), varying loads (6 N and 10 N), and temperatures (25 °C and 850 °C) against alumina (Al2O3) ball. The phase evolution, thermal expansion, crystallite size, and lattice strain were determined by the Williamson-Hall method. Field emission scanning electron microscopy and a non-contact optical profilometer was used to characterize the wear scar and calculate the wear rate. The wear test results demonstrated that the as-deposited coatings coefficient of friction (CoF) and wear rate (ω) continuously decreased as the temperature increased. The primary wear mechanism changed from abrasive and surface fatigue to adhesive and oxidative wear. The impact of stress relieving, recrystallization, and forming a composite tribolayer (Cr2O3, NiO) at elevated temperatures reduced the friction and enhanced the wear resistance. The effect of stress relieving, recrystallization, thermal expansion, and oxidation on the wear resistance of the coating has been discussed with a suitable mechanism.

On the pressure–deflection relations and instability of carbon-based composite nonlinear pipes

In this paper, for the first time, the nonlinear buckling of curved pipes is investigated for different distributions of single-walled carbon nanotubes (SWCNTs) in the matrix. The curved pipe is subjected to uniformly distributed transverse pressure and experiences uniform temperature rise. Additionally, the pipe is in one-sided contact with an elastic nonlinear medium. Defined thickness-dependent and temperature-dependent material properties of SWCNTs are taken from the results of molecular dynamics (MD) simulations, well-established in the literature on the subject. Five technologically justified types of CNT distributions are considered. Shen’s rule of the mixture is applied to determine the effective properties of CNT-based composites. To avoid determining shear correction factor, the higher-order shear deformation theory is used. The nonlinear components of the Green–Lagrange strain tensor and the principle of virtual displacements are applied to derive the nonlinear system of partial differential equations of motion of the curved pipe. The solution to formulated boundary value problem is obtained by the perturbation technique for both simply-supported and clamped-clamped boundary conditions. The pressure–deflection curves of the curved pipe are obtained and discussed. The investigation of snap-buckling intensity and upper/lower limit load of the curved pipe is presented and new insights for its nonlinear stability are presented. For instance, it is shown that the V-type of CNT distribution profile affects on lower deflection of the curved pipe while the higher deflection exists for the Λ-type profile.

Role of temperature and preexisting dislocation network on the shock compression of copper crystals

Shock wave experiments show that many annealed face-centered cubic metals exhibit an anomalously increasing yield strength with temperature at high strain rates. Such an increase is usually associated with the multiplication of dislocations in the phonon friction mode, which slows with temperature. However, the effect of temperature on the structure of the shock wave and the yield strength of metal crystals, including those with microstructure, remains elusive. In this paper, we perform molecular dynamic simulations of shock-wave loading for [110] and [111] copper crystals of 0.45 and 0.80μm length in a wide range of temperatures between 100 and 1100K to understand the role of temperature and preexisting dislocations on the Hugoniot Elastic Limit (HEL). We show that, in ideal copper crystals, the elastic precursor exhibits a form of plateau, and the HEL almost does not change with shock propagation distance. However, at higher impacts, the perturbations of an elastic precursor are observed leading to fluctuations in the HEL value. We show that temperature dependencies of the HEL are strongly anisotropic. The HEL values tend to decrease with temperature for [110] perfect copper crystals, and to increase with temperature for [111] copper crystals. This surprising result is explained by the presence of dislocation substructures in a plastic wave in [110] crystals, which reduces the mobility of dislocations and makes the process of dislocation nucleation more dominant than in [111] crystals. Preexisting dislocations in copper crystals allow the HEL to decay much faster than in ideal crystals. In contrast to ideal [110] crystals, [110] crystals with dislocations exhibit increasing HEL values with temperature, as do [111] crystals. We find that the HEL dependence could be well approximated by a power law, but the decay power changes as the wave propagates. The decay power values lie between 0.5 to 0.7 in the second stage for both [110] and [111] crystals, which is consistent with experimental results with polycrystalline annealed copper. Our findings extend our understanding of temperature-dependent mechanical properties of materials under high strain rate and crystal plasticity.

Buckling analysis of non-uniform Timoshenko columns under localised fire

The buckling analysis of non-uniform steel columns with various boundary conditions under localised fire is investigated based on the Timoshenko beam theory (TBT). The temperature-dependent (TD) material properties are taken into account. First, based on the differential quadrature (DQ) method, the temperature field in the column is determined by solving the heat transfer equation considering the convection and radiation boundary conditions. Then, a segmented model is presented to solve the stability problem for the column with the variable flexural rigidity resulting from the non-uniform temperature distribution and cross-section. The transfer-matrix method is employed to obtain the critical buckling load and corresponding buckling mode. Finally, an example is conducted to study the temperature field and buckling response of tapered circular hollow steel columns under localised fire. The feasibility of the present method is verified by comparing the present results with those predicted by the finite element (FE) method and those reported in the literature. Numerical results show the influences of the localised fire and shear deformation on the buckling response of the column.

Modeling of annular thermoelectric generator considering temperature-dependent material properties and side surface heat convection

An annular thermoelectric generator (ATG) contributes to energy utilization in round structures. An accurate prediction of thermoelectric (TE) performance is key to the design of the ATG. By using the perturbation theory and the equivalent substitution of integrals method, an analytical model is proposed, which can easily deal with the nonlinear heat equation induced by temperature-dependent material properties. The TE performance of the ATG including the Thomson effect is studied by the proposed model, and the effect of structural parameters and operating conditions on the TE behavior is analyzed. The results indicate that if the Thomson effect is neglected, the predicted power output and efficiency will be much higher than the actual cases. Significantly, in both working conditions, the relative error of the predicted temperature field of the proposed model is less than 0.1%, far below the available theoretical models. In addition, the influence of side surface heat convection is also analyzed using a numerical method. Remarkably, the maximum power output may increase as the heat convection coefficient grows.

Radiative energy transfer model for high frequency vibration of functionally graded beams in thermal environment

A simple and efficient energy flow model is developed by radiative energy transfer method (RETM) to predict the high frequency vibration response of functionally graded(FG) beams in thermal environment. The Timoshenko beam theory is applied to derive the motion governing equations. Thermal effects are incorporated into the dynamic model through the temperature dependent material properties and the thermal stresses. The wavenumber and group velocity associated with thermal stress are included in the energy governing equation. By introducing the artificial springs to simulate different boundary conditions, the energy conversion relationship of the two waves at boundaries are deduced. The response of FG beam loaded by a high-frequency harmonic force is described by energy density and energy flow intensity. They are composed of energy rays from the real source at the load point and energy rays reflected from the imaginary sources at the boundaries. Numerical simulations are performed in various forms of thermal environments to verify the proposed model. The RETM results are compared with those obtained by the wave propagation approach under different parameters, and good consistencies are observed. Numerical results show that the vibrational energy density of FG beams are affected by thermal effects and can be reduced by optimising the gradient factors.

Investigation on Thermal Buckling of Functionally Gradient Material-Coated Cylindrical Shell Considering Material Properties Varying With Temperature

Abstract Although the thermal buckling problem of functionally gradient material (FGM) cylindrical shells has been investigated for many years, its theoretical solution is rarely reported when considering the material properties varying with temperature, and the existing commercial software also cannot directly solve the critical temperature rise of thermal buckling. Therefore, the theoretical solution of critical temperature rise was first derived for the FGM-coated cylindrical shell with temperature-dependent material properties based on the Donnell thin shell theory. And then, a stepped layer discrete finite element (FE) model was developed by integrating the bisection method into a user subroutine to calculate the critical temperature rise. The results show that the theoretical solutions are in good agreement with the numerical ones, and find out the temperature has a relatively large negative effect on the thermal buckling resistance of the FGM-coated cylindrical shell. Finally, the influence factors on the critical temperature rise were discussed in detail, and some suggestions have been formed to improve the calculation accuracy. This work not only provides a theoretical calculation formula but also develops an FE numerical method to calculate the critical temperature rise of the FGM-coated cylindrical shell, which will help the engineers to design the FGM-related structures easily.

Thermo-mechanical buckling analysis of non-uniformly heated rectangular plates with temperature-dependent material properties

This paper examines the thermo-mechanical buckling behavior of a rectangular plate with temperature-dependent (TD) material properties exposed to non-uniform heating. The buckling analysis was performed by using the differential quadrature (DQ) method, which mainly includes three steps: (i) a two-dimensional (2D) non-linear heat transfer equation was proposed to obtain the temperature distribution in the plate considering the convective–radiative conditions on the plate surface; (ii) the in-plane stress distribution of the plate was obtained by solving the thermoelastic equilibrium equation; (iii) the critical load was determined by solving the stability equation based on the stress distribution in the previous step. The comparison study shows that the present results were in good agreement with the finite element (FE) solutions and the results reported in the literature. The effects of the surrounding temperature fields and in-plane load cases on the thermo-mechanical behavior of the plate are analyzed in detail.

A thermo-elastic-hydrodynamic model for air foil thrust bearings considering thermal seizure and failure analyses

This study aims to investigate the thermo-elastic performance of an air-lubricated thrust bearing under the thermal failure effect. A thermo-elastic-hydrodynamic model was established using temperature-dependent alloy material properties. The thermo-elastic deformation characteristics were analyzed based on the fluid-thermal-structure interaction approach. The mechanisms of bearing thermal seizures and failure behavior were studied. The results show that the rotor thermal warping deformation at low rotating speed plays a leading role in the increase of the film thickness. The rotor-foil thermal seizure occurs in a high rotating speed. The additional forced cooling conditions effectively reduce the risk of thermal failure.

Experiments and Modeling on the Stain-Controlled Time- and Temperature-Dependent Cyclic Ratchetting Plasticity of the Nickel-Based Superalloy IN100

In this paper, the time- and temperature-dependent cyclic ratchetting plasticity of the nickel-based alloy IN100 is experimentally investigated in strain-controlled experiments in the temperature range from 300 °C to 1050 °C. To this end, uniaxial material tests are performed with complex loading histories designed to activate phenomena as strain rate dependency, stress relaxation as well as the Bauschinger effect, cyclic hardening and softening, ratchetting and recovery from hardening. Plasticity models with different levels of complexity are presented that consider these phenomena, and a strategy is derived to determine the multitude of temperature-dependent material properties of the models in a step-by-step procedure based on sub-sets of experimental data of isothermal experiments. The models and the material properties are validated based on the results of non-isothermal experiments. A good description of the time- and temperature-dependent cyclic ratchetting plasticity of IN100 is obtained for isothermal as well as non-isothermal loading with models including ratchetting terms in the kinematic hardening law and the material properties obtained with the proposed strategy.

Estimation of aerothermal heating for a thermal protection system with temperature dependent material properties

In this paper the aerothermal heating of a reusable launch vehicle with the material parameters depending on temperature is retrieved. An additional information, necessary for solving the corresponding inverse problem, is taken from the temperature values in the selected point of thermal protection system. Minimization of the constructed functional, defining the error of approximate solution, is executed with the aid of Levenberg–Marquardt method. Whereas the direct problem, needed to be solved in order to determine the value of functional mentioned above, is solved by using the implicit scheme of the finite difference method. In this approach a system composed from three layers is considered, which represents an integrated thermal protection system with material parameters depending on temperature.

Temperature dependent performance of Schmidt-Boelter heat flux sensors.

The total heat flux sensors for NASA's Mars Entry, Descent, and Landing Instrumentation 2 (MEDLI2) sensor suite on the Mars 2020 vehicle and the Low-Earth Orbit Flight Test of an Inflatable Decelerator (LOFTID) technology demonstration mission are passively cooled Schmidt-Boelter gauges. The output of these sensors has been experimentally demonstrated to be dependent on the temperature of the sensing element. The experimental results are shown to align with a model that assumes temperature-dependent material properties, specifically the Seebeck coefficient. The MEDLI2 and LOFTID flight total heat flux sensors did not undergo a full thermal calibration prior to being installed on the flight vehicles since the temperature dependence was unknown ahead of time. Additionally, the material properties are not known due to the designs being proprietary. For these reasons, an approximate correction factor was derived. The applicability and associated uncertainty of this temperature-dependent correction factor are presented. The error that would be introduced into the measurement if temperature effects were not accounted for would be as high as 9.5% and 16% for the MEDLI2 and LOFTID total heat flux sensors, respectively. As a best practice for future flight missions and ground-based applications that employ similar passively cooled heat flux sensors, it is recommended to individually calibrate each sensor across all applicable use temperatures to account for sensor-to-sensor variations and minimize measurement uncertainty.

A thermodynamic model of integrated liquid-to-liquid thermoelectric heat pump systems

Thermoelectric (TE) heat pumps (TEHPs) are advantageous for heating and cooling in various applications because of their modularity and simple design. A TEHP system includes the TE modules with p- and n-type materials bonded to substrates, plus heat exchangers, thermal interfaces to the heat exchangers, and heat transfer fluids. Although modeling an individual TE module has been extensively studied, limited studies have reported performance at the larger system-level. Furthermore, no prior study has addressed the impact of temperature-dependent TE material properties (e.g., electric resistivity, thermal conductivity, and Seebeck coefficient) on overall heat-pump-system-level performance. This work presents a mathematical model for TEHP system performance based on Goldsmid's approach for TE material performance, “effective” TE material properties, Gnielinski's correlation for convective heat transfer, and thermal balance theory for a heat exchange network. This combined approach provides an accurate model of the liquid-to-liquid TEHP system. Three different approaches—one empirical, one based on the manufacturer's specifications, and one drawn from the literature—were then used to determine values for TE material properties. The first two methods treated properties as constants, while the last approach treated properties as surface-temperature-based functions. Finally, experimental TEHP data was used to validate the models, all with relative absolute deviations of approximately 10% when predicting heating capacity and 10%–25% when forecasting cooling capacity up to a 30 K surface temperature lift. The results demonstrated that, at the TEHP system level, the TE material properties could be treated as constants, avoiding solver iterations and reducing the performance uncertainty by up to 95%.

A Temperature-Dependent Viscoplasticity Model for the Hot Work Steel X38CrMoV5-3, Including Thermal and Cyclic Softening under Thermomechanical Fatigue Loading.

In this paper, a temperature-dependent viscoplasticity model is presented that describes thermal and cyclic softening of the hot work steel X38CrMoV5-3 under thermomechanical fatigue loading. The model describes the softening state of the material by evolution equations, the material properties of which can be determined on the basis of a defined experimental program. A kinetic model is employed to capture the effect of coarsening carbides and a new isotropic cyclic softening model is developed that takes history effects during thermomechanical loadings into account. The temperature-dependent material properties of the viscoplasticity model are determined on the basis of experimental data measured in isothermal and thermomechanical fatigue tests for the material X38CrMoV5-3 in the temperature range between 20 and 650 ∘C. The comparison of the model and an existing model for isotropic softening shows an improved description of the softening behavior under thermomechanical fatigue loading. A good overall description of the experimental data is possible with the presented viscoplasticity model, so that it is suited for the assessment of operating loads of hot forging tools.

Performance assessment and optimization of a thin-film thermoelectric cooler for on-chip transient thermal management

On-demand cooling of thin-film thermoelectric cooler (TFTEC) is a promising technique for energy-saving and high efficiency. However, the transient cooling process of TFTEC is complex and systematic, involving temperature-dependent material properties, geometry factors, parasitic parameters and control parameters. In this work, a system-level optimization of the on-chip transient thermal management (TTM) performance of a Bi2Te3-based TFTEC is performed using a transient three-dimensional numerical model. The response surface method is applied to obtain a predictive model for evaluating the transient cooling performance of TFTEC in terms of four different design factors of thermoelectric leg height, electrode height, current pulse width and amplitude. The relationships between the above design factors and responses including passive cooling, active cooling, temperature overshoot, and time delay and their interactive effects are investigated. Finally, single- and multi-objective optimizations are employed to optimize these responses in different scenarios. The results show that the TFTEC with the optimal configuration enables a passive cooling of 15.57 °C and an active cooling of 5.85 °C simultaneously for a chip hotspot with a transient heat flux of 1300 W/cm2. Furthermore, the hotspot temperature can be limited to 7.15℃ lower than the predefined temperature limit, while the high-power pulse loading time can be extended by 690.2 ms.