Value Engineering of Engine Rear Cover by Virtual Simulation Vishaldeep Sr. Engineer - R&D, CAE vishaldeep.dadwal@sonalika.com Vibhay Kumar Sr. Manager - R&D, CAE vibahy.kumar@sonalika.com Satpal Singh Saini Head - R&D, CAE satpal@sonalika.com Abbreviations: CAE - Computer Aided Engineering; FEA - Finite Element Analysis Keywords: Rear Cover, Bolt Pretension, Modal Analysis, Static Analysis Abstract Rear cover is mounted on the radiator side of engine to cover the crankshaft end. This component protect engine from dust entering inside and also it is exposed to vibration coming from engine. HyperWorks helped in performing value engineering on existing and proposed design with change in material. Modal & static analysis are performed on existing & proposed models. Bolt pretension is also considered in analysis to check effect of bolt torque on changed material. After simulating various load cases it showed that proposed model is better as compared to existing. A mass reduction of 68% with desired strength and manufacturing feasibility is achieved by performing the analysis. Introduction Engine is the heart of the tractor and performance of the tractor depends on the engine capacity, appropriate engine weight & smooth engine running. Rear cover for engine is not a working component in engine but it provides safety against dust and its also work against leakage. It is mounted on the radiator side of the engine & it does not provide any extra stiffness to the block. As a part of value engineering, Finite element analysis was done to reduce its weight & cost by changing material & design of the component. Major loads coming on rear cover is assembly load i.e bolt pretension and vibration from engine. Static analysis has been done considering bolt pretension & constrained modal analysis are performed on both the existing & modified designs. Analysis is carried out for both existing material i.e. Cast iron and proposed material i.e aluminium. Existing design and material is considered as benchmark. FEA Modeling Details The rear cover for engine is mounted on the crankcase. Both existing & proposed design of rear cover are modeled using tetrahedral second order elements. To reduce the effect of boundary condition and to capture the stiffness at the interface of rear cover and crankcase, portion of crankcase is modeled using tetrahedral second order elements. Contact is defined at the interface of rear cover and crankcase. Bolt is modeled using rigid & beam elements. 1
Figure 1: 3D CAD of Rear Cover Existing & Proposed model Figure 2: FE Model of Rear cover Existing & Proposed No. of elements No. of nodes Existing Design 119488 199711 Proposed Design 486549 730486 2
Loads and Boundary Condition Details Calculated clamping force for the designed bolting torque is applied as bolt pretension on all the mounting holes of component. Both the models are also simulated for constrained modal analysis by using EIGRL card. The harmonic frequencies of both the proposed & existing design are extracted from modal analysis and compared with calculated engine harmonics. Results & Discussions Modal Analysis Observed 1 st natural frequency for the proposed design is well above the benchmark model natural frequency. The 1 st natural frequency on benchmark model is 1398 Hz and on proposed model 1481 Hz. Also, the 1 st natural frequency on proposed model is well above the 3 rd engine harmonic in all operating conditions. Figure 3: 1 st Mode shape plot for existing & proposed design 3
Static Analysis Stress observed on the proposed design is less as compared to existing design and it also well within the allowable stress of material for bolt pretension load case. The maximum displacement on proposed design is more as compared to existing design but it well within the target displacement. Figure 4: Stress plot for existing & proposed design in bolt pretension load Figure 5: Displacement plot for existing & proposed design Benefits Summary The proposed design is lighter in weight with 68 % weight reduction from existing design. Challenges To achieve desired strength & target natural frequencies as compared to benchmark model. Conclusions CAE capability of HyperWorks enable us to do several design iteration in less time for achieving target goal. By doing FEA, we were able to reduce the weight of rear cover by 68%. 4
ACKNOWLEDGEMENTS The authors would like to thank - R&D & Altair India for their support. REFERENCES [1] The Metals data book by Alok Nayar [2] Design of Automotive Engines by A. Kolchin & Veniamin Palvovich Demidov. [3] The Mechanics of Tractor - Implement Performance by R.H.Macmillan. 5