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 HBK, and uses an MGCplus data acquisition system by HBK for instance, it came as no surprise that HBK 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.