Bennewart Flex Tester is intended to determine the resistance of a component of material to cut growth under repeated flexing. It can also be used to assess the effect of surface patterns on crack initiation and growth.
This test is especially applicable to the outsoles of footwear, but may also be used with certain other flexible components.
One of the methods for determining the abrasion resistance of elastomers is by a Rotating Drum Abrasion Tester. In this test the elastomer under test is abraded against an abrading surface mounted over a rotating drum. The abrading surface has a specified abrading power. The test specimen, which is in form of a button, is held against it under a fixed load. The abrading surface is made to rub against the test specimen by rotating the drum at a fixed speed, the test specimen being meanwhile made to move along the axis of the drum.
Out-soles of footwear or other flexing components may suffer cracking due to flexing in use. Cracks usually develop at points of high surface strain resulting from the design of the sole pattern, without there being any cuts due to grit etc. to initiate them.
The Belt Flex Tester is designed to flex complete soles with their patterns intact in a way similar to flexing in actual use. Tests carried out using it provide a guide to the risk of such cracks developing during use.
In this test, test specimens are attached to the outside of a continuous belt, which is driven round two rollers. The larger roller drives the belt, while movement of the belt round the smaller roller provides the main flexing action. The radius of the smaller roller is chosen to make the flexing either more severe or less severe than in actual use.