Advanced Materials Research Vols. 148-149 (2011) pp 601-605© (2011) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMR.148-149.601Finite Element Analysis and Structural Optimization of Heavy-duty Truck’s Carriage Xiaonan Wang1, a, Linxiu Du1,b and Hongshuang Di1,c 1The State Key Laboratory of Rolling and Automation , Northeastern University, Shenyang, Liaoning 110819, China awxn_neu@qq.com, bdulx@ral.neu.edu.cn, cdhshuang@mail.neu.edu.cn Keywords: heavy-duty truck; carriage; finite element; optimization design; expansion of carriage Abstract. The purpose of this paper was the optimization design of heavy strength carriage for 50t heavy-duty truck. Two optimization schemes B and C were provided based on original scheme A, which have different thickness of sole/side plate and main longitudinal girder and different number of strengthening ribs. ANSYS was used to do the finite element analysis of equivalent stress and elastic displacement of truck carriages. The equivalent stress of main longitudinal girder, soleplate and transverse bars of soleplate will increase when the soleplate’s thickness was reduced. The maximum of equivalent stress will increase 13%~15% with 1mm reduction. When the thickness of side plate or the number of side plate’s strengthening ribs was reduced, the elastic displacement of side plate would increase. Scheme C fulfilled the requirement of structure strength, in which the elastic displacement increases in the allowable range and the lightening ratio was 12.6%. Scheme B didn’t fulfill the requirement of structure strength. The numerical results provided theoretical foundations for optimization design of carriage in actual production and the solutions of expansion of carriage. Introduction In recent years, with the technology’s rapid growth, the position of the traditional transportation industry which is headed by railage, highway transportation and air transportation is undergoing dramatically changes. Since heavy-duty trucks have the traits like: big loadage, high conveying efficiency and good economical efficiency, the usage of heavy-duty trucks is increasing in heavy construction, special transit work, dock container transit and cross-border transit. The major types of heavy-duty trucks are tractor and dump truck [1-4]. The industry recognized development trend of truck production is large-tonnage and heavy duty type. The market demand of heavy-duty truck is increasing, which creates the Chinese heavy-duty truck market in an increasingly competitive. Heavy-duty truck’s carriage as the supporting mechanism of truck is made by Q235 or Q345 steel in tradition. But with the light weight tendency and user requirement for product performance, the high strength carriage plate instead of the traditional Q345 will be the future trend of heavy-duty truck[5,6]. The dimension of the carriage is 7.32m×2.3m×1.5m (long×wide×high). According to the actual work of heavy-duty trucks, primarily for the transport of coal, sand and the road conditions during transport is well, the whole carriage’s stress condition and distribution of elastic displacement were studied under static load action. Through the finite element analysis of the 50t load dump truck’s carriage (the material was 600MPa grade high strength carriage plate), the structure strength and stiffness’s transformation rule of different optimization schemes can be obtained. This study provided the theoretical foundation for actual production and the solution of expansion of carriage [7-9]. Finite Element Model By choosing the appropriate welding process and welding wire, the strength of the carriage’s welding seam and the carriage plate’s steel was consistent. So the carriage plate and the welding seam 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 thepublisher: Trans Tech Publications Ltd, Switzerland, www.ttp.net. (ID: 219.234.81.135-27/10/10,06:33:49)602Manufacturing Processes and Systems transverse bar, main longitudinal girder and jack stringer were as a whole body, that’s had the same material property. The basic schemes of numerical simulation were listed in Table 1. The scheme A was the actual loading plan onsite, scheme B was the optimization plan offered by factory and scheme C was the optimization plan offered by writer. The carriage’s finite element model shows in Fig.1 was dispersed with 10-node tetrahedron units. Since the finite element model was too large for the existing computer hardware, the search for an optimal balance between element numbers and calculation accuracy was crucial. Therefore, the model’s grids were divided by using the global element size control mode, and the carriage was divided into almost 210,000 elements. The unit system of this model used the international system of units, that’s kg/m/s. The large displacement static analysis and the time integration step self-regulation function were opened in solution set, that’s the nonlinearity static analysis was executed. Table 1 Basic scheme of numerical simulation study A B C Thickness of soleplate(mm) 8 6 7 Thickness of side plate(mm) 6 4 4 Thickness of main longitudinal girder(mm) 8 7 7 The number of side plate’s strengthening ribs 8 6 6 Other places no change Yield strength of plate(MPa) 680 Static load value of numerical simulation(kg) 50,000 Total mass of heavy-duty truck’s carriage(kg) 48 3844 3975 Fig. 1 Finite element model of carriage The basic theory of mechanics In order to ensure the accuracy of the numerical simulation results, the simulation taking into account the pressure on carriage side plate. The side plate moves away from the soil under the soil thrust. As the displacement increases, the soil pressure will gradually reduce from the static soil pressure value to its equilibrium state which called active earth pressure. According to the Rankine’s earth pressure theory, the active earth pressure intensity of cohesiveless soil is distributed as triangle in depth, like the Fig. 2 shows. If the carriage side plate’s high is H, the total soil pressure on carriage’s unit length can be calculate as the triangle’s area, that’s: Ea=γH2K0/2 (1) Wherein: γ is soil’s density, kg/m3, the value is 1850 kg/m3; K0 is soil’s hydrostatic earth pressure coefficient, for sand is amongst 0.34~0.45, Ea goes through the triangle’s figure centre, that’s at H/3 away from the bottom, and the horizontally in the direction[10]. Advanced Materials Research Vols. 148-149603 Fig. 2 Distribution map of cohesionless soil’s pressure Results and analysis Equivalent stress Fig. 3 is the distribution maps of carriages’ equivalent stress (SEQV). Distribution of SEQV before and after weight reduction consistent, only the value is slightly different. This shows that without changing the whole carriage construction, adjust the thickness of soleplate and main longitudinal girder and the number of strengthening ribs on side plate dose not change the overall stress distribution. Table 2 is the maximum equivalent stresses on different positions. Comparing scheme A and B, if the thickness of soleplate decrease 2mm, the consequence is the SEQV of main longitudinal girder, soleplate and soleplate’s transverse bar will increase around 31%. Also the SEQV of main longitudinal girder in scheme B has reached the offset limit (680MPa), which means the scheme B doesn’t fulfill the structural strength requirement. Comparing scheme A and C, the distribution rule is like A and B: when the soleplate’s thickness decreases 1mm, the maximum of SEQV will increase around 13%. In scheme C, the maximum SEQV is only 590MPa, with 90MPa strength margin that’s the strength safety margin is 1-590/680=13%. Base on the work before, we can see that changing the thickness of soleplate will remarkably affect the SEQV of main longitudinal girder, soleplate and soleplate’s transverse bar. If the optimization needs the reduction of soleplate, the scheme C is only available; therefore the scheme B will not be discussed below. Fig. 3 Distribution maps of carriages’ equivalent stress (a) scheme A；(b) scheme B；(c) scheme C Table 2 Maximum equivalent stress of different positions (MPa) A B C Main longitudinal girder 521 681 590 Side/front/back plate 145 190 165 Soleplate 261 341 296 Soleplate’s transverse bar 319 417 361 Side plate’s strengthening ribs 145 190 165 Elastic displacement in different directions Elastic displacement in width (axis Z) Fig.4 is the distribution maps of carriage’s elastic displacement in width (axis Z). The color contour map’s numeric color code corresponding to negative value imply that a displacement on the axis Z’s negative direction which means there are expansions on both sides of the carriage. Comparing Fig.4a and Fig.4b, under 50t static load, the rules of displacement distribution of carriages in width are 604Manufacturing Processes and Systems basically the same. That is the elastic displacement along the length direction is symmetric. The maximums 8.235mm and 11.902mm generated at the upper part of the carriage’s side plate, in Fig.4a (a)-0.-0.008235-0.0005-0.004575-0.0027450.0009150.0009150.0027450.0045750.0005008235Fig. 4 Distribution maps of elastic displacement of carriages’ width direction (a) scheme A ；(b) scheme C and Fig.4b. The minimums 1.315mm and 0.915mm appeared at the lower part of the carriage’s side plate. To analyze the causes: Compare to scheme A, the side plates of carriage in scheme C are 2mm thickness decreased and the number of strengthening ribs from 8 to 6. Under the same static load, in scheme C, the carriage’s ability to resist elastic deformation is weaker and the elastic displacement in width is bigger. Elastic displacement in high (axis Y) Fig. 5 is the distribution maps of carriage’s elastic displacement in high (axis Y). The color contour map’s numeric color code corresponding to negative value imply that a displacement on the axis Y’s negative direction. Comparing Fig.5a and Fig.5b, under 50t static load, the rules of displacement distribution of carriages in high are basically the same. That is, like in width, the elastic displacement also distribute symmetrically along the length direction. The maximums 8.814mm and 10.775mm appear at both sides of the carriage’s soleplate, in Fig.5a and Fig.5b. The minimums 0.455mm and 0.55mm appear at the middle part of the carriage’s soleplate. This is because the main longitudinal girder on carriage’s soleplate is fully contacted to the longitudinal girder on sub-frame, so in the numerical simulation the degrees of freedom on the sub-frame’s longitudinal girder are restrained. Under static load, the steel between transverse bars on soleplate is under compression. The displacement in the middle is small with the main longitudinal girder’s support while in sides are big without support. Advanced Materials Research Vols. 148-149605 changed because of the carriage plates’ reduction. So the total elastic displacements of scheme C is bigger but still has 90MPa surplus, that’s the scheme C has reached the purpose of carriage weight Fig. 6 Distribution maps general of elastic displacement of carriages (a) scheme A ； (b) scheme C reduction. Using the ANSYS software to calculate the total capacities of scheme A and C, the total qualities are 48kg and 3975kg, the reduction ratio is 12.6%. The result fulfills the purpose of structure optimization and also provides the theoretical foundation for further production and the solution of carriage expansion. Conclusions The purpose of the finite element analysis in this paper was to find an optimization structure of the 50t dump truck. The different optimization schemes were analyzed by the numerical simulation, from which the transformation rule of the carriage’s structural strength and structural stiffness were obtained. By analyzing the simulation results indicate that: (1) The decrease of the carriage soleplate’s thickness would directly induce the increase of the equivalent stress on main longitudinal girder, soleplate and soleplate’s transversal bar. With 1mm decrease, the peak value of equivalent stress would increase 13%~15%. (2) The elastic displacement of side plate would increase if the thickness of the side plate or the number of the strengthening ribs on side plate was decreased. (3) In the case that only change the thickness of soleplate/side plate/main longitudinal girder and the number of side plate’s strengthening ribs， the carriage of scheme C fulfills the structural strength requirement. But compared to scheme A, the elastic displacement has raised and structural stiffness has descended. The weight reduction ratio was up to 12.6% while the safety surplus was 13%. The scheme B doesn’t fulfill the requirement. (4) The results of the numerical simulation provide essential theoretical foundation for the optimization design of the carriage in production and the solution of the carriage expansion problem in application. References [1] Tao Huai, Sandip D. Shah, J. Wayne Miller, et al. Atmospheric Environment. Vol. 40(2006), p. 2333. [2] Christie-Joy Brodrick, Timothy E. Lipman, Mohammad Farshchi, et al. Transportation Research. Vol. 7(2002), p. 303. [3] Dong-Hee Kim, Mridul Gautam, Dinesh Gera. Atmospheric Environment. Vol. 35(2002), p. 5267. [4] Wang Liangsheng, BASU P K, LEIVA J P. Finite Elements in Analysis and Design. Vol. 40(2004), p. 879. (In Chinese) [5] Kang Yonglin. Iron and Steel. Vol. 43(2008), p. 1. (In Chinese) [6] Wang Li, Yang Xiongfei, Lu Jiangxin. Iron and Steel. Vol. 41(2006), p. 1. (In Chinese) [7] Mehmet Firat, Recep Kozan, Murat Ozsoy, et al. Engineering Failure Analysis. Vol. 16(2009), p. 1533. [8] Wang Xiaonan, Di Hongshuang, Liang Bingjie, et al. Journal of Northeastern University: Natural Science. Vol. 31(2010), p. 60. (In Chinese) [9] BoYi studio, in: ANSYS 9.0 basic course and example detailed annotation of classical products, edited by China Water Conservancy and Electric Power Press, Beijing(2006). (In Chinese) [10] Xi Yonghui, Chen Jianfeng, in: Soil mechanics and foundation engineering . Tung chi university press, Shanghai(2006). (In Chinese) Manufacturing Processes and Systems doi:10.4028/www.scientific.net/AMR.148-149
Finite Element Analysis and Structural Optimization of Heavy-Duty Truck's Carriage doi:10.4028/www.scientific.net/AMR.148-149.601
