How To Evaluate Rigid-Body Modes in a Modal Analysis — Lesson 4

While we may analyze single parts in most practical engineering applications, typically, we have an assembly of parts of different sizes made from different materials, all interacting with each other. Contact conditions allow us to define whether parts are bonded together, if they can slide relative to each other, or if they can separate from each other. In short, without contact, we can’t model realistic interactions between parts, so understanding the basics of contact is important in our journey to model physical systems more accurately.

In this video lesson, we will focus our attention on setting up models with contact for linear or small deflection analysis, providing the foundation for our understanding of realistically representing part interactions. In Ansys Workbench, the contacts are automatically created and it’s always a good practice to check automatically created connections. We will do this via a short lecture and a walkthrough example using Ansys Mechanical. Also, we will show some tips and tricks to keep in mind when using contact conditions.

Alternate video link.

Video Highlights

0:18 - What are Rigid Body Modes?

2:26 - Checking Initial Contact Status using Contact Tool

3:28 - First Six Natural Frequencies for Free-Free Modal Analyses

4:05 - Directions of Rigid-Body Modes

4:15 - What is Grounding?

7:58 - How to Specify Max Modes to Find?

8:50 - How to change Contact Formulation?

9:31 - Participation Factor of Rigid-Body Modes

Simulation Files

Download the accompanying geometry and archived files here. The student version of Ansys Simulation Software can be downloaded here.