Background

Many nonlinear material models in ANSYS require either predetermined material constants, or experimental data to be used for curve fitting. The main allowable experimental data set inputs to be used for curve fitting for hyperelastic material models such as Ogden, Mooney-Rivlin, or Neo-Hookean are uniaxial, biaxial, shear, and volumetric test data. Biaxial test data is the most difficult data to acquire due mostly to the rarity of biaxial test machines in labs. In order to reduce costs, there have been several test fixtures designed to allow the performance of biaxial tension tests in uniaxial test machines, none-of-which have been found to be commercially available.

Project Summary

• Research previously designed systems and analyze their shortcomings and strengths
• Develop a project plan (milestones and dates)
• Submit plan for approval
• Generate design concepts for test fixture, data acquisition, and sample specimen manufacturing (sample material will be provided)
• Analyze design concepts using appropriate means (kinematic modeling, compliance calculations etc.)
• Submit final design for approval
• Build prototype and manufacture specimen pieces for testing
• Validate the fixture and data acquisition, compare to expected results
• Operate the test fixture to gather data on multiple materials (materials will be provided)
• Develop operations manual
• Document the project and give final presentation

Design Expectations

• Fixture should be designed for use with an MTS machine
• Use of the fixture should require no modifications of the test machine
• Alignment of the fixture should be considered so that no bending moments or shear forces are transmitted through the specimen being tested