A vehicle's suspension system is one of the most critical mechanical systems affecting ride comfort, handling, safety, and durability. However, in many Multi-Body Dynamics (MBD) analyses, suspension components are still modeled as rigid bodies.
Although rigid-body modeling is a fast and effective approach for initial design validation, mechanism motion studies, and basic vehicle dynamics analyses, it cannot accurately represent the elastic deformations that occur under real operating conditions. In reality, components such as control arms, connecting links, knuckles, subframes, and even the vehicle chassis deform under load. These seemingly small deformations can significantly influence load distribution, contact forces, vibration characteristics, and fatigue life.
This is where Flexible Body technology comes into play.
A Flexible Body is created by incorporating the elastic behavior obtained from a Finite Element (FE) model into a multi-body dynamics simulation.
This allows a component not only to move but also to deform, vibrate, and generate stress under actual loading conditions.
As a result, a single simulation can simultaneously evaluate:
This approach produces results that are much closer to real-world physical testing.
Modern vehicles increasingly use lightweight, high-strength materials to reduce overall vehicle weight and improve efficiency. While this improves performance, it also makes elastic deformations more significant.
Even micron-level deformations in the following components can noticeably affect overall suspension behavior:
These deformations directly influence:
As a result, accurately capturing elastic behavior becomes essential for realistic vehicle performance predictions.
| Feature | Rigid Body | Flexible Body |
|---|---|---|
| Elastic deformation | No | Yes |
| Stress calculation | No | Yes |
| Load distribution | Limited | Highly realistic |
| Fatigue analysis | Indirect | Generates direct load history |
| NVH analysis | Limited | Highly effective |
| Computational speed | Faster | Slower |
| Accuracy | Moderate | High |
Flexible Body modeling offers significant advantages, particularly for durability and fatigue analyses.
The Flexible Body modeling process generally consists of the following steps.
The suspension component to be analyzed is first prepared.
Typical examples include:
The CAD model is imported into a finite element software package such as:
The following steps are then performed:
The finite element analysis provides:
These data are converted into a Flexible Body representation.
The Flexible Body model is then integrated into the RecurDyn multi-body dynamics environment.
From this point onward, the component is capable of both rigid-body motion and realistic elastic deformation during simulation.
One of the greatest advantages of Flexible Body technology is its ability to reproduce realistic driving scenarios.
Typical simulation events include:
These scenarios generate realistic dynamic load histories throughout the suspension system.
The most critical input for fatigue analysis is the time-dependent load history experienced by a component.
Flexible Body simulation provides time histories of:
These load histories can then be exported to dedicated fatigue analysis software such as:
Millions of loading cycles can subsequently be evaluated to accurately predict component fatigue life.
This enables engineers to identify potential fatigue-critical regions before physical prototypes are manufactured, significantly accelerating the product development process.
Flexible Body technology enables engineering teams to:
Flexible Body technology is widely used across numerous vehicle platforms, including:
The growing weight of battery systems in electric vehicles has made suspension durability analysis even more critical than ever before.
RecurDyn combines Multi-Body Dynamics (MBD) with Flexible Body technology in a single simulation environment, enabling highly realistic system-level analyses.
This integrated approach allows engineers to simultaneously evaluate:
within one comprehensive simulation workflow.
When the resulting load histories are coupled with fatigue analysis, design decisions can be validated long before prototype manufacturing, reducing development time while improving product reliability.
In today's automotive industry, ensuring that a mechanism simply functions correctly is no longer sufficient. Modern vehicles must also be lightweight, durable, reliable, and capable of withstanding real-world operating conditions throughout their service life.
Flexible Body technology extends beyond the limitations of conventional rigid-body modeling by accurately capturing the true structural behavior of suspension systems under dynamic loading.
By combining RecurDyn's advanced Multi-Body Dynamics capabilities with finite element-based Flexible Body models, engineers can improve design accuracy, reduce prototype costs, shorten development cycles, and obtain far more reliable durability predictions.
For engineering teams striving to develop lighter, safer, and longer-lasting vehicles, Flexible Body technology is no longer just an option—it has become an essential component of modern product development.