Which material combination provides most friction?
The study examined
three types of rubber and five different types of braided steel cables in fifteen different combinations. The objective was to determine what type of rubber and what type of cable provided the
most friction. The cables were standardly braided steel cables with thicknesses from 0.18 to 0.45 millimeters that are used in everyday applications for hanging picture frames or as bicycle brake cables.
For the
test, a setup was developed by the team. It consisted of a
clamping module with two rubber-clad blocks, with a third block wrapped in steel wire pulled between these two. Measurements were taken of both the
clamping force of the clamping module and the
tensile force of the block with the steel wire. The setup needed a
suitable force sensorto measure the force exerted on the block with the steel cable. This ultimately enabled the friction to be mapped out. The force sensor had to meet specific
requirements related to measurement range and accuracy.
The specifications were drawn up at what is known as the "
Meetshop" (Measurement Shop) in the Faculty of Mechanical, Maritime and Materials Engineering, where students and doctoral candidates can
request support with measurement applications. Because the Meetshop does a lot of business with HBM, and uses an
MGCplus data acquisition system by HBM for instance, it came as no surprise that HBM was selected to supply a force transducer. The force transducer was exposed to
weights of up to 180 kg. Incidentally, the force sensor was not only used for the tests with the clamping module, but also for
calibration of the tensile module.
“Including development of the test setup and clamping modules, the study lasted
a year and a half and has produced a treasure trove of useful data,” adds Arjo Loeve. “After publication of the study in WEAR, the scientific journal for tribology, and in IEEE Transactions on Biomedical Engineering, the basic principle of the technology attracted the interest of other organizations. The stiffening principle also appears to be applicable for the
stiffening of controllable forceps during operations. The friction data from the measurements have proven their worth in many areas where steel cables come into contact with rubber parts. Even the
army and the police are interested in testing the technology for stiffening hoses in the field. Some other examples of potential applications include
detection of explosives and booby traps and visual inspection of enclosed spaces.