Structural Analysis for Space-swing Mechanism on Gyratory Compactor Jing Qian 1, Lingwei Meng 2

Transcription

1 Key Engineering Materials Online: ISSN: , Vol. 621, pp doi: / Trans Tech Publications, Switzerland Structural Analysis for Space-swing Mechanism on Gyratory Compactor Jing Qian 1, Lingwei Meng 2 1 Jiangnan University, China, qj639@jiangnan.edu.cn 2 HLJ August First Land Reclamation University, China, mengsan72@163.com Keywords: Space-swing mechanism, Gyratory-kneading, Compaction angle, Rigid model Abstract. Based on the automatic dynamic analysis of mechanical systems software, both rigid and flexible models of the space-swing mechanism for the superpave gyratory compactor are developed. The structural analysis shows that the length and the initial phase of cranks, and the assembling accuracy (coordinates) of some points are very sensitive relative to the waving of compaction angle. Greater rigidity helps stabilize the change of the compaction angles. Introduction The gyratory compactor is an apparatus to test paving material by compaction and gyration. This type of materials-testing machine is designed for simulating actual forces acting upon material, such as the force of vehicular traffic upon an asphalt surface of a road bed. These forces have been devised to produce a sample of material which shows the physical effects of repeated loading by, for example, compression, compaction, shear strain, plane-strain, and thermal reactivity. Such machines typically include a material-holding mold that is inserted into a chamber which positions the mold for insertion of a ram into the mold cavity in order to compress the material within the mold. The mold may be gyrated about a small angle relative to the vertical axis of motion of the mold carriage. The material in the mold is compressed by the ram to simulate actual forces applied to the material intended for actual paving. The superpave gyratory compactor is the key laboratory device used in Superpave mix design. A superpave gyratory compactor consists of a rigid reaction frame, a loading system, and an instrument for measuring and recording specimen height [1]. The superpave gyratory compactor produces compacted cylindrical test samples of the asphalt paving-mix for determining volumetric and mechanical properties. The compactor simulates the kneading action of large rollers used to compact asphalt pavement during highway construction. Thus, the compacted samples simulate the density, aggregate orientation, and structural characteristics obtained in an actual roadway using proper construction procedures in the placement of the paving mix. Typically, a sample of the asphalt-paving mix is placed in an open-ended cylindrical mold, with circular disks or plugs placed within opposite ends of the mold. The gyratory compactor device applies pressure through these disks to the sample in the mold while gyrating the mold at a specified angle to produce a gyrator-kneading action. Specifications for the superpave gyratory compactor call for the mold to be gyrated at a compaction angle of 1.25 degrees, while applying a constant pressure of 600 kpa [2]. The traditional gyratory compactor uses cone pendulum motion to simulate the kneading action on asphalt pavement. This kind of compactor is huge with complicated structure, which is good in great laboratories. To adapt the requirement of site operation of highway, a removable compactor with semi-corn pendulum was designed, as shown in Fig.1. However, in this case the angle of compaction (γ in Fig. 3) will never be constant. The angle of compaction has to change while swing mechanism moving. To reduce the waving amplitude of compaction angle under reasonable range, the structural analysis will give more help. 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, (# , Pennsylvania State University, University Park, USA-18/09/16,22:32:00)

2 254 Manufacturing Automation Technology and System II Reaction Frame Fig. 1 Superpave gyratory compactor Studies have shown that the angle of compaction plays a key role in determining the amount of compaction a material specimen experiences during gyration, and it should be in controllable range. The precision of the compaction angle can be affected by many parameters. To reduce both manufacturing costs and assembling time, the structural analysis of the space-swing mechanism is necessary. Research shows the change rules of compaction angle while the geometryical and locational parameters change [3]. In this research, based on automatic dynamic analysis of mechanical systems (ADAMS), the effects of varying the parameters of the space-swing mechanism are discussed when both the connecting rods and cranks are regarded as rigid and flexible [4-6]. Space-swing Mechanism The locus of movement of the rigid reaction frame (mold carriage) is a kind of semi-cone pendulum driven by a space-swing mechanism. The angle of compaction is mechanically set and calibrated during the initial assembly phase and is not adjusted thereafter unless required. The angle-adjustment mechanism is compelled to move along a circular orbit by the kinematic properties of the machine. Fig.2 shows a structure diagram according to the compactor in Fig.1. The rigid reaction frame ABCD is a pendulum mass, which connects to the machine frame by the top rod DE. Connecting rods GI and FH connect the reaction frame to cranks IK and HJ. These two cranks produce clockwise rotation within a horizontal surface. The movement of the rigid reaction is shown as Fig.3. The compaction angle is γ. Fig. 2 Space-swing Mechanism Fig. 3 Movement of the Reaction Frame The kinematic equations of the two cranks are as shown below. Front crank HJ Displacement (time) =30.0d * DIM (36, time) (1) Back crank IK Displacement (time) =-30.0d * DIM (time, 3) (2) The front crank starts a quarter circles earlier than the back one. The time for one complete circle of the mechanism to be traced is 12 seconds. In the research, four positions of the mechanism are selected for measurement to show the change in compaction angle. The initial position is where the

3 Key Engineering Materials Vol back crank starts rotating, and the other four positions are uniformly distribution within one complete circular period. In other words, positions 1-4 in the following tables represent the status of the mechanism at 3s, 6s, 9s, and 12s, respectively. Physical Model Development The automatic dynamic analysis of mechanical systems (ADAMS) is one of world s widely used Multi-body Dynamics software. It helps engineers to study the dynamics of moving parts, and how loads and forces are distributed throughout mechanical systems. The physical model of Space-swing Mechanism based on ADAMS is developed as shown in Fig.4 [7,8]. Fig. 4 Physical model for the space-swing mechanism The simulation works under ADAMS/View, and data processing was under ADAMS/Postprocessor module. The initial physical model was a rigid model where all parts in the model were regarded as a rigid body. The space-swing mechanism was composed of a rigid barrel, three connecting rods and two cranks. The coordinates of each point correspond to the points in Fig.2 and are shown in Tab. 1. Table 1 The coordinates of the points in the Adams model Point X-coordinate Y-coordinate Z-coordinate A D E F G J K The front crank moves first. After completing a quarter of a circle rotation (3s), the back crank moves. The compaction angles on the four positions (the interval is 90 degrees or 3s) are recorded to estimate the accuracy of the movement in each period. In this research, the lengths of the cranks, the initial phase of the crank, the positions of the points in the space-swing mechanism, and the flexibility of the connecting rods and cranks are discussed [9-12]. Structural Analysis on Rigid Space-swing Mechanism Model When the machine is at noload, the reaction frame swings and the entire mechanism can be regarded as a rigid spatial linkage. According to the demands of the movement, the compaction angle(γ) should be controled at 1.29±0.015 when all parts are regarded as rigid body. The dimension of parts and the positions of assembling will be discussed. After applied the kinematic equations (Eq.1 and 2) on two cranks, the variation law of the compaction angle can be shown as Fig.5, which the length of crank changes and the initial phase of the crank (the angle between crank and X-axis) is fixed on The compaction angles fluctuate while time changes in one period of motion.

4 256 Manufacturing Automation Technology and System II Fig. 5 The variation law of the compaction angle when the length of the crank changes Fig.5 shows that the compaction angle exhibits periodic change and the curve of the compaction angle is almost moving parallel. When the length of the crank is increased, the center line of the curve moves up. In another word, a shorter crank produces a smaller compacter angle. The best length of the crank is 7.3 mm while the initial phase of crank is 43.5 as shown intab.2. Table 2 The change of compaction angles with the change of crank length Initial phase Position Position Position Position When the length of the crank is fixed (7.3 mm), Fig.6 shows the law of movement on the compaction angle when the initial phase change. Tab.3 gives the degrees and the accuracy for each status. Fig. 6 The change of the compaction angle when the initial phase of the crank changes Fig.6 shows that accuracy will be less when the initial phase of the crank is When the initial phase of the crank is beyond that range, the amplitudes of the compaction-angle curves become larger. According to the demand of the mechanism, the amplitudes of the compaction angle should be controlled at 1.29±0.015 when the mechanism is unloading (the pressure on sample is zero). Table 3 The change of compaction angles when the initial phase of the crank changes Length of crank (mm) Position Tab.3 shows that the best initial phase of the crank is 43.5 when the length of the crank is 7.3 mm. In this case, the physical structure was determined. When the length of the crank is 7.3 mm and the initial phase of the crank is 43.5, then the requirements for the mechanism are satisfied. The assembling accuracy of connecting points (A, G, F, and D) is another important factor which affects the movement accuracy of the mechanism. These points could be very sensitive. The ideal coordinates of these points are A (-140, 0, 267), G (-98,-106.5,-57), F (-98,106.5,-57) and J

5 Key Engineering Materials Vol (113,325.5,-57). Tab.4 to Tab.6 show the changes of the compaction angle when the coordinates of the points are changed. Table 4 The change in compaction angles when Z-coordinates of point A change Z-coordinate of A Position It is clear that the compaction angle will be beyond the requirement of the mechanism even when the Z-coordinate of point A makes 0.5 mm difference. Thus the assembling accuracy of the mechanism should be in control. The study of the assembling accuracy of sensitive points could improve machine manufacturing. This study could determine how to adjust these sensitive points to satisfy the requirements of the compaction angle. Table 5 The change in compaction angles when Z-coordinates of points G and F change Z-coordinate of G,F Position Table 6 The change in compaction angles when coordinates of point J change Coordinate of J X-coordinate 112 Y-coordinate 326 Z-coordinate -56 Position From Tab.4 to 6, it is clear that the assembling accuracy of points A, J, G and F could be very sensitive, especially the Z-coordinates of A, G, F and the X- and Y-coordinates of J. Simulation on Flexible Space-swing Mechanism Model When the machine is loaded under a pressure of 600 kpa, but allows for the reaction frame to swing, then all of the connecting rods and frame columns should be regarded as flexible. The geometrical parameters of the connecting rods and frame columns are shown in Tab.7. Table 7 The geometrical parameters of the connecting rods and cranks Parameters Connecting rod GI\FH Connecting rod When the connecting rods and frame columns are regarded as flexible, then the material of these rods and columns first should be considered. Tab.8 shows some of the physical parameters of some materials which are considered. DE Frame column AB\CD Length (mm) Radius of cross section (mm)

6 258 Manufacturing Automation Technology and System II Material Table 8 The physical parameters of different materials Modulus of elasticity (N/m 2 ) Poisson ratio Density (Kg/m 3 ) Cast iron Steel Stainless steel Applied the parameters of Tab. 7 and 8 on physical model, the changes in the compaction angle are shown in Tab.9. Table 9 The change in compaction angles when the material changes Material Cast iron Steel Stainless steel Position Comparing Tab. 9 with Tab.1 when the length of the crank is 7.3 mm and the initial phase of the crank is 43.5, the compaction angles become smaller when all of the cranks and connecting rods are regarded as flexible. Tab.9 shows that steel is a reasonable choice for connecting rods and frame columns. Tab.10 and Tab.11 show the change of compaction angles when the radius of connecting rods and frame columns change, respectively. The simulation shows that the larger the intersection surface of rods and columns are (the better rigid rods and columns have), the smaller change the compaction angles of reaction frame have. When the radius of connection rods and frame columns are 10 mm and 20 mm respectively, the change of compaction angles is smaller. Table 10 The change of compaction angles when the radius of the connecting rods change Radius of connection rod GI\FH 6 mm 8 mm 10 mm Position Table 11 The change of compaction angles when the radius of the frame columns change Radius of frame column AB\CD 10mm 15mm 20mm Position Conclusions Analysis and simulation of the space-swing mechanism and the length of the cranks, demonstrate that the initial phase of the cranks and the assembling accuracy of some points (A, D, G and F) are both very sensitive. Greater rigidity also helps to stabilize the change in compaction angles. A gyratory-kneading action could be developed with a stable compaction angle range on the gyratory compactor, when all these parameters get optimized choice. The research shows the optimised length

7 Key Engineering Materials Vol of cranks is 7.3mm, the initial phase of the crank is 43.5, and the sensitive coordinate of points should be as in Tab.1. Acknowledgements The research was supported by the Special Foundation for Six Talent of Jiangsu Province and Wuxi Innovation Fund. Corresponding author: Jing Qian Cell phone#: References [1] T.G. Hines and R.A: Pyle. Gyratory compactor, US Patent, US , Pine Instrument Company, [2] R.A. Pyle and E.F. Dalton: Devices and Methods for Applying Known Resistance Loads and Measuring Internal Angles of Gyration in Gyratory Compactors, US Patent, US , Pine Instrument Company, [3] P. Du and Y. Jia: The History of Superpave Gyratory Compactor and Its Periscope in China, Chinese Highway Construction Market, Vol. 11, Issue 7 (2004) p [4] Y.J. Yuan and C.S. Hu: Research on Principle of Gyrate Compaction and Parameters Setting, Traffic Science in Guangxi, Vol. 28, Issue 2 (2003) p [5] Z.G. Li: Introduction and Example for ADAMS, National Defense Industry Publishing House, 2006, (in Chinese). [6] H.L. Hou and Y.Q. Zhao: Dynamic Analysis Based on ADMAS and ANSYS, Modern Machinery, Vol. 5, Issue 4 (2005) p [7] J.W. Xing, Y.Z. Tao: MSC ADAMS/View Senior Training Tutorial, Tsinghua University Press, 2004, (in Chinese). [8] Darku and D. Duaquaye: Evaluation of the Superpave Gyratory Compactor to Assess the Rutting Resistance of Asphalt Mixtures, University of Florida, [9] Y.Z. Li, R.H. Yang and L.G Shao, etc. Compaction Character Analysis on Bituminous Mixture, Highway Traffic Science, Vol. 23, Issue 5 (2006) p [10] Li Zhen Zhang et al. The Study on Comparison of the Virtual Prototype Modeling Methods Based on Adams/View. Key Engineering Materials, Vol.522, Issue 2 (2012) p [11] Fang Hua Liu et al. Application of Genetic Algorithm in the Structural Optimization of Parallel Sensor. Key Engineering Materials, Vol. 464 (2011) p [12] J.R. DeVol, J.K. Krause and S.P. McLaughlin, etc. Superpave Gyratory Compactor Internal Angle of Gyration Study, Bituminous Materials Report, WA-RD 677.1, Washington State Department of Transportation, 2007.