TTZH Tribologie & Hochtechnologie GmbH  Tribometers

Low Temperature Torque Tester LT3

3D Surface Profilometers

Basalt MUST: Modular Universal Surface Tester

Tribometers

(↓ Designations)

(Universal Tribometers, Multistation Tribometers, Special Tribometers)

SCHEMES OF TRIBOTESTING.

Comprehensive testing of machines and equipment, is usually a multilevel and multiscale task, involving the field tests, bench tests, tests of specific units and components, whereas the last would be always subdivided into natural tests of real components and simplified elements, modeling a real tribology contact. On the other hand, versatile tribology systems in various industries are making a scientist, practically in all situations to keep in a mind some friction and wear fundamentals, including the laws of friction, describing physically, chemically and mechanically a real contact between moving solids. Despite some mutual effects in hard discs of computers, watches, orthopedic implants, autos, airplanes, machine tools, pumps, wind energy plants, etc., modeling of a specific contact situation, requires different approaches and surface analyses varying from nano- to micro- and macro scale.

REALISTIC SCHEMATIZATION.

Realistic schematization of a tribosystem could involve several geometries like “pin-on-disk”, “pin-on-plate”, “ball-on-disk”, ”ball-on-plate”, “block-on-ring”, ”disk-on-disk”, “parallel cylinders”, “crossing cylinders”, “4-ball” and some special ones, including various combinations of those mentioned above and multi-station testing systems. Additional specific features are coming with the different sizes of the samples concerned, with their relative positioning, with their overlapping on the contact. Turning from geometry only to the materials aspects bring more variables to a tribotester.

INPUT PARAMETERS.

The most important parameters, characterizing a tribosystem are force (torque) and speed, which are fully predefining a choice of loading system and drive in a testing device. Of critical importance is a precision of measurements of these parameters, which requires a right selection of force and torque sensors, especially for a problem of distinguishing between several thin films, including those of nanometer thickness, determined by either their different compositions, or structures, or a combination of them both together with formation of some natural and lubricating films, occurring in friction and wear processes. Load, measured in Newtons, milliNewtons, or microNewtons is considered to be a basic parameter, while important related parameters are contact stress, impact force, oscillating load, etc. Parameters, related to sliding speed are average speed, rolling speed, spinning speed, impact speed, sliding/rolling ratio. Sliding distance (often given as a time of specific tests) can be in case of reciprocating tests characterized by amplitude (connected with a precision of positioning) and frequency. Relevance of the model bench tests is usually a subject of thorough analyses. It always remains of primarily importance in adequate experiments for reproducing the wear mechanisms of the field tests. Another aspect is reproducing a temperature level and environmental situation of the test materials and coatings. The latter question is technically implemented using elevated and high temperature chambers (incl. devices and sensors for precise temperature measurements) for the tests under elevated and high temperatures (depending on techniques used up to 200°C, 800°C and 1600°C), including those, running in the protective gases; chillers and special cooling devices for negative, low and cryogenic temperatures (down to -30°C, -73°C and -269°C); vacuum chambers for the tests in vacuum (and alternatively in special gases) 10^-5 – 10^-7 mbar and in high vacuum 10^-9 - 10^-12 mbar; humidity chambers for the tests under the controlled atmospheres, circulating oils, etc.

OUTPUT PARAMETERS.

Tribotests have since years demonstrated themselves to be much more complicated procedures, than only measuring friction and wear as performed in the mediaeval triboegineering. On the other side PC controlled input parameters being changed against time or sliding distance are causing the respective variations of the response in both open and closed engineering systems. So, the output parameters include measured forces and torques of friction, coefficient of friction COF, contact temperature, distribution of contact stresses and temperatures, changes of physical parameters of tribological surfaces and contacts. The latter aspect is connected with in situ (or in vivo) measurements of electrical contact resistance or conductivity and remains an extremely sensitive method for catching a moment of breaking through of the deposited coatings and thin films. selection of a relevant test. Relevant tribology test arranged in a bench top tribometer is a model, possibly repeating the prevailing wear mechanism of the real components and implementing the same type of contact, like point, linear or flat ones. This is not a must, that a complicated tribocontact has to be modeled using one scheme only, while an adequate simulation of some practical situations can be done using several geometrical schemes.

COMPREHENSIVE TRIBOANALYSIS.

Comprehensive triboanalysis requires full scale tribotests plus a number of methods for chemical, physical and mechanical characterization of contacting coatings and films, aiming to distinguish specific tribophysical phenomena, serving to a longer life of coated and modified components. Full scale characterization involves multi-sensing tests, multilevel analysis and multi-resolution estimation of the triboparameters.