Advanced Materials Research Vols. 199-200

Abstract: Healing processing of the samples of a 45 steel was carried out. The healing area of inner cracks in the sample made by method “Drilling – Compressing” was observed and analyzed. SEM and FESEM analysis displayed that the microstructure in healing area is should be was mainly ferrite, and ferrite grain growth across the interface of inner crack, and there exists should be exist many polyangular grains of several hundreds nanometer in ferrite of healing area. Vickers-hardness test showed that the hardness of ferrite in healing area is should be was higher than that in matrix, which may result from the strengthening of polyangular grains.

Abstract: For improving fast-start performance of underwater propeller, the robot fish with high maneuverability is developed using the fish-like swimming mode characterized by undulatory flexible body. Through observations of C-start in crucian carp, the kinematic model of fast-start in robot fish is set up. According to hydrodynamic analysis on unsteady effect of added mass and wake vortices, liquid reaction forces on bionic fish-body are derived. Based on simulation experiment of C-start, propulsive performance indexes including kinetic energy, power and propulsion efficiency are presented respectively. The research results can provide theoretical basis of raising propulsive efficiency of C-start in subsequent underwater experiments, and optimization design of robot fish.

Abstract: As non-contact seal, labyrinth seal is widely used in rotor system of high speed. However, with the development of turbo-machinery toward high performance and huge capacity, gas excitation vibration within the labyrinth seal becomes the main reason threatening safe operating of machinery sets. Recently three dimensional computational fluid dynamic was applied to analyse inside flow in labyrinth seal. These researches, while greatly improve rotordynamic prediction of labyrinth seals, are mostly focused in steady calculation. In fact, rotor inside the seal is whirling in a nonlinear behaviour, which makes the flow unstable. In an effort to analyse the non-linear behaviour of flow in labyrinth seal, this paper utilizes an improved dynamic mesh technology to realize unsteady calculation. The Reynolds Averaged Navier Stokes equations is solved by a commercial CFD program, FLUENT. Steady calculations are firstly done to determine mesh density and turbulence model, then an unsteady analysis is used to study gas excitation force. The influence of initial condition to the unsteady analysis is discussed. This method allows modeling of rotor orbit around the eccentric position and gives prediction of nolinear gas excitation force.

Abstract: In order to foresee the influence of random processing errors on geometric curve in design stage, meanwhile including success and failure process during the gradual change process in the forecast. Based on probabilistic fuzzy reliability point of view, the success or failure determination will be extended to fuzzy events. The geometric curve deign method will be also given when taking the impact of random engineering error into account. Related analysis formulae and the fuzzy criterion of success or failure of designing the curve process are established and derived. Through which, design and engineering process are integrated, the designer will be more reliably to predict the success or failure of the geometric curve design during the design stage. The processing error of lack of statistical data and the objectivity of the success or failure determination criterion will be easily solved. Economy cost and reliability design of geometrical curve design will be also considered.

Abstract: A V-shaped linear ultrasonic motor with a stator and a slider has been developed. The stator consists of two orthogonal Langevin actuators which is joined together in their ends. The Langevin actuators are symmetrical and have same first order longitudinal mode. A linear motion of the slider is generated by friction between the stator and the slider when the two first order longitudinal modes are combined. In this paper, structural dynamic design on the stator is completed with Finite Element Method(FEM). The prototype motor is manufactured based on the design results. The operation modes of the stator and the output performances of the motor are tested. The diameter and length of the Langevin actuator are 20mm and 58mm, respectively. The mass of the stator is 290g. The first order longitudinal frequency of the Langevin actuator is 27.47 kHz (FEM simulating result) and 27.36 kHz (expermental result), respectively. The maximum driving force of the motor approaches 40N. The maximum velocity of the motor is about 100 mm/s. So the stator’s operation modes are consistent with the design results, and the motor output properties have characteristics of slower velocity and stronger force.

Abstract: To prepare novel polyimides with enhanced thermal stability and low melt viscosity, a novel three-branched phenylethynyl-terminated imide oligomer was introduced. The oligomer can be used to prepare high performance resin-based composite material via resin transfer molding (RTM) due to its low melt viscosity (<2Pa.s) between 250°C and 320°C. The cured resin exhibits excellent thermal stability and higher glass transition temperature than PETI series as a result of the introduction of star-branched units. In this research, the rheological properties of the oligomer were measured and numerically fit with the dual Arrhenius model to predict the progression of the viscosity during cure. The calculated kinetic activation energies for gelation with two different Arrhenius equations, 120.8kJ/mol and 164kJ/mol, respectively,had some differences. The numerical results were compared with the experimental measurements, and it was found that the model predicts the experimental observations quite well.

Abstract: In China, the 64-type rush-repair steel girder developed in 1964 has played a huge role in the railway and highway transportation engineering construction. When it is used as a temporary railway bridge, the original biggest design traffic speed only is 30 km/h. With the rapid development of domestic railway, the dynamic performance of the 64-type rush-repair steel girder must be studied in detail in order to make clear what it can adapt the current technical requirements. In the paper, the structure and technical characteristics of the 64-type rush-repair steel girder are introduced and the dynamic responses of the 64-type rush-repair steel girder are calculated using the train-bridge coupling vibration theory. The main objects of study in paper are the 24m-span and 32m-span girders. The vibration-related laws of the 64-type rush-repair steel girder versus the different train speeds are revealed, and the proposals about the largest reasonable traffic safety speed are given.

Abstract: The pressures and the temperatures in compression chambers are analyzed, and a load model including the pressure loads and the temperatures is proposed. For the small parameter scroll wraps, the pressure loads can be simplified on the mid-areas and the temperatures are equal to the temperatures of the mid-areas. The pressure loads are of π-region pressures which have a normal angle interval of π, the number of acting regions for pressure loads is equal to the number of scroll compression chamber pairs. Apart from the part situated in the center compression chamber, the temperatures of scroll wrap decrease linearly with the normal angle. Selecting the reasonable discharge, specifying the appropriate material and the parameters, and modifying the starting part of scroll wrap are significant methods to improve fatigue strength of scroll wraps in practice.

Abstract: A Magneto-rheological(MR) fluid damper based on squeeze model is put forward. The squeeze flow differential equation is obtained. Navier slip condition is considered on two boundary surfaces and compatible condition is established. The radial velocity profile and the radial pressure distributions are derived respectively. The mathematical expression of damping force is devloped. In order to verify rationality of analytical method, MR fluid damper based on squeeze mode is designed and fabricated according to technical requirements of engine vibration isolation system. The experimental damping forces from MTS870 Electro-hydraulic Servo with sine wave excitation show that analytical method proposed in this paper is feasible and has the reference value to design MR fluid damper based on squeeze mode.

Abstract: A kind of sulfate-reducing bacteria was isolated from the actual marine environment, cultured and enriched for phylogenetic analysis by molecular biology methods, and observed under fluorescent microscopy and transmission electron microscopy to determine the species and morphology. Taking the bacteria as the main object, the influenced corrosion behavior of steels in marine environment was studied in follow-up experiments.