Mechanical response analysis of asphalt microstructure under tensile and compressive loading based on finite element methods

Strain-induced work function in h-BN and BCN monolayers

First principle study of strain tunable electronic and optical properties of half-Heusler alloys XCoGe (X=V, Nb, Ta)

Al2O3 atomic layer deposition (ALD) is a model ALD system and Al2O3 ALD films are excellent gas diffusion barrier on polymers. However, little is known about the response of Al2O3 ALD films to strain and the potential film cracking that would restrict the utility of gas diffusion barrier films. To understand the mechanical limitations of Al2O3 ALD films, the critical strains at which the Al2O3 ALD films will crack were determined for both tensile and compressive strains. The tensile strain measurements were obtained using a fluorescent tagging technique to image the cracks. The results showed that the critical tensile strain is higher for thinner thicknesses of the Al2O3 ALD film on heat-stabilized polyethylene naphthalate (HSPEN) substrates. A low critical tensile strain of 0.52% was measured for a film thickness of 80 nm. The critical tensile strain increased to 2.4% at a film thickness of 5 nm. In accordance with fracture mechanics modeling, the critical tensile strains and the saturation crack densities scaled as (1/h)1/2 where h is the Al2O3 ALD film thickness. The fracture toughness for cracking, KIC, of the Al2O3 ALD film was also determined to be KIC = 2.30 MPa m1/2. Thinner Al2O3 ALD film thicknesses also had higher critical strains for cracking from compressive strains. Field-emission scanning electron microscopy (FE-SEM) images revealed that Al2O3 ALD films with thicknesses of 30–50 nm on Teflon fluorinated ethylene propylene (FEP) substrates cracked at a critical compressive strain of ∼1.0%. The critical compressive strain increased to ∼2.0% at a film thickness of ∼20 nm. A comparison of the critical tensile strains on HSPEN substrates and critical compressive strains on Teflon FEP substrates revealed some similarities. The critical strain was ∼1.0% for film thicknesses of 30–50 nm for both tensile and compressive strains. The critical compressive strain then increased more rapidly than the critical tensile strain for thinner films with thicknesses < 30 nm. The high critical tensile and compressive strains for thin Al2O3 ALD films should be very useful for flexible gas diffusion barriers on polymers.

In this paper, we create an integral‐rotation linear‐strain model (IRLSM) for the Philippine Sea plate (PHIL) on the basis of the ITRF2000 velocities of 7 sites on the PHIL. Our study indicates that the current‐day tectonic motion of PHIL is a clockwise rotation, which is consistent with the rotational direction estimated by NNR‐NUVEL‐1A, but largely different from the rotational pole position and angle velocity of NNR‐NUVEL‐1A. Our model can uniformly and accurately describe the current tectonic movement and interior deformation of PHIL as compared with Sella's rigid motion model (RMM). There is an intensive deformation‐strain field within the PHIL and there is consistent eastward deformation on the plate. The deformation rate is small near the central tectonic line and large near the eastern and western boundaries, small at the southern and northern ends and large in the central part. The eastward deformation rate on the Mariana Arc is as large as 48.4mm/a. The NS‐trending deformation on the plate differs evidently in the eastern and western parts with a very small rate in the eastern part and a larger rate near the Manila Trench in the western part. The northward deformation rate at the north end is 11.3mm/a and the southward deformation rate at the south end is 29.3mm/a. The principal strain field is divided into the eastern and western areas from the central tectonic line. In the eastern area, the tensile strain is very intensive, while the compressive strain is very weak. The principal tensile strain is in near‐EW direction, the principal tensile and compressive strain rates increase gradually from the central tectonic line to the east, and the principal tensile strain rate reaches the highest value of 8.58×10−8/a near the southeast boundary (148°E, 15°N). In the western area, the principal compressive strain is very strong in a direction of NW‐SE, while the principal tensile strain is rather weak. From the central tectonic line to the west, the principal compressive and tensile strain rates increase gradually and the principal compressive strain rate reaches the maximum value of 5.71×10−8/a near the northwest boundary (122°E, 23°N). Closely related to the intraplate and surrounding tectonic settings, the spatial variation of deformation‐strain field of PHIL can be considered as a reflection of tectonic stress field.

High-resolution finite element models with tissue strength asymmetry accurately predict failure of trabecular bone

Tuning of optical performance of CrS2 monolayer using strain engineering

The structural, electronic, vibrational, and optical properties of 2D- 2H-WTe2 monolayer are investigated using density functional theory with respect to a plane wave ultrasoft pseudopotentials (PW-USPPs) in a generalized gradient approximation (GGA) and with the Hubbard potential (GGA + U). The equilibrium state properties such as lattice parameters, unit cell volume, bulk modulus, and its derivative are determined. The band gap values of monolayer 2H-WTe2 are investigated for unstrained, 2% biaxial compression, and biaxial tensile stress using GGA, respectively. The obtained band gap values of 2H-WTe2 with respect to GGA are 1.043, 1.1487, and 0.9439 eV for unstrained, biaxial compression, and tensile strain, respectively. Moreover, the band gap values determined using Hubbard correction (GGA + U) are 1.1089 eV (unstrained), 1.2332 eV (2% biaxial compression), and 0.9945 eV (2% biaxial tensile stress), respectively. The band gap value obtained using Hubbard correction predicts the experimental value more precisely. The projected density of state shows W (3d) orbital is more dominant both in the valence band maximum and conduction band minimum. Moreover, a small amount of tensile or compressive strain is used to tune the band gap of the monolayer without affecting its direct band gap nature. In addition to this, the phonon dispersion and optical properties are discussed for tensile strain, unstrained, and compressive strain, respectively.

Over the decades, there has been a significant increase in the use of fibres in concrete for improving its properties such as tensile strength and ductility. The fibre concrete is also used in retrofitting existing concrete structures. Among many different types of fibres available today, glass fibre is a recent introduction in the field of concrete technology. Glass fibre has the advantages of having higher tensile strength and fire resistant properties, thus reducing the loss of damage during fire accident of concrete structures. In this investigation glass fibres of 450 mm length are added to the concrete by volume fraction of up to 1% to determine its strength and fire resistant characteristics. Comparison of the strength and fire-resistance performance of conventional concrete and glass fibre concrete was made. The paper presents the details of the experimental investigations and the conclusions drawn there from. Generally, concrete is strong in compression and weak in tension. Concrete is brittle and will crack with the application of increasing tensile force. Once concrete cracks it can no longer carry tensile loads. In order to make concrete capable of carrying tension at strains greater than those at which cracking initiates, it is necessary to increase the tensile strength. To increase the tensile and flexural strength, fibres are added in concrete. The addition of fibres to concrete will result in a composite material that has properties different from those of un-reinforced concrete. The extent of this variation depends not only on the type of fibres, but also on the fibre dosage. The incorporation of fibres into a brittle concrete can have the effect of controlling the growth and propagation of micro cracks as the tensile strain in the concrete increases. Care is needed in using fibre as additive in concrete. The use of fibres in concrete has increased with the development of fast-track construction. In fact, nearly 65 per cent of the fibres produced worldwide is currently used in concrete. It offers increasing toughness and ductility, tighter crack control and improved load-carrying capacity. Different types of fibres are available in the market for reinforcing concrete and they are: steel, glass, acrylic, aramid, carbon, nylon, polyester, polyethylene, polypropylene, etc. Besides, natural fibres like sisal, wood cellulose, banana, jute, etc., have also been used. From the above mentioned fibres, glass fibre is more advantageous on the basis of strength and fire resistant characteristics. It has been recognized that adding small, closely spaced and uniformly dispersed fibres to concrete serves to arrest cracks and improve its properties under static and dynamic loading. Round steel fibre is the most common variety in use for improving the tensile, flexural, impact and fatigue strength of concrete. The ductility and toughness of concrete are also improved with the addition of this fibres. Steel fibre have been used in various types of structures such as earthquake resistant structures, road overlays, airfield pavements and bridge decks. Alkali resistant glass fibre reinforcement is a relatively new addition to the family of fibres that impart high tensile strength, high stiffness, high chemical resistance and considerable durability to FRC (Fibre Reinforced Concrete). Adding polyesters fibre to concrete pavements resulted in the developments of the micro shrinkage cracks induced during hydration. These fibres improve the flexural strength and energy absorption of concrete . Glass fibres are useful because of their high ratio of surface area to weight. However, the increased surface area makes them much more susceptible to chemical attack. By trapping air within them, blocks of glass fibre makes good thermal insulation, with a thermal conductivity of order of 0.05 w/(mk). The strength of the glass fibre is usually tested and reported for virgin or pristine fibres those which have just been manufactured. The freshest and thinnest fibers are more ductile. The more the surface is scratched, the less the resulting tenacity. Because glass has an amorphous structure, its properties are the same along the fiber and across the fiber. Humidity is an important factor in the tensile strength. Moisture is easily absorbed, and can worsen microscopic cracks and surface defects, and lessen tenacity. Glass fibres improve the strength of the material by increasing the force required for deformation and improve the toughness by increasing the energy required for

Optimization of matrix viscosity improves polypropylene fiber dispersion and properties of engineered cementitious composites

Effect of strain on the optical properties of LaNiO3: A first-principle study

Electronic and phononic modulation of MoS2 under biaxial strain

Over the past decade, the certified power conversion efficiency of perovskite solar cells (PSCs) has increased to 26.1%. However, phase instability originating from lattice strains, has limited their commercialization. Strains will inevitably be generated during the PSC fabrication and service process due to the “soft lattice” nature of halide perovskites. In particular, flexible PSCs are subjected to not only mechanical tensile and compressive loads, but also suffer from thermal stresses. In this study, strain-induced changes in the phase stability and the corresponding optoelectronic properties of CsPbI3−xBrx (CsPbI3, CsPbBr3, and CsPbI2Br) systems under tensile and compressive stresses were investigated using first-principles calculations. The results showed that compressive stresses reduce the bandgap value and increase the light absorption coefficient; thus, the optoelectronic performance is improved, whereas the light absorption coefficient decreases regardless of how the bandgap changes under tensile stresses. Moreover, under the same stress, the tensile strain value was twice that of the compressive strain, and the critical value of the transition from the cubic to tetragonal phase was lower, indicating that phase stability was worse under tensile stresses. Therefore, during the fabrication of PSCs, the tensile stress state should be adjusted to the compressive stress state, which is favorable for enhancing PSCs photovoltaic performance and phase stability. The results not only provide direct evidence of tensile and compressive strains influencing the phase stability and optoelectronic property changes in halide perovskites, but also highlight lattice-strain tailoring for the composition design, process optimization, and interface engineering of efficient and stable PSCs.

The REBCO tapes with high irreversible field and large current density, which can be industrially produced, have great potential for future fusion reactor. In the high temperature superconductors (HTS) magnets, REBCO tapes will be subjected to various kinds of strain/stress, the research in the effect of uniaxial strain effect on the performance of REBCO tapes is very necessary. The tensile and compressive axial strains dependence of critical current have been investigated at 77K in self-field with the U-spring devices of YBCO tapes, manufactured by Shanghai Superconducting Technologies Co. (SSTC) in China. Until the compressive strain to -8%, no degradation behavior of critical current could be seen, and the n-value of YBCO tapes hardly depended on compressive strain. The irreversible tensile strain limit was ~0.35%. Before reaching irreversible tensile strain limit, the degradation of I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> was slight and reversible. When the applied tensile strain exceeded 0.35%, the I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> and n-value reduced rapidly and was not recovered back anymore.

Circular deformation as a means of simultaneously evaluating the compressive and tensile strain in vulcanized rubber

Stability and thermoelectric properties of the MgO monolayers under tensile and compressive strain