Temperature-dependent Material Research Articles

Soft fingers with variable stiffness for space gripping tasks: An assessment

The miniaturization of satellites and the problem of uncontrolled space debris demand highly flexible methods for space grippers. Soft grippers have surged as viable alternatives to overcome the limitations of traditional rigid grippers, such as lack of adaptability and dexterity. Although existent models have shown promising features, most have a high part count or make use of actuation systems that are inadequate for space, like pneumatic pumps or temperature-dependent materials. This work introduces novel designs of soft fingers that address the inherent challenges of grasping objects in space while overcoming these limitations. The proposed fingers use compliant structures based on several geometries of metamaterials. A detailed compliance and compressibility analysis is conducted using finite element methods to highlight the performance and behavior of each proposed design. Prototypes were fabricated, and their ability to exhibit different modes of actuation (variability in stiffness) by tendon compression was confirmed. The most apt design was selected and showcased in a three-fingered gripper to demonstrate the ability to grasp a given set of geometries with different sizes.

Contactless thermal diffusivity characterization of second order magnetocaloric materials under magnetic field using modulated photo-thermal radiometry method with very low power probe beam

The thermal diffusivity of magnetocaloric materials has a transition point at a given temperature that depends on the intensity of the applied magnetic field. Consequently, a fine temperature resolution on the material sample is needed to obtain an accurate determination of the thermal diffusivity variation with temperature. The coupling between the external and the internal fields has to be carefully mastered since the pertinent operating condition is fixed by the actual internal field which is not directly measurable and may be heavily affected by any element in contact with the sample. Therefore, contactless methods such as Photo-Thermal Radiometry (PTR) are privileged. The latter is based on a radiative excitation of the front face of a thin sample and the detection of the thermal effect on the opposite face. However, the powerful radiative source may significantly increase the sample temperature which is not suitable for caloric materials. In this work, a low power modulated PTR method is proposed to characterize second order magnetocaloric materials under magnetic field. It was compared to high energy thermo-flash PTR and validated on common materials such as steel and stainless steel, and then applied to gadolinium which is the reference magnetocaloric material for magnetic refrigeration and heat pumping study. The thermal diffusivity of gadolinium samples is measured in the 285.1 K to 305.1 K temperature range, including the magnetic transition temperature without and under an external magnetic flux density of 0.5 T in the 13 mm air gap of the permanent magnet magnetic circuit. The low power probe beam ensures a temperature stability with a negligible sample temperature fluctuation less than 0.05 K on the incident sample surface and less than 0.03 K on the measurement surface. The experimental results without magnetic field align with those using other methods including the magnetic transition temperatures determination. This low-power optical method proved its efficiency to characterize highly temperature dependent materials such as magnetocaloric materials sensitive to magnetic field. The data obtained partly fills the lack of information in the literature on excited gadolinium.

An elastoplastic damage ice material model based on modified Tsai-Wu yield criterion: Experiment, theory and numerical application

Ice, as a novel green and sustainable building material, has attracted more and more attention in building engineering. Appropriate ice material models are crucial for the performance analysis of the increasing ice structures. There is still challenging in modelling ice responses due to the complexity of ice. This study aims to present a nonlinear elastoplastic damage model for ice material. First, a triaxial compression test of artificial ice is conducted. Based on the test results, the modified Tsai-Wu failure criterion with better performance in the tensile zone and physical meaning for hydraulic strength is established. Then, combining plasticity theory with damage mechanics, an elastoplastic damage constitutive law considering the difference between tensile and compressive properties is proposed. The piecewise damage model and the Weibull exponential damage model are employed for compression and tension damage, respectively. Moreover, the numerical iterative algorithm is developed and a user-defined material subroutine (UMAT) is embedded in the finite element software ABAQUS to simulate the mechanical properties of ice. Furthermore, the constitutive model is verified by comparing the FEM results with the results of uniaxial compression, triaxial compression, and three-point bending tests. The results show that the constitutive model can well describe the stress-strain nonlinear behavior and capture the basic failure mode of ice materials. Finally, considering temperature affecting on the failure surface, a temperature dependent ice material model is developed. The current study would help in the design, operation and maintenance of ice structures.

Recent developments in modeling and analysis of rotating functionally graded panels: A review

This article presents a comprehensive review on recent developments in the techniques for modeling and exploration of rotating functionally graded material (FGM) panels carried out between periods 2000 to 2023. Special attention is given on literature pertaining to analysis of rotating FGM panels subjected to thermo-mechanical loading. This study scrutinizes the advancements made in analysis of panels such as beam, plate, shell and blades that includes effects like porosity, thermal stress, and piezo-electric in the mathematical model. The present article also highlights the importance and ease in implementation of rule of mixture for calculation of different temperature dependent material properties used in the analysis of rotating FGM panels. An in-depth review of literature clearly indicates the importance of taking thermal effect in the estimation of elastic properties for accurate analysis of rotating FGM panels. Further, a detailed analysis of temperature profile viz., linear/non-linear, is carried out. Finally, the article concludes with the future areas that need to be explored for the analysis of rotating FGM panels.

Combined effect of temperature dependent material properties and boundary conditions on non-linear thermal stability of porous FG beams

Combined effect of temperature dependent material properties and boundary conditions on non-linear thermal stability of porous FG beams

Temperature Monitoring of Through-Thickness Temperature Gradients in Thermal Barrier Coatings Using Ultrasonic Guided Waves

Ultrasonic guided waves offer a promising method of monitoring the online temperature of plate-like structures in extreme environments, such as aero-engine nozzle guide vanes (NGVs), and can provide the resolution, response rate, and robust operation that is required in aerospace. Previous investigations have shown the potential of such a system but the effect of the complex physical environment on wave propagation is yet to be considered. This article uses a numerical approach to investigate how thermal barrier coatings (TBCs) applied to the surface of many components designed for extreme thermal conditions will affect ultrasonic guided wave propagation, and how a system can be employed to monitor through-thickness temperature changes. The top coat/bond coat boundary in NGVs has been shown to be a temperature critical point that is difficult to monitor with traditional temperature sensors, which highlights the potential of ultrasonic guided waves. Differences in application method and layer thickness are considered, and analysis of through-thickness displacement profiles and dispersion curves are used to predict signal response and determine the most suitable mode of operation. Heat transfer simulations (COMSOL) have been used to predict temperature gradients within a TBC, and dispersion curves have been produced from the temperature dependant material properties. Time dependant simulations of wave propagation are in good agreement with dispersion curve predictions of wave velocity for the two lowest order modes in three thicknesses of TBC top coat (100, 250, and 500 μm\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\upmu \\hbox {m}$$\\end{document}). When wave velocity measurements from the simulations are compared to dispersion curves generated at isotropic temperatures, the corresponding temperature represents the average temperature of a gradient system well. Such a measurement system could, in principle, be used in conjunction with surface temperature measurement systems to monitor through-thickness temperature changes.

Functionally graded doubly-curved shell with temperature dependent material properties and surface-mounted MEE layers

In the present work, the geometrically nonlinear behavior of a simply supported functionally graded doubly curved shell with a surface-mounted magneto-electro-elastic layer is investigated based on Donnell’s theory. Kirchoff’s assumption and von Kármán’s strain-displacement relationship are used to obtain the governing differential equations. The through-the-thickness shell temperature is computed using Fourier’s heat conduction equation. Elastic material properties are assumed to be temperature-dependent and follow the power-law distribution function of the constituent ceramic-metal volume fractions. The magneto-electro-elastic layer is polarized along the thickness direction, which is subjected to electric and magnetic potentials. Gauss’s laws for electrostatics and magnetostatics are satisfied for magneto-electric materials. Nonlinear partial differential equations of motion are reduced to ordinary differential equations by introducing a stress function and using a single-term time-dependent assumed displacement function. Nonlinear free vibration response is obtained by direct numerical integration. After comparing the derived model with published literature results, numerical studies on the effects of applied electric and magnetic coupled fields of surface-mounted magneto-electro-elastic layers on shell vibration are reported. The nonlinear frequency ratios with respect to specified displacement for both spherical and cylindrical shells with thin Piezoelectric BaTiO 3 and Piezomagnetic CoF e 2 O 4 panels across material compositions, the radius of curvature, and thermal conduction are studied.

A multiphase modeling for investigating temperature history, flow field and solidification microstructure evolution of FeCoNiCrTi coating by laser cladding

In this work, a multiphase numerical model was established to investigate the non-isothermal flow and microstructure evolution during laser cladding. The model considered the beam-powder interaction, temperature dependent material properties, the effect of buoyancy and surface tension on convection. The accuracy of the model was verified comparing the simulated coating geometric morphology with the experimental results. Simulation indicated that the temperature and flow of the molten pool were interactive and mutually causal. On the one hand, the temperature field affected the tension gradient and the liquid flow direction. On the other hand, the velocity field significantly affected the heat transfer in the molten pool. Specifically, the maximum fluid velocity was 9.58 mm/s and the Peclet number (PeT) value was less than 5 at the initial stage, indicating that conduction dominated in heat transfer. Furthermore, the PeT value was greater than 200 when the maximum velocity reached 344 mm/s. The heat transfer in the molten pool was mainly thermal convection. In addition, the distribution diagram of solidification parameters (G and R) was calculated to quantitatively establish the internal correlation between solidification parameters and microstructure combing with experimental observation, and revealed the columnar-to-equiaxed transition (CET). Eventually, the microhardness results showed that HEA coating could improve the Ti6Al4V surface microhardness. Simultaneously, the CET behavior significantly affected the microhardness of the coating.

Residual Stress Measurements on Rectangular Specimen SS316L using Numerical Computation Software and Selective Laser Melting

This research aimed to predict the residual stress of additively manufactured rectangular specimen using Selective Laser Melting (SLM) by means of non-linear numerical computation based on Thermo-mechanical method (TMM). The procedure starts with the geometrical and material modelling of rectangular specimen with regards to Austenitic Stainless Steel 316L (SS316L) in which the temperature dependent material data properties such as Young’s Modulus, Thermal Expansion Coefficient, Specific Heat Capacity and Thermal Conductivity are taken into account. The next phase consists of numerical computation procedure which is where the specimen is position 60° of inclination angle from the substrate plate. The support structure is to be generated within the lower surface of the specimen in order to avoid material to collapse during printing process. Laser heat source is to be modelled based on the laser beam width, power, efficiency and scanning speed in order for the numerical computation to accurately predict the thermal problem in SLM process. Furthermore, layer parameters used to fabricate the specimen such as hatch distance, hatch scan width and layer thickness are taken into TMM consideration. Similar set-up from numerical computation by means of laser and layer parameters to fabricate SS316L rectangular specimen is utilized in real fabrication process using SLM machine, Renishaw RenAM 500E. After fabrication of the specimen, electropolishing as for the sample preparation for X-Ray Diffraction (XRD) measurement are to be conducted by means of various depth on both sides of the specimen. For the validation procedure, residual stress on every depth is to be analysed and compared with the result from numerical computation. In conclusion, TMM simulation forecasting an acceptable residual stress on SLM product with relative error up to 14% and the computational time taken to predict the residual stress is only 56 minutes. This exploratory research using TMM simulation to predict residual stress on SLM product could benefit metal additive manufacturing (MAM) production as a whole by neglecting expensive trial and error approach.

(Invited) Bubble Trouble: Simulation of Molten Oxide Electrolysis in Reduced Gravity

Molten Oxide Electrolysis (MOE) is a leading contender for processing extra-terrestrial minerals because it produces oxygen and liquid metal without the use of consumables. During electrolysis a gravitational field stratifies gas, electrolyte, and metal from each other by density. Processing on the moon, with ~1/6g, or Mars, with ~1/3g, will reduce the buoyancy force slowing bubble velocity and lowering convection intensity. Low thermal conductivity, (~1Wm-1K-1) and high viscosity, (~1Pa⋅s) of molten regolith contribute to thermal and chemical transport being dominated by convection, even as convection velocity decreases. We explore MOE system dynamics in Earth’s (1g), Mars’ (1/3g), and the Moon’s (1/6g) gravity through simulations that include composition and temperature dependent material properties and two phase flow. We implement the level set method to track the interface between the bubble laden flow near the anode and the bubble free flow far from the anode. By grouping bubble dynamics into the material properties of the fluid near the anode we relax the requirements for a fine mesh to track individual bubble-fluid interfaces, and are able to use a mesh that is finer than that required for a bubbly flow mixture model. Thus, all physics can be captured on one mesh. This is particularly relevant because bubble sizes for proposed systems are 1/10 to 1/100 of the system scale. While other simulations have been presented and experiments performed in micro and zero gravity for gas evolving electrolysis systems, none have investigated the downward facing electrode, heat transfer, or species diffusion. The focus of this work is to address this gap in the literature through simulation. Here, multiphysics simulation is supported by inspection of dimensionless groups and observations from other electrolysis systems. This work demonstrates that combining heat and mass transfer with temperature and composition dependent material properties is critical to designing MOE and other electrolysis systems for earth and beyond.

Experimental and numerical investigation of the thermal properties and related microstructural influences of an interpenetrating metal ceramic composite at elevated temperatures

An interpenetrating metal-ceramic composite (IMCC), consisting of an open-porous alumina preform (26vol%), infiltrated with an AlSi10Mg alloy is investigated for its thermal properties and the microstructural impact on the thermal cycling behavior. Specific heat capacity, thermal conductivity and the coefficient of thermal expansion are investigated experimentally. Next to dilatometry experiments, an in-situ SEM setup with digital image correlation of the natural microstructure of the composite is used as a recognizable pattern on the sample surface to evaluate strain and microstructural changes during heating and cooling. The interpenetrating phase composite is also modelled based on reconstructed and generated microstructures. Extensive numerical studies are conducted with varying boundary conditions, interface properties, initial cooling temperatures, temperature dependent material properties and inclusion of pores. Microstructural investigations show phenomena of plasticity, creep, crack formation and interface detachment which is supported by numerical findings. Microstructural changes during heating and cooling in form of crack formation occur in the metallic phase and metallic precipitation. The influence of the microstructural processes on the thermal expansion behavior are discussed in comparison to existing hypotheses from literature.

In silico quantification of 3D thermal gradients and voids during fused filament fabrication deposition to enhance mechanical and dimensional stability

Fused filament fabrication (FFF) is one of the most widely used additive manufacturing techniques for polymeric materials. However, the mechanical and dimensional quality of the final printed parts are still deviating from the maximal performance, due to the presence of voids, and incomplete inter- and intralayer bond formation implying suboptimal molecular chain entanglement. The current work puts forward a three-dimensional Ansys Polyflow® computational study in which temperature gradients and void formation are analysed for the deposition of up to eight strands, accounting compared to the state of the art for (i) bond formation at the strand interfaces by material deformation; (ii) non-Newtonian viscosity variations; (iii) measured temperature dependent material properties, including conductivity, specific heat capacity and viscosity; and (iv) convection. Selecting acrylonitrile butadiene styrene (ABS) as polymeric material, it is demonstrated that a dynamic heat transfer is obtained with contributions from the heated bed to layers printed above, and from just printed warmer layers to colder layers printed before in both the vertical and transversal direction. These extra heat transfers renew the interlayer contact between two strands, as the temperature at the weld line can be pushed several times above the glass transition temperature. A tuning of this renewable welding is possible based on a variation of the bed and nozzle temperature; the latter more relevant upon increasing the number of layers printed. It is further highlighted that the void shape and size is different close and away from the bed (2.5-8% void percentage variation). Moreover, a novel computational method is put forward to quantify the surface roughness based on edge analysis (80-120 μm variation).

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.

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.

Procedure to generate a selection chart for microwave sol-gel synthesis of nanoparticles

Numerical simulation is used to compare the temperature distribution existing during microwave or conventional heating by hot oil bath of a reaction volume. The simulation is applied to the sol-gel synthesis of TiO2 nanopowders, considering temperature dependent materials parameters. A WR340-based single mode applicator operating at 2.45 GHz is considered, with a cylindrical load positioned in regions of predominant electric field. A temperature homogeneity index, defined as the ratio between the average temperature and its standard deviation at a certain time, is used to compare homogeneity of conventional and microwave heating at different power densities, from 370 to 7400 W/L. Based on that comparison, a selection chart of the more homogenous heating process as a function of power density and average temperature of the reaction volume is defined and can be used to select the experimental conditions expected to lead to a more or less homogeneous particle size of the products.A dedicated instrumented model, including three optical fibres, is developed as well, for validation purposes. Experimental validation showed a very good predictive capability of the model, with errors on estimated temperature lower than 3 °C at temperatures lower than 80 °C.

Dual-emitting temperature dependent material based on Bi3+/Eu3+ co-activated Ba2Y2Si4O13 phosphor with multicolor anti-counterfeiting

Bi3+, Eu3+ co-doped Ba2Y2Si4O13 phosphors with multi-color luminescence properties were prepared by high temperature solid state method. The structure, luminescent properties and temperature characteristics were studied by X-ray diffraction, scanning electron microscope, fluorescence spectrum and temperature-dependence of emission spectrum. Ba2Y2Si4O13: Bi3+, Eu3+ phosphors can emit color from cyan to red when the excitation wavelength was changed from 340 nm to 390 nm, which is attributed to that there are two Bi3+ ion emission centers, and their emission intensity will change with the change of excitation wavelength. Moreover, the emission of the phosphor has good temperature sensing characteristics, based on the fluorescence intensity ratio of the two blue emission bands of Bi3+ and the red emission peak of Eu3+, a multimode thermometer with high temperature sensitivity was constructed. At the same time, based on the dynamic luminescence characteristics of the phosphor, the dynamic anti-counterfeiting experiments are designed. Therefore, the results show that the material has a bright prospect in the field of temperature sensing and anti-counterfeiting.

Mathematical Model to Calculate Heat Transfer in Cylindrical Vessels with Temperature-Dependent Materials

In this article, a mathematical model capable of simulating the heat transfer of cylindrical vessels whose properties are dependent on temperature is proposed. As a case study, it compares, from an approach of their heat transfer and chemical migration characteristics as a function of the temperature reached, different materials commonly used for the manufacture of water bottles. More specifically, the materials studied were aluminium, polyethylene terephthalate, and polypropylene. The validation of the model consists of an experiment carried out in the laboratory with three water bottles of each of the materials under study, as well as simulations using the Network Simulation Method to recreate the heat transfer that occurs through the walls of the bottles. On the other hand, the nondimensionalization technique is also applied, which allows us to obtain the weight of each of the variables on the problem, as well as the existing relationship between them. Finally, an outside temperature of 30 °C to 50 °C is simulated, which is a common temperature range in southern Europe during the summer season, and an initial temperature of 20 °C for the water contained in the bottle to know the behaviour of the materials and what the final temperature of the water would be after one hour.

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.

Slow dynamics in a single bead with mechanical conditioning and transient heating

The ultrasonically-measured contact stiffness of an aluminum bead confined between two slabs diminishes on mechanical conditioning, and then recovers like log(t) after the conditioning ceases. Here that structure is evaluated for its response to transient heating and cooling, with and without accompanying conditioning vibrations. It is found that, under heating or cooling alone, stiffness changes are mostly consistent with temperature dependent material moduli; there is little or no slow dynamics. Hybrid tests in which vibration conditioning is followed by heating or cooling lead to recoveries that begin like log(t) and then become more complex. On subtracting the known response to heating or cooling alone we discern the influence of higher or lower temperatures on slow dynamic recovery from vibrations. It is found that heating accelerates the initial log(t) recovery, but by an amount more than predicted by an Arrhenius model of thermally activated barrier penetrations. Transient cooling has no discernable effect, in contrast to the Arrhenius prediction that it inhibits recovery. [Supported by the DOE, DE-SC0021056].

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.