Temperature Dependence Of Mechanical Properties Research Articles

Temperature-dependent elastic and plastic properties of α2-Ti3Al

The systematic in-depth investigation of the temperature-dependent mechanical properties of α2-Ti3Al is a critical issue owing to its practical application in the aviation industry. In this work, temperature-dependent elastic and plastic behaviors for α2-Ti3Al were studied by employing first-principles method based on density functional theory. The results indicate that the elastic constants and elastic modulus gradually decreases with the increase of temperature, while the elastic anisotropy shows an increasing tendency with increasing temperature. Based on the Sachs model, we discovered that 30°and 90°partial dislocations of basal plane dominate the plastic deformation of α2-Ti3Al at a temperature range of 600–1100 K. It also demonstrates that the strength and hardness decrease with increasing dislocation density and decreasing strain rate. These results may provide beneficial guidelines for designing new intermetallic compounds.

Investigation of the damping properties of polylactic acid-based syntactic foam structures

Nowadays, environmental awareness is more and more important. Therefore, the importance of weight reduction and creating a circular economy has increased. In this study, we foamed bio-based polylactic acid (PLA) with thermally expandable microspheres to create homogenous, compostable polymer foams. The polylactic acid-based foamed sheet samples were produced with a flat sheet extruder at 190 °C. We investigated the temperature-dependent mechanical properties of the samples—they show maximum damping capacity in the glass transition region. We also examined the frequency-dependent properties of the foamed samples and successfully extended these properties with the time-temperature superposition principle, to broaden the potential field of application of the foams. The damping properties of homogeneous, closed-cell foam structures produced with thermally expandable microspheres increased in the range of 0.1–20 000 Hz as a function of foaming agent content. We also produced foamed sheets from PLA/PBAT (polybutylene succinate) blends. The storage modulus of unfoamed reference samples showed a decreasing tendency. The tanδ of foamed systems containing only PLA or PBAT increased. The tanδ of foamed blends decreased in 25%/75% and 50%/50%PBAT/PLA systems, except for the 75%/25%PBAT/PLA blend. Therefore, PBAT/PLA blends can only be used to improve the damping ability of foamed samples above 75 wt% PBAT.

Panel flutter analysis of cracked functionally graded plates in yawed supersonic flow with thermal effects

In the present paper, an isogeometric analysis formulation along with the Nitsche technique is implemented based on the first order shear deformation plate theory to investigate the aero-thermo-elastic panel flutter behavior of a functionally graded (FG) plate containing cracks in the supersonic flow field. A FG material is considered with temperature-dependent mechanical properties distributed in the plate thickness according to the power law. The temperature distribution in the plate thickness is calculated through solution of the one-dimensional steady-state conductive heat transfer equation while the surface temperatures are kept fixed. The physical contact and the crack growth phenomena are overlooked in the present research. The panel flutter behavior is investigated under combination of crack orientation, crack length, thermal conditions, flow direction, FG volume fraction index and boundary conditions. The accuracy and quality of the present isogeometric formulation is shown in comparison with those available in literature.

Influence of starting powder choice on structure property relations in gadolinia stabilized zirconia 3Gd-TZP manufactured from co-milled starting powders

Two 3Gd-TZP materials were manufactured from powders produced by intense mixing and milling of unstabilized zirconia starting powders and gadolinia as stabilizer oxide by hot pressing at 1250 °C – 1400 °C. The materials show a combination of high toughness and moderate strength. In detail depending on starting powder the two TZP showed distinct differences concerning transformation characteristics, sintering temperature dependence of mechanical properties and the tendency to develop R-curve related deformation features such as non-linear stress strain curves and formation of transformation bands prior to fracture.

Temperature-Dependent Creep Behavior and Quasi-Static Mechanical Properties of Heat-Treated Wood

In this paper, Berkovich depth-sensing indentation has been used to study the effects of the temperature-dependent quasi-static mechanical properties and creep deformation of heat-treated wood at temperatures from 20 °C to 180 °C. The characteristics of the load–depth curve, creep strain rate, creep compliance, and creep stress exponent of heat-treated wood are evaluated. The results showed that high temperature heat treatment improved the hardness of wood cell walls and reduced the creep rate of wood cell walls. This is mainly due to the improvement of the crystallinity of the cellulose, and the recondensation and crosslinking reaction of the lignocellulose structure. The Burgers model is well fitted to study the creep behavior of heat-treated wood cell walls under different temperatures.

Performance of Ti6Al4V fabricated by electron beam and laser hybrid preheating and selective melting strategy

Electron beam selective melting (EBM) and selective laser melting (SLM) are regarded as significant manufacturing processes for near-net-shaped Ti6Al4V components. Generally, in the conventional EBM process, preheating is necessitated to avoid “smoke” caused by the charging of electrons. In the conventional SLM process, laser as an energy source without the risk of “smoke” can be employed to melt metal powder at low temperatures. However, because of the low absorption rate of laser, the powder bed temperature cannot reach a high level. It is difficult to obtain as-built TiAl4V with favorable comprehensive properties via conventional EBM or SLM. Hence, two types of electron beam and laser hybrid preheating (EB-LHP) combined with selective melting strategies are proposed. Using laser to preheat powder allows EBM to be performed at a low powder bed temperature (EBM-LT), whereas using an electron beam to preheat powder allows SLM to be performed at a high powder bed temperature (SLM-HT). Ti6Al4V samples are fabricated using two different manufacturing strategies (i.e., EBM-LT and SLM-HT) and two conventional processes, i.e., EBM at a high powder bed temperature (EBM-HT) and SLM at a low powder bed temperature (SLM-LT). The temperature-dependent surface quality, microstructure, density, and mechanical properties of the as-built Ti6Al4V samples are characterized and compared. Results show that EBM-LT Ti6Al4V exhibits a higher ultimate tensile strength (981±43 MPa) and a lower elongation (12.2%±2.3%) than EBM-HT Ti6Al4V owing to the presence of α′ martensite. The SLM-HT Ti6Al4V possesses the highest ultimate tensile strength (1,059±62 MPa) and an elongation (14.8%±4.0%) comparable to that of the EBM-HT Ti6Al4V (16.6%±1.2%).

A Thermo-Mechanical Analysis of Laser Hot Wire Additive Manufacturing of NAB

There is increased interest in using nickel aluminum bronze (NAB) alloys in large-scale directed energy deposition additive manufacturing (DEDAM) processes for maritime applications, but one challenge lies in the component distortion that results from residual stress generated during fabrication. This paper describes the development and evaluation of thermo-mechanical simulations for laser hot wire (LHW) DEDAM of NAB to predict part distortion. To account for the dearth of temperature-dependent properties for NAB C95800 in open literature and public databases, temperature-dependent material and mechanical properties for NAB C95800 were experimentally measured using test specimens fabricated with a variety of DEDAM processes. Autodesk’s Netfabb Local Simulation software, a commercial finite-element based AM solver, was employed but with its heat source model modified to accommodate LHW DEDAM’s oscillating laser path and additional energy input supplied by the preheated wire feedstock. Thermo-mechanical simulations were conducted using both the acquired temperature-dependent material and mechanical properties and the constant room-temperature properties to assess the impact on simulation accuracy. The usage of constant properties in the thermo-mechanical analysis resulted in significantly different predicted distortion compared to those using the temperature-dependent properties, at times even predicting substrate displacement in an opposite direction.

A General Expression for the Welding Tendon Force

Abstract This study presents a novel expression for the tendon force associated with residual stresses produced during welding of large, thin sections. A general engineering equation is presented as the combination of a closed-form expression, based on idealized treatment, and correction factors to account for the effects of temperature-dependent thermal and mechanical material properties. The closed-form expression corresponds to the assumption of constant material properties. A rigorous mathematical treatment is utilized to derive explicit, exact expressions for the temperature-dependent correction factors without the need for empirical correlations. The temperature-dependent behavior of materials is captured accurately using four dimensionless groups. The analysis was validated through numerical simulations with common structural grades of low-carbon steel, stainless steel, aluminum, and titanium. The idealized treatment resulted in predictions with a mean difference of 18%, which was reduced to 7% by incorporating the correction factors. The remaining error is a systematic overestimate, which can be attributed to compliance effects of the finite plate used in the simulations, and is the focus of ongoing research. The utility of applying the novel tendon force equation to problems in fabrication procedure design is demonstrated with an example predicting distortion during manufacturing of hollow structural sections.

Temperature-dependent mechanical properties of polyetherimide composites reinforced by graphene oxide-coated short carbon fibers

Graphene oxide (GO) has been well accepted as one novel fiber sizing agent for enhancing the mechanical properties at low temperature or room temperature (RT) of short carbon fiber reinforced polymer composites. But knowledge is still lacking about the mechanical behaviors at elevated temperature of GO-coated short fiber reinforced polymer composites. Here the temperature-dependent tensile properties of GO-sized short carbon fiber (GO@SCF) reinforced polyetherimide (PEI) composites were systematically investigated from −70 °C to 170 °C. The GO@SCF/PEI composites with varied GO sizing contents were prepared via an efficient injection molding technique. The GO@SCF/PEI composite with 0.4 wt% GO content was shown to be optimal for the tensile strength at RT and thus was selected to investigate temperature-dependent tensile behaviors. The results show that the GO sizing treatment plays a positive role in enhancing the tensile strength of SCF/PEI composites at −70 °C and 30 °C whereas a negative role at 100 °C and 170 °C. Morphological observations indicate that the fiber–matrix interfaces are enhanced at −70 °C and 30 °C but deteriorated at 100 °C and 170 °C due to the thermal expansion mismatch between SCF (or GO) and PEI. In addition, appropriate empirical equations were established for elucidating the relationships between their strength/modulus and temperature of PEI, SCF/PEI and GO@SCF/PEI composites.

Adhesive Behavior of Propolis on Different Substrates

Propolis is a sticky substance used by bees to seal their hive and protect the colony against pathogens. Its main components are plant resins, beeswax, essential oils, pollen, and other organic substances. The chemical and medicinal properties of propolis have been extensively studied, but little is known about its physical and especially adhesive properties. To gain a better understanding of propolis and its potential for adhesive applications, we performed several experiments, including adhesion tests with propolis in different conditions and on various substrates, differential scanning calorimetry analysis, and compression tests. Propolis shows clear viscoelastic behavior and temperature-dependent mechanical properties. Our results demonstrate that propolis adheres well to a wide range of substrates from glass to PTFE, but also enables stronger adhesion at higher temperatures and longer contact times. Even underwater, in wet conditions, quite a substantial adhesion was measured. The data are interpreted from a biomechanical point of view, and the significance of the obtained results for bee biology is discussed.

Ab initio investigation of the atomic volume, thermal expansion, and formation energy of WTi solid solutions

WTi is used as an adhesive layer in integrated circuit devices. The temperature dependent mechanical properties of WTi are still largely unexplored. In this paper we investigate WTi solid solutions with density functional theory calculations to determine the temperature and concentration dependent behavior of volume and coefficient of thermal expansion. The coefficient of thermal expansion is analyzed in terms of the bulk modulus, heat capacity, and Gr\"uneisen parameter. Furthermore, we gain insight into the bonding of the system via investigation of the electronic structure, phonon density of states, and analysis of the formation energy. Low Ti concentrations lead to strong W-Ti bonding, as manifested in additional high frequency peaks in the phonon density of states. As a consequence, deviations from Vegard's law are found at low Ti concentrations, with a minimum of the lattice constant at about 15 at. % Ti. The CTE as a function of Ti concentration shows a negative trend at low temperatures and Ti concentrations, which is related to a strong decrease of heat capacity. Finally we show that the Debye-Gr\"uneisen model yields results for WTi comparable to the quasiharmonic approach at a fraction of the computational cost.

Analysis of a HDPE flanged connection with a time and temperature dependent constitutive behavior

High density polyethylene (HDPE) piping systems are used extensively in both industrial and societal infrastructure. However, their performance is sometimes impacted due to leakage through flanges, especially HDPE pipes with large diameters. Many factors affect leakage, including stress relaxation in the HDPE material and ambient temperature effects. Hence, this study investigates the effect of temperature on the leakage of a HDPE flanged connection with steel backing rings. It incorporates the effects of stress relaxation and temperature on the HDPE material and assesses the degradation of performance of the connection with time by means of finite element analysis (FEA). The temperature and time dependent mechanical properties of the HDPE material are determined experimentally through tensile, compression and relaxation testing conducted at various temperatures under isothermal conditions. The constitutive behavior of the HDPE material is modeled using the nonlinear visco-elastic plastic three network model (TNM), which predicts the mechanical behavior of HDPE markedly well. The calibrated TNM is used in the FEA study to investigate the leakage performance of the HDPE connection at various temperatures (23, 40, 60 and 80 °C) at isothermal conditions over a service time of one year. The FEA results reveal that the flanged connection can experience leakage at all temperatures due to insufficient bolt preload. It is also found that leakage occurs prematurely as temperature increases. To simulate a realistic scenario resembling an above ground piping system, an annual temperature profile for a selected geographic location was prescribed to the model to simulate leakage over a one year period. Based on the results, several bolt re-torqueing plans were explored and suggestions are made on the best bolt re-torqueing practice for preventing leakage over the service life of the HDPE connection.

A study of dynamic energy partition in belt grinding based on grinding effects and temperature dependent mechanical properties

• A dynamic energy partition calculating model in abrasive belt grinding is proposed. • Cutting and ploughing dominate material removal for soft material while ploughing is more dominant for hard material. • Heat accumulation of grains reduces cooling capacity of abrasive belt during grinding. • High grinding temperature softens workpiece and makes cutting action occur easily. Analyzing and modelling the dynamic energy partition is of great significance to revealing the mechanism of belt grinding and improving grinding quality. However, there is lack of comprehensive studies on energy partition in belt grinding, especially when the dynamic characteristics are under consideration. To fill this gap, this paper analyzed the grinding energy partition from the perspective of grinding effects and thermal aspects. Grinding effects are distinguished by combination of single grain scratch tests and force balance of one grain in view of dynamic and elastic contact conditions. Thermal aspects are obtained by a fusion method of finite element method (FEM) and optimization algorithm. Then, by utilizing the iterative approach, heat accumulating effect and temperature dependent mechanical properties of workpieces are taken into account either and the dynamic energy partition is calculated in a continuous grinding process. Validations on two workpieces (made by SUS304 and AA6061-T6) prove that the proposed dynamic energy partition calculating method is effective and the maximum error of q w is 17.2 %. The proposed method not only enhances the understanding of dynamic energy partition in robotic belt grinding, but also offers a new venue for studying abrasive belt grinding.

Temperature-Dependent Hydration and Mechanical Properties of High-Volume Fly Ash Cement with Chemical Additives

AbstractThis research investigates the effects of Na2SO4 and Na2CO3 on the mechanical and hydration properties of high-volume fly ash (FA) cement (HFC) at three curing temperatures: 25°C, 40°C, and...

Thermostructural Responses of Metallic Lattice-Frame Sandwich Structure for Hypersonic Leading Edges

Metallic lattice-frame materials, due to excellent heat transfer performance under high heat flux and mechanical property, are regarded as the potential candidates for a vehicle leading edge. This paper presents a new-style lattice-frame sandwich panel with active heat transfer wall-plate. The heat transfer performance and thermal–structural responses are numerically studied, considering the temperature-dependent mechanical and thermal properties. The effects of geometrical characteristics of the wall-plate channel on heat exchange and hydraulic behavior are explored. The different parent materials and channel types are respectively compared based on the thermal–structural responses of sandwich structure. A relatively optimized sandwich panel is employed as the vehicle leading edge, and the effects of attack angle on heat transfer and thermostructural behavior are discussed, subjected to intense localized heat flux. The metallic lattice-frame sandwich panel with an active heat exchange wall-plate shows attractive potential for a higher- temperature leading edge, which can withstand the hypersonic thermal–mechanical environment. It can still offer a great improvement space in thermal management as leading edges for hypersonic vehicles.

Morphological origins of temperature and rate dependent mechanical properties of model soft thermoplastic elastomers

AbstractThermoplastic elastomers (TPEs) combine high elasticity with melt processability due to their structural features being based on physical associations rather than chemical crosslinking. Their mechanical properties are governed by the interplay of the different dynamics present in the system (i.e., hard block associations and soft block mobility) combined with their morphology. Irrespective of their exact chemical structure or type of association (crystals, hydrogen bonds, or glassy domains), many soft TPEs show a reduction in toughness at elevated temperatures. In this study, we investigate the high‐temperature mechanical properties of a model series of industrially relevant TPEs via systematically varying composition and molecular weight. The results show an increase in temperature resistance and in large‐strain stress response as chain length increases. We underline the key parameters that influence the mechanical behavior and explain the observed effect of molecular weight on both the temperature‐ and rate‐dependent large‐strain response. A physical network‐based model is presented that can explain the experimental findings assuming an improved network connectivity and extended lifetime of the entangled segments with increasing molecular weight.

Constitutive Model of Isotropic Magneto-Sensitive Rubber with Amplitude, Frequency, Magnetic and Temperature Dependence under a Continuum Mechanics Basis.

A three-dimensional nonlinear constitutive model of the amplitude, frequency, magnetic and temperature dependent mechanical property of isotropic magneto-sensitive (MS) rubber is developed. The main components of MS rubber are an elastomer matrix and magnetizable particles. When a magnetic field is applied, the modulus of MS rubber increases, which is known as the magnetic dependence of MS rubber. In addition to the magnetic dependence, there are frequency, amplitude and temperature dependencies of the dynamic modulus of MS rubber. A continuum mechanical framework-based constitutive model consisting of a fractional standard linear solid (SLS) element, an elastoplastic element and a magnetic stress term of MS rubber is developed to depict the mechanical behavior of MS rubber. The novelty is that the amplitude, frequency, magnetic and temperature dependent mechancial properties of MS rubber are integrated into a whole constitutive model under the continuum mechanics frame. Comparison between the simulation and measurement results shows that the fitting effect of the developed model is very good. Therefore, the constitutive model proposed enables the prediction of the mechanical properties of MS rubber under various operating conditions with a high accuracy, which will drive MS rubber’s application in engineering problems, especially in the area of MS rubber-based anti-vibration devices.

Thermal conductivity of a thick 3D textile composite using an RVE model with specialized thermal periodic boundary conditions

Finite element analysis is performed to virtually measure homogenized thermal conductivity of a thick 3D woven textile composite (T3DWC). Temperature-dependent thermal and mechanical properties of constituents are considered for the measurements over a wide range of temperature. A two-step homogenization approach is adopted here to simplify the analysis at the microscopic level without losing heterogeneity of the material at the macroscopic scale. First-step homogenization is carried out at a tow level using an analytical homogenization scheme. Fiber tows are homogenized and assigned with effective elastic and thermal properties. The solid tows are then implemented into a representative volume element considering the unique in-plane periodic fiber architecture of the thick composite material. Due to the unique in-plane periodicity, conventional periodic boundary conditions for thermal and mechanical loading conditions are reformulated. Anisotropic thermal conductivity of T3DWC is obtained from the second-step homogenization based on virtual thermal tests performed at ambient to elevated temperatures.

Temperature dependence of mechanical and thermodynamic properties of Ti(25+x)Zr25Nb25Ta(25-x) (x ≤ 20) refractory high entropy alloys: Influences of substitution of Ti for Ta

Temperature dependence of mechanical and thermodynamic properties of refractory high entropy alloys Ti(25+x)Zr25Nb25Ta(25-x) (x ≤ 20) are studied from ab initio quasi-harmonic Debye-Grüneisen model, and the influences of substitution of Ti for Ta are emphasized. The substitution of Ti for Ta results in the significantly reduced densities and the apparently enhanced specific elastic properties of Ti(25+x)Zr25Nb25Ta(25-x) alloys. Moreover, the increases of Ti content obviously improves ductility. At high temperature, the alloys with higher Ti content demonstrate the stronger thermal expansion behavior and thermal conductivity. Importantly, the alloys with higher Ti content possess the greater specific elastic properties at high temperature. Especially, in the studied temperature range, the present alloys exhibit good anti-softening ability based on temperature-dependent mechanical properties. Therefore, the replacement of Ta by Ti in refractory Ti(25+x)Zr25Nb25Ta(25-x) alloys is beneficial for formation of novel high temperature light-weight structural materials with lower density, better ductility and higher specific mechanical properties.

Theoretical characterization of the temperature dependence of the contact mechanical properties of the particulate-reinforced ultra-high temperature ceramic matrix composites in Hertzian contact

The novel theoretical models for the temperature dependence of the contact mechanical properties of the particulate composites in Hertzian contact are proposed in this paper, based on an assumption of the temperature-independent constant energy storage capacity for a specific brittle particulate composite, associating with the material yielding, and the theory of Hertzian contact. The yield stress, critical loads for the onset of the brittle and quasi-plastic damage modes, indentation strength, and the more commonly used fracture strength of the composites are expressed in terms of the basic material properties—the temperature-dependent Young’s modulus and specific heat capacity, and the critical flaw size. The models enable the priori and quantitative predictions of the contact damage behavior of the composites during the whole process of the Hertzian contact. The models are validated by comparing against the experimental measurements of the temperature-dependent contact mechanical properties of the particulate-reinforced ultra-high temperature ceramic matrix composites in the temperature range of 25 ∼ 800 °C, which were found probably to be the only reported experimental studies of the particulate composites. The temperature dependence of the contact damage behavior of the composites is revealed to be mainly governed by the temperature-dependent Young’s modulus and specific heat capacity, and the change of the flaw size above a certain temperature point. The models provide additional adequate methods for the determination of the nature and the underlying physical control mechanisms of the damage behavior of the composites at high temperatures.