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In the present work, thermo-electro-mechanical buckling behavior of functionally graded piezoelectric (FGP) nanobeams is investigated based on higher-order shear deformation beam theory. The FGP nanobeam is subjected to four types of thermal loading including uniform, linear, and sinusoidal temperature rise as well as heat conduction through the beam thickness. Thermo-electro-mechanical properties of FGP nanobeam are supposed to change continuously in the thickness direction based on power-law model. To consider the influences of small-scale sizes, Eringen's nonlocal elasticity theory is adopted. Applying Hamilton's principle, the nonlocal governing equations of an FGP nanobeam in thermal environments are obtained and are solved using Navier-type analytical solution. The significance of various parameters, such as thermal loadings, external electric voltage, power-law index, nonlocal parameter, and slenderness ratio on thermal buckling response of size-dependent FGP nanobeams is investigated. [ABSTRACT FROM AUTHOR]

Alumina- and cordierite-based honeycombs with varying relative densities were extruded and sintered at the respective sintering temperatures. Solid samples are also prepared under identical conditions and flexural strength (σf) was estimated by three-point bend measurements. Buckling stress of honeycombs are predicted based on σf using standard equations and validated with quasi-static compression test along the channels of honeycombs with varying relative densities. The discrepancy observed on calculated and measured values is correlated with the pre-existing flaws indicating the criticality in close control of processing parameters. [ABSTRACT FROM AUTHOR]

Ascribed to its wide sensing range, high sensitivity, and low stiffness to match target objects with complex 3D shapes, the stretchable strain sensor has shown its promising applications in various fields, ranging from healthcare, bodynet, and intelligent traffic system, to the robotic system. This paper presents a low-cost and straightforward fabrication technology for the stretchable strain fiber with the combined attributes of a wide sensing range, exceptional linearity, and high durability. The hybrid composite consisting of carbon black and silicone is utilized as the functional material to respond to the external mechanical deformation due to the piezoresistive effect. To address the remarkable hysteresis of the CB-silicone composites, the latex tubes with excellent mechanical robustness and a considerable accessible tensile strain are introduced as the outer supporting components. After injecting the conductive CB-silicone composite into these tubes, the stretchable strain fibers are successfully prepared. Notably, the stretchable strain sensor exhibits linearity (R2 = 0.9854) in a wide sensing range (0–400%) and remarkable durability even after the 2500 cycles under 100% tension. Additionally, the potential of this stretchable strain fiber as the wearable strain sensor and the real-time feedback is demonstrated by detecting the body motion and the expansion devices. [ABSTRACT FROM AUTHOR]

In this work, we use in-situ TEM in combination with finite elemental analysis to reveal the sub-grain boundary formation during bending of Cu single crystal. The deformation process is featured by dislocations propagation, formation of stacking faults and deformation twins, and subsequent formation of a sub-grain boundary. Finite element analysis of stress distribution indicates the stacking faults and deformation twins are all initiated from the region that corresponds to the maximum shear stress. The formation of the sub-grain boundary is through the intersection between primary and secondary stacking faults/deformation twins. Real-time observation of the plastic deformation process during the bending of Cu single crystal, reveals the sub-grain boundary formation through the intersection between primary and secondary stacking faults/deformation twins. [ABSTRACT FROM AUTHOR]

Creep and shrinkage effects in concrete structures increase deformations over time but do not normally affect the strength of the structure in any appreciable way. However, for a concrete structure which is subject to second order effects, the loads experienced by the structure are dependent on its deformed shape and therefore the capacity of the structure to withstand the applied loads is dependent on the way it deforms over time. A slender reinforced concrete column is such a structure. This paper presents a first-principles method of analysing the time-dependent behaviour of slender concrete columns subjected to sustained eccentric loads and compares theoretical estimates of critical loads (at which the strength of the critical cross-section is exceeded by creepinduced internal actions) to the allowances made for the design of slender concrete columns by the Australian Standard for Concrete Structures AS3600-2009. In particular, the effects of the concrete compressive strength and the reinforcement ratio are investigated in terms of their infl uence on the creep-induced reduction of strength of slender columns. The method is based on the principle of superposition and makes use of the age-adjusted effective modulus method to predict the time-dependent behaviour of columns. [ABSTRACT FROM AUTHOR]

Nanoporous gold (NPG) provides a model material for studying small-scale deformation and the mechanical behavior of network solids. We report a transmission electron microscopy study of the defect structure in electron-transparent NPG leaf deformed by rolling. The results confirm that plastic deformation significantly enhances the defect density. Specifically, twins are formed on several sets of crystallographic planes, and their interaction forms Lomer-Cottrell locks. This inhibits dislocation escaping from NPG, thus avoiding the dislocation starvation scenario that is often considered in the 'smaller is stronger' context of small-scale plasticity. Instead, strain hardening is apparently linked to accumulation and interaction of twins. This paper provides a direct observation of the lattice defects in plastically deformed nanoporous gold, confirming the contribution of accumulation and interaction of defects to the strain hardening rate. [ABSTRACT FROM AUTHOR]

As the forging counterpart of fusion-based additive processes, additive friction stir deposition offers a solid-state deformation processing route to metal additive manufacturing, in which every voxel of the feed material undergoes severe plastic deformation at elevated temperatures. In this perspective article, we outline its key advantages, e.g. rendering fully-dense material in the as-printed state with fine, equiaxed microstructures, identify its niche engineering uses, and point out future research needs in process physics and materials innovation. We argue that additive friction stir deposition will evolve into a major additive manufacturing solution for industries that require high load-bearing capacity with minimal post-processing. This paper delineates additive friction stir deposition, which offers a solid-state deformation processing route to metal additive manufacturing and renders fully-dense material with fine, equiaxed microstructures in the as-printed state. [ABSTRACT FROM AUTHOR]

Herein, we report on mechanical deformation of single-crystal Ti2AlC MAX phase using compression testing of micropillars with a range of crystallographic orientations. Our results show that depending on the crystallographic orientation, the Ti2AlC micropillars either undergo only non-classical (non-Schmid) crystallographic slip, non-classical crystallographic slip followed by cleavage or cleavage without any appreciable crystallographic slip. The non-classical crystallographic slip is found to be a result of the strong dependence of crystallographic slip on both, the resolved shear stress and the stress normal to the slip plane. This work elucidates single-crystal level non-classical deformation mechanism(s) of a MAX phase and unravels the observed extreme plastic anisotropy of MAX phases. [ABSTRACT FROM AUTHOR]

This investigation is focused on the effects of nonlocality due to 2-D deformations arising in a nonlocal homogeneous isotropic thermoelastic solid which is subjected to a ramp type heat source with two temperature. There has been the use of Laplace and Fourier transforms for solving the equations. The expressions for displacement components, stress components and conductive temperature have been computed in the transformed domain. The numerical inversion technique has been used for obtaining the results in the physical domain. The effect of nonlocal parameter on the displacement components, conductive temperature and stress components have been represented graphically. [ABSTRACT FROM AUTHOR]

Effect of solutes, crystal orientation, sample's size, and dislocation density on the nano/microscale deformation of solute-strengthening Al alloys has been investigated via pillar compression tests. The Mg-solute-strengthening pillar with dislocation density of 1012 m−2 shows size- and orientation-dependent strength, while the strength of Si-Mg-solute-strengthening pillar with dislocation density of 1013 m−2 is size- and orientation- independent. With increasing the dislocation density, the strength of pillars increased and become size-independent. Links between the microstructure, sample's size and nano/microscale plasticity of solute-strengthening Al alloys were made via pillar compression testing. Deformation mechanism at nano/microscale was quantitatively explored. [ABSTRACT FROM AUTHOR]

The response of [100]-oriented single-crystal face-centered-cubic Al0.1CoCrFeNi and Al0.3CoCrFeNi high-entropy alloy (HEA) microcrystals tested from 293 to 573 K by means of in situ micro-compression is reported. At all temperatures, plasticity is governed by dislocation slip with significant strain hardening and intermittent strain bursts observed. A model, which is in good agreement with experimental measurements, is also developed to predict the effects of Al concentration, temperature, and crystal size on the strength of HEAs. The model interestingly predicts a softening response with an increase in Al concentration when the crystal size is ≤0.1 µm. Finally, this model can guide the development of advanced HEAs for small-scale applications. In situ scanning electron microscopy (SEM) experiments are performed to quantify the thermo-mechanical response of AlxCoCrFeNi microcrystals. A physics-based model is also proposed to predict the strength of high-entropy alloys as a function of crystal size, temperature, and Al concentration. [ABSTRACT FROM AUTHOR]

Pipelines are generally used to transmit energy sources from production sources to target places. Buried pipelines in saturated deposits during seismic loading could damage from resulting liquefaction due to accumulative excess pore-water pressure generation. In this paper, the evaluation of liquefaction potential in the vicinity of an offshore buried pipeline is studied using the control-volume-based finite element method. The objective of the present work is to study the effect of different governing parameters such as the specific weight of pipeline, Poisson's ratio, permeability of the soil, deformation module, pipeline diameter and pipeline burial depth on the soil liquefaction around a marine pipeline. The results of analysis indicated that with the increase of deformation module, Poisson's ratio and permeability of the soil coefficient, the liquefaction potential reduces. The liquefaction potential around the gas pipeline is much more than oil pipeline. [ABSTRACT FROM PUBLISHER]

The effects of varied shear correction coefficient on the first-order transverse shear deformation result of functionally graded material (FGM) thick circular cylindrical shells under thermal vibration are investigated and computed by using the generalized differential quadrature method. The computed and varied values of shear correction coefficient are usually functions of FGM power law index and environment temperature. In the thermoelastic stress-strain relations, the simpler form stiffness of FGM shells under linear temperature rise is considered. The equation of shear correction coefficient is derived and obtained by using the total strain energy principle. Two parametric effects: environment temperature and FGM power law index on the thermal stress and center deflection of FGM thick circular cylindrical shells are obtained and investigated. [ABSTRACT FROM AUTHOR]