Applied Mechanics and Materials Vols. 198-199

Abstract: Because of such merits of servo turret like fast speed of tool changing, high accuracy of first location, simple mechanical structure, high reliability and so on, servo turrets are widely used in turning processing and turning and milling complex processing center.Control mode of servo motor speed is one of the critical problems in the designing of servo turret.S curve acceleration and deceleration control is to make the derivative of acceleration as constant in this procession, and maximize to reduce the impact of mechanical system by controlling acceleration derivative. Otherwise, by setting parameter or programming acceleration and its derivative, flexible acceleration and deceleration will be controlled to fit for different kinds of situation of machines.

Abstract: This paper summarizes the characteristics of variable thickness boom parts. The article discusses the principle of the CATIA Law line and the application of CATIA Law line method in parts design of the variable thickness boom, and solves the technical problem that the boom thickness can't linear and smooth change when we design parts. We have given two kind of the design operation process of variable thickness boom parts.

Abstract: To obtain fatigue design data of the train wheel steel , the fatigue tests were carried out for the steel of K type and B type train wheel separately, which fatigue limit was measured using the fluctuation method, the fatigue life of two kinds of wheel steels were tested using the grouping method at the three stress levels, two different materials and different structures have an influence on the fatigue properties of the wheels using reliability principle. The fatigue life distribution of the B type is scattered relatively . S-N curve equation and P-S-N curve equation of the two kinds of steel were calculated . The theoretical basis were put up for developing design standards and safety evaluation of the both wheel.

Abstract: Structural steel has been used to make building structures higher and wider than that constructed with conventional structural materials such as concrete, brick, etc since 1960’s in Korea. But the steel structure has fatal demerits. One is the deteriation of structural performance when exposed to severe fire and the other is rusting. The structural behavior has to be sustained during unexpected fire and this can be done by fire design. The fire design consists of two methods. One is prescriptive and the other is performance-base fire engineering design. Recently, the fire engineering design has become a reasonable alternative against the prescriptive method in the world. But the fire engineering method is now preparing for adoption into Korea building regulation. The main purpose of this paper is to build the databases of fire resistant and limiting temperatures of beams made of H-section and the results from fire tests under loadings showed that the corelations between the limiting temperatures and load ratios applied were in reverse proportion.

Abstract: This paper put forward a systematic design method based on virtual prototyping technology to simulate lifting platform of jacking system in jack-up offshore platform. After the main parameters of lifting platform in jack-up offshore platform were introduced, the 800T offshore platform modeling techniques were put forward, such as rigid body modeling techniques, flexible body modeling techniques, modal analysis techniques and kinematics analysis. The dynamics analysis was present with the simulation results, which demonstrates that this method is obviously helpful to get more accurate simulation results to verify the rationality of lifting platform in jack-up offshore platform.

Abstract: To detect the pipes, this paper introduces the electro-mechanical impedance (EMI) method into online monitoring for the pipes. The pipes model with a Polyvinylidene Fluoride (PVDF) bonded on it is built. The finite element method is employed to analyze the electro-mechanical impedance of the PVDF, the conductance curves of PVDF are obtained with different damaging phase of the pipes, the root-mean-square deviation (RMSD) is used to assess the damage extent. The result indicates that EMI as a new detection method is effective in identifying the existence and severity of cracks in pipes. As the corrosion area increases, the difference of conductance curves becomes more obvious and the RMSD becomes larger.

Abstract: The mathematical model of steady state thermal analysis of accessory transmission system is built according to heat transfer theory, the governing equation functional of the steady state temperature field of accessory transmission system is derived on the basis of the variation principle, and the method to calculate the steady state temperature field of accessory transmission system is proposed with the finite element software ANSYS and its secondary switching language APDL. The result shows that the prediction of temperature field fit in with the heat flow law, then the correctness and validity of the proposed thermal analysis method is verified.

Abstract: To the super long shaft workpieces, because of the particularity of itself, mechanical processing process is hard to control, along with the process system derived error (factors error) can be produced, how to solve the derived error in super long shaft processing production, the author has conducted the qualitative analysis on three types of derived error, and put forward the corresponding countermeasures.

Abstract: This paper reviews principle and characteristics of the tennis serving machine and the tennis picking machine on the market. According to the actual situation, it intends to design a new type of tennis equipment for the tennis practitioners, which is named intelligent tennis vehicle. This machine consists of ball-storage mechanism, supply mechanism, serving mechanism, picking mechanism, frame and control circuit. This machine uses storage battery for the power supply, and it uses MCU (micro controller unit) as the controller, controlling all kinds of the mechanisms. It can help people to practice tennis, and pick up the large number of scattered tennis balls conveniently. This machine can meet the needs of different requirements, so that practitioners can better improve the tennis technology in order to achieve the purpose of fitness and training.

Abstract: The microstructure and mechanical properties of aged AZ81 magnesium alloy with Ca addition have been investigated. The results show that with proper content of Ca addition, the microstructure of AZ81 magnesium alloy is refined. Meanwhile, high melting point granular compounds Al4Ca are formed, and the quantity of β-Mg₁₇Al₁₂ phase is reduced significantly. And the mechanical properties of AZ81 magnesium alloy are enhanced at room temperature and 150°C.