Soft Contact Investigation
Overview
The characteristics of soft contacts are different from the more usual steel on steel contact. The low stiffness of soft materials means that there is considerable elastic deformation of the specimens under load.
Furthermore, the elastic hysteresis of the materials means that there is significant rolling friction in addition to the usual sliding friction. The MTM2 has been designed with the study of soft contacts in mind through the addition of load feedback and a capability to calculate both the sliding and rolling friction. In addition the MTM2 offers great flexibility when choosing specimens to create soft contacts.
Soft specimens selection
Several options are available to produce a soft compliant contact in the MTM2. The upper specimen can be a soft ball or a readily available standard size O ring supported by the O ring holder as show on the right. Alternatively custom made specimens can easily be produced. The simple plane shape of the disc means it can be made of virtually any material and supported by a backing plate.
O Ring holder in place in MTM2. For O rings of section 3 mm, ID 12.5 mm
Applications
The MTM2 has been used to study a wide variety of soft contact applications, including research on foods, cosmetics, seal materials and rubber shoe to ground contact. Soft discs have been particularly successful when used to carry out fundamental research on food components and cosmetics. When using the reciprocating option, the MTM2 can reproduce the low frequency oscillation typically found in food processing or skin cream applications.
Examples of silicon elastomer grades Fitted on the Backing plate
Testing seal material properties
Testing of seal material is traditionally split into 2 categories: simple wear testing such as pin-on-disc test or testing the complete seal in place on the application. The first method often bears little relevance to the final application and the second is generally too expensive and unsuitable for developing new materials. Thanks to the flexible choice of specimen materials, surface finish, hardness and coatings, the MTM2 is ideally suited to study the friction and wear properties of seal material.
O ring on steel disc SRR 50%, load 3N, temperature 60°C, Mineral oil Influence of counterface roughness
