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# Finite Element Analysis for stress calculations and safety

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### Finite Element Analysis for stress calculations and safety

1. 1. M.E. Seminar 3 Harshal R. Borole Finite Element Analysis Techniques for Stress Calculations and safety of Dump Truck Frame
2. 2. Introduction Nowadays, transportation industry plays a major role in the economy of modern industrialized and developing countries. The goods and materials carried through heavy trucks are dramatically increasing.  There are many aspects to consider when designing a heavy trucks chassis, including component packaging, material selection, strength, stiffness and weight. A dump truck frame is the most crucial part of the truck that gives strength and stability to the vehicle under different conditions. A dumper frame – rigid to withstand shock, twist, vibration and other stresses. A well structured and properly built frame improves crash worthiness, passenger safety and weight efficiency
3. 3. Significance of the dumper frame Dump truck is the variant on the basis of chassis, mainly consisted of the chassis, power transmission device, lifting mechanism, sub-frame, special-purpose box and back flip axis etc. The sub-frame plays the role of transitional frame to enable the main frame support as much homogeneous load as possible. Sub-frame is connected to main frame through u-shape bolts and thrust connection board, and is hinged with cargo body through the back flip axis and lifting cylinder. Frame is subjected to various loads at different conditions.
4. 4. A 3D model of various mountings on the dump truck frame during unloading process
5. 5. Dump Truck Frame A Dumper truck frame is a complex assembly which supports the loads from lifting cylinder and carriage and also is subjected to harsh, uneven road conditions. The frame should have optimum strength along with adequate bending and torsional stiffness to withstand such loads and conditions. FEA study provides the basis for designing the frame since the frame is modeled in various CAD softwares and analysis for strength and bending is done by applying boundary conditions and different loads. Different researchers have used different analysis techniques for optimizing the design of frame for strength and weight reduction.
6. 6. AGENDA Statement of Purpose Design Considerations FEA Techniques Modeling and Analysis Results & Discussions
7. 7. Statement of Purpose To Study various finite element analysis techniques used for a) Calculating different types of stresses induced and deformation of dump truck frame subjected to various loading conditions. b) Determining the critical areas of stress concentration for a fail-safe and lightweight structure.
8. 8. Design Considerations The dumper frame is very critical in designing as there are various factors to be considered while a) Dumper frame at rest – Static loads supported by the frame. b) Dumper is moving - different sets of vibration modes of the frame. c) Dumper is unloading – Dynamic loads and torque reactions.  For the first case, FEA is done on different sections of the frame for determining the critical areas of stress concentration.  For second case, FEA is done on the whole frame which is excited to different low frequencies which are close to potential exciting sources like oscillations of
9. 9. Finite Element Analysis Techniques Based on the conditions, dumper truck frame is analyzed for stress optimization by following techniques : 1) FEA for Static load. 2) Modal analysis for determining various mode shapes and predicting different dynamic responses under excitations. 3) Dynamic analysis of the frame structure during initial state of cylinder lifting and critical state of goods declining. 4) FEA by reinforcement technique for stress optimization.
10. 10. Static Load Analysis  For this analysis, a standard dump truck with following specifications was used and the frame model was prepared in CATIA and finally analyzed with the help of ANSYS software.  Gross Vehicle Weight (GVW): 25000kg.  Gross Combined Weight (GVW + Payload): 26200kg.  Frame: Ladder type heavy duty frame, depth- 285mm, width- 65mm, frame width- 903mm.  The magnitude of pressure on the upper side of chassis is determined by dividing it into 3 parts. 1) P1= F/A = 128511 / 65 * 10-6 * 6670 = 290321.9248 N/m2 2) P2 = 1200 * 9.81 / 65 * 10-6 * 1400 = 129362.6374 N/m2 3) P3 = 1200 *9.81 / 65 * 10-6 * 740 = 244740.1247 N/m2
11. 11. Total Deformation of frame by static analysis
12. 12. Modal Analysis Of Truck Frame  Frame forms the backbone of the dump truck, when the truck travels along the road, the truck chassis is excited by dynamic forces caused by the road roughness, engine, transmission etc.  After constructing a finite element model for the frame, modal analysis can be used a tool to determine natural frequencies and mode shapes.
13. 13. Sr. no. Mode no. Frequency Displacement 1 1 16.894 Twisting about X-axis 2 2 25.537 Bending about Y-axis 3 3 27.427 Deformation about X-axis and bending about Y-axis 4 4 28.746 Twisting about X-axis and Bending about Y-axis 5 5 33.971 Twisting about X-axis 6 6 34.316 Deformation about X-axis and bending about Y-axis 7 7 36.564 Deformation about X-axis and Y-axis 8 8 46.316 Deformation about X-axis
14. 14. FEA Of Frame During Unloading Condition  The dump truck loads the goods by large construction machinery, so the phenomenon of biased loading goods frequently happens.  In the unloading process, because of the biased load of goods, the stresses induced in the frame are worse.  So force analysis should be carried out to detect critical areas of stress concentration.  The unloading of goods condition consists of two parts – 1) Initial state of oil cylinder lifting 2) Critical state of goods declining
15. 15. Initial State Of Oil Cylinder Lifting  In this state, because the static friction torque of each hinge point in lifting system is large and the lifting Angle of oil cylinder is the most adverse, the lifting force should be the largest.  Meanwhile, the reaction force oil cylinder against to the secondary frame is also the largest.
16. 16. Critical State Of Goods Declining  In this state, the cargo body has left away from the surface of the frame when goods are about to decline, so all the weight is carried by the back flip axis and the oil cylinder.
17. 17. FEA By Reinforcement Technique For Stress Optimization  In this, finite element analysis is performed on a truck frame and critical areas of stress concentration are determined in terms of von-mises stresses.  Reinforcement is the technique of adding cover plates on external side members at highly stressed regions to improve the strength and life of the frame.
18. 18. A CAD model of the frame is prepared in CATIA V5R19 and structural analysis is done in ANSYS workbench.  The meshed model has applied boundary conditions and load is applied on side rails. The load is applied on complete span of the side rail as uniformly distributed load.
19. 19. Von mises stress distribution in original frame Von mises stress distribution in reinforced frame
20. 20. Total deformation of original frame Total deformation of reinforced frame
21. 21. Maximum principal stress in original frame Maximum principal stress in reinforced frame
22. 22. Type Main frame Reinforced frame Pressure (MPa) 0.07395 0.07148 Total Deformation (mm) 5.0671 4.8307 Von-Mises Stress (MPa) 295.21 200.45 Max Principal Stress 132.79 128.89 Table no. 2 Structural analysis results for original frame and reinforced frame From the above table and analysis, we can conclude that –  Maximum stress and maximum displacement in reinforced frame is lower than original frame.  Reinforced technique decreases deformation of frame by 4.7 % and stress by 31.42 %  In order to obtain same deformation or stress level, we can apply additional load of 600 kg on the frame.  So reinforced frame increases the load carrying capacity with same factor of safety as of original frame.
23. 23. References Jing-ping Si, Guo-sheng Wang, Xian-long Ding, ‘Analysis of Dump Truck Unloading Condition Based on ANSYS’, Advanced Materials Research Vol. 548 [2012] Z. Chen et. Al.,‘The Lightweight Design of a Dump Truck Frame based on Dynamic Responses’, 18th International Conference on Automation & Computing, September [2012] Pratik Sarda, Prof. Baskar P. et. al., ‘Stress Optimization of Frame with Reinforcement Technique by FEA’, International Journal of Engineering Research & Technology (IJERT) Vol. 3 Issue 5 [2014]
24. 24. References Monika S. Agrawal, Md. Razik ‘Finite Element Analysis of Truck Chassis’, International Journal of Engineering Research & Technology (IJERT) [2013] Nouby M. Ghazaly, ‘Applications of Finite Element Stress Analysis of Heavy Truck Chassis: Survey and Recent Development’, Journal of Mechanical Design and Vibration, [2014] Patel Vijaykumar V, Prof. R. I. Patel, ‘Structural Analysis of Automotive Chassis Frame and Design Modification for Weight Reduction’, International Journal of Engineering Research & Technology (IJERT) Vol. 1 Issue 3 [2012]