Xiaoqing Xu

Mechanism of water infiltration and defiltration through ZSM-5 zeolite: heating and sodium chloride concentration effect

Hydrophobic nanoporous material and wetting liquid together comprise a system with promising energy related applications. The mechanism of the interaction between liquid and solid phase is not fully explored. In this paper, based on the quasistatic compression experiments on investigating the mechanical behavior of ZSM-5 zeolite/NaCl solution system, the effects of two key parameters, that is, the pretreatment temperature of ZSM-5 zeolite and NaCl concentration, are parametrically and quantitatively investigated based on Laplace-Washburn equation. Results show that both pretreatment temperature and NaCl concentration raise the infiltration pressure and NaCl can also promote defiltration. The advancing contact and receding contact angle of zeolite-NaCl-air system increase with both pretreatment temperature and NaCl concentration, and the contact angle hysteresis decreases with NaCl concentration. Results may provide fundamental explanation to the nanoconfined liquid behavior and liquid-solid interaction, thus, to smartly control the mechanical properties of the liquid spring and bumpers for energy dissipation function.

Statistical analysis of cleavage fracture load of notched bar with granular bainitic microstructure

Abstract Based on a three-parameter Weibull statistical model of transgranular cleavage fracture in granular bainite in a weld heat-affected zone, some factors influencing cleavage fracture load of a notched bar under pure bending have been investigated. The cleavage fracture load decreases as strain-hardening exponent n increases. When the Weibull shape factor, m or the critical stress for the largest cracked M-A constituent to initiate cleavage, σ L is raised, improvement in the cleavage fracture load results. With the combination of large m and high σ L , the cleavage fracture load can be enhanced significantly.

A tensile stress criterion for cleavage in precracked, notched and smooth bars

Using a statistical model derived for cleavage induced by hard particles, an analysis has been carried out of a newly defined critical tensile stress for cleavage, i.e. the statistical mean stress with respect to cleavage fracture probability. The results of the analysis show that the critical tensile stress (cleavage stress) is highest for a precracked bar, intermediate for a notched bar and lowest for a smooth bar, owing to the fact that small particles are possible to trigger cleavage when stress distribution in a bar is uneven. The cleavage stress for the precracked bar is found to decrease rapidly with increasing temperature while those for the notched and smooth bars remain almost constant. The cleavage stresses for the precracked, notched and smooth bars can be correlated through a definite formula. For a pure-bending notched bar, the conventional cleavage stress (maximum stress in the bar) is found to be a good approximation of the new cleavage stress. The difference between the two will increase when stress gradient becomes steeper.

Investigation on Dynamic Propagation Characteristics of In-Plane Cracks in PVB Laminated Glass Plates

Polyvinyl butyral (PVB) laminated glass has been widely used as an important component of mechanical and construction materials. Cracks on PVB laminated glass are rich in impact information, which contribute to its impact resistance design. In this paper, a three-dimensional (3D) numerical simulation model describing PVB laminated glass under impact loading is firstly established and validated qualitatively and quantitatively compared with the corresponding experimental results recorded by the high-speed photography system. In the meantime, the extended finite element method (XFEM) is introduced to analyze the crack propagation mechanism of laminated glass based on dynamic stress intensity factors (DSIFs) and propagations of stress waves. Parametric studies are then carried out to investigate the influence of five critical parameters, that is, plate dimension, crack length, impact energy, glass properties, and PVB properties, on crack propagation characteristics of laminated glass. Results show that the interaction between crack tip and stress waves as well as the propagations of stress waves corresponds to the fluctuations of DSIFs at crack tip. Both the structure and material variables are proven to play a very important role in glass cracking DSIFs and thus govern the crack propagation behavior. Results may provide fundamental explanation to the basic crack propagation mechanism on radial cracks in PVB laminated glass under impact loading conditions, thus to instruct its impact design improvement.

STATISTICAL ANALYSIS OF CLEAVAGE IN PRECRACKED, NOTCHED AND SMOOTH BARS

ABSTRACT Using a general statistical model of cleavage in HSLA steel, KIC of three-point-bend precracked bars, fracture load LF of four-point-bend notched bars and true fracture stress σF of smooth tension bars were predicted. To verify the prediction, three-point-bend KIC test, four-point-bend test and uniaxial tension test were conducted on a simulated weld heat-affected zone in 15MnVN steel over the temperature range of -196°C to 20°C. The experimental KIC, LF and σF were well embraced by the corresponding scatter bands predicted by the model over the temperature range where cleavage is propagation controlled.

Statistical Analysis of Maximum Tensile Stress Criterion for Cleavage Fracture in Notched Specimen

ABSTRACT Using a three-parameter Weibull statistical model derived for M-A constitute initiated cleavage in granular bainite in weld HAZ, a statistical analysis has been carried out of a cleavage criterion based on the maximum tensile stress in a notched specimen at cleavage, σσ-the cleavage fracture stress. The results of the analysis show that the cleavage fracture stress is almost temperature independent from −120°C to −60°C, and that below −120°C it increases as temperature decreases. Model predictions reveal that the cleavage fracture stress is insensitive to the change in strain-hardening exponent, and that increasing the Weibull shape factor and/or the lowest fracture strength of M-A constituent can effectively raise the cleavage fracture stress.