Tatsuro Fujimitsu

A measurement of three-dimensional strains around a creep-crack tip

A new method for measuring the strain around the high-temperature creep-crack tip is proposed in the present paper. A grid pattern was described in a space of about 30 μm with a diamond stylus in the area ahead of the precrack of the specimen. Then, the distortion of the grids and the change in specimen thickness which were induced by the creep deformation were measured by means of a photo-microscope and a roughness-measuring system, respectively. The three-dimensional components of the strain were calculated using the Lagrangian equation, into which the above measurement was introduced. The route of the creep-crack extension was examined in association with the local strain measured by the proposed method.

Low-Cycle Fatigue Life Prediction of Circumferentially Notched Cylindrical Components

Circumferentially notched cylindrical components of medium carbon steel and Ti-6A1-4V alloy were low-cycle fatigued. Then their lives required for crack initiation and spent during crack growth period were investigated. The crack initiation life was dominated by the equivalent plastic strain calculated at the notch root through the elastic-plastic finite element method. The life spent in crack growth process was successfully estimated by analyzing the surface crack growth through cyclic J-integral range evaluated in the proposed way.

WS6d6 – FATIGUE LIFE PREDICTION OF CIRCUMFERENTIALLY NOTCHED COMPONENT BASED ON ELASTIC-PLASTIC FRACTURE MECHANICS

ABSTRACT The elastic-plastic fracture mechanics parameters for the three dimensional surface and circumferential cracks generated in the circumferentially grooved cylinder component were analyzed from the viewpoint of engineering. Then, fatigue life spent during crack growth was estimated for the bluntly and acutely notched cylindrical components. Consequently, it was found that the crack propagation life of the notched cylinder component was successfully predicted by analyzing the extension of the semielliptical surface crack and the circumferential crack based on the proposed method.