Figure 4: Principle of the crack-bridging test equipment

As mentioned before one distinguishes protective coating systems for temperature induced crack movements (Index T) and additionally load induced crack movements (Index T+L) . The crack width cycle in the tests for the classes IT, IIT, IIIT and IVT as function of time is shown in Figure 5. The period for a test consisting of 1.000 cycles is 9.25 h.