Advanced Materials Research Vols. 146-147

Abstract: Cyclic stress-strain curve and cyclic strain-life curve appear distinct scatters, and the scatter of fatigue life increases with reducing of the strain levels. A methodology for reliability simulation of low cycle fatigue (LCF) life for turbine disk structures is developed in this paper. First, probabilistic cyclic stress-strain model and linear heteroscedastic probabilistic cyclic strain-life model are founded based on the fatigue test data. Second, three dimensional model of a turbine disk is built, and the fatigue reliability analysis of this turbine disk is implemented in probabilistic design module (PDS) of ANSYS by the combination of response surface method (RSM) and Monte Carlo simulation (MCS). The predicted life with reliability 0.9987 is well consistent with the technology life obtained from disks LCF tests by scatter factors method.

Abstract: The aging hardening curve of AZ91D magnesium alloy was gained, and aging behavior of the alloy was investigated with Vickers hardness measurement, differential scanning calorimetry (DSC), transmission electron microscope (TEM) after solution treated at 415°C for 10h , and water quenched at room temperature , afterwards aged at 175°C for 0-38h with a 2h interval. The result show that there are three aging peaks at aging hardening curve of AZ91D magnesium alloy, and that four types of β-Mg17Al12 precipitates were responsible for the aging peaks.

Abstract: Zn electrodeposited directly on the surface of AZ31 Mg alloy was researched in this paper. Zinc fluoride which was dissolved in ammonium citrate solution was used as metal ion source. The interface and morphology of Zn coating were observed by scanning electron microscopy (SEM).The results showed that Zn coating was smooth and dense. The experiment of making lattice on Zn coating showed good adhesion. The corrosion resistance of Zn coating was carried out in 5% NaCl solution, and its stabilization time was more than 5hrs. Cyclic voltammetry and polarization curve were used to investigate the transfer behavior and state of zinc ion in electrolyte. It indicated that Zn existed in the forms of three complex states in electroplating solution and ZnL proportion increased with increasing pH value. It was known that complex Zn electrodeposited directly on the cathode.

Abstract: Chemical-looping combustion (CLC) is a new kind of efficient method to separate CO2. At present, most of CLC research focuses on the development of oxygen carriers. The sustainable capability is the one of important standards to evaluate performance of oxygen carrier. The iron- based and copper- based oxygen carrier were chosen in this paper. The comparative study between the analytically pure oxygen carriers and the prepared oxygen carriers with Al2O3 were made according to the reactivity of reduction and oxidation. The data was obtained by the TGA, SEM and XRD. The results show that the prepared carriers with Al2O3 are greatly improved both in reaction ratio and sustainable capability, and Fe- based oxygen carrier is better than the Cu- based oxygen carrier in the sustainable capability.

Abstract: AA6061 Aluminum alloy welded joint using two different filler metals were studied by using X-ray CT-Scan. The filler metals ER 4043 and ER 5356 were used in this present work in order to investigate the effect of using different filler metals on the welded joint quality of AA 6061 aluminum alloy in welded zone microstructure. Gas metal arc welding (GMAW) technique and V grove butt joint with four layers and five passes welded joint were performed. From this investigation, it is found that AA6061 with ER 4043 showed less distribution of porosity compared to AA6061 with ER 5356 welded joint confirmed by X-ray Ct-Scan. The decreasing of porosities and presence of very fine grains in weld region area with ER 5356 compared to ER 4043 will be discussed in term of microstructure analysis.

Abstract: In order to improve the sweep efficiency of water flooding in matured oilfield, soft moveable gels (SMG) are developed. The new types of SMG are made of novel, expandable particulate materials. The gels are preformed, stable, size controlled, non-toxic and can reduce water permeability without affecting oil permeability significantly. In this paper, some relevant laboratory methods are carried out for the determination of their main characteristics, including the displacement mechanism, the physio-chemical properties, moblility in porous media and the adjustment of permeability. Furthermore, the properties in bottles and behavior in porous media have also been investigated. The results shows that: 1)the swelling times of SMG are approximately 10, 2)SMG can remarkably improve the efficiency of water flooding, 3)remaining oil startup in low permeability formation, multistage fluid diverting and deep profile control are the main oil displacement mechanisms, 4）the new promising gel system of SMG have extensive application prospects in deep water shutoff and conformance control.

Abstract: Fracture tests of 10 plates with elliptical hole fabricated from Q235 steel with the thickness of 4mm were conducted. The effecting of sharpness of elliptical hole (a/b) on fracture mode and fracture ductility of structure steel was studied. The experiment results show that the first crack initiates at the edge of the major axis of elliptical hole and expands towards the thickness of the plates. And then the crack expands quickly vertical to loading direction until the specimen ruptures. The fracture ductility is low for the specimen with the sharp elliptical hole. Numerical simulation and analysis of Q235 steel plates with elliptical hole were implemented based on an elliptical yield model and an elliptical fracture model. The simulated stress field shows that the stress concentration severely at the edge of the major axis of elliptical hole. The accuracy of the proposed elliptical fracture model is proved for predicting the fracture of Q235 thin steel plates with elliptical hole.

Abstract: In this paper, the Al-8.5Fe-1.3V-1.7Si alloy was fabricated by spray forming and forging processes. The microstructure and mechanical properties of the alloy were investigated by means of metallographic, scanning electron microscope and tensile test. The results indicate that spray formed Al-8.5Fe-1.3V-1.7Si alloy after pressing plus can forging processes displays excellent microstructure and characterization.

Abstract: The effect of TIG-dressing on fatigue strength in support of the fillet weld of offshore platform was investigated experimentally in the paper. According to the causes in which most cracks are produced in actual structure, the model tests have been performed based upon cruciform weld bead characteristic. The TIG-dressing technique parameters were established by the actual structure and the fatigue specimen tests were done also. The life estimation equation after TIG-dressing is presented by least square method. The fatigue life used by TIG-dressing has increased over 100%. Therefore the TIG-technique gives a big potential for engineering application.

Abstract: Fracture tests at low temperature (-47°C~-43°C) of 20 notched bars fabricated from E43 solder were conducted. The effect of notch radius, r, and notch depth, d/D, on fracture mode of E43 solder was studied. The experimental results demonstrate that cracks initiate at the center of notch section and the notched bars fracture at the notch section at low temperature. The fracture mode is cleavage fracture and the fracture sections are coarse. Specimens with a sharper notch radius (a smaller r) and a larger notch depth (a smaller d/D ratio) show poor ductility. The stress-strain curve of E43 solder tested on standard specimen at low temperature (-47°C~-43°C) exhibits the character of yielding, hardening and necking. The ratio of ultimate strength to yield strength, σu/σy, and the ductility, δ5, at low temperature meet to the requirement in plastic design for structural steel.