Advanced Materials Research Online: 2012-01-24 ISSN: 1662-8985, Vols. 452-453, pp 1296-1300 doi:10.4028/www.scientific.net/amr.452-453.1296 2012 Trans Tech Publications, Switzerland Dynamic Simulation of the Impact Mechanism of Hydraulic Rock Drill Based on AMESim Yin Zhong-jun 1,a, Hu Yi-xin 1,b 1 School of Mechanical Engineering, University of Science and Technology Beijing, Beijing 100083, China a yinzhongjun@ustb.edu.cn, b huyixin_ustb@126.com Keywords: Rock drill; Impact mechanism; AMESim; Simulation Abstract. Through analysis of the dynamics process of hydraulic rock drill, this paper builds a model of the impact mechanism of hydraulic rock drill with AMESim software, obtains curves of the displacements of the piston and valve core, and gets the pressure of the piston chamber. The dynamic analysis of the results indicates that the model of the impact mechanism of hydraulic rock drill agrees well with the principle of hydraulic rock drill. As a result, this research provides a new theoretical basis and method for the hydraulic rock drill. Introduction Hydraulic rock drill is a kind of essential drilling equipment,which has been applied in mines, railways, roads, hydropower, coals, constructions and other projects [1]. Compared with traditional rock drilling equipment, such as pneumatic rock drill, hydraulic rock drill is smaller, easier and simpler to control, and is widely used in a variety of constructions [2]. As technology advances, the combination of hydraulic control technology and computer technology makes great simulation efficiency on the design of hydraulic rock drill, and provides consistent simulation results with realistic conditions, which gives a reliable basis to the design and manufacture of rock drilling machine. The Composition and Working Principle of the Impact Mechanism of Hydraulic Rock Drill The impact mechanism is a key part of the hydraulic rock drill, mainly formed by the cylinder, valve and accumulator components, as shown in Fig. 1. Fig. 1 The working principle of the impact body of hydraulic rock drill 1 Cylinder;2 Liner;3 Flange;4 Back Cover; 5 Plug;6 Valve;7 Accumulator;8 Piston; The high-pressure oil from the pump is transferred into the high-pressure chamber of the cylinder, and then into the valve body. The rear chamber of piston connects the tank by the valve port, which is full of low-pressure oil, while the high-pressure oil is directly transferred into the front chamber of All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, www.ttp.net. (ID: 130.203.136.75, Pennsylvania State University, University Park, USA-11/05/16,03:12:13)
Advanced Materials Research Vols. 452-453 1297 piston, returning the piston to the right to promote accelerated motion. When the piston shoulder passes over the edge of the signal port, the high-pressure oil gets into the left chamber and right chamber through front chamber, which changes the forces of both ends of the valve spool change. At this time, the valve quickly alters its direction to move. The front and rear chambers which are full of high pressure oil achieve a different connection, and then the accelerative return period ends. Due to inertia, the piston continues to make the return movement, and the kinetic energy of the piston is converted to hydraulic operation which can be stored on the accumulator. The piston continues the decelerative return until it stops. As different areas of the front and rear chambers lead to the different the pressure force, the piston accelerates to the left. With the increasing flow rate of rear chamber, which makes the needs greater than the supply by the pump, the front chamber and the accumulator connect to the rear chamber to meet the needs of the stroke. As soon as the signal port of the front piston opens, the signal port and tank port connects to each other, and low-pressure oil comes into the valve body through the signal port. While both ends of the valve spool forces are changing, the valve core quickly alters its direction and moves. At the same time, the piston has shocked the tail of drill rod which means the end of the stroke [3]. Then the next working cycle starts. The piston achieves the reciprocating motion through making the signal port connect to the high or low pressure opening, constantly impacts the end of drill rod, outputs the impact energy, and breaks the rock eventually [4]. The Modeling of the Impact Mechanism with AMESim Hydraulic rock drill is a valve control system which regards the hydraulic oil as the energy transferring medium, and the model must follow its dynamic and hydraulic characteristics of the system which should reflect the actual physical process as fully as possible. Meanwhile, taking feasibility and convenience in the process of simulation and analysis into account, some secondary factors in the actual system make the following assumptions: hydraulic oil viscosity does not change with pressure; oil temperature remains the same when the machine is in operation; the quality of accumulator diaphragm is zero, which has no resistance with the deformation [5]. AMESim software provides a complete, superior simulation environment and flexible solutions to fluid dynamics (fluid and gas), mechanical, thermal fluid and control systems [6]. Based on the drilling machine's physical structure and working principle, this article uses HCD (Hydraulic Component Design) and AMESim to create the following model. Fig. 2 The AMESim model of the impact mechanism of hydraulic rock drill As shown in Figure 2, the models of the piston and valve have been built in AMESim. It can be seen that the top part shows the model of valve, the bottom part piston. According to the control link between the piston and the valve, we connect each module to complete the modeling [7]. Once the model is established, we need to select the sub-model for the various components of the system. Each component has one or several sub-models for users to meet realistic requirements with regard to their respective system. Based on the realistic structure and working condition of the machine, this paper matches each component and sub-model, and sets all structural parameters of components of the system [8]. Here are some explanations about some important modules and the model parameters.
1298 Management, Manufacturing and Materials Engineering Fig. 3 Piston mass parameters Fig. 4 Variable orifice module parameters Fig. 5 Leakage module parameters Fig. 6 Volume module parameters In figure 3, the sub-model is used to set the piston quality and the restriction of piston displacement. The valve is set by the same way. Figure 4 is the variable orifice module parameter setting interface. The module can simulate the process of fluid power alteration which is caused by the change of flow area of piston or valve. The flow area transformation is related to the change of the valve displacement. In order to achieve mutual control by their own motion, and achieve the constant stroke and return movement, the piston and valve make the related valve port open and close [9]. In this module, the value of valve opening of the initial setting is particularly critical. In figure 5, there is small ring seal gap between the piston and the cylinder sleeve. It will leak as the pressure difference exists between gaps, so we add the leakage module in the modeling of the piston to make the model more consistent with the realistic structure. By setting the parameters of the gap, we can improve the accuracy of the simulation results In figure 6, taking the volume effect and the volume of time-varying effect of oil into account, the model is added a volume module. This module can reflect the phenomenon of oil's volume of time-varying which is caused by the fluid pressure, hydraulic volume and the pressure rapid change in the simulation, and then the module can correct the pressure. The Simulation Results and Analysis The simulation time is set to 2 seconds. The simulation step is automatic step. Fig. 7 The enlargement of displacement curve of the piston and the valve spool
Advanced Materials Research Vols. 452-453 1299 In figure 7, the top solid line is the piston displacement curve, and the bottom dashed curve is the valve spool displacement. From the figure, we can clearly see that all the stages are in a cycle of the piston and the valve. The piston and the valve hmatch fairly, and each switching of state can be found in the corresponding transition point. The precedence relationship of the piston and the valve stage change is in line with the machine movement mechanism, showing that the simulation results coincide with the realistic situation. We can also see from the figure that the pause time is 2ms after the piston hits the drill rod. After dealing with the processing data of the FFT, we can come to conlusion that the piston working frequency is 52.997HZ, which meets the design requirement of the drilling machine. Fig. 8 The pressure curve of the piston front chamber Figure 8 shows the pressure characteristics of the piston front chamber. From the figure, we know that the rear chamber pressure remains 19Mpa after the system reaches a steady state. This pressure is not completely steady, but within the range of about 0.8Mpa regular fluctuations, and the pressure fluctuation reaches the peak when the piston begins to change direction to move. Fig. 9 The pressure curve of the piston front chamber, the rear chamber pressure and displacement of the piston Figure 9 shows the matching relationship between the rear chamber pressure and the displacement of the piston. From the figure, we can see clearly that each transformation of the piston state corresponds with a pressure inflection point of the rear chamber pressure curve. The rear chamber pressure changes between low pressure1.5mpa and high pressure19.6mpa in cycles. When the rear chamber connects to the tank, the pressure drops to the minimum value 1.5Mpa. At this turning point, the piston comes into the speed-up stage of returning from the stage of pause. When the piston passes the returning signal port, the valve changes its direction, which makes the rear chamber connect to the high pressure oil, and then the pressure reaches the peak instantaneous -19.6Mpa. At this pressure inflection point, both the front and the rear chambers are full of high-pressure oil. The pressure difference, caused by the difference of the force areas, makes the piston brake. When the piston turns into the stroke phase, the volume of rear chamber increases gradually. Due to the liquid volume effect, the chamber pressure has been reduced, and reaches the minimum value when the piston impacts the drill rod. After that, the volume does not increase any more as the reason of piston pause. Then the high-pressure oil adds in, which raises the pressure of rear chamber to 19.6Mpa again. After 2ms, the valve starts to move to the other side, and the rear chamber connects to the tank, which makes the pressure of rear chamber drop quickly. The piston comes into the speed-up stage of return, which means a cycle is completed.
1300 Management, Manufacturing and Materials Engineering Conclusions This article builds the model of the impacting body of hydraulic rock drill based on HCD library of AMESim software, obtains the critical characteristic curves of the machine, and then analyzes the dynamic characteristics 1) This article provides a new concept and method of dynamic analysis of the impact body of hydraulic rock drill, and gets rid of the single means of hydraulic system simulation which must establish the mathematical model first and then uses programming language to simulation by computer. We use AMESim software without writing any code, which liberates us from the tedious mathematical modeling and make us concentrate on the design of the physical system itself [10]. It also enable us to build the model of the machine on the basis of work principle, and then to adjust parameters to run the final simulation. 2) From the simulation results, it can be seen that the piston and valve show good matching relations, that the pressure alteration between the front and rear chamber of piston has a corresponding correlation with the displacement of piston, and that the process of simulation is consistent with the realistic operation mechanism, which indicates the feasibility and rationality of using AMESim software to simulate the work process of the impact mechanism of hydraulic rock drill. This article provides an effective way to comprehend the impact performance of the institution and improve its structure, and it also provides a basis and method for in-depth researches in improving the efficiency of the machine. In the future, we can adjust the key parameters and optimize the design, based on the deep study of the dynamic characteristics of the machine, and then improve the performance and efficiency. References [1] Gao Lan-qing: The theory, design and application of hydraulic rock drill machine (Machinery industry press, Beijing 1998). [2] Zhou Zhi-hong: Underground drilling equipment (Metallurgical Industry Press, Beijing 2004). [3] He Qing-hua: Reaerch and design of impact mechanism (Central South University Press, Changsha 2009). [4] Qin Jia-sheng, You Shan-lan: The features and application of AMESim software. Construction Machinery and Equipment, Vol. 12 (2004), p. 6-8 [5] Qin Zhen-chao: Modeling and Simulation of the Impact of Institutions of Hydraulic Rock Drill Based on AMESim. Hydraulics Pneumatics&Seals, Vol. 12 (2010), p. 32-34 [6] Li Hua-cong, Li Ji: Modeling and Simulation Software AMESim for Mechanical/Hydraulic System. Computer Simulation, Vol. 23 (2006), p. 294-296 [7] Yu You-guan, Gong Guo-fang, Hu Guo-liang: Simulation technique of AMESim and its application in hydraulic system. Hydraulics Pneumatics&Seals,Vol 3 (2005), p. 28-30 [8] Bai Zhong-fei: Design and Research of Hydraulic Rock Drill Impact Mechanism. Beijing: University of Science and Technology Beijing, 2010 [9] Fu Yong-ling, Qi Xiao-ye: The modeling and simulation based on AMESim system: from getting started to mastering (Beijing Aerospace University Press, Beijing 2006) [10] Liu Hai-li: Modeling and Simulation Software AMESim and its Application for Hydraulic-mechanic System. Machine Tool &Hydraulics, Vol.7 (2006), p. 124-126
Management, Manufacturing and Materials Engineering 10.4028/www.scientific.net/AMR.452-453 Dynamic Simulation of the Impact Mechanism of Hydraulic Rock Drill Based on AMESim 10.4028/www.scientific.net/AMR.452-453.1296