Mechanical behavior and failure modes of aluminum/bamboo sandwich plates under quasi-static loading

Experimental investigations have been made on the quasi-static mechanical behavior and failure modes of aluminum/bamboo sandwich plates. Thermosetting epoxy resin and thermoplastic Polybond resin were used to bond the aluminum sheets and the bamboo. Tensile, compressive and flexural properties were evaluated. The effects of bond conditions on the mechanical behavior and failure modes were examined. The thermoplastic Polybond resin resulted in a stronger interface bond than the thermosetting epoxy resin. The improvement of the interface bond led to significant increases in compressive and flexural properties. The tensile properties were found to be insensitive to the interface bond. The dominant failure mechanisms affected by the interface bond dictated the mechanical properties of the sandwich plates in individual loading conditions.     

电磁场作用下的金属凝固与成形

综述了电磁场在金属凝固成形过程中的主要应用及其基本原理，指出了应用计算机数值模拟方法求解材料电磁加工问题的重要性及其今后的发展方向。     

Influence of high-temperature air pre-exposure on mechanical strength of a directionally solidified cobalt-base superalloy

The present work investigated the influence of air pre-exposure at 850°C for 1000 h on the mechanical properties and microstructures of the directionally solidified cobalt-base alloy DZ40M. The results show that the air pre-exposure did not embrittle the alloy, but resulted in a marked strengthening. Microstructural observations and energy dispersive X-ray spectroscopy (EDS) indicates that the air pre-exposure caused a substantial external and internal oxidation, which is assumed to protect the alloy from being oxidized further and make a significant contribution to alloy strengthening, respectively. The immunity of the alloy to air embrittlement is attributed to elimination of transverse grain boundaries by directional solidification.     

Temperature Effect of Infrared Rays Absorbed by the Protein Molecules in the Living Systems

The principal features of Infrared absorption of the protein molecules are anomalous red shifts of the main peaks and increases of intensity of the anomalous bands with decreasing temperature which are proved by experiments. We think that these anomalous phenomena are caused by the self-trapping of amide-I vibrational quantum (vibron). We thus proposed a soliton model of the vibrons interacting with optical vibration of amino acid residue (phonon) to study theoretically these phenomena. We find farther out the exponential-reductions of the intensity of the anomalous bands in the infrared absorption with increasing temperature in the protein molecules by using this model. This shows that the living things including human beings and animals can absorb more much infrared lights at low temperature than that at high temperature.     

Fatigue and fracture behavior of an aluminum-lithium alloy 8090-T6 at ambient and cryogenic temperature

An investigation has been made of the fatigue and fracture behavior of an Al-Li-Cu-Mg-Zr 8090-T6 alloy at room (300 K) and liquid nitrogen (77 K) temperatures. The fatigue and fracture strengths, as well as ductility of the alloy, have been found to increase with decreasing temperature. The observations by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) reveal that the changes in fatigue and fracture behavior with temperature are considered to be associated with the change in the deformation and fracture modes. It has been found that the occurrence of the localized shear deformation bands in which the hard precipitates are sheared by moving dislocations is responsible for the reduction of fatigue and fracture strengths as well as ductility of the alloy at room temperature. However, the improvement of both strength and ductility of the alloy at liquid nitrogen temperature might be attributed to the deeper and larger delamination that occurred on the fracture surface.     

URANS study of pulsed hydrogen jet characteristics and mixing enhancement in supersonic crossflow

In this paper, three-dimensional pulsed hydrogen jet in supersonic crossflow (PJISC) is investigated by the unsteady Reynolds Averaged Navier-Stokes (URANS) simulations with the k-ω shear stress transport (SST) turbulence model. The numerical validation and mesh resolution have been carried out against experiment firstly. The effects of the pulsed frequency and amplitude on the jet flow field and mixing performance in supersonic cross-flow are all addressed. It significantly changes the distribution of the hydrogen jet flow by comparing with the steady jet in supersonic crossflow. The fuel jet penetration, mixing efficiency, decay rate of the maximum hydrogen mass fraction and total pressure losses are used to quantitatively analyze the mixing performance. The mixing of fuel and incoming air flow is enhanced by the pulsed jet, especially for the case of 50 kHz, which is the optimal pulsed frequency while considering the effects of jet excitation frequency in the present simulations. The decay rate of the maximum mass fraction of hydrogen in the far field downstream is related to the frequency of the pulse jet. Moreover, the pulsed frequency and amplitude have little effects on the total pressure recovery coefficient for the cases studied in the present simulations.     

硫铁镍共存对工业用甲醇催化剂活性影响的研究

采用电子能谱仪、X光衍射仪、吸附仪等物化仪器和化学分析法，对工业甲醇催化剂使用过程中硫铁镍元素的来源、危害进行实验研究。结果表明：硫、铁、镍的存在影响催化剂的活胜。在高强度生产过程中，硫的危害不容忽视，铁会影响甲醇的质量，镍会增加副反应、影响甲醇催化剂的活性。