FEM Analysis On A Rear Axle Housing Oil-Leakage Prediction Of Four-Wheel Farm Transporters On COSMOS

FEM Analysis On A Rear Axle Housing Oil-Leakage Prediction Of Four-Wheel Farm Transporters Based On COSMOS SenKai LU1, 2, a,Jianhuan Su1,Shude Liao1, Jiaqiang Su1, Bo Wang1,Liang Yu3,b, Yanli Jiang3,c and Shouhong Wen2,d1 Department of Physics and Electronic Technology, Hechi University, Hechi 546300, China2 Department of Physics and Information Technology, Guilin Normal College, Guilin 541001, China3 Key laboratory of new processing technology for nonferrous metals & Materials, Ministry ofEducation, Guilin University of Technology, Guilin 541004, Chinaa lusky3616@,b syyuiang@,c jiangyanli024@,d wenshouhong0773@Keywords: Finite Element Method, Rear Axle Housing, Oil Leakage, COSMOSAbstract. A finite element method (FEM) analysis based on COSMOS study with the aim to find the causes and effects of deformations in the interface between the rear axle housing and the central gear house of the four-wheel farm transporters during operation has been performed. The present design is analyzed with the aid of a mixed-fidelity, or mixed-grain, FE-model. Boundary conditions are defined on the bushings in front of the rear axle and on the air bellows behind the rear axle. The different load scenarios are represented by forces either on the wheels, the central gear or on the rear axle housing. The simulated results showed that with the worst combined load case for the different proposed design solutions suggested that modified design with a thicker flange and a removed stiffener would be significantly better than the present design; the simulated max displacement is about 0.5 mm and satisfied the design requirement. It indicated that the proposed method of finite element analysis was a good and efficient method predicts the oil leakage of rear axle housing, which can increased the knowledge of how oil leakage from the rear axle central gearbox can be controlled by design measures.IntroductionThe four-wheel farm vehicle transporter is one of the most vital subsystems in the vehicles, which is normally composed of the engine, clutch, gearbox, shafts, and a rear axle which integrates a central differential gearbox, hub reductions and disc/drum brakes [1]. The torques in the four-wheel farm vehicle transporter from the engine as well as from the rear axle brakes are focused at the differential mounted in the rear axle bridge [2]. Elastic deformations of the gear teeth, shafts, bearings, and the housing cause undesirable side-effects, such as a dynamic transmission error. It may also cause oil leakage in the gearbox housing and cap interface [3-5]. The oil leakage problem has been also observed in the screw-joint interface between the differential housing and cap [6]. The gearbox housing consists of two parts that are mounted with guides and connected with a screw joint shown in Fig. 1(a) and Fig. 1(b). Oil leakage has been observed at severe field operations, e.g. braking with full load on rough terrain [7]. The housing contains a large amount of oil, and there is a thin sealing gasket object between the two mating surfaces, which maybe causes oil leakage, but the problems have not been fully understood [8]. Researches have been developed to prevent the oil leakage, for example, silicon, o-ring (proposed), and thin paper gasket (presently favored) sealing solutions the silicon sealing [9-11]. But o-ring is rejected for manufacturing cost reasons [10], and a thin paper basket does not complete solve the leakage problem. Tobias Lööf, et al reported that a strive for perfection in the vehicle transporters design requires that the design parameters must be carefully tuned [11].The aim of the paper was to study the deformations in the rear axle housing of four-wheel farm vehicle transporters based on the finite element method (FEM) software COSMOS and to suggest design changes that would increase the sealing capability of the favored paper gasket interface.Fig. 3 Applied loads of the rear axle housing of four-wheel farm vehiclet t MethodThe explorative nature of the study close relation between shape and behavior of the studied components justified a simulation-driven approach based on the Solidworks 2006 for composing CAD model [12], and calculated by FEM simulating software COSMOS 2006 [13]. To analyze the distribution of the contact pressure and the occurrence and the location, size and shape properties of local clearances between the mating surfaces requires a highly detailed model of the interface region and the directly related components[1, 3] .The FE- model of the rear axle housing is shown in Fig. 1(c). To actual study the sealing performance of the interface, it was decided to study static load cases defined from elementary driving operations such as wheel braking, driveshaft (pinion) torque, motor braking, rolling, vertical bending, lateral loading, longitudinal loading, and combinations of these elem entary load cases [9, 10]. It is convenient to apply those loads directly to the driveshaft, wheels, and frame. Consequently, models of the load interacting components, such as the differential gearbox, rear wheels, and the suspension units were included in the systems model. A mixed-fidelity finite element representation of the studied system is shown in figure 2(b). The total size of the systems model is 20070 nodes and 67456 elements in contact.Of simulation performance reason, these “non-focused” components were modeled as simple as possible and as detailed as judged necessary[1, 5], which implies that systems modeling were a non-routine and iterative process.Fig.1 Model of the axle housing of four-wheel farm vehicle transporter(a) Geometry , (b) Cutaway view, (c) A mixed-fidelity FE- model of the rear axle housingTo study the sealing performance of the interface, it was decided to study static load cases defined from elementary driving operations such as braking, driveshaft (pinion) torque, motor braking, rolling, vertical bending, lateral loading, longitudinal loading, and combinations of these elementary load cases [3]. Theforces defined for the elementary loading case rolling, i.e.a presentation of the centripetal forces that appear whenwe are driving in a curve shown in Fig.2. Anotherelementary load case is motor braking. In the model, braking is represented by force-pairs in the gearbox, as shown in the right portion of Fig.1 in Ref [11]. ResultsThe results can be classified into analyzed results that are clarifying the identified sealingproblem and solutions to the design problem, i.e. design proposals.a c pressur on screws case due to motor braking Rolling (left) andpinion torque (right) loadClarification of the sealing problem. Fig.3(a) shows the simulated contact pressure distribution in the targeted interface, when the screw joint is preloaded only, i.e. when there is no external loading of the system. The simulated interface clearance for a combined load case is presented in Fig.3(b). The clearance in the region identified in Fig.3(c) shows a large gradient in the radial direction of the interface. During field operations, some gasket creep resulting in a risk for oil leakage has-been observed [4] The values on screw and welded stiffener areas are 458 MPa, which are lower than that of the holding teeth.. If we compare the location of the observed gasket creep with the expected gearbox oil level and the computed clearance anomaly identified in Fig.3(b), a likely explanation of the leakage problem is that a conically shaped clearance may destroy the sealing capacity of the paper gasket at some complex driving operations [11]. It may be noted that the largest conical clearance in the identified problem region was obtained for a load case composed of rolling and 50 % of maximum drive shaft torque.Fig. 3 The simulated contact pressure distribution in the targeted interface,(a) no external loading ,(b)combined load , oil level (red line), and observed gasket creep, (c) large clearance gradientProposed design solutions. The FE-simulated displacements as a function of the applied longitudinal force, worst combined load case ,are presented in Fig.3. The observed problem is located close to a stiffened region. One proposed design solution is to reduce the influence of the stiffener by making it more slender, modifying it locally, or by removing it as shown in Fig.4(a). Examples of other proposed design solutions are to thicken the flange, or to locally alter the decrease the distance between the screws shown in Fig.4(b). Simulations with the worst combined load case for the different proposed design solutions suggested that the max displacement of rear housing, which is modified design with a thicker flange and a removed stiffener, is about 0.5 mm. It means design with a thicker flange and a removed stiffener it would be significantly better than the present design shown in Fig.4(c). An analysis of the simulated interface clearance and contact pressure results suggests that the interface gasket, and thus its sealing capacity, isdestroyed by extensive micro-sliding in interface regions where conically shaped clearances appear atcertain complex loading conditions. It means that by strengthening the central gear housings flange reduction of the conical openings can be achieved. The simulated result is conceptually similar with Ref [1,3]. However, the FEM results can only be validated with an independent method. If a rear axle housing system of farm vehicle transporter meets its specified requirements, it should be applied with physical testing. [9,11,14]. The results need to be compared with experimental results, which is also our suggestion for future work.Fig. 4 FE-simulated force-displacement relation.(a) reduced stiffness of the stiffener and increased interface stiffness, (b) thicken flange, (c) present design aagasket creepoil levelReducing siffener Max displacement 0.9~1.2 mm Present desing altered screws, Max displacement 1.0~1.5 mmlarge gradientThicken flange Max displacement0.4~0.5mmConclusions and discussionAn oil leakage problem has been observed during four-wheel farm vehicle transporter operation. The problem is located to the rear axle differential gearbox housing. An FE-based on COSMOS study with the aim to find the causes and effects of deformations in the interface between the rear axle housing and the central gear house during operation has been performed. The present design is analyzed with the aid of a mixed-fidelity FE-mode. The simulated results shown that when the rear axle housing is loaded with both interior and exterior forces it tends to locally open the interface between the rear axle housing and the central gear housing. Simulations with the worst combined load case for the different proposed design solutions suggested that the max displacement of rear housing, which is modified design with a thicker flange and a removed stiffener, is about 0.5 mm satisfied the design requirement. This design change will most likely minimize the leakage problem observed on the vehicle transporter.AcknowledgementsThis work was supported by the project named Dynamics Simulation and Experimental Research of Four-wheel farm vehicle stamping and welding-type rear axle(200911MS218), the Basic Research Fund for the Northeastern University (N090302005), the National Natural Science Foundation of China (No. 50902018, No. 50872018) and Province science and technology in the Guangxi offends pass item (1099043).References[1] Scania Home Page, , 2006.[2] T. Lööf, F.,Videll. “FEM-based design study of rear axle housing ADA1100 and central gear house R780 interface deformations”. (in Swedish), Master of Science Thesis MMK 2006:11[3] Sellgren, U., “Architecting models of technical systems for non-routine simulations”, Proc. International Conference on Engineering Design – ICED 03, Stockholm, Sweden, 2003.[4] N. Cong, J.Z. Shang, X. 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