eXpert 8000 planar biaxial fatigue testing machine

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ADMET recently designed a planar biaxial testing system for a group that’s developing the newest evolution of wave energy capturing devices that are deployed in coastal areas to produce renewable energy. Some of these devices feature soft rubber membranes, which face very unique and complex stress states. By performing various controlled planar biaxial fatigue tests on these membrane materials in a seawater media, the design of the wave energy capturing devices can be optimized.

The customer needed to perform cyclic fatigue testing on cruciform shaped specimens at a frequency of 2 Hz and strain of 150%. ADMET’s eXpert 8000 system design accommodated this with 1 kN capacity actuators capable of 835 in/min speed.

Testing would also be conducted in marine water conditions, so all fixturing and load cells used in the included environmental bath needed to be able to withstand the highly corrosive environment. ADMET’s bath also included a recirculating heating/cooling system capable of providing water temperatures ranging from 10C to 30C.

In addition to cruciform shaped specimens for which simple grips could be used, the customer also wanted to test larger square shaped specimens, which required a unique gripping technique to ensure a consistent strain field without introducing shear stresses. To accommodate this, ADMET provided a custom grip set that utilized multiple clamping “fingers” that could slide laterally on linear bearings during biaxial tensile testing.

Closeup of test fixtures gripping a square sample
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