Advanced Materials Research Vols. 146-147

Abstract: Due to their high-performance and improved safety, gel propellants can be used in various boost motors and large launchers. The evaporation and combustion characteristics of gel propellants are the foundation for the gel-engine design. Especially, it is basal and important to study the gel droplet evaporation process. In this paper, the gel droplet evaporation model is developed to simulate the gel droplet evaporation process at first. Then the experiments to record the gel droplet evaporation process are conducted. During the droplet evaporation process, the decreased velocity of the droplet diameter increases gradually, whereas that of the droplet mass decreases gradually. The mass of both the liquid fuel and the gellant decreases gradually, however, the gellant mass concentration increases gradually and at the evaporation later stage the gellant mass is larger than that of the liquid fuel. The typical evaporation process characteristics captured by experiments are in reasonable agreement with the gel droplets evaporation mechanism. Especially, the “micro-burst” phenomenon of the gelled propellant may appears in rocket engines.

Abstract: The Design Failure Modes and Effects Analysis (DFMEA) are generally applied to risk management of New Product Development (NPD) through standardization of potential failure modes and effect-ranking of rating criterion with failure modes. Typical 1 to 10 of effect-ranking are widely weighed the priority of classification, that framing effects and status quo senses might cause decision trap happening thus. The FMEA follows considerable indexes which are including Severity, Occurrence and Detection, and need be associated with difference between every two failures individually. However, we suspect that a more systematic construction of the analysis by which failure modes belong is necessary in order to make intellectual progress in this area. Two ways of such differentiation and construction are improvable effect-ranking and systematized indexes; here we resolve for attributes of failures with classification, maturity and experiance of indexes according to an existing rule. In Severity model, the larger differentiation is achieved by separating indexes to the classification of the Law & Regulation, Function and Cosmetic. Occurrence model has its characteristic a reliable ranking indexwhich assists decisionmakers to manage their venture. This is the model most closely associate with product maturity by grouping indexes to the new, extend and series product. Detection model offers a special perspective on cost; here the connections concerned with phase occasion of the review, verification and validation. Such differentiations will be proposed and mapped with the Life Cycle Profile (LCP) to systematize FMEA. Meanwhile, a more reasonable Risk Priority Number (RPN) with the new weighting rule will be worked out for effect-ranking and management system will be integrated systematiclly

Abstract: In view of the spiral bevel gear machined by the semi-generating means, a new method to create 3D solid model is proposed. The equation of tooth profile surface is deduced from the principles of spiral bevel gear engagement and cutting, according to the position relationship of the machine tool, the cutting tool and the workpiece, along with the cutting tooth process. Then the three-dimensional solid model of spiral bevel gear is developed with the delphi program using the known parameters and the above mathematic equations. The effectiveness of this method has been demonstrated.

Abstract: Direct electro-deoxidation of zirconium oxychloride powder without sintering in molten CaCl2 and NaCl mixture salt was studied. Molten CaCl2 and NaCl mixture salt as electrolyte, a little graphite crucible filled with zirconium oxychloride powder as novel cathode and a graphite rod as anode, deoxidation experiments were performed at 700 and 3.2V for 8h and 15h, respectively. Results show that using new material of zirconium oxychloride and the method of direct electro-deoxidation without sintering can be applied to the preparation of fine zirconium metal particles, which have a great advantage in cheap cost, short technical process, and energy saving.

Abstract: Anelastic behavior of nanocrystalline Fe-17 wt.%Cr alloy obtained by mechanical alloying was investigated using a multifunctional internal friction apparatus. Internal friction (Q-1) and relative dynamic modulus (f2) have been measured as a function of temperature by free-decay method from room temperature to 400oC for the ball-milled Fe-17 wt.%Cr alloy The specimens with different milling time were examined by XRD to determine the solid solubility of Fe and Cr atoms and detect the lattice strain of the compacted specimen before and after annealing. TEM observation was employed to obtain further information about the morphology and microstructure, especially crystalline size, of the milled Fe and Cr mixture powders. It has been suggested that the anelastic behavior of ball-milled nanocrystalline Fe-17 wt.%Cr alloy origins from the viscoelastic sliding at the interfaces resulting from the thermally-activating process. The damping increasing of the specimen with smaller grain sizes is larger than that of the specimen with larger grain sizes with increasing temperature since the former contains more interfaces. The increase in the relative dynamic modulus is attributed to the structural reordering with the lowering of lattice micro-strain that is produced during milling when temperature is over 300oC.

Abstract: In this paper, Mg-Li alloy anodic oxide films were prepared with different amino acid as additive. The microstructure and phase composition of the coatings were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The corrosion resistance was evaluated by potentiodynamic polarization techniques and electrochemical impedance spectroscopy (EIS). The results show that the main compositions of the anodic oxide films are MgO, Mg(OH)2 and LiOH. The anodic oxide films with amino acid as additive have uniformer surface and higher corrosion resistance than that without additive, but with the increase of the carbon chain of amino acid, the effect is reduced gradually.

Abstract: This paper presents a new method for the damage localization and severity estimate for lattice material based on substructure modal energy. The significant advantage associated with new method over traditional modal energy methods is that the spatially complete mode shape isn’t needed. Additionally, the new method does not require the analytical and measured modes to be consistent in scale, or to be normalized. Numerical studies in this paper are conducted for lattice material based on synthetic data generated from finite element models.

Abstract: In flatness measurement system, the flatness measuring signal can be affected by the flatness roll deflection. The flatness roll stress was analyzed and the flatness roll deflection model was obtained by using the influence function method in this paper. The model has been developed based on the deformation of flatness roll in rolling and compensating curve has been obtained. The results indicated that the setting curve of flatness is preferably accordant with the curve of online measuring flatness, and good strip flatness can be obtained.

Abstract: Microstructure evolution during dynamic recrystallization (DRX) of hot deformed GH625 superalloy was investigated by optical microscope (OP) and transmission electron microscope (TEM). Hot compression tests were conducted using Gleeble-1500 simulator. It was found that the nucleation mechanism of DRX for the alloy deformed at 1150°C is composed of discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX) in the vicinity of the serrated grain boundaries. With the increasing strain, the fraction of the DRX grains increases, while the size of the DRX grains almost remains in the same range. As the deformation temperature increasing, the size and fraction of the DRX grains increase, and no precipitation of intergranular carbides are found when the deformation temperature increases to 1150°C. At lower strain rate, the size and volume fraction of DRX grains decrease with the increasing strain rates. However, the size and volume fraction of DRX grains increase at higher strain rates due to the deformation thermal effect.

Abstract: The investigations including the acid treatment to multi-walled carbon nano-tubes (MWNTs) and the synthesis of MWNTs/polyurethane composites via in situ polymerization were done. X-ray Photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and dynamic mechanical analysis (DMA) were utilized for evaluating the effects of acid-treated MWNTs on the properties and microstructure of the composites. The results indicated that carboxyl groups could be successfully introduced onto the surface of MWNTs by acid treatment. The dynamic storage modulus and glass transition temperature of composites increased with the existence of MWNTs. The improvement of polyurethane by acid-treated MWNTs performed better compared to raw MWNTs.