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Basics of Time-Dependent Analysis in Structural Mechanics

In Part 3 of this course on structural mechanics modeling in COMSOL Multiphysics^®, we focus on performing time-dependent analysis for structural dynamics models. We begin with an overview of this type of analysis before completing a step-by-step modeling demonstration in which we build a model of a transient, structural application.

Discussion: Time-Dependent Analysis

Time-dependent analysis includes inertial forces, viscous forces and time-varying loads. Here we discuss various foundational questions important to address when performing a time-dependent study and how the answers feed into what class of dynamics your structural model falls under. We then provide further background into each of these classes of structural models and the respective settings used in the software to account for each. A brief overview of the general solvers used for time-dependent studies in COMSOL Multiphysics is also provided. Lastly, the impact of including damping in your analysis, depending on the application, is discussed.

Demo: Modeling a Transient, Structural Application

Follow along in the software, using the start model file provided, as we perform a transient analysis of the bracket model. In this guided, step-by-step demonstration we cover the fundamentals when modeling transient, structural applications. To apply a time-dependent load to the bracket, we define a Step function and Rectangle function, which we then use in the physics settings for the model. Additionally, when defining the physics for the model, a Damping feature is added to the Linear Elastic Material node to include damping effects, after which we use a Rigid Connector feature to apply the load in our model. We also discuss the various settings for the Time-dependent study node in detail as well as the advantages of setting up probes to track the values of quantities while solving.

Further Learning

For time-dependent studies it can be important to include damping. For more information on sources of damping, the theory, and the different types of damping please see the blog posts on "Damping in Structural Dynamics: Theory and Sources" and "How to Model Different Types of Damping in COMSOL Multiphysics^®".