2D hierarchical lattices' imperfection sensitivity to missing bars defect

Commercially available lattices contain various kinds of morphological imperfections which result in great degradation in lattices＇ mechanical properties, therefore, to obtain imperfection insensitive lattice structure is obviously a practical research subject. Hierarchical structure materials were found to be a class of promising anti-defect materials, This paper builds hierarchical lattice by adding soft adhesion to lattice＇s cell edges and numerical results show that its imperfection sensitivity to missing bars is minor compared with the classic lattice. Soft adhesion with appropriate properties reinforce cell edge＇s bending stiffness and thus reduce the bending deformation in lattice caused by missing bars defect, which is confirmed by statistical analysis of normalized node displacements of imperfect lattices under hydrostatic compression and shear loads.

SHARP H?LDER CONTINUITY OF THE INTEGRATED DENSITY OF STATES FOR EXTENDED HARPER’S MODEL WITH A LIOUVILLE FREQUENCY

In this article, the non-self dual extended Harper's model with a Liouville frequency is considered. It is shown that the corresponding integrated density of states is 1/2-Holder continuous. As an application, the homogeneity of the spectrum is proven.

Quantitative Green's function estimates for lattice quasi-periodic Schrodinger operators

In this paper,we establish quantitative Green’s function estimates for some higher-dimensional lattice quasi-periodic(QP)Schrodinger operators.The resonances in the estimates can be described via a pair of symmetric zeros of certain functions,and the estimates apply to the sub-exponential-type non-resonance conditions.As the application of quantitative Green’s function estimates,we prove both the arithmetic version of Anderson localization and the finite volume version of(1/2-)-Holder continuity of the integrated density of states(IDS)for such QP Schrodinger operators.This gives an affirmative answer to Bourgain’s problem in Bourgain(2000).

Single asperity friction in the wear regime

We used molecular dynamics simulation to investigate the friction of a single asperity against a rigid substrate, while generating debris. In the low wear regime(i.e., non-linear wear rate dependence on the contact stress, via atom-by-atom attrition), the frictional stress is linearly dependent on the normal stress, without any lubrication effect from the wear debris particles. Both the slope(friction coefficient) and friction at zero normal stress depend strongly on asperity-substrate adhesion. In the high wear regime(i.e., linear wear rate dependence on the contact stress, via plastic flow), the friction-normal stress curves deviate from a linear relation merging toward plastic flow of the single asperity which is independent of the interfacial adhesion. One can further link wear and friction by considering debris generation as chemical reaction, driven by both normal and frictional forces. The coupling between wear and friction can then be quantified by a thermodynamic efficiency of the debris generation. While the efficiency is less than 5% in the low wear regime, indicating poor mechanochemical coupling, it increases with normal stress toward 50% in the high wear regime.

FEM Simulation of the Hydrogen Diffusion in X80 Pipeline Steel During Stacking for Slow Cooling

The influence of temperature on the hydrogen diffusion behavior in X80 pipeline steel during stacking for slow cooling was studied using electrochemical penetration method, the temperature field and the hydrogen diffusion in this pipeline steel during stacking for slow cooling were simulated by ABAQUS finite element method （FEM） software. The results show that in this process there is a reciprocal relationship between the natural logarithm of hydrogen diffusion coefficient and temperature. The cooling rate decreases gradually with the increase of steel plate thickness. The hydrogen content is higher at high temperature （500-400 ℃） than that in low temperature region （300-100 ℃）. The FEM simulation results are consistent with the experimental ones, and the model can be used to predict the hydrogen diffusion behavior in industrial production of X80 pipeline steel.