Advanced Materials Research Vols. 941-944

Abstract: There are wide scale of porous carbonate reservoirs in around the world, that have low permeability with undeveloped fracture. With study target of Savark formation in Middle East, core gas flooding experiments are conducted and microscope seepage mechanism is researched further. The study results indicate, with formation condition, miscible associated gas flooding is not achieved easily because of high minimum miscible pressure; flooding efficiency of hydrocarbon gas injection is high, especially for miscible flooding, because gas flooding makes oil volume expanse and viscosity decrease, and then oil mobility will be improved. In the experiments, gas injection mainly displace mobile oil in macropore, so changing displacement manner should be considered to improve flooding efficiency further.

Abstract: Isothermal compression tests were carried out on GH4133B superalloy at 940–1060°C (below nominal γ΄-transus temperature of 1080°C) and 0.001–1.0s^-1. The processing maps were constructed to evaluate the efficiency of power dissipation (η) and recognize the flow instability regimes. Our investigations demonstrate that true strain takes great effect on processing maps' evolution. At 1020°C/1.0s^-1, the efficiency value η undergoes a small decline at low strains, and then increases linearly from 0.26 to 0.58 at high strains. However, the efficiency value remains high constant (η=0.40) with the increased strain under the condition of 980°C/0.001s^-1. As a result, hot deformation can be carried out firstly at 980°C/0.001s^-1 with small strain about 0.35 and then carried out at 1020°C/1.0s^-1 to get fine homogeneous microstructure. There are two instability regimes respectively located around 940°C/1.0s^-1 and 1060°C/0.001s^-1 when the strains are 0.05–0.40. Moreover, there is another instability regime located around 1060°C/1.0s^-1 when the strains are 0.45–0.69.

Abstract: The SCRAM steel was processed by warm deformation on Gleeble-3500 thermo-simulation machine. The effect of strain on the microstructures and mechanical properties of SCRAM steel was investigated. The results show that an increase in the strain can result in refining the martensitic laths, increasing the volume fraction of precipitates and the dislocation density in SCRAM steel. The martensitic lath width decreases from 0.83 μm to 0.48 μm and the dislocation density increases from 1.3 × 10¹⁵ m^-2 to 6.4 × 10¹⁵ m^-2 in SCRAM steel. The specimen exhibits high ultimate tensile strength and yield strength but low reduction of area and total elongations when the strain (ε) is up to 0.5. The tensile fracture surface observation indicates that dimples become smaller and shallower while tear ridges drastically grow up with the strain increasing.

Abstract: Fe-Mn-C alloys with different carbon content were developed as automobile sheet. Their mechanical properties were studies after hot rolled-cold rolled-different temperature annealed. It was found that carbon element effected mechanical behavior of Fe-Mn-C system alloys seriously. With carbon element increasing its deformation mechanisms turned transformation-induced plasticity (TRIP) effect into twinning-induced plasticity (TWIP) effect. Then the Fe-Mn-C alloys with different carbon content showed different mechanical behavior and different microstructure characterization.

Abstract: A multiscale simulation approach is developed to investigate mechanism of crack propagation from the atomistic perspective. The finite elements (FE) method has been applied to obtain displacement load of the model. The quadrangle region around the crack tip crack tip has been prepared for the molecular dynamics (MD) model. The displacement load calculated by FE was applied to boundaries of the MD model. The simulation results show that the evolution of atomic configuration of the system includes dislocation emission, atomic disorder, atom bond rupture and microcrack propagation.

Abstract: High-cycle fatigue damage analysis and life prediction is a most crucial problem in the research field of solid mechanics. Based on the thermodynamic potentials in the framework of thermodynamics a numerical method for high-cycle fatigue damage was studied and provided by using a two-scale damage model. Furthermore, according to the “jump-in-cycles” procedure the numerical simulation of high-cycle fatigue damage was implemented in a user subroutine of ABAQUS software. Finally, a numerical simulation instance of high-cycle fatigue damage was provided and compared with a set of test data, which indicates that the numerical simulation method presented is reasonable and applicable.

Abstract: Mechanical properties of the electron beam weld zone, which are different from the base metal, of Hastelloy C-276 were studied by small punch test (SPT) technology. Load–displacement curves and material properties were obtained by using miniaturized plate-type specimens (3mm diameter×(0.15-0.4) mm thick) from the weld and base metal respectively. The result shows that the maximum load of weld is larger than that of the base metal under the same thickness, meaning the higher strength of the weld. Furthermore, finite element method analysis was performed to investigate the effects of specimen thickness, the diameter of loading ball and the diameter of center hole in holder on the plastic damage of Hastelloy C-276.

Abstract: In order to precisely describe superplastic flow behavior of H62 alloy, a empirical constitutive equation was established based on the experimental data, which were obtained from the constant strain rate tensions (2.0×10^-4~4.0×10^-2 s^-1) at 720 °C. Through verification of the constitutive equation with the experimental data in constant strain rate tensions and constant velocity tensions, it was indicated that the empirical constitutive equation has high accuracy and comprehensive reliability in a wide range of strain rates (2.0×10^-4~2.0×10^-2 s^-1) and strains (0~1.8). In addition, the empirical constitutive equation has a good ability to model the superplastic flow behavior of H62 alloy at 720 °C under other deformation conditions besides constant strain rate tension.

Abstract: Temperature and operating pressure are important to stress corrosion cracking (SCC) of stainless steel. The SCC susceptibility of 18-8 type austenitic stainless steel, 06Cr18Ni11Ti (S32168), in an environment containing hydrogen chloride was assessed using the slow strain rate tensile (SSRT) test under different temperature and operating pressure. Results of the SSRT test indicated that the impact of operating pressure on the SCC susceptibility was different at different temperatures. The correlation degrees of temperature and operating pressure to SCC susceptibility were calculated using the grey relational theory. The correlation degree of temperature to the SCC susceptibility was greater than that of operating pressure to the SCC susceptibility.

Abstract: In the modern automotive industry, diaphragm spring clutch is widely used in light-duty and mini cars. Its service life depends on the performance and quality of pressure element-diaphragm spring. Improving diaphragm spring fatigue life and reducing elastic force decay rate will extend service life of diaphragm spring clutch. By comparing the fatigue life through bench test, shot peening on diaphragm spring can observably improve working fatigue life.