Coupling Discrete Element Method (DEM) and Finite Element Analysis (FEA) to enhance truck body performance: minimize weight while maintaining strength.
Challenges
Industries that handle bulk materials or heavy equipment face significant challenges related to structural performance, wear, and operational efficiency. Traditional design methods often rely on experimental testing and empirical correlations, which can be costly, time-consuming, and limited in scope. This is where computational simulation, specifically the coupling of Discrete Element Method (DEM) and Finite Element Analysis (FEA), becomes a powerful tool. Key challenges that some industries face include:
Structural integrity under heavy loads
- Mining. Dump truck beds and excavator buckets suffer repeated rock impacts, leading to fatigue and cracks.
- Cement. Rotary kilns endure mechanical stress from clinker movement.
Wear and material degradation
- Mining. Slurry pipelines and pumps erode due to abrasive particle flows.
- Steel. Blast furnace hoppers wear out from continuous iron ore impact.
Load distribution and stress concentration
- Agriculture and food. Silos develop stress concentrations due to uneven grain flow.
- Industrial filtration. Cyclones handling powders experience structural stress from high-velocity particles.
Optimization of weight and material usage
- Heavy machinery. Conveyor belt frames must be lightweight yet resistant to impact loads.
- Automotive. Bulk material transport trailers require material optimization to reduce weight while maintaining durability.
Engineering Solutions
The coupling of Discrete Element Method (DEM) and Finite Element Analysis (FEA) offers a powerful solution for evaluating the structural performance of equipment handling bulk materials. By integrating particle interactions with structural response, this approach enables engineers to predict wear, stress distribution, and fatigue, optimizing designs for greater durability and efficiency.
Methods
To accurately assess the impact forces on a truck body and determine the resulting structural stresses, engineers rely on two powerful numerical methods: the Discrete Element Method (DEM) and the Finite Element Method (FEM or FEA). Each method plays a crucial role in understanding different aspects of the problem.
DEM is used to simulate the behavior of particles (like rock fragments) during loading. It provides key insights into how rocks interact, their velocities, impact locations, and the resulting forces applied to the truck body. To achieve realistic results, engineers must define critical input parameters such as rock size distribution, shape, density, and mechanical properties.- FEA focuses on the structural response to different forces. It allows engineers to analyze stress distribution, deformation, and potential failure zones based on the material properties of the structural components. Essential inputs include material properties, info about the supports and loading state, and fatigue limits.
Beyond these fundamental capabilities, the DEM-FEA approach enables advanced analyses, such as geometry optimization, fatigue prediction, and impact energy assessment, giving engineers a deeper understanding of how bulk materials affect structural components over time. This methodology is essential for industries looking to enhance durability, reduce maintenance costs, and improve operational efficiency.
To demonstrate the power of this approach, we present a demo on the structural analysis and optimization of a truck's dump body, where DEM-FEA is applied to evaluate material loads, stress levels, and design improvements. Ansys Rocky is the DEM tool that allows handling particles with different shapes, sizes (including distributions), particle inlet types, and so on. The following table shows some general particle types (in red color) and the shapes that can be achieved by changing some internal parameters.
Results
For this demo, a 3.3m x 1.7 m x 0.95 m dump body of a truck is analyzed. it is assumed that bulk material -rocks with a Particle Size Distribution (PSD)- is released to fill the body. The modules involved in the workflow involved are described as follows:
- Module A: Geometry of the surface of the dump truck
- Module B: Rocky module to solve DEM simulation
- Module C: Geometry of the surface of the dump truck and the structural supports
- Module D: Static Structural analysis in Mechanical
- Module E: Direct Optimization
The geometry in Module A is shown below on the left animation of the rocks filling the box. The animation on the right is a view from below to observe the instantaneous magnitude and location of the vertical force (Y-axis) generated by the rocks impact. Rocky in Module B provides also generates time plots to identify the behavior of a variable over time. Notice the maximum force of -101,296 N is produced when t = 2.95 s. Next, the set of pressure results is exported into Ansys Mechanical. The user can select among these options to export the pressure: all instants, last output, time range, specific time, and after time. The total elapsed simulation time was determined to be 140 s (2 min 20 s).
The geometry in Module C, including the supports, serves as input for the Static Structural Analysis in Module D. The mesh size must be similar to that used in the DEM analysis to ensure consistency in the load transfer. Once the results are updated in the Rocky module, the pressure—imported as a load—can be properly set up and will appear as shown in the image below. The simulation time for this case is relatively short.
A fixed support is also used to generate the vertical reaction force of 101,570 N, which is then compared to the value calculated in Rocky at 2.95 s equal to 101,296 N. For this initial design, there are three supports, and the shell thickness is 10 mm. Based on the results, this design requires improvement, as the stress level is close to the yield strength limit (250 MPa) and the safety factor is 1.16.
Optimization
For the redesign, the following parameters are considered:
- Inputs. [1] plate thickness (between 1-20 mm), [2] number of supports (between 3-6).
- Outputs. [1] Plate mass, [2] Maximum deformation, [3] Maximum equivalent stress, [4] minimum static safety factor.
The Direct Optimization tool in Module D is used to improve the geometry and strength of the dump body. This module is based on the Adaptive Single-Objective method to minimize the plate mass (target: 0), while imposing constraints on the maximum equivalent stress (200 MPa) and the minimum safety factor (1.5). Using the default settings, 33 additional Design Points are automatically generated and solved, eliminating the need to reopen Ansys Rocky or Mechanical. The number of supports is rounded to a whole number. The simulation time for each design point remains similar to that of the initial design in both Ansys Rocky and Mechanical.
As a result, the Direct Optimization module identifies three candidate points that meet all the conditions defined in the previous step. These are shown in the next figure. Note that the mass is marked with a star, indicating that it is still "far" from zero (the objective), but the values remain acceptable. Recall that "Parameter 1" refers to the number of supports, which is rounded to a whole number accordingly. With this information, the engineer or designer can make informed decisions on how to proceed with the design.
Ansys Solution Benefits
Ansys Rocky is a leading discrete element method (DEM) software used for simulating the motion of granular and discontinuous materials. It is designed to solve engineering problems by accurately simulating particle flows. Rocky is capable of modeling real particle shapes, including solids, 2D shells, and rigid and flexible fibers. The software is known for its fast and accurate simulations, utilizing multi-graphics processing unit (GPU) solver technology to handle different shaped and sized particles in various industrial applications.
It offers features like multi-GPU processing, realistic particle shapes, wear modeling, particle breakage, and cohesion. Ansys Rocky is recognized for its ability to accelerate complex particle simulations with its powerful DEM software capabilities. Additionally, Ansys Rocky unlocks the potential of solving large-scale DEM simulations, handling millions of particles with ease. It supports multi-GPU processing, realistic complex particle shapes, and offers coupling with fluids, structural mechanics, and electromagnetic fields. The software also includes advanced features like breakage modeling and smoothed-particle hydrodynamics, making it a comprehensive tool for particle dynamics simulation.
Ozen Engineering Expertise
Ozen Engineering Inc. leverages its extensive consulting expertise in CFD, FEA, optics, photonics, and electromagnetic simulations to achieve exceptional results across various engineering projects, addressing complex challenges like multiphase flows, erosion modeling, and channel flows using Ansys software.
We offer support, mentoring, and consulting services to enhance the performance and reliability of your systems. Trust our proven track record to accelerate projects, optimize performance, and deliver high-quality, cost-effective results for both new and existing water control systems. For more information, please visit https://ozeninc.com.
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