Temperature Dependence Of Mechanical Properties Research Articles

Temperature and size dependent mechanical properties of vapor synthesized zinc tungstate nanowires

Monoclinic structured zinc tungstate (ZnWO4) nanowires were synthesized using a simple physical vapor deposition procedure. The nanowires grew along the [001] direction and exhibited faceted surfaces. The Young's modulus of the nanowires was characterized by a resonant method based on laser Doppler vibrometry. The modulus of nanowires with thicknesses greater than ∼120 nm was close to that of their bulk counterparts, whilst the modulus of those with thicknesses in the range of 120 nm–67 nm decreased by ∼10%. Their modulus was also characterized over a temperature range from 300 to 650 K, and a dependency with temperature was observed. The fracture strain of the nanowires was characterized using a bending test based on optical microscope nanomanipulation in ambient atmosphere. The fracture strain of the nanowires slightly increased from 4% to 5% as their widths decreased from 325 to 50 nm, and no evidence of plastic deformation is observed during the direct fracture analysis by transmission electron microscope.

Temperature-dependent structural, thermal, and mechanical properties of Mo-10Nb joints prepared by SPS

Temperature-dependent structural, thermal, and mechanical properties of Mo-10Nb joints prepared by SPS

Cryogenic Temperature Dependence of Mechanical Properties and Strain Dependence of Critical Current of Commercial REBCO Coated Conductors

Cryogenic Temperature Dependence of Mechanical Properties and Strain Dependence of Critical Current of Commercial REBCO Coated Conductors

Impact of the Dopant Species on the Thermomechanical Material Properties of Thermoelectric Mg2Si0.3Sn0.7.

Thermoelectric generators are an excellent option for waste heat reuse. Materials for such devices have seen their thermoelectric properties improving constantly. The functioning of a generator, however, does not only depend on thermoelectric properties. Thermal and mechanical properties play a decisive role in the feasibility of any thermoelectric generator. To shed light on the properties exhibited by thermoelectric materials, we present the temperature dependent characterization of Young’s modulus and coefficient of thermal expansion for Mg2Si0.3Sn0.7. Comparing undoped to Bi-doped n-type and Li-doped p-type material, we investigated the influence of doping in the relevant temperature regime and found the influences to be minor, proving similar properties for n- and p-type. We found a Young’s modulus of 84 GPa for the p-type and 83 GPa for the n-type, similar to that of the undoped compound with 85 GPa. The thermal expansion coefficients of undoped, as well as n- and p-type were equally similar with values ranging from 16.5 to 17.5 × 10−6 1/K. A phase analysis was performed to further compare the two materials, finding a similar phase distribution and microstructure. Finally, using the gathered data, estimations on the possible thermally induced stresses under a temperature difference are provided to evaluate the relevance of knowing temperature dependent thermal and mechanical properties.

Finite element simulation and experimental investigation on the effect of temperature on pseudoelastic behavior of perforated Ni–Ti shape memory alloy strips

In the present study, the temperature-dependent pseudoelastic behavior of shape memory alloy (SMA) sheets is studied experimentally and by finite element (FE) modeling. For this purpose, temperature-dependent mechanical properties for Ni–Ti alloy materials are first obtained by using direct tensile and three-point bending experiments at 23 °C, 50 °C, and 80 °C temperatures, respectively. The structure of these materials is examined at different temperatures using SEM images and the XRD test. Furthermore, using the FE model, the pseudoelastic behavior and the effect of temperature on the residual deflection of the prose-shape memory strips with a circular hole under three-point bending loads are studied. After validating the results of the FE model with the results of experimental tests, the effects of various parameters such as the diameter and number of holes on residual deformation and residual strains are investigated. The results show that with increasing temperature, the mechanical properties including the tensile strength, Young’s modulus, yield stress, and flexural strength of SMA strips increase significantly. For solid strips, although increasing the temperature increases the maximum flexural force, in contrast, it reduces the flexural stiffness. In solid strips, flexural stiffness decreases by 5.5% with increasing temperature from 23 °C to 80 °C.

Numerical simulation of 14Mov6-3 steel CT-specimen Fracture Behavior

Steel grade 14MoV6 3 is used for manufacturing of boilers and steam pipelines designed for steam temperatures up to 560°C. This paper presents the numerical simulation of a CT-specimen, using the finite element method. The analysis was performed using Ansys Workbench R21, and represents the initial stage of extensive research involving the behaviour of 14MoV6 3 steel. The goal was to simulate the real experimental conditions, including boundary conditions and loads, which were defined in accordance with relevant standards, and to obtain representative results. The temperature dependent mechanical properties needed for the simulation of plastic behaviour of such specimens under tensile loads were obtained from the experimental data and the literature.

Modeling the behavior of CFRP-strengthened RC slabs under fire exposure

This paper presents the development of a numerical model that simulates the fire response of reinforced concrete (RC) slabs externally strengthened with carbon fiber-reinforced polymer (CFRP)laminates using two different techniques, externally bonded (EB) and near-surface mounted (NSM). A three-dimensional (3D) nonlinear finite element (FE) model is developed to predict the thermal and structural behavior of strengthened RC slabs subjected to fire. The model incorporates temperature-dependent thermal and mechanical properties of concrete, steel reinforcement, and CFRP, as well as mechanical bond interaction between CFRP and concrete interfaces. The predicted temperature profiles, ultimate loads, and midspan deflections are compared with previously published experimental data. Results from the proposed model show a good correlation with the experimental data throughout the fire exposure duration. The validated model can be adapted to conduct parametric studies intended to inspect the effect of important factors that influence the behavior of strengthened RC slabs under fire.

Temperature-dependent mechanical properties of Al/Cu nanocomposites under tensile loading via molecular dynamics method

Abstract Al-Cu Nanocomposites (NCs) are widely used in industrial applications for their high ductility, light weight, excellent thermal conductivity, and low-cost production. The mechanical properties and deformation mechanisms of Metal Matrix NCs (MMNCs) strongly depend on the matrix microstructure and the interface between the matrix and the second phase. The present study relies on Molecular Dynamics (MD) to investigate the effects of temperature on the mechanical properties and elastic and plastic behavior of the Al-Cu NC with single-crystal and polycrystalline matrices. The effects of heating on microstructural defects in the aluminum matrix and the Al/Cu interface were also addressed in the following. It was found that the density of defects such as dislocations and stacking fault areas are much higher in samples with polycrystalline matrices than those with single-crystal ones. Further, by triggering thermally activated mechanisms, increasing the temperature reduces the density of crystal defects. Heating also facilitates atomic migration and compromises the yield strength and the elastic modulus as a result of the increased energy of atoms in the grain boundaries and in the Al-Cu interface. The results showed that the flow stress decreased in all samples by increasing the temperature, making them less resistant to the plastic deformation.

Effect of ultrasonic forging strain processing on the surface layer microstructure and temperature-dependent mechanical properties of high nitrogen austenitic steel

The paper presents the research results on the effect of ultrasonic forging strain (UFS) processing of the high-nitrogen Cr–Mn–N austenitic stainless steel on the surface layer microstructure and tensile properties in the temperature range from −80 up to 20 °C. The high dispersion microstructure, strain aging with the formation of both CrN and Fe2N nitrides, as well as twinning were revealed in the surface layer 2–3 μm thick using a transmission electron microscope (TEM). In addition, ε-martensite with the hcp lattice was observed at a depth of more than 80 μm from the surface after UFS processing. Tensile tests showed that UFS processing had increased the yield strength. Elongation level of about 40% did not differ over the entire test temperature range. A ductile type of the fracture surfaces was observed for all test temperatures down to −80 °C.

Spatiotemporal Evolution of Stress Field during Direct Laser Deposition of Multilayer Thin Wall of Ti-6Al-4V.

The present work seeks to extend the level of understanding of the stress field evolution during direct laser deposition (DLD) of a 3.2 mm thick multilayer wall of Ti-6Al-4V alloy by theoretical and experimental studies. The process conditions were close to the conditions used to produce large-sized structures by the DLD method, resulting in specimens having the same thermal history. A simulation procedure based on the implicit finite element method was developed for the theoretical study of the stress field evolution. The accuracy of the simulation was significantly improved by using experimentally obtained temperature-dependent mechanical properties of the DLD-processed Ti-6Al-4V alloy. The residual stress field in the buildup was experimentally measured by neutron diffraction. The stress-free lattice parameter, which is decisive for the measured stresses, was determined using both a plane stress approach and a force-momentum balance. The influence of the inhomogeneity of the residual stress field on the accuracy of the experimental measurement and the validation of the simulation procedure are analyzed and discussed. Based on the numerical results it was found that the non-uniformity of the through-thickness stress distribution reaches a maximum in the central cross-section, while at the buildup ends the stresses are distributed almost uniformly. The components of the principal stresses are tensile at the buildup ends near the substrate. Furthermore, the calculated equivalent plastic strain reaches 5.9% near the buildup end, where the deposited layers are completed, while the plastic strain is practically equal to the experimentally measured ductility of the DLD-processed alloy, which is 6.2%. The experimentally measured residual stresses obtained by the force-momentum balance and the plane stress approach differ slightly from each other.

Temperature Dependence of Mechanical Properties and Plastic Flow Behavior of Cast Multicomponent Alloys Fe20Cr20Mn20Ni20Co20-xCx (x = 0, 1, 3, 5)

Temperature Dependence of Mechanical Properties and Plastic Flow Behavior of Cast Multicomponent Alloys Fe20Cr20Mn20Ni20Co20-xCx (x = 0, 1, 3, 5)

Temperature-dependent axial mechanical properties of Zircaloy-4 with various hydrogen amounts and hydride orientations

The effects of hydride amount (20–850 wppm), orientation (circumferential and radial), and temperature (room temperature, 100 °C, 200 °C) on the axial mechanical properties of Zircaloy-4 cladding were comprehensively examined. The fraction of radial hydride fraction in the cladding was quantified using PROPHET, an in-house radial hydride fraction analysis code. Uniaxial tensile tests (UTTs) were conducted at various temperatures to obtain the axial mechanical properties. Hydride orientation has a limited effect on the axial mechanical behavior of hydrided Zircaloy-4 cladding. Ultimate tensile stress (UTS) and associated uniform elongation demonstrated limited sensitivity to hydride content under UTT. Statistical uncertainty of UTS was found small, supporting the deterministic approach for the load-failure analysis of hydrided Zircaloy-4 cladding. These properties notably decrease with increasing temperature in the tested range. The dependence of yield strength on hydrogen content differed from temperature to temperature. The ductility-related parameters, such as total elongation, strain energy density (SED), and offset strain decrease with increasing hydride contents. The abrupt loss of ductility in UTT was found at ∼700 wppm. Demonstrating a strong correlation between total elongation and offset strain, SED can be used as a comprehensive measure of ductility of hydrided zirconium alloy.

Effect of varying Bi content on the temperature-dependent mechanical, dielectric, and structural properties of nominal Na1/2Bi1/2TiO3

Na1/2Bi1/2TiO3 (NBT) with varying Bi content has gained significant interest as a potential new material for solid-oxide fuel cells and oxygen separation membranes because of its excellent oxygen-ion conductivity. In this work, the effect of varying Bi content in NBT ceramics of compositions Na1/2BixTiO2.25+1.5x, where x = 0.485–0.510, on the temperature-dependent mechanical and dielectric properties and the crystal structure has been investigated, as these applications expose the components to high thermal and mechanical fields. The effects of Bi variation on phase compositions and structural transitions were systematically investigated by scanning electron microscopy-energy dispersive x-ray analyses and neutron diffraction at room temperature, in situ high-temperature x-ray diffraction, dielectric permittivity, and mechanical measurements. In-depth analysis of the temperature-dependent data shows that the Bi content of the samples does not alter the average crystal structure of the NBT; however, the temperature-dependent behavior of the latter depend on variations in Bi content and the associated oxygen vacancy concentration. This change in phase transition temperature displays a good correlation with the temperature-dependent ferroelastic response and with the Bi content.

Temperature-dependent mechanical response of 4D printed composite lattice structures reinforced by continuous fiber

Four-dimensional (4D) printing endows three-dimensional (3D) objects with structural customizability and functional tunability, which offers the potential to manufacture advanced equipment and devices for specific structural or functional requirements. Here, we investigated the temperature-dependent mechanical and shape memory properties of 4D printed continuous fiber reinforced composite horseshoe lattice structures (CFRCHLSs). Rectangular modified CFRCHLSs with diverse cell configurations were designed and prepared by fiber/matrix co-extrusion process utilizing continuous fibers and shape memory polymer (SMP). Isothermal compression experiments and thermo-mechanical cycle experiments were conducted to investigate the temperature-dependent mechanical properties and thermally-induced active deformation capabilities of 4D printed CFRCHLSs. The results indicate that 4D printed CFRCHLSs possess temperature-dependent equivalent stiffness and peak load, and exhibit shape recovery capabilities affected by geometric configuration. Furthermore, multi-step relaxation experiments were carried out, which revealed the relaxation phenomenon of 4D printed CFRCHLSs at continuous multiple displacements. This work provides guidance for structural design, integrated preparation and characterization of thermodynamic properties of fiber reinforced composite lightweight structures with intelligent deformation behavior.

Simplified calculation of flexural strength deterioration of reinforced concrete T-beams exposed to ISO 834 standard fire

Reinforced concrete (RC) T-shaped cross-section beam (so-called T-beam) is a common structural member in buildings where beams and slabs are monolithically cast together. In this paper, a simplified calculation method based on Russian design standard SP 468.1325800.2019 is introduced to determine the flexural strength of RC T-beams when exposed to ISO 834 standard fire. The idea of 500oC isotherm method, which is stipulated in both Eurocodes (EC2-1.2) and SP 468, is applied associated with specifications of temperature distribution on T-beams’ cross sections and the temperature-dependent mechanical properties of concrete and reinforcing steel. A case study is conducted to explicitly calculate the flexural strength deterioration (FSD) of T-beams compared to that at ambient temperature. A calculation sheet is established for parametric studies, from which the results show that the FSD factor of RC T-beams is adversely proportional to the dimensions of the beam’s web and flange. However, the effect of these components of T-beams is not significant.

Dynamic Polyamide Networks via Amide-Imide Exchange.

The diamide–imide equilibrium was successfully exploited for the synthesis of dynamic covalent polymer networks in which a dissociative bond exchange mechanism leads to high processibility at temperatures above ≈110 °C. Dynamic covalent networks bridge the gap between thermosets and thermoplastic polymers. At the operating temperature, when the network is fixed, dynamic covalent networks are elastic solids, while at high temperatures, chemical exchange reactions turn the network into a processible viscoelastic material. Upon heating a dissociative network, the viscosity may also decrease due to a shift of the chemical equilibrium; in such materials, the balance between processibility and excessive flow is important. In this study, a network is prepared that upon heating to above ≈110 °C dissociates to a significant extent due to a shift in the amide–imide equilibrium of a bisimide, pyromellitic diimide, in combination with poly(tetrahydrofuran) diamines. At room temperature, the resulting materials are elastic rubbers with a tensile modulus of 2–10 MPa, and they become predominantly viscous above a temperature of approximately 110 °C, which is dependent on the stoichiometry of the components. The diamide–imide equilibrium was studied in model reactions with NMR, and variable temperature infrared (IR) spectroscopy was used to investigate the temperature dependence of the equilibrium in the network. The temperature-dependent mechanical properties of the networks were found to be fully reversible, and the material could be reprocessed several times without loss of properties such as modulus or strain at break. The high processibility of these networks at elevated temperatures creates opportunities in additive manufacturing applications such as selective laser sintering.

Numerical simulation of hardfacing remanufacturing for large-scale damaged grinding roller

The present study is directed to the temperature and residual stress fields in the hardfacing remanufacturing for a large-scale grinding roller with damage. For this purpose, a numerical procedure for the hardfacing process based on the thermal cycle curve method was established, and the effectiveness of the proposed procedure was verified by the measurements of a multi-pass welding experiment with V-groove butt joint. A local model of bead-on-plate welding was used to check the heat source and extract the thermal cycle curve. The resulting thermal cycle curve was applied as a thermal load to the corresponding welding layer one by one. Based on the calculated material properties, the data files of the base metal (Grade:KmTBCr26) and the filling layers (Grade:ARCFCW9024) were re-developed to define the temperature-dependent physical and mechanical properties of the materials used in the hardfacing remanufacturing. The numerical simulation results reveal the changing trend and distribution of the temperature and residual stress fields during the hardfacing remanufacturing for the damaged grinding roller. The distribution of temperature and residual stress is very complicated due to the numerous welding layers in the hardfacing process. It is pointed out that with the increase of welding layers, the heat-affected zone of the grinding roller expands gradually, and the maximum tensile stress always appears at the position near the weld toe, which is prone to fatigue failure or interface peeling due to stress concentration.

Temperature-dependent mechanical properties and crack propagation modes of 3D printed sandstones

We aim to investigate the mechanical properties and crack propagation modes of 3D printed sandstone after high temperature, focusing on the alteration of furan resin during heating. Unlike the most current printed sandstone studies that are conducted at room temperature, we attempt to explore the performance of the heated printed sandstone, dominated by the furan resin. The heated 3D sandstones are investigated with a series of sophisticated in-door experiments at macro, meso, and microscopic levels. It is found that the uniaxial compressive strength and splitting tensile strength of the printed sandstones reached the maximum of 150 °C, at which the furan resin transforms from solid to liquid state, enabling to bond more sand particles. This is followed by the studies of crack propagation patterns and mechanical properties of heated specimens, where man-made cracks of different inclination angles are prefabricated and uniaxial compressive strengths are conducted. The results indicated that the peak strength of the cracked specimens first decreases and then increases with the increases of cracks inclination angle after heating. Furthermore, an X-ray computed tomography image is constructed, showing the difference between the internal fracture and the apparent fracture of the specimen. Our above findings show that these well-fabricated and easy-to-observing printed specimens could, to some extent, reflect heated natural sandstone behaviours, such as strength, crack initiation, and propagation. Nevertheless, when heated to 300 °C, the furan resin is becoming further dehydrated, almost losing its bonding capability and so the printed sandstone's initial structure could not be maintained any longer.

Temperature Dependent Mechanical Properties of Natural and Synthetic Rubber in Practical Structures

In this proposal the mechanical properties of natural and synthetic rubbers are studied under different temperatures both real and ageing heat treatment conditions. For this purpose, tire rubber and bearing pad rubber are considered as they are most governed in natural and synthetic rubber respectively. The experimental results confirm that the impact of real temperature is higher on the mechanical properties than that of ageing temperature because of ambient temperature aggravate thermal motion and changes the molecular arrangement of rubber other than the ageing samples recovers the mechanical properties during breezy. Except hardness, all the cases in terms of mechanical properties like tensile strength, elongation, Young's modulus and Poisson's ratio of bearing pad rubber provide the higher performance than the tire rubber. Under ageing treatment condition the degraded mechanical properties recover well by the natural rubber since extremely ordered long chain of the molecular structure. The significant differences in the micrographs of the two rubbers suggest that tire rubber consists of uniform grains because of its highly controlled molecular arrangement. Under heat treatment the microstructure turned rougher and the size of the voids became larger as temperature increases the secondary cross linking reaction which initiate to cracks.

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.