Advanced Materials Research Vols. 160-162

Abstract: Fatigue damage growth can be described by the gradual reduction of the stiffness and strength, and damage expressed by the two degradation methods are equivalent. According this assumption, a pair of cumulative fatigue damage models based on residual stiffness and residual strength is proposed, and then the connection between the two damage indices is established. The two damage models follow equation with the same form, but the parameters in them are not equal. Each of the two models contains three unknown parameters which have pertinent effect on the damage growth rates, in addition, the models also take into account of the effects of stress levels and stress ratios. By fitting the experimental data, it is observed that the parameters in damage functions obey the linear relation well, and the unknown constants are deduced with finite tests easily. Finally, the models are found to give a good description of fatigue damage evolutions of different stacking sequence for both of the stiffness and strength.

Abstract: Ni-Bi alloys were selected to bond to ZrO2 ceramic by diffusion bonding at atmosphere for researching their bondability. The Ni-Bi alloys were Ni-xmass%Bi (x=0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0) and ZrO2 ceramic was Z201N. The bonding was carried out at 973 K, 1037 K and 1173 K for 3.6 ks, 5.4 ks, 7.2 ks, 9.0 ks and10.8 ks under the pressure of 2 MPa, 4 MPa, 6 MPa, 8 MPa, 10 MPa and 12 MPa. The bonding strength was examined by the shear fracture test from room temperature to high temperature. The results indicate that pure nickel could be bonded to ZrO2. Adding bismuth into nickel alloy could obviously improved shear strength at room temperature. The optimum content of bismuth was 2%. The shear strength of vacuum-free diffusion bonding joint was higher than that of vacuum diffusion bonding joint. ZrO2/Ni-2Bi joint was bonded at 1173 K for 7.2 ks under 8 MPa, which shear strength was up to 22 MPa until the test temperature of 873 K.

Abstract: Asphalt emulsion composites are energy-saving, ecologically safe materials because they do not need any heating processes which can emit gas and fire hazard in their use. Their use for highway structural layers has attracted relatively little attention largely in China because of the problems associated with the time taken for full strength to be achieved after paving and the susceptibility to early life damage by rainfall. This research work aims at studying influences of using ordinary Portland cement to asphalt emulsion composites. The asphalt emulsion composites were prepared using a three step; road properties were studied and mechanisms were analyzed with Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Analysis (EDXA). The results indicate that ordinary Portland cement addition improves road properties of the composites, such as Marshall stability, compressive strength, dynamic stability and ratio of splitting strength after freezing-thawing cycles. Splitting strength at low temperature of the composites increases with the cement increase, but if the cement dosage surpasses 3.0%, the composites become brittle. So optimal cement dosage is 3.0% in aggregate mass. There is much hydrated calcium silicate(C-S-H) gel in the composites with the cement, which can increase mass and atom percentage of Ca element and Si element, decrease proportions of free asphalt and make mastics in the composites more dense. Road properties of asphalt emulsion composites can be improved.

Abstract: Different distributed residual stresses were introduced by quenching and two shot-peening treatments on 7075 aluminum alloy. The residual stress distributions and micro-hardness profiles in surface layers were measured. Pre-stress coefficient characterizing contribution of local residual stresses to local yield strength is introduced to analyze residual stress relaxation under cyclic loading. Load testing shows that re-distribution of residual stresses and proportional decrease of the pre-stress coefficient would occur in the non-uniform structural residual stresses introduced by quenching, while great stress relaxation and non-linear decrease of the pre-stress coefficient would occur in the uniform surface residual stresses introduced by shot-peening. Additionally, advantages of surface compressive residual stress and micro yield strength on anti-fatigue property and on restraining initiation and propagation of surface micro cracks should be considered in the usually conservative engineering design.

Abstract: So far, there are major weaknesses in applying existing life cycle impact assessment characterization models to metals and more specifically to Aluminum-based products, which can lead to biased estimates of damage. To estimate the damage of polycyclic aromatic hydrocarbons (PAHs) in aluminum production sites, this study applies a life cycle assessment for pre-training electrolytic aluminum production in China. Results showed approximately 46% impact of the "average PAHs" was overestimated than existing life cycle impact assessment model (Impact2002+). Results also demonstrated the feasibility and the potential significance of including worker exposure to PAHs. Recommendations are presented to consider and compare both indoor (worker exposure) and outdoor emission of PAHs, differentiating the impact between various PAHs. These improvements are crucial for the future development of impact assessment methods that lead to comparable results between organic and inorganic substances.

Abstract: Lithium tetraborate (LBO or LTO) single crystal seems to be a promising new material for thermoluminescent dosimeter (TLD) and SAW resonators. In the present work, thermoluminescence (TL) characteristic and TL spectra of LTO single crystal grown by Bridgman method were measured, the kinetic parameters of TL traps were calculated, and TL spectra were analyzed. The result shows: The primary glow peaks are at about 186oC and 313oC. The activation energies of the traps corresponding to the two TL peaks are 0.96eV and 1.56eV, and the frequency factors are about 7.94×109s-1 and 6.31×1012s-1. The TL spectra of LTO crystal extends from 350nm to 460nm, and has its maximum at about 381nm. The intrinsic luminescent centers can send the energy from crystal lattice to Cu+ ions, because the activation energies of two are quite similar, and the Cu+ ions become new luminescent centers to increase TL sensitivity when Cu ions are doped into LTO crystals.

Abstract: The water bursting disaster from the floor of mine is a complicated program involving several of subjects such as geology, coal mining, rock hydraulics and rock crack mechanics. In the paper, the two dimensional non-linear solid-fluid coupling model is used to study the difference of the water-holding capacity of the different floor combination under the condition of mining. The mini damage rock layer combination is obtained by analyzing the failure extent of floor under the mining pressure and water pressure. The water resisting capacity of the combination of b is the worst. The water resisting capacity of the combination of c is the best.

Abstract: In this paper, ultra-fine grained copper fabricated by equal channel angular pressing method and annealed coarse grained copper were tensioned under both quasi-static and dynamic loading conditions using an electronic universal testing machine and the split Hopkinson tension bar respectively. The rapture surface of specimen was also observed via a Scanning Electron Microscope (SEM). The experimental results show that the ductility of polycrystalline copper decreases remarkably due to the grain refinement. However, with the increase of applied strain rate, ductility of the UFG-Cu is enhanced. The fracture morphologies also give the evidence of enhanced ductility of UFG-Cu at high strain rate. It is believed the enhanced ductility of UFG materials at high strain rate can be attributed to the restrained dislocation dynamic recovery.

Abstract: This based on the analysis of the structure characteristics and thermal properties etc of the new XH self-insulation block as results that the application of new material has a positive effect in construction of energy-saving. Through the calculation verified the thermal performance of XH self-insulation block the heat transfer coefficient of subject site wall. The results showed that its full compliance with existing norms and standards on the thermal performance of external wall insulation requirements, meet the requirements of energy conservation. Compared with the traditional material XH self-insulation block have an obvious advantage in thermal insulation property, service life, economy and so on. Finally, use its application in the ladder classroom of Southwest University of Science and Technology for a description of the project application.

Abstract: The main application problems of radiant panel in summer include lower cooling capacity owing to high temperature of water supply and condensation. A new radiant panel was developed. Water duct and panel are straight forming which eliminates the thermal contact resistance .The panel are installed in an angle in order to discharge condensate water. The guiding gutter in the face of panel and condensate pipe are to collect and outlet condensate water. The summer test was done. The results show that the new radiant panel has higher cooling efficiency compare with conventional panel .The cooling efficiency is above 1000w/m2, and condensate water can be discharged quickly. Although new Ceiling Radiant Cooling Panel is still not perfect, but it is provides us with more choice.