Yoshio Fukuda

Crack Growth Behavior under Multiaxial Low Cycle Fatigue at High Temperature for 1CrMoV Steel.

Microcrack growth behavior under axial and torsional loading at 550°C was observed. Cracking behavior was correlated with the results of microdamage observations using several strain parameters. From the microdamage observation, micro-cracking of oxide film at the crack tip in the strain localized region seems to be a dominant factor of micromechanism of fatigue crack growth. The maximum principal strain, which is the linear summation of the shear strain and the normal strain perpendicular to the crack path, has been identified as an important parameter in multiaxial fatigue at high temperature. A good correlation was obtained between the principal strain range and the crack growth rate.

A Study of Wear Resistance of Steels without Lubricants and their High Temperature Hardness

In the present paper, the relations between wear resistance of steels and their high temperature hardness have investigated with the wear tests under dry condition and the measurments of high temperature hardness in a vacuum. The wear tests have been carried out under various sliding speeds.The wear resistance of steels, that is a reciprocal of steady wear rate, is found to be affected by the surface hardness attained during the abrading. Hence, there have been observed close relations between wear resistance and high temperature hardness. Especially for low carbon steel, specimen with larger size of ferrite grain shows lower wear resistance than the one with smaller size of ferrite grain within a lower range of sliding speed, but at higher speed the reverse is obtained. This relation of wear resistance is compatible with that of high temperature hardness, and it is considered that the grain boundary plays considerable roles in wear.For high carbon steel of pearlite structures, wear resistance depends also on high temperature hardness up to certain sliding speed, but at the higher speed, the wear resistance tends to be extremely high because the rubbing surface is hardened due to structural change.