Advanced Materials Research Vols. 415-417

Abstract: In order to reduce production cost of Fuel Cells, one of the key points was to reduce Pt loading in Pt/C catalytic electrode. In our study, a new type of Pt/C membrane electrodes, PtCu-LaO_x composite structure, on the surface of carbonaceous substrates was manufactured by Ion Beam Sputtering technology, and also was treated in different concentration H₂SO₄ solution. Phase composition, surface topography and microarea elements of these electrodes were analyzed by X-ray Diffraction, Scanning Electron Microscopy combined with Energy Dispersive Spectrometry, respectively. It was found that PtCu-LaO_x composite membrane with Pt loading less than 0.045mg/cm² (the electrode area), and that the orientation growing of Pt(111) and Pt(200) would be promoted, and that Pt-Pt interval on surface of PtCu-LaO_x would reduce owing to Cu was dissolved from (Pt) through H₂SO₄ solution treatment, and that average grain size of PtCu-LaO_x decreased and crystal face spacing steady along with rising concentration.

Abstract: Metal magnetic memory technology is a passive magnetic method of non-destructive testing based on the residual magnetic field of a ferromagnetic component. The MMM measurements were performed on a series of X70 pipeline steel samples for various values of uniaxial elastic and plastic deformation from zero up to about 20% strain. The outcomes evidence that the metal magnetic memory gradient index m can be used to evaluate the stress-strain state of ferromagnetic materials under tensile stresses. The tensile stress effect on the gradient index m significantly in elastic stage, but the gradient index m remained unchanged in the plastic deformation stage.

Abstract: A new extensional viscosity model based on the Cross model is introduced. The proposed model can correctly describe the relation between extensional viscosity and extension rate. Effect of the four parameters in the new model is analyzed in detail. Compare the predictive curves to the measurement results reported in the references. It shows that the model calculation gives a good fit to the experiment data. This simple model has only a few parameters and is easy to use.

Abstract: Tensile and fracture toughness tests of coolant piping materials were performed at various loading rates and temperatures. The crack measurement method for coolant piping materials consisted of the unloading compliance method for quasi-static loading conditions and condition, while the electric potential drop method and the normalization method for quasi-dynamic loading conditions. Tensile and fracture toughness tests of coolant piping materials were performed at the design temperatures of the primary piping system of nuclear power plants, which are 449K (176°C) and 589K (316°C). Also, the plastic η factor considering strength mismatch of welding part was applied to the fracture toughness test results and the J-R curves by the plastic η factor considering strength mismatch of welding part was compared with the J-R curves by the plastic η factor introduced in ASTM E1820-01.

Abstract: Pathologies in soft tissues are associated with changes in their elastic properties. Tumor tissues are usually stiffer than the fat tissues and other normal tissues and show the nonlinear behavior in large deformations. There have been a lot of researches about elastography (linear and nonlinear) as a new detecting technique based on mechanical behavior of tissue. In order to formulate the tissue’s nonlinear behavior, a strain energy function is required. For better estimation of nonlinear tissue parameters in elasticity imaging, non linear stress-strain curve of phantom is used. This work presents hyperelastic measurement results of tissue-mimicking phantom undergoing large deformation during uniaxial compression. For phantom samples, 8 hyperelastic models have been used. The results indicate that polynomial model with N=2 is the most accurate in terms of fitting experimental data. To compare the results between elastic and hyperelastic model, a 3-D finite element numerical model developed based on two different materials of elastic and hyperelastic material properties. The comparison confirm the approach of other recent studies about necessity of hyperelastic elastography and state that hyperelastic elastography should be used to formulate a technique for breast cancer diagnosis.

Abstract: Casing collapse resistance strength is an important parameter for its properties in using. Specification, geometry accuracy, material properties, and many other reasons can influence casing collapse resistance property. Study each factors influence for casing collapse resistance strength based on full scale collapse test results of seventeen Φ177.80mm casings and there geometry and material properties test results. The results show that casing collapse resistance strength was influenced by geometry accuracy, yield strength and residual stress together. Ovality greater than 0.5% and fluctuated more than 0.5%, or eccentricity more than 10%, casing collapse resistance strength will be reduced obviously. Casing with excellent collapse resistance strength will be produced through making yield strength in appropriate level, controlling the geometry accuracy and reducing residual stress.

Abstract: Fire hazard is one of the severe casualty accident, which injures the life-safety of the miner crucially and disturbs the sustained development of the coal mine. Recently the check-up table is the mere method applying for the assessment of the fire hazard, and the assessment conclusion is subjective intensively and the Index System of the Safety Assessment is not perfect, because the dangerous degree of fire hazard is set up by the professional. In this paper, the seven factors were generalized through the statistic and analysis of the 56 fire hazards, which included self-ignite gradation of coal bed, miner stuff, management of ventilation of coal pits, fire control system, safety administration, mine combustible, risk ratio of the electrical equipment. The ratio of each factor was confirmed by the method of layered analysis, the safety degree was set up through data processing and the proper measure and suggestion were put forward according to the safety result.

Abstract: This paper adopts Macroscopic Phenomenological Method to establish constitutive relation. In order to maintain better approximation, it adopts testing data of typical stress path, testing data of uniaxial tension and torsion test. Applying multidimensional incremental theory under general loading law, on the base of certain loading function of stress space and loading function of strain space, this essay drives heat-elasto-plastic constitutive relation of heated isotropic hardening material under the condition of elasto-plastic decoupling. Meanwhile, this constitutive relation also suits for kinematic hardening material and elastic-perfectly plastic material. This paper builds a means of driving constitutive relation of multidimensional incremental theory under general loading law in strain space.

Abstract: The features of grain boundary relaxation of a (wt.%)Fe-25Cr-5Al alloy have been investigated using a multifunction internal friction apparatus. The grain boundary relaxation peak appears at about 630oC on the internal friction-temperature curves for the alloy. The peak temperature shifts toward high temperature with increasing frequency. In terms of Arrihenius relation, the activation energy is calculated to be 4.07(±0.15)eV and the pre-exponential factor is 6.2×10^-24±1s. Grain boundary relaxation strength remarkably decreases with increasing grain size. When grain size reaches 520μm, the grain boundary relaxation peak almost disappears.

Abstract: Wear behaviours of La₂O₃-MoSi₂ composite against SiC under different loads at 1000°C and 0.126m/s sliding speed in air were investigated by using an XP-5 type high temperature friction and wear tester. The worn surfaces and phase of the sample were observed by scanning election microscopy (SEM) and X-ray diffraction (XRD), respectively. Results showed that friction coefficient and wear rate of La₂O₃-MoSi₂ composite and SiC decreased with the increase of loads. The wear mechanisms of La₂O₃-MoSi₂ composite are oxidation, adhesion abrasion and fatigue pitting.