Wednesday, May 21, 2008

Challenges in the Finite Element Analysis of Tire Design using ABAQUS

Finite Element Analysis of Vehicle and Tire has become a very important aspect of a tire design and failure analysis to most Tire companies. Tire modeling with ABAQUS is a very complicated process involving complex materials like hyperelastic rubber and textile reinforcements, large model size, prolonged simulation time and various convergence issues. This white paper intends to help in understanding the challenges in tire analysis and several tips and tricks that makes a difference in the quality of the results and processing time. AEG hopes that this article will be useful to ABAQUS users working in the field of tire design and analysis.

A general tire has the following major tire components

  1. Tread
  2. Belt Region
  3. Inner Liner
  4. Sidewall Region
  5. Inner Carcass Region
  6. Bead Filler Region
  7. Apex/Chafer Region
  8. Beads
  9. Reinforcements
    1. Nylon Cap Ply
    2. Steel Belts
    3. Carcass Ply

Constructing the structure of the tire and modeling of each component is the first step into the analysis. AEG found that utilizing the combination of AutoCAD and ABAQUS-Sketch is a very good way to start the modeling. It is important to have the understanding that when an AutoCAD drawing is imported to ABAQUS sketch it creates splines and contains large number of node points. A thorough simplification of the geometry is recommended, i.e. flattening up crooked lines, reducing the number of nodes, deleting unnecessary wedge or fringes, taking off rounds/fillets and simplifying the corners is highly recommended. In this process the dimension and shape and tire should not be compromised. If the geometric complexities can be avoided at this point, it will save considerable amount of computational time, money and resources later. Features in the Sketch module of ABAQUS such as offset can be intelligently used to maintain excellent dimensioning consistency of the different reinforcement layers inside the tire. ABAQUS has a very comprehensive guideline for tire analysis in their example manual and it has been proved that an axisymmetric modeling approach with half geometry is the best way to start the modeling. Also it is widely accepted by the FEA community in the Tire industry that a smooth tire model (3D model by revolving a 2D tire model by 360°) is sufficient enough to capture the overall efficiency of the core design. The complex tread geometry with random pitch or asymmetry in the thread can be used in the later stages to get very accurate results for a specific tire model. The basic steps for tire FEA analysis can be described as below.

  1. 2D axisymmetric Tire geometry modeling
  2. 2D Rim Mounting and Inflation Analysis
  3. 3D model generation by Revolve and Reflect features in Symmetric Model Generation (SMG) option in ABAQUS
  4. Foot Print Analysis with rated load and rated inflation pressure
  5. Steady state rolling analysis using Steady State Transport option in ABAQUS
  6. Dynamic Analysis, Hydroplaning analysis



Sample picture of Foot Print Analysis of Smooth Tire

The complete article can be downloaded from the link below
http://www.engineering-group.com/technical_briefs.php

Composed by American Engineering Group