Mechanical properties of cement mortar in sodium sulfate and sodium chloride solutions

To investigate the mechanical properties of cement mortar in sodium sulfate and sodium chloride solutions, uniaxial compression test and ultrasonic test were performed. Test results show that the relative dynamic elastic modulus, the mass variation,and the compressive strength of cement mortar increase first, and then decrease with increasing erosion time in sodium sulfate and sodium chloride solutions. The relative dynamic elastic moduli and the compressive strengths of cement mortars with water/cement ratios of 0.55 and 0.65 in sodium sulfate solution are lower than those in sodium chloride solution with the same concentration at the420 th day of immersion. The compressive strength of cement mortar with water/cement ratio of 0.65 is more sensitive to strain rate than that with water/cement ratio of 0.55. In addition, the strain-rate sensitivity of compressive strength of cement mortar will increase under attacks of sodium sulfate or sodium chloride solution.

Stabilities,mechanical and thermodynamic properties of Al-RE intermetallics:A first-principles study

Stabilities,mechanical and thermodynamic properties of 87 intermetallics in Al-RE binary system were studied by first-principles based on density functional theory(DFT).The results show that the calculated stabilities at T=0 K are in good agreement with experimental values.Al2 RE intermetallics exhibit the best stability in Al-RE binary compounds;and the stabilities in descending order are Al2 RE,Al3 RE,AlRE,Al11RE_(3),AlRE2 and AlRE_(3).The calculated Al-RE intermetallics possess mechanical stabilities.The hardness and strength of the most Al-RE intermetallics are greater than pure aluminum except AlCe,AlPr,AlEu and AlYb.The hardness and strength in descending order are Al11RE_(3),Al3 RE,Al2 RE and AIRE.Part of AlRE intermetallics exhibit ductility;the others are brittle.The heat capacities of Al-RE intermetallics in ascending order are Al-Sc,Al-Y,Al-lanthanides.On the contrary,the coefficient of thermal expansion(CTE)in ascending order is Al-lanthanides,Al-Y and Al-Sc.

Interaction between Weibull parameters and mechanical strength reliability of industrial-scale water gas shift catalysts

A fundamental step in the production of an industrial catalyst is its crushing strength assessment. Limited literature exists in which the strength reliability of supported catalysts is investigated from production to their application in a reactor. In this work, cylindrical supports were prepared by pelletizing high poros- ity γ-alumina powder, and Cu-Znf/γ-Al2O3 catalysts were prepared by impregnation of the pelletized γ-alumina supports with an aqueous solution of copper and zinc nitrates. The support-forming variables, such as binder concentration, compaction pressure, calcination temperature, and drying procedure were investigated. The Weibull method was used to analyze the crushing strength data of the supports, and the fresh and used catalysts before and after the low-temperature water gas shift reaction. Support formation at a 50 wt% binder concentration, 1148 MPa compaction pressure, 500 ℃ calcination temperature, and rapid drying （100 ℃, 8 h） led to the maximum support mechanical reliability. The most reliable catalyst with respect to simultaneous appropriate catalytic performance and mechanical strength was prepared from a support with the lowest mean crushing strength （26.25 MPa）. This work illustrates the impor- tance of the Weibull modulus as a useful mechanical reliability index in manufacturing a supported solid catalyst.

Analyses toward factors influencing sealing clearance of a metal rubber seal and derivation of a calculation formula

Sealing clearance is a key factor for a metal rubber seal＇s sealability. The expansion coef- ficient and expansion deformation in the radial direction of metal rubber have been obtained through a thermal expansion experiment of metal rubber. The influence of the elastic modulus to the sealing clearance has been analyzed theoretically. By combining the temperature and elasticity factors of metal rubber with the elastic mechanics theory, the calculation formula of the sealing clearance has been derived, and the values of the sealing clearance and the leakage rate in certain working conditions have been calculated. Experimental results are consistent with calculation results in a high degree. The calculation formula of the sealing clearance can explain the influences of the temperature and elastic modulus factors of metal rubber on the sealing clearance. It can pro- vide guidance for the study of sealing mechanism of metal rubber seals.

Analytical Solution for Predicting In-plane Elastic Shear Properties of 2D Orthogonal PWF Composites

This paper proposes a new analytical solution to predict the shear modulus of a two-dimensional（2D） plain weave fabric（PWF） composite accounting for the interaction of orthogonal interlacing strands with coupled shear deformation modes including not only relative bending but also torsion,etc.The two orthogonal yarns in a micromechanical unit cell are idealized as curved beams with a path depicted by using sinusoidal shape functions.The internal forces and macroscopic deformations carried by the yarn families,together with macroscopic shear modulus of PWFs are derived by means of a strain energy approach founded on micromechanics.Three sets of experimental data pertinent to three kinds of 2D orthogonal PWF composites have been implemented to validate the new model.The calculations from the new model are also compared with those by using two models in the earlier literature.It is shown that the experimental results correlate well with predictions from the new model.

Atomic force microscopy studies on cellular elastic and viscoelastic properties

In this work, a method based on atomic force microscopy (AFM) approach-reside-retract experiments was established to simultaneously quantify the elastic and viscoelastic properties of single cells. First, the elastic and viscoelastic properties of normal breast cells and cancerous breast cells were measured, showing significant differences in Young’s modulus and relaxation times between normal and cancerous breast cells. Remarkable differences in cellular topography between normal and cancerous breast cells were also revealed by AFM imaging. Next, the elastic and viscoelasitc properties of three other types of cell lines and primary normal B lymphocytes were measured; results demonstrated the potential of cellular viscoelastic properties in complementing cellular Young’s modulus for discerning different states of cells. This research provides a novel way to quantify the mechanical properties of cells by AFM, which allows investigation of the biomechanical behaviors of single cells from multiple aspects.