Advanced Materials Research Vols. 631-632

Abstract: It is important for evaluating the condition of rock bolts to theoretically investigate the propagation of elastic waves in Rock bolt .In this paper, ultrasonic guided wave propagation and the interaction law with the artificial corrosion ring defect in the solid cylinder were studied through the rock bolt was modeled as a cylindrical. A large number of numerical simulation experiments were carried out using finite element method based on ABAQUS, The longitudinal mode of the propagation characteristics and law were analyzed in the solid cylinder, and the best excitation model and frequency were selected for the signal dispersion by combining curve with wave structures knowledge. The outcome of this research indicated that L(0,1) reflection coefficient is increased as well as during the depth incremental change when given a particular axial length; With the increment of the axial, L(0,1) and F(1,1) of the reflection coefficient maintain the similar trend when the ring defect depth coefficient 10%.

Abstract: The metallurgical composite bimetallic tube, Incoloy825/X60, has been manufactured by a novel centrifugal casting plus extrusion compound technique. Based on the Incoloy825/X60 bimetallic tube, the limiting inner pressure and stress distributions were investigated by the finite element analysis software ABAQUS. The results indicate that the pressure-resistant capacity of the metallurgical composite bimetallic tube is equivalent to the internal metal in elastic state while the limiting inner pressure is much larger than the single metal tube with the same sizes in plastic state. The pressure-resistant capacity of the metallurgical composite bimetallic tube has increased more than two times compared with the external metal tube because of the transition layer which has a complete metallurgical bonding.

Abstract: Regular formulae for lateral aerodynamic force cannot give precise prediction under unsteady crosswind. By generalizing potential flow theory and taking the aerodynamic derivative into consideration, the semi-empirical expression for lateral aerodynamic force is derived. In order to determine the coefficients in the semi-empirical formula, the model of a typical double-deck coach is investigated in a sequence of numerical simulations under pure crosswind condition (i.e. linear crosswind, pseudo-step crosswind, sinusoidal crosswind). Moreover, advantages of the semi-empirical formula over the regular one are revealed. Further inspections into the flow field derived from the theory of vortex motion indicate that the deviation between the prediction given by semi-empirical formulae and that by numerical simulation is caused by the non-viscous assumption in potential flow theory. The lateral aerodynamic force depends linearly on the crosswind aerodynamic derivative. Situations in which the coach is moving in the direction perpendicular to the wind velocity are also studied to find the cause of the error in semi-empirical formula. Furthermore, the semi-empirical formula is revised by introducing the “damping model method”. A relatively complete system of prediction for lateral aerodynamic force on a coach, which is of practical engineering significance, has been constructed.

Abstract: This paper aims to propose a design method for tooth profiles of spur gears based on given line of action. A simplified derivation of the mathematical model of tooth profiles is introduced according to the meshing theory. Tooth profiles of spur gears, using a parabola as line of action, is established. The result shows that it will be better to control the performances of a gear set by specifying the shape of the line of action rather than specifying tooth profiles of mating gear.

Abstract: Based on the flammability requirements of toy and textile product in Entry-Exit Inspection, design and development the automation tester of flammability combined with PLC control technology, high-performance and fine-segmentation driver as well as step-in motor. It demonstrated the tester machinery design, work principle, control system and programming of software. It is pointed out the tester can settle for testing requirement of International standard toy safety, and also settle for testing requirement of International standard textile safety.

Abstract: In this study, 3-dimensional flow characteristics around three concept EV models were computed for steady, incompressible, and viscous flow, adopting a realizable k-εturbulence model. In order to research the relationship between different structure of models and aerodynamic drag, comparative study were carried out for the aerodynamic characteristics of three concept EV models at a high Reynolds number, Re≈8.2×10⁶ (base on the vehicle length). As a result of this study, the new concept EV model with low aerodynamic drag was completed by integrating the advantages of three reference models.

Abstract: Magnetic interactions may lead to errors in precision mass metrology. There are two factors named magnetic susceptibility and magnetic polarization which need to be determined before mass metrology. First four methods are compared and analyzed suitable range, requirement, uncertainty and note in comparison process. Then uncertainty factors are given out, and description of differences between normal weights and micro-gram standards are presented in the paper. It is easy to become magnetized if the weight is not well protected in manufacture or daily using. So it is important to control its safe and perform periodic self-verification on it.

Abstract: A schlieren system with high time and space resolution was developed to diagnose the hypersonic flow field with high speed, low density and intensive shock interactions. The key technique of color filter used for color schlieren was developed. The time resolution reached to 100ns and the space resolution reached to 0.1mm. In shock tunnel with Mach 5, bow shock controlled by single laser pulse was investigated with the schlieren system, and the interaction of oblique shocks generated by double ramps was detected with color schlieren. The complex flow fields are clearly exploded, which proves that the schlieren system designed in this paper supplies an efficient method in the diagnostics of hypersonic flow field.

Abstract: The course and phenomena of oxygen cylinder explosion are introduced. Chemical composition analysis, mechanical properties, metallographic tests and spectrum analysis of the cylinder fragments have been carried out. Based on the fact that the explosion is concluded as a chemical explosion because of grease. Filling grease into oxygen cylinder was due to misuse. Violent oxidation exothermic reaction occurred when grease was exposed to pure high-pressure oxygen. The instantaneous releasing of heat produced extreme high temperature and extreme high pressure in the cylinder, which exceeded its limits and caused burst. During the process for risk, pressure gauge shows that cylinder explosion occurred while oxygen cylinder is charged to 13.5MPa. According to the GB 5099, the minimum explosion pressure of oxygen cylinder is 43.8MPa. Moreover, inverse calculation shows that minimum grease amount leading to burst of cylinder is between 79.6g to 95.5g. The experiences and lessons for the management and use of gas cylinder are discussed and emphasized.

Abstract: Taking pressure compensation valve in load sensing multi-way valve as research object, based on the dynamic mathematical model, the dynamic characteristics and the law that the structure parameters affected the characteristics were analyzed. The research methods and results provide analytical tools and design documentation for the structure design and the theoretical study on the outlet pressure compensation multi-way valve.