Crack Paths 2012

Pulsed reflection microscope (PRM)

Within this work an optical measurement system, hereinafter called pulsed reflection

microscope (PRM), was used in order to study the micromechanical effects during

overloads in nodular cast iron. The P R Mwas initially developed for the optical

investigation of flow fields [8] and has been recently applied by Zybell et al. [6] for the

microstructural investigation of overload phenomena in nodular cast iron. The setup of

the P R Mis basically in accordance with that of a reflected-light microscope, where the

light is emitted by a L E Dand the specimen’s surface acts as a mirror. Finally, the light

is detected by a L C Dcamera and the image files are transferred to a laptop via U S B

connection. Fig. 2 shows the optical and mechanical setup of the P R Mwithin a servo

hydraulic M T Stesting machine. The main advantage of the P R Mis the flexibility of the

system to fit into numerous standard testing machines, so that time consuming mounting

and demounting processes like in ex-situ techniques can be avoided. Using the PRM,it

is now possible to investigate the microstructural effects in fatigue crack growth under

variable amplitude loading on standard specimens under real, i.e. random, loading

conditions.

Figure 2. Experimental setup within servo-hydraulic M T Stesting machine:

SENB3specimen with integrated pulsed reflection microspcope.

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