A Program Development of Life Prediction Simulation for Multi-Surface Cracks on the Finite Plate

J. Ocean Eng. Technol. 1997;11(4):61-75.

무한 평면체에 존재하는 복수 표면균열의 성장에 대한 수명예측용 시뮬레이션 개발에 관한 연구

황남성,서창민,남승훈

영남전문대학 기계과,경북대학교 기계공학과,한국표준과학연구원

Keywords: Simulation, Small Crack, High Temperature Fatigue, Crack Closure, Coalescence, Expert System

핵심용어: 시뮬레이션, 작은 균열, 고온 피로, 균열닫힘, 합체, 전문가 시스템

Abstract

The social demand urges us to use some equipments and structures in high temperature environment. By this occasion, the necessity of studying the fatigue crack growth is an important aspect of new materials. However, the present situation is rarely to accumulate the fatigue data. Especially, 1Cr-1Mo-0.25V steel and 304 stainless steel have been increased to be used under the severe condition of high temperature. And so, the fatigue estimation of those materials is important and appropriate. Fatigue tests have been carried out to examine the crack initiation, growth behaviour for the small fatigue crack of 1Cr-1Mo-0.25V steel and 304 stainless steel at room temperature and 538^{circ}C$. The remote measurement system which has many merits of checking and saving the image for detailed examination was applied to closely detect the crack length. Generally, the fatigue crack initiated in the form of multiple cracks and grew each other. And then it coalesced to become a major crack. The major crack governed the rest of the fatigue life. In the growing process, each peripheral cracks interact and grow for a certain period. After then, it coalesced and fractured. On the basis of the above experimental data for the small crack, a simulation program was developed to predict the residual life time and to estimate the integrity of machine elements and structures. At the same time, the simulation was extended to 1Cr-1Mo-0.25V steel. The simulation results have shown a good agreement to those of the experimental ones for both materials of 1Cr-1Mo-0.25V steel and 304 stainless steel with small cracks. The NASCRAC has applied to compare the fatigue life with the experimental results. And so, it can be said that the simulation program is valuable tools to the industrial fields.