Automated measurement of crack length and load line displacement at elevated temperature

Automated measurement of crack length and load line displacement at elevated temperature

van Leeuwen, H.P.
Groep, F.F.
Schra, L.
Dam, N.

National Aerospace Laboratory NLR

1987-07-20

Test results reported in the literature show that in creep cracking tests at elevated temperature under steady load, the crack growth rate correlates best with the contour integral C*, also called J*, in comparison to other possible parameters. In the case of fatigue at elevated temperature, the crack growth rate correlates best with C* if cracking Is predominantly time dependent. If, however, cracking is predominantly cycle dependent the crack growth rate correlates best with the range A J of the contour integral J. It is discussed that in such testing C* and J are fairly easily determined if, apart from load and crack length, the load line displacement is measured. A description is given of a test set-up developed for elevated temperature creep cracking tests in which crack length was measured with the electrical potential drop method and load line displacement was measured with two inductive transducers located inside the furnace. Measurement was automated with the aid of a Personal Computer which controlled the measurements and processed the results automatically. This set-up can be adapted for elevated temperature fatigue testing.

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Nationaal Lucht- en Ruimtevaartlaboratorium

Campus only

NLR MP 87049 U

Aerospace Engineering Reports

report

(c) 1987 National Aerospace Laboraotry NLR