Just One of Many Reasons to Attend the SCC...technical highlights below!

There are many mechanical systems that can be classified as a combination of flexible components and mechanisms; a few examples are gear systems, aircraft landing gears, or systems including linear bearings. Historically dedicated multi-body dynamics (MBD) codes were used for the loads development in these systems, with subsequent detailed stress evaluations performed on the individual parts. Several problems with this approach is that it tends to greatly over predict loads leading to overly conservative designs, it neglects the coupling of component flexibility,  and also requires maintaining two different models which may be difficult in a dynamic design environment. MBD codes have capabilities to include modal representations of bodies that can better represent component flexibility and these models are sometimes used for stress predictions. While this approach has the benefit of representing component flexibility and therefore producing better system-level loads, the displacement and stress predictions from the system-level models are often inaccurate due to inherent limitations of a modal representation.

Another approach to solve this class of problems is to use an all-FEM representation that enables accurate stress predictions, including local contact stresses, while simultaneously incorporating the coupling of flexible members. As a demonstration a rigid, articulating mannequin with sliding contact along a flexible rail was developed.

A few highlights of this approach are listed below with a more thorough presentation and accompanying paper to be delivered at the May 2014 SIMULIA Community Conference in Providence, Rhode Island.

Technical Highlights

• Using a single model for stress evaluations and actuator loads predictions streamlines the design process, eliminating the need for multiple models in different analysis environments
• The model can be quickly updated to keep pace with a dynamic design environment
• The rigid mannequin can be represented with lumped mass/*DISPLAY BODY for early design studies or detailed mesh/*RIGID BODY for more refined studies
• Mannequin joint actuators are modeled with connectors, allowing sophisticated representations of joints if necessary
• This approach enables accurate stress prediction in the flexible components while also incorporating nonlinear effects and contact if applicable, allowing structural integrity evaluations from the dynamic results directly
• Mannequin actuator forces and moments include the effects of coupling with flexible components, enabling more accurate actuator sizing and fatigue evaluations

Sliding base/rail connection through contact between rigid bearing blocks and flexible T-slots.