SEDL / STP / STP1380-EB / STP14406S

Use of Instrumented Charpy Test for Determination of Crack Initiation Toughness

Viehrig, H-W
Senior Scientist, Institute for Safety Research, Forschungszentrum Rossendorf e.V., Dresden,

Boehmert, J
Head of Department, Institute for Safety Research, Forschungszentrum Rossendorf e.V., Dresden,

Richter, H
Research Scientist, Institute for Safety Research, Forschungszentrum Rossendorf e.V., Dresden,

Valo, M
Group Manager, VTT Manufacturing Technology, VTT

Pages: 12    Published: Jan 2000

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Abstract

The instrumented Charpy test provides the opportunity to determine dynamic crack initiation (J^id) toughness. Under the condition of the impact bending test, the critical step for evaluating J^id is the identification of the ductile crack initiation point on the impact load versus displacement curve. Therefore, acoustic emission (AE) was monitored and used as a tool for ductile crack initiation detection. With a tup-integrated AE sensor, different types of AE events could be identified during loading of a Charpy size specimen. One type of AE signal appeared in the temporal vicinity of crack initiation and was applied to define J^id. A verification of these results was performed by simultaneous optical measurement of COD with an inverted impact pendulum. Additionally “Cleavage R-Curves” (J^dΔa) were evaluated and physical crack initiation toughness (J^idszw) values were determined by measurement of the stretch zone width (SZW).