Multibody model of a combine for mission loads estimation

Transcription

1 Multibody model of a combine for mission loads estimation Nicola Poerio, Vincenzo Puleo CRF, Product Research Thomas Yi, Venu Chiratanagandla, Jishan Jin CNH, PD Design Analysis & Digital Prototyping 1

2 Activity overview The goal of the activity is to create and validate a Multibody vehicle model of a combine in order to calculate accelerations, forces and stresses on a bumped track. 2

3 Activity contents Development of basic ADAMS combine model with rigid bodies and first validation with respect to experimental data Upgrade of ADAMS combine model with unload tube and grain tank flexible bodies, including significant modal shapes only, and second validation with respect to experimental data Effect of different unload tube length on accelerations and forces Development of unload tube flexible body including also modal stresses attempt of stress evaluation in MB environment Conclusions and next developments 3

4 Bumped track experimental tests 1 test condition : vehicle speed = 4.5 mph. 1 test configuration : auger out configuration of unloading tube, dummy header installed. Bump shape 4

5 Rigid multibody model Overview ADAMS View Multibody model - Rigid bodies only - Kinematic joints - Cab Mounts General forces - Handling tires (Fiala) With the available tire data (vertical non linear stiffness), Fiala tire model is fit to perform the simulations. This tire model is not the best to simulate ride/fatigue missions. A road geometry enveloping model, including longitudinal input, should be recommended. 5

6 Multibody model Fiala Tires The following vertical load-deflection curves have been used with Fiala tire models. Nominal Front Nominal Rear 900/60R32 480/70R30 STR Deflection [mm] Deflection [mm] Load [N] Load [N] Nominal curves have been tuned using the pressure dependency formula, provided by tire manufacturer. The tire damping model is linear. 6

7 Rigid multibody model Parameterization The following scheme illustrates the most significant parameterization steps performed. Geometrically enveloped profile Deflection [mm] base modif. Base version Front damping increased Front pressure decreased Load [N] Load [N] Best validation found Front damping +100% Rear damping -50% 7

8 Multibody model Full vehicle validation FFT at measure points axles vertical 4.5 mph Experimental tests Base version Best validation rearaxle vertical rhsfrontaxle vertical lhsfrontaxle vertical rear axle center vertical front axle rhs vertical front axle lhs vertical rear axle center vertical front axle rhs vertical front axle lhs vertical Base version model already catches peak frequency value, not the levels. The best validation is improved in level matching, even if not yet completely satisfactory. A more complex tire model (road geometry envelopment, longitudinal input) could play a significant role in order to improve the validation. Rear axle vertical Front axle left vertical Front axle right vertical 8

9 Flexible multibody model Overview ADAMS View Multibody model - Rigid bodies + flexible unloader, graintank and actuator - Kinematic joints - Cab Mounts General forces - Handling tires (Fiala) Revolute joints Flexible actuator - Unloader modal condensation: reduced graphics. - Graintank modal condensation: reduced graphics. [N] [mm] Spherical joints 9

10 Flexible multibody model validation 1/2 FFT at measure points unload tube outerend 4.5 mph Experimental tests Flex tube, locked actuator Flex tube and tank, locked actuator outerend vertical outerend foreaft outerend lateral unloadtube outerend vertical unloadtube outerend foreaft unloadtube outerend lateral unloadtube outerend vertical unloadtube outerend foreaft unloadtube outerend lateral 0 0 The introduction of unloading tube and tank flexibilities improves the validation in frequency, but not completely in levels (lateral direction). NOTE: Directions referred to the tube Vertical Foreaft Lateral 10

11 Flexible multibody model validation 2/2 FFT at measure points unload tube outerend 4.5 mph Experimental tests outerend vertical outerend foreaft outerend lateral Flex tube, tank and actuator unloadtube outerend vertical unloadtube outerend foreaft unloadtube outerend lateral Friction torque on revolute joints unloadtube outerend vertical unloadtube outerend foreaft unloadtube outerend lateral The introduction of actuator flexibility again improves the validation in frequency; in order to match also levels, a friction joint estimation and tuning has been done. The correlation with experimental data is very satisfactory. Vertical Foreaft Lateral 11

12 Flexible multibody model forces Mission load time histories Bumped Track 4.5 mph Unloader actuator axial load Unloader revolute 1 loads Unloader revolute 2 loads vertical foreaft lateral 8 vertical foreaft lateral [N] [N] [N] 0 [s] [s] [s] Constraint and force element load time histories have been retrieved from multibody simulation. They can be passed to a FE non-linear solver for structural analyses. 12

13 Flexible multibody model tube parameterization FFT at measure points unload tube outerend 4.5 mph Base version unloadtube outerend vertical unloadtube outerend foreaft unloadtube outerend lateral 4.4 feet extension unloadtube outerend vertical unloadtube outerend foreaft unloadtube outerend lateral 6.0 feet extension unloadtube outerend vertical unloadtube outerend foreaft unloadtube outerend lateral The 4.4 ft configuration is not different in frequencies and slightly different in levels from the base one. The 6.0 ft configuration shows a frequency lowering and higher acceleration levels. Vertical Foreaft Lateral 13

14 Flexible multibody model tube parameterization Mission loads Bumped Track 4.5 mph Unloader actuator axial Unloader revolute 1 lateral Unloader revolute 2 lateral Also for loads levels 6.0 feet extension configuration shows an evident increase. 14

15 Flexible multibody model Overview ADAMS View Multibody model - Rigid bodies + flexible unloader, graintank and actuator - Kinematic joints - Cab Mounts General forces - Handling tires (Fiala) - Unloader modal condensation: full graphics + stresses info. - Graintank modal condensation: reduced graphics. 15

16 Flexible multibody model Unloader stress evaluation Time histories unload tube outerend Bumped Track 4.5 mph unloadtube outerend vertical unloadtube outerend foreaft unloadtube outerend lateral # 2 # 1 In green color the instants that have been taken into account for stress analysis. They have been chosen as maximum solicitations for different type of deformation. # 4 [s] # 3 16

17 Flexible multibody model Unloader stress evaluation Von Mises stress contour plot Bumped Track 4.5 mph instant #1 Stress maps seem to be qualitatively reliable and useful to have an idea of the most stressed areas. Stress absolute maximum values are not fully reliable due to the linear approach of modal condensation. Simulation time and measured channels do not change with the addition of unloader stress information. 17

18 Conclusions Activity conclusions and next developments A rigid body model of the combine has been created. The model validation catches certain experimental dynamics, but could be improved with a more accurate tire model. Unloader and grain tank modal condensations as well as flexible actuator model have been introduced in the model. Unloading tube frequencies and levels have been caught; for levels, the introduction of a sliding friction on tube revolute joints has been necessary. A parameterization on tube length has been done, evidencing some differences in acceleration levels, in frequency distribution and loads, especially for 6.0 ft configuration. Unloader modal condensation with stress information has been included in the full-vehicle model. Unloader stress calculation has been retrieved, considering most significant instants of the mission. This approach is useful to have an idea of the most stressed areas. Next developments A more accurate tire model (more tire manufacturer data needed). 18