RCP Under Static Loading

Session 10A
3:00 pm

Sunwoong Choi, Hannam University

A method for creating rapid crack propagation on pressurized pipes under slow static loading is described. In the development of the method a complexity related with dynamic loading is eliminated by the use of a displacement controlled static loading machine. The experimental system consisted of an universal testing machine, a low compliance wedge loading device, crack tip quenching apparatus and a pipe specimen where a through thickness hole is drilled to accommodate the wedge loading device. The pipe specimen is made in such a way that a section containing a hole is free from the internal pressure while the rest of the specimen is made to carry the internal pressure which would eventually drive the unstable crack along the pipe axis. The idea of such rapid crack initiation under static loading was derived from the concept of time-temperature equivalence, where the loading like impact may in part be simulated by lowering the temperature at the site of rapid crack initiation. This idea has been tested within the frame work of crack-arrest-toughness studies whereby the utilization of localized crack-tip temperature control has shown to work for both very tough (hard to crack initiate) and very brittle materials (hard to crack arrest) in generating the rapidly running crack initiation as well as crack arrest.

Within the findings of the preliminary work performed the details of the method for rapid crack initiation under static loading are described and the correlation of the result to rapid crack propagation obtained per ISO method is illustrated. For this preliminary study, the pipe specimen was produced from the 110 SDR11 PE100 grade gas pipe and the experimental requirements are made to comply with the ISO 13477 as much as possible in terms of use of baffles, cages and other details, except the loading method. The value of utilizing static loading versus dynamic loading will be also presented.

Sooho Pyo*, Junghyun Nam*, Jongho Woo* and Sunwoong Choi**
Hannam University, Daejeon 305-811, Korea

*Graduate student, ** Professor