Advanced FEA Compaction Model Using CEL Method

Transcription

1 Advanced FEA Compaction Model Using CEL Method Liqun Chi, Ph.D. Machine and Machine Systems Research and Advanced Engineering Product Development & Global Technology Caterpillar Inc. Greg Zhang Compactors &Wheel Dozers Performance & Controls Industrial & Waste Group Caterpillar Inc.

2 Outlines Slide 2 Brief Introduction of of Motivation Material Models for Refuse FEA Compaction Model Development Early Model with Smooth Drum Tip Models using Lagrangian Method Latest CEL models Model Validation Introduction on Model Applications Future Model Development Need Q & A

3 Real World Problems Slide 3

4 Motivation Slide 4 Develop VPD Model to predict the compactor performance Compaction Performance Machine Mobility Drive train requirement Wheel Torque Fuel Consumption (coupling with other software) To define the optimum operation procedures Able to determine the optimum wheel configuration for a particular market Guide the Basic Machine Configuration Specs Improving Current Products New Product Development Guide the powertrain design: Reliability Fuel efficiency (coupling with other software)

5 Mechanical Behavior of Refuse Barrel Tests Slide 5 Force Refuse Mechanical behavior of waste under applied load Elasto-Plastic behavior reversible elastic rebound and permanent, irreversible plastic deformation Elastic rebound is stress dependent Work-hardening plastic deformation behavior hyperbolic or exponential shape

6 Testing Shear Strength of Waste Material Slide 6

7 Crushable Foam Material Models for Refuse Slide 7 Plastic potential q 1 a Yield surfaces -p t p o p o c p c p Characteristics: Volumetric hardening Non-associated flow rules User Material Subroutine Stress dependent elasticity f g q 2 q 2 a 2 2 p p B 0 2 p 2 o

8 Total Strain Material Model Validation - VUMAT Slide 8 Single Element Lagrangian Mesh CEL Mesh Test Data Lag Model CEL Model

9 Early Models with Smooth Drums Slide 9 Model Description: FEA-based model with ABAQUS/Explicit Rolling the the wheel on the deformable ground Analytical rigid surface for the drum Friction-type wheel/ground interface Multiple layers for ground model Controlled the wheel motion (rotational and translational). Study the feasibility of the model ABAQUS v5.8 first release with contact algorithm Explored both ABAQUS/Standard and ABAQUS/Explicit Run time with the computer power at the time Excises of Early Model Model validation in laboratory soil bin with artificial soils Sizing the drum and powertrain Competitive Studies Study optimum optional procedures

10 Soil Bin Validation Slide 10 Scaled model of smooth drum Artificial Soil Mix Soil Model Drucker-Prager s Cap Model Soil Behavior Triaxial tests One dimensional compression tests

11 New Laboratory Soil Bin Facility at Technical Center Slide 11

12 Refuse Density Early Model with Smooth Drum Machine Size Slide 12 The effect of machine passes The effect of machine weight Determine the optimum operation procedures Number of Machine Passes CAT816 CAT826 CAT836

13 Early Smooth Drum Model - Effect of Layer Thickness Slide cm Layer 90 cm Layer 120 cm Layer CAT 836 with three passes

14 Field Validation Test (US Landfill) Slide 14 GPS - Measure Speed GPS Survey for Layer thickness, slopes and density Drive Shaft Torque and Speed Crusher Barrel Tests (refuse compaction behavior)

15 Field Validation Test US Landfill Slide 15 Level Ground 5:1 Slope

16 Early Model with Smooth Drum Stress Under Wheel Slide 16

17 Early Model with Smooth Drum Volumetric Strain Slide 17

18 Density Density Results with Smooth Drum Models Slide 18 Level Ground 5:1 Slope Field data Model Field data Model Machine passes Machine passess Model Accurately Predicted Average Density Change Model Prediction of Wheel Torque is Significantly Lower Not Able to Consider the Effects of Detailed Wheel Design (tips shapes, number of tips and tip arrangement)

19 Tip Model Lagrangian Mesh Slide 19 Model Description Wheel model included detailed tip shape and tip arrangement pattern General finer mesh to accommodating the tip shape VUMAT was used for the model Mesh distortion was key problem with Lagrangian mesh Methods Explored for Distortion Control ALE Method Automatic remeshing (moving the location of nodes, no nodes or element added, and the node on the material boundary followings the material deformation) Various mesh smoothing algorithms (volume average, Poisson equation, and combination of these methods) Advection of mass, momentum, and energy Flexible control of remeshing frequencies Not able to find an effective remeshing method for our problem Solid Section Distortion Control Distortion control option at Solid Section With Enhanced Hourglass Control Limited Success

20 Model with Tips Lagrangian Method Slide 20

21 Model with Tips Lagrangian Method Slide 21

22 Model with Tips Lagrangian Method Slide 22

23 Relative Wheel Torque, % Lagrangian Mesh Tip Model Validation Slide 23 Limited Success of Distortion Control in Lagrangian Formulation Only single machine pass And with gentle slope With relatively small wheel slips Much Improved Model Predictions Accurate wheel torque prediction for first pass (including torque split between front and rear axles) Accurate the average density prediction for first pass Wheel Torque during 1 st Pass fwd trips Front Rear Model Dataset 1 Dataset 2 Dataset 3

24 CEL Method Slide 24 Coupled Eulerian-Lagrangian (CEL) Formulation: Lagrangian phase Remeshing phase The CEL method is based on an operator split of the governing equations, resulting in a traditional Lagrangian phase followed by an Eulerian, or transport, phase. Lagrangian phase of the increment- nodes temporarily fixed within the material, and elements deform with the material. Eulerian phase of the increment - deformation is suspended, elements with significant deformation are automatically remeshed. Mass and momentum advections between neighboring elements are computed. Eulerian mesh did not follow material need to construct the surface for contact Void and partially filled elements Elements can be filled with different materials

25 Field Validation Test - China Slide 25 Spreading Field compaction test Survey In-site compression test

26 CEL Landfill Compaction Model Slide 26 Compactor Wheels Void Layer Loose Refuse Precompacted Layer Base Eulerian Mesh Special Eulerian element (EC3D8R 3D analysis only) Generally finer than Lagrangian mesh for similar analysis Cover the region the material potential can move into void element Eulerian-Lagrangian Contact General Contact in Explicit Penalty Method Surface of Eulerian mesh is defined using material instance No need to define contact interactions between Eulerian materials Boundary Conditions Define material flow at Eulerian nodes/boundary Surface No displacement type constrain at Eulerian node ABAQUS internal crushable foam model for top loose refuse

27 CEL Model Simulation - Video Slide 27

28 Model Validation Samples of Machine Data Slide 28 RVS RVS FWD FWD FWD RVS

29 Density Model Validation Compaction Prediction Slide 29 Field Data Model (F-R-F-R) Model (R-F-R-F) Machine Passes

30 Total Wheel Torqm Model Validation Wheel Torque Slide 30 Forward Reverse Forward Reverse (6% Downhill Slope during Forward) Field Data - Trip 1 Field Data - Trip 2 Field Data - Trip 3 Model Machine Pass

31 Total Wheel Torque Model Validation Wheel Torque Slide 31 Reverse Forward Reverse - Forward (6% Downhill Slope during Forward) Field Data - Trip 1 Field Data - Trip 2 Field Data - Trip 3 Model Machine Pass

32 Machine Speed Model Validation Machine Speed Slide 32 Forward Reverse Forward Reverse (6% Downhill Slope during Forward) Field Trip 1 Field Trip 2 Field Trip 3 Model Machine Pass

33 CEL Model to Simulate Drawbar Test Slide 33

34 WTL VPD Modeling Domain Slide 34 Machine Dynasty Compaction Traction Steering Braking Cooling Productivity Fuel efficiency Performance Environment Real World Abaqus Explicit Virtual World Structure Stress Fatigue

35 Landfill Compactor Performance Model Slide 35 3D Tire Model Traction Coefficient Rolling Resistance Rolling Radius FEA Landfill Compaction Model P&C Productivity Fuel Efficiency Dynasty Machine System Model Cooling Heat Power Train, Structure Loads

36 Typical Model Applications Slide 36 Tip/wheel designs to achieve optimized machine performance, power train, cooling and structural integrity China specific wheel/tip designs to suit the characteristics of Chinese waste Belly guard designs to reduce drag Customer support to help market the products Competitive studies to understand our products strengths and weaknesses.

37 Summaries & Conclusions Slide 37 ABAQUS/Explicit is powerful tool for simulating the machine and ground interactions The CEL method resolved the element distortion problems experienced in the previous compaction models using Lagrangian method. The CEL model can simulate multiple passes for the compaction wheels with detailed tip shapes. The CEL model can simulate the excessive ground deformation at high wheel slip The model accurately predicts the average density changes made by landfill compactor and machine speed. The CEL model was able to predict the correct trend of changes in wheel torque between passes and capture the effect of slopes on the wheel torque. Lower wheel torque with more compacted ground conditions Correct trend of effect of ground slopes Lack of material damping for Eulerian elements results in under-prediction of wheel torque by the current landfill compaction models numerical material damping for soil like plastic material models is critical. The VUMAT was successfully used for simulating the barrel tests. The model accurately predicted both elastic rebound and permanent plastic strain. The use of VUMAT of the same material subroutine failed for the full landfill compactor model. The robustness of using user-defined material subroutine (VUMAT) with Eulerian elements in ABAQUS needs to be further improved.

38 Slide 38 Thank You! & Questions?