Understanding Flexible Body Simulation in MotionView and MotionSolve

Welcome to the Multibody Dynamics for Automotive Applications using MotionView and MotionSolve blog series. In this blog, we will explore one of the most important and trending topics in multibody dynamics (MBD)—Flexible Body Simulation. Compared to rigid body simulations, flexible bodies allow us to capture stress, strain, and deformation more accurately, making them widely used in automotive engineering simulation and mechanical system simulation. 

Why Use Flexible Bodies in Multibody Dynamics? 

Multibody dynamics simulations have traditionally used rigid body models to represent components. However, real-world structures experience deformations under load, which rigid bodies cannot simulate. This is where flexible bodies become essential. 

Using multibody dynamics software like MotionView and MotionSolve, engineers can convert finite element (FE) models into flexible bodies and integrate them into an MBD simulation. This approach enables: 

• More accurate load predictions for automotive dynamics analysis. 
• Stress and strain analysis within an MBD model. 
• Fatigue analysis using dynamic load simulations. 

More realistic vehicle system modeling, especially for components like control arms, suspension links, and engine mounts. 

 Creating Flexible Bodies in MotionView 

MotionView provides an intuitive way to create flexible bodies using the built-in FlexPrep Utility. This tool is used for: 

• Generating flexible bodies from finite element models. 
• Converting flexible bodies into other file types for compatibility with different solvers. 

The FlexPrep tool simplifies the process compared to other automotive simulation software, making it easier for MotionView beginners to implement multibody dynamics simulation. 

How Do Flexible Bodies Work? 

The behavior of flexible bodies is based on modal superposition, a concept commonly used in finite element analysis (FEA). This technique: 

• Breaks down deformation into multiple mode shapes. 
• Uses modal participation factors to reconstruct the deformed shape. 
• Greatly reduces computational complexity compared to solving full FE models. 

A flexible body is essentially a condensed version of an FE model that captures key deformation characteristics while remaining computationally efficient. 

Applications of Flexible Body Simulation 

Flexible bodies have numerous applications in multibody dynamics for automotive applications, including: 

• Suspension system analysis (e.g., modeling a flexible lower control arm to analyze deformations). 
• Engine component analysis, such as pistons, crankshafts, and connecting rods. 
• Fatigue load prediction, improving automotive durability. 
• Evaluating stress and strain distribution in key components. 

By replacing rigid bodies with flexible bodies, engineers can achieve greater accuracy while maintaining computational efficiency. 

Conclusion 

Flexible body simulation in MotionView for automotive engineers provides a powerful way to analyze stress, strain, and deformation in real-world structures. By utilizing modal superposition and the FlexPrep Utility, engineers can efficiently integrate finite element models into MBD simulations. 

In our next blog, we will explore the Component Mode Synthesis (CMS) methods, which are used to generate flexible bodies in multibody simulation software like MotionSolve. 

This blog is part of our ongoing Multibody Dynamics blog series. If you missed the previous posts, check them out here.  

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