APPLICATION OF FRACTURE SURFACE TOPOGRAPHIC ANALYSIS TECHNIQUE TO THERMAL FATIGUE-CRACK EXTENSION IN STAINLESS-STEEL VESSEL

The fracture surface topographic analysis (FRASTA) technique is applie d to investigate the propagating process of fatigue crack in a model v essel made of type 304 stainless steel due to repetitive thermal shock s for 1000 cycles. FRASTA is a procedure for reconstructing the proces s of crack extension by comparing topographic features of coupled area s of opposing fracture surfaces via computer. Based on the result, fra cture mechanics analysis is made to estimate the relationship between crack depth and applied number of thermal cycles. During the thermal t ransient test, acoustic emission (AE) is monitored using four channel AE sensors. The estimated number of initiating cycles and propagating behavior of macroscopic crack by fracture mechanics analysis is compar ed with the result of AE monitoring examination, and the usefulness of the FRASTA technique is discussed.