Applied Mechanics and Materials Vols. 325-326

Abstract: Three-dimensional integrated modeling method and the numerical simulation of elastoplastic finite element are adopted in the paper. The mechanical response of the five holes anchorage is analyzed in certain prestressed state. The stress and strain distribution information of the anchor ring, clip and steel strand is obtained respectively, and the structure safety is discussed by investigating on the maximum stress and strain.

Abstract: In this paper free vibration analysis of cracked composite beams subjected to coupled bending-torsion loads are presented. The composite beam is assumed to have an open edge crack. A first order theory is applied to count for the effect of the shear deformations on natural frequencies as well as the effect of coupling in torsion and bending modes of vibration. Local flexibility matrix is used to obtain the additional boundary conditions of the beam in the crack area. After obtaining the governing equations and boundary conditions, GDQ method is applied to solve the obtained eigenvalue problem. Finally, some numerical results are given to show the efficacy of the method. In addition, to count for the effect of coupling on natural frequencies of the cracked beams, different fiber orientations are assumed and studied.

Abstract: The paper indicates the role of 3D modeling of concrete gravity dams in evaluation of dynamic response of dams to mining tremors which occur in mining activity regions. 2D and 3D models of a concrete gravity dam were prepared in order to compare two-and three-dimensional analysis of the dynamic response of dam to mining shock. Firstly, values of natural frequencies obtained for 2D and 3D models occurred to be very similar, but only the 3D model allowed to predict the dam behaviour under longitudinal kinematic excitation. Secondly, the comparison of the maximal principal stresses obtained for 2D and 3D models indicates that the simplified 2D analysis underestimates the values of dynamic response on about 20 %. Three-dimensional dynamic analysis allows to assess internal stresses resulting from mining shock more precisely, since the amplitudes of ground vibrations during mining tremors are comparable in three directions.

Abstract: This paper puts forward a safety evaluation model of large space building based on AHP (Analytical Hierarchy Process) algorithm. It is for the purpose of the electrical equipments zone control when on fire. This will make some safe areas in large buildings be able to use normal illumination and the elevators for personnel evacuation.

Abstract: The debarking location of a gas pipeline is at the area where typhoons take place frequently and the geotechnical condition of the slope is very complex. A sloping breakwater type structure is selected in this paper for the purpose of pipeline scour protection. Since part of the sloping foundation soil consists of silty clay whose strength is very low, the bearing capacity is checked with the base pressure induced by the breakwater. The stability of the foundation of the breakwater is analyzed with the method developed by Meyerhof. The scour protection structure is proved effective and stable.

Abstract: Metal vapor arc in vacuum breaker is a very complex phenomena and the researches on the process of arc creating are the effective method to improve breaking ability. By the theoretical study and numerical simulation, exploring the formation of plasma sheath near the cathode, charged particles energy distribution and influence elements in before-arc process are the fundamentals of this paper. Before-arc process is the fundermental of arc energy and the proximal cathode region is the important area for vacuum arc forming, so before-arc process of metal vapor arc was simulated here. The modification to electron motion produced by the interaction between charged particles and plane electrodes and both elastic and charge exchange collisions between electrons and neutral gases were considered here. The copper cross section adopted here was related to the particle energy. The tracks of electrons were traced until they reached to the anode surface. Based on this method, the formation of proximal cathode region and some microscopic parameters were simulated here. The results show that the collision between charged particles with the electrodes is the necessary condition in proximal cathode regions formation.

Abstract: The moment of vacuum breaker contacts opening to arc creating process is an unbalanced gaseous breakdown process. This before-arc process is the foundation of studying arc process. The mechanism of the metal vapor arc is different from other gas medium and contains complex electrode process. The proximal cathode region is the important area for vacuum arc forming and it is affected by many factors. The influences of the different electrode separations, different secondary emission coefficient on electronic density, electronic temperature and electric potential, were analysed in this paper. The simulation results show that the change of electrode separations barely impacts the thickness of sheath and the decrease of electrode separations will lead to the decrease of electronic energy near the cathode sheath. The increase of secondary electron emission will increase charged particles energy, which is the important condition of forming cathode sheath.

Abstract: Diesel particulate filter (DPF) are considered to be the most effective means to reduce particulate emissions, and the key of DPF lies in their regeneration. O₃ and O which have strong oxidability can be produced by non-thermal plasma (NTP) reactor. PM can be decomposed by these active substances to generate CO and CO₂. The results show that PM deposited in the DPF can be removed by NTP technology without any catalyst and DPF can be completely regenerated at a lower temperature.

Abstract: The geological characteristics of Pingdingshan mining area in China is fault block uplift and the depression in all around. The faults in the region are dominated by NW trending faults. Our researches show that most of faults experience different mechanics process and movement character because of the evolution of tectonic stress field. The regional distribution of coal and gas outburst is consequent on the regional distribution of regional tectonic stress, tectonic coal and gas storage. At the action of SW-NE extrusion stress by the effect of Qinling orogeny belt, the NWW strike structure and the NNE composite tectonics are prone to occur coal and gas outburst because of concentrated stress, low penetrability and good gas storage condition. Also incorporated with in situ stress measurements and the numerical simulation of regional tectonic stress field by using self-developed Rock Mass Stress-state Analysis System software, the mechanism of the tectonic stress field on coal and gas outbursts is analyzed. The results indicate that the distribution of rock stress depends upon the faults and is formed again because of superposition of the action of faults. Tectonic stress field and its uneven distribution provide dynamic conditions for the occurrence of coal and gas outbursts.

Abstract: Experiments were carried out to study the effect of ultrasonic vibration on the surface roughness and subsurface damage (SSD) in rotary ultrasonic machining (RUM) of glass BK7. As a comparison, some conventional grinding (CG) experiments were also performed under the same process parameters with there of the RUM ones. The surface roughness of the RUM/CG samples was measured with a surface profilometer. The SSD of these specimens was assessed and characterized by a measuring microscope with the help of the taper polishing method. Also, the influence of process parameters (cutting depth, feed speed, and spindle speed) on the surface/subsurface quality was discussed. As a result, both the surface roughness and the SSD depth of the RUM/CG specimens were reduced with the increased spindle speed, while increased with the increasing of feed speed and cutting depth of the diamond tool. Compared with the CG process, the introduction of ultrasonic vibration resulted in the higher surface roughness and SSD depth, due to the fact that the max cutting depth of the abrasive in the RUM process increased by an amplitude compared with that in the CG process.