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Long R.-S.,Taiyuan University of Technology | Long R.-S.,Shanxi Key Laboratory of Fully Mechanized Coal Mining Equipment | Sun S.-N.,Northeastern University China | Lian Z.-S.,Taiyuan University of Technology | Lian Z.-S.,Shanxi Key Laboratory of Fully Mechanized Coal Mining Equipment
Materials Science and Technology (United Kingdom) | Year: 2016

In order to restrict the generation and propagation of cracks in thin wall metal parts fabricated by laser direct deposition shaping method, using 'element birth and death' technique, a three-dimensional multitrack and multilayer thin wall model was developed, and the deposition process was simulated. Different scanning methods, including long edge parallel reciprocating scanning, short edge parallel reciprocating scanning and interlayer orthogonal parallel reciprocating scanning, were introduced. The effects of different substrate preheating temperatures were also researched. The von Mises equivalent stress and its X-, Y-and Z-directional principal stresses were analysed in detail. Under the same conditions used in the simulations, the deposition experiments were conducted, and the crack generation and restriction mechanism of thin wall metal parts were further discussed. © 2016 Institute of Materials, Minerals and Mining. Source


Ri-Sheng L.,Taiyuan University of Technology | Ri-Sheng L.,Shanxi Key Laboratory of Fully Mechanized Coal Mining Equipment | Shao-Ni S.,Northeastern University China | Zi-Sheng L.,Taiyuan University of Technology | Zi-Sheng L.,Shanxi Key Laboratory of Fully Mechanized Coal Mining Equipment
Engineering Failure Analysis | Year: 2016

In order to improve the quality of thin-wall metal parts fabricated by laser direct deposition shaping method, using "element birth and death" technique, a three-dimensional multitrack and multilayer thin-wall model was developed. Different scanning methods, including long-edge parallel reciprocating scanning, short-edge parallel reciprocating scanning and inter-layer orthogonal parallel reciprocating scanning, were researched. The Von Mises equivalent stress, and its X-directional, Y-directional and Z-directional principal stresses were analyzed in detail. Under the same conditions used in the simulations, the deposition experiments were conducted, and the influence of different scanning methods on the cracking failure behavior of thin-wall metal parts was discussed. © 2015 Elsevier Inc. Source


Long R.,Taiyuan University of Technology | Long R.,Shanxi Key Laboratory of Fully Mechanized Coal Mining Equipment | Sun S.,Northeastern University China | Lian Z.,Taiyuan University of Technology | Lian Z.,Shanxi Key Laboratory of Fully Mechanized Coal Mining Equipment
Mathematical Problems in Engineering | Year: 2015

In order to realize the rapid hard-rock tunneling in a safe, highly effective, and economic manner, the hydraulic drilling impact hard-rock tunneling (HDIHT) technology and method were introduced based on the theories of rock mechanics and hydraulic impact. The key parameters, including drilling radius and impact distance, were researched to reveal the stress behavior during HDIHT process. The Von Mises equivalent stress and its principal stress components were analyzed, and the breaking mechanism of HDIHT was also discussed. The simulation results show that, to ensure the effectiveness of "secondary breaking" caused by drilling hole free surfaces, the impact distance should not exceed 200 mm, and the optimal drilling radius was about 35 mm. Copyright © 2015 Risheng Long et al. Source


Long R.,Taiyuan University of Technology | Long R.,Shanxi Key Laboratory of Fully Mechanized Coal Mining Equipment | Long R.,Shenyang Puyue Group | Sun S.,Northeastern University China | And 5 more authors.
International Journal of Mining Science and Technology | Year: 2015

In order to realize the safety, high efficiency and rapidity of hard rock tunneling, we propose the drilling & hydraulic impact hard-rock tunneling (DHIHT) technology and method. Based on the LS-DYNA explicit module and APDL programming, the key parameters of DHIHT, including drilling spacing and drilling radius, were investigated. The simulation results show that: the drilling spacing should not exceed 0.20 m-larger distances weaken the actual breaking effect; the best drilling radius is about 0.035 m, larger or smaller distances would both decrease the effect of drilling-hole free surfaces. The field impact breaking experiments were conducted in Baitaizi township granite quarry, Jinzhou, Liaoning province, China. The experiment results indicate that DHIHT is a feasible method for hard-rock tunneling, but its efficiency still needs to be further optimized and improved. © 2015 Published by Elsevier B.V. on behalf of China University of Mining & Technology. Source


Liao Y.,Taiyuan University of Technology | Liao Y.,Shanxi Key Laboratory of Fully Mechanized Coal Mining Equipment | Yuan H.,Taiyuan University of Technology | Yuan H.,Shanxi Key Laboratory of Fully Mechanized Coal Mining Equipment | And 5 more authors.
Strojniski Vestnik/Journal of Mechanical Engineering | Year: 2015

The 1000 L/min large flow hydraulic system for the hydraulic support used in a coal mine is currently a topic of great interest. The large flow directional valve is a key component for hydraulic systems, so the design of the 1000 L/min large flow directional valve is essential. The designed single-channel valve shows serious hysteresis characteristics in a 1000 L/min large flow condition, but it does not happen in a 16 L/min small flow condition. Based on this phenomenon, the computational fluid dynamics (CFD) technology was used to simulate the flow in the valve. It was discovered that the single-channel caused unbalanced pressure in the annular region and on the surface of the valve spool, so the valve spool is subjected to great radial unbalanced force. Then a double-channel valve was designed to improve the pressure distribution. The simulated radial unbalanced force on the double-channel valve is 67.2% lower than that of the single-channel valve. The experimental results showed that the hysteresis characteristics also disappeared under the 1000 L/min large flow condition. Therefore, the conclusion can be drawn that the hysteresis characteristics of the single-channel valve is due to the radial unbalanced force caused by the unsymmetrical flow field. The results show that the maximum radial unbalanced force the valve spool can withstand is 170 N. Furthermore, symmetrical flow passages have to be taken into account in large flow conditions. This paper provides valuable references for the design of large flow valves. © 2015 Journal of Mechanical Engineering. All rights reserved. Source

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