Papers by Author: S. Hillmansen

Abstract: Static ductile crack propagation tests were conducted using two pressurised thin carbon-manganese steel tube specimens, and the crack tip opening angle (CTOA) was measured using digital images captured on specimen surface. The critical values of CTOA for static crack propagation decreased with crack extension while propagating crack was short. After the crack grew up to the distance of the tube specimen thickness, the critical CTOA exhibited nearly constant. These tendencies were the same as those of referential data in the thin single edge notched tension (SENT) specimens of the same tubes. Using the data of both tube specimens and SENT specimens, it was noted that the higher crack velocities slightly reduced the constant CTOA. A global constraint factor was calculated for each tube specimen, and the constant CTOA decreased with the increase of the global constraint factor. In addition, a dynamic ductile crack propagation test of a tube specimen was carried out, and a crack velocity was measured. The estimation of the constant CTOA for dynamic crack propagation in the tube specimen was performed by using the crack velocity.

Abstract: Static and dynamic ductile crack propagation tests were carried out using thin single edge notched tension (SENT) specimens of carbon-manganese steel, each of which had a fatigue pre-crack or a sharp V-notch as a crack initiator. The crack tip opening angle (CTOA) was measured using digital images on the surface of the SENT specimens, and the critical values of CTOA for crack propagation decreased with increasing crack length while initial crack growth was still small. After the initial crack growth up to the distance of the specimen thickness, the critical CTOA remained almost constant. These tendencies were common in static and dynamic crack propagation specimens as well as fatigue pre-cracked and sharp V-notched specimens. There was no particular difference in the static crack propagation characteristics of both fatigue pre-cracked and sharp V-notched specimens. On average, it was observed that higher crack speeds affected the constant values of the critical CTOA by slightly reducing them. The constant CTOA tends to decrease with an increasing global constraint factor, and this suggests that the factor is insensitive to a crack starter, fatigue pre-crack or a sharp V-notch, but relatively sensitive to crack speed.