Temperature Dependence Of Mechanical Properties Research Articles

Incorporation of plasticity and temperature effects on bituminous stabilised materials in a multi-layered pavement model

The mechanical properties of Bituminous Stabilized Materials (BSMs) have been widely studied in the past, however the influence of temperature on their non-linear constitutive properties has never been addressed. In this research, the role of temperature on the mechanical properties of a BSM prepared with asphalt emulsion and hydrated lime was investigated. Triaxial shear strength tests were performed at different temperatures and confining pressures. The experimental results allowed the development of finite element models defining the local stress and temperature-dependent mechanical properties. An approach for incorporating plasticity and temperature effects through a 2D axisymmetric finite element model of multilayer pavement was developed. Three pavement structures were subjected to the same load applications at different temperatures. Their responses were compared to determine the most critical scenario. In conclusion, plasticity and temperature are key factors for BSMs analysis and design while linear-elastic assumptions lead to overestimating the service life of rehabilitated pavements.

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.

Temperature dependence of mechanical properties and deformation mechanism of Fe–25Mn–3Al–3Si alloy at high strain rate

High-Mn steels exhibit an excellent combination of strength and ductility owing to the twinning induced plasticity (TWIP) effect or transformation induced plasticity (TRIP) effect, and have become an important material under service conditions of high strain rate and low temperature. However, the mechanical properties and deformation mechanism have not been fully understood during this extreme service conditions. Using impact test on Split Hopkinson Pressure Bar apparatus and microstructure characterization, the relationship among deformation temperature, mechanical properties and the underlying deformation mechanisms of high-Mn TRIP/TWIP steels during high strain rate (HSR) deformation was investigated. Our study shows that no matter the high temperature impact or low temperature impact, the Fe–25Mn–3Al–3Si alloy has good mechanical properties under large impact load and HSR deformation. Moreover, the strain hardening rate of the HSR impact samples at 300 °C are significantly higher than that at −80 °C and room temperature (RT). Detailed transmission electron microscopy results revealed that the strain rate has an important influence on the deformation mechanism of high-Mn TRIP/TWIP steel. Thus, TWIP effect also become the main deformation mechanism of Fe–25Mn–3Al–3Si alloy with a high SFE at 300 °C during HSR deformation. Higher strain rate and lower temperature can promote the formation of ε-martensite twinning (εT) and the occurrence of reversible transformation of ε-martensite ⇆ γ-austenite, which improve great the toughness of the alloy at low temperature (such as −80 °C). The models of reversible transformation are proposed based on the detailed microstructural characterization.

The mechanism and machinability of laser-assisted machining zirconia ceramics

Laser-assisted machining (LAM) is regarded as a useful technique which can process ceramic materials without damage and efficiently. This work reported a study on the mechanism by which LAM technology can improve the machinability of zirconia ceramic. The absorptivity of zirconia ceramic to fiber laser energy was obtained through the combination of experiment and simulation. The temperature-dependent mechanical property of zirconia ceramic was studied by nanoindentation experiments. Meanwhile, scratch tests were used to investigate the plastic-brittle transition and damage mechanism under various high-temperature conditions. The results showed that the absorptivity of zirconia ceramic to fiber laser energy is 0.52. The hardness and elasticity modulus are decreasing as the temperature increases. The functions that relate them to temperature are fitted. Moreover, the increase in temperature can enhance the plastic-brittle transition depth of ceramic and suppress median cracks and chipping. Furthermore, the shape of the chips is changed from discontinuous lumpy chips to continuous coiled chips. These evidence and research can clearly explain the mechanism by which LAM technology can improve the machinability of zirconia ceramics. They can also provide guidance and theory for the industrialization of LAM technology.

Crystallinity and temperature dependent mechanical properties of Poly(4-methyl-1-pentene)

Crystallinity and temperature dependent modulus in poly(4-methyl-1-pentene) were investigated over a wide temperature range covering glass transition of the amorphous phase. It turns out that the storage moduli of different samples decrease with the increase of crystallinity below Tg. The storage moduli of different samples are the same regardless of crystallinity at around 45 °C where the densities of crystalline and amorphous phases are identical. A model considering parallelly arranged crystalline skeleton and amorphous network allows a decomposition of the measured modulus into moduli of both phases. In addition to the fact that the modulus of amorphous phase in the glassy state is much larger than that of crystalline phase due to a higher density in amorphous phase than that of the crystals, a peculiar positive temperature dependent apparent crystalline phase modulus below Tg was observed. This seemingly anti-intuitive result can be understood by considering the strong constraint of the crystalline phase by the denser amorphous network at lower temperatures due to different thermal expansion coefficients of the two phases.

Temperature dependent mechanical properties of MAB phase Fe2AlB2

As a new type of laminate materials, the MAB phase Fe2AlB2 is attractive due to its near-room magnetocaloric properties. In this work, we propose the energy-strain approach to the elastic constants of MAB phase Fe2AlB2. The quasi-static approximation in combination with first-principles calculations is used to study the magnetic and elastic properties of Fe2AlB2 at finite temperature (0–1300K). Our temperature dependent polycrystalline moduli have similar tends to experiments, due to the proper approximation to the paramagnetic state above room temperature. Both the lattice parameters and elastic constants show the strong anisotropy in a range of 0–1300K. Although only Fe atoms contribute the magnetic property, their local magnetism plays a key role in the phase stability and the temperature dependent mechanical properties of Fe2AlB2.

Model-based analysis of temperature-dependent dynamics in CFRP spindle unit

The application of CFRP to machine tool structures can potentially improve their dynamic characteristics and energy efficiency owing to its highly specific material properties. The different thermal characteristics of CFRP and steel in spindle units likely induce unique thermal deformation, which affects the bearing dynamics. This research proposes a modeling method of CFRP spindle unit dynamics via generalized multipoint receptance coupling with contact characteristics at the spindle-holder interface. The temperature-dependent mechanical properties are analyzed by parameter identification from the model. The translational stiffness and damping of bearings in the CFRP spindle increase with temperature increase at high rotational speed.

Unraveling the molecular mechanism of collagen flexibility during physiological warmup using molecular dynamics simulation and machine learning

Physiological warmup plays an important role in reducing the injury risk in different sports. In response to the associated temperature increase, the muscle and tendon soften and become easily stretched. In this study, we focused on type I collagen, the main component of the Achilles tendon, to unveil the molecular mechanism of collagen flexibility upon slight heating and to develop a model to predict the strain of collagen sequences. We used molecular dynamics approaches to simulate the molecular structures and mechanical behavior of the gap and overlap regions in type I collagen at 307 K, 310 K, and 313 K. The results showed that the molecular model in the overlap region is more sensitive to temperature increases. Upon increasing the temperature by 3 degrees Celsius, the end-to-end distance and Young’s modulus of the overlap region decreased by 5% and 29.4%, respectively. The overlap region became more flexible than the gap region at higher temperatures. GAP-GPA and GNK-GSK triplets are critical for providing molecular flexibility upon heating. A machine learning model developed from the molecular dynamics simulation results showed good performance in predicting the strain of collagen sequences at a physiological warmup temperature. The strain-predictive model could be applied to future collagen designs to obtain desirable temperature-dependent mechanical properties.

Determination of the frequency- and temperature-dependent stiffness and damping properties of thermoplastics for the prediction of the vibration and heating behaviour during ultrasonic welding

The precise and realistic simulation of the vibration and heating behaviour of thermoplastics in the ultrasonic welding process has so far been associated with great challenges. In particular, the determination of the required frequency- and temperature-dependent mechanical stiffness and damping properties in the high-frequency vibration range is only insufficiently possible according to the current state of the art, which prevents an early and valid numerical prediction of the weldability in the development process of new joining components. In order to provide more precise input data (storage and loss modulus) for describing the material behaviour of thermoplastics in the ultrasonic welding process in the future, a novel measurement concept was implemented that is based on the adaptation of simulation results to real structure-borne sound measurements. The test rig concept was successfully commissioned and calibrated at room temperature and the calculation routine for material data determination was implemented. On the basis of the generated material data, an increase in the prediction quality of the vibration behaviour in a frequency range of 1 Hz to 22.5 kHz of rectangular specimens at room temperature could already be achieved compared to the state of the art using dynamic mechanical analysis and a time–temperature shift approach. Measurements at different ambient temperatures up to 60 °C were also carried out. Although the prediction quality of the vibration behaviour was slightly improved at 60 °C, there is still a need for optimisation with regard to the test specimen geometry and the further development of the evaluation routine in order to increase the analysable temperature range on the one hand and the quality of the generated material data on the other.

Temperature-Dependent Thermal and Mechanical Properties of a Wire Arc Additively Manufactured Low Transformation Temperature Steel

Temperature-Dependent Thermal and Mechanical Properties of a Wire Arc Additively Manufactured Low Transformation Temperature Steel

Free axisymmetric vibrations of heated non-uniform Bi-directional FGM Mindlin rings employing quadrature approaches

The present article investigates the axisymmetric vibrations of non-uniform bi-directional functionally graded rings under two-dimensional temperature distribution on the basis of first-order shear deformation theory. The linear variation of thickness along the radial direction is controlled by a taper parameter. The temperature-dependent mechanical properties are assumed to be graded in thickness as well as radial direction. The separation of variables method is applied to obtain the classical solution of two-dimensional heat conduction equation by imposing the thermal boundary conditions. The governing differential equations of thermoelastic equilibrium and axisymmetric motion together with boundary conditions are extracted from Hamilton’s principle. The quadrature technique is used to obtain the frequency equations and then the lowest three roots of these equations are calculated by MATLAB. After validating the results for the present approach, numerical results are given to analyze the effects of thermal environment, taper parameter, volume fraction index, heterogeneity and density parameters on the frequency parameter. Mode shapes for the specified rings are illustrated.

Investigation the temperature-dependent surface mechanical properties of PolyJet printed samples by cyclic indentation testing in a DMA system

Tools and products used in everyday life are regularly exposed to dynamic, cyclical stress. These stresses are particularly significant in the case of polymers, as their viscoelastic behavior means that creep can be considerable even at room temperature. Therefore, polymer components are often tested for maximum deformation rather than for maximum load-bearing capacity. Basic material testing methods are tensile, compression, and flexure tests, which are excellent for determining the material properties of the bulk material. However, in some cases, it is more appropriate to investigate surface mechanical properties. The ideal method for this is the depth-sensing indentation test. This method has been widely applied to polymers in the last ten years, but cyclic tests are rare, and creep is not considered in this type of indentation test. In the case of cyclical tests, temperature dependence is not fully examined, either. This paper presents the results of cyclic indentation tests on photopolymer specimens produced by additive manufacturing with the use of a dynamic mechanical analyzer with a unique indentation clamp. We performed the tests at three temperatures to investigate the influence of temperature on cyclic indentation tests. The test results show the variation of deformation between cycles and the significant effect of temperature.

Time-and temperature-dependent compressive behavior of woven carbon fabric reinforced polyamide composite laminate

Plain woven carbon fabric reinforced polyamide (CF/PA) composite laminate was developed using hot-pressed processing with a vacuum-assisted system. Temperature-dependent mechanical properties of the CF/PA composite laminate under longitudinal compressive loading were examined. The compressive mechanical properties of the composite laminate decreased considerably with increasing the temperature to 120°C. The compressive strength and strain at maximal stress reduced rapidly below 80°C, while the compressive modulus declined slightly underneath 50°C. The glass transition temperature of the CF/PA composite was found to be about 50°C by the differential scanning calorimetry, which almost corresponded to the slight reduction of the elastic modulus at temperatures below 50°C. The time-dependent creep behavior of the CF/PA laminate under compressive loading at isotherms between 25°C and 50°C was studied. Creep strains of the CF/PA composite samples increased with rising temperature. The smooth creep compliance master curve of the CF/PA composite was obtained by shifting short-term creep compliance curves using the time–temperature superposition principle. The master curve provided a creep prediction to 961.6 days with the measured data in only 12.5 days.

Temperature-dependent mechanical properties and elastocaloric effects of multiphase nanocrystalline NiTi alloys

We investigate the temperature-dependent mechanical properties and elastocaloric effects of different multiphase nanocrystalline NiTi alloys with grain sizes of 10 nm, 15 nm, 20 nm, 27 nm, 34 nm and 55 nm. These multiphase nanocrystalline NiTi alloys mainly consist of B2, B19′ and R phases and can undergo the thermally induced phase transition over a wide temperature range from 208 K to 353 K. Their superelastic deformation (loading to a strain of 4%) is contributed by combinations of the elastic deformation of B2 phase, the R → B2 phase transition, the reversible martensite reorientation and the B2 → R and B2/R → B19' phase transitions. Such complex deformation mechanism together with the microstructure evolution with temperature brings strong temperature-dependences of the mechanical properties and elastocaloric effects. As results, at the grain sizes of 15 nm ∼ 20 nm, the stress under a constant superelastic strain can show a significant V-shaped variation with temperature. At the grain size of 55 nm, the adiabatic temperature drop can even change from −8.5 K to −29 K ∼ −35.8 K as the ambient temperature rises from 293 K to 333 K. By comparison of the mechanical properties and elastocaloric effects of the different multiphase nanocrystalline NiTi alloys, it is found that the one with the grain size of 20 nm exhibits the best comprehensive cooling performances, which has a soft near-linear superelasticity (a moderate driving force), a very wide refrigeration temperature window (> 245 K) with considerable adiabatic temperature drops (∆Tmax= −17.1 K), and a good functional stability. This work provides an experimental basis for using the multiphase nanocrystalline NiTi alloys as solid-state refrigerants.

Temperature-dependent mechanical properties of TaC and HfC

Temperature-dependent mechanical properties of TaC and HfC

Homogenization temperature dependent microstructural evolution and mechanical properties in a Nb-stabilized cast austenitic stainless steel

A Nb-stabilized cast austenitic stainless steel is processed by homogenization treatments at 1050 °C, 1150 °C, and 1250 °C respectively to investigate microstructure dependent deformation behaviors and mechanical properties. Homogenization treatment at 1050 °C could not change the size of primary NbC, while significant dissolution of primary NbC destroys the network connectivity after homogenization treatments at temperatures above 1150 °C. Meanwhile, dissolution of NbC will increase C and Nb content in austenite matrix, leading to an increase in SFE. Nucleation of microcracks within NbC at the initial stage of deformation is caused by plastic strain incompatibility at the NbC/γ interface. Fast crack propagation along the continuous network of primary NbC leads to premature fracture at a lower stress level, and resultant lower ultimate tensile strength and elongation in as-cast and 1050-H samples. A higher SFE reduces the susceptibility to localization of deformation and crack propagation along the discrete primary NbC is suppressed, resulting in an obvious improvement in the ultimate tensile strength and elongation in 1150-H and 1250-H samples. • The dissolution and precipitation of NbC during homogenization treatments by different temperatures were revealed. • A higher SFE is responsible for the lower rate of deformation-induced α'-martensitic transformation by suppressing the planar slip. • A higher SFE reduces the susceptibility to localization deformation and the crack propagation along the primary NbC is suppressed. • A noticeable improvement in the ultimate tensile strength and elongation after homogenization treatment at temperatures above 1150 °C.

An energy-based elastoplastic damage model for concrete at high temperatures

Although structural concrete is widely used in civil engineering, the proper modeling of its thermo-mechanical behavior remains a challenging issue for the academic and engineering communities due to the complexity involved in the underlying micro-cracking process. In this work, the previous thermodynamically consistent energy-based elastoplastic damage model is extended to concrete at high temperatures, with the aim to describe the material nonlinear behavior and provide numerical predictions of concrete structures. Both the thermal expansion and transient creep strain are incorporated in the kinematics. Within the framework of continuum damage mechanics, two mechanical damage variables that lead to a fourth-order damage tensor are introduced to describe stiffness degradation of concrete under predominant tension and compression, respectively. Moreover, temperature-dependent mechanical properties are adopted to describe the thermal degradation and the thermo-mechanically coupled behavior of concrete at high temperatures. The plastic flow is described by the effective stress space plasticity and the evolution laws for the mechanical damage variables are driven by the conjugate elastoplastic damage energy release rates. The proposed model is validated by several benchmark experiments of plain concrete and then applied to reinforced concrete (RC) structures. The well agreement between the numerical predictions and experimental results indicates that the proposed model is promising in quantifying the global responses and assessing the safety of plain concrete and RC structures at high temperatures.

L-Arginine as Bio-Based Curing Agent for Epoxy Resins: Temperature-Dependence of Mechanical Properties.

The precise characterization of new bio-based thermosets is imperative for the correct assessment of their potential as matrix material in fiber-reinforced polymer composites. Therefore, the mechanical properties of diglycidyl ether of bisphenol a (DGEBA) cured with l-arginine were investigated to determine whether the bio-based thermoset possesses the required mechanical properties for application as a matrix material. The cured thermoset is called Argopox. The mixture of amino acid and epoxy resin was prepared via three-roll milling and cured in the presence of an urea-based accelerator. The tensile, compression, flexural and toughness properties of Argopox were characterized at T=−40 ∘C, 22 ∘C and 80 ∘C to determine the temperature-dependence of the thermoset’s mechanical properties in its service temperature range. The glass transition temperature Tg was analyzed via dynamic mechanical analysis (DMA) and is approximately 119 ∘C. The tensile, compression and flexural strength at 22 ∘C are about 56 MPa, 98 MPa and 85 MPa, respectively. The critical stress intensity factor KIC and fracture energy GIC at 22 ∘C are roughly 1.1 MPam0.5 and 510 Jm−, respectively. Consequently, Argopox possesses mechanical properties that reach performance levels similar to that of materials which are already used as matrix for fiber reinforced composites.

Temperature-dependent mechanical properties and the microscopic deformation mechanism of bilayer γ-graphdiyne under tension

γ-graphdiyne (γ-GDY) is a new two-dimensional carbon allotrope that has received increasing attention in scientific and engineering fields. The mechanical properties of γ-GDY should be thoroughly understood for realizing their practical applications. Although γ-GDY is synthesized and employed mainly in their bilayer or multilayer forms, previous theoretical studies mainly focused on the single-layer form. To evaluate the characteristics of the multilayer form, the mechanical properties of the bilayer γ-GDY (γ-BGDY) were tested under uniaxial tension using the molecular dynamics simulations. The stress–strain relation of γ-BGDY is highly temperature-dependent and exhibits a brittle-to-ductile transition with increasing temperature. When the temperature is below the critical brittle-to-ductile transition temperature, γ-BGDY cracks in a brittle manner and the fracture strain decreases with increasing temperature. Otherwise, it exhibits ductile characteristics and the fracture strain increases with temperature. Such a temperature-dependent brittle-to-ductile transition is attributed to the interlayer cooperative deformation mechanism, in which the co-rearrangement of neighboring layers is dominated by thermal vibrations of carbon atoms in diacetylenic chains. Furthermore, the brittle-to-ductile transition behavior of γ-BGDY is independent of loading direction and loading rate. The ultimate stress and Young’s modulus decrease at higher temperatures. These results are beneficial for the design of advanced γ-GDY-based devices.

Temperature-dependent structural, mechanical, and thermodynamic properties of B2-phase Ti2AlNb for aerospace applications

Temperature-dependent structural, mechanical, and thermodynamic properties of B2-phase Ti2AlNb for aerospace applications