Advanced Materials Research Vols. 179-180

Abstract: The effect of grain size on the mechanical properties in ultra-high pure aluminum had been investigated as a function of strain rate. Specimens with average grain diameter sizes of 243, 678 and 1070 m were compressed and elongated at quasi-static and high strain rates by a computer controlled servo-hydraulic testing machine and a Split Hopkinson Pressure (Tension) Bar (SHPB and SHTB). The mechanical properties were found to vary significantly with grain size, and strain rate. The relationship between flow stress and grain size can be expressed by a Hall - Petch relation with the different slope for both compressive tests and tensile tests. The influence of strain rate on the slope of the Hall - Petch relation is such that in compression, the slope does not change much, but in tension, there is an increase in the slope value. The strain hardening rate was seen to increase with increasing strain rate. The strain rate dependence of flow stress is obvious, and is seen to be more significant for the smallest grain size specimens. The 3D fractographs illustrated that the numbers of the dimples decrease with the increase of the grain size.

Abstract: Nonwoven samples are collected from industrial equipments in four nonwoven factories. The processing parameters and equipment parameters are also obtained. The fiber diameters of the nonwoven samples are measured by using the image analysis method and compared with the predicted fiber diameters by solving the polymer air drawing model. The results show that the predicted fiber diameters coincide with the measured fiber diameter very well, which confirms that the polymer air drawing model is effective in predicting fiber diameters of nonwoven fabrics produced by industrial equipments in nonwoven factories. The results reveal the practical value of this theoretical research on the melt blowing technology.

Abstract: Twin zone cooling process with high extraction ratio is established by studying the effect of cooling rate on the boron extraction ratio of boron-containing slag. The viscosity increases rapidly by continuous cooling and the prior crystallization of forsterite, which hinders the nucleation and growth of suanite, result in the low extraction ratio of boron. With the twin zone cooling process, the rapid cooling in 1500°C-1200°C, restrains the formation of forsterite and reduces the inhibition effect of forsterite on the nucleation and growth of suanite. Heat is preserved at 1200°C to ensure the sufficient interaction time among the particles, which is favorable toward the nucleation and growth of suanite. As a result, the extraction ratio of boron-rich slag is improved.

Abstract: On the basis of analyzing multiple fault mechanism of the flexible manufacturing system (FMS), the FMS diagnosis system architecture frameworks are built. The FMS status monitoring and fault diagnosis system and software model are especially proposed. The monitoring system structure and hardware composition are discussed, and software structure is also given. Finally, the FMS monitoring and diagnosis system are developed.

Abstract: Graph based learning has been an active research topic in machine learning community as well as many application areas including image annotation recently. In order to exploit the correlation between keywords and images, we proposed a novel image annotation method via graph based learning and semantic fusion to estimate the probability of keywords being the caption of an image, and present a new framework to solve the problem. The experiments over Corel images have shown that this approach outperforms other methods and is effective for image annotation.

Abstract: An axial collapse test of Oxygen-Free High-Conductivity copper (OFHC) cylindrical specimen subjected to impact against a steel plane target at the velocity range between 64 m/s and 165 m/s was performed on a single gas gun. The deformation process of the OFHC cylindrical shell in the specimen was a sequence of the thermovisco-plastic wave propagation between target plate and the structural plate. The experimental results were simulated numerically by use of LS-DYNA. The influences of OFHC constitutive models on the deformations of OFHC cylindrical shells were shown in the paper. It seems that the Johnson－Cook(J-C) constitutive model gave a better prediction of the shape of the OFHC cylindrical shell in such an impact test. The deformation of cylindrical shell is sensitive to the work-hardening coefficient. The energy absorption behaviors of the OFHC cylindrical shells were also investigated. The energy absorption capability of the shells influenced by their geometries were also shown in the paper.

Abstract: Based on the partial derivative of working space function, define the integral field of serial mechanism and parallel mechanism and serial-parallel mechanism respectively, judge conditions of singularityity including dead point and limit point with one and two and three input parameters obtained. Define the coupling degree of each input variable of mechanism use the second-order partial derivative of working space function, decoupling property between input variable identified by judging the coupling degree equal zero or not. Based on the realtionship between working space function and input variables, as well as relationship between input variables and time, three new index to weigh the kinematical properties of mechanism defined, positioning accuracy influence factor and dynamic response influence factor and sensitivity influencefactor included, its physical meaning and computation process presented as well, new direction provided for the research of kinematical properties of mechanism.

Abstract: To obtain failure characteristic of jointed rock mass, the propagation mechanism of twin collinear cracks with different angle is simulated by finite element under different consolidated condition. The change laws of stress strength gene, the slipping displacement of middle nodes of faces of crack, shear strain and plastic strain near crack tip is derived under different consolidated condition. It is shown that the consolidation role is the evident and the stress concentration is weakened when the inclination angle of crack is in range of 30°-60°. The corresponding value under consolidated condition is smaller than that under without consolidated condition. The slipping displacement of middle points of crack faces in y direction is mainly. The slipping displacement in y direction decreases and the slipping displacement in x direction increases with the increases of the inclination angle of crack. The compressive effect is bigger than that the shear effect.

Abstract: With the widely use of Permanent Magnet Brushless DC Motor (BLDCM) in many fields, the superiority in the control method of position sensor-less is more and more obvious. In this paper several control methods of position sensor-less for BLDCM are presents, and a novel technique, the method of speed-independent position function, is introduced to detect the rotor position of BLDCM. This method may detect the rotor position from almost zero speed to high speed, and may also give the commutation time.

Abstract: Direct torque control (DTC) technology in asynchronous motor is one of new frequency transformation drive technology after the vector control technology. In recent years people begin to apply it to the synchronous motors. This paper introduces the application station of direct torque control in permanent magnet synchronous motor drives, discusses several key problems and analyses its development direction in the future.