Strain effect on graphene nanoribbon carrier statistic in the presence of non-parabolic band structure

The effect of tensile uniaxial strain on the non-parabolic electronic band structure of armchair graphene nanoribbon（AGNR） is investigated.In addition,the density of states and the carrier statistic based on the tight-binding Hamiltonian are modeled analytically.It is found that the property of AGNR in the non-parabolic band region is varied by the strain.The tunable energy band gap in AGNR upon strain at the minimum energy is described for each of n-AGNR families in the non-parabolic approximation.The behavior of AGNR in the presence of strain is attributed to the breakable AGNR electronic band structure,which varies the physical properties from its normality.The linear relation between the energy gap and the electrical properties is featured to further explain the characteristic of the deformed AGNR upon strain.

Deformation and damage properties of rock-like materials subjected to multi-level loading-unloading cycles

In the process of engineering construction such as tunnels and slopes,rock mass is frequently subjected to multiple levels of loading and unloading,while previous research ignores the impact of unloading rate on the stability of rock mass.A number of uniaxial multi-level cyclic loading-unloading experiments were conducted to better understand the effect of unloading rate on the deformation behavior,energy evolution,and damage properties of rock-like material.The experimental results demonstrated that the unloading rate and relative cyclic number clearly influence the deformation behavior and energy evo-lution of rock-like samples.In particular,as the relative cyclic number rises,the total strain and reversible strain both increase linearly,while the total energy density,elastic energy density,and dissipated energy density all rise nonlinearly.In contrast,the irreversible strain first decreases quickly,then stabilizes,and finally rises slowly.As the unloading rate increases,the total strain and reversible strain both increase,while the irreversible strain decreases.The dissipated energy damage was examined in light of the aforementioned experimental findings.The accuracy of the proposed damage model,which takes into account the impact of the unloading rate and relative cyclic number,is then confirmed by examining the consistency between the model predicted and the experimental results.The proposed damage model will make it easier to foresee how the multi-level loading-unloading cycles will affect the rock-like materials.

DUCTILE CRACK INITIATION AND STEADY-STATE PROPAGATION OF HIGH STRENGTH STRUCTURAL STEEL

The resistance to crack propagation at earlier stage for a high strength structural steel with certain ductility and its correlation to microstructures,stress states,deformation history and strain characteristics have been investigated.The resistance to crack propagation is mainly de- termined by the plastic constrain ahead of the crack tip,the elastic energy and plastic work absorbed in the stress-strain field.These are connected with the state function of triaxial stress.The deformation history and strain characteristic during deformation of material are described by the flow line in which the deformation history and strain characteristic restrain the crack initiation at stage Ⅱ and the crack propagation at stage Ⅲ.The strain hardening rate may sensitively reflect the stress distribution and micro-fracture mechanism in the interi- or of material.

Mapping three-dimensional co-seismic surface deformations associated with the 2015 MW7.2 Murghab earthquake based on InSAR and characteristics of crustal strain

Three-dimensional(3 D) co-seismic surface deformations are of great importance to interpret the characteristics of coseismic deformations and to understand the geometries and dynamics of seismogenic faults. In this paper, we propose a method for mapping 3 D co-seismic deformations based on InSAR observations and crustal strain characteristics. In addition, the search strategy of correlation points is optimized by adaptive correlation distance, which greatly improves the applicability of the proposed method in restoring deformations in decorrelation areas. Results of the simulation experiment reveal that the proposed method is superior to conventional methods in both the accuracy and completeness. The proposed method is then applied to map the 3 D co-seismic surface deformations associated with the 2015 MW7.2 Murghab earthquake using ascending and descending ALOS-2 PALSAR-2 images. The results show that the seismogenic fault is the Sarez-Karakul fault(SKF), which is dominated by NE-SW strike slips with an almost vertical dip angle. The north section and the south segment near the epicentre have obvious subsidence along with a southwestward motion in the northwest wall, and the southeast wall has northeast movement and surface uplift trend along the fault zone. The strain field of the earthquake is also obtained by the proposed method. It is found that the crustal block of the seismic area is obviously affected by dilatation and shear forces, which is in good agreement with the movement character of the sinistral slip.

Tailoring the microstructure,martensitic transformation and strain recovery characteristics of Ti-Ta shape memory alloys by changing Hf content

In the present work,the microstructure features,martensitic transformation,mechanical properties and strain recovery characteristics of Ti-Ta based shape memory alloys were tailored by changing Hf contents.The singleα"martensite phase was dominated in Ti-Ta alloy with 2 at.%H f.Upon Hf content exceeded2 at.%,βphase started to appear.Moreover,the amount ofβphase gradually increased with Hf content increasing.The martensitic transformation temperatures continuously decreased with the increased Hf content,which was attributed to the rising of valence electron concentration.Meanwhile,Hf addition improved the thermal cycling stability of Ti-Ta alloys due to the suppression ofωprecipitation.The yield stress of Ti-Ta based alloys firstly decreased and then increased with Hf content increasing.In addition,the completely recoverable strain of 4%can be obtained in Ti-Ta alloy with 6 at.%Hf as a consequence of the higher critical stress for dislocation slip.Besieds,the Ti-Ta based alloy containing 8 at.%Hf had the superior superelasticity behavior with the fully recoverable strain of 2%at room temperature.

Plastic deformation behavior of Fe_(40)Ni_(40)P_(14)B_6 bulk metallic glass investigated by nanoindentation

Fe40Ni40P14B6 bulk metallic glass rods have been prepared by water quenching the fluxed alloy. The deformation behavior was investigated by nanoindentation tests and compressing tests. The average hardness and elastic modulus of the as-prepared Fe40Ni40P14B6 BMG (bulk metallic glass) measured by nanoindentation tests are 8.347 and 176.61 GPa respectively. The displace- ment-load curve shows “pop-in” characteristics which correspond to the loading rate bursts. Many shear bands around the indent were observed. The as-prepared Fe-based BMG exhibits a compressive plastic strain of 5.21%, which is much larger than that of other Fe-based glassy alloys and most of other BMGs.