Mechanical Property Evaluation on the Bending and Compressing Behaviour of Nano-beam

Based on quasicontinuum（QC） multiscale simulation method,a series of simulation models were set up for bending and compressing rod-shaped microstructure of single crystal Cu.The effects of structural parameters on typical mechanical properties were analyzed,such as elastic modulus,elastic limit,yield strength,and Poisson’s ratio.According to the analysis of displacement,inner stress and strain energy,the mechanisms of deformation and failure were also revealed.The experimental result shows that the mechanical properties exhibit obvious size effect during the bending and compression process.In the bending simulation,when the span-thickness ratio is more than 10,the elastic modulus rises slightly with the increase of strain.And the smaller the beam is,the faster the elastic modulus grows.Meanwhile,when the spanthickness ratio keeps constant the elastic modulus will decrease with the growth of the beam sizes.However,in the compression model,the size effect on Poisson’s ratio is not remarkable.The dimensional change in one direction cannot influence the mechanical parameters greatly.Mechanical twins and dislocation contribute to the compression behaviour greatly.Meanwhile,the stress concentration can also be found in the inner partial area and the strain energy decreases abruptly after the crush of beam microstructure.

玻璃钢蜂窝夹层结构弯曲性能理论分析研究

In this article,theoretical calculations on the bending performance(bending strength and bending modulus)of fiberglass reinforced plastic(FRP)honeycomb sandwich structures were conducted initially,and then the bending performance of two FRP honeycomb sandwich structures with different thicknesses were measured by the Aerospace Materials Failure Analysis Center.By comparing and analyzing the theoretical calculations and experimental results,it was found that the theoretical calculated bending strength and bending modulus were in good agreement with those of the experimental tested within 26.5%.When designers and technicians conduct theoretical calculations on the performance of FRP honeycomb sandwich structures,they can use the formulas derived in this article,which will more accurately predict the mechanical properties of components made of composite materials.

Preparation of Ultra-nano Talcum in Sand Mill and Its Application in the Polypropylene

The grinding of ultra-fine talcum powder and its application in a polypropylene （PP） matrix were investigated. Ultra-fine talcum powder was prepared by adjusting the grinding parameters of the physical milling process. The talcum powder exhibited polymodal distribution. The layered morphology of talcum particles in a horizontal sand mill was rarely damaged or destroyed. PP-talcum nanocomposites were prepared by melt blending using a twin-screw extruder. Nano talcum can be seen as a single particle, although it is not very apparent. The bending strength of talcum-filled PP was gradually increased by approximately 28%. The impact strength linearly decreased as the filler weight ratio increased. The overall maximum improvement in mechanical properties was recorded when the filler ratios increased from 15 wt% to 20 wt%.

Breakup of spherical vesicles caused by spontaneous curvature change

We present our theoretical analysis and coarse- grained molecular dynamics （CGMD） simulation results to describe the mechanics of breakup of spherical vesi- cles driven by changes in spontaneous curvature. System- atic CGMD simulations reveal the phase diagrams for the breakup and show richness in breakup morphologies. A the- oretical model based on Griffith fracture mechanics is devel- oped and used to predict the breakup condition.

Flexural rigidity of honeycomb consisting of hexagonal cells

In this study,the flexural rigidity of a honeycomb consisting of regular hexagonal cells is investigated.It is found that the honeycomb bending can not be evaluated by using the equivalent elastic moduli obtained from the in-plane deformation because the moments acting on the inclined cell wall are different for in-plane deformation and bending deformation.Based on the fact that the inclined wall is twisted under the condition of the rotation angle in both connection edges being zero,a theoretical technique for calculating the flexural rigidity of honeycombs is proposed,and the validity of the present analysis is demonstrated by numerical results obtained by BFM.

Simulation of thermal stress in Er2O3 and Al2O3 tritium penetration barriers by finite-element analysis

The physical vapor deposition method is an effective way to deposit Al2O3 and Er2O3 on 316 L stainless steel substrates acting as tritium permeation barriers in a fusion reactor. The distribution of residual thermal stress is calculated both in Al2O3 and Er2O3 coating systems with planar and rough substrates using finite element analysis. The parameters influencing the thermal stress in the sputter process are analyzed, such as coating and substrate properties, temperature and Young＇s modulus. This work shows that the thermal stress in Al2O3 and Er2O3 coating systems exhibit a linear relationship with substrate thickness, temperature and Young＇s modulus.However, this relationship is inversed with coating thickness. In addition, the rough substrate surface can increase the thermal stress in the process of coating deposition. The adhesive strength between the coating and the substrate is evaluated by the shear stress. Due to the higher compressive shear stress, the Al2O3 coating has a better adhesive strength with a 316 L stainless steel substrate than the Er2O3 coating. Furthermore, the analysis shows that it is a useful way to improve adhesive strength with increasing interface roughness.

Evaluation of the use of surrogate Laminaria digitata in eco-hydraulic laboratory experiments

Inert surrogates can avoid husbandry and adaptation problems of live vegetation in laboratories. Surrogates are generally used for experiments on vegetation-hydrodynamics interactions, but it is unclear how well they replicate field conditions. Here, surrogates for the brown macroalgae Laminaria digitata were developed to reproduce its hydraulic roughness. Plant shape, stiffness and buoyancy of L. digitata were evaluated and compared to the properties of inert materials. Different surrogate materials and shapes were exposed to unidirectional flow. It is concluded that buoyancy is an important factor in low flow conditions and a basic shape might be sufficient to model complex shaped plants resulting in the same streamlined shape.

Application of finite element analysis in properties test of finger-jointed lumber

Finger-jointed lumber production has now become the most extensively used method for spliced lumbers jointing together endwise.The properties of finger-jointed lumber are affected by many different factors such as the end-pressure.The main mechanical properties to be tested for struc-tural use finger-jointed lumber include the modulus of elasticity in static bending and the bending strength.The most commonly used method for testing these properties at present is the experi-mental test.In this study,we used finite element method to investigate the end-pressure range,the modulus of elasticity in static bending and the bending strength for Pinus sylvistriv var.finger-jointed lumber under three different fitness ratios(0 mm,0.1 mm,0.3 mm).With finite element analysis(FEA)modelling results compared with the experimental test results,it is possible to find the relationship between these two kinds of results and use the FEA to predict the properties of finger-jointed lumber.The FEA applied in the end pressure tests showed a narrower range com-pared with the modelling results.It indicated that the FEA could be used in the prediction of the end pressure for finger-jointed lumber.The modelling results for modulus of elasticity(MOE)test and bending strength(MOR)test showed about 20%discrepancies compared with the experimen-tal results.Moreover,the MOE modelling results showed the same trend as experimental results under three different fitness levels while the MOR modelling results showed the different trend.It can be concluded that the FEA is a feasible way in analysing the properties of finger-jointed lumber if the errors could be eliminated properly.Some modifications should be made in order to realize the prediction of the properties of finger-jointed lumber more accurately.