On the variation of fatigue-crack-opening load with measurement location

The work presented here evaluates the vlidity of using the load at the point of linearity on the displacement-load curve, as suggested by Elber, as an experimental measure of the crack-tip-opening load. Displacement-load behavior was investigated for a fatigue-cracked modified compact specimen of a nickel-base superally. Displacements were determined at the notch mouth using a standard clip-on gage, along the crack surface using a laser-interferometric displacement gage and, in the plastic zone ahead of the crack, using an optical-interferometry technique. Acoustic-emission monitoring was employed as a means to detect potential crack extension during measurement-load cycles and to detect physical-crack closure.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43930/1/11340_2006_Article_BF02324983.pd

Fatigue of polycrystalline silicon under long-term cyclic loading

The long-term mechanical behavior of 3.5 µm thick and 50 µm wide polysilicon tensile specimens under tension-tension cyclic loading was investigated. The use of an external actuator allows the variation of the test frequency between 50 and 6000 Hz. It was shown, that the strength of the samples decreases with an increasing number of cycles. The tensile strength of ?c=1.1 GPa of virgin samples was reduced by about 35 % to a fatigue strength of ?f = 0.70 GPa after 109 cycles. No influence of frequency of the fatigue behavior in the range of 50 to 6000 Hz was observed