Round Robin Frame Structure
With the formation of the Dynamic Substructures TD, the dynamic substructuring focus group has chosen a new simplified test bed structure - the four unit frame. This structure can be modified to a variety of applications including: aerospace, automotive, and civil uses.
Four Unit Frame
A subteam on the Dynamic Substructures TD designed this four unit frame after brainstorming some criteria for the structure.
Key Features:
- Manufactured from one piece of metal of stock
- Subcomponent and shaker attachment points machined into frame
- Adaptable to many types of studies
- Possible circular/recursive transfer path
- Large enough to minimize error due to mass loading
More information can be found here:
Testbed Assembly Instructions, Frame Substructuring Kickoff
Lots of test bed information already exists on the wiki. If you would like to add more please contact the wiki manager to get set-up with an account!
Thin & Thick Wing Challenge
To sign up for the challenge, e-mail Dan Roettgen. At IMAC XLI [2023] and XLII [2024] - we hope to have many universities and research institutions show their ability to perform dynamic substructuring predictions with the four unit frame. Presently there are 9 sets of hardware available so we will rotate those through different groups and continue to manufacture more systems for the next two years.
To complete this task:
- You will be provided with a frame, thin wing, thick wing, and required fasteners.
- Complete a test of the assembly of the Frame and Thin Wing
- Use Dynamic Substructuring to add an experimental or numerical model of the Thick Wing
- Present results at IMAC in an extended abstract session that will act as an open forum to discuss dynamic substructuring
Future years hope to focus on:
- Improving Blind Predictions
- Damping Challenges
Available Information:
- Analytical Data
- Experimental Data
Results:
- IMAC 2022 - Four Unit Frame Dynamic Substructuring Results
- IMAC 2023 - Straight to Swept Wing Substructuring
- IMAC 2023 - Thin to Thick Wing with Nonlinearity
Nonlinear Subcomponent Challenge
While Dynamic Substructuring has generally been concerned with modeling linear dynamics, assembled structures tend to exhibit some degree of nonlinear behavior - especially those containing bolted joints. In previous demonstrations, Linear Substructuring techniques have been used to successfully combine linear and weakly nonlinear subcomponents. However, further work is needed to investigate how to consistently incorporate more complicated nonlinear behavior into substructuring results to increase the reliability and accuracy of blind predictions.
To that end, a set of nonlinear attachments for the Four Unit Frame have been designed by the team at Sandia National Labs. These include:
- A variation of the thick wing that has been modified to incorporate a lap joint on each side, allowing for interchangeable straight and swept modular wing tips.
- A pylon that attaches to the underside of the modular wing, featuring a contact nonlinearity defined by a smooth radius or sudden gap.
These designs were presented at IMAC2024 along with a set of challenges for the community. Below is that presentation, the drawings and models of the nonlinear subcomponents, and the proposed challenges.
IMAC2024 Presentation - Contains information on the designs and a preliminary look at dynamic response data of the frame and nonlinear subcomponent assemblies
Nonlinear Subcomponent Designs:
- Technical Drawings - PDFs
- CAD Models - .stp files
Frame & Straight Modular Wing
Frame & Swept Modular Wing
Gap Pylon
Radius Pylon
Community Challenge Objectives:
- IMAC 2025: Design and build a nonlinear component, either based on those described above or self-designed, and test it to determine the level and/or type of nonlinear response.
- IMAC 2026: Attempt to complete a Dynamic Substructuring process involving the nonlinear components and identify any issues or deficiencies in your current approaches.
- IMAC 2027: Formulate methods to address the identified deficiencies and compare across the community to enrich our collective understanding of substructuring with nonlinear subcomponents.
For questions or more information, feel free to contact Ben Moldenhauer and/or Dan Roettgen.