Biomedical Design & Analysis

MDC engineers have experience with a range of implantable and non-implantable biomedical devices, as well as device testing and lab equipment. Metis Design's extensive resources allow us to perform complex, non-linear analyses as well as more traditional FEA work.

One recent project for Metis involved complex CAD as well as FEA. The project focused on a braided nitinol part. MDC was charged with creating a FEA model that simulated the slipping between the nitinol wires under loading. Due to the complexity of the analysis, ANSYS was used. A text based input deck was created that imported an IGES model with the wire geometry and then created the appropriate elements. These elements were then patterned and connected with contact elements. This allowed the wires to slip but not separate, as occurs in the physical part.

The results of the model were correlated and compared with results where the braid joints were bonded together to confirm the need for the non-linear contact model. In addition, MDC engineers carefully evaluated the contact results to make sure that the FEA results were physically possible and probable. Modifications in the element formulations and connections were made until the MDC was sure the results were accurate.

Although this load case required only a linear model of nitinol, part of the project was to research non-linear, shape memory alloy formulations for later work. One of the reasons that ANSYS was chosen for this project is that it has complex material model built in that can be modified to accurately simulate the shape memory characteristics of nitinol.

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