Influence of construction interfaces on dynamic characteristics of roller compacted concrete dams

To study the influence of construction interfaces on dynamic characteristics of roller compacted concrete dams(RCCDs),mechanical properties of construction interfaces are firstly analyzed. Then, the viscous-spring artificial boundary(VSAB) is adopted to simulate the radiation damping of their infinite foundations, and based on the Marc software, a simplified seismic motion input method is presented by the equivalent nodal loads. Finally, based on the practical engineering of a RCC gravity dam, effects of radiation damping and construction interfaces on the dynamic characteristics of dams are investigated in detail. Analysis results show that dynamic response of the RCC gravity dam significantly reduces about 25% when the radiation damping of infinite foundation is considered. Hot interfaces and the normal cold interfaces have little influence on the dynamic response of the RCC gravity dam.However, nonlinear fracture along the cold interfaces at the dam heel will occur under the designed earthquake if the cold interfaces are combined poorly. Therefore, to avoid the fractures along the construction interfaces under the potential super earthquakes,combination quality of the RCC layers should be significantly ensured.

Tensile and fracture properties of an Mg-RE-Zn alloy at elevated temperatures

Magnesium alloy EZ10 （Mg-RE-Zn） was deformed in tension at temperatures from 20 up to 520℃. A rapid decrease of the yield and tensile strength with temperature was observed at temperatures higher than 300 ℃. On the other hand, ductility of sam-ples rapidly increased in the same temperature range. Light microscopy and scanning electron microscopy was used to reveal the rea-son for these behaviours. Intermetallic particles in grain boundaries are responsible for excellent mechanical properties at lower tem-peratures. Diffusional processes occurring at temperatures higher than 300 ℃ significantly influenced the deformation mechanism as well as the fracture character.

Semi-permeable Yoffe-type interfacial crack analysis in MEE composites based on the strip electro-magnetic polarization saturation model

Fracture analysis of a semi-permeable Yoffe-type interfacial crack propagating subsonically in magneto-electro-elastic （MEE） composites is presented based on the strip electro- magnetic polarization saturation （SEMPS） model. The electro-magnetic fields inside the crack are considered under the semi-permeable boundary condition. Nonlinear effects near the interfacial crack tip are represented by different electro-magnetic saturation zones. Utilizing the extended Stroh＇s method, we derive the moving dislocation densities as well as intensity factor and energy release rate for Yoffe-type MEE interracial crack. Numerical re- sults through an iterative approach are presented to show the characteristics of fracturedominant parameters with respect to propagation velocity and boundary condition category. The fracture-dominant parameters under the semi-permeable boundary condition are lower than those under the impermeable one, which implies that the electro-magnetic fields in the crack gap can retard the propagation of MEE interfacial crack.