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Super Elastic Alloy Eyeglass Frame Design Using the ANSYS Workbench EnvironmentSuper Elastic Alloy Eyeglass Frame Design Using the ANSYS Workbench Environment
• The goal of the analysis is to determine the configurations of the eyeglass frame that can tolerate being stepped on and still be capable of recovery meeting stiffness design requirements.
• The geometric model is built using the parametric feature capabilities of the Workbench/DesignModelertool.
• Each dimension used in the development of the geometry is converted to a named parameter that is accessible as an input variable for the sensitivity study.
• Parameter relationships and dependences are defined to prevent conflicts during model regeneration
• Nitinol is an acronym for Nickel Titanium Naval Ordinance Laboratory since the alloy was originally developed at the U.S. Naval Laboratory.
• It is used to describe a family of materials, which contain a nearly equal mixture of nickel and titanium.
• Nitinol alloys are attractive because they are biocompatible and are at their optimum super-elastic behavior (9% strain fully recoverable) at room temperature when processed properly.
Stress vs. Strain for a Nitinol Material Model using ANSYS
• Constant Definition • SIG-SAS (C1) Starting stress value for the forward phase transformation • SIG-FAS (C2) Final stress value for the forward phase transformation • SIG-SSA (C3) Starting stress value for the reverse phase transformation • SIG-FSA (C4) Final stress value for the reverse phase transformation • EPSILON (C5) Maximum residual strain • ALPHA (C6) α material responses ratio between tension and compression• YMRT (C7) Modulus for Martensite (This is Beta in 8.0/8.1)
Notes: – A self contact pair is defined around the perimeter of
the lens frame. This pair could also have been defined using the manual contact capability in the Workbench Simulation tool.
– The target surfaces could also be defined using surface geometry and the resulting shell elements converted to rigid target elements using the EMODIF command in the Preprocessing Commands worksheet.
• The following boundary conditions are applied to the model:
1. A frictionless support is applied on the bridge of the glasses to establish reflective symmetry. This is applied as a support inside the Simulation environment.
2. The lower rigid target is fixed in all degrees of freedom. This constraint is defined using the Processing Command worksheet.
3. The upper rigid target is displaced –1” in the vertical direction. This constraint is defined using the Processing Command worksheet.
• Postprocessing of the initial simulation run can be done with a combination of the standard Simulation solution tools and the Postprocessing Command Builder.
• The Simulation environment only has access to the last converged solution and the results are limited to linear quantities with the exception on contact results.
Time History plots using the PostprocessingCommand Builder
• Result plots and listings from the PostprocessingCommand Builder can be returned to the Simulation Environment. These figures are then included in the design report.
• For the DOE method used by DesignXplorer the number of deterministic solutions required is automatically determined based on the number of input variables.