Tensile testing conveyer belts is important in quality testing of manufactured products to ensure that the products pass industry standards for durability. Conveyer belts are typically engineered to withstand high tensile forces, and are often challenging to test. The toughness of the material in combination to multiple fibers and fiber orientation may result in specimen slippage or specimen failure at the gripping point.
A manufacturer of conveyer belt material contacted us after they experienced both specimen slippage and failures at the grips - the inherit lubricity of the material caused the specimens to slip out of the grips. When the clamping pressure increased, the specimen began to fail at the grips. This is a challenging issue that often presents itself when specimens do not have tabs or when the cross-sectional area is the same throughout the full length of the specimen.
We used a standard configuration with the exception of one minor custom component was necessary to successfully test the specimens. First, we recommend using pneumatic side acting grips with sufficient clamping pressure - either the 5 kN or 10 kN pneumatic side acting grips. In some cases, a material may fail below 5 kN, so the additional clamping pressure that is available with the 10 kN is necessary to successfully grip the specimens. This is true when individual fibers slip during a test. When individual fibers slip, stress concentrations develop and result in specimen failures within the grips. We found that for this test, the 10 kN grips were ideal even though all of the specimens failed below 5 kN.
In addition to the larger capacity grips, custom wedge inserts along with custom jaw faces were required to grip the specimens. Specimens were wrapped around wedge inserts to prevent the specimens from slipping. The inserts increased the contact area between the specimen and jaw faces. Custom 50 mm x 50 mm serrated jaw faces with rounded edges were necessary to eliminate specimens failing at the jaw faces. The rounded edges prevented the specimens from contacting the sharp corner of a jaw faces during testing
Tests were run at a speed of 100 mm/min, and all specimens failed within the test area. A suitable system for testing these types of samples would either be our 3300 or 5500 electromechanical testing machine, with along with the appropriate pneumatic side acting grips and jaw faces.