Zhang J.,China Railway Construction Heavy Industry Co. |
Zhang Y.,Nanchang University
Advanced Materials Research | Year: 2014
In this paper, a nonnegative tri-Matrix factorization (NTMF) algorithm is proposed for underdetermined blind sources separation with the assumption of that the source signals are nonnegative and sparse. By incorporating the regularization and sparse penalty into the cost function, a novel multiplicative update rules is proposed to solve the problem of UBSS based on NTMF. The simulation results are presented to show the validity and competitive performances of the proposed algorithm. © (2014) Trans Tech Publications, Switzerland.
Zhu S.Y.,Southwest Jiaotong University |
Cai C.B.,Southwest Jiaotong University |
Luo Z.,China Railway Construction Heavy Industry Co. |
Liao Z.Q.,China Railway Longchang Materials Co.
Science China Technological Sciences | Year: 2014
A frequency and amplitude dependent model is used to describe the complex behavior of rail pads. It is implemented into the dynamic analysis of three dimensional coupled vehicle-slab track (3D-CVST) systems. The vehicle is treated as a 35-degree-of-freedom multi-body system, and the slab track is represented by two continuous Bernoulli-Euler beams supported by a series of elastic rectangle plates on a viscoelastic foundation. The rail pad model takes into account the influences of the excitation frequency and of the displacement amplitude through a fractional derivative element, and a nonlinear friction element, respectively. The Grünwald representation of the fractional derivatives is employed to numerically solve the fractional and nonlinear equations of motion of the 3D-CVST system by means of an explicit integration algorithm. A dynamic analysis of the 3D-CVST system exposed to excitations of rail harmonic irregularities is primarily carried out, which reveals the dependence of stiffness and damping on excitation frequency and displacement amplitude. Subsequently, sensitive analyses of the model parameters are investigated by conducting the dynamic analysis of the 3D-CVST system subjected to excitations of welded rail joint irregularities. Following this, parameters of the rail pad model are optimized with respect to experimental values. For elucidation, the 3D-CVST dynamic model incorporated with the rail pads model is used to calculate the wheel/rail forces induced by excitations of measured random track irregularities. Further, the numerical results are compared with experimental data, demonstrating the reliability of the proposed model. © 2014, Science China Press and Springer-Verlag Berlin Heidelberg.
Wang W.-X.,Southwest Jiaotong University |
Wang W.-X.,China Railway Construction Heavy Industry Co. |
Cai Z.-B.,Southwest Jiaotong University |
Qian H.,Shanghai Nuclear Engineering Research and Design Institute |
And 5 more authors.
Zhongguo Youse Jinshu Xuebao/Chinese Journal of Nonferrous Metals | Year: 2014
Tangential fretting wear characteristics of alloy 690 tubes against 405 stainless steel plates were studied on a fretting wear tester (PLINT TE77) under the dry condition at different temperatures by linear contact. At the test parameters, such as normal load of 40 N, displacement amplitude of 100 μm, frequency of 5 Hz and cycle number of 1×105, the fretting wear test were carried out at 25, 90, 200 and 285℃. The results show that, the fretting condition are all running in gross slip regime. The friction coefficient at 90℃ reaches the highest steady state value, and it occurs a more obvious decrease stage after a period of decline while the temperature increases to 200 and 285℃, which is related with the high-temperature oxidation at the interface. The wear mechanisms are complex with abrasive wear, oxidation wear and delamination. The oxidation of the worn surface at low temperatures (25 and 90℃) is more serious than that at high temperatures (200 and 285℃). The wear volume at 90℃ is higher than that at the other temperatures, this may be related with the water vapor at the interface and the oxide film at the surface. ©, 2014, Zhongguo Youse Jinshu Xuebao/Chinese Journal of Nonferrous Metals. All right reserved.
Zhang Q.,Tianjin University |
Zhang Q.,Australian National University |
Su C.,China Railway Construction Heavy Industry Co. |
Qin Q.,Australian National University |
And 3 more authors.
Science China Technological Sciences | Year: 2016
EPB TBMs (Earth pressure balance Tunneling Boring Machines) are extensively used in tunneling constructions because of its high efficiency and low disturbance on structures above ground. It is critically significant to predict the thrust acting on TBMs under different geological conditions for both the design of power system and the control of tunneling process. The interaction between the cutterhead and the ground is the core of excavation, through which geological conditions determine the thrust re-quirement combined with operating status and structural characteristics. This paper conducted a mechanical decoupling analysis to obtain a basic expression of the cutterhead-ground interactive stress. Then more engineering factors (such as cutterhead topological structure, underground overburden, thrusts on other parts, etc.) were further considered to establish a predicting model for the total thrust acting on a machine during tunneling. Combined with three subway projects under different geological conditions in China, the model was verified and used to analyze how geological, operating and structural parameters influence the acting thrust. © 2016 Science China Press and Springer-Verlag Berlin Heidelberg
Zhang J.,China Railway Construction Heavy Industry Co.
Advanced Materials Research | Year: 2014
This paper deals with contact to carry on tension, bend, impact toughness's stretch and the inclined Y type ascent experiments of the Hardox400 high strength steel's welding. It research weld, fusion zone and heat affected zone's micro organization of Hardox400 high strength steel in making use of the optical microscope, and prepare hot temperature, weld hot importation and empress hot temperature influence weld strength, bend and impact toughness, and the weld craft parameter can be assured under physically produces condition. © (2014) Trans Tech Publications, Switzerland.
Xia Y.-M.,Central South University |
Tang L.,Central South University |
Ji Z.-Y.,Central South University |
Ji Z.-Y.,China Railway Construction Heavy Industry Co. |
And 3 more authors.
Journal of Central South University | Year: 2015
In order to improve the strength and stiffness of shield cutterhead, the method of fuzzy mathematics theory in combination with the finite element analysis is adopted. An optimal design model of structural parameters for shield cutterhead is formulated, based on the complex engineering technical requirements. In the model, as the objective function of the model is a composite function of the strength and stiffness, the response surface method is applied to formulate the approximate function of objective function in order to reduce the solution scale of optimal problem. A multi-objective genetic algorithm is used to solve the cutterhead structure design problem and the change rule of the stress-strain with various structural parameters as well as their optimal values were researched under specific geological conditions. The results show that compared with original cutterhead structure scheme, the obtained optimal scheme of the cutterhead structure can greatly improve the strength and stiffness of the cutterhead, which can be seen from the reduction of its maximum equivalent stress by 21.2%, that of its maximum deformation by 0.75%, and that of its mass by 1.04%. © 2015, Central South University Press and Springer-Verlag Berlin Heidelberg.
Liu G.-W.,Central South University |
Xia X.,China Railway Construction Heavy Industry Co. |
Wang Q.-Y.,Central South University |
Dong R.-L.,China Communications Construction Company Ltd.
Jiaotong Yunshu Gongcheng Xuebao/Journal of Traffic and Transportation Engineering | Year: 2015
Based on considering the influence of cutting heat, the inertia effects of cutting energy absorption were studied by numerical simulation, and stable cutting force, cutting displacement, maximum temperature, heat dissipative energy and the dissipative proportion of thermal energy were computed under different initial impact conditions. Computation result shows when the initial impact energy is 20 kJ and there are no distinct initial cutting force peaks in chip formation, the stable cutting force ranges from 63.0 kN to 63.8 kN, and the changing rules and trends of cutting force curves are approximately same. When the impact mass is 200 kg and the impact velocity changes from 3 m·s-1 to 10 m·s-1, the stable cutting force ranges from 63.0 kN to 64.4 kN. When the impact velocity is 10 m·s-1 and the impact mass changes from 0.4 t to 3.2 t, the heat dissipative energy increases from 4.12 kJ to 36.64 kJ, the maximum temperature changes between 586℃ and 602℃, the dissipative proportion of thermal energy ranges from 20.6% to 23.2%, and the stable force ranges from 63.0 kN to 64.1 kN. Obviously, when the cutting depth and the geometrical parameters of cutting tool are defined, the initial impact energy, impact mass and impact velocity have little effect on the cutting force, the inertia effects of cutting energy-absorbing process are insensitive, and the cutting energy-absorbing structure belongs to typeI. The cutting heat accounts for a large proportion of energy dissipation and is greatly influenced by the initial impact velocity. ©, 2015, Chang'an University. All right reserved.
Li D.P.,China Railway Construction Heavy Industry Co. |
Hu Y.C.,Hangzhou Dianzi University
Applied Mechanics and Materials | Year: 2013
A mesh partition based explicit integration method for dynamic structure FEA is proposed in this article. With this method, the whole finite element mesh is partitioned into several zones according to the elements' increment feature size, and then variable time increments are applied to the mesh zones for explicit integration while the parameter transfer and interpolation is performed over the interfaces to ensure the continuity. This method has the capability of boost the analysis efficiency without much precision loss to the analysis results of interested zones, which is proven by some 2D analysis examples. © (2013) Trans Tech Publications, Switzerland.
Xia Y.,Central South University |
Yang D.,Central South University |
Hu C.,Central South University |
Wu C.,Central South University |
Han J.,China Railway Construction Heavy Industry Co.
Tunnelling and Underground Space Technology | Year: 2016
In order to study the characteristics of the ventilation and dust suppression system for open-type TBM tunneling work area in a Ø8.53 diversion project, the numerical simulation method is adopted, and a three-dimensional steady airflow model, a dust flow model as well as other related flow characteristic equation models are established by considering the dust production mechanism of TBM construction. Besides, corresponding simulation models validated by experiment are established using CFD software, and the impacts of the main vent location, the air baffle length in the main beam and the exhausting air flow quantity on flow field distribution and dust flow behavior in open-type TBM tunneling work area are investigated. The results show: when the main vent is located 70-80 m away from the working face, the ventilation in TBM tunneling work area is optimal; when the air baffle is as long as the main beam, the dust collection efficiency is the highest, reaching 89.4%; under the condition that the exhausting air flow quantity is less than half of the ventilation air flow quantity required by energy consumption and the minimum backflow velocity, the best dust suppression effect can be achieved when the exhausting air flow quantity is 40% of the ventilation air flow quantity. © 2016 Elsevier Ltd.
Xia Y.-M.,Central South University |
Qian C.,Central South University |
Tian Z.-Y.,China Railway Construction Heavy Industry Co. |
Chen L.,China Railway Construction Heavy Industry Co. |
And 2 more authors.
Journal of Railway Engineering Society | Year: 2016
Research purposes: In order to study the cutting characteristics of pre-cutting machine with different layout of the cutters, the finite element software was used and the simulation model of cutters breaking the rock with four kinds of cutters' layouts was established. The process of multi-cutters' breaking the rock with different layout of the cutters was simulated. The horizontal load and the specific energy of cutters' breaking rock were analysed. Research conclusions: (1) The vertical resistance of the cutter is much less than the horizontal resistance when the cutters break the rock. (2) At the penetration of 6 mm, among the four kinds of cutters' layout, the average horizontal load of the cutter in scheme a which is 485 N is the minimum and the average horizontal load of the cutter in scheme d which is 548 N is the maximum. (3)The average horizontal loads of the cutters in scheme b are the most even and the average horizontal loads of the cutters in scheme a and scheme d are more uneven. (4)Overall, at the penetration of 4 mm, 6 mm and 8 mm, the specific energy in scheme a is the minimum and the specific energy in scheme b is the maximum. The viration law between the specific energy and the penetration is not obvious. (5) On the whole, scheme a is the best. This scheme has been initially tested on the pre-cutting machine and the cutting peformance was good. (6)The research results can provide references for the study of tunnel pre-cutting machine cutters' layout. © 2016, Editorial Department of Journal of Railway Engineering Society. All right reserved.