Advanced Materials Research Vols. 189-193

Abstract: The eccentric wear of the sucker rods and tubes has already become the greatest bottleneck restricting the development of oil recovery technology of pumping wells. There is lots of inadaptability of the current control measures. The laboratory study and field tests showed that the NHW-1type coated tubing had a good protection of the rods and tubes of the well pumps. Compared with ordinary tubing, coating can prolong the life cycle of the tubes for more than 2.6 times. At present, the eccentric wear control technology is advanced both at home and abroad.

Abstract: Equal channel angular pressing (ECAP) of 3003Al ingot has been performed at room temperature, with an imposed equivalent strain of ~0.5 for single pass, and the refinement/distribution of inclusions and the hardness/dislocation of the alloy were examined. The results show that the first pass ECAP processing refined the inclusions (AlFe (Mn)Si) of the alloy considerably, with the size variation from 5-15μm length/1-2μm width to 1-3μm length/1-2μm width. In addition to the refinement, the first pass ECAP processing improved significantly the distribution of the AlFe(Mn)Si inclusions, and introduced high density of dislocations, leading to ~66.7 % increase of hardness. It was found that with the increase of number of ECAP processing passes, the distribution of AlFe(Mn)Si inclusions were increasingly more uniform, while the size of inclusions, the hardness and dislocation density (dislocation strengthening) of the alloy kept almost unchanged. The present results demonstrate the possibility of ECAP as an effective tool to refine AlFe(Mn)Si inclusions of aluminum alloys.

Abstract: How to implement security obstacle avoidance is important to the Mobile Robots. Now the robots become more and more intelligent. How to sense the uncertain surrounding environment and to act directly are basic factors for intelligent robots. But single range-sensor cannot do well to ensure the precision, the quick response and the reliability of measuring data. Multi-sensors are designed for the Range-Measurement System of Mobile Robots based on ARM. The system can fulfill the data acquisition from different sensors simultaneously and process them by the Adaptive Weighted Data Fusion Algorithm. Then it transmits the real-time and precision ranging-data to the upper controller. At last the testing data indicate that the system can improve the range-measurement precision.

Abstract: The difference of forcing status between coal and gangue in the process of impact was a fundamental problem in separation of them. In order to finding out forcing status of coal and gangue, the impact process was emulated by finite element software. The variation curves of contact force, the time-course curves of stress and pressure at different locations on material and board hammer were gained. The simulation results showed that for the different material properties, stress and pressure variation of coal were less than gangue, and the impact point in board hammer has the worst forcing status.

Abstract: In this paper, the ultrasonic shot peening (USSP) technology was used to obtained surface nanocrystalline of 20 carbon steel. The grain size of test surface and the thickness of nanocrystallization layer were analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). The three electrode electrochemical measurement was employed to investigate the electrochemical corrosion performance and the critical character of USSP surface nanocrystallization samples in different impact strength. The results showed that the USSP surface nanocrystallization could obtain the nanocrystalline grain. The thickness of nanocrystallization layer increased and grain sizes reduced with the increase of the impact strength. Nanocrystallization layer took the way to expand concentric circles with impact crater as the center. The corrosion current of nanocrystallization sample was much larger than as-received. The controlled step of corrosion process was turned from cathodic process to anodic process by USSP surface nanocrystallization. The sample surface formed two layers corrosion product films in condensate water, which were compact Fe₃O₄ membrane as inner corrosion product film and loose Fe₃O₄ membrane or Fe₂O₃ membrane as outer layer. With the increase of the impact strength, critical velocity of the outer corrosion product film increased gradually. The critical velocity of inner corrosion product film had an increasing trend, but the critical velocity tended to be a constant value when impact strength was more than 1.9904min/cm²

Abstract: The corrosion behavior of Fe₃Al was studied by high temperature autoclaves in H₂S/CO₂ environment. By Stereo Microscope, we found that the corrosion film of Fe₃Al is thin and crack at 60°C, 4.0 Mpa,after 72h in autoclaves; Phase analysis by XRD showed that the main composition of corroded products is FeS; its corrosion are Ⅲ corrosion resistant type and corrosion rating of 4, mainly pitting, and average corrosion rate of 0.2106 mm/a.

Abstract: Grind-hardening test were performed on MM7132 surface grinder with corundum grinder wheel in the mesh of 60#. The result shows that the structure of grind-hardened layer is composed with lath martensite and small mixed martensite; the depths of grind-harden layer is largest when the grind depth is 0.3mm, while the depths of grind-harden layer decreased when the grind depth is 0.2mm, 0.4mm, 0.5mm,respectively. The range of microhardness of grind-harden layer is from 754 to 853. The depths of grind-harden layer along the direction of working appeared ladderly.

Abstract: Rollers’angular velocity matching of rolling driven equal channel angular deformation technology was investigated numerically by using finite element code DEFORM-3D. The results show that as the angular velocity of primary feeding roller is constant, the rollers’ angular velocity matching had only small influences on effective strain and output velocity, but had significant influence on torque of feeding rollers. With the decrease of angular velocity ratio of primary feeding roller to secondary feeding roller from 1.37 to 0.073, the torque of feeding rollers tend to become uniform. It was found that an appropriate selection of rollers’ angular velocity matching and friction factor can save energy consumption significantly.

Abstract: The microstructure and friction/wear properties of TiB₂-C (carbon-doped TiB₂) films in TiB₂-C/SiC double layer films (SiC films as interlayer) deposited on Ti6Al4V alloy substrate using magnetron sputtering technique at room temperature were investigated. The results show that the TiB₂-C films exhibited the microstructural characteristics with nano-scale particles (domains), and the doped-carbon presented in manner of sp³ C-C and sp² C-C bonds i.e. DLC (diamond-like carbon). The interface between the substrate and the SiC films and the interface between the SiC films and the TiB₂-C composite films both showed good adhesion, with obvious element diffusions. As sliding against Si₃N₄ (silicon nitride) balls (2 mm in radius) using ball-on-disc type wear tester at room temperature under Kokubo simulation body fluid (SBF) and 50g load, the TiB₂ -C composite films exhibited the friction coefficient of about 0.14 and the specific wear rate of 10.710-6 mm³ m⁻¹ N⁻¹. It is believed that the superior friction properties of the TiB₂-C films are due to the role of the doped-carbon.

Abstract: Adding suitable quantity of polypropylene fiber is very effective for controlling plastic crack of cement mortar. During the experience stage, adding quantity of polypropylene fiber is 1.5 kg/m3, and crack rate of mortar is only 7.7%. Theoretical analysis is made for plastic crack mechanism of cement mortar, the results indicate that adding polypropylene fiber improves critical stress of crack expansion in mortar and notably reduces crack of cement mortar.