Applied Mechanics and Materials Vols. 152-154

Abstract: In order to improve stiffness of the flotation cushion, a new type of flotation cushion with variable-section pressure equalizing groove of elastic plate for aerostatic slideway was designed. Gas film pressure distribution and load carrying capacity of this flotation cushion was studied through theoretical analysis. The grid was generated by taking advantage of overlapping stitching technique. By using the coupling calculation of the gas lubrication governing equation and elastic deformation of thin plate governing equation, the load carrying capacity and stiffness of the new flotation cushion were obtained. Some experiments were made to verify the result of theoretical calculation. The experimental results show that the stiffness of new flotation cushion is much higher than conventional flotation cushion.This new flotation cushion has a wider application space.

Abstract: Flexible tubes are commonly used in automobile and piping systems to absorb expansion and contraction in order to reduce stress. Unlike to other piping components, flexible tubes consist of a thin walled shell of revolution with a corrugated meridian, in order to provide the flexibility needed to absorb mechanical movements. It is very complicated to analyze the behavior of flexible tubes because of its complex figure. Some fundamental behavior of the flexible tube for automobile is reported with analysis method. Obtained results are as follows; (1) The von-Mises stress is increased with increase of deflection at the flexible tube end and the linearity of stress variation depends on length of the flexible tube. (2) The number of cycles to failure is decreased with increase of deflection at the flexible tube end.

Abstract: The aim in this paper is to analyze tooth surface contact stress and transmission errors, verify existence of tooth end effect and discuss symmetry of symmetrical bevel gear differential (SBGD), etc. With this aim, a 3D elastic FE model of SBGD is established under the ANSYS software environment and its meshing characteristic is determined. Starting from here, by analyzing stress and circumferential displacement of tooth, the phenomena of stress concentration is acquired; the distribution of tooth surface contact stress is studied; tooth end effect is confirmed; transmission error is assessed. The analysis is ended by assessing the symmetry of SBGD. Research results provide valuable guidelines for the design of SBGD. The developing model method proposed in this paper makes it possible to study other complex gear mechanisms such as planetary gear system.

Abstract: The paper presents a novel approach in torque sharing between an internal combustion engine (IC engine) and two electrical motors for optimal drive of a hybrid vehicle. The concept of the system is realized by employing the three degrees of freedom (DOF) twin epicyclic gear train with specially selected gear ratios to satisfy an optimal power sharing strategy. The first stage of the train provides high torque from the IC engine and moderate torque from the motor M1. The second stage provides lower torque but higher speed from the motor M2. Such arrangement of power sources is achieved by carefully selecting of all the gear ratios in the train. The designed system is able to minimize the power usage of the IC engine and thus to minimize the exhaust gas emission, save cost of petrol as compared to normal petrol vehicle. It also provides a quite wide range of torque and speed values to drive the vehicle.

Abstract: To obtain the crack life and value of the external load applied on the bar in the course of the bar precision cropping, the mathematic expression of the theoretical stress concentration factor in the tip of the V shaped notch containing its geometric parameters is built theoretically by analyzing the stress field distribution of V shaped notch tip and the stress intensity factor. The influences of the flare angle Φ, the radius at the groove bottom, and the groove depth d on the theoretical stress concentration factor are analyzed in detail and the obtained rational value is d/D=0.1 , s/D=0.015, Φ=90 in engineering practice. The analytical results show that the data obtained by the mathematic expression of theoretical stress concentration factor in the tip of the V shaped notch presented in the paper are coincident with the results of the corresponding parameters obtained by stress concentration manual in some extension.

Abstract: In order to solve the narrow range and control difficulties of the excited frequency in metal bar cropping with variable frequency vibration, the structure of the eccentric block in cropping machine was improved on in the paper and a new structure model of changing the integral eccentric block into one of main eccentric block and some small adjustable eccentric blocks, was also proposed. The key parameters of the cropping machine in the action of two different types of eccentric blocks were analyzed theoretically in detail. At the same time, the corresponding amplitude frequency characteristics of the cropping machine were also obtained. The cropping experimental results of 45 steel bar show that the cross-section quality and the cropping time are improved remarkably in the action of one main eccentric block and four adjustable eccentric blocks, comparing with the cropping results in the action of the whole eccentric block.

Abstract: The dispersion characteristics, damage region and destroy results of typical defending materials by pre-fragment warhead using explosively driven were numerical studied by non-linear finite code of LS-DYNA with fluid-structure interaction algorithm, meanwhile, the influence of different detonation types and explosive properties on dispersion characteristics and damage results of kinetic energy rod were analysed. Results show that: 1.fragments disperse symmetrically with greater damage region when center detonation and line detonate are adopted, and the dispersion velocity of fragments reach the maximum when line detonate is used; 2.explosive of higher detonation velocity in favour of improving the initial velocity of fragments, strengthing the damage ability; 3.the penetration kinetic energy of fragments increase with the decrease of axial angle between fragment and damage target.

Abstract: Enhancing the accuracy of machine tool is a key goal of machine tool manufactures and users. To characterize the Quasi-static errors and then use software compensation is an important step for accuracy enhancement. The effectiveness of an error compensation scheme relies heavily on the error model. The model must be concise and roust which can be applied to any machine tool. The total Quasi-static errors within the workspace of a five-axis gantry machine tool is composed of geometric error, kinematic error, thermal error. This paper presents an error model which can be used for practical compensation scheme. Homogeneous transformation matrix, rigid body kinematic and small angle approximations are used in this paper for error modeling.

Abstract: To improve the machining precision and reduce the geometric errors for 4-axis machine tool, multi-body system theory is introduced . Based on of the theory, ,through analysing the matrix of the position transformation and the displacement transformation, a model for the machine tool is put forth. By the laser Doppler displacement measurement, test is done and value of the errors is achieved which will benefit for later compensation.

Abstract: This paper presents an application of artificial neural network for damage identification of benchmark structure that is developed by the ASCE Task Group on Structure Health Monitoring. Many SHM studies apply their methods to the benchmark structure and test their methods. The benchmark structure is divided to three substructures such as brace, column and beam, so the first stage of damage identification is that the damage substructure is identified and the second stage of damage identification is that damage location in substructure is identified. When the damage identification is numerical simulated, the single damage and multi-damage are considered. The method of two stages is applied in the two conditions and ANN is used in every stage. From the result of numerical simulation, ANN can correctly identify the damage substructure and damage location in brace substructure and column substructure.